Coronary occlusive disease and late graft failure after cardiac transplantation

Application of nanomaterials in heart transplantation: a narrative review

Background and Objective

Heart transplantation (HT) is a therapeutic option for end-stage heart disease. Still, it faces many challenges, especially the shortage of donor sources and the poor durability of grafts, which are the two critical issues. In this review, we generalize the application of existing nanomedicine technologies in donor management as well as prevention and diagnosis of post-transplantation complications, also including the current preclinical studies of nanomaterials in cardiac tissue engineering and gene-editing xeno-donor grafts. Finally, we discuss the remaining problems and future directions of nanomaterials in the field of HT.

Methods

A narrative review using current search of the most recent literature on the topic. The terms "nanomaterials", "nano medicine'', "Heart transplantation (HT)", "Nano-drug delivery system (NDDS)" or their combination were searched in PubMed and Google Scholar. The specified timeframe began from 1990, and we prioritized publications mainly from the last 10 years.

Key Content and Findings

Nano-systems integrating therapeutic and diagnostic functions have been applied to cardiovascular diseases (CVDs) with their unique advantages in multiple fields such as drug delivery, tissue engineering, gene editing, imaging, biomarker editing, and many other aspects. In terms of transplantation, the preservation, transportation, and pretreatment of donor hearts machine perfusion (MP) provide the possibility for nano-systems with unique features, and therapeutic and diagnostic functions to be directly and passively targeted in order to improve the functional status of the transplanted organs or to increase the ability to tolerate the graft of patients. The development of nano-imaging, nanosensor, and nano biomarker technologies are also being applied to monitor the status of transplant recipients for early prevention and treatment of post-transplantation-related complications. Nanomaterials combined with cardiac tissue engineering and gene editing technologies could also expand graft sources and alleviate donor shortages.

Conclusions

Although the overall research on nanomaterial applications in the field of HT is in its infancy, its role in improving the prognosis of transplant recipients and breaking the current dilemma of HT is clear. However, before nanotechnologies can be translated into clinical applications in the future, they must be aimed at ensuring the drug delivery system's safety and pose a challenge in the direction of the ability to intervene with multiple drugs in combination.

Outcomes among heart transplant recipients following acute coronary syndrome: A nationwide population based study

BACKGROUND

For patients with refractory heart failure despite optimal medical therapy, orthotopic heart transplantation (OHT) remains the treatment of choice. Since transplanted hearts have variable cardiac denervation and acute coronary syndrome often presents as a silent myocardial infarction or with atypical symptoms, the true impact of ACS on outcomes within this population needs more study. The aim of this study is to evaluate in-hospital mortality in post-transplant patients with ACS.

METHODS

Utilizing data from the 2002-15 Nationwide Inpatient Sample database, patients with a primary diagnosis of acute coronary syndrome among those with prior heart transplantation were included. A risk adjusted regression analysis was performed to assess if ACS post-OHT had an independent impact on the risk of in-hospital mortality. A 2:1 propensity matching was used to match ACS patients with and without OHT, respectively to assess differences in mortality.

RESULTS

A total of 3,224,073 patients with a primary diagnosis of acute coronary syndrome were included, of which 842 (0.03%) were heart-transplant recipients. The type of ACS: NSTEMI (76.0% vs 74.5%; p = 0.32) and STEMI (24.8% vs 26.7%; p = 0.21) between heart transplant and non-heart transplant patients was similar in both groups. Following ACS, patients with heart transplant were more likely to have accompanying shock of any etiology (15.6% vs 3.8%; p < 0.001) and cardiogenic shock (11.2% vs 2.6%; p < 0.001) compared to those with native hearts. OHT patients also had significantly higher in-hospital mortality (14.3% vs. 3.7%; p < 0.001) that remain significant following regression analysis (aOR 3.6, 95% CI 2.8-4.5; p < 0.001) irrespective of the presence of cardiogenic shock compared to native hearts. This relationship remained consistent following propensity matching where patients with OHT had significantly higher in-hospital mortality (13.5% vs. 7%; p < 0.001).

