Changes in left ventricular mechanical and hemodynamic function during acute rejection of orthotopically transplanted hearts in dogs

Abnormal total ejection isovolume index as early noninvasive marker of chronic rejection in heart transplantation*

Abnormally high myocardial performance index (MPI) is a Doppler-derived marker of combined systolic and diastolic left ventricular (LV) dysfunction. To identify early stage allograft dysfunction by MPI, we studied 154 long-term heart transplantation (HT) recipients (131 male, aged 51 +/- 13 years at HT, mean follow up 8.4 +/- 3.5 years), with normal left ventricular ejection fraction (LVEF) and free from acute rejection (AR), and 25 normals (13 male, aged 39 +/- 16 years). Rejection score (RS) on endomyocardial biopsy was calculated in the first year. MPI was prolonged (0.45 +/- 0.18 vs. 0.28 +/- 0.10, P = 0.0001) in patients and directly related with mean time from HT (P = 0.001), higher cumulative dosages of cyclosporine at 3 months (P = 0.01), 6 months (P = 0.03), 1 year (P = 0.02), 3 years (P = 0.04) and with cumulative dosage of methylprednisolone at 1 year (P = 0.002). The index was inversely related with mean age at HT (P = 0.002) and tended to be directly related with RS at 1 year (P = 0.05). Thus, MPI is abnormal in long-term HT recipients with normal LVEF. Its direct relation with time from HT as well as immunosuppressive load suggests an early stage of graft dysfunction because of chronic rejection. Extended prospective studies are warranted to clarify its potential role as a negative prognostic marker in HT.

Can the index of myocardial performance be used to detect acute cellular rejection after heart transplantation?

The index of myocardial performance (IMP), combining systolic and diastolic function, was measured in 50 orthotopic heart transplant recipients to determine if it could be used to detect acute rejection. It was calculated as the sum of the isovolumic contraction time (IVCT) and isovolumic relaxation time (IVRT) divided by the ejection time. Comparison of intrarecipient changes in Doppler intervals between rejection and nonrejection states demonstrated an increase in IVCT and decrease in IVRT during rejection with no significant change in the IMP. Rejection is likely to be best detected by assessing these parameters independently rather than by measuring the IMP.

Transforming growth factor beta and diastolic left ventricular dysfunction after heart transplantation: echocardiographic and histologic evidence

BACKGROUND

The mechanism for chronic left ventricular diastolic dysfunction in the non-rejecting cardiac allograft has not been fully studied.

OBJECTIVES

The purposes of this study were to analyze the significance and frequency of left ventricular diastolic dysfunction after heart transplantation and to examine the involvement of fibrotic cytokines (transforming growth factor beta [TGF-beta]) in development of clinical and echocardiographic changes in cardiac allograft recipients.

METHODS

We studied 152 heart transplant recipients who had survived for at least 24 months. We compared histopathologic findings (staining of endomyocardial biopsy specimens using hematoxylin and eosin, and polyclonal antibodies expressed as TGF-beta score), left ventricular function (Doppler echocardiography), and clinical course (New York Heart Association [NYHA] status). We classified patients into Group 1 (n = 41 recipients) with a restrictive filling pattern, mitral deceleration time (MDT) <140 milliseconds, and Group 2 (n = 111 recipients), MDT >or=140 milliseconds.

RESULTS

The MDT was 122 +/- 7 milliseconds in Group 1 compared with an MDT of 177 +/- 17 milliseconds in Group 2 (p = 0.0003). Group 1 showed significant immunohistochemical staining in endomyocardial biopsy specimens (a mean TGF-beta score of 9.1 +/- 1.2 for Group 1 compared with a mean TGF-beta score of 3.6 +/- 0.8 for Group 2 p = 0.001). The TGF-beta expression correlated inversely with both MDT and isovolumic relaxation time (r = -0.77, p = 0.0004, and r = -0.69, p = 0.004, respectively). Mean NYHA status in Group 1 recipients was 2.2 +/- 1.1 compared with 1.37 +/- 0.6 for Group 2 (p = 0.006).

