Evaluation of early postoperative results after bicaval versus standard cardiac transplantation and review of the literature

OBJECTIVE

Previous studies have been inconsistent in defining a clinical benefit to the bicaval cardiac transplantation technique relative to the standard technique, and many major centers have not adopted this newer approach. The purpose of this study was to determine whether clinically significant benefits support utilization of the bicaval technique.

METHODS

Sixty-eight consecutive adult patients undergoing a standard cardiac transplant were compared with 75 consecutive patients who underwent the bicaval technique during the period from 1991 to 1999. Etiology, recipient sex, recipient age, donor age, and pulmonary vascular resistance were similar between the two groups.

RESULTS

Cardiac index at 24 hours after operation was increased for the bicaval group relative to the standard group (3.15 +/- 0.7 vs 2.7 +/- 0.5 L/min/m(2), P <. 05). Inotropic requirements were significantly less, and there was significantly less tricuspid regurgitation in the bicaval group relative to the standard group. In addition, the bicaval group more frequently had a nonpaced normal sinus rhythm at 24 hours after operation (73.9% vs 50.7% [standard group], P =.025) and had fewer postoperative arrhythmias (29.3% vs 47.7% [standard group], P <.01). Finally, although mortality was similar for the two groups, length of postoperative hospitalization was longer for the standard group relative to the bicaval group (12.1 +/- 11 vs 20.4 +/- 12 days, P <. 001). Review of the literature identified reduced tricuspid regurgitation and improved rhythm as consistent benefits of the bicaval technique.

CONCLUSION

This review demonstrates a clinical benefit during the early postoperative period with bicaval cardiac transplantation (relative to standard) and encourages further utilization of this technique.

Efficacy of the internal mammary artery in combined aortic valve replacement-coronary artery bypass grafting

BACKGROUND

While internal mammary artery (IMA) use predicts improved survival after coronary bypass grafting (CABG), it remains unknown whether patients undergoing concomitant aortic valve replacement (AVR) realize a similar benefit.

METHODS

All patients at a single teaching institution, undergoing combined AVR-CABG, which included a graft to the left anterior descending coronary artery (LAD) from 1984 to 1994 (n = 227) were examined retrospectively.

RESULTS

Patients receiving an IMA graft (yesIMA, n = 135) and patients receiving only saphenous vein grafts (nonIMA, n = 92) were not different in their presenting symptoms, or in their incidence of preoperative risk factors. The patients with IMA were more likely to be male, have a later year of operation, be younger, and have a greater body surface. Morbidity was not different between groups. IMA use did not affect 30-day mortality. Long-term actuarial survival was greater in the group with IMA (63% +/- 7% vs 42% +/- 6% at 5 years, p < 0.01). A multivariate Cox proportional hazards model demonstrated that use of an IMA graft improved survival, while recent myocardial infarction, diabetes, earlier year of operation, and lower ejection fraction diminished long-term survival. The relative risk of IMA grafting was 0.570.

CONCLUSIONS

Within the limits of a retrospective analysis, patients in a modern era of cardiac operation, who undergo combined AVR-CABG, do not suffer increased morbidity from IMA use, and may realize a survival benefit from use of the IMA as a conduit for bypass of the LAD coronary artery.

Right ventricular dysfunction after cardiac transplantation: primarily related to status of donor heart

BACKGROUND

It is unclear whether right ventricular dysfunction after transplantation is due to donor brain death-related myocardial injury or recipient pulmonary hypertension.

METHODS

A canine donor model of brain death and a monocrotaline pyrrole-induced chronic pulmonary hypertension recipient model were established, and used for 30 orthotopic bicaval cardiac transplantations divided into three groups: Controls (group A, normal donor/recipient), group B (brain-dead donors/normal recipient), and group C (normal donor/recipients with pulmonary hypertension). Right ventricular function was measured before transplant and brain death, 4 hours after brain death, and after transplant (1 hour off bypass) by load-independent means plotting stroke work versus end-diastolic volume during caval occlusion. Right ventricular total power and pulmonary vascular impedance were determined by Fourier analysis.

RESULTS

In comparison to the control group right ventricular preload-recruitable stroke work and total power decreased significantly after brain death and transplant in group B (from 22.7 x 10(3) erg (+/-1.2) at baseline to 15.6 x 10(3) (+/-0.9) after brain death and to 11.3 x 10(3) (+/-0.9) after transplant). In group C there was a significant increase in pulmonary artery pressure, impedance, right ventricular preload-recruitable stroke work, total power after transplant.

CONCLUSIONS

Normal donor hearts adapt acutely to the recipient's elevated pulmonary vascular resistance by increasing right ventricular power output and contractility. Brain death caused significant right ventricular dysfunction and power loss, which further deteriorated after graft preservation and transplantation. The effects of donor brain death on myocardial function contribute to right ventricular dysfunction after cardiac transplantation.

Molecular and functional mechanisms of right ventricular adaptation in chronic pulmonary hypertension

BACKGROUND

Chronic pulmonary hypertension can lead to compensatory changes in the right ventricle. In this study, the adaptive mechanisms of the right ventricle in the setting of pulmonary hypertension were assessed at the molecular and functional level using a canine model of monocrotaline pyrrole-induced pulmonary hypertension.

METHODS

Animals underwent pulmonary artery catheterization to measure pulmonary hemodynamics before and 8 weeks after an injection of monocrotaline pyrrole, 3 mg/kg (n = 8) or placebo (n = 8) (controls). Systolic function was assessed with load-insensitive means (preload-recruitable stroke work). Myocardial biopsy specimens were collected to analyze membrane alpha1- and beta-adrenergic receptor density and adenylate cyclase activity.

RESULTS

Eight weeks after injection, significant increases in pulmonary hemodynamic indices were noted in monocrotaline-injected dogs. Significant increases in right ventricular preload-recruitable stroke work were also observed in these animals compared with controls and occurred in association with significant increases in right ventricular alpha1- and beta-adrenergic receptor density and isoproterenol hydrochloride-stimulated adenylate cyclase activity. No significant differences in basal adenylate cyclase activity in the right ventricle were noted between the two groups.

CONCLUSIONS

These data suggest that alterations in right ventricular function in the setting of chronic pulmonary hypertension may partially be due to changes in myocardial adrenergic receptor signaling.

Right ventricular function in orthotopic total atrioventricular heart transplantation

BACKGROUND

Total orthotopic heart transplantation was recently introduced into clinical practice as an alternative technique of orthotopic heart transplantation, adding bicaval and left and right pulmonary vein anastomoses to pulmonary artery and ascending aorta connection (total technique). The conventional technique (ventricular transplantation with atrioplasty) is compared with the total technique with particular emphasis on right ventricular performance.

METHODS

Forty-eight mongrel dogs (23 to 31 kg) were used for 12 total and 12 standard orthotopic heart transplantations. Right ventricular (RV) function and atrial systole were analyzed with the use of micromanometry, sonomicrometry, and ultrasonic flow probes (preload-independent RV recruitable stroke work, RVPRSW). Fourier analysis was used to calculate RV power and pulmonary vascular impedance.

RESULTS

There was no significant difference in cardiac ischemic and bypass times between the two groups. After transplantation, sinus rhythm was preserved after all total transplantations and after only one standard transplantation; no significant hemodynamic differences were observed. RVPRSW in the total group was conserved after transplantation; however, RVPRSW decreased by 39% (+/-8, p < .05) in the standard group. There was also a significant decrease in the rate of RV filling in the standard group after transplantation, suggesting decreased right atrial function. Pulmonary vascular impedance and RV power output were not significantly different after transplantation between the two groups.

CONCLUSIONS

Total atrioventricular transplantation is a feasible alternative and conserves normal sinus rhythm. Ischemic and bypass times were not significantly different when the superior vena cava anastomosis is performed last after the release of the aortic cross-clamp. The insignificant decrease in the rate of RV filling with the use of the total technique suggests conserved RV diastolic function after transplantation with less decreased RV function in the total group.

Hemodynamic and inotropic effects of milrinone after heart transplantation in the setting of recipient pulmonary hypertension

BACKGROUND

Right ventricular failure remains an important cause of early morbidity and death after heart transplantation and is commonly related to preexistent recipient chronic pulmonary hypertension, which occurs as a result of long-standing congestive heart failure. In this study, the hemodynamic and inotropic effects of milrinone were assessed after bicaval heart transplantation in the setting of monocrotaline pyrrole-induced recipient chronic pulmonary hypertension.

METHODS

Twenty dogs were used for 10 successfully completed transplantation experiments. Recipient animals underwent right atrial injection of 3 mg/kg monocrotaline pyrrole 4 months before transplantation. Hemodynamic and functional data were taken 1 hour after termination of cardiopulmonary bypass and after milrinone infusion. Myocardial function was assessed with load-insensitive means (preload-recruitable stroke work) and pulmonary vascular impedance was calculated with Fourier analysis.

RESULTS

At the time of transplantation, before cardiopulmonary bypass, pulmonary hemodynamic indexes in recipient animals were significantly increased when compared with donors and were further significantly increased after cardiopulmonary bypass. Two animals died after transplantation as a result of acute right ventricular failure. In surviving animals milrinone infusion led to significant increases in right ventricular function, which occurred in association with significant improvements in pulmonary vascular impedance and transpulmonary efficiency.

CONCLUSIONS

In the setting of monocrotaline pyrrole-induced recipient pulmonary hypertension, milrinone was associated with significant improvements in pulmonary vascular impedance, right ventricular function, and transpulmonary efficiency. These data suggest that milrinone is an effective means to improve right ventricular dysfunction and pulmonary vascular efficiency after bicaval heart transplantation in the setting of recipient chronic pulmonary hypertension.

