Cardiovascular responses of cardiac transplant patients to arm and leg exercise

Orthostatic hypotension in the elderly: Prevalence and its management by simple isometric limb tensing exercises

Objective

Orthostatic hypotension (OH), an important cause of falls in the elderly, is grossly underdiagnosed. Our study aimed to determine the prevalence and associated factors of OH among the elderly attending a secondary care hospital. Furthermore, we assessed and compared the effectiveness of simple arm and leg tensing exercises, performed just prior to standing, to mitigate the orthostatic fall in blood pressure (BP) in elderly OH patients.

Materials and Methods

A cross-sectional study screened elderly patients (≥65 years) for OH and recruited them into a randomized controlled trial (CTRI/2020/08/027182) of two parallel groups performing either arm tensing or leg tensing exercises just before standing up. We performed an interim analysis of the ongoing trial using paired t-test for within-group comparisons. Patients identified to have OH based on systolic or diastolic fall in BP were analyzed separately. Chi-square analysis compared the improvement in OH status between the two groups.

Results

Nineteen out of 186 screened elderly patients were diagnosed with OH (10.21%, 95% CI: 7.99-12.43). Arm exercise significantly reduced the orthostatic-induced fall in systolic and diastolic BP, while leg exercise effectively reduced only the systolic fall in BP among patients with OH. The proportion of patients with OH after arm exercise (20%) was significantly lower than after leg exercise (77.8%) (P = 0.023, Fischer's exact test).

Conclusion

We found a 10.21% prevalence of OH in our elderly population. Furthermore, we found that simple isometric arm tensing exercise ameliorates the fall in BP on standing up in OH patients.

Central and peripheral hemodynamics in exercising humans: leg vs arm exercise

In humans, arm exercise is known to elicit larger increases in arterial blood pressure (BP) than leg exercise. However, the precise regulation of regional vascular conductances (VC) for the distribution of cardiac output with exercise intensity remains unknown. Hemodynamic responses were assessed during incremental upright arm cranking (AC) and leg pedalling (LP) to exhaustion (Wmax) in nine males. Systemic VC, peak cardiac output (Qpeak) (indocyanine green) and stroke volume (SV) were 18%, 23%, and 20% lower during AC than LP. The mean BP, the rate-pressure product and the associated myocardial oxygen demand were 22%, 12%, and 14% higher, respectively, during maximal AC than LP. Trunk VC was reduced to similar values at Wmax. At Wmax, muscle mass-normalized VC and fractional O2 extraction were lower in the arm than the leg muscles. However, this was compensated for during AC by raising perfusion pressure to increase O2 delivery, allowing a similar peak VO2 per kg of muscle mass in both extremities. In summary, despite a lower Qpeak during arm cranking the cardiovascular strain is much higher than during leg pedalling. The adjustments of regional conductances during incremental exercise to exhaustion depend mostly on the relative intensity of exercise and are limb-specific.

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.

Autonomic reflexes in heterotopic heart transplantation

Heterotopic heart transplantation (HHT) is useful in the setting of irreversible pulmonary hypertension or donor/recipient size mismatch. The resulting pump is composed of two hearts attached to one another. Autonomic tone can be lost in orthotopic heart transplantation, but HHT is unique in that the donor heart lacks an autonomic nervous supply. This is relevant in terms of increasing cardiac output for example during exercise. We document altered autonomic tone in two of our patients who underwent HHT, and discuss the bearing this has on cardiac function.

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.

Exercise following heart transplantation

During the past 2 decades, heart transplantation has evolved from an experimental procedure to an accepted life-extending therapy for patients with endstage heart failure. However, with dramatic improvements in organ preservation, surgery and immunosuppressive drug management, short term survival is no longer the pivotal issue for most heart transplant recipients (HTR). Rather, a return to functional lifestyle with good quality of life is now the desired procedural outcome. To achieve this outcome, aggressive exercise rehabilitation is essential. HTR present unique exercise challenges. Preoperatively, most of these patients had chronic debilitating cardiac illness. Many HTR have had prolonged pretransplantation hospitalisation for inotropic support or a ventricular assist device. Decrements in peak oxygen consumption (VO2peak) and related cardiovascular parameters regress approximately 26% within the first 1 to 3 weeks of sustained bed rest. Consequently, extremely poor aerobic capacity and cardiac cachexia are not unusual occurrences in HTR who have required mechanical support or been confined to bed rest. Moreover, HTR must also contend with de novo exercise challenges conferred by chronic cardiac denervation and the multiple sequelae resulting from immunosuppression therapy. There is ample evidence that both endurance and resistance training are well tolerated in HTR. Moreover, there is growing clinical consensus that specific endurance and resistance training regimens in HTR can be efficacious adjunctive therapies in the prevention of immunosuppression-induced adverse effects and the reversal of pathophysiological consequences associated with cardiac denervation and antecedent heart failure. For example, some HTR who remain compliant during strenuous long term endurance training programmes achieve peak heart rate and VO2peak values late after transplantation that approach age-matched norms (up to approximately 95% of predicted). These benefits are not seen in HTR who do not participate in structured endurance exercise training. Rather, peak heart rate and VO2peak values in untrained HTR remain approximately 60 to 70% of predicted indefinitely. However, the mechanisms responsible for improved peak heart rate, VO2peak and total exercise time are not completely understood and require further investigation. Recent studies have also demonstrated that resistance exercise training may be an effective countermeasure for corticosteroid-induced osteoporosis and skeletal muscle myopathy. HTR who participate in specific resistance training programmes successfully restore bone mineral density (BMD) in both the axial and appendicular skeleton to pretransplantation levels, increase lean mass to levels greater than pretransplantation, and reduce body fat. In contrast, HTR who do not participate in resistance training lose approximately 15% BMD from the lumbar spine early in the postoperative period and experience further gradual reductions in BMD and muscle mass late after transplantation.