CONCLUSIONS

Transforming growth factor beta expression in cardiac allografts is associated with impaired left ventricular diastolic function. The pathogenesis of diastolic dysfunction may be an aberrant repair process after rejection-caused TGF-beta expression in the allograft.

Does total orthotopic heart transplantation offer improved hemodynamics during cellular rejection events?

BACKGROUND

We hypothesized that total orthotopic heart transplantation (TOHT) improves hemodynamics during cellular rejection compared with biatrial transplantation (SOHT).

METHODS

We reviewed 1942 biopsies from 134 patients (pts) and right heart catheterization data obtained at endomyocardial biopsy. Biopsies that displayed cellular rejection grade 1B as classified according to International Society for Heart and Lung Transplantation (ISHLT) criteria were analyzed. Pts with pacemakers, atrial fibrillation, or beta-blocker therapy at the time of biopsy were excluded. Twenty-three pts after TOHT and 38 after SOHT were identified to match these criteria.

RESULTS

Demographic data and pretransplant hemodynamics were similar. TOHT pts had a higher mean cardiac index than SOHT recipients (3.3 +/- 0.8 vs 2.7 +/- 0.5 L/min/m(2); P =.002). Right atrial mean pressure was lower after TOHT (8 +/- 4 vs 11 +/- 4 mm Hg; P =.006). Pulmonary pressures, pulmonary vascular resistance, and heart rate were similar.

CONCLUSIONS

TOHT offers improved hemodynamics during cellular rejection grade 1B as evidenced by higher cardiac output and index with lower right atrial pressures. Future studies must examine the potential benefits of TOHT during more severe rejection events.

Modulation of catecholamine responsiveness and beta-adrenergic receptor/adenylyl cyclase pathway during cardiac allograft rejection1 2

BACKGROUND

This study investigated the changes of catecholamine responsiveness and beta-adrenergic receptor/adenylyl cyclase pathway during acute cardiac transplant rejection.

METHODS

Isogeneic Lewis to Lewis and allogeneic Dark Agouti (DA) to Lewis rat cardiac transplants were studied 3 and 5 days after heterotopic intraabdominal transplantation (n=6/group). Myocardial blood flow (MBF), left ventricular systolic pressure (LVSP), maximum pressure development (+dP/dt), and end-diastolic pressure (LVEDP) were measured using an intraventricular balloon. Contractile response to dobutamine (5 microg/kg/min) was also assessed. In separate groups beta-adrenergic receptor density and adenylyl cyclase activity were measured in the grafts, in the recipients' native hearts and in native hearts of sham-operated controls.

RESULTS

During mild to moderate rejection cardiac function indices remained unchanged, although MBF and contractile response to dobutamine decreased significantly (P<0.05) in the allogeneic group. The beta-adrenergic receptor density was significantly (P<0.05) increased in both isografts and allografts and in the native hearts of allografted recipients in comparison to native hearts of controls. Adenylyl cyclase activity showed a significant decrease (P<0.05) only in allografts. During severe rejection, LVSP and +dP/dt decreased and LVEDP increased in allografts in comparison to isografts (P<0.05). This was accompanied by a significant decrease in MBF, contractile response to dobutamine, beta-adrenergic receptor density, and adenylyl cyclase activity (P<0.05).

CONCLUSIONS

Both microcirculatory disturbances and primary alteration in adenylyl cyclase activity may contribute to decreased contractile reserve in mild to moderate cardiac allograft rejection, whereas beta-adrenergic receptor density seems to be also influenced by cardiac denervation. Severe rejection leads to systolic and diastolic heart failure with complex dysregulation of the beta-adrenergic receptor/adenylyl cyclase pathway and impaired microcirculation.

Cardiac function of transplanted rat hearts using a working heart model assessed by magnetic resonance imaging

BACKGROUND

A direct correlation between graft rejection and cardiac contractile function in small-animal models has been difficult to establish because (i) the conventional non-working heart model is greatly different from the orthotopic heart in terms of left ventricular work and (ii) it is difficult to obtain hemodynamic data in situ. We have used magnetic resonance imaging (MRI) techniques to obtain noninvasive, in-situ quantitation of ventricular volume after heterotopic cardiac transplantation.