Pharmacological strategies for improving diastolic dysfunction in the setting of chronic pulmonary hypertension

BACKGROUND

Right ventricular (RV) hypertrophy is an adaptive process that occurs in the setting of chronic pulmonary hypertension (CPH) and can lead to alterations in normal RV diastolic properties. This study was designed to investigate the effects of NO and milrinone on RV diastolic dysfunction in the setting of CPH and RV hypertrophy by use of a canine model of monocrotaline pyrrole (MCTP)-induced CPH.

METHODS AND RESULTS

Sixteen mongrel dogs (22 to 24 kg) were used. Animals underwent percutaneous pulmonary artery (PA) catheterization to measure pulmonary hemodynamics before and 8 weeks after injection of 3 mg/kg MCTP (n=8) or placebo (control, n=8). Eight weeks after injection, all hearts were instrumented with a PA flow probe, sonomicrometric dimension transducers, and micromanometers. Data were collected at baseline and after both NO and milrinone administration. Diastolic properties were quantified by use of the end-diastolic pressure-volume relationship and the time constant of ventricular isovolumic relaxation. Eight weeks after injection, significant increases in the PA pressure and pulmonary vascular resistance were observed in MCTP dogs. Significant worsening of RV diastolic function occurred in association with significant increases in the ratio of RV dry weight to LV+septal dry weight. NO and milrinone administration both led to significant improvements in RV diastolic properties.

CONCLUSIONS

In the setting of MCTP-induced CPH, significant worsening of RV diastolic function was observed in association with significant increases in the ratio of RV dry weight to LV+septal dry weight, suggesting that these changes are partially due to RV hypertrophy. The significant improvement in RV diastolic properties after both NO and milrinone administration suggests that these agents may be effective forms of pharmacological therapy for improving RV diastolic dysfunction in the setting of CPH.

Physiologic effects of extracellular superoxide dismutase transgene overexpression on myocardial function after ischemia and reperfusion injury

OBJECTIVE

Myocardial injury after ischemia and reperfusion may be mediated, in part, by oxygen-derived free radicals. In this study the protective effects of extracellular superoxide dismutase overexpression were directly assessed in the hearts of transgenic mice, after ischemia and reperfusion injury, using an isolated work-performing murine heart preparation and computerized analysis of functional data.

METHODS

A blinded study was performed to compare cardiac function in the hearts of both transgenic mice with a 3.5-fold overexpression of myocardial extracellular superoxide dismutase (n = 6, 22 to 26 gm) and littermate controls (n = 8, 22 to 26 gm). Preload-dependent cardiac output, contractility, heart rate, stroke work, and stroke volume were evaluated in the two groups before and after a 6-minute period of normothermic ischemia.

RESULTS

No differences were found between extracellular superoxide dismutase hearts and control hearts in any parameter of myocardial function before ischemia. After ischemia, decreases in cardiac output occurred in both groups; however, this decrease was larger in control mice compared with extracellular superoxide dismutase mice. A higher percentage of recovery was also observed in the contractility, heart rate, stroke work, and stroke volume of extracellular superoxide dismutase hearts compared with control hearts.

CONCLUSION

After global normothermic ischemia and subsequent reperfusion, decreases in cardiac function occurred in both extracellular superoxide dismutase and control mice; however, a higher percentage of recovery was observed in the extracellular superoxide dismutase overexpressed hearts. These data suggest that extracellular superoxide dismutase transgene overexpression significantly improves preservation of myocardial function after ischemia and reperfusion injury.

Pulmonary vascular impedance and recipient chronic pulmonary hypertension following cardiac transplantation

STUDY OBJECTIVES

Recipient chronic pulmonary hypertension (CPH), secondary to long-standing congestive heart failure, represents a significant risk factor for right ventricular (RV) dysfunction following orthotopic cardiac transplantation (TX). This study was designed to characterize the changes occurring in pulmonary hemodynamics, pre-TX and post-TX, using Fourier analysis, a canine model of bicaval TX, and monocrotaline pyrrole (MCTP)-induced recipient CPH.

DESIGN

Prospective, controlled study.

SETTING

Experimental laboratory.

PARTICIPANTS

Twenty adult male mongrel dogs (23 to 26 kg).

INTERVENTIONS

Recipients underwent pulmonary artery injection of 3 mg/kg MCTP 4 months pre-TX. On the day of TX, donor hearts were instrumented with an ultrasonic flow probe and micromanometers. Harmonic derivation of functional data was achieved with Fourier analysis.

MEASUREMENTS AND RESULTS

At the time of TX, significant increases were observed in the mean pulmonary artery pressure and pulmonary vascular resistance of recipient animals in comparison to donors, which were further significantly increased following the termination of cardiopulmonary bypass. Significant increases were also observed in the input resistance, characteristic impedance, and RV hydraulic power post-TX compared to pre-TX, and occurred in association with a significant decrease in the transpulmonary efficiency.

CONCLUSIONS

In the setting of MCTP-induced recipient CPH donor hearts were exposed to significant alterations in cardiopulmonary hemodynamics following bicaval TX. Pulmonary blood flow is maintained by a significantly higher energy expenditure by the RV, but at a lower level of efficiency. This experimental model may provide a useful means by which to evaluate therapeutic options to better manage cardiopulmonary hemodynamics in order to prevent RV failure following TX in the setting of recipient CPH.

Right ventricular adaptation to increased afterload after orthotopic cardiac transplantation in the setting of recipient chronic pulmonary hypertension

BACKGROUND

Right ventricular (RV) failure remains an important risk factor for early morbidity and mortality after orthotopic cardiac transplantation and is most commonly related to preexistent chronic pulmonary hypertension (CPH) in the recipient, which occurs secondary to long-standing congestive heart failure. This study was designed to assess the compensatory mechanisms of the acutely transplanted RV in the setting of recipient CPH using a canine model of bicaval cardiac transplantation (TX) and monocrotaline pyrrole (MCTP)-induced CPH.

METHODS AND RESULTS

Twenty adult mongrel dogs were used for 10 successfully completed TX experiments. Recipients received an injection of 3 mg/kg MCTP 4 months before TX. RV function was assessed with load-insensitive means (preload recruitable stroke work), and Fourier analysis was used to calculate RV hydraulic power and transpulmonary efficiency. At the time of TX, significant increases in the mean pulmonary artery pressure, mean right ventricular pressure, and pulmonary vascular resistance were observed in recipients compared with donors and were further significantly increased after cardiopulmonary bypass. Significant increases in RV preload recruitable stroke work and RV hydraulic power were observed after TX compared with before TX and occurred in association with significant decreases in transpulmonary efficiency.

CONCLUSIONS

Significant increases in pulmonary hemodynamic indexes occurred after MCTP injection and were further significantly increased after cardiopulmonary bypass. In the setting of recipient CPH, RV performance adapts acutely after bicaval TX with significant increases in power and contractility. However, a significant decrease in transpulmonary efficiency was also observed, which may improve over time as the RV adapts to the increased afterload.

Effects of nitric oxide after cardiac transplantation in the setting of recipient pulmonary hypertension

BACKGROUND

Recipient pulmonary hypertension secondary to chronic congestive heart failure is a significant risk factor for right ventricular failure after cardiac transplantation. In this study, the hemodynamic and inotropic effects of nitric oxide (NO) were examined after bicaval cardiac transplantation in the setting of monocrotaline pyrrole-induced recipient chronic pulmonary hypertension.

METHODS

Twenty dogs underwent 10 successfully completed transplantation experiments. Recipients underwent pulmonary artery injection of 3 mg/kg monocrotaline pyrrole 4 months before transplantation. Measurements were taken 1 hour after cessation of cardiopulmonary bypass and after NO inhalation. Pulmonary vascular impedance was calculated using Fourier analysis, and cardiac function was assessed with load-insensitive means (preload recruitable stroke work).

RESULTS

At the time of transplantation, the precardiopulmonary bypass levels of pulmonary vascular resistance in recipient animals were significantly greater when compared with donor levels, and were further significantly increased after cardiopulmonary bypass. Three recipients died after transplantation secondary to acute right ventricular failure. In the surviving animals, NO led to significant improvements in pulmonary vascular resistance and vascular impedance, which occurred in association with significant increases in transpulmonary efficiency. No significant changes were observed in right and left ventricular preload recruitable stroke work after NO inhalation.

CONCLUSIONS

These data suggest that NO may be an effective means to improve vascular impedance and pulmonary vascular efficiency after cardiac transplantation in the setting of recipient chronic pulmonary hypertension.

Hemodynamic and inotropic effects of nitric oxide in pulmonary hypertension

Right ventricular failure following cardiac transplantation is most commonly related to pre-existent recipient pulmonary hypertension secondary to chronic congestive heart failure. Although nitric oxide has had some role clinically in improving pulmonary hemodynamics and right ventricular function in this setting, an appropriate large-animal model of stable pulmonary hypertension has not been available for basic investigation of this problem. This study was designed to examine the hemodynamic and inotropic effects of inhaled nitric oxide using a canine model of monocrotaline pyrrole-induced chronic pulmonary hypertension. Eight mongrel dogs (22-25 kg) were used. All animals underwent percutaneous pulmonary artery catheterization to measure right heart hemodynamics prior to and 8 weeks after a right atrial injection of monocrotaline pyrrole. Eight weeks post-injection, all hearts were instrumented with a pulmonary artery flow probe, sonomicrometric dimension transducers, and micromanometers. Data were collected at baseline and following nitric oxide administration. Eight weeks post-monocrotaline pyrrole injection, significant increases were observed in the pulmonary hemodynamics compared to pre-injection. Nitric oxide led to significant decreases in pulmonary vascular impedance. Significant improvements in pulmonary blood flow, transpulmonary efficiency, and right ventricular contractility were also observed. This investigation demonstrates the well-known clinical effects of nitric oxide in improving pulmonary hemodynamics which were also associated with an increase in pulmonary blood flow, transpulmonary efficiency, and right ventricular contractility in the setting of monocrotaline pyrrole-induced pulmonary hypertension.

