Impaired exercise capacity late after cardiac transplantation: influence of chronotropic incompetence, hypertension, and calcium channel blockers

The role of non-invasive imaging modalities in cardiac allograft vasculopathy: an updated focus on current evidences

Cardiac allograft vasculopathy (CAV) is an obliterative and diffuse form of vasculopathy affecting almost 50% of patients after 10 years from heart transplant and represents the most common cause of long-term cardiovascular mortality among heart transplant recipients. The gold standard diagnostic technique is still invasive coronary angiography, which however holds potential for complications, especially contrast-related kidney injury and procedure-related vascular lesions. Non-invasive and contrast-sparing imaging techniques have been advocated and investigated over the past decades, in order to identify those that could replace coronary angiography or at least reach comparable accuracy in CAV detection. In addition, they could help the clinician in defining optimal timing for invasive testing. This review attempts to examine the currently available non-invasive imaging techniques that may be used in the follow-up of heart transplant patients, spanning from echocardiography to nuclear imaging, cardiac magnetic resonance and cardiac computed tomography angiography, weighting their advantages and disadvantages.

Heart rate kinetics during standard cardiopulmonary exercise testing in heart transplant recipients: a longitudinal study

AIMS

Heart transplantation (HTx) results in complete autonomic denervation of the donor heart, causing resting tachycardia and abnormal heart rate (HR) responses to exercise. We determined the time course of suggestive cardiac reinnervation post HTx and investigated its clinical significance.

METHODS AND RESULTS

Heart rate kinetics during standard cardiopulmonary exercise testing at 2.5-5 years after HTx was assessed in 58 patients. According to their HR increase 30 s after exercise onset, HTx recipients were classified as denervated (slow responders: <5 beats per minute [b.p.m.]) or potentially reinnervated (fast responders: ≥5 b.p.m.). Additionally, in 30 patients, longitudinal changes of maximal oxygen consumption and HR kinetics were assessed during the first 15 post-operative years. At 2.5-5 years post HTx, 38% of our study population was potentially reinnervated. Fast responders were significantly younger (41 ± 15 years) than slow responders (53 ± 13 years, P = 0.003) but did not differ with regard to donor age, immunosuppressive regime, cardiovascular risk factors, endomyocardial biopsy, or vasculopathy parameters. While HR reserve (56 ± 20 vs. 39 ± 15 b.p.m., P = 0.002) and HR recovery after 60 s (15 ± 11 vs. 5 ± 6 b.p.m., P < 0.001) were greater in fast responders, resting HR, peak HR of predicted, and peak oxygen consumption of predicted were comparable.

CONCLUSIONS

Signs of reinnervation occurred mainly in younger patients. Maximal oxygen consumption was independent of HR kinetics.

Pharmacological vs Exercise Stress Echocardiography for Detection of Cardiac Allograft Vasculopathy

Objective

To test the hypothesis that exercise and dobutamine would provide levels of cardiac stress that are comparable to those achieved in a general stress test population, and to one another, in heart transplant recipients.

Patients and Methods

From February 10, 2015, to December 31, 2017, 81 patients underwent exercise stress (N=45) or dobutamine stress (N=36) echocardiography at a mean ± SD of 11±14 years (range, 1-29 years) after heart transplant. Hemodynamic and inotropic responses were compared between groups, and to a prior test, longitudinally. The primary outcome was peak heart rate (HR) × systolic blood pressure (SBP).

Results

Peak exercise HR × SBP × 10⁻³ was a mean ± SD of 24.9±4.9 mm Hg/min for exercise stress vs 21.2±3.4 mm Hg/min during dobutamine stress (P<.001). In 35 patients who underwent a dobutamine stress test followed later by another dobutamine stress test, peak HR × SBP changed by 4.2%±16% (P=.05). In 25 patients who underwent a dobutamine stress test followed later by an exercise stress test, peak HR × SBP increased by 12%±23% (P=.002 vs serial dobutamine stress tests). Peak exercise HR did not correlate with time since heart transplant, patient age, or graft age. Peak dobutamine HR correlated modestly with patient age (r²=0.28). Inotropic responses were similar in both groups. Overall, patients preferred exercise stress testing to dobutamine stress tests. Dobutamine stress testing was more expensive than exercise stress tests.