METHODS

Infra-renal heterotopic cardiac transplantation was performed on rats using syngeneic and allogeneic untreated donors in both working and non-working left heart models. An occluding balloon catheter in the inferior vena cava was used to vary the pre-load to the graft. An arteriovenous fistula was created to raise inferior caval oxygen saturation. Magnetic resonance imaging measurements were carried out at day 3, 4, and 5 post-transplantation. Left ventricle end-diastolic and end-systolic volumes were calculated using a biplanar ellipsoid model.

RESULTS

Stroke volume was significantly increased in the working heart model as compared to the non-working model. At day 4 post-transplant, the diastolic pressure-volume relationship in the allograft group was significantly shifted, indicative of decreased myocardial distensibility, whereas the indices of systolic function were preserved.

CONCLUSIONS

We have developed a heterotopic transplant working rat heart model and have used it to assess in-situ cardiac function by MRI. Sensitive indices of diastolic contractile function can be obtained in this rodent transplant model that correlate well with histologic evidence of early rejection.

Effects of alloimmune injury on contraction and relaxation in cultured myocytes and intact cardiac allografts

OBJECTIVES

This study was performed to determine the mechanisms by which allosensitized lymphocytes cause contractile dysfunction in cultured ventricular myocytes and to compare the effects on isolated myocytes with those observed in an intact heart preparation during allograft rejection.

BACKGROUND

Allograft rejection may be associated with reversible abnormalities of both systolic and diastolic function. The immunologic mechanisms that cause ventricular dysfunction are poorly understood.

METHODS

Vascularized heterotopic abdominal heart transplantation was performed in mice. Contractile function of excised allografts undergoing rejection was assessed using a Langendorff perfusion apparatus and a strain gauge. Spontaneously beating monolayers of cultured ventricular myocytes from donor strain fetal mice were exposed to the allosensitized cytotoxic T lymphocytes, and the effects on myocyte motion, intracellular calcium transients, relaxation half-time, membrane potential and myocyte lysis (chromium-51 release) were measured.

RESULTS

In intact hearts, histologically mild rejection without myocyte necrosis was associated with decreased systolic function without slowing of relaxation. In cultured fetal myocytes, sensitized lymphocytes induced a progressive decrease in the amplitudes of myocyte motion and calcium transients, with cessation of beating within 40 min. Also, the diastolic membrane potential and amplitude of the action potential decreased. Relaxation half-time, as estimated by measurement of cell motion, was unchanged. The effect was allospecific and was reversible with early removal of lymphocytes from the myocyte monolayer. Pretreatment of lymphocytes with the degranulation inhibitor 4,4'-diisothiocyano-2,2'-disulfonic acid stilbene blocked both the negative inotropic effect and myocyte lysis.

CONCLUSIONS

We conclude that impaired relaxation is not a prominent feature of contractile dysfunction caused directly in myocytes by alloimmune injury from cytotoxic lymphocytes. Allosensitized lymphocytes can cause reversible systolic dysfunction in myocytes by means of a direct cell-cell interaction. This effect may be in part responsible for the reversible systolic dysfunction associated with allograft rejection.

Pathophysiology and mediators of ischemia-reperfusion injury with special reference to cardiac surgery. A review

Although necessary for the ultimate tissue survival, reperfusion may paradoxically exacerbate the ischemic injury. Ischemia and reperfusion injury is intimately woven together. The relative role of reperfusion injury is not clarified and probably varies with the ischemic insult: Reperfusion is always preceded by ischemia, and some of the reperfusion-related events may represent a process continuing from the ischemic period; thus the proper designation should be ischemia-reperfusion injury. The reperfusion-related events are: arrhythmias, myocardial stunning with both systolic and diastolic dysfunction, and low reflow and microvascular stunning. Of pathogenetic importance are the mode and speed of reperfusion as well as the initiation of an intracoronary inflammatory reaction during reperfusion, including endothelium-leukocyte interaction, platelets, generation of oxygen free radical, generation and release of arachidonic acid metabolites, platelet activating factor, endothelium derived relaxing factor, endothelins, kinins, and histamine, complement activation, disturbances in calcium homeostasis, and disturbances in lipid and fatty acid metabolism.