Nitric oxide improves pulmonary vascular impedance, transpulmonary efficiency, and left ventricular filling in chronic pulmonary hypertension

OBJECTIVE

Chronic pulmonary hypertension is difficult to treat and despite the introduction of several therapeutic options, no single therapy is universally recommended. Nitric oxide has had some role clinically in improving pulmonary hemodynamics in this setting; however, basic investigation has not been performed in an appropriate large animal model of stable pulmonary hypertension. This study was designed to examine the effects of inhaled nitric oxide on pulmonary hemodynamics in the setting of a canine model of monocrotaline pyrrole-induced chronic pulmonary hypertension and used Fourier analysis for assessment of pulmonary vascular impedance.

METHODS

Sixteen mongrel dogs (22 to 25 kg) were used. Animals underwent percutaneous pulmonary artery catheterization to measure-right-sided hemodynamics before and 6 weeks after a right atrial injection of either monocrotaline pyrrole (n = 8) or placebo (n = 8). Six weeks after the injection all hearts were instrumented with an ultrasonic flow probe, sonomicrometric dimension transducers, and micromanometers. Data were collected at baseline and after nitric oxide administration. Harmonic derivation of functional data was achieved with Fourier analysis.

RESULTS

Six weeks after the injection, significant increases in pulmonary artery pressure and pulmonary vascular resistance were observed in the monocrotaline pyrrole group. Nitric oxide led to significant decreases in pulmonary vascular impedance. Significant improvements in pulmonary blood flow, transpulmonary efficiency, and left ventricular filling were also observed.

CONCLUSIONS

This investigation demonstrates the well-known clinical effects of nitric oxide in improving pulmonary hypertension, which were also associated with an increase in pulmonary blood flow, transpulmonary efficiency, and left ventricular filling in the setting of monocrotaline pyrrole-induced pulmonary hypertension.

An adult canine model of chronic pulmonary hypertension for cardiopulmonary transplantation

BACKGROUND

This study establishes a chemically-induced canine model of chronic pulmonary hypertension (CPH) using monocrotaline pyrrole (MCTP) and then characterizes this model in terms of hemodynamic, morphologic, and cardiac functional changes.

METHODS

Thirty-three adult mongrel dogs (22 to 25 kg) were used. All animals underwent pulmonary artery catheterization to measure central venous pressure, mean right ventricular pressure (mRVP), mean pulmonary artery pressure (mPAP), and pulmonary capillary wedge pressure before and 6 weeks after a right atrial injection of either 60 mg/kg monocrotaline (group A, n = 8), 5 mg/kg MCTP (group B, n = 4), 3 mg/kg MCTP (group C, n = 13) or placebo (control, n = 8). Six weeks after injection, hearts in control and group C dogs were instrumented with flow probes, dimension transducers, and micromanometers to measure dynamic ventricular pressures and volumes.

RESULTS

No significant differences in baseline hemodynamic indexes were observed between groups. All animals in group B and five in group C died after MCTP injection as a result of pulmonary edema. No significant increase in any hemodynamic parameters occurred in group A or in control dogs 6 weeks after injection. In group C, significant increases in central venous pressure, mRVP, and mPAP were observed 6 weeks after injection. Significant increases in right ventricular (RV) function and the weight ratio of the RV to left ventricle were observed in group C when compared with controls.

CONCLUSIONS

A chemically-induced canine model of CPH has been created. Significant increases in mRVP, mPAP, and pulmonary capillary wedge pressure were observed 6 weeks after MCTP injection. RV function adapts to the increased afterload in the short term without evidence of failure. A stable model of pulmonary hypertension is provided as a potential means to evaluate posttransplantation RV dysfunction in the setting of CPH.

Right ventricular function in the donor heart

OBJECTIVES

Early morbidity and mortality post cardiac transplantation is frequently caused by right ventricular failure; this is usually attributed to an elevated pulmonary vascular resistance in the recipient. Brain death in the donor is recognised as causing left ventricular dysfunction, but its effects on the right ventricle have not previously been studied. The aim of this study was to investigate right ventricular function following brain death, using a canine model.

METHODS

The hearts of 33 dogs were instrumented with micromanometers, flow probes and dimension transducers to measure minor/major axes, and right and left ventricular free wall to septal distances. Left ventricular volume was calculated according to the prolate ellipsoid model and right ventricular volume was calculated according to the shell subtraction method. Systolic function for left and right ventricles was analysed by plotting ventricular stroke work vs. end-diastolic volume during a caval occlusion (preload-independent recruitable stroke work PRSW). Brain death was instigated by inflation of a subdurally placed intracranial balloon; subsequently blood pressure was maintained with intravenous fluid whilst no inotropic medications were given. Data were collected at baseline, and at 2 and 4 h thereafter. A two-tailed paired Student's t-test was applied to compare post-brain death data with baseline measurements.

RESULTS

All animals had an initial hyperdynamic response post brain death ensued by the development of diabetes insipidus. Brain stem death was validated by neuropathological examination at the termination of the experiments. Right and left ventricular systolic function had deteriorated significantly 2 h post brain death by 34.4% (+/- 5.1%, P < 0.001) and 20.4% (+/- 3.4%, P < 0.001), respectively, from baseline PRSW [RV = 23.6 erg.10(3) (+/- 1.5), LV = 76.2 erg.10(3) (+/- 3.5)]. This deterioration remained at 4 h post brain death (29.4% (+/- 4.9%, P < 0.001) and 21.2% (+/- 4.3%, P < 0.001), respectively). (The results are expressed as mean and S.E.M.).

CONCLUSIONS

Brain death causes a significant decrease in left and right ventricular function. The injury to the right ventricle is more prominent than the left ventricle, and at 2 h post brain death it is significantly greater. Failure of the right ventricle post transplantation in clinical practice may be related to this brain death induced injury. Further studies are required to investigate the mechanisms of this injury.

Milrinone improves pulmonary hemodynamics and right ventricular function in chronic pulmonary hypertension

BACKGROUND

Right ventricular failure after cardiac transplantation is commonly related to preexisting recipient pulmonary hypertension. This study was designed to investigate the effects of intravenous milrinone on pulmonary hemodynamic indices and right ventricular function in a canine model of monocrotaline pyrrole-induced chronic pulmonary hypertension.

METHODS

Eight mongrel dogs underwent pulmonary artery catheterization to measure right-sided hemodynamic indices before and 6 weeks after a right atrial injection of monocrotaline pyrrole. Six weeks after injection, all hearts were instrumented with a pulmonary artery flow probe, ultrasonic dimension transducers, and micromanometers. Data were collected at baseline and after milrinone infusion.

RESULTS

Six weeks after monocrotaline pyrrole injection, significant increases in the pulmonary artery pressure and pulmonary vascular resistance were observed. Milrinone led to significant increases in right ventricular function as well as significant improvements in pulmonary vascular resistance, pulmonary blood flow, and left ventricular filling.

CONCLUSIONS

This investigation demonstrates the well-known hemodynamic and inotropic effects of milrinone which, in the setting of monocrotaline pyrrole-induced pulmonary hypertension, were also associated with significant increases in pulmonary blood flow and left ventricular filling.

Functional analysis of myocardial performance in murine hearts overexpressing the human beta 2-adrenergic receptor

Transgenic mice overexpressing the human beta 2-adrenergic receptor gene were compared with wild mice type in terms of cardiac function, using a modified work-performing isolated murine heart preparation and on-line computer analysis. A preload-dependent experiment was performed, in which venous return was gradually increased in 5 mmHg increments from 5 mmHg to 25 mmHg. At each preload, aortic flow, left atrial pressure and aortic pressure were measured in all hearts, and from these parameters stroke volume, contractility, and cardiac index (cardiac output divided by body weight in g) were calculated and compared between groups. At increasing preload levels, the heart rates ranged from 322 beats/min (+/-29) to 369 beats/min (+/-39) in control mice and from 469 beats/min (+/-36) to 540 beats/min (+/-39) in transgenic mice. Cardiac index increased from 138 microliters/min/g (+/-13) and 48 microliters/min/g (+/-5) for transgenic and control mice, respectively at 5 mmHg preload to 262 microliters/min/g (+/-51) and 167 microliters/min/g (+/-15), respectively at 20 mmHg preload. The contractility in the transgenic mice were significantly increased at lower preload levels compared to control mice (1420 mmHg/s +/- 204 v 1187 mmHg/s +/- 127). An increase in myocardial adrenergic receptor density (100-200 fold) leads to significantly higher indices of cardiac function in transgenic mice compared to control mice. The increased heart rate leading to a positive inotropic effect in the hearts of transgenic mice is, at least in part, due to the overexpression of adrenergic receptors. These findings suggest a possible alternative method of establishing a positive chronotropic and inotropic state without the use of pharmacological agents.

Pulmonary hemodynamics and blood flow characteristics in chronic pulmonary hypertension

BACKGROUND

Lung transplantation is now an acceptable form of therapy for pulmonary hypertension, but controversy remains regarding the most appropriate surgical procedure. In this study, the changes in pulmonary vascular mechanics occurring in the setting of pulmonary hypertension were investigated using an adult canine model of monocrotaline pyrrole-induced pulmonary hypertension.

METHODS

Animals underwent pulmonary artery catheterization to measure right heart pressures before and 8 weeks after injection of either 3 mg/kg of monocrotaline pyrrole (n = 8) or placebo (n = 8). Eight weeks after injection, hearts underwent instrumentation with an ultrasonic flow probe and micromanometers. Harmonic derivation of functional data was achieved with Fourier analysis.

RESULTS

Significant increases in mean pulmonary artery pressure and pulmonary vascular resistance were observed after monocrotaline pyrrole injection. There was no significant difference in pulmonary blood flow. However, significant increases in input resistance and right ventricular hydraulic power with significant decreases in transpulmonary efficiency were observed.

