Prevention of retrosternal adhesion formation in a rabbit model using bioresorbable films of polyethylene glycol and polylactic acid

The purpose of this study was to test the efficacy of three bioresorbable films of polyethylene glycol (EO) and polylactic acid (LA) (EO/LA = 1.5, 2.5, and 3.0) in the prevention of adhesion formation between the epicardium and the sternum (retrosternal adhesions) in a rabbit model. Retrosternal adhesions were generated by sternotomy, pericardiotomy, and abrasion of the anterior epicardium. The adhesion barrier was placed between the epicardium and the sternum and sutured to the edge of the pericardium. Epicardial adhesions were evaluated 14-20 days later by assessing the area of the epicardium covered by adhesions. In the control rabbits, tenacious adhesions were observed between sternum and the central portion of epicardium (portion exposed through the pericardiotomy) which were difficult to dissect. When a bioresorbable film was placed over the pericardium, adhesion formation at the central strip of the epicardium (area between the sternum and the epicardium exposed through the pericardium) could be reduced or prevented. At this site, the areas of adhesion formation were 0% (EO/LA = 1.5), 8.4 +/- 2.8% (EO/LA = 2.5), and 5.6 +/- 4.7% (EO/LA = 3.0) of the central strip, significantly less than that observed in the control group, 78.0 +/- 5.8% (P < 0.01). At the anterior left and right and posterior apex of the heart (sites where the film was not placed), there were no differences between control and treatment groups. The films were completely resorbed at the time of necropsy in group EO/LA = 2.5 and 3.0. Small pieces of film were observed in group EO/LA = 1.5. In conclusion, the bioresorbable films [EO/LA = 1.5 (REPEL-CV), 2.5, or 3.0] were efficacious in the reduction of retrosternal adhesions to the epicardium.

An immunological algorithm to predict risk of high-grade rejection in cardiac transplant recipients

BACKGROUND

Transplant-related coronary-artery disease (TCAD) develops frequently in cardiac-allograft recipients, and limits long-term survival. We examined the relation between this disorder and cumulative frequency of high-grade rejection, and investigated whether concomitant use of three immunological factors at the time of a low-grade endomyocardial biopsy can predict progression to high-grade rejection.

METHODS

We investigated the relation between the cumulative annual frequency of high-grade rejection and TCAD in 198 recipients of cardiac transplantation between 1992 and 1996 by means of Kaplan-Meier actuarial life-tables. Endomyocardial biopsy, lymphocyte-growth assays, and anti-HLA antibody measurements were compiled over 12 months in 102 patients during their first post-transplant year. We calculated predictive values for high-grade rejection within 90 days by chi2, Kaplan Meier survival curves, and by multivariable logistic regression analyses.

FINDINGS

We found a direct correlation between cumulative annual frequency of rejection and TCAD onset with highest risk in those with more than 0.75 rejections per year (p=0.0002). After a low-grade endomyocardial biopsy (0 or 1A), one or more donor-recipient HLA-DR matches protected against high-grade rejections (p<0.001). Among individuals with one or two DR matches, the negative predictive value for progression from a low-grade biopsy to a high-grade rejection was 87% in the presence of a negative lymphocyte-growth assay. Among individuals with no DR matches, the presence of either a positive lymphocyte-growth assay or IgG anti-major-histocompatibility complex (MHC) class II antibodies was independently associated with high probability of progression to rejection (64% and 66%, respectively, p<0.0005). When both assays were positive, concomitantly with a low-grade endomyocardial biopsy, the positive predictive value for progression to a high-grade rejection was 86% (p<0.0001). For endomyocardial-biopsy grades 1B or 2, a positive lymphocyte-growth assay alone was associated with high-grade rejection in 100% of cases.

INTERPRETATION

Use of an algorithm combining three immunological factors at the time of a low-grade endomyocardial biopsy enables prospective stratification of cardiac transplant recipients into risk categories for progression to high-grade rejection. Low-risk individuals require fewer biopsies, moderate-risk individuals require an ongoing schedule of surveillance biopsies, and high-risk individuals require rational organisation of interventional strategies aimed at preventing rejection. Additional predictive factors are needed to identify moderate-risk individuals who will progress to rejection. Ultimately, successful intervention may have an impact on the subsequent complication of TCAD.

Heparinless cardiopulmonary bypass with active-site blocked factor IXa: a preliminary study on the dog

OBJECTIVE

Cardiopulmonary bypass is a potent stimulus for activation of procoagulant pathways. Heparin, the traditional antithrombotic agent, however, is often associated with increased perioperative blood loss because of its multiple sites of action in the coagulation cascade and its antiplatelet and profibrinolytic effects. Furthermore, heparin-mediated immunologic reactions (that is, heparin-induced thrombocytopenia) may contraindicate its use. Cardiopulmonary bypass with a selective factor IXa inhibitor was tested to see whether it could effectively limit bypass circuit/intravascular space thrombosis while decreasing extravascular bleeding, thereby providing an alternative anticoagulant strategy when heparin may not be safely administered.