Arrhythmias after cardiac transplantation

The etiology and clinical significance of sustained arrhythmias, and atrial and ventricular premature complexes (APCs and VPCs, respectively) after heart transplantation are controversial. Fifty adult recipients surviving > 2 weeks were studied by continuous telemetry while in the hospital and by ambulatory electrocardiographic monitoring at 2, 4, 6, 12 and 24 weeks after transplantation. The median APC frequency was greater among subjects who experienced allograft rejection in the early postoperative period (0.7/hour, range 0 to 23) than among those who did not (0.2/hour, range 0 to 10.4) (p = 0.04). The APC frequency in all subjects decreased from 0.25/hour (range 0 to 23) early to 0/hour (0 to 14) later (p = 0.04). Atrial flutter was the most frequent sustained arrhythmia; it was recorded in 5 of 21 rejectors and in 1 of 29 nonrejectors (p = 0.04), and 11 of 16 episodes (69%) were related to acute rejection temporally. VPCs were recorded in all patients early after transplantation, but the median frequency subsequently decreased from 4.6/hour (range 0.5 to 470) early to 1.25/hour (range 0 to 225) later (p < 0.001). VPC frequency was unrelated to rejection. Sustained ventricular tachycardia was recorded once and was caused by the proarrhythmic effect of flecainide. Thus, APCs and VPCs occur frequently after transplantation. Frequent APCs are associated with rejection, whereas the main determinant of VPC frequency is time after transplantation. Atrial flutter is closely associated with rejection and should be regarded as an indication for endomyocardial biopsy. Ventricular tachycardia occurs seldom, and in this study was due to proarrhythmic drug effects.

Ventricular function during the acute rejection of heterotopic transplanted heart: gated blood-pool studies

Twenty patients who had undergone a heterotopic heart transplant were studied prospectively to determine the relationship between rejection and ventricular dysfunction assessed from gated blood-pool studies. A fully automated method for detecting ventricular edges was implemented; its success rate for the grafted left and right ventricles was 94% and 77%, respectively. The parameters, peak ejection and filling rates, were calculated pixel per pixel using a two-harmonic Fourier algorithm and then averaged over the ventricular region of interest. Peak filling and ejection rates were closely related with the severity of the rejection, while the left ventricular ejection fraction was not. Peak filling rates of both ventricles were the indices closely related to the presence of moderate rejection. Despite the low number of patients, these data suggested that gated blood-pool-derived indices of ventricular function are associated with ventricular dysfunction resulting from myocarditis rejection. Radionuclide ventriculography provides parametric data which are accurate and reliable for the diagnosis of rejection.

Alterations in left ventricular diastolic twist mechanics during acute human cardiac allograft rejection

BACKGROUND

Contraction of obliquely oriented left ventricular (LV) fibers results in a twisting motion of the left ventricle. The purpose of this study was to assess the effects of acute human cardiac allograft rejection on LV twist pattern and the twist-volume relation.

