Adaptation to exercise following cardiac transplantation

Abstract

Cardiac transplantation has been the treatment of choice for patients with terminal cardiac insufficiency, increasing survival time by more than 80% in the first year 1 and by more than 50% over ten years 2 . Following cardiac transplantation, the quality of life improves considerably, and many transplanted patients return to work becoming reintegrated into the community 3 . During regular activity, transplanted subjects have shown physical conditioning similar to that of healthy individuals 4-7 . Starling's axiom, "today's physiology will be tomorrow's medicine" 8 , emphasizes the need for knowledge about post-transplantation cardiovascular adaptations, to serve as the basis for clinical treatment and rehabilitation. The present article has the aim of discussing the state-of -the-art of this subject.Aerobic capacity -Aerobic capacity is the total amount of O 2 capable of being metabolized by an organism. Aerobic potency is the amount of 0 2 consumed per unit of time (VO 2 ). Maximal O 2 consumption (VO 2 max.) or maximal aerobic potency is the maximum VO 2 obtained in an endurance (of progressive loads) test, in which VO 2 reaches a maximal value without additional increase due to an additional work load. In tests in which the patient does not reach maximum oxygen consumption, as frequently occurs in cardiopathy patients and transplanted subjects, peak VO 2 is defined as the highest value of VO 2 obtained. Following cardiac transplantation, patients progress with a reduction of peak VO 2 9-15 of 30-50% [16][17][18][19][20][21][22] . In our study 6,7 , deficits were 32.4% and 25.7% at peak exercise and at the anaerobic threshold, respectively. Marzo et al 18 found a 35% reduction in the absolute values of the anaerobic threshold. Degré et al 23 reported an early and intense accumulation of lactate during exercise, attributed to increased production in active tissues and reduced clearance secondary to decreased blood flow in the liver and other inactive tissues. In our study 7 , VO 2 in light to moderate submaximal exercise (40 watt load) below the anaerobic threshold was 12.34 and 12.38ml/kg/ min, in transplanted and healthy subjects, respectively, without significant differences between these groups. Meyer et al 24 , working with a load of 50 watts, reported a VO 2 of 0.96 ±0.1 and 0.95±0.08 L/min -1 in transplanted and control subjects, respectively.The reduction of peak VO 2 is due to multiple factors, both central and peripheral. Chronotropic incompetence and alteration in diastolic function are central factors 21,22,25,26 . At the peripheral level, reduction of peripheral oxygen extraction occurs 17,21,22,[27][28][29] . An exaggerated neuroendocrine response 19 and reduced capacity of pulmonary diffusion 20,30 also seem to be involved in decreased tolerance to exercise.Heart Rate -Heart rate values at rest have been observed to be higher in transplanted compared with healthy individuals due to the absence of parasympathetic innervation and corresponding to the intrinsic frequency of the sinus node 17,23,[31...

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

“…In the general population, exercise should be the preferred stressor when stress echocardiography is performed. Nonetheless, physical exercise might not represent an adequate cardiovascular stressor for the denervated allograft, mostly because of impaired chronotropic response [10,[35][36][37]. Thus, in this population of patients, stress echocardiography with pharmacological agents seems to be more favorable when this technique is indicated.…”

Diretriz Brasileira de Reabilitação Cardiovascular – 2020

“…223,224 Among other factors, this can be explained by: 1) in the immediate post-transplant period, the allograft is devoid of sympathetic and parasympathetic innervation (autonomic denervation), causing an increase in resting HR, attenuating its natural elevation in response to exercise, and impairing recovery after exertion 224,225 ; 2 ) patients often exhibit skeletal muscle dysfunction (sometimes to the point of cachexia), in which immunosuppressive therapy and pre-transplant HF play prominent roles 226 ; and 3) impairment of vascular and diastolic function. 227 During the acute phase of exercise, the increase in cardiac output of HTx recipients depends fundamentally on the Frank-Starling mechanism, i.e., on increase in venous return, inotropy, chronotropy, and reduction in afterload. 228,229 In addition, there is an increase in the concentrations of circulating catecholamines, 227 which decrease slowly after the end of exercise, explaining the slow recovery of HR in these patients.…”

“…227 During the acute phase of exercise, the increase in cardiac output of HTx recipients depends fundamentally on the Frank-Starling mechanism, i.e., on increase in venous return, inotropy, chronotropy, and reduction in afterload. 228,229 In addition, there is an increase in the concentrations of circulating catecholamines, 227 which decrease slowly after the end of exercise, explaining the slow recovery of HR in these patients. 230 Immunosuppression may predispose HTx recipients to a higher risk of other complications, 231 and these patients may develop HTN, diabetes mellitus, and CAD.…”

Reabilitação Baseada em Exercícios para Pacientes Pré e Pós Transplante de Órgãos Sólidos

“…Although the recipients improve both in functional capacity and quality of life (QoL), these are still not equivalent to the same levels of healthy individuals. 3 The long waiting period, caused by the lack of organ donors, often makes patients unprepared for the transplant physically and mentally. In addition to the classic cardiovascular risk factors, we still have the patient's lack of adherence to the programs, knowledge deficits about the rules of conduct after transplantation, non-acceptance of the new organ, fear of rejection, lack of a physical exercise routine, strategies for coping and occupational health issues and social rights.…”