METHODS

Active site-blocked factor IXa, a competitive inhibitor of the assembly of factor IXa into the factor X activation complex, was prepared by modification of the enzyme's active site by the use of dansyl glutamic acid-glycine-arginine-chlormethylketone. Twenty mongrel dogs (five were given standard heparin/protamine; 15 were given activated site-blocked factor IXa doses ranging from 300 to 600 microg/kg) underwent 1 hour of hypothermic cardiopulmonary bypass, and blood loss was monitored for 3 hours after the procedure.

RESULTS

Use of activated site-blocked factor IXa as an anticoagulant in cardiopulmonary bypass limited fibrin deposition within the extracorporeal circuit as assessed by scanning electron microscopy, comparable with the antithrombotic effect seen with heparin. In contrast to heparin, effective antithrombotic doses of activated site-blocked factor IXa significantly diminished blood loss in the thoracic cavity and in an abdominal incisional bleeding model.

CONCLUSION

These initial studies on the dog suggest that administration of activated site-blocked factor IXa may be an effective alternative anticoagulant strategy in cardiopulmonary bypass when heparin is contraindicated, affording inhibition of intravascular/extracorporeal circuit thrombosis with enhanced hemostasis in the surgical wound.

Inhaled nitric oxide is not a myocardial depressant in a porcine model of heart failure

BACKGROUND

Inhaled nitric oxide has been shown to be a potent and selective pulmonary vasodilator. Reports of increases in left ventricular end-diastolic pressure and episodes of pulmonary edema during the clinical use of inhaled nitric oxide in patients with preexisting left ventricular dysfunction have raised concerns that this agent may have myocardial depressant effects. We therefore undertook a study of the effects of inhaled nitric oxide on myocardial contractility in a porcine model of ventricular failure and pulmonary hypertension.

METHODS

After inducing heart failure in 10 pigs by rapid ventricular pacing, hemodynamic measurements and pressure-volume diagrams (by the conductance method) were obtained in six animals at baseline and during administration of inhaled nitric oxide at concentrations of 20 and 40 ppm. Myocardial contractile state was assessed by the end-systolic pressure-volume relationship and preload-recruitable stroke work, whereas diastolic function was measured in terms of the end-diastolic pressure-volume relationship and the pressure decay time constant T.

RESULTS

Baseline hemodynamics reflected heart failure and pulmonary hypertension, and inhaled nitric oxide induced significant reductions in mean pulmonary artery pressure and pulmonary vascular resistance. Although left ventricular end-diastolic pressure increased during administration of inhaled nitric oxide, no changes were observed in measures of systolic or diastolic function.

CONCLUSIONS

Inhaled nitric oxide reduced pulmonary vascular resistance but did not alter myocardial contractility or diastolic function. Increases in left ventricular end-diastolic pressure during inhaled nitric oxide therapy are therefore not due to myocardial depression and may be related to increases in volume delivery to the left side of the heart resulting from reduced pulmonary vascular resistance.

Inflow valve regurgitation during left ventricular assist device support may interfere with reverse ventricular remodeling

BACKGROUND

Left ventricular assist devices have been reported previously to reverse ventricular remodeling in patients with dilated cardiomyopathy. In patients with prolonged mechanical support, structural failure of the left ventricular assist device inflow valve can cause regurgitation into the left ventricle, which may affect adversely this process.

METHODS

Left ventricular end-diastolic pressure-volume relation of hearts explanted from 8 patients with left ventricular assist device and 8 control subjects with idiopathic cardiomyopathy was determined ex vivo at the time of transplantation.

RESULTS

Duration of mechanical support ranged from 210 to 276 days (mean +/- standard deviation = 283 +/- 76 days) in 3 patients with inflow valve regurgitation versus 100 to 155 days (132 +/- 22 days) in 5 patients without (p = 0.005). The end-diastolic pressure-volume relation of all hearts supported mechanically was shifted to the left toward normal controls. This effect was markedly attenuated in patients with inflow valve regurgitation.

CONCLUSIONS

Mechanical assistance can cause reverse remodeling in patients with dilated cardiomyopathy as evidenced by the shift in the end-diastolic pressure-volume relation curve to the left. Inflow valve failure, associated with prolonged support, can attenuate changes in left ventricular structure and dimension. Ineffective pressure and volume unloading may explain these observations.