CONCLUSIONS

ACS following OHT was more likely to have accompanying cardiogenic shock. ACS in the setting of prior OHT remained a strong independent predictor of higher mortality as compared to native hearts.

Interventions for preventing thrombosis in solid organ transplant recipients

BACKGROUND

Graft thrombosis is a well-recognised complication of solid organ transplantation and is one of the leading causes of graft failure. Currently there are no standardised protocols for thromboprophylaxis. Many transplant units use unfractionated heparin (UFH) and fractionated heparins (low molecular weight heparin; LMWH) as prophylaxis for thrombosis. Antiplatelet agents such as aspirin are routinely used as prophylaxis of other thrombotic conditions and may have a role in preventing graft thrombosis. However, any pharmacological thromboprophylaxis comes with the theoretical risk of increasing the risk of major blood loss following transplant. This review looks at benefits and harms of thromboprophylaxis in patients undergoing solid organ transplantation.

OBJECTIVES

To assess the benefits and harms of instituting thromboprophylaxis to patients undergoing solid organ transplantation.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 10 November 2020 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) and quasi-RCTs designed to examine interventions to prevent thrombosis in solid organ transplant recipients. All donor types were included (donor after circulatory (DCD) and brainstem death (DBD) and live transplantation). There was no upper age limit for recipients in our search.

DATA COLLECTION AND ANALYSIS

The results of the literature search were screened and data collected by two independent authors. Dichotomous outcome results were expressed as risk ratio (RR) with 95% confidence intervals (CI). Random effects models were used for data analysis. Risk of bias was independently assessed by two authors using the risk of bias assessment tool. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

We identified nine studies (712 participants). Seven studies (544 participants) included kidney transplant recipients, and studies included liver transplant recipients. We did not identify any study enrolling heart, lung, pancreas, bowel, or any other solid organ transplant recipient. Selection bias was high or unclear in eight of the nine studies; five studies were at high risk of bias for performance and/or detection bias; while attrition and reporting biases were in general low or unclear. Three studies (180 participants) primarily investigated heparinisation in kidney transplantation. Only two studies reported on graft vessel thrombosis in kidney transplantation (144 participants). These small studies were at high risk of bias in several domains and reported only two graft thromboses between them; it therefore remains unclear whether heparin decreases the risk of early graft thrombosis or non-graft thrombosis (very low certainty). UFH may make little or no difference versus placebo to the rate of major bleeding events in kidney transplantation (3 studies, 155 participants: RR 2.92, 95% CI 0.89 to 9.56; I² = 0%; low certainty evidence). Sensitivity analysis using a fixed-effect model suggested that UFH may increase the risk of haemorrhagic events compared to placebo (RR 3.33, 95% CI 1.04 to 10.67, P = 0.04). Compared to control, any heparin (including LMWH) may make little or no difference to the number of major bleeding events (3 studies, 180 participants: RR 2.70, 95% CI 0.89 to 8.19; I² = 0%; low certainty evidence) and had an unclear effect on risk of readmission to intensive care (3 studies, 180 participants: RR 0.68, 95% CI 0.12 to 3.90, I² = 45%; very low certainty evidence). The effect of heparin on our other outcomes (including death, patient and graft survival, transfusion requirements) remains unclear (very low certainty evidence). Three studies (144 participants) investigated antiplatelet interventions in kidney transplantation: aspirin versus dipyridamole (1), and Lipo-PGE₁ plus low-dose heparin to "control" in patients who had a diagnosis of acute rejection (2). None of these reported on early graft thromboses. The effect of aspirin, dipyridamole and Lipo PGE₁ plus low-dose heparin on any outcomes is unclear (very low certainty evidence). Two studies (168 participants) assessed interventions in liver transplants. One compared warfarin versus aspirin in patients with pre-existing portal vein thrombosis and the other investigated plasmapheresis plus anticoagulation. Both studies were abstract-only publications, had high risk of bias in several domains, and no outcomes could be meta-analysed. Overall, the effect of any of these interventions on any of our outcomes remains unclear with no evidence to guide anti-thrombotic therapy in standard liver transplant recipients (very low certainty evidence).