Conclusion

Exercise induces a level of cardiac stress that is equal to or greater than dobutamine-induced stress, at lower cost, in heart transplant recipients who express preference for exercise stress testing.

Effects of Exercise and Sport in Solid Organ Transplant Recipients: A Review

Solid organ transplantation is the criterion standard treatment for many with end-organ failure and can offer a new independence from the burden of disease. However solid organ transplant recipients (SOTRs) remain at high risk of cardiovascular (CV) disease, and poor quality of life and physical functioning. Increasing physical activity and exercise can improve the health of the general population; however, the effects on those with a transplant remain unclear. Intensive exercise and sporting activity has the potential to be beneficial, although there remain concerns particularly around the effects on immune function and the CV system. This review summarizes what is known about the effects of exercise on determinants of health in SOTRs and then collates the available literature investigating the consequences of intensive exercise and sport on the health of SOTR. There is a paucity of high-quality research, with most evidence being case studies or anecdotal; this is understandable given the relatively few numbers of SOTRs who are performing sport and exercise at a high level. However, if suitable evidence-based guidelines are to be formed and SOTRs are to be given reassurances that their activity levels are not detrimental to their transplanted organ and overall health, then more high-quality studies are required.

Acute blood pressure response in hypertensive elderly women immediately after water aerobics exercise: A crossover study

Water aerobics exercise is widely recommended for elderly people. However, little is known about the acute effects on hemodynamic variables. Thus, we assessed the effects of a water aerobic session on blood pressure in hypertensive elderly women. Fifty hypertensive elderly women aged 67.8 ± 4.1 years, 1.5 ± 0.6 m high and BMI 28.6 ± 3.9 kg/m², participated in a crossover clinical trial. The experiment consisted of a 45-minute water aerobics session (70%-75% HRmax adjusted for the aquatic environment) (ES) and a control session (no exercise for 45 minutes) (CS). Heart rate was monitored using a heart rate monitor and systolic blood pressure (SBP) and diastolic (DBP) measurements were taken using a semi-automatic monitor before and immediately after the sessions, and at 10, 20 and 30 minutes thereafter. It was using a generalized estimating equation (GEE) with Bonferroni's post-hoc test (p < 0.05). At the end of the experimental session, ES showed a rise in SBP of 17.4 mmHg (14.3%, p < 0.001) and DBP of 5.4 mmHg (7.8%, p < 0.001) compared to CS. At 10 minutes after exercise, BP declined in ES by a greater magnitude than in CS (SBP 7.5 mmHg, 6.2%, p = 0.005 and DBP 3.8 mmHg, 5.5%, p = 0.013). At 20 minutes after exercise and thereafter, SBP and DBP were similar in both ES and CS. In conclusion, BP returned to control levels within 10-20 minutes remaining unchanged until 30 minutes after exercise, and post-exercise hypotension was not observed. Besides, BP changed after exercise was a safe rise of small magnitude for hypertensive people.

Adrenergic Receptor Polymorphism and Maximal Exercise Capacity after Orthotopic Heart Transplantation

Background

Maximal exercise capacity after heart transplantion (HTx) is reduced to the 50–70% level of healthy controls when assessed by cardiopulmonary exercise testing (CPET) despite of normal left ventricular function of the donor heart. This study investigates the role of donor heart β₁ and β₂- adrenergic receptor (AR) polymorphisms for maximal exercise capacity after orthotopic HTx.

Methods

CPET measured peak VO₂ as outcome parameter for maximal exercise in HTx recipients ≥9 months and ≤4 years post-transplant (n = 41; mean peak VO₂: 57±15% of predicted value). Donor hearts were genotyped for polymorphisms of the β₁-AR (Ser49Gly, Arg389Gly) and the β₂-AR (Arg16Gly, Gln27Glu). Circumferential shortening of the left ventricle was measured using magnetic resonance based CSPAMM tagging.