Cardiac transplantation for endstage heart disease

Orthotopic heart transplantation (OHT), first accomplished in 1967, is currently performed in over 2000 patients per year at hundreds of centers worldwide. Selection criteria include end-stage heart failure with a limited life expectancy, intractable angina due to inoperable coronary artery disease, malignant ventricular arrhythmias refractory to maximal therapy, and unresectable cardiac tumors. While early immunosuppression was based on azathioprine and steroids, the current success of OHT is based on the addition of cyclosporine A (CyA) to this regimen. At Columbia-Presbyterian Medical Center, steroids and azathioprine are given perioperatively, and cyclosporine (OKT3 in patients with renal dysfunction) begun postoperatively. Survival rates at our institution parallel those reported by other centers, with 1- and 5-year actuarial survival of 85% and 70%, respectively. The most frequent causes of early mortality are allograft rejection and infection, while graft coronary artery disease (CAD) is responsible for most deaths occurring after the first post-transplant year. Regular endomyocardial biopsy is used to monitor for rejection, which occurs in 55% of patients within the first year. Mild or asymptomatic rejection is managed with oral steroids, followed by intravenous steroids and/or OKT3 or anti-thymocyte globulin (ATG) in refractory cases. Graft CAD occurs in 45% of patients surviving 3 years, and may require retransplantation. Heart transplantation is a proven, effective form of cardiac replacement. The recent trend of increasingly critically ill transplant candidates, however, has driven the costs of OHT to unprecedented levels. This issue, as well as the continuing organ short-age and current developments in mechanical cardiac assistance and xenotransplantation will undoubtedly assure a continually evolving role for cardiac transplantation in the treatment of endstage heart disease.

Randomized, double-blind trial of inhaled nitric oxide in LVAD recipients with pulmonary hypertension

BACKGROUND

Pulmonary vascular resistance is often elevated in patients with congestive heart failure, and in those undergoing left ventricular assist device (LVAD) insertion, it may precipitate right ventricular failure and hemodynamic collapse. Because the effectiveness of inotropic and vasodilatory agents is limited by systemic effects, right ventricular assist devices are often required. Inhaled nitric oxide (NO) is an effective, specific pulmonary vasodilator that has been used successfully in the management of pulmonary hypertension.

METHODS

Eleven of 23 patients undergoing LVAD insertion met criteria for elevated pulmonary vascular resistance on weaning from cardiopulmonary bypass (mean pulmonary artery pressure > 25 mm Hg and LVAD flow rate < 2.5 L x min[-1] x m[-2]) and were randomized to receive either inhaled NO at 20 ppm (n = 6) or nitrogen (n = 5). Patients not manifesting a clinical response after 15 minutes were given the alternative agent.

RESULTS

Hemodynamics for the group at randomization were as follows: mean arterial pressure, 72 +/- 6 mm Hg; mean pulmonary artery pressure, 32 +/- 4 mm Hg; and LVAD flow, 2.0 +/- 0.3 L x min(-1) x m(-2). Patients receiving inhaled NO exhibited significant reductions in mean pulmonary artery pressure and increases in LVAD flow, whereas none of the patients receiving nitrogen showed hemodynamic improvement. Further, when the nitrogen group was subsequently given inhaled NO, significant hemodynamic improvements ensued. There were no significant changes in mean arterial pressure in either group.

CONCLUSIONS

Inhaled NO induces significant reductions in mean pulmonary artery pressure and increases in LVAD flow in LVAD recipients with elevated pulmonary vascular resistance. We conclude that inhaled NO is a useful intraoperative adjunct in patients undergoing LVAD insertion in whom pulmonary hypertension limits device filling and output.

Persistent allopeptide reactivity and epitope spreading in chronic rejection of organ allografts

The role of the indirect allorecognition pathway in acute allograft rejection has been documented both in organ recipients and in experimental models. However, it is unknown whether self-restricted recognition of donor alloantigens also contributes to chronic allograft rejection. The aim of this study was to determine the relationship between allopeptide reactivity, epitope spreading, and chronic rejection. Using synthetic peptides corresponding to the hypervariable region of 32 HLA-DR alleles, we have followed the specificity of self-restricted T cell alloresponses to the donor in a population of 34 heart allograft recipients. T cells from sequential samples of blood collected from the patients up to 36 mo after transplantation were studied in limiting dilution analysis for allopeptide reactivity. The incidence of coronary artery vasculopathy (CAV) was significantly higher in patients who displayed persistent alloreactivity late after transplantation than in patients who showed no alloreactivity after the first 6 mo after transplantation. Both intra- and intermolecular spreading of epitopes was observed with an increased frequency in patients developing CAV in less than 2 yr, compared with patients without CAV; this suggests that diversification of the immune response against the graft contributes to chronic rejection. These data provide a strategy for identifying patients at risk of developing CAV and a rationale for therapeutic intervention aimed to prevent the progression of the rejection process.