AUTHORS' CONCLUSIONS

Overall, there is a paucity of research in the field of graft thrombosis prevention. Due to a lack of high quality evidence, it remains unclear whether any therapy is able to reduce the rate of early graft thrombosis in any type of solid organ transplant. UFH may increase the risk of major bleeding in kidney transplant recipients, however this is based on low certainty evidence. There is no evidence from RCTs to guide anti-thrombotic strategies in liver, heart, lung, or other solid organ transplants. Further studies are required in comparing anticoagulants, antiplatelets to placebo in solid organ transplantation. These should focus on outcomes such as early graft thrombosis, major haemorrhagic complications, return to theatre, and patient/graft survival.

A primer for managing cardiac transplant patients in the emergency department setting

BACKGROUND

Cardiac transplant is an effective long-term management option for several severe cardiac diseases. These cardiac transplant patients may present to the emergency department with a range of issues involving the cardiac transplantation, including complications due to their transplant as well as altered presentations of disease resulting from their transplant.

OBJECTIVE

This narrative review provides a focused guide to the evaluation and management of patients with cardiac transplantation and its complications.

DISCUSSION

Cardiac transplant is an effective therapy for end-stage heart failure. A transplanted heart varies both anatomically and physiologically from a native heart. Several significant complications may occur. Graft failure, rejection, and infection are common causes of morbidity and mortality within the first year of transplant. As these patients are on significant immunosuppressive medication regimens, they are at risk of infection, but inadequate immunosuppression increases the risk of acute rejection. A variety of dysrhythmias such as atrial fibrillation and ventricular dysrhythmias may occur. These patients are also at risk of acute coronary syndrome, cardiac allograft vasculopathy, and medication adverse events. Importantly, patients with acute coronary syndrome can have an altered presentation with the so-called "painless" myocardial infarction. Consultation with the transplant physician is recommended, if available, for these patients to assist in evaluation and management.

CONCLUSIONS

An understanding of the presentations and various complications that may affect patients with cardiac transplant will assist emergency clinicians in the care of these patients.

Diagnostic accuracy of dobutamine stress echocardiography in the detection of cardiac allograft vasculopathy in heart transplant recipients: A systematic review and meta-analysis study

BACKGROUND

Dobutamine stress echocardiography (DSE) is a well-established imaging modality used to screen patients with mild-to-moderate risk for coronary artery disease. In heart transplantation recipients, cardiac allograft vasculopathy (CAV) is a common and lethal complication. The use of DSE to detect CAV showed promising results initially, but later studies showed limitation in its use to detect CAV. It is unclear if this cohort of patients derives benefit from DSE.

METHODS

We searched PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), Embase, and Scopus from inception through March 2018 for studies examining the accuracy of DSE in correlation to coronary angiography (CA) or intravascular ultrasound (IVUS) to detect CAV. Original studies comparing the ability of DSE to detect CAV in comparison with CA or IVUS were included. Relevant data were extracted and hierarchical summary receiver operating characteristic analysis was conducted to test the overall diagnostic accuracy of DSE for patients with CAV.

RESULTS

Eleven studies (749 participants) met the inclusion criteria. The sensitivity of DSE varied from 1.7% to 93.8%, and specificity, from 54.8% to 98.8%. Pooled sensitivity was 60.2% (95% confidence interval (CI), 33.0%-82.3%) and specificity 85.7% (95% CI, 73.8%-92.7%). DSE had an overall diagnostic odds ratio (OR) of 9.1 (95% CI, 4.6-17.8), positive likelihood ratio (LR+) of 4.1 (95% CI, 2.8-6.1), negative likelihood ratio (LR-) of 0.47 (95% CI: 0.23-0.73), and area under curve (AUC) of 0.73 (95% CI, 0.72-0.75). Heterogeneity among studies was not statistically significant (τ²  = 0.32, Cochran's Q = 9.5, P = 0.483).

