A prospective multicenter study on the safety of a pacemaker with automatic energy control: Influence of the electrical factor on chronic stimulationthreshold.

The effectiveness and safety of a pacemaker with automatic control of captu re was evaluated in 162 patients followed at 27 Spanish centers. The aim of our prospective, multicenter, and randomized trial was to determine the re lationship between the voltage output of the pulse generator and the stimul ation threshold. We randomized 162 patients (107 men, mean age 75 +/- 12 ye ars). We implanted a ventricular pacemaker model Regency SR+ or SC+ with Pa cesetter's low polarization bipolar leads Membrane E 1450. The patients wer e randomized to receive Autocapture or not; group I (81 patients) Autocaptu re On, pulse output automatically adjusted and group II (81 patients) Autoc apture Off, fixed output parameters (3.9 V, 0.37 ms). We performed a 6-mont h follow-up measuring stimulation threshold by means of the VARIO test and Autocapture test, evoked response signal, and R wave signal. The mean R wav e was 15.77 +/- 3.5 mV at the end of the follow-up for group I; and 14.91 /- 6.8 mV for group II (P = NS). The measured evoked response at the end of the follow-up was 9.25 mV in Group I and 8.48 mV in Group II (P = NS). The stimulation threshold was not different between groups. The current densit y created with the voltage and pulse width used in this study (less than or equal to 3.9 V and 0.37 ms) at the tip of this electrode during the matura tion process had no influence on the development of the chronic detection a nd stimulation thresholds.