CONCLUSIONS

Pulmonary hypertension causes significant alterations in pulmonary hemodynamics. Pulmonary blood flow is maintained by a significant increase in total power but with a significant decrease in transpulmonary efficiency. This adult canine model of pulmonary hypertension provides a useful means by which to evaluate surgical options of lung transplantation for improving pulmonary hemodynamics in the setting of chronic pulmonary hypertension.

Brain death alters cardiopulmonary hemodynamics and impairs right ventricular power reserve against an elevation of pulmonary vascular resistance

Right ventricular (RV) failure, which is a leading cause of early morbidity and mortality following cardiac transplantation, is attributed to the inability of the donor RV to acutely compensate for the recipient's elevated pulmonary vascular resistance (PVR). Furthermore, the effect of donor brain death (BD) on RV function is unclear. The purpose of this study was to investigate the effects of donor BD on RV function in the setting of elevated PVR. The interactions of the RV and its afterload, the pulmonary vasculature, and left atrial pressure were assessed by measurements of pulmonary vascular energetics and their oscillatory nature using proximal ultrasonic pulmonary artery (PA) flow probe and micromanometers in the proximal and distal PA in 20 mongrel dogs (25.8 +/- 0.4 kg, five control animals). A band was placed around the distal PA (PA-systolic gradient > 15 mm Hg). BD was induced by rising intracranial pressure and was validated neuropathologically. Data were collected at 0, 2, 4, and 6 h after BD in both banded and control animals. Fourier analysis was used to calculate RV oscillatory power, mean power, and total power (TP). Comparison of changes due to banding were made to baseline measurements using multivariate analysis and paired Student's t test (p < 0.05). A significant twofold to fourfold increase in pulmonary impedance and PVR occurred with an acute rise in PA gradient. Control animals tolerated acute increases in PVR without significant changes in TP. There was a significant increase of RV TP from 73 (+/-11) to 98 (+/-10) mW at baseline after the acute rise in PVR and impedance. After BD, the response to increased PVR and impedance was abolished significantly compared with baseline and control animals, suggesting a significant loss of compensatory TP to sustain pulmonary vascular blood flow. The data indicate that BD is detrimental to RV mechanical function.

Swine lungs expressing human complement-regulatory proteins are protected against acute pulmonary dysfunction in a human plasma perfusion model

Pulmonary transplantation is currently limited by the number of suitable cadaver donor lungs. For this reason, pulmonary xenotransplantation is currently being investigated.

OBJECTIVE

Our goal was to assess the role of complement in pulmonary xenograft dysfunction.

METHODS

The pulmonary function of swine expressing human decay accelerating factor and human CD59 (n = 6) was compared with that of the lungs from nontransgenic (control) swine (n = 6) during perfusion with human plasma.

RESULTS

After 2 hours of perfusion, the pulmonary vascular resistance was 1624 +/- 408 dynes.sec.cm-5 in control lungs and 908 +/- 68 dynes.sec.cm-5 in transgenic lungs (p < 0.05). Control lungs had a venous oxygen tension of 271 +/- 23 mm Hg with a ratio of venous oxygen tension to inspired oxygen fraction of 452 +/- 38 at 2 hours of perfusion; transgenic lungs had a venous oxygen tension of 398 +/- 11 mm Hg and a ratio of venous oxygen tension to inspired oxygen fraction of 663 +/- 18 (p < 0.05). Control lungs showed a decrease of 79.8% +/- 3.7% in static pulmonary compliance by 2 hours, versus a 12.0% +/- 8.1% decrease by the transgenic lungs (p < 0.05). The control lungs also developed 561.7 +/- 196.2 ml of airway edema over 2 hours, in contrast to 6.5 +/- 1.7 ml in transgenic lungs (p < 0.05).

CONCLUSION

Lungs from swine expressing human decay accelerating factor and human CD59 functioned better than nontransgenic swine lungs when perfused with human plasma. These results suggest that complement activation is involved in producing acute pulmonary xenograft dysfunction and demonstrate that lungs from swine expressing human decay accelerating factor and human CD59 are protected against pulmonary injury when perfused with human plasma.

Right ventricular failure--insights provided by a new model of chronic pulmonary hypertension

This study was designed to examine the effects of both nitric oxide and milrinone on pulmonary hemodynamics and right ventricular function using a newly established model of monocrotaline pyrrole-induced chronic pulmonary hypertension. Sixteen mongrel dogs (23-25 kg) were used. All animals underwent percutanous pulmonary artery catheterization to measure right heart hemodynamics prior to and 8 weeks after a right atrial injection of either monocrotaline pyrrole (MCTP, n=8) or placebo (CTL, n=8). Eight weeks postinjection, all hearts were instrumented with a pulmonary artery flow probe and intracavitary micromanometers. Data were collected at baseline as well as following both nitric oxide and milrinone administration. There was no significant difference in the baseline hemodynamic measurements between the two groups. Eight weeks postinjection, significant increases in the pulmonary artery pressure and pulmonary vascular resistance were observed in MCTP compared with CTL. Both nitric oxide and milrinone resulted in significant improvements in pulmonary vascular resistance, pulmonary blood flow, and right ventricular contractility. In addition, nitric oxide caused a significant improvement in pulmonary artery pressure and transpulmonary efficiency, while milrinone led to a significant increase in right ventricular hydraulic power. This study demonstrates the well-known clinical effects of nitric oxide and milrinone in improving pulmonary hypertension, which were also associated with an increase in pulmonary blood flow, transpulmonary efficiency, and right ventricular hydraulic power in the setting of monocrotaline pyrrole-induced chronic pulmonary hypertension.

Brain death further promotes ischemic reperfusion injury of the rabbit myocardium

BACKGROUND

Little is known about preload-dependent cardiac function after brain death (BD) and subsequent graft preservation.

METHODS

A validated model of BD in rabbits was developed and myocardial performance was studied after BD induction and 1 hour of subsequent global hypothermic ischemia using a validated rabbit model and an isolated work-performing heart preparation.

RESULTS

Significant decreases in stroke work, left ventricular contractility, and left ventricular relaxation were observed 2 hours after BD. After global hypothermic ischemia, significant decreases in stroke work, left ventricular contractility, and left ventricular relaxation were observed in the BD group compared with controls. Cardiac output and coronary flow were also significantly decreased in BD hearts compared with controls. Creatine kinase release was increased by 32.5% in BD hearts compared with controls.

CONCLUSIONS

In a rabbit model, BD combined with global hypothermic ischemia causes a significant decrease in left ventricular function compared with global hypothermic ischemia. This dysfunction may be attributed to a significant decrease in coronary flows in BD hearts.

Total atrioventricular cardiac transplantation preserves atrial systole and ventricular diastolic filling

BACKGROUND

Total orthotopic heart transplantation was recently introduced into clinical practice as an alternative technique for orthotopic cardiac transplantation. Total cardiac transplantation uses separate bicaval and left and right pulmonary anastomoses, whereas the standard technique of cardiac transplantation uses atrioplasty. Because the anatomic differences between total and standard orthotopic heart transplantation occur at the atrial level, this study compares atrial systolic function and biventricular filling (dV/dt) between the standard and total transplantation techniques.

METHODS AND RESULTS

Forty-eight mongrel canines (23 to 31 kg) were used for 12 total and 12 standard orthotopic cardiac transplantations. Right and left ventricular (RV/LV) function and AV synchrony were analyzed with micromanometry, sonomicrometry, ultrasonic flow meters, and intraoperative echocardiography. Results are expressed as mean +/- SEM (ANOVA, paired and unpaired t tests, and chi 2 test). There were no significant differences in baseline function (pretransplantation), bypass times, and cardiac ischemic times between the two groups. Posttransplantation sinus rhythm was preserved in all total (P < 0025) and in only one standard transplantation recipient (all required atrial diastole pacing). Significant decreases in RV/LV dV/dt from 113 +/- 13 and 123 +/- 14 mL/s to 69 +/- 6 and 85 +/- 10 mL/s after transplantation were measured in the standard group. No significant changes occurred in the total group after transplantation with respect to RV/LV diastolic filling. After transplantation, left atrial contractility and relaxation (-dP/dt) decreased significantly in the standard group by 43% and 70%, respectively, whereas in the total transplantation group, there were no observed changes in left atrial contractility and-dP/dt. A significant increase in the septum to RV free wall dimension in the standard group suggests altered geometry.

CONCLUSIONS

Total AV transplantation is a feasible alternative to standard cardiac transplantation and conserves both normal sinus rhythm and synchronized beating of the atria and ventricles. Ischemic and bypass times are comparable in patients undergoing either method. These data suggest that RV/LV diastolic function and geometry and atrial systole are better preserved in the total AV transplantation technique.

Extracellular superoxide dismutase transgene overexpression preserves postischemic myocardial function in isolated murine hearts

BACKGROUND

Myocardial injury after ischemia and reperfusion may be mediated, at least in part, by oxygen-derived free radicals; this supposition is supported by the observation that significant quantities of these radicals are generated during reperfusion. To directly assess the protective effect of extracellular superoxide dismutase (EC-SOD), this study was designed to investigate the ability of EC-SOD overexpression in the hearts of transgenic mice to protect myocardial tissue against ischemiareperfusion injury by use of an isolated work performing murine heart preparation and functional analysis.

