Impaired exercise parameters in pediatric heart transplant recipients: comparison of biatrial and bicaval techniques

Chronotropic incompetence in paediatric heart transplant recipients with prior congenital heart disease

BACKGROUND

Cardiopulmonary exercise testing has been used to measure functional capacity in children who have undergone a heart transplant. Cardiopulmonary exercise testing results have not been compared between children transplanted for a primary diagnosis of CHD and those with a primary diagnosis of cardiomyopathy despite differences in outcomes. This study is aimed to compare cardiopulmonary exercise testing performance between these two groups.

METHODS

Patients who underwent heart transplant with subsequent cardiopulmonary exercise testing at least 6 months after transplant at our institution were identified. They were then divided into two groups based on primary cardiac diagnosis: CHD or cardiomyopathy. Patient characteristics, echocardiograms, cardiac catheterisations, outcomes, and cardiopulmonary exercise test results were compared between the two groups.

RESULTS

From the total of 35 patients, 15 (43%) had CHD and 20 (57%) had cardiomyopathy. Age at transplant, kidney disease, lung disease, previous rejection, coronary vasculopathy, catheterisation, and echocardiographic data were similar between the groups. Mean time from transplant to cardiopulmonary exercise testing, exercise duration, and maximum oxygen consumption were similar in both groups. There was a difference in heart rate response with CHD heart rate response of 63 beats per minute compared to cardiomyopathy group of 78 (p = 0.028). Patients with CHD had more chronotropic incompetence than those with cardiomyopathy (p = 0.036).

CONCLUSION

Primary diagnosis of CHD is associated with abnormal heart rate response and more chronotropic incompetence compared to those transplanted for cardiomyopathy.

Right atrial function in pediatric heart transplant patients by echocardiographic strain measurements

BACKGROUND

CAV is a major cause of mortality in PHTx patients. Research on echocardiographic indices to detect CAV focuses primarily on ventricular function and less is known about RAF. Thus, we primarily sought to evaluate RAF in PHTx patients with CAV. For secondary analysis, we compared RAF between PHTx patients and control patients and evaluated RAF with respect to rejection and surgical type.

METHODS

We retrospectively evaluated echocardiography derived RA strain indices in recipients <18 years old and >1 year from time of transplant. The RA strain phases included, reservoir (εs), conduit (εe), pump (εa), and respective strain rate indices (SRs, SRe, SRa).

RESULTS

There were 36 PHTx patients and 14 age-, sex-matched control patients. There was a significant reduction in εs, εe, SRs, and SRe (P < 0.001) in the PHTx patients when compared to controls. There was no difference between the CAV (+) and CAV (-) patients with respect to RAF indices. Furthermore, εs, εe, and SRe (P < 0.05) were lower in patients with acute rejection (n = 7) compared to those without (n = 26). Patients with a bi-atrial anastomosis (n = 14) had decreased εs, εa, SRs, SRa (P < 0.05), compared to bi-caval anastomosis (n = 24).

CONCLUSION

PHTx patients have decreased RAF compared to healthy children. RAF does not differentiate PHTx patients based on the presence of CAV. RAF is also decreased in PHTx patients with rejection and in those transplanted with a bi-atrial anastomosis.

Healthy hearts in pediatric heart transplant patients with an exercise and diet intervention via live video conferencing-Design and rationale

BACKGROUND

Pediatric heart transplant (PedHtx) patients have increased cardiovascular risk profiles that affect their long-term outcomes and quality of life. We designed a 12- to 16-week diet and exercise intervention delivered via live video conferencing to improve cardiovascular health. Our methodology and baseline assessment of the first 13 enrolled patients are reported.

METHODS

Inclusion criteria are as follows: (a) 8-19 years old; (b) heart transplant >12 months; (c) ability to fast overnight; (d) cardiac clearance by cardiologist; and (e) presence of an adult at home during exercise sessions for patients <14 years old. Exclusion criteria are as follows: (a) acute illness; (b) latex allergy; (c) transplant rejection <3 months ago; and (d) multi-organ transplantation. The intervention consists of one diet and three exercise sessions weekly via live video conferencing. Study visits are conducted at baseline, intervention completion, and end of maintenance period.