PR interval adaptation in the denervated transplanted heart

In the present study, the dynamic PR response upon standardized treadmill exercise was investigated in 21 transplant recipients (recipient age 48 +/- 17 years, donor age 31 +/- 12 years, > 1 year after transplantation). HR and PR interval were measured at rest and at the end of each 25-W increase in workload till peak exercise. In 17 cases norepinephrine (NE) was assessed at rest, and at the end of each workload the HR increased from 99.3 +/- 14 to 143.4 +/- 25 beats/min at individual peak exercise, and NE increased from 1,307 +/- 1,163 to 3,688 +/- 2,036 pg/mL, while the PR interval shortened from 149.2 +/- 13 to 119.3 +/- 20 ms. On average, PR decreased by 3.4 ms for a 10-beat increase in HR, and the HR-PR interval relationship was described by a linear regression (y = 176.8-0.3469x, P = 0.0001). One patient who was unable to increase his NE levels upon exercise showed virtually no decrease in the PR interval and no HR increase. Both recipient age and donor age were moderately and significantly related to the minimum PR interval achieved at peak exercise (r = 0.6, P = 0.008 and r = 0.51. P = 0.049, respectively). These data show the following: (1) adaptation of the PH interval upon exercise does occur in the denervated transplanted heart; (2) the HR-PR relation is similar to that reported in the innervated heart; (3) the overall decline in PR interval is blunted, since denervated patients start at shorter resting PR intervals and achieve relatively longer PR intervals at peak exercise when compared to their innervated counterparts; (4) these exercise induced changes of the PR interval may be explained by circulating NE; and (5) NE levels achieved at peak exercise and the sensitivity of the AV node to NE seem to be age related.

Rehabilitation after cardiac transplantation. Case series and literature review

Twelve heart transplant recipients were admitted to the rehabilitation unit (RU) of a tertiary general hospital during a five-year period. Demographic, medical, and functional data were collected on these patients in a prospective and retrospective chart review. Functional status of each patient was assessed at both admission and discharge by means of the Modified Barthel Index (MBI). All transplant patients admitted to the RU were male, with an average age of 58 (range, 48-64) years. The mean MBI at admission was 57 (range, 31-75), and mean MBI at discharge was 86.5 (range, 55-100). The difference between the mean MBI admission score and that at discharge was demonstrated to be statistically significant (P < 0.001) using the paired t test. The average length of stay on the RU for the 12 patient cohort was 26 (range, 10-63) days. Ten of the 12 patients (83%) were discharged from the RU to the community. Two patients had to be transferred back to the acute care units after developing significant medical problems. Of the patients who returned to the community, the average number of medications at discharge was nine (range, 7-13), with all patients taking prednisone and cyclosporine. At the time of admission, all patients presented with numerous secondary medical problems. Six patients (50%) had hypertension, which required a medical regimen for control. Five patients had either inadequate oral intake or swallowing problems, thus requiring a feeding tube. In four of the five patients, the feeding tube was able to be removed during the RU course. Seven patients had associated neuromuscular deficits, which included hemiparesis (2 patients), paraparesis (1 patient), and myopathy (1 patient). Four patients were found to have pressure sores on admission to the RU, three of whom were completely healed by the time of discharge. Two of the patients had affective disorders that required follow-up by the psychiatry service during their stay on the RU. One patient was found to have radiographic evidence of a vertebral compression fracture but no other recipients had known fractures, osteoporosis, or osteopenia. As well as discussing the above data, the authors will also review basic exercise guidelines for cardiac transplantation patients.

Responses to arm exercise in patients with compensated heart failure

PURPOSE

This study compares the responses of 20 male patients (mean age 51 +/- 11 years) with stable heart failure during peak and submaximal arm and leg exercise.

METHODS

On day 1, subjects completed two symptom-limited graded exercise tests, one with their arms and one with their legs. On day 2, subjects performed arm only and leg only exercise at a matched power output of 30 Watts (W). Ten age-matched healthy subjects served as controls.

RESULTS

During peak arm exercise power output, oxygen consumption (VO2), ventilation, and rate-pressure product were higher in healthy subjects than in patients with heart failure. However, when a subject's peak VO2 or power output during arm exercise was expressed as a percentage of that achieved during peak leg exercise, no significant differences were noted between patients with heart failure and healthy subjects. Among both groups, rate-pressure product, VO2, ventilation, the ventilatory equivalent for O2, and respiratory exchange ratio were all higher when exercising at 30 W with the arms versus 30 W with the legs. Also, in patients with heart failure heart rate was higher (+6 min-1) and stroke volume index lower (-4 mL/m2) during submaximal arm than leg exercise.

CONCLUSIONS

Although peak exercise capacity (Watts, VO2) during arm exercise is lower in patients with heart failure than healthy subjects, when expressed as a percentage of peak leg capacity, the extent of the exercise intolerance they experience during arm exercise does not differ from healthy subjects.