METHODS AND RESULTS

Ten transgenic mice (EC.SOD, 28 to 31 g) were studied and compared with 10 control mice (Ctl, 28 to 31 g) in terms of preischemic and postischemic myocardial function. All hearts underwent cardiac harvest and arrest, followed by instrumentation and subsequent reperfusion with warm Krebs-Henseleit solution. Preload-dependent functional analysis was then performed to evaluate cardiac output, contractility (dP/dt), heart rate, stroke work, and stroke volume before and after a 7-minute period of warm ischemia. Results are expressed as mean +/- SEM (ANOVA, paired unpaired t tests). There was no significant difference in preischemic myocardial performance for Ctl and EC-SOD mice. After warm ischemia, cardiac output in EC-SOD was significantly improved compared with Ctl (EC-SOD, 4.55 +/- 0.37 mL/min; Ctl, 2.55 +/- 0.28 mL/min; P < .05). Postischemic dP/dt, stroke work, and stroke volume were also significantly improved in EC-SOD compared with Ctl mice (EC-SOD, 1808 +/- 39 mm Hg/s, 745 +/- 67 dyne.cm, and 13.1 +/- 1.2 microL, respectively; Ctl, 1497 +/- 87 mm Hg/s, 472 +/- 83 dyne.cm, and 8.2 +/- 1.5 microL; P < .05).

CONCLUSIONS

EC-SOD overexpressed mice showed significant improvement in postischemic cardiac function compared with Ctl mice. Thus, EC-SOD overexpressed hearts are less susceptible to mild degrees of ischemia-reperfusion injury than normal hearts.

Preload-recruitable stroke work relationships and diastolic dysfunction in the brain-dead organ donor

BACKGROUND

Acute graft failure is an important cause of morbidity and mortality in cardiac transplantation, and it may be associated with myocardial changes that occur during brain death (BD). This study investigates the changes in biventricular systolic and diastolic function that occur after BD in a validated canine model.

METHODS AND RESULTS

The hearts of 20 mongrel canines (23 to 31 kg) were instrumented with micromanometers, flow probes, and dimension transducers to measure minor/major axes as well as left and right ventricular (LV/RV) septum-to-free wall distances. LV/RV volumes were measured according to the shell subtraction method. LV/RV systolic function was analyzed by ventricular stroke work plotted versus end-diastolic volume during a caval occlusion (preload-independent recruitable systolic work, PRSW). The nonlinear relationships between diastatic pressure (stress) and LV/RV septum-to-free wall distances and volumes (strain) from successive diastoles during caval occlusion were used to evaluate LV/RV diastolic mechanics. The Cushing phenomenon, hyperdynamic response, and diabetes insipidus were observed in each animal after BD. Results are expressed as mean +/- SEM (P < .05 versus baseline, ANOVA, paired two-tailed Student's t test). Biventricular systolic function deteriorated significantly from baseline PRSW 6 to 7 hours after BD. The diastatic LV/RV pressure dimension relationships were significantly different after BD, indicating a decrease in ventricular chamber compliance during diastole.

CONCLUSIONS

BD causes a significant loss of systolic and diastolic LV/RV function in the brain-dead, heart-beating cadaver, which may contribute to early postoperative cardiac graft failure in the recipient. These findings have significant clinical applications and may help to avoid suboptimal donor/recipient matches.

Hormonal and hemodynamic changes in a validated animal model of brain death

OBJECTIVE

To examine the hormonal and hemodynamic changes in a validated animal model of brain death.

DESIGN

Prospective, controlled study.

SETTING

Experimental research laboratory.

SUBJECTS

Adult male mongrel dogs (n = 10).

INTERVENTIONS

Brain death was induced by inflation of a subdural balloon in ten mongrel dogs weighing 23 to 30 kg and validated neuropathologically. The hearts were instrumented with micromanometers and ultrasonic flow probes to measure cardiovascular changes. No inotropic or vasoactive support was given. Hemodynamic stability was maintained with intravenous fluids. Blood samples and hemodynamic readings were collected before and after the induction of brain death.

MEASUREMENTS AND MAIN RESULTS

A Cushing reflex, followed by a hyperdynamic response and diabetes insipidus, occurred in every animal following brain death. Mean arterial pressure, heart rate, contractility, and cardiac output increased to > 350 mm Hg, 230 beats/min, 4200 mm Hg/sec, and 2.8 L/min, respectively, at the peak of this phenomenon before returning to baseline. A plasma catecholamine surge was observed in every animal 15 mins after brain death, while the circulating concentrations of the pituitary gland hormones vasopressin and adrenocorticotrophic hormone decreased significantly after 15 and 45 mins of brain death, respectively, and continued to decrease throughout the experiments. Circulating triiodothyronine, thyroxine, and glucagon concentrations decreased significantly (p < .01) from 0.58 +/- 0.05 ng/mL, 2.20 +/- 0.15 micrograms/dL, and 49.7 +/- 9.1 pg/mL, respectively, to 0.34 +/- 0.03 ng/mL, 1.14 +/- 1.14 micrograms/dL, and 6.9 +/- 1.4 pg/mL, respectively, 420 mins after brain death. The hematocrit increased significantly 15 mins after brain death and then gradually decreased throughout the duration of the experiments.

CONCLUSIONS

In a validated animal model of brain death, significant decreases in the circulating concentrations of stress hormones, as well as hemodynamic instability, occurred after brain death. Measurements of plasma adrenocorticotrophic hormone and vasopressin values may be useful as diagnostic predictors of brain death. Furthermore, the observed changes may contribute to organ dysfunction after brain death and may necessitate hormonal as well as inotropic and vasoactive support to maintain donor organ function in the clinical setting.

Esophageal varices in association with unilateral pulmonary vein atresia

A 27-yr-old woman with recurrent episodes of hemoptysis (and hematemesis due to esophageal varices) was found to have unilateral pulmonary vein atresia. Reversed flow in the left pulmonary artery, a finding highly suggestive of this rare congenital anomaly, was demonstrated during cardiac catheterization. The definitive diagnosis was afforded by pulmonary wedge angiography, which not only demonstrated the atretic leftsided pulmonary veins, but also revealed a serpiginous system of systemic collateral veins to be the cause of her esophageal varices. Pneumonectomy of the nonfunctioning hypoplastic lung, the most successful approach to this disorder, may be complicated by severe bleeding of the numerous systemic arterial collateral vessels transected during surgical mobilization of the affected lung. Percutaneously delivered vascular occlusion coils were used in this case to occlude the large systemic to pulmonary artery collateral arteries immediately prior to pneumonectomy. Intra- and perioperative bleeding was minimal, and the patient has done well without further episodes of hemoptysis or hematemesis. Percutaneous occlusion of systemic to pulmonary collaterals may prove useful as a preoperative step for other congenital heart disease patients requiring lung or heart/lung transplantation.

The combined effects of brain death and cardiac graft preservation on cardiopulmonary hemodynamics and function before and after subsequent heart transplantation

BACKGROUND

The combined effects of brain death and graft preservation on right and left ventricular function and on pulmonary hemodynamics after subsequent heart transplantation have not been previously studied.

METHODS

Fifty-seven dogs (25.5 +/- 0.3 kg) were divided into three groups and underwent a total of 20 brain death experiments and 16 orthotopic complete atrioventricular transplantations with the use of a validated brain death organ donor model, hypothermic heart preservation, and right and left ventricular functional analysis (preload-independent recruitable stroke work, Fourier analysis). In the first group, changes in cardiopulmonary function were assessed over a period of 6 to 7 hours after brain death. In the second group, the hearts were procured from a donor with brain death and immediately transplanted whereas in the third group cardiac graft preservation for a period of 4 hours followed harvest from a donor with brain death before heart transplantation and assessment of heart transplant function.

RESULTS

After brain death alone, a significant increase in right and left ventricular end-diastolic pressures and a decrease in systemic and pulmonary resistance and pulmonary impedance occurred. Furthermore, right and left ventricular function decreased significantly by 35% and 19%, respectively, and subsequent transplantation did not cause further cardiac dysfunction. Preservation in combination with brain death led to further significant decreases in right ventricular function after subsequent transplantation compared with brain death alone, necessitating the use of dopamine to wean four animals from cardiopulmonary bypass.

CONCLUSION

Brain death causes a significant loss of right and left ventricular function. These injuries are greater in the right ventricle and may contribute to early right ventricular failure after transplantation. Brain death and cardiac graft preservation have significantly additive deleterious effects on right ventricular function after transplantation.

A work-performing heart preparation for myocardial performance analysis in murine hearts

The mouse has become the animal of choice for genetic manipulations resulting in altered myocardial function, but assessment of cardiac function is extremely difficult due to the animal's size. This study was designed to establish a work-performing isolated mouse heart preparation to objectively investigate myocardial performance in murine hearts. Isolated work-performing cardiac functional studies were performed on a modified Langendorff apparatus using 15 mice [25 to 28 g, +/-0.4 (SEM)]. The hearts were instrumented with a transonic flow meter and micromanometers to measure on-line aortic flow (AF), aortic pressure, and left atrial pressure (preload). A VAX cardiac function analyzing system was used to determine cardiac parameters including heart rate, contractility (max dP/dt), stroke volume (SV), and stroke work (SW) at various preload levels compared to a baseline preload of 5 mm Hg before and after 7 min of warm ischemia. AF increased from 1.01 ml/min (+/- 0.26) at 5 mm Hg of preload to 4.15 ml/min (+/- 1.03, P < 0.05) at 20 mm Hg of preload and decreased to 3.64 ml/min (+/- 0.62) at 25 mm Hg. SV, dP/dt, and SW increased with higher preload levels. There was a significant decrease in cardiac function postischemia.

CONCLUSIONS

A valid isolated work-performing preload-dependent murine heart preparation involving minimal instrumentation of the heart is established to measure cardiac function and myocardial performance. Significant ischemia-reperfusion injury occurred after 7 min of ischemia. This model is a reliable and objective tool by which to evaluate murine cardiac function and to study ischemia-reperfusion injury.

Survival benefits of heart and lung transplantation

OBJECTIVE

Heart and lung transplantation has gained acceptance as therapy for end-stage cardiac and pulmonary failure. The early and intermediate survival benefits of one center's 10-year experience with 177 patients undergoing thoracic transplantation were examined.

