Clinical and Exercise Test Determinants of Survival After Cardiac Transplantation *

Prognostic Role of Metabolic Exercise Testing in Heart Failure

Heart failure is a clinical syndrome with significant heterogeneity in presentation and severity. Serial risk-stratification and prognostication can guide management decisions, particularly in advanced heart failure, when progression toward advanced therapies or end-of-life care is warranted. Each currently utilized prognostic marker carries its own set of challenges in acquisition, reproducibility, accuracy, and significance. Left ventricular ejection fraction is foundational for heart failure syndrome classification after clinical diagnosis and remains the primary parameter for inclusion in most clinical trials; however, it does not consistently correlate with symptoms and functional capacity, which are also independently prognostic in this patient population. Utilizing the left ventricular ejection fraction as the sole basis of prognostication provides an incomplete characterization of this condition and is prone to misguide medical decision-making when used in isolation. In this review article, we survey and exposit the important role of metabolic exercise testing across the heart failure spectrum, as a complementary diagnostic and prognostic modality. Metabolic exercise testing, also known as cardiopulmonary exercise testing, provides a comprehensive evaluation of the multisystem (i.e., neurological, respiratory, circulatory, and musculoskeletal) response to exercise performance. These differential responses can help identify the predominant contributors to exercise intolerance and exercise symptoms. Additionally, the aerobic exercise capacity (i.e., oxygen consumption during exercise) is directly correlated with overall life expectancy and prognosis in many disease states. Specifically in heart failure patients, metabolic exercise testing provides an accurate, objective, and reproducible assessment of the overall circulatory sufficiency and circulatory reserve during physical stress, being able to isolate the concurrent chronotropic and stroke volume responses for a reliable depiction of the circulatory flow rate in real time.

Prognostic value of cardiopulmonary exercise test after heart transplantation

BACKGROUND

The clinical utility of cardiopulmonary exercise testing (CPET) has not been extensively studied yet in heart transplantation (HTX) patients.

OBJECTIVE

To analyze the predictive value of the CPET on hospitalizations and mortality in HTX recipients.

METHODS

A retrospective cohort was performed from a secondary database. Patients > 18 years with HTX who underwent a CPET between 3 and 12 months after transplantation were included. Time to the first primary endpoint (HTX-related hospitalization) was analyzed and adjusted using Cox proportional hazards regression model.

RESULTS

A total of 122 patients (mean age 50.1 years, 77.0% men) were included. Fifty-seven patients (46.7%) had the primary endpoint. Peak VO₂ (HR .95; CI 95% .90-.99, P = .03), oxygen pulse (HR .57; CI 95% .34-.96, P = .03) and predicted VO₂ (HR .97; CI 95% .96-.99, P = .002) were associated with the endpoint. We did not find a significant association between the other variables and the outcome.

CONCLUSION

In HTX recipients, peak VO₂ , oxygen pulse, and predicted VO₂ were independently associated with hospitalizations at follow up.

New therapy, new challenges: The effects of long-term continuous flow left ventricular assist device on inflammation

Surgically implanted continuous flow left ventricular assist devices (CF-LVADs) are currently used in patients with end-stage heart failure (HF). However, CF-LVAD therapy introduces a new set of complications and adverse events in these patients. Major adverse events with the CF-LVAD include right heart failure, vascular dysfunction, stroke, hepatic failure, and multi-organ failure, complications that may have inflammation as a common etiology. Our aim was to review the current evidence showing a relationship between these adverse events and elevated levels of inflammatory biomarkers in CF-LVAD recipients.

Exercise limitation following transplantation

Organ transplantation is one of the medical miracles or the 20th century. It has the capacity to substantially improve exercise performance and quality of life in patients who are severely limited with chronic organ failure. We focus on the most commonly performed solid-organ transplants and describe peak exercise performance following recovery from transplantation. Across all of the common transplants, evaluated significant reduction in VO2peak is seen (typically renal and liver 65%-80% with heart and/or lung 50%-60% of predicted). Those with the lowest VO2peak pretransplant have the lowest VO2peak posttransplant. Overall very few patients have a VO2peak in the normal range. Investigation of the cause of the reduction of VO2peak has identified many factors pre- and posttransplant that may contribute. These include organ-specific factors in the otherwise well-functioning allograft (e.g., chronotropic incompetence in heart transplantation) as well as allograft dysfunction itself (e.g., chronic lung allograft dysfunction). However, looking across all transplants, a pattern emerges. A low muscle mass with qualitative change in large exercising skeletal muscle groups is seen pretransplant. Many factor posttransplant aggravate these changes or prevent them recovering, especially calcineurin antagonist drugs which are key immunosuppressing agents. This results in the reduction of VO2peak despite restoration of near normal function of the initially failing organ system. As such organ transplantation has provided an experiment of nature that has focused our attention on an important confounder of chronic organ failure-skeletal muscle dysfunction.