METHODS AND RESULTS

Tantalum markers were implanted into the LV midwall in 15 transplant recipients to measure time-varying, three-dimensional chamber twist using computer-assisted analysis of biplane cinefluoroscopic images. Twist was defined as the mean longitudinal gradient of circumferential rotation about the LV long axis. When plotted against normalized percent ejection fraction (%EF), the resulting twist-normalized %EF relation could be divided into three phases. In systole, LV twist was linearly related to ejection of blood. In contrast, diastolic untwist was characterized by early rapid recoil with little change in LV volume, followed by more gradual untwisting when the bulk of diastolic filling occurred. During 10 acute rejection episodes in 10 patients, maximum twist, peak systolic twist rate, and the slope of the systolic twist-normalized %EF relation did not change. In contrast, the slope of the early (first 15% of filling) diastolic twist-normalized %EF relation (M(early-dia)) decreased significantly (-0.194 +/- 0.062 [prerejection] versus -0.103 +/- 0.054 rad/cm [rejection], p = 0.0003), resulting in a prolonged tau 1/2 (time required to untwist by 50% [20 +/- 5% versus 28 +/- 5% of diastole], p = 0.0003) and decrease in percent untwisting at 15% diastolic LV filling (62 +/- 11% versus 36 +/- 13%, p = 0.0003). Therefore, a greater proportion of LV untwisting occurred later in diastole during rejection, as reflected by an increase in the slope (M(mid-dia)) of the middle to late (from 15 to 90% filling) diastolic twist-normalized %EF relation (-0.018 +/- 0.009 versus -0.030 +/- 0.010 rad/cm, p = 0.0015). Peak rate of untwist was not affected. With resolution of rejection, M(early-dia) and percent untwist during early diastole returned to baseline levels (p = NS versus baseline). There was also a trend for M(mid-dia) to return toward prerejection values (p = NS versus baseline), but this change did not reach statistical significance compared with rejection values.

CONCLUSION

Acute cardiac allograft rejection is associated with altered diastolic twist mechanics in the absence of any demonstratable systolic abnormalities. During rejection, myocardial edema and other factors may result in intrinsic changes of the elastic properties of the myocardium, thereby leading to modification of recoil forces responsible for the early, rapid unwinding of the deformed ventricle.

Changes in left ventricular systolic function that accompany rejection of the transplanted heart: a serial radionuclide assessment of fifty-three consecutive cases

To examine the functional changes that accompany the development of rejection of the orthotopically transplanted heart, radionuclide ventriculograms, right heart catheterizations, and endomyocardial biopsies were performed at weekly intervals during the posttransplantation hospitalization of 53 consecutive transplant recipients. Left ventricular ejection fraction decreased in those (n = 10) who had sequential biopsies that changed from no rejection to moderate rejection (63% +/- 7% to 57% +/- 7% respectively, p = 0.007). There was an associated decrease in the peak ejection rate (4.4 +/- 1.0 to 3.9 +/- 0.8 end-diastolic volumes per second, p = 0.008) and an increase in the time to peak ejection rate (137 +/- 27 msec to 153 +/- 20 msec, p = 0.004) that accompanied the development of rejection. There was a similar decrease in left ventricular ejection fraction in those (n = 9) who had sequential biopsies that changed from no rejection to mild rejection (63% +/- 6% to 59% +/- 8%, p = 0.009). Only two of 19 patients whose biopsies changed from no rejection to either mild or moderate rejection did not have an associated decrease in ejection fraction. In patients who had a biopsy that showed definite rejection, which was then followed by histologic resolution after treatment (n = 11), left ventricular ejection fraction increased from 56% +/- 8% to 61% +/- 8%, p = 0.03. There were no significant changes in any of the parameters of diastolic function or in any of the hemodynamic parameters measured, which were associated with either the development or resolution of rejection.(ABSTRACT TRUNCATED AT 250 WORDS)

Left ventricular diastolic function. Doppler echocardiographic changes soon after cardiac transplantation

In acute cardiac rejection, left ventricular diastolic function is altered, and a restrictive ventricular filling pattern occurs. Doppler echocardiographic indexes of mitral inflow have been proposed as sensitive markers of the rejection process. As rejection progresses, the restrictive ventricular filling pattern is reflected by a shortening of isovolumic relaxation time and mitral valve pressure half-time and by an increase in early transmitral filling velocity. Diastolic function is also compromised in the nonrejecting cardiac transplant recipient during the early postoperative period. This study examined the progression in Doppler-derived mitral filling indexes in 25 recent cardiac transplant recipients who demonstrated no histological evidence of transplant rejection. Isovolumic relaxation time, mitral valve pressure half-time, and early transmitral filling velocity were measured at postoperative weeks 1, 2, 4, and 6 on the day that surveillance right ventricular endomyocardial biopsies were performed. The initial indexes were comparable to previously described restrictive parameters and over the 6-week study period evolved into a nonrestrictive filling pattern. This evolution reflects a progressive improvement in postoperative diastolic function and a decrease in left heart filling pressures. None of the evaluated clinical characteristics, including preoperative pulmonary pressures, total ischemic time of the transplanted heart, cardiopulmonary bypass time, and age of the donor heart, correlated with this process. Given the increasing use of Doppler echocardiography as a means of screening for transplant rejection, it is important to have a thorough understanding of normal postoperative changes in left ventricular diastolic function.