SUMMARY BACKGROUND DATA

As experience in cardiac and pulmonary transplantation has increased, improvements in patient selection, organ preservation, preoperative support, and perioperative care have significantly reduced the early threats to patient survival. Graft dysfunction due to chronic rejection appears to be the main risk for longer-term survival, and data compiled by the United Network for Organ Sharing (UNOS) indicate a 70% 5-year survival for heart transplants and a 50% 5-year survival for lung transplant recipients.

METHODS

The medical records of 120 heart recipients, 52 lung transplant recipients, and 5 heart-lung recipients were reviewed. Cumulative survival estimates were made using Kaplan-Meier analysis. The etiologies of operative and long-term mortality in each transplant population were identified. A comparison of long-term survival after heart transplantation versus coronary revascularization in a group of patients with ischemic cardiomyopathy was performed.

RESULTS

Operative mortality in both the cardiac and pulmonary transplant recipients was 8%. From 1990 to 1995, 70 consecutive adult cardiac transplant procedures were performed without an operative mortality. Three of five patients survived heart-lung transplantation. The extended actuarial survival rate at 5 years was 80% for the cardiac transplant recipients. The 2-year actuarial survival rate for the lung transplant recipients was 88%. Graft dysfunction was the most common cause of operative mortality in the heart transplant group whereas infection was responsible for most of the operative mortality after lung transplantation.

CONCLUSIONS

Cardiac and pulmonary transplantation can be applied to morbidly ill patients with excellent operative and intermediate-term survival.

Nitric oxide in brain death related cardiovascular dysfunction

PURPOSE

Nitric oxide (NO) is a major regulator of vascular tone, blood pressure, and blood flow, and plays a significant role in disease states associated with hemodynamic alterations. However, the role of NO in association with the effects of brain death (BD) has not yet been evaluated.

METHODS

In 17 mongrel dogs (23 to 31 kg), right atrial serum measurements of nitrite and L-arginine as well as NO ex vivo tissue nitrite extraction were performed at baseline (0), and 120, 240, and 360 minutes after BD. The hearts were instrumented with micromanometers, transonic flow probes, and ultrasonic dimension transducers to determine systolic function and to analyze the pulmonary vasculature flow characteristics by Fourier analysis. Brain death was induced by inflation of a subdurally placed balloon and validated neuropathologically. The results are expressed as mean and standard error of the mean (+/- SEM) (P < .05, paired t-test).

RESULTS

Right and left ventricular function deteriorated significantly (P < .001) by 37% (+/- 10) and 22% (+/- 7) respectively following BD. Pulmonary and systemic vascular resistance as well as pulmonary impedance decreased significantly over 6 hours after BD. Pulsatile flow, a potent stimulant of NO release, converted significantly to more steady flow. Myocardial NO extraction values remained unchanged after BD and serum L-arginine decreased from 12.84 mu g/L (+/- 0.60) to 11.77 mu g/L (+/- 0.55).

CONCLUSIONS

The decreases in pulmonary and systemic vascular resistance, pulmonary impedance, and cardiac function associated with BD are not related to major changes in the NO pathway. NO may not play a key role in the early changes after BD.

Glutathione depletion in epithelial lining fluid of lung allograft patients

The lower respiratory tract is protected against reactive oxygen species (ROS) by a complex antioxidant system. In the epithelial lining fluid (ELF), glutathione (L-alpha-glutamyl-L-cysteinylglycine, GSH) is essential for adequate protection of pneumocytes from potential toxicity mediated by extracellular hydrogen peroxide (H2O2). We assessed the concentration of total GSH in bronchoalveolar lavage fluid (BALF) in lung allograft patients in the absence and presence of acute rejection. Bronchoalveolar lavage (BAL) and biopsies were performed concurrently on 36 occasions in 17 patients who had undergone lung transplantation. BALF samples were divided into two groups on the basis of presence or absence of acute lung rejection on transbronchial biopsy. Seven BALF samples were obtained from control subjects for comparison. The BALF data demonstrated significantly lymphocyte recruitment and evidence of lung injury during acute rejection episodes. Transplant allografts without rejection showed significant depletion of total GSH in the ELF as compared with that of normal volunteers (94.0 +/- 9.7 microM versus 302.6 +/- 40.8 microM, p < 0.01). Transplant allografts with acute rejection had a slightly higher GSH concentration in their ELF (179.8 +/- 34.7), but this was still lower than control values. The deficiency of total GSH in the alveolar fluid may predispose lung allografts to extracellular H2O2-mediated toxicity.

The effects of brain death on cardiopulmonary hemodynamics and pulmonary blood flow characteristics

Deterioration of donor lung function contributes to the shortage of donor organs and early postoperative failure after transplantation. A decrease in donor pulmonary function is associated with opacification of lung fields on radiographs, rendering the lungs unsuitable for transplantation, which may be related to the effects of brain death (BD) on pulmonary hemodynamics. Twenty mongrel canines (25.5 +/- 0.7 kg) underwent 20 BD experiments using a previously validated BD organ donor model. An ultrasonic flowmeter was applied on the pulmonary artery and micromanometers were inserted into the right ventricle, pulmonary artery, and left atrium to measure, which allowed the hemodynamic assessment and impedance profile analysis of the pulmonary vasculature by Fourier transformation. Characteristic impedance (Zo) was compared with input resistance (RIN) and with calculated pulmonary vascular resistance (PVR), the conventional index. Right ventricular hydraulic power was analyzed and divided in its components oscillatory and steady power. The results are expressed as means and SEM (analysis of variance, paired two-tailed t tests). Cushing reflex, hemodynamic response, and diabetes insipidus were consistent findings following BD. PVR, Zo, and RIN decreased significantly (p < 0.05) from 367 +/- 40 dyne.s.cm-5, 226 +/- 13 dyne.s.cm-5, and 771 +/- 52 dyne.s.cm-5 to 261 +/- 25 dyne.s.cm-5, 159 +/- 10 dyne.s.cm-5, and 651 +/- 69 dyne.s.cm-5 6 h after BD. Pulmonary artery blood flow increased significantly from 1,499 +/- 107 mL/min to 2,064 +/- 209 mL/min (p < 0.05) after BD. Hydraulic power increased from 69 +/- 6 mW to 104 +/- 13 mW (p < 0.05) and the oscillatory power to steady power ratio of 33%/67% changed to 23%/77% following BD. Extravascular pulmonary water content increased significantly by 10% after BD. BD causes a significant change in pulmonary vascular hemodynamics. The decrease in impedance and right ventricular afterload may lead to significant pulmonary overflow injury and edema. The increase in steady power represents an important reserve of the right ventricle to sustain pulmonary blood flow following BD.

Myocardial beta-adrenergic receptor function and high-energy phosphates in brain death--related cardiac dysfunction

BACKGROUND

Cardiac failure remains an important problem after heart transplantation and may be associated with events that occur during brain death (BD) before transplantation. In this study, cardiac function is studied after BD, and biochemical evaluation of myocardial high-energy phosphates and the beta-adrenergic receptor system is presented.

METHODS AND RESULTS

The hearts of 17 mongrel dogs (23 to 31 kg) were instrumented with flow probes, micromanometers, and ultrasonic dimension transducers to measure ventricular pressure and volume relationships. In a validated canine BD model, systolic right and left ventricular (RV/LV) function was analyzed by load-insensitive measurements during caval occlusion (preload-recruitable stroke work, PRSW). The beta-adrenergic receptor (BAR) density, adenylate cyclase (AC) activity, and myocardial ATP and creatine phosphate (CP) were measured before and 6 to 7 hours after BD. Results are expressed as mean +/- SEM (*P < .05 versus baseline, paired two-tailed Student's t test). Myocardial function deteriorated significantly from baseline PRSW (RV, 22 +/- 1 erg x 10(3); LV, 75 +/- 4 erg x 10(3)) by 37 +/- 10% for the RV (P < .001) and 22 +/- 7% for the LV (P < .001). BAR density increased from 282 +/- 42 to 568 +/- 173 fmol/mg for the RV and from 291 +/- 64 to 353 +/- 56 fmol/mg for the LV. Isoproterenol-stimulated AC activity was also significantly enhanced after BD. ATP and CP, however, remained unchanged after BD compared with baseline values before BD.

CONCLUSIONS

BD causes significant systolic biventricular dysfunction. The loss of ventricular function after BD was more prominent in the right ventricle and may contribute to early postoperative RV failure in the recipient. These injuries occurred despite BAR system upregulation after BD. Global myocardial ischemia is unlikely, since ATP and CP remained normal before and after BD.

Generation of tumor-specific T lymphocytes for the treatment of posttransplant lymphoma

BACKGROUND

The incidence of lymphoproliferative disease, including B-cell lymphomas (BCL) in patients who have undergone heart or combined heart-lung transplants, has been reported to be as high as 15%. The majority of these tumors contain Epstein-Barr virus (EBV) DNA and regress when immunosuppressive agents are discontinued. This tumor regression is thought to be secondary to cytotoxic T lymphocytes (CTL) reactive to EBV-infected cells whose function is impaired in patients receiving immunosuppressive agents. We hypothesize that EBV-CTL expanded in the absence of these agents may demonstrate an antitumor effect against an EBV-expressing human BCL in vitro and in vivo.

METHODS AND RESULTS

An EBV-expressing BCL from a heart transplant recipient was isolated and expanded in culture. EBV-CTL were generated by stimulation of peripheral blood leukocytes with irradiated autologous tumor cells in low-dose interleukin-2. Autologous BCL, HLA-mismatched BCL, lymphokine-activated killer target cell line (Daudi), and the natural killer target cell line (K562) were used in a standard 4-hour cytotoxicity assay using 51CrO4 after 7, 14, and 28 days of stimulation. There was significant percent specific lysis of autologous BCL targets (78%) at an effector-to-target ratio as low as 20:1 as compared with control cells. EBV-CTL were then adoptively transferred into SCID mice (provided by Duke University Vivarium) that had been engrafted with autologous BCL 7 days before. There was a significant survival advantage to those mice engrafted with EBV-CTL as compared with control cells.