CONCLUSION

Dobutamine stress echocardiography has a limited sensitivity to detect early CAV but its specificity is much higher. There remains a need for an alternative noninvasive modality which will have both high sensitivity and high specificity for detecting CAV.

Lipid profile and cardiovascular risk factors in pediatric liver transplant recipients

Cardiovascular diseases induce long-term morbidity and mortality of adult LT recipients. The aim of this retrospective study was to assess CVRF, lipid abnormalities, and atherosclerosis (appraised by c-IMT), more than 10 yr after pediatric LT. Thirty-one children who underwent LT between December 1990 and December 2000 were included. Median age at LT was 14 months (range 4-64), and median follow-up after LT was 11.9 yr (range 9.0-17.3). In our cohort, obesity (9.7%) and treated hypertension (9.7%) were rare. None of the patients was smoker or diabetic. High TC and TG were both observed in 6.5% of the patients. The mean c-IMT for male patients was 1.22 ± 1.55 and 1.58 ± 1.23 mm in female patients. Seven patients (22%) had a mean c-IMT above +2 s.d. Values below the 5th percentile were noted for LDL-cholesterol (58.1%), HDL-cholesterol (25.8%), apolipoprotein B (40%), and apolipoprotein A1 (20%). LDL-cholesterol and apolipoprotein B levels were significantly lower in patients treated by tacrolimus in comparison with CsA (p < 0.05). In conclusion, our results suggest that pediatric LT patients do not present significant CVRF; moreover, instead of hyperlipidemia, hypocholesterolemia (LDL-C) is frequent and immunosuppressive therapy is probably the cause.

Cold ischemia contributes to the development of chronic rejection and mitochondrial injury after cardiac transplantation

Chronic rejection (CR) remains an unsolved hurdle for long-term heart transplant survival. The effect of cold ischemia (CI) on progression of CR and the mechanisms resulting in functional deficit were investigated by studying gene expression, mitochondrial function, and enzymatic activity. Allogeneic (Lew→F344) and syngeneic (Lew→Lew) heart transplantations were performed with or without 10 h of CI. After evaluation of myocardial contraction, hearts were excised at 2, 10, 40, and 60 days for investigation of vasculopathy, gene expression, enzymatic activities, and mitochondrial respiration. Gene expression studies identified a gene cluster coding for subunits of the mitochondrial electron transport chain regulated in response to CI and CR. Myocardial performance, mitochondrial function, and mitochondrial marker enzyme activities declined in all allografts with time after transplantation. These declines were more rapid and severe in CI allografts (CR-CI) and correlated well with progression of vasculopathy and fibrosis. Mitochondria related gene expression and mitochondrial function are substantially compromised with the progression of CR and show that CI impacts on progression, gene profile, and mitochondrial function of CR. Monitoring mitochondrial function and enzyme activity might allow for earlier detection of CR and cardiac allograft dysfunction.

Vitamins and cardiovascular disease

CVD is a major cause of mortality and morbidity in the Western world. In recent years its importance has expanded internationally and it is believed that by 2020 it will be the biggest cause of mortality in the world, emphasising the importance to prevent or minimise this increase. A beneficial role for vitamins in CVD has long been explored but the data are still inconsistent. While being supported by observational studies, randomised controlled trials have not yet supported a role for vitamins in primary or secondary prevention of CVD and have in some cases even indicated increased mortality in those with pre-existing late-stage atherosclerosis. The superiority of combination therapy over single supplementation has been suggested but this has not been confirmed in trials. Studies have indicated that beta-carotene mediates pro-oxidant effects and it has been suggested that its negative effects may diminish the beneficial effects mediated by the other vitamins in the supplementation cocktail. The trials that used a combination of vitamins that include beta-carotene have been disappointing. However, vitamin E and vitamin C have in combination shown long-term anti-atherogenic effects but their combined effect on clinical endpoints has been inconsistent. Studies also suggest that vitamins would be beneficial to individuals who are antioxidant-deficient or exposed to increased levels of oxidative stress, for example, smokers, diabetics and elderly patients, emphasising the importance of subgroup targeting. Through defining the right population group and the optimal vitamin combination we could potentially find a future role for vitamins in CVD.