A hemodynamic and Doppler echocardiographic study of ventricular function in long-term cardiac allograft recipients. Etiology and prognosis of restrictive-constrictive physiology

Conventional hemodynamic measurements and Doppler echocardiography were used to assess ventricular physiology of the human cardiac allograft and to examine the influence of pertinent clinical factors on chronic myocardial performance. Sixty-four patients (18-55 years old; mean, 39 years) undergoing routine annual hemodynamic assessment were studied. Blood-flow velocity properties across the mitral, tricuspid, and aortic valves were analyzed from Doppler ultrasound recordings. Ten of these patients had elevated diastolic pressures associated with a sharp early diastolic dip followed by an exaggerated and abrupt rise in pressure, consistent with restrictive-constrictive ventricular physiology. Left ventricular dP/dt and stroke volume were lower in these patients compared with the other 54 patients. Doppler echocardiographic indexes of left ventricular filling and ejection in these 10 patients differed significantly. Isovolumic relaxation time and pressure half-time were shorter, peak early mitral and tricuspid flow velocities were higher, and mean aortic flow velocity and acceleration were lower. A higher rejection incidence was the only demonstrable clinical factor associated with impaired ventricular function. Doppler echocardiography may, therefore, noninvasively identify patients with hemodynamic evidence of restrictive-constrictive physiology. This abnormality occurs in approximately 15% of allograft recipients, is associated with impaired systolic performance, and may be related to rejection incidence.

Patent foramen ovale complicating heart transplantation. A window on posttransplantation hemodynamics

A patient developed refractory hypoxemia and right-to-left shunt across a patent foramen ovale after orthotopic cardiac transplantation. The right-to-left shunt was produced by volume overload of the donor right ventricle during the period of early postoperative myocardial depression and resolved with preload reduction and diuresis. Increased preload of the right heart needs to be considered in the early postoperative management after cardiac transplantation. The foramen ovale of the donor and recipient should be evaluated at operation by visual and probe examination and securely closed if either is patent, since this pattern of hemodynamic changes is common following cardiac transplantation.

Heart transplantation

Modern concepts of cardiac transplantation are reviewed. Selection of potential recipients and donors is discussed with particular attention to those aspects of procurement that involve coordination with other transplant teams. Technical aspects of the operation, postoperative management, immunologic regimens, and late results, including physiologic testing and complications, are also reviewed.

Extended evaluation of effects of anoxia on ventricular performance and compliance

Eight dogs were prepared by implanting a left ventricular pressure transducer, aortic flow probe, and endocardial ultrasound crystals across the maximum transverse left ventricular diameter. In an unanesthetized state, the dogs were evaluated at rest and with acute volume loading, both before ischemic cardiac arrest and sequentially (2, 4, 6, 12, 24, and 48 hours) after 20 minutes of arrest during normothermic cardiopulmonary bypass. At a left ventricular end-diastolic diameter comparable to preoperative levels, left ventricular systolic pressure, heart rate, and rate of rise of left ventricular pressure were not changed, but at 2 to 6 hours there was a significant decrease in cardiac output (p less than 0.01), left ventricular stroke work (p less than 0.01), ejection fraction (p less than 0.05), maximum rate of systolic diameter shortening (p less than 0.05), and circumferential fiber shortening (p less than 0.05). They gradually returned to control levels by 24 hours postoperatively. Left ventricular compliance, as measured by left ventricular end-diastolic pressure at a set end-diastolic diameter and by left ventricular diastolic pressure/diameter, was reduced at 2 hours (p less than 0.01) and gradually returned to control values at 48 hours. Thus, reversible myocardial injury due to anoxia is associated with both decreased contractility and compliance, with resultant depressed left ventricular performance for 24 to 48 hours after injury.