Sympathetic response during cardiopulmonary bypass: mild versus moderate hypothermia

OBJECTIVE

To determine the sympathetic response during cardiopulmonary bypass at mild (34 degrees C) and moderate (28 degrees C) hypothermia.

DESIGN

A randomized study.

SETTING

Tertiary university hospital.

PATIENTS

Adults undergoing elective coronary artery bypass graft surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Plasma norepinephrine, epinephrine, and neuropeptide Y concentrations were measured. Moderate, but not mild, hypothermic cardiopulmonary bypass evoked a significant sympathetic response with increases in plasma norepinephrine and neuropeptide Y concentrations. A significantly higher incidence of postoperative atrial fibrillation was also observed in the moderate hypothermic compared with the mild hypothermic group.

CONCLUSIONS

Our results indicate that the degree of hypothermia significantly influences the sympathetic response during cardiopulmonary bypass. The higher incidence of postoperative atrial fibrillation in the moderate hypothermic group suggests that the enhanced sympathetic response might be one contributing factor in the development of atrial fibrillation.

Implantable left ventricular assist devices provide an excellent outpatient bridge to transplantation and recovery

OBJECTIVES

Our recent experience with outpatient left ventricular assist device (LVAD) support is presented to demonstrate the possibilities and limitations of long-term outpatient mechanical circulatory assistance.

BACKGROUND

The experience with inpatient LVAD support as a bridge to transplantation has proved the efficacy of such therapy in improving circulatory hemodynamic status, restoring normal end-organ function and facilitating patient rehabilitation. With miniaturization of the power supplies and controllers, such mechanical circulatory support can now be accomplished in an outpatient setting.

METHODS

Between March 1993 and February 1997, 32 patients (26 male, 6 female, mean [+/-SEM] age 49 +/- 15 years) underwent implantation of the ThermoCardiosystems (TCI) Heartmate vented electric (VE) LVAD. The VE LVAD is powered by batteries worn on shoulder holsters and is operated by a belt-mounted system controller, allowing unrestricted patient ambulation and hospital discharge.

RESULTS

Mean duration of support was 122 +/- 26 days (range 3 to 605), with a survival rate to transplantation or explantation of 78%. Nineteen patients were discharged from the hospital on mean postoperative day 41 +/- 4 (range 17 to 68), for an outpatient support time of 108 +/- 30 days (range 2 to 466). Four patients underwent early transplantation and could not participate in the discharge program, and three patients currently await discharge. The complication rate was not statistically different from that encountered in our previous 52 patients with a pneumatic LVAD.

CONCLUSIONS

Outpatient LVAD support is safe and provides improved quality of life for patients awaiting transplantation. Wearable and totally implantable LVADs should be studied as permanent treatment options for patients who are not candidates for heart transplantation.

Improved results for postcardiotomy cardiogenic shock with the use of implantable left ventricular assist devices

BACKGROUND

Over the past decade, the use of mechanical circulatory support in patients with postcardiotomy cardiogenic shock has resulted in hospital discharge rates of 25% to 40%. In an attempt to improve patient survival, we initiated a program of early insertion of an implantable Thermocardiosystems Incorporated Heartmate left ventricular assist device in patients who have circulatory failure after having undergone high-risk cardiac operations.

METHODS

Between April 1993 and February 1997, 12 patients underwent insertion of an implantable left ventricular assist device for postcardiotomy cardiogenic shock after coronary artery bypass grafting. Indications for insertion included postoperative cardiogenic shock (7 patients), postoperative cardiac arrest (3 patients), and failure to wean from cardiopulmonary bypass (2 patients).

RESULTS

The median time to device insertion was 3.5 days. The mean duration of left ventricular assist device support was 103 +/- 19 days (range, 2 to 225 days). Nine of 11 patients (82%) survived to undergo either transplantation (8 patients) or explantation (1 patient), with successful hospital discharge of all 9 patients. The major complication was device-related infection (42%). A single thromboembolism occurred in a patient with an infection.

CONCLUSIONS

Long-term outcome after postcardiotomy cardiogenic shock is improved substantially with the use of an implantable left ventricular assist device early in the postoperative course. Access to such a device is an important consideration before undertaking a high-risk cardiac operation, and early implantation of the device is a critical factor in ensuring long-term survival.