Results

Peak VO₂ was higher in donor hearts expressing the β₁-Ser49Ser alleles when compared with β₁-Gly49 carriers (60±15% vs. 47±10% of the predicted value; p = 0.015), and by trend in cardiac allografts with the β₁-AR Gly389Gly vs. β₁-Arg389 (61±15% vs. 54±14%, p = 0.093). Peak VO2 was highest for the haplotype Ser49Ser-Gly389, and decreased progressively for Ser49Ser-Arg389Arg > 49Gly-389Gly > 49Gly-Arg389Arg (adjusted R² = 0.56, p = 0.003). Peak VO₂ was not different for the tested β₂-AR polymorphisms. Independent predictors of peak VO₂ (adjusted R² = 0.55) were β₁-AR Ser49Gly SNP (p = 0.005), heart rate increase (p = 0.016), and peak systolic blood pressure (p = 0.031). Left ventricular (LV) motion kinetics as measured by cardiac MRI CSPAMM tagging at rest was not different between carriers and non-carriers of the β₁-AR Gly49allele.

Conclusion

Similar LV cardiac motion kinetics at rest in donor hearts carrying either β₁-AR Gly49 or β₁-Ser49Ser variant suggests exercise-induced desensitization and down-regulation of the β₁-AR Gly49 variant as relevant pathomechanism for reduced peak VO₂ in β₁-AR Gly49 carriers.

Lifestyle and Health Status Differ over Time in Long-Term Heart Transplant Recipients

Objective

To describe differences in lifestyle and health status across 5 posttransplant periods.

Methods

The sample consisted of 126 heart transplant recipients (87% men) grouped by time after transplantation: group 1, 12 to 24 months (n = 13); group 2, 25 to 48 months (n = 19); group 3, 49 to 72 months (n = 24); group 4, 72 to 96 months (n = 27); and group 5, ≥ 97 months (n = 43). Data were obtained using demographic and health status evaluation forms and the Lifestyle Profile-II, which measures physical activity, nutrition, health responsibility, interpersonal relationships, stress management, and spiritual growth.

Results

Most often reported lifestyle attributes were spiritual growth and interpersonal relationships. Least often reported was physical activity. Pairwise comparisons revealed that groups 3 (χ2= 16.4; SD = 4.8; P = .03) and 4 (χ2 = 16.6; SD = 5.8; P = .04) had lower physical activity than group 2 (χ2 = 21.3; SD = 5.2). Health status evaluation revealed that there were no group differences in systolic ( P = .46) or diastolic ( P = .77) blood pressure. Although creatinine was elevated, there were no group differences ( P = .86). High-density lipoprotein was higher than 42 mg/dL in all groups, but there were differences across groups in low-density lipoprotein ( P = .003). Groups 1 (χ2 = 139.2; SD = 38.5) and 2 (χ2 = 141.0; SD = 47.8) were different than group 5 (χ2 = 112.9; SD = 36.1; P = .05). There were group differences in cholesterol ( P = .002), with lower levels in groups 4 (χ2 = 190.5; SD = 38.6) and 5 (χ2 = 186.3; SD = 37.7) as compared to group 2 (χ2 = 230.8; SD = 66.5).

Conclusions

Identifying posttransplant periods in which healthy behaviors and health status may be vulnerable to decline is important for providing ongoing education and psychological support to transplant recipients who manage a complex regimen.

Effect of lung transplantation on heart rate response to exercise

OBJECTIVES

To evaluate if patients have a change in percent of predicted heart rate reserve used at peak exercise (%HRR) after lung transplantation, even at matching workloads.

BACKGROUND

Lung disease of obstructive, restrictive, and mixed types may be associated with an autonomic imbalance. Lung transplantation may improve the effects of pulmonary disease on cardiac function. However, the effect of lung transplantation on heart rate responses during exercise has not been investigated in detail.

METHODS

Retrospective review of patients who underwent lung transplantation. Pre and post transplant cardiopulmonary exercise tests were reviewed.

RESULTS

The %HRR significantly improved by a median of 37% (p < 0.001) following lung transplantation. When matching workloads were analyzed, the %HRR also decreased from a median of 36% to 24% (p < 0.001).

CONCLUSIONS

Corresponding to an increase in peak exercise capacity, percentage of heart rate reserve used improves significantly after lung transplantation, even at matching workloads, indicating a likely improvement in autonomic modulation.

Does recipient age impact functional outcomes of orthotopic heart transplantation?

BACKGROUND

This study evaluated changes in physical functional performance after orthotopic heart transplantation (OHT) with particular attention to the impact of recipient age on functional outcomes.