RESULTS

A total of 13 participants (15.2 [2.3] years) have been enrolled. Median percent-predicted VO₂ max was 56.8 [20.7]% (10 patients <70%). Ten patients had abnormal endothelial function (reactive hyperemia index <1.9; 1.4 [0.325]) and 11 patients had stiff arteries (pulse wave velocity ≧5.5 m/s for 15-19 years, ≧4.5 m/s for 8-14 years; 5.6 [0.7] m/s). Patients had suboptimal diets (saturated fat: 22.7 [23.8] g/d, sodium: 2771 [1557] mg/d) and were sedentary at a median of 67.5 [13.8]% of their time.

CONCLUSIONS

Baseline assessment confirms that PedHtx patients have abnormal cardiac, vascular, and functional health indices, poor dietary habits, and are sedentary. These results support the rationale to test the feasibility and impact of a non-pharmacologic lifestyle intervention in this patient population.

Exercise capacity following pediatric heart transplantation: A systematic review

Pediatric HTs account for 13% of all HTs with >60% of recipients surviving at least 10 years post-HT. The purpose of this systematic review is to synthesize the literature on exercise capacity of pediatric HT recipients to improve understanding of the mechanisms that may explain the decreased exercise capacity. Six databases were searched for studies that compared the exercise capacity of HT recipients ≤21 years old with a control group or normative data. Sixteen studies were included. Pediatric HT recipients, as compared to controls or normative data, exhibit significantly higher resting HR, and at peak exercise exhibit significantly decreased HR, VO₂ , power, work, minute ventilation, and exercise duration. Peak VO₂ appears to improve within the first 2.5 years post-HT; peak work remains constant; and there is inconclusive evidence that peak HR, HR recovery, and HR reserve improve with time since HT. These results are discussed in the context of the mechanisms that may explain the impaired exercise capacity of pediatric HT recipients, including chronotropic incompetence, graft dysfunction, side effects of immunosuppression therapy, and deconditioning. In addition, the limited literature on rehabilitation after pediatric HT is summarized.

Long-term pulmonary vascular reactivity after orthotopic heart transplantation by the biatrial versus the bicaval technique

INTRODUCTION

Advantages of the bicaval versus the biatrial technique have been reported, emphasizing atrial electrical stability and less tricuspid regurgitation.

OBJECTIVE

To analyze the impact of the surgical technique on long-term pulmonary pressures, contractility, and graft valvular behavior after heart transplantation.

METHODS

Among 400 orthotopic heart transplantation recipients from 1985 to 2010, we selected 30 consecutive patients who had survived beyond 3 years. The biatrial versus bicaval surgical technique groups included 15 patients each. Their preoperative clinical characteristics were similar. None of the patients displayed a pulmonary vascular resistance or pulmonary artery pressure over 6U Wood or 60 mm Hg, respectively. We evaluated invasive hemodynamic parameters during routine endomyocardial biopsies. Two-dimensional echocardiographic parameters were obtained from routine examinations.

RESULTS

There were no significant differences regarding right atrial pressure, systolic pulmonary artery pressure, pulmonary capillary wedge pressure, pulmonary vascular resistance, cardiac index, systolic blood pressure, left ventricular ejection fraction, and mitral regurgitation (P > .05). Tricuspid regurgitation increased significantly over the 3 years of observation only among the biatrial group (P = .0212). In both groups, the right atrial pressure, pulmonary wedge capillary pressure, transpulmonary gradient, and pulmonary vascular resistance decreased significantly (P < .05) from the pre- to the postoperative examination. In both groups cardiac index and systemic blood pressure increased significantly after transplantation (P < .05). Comparative analysis of the groups only showed significant differences regarding right atrial pressure and degree of tricuspid regurgitation; the bicaval group showing the best performance.

CONCLUSIONS

Both surgical techniques ensure adequate left ventricular function in the long term; however, the bicaval technique provided better trends in hemodynamic performance, as well as a lower incidence and severity of tricuspid valve dysfunction.

Quality of life in adult survivors greater than 10 years after pediatric heart transplantation

BACKGROUND

This study assessed quality of life (QOL) in adult survivors of pediatric heart transplantation who survived > or = 10 years after transplantation.

METHODS

Prospective data were collected from heart transplant recipients who were aged > or = 18 years and had survived > or = 10 years after transplantation (transplantation between July 3, 1986, and April 4, 1997). QOL data were collected from patients using the Medical Outcomes Study 36-Item Short Form (SF-36) Health Survey. Clinical data were collected from medical records. Statistical analyses included frequencies and measures of central tendency.