What is 'minimally invasive' coronary bypass surgery? Experience with a variety of surgical revascularization procedures for single-vessel disease

BACKGROUND

Although the use of small incisions is theoretically appealing, it has been argued that the true advantage of minimally invasive approaches to myocardial revascularization lies in the avoidance of cardiopulmonary bypass.

METHODS

Of 25 patients referred for surgical revascularization of single-vessel coronary disease, 20 elected to undergo a minimally invasive coronary artery bypass grafting (MICABG) procedure, while 5 opted to have conventional surgery with cardiopulmonary bypass (CPB). Patients having MICABG underwent single-vessel revascularization without CPB, via limited anterior thoracotomy, hemisternotomy, or median sternotomy. Intraoperatively, hemodynamics, anastomotic time, and total operative time were recorded. Postoperatively, length of hospital stay, incidence of myocardial infarction, indexes of end-organ function, and morbidity rates were recorded. In addition, patient questionnaires were used to assess subjective end points such as postoperative pain, wound drainage, and quality of life.

RESULTS

Fifteen of 20 patients undergoing MICABG underwent revascularization without CPB, while 4 were converted to standard coronary artery bypass grafting with CPB due to technical reasons and 1 for intraoperative ventricular fibrillation. Patients undergoing MICABG had no perioperative myocardial infarctions, while those having CPB had two infarctions (20%). Furthermore, there were no differences in length of stay or postoperative morbidity among the various approaches, while the MICABG procedures, especially via median sternotomy, were associated with shorter operative times.

CONCLUSIONS

The advantage of MICABG lies mainly in the avoidance of CPB. Thus, we advocate that surgeons initially utilize the median sternotomy and limited skin incision for MICABG to assure adequate exposure, technical precision, and patient safety. After a reasonable level of technical proficiency and experience are attained, the limited anterior thoracotomy approach can be used.

A prospective randomized trial of arginine vasopressin in the treatment of vasodilatory shock after left ventricular assist device placement

BACKGROUND

Vasodilatory shock requiring catecholamine pressors occurs in some patients following cardiopulmonary bypass. Prompted by a clinical observation, we investigated the use of vasopressin as a treatment for this syndrome in a randomized, controlled trial.

METHODS AND RESULTS

Patients undergoing placement of a left ventricular assist device (n=23) were evaluated for post-bypass vasodilatory shock requiring catecholamine pressors, and consecutive eligible subjects (n=10) were evenly randomized to blinded intravenous vasopressin or saline placebo. Vasopressin (0.1 U/min) increased mean arterial pressure (57+/-4 to 84+/-2 mm Hg, P<.001) and systemic vascular resistance (813+/-113 to 1188+/-87 dyne-s/cm5, P<.001), with decreased norepinephrine administration. There was no significant response to saline, but in three subjects who crossed over, blinded vasopressin increased mean arterial pressure (69+/-8 to 93+/-4 mm Hg) and systemic vascular resistance (898+/-88 to 1443+/-72 dyne-s/cm5) with decreased norepinephrine administration. Plasma vasopressin concentrations prior to randomization clustered in two groups: one (n=5) with concentrations inappropriately low for the degree of hypotension (8.4+/-2.1 pg/mL) and a second (n=3) with moderately elevated levels (33.7+/-1.6 pg/mL); vasopressin increased mean arterial pressure in the low vasopressin group from 57+/-4 to 85+/-2 mm Hg (P<.01) and in the high vasopressin group from 68+/-8 to 86+/-4 mm Hg.

CONCLUSIONS

Vasopressin is an effective pressor in vasodilatory shock after cardiopulmonary bypass. An absolute vasopressin deficiency was observed in the majority of patients, but all subjects responded to vasopressin administration.

Treatment of endstage heart disease with mechanical circulatory assistance

A great number of patients suffer and die from the sequelae of acute and chronic heart failure each year. Although advances in medical and surgical therapy have benefited many of these patients, the majority suffer from disease refractory to any definitive therapy. For these patients, cardiac transplantation is the only remaining hope. Unfortunately, because of the increasing demand for donor organs in the face of a fixed and limited supply, this option is only available to a small percentage of these patients. Even in patients accepted for transplantation, a significant waiting list mortality has been observed. A variety of ventricular assist devices (VAD) have been developed since the first successful case of mechanical cardiac assistance over 30 years ago. These devices differ in basic mechanical function, method of insertion, and degree of implantability, and thus have different indications and potential applications. While the intra-aortic balloon pump and centrifugal pumps are effective short-term support modalities, extracorporeal and implantable pulsatile devices have been used successfully for long-term support of patients with reversible and non-reversible cardiac failure. These pumps have most commonly been utilized as bridges to transplantation, but increasing clinical experience has supported the notion of long-term mechanical assistance as a definitive therapy for endstage heart disease. While complications, particularly infection and thromboembolism, pose significant challenges and long-term device reliability remains to be fully determined, available implantable devices seem capable of providing effective long-term support. As data is obtained from currently ongoing trials comparing VAD support to medical therapy for endstage heart failure, ethical and economic issues will assume increasing importance.