Influence of different implantation techniques on long-term survival after orthotopic heart transplantation: an echocardiographic study

BACKGROUND

Orthotopic heart transplantation (OHT) was initially done by the biatrial technique, although the bicaval technique has recently become more popular. The aim of this study was to compare OHT outcomes when using the bicaval technique vs the biatrial technique.

METHODS

A total of 615 patients were transplanted at the Cleveland Clinic Foundation from January 1993 and October 2003 (biatrial technique: n = 293; bicaval technique: n = 322). The average follow-up period was 4.2 +/- 2.9 years (range 1 to 11 years). Patients who were supported with a left ventricular assist device (prior to transplant) and who could not be weaned off respiratory support were excluded.

RESULTS

Patients in both groups were similar with regard to pre-operative characteristics. The peri-operative mortality showed no statistical significant differences between the two groups. The left atrium was significantly more enlarged in the biatrial group. The bicaval group showed a significantly reduced incidence of tricuspid regurgitation. Survival at 10-year follow-up was 87.3% in the bicaval group and 79.9% in the biatrial group (p < 0.05). Left ventricular ejection fraction (LVEF), right ventricular ejection fraction (RVEF) and moderate to severe tricuspid regurgitation were significant risk factors for death in both groups. The bicaval technique showed a significantly better mortality outcome.

CONCLUSIONS

This study showed that the bicaval technique for OHT offers a better outcome than the biatrial technique. The significant reduction of left atrial size and atrioventricular valve regurgitation in the bicaval group may have a major impact on the long-term preservation of cardiac function and survival.

Heart transplantation in patients with extreme right ventricular failure

OBJECTIVE

Donor shortage and improved medical treatment of heart failure increase the prevalence of patients with extreme right ventricular failure and ascites to heart transplantation. The clinical outcome of heart transplantation in these patients has rarely been reported. Here, we sought to evaluate the clinical outcome of heart transplantation in patients with extreme right ventricular failure and refractory ascites.

METHODS

Data were collected by retrospective chart review.

RESULTS

Between 1993 and 2005, 12 patients with extreme right ventricular failure and refractory ascites underwent orthotopic heart transplantation at the authors' hospital. The causes of heart failure were congenital heart disease in four patients, dilated cardiomyopathy in two patients, rheumatic heart disease in two patients, coronary artery disease in two patients, and restrictive cardiomyopathy and transplant coronary artery disease each in one patient. Eight of 12 patients had previous cardiac operation. The findings of preoperative abdominal sonography were massive ascites in all patients, congestive liver in 11 patients, and probably cardiac cirrhosis in 1 patient. One patient underwent combined heart and kidney transplantations. There were six in-hospital deaths: bleeding in three patients and multiple organ failure in three patients. Major postoperative complications occurred in 10 patients: renal failure requiring dialysis in 9, bleeding requiring reoperation in 8 patients. Patients with previous cardiac operation had a higher mortality rate (5/7 vs 1/5).

CONCLUSIONS

Heart transplantation in patients with extreme right ventricular failure and refractory ascites was associated with high mortality and morbidity. The presence of previous cardiac operation implied even poor prognosis.

Clinical and Hemodynamic Profile of Patients With Advanced Heart Failure Considered for Heart Transplantation

INTRODUCTION

The present study evaluated the clinical and hemodynamic situation of patients with advanced heart failure considered for heart transplantation (HT) to examine the possible impact of prior cardiac disease.

METHODS

We analyzed the pretransplant clinical, echocardiographic, and hemodynamic parameters of 422 consecutive HT patients. Pediatric and heart plus lung transplants were excluded, as were retransplantations. The results were compared by dividing the patients into three groups according to the background heart disease that led to HT: ischemic heart disease (IHD), dilated myocardiopathy (DMC), or valvular disease.

RESULTS

Differences were observed in the baseline characteristics according to the type of heart disease. Male gender, hypertension, and diabetes were more frequent among IHD, while DMC patients tended to be younger. There were no differences in the clinical parameters such as liver and kidney function, in the functional class, or in the need for inotropic treatment over the days prior to transplantation. Likewise, no differences were recorded in the hemodynamic parameters, such as pulmonary pressure, pulmonary vascular resistance, or transpulmonary pressure gradient. As regards the echocardiographic parameters, the patients with DMC showed greater ventricular diameters and lesser ejection fractions for both ventricles.

CONCLUSION

No important differences were recorded in the clinical situation or hemodynamic parameters of patients with advanced heart failure accepted for transplantation, according to the background cardiac disease. This observation could be due to the homogenization by strict transplant waiting list inclusion criteria.

Hemodynamic and metabolic changes during exercise in calves with total artificial hearts of different sizes yet similar output

To evaluate the effects of downsizing of the total artificial heart (TAH), we compared the anaerobic threshold (AT) values in calves with two different types of TAH (Cleveland Clinic-Nimbus TAH and the downsized MagScrew TAH). Exercise studies were performed using a treadmill in 12 calves. During the exercise, parameters to obtain the AT were measured. To evaluate the determinants of the AT, a linear regression analysis was performed between AT and potential variables. AT values from 29 studies revealed no significant differences between the two different TAHs, with no significant differences in hemodynamic or oxygen metabolic parameters. AT values correlated well with pump flow/body weight (Q) multiplied by the hemoglobin level, regardless of the TAH used. In conclusion, downsizing of the original TAH design did not reduce AT without any significant differences in hemodynamic or oxygen metabolic parameters during exercise in calves.

