Heart Transplantation HESS 509 Heart Transplantation CHAPTER FOURTEEN Heart transplantation is the gold standard treatment for selected individuals with end-stage heart failure who continue to have symptoms despite optimal medical and device therapy. Heart transplantation significantly improves quality of life and dramatically increases survival (90% and 70% after 1 and 5 years, respectively, with a median survival of 10 years). Despite receiving a healthy heart in an orthotopic heart transplant (which involves the complete removal of the recipient’s own heart), most people continue to experience some exercise intolerance due to peripheral muscle dysfunction and reduced aerobic capacity.

Heart Transplantation HESS 509 Heart Transplantation CHAPTER FOURTEEN Effects on the Exercise Response Because the donor heart’s innervation is transected in order for the heart to be transplanted, immediately after transplantation there is no parasympathetic or sympathetic innervation to the heart. Some people demonstrate signs of partial cardiac re-innervation, so most heart transplant recipients must rely on circulating catecholamines to provide adrenergic stimulation to the heart. This results in heart transplant recipients having different heart rate (HR) and hemodynamics, both at rest and during exercise, when compared to healthy individuals with a normal heart. Thus, Resting HR is increased ~20 beats/min. Onset of increased HR is delayed for the first several minutes of exercise. This is followed by an increase in HR that is more gradual than normal. Peak HR is slightly lower than normal (~150 beats/min) Heart rate may remain near its peak value for several minutes during recovery. Return to resting levels is delayed

Heart Transplantation HESS 509 Heart Transplantation CHAPTER FOURTEEN Effects on the Exercise Response The systemic circulation is also affected by heart transplantation because the heart is denervated, which disrupts the baroreflex control mechanisms (baroreceptors are also present in the auricles of the heart and vena cava), that maintain the balance between cardiac output and vascular resistance. Thus, Blood pressure at rest is often mildly elevated. Systolic pressure is lower than normal at peak exercise. Cardiac output is lower than normal at peak exercise (≈60-70% peak cardiac output compared to that in age-matched healthy controls)

Heart Transplantation HESS 509 Heart Transplantation CHAPTER FOURTEEN Effects of Exercise Training The clinical and physiological benefits of exercise training in heart transplantation recipients include the following: Resting HR and blood pressure are lower. Maximal HR is higher. Peak VO2 and VO2 at ventilatory threshold are higher. Submaximal exercise endurance is improved. Blood lactate concentrations are lower at the same work rate. Ventilatory efficiency improves. Exertional fatigue and dyspnea are diminished

Heart Transplantation HESS 509 Heart Transplantation CHAPTER FOURTEEN Management and Medications Medical management of organ transplantation requires immunosuppressive drug (see Table 14.1 below – FYI ) Controlling immune system rejection of the donor heart and avoiding the adverse side effects of immunosuppressive therapy are thus primary concerns following heart transplantation. Acute graft rejection is common, especially within the first year.

Heart Transplantation HESS 509 Heart Transplantation CHAPTER FOURTEEN Recommendations for Exercise Testing Exercise testing for heart transplant recipients can be done with either a treadmill or a stationary cycle ergometer and should follow a conservative exercise testing protocol that has relatively small increases in work rate per stage - e.g., 0.5-1.0 metabolic equivalents Measuring respired gases allows accurate quantification of functional capacity . Peak VO2 in untrained cardiac transplant recipients is generally ≤20 to 25 mL O2 · kg−1 · min−1 Although isolated cases of chest pain associated with accelerated graft atherosclerosis have been observed, autonomic denervation reduces the likelihood of angina symptoms, especially during the initial months or years following surgery when partial re-innervation is less likely. Radionuclide testing is more useful for diagnosis of ischemic heart disease than the ECG. Only professionals who are experienced with exercise testing in high-risk populations should perform an exercise test in a heart transplant recipient

Heart Transplantation HESS 509 Heart Transplantation CHAPTER FOURTEEN Recommendations for Exercise Training Exercise training is strongly recommended for this population, including both aerobic and resistance exercise. Improvements in peak VO2 range between 15% and 40% Resistance exercise is also strongly encouraged, with the goal of improving muscle strength and bone density and to prevent the adverse effects that antirejection medications have on skeletal muscle. During upper-limb strength or flexibility evaluations, sternal precautions should be strictly observed in the initial weeks or months following heart transplantation. The use of HR alone to guide exercise intensity is not appropriate in this population. It is not uncommon for heart transplant recipients to achieve an exercise HR that exceeds 85% of measured peak HR. Combined assessment of systolic blood pressure and rating of perceived effort (RPE) (recommended range 11-14 out of 20) is a better gauge of exercise training intensity

Heart Transplantation HESS 509 Heart Transplantation CHAPTER FOURTEEN Recommendations for Exercise Training Important considerations during exercise programming: Progress conservatively, as severe deconditioning is common, especially if prolonged bed rest was required before surgery. Intermittent exercise throughout the day may be needed until longer, continuous exercise can be tolerated. Range of motion and stretching exercises are important for the upper body to restore normal thoracic biomechanics after sternotomy. However, these exercises should be limited for up to 6 to 8 weeks after surgery. The RPE is the preferred method of monitoring exercise intensity, particularly as the individual progresses to an independent exercise program. Longer periods of warm-up and cool-down are indicated because the physiological responses to exercise are delayed. END