Cardiac lymphatic interruption is a major cause for allograft failure after cardiac transplantation

Cardiac transplantation is one of the most effective treatments of end stage heart failure to date, although it comes with risks. One of the major complications of cardiac transplantation is allograft failure, which is caused by ischemic injuries, pulmonary hypertension and chronic rejection. Recent animal and human studies have demonstrated that cardiac lymphatic obstruction leads to significant myocardial fibrosis and depression in contractile forces. We hypothesize that lymphatic interruption, which is almost inevitable after cardiac transplantation, is a major cause of cardiac allograft failure through direct damages to the myocardium and also through the formation of allograft coronary vasculopathy.

Treatment of allograft vasculopathy in heart transplantation

Cardiac allograft vasculopathy remains one of the main causes of morbidity and mortality after heart transplantation, although its impact is becoming somewhat smaller as prophylactic measures are implemented. Advances in the understanding of the molecular and cellular mechanisms involved in the genesis and development of cardiac allograft vasculopathy are opening ways for new diagnostic and therapeutic strategies. Successful prophylaxis of the early stages of the disease has been demonstrated with the use of newer immunosuppressive agents, such as sirolimus and everolimus, that will probably be included in future protocols. For most patients with established cardiac allograft vasculopathy, currently available revascularisation methods and retransplantation are not appropriate options. Antiproliferative agents could provide significant improvement in terms of symptom relief and prognosis, but their definite value must be proven in well-designed trials.

Plasma kinetics of a cholesterol-rich microemulsion in patients submitted to heart transplantation

BACKGROUND

Development of coronary graft disease is currently the main cause of late heart-transplantation (HT) failure. HT patients frequently show hypercholesterolemia as well as alterations in chylomicron metabolism. These postHT changes may be important in coronary graft disease development. To clarify whether hypercholesterolemia is caused by decreased low-density lipoprotein (LDL) removal from the plasma, we studied the plasma kinetics of a cholesterol-rich emulsion that binds to LDL receptor.

METHODS

We studied 13 HT patients and 13 healthy normolipidemic subjects paired for sex, age, and body mass index. An emulsion labeled with C-cholesteryl oleate was injected intravenously, and blood samples were collected in predetermined intervals (5 minutes, 1, 2, 4, 6, and 8 hours) to determine the radioactivity decay curves and to calculate the fractional clearance rates (FCR).

RESULTS

The plasma level of total cholesterol, LDL cholesterol, high-density lipoprotein cholesterol, and apo B were greater in HT group than in the control group (P<0.005). FCR C-cholesteryl oleate was smaller in HT patients when compared with the control group (P=0.02).

CONCLUSION

The results showed that HT patients have a deficiency in the mechanisms of LDL removal from the plasma, as tested by the cholesterol-rich emulsion, and this may be important in the development of coronary graft disease.

Influence of tumor necrosis factor-alpha gene-308 polymorphism on the development of coronary vasculopathy after cardiac transplantation

BACKGROUND

Tumor necrosis factor-alpha (TNF-alpha) has been implicated in cardiovascular disease. Polymorphism of the TNF-alpha gene promoter region (position -308) influences an individual's production of TNF-alpha. This affects susceptibility to acute rejection after cardiac transplantation. Because the highest serum levels of TNF-alpha have been found in recipients with cardiac transplant vasculopathy and because TNF-alpha blockade can prevent the disease in rabbits, we investigated the effect of TNF-alpha promoter polymorphism on the development of vasculopathy in human cardiac allograft recipients.