RESULTS

Twenty-three patients (65% men, 91% white) completed the study. At the study initiation, they were a mean age of 9.0 +/- 7.1 years at transplantation, and were a mean age of 25.2 +/- 5.5 years (range, 18-34 years) and a mean of 16.2 +/- 3.0 years (range, 11-22 years) post-transplantation. Most were in school or working. Mean patient QOL scores from the SF-36v2 survey were 50.56 +/- 0.5 (range, 27.3-68.9) for physical health and 49.88 +/- 11.72 (range, 23.56-62.84) for mental health, similar to the general United States population. Late complications were frequent, including transplant coronary artery disease, 3; repeat heart transplantation, 2; post-transplantation lymphoproliferative disorder, 6; kidney transplantation, 5; acute late rejection, 5; and arrhythmias, 4.

CONCLUSION

This report of QOL in adult survivors of pediatric heart transplantation shows patient perception of physical and mental health is similar to the general population despite serious late complications. A multicenter study is planned to further evaluate QOL in this unique cohort.

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.

Decreased exercise performance with age in children with hypoplastic left heart syndrome

OBJECTIVE

Children born with hypoplastic left heart syndrome (HLHS) may experience cardiac dysfunction after staged surgery or transplantation, which may worsen with age. We examined the hypothesis that exercise testing can address cardiovascular capacity and suggest interventions to improve quality of life.

STUDY DESIGN

Children with HLHS > or = 8 years old performed treadmill or bicycle ergometric testing at 4 centers. Results were compared with norms for age and sex.

RESULTS

Of the 42 participants, the mean age was 12.9 years (range, 8.5-17.0 years), 64% were boys, 20 had staged surgery, and 34 completed metabolic assessment. The percent of predicted maximal oxygen uptake (mVO2) was higher in younger children. Children aged 8 to 12 years achieved 70% of predicted mVO2; children aged 13 to 17 years achieved 60% of predicted mVO2 (P = .02). The percent of predicted peak heart rate trended higher in younger patients (83% versus 75%, P = .07). Electrocardiographic changes were more common in older children. In treadmill testing, patients who had a transplant had better exercise performance than patients who underwent staged surgery in percent of predicted exercise time (82% versus 54%, P < .0001) and peak rate-pressure product (241 x 10(3) versus 195 x 10(3), P = .02). The percent of predicted mVO2 did not differ between patients who had a transplant (66%) and patients who underwent staged surgery (61%, P = .25).

CONCLUSION

Children with HLHS showed considerable age-related decline in exercise performance, regardless of surgical strategy.

Exercise assessment in infants after cardiac transplantation

BACKGROUND

Few data describe exercise performance after cardiac transplantation during infancy. The aim of this study was to compare the cardiorespiratory response to exercise in healthy subjects with that of subjects who had undergone heart transplantation during infancy to treat hypoplastic left heart syndrome.

METHODS

Subjects (24 heart transplant recipients and 25 healthy controls) exercised on a treadmill using pediatric ramp protocols. We measured heart rate (HR), blood pressure, and metabolic data. Median age at transplantation was 20 days (range, 4 to 97 days). Age of recipients at exercise testing was 9.7 +/- 2.3 years and in healthy subjects was 10.5 +/- 1.4 years (p=not significant [NS]).

RESULTS

Exercise duration was similar in both groups (10.3 +/- 2.0 minutes in recipients vs 11.1 +/- 1.5 minutes in healthy subjects, (p=NS). Heart rate at rest was greater in recipients (94 +/- 15 beats per minute [bpm] vs 85 +/- 11 bpm, p=0.02). Peak HR also was less in the recipient group (158 +/- 15 bpm vs 189 +/- 12 bpm, p <0.001). Peak oxygen consumption was 14% less in the recipients (32.3 +/- 5.6 ml/kg/min vs 36.8 +/- 5.5 ml/kg/min, p <0.01). Ventilatory anaerobic threshold was decreased in recipients, 27.6 +/- 9.6 vs 32.8 +/- 6.0, p <0.05. Respiratory exchange ratio at peak exercise was equal in both groups (1.06 +/- 0.06 vs 1.06 +/- 0.08). Oxygen pulse index did not differ significantly, 5.5 +/- 1.1 ml/beat/m2 in recipients and 6.1 +/- 1.7 ml/beat/m2 in healthy subjects (p=NS).

CONCLUSIONS

Overall, children who undergo cardiac transplantation in infancy have exercise capacities within the normal range. These recipients have a decreased heart rate reserve that may account for the differences in peak oxygen consumption when compared with healthy subjects.