CONCLUSIONS

The results indicate that ex vivo expansion of EBV-CTL in the absence of immunosuppressive agents results in a population that has significant antitumor activity. This strategy may be useful in the generation of EBV-CTL that might be effective antitumor agents in transplant recipients with EBV-associated lymphomas.

Desensitization of myocardial beta-adrenergic receptors and deterioration of left ventricular function after brain death

Brain death often results in a series of hemodynamic alterations that complicate the treatment of potential organ donors before transplantation. The deterioration of myocardial performance after brain death has been described; however, the pathophysiologic process of the myocardial dysfunction that occurs after brain death has not been elucidated. This study was designed to analyze the function of the myocardial beta-adrenergic receptor and the development of left ventricular dysfunction in a porcine model of experimental brain death. Analysis of the beta-receptor included determination of receptor density and adenylate cyclase activity after stimulation independently at the receptor protein, the G protein, and the adenylate cyclase moiety. Myocardial beta-receptor density did not change after the induction of brain death. A decrease in stimulated adenylate cyclase activity was observed within the first hour after brain death at the level of the beta-receptor, the G protein, and the adenylate cyclase moiety, which suggests the occurrence of rapid desensitization of beta-receptor function. Significant deterioration of myocardial performance also occurred within the first hour after brain death, represented by a decrease in preload-recruitable stroke work compared with the baseline value. The deterioration of myocardial performance after brain death correlates temporally with desensitization of the myocardial beta-receptor signal transduction system. The mechanism of impairment appears to be localized to the adenylate cyclase moiety itself.

Complete atrioventricular cardiac transplantation: improved performance compared with the standard technique

BACKGROUND

There has been renewed clinical interest in an alternative technique to orthotopic cardiac transplantation involving six anastomoses: left pulmonary veins, right pulmonary veins, inferior vena cava, pulmonary artery, aorta, and superior vena cava (complete technique). In this study, the results of the complete technique are compared with those of the standard operation (ventricular transplantation with atrioplasty).

METHODS

Dogs were used for ten acute standard and ten acute complete atrioventricular transplantations. There were no significant differences in the baseline cardiac function (preload-independent right and left ventricular recruitable stroke work), bypass times, and cardiac ischemic times between the two groups.

RESULTS

After transplantation, sinus rhythm was preserved after all ten complete and after only one standard transplantation but no significant hemodynamic differences were observed. The right and left ventricular preload-independent recruitable stroke work in the complete group and the left ventricular preload-independent recruitable stroke work in the standard group were conserved after transplantation, but the right ventricular preload-independent recruitable stroke work decreased by 39% +/- 8% (p < 0.05) in the standard group. There was also a significant decrease in the rate of biventricular filling in the standard group after transplantation.

CONCLUSIONS

Complete atrioventricular transplantation is a feasible alternative technique and conserves normal sinus rhythm. The ischemic and bypass times are comparable for both methods. The insignificant change in the rate of biventricular filling in the dogs undergoing the complete technique indicates right and left ventricular diastolic function may be conserved after transplantation.

Management of biliary complications after heart transplantation

BACKGROUND

Immunosuppression increases the risk of biliary complications in heart transplant recipients.

METHODS

Patients undergoing heart transplantation since 1986 who were at risk for cholelithiasis (n = 60) were retrospectively studied.

RESULTS

Cholestatic jaundice developed in all patients after the operation because of biliary obstruction from cholelithiasis, cyclosporine toxicity, Imuran toxicity, or Gilbert's disease. The incidence of cholelithiasis or sludge was 42% (n = 25 of 60). Gallstones developed within 1.8 +/- 1.1 years in 17% of patients (n = 8 of 48) with a normal pretransplantation ultrasonogram. Biliary colic or gallstone pancreatitis developed 2 +/- 1.2 years after transplantation in 58% of patients (n = 7 of 12) with asymptomatic gallstones diagnosed before transplantation. The overall incidence of cholecystectomy or cholecystectomy with Roux-en-Y cystojejunostomy was 40% (n = 24). Both open cholecystectomy (n = 5) and laparoscopic cholecystectomy (n = 19) were performed without significant complications. Recovery is significantly more rapid (p < 0.05) after laparoscopic cholecystectomy versus open cholecystectomy (1 week versus 3 weeks).

CONCLUSIONS

This analysis indicates that transplant candidates who have gallstones on pretransplantation evaluation or in whom gallstones develop after transplantation should undergo laparoscopic cholecystectomy at the earliest time in their posttransplantation course (i.e., 3 months) regardless of their symptomatic status. Removal of the diseased gallbladder not only simplifies the evaluation of cholestatic jaundice by eliminating the need for multiple ultrasonograms to exclude acute cholecystitis or choledocholithiasis but also safely minimizes the risk of the development of severe biliary complications.

Myocardial performance after graft preservation and subsequent cardiac transplantation from brain-dead donors

BACKGROUND

This study examined the effects of brain death and graft preservation on right and left ventricular function after subsequent cardiac transplantation.

METHODS

Seventy-eight dogs underwent 34 orthotopic complete atrioventricular transplantations using a validated brain-dead organ donor model, hypothermic cardiac preservation, and right and left ventricular function analysis (preload-independent recruitable stroke work). Four groups were studied: controls, transplantation from brain-dead organ donors, graft preservation without brain death, and donor brain death and graft preservation before transplantation.

RESULTS

Without brain death, cardiac arrest alone as well as the combination of cardiac arrest and preservation did not significantly decrease cardiac function after transplantation. After brain death alone, right ventricular and left ventricular function decreased significantly by 30% and 25%, respectively, but subsequent transplantation did not cause further cardiac dysfunction. Preservation after brain death led to a further significant decrease in right ventricular function after subsequent transplantation, and dopamine hydrochloride was required to wean 4 animals from cardiopulmonary bypass.

CONCLUSIONS

Brain death causes a significant loss of right and left ventricular function. These injuries are greater in the right ventricle and may contribute to early right ventricular failure after transplantation. Brain death and cardiac preservation interact significantly to impair right ventricular function further. Future studies of graft preservation should use brain-dead organ donors.

Endocrine changes and metabolic responses in a validated canine brain death model

PURPOSE

Endocrinologic and metabolic changes after brain death (BD) have not yet been investigated in a validated animal model. Therefore, the effects of BD on hormonal and metabolic function were studied in 10 dogs (23 to 31 kg).

METHODS

BD was induced by intracranial pressure increase and validated neuropathologically. Plasma concentrations of pituitary, thyroid, adrenal, and pancreatic hormones were measured pre/post BD. The results are expressed as mean (+/- SEM).

RESULTS

A Cushing reflex and diabetes insipidus occurred after BD. Elevated catecholamine levels were documented after 15 minutes whereas the pituitary gland hormones vasopressin and adrenocorticotrophic hormone (ACTH) decreased significantly after 15 and 45 minutes of BD respectively. Thyroxine, triiodothyronine, and glucagon decreased significantly (P < .01) from 0.58 ng/mL (+/- 0.05), 2.20 micrograms/dL (+/- 0.15), and 49.7 pg/mL (+/- 9.1) respectively to 0.34 ng/mL (+/- 0.03), 1.14 micrograms/dL (+/- 1.14), and 6.9 pg/mL (+/- 1.4) respectively 420 minutes after BD. The hematocrit increased significantly after BD and declined toward the end of all experiments. Metabolic acidosis occurred immediately after BD and at the end of the experiments.

CONCLUSIONS

In a simple, reproducible, and reliable animal model of BD, a catecholamine storm, vasopressin and ACTH cessation, and diabetes insipidus were consistent findings. The decrease in cortisol and vasopressin levels warrant consideration of hormonal therapy.

Mechanisms of transplant right ventricular dysfunction

OBJECTIVE

Right ventricular (RV) dysfunction remains the leading cause of early mortality after cardiac transplantation. The effect of brain death and subsequent hypothermic cardioplegic arrest and storage on subsequent post-transplant right ventricular function was examined.

SUMMARY BACKGROUND DATA

Right ventricular dysfunction in the donor heart usually is attributed to failure of the donor right ventricle to adapt to the sudden increase in afterload (pulmonary vascular resistance) in the recipient. Strategies to improve ventricular mechanics in the postoperative period are aimed at reducing pulmonary vascular resistance with vasodilators or augmenting right ventricular contractility with inotropic agents. Events occurring in the donor heart (brain death, hypothermic cardioplegic arrest, and storage) also may be directly related to post-transplant RV dysfunction.

METHODS

A canine model of brain death and orthotopic cardiac transplantation was used. A dynamic pressure-volume analysis of RV mechanics was performed using micromanometers and sonomicrometric dimension transducers. Systolic function was assessed by measurement of preload recruitable stroke work (PRSW). Brain death was induced in 17 dogs by inflation of an intracranial balloon. Right ventricular function then was assessed serially to 6 hours (PRSW). Right ventricular adrenergic beta receptor density and function was sampled at control and after 6 hours of brain death. The effect of cardioplegic arrest and hypothermic storage was assessed in a second group of 17 dogs, using the same instrumentation and method of RV analysis.

RESULTS

A significant decrease in right ventricular PRSW occurred after brain death, with the average decrease being 37% +/- 10.4% from the control. The RV myocardial beta adrenergic receptor density did not significantly change (253 +/- 34 fmol/ng control vs. 336 +/- 54 fmol/ng after brain death). The adenylyl cyclase activity of the RV beta receptor was assessed and was not altered by brain death. Orthotopic transplantation after cardioplegic arrest and hypothermic storage significantly decreased RV PRSW from 23.6 +/- 2.0 x 10(3) erg to 13.5 +/- 1.4 x 10(3) erg.