METHODS

Retrospective review of all first-time, single-organ adult OHTs in the United States between 2005 and 2010. Patients were primarily stratified by age. The validated Karnofsky performance scale, which ranges from 0 (death) to 100 (fully independent with no evidence of disease and no complaints), was used to measure functional status.

RESULTS

A total of 10,049 OHT recipients were identified, with 1,431 (14%) aged 65 years or greater. Mean Karnofsky score prior to OHT was comparable between cohorts (younger: 50.7±25.2 versus older: 50.1±25.0; p=0.38). At a median follow-up of 2.1 years (interquartile range 0.7 to 3.3 years), 64% of OHT recipients had improved functional performance. The mean improvement in Karnofsky score was similar between younger and older patients (19.6±42.0 vs 17.5±41.8; p=0.10). Twenty percent of younger patients were functionally independent prior to OHT, with 67% being functionally independent at last follow-up (p<0.001). Similarly, in the older cohort, 20% were functionally independent prior to OHT, with 66% being functionally independent at last follow-up (p<0.001). Multivariable analysis adjusting for potential confounders confirmed that age, both as a continuous and categoric variable, did not impact odds of functional improvement after OHT. Subanalysis using 70 years as the age cutoff produced similar results.

CONCLUSIONS

In the modern era, OHT is associated with improvements in functional performance in most recipients, and this beneficial effect is preserved across the age spectrum. These data provide a benchmark for functional outcomes after OHT and may have important implications in organ allocation.

Interval training does not modulate diastolic function in heart transplant recipients

OBJECTIVES

This study investigates the effect of aerobic interval training on diastolic function at rest and during exercise in stable heart transplant (HTx) recipients.

DESIGN

Twenty-three stable HTx recipients (74% males, mean age 50 ± 14.9 years) were recruited to a training programme. Intervention was 8 weeks intensive training or control in a randomized controlled design.

RESULTS

At baseline, participants had normal or mild diastolic dysfunction at rest. During exercise, mean E/e' increased from 9.0 (± 2.8) to 12.8 (± 7.7) (p = 0.09), E/A increased from 2.1 (± 0.6) to 2.6 (± 0.7) (p = 0.02), and deceleration time decreased by over 50 ms, all markers of increased filling pressure. There were no correlations between diastolic function and VO 2 peak at baseline. After intervention VO 2 peak increased from 23.9 (± 4.5) to 28.3(± 6) ml/kg/min in the training group (difference between groups p = 0.0018). No consistent pattern of improvement in diastolic function at rest or during exercise was seen.

CONCLUSION

The study does not support a role of diastolic dysfunction in the limited exercise capacity of HTx recipients and suggests that in these patients peripheral factors are of greater importance.

Improved exercise performance in pediatric heart transplant recipients after home exercise training

Pediatric heart transplant recipients have been shown to have reduced exercise performance. Studies of adult heart transplant recipients demonstrate improved endurance from regular aerobic exercise; however, this strategy has not been studied in children. We hypothesized that regular aerobic/strength training would improve exercise performance in children post-heart transplant. After an initial training session, an exercise protocol was performed at home for 12 wk, three days/wk. Aerobic exercise consisted of either running or use of an exercise bicycle to an established target HR for >or=20 min of a 30-min session for three days/wk. Subjects wore a HR monitor and kept a diary to monitor compliance. Two days/wk, strength training was performed with elastic bands to specifically exercise biceps and triceps groups for 15-20 min/session. Aerobic exercise capacity was assessed at baseline and post-training using the standard Bruce treadmill protocol. Strength was measured at baseline and post-intervention by dynamometer. Exercise and strength parameters at baseline and post-intervention were compared using paired student t-tests. Eleven subjects completed the 12-wk program, eight females and three males. The mean age at enrollment was 14.7 +/- 5.3 yr (8-25) and mean time from transplant was 5.26 +/- 5.34 yr (0.58-14.71). Endurance time and peak oxygen consumption improved significantly post-exercise; there was no difference in peak HR or systolic blood pressure. Strength improved in the triceps, quadriceps, and biceps groups. After a 12-wk in home exercise intervention, pediatric heart recipients had improved exercise endurance and strength. The protocol was safe and implemented at relatively low cost. Further study is warranted to determine if the intervention can be extended to more children and whether benefits after such a short-term intervention can be sustained.