Reevaluating the significance of pulmonary hypertension before cardiac transplantation: determination of optimal thresholds and quantification of the effect of reversibility on perioperative mortality

OBJECTIVES

Right-sided circulatory failure resulting from severe preoperative pulmonary hypertension is a source of mortality early after cardiac transplantation. We undertook the present study (1) to analyze the association of elevated pulmonary hemodynamic indices with 30-day mortality, (2) to define threshold ranges associated with an increase in 30-day mortality, and (3) to evaluate the effect of vasodilator reversibility on 30-day mortality.

METHODS

Preoperative hemodynamic profiles were evaluated in 476 patients who ultimately underwent cardiac transplantation. From these data, receiver-operating characteristic curves and stratum-specific likelihood ratios were generated to compare the efficacy of each hemodynamic index. A subset of patients with elevated hemodynamic profiles at baseline additionally underwent graded sodium nitroprusside infusion.

RESULTS

Analysis of receiver-operating characteristic curves demonstrated no statistically significant difference among the indices in their ability to predict 30-day mortality. Analysis of stratum-specific likelihood ratios demonstrated three risk strata that correlated with significant differences in 30-day mortality, with patients in the high-risk stratum having a 3.2 to 4.4 increase in odds of 30-day mortality when compared with patients in the low-risk stratum. Nitroprusside data demonstrated that although 30-day mortality was better in patients with reversible pulmonary hypertension than in those with fixed pulmonary hypertension, it was not comparable with that of patients without pulmonary hypertension at baseline.

CONCLUSIONS

Candidates for cardiac transplantation may be categorized into three risk strata on the basis of their preoperative pulmonary hemodynamic profile; the association of this profile with 30-day mortality is not linear. Reversibility with nitroprusside appears to confer some improvement in the risk of 30-day mortality, but it may not eliminate the risk entirely.

Implantable left ventricular assist devices: an evolving long-term cardiac replacement therapy

OBJECTIVE

The authors' 8-year experience with both inpatient and outpatient left ventricular assist device (LVAD) support is presented to show the possibilities and limitations of long-term outpatient mechanical circulatory assistance.

SUMMARY BACKGROUND DATA

The limitation of suitable cardiac donors has led to the use of LVADs as a temporizing measure for patients awaiting cardiac transplantation. The success of such devices in the short and medium term as a bridge to transplantation has led to their evaluation as a long-term destination therapy for end-stage heart disease.

METHODS

Between August 1990 and February 1997, 85 patients with end-stage heart disease underwent insertion of implantable LVADs. Fifty-two patients underwent pneumatic device insertion and 32 patients received a vented electric device.

RESULTS

Patients were supported for a mean of 109+/-13 days for an overall survival to transplant (54) or explant (3) of 73%. Nineteen patients were discharged from the hospital on a mean of postoperative day 41+/-4 (range, 17-68) for an outpatient support time of 108+/-30 days (range, 2-466). Of 12 patients supported after postcardiotomy cardiogenic shock, 10 (82%) survived to hospital discharge. Perioperative right ventricular failure was treated in most patients with inotropic agents and inhaled nitric oxide with only six patients requiring right ventricular assist device support. Thromboembolic rate was low (0.016 events/patient-month) despite minimal or no anticoagulation in all cases.

CONCLUSIONS

Left ventricular assist device support has evolved to become an outpatient therapy with excellent survival rates and an acceptable morbidity. Accordingly, wearable LVADs should be studied as permanent treatment options for patients who are not transplant candidates.

New strategies for early diagnosis of heart allograft rejection

BACKGROUND

Allograft rejection is mediated by T cells that recognize allogeneic major histocompatibility complex (MHC) molecules via the direct and indirect pathway. The direct pathway involves T cells that react against MHC/peptide complexes expressed on the surface of donor antigen-presenting cells (APCs). In contrast, T cells involved in the indirect pathway recognize peptides derived from processing and presentation of allogeneic MHC molecules by self (recipient) APCs. To explore the relative contribution of these two pathways to rejection, we have evaluated the response of peripheral blood T cells from 50 heart transplant recipients against donor APCs (direct recognition) and against self APCs pulsed with synthetic peptides corresponding to the hypervariable region of the mismatched HLA-DR antigens of the donor (indirect recognition).

