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ORIGINAL ARTICLE

Evaluation of the activity mode rate variable pulse generator

Paulo R BrofmanI; Danton R. da Rocha LouresI; Paulo R. F RossiI; Roberto V ArditoII; Osvaldo T GrecoII; Domingo M BraileII; João R Sant'AnnaIII; Fernando A LuccheseIII; Renato A. K KalilIII; Ricardo EloyIV; Rubens T BarrosV; José Carlos S AndradeVI; Aldo PesariniVII; Paulo R. A GauchVIII

DOI: 10.1590/S0102-76381987000300004

ABSTRACT

To evaluate the physiologic benefits of the rate response estimulation, 48 patients were submited to a 24 hours Holter recording and paired tolerance treadmill test (AAI VVI and AAI-R/VVI-R modes, selected in random order) one month after implantation of an activity sensing pacemaker Activitrax 8400. Mean age of the patients was 46 years and indications for pacing included atrial arrhythmias (16 patients) or A-V conduction disturbances (32 patients, including 25 with complete A-V block). The underlying disease was Chagas cardiomiopathy, in 32 patients. Initial pacemaker setting was: basic rate: 60 or 70 ppm; maximum activity rate: 125 ppm; activity threshold: medium, rate response: 5. The 24 hours Holter recording documented appropriate changes in heart during daily activities. Oversensing, which resulted in pacing interval fluctuations, was diagnosed in two patients and required pacemaker reprograming. Treadmill test showed a significant increase in heart rate during exercise: mean control value: 66.9 ppm; 4 min.: 84.6 ppm; 6 min.: 90.5 ppm (P < 0.05). In the paired test, the AAI/VVI-Activity mode enabled the patients to increase heart rate (12.5%) and exercise time (20.2%; P < 0.05). None of the patients presented exercise induced ventricular arrhythmias in mode AAI/VVI-Activity; on the other hand, 12 patients showed ventricular arrhythmia during exercise in mode AAI/VVI. Clinical improvement and more active life was referred by all patients in this short follow-up period. The Activitrax 8400 was effective in improving patients exercise capacity.

RESUMO

Quarenta e oito pacientes com marcapasso unicameral de ajuste automático de freqüência de pulso mediado por movimentação corporal (AAI-R/VVI-R) foram avaliados através da eletrocardiografia dinâmica, para correlacionar a atividade física com a variação da freqüência de estímulos e teste ergométrico em esteira (pareados e randomizados em modo AAI/VVI e modo AAI-R/VVI-R), para quantificar a capacidade de realizar esforço físico, um mês após o implante do gerador de pulso Activitrax 8400. A idade média dos pacientes era de 46 anos e a etiologia predominante da arritmia que motivou o implante era a miocardiopatia chagásica. O eletrocardiograma ambulatorial mostrou modificações apropriadas na freqüência cardíaca (exceto em 1 paciente, que permaneceu em ritmo sinusal). Teste ergométrico no modo AAI-R/VVI-R mostrou elevação significativa na freqüência cardíaca com relação ao valor médio controle: de 66,9+0,8 ppm para 84,6+2,1 ppm aos 14 minutos 90,5*2,8 ppm aos 6 minutos e 95,7+2,9 ppm aos 8 minutos (P < 0,05). O modo AAI-R/VVI-R possibilitou um aumento no tempo de exercício de 20,2% quando comparado ao modo AAI/VVI (P < 0,05). Em 12 pacientes, arritmias ventriculares foram detectadas durante o exercício em modo AAI/VVI, mas não no modo AAI-R/VVI-R. No curto período avaliado (1 mês), os pacientes referiram melhora clínica e puderam reassumir vida mais ativa. O gerador de pulsos Activitrax 8400 mostrou-se efetivo e seguro. A estimulação unicameral com variação da freqüência de pulso melhorou a capacidade de realizar exercícios físicos, quando comparada com a estimulação em freqüência pré-determinada.

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