METHODS

Using sequence-specific primers to the TNF-alpha gene and polymerase chain reaction, the genotypes of 147 cardiac transplant recipients and 134 heart donors were identified. An association was sought between the presence of high-producing (A homozygotes, GA heterozygotes) or low-producing (G homozygotes) TNF-alpha genotype and the development of coronary vasculopathy, diagnosed by routine surveillance coronary angiography.

RESULTS

We found that 31.9% of recipients and 27.0% of donors were high TNF-alpha producers. The presence of the high-producing TNF-alpha allele led to an earlier diagnosis of vasculopathy; 3.42 years (+/- 91.3 days) vs 3.84 years (+/- 76.3 days) for high- and low-producing cardiac graft recipients, respectively; 3.52 years (+/- 87.3 days) vs 3.78 years (+/- 77.4 days) for high- and low-producing donor grafts, respectively. However, neither of these differences were significant. By Kaplan Meier actuarial analysis and log-rank test, TNF-alpha polymorphism had no effect on the freedom from vasculopathy when considering either recipient (p = 0.99) or donor (p = 0.86) TNF-alpha genotype. Multivariate analysis identified increasing donor age and the number of acute rejection episodes of International Society for Heart and Lung Transplantation grade 3 or greater as independent risk factors for vasculopathy in both the recipient and donor cohorts.

CONCLUSIONS

Polymorphism at position -308 in the promoter region of the TNF-alpha gene fails to predict the development of cardiac transplant-related vasculopathy and cannot be used as a genetic risk marker. This may be because of the effects of immunosuppressive treatment.

Heterogeneity of coronary flow reserve in the examination of multiple individual allograft coronary arteries

BACKGROUND

Epicardial and resistance vessel function in the transplanted heart has been evaluated primarily in regions supplied by a single vessel. Heterogeneity of flow among multiple perfusion fields as a marker of early endothelial dysfunction in the microcirculation has not been evaluated previously. This study tested the hypothesis that increased variability of coronary flow reserve (CFR) among multiple vascular regions would be associated with allograft coronary vasculopathy.

METHODS AND RESULTS

One hundred six posttransplant patients undergoing cardiac catheterization had measurement of CFR in at least 3 major epicardial vessels. Patients were divided into those with minimal angiographic abnormalities (n=37) and those with no angiographic abnormalities (n=69). The ranges, coefficients of variation, and univariate and multivariate regression analyses of CFR were computed to determine the major clinical factors influencing the degree of variability. The abnormal angiographic group was older (54+/-11 versus 47+/-13 years; P<0.003), had older hearts (35+/-11 versus 27+/-10 years; P<0.005), and were further posttransplant (1626+/-1022 versus 931+/-984 days; P<0.0009). There was no difference in global CFR between groups (normal, 3.4+/-0.8 versus abnormal, 3.4+/-0.7; P=NS). The coefficient of variation of CFR was higher for the abnormal group (16.3+/-8.6% versus 11.0+/-5.5%; P<0. 0006). Univariate and multivariate predictors of increased variability in CFR included angiographic abnormalities, patient age, and body mass index. Both angiographic abnormalities and an elevated CV of CFR were predictive of a combined end point of death, congestive heart failure, or subsequent development of >/=50% coronary stenosis.

CONCLUSIONS

These data demonstrate that increased variability of CFR is associated with discernible allograft coronary arteriopathy and is predictive of outcome in patients after heart transplantation.

Myocardial lactate dehydrogenase subunit ratio in cardiac allograft recipients

BACKGROUND

Allograft coronary artery disease (CAD) is a major long-term complication in heart transplanted patients. However, the metabolic basis of allograft CAD remains to be fully elucidated. We analyzed the lactate dehydrogenase heart (H) and muscle (M) isoenzyme pattern in endomyocardial biopsy specimens and the evolution of the H/M ratio to test whether changes in this ratio could be the earliest manifestation of allograft CAD.