METHODS

T cell reactivity against donor APCs was quantitated by measuring the expression of CD69 on allostimulated CD3+ LDA1+ cells. Reactivity to synthetic allopeptides was determined in limited dilution assays.

RESULTS

Serial studies of the kinetics of direct and indirect recognition showed that both pathways contribute to early acute rejection episodes. Primary rejection was accompanied invariably by indirect recognition of a dominant allopeptide. Intermolecular spreading of T cell epitopes was observed during recurrent rejections. Enhanced recognition of donor alloantigens via the direct pathway was found predominantly during early rejection episodes. A single form of allorecognition was shown to occur in some rejection episodes.

CONCLUSIONS

Monitoring of the direct and indirect pathway of allorecognition provides a reliable method for prediction and differential diagnosis of acute rejection of heart allografts.

TQM in health care: mistaken identity?

Total Quality Management is a powerful tool in health care today. The definition of quality improvement in the medical literature focuses on improving patient outcomes. However, most quality initiatives in the health care field focus on improving productivity, cost-effectiveness, market share, employee morale, and efficiencies of processes. This disparity between the medical definition of quality and the actual application of quality improvement may have the effect of alienating many physicians, the very people who must be involved. The semantics are important to address in a TQM initiative.

Selective anticoagulation with active site blocked factor IXa in synthetic patch vascular repair results in decreased blood loss and operative time

Heparin has been the mainstay of anti thrombic therapy in arterial repair procedures. With increasing use of synthetic patch angioplasty (polytetrafluoroethylene [PTFE] or Dacron, Medical Products, Flagstaff, AZ) to improve long-term patency and limit aneurysmal dilation, however, the use of heparin has been associated with excessive needle hole bleeding, resulting in time delay in the operating room to achieve hemostasis, as well as clinically significant blood loss. Because of the multiple sites of action of heparin in the coagulation cascade, both intravascular (desired effect) and extravascular (untoward side effect) hemostasis are impaired. The authors therefore tested the hypothesis that selective inhibition of intravascular coagulation, without significant impairment of extravascular hemostasis, would prevent clotting intraluminally while preserving hemostasis at the suture line of the patch graft. The unique position of factor IX/IXa in the coagulation cascade renders its inhibition an ideal target in this setting. The authors prepared active site blocked factor IXa (IXai) using dansyl-Glu-Gly-Arg chloromethylketone, and tested this hypothesis in a New Zealand rabbit aortotomy model with PTFE patch closure using either heparin (25 i.u./kg; n = 16) or IXai (300 micrograms/kg; n = 21). The infrarenal aorta was identified and isolated, the anti coagulant infused, aortic cross clamp placed, and aortotomy repaired with a 2 x 6 mm PTFE patch. After cross-clamp removal, blood loss was measured and time to hemostasis was recorded. Compared with heparin, IXai resulted in significantly reduce blood loss (6.97 +/- 4.4 g vs 2.72 +/- 2.51 g, respectively, p < 0.008), and time to hemostasis (2.94 +/- 0.77 min vs 2.0 +/- 0.63 min, respectively, p < 0.003). To assess long-term patency and thrombosis, 12 rabbits (given heparin; n = 6 and IXai; n = 6) were observed for up to 2 months post-operatively. No differences were observed between rabbits treated with heparin or IXai; 100% of the grafts were patent with no differences in degree of intimal hyperplasia by histologic analysis. Together, these data suggest that use of IXai in PTFE vascular repair will safely allow realization of the benefits of long-term patency and decreased aneurysmal dilatation, while eliminating the intraoperative morbidity of needle hole bleeding.

Mechanical unloading with a miniature in-line axial flow pump as an alternative to cardiopulmonary bypass

Cardiopulmonary bypass (CPB) causes a well described systemic inflammatory response. To avoid these potential detrimental effects, coronary artery bypass grafting (CABG) has been attempted off CPB on the beating heart. With the use of a left ventricular (LV) assist device during CABG, the heart can be made flaccid with beta-blockade, and the systemic circulation can continue to be supported. The hemodynamic and hematologic consequences of left heart bypass with a miniature axial flow pump were studied in a sheep CABG model. The pump weighs 45 g and was connected to standard venous and arterial cannulas. Left sided inflow and brachiocephalic outflow were employed. A pump speed of 14,000 rpm resulted in a flow of 5.63 +/- 0.18 L/min and provided 75% of the LV output during a 2 hr pump run. This resulted in complete capture of the aortic pressure tracing (mean 56.3 mmHg) with a 15.5 mmHg augmentation in the esmolol depressed ventricle. Reductions in LV end diastolic pressure and LV end systolic pressure resulted in a 66% reduction in LV external work under baseline conditions and an 83% reduction in the beta-blocked ventricle. Myocardial oxygen demand was reduced 16% after axial flow unloading in the esmolol depressed condition. Right ventricular pressures, pulmonary artery flow, LV filling, and oxygenation were adequate in the esmolol depressed animal and remained unchanged throughout the experiment. No changes in hematocrit, total bilirubin, lactate dehydrogenase, or plasma free hemoglobin were detected after 2 hr of assist. Axial flow left heart bypass results in acceptable hemodynamics with no hemolysis and may provide an alternative to CPB during CABG.