CONCLUSIONS

These data indicate that the donor right ventricle is exposed to factors significantly detrimental to its mechanical performance well before facing an increased afterload in the recipient. Strategies to reduce RV dysfunction associated with brain death and hypothermic storage could positively impact post-transplant survival.

Cytomegalovirus pericarditis: a case series and review of the literature

Cytomegalovirus (CMV) commonly infects both normal and immunocompromised hosts. Although it usually produces an asymptomatic infection to mild illness, CMV has the potential to significantly injure many different organs. Reports of CMV causing pericardial disease, however, are limited and documentation of infection by growth of the virus from tissue or fluid is rare. As part of a prospective trial of subxiphoid pericardial biopsy in 57 adult patients with large pericardial effusions, three culture-proven cases and one serologically confirmed case of CMV pericardial disease were discovered. Subsequently, CMV was grown from the pericardium of an infant with congenital heart disease. A review of the documented cases of CMV pericarditis is provided along with a discussion of the pathogenesis and significance of this perhaps not so uncommon disease.

A valid experimental brain death organ donor model

BACKGROUND

This study was designed to establish a validated canine brain death model. Ten consecutive dogs were studied to investigate the effects of brain death on hemodynamic, metabolic, and hormonal function.

METHODS

Brain death was induced by inflation of a subdurally placed balloon and was validated neuropathologically. Functional data and blood samples were collected before and 15, 45, 90, 240, 360, and 420 minutes after the induction of brain death. No inotropic or vasoactive support was given. The results are expressed as mean +/- standard error of the mean.

RESULTS

The Cushing reflex occurred in all animals and lasted 13.3 +/- 1.5 minutes. Raised catecholamine levels were documented at 15 minutes, whereas the pituitary gland hormones vasopressin and adrenocorticotrophic hormone decreased significantly after 15 and 45 minutes, respectively. Triiodothyronine, thyroxine, and glucagon decreased significantly from 0.58 +/- 0.05 ng/ml, 2.20 +/- 0.15 micrograms/dl, and 49.7 +/- 9.1 pg/ml to 0.34 +/- 0.03 ng/ml (p < 0.05 versus baseline; paired two-tailed t-test), 1.14 +/- 1.14 micrograms/dl (p < 0.05), and 6.9 +/- 1.4 pg/ml (p < 0.05). Insulin and lactate dehydrogenase showed a moderate increase after brain death. Diabetes insipidus occurred after 45 minutes in nine animals (urine output 13.5 +/- 1.8 ml/kg/hour). Left and right ventricular end-diastolic pressure increased significantly toward the end of all experiments. Cardiac output increased and systemic and pulmonary vascular resistance decreased, but heart rate remained unchanged.

CONCLUSION

This simple, reproducible, moderately invasive, and reliable model of brain death in animals assesses donor organ function and preservation. Cushing reflex, hyperdynamic state, catecholamine storm, vasopressin and adrenocorticotropic hormone cessation, total cerebral necrosis, and diabetes insipidus were consistent findings.

Recurrence of diffuse panbronchiolitis after lung transplantation

Diffuse panbronchiolitis (DBP) is characterized by chronic inflammation of the upper and lower respiratory tract. DPB has been found almost exclusively in oriental populations. We describe the occurrence of a case of DPB in an African American patient who underwent bilateral sequential lung transplantation. Ten weeks after transplantation, DPB recurred in the lung allograft, with rapid and significant deterioration in graft function. Allograft function improved within a few weeks after beginning treatment with erythromycin. This early recurrence is suggestive of a systemic etiology of DPB. Although recurrence of other systemic diseases has been reported after lung transplantation, no previous patients have been reported with early functional deterioration based solely on disease recurrence.

Load-independent analysis of a pulsatile right ventricular assist device

BACKGROUND

Right ventricular assist devices are becoming increasingly used as both a bridge to heart transplantation and as a means of temporary support after cardiopulmonary bypass. There has also been a resurgence of interest in pulsatile devices fueled by anecdotal, clinical reports. However, a load-independent analysis of biventricular function after right ventricular assistance comparing a pulsatile versus a continuous-flow right ventricular assist device has not been performed, and we hypothesize that a pulsatile device is less detrimental to cardiac function than a conventional, nonpulsatile pump.

METHODS

Sixteen dogs (20 to 25 kg) were instrumented through a median sternotomy for placement of left ventricular and right ventricular epicardial dimension transducers in the major, minor, and septal-free wall axes. Intracavitary micromanometers were placed in both ventricles as well. Baseline pressure-dimension data were collected, and the right atrium and pulmonary artery were cannulated. Right ventricular bypass with the use of a pneumatically driven pulsatile right ventricular assist device (SV = 60 ml; n = 7) or a conventional continuous-flow centrifugal right ventricular assist device (n = 9) was instituted for a 4-hour duration. Animals were then weaned from right ventricular support and decannulated. After bypass, biventricular function data were then collected. The load-insensitive stroke work-end diastolic volume relationship known as preload recruitable stroke work was derived and expressed as a fraction of baseline function along with conventional hemodynamic indexes, cardiac output, and pulmonary vascular resistance.

RESULTS

Results of this analysis show no significant benefit to either right ventricular or left ventricular function (right ventricular preload recruitable stroke work index: 0.863 +/- 0.3 [pulsatile] versus 0.849 +/- 0.2 [continuous], left ventricular preload recruitable stroke work index: 0.880 +/- 0.4 [pulsatile] versus 0.821 +/- 0.3 [continuous] after pulsatile right ventricular support. Likewise, cardiac output (1.4 +/- 0.1 [pulsatile] versus 1.5 +/- 0.2 [continuous] L/min) and pulmonary vascular resistance (4.8 +/- 1.0 [pulsatile] versus 3.2 +/- 1.1 [continuous] Wood Units) were not significantly different in either study group.

CONCLUSIONS

We conclude from these data that pneumatically driven pulsatile right ventricular assist devices provide no additional benefit to myocardial performance beyond that of conventional, nonpulsatile pumps. Further studies investigating a speculative benefit from pulsatile circulatory support are necessary to further define a potential role for these novel devices.

Allograft diastolic dysfunction and chronotropic incompetence limit cardiac output response to exercise two to six years after heart transplantation

BACKGROUND

Because prolonged survival of heart transplant recipients is expected with the current immunosuppressive treatment, the functional capacity of these long-term survivors is of interest. Previous exercise studies showed no objective improvement in exercise tolerance several years after transplantation, but the extent to which chronotropic incompetence and allograft diastolic dysfunction observed early after transplantation may improve over time has not been defined.

METHODS

Thirteen untrained heart transplant recipients without symptoms, between 27 and 70 months after transplantation, and 13 age-matched sedentary normal controls underwent maximal upright bicycle exercise testing with simultaneous hemodynamic, radionuclide, and expired gas measurements.

RESULTS

Systolic function as measured by ejection fraction was supranormal at rest in the transplant group and normalized with exercise. Despite their maximal exercise effort, transplant recipients had a 60% reduction in their exercise capacity compared with nontransplant recipients. Peak oxygen consumption was similarly reduced by 52%. Cardiac output response to exercise was 43% lower in the transplant group because of a 78% reduction in heart rate reserve and an 18% reduction in maximal stroke volume. Ventricular volumes were similarly reduced after transplantation, but filling pressures remained normal, indicating allograft diastolic dysfunction. Despite the significantly reduced maximal cardiac output, maximal arteriovenous oxygen difference was 25% lower in the transplant recipients, suggesting a peripheral deficit in oxygen handling.

CONCLUSIONS

Therefore, patients, 2 to 6 years after transplantation, continue to have a significant reduction in exercise tolerance as a result of a combination of severe chronotropic incompetence, limited stroke volume reserve caused by a reduced ventricular size and allograft diastolic dysfunction, and an abnormality in peripheral oxygen delivery or use. Efforts aimed at improving these factors may further enhance the functional capacity of these long-term survivors of heart transplantation.

Aortic valve replacement in adults after balloon aortic valvuloplasty

BACKGROUND

Percutaneous balloon aortic valvuloplasty is limited by a high risk of procedural morbidity, transient clinical benefit, and a high restenosis rate. The management of patients with symptomatic aortic valve restenosis after percutaneous balloon aortic valvuloplasty is unclear. We hypothesized that aortic valve replacement would produce superior midterm survival compared with repeat balloon aortic valvuloplasty or medication alone in patients with symptomatic aortic valve restenosis after prior balloon aortic valvuloplasty.

METHODS AND RESULTS

Baseline clinical, echocardiographic, and hemodynamic data were collected on 165 patients who underwent percutaneous balloon aortic valvuloplasty as treatment for symptomatic degenerative calcific aortic stenosis. In 144 of these patients (87%), aortic valve replacement was originally considered to carry excessive risk. The survival of three subgroups was calculated during a median follow-up period of 3.9 years (range, 1 to 6 years). Ninety-four patients (57%) had no further mechanical intervention (subgroup 1-BAV), 31 patients (19%) developed symptomatic aortic valve restenosis and underwent a repeat balloon aortic valvuloplasty (subgroup 2-BAV), and 40 patients (24%) subsequently underwent aortic valve replacement (subgroup BAV+AVR). Follow-up was 99% complete. Patients in subgroup BAV+AVR tended to be younger and have a lower prevalence of coronary artery disease or mitral regurgitation. Only 1 patient (2.5%) suffered a perioperative death during aortic valve replacement. The probability of survival 3 years from the date of the last mechanical intervention was 13% for subgroup 1-BAV, 20% for subgroup 2-BAV, and 75% for subgroup BAV+AVR. At the conclusion of follow-up, only 2 patients had symptoms of congestive heart failure or angina after aortic valve replacement.

CONCLUSIONS

Aortic valve replacement may be performed with a low mortality rate, excellent palliation of symptoms, and prolongation of survival in selected high-risk patients with a history of previous balloon aortic valvuloplasty.