ABSTRACT
Objective - To assess the changes in ventricular evoked responses (VER) produced by the decrease in left ventricular outflow tract gradient (LVOTG) in patients with hypertrophic obstructive cardiomyopathy (HOCM) treated with dual-chamber (DDD) pacing. Methods - A pulse generator Physios CTM (Biotronik, Germany) was implanted in 9 patents with severe drug-refractory HOCM. After implantation, the following conditions were assessed: 1) Baseline evaluation: different AV delay (ranging from 150ms to 50 ms) were sequentially programmed during 5 to 10 minutes, and the LVOTG (as determined by Doppler echocardiography) and VER recorded; 2) standard evaluation, when the best AV de lay (resulting in the lowest LVOTG) programmed at the initial evaluation was maintained so that its effect on VER and LVOTG could be assessed during each chronic pacing evaluation. Results - LVOTG decreased after DDD pacing, with a mean value of 59 + 24 mmHg after dual chamber pacemaker, which was significantly less than the gradient before pacing (98 + 22mmHg). An AV delay > 100ms produced a significantly lower decrease in VER depolarization duration (VER(DD)) when compared to an AV delay =100ms. Linear regression analyses showed a significant correlation between the LVOTG values and the magnitude of VER (r=0.69; p<0.05) in the 9 studied patients. Conclusion - The telemetry obtained intramyocardial electrogram is a sensitive means to assess left ventricular dynamics in patients with HOCM treated with DDD pacing.
Subject(s)
Humans , Male , Female , Adolescent , Adult , Middle Aged , Cardiomyopathy, Hypertrophic/physiopathology , Pacemaker, Artificial , Cardiomyopathy, Hypertrophic/therapy , Heart Ventricles/physiopathologyABSTRACT
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.