Assessing exercise performance after heart transplantation

OBJECTIVE

Heart transplantation improves the survival rate and quality of life in patients with severe symptoms of congestive heart failure and an ejection fraction of 20% or less. Despite marked symptomatic and clinical improvement in those who undergo heart transplantation, exercise capacity often remains reduced, and the factors limiting exercise performance during the post-transplantation period remain unclear. This study was performed to investigate the factors affecting exercise capacity in heart transplantation recipients.

PATIENTS AND METHODS

Fourteen patients with cardiomyopathy were enrolled in this study. We measured peak exercise oxygen uptake (peak VO(2)) in seven patients (age range: 42 +/- 14 yr) 10-28 months after transplantation, in seven patients (age range: 33 +/- 18 yr) with dilated cardiomyopathy before heart transplantation, and in 14 healthy control subjects (age range: 44 +/- 12 yr). The left ventricular ejection fraction, Beck Depression Inventory score, Medical Outcome Health Survey Short Form-36 Questionnaire (SF-36) results, and immunosuppressive therapy administered were recorded in all patient groups.

RESULTS

All patients in the post-transplantation group terminated exercise testing before the anaerobic threshold because of general fatigue. All heart transplantation recipients exhibited a left ventricular ejection fraction within the normal range (mean +/- SD = 57% +/- 2%). The peak VO(2) mean values were significantly different among the three groups (p = 0.001). There were statistically significant correlations between the peak VO(2) values and the Beck Depression Inventory scores (r = -0.637, p = 0.01), between the peak VO(2) values and bodily pain (r = 0.717, p = 0.006), between the peak VO(2) values and general health perceptions (r = 0.706, p = 0.007), and between peak VO(2) values and postoperative duration (r = 0.843, p = 0.03) in all patient groups.

CONCLUSION

In the long-term treatment of heart transplant recipients, exercise training should be considered an important therapeutic tool that enables patients to achieve a good quality of life.

Arrhythmias after orthotopic heart transplantation

BACKGROUND

Arrhythmias frequently occur after orthotopic heart transplantation (OHT).

METHODS AND RESULTS

The most common are ventricular premature complexes, atrial premature complexes, sinus or junctional bradycardia, atrial fibrillation, and atrial flutter, all of which have varying clinical significance depending on associated or causative conditions. Unique etiologic factors such as allograft rejection, transplant coronary artery disease, and altered anatomy and autonomic nervous system changes require that arrhythmias be treated differently after OHT compared with the general population.

CONCLUSION

The potentially severe ramifications of allograft rejection and coronary artery disease make treatment of these disorders in the setting of arrhythmias as important as treating the arrhythmias themselves. At the same time, autonomic denervation and altered anatomy after transplantation complicate drug and device therapies.

A simple tool to predict exercise capacity of obese patients with ischaemic heart disease

OBJECTIVE

To define an equation that predicts exercise capacity taking into account body mass index (BMI).

DESIGN

Retrospective analysis and validation study of a multidisciplinary programme aimed at weight loss and physical rehabilitation.

SETTING

Tertiary referral hospital.

PATIENTS AND METHODS

372 consecutive obese participants (249 men) with stable ischaemic heart disease, aged mean 60.1 (SD 8.7) years, underwent a treadmill exercise test. BMI was 37.8 (4.5) kg/m(2). In the validation study the model was tested in 87 patients with similar characteristics.

RESULTS

Mean exercise intensity was 6.6 (SD 2.4) metabolic equivalents (METs). Multivariate linear regression analysis defined two simple models that considered exercise intensity as the dependent variable and a set of independent variables such as anthropometric measures, age and sex in the first one, plus associated clinical conditions and drug treatment in the second one. The correlation coefficients of the two models were R = 0.630 and R = 0.677, respectively. Age, BMI and sex were the strongest predictors of exercise capacity. The first derived equation efficiently predicted exercise capacity: in the validation study predicted exercise intensity was 6.3 (1.6) METs and attained exercise intensity was 6.3 (2.4) METs (p = 0.903) with a highly significant correlation (R = 0.534, p < 0.001).

CONCLUSION

BMI is an important determinant of exercise capacity of obese people with ischaemic heart disease. The use of a simple equation may help in predicting exercise capacity, in individualising exercise protocol and in setting up rehabilitation programs for obese patients.