METHODS

Twenty-four heart transplant recipients were followed up for 12 months. Endomyocardial biopsy was performed at 1, 2, 3, 6, and 12 months after transplantation. Lactate dehydrogenase 1 through 5 isoenzymes were separated by electrophoresis, and the H/M ratio was calculated. Two groups of patients were identified: group 1 (n = 20), patients without allograft CAD; and group 2 (n = 4), patients with poor outcome (three deaths, 1 case of low cardiac output) and angiographic and histologic evidence of allograft CAD.

RESULTS

Both groups had similar H/M baseline values. The H/M ratio was higher (p = 0.01) in group 1 at 6 months (3.48 +/- 0.64 versus 2.17 +/- 0.43) and 12 months (3.76 +/- 0.92 versus 2.18 +/- 0.45) when compared with group 2. The H/M ratio increased from 2.78 +/- 0.89 at 1 month to 3.76 +/- 0.92 at 12 months (p = 0.02) in group 1 and decreased in group 2 (2.86 +/- 0.49 versus 2.18 +/- 0.45; not significant).

CONCLUSIONS

Changes in H/M ratio reflect an anaerobic shift in the lactate dehydrogenase isoenzyme composition and can be taken as an early indicator of allograft CAD.

Dobutamine stress echocardiography in orthotopic heart transplant recipients. VACOMED Research Group

OBJECTIVES

This study sought to determine whether dobutamine stress echocardiography could accurately identify coronary artery disease after heart transplantation.

BACKGROUND

After heart transplantation, coronary artery disease is related to either diffuse concentric intimal thickening or focal stenosis and may be underdiagnosed by coronary angiography.

METHODS

We enrolled 41 patients, a mean (+/- SD) of 40 +/- 20 months after heart transplantation, at the time of their routine control coronary angiogram. Three patients were excluded because of poor echogenicity on the angiogram and one because of ventricular premature beats. Standard echocardiographic views were acquired at baseline and at incremental dobutamine infusion levels (from 5 to a maximal dose of 40 micrograms/kg body weight per min at 3-min intervals). Regional wall motion score was calculated from a 16-segment model, and each segment was graded from 1 (normal) to 4 (dyskinesia). Coronary angiography was performed 24 h after dobutamine stress echocardiography, and angiograms were analyzed in blinded manner.

RESULTS

Twenty-three (62%) of 37 patients had normal coronary angiographic findings. Dobutamine stress echocardiography showed abnormalities in only 2 of 23 patients. Fourteen patients (38%) had abnormal angiographic findings, seven of whom had stenoses > 50%. Dobutamine stress echocardiography correctly identified the corresponding hypoperfused segments in these seven patients. More of interest were the other seven patients, of whom three had angiographic nonsignificant stenoses (< 50%), and four had minor diffuse coronary irregularities. Dobutamine stress echocardiography showed hypokinesia in five of these seven patients despite nonsignificant lesions at coronary angiography. The respective overall sensitivity and specificity of dobutamine stress echocardiography were 86% and 91%. At follow-up, 2 of the 37 patients had an acute myocardial infarction. Both had abnormal findings on dobutamine stress echocardiography: One had normal coronary angiographic results, and one had significant coronary lesions.

CONCLUSIONS

Dobutamine stress echocardiography is a useful technique for the diagnosis of coronary artery disease after heart transplantation. These preliminary results indicate that dobutamine stress echocardiography may have a predictive value for further ischemic events in heart transplant recipients.

Cardiac transplantation: a review

Cardiac transplantation is currently a highly successful treatment for selected patients with end-stage cardiac failure. The long-term results are limited by the development of coronary artery vasculopathy, infection and malignancy. The activity of transplantation programmes worldwide is severely limited by the availability of donor organs. Further refinements of immunosuppressive agents are likely to result in improved prevention of both acute and chronic rejection. The donor pool is unlikely to be significantly extended as a result of measures to increase donor organ supply. Alternative methods to allograft transplantation need further investigation to increase the number of therapeutic options available for those patients with end-stage heart failure.