ABSTRACT
Introduction: The treatment of AV conduction disorders associated with sinus node illness employing DDDR pacemakers, has motivated the surch for an ideal sensor. Objective: Evaluate the heart rate response of the contractility sensor pacemaker both during the physical effort and mental stress of daily life in out patient tests for patients with bradycardia and chronotropic incompetence. Material and Methods: We use the brazilian Multicentric Study "Inos DR Project - Brazil" working with a DDDR stimulation system which uses the myocardial contractility state chronotropic 38 patients presenting; incompetence were selected, 21 men and 17 women, with age ranging from 13 to 83 years (mean 57 years). The pacemaker utilizes intrinsic cardiovascular information (cardiac contractility from the measure of the unipolar cardiac impedance) for heart rate adaptation, in a closed loop system that theoretically adjusts to all physiologic needs. The system calibration and programation were performed 30 days after implantation (stabilization of heart-lead interface), based on the tests of mental stress (mathematical) and treadmill test, monitoring heart rate histogram of frequency and oxygen consumption. Results: The acute stimulation threshold mean is 0.82 volts and 0.55 volts, and the mean sensibility is 2.37 mV and 10.61 mV, to atrium and ventricle respectively. The mean chronic stimulation threshold is 1.44 V and 1.18, and the mean sensibility threshold mean is 2.81 mV and 6 mV, to atrium and ventricle respectively. The heart rate varied from 5 per cent to 128 per cent on physical activity and from 5 per cent to 80 per cent on mental activity, with elevation right at the beginning of activity, permitting a normal oxygen consumption curve similar to that of normal person of the same age, sex and weight. The average data were compared using T Student test and the variables using variance analysis. Conclusion: The cardiac contractility sensor has an excelent performance on heart rate adaptation, with similar values produced by the autonomous nervous system of normal subjects.