Physical functional outcomes after cardiothoracic transplantation

The study of patient healthcare outcomes after cardiothoracic transplantation has increased substantially over the last 2 decades. Physical function after heart, lung, and heart-lung transplantation has been studied using both subjective and objective measures. The majority of reports in the literature on physical function after cardiothoracic transplantation are descriptive and observational. The purposes of the article are to review and critique the existing literature on cardiothoracic recipients' subjective and objective physical function, including respiratory function for heart-lung and lung transplant recipients. In addition, the literature on sexual function in cardiothoracic recipients is examined, the gaps in the literature are identified, and recommendations are given for future research.

Outcomes and Complications After Heart Transplantation

In more than 35 years of experience with heart transplantation, improvements in patient selection, surgical techniques, organ preservation, and postoperative management have increased survival rates and reduced complications. However, a number of significant complications continue, limiting the benefit of heart transplantation as the long-term solution for patients. Current survival rates are 83% at 1 year and 72% at 5 years, with 50% of patients surviving 9.4 years or more. Recipient and donor characteristics influence survival outcome. Primary graft dysfunction is the most frequent cause of death during the first 30 days. The function of the transplanted heart allows return to pre-illness activities, though denervation limits peak exercise capacity. Advances in immunosuppressive medications have decreased the incidence and severity of rejection, though only recently have shown promise in attenuating the incidence of cardiac graft vasculopathy, the major complication limiting long-term graft function. This review addresses current outcomes and the short- and long-term complications of heart transplantation.

Adherence to the Therapeutic Regimen in Heart, Lung, and Heart-Lung Transplant Recipients

Optimal outcome after heart, lung, and heart-lung transplantation can only be obtained if patients are supported in adhering to a lifelong therapeutic regimen. The transplant patient's therapeutic regimen consists of a lifelong medication regimen, including immunosuppressive drugs; monitoring for signs and symptoms related to complications; avoidance of risk factors for cardiovascular disease and cancer (ie, diet and exercise prescriptions, nonsmoking); avoidance of abuse/dependence of alcohol or illegal drugs, as well as attending regular clinical checkups. Nonadherence to all aspects of this regimen is substantial. Nonadherence has been related to negative clinical outcome in view of acute rejections, graft vasculopathy, higher costs, and mortality. This review focuses on the prevalence, correlates, and consequences of nonadherence to the therapeutic regimen in heart, lung, and heart-lung transplantation. The current state of the-art on adherence-enhancing interventions is reported. Priorities for future research are outlined.

Exercise after heart transplantation

Exercise intolerance in heart transplant recipients (HTR) has a multifactorial origin, involving complex interactions among cardiac, neurohormonal, vascular, skeletal muscle and pulmonary abnormalities. However, the role of these abnormalities may differ as a function of time after transplantation and of many other variables. The present review is aimed at evaluating the role of cardiac, pulmonary and muscular factors in limiting maximal aerobic performance of HTR, and the benefits of chronic exercise. Whereas pulmonary function does not seem to affect gas exchange until a critical value of diffusing lung capacity is attained, cardiac and skeletal muscle function deterioration may represent relevant factors limiting maximal and submaximal aerobic performance. Cardiac function is mainly limited by chronotropic incompetence and diastolic dysfunction, whereas muscle activity seems to be limited by impaired oxygen supply as a consequence of the reduced capillary network. The latter may be due to either immunosuppressive regimen or deconditioning. Endurance and strength training may greatly improve muscle function and maximal aerobic performance of HTR, and may also reduce side effects of immunosuppressive therapy and control risk factors for cardiac allograft vasculopathy. For the above reasons exercise should be considered an important therapeutic tool in the long-term treatment of heart transplant recipients.

Clinical predictors of exercise capacity 1 year after cardiac transplantation

BACKGROUND

The exercise capacity of cardiac transplant recipients is reduced compared with normal controls. However, clinical variables predictive of post-transplant exercise capacity have not been well defined. The objective of the present study was to identify clinical features predictive of post-transplant exercise capacity.

METHODS

Ninety-five cardiac transplant recipients underwent cardiopulmonary testing at 1 year after transplant. The exercise parameters were compared with both pre-transplant values and normal subjects. The relationships between exercise parameters and clinical characteristics were analyzed.