The influence of infection on survival and successful transplantation in patients with left ventricular assist devices

BACKGROUND

Mechanical cardiac assistance has recently emerged as a tenable option in the treatment of end-stage heart failure. In spite of recent technical improvements that have reduced the incidence of life-threatening complications, the reported frequency of infections in these patients has remained high.

METHODS

Over a 5-year period, 60 patients underwent insertion of a left ventricular assist device (LVAD) at our institution. Detailed medical records were kept prospectively for all patients, and a variety of endpoints were analyzed, including the incidence, nature, and sequelae of infections before and after LVAD implantation and after transplantation.

RESULTS

Twenty-nine of 60 patients (48%) undergoing LVAD insertion subsequently had development of infections. The most frequent sites of infection were blood, LVAD drivelines, and central venous catheters, representing 61% of all infections. At the time of LVAD implantation, 13 of 60 patients (22%) had culture-proven infections. In spite of an increased incidence of subsequent infection (77% vs 40%), there were no differences in rates of mortality (31% vs 26%), LVAD endocarditis, (23% vs 11%) and eventual transplantation (62% vs 57%) between these patients and those without periimplantation infections. Although the overall mortality rate was not influenced by infections during LVAD support (28% vs 26%), the development of LVAD endocarditis was associated with a high mortality rate. Finally, although patients with infections during LVAD support had significantly longer median support times than those who remained infection free (101 vs 49 days, respectively), there was no difference in the rate of successful transplantation (59% vs 58%) or in the rate of infection after transplantation (35% vs 28%).

CONCLUSIONS

Infections are common in patients undergoing LVAD support, but they do not adversely affect survival, the rate of successful transplantation, or the incidence of posttransplantation infection. Periimplantation infections may increase the risk of subsequent infections, but they also do not influence survival or transplantability. Patients with development of LVAD endocarditis are at increased risk for morbidity and death and require early and aggressive therapy, potentially including device explantation.

Cerebral dysfunction after coronary artery bypass grafting done with mild or moderate hypothermia

OBJECTIVE

Ninety-nine patients undergoing elective coronary artery bypass grafting were enrolled in a prospective, randomized study to evaluate the incidence of cerebral dysfunction after "mild" or "moderate" hypothermia during cardiopulmonary bypass.

METHODS

Patients were evaluated before and after operation before hospital discharge and in some cases at follow-up at least 6 weeks later with a complete neurologic examination (85 patients) and a battery of standard neuropsychometric tests (86 patients).

RESULTS

Postoperative changes detected by neurologic examination consisted of the appearance of new primitive reflexes in both groups. No statistically significant differences in incidence were found. The neuropsychometric performances of the two groups were statistically similar by either event-rate or group-rate analysis.

CONCLUSIONS

There is no detectable difference in postoperative cerebral dysfunction in patients undergoing coronary artery bypass grafting who are supported by cardiopulmonary bypass with either mild or moderate hypothermia.

Functional comparison of unilateral versus bilateral lung volume reduction surgery

BACKGROUND

Lung volume reduction surgery (LVRS) has shown early promise as a palliative therapy in severe emphysema. A number of patients, however, are not candidates for a bilateral operation, or exhibit a predominantly unilateral disease distribution.

METHODS

Over 20 months, we performed LVRS in 92 patients selected on the basis of severe hyperinflation with air trapping, diaphragmatic dysfunction, and disease heterogeneity. Twenty-eight patients underwent unilateral LVRS on the basis of asymmetric disease distribution, prior thoracic operation, or concomitant tumor resection.

RESULTS

Unilateral LVRS resulted in comparable improvements in exercise capacity and dyspnea as the bilateral procedure, with a similar perioperative mortality and actuarial survival to 24 months. Improvements in spirometric indices of pulmonary function, however, were less in patients undergoing unilateral than bilateral LVRS.

CONCLUSIONS

In properly selected patients, unilateral LVRS provides functional and subjective benefits of comparable magnitude to those associated with a bilateral operation. Unilateral LVRS is therefore an option in the therapy of end-stage emphysema in patients with asymmetric disease distribution, a prior thoracic operation, or contraindications to sternotomy, and may have a role as a bridge to transplantation in selected cases.