In vivo evaluation of the improved MCMS-0102 pacemaker with a rapid pacing mode for induction of experimental heart failure in animals.

The MCMS-0102 cardiac pacemaker for rapid ventricular pacing to induce heart failure in animals has been improved in terms of miniaturization and performance. To determine the performance of the new MCMS-0102, six devices were implanted in beagle dogs, and two of these devices were reimplanted for continued pacing in a total of eight beagle dogs. The hearts were paced at 260 beats per minute for 4 weeks (P group: n = 8). The hemodynamic status of the P group was examined and compared with nonpaced dogs (NP group: n = 8). The neurohumoral status of the P group was evaluated before and after rapid pacing. Stable operation of the six devices during rapid pacing was confirmed using the telemetry system. Postmortem examinations revealed features similar to clinical heart failure characterized by massive ascites, pleural effusion, cardiomegaly, and liver congestion in all the paced dogs. Cardiac output was 1.1 +/- 0.2 l/min in the NP group and 0.5 +/- 0.1 l/min in the P group (P < 0.0001). The left atrial pressure and the central venous pressure of the P group and the NP group were 23 +/- 6 versus 6 +/- 2 mmHg (P < 0.0001) and 10 +/- 3 versus 4 +/- 3 mmHg (P < 0.001), respectively. In the paced dogs, plasma renin activity increased from 0.5 +/- 0.4 to 8.5 +/- 7.4 ng/ml/h (P < 0.05) and atrial natriuretic peptide levels increased from 69 +/- 41 to 229 +/- 72 pg/ml (P < 0.001). The improved MCMS-0102 was successfully implanted in beagle dogs and it succeeded in inducing the congestive heart failure model.