RESULTS

Mean peak oxygen consumption (VO(2)) and exercise test duration at 1-year post-transplant improved significantly from 16.4 to 19.9 ml/kg/min and 5.5 to 7.6 minutes, respectively (p < 0.001), but were significantly lower than for normal controls (peak VO(2) 34.0 ml/kg/min; exercise duration 11.2 minutes; p < 0.001). Age- and gender-adjusted VO(2) was 54% of predicted. Pre-operative body weight correlated strongly with post-transplant weight (r = 0.80, p < 0.001). Significant recipient predictors of 1-year post-transplant peak VO(2) identified by multivariate regression analysis were age, male gender, body mass index, exercise peak heart rate and duration of post-operative intensive care. Donor variables did not contribute significantly to post-transplant peak VO(2).

CONCLUSIONS

Peak VO(2) improved after cardiac transplantation but remained significantly impaired compared with normal subjects. In estimating the impact of cardiac transplantation on exercise capacity the most important pre-transplant factors to consider are age, gender and height and weight (or, alternatively, body mass index).

Weight gain and cardiovascular risk after organ transplantation

Organ transplantation has become a common and effective approach to the management of patients with organ failure. The improvement in long-term survival has resulted in the emergence of cardiovascular disease as the primary cause of death in renal transplant patients and a significant complication in other organ recipients. A number of factors explain this trend, including a high incidence of hypertension, posttransplant diabetes, hyperlipidemia, and obesity-risk factors that are mediated by direct effects of immunosuppressive medications. Weight gain posttransplant affects approximately 50% of patients and represents a significant problem because of the potential synergism between obesity and immunosuppressive medication-induced effects on cardiovascular disease risk factor development. This review discusses the incidence and implications of cardiovascular disease risk factors in organ transplant recipients, strategies for clinical management, and future research directions.

Long-term assessment of heart rate variability in cardiac transplant recipients

Sympathetic and parasympathetic reinnervation of the transplanted heart were evaluated by assessing time and frequency domain measurements of heart rate variability at 5 and 8 years. Continuous 24-hour ECG measurements were performed in 13 patients (57 +/- 6 months and 90 +/- 7 months) after orthotopic cardiac transplantation and in 22 healthy age and gender-matched controls, and were analyzed for heart rate variability in the time and frequency domains. Heart rate variability measures reflective of sympathetic reinnervation were sub-normal at 5 years and unchanged at 8 years: those reflective of parasympathetic reinnervation were absent.

Predictors of early post-cardiac transplant exercise capacity

BACKGROUND

This study was conducted to identify which pre- and perioperative clinical parameters were predictive of predischarge submaximal exercise capacity and early postdischarge maximal exercise capacity in cardiac transplant recipients.

METHODS

We studied 24 patients (mean age = 46; 25% African American) who underwent cardiac transplantation followed by an early (immediately posttransplant) postoperative exercise training program. The patients' submaximal exercise capacity was measured at hospital discharge (25 days posttransplant) using the 6-minute distance walk test. Maximal cardiopulmonary exercise testing was done within 4 months of hospital discharge (68 days) to measure peak exercise oxygen consumption (VO2) and to estimate peak exercise capacity as measured by metabolic equivalents (METs). Six clinical variables were assessed for their relationship with predischarge submaximal exercise capacity and 10 clinical variables were evaluated for their relationship with early posttransplant maximal exercise capacity.

RESULTS

Predischarge submaximal exercise capacity was correlated with postdischarge estimated METs (r = 0.43; P = 0.04). No predictors of predischarge submaximal exercise capacity were identified. Predictors of estimated peak exercise METs following discharge were younger age, longer time since resolution of rejection, and shorter postoperative hospitalization. Younger age was the only predictor of peak VO2.

CONCLUSION

Postoperative physical training may improve exercise capacity early after transplantation and minimize effects of preoperative clinical factors that could negatively affect exercise capacity. Interpretation of these results, however, is limited by the small sample and absence of a nonexercising control group. Older recipients, those with a longer length of hospital stay, and shorter duration of time since resolution of rejection may be at risk of reduced early postoperative maximal exercise capacity. Identification of these predictors is important to maximize early reconditioning efforts and plan outpatient rehabilitation.