Catecholamine response to exercise in patients with non-obstructive hypertrophic cardiomyopathy.

KEY POINTS: Intense physical activity, a potent stimulus for sympathetic nervous system activation, is thought to increase the risk of malignant ventricular arrhythmias among patients with hypertrophic cardiomyopathy (HCM). As a result, the majority of patients with HCM deliberately reduce their habitual physical activity after diagnosis and this lifestyle change puts them at risk for sequelae of a sedentary lifestyle: weight gain, hypertension, hyperlipidaemia, insulin resistance, coronary artery disease, and increased morbidity and mortality. We show that plasma catecholamine levels remain stably low at exercise intensities below the ventilatory threshold, a parameter that can be defined during cardiopulmonary exercise testing, but rise rapidly at higher intensities of exercise. These findings suggest that cardiopulmonary exercise testing may be a useful tool to provide an individualized moderate-intensity exercise prescription for patients with HCM. ABSTRACT: Intense physical activity, a potent stimulus for sympathetic nervous system activation, is thought to increase the risk of malignant ventricular arrhythmias among patients with hypertrophic cardiomyopathy (HCM). However, the impact of exercise intensity on plasma catecholamine levels among HCM patients has not been rigorously defined. We conducted a prospective observational case-control study of men with non-obstructive HCM and age-matched controls. Laboratory-based cardiopulmonary exercise testing coupled with serial phlebotomy was used to define the relationship between exercise intensity and plasma catecholamine levels. Compared to controls (C, n = 5), HCM participants (H, n = 9) demonstrated higher left ventricular mass index (115 ± 20 vs. 90 ± 16 g/m2 , P = 0.03) and maximal left ventricular wall thickness (16 ± 1 vs. 8 ± 1 mm, P < 0.001) but similar body mass index, resting heart rate, peak oxygen consumption (H = 40 ± 13 vs. C = 42 ± 7 ml/kg/min, P = 0.81) and heart rate at the ventilatory threshold (H = 78 ± 6 vs. C = 78 ± 4% peak heart rate, P = 0.92). During incremental effort exercise in both groups, concentrations of adrenaline and noradrenaline were unchanged through low- and moderate-exercise intensity until reaching a catecholamine threshold (H = 82 ± 4 vs. C = 85 ± 3% peak heart rate, P = 0.86) after which levels of both molecules rose rapidly. In patients with mild non-obstructive HCM, plasma catecholamine levels remain stably low at exercise intensities below the ventilatory threshold but rise rapidly at higher intensities of exercise. Routine cardiopulmonary exercise testing may be a useful tool to provide an individualized moderate-intensity exercise prescription for patients with HCM.

O tratamento da miocardiopatia hipertrófica por meio de um marcapasso DDD capaz de registrar o eletrograma intramiocárdico / The intracardiac electrogram in a patient with hypertrophic obstructive cardiomyopathy treated with DDD pacing

Paciente do sexo feminino de 48 anos, portadora de miocardiopatia hipertrófica obstrutiva refratária ao tratamento clínico, implantou um marcapasso DDD com capacidade de registrar o eletrograma intramiocárdico por telemetria, sob a forma da resposta ventricular evocada (VER). O gradiente sistólico máximo na via de saída do ventrículo esquerdo (GSVSVE) obtido por ecocardiograma bidimensional com Doppler foi reduzido pela estimulaçäo DDD com intervalo atrioventricular curto (50ms) de um valor controle de 121mmHg para 100mmHg. Um valor inferior foi encontrado nas programaçöes mensais subsequentes, acompanhado de modificaçöes na VER. Nestas avaliaçöes, intervalos atrioventriculares progressivamente reduzidos (150, 100 e 50ms) determinaram variaçöes agudas no GSVSVE também associadas com alteraçöes no traçado da VER, tais como reduçäo na amplitude do sinal no tempo de 150ms. Fica aberta perspectiva de um estudo para correlacionar o eletrograma intracardíaco com o GSVSVE e o intervalo AV, buscando-se um ajuste automático do marcapasso para manter a menor obstruçäo intraventricular na miocardiopatia hipertrófica obstrutiva.