Validation by serial standardized testing of a new rate-responsive pacemaker sensor based on variations in myocardial contractility

Aims Preliminary studies have shown that peak endocardial acceleration (PEA ), measured by a micro-accelerometer at the right ventricular apex, is high ly correlated with left ventricular contractility (dp/dt max). Furthermore, changes in PEA are closely correlated with sinus node rate changes during exercise and during pharmacological interventions. Peak endocardial acceler ation has, therefore, been used to drive a rate-responsive DDD pacemaker. T his study compared the chronotropic performance of such devices implanted i n 14 patients suffering from chronotropic incompetence with that observed i n Is control subjects in normal sinus rhythm. Methods and Results Five standardized daily life activities (hall walk, cli mbing up and down stairs, squatting and hyperventilation) and two types of exercise (Bruce treadmill protocol and bicycle ergometry) were performed in a random order after individual programming of each pacemaker. For each te st, a correlation coefficient was calculated between changes in PEA and var iations in paced rate, between instantaneous variations in heart rate monit ored by telemetry and continuous measurement of heart rate by the pacemaker , and between sensor-driven rate in patients and normal sinus rhythm in con trols. The variations in paced heart rate were closely correlated with thos e observed in subjects with normal sinus rhythm, and proved to be sensitive , specific, rapid and independent of the type of exercise. After optimal pr ogramming of the sensor, PEA modulates the heart rate as expected during no rmal sinus rhythm. Conclusions In this study, a single PEA sensor successfully restored chrono tropic response in a population of paced patients with severe chronotropic incompetence. Peak endocardial acceleration can be monitored on a beat-to-b eat basis, in parallel with heart rate, and the pacemaker can be accurately programmed with a single exercise test. (Europace 2001; 3: 124-131) (C) 20 01 The European Society of Cardiology.