Risk stratification for renal transplantation after cardiac or lung transplantation: single-center experience and review of the literature

BACKGROUND

Long-term survival after heart (HTx) or lung (LuTx) transplantation increases the risk for end-stage renal disease (ESRD). After HTx ESRD was reported to enhance mortality, and kidney transplantation (KTx) was shown to improve survival. However, prognostic factors in ESRD after HTx or LuTx are largely unknown.

METHODS

Single-center observational study in HTx and LuTx patients who accessed the KTx waiting list; baseline characteristics were correlated with mortality.

RESULTS

KTx was performed in 15 of 65 study patients. Survival was comparable on the KTx waiting list and in reference patients from the same center without ESRD. KTx significantly improved survival (5 years' survival 84.6% with KTx vs. 56.5% on the KTx waiting list, p = 0.030). None of the baseline parameters predicted mortality in the KTx group. Only on the KTx waiting list BMI (median 24.7 vs. 20.7; p < 0.05) and left ventricular ejection fraction (LVEF, median 63 vs. 53%, p < 0.008) significantly correlated with survival.

CONCLUSIONS

The risk for mortality after HTx or LuTx is not increased by ESRD, provided that patients meet access criteria for the KTx waiting list. KTx improves survival in ESRD after HTx or LuTx. BMI and LVEF may predict outcome in HTx/LuTx patients on the KTx waiting list.

A dilated inferior vena cava is a marker of poor survival

BACKGROUND

The inferior vena cava (IVC) morphology is often used to estimate right atrial pressure; however, the association of IVC morphology and outcome is poorly described.

METHODS

We evaluated 4383 consecutive outpatients (98% men) undergoing echocardiography at 1 of 3 Veterans Affairs laboratories.

RESULTS

Of the 3729 with adequate images, 3295 (88%) had a normal IVC (< 2 cm), 358 (10%) had a dilated IVC that collapsed at least 50% with inspiration, and 76 (2%) had dilated IVC that did not collapse. Compared with patients with a normal IVC, those with a dilated IVC were older (66 +/- 13 vs 69 +/- 12 years if dilated with collapse and 70 +/- 12 years if dilated without collapse, P = .0005) and were more likely to have a history of heart failure (11% vs 18% if dilated with collapse and 38% if dilated without collapse, P < .0001). The 90-day and 1-year survival rates were 99% and 95% for those with a normal IVC, 98% and 91% for those with a dilated IVC with collapse, and 89% and 67% for those with a dilated IVC without collapse (P < .0001). After adjustment for clinical and echocardiographic characteristics including left and right ventricular function and pulmonary artery pressure, a dilated IVC without collapse remained associated with increased mortality: hazard ratio 1.43 (1.29-1.57 compared with a normal IVC, P < .0001).

CONCLUSION

A dilated IVC without collapse with inspiration is associated with worse survival in men independent of a history of heart failure, other comorbidities, ventricular function, and pulmonary artery pressure.

Serial measurements of peripheral vascular reactivity and exercise capacity in congestive heart failure and after heart transplantation

BACKGROUND

The regulation of nutritive blood flow to skeletal muscles during exercise seems to make an important contribution to exercise capacity. In congestive heart failure (CHF) this regulation seems to be impaired, with attenuated peripheral vasodilatory capacity. The results regarding improvement of peripheral vasoreactivity after heart transplantation (HTx) are conflicting, and the contribution of impaired peripheral vasoreactivity to the observed reduced exercise capacity among heart transplant recipients (HTR) has not been well elucidated. We therefore assessed the reversibility of impaired vasoreactivity in forearm and calf after HTx with relationship to exercise capacity.

METHODS AND RESULTS

The vasoreactivity of both forearm and calf was studied with venous occlusion plethysmography and related to exercise capacity in 64 patients with CHF and in 22 controls. Of these patients, 29 patients underwent HTx, and the same measurements were performed 10 days, 6 months and 1 year after HTx, and in a group of 15 HTR who had undergone HTx several years ago. Our main findings were (1) impaired resting blood flow in patients with CHF improved after HTx and even surpassed levels of controls; (2) peak forearm blood flow remained attenuated early after HTx, but normalized during the first year postoperatively; (3) both forearm and calf minimal resistance remained elevated after HTx; (4) vascular reactivity displays regional variations in forearm and calf both during CHF and after HTx; and (5) peripheral vascular reactivity relate to exercise performance in both patients with CHF and HTR, but the relationship seemed more pronounced in CHF.

CONCLUSION

With impaired vasoreactivity related to limited exercise capacity in CHF, improvement is evident after HTx, but both forearm and calf minimal resistance remains elevated. These findings suggest increased vasoconstrictor drive to both exercising and non-exercising muscles, possibly contributing to persistent physical limitation after HTx.