Background: Pacemaker lead complications and failures remain clinical problems. New devices incorporating three leads are associated with even greater limitations.
Objectives: The purpose of this study was to investigate the feasibility and safety of a technology enabling cardiac pacing without leads in an acute porcine model.
Methods: The system is composed of an ultrasound transmitter delivering energy from the chest wall to a receiver-electrode in contact with the myocardium that then converts the ultrasound energy to electrical energy sufficient to pace. In five feasibility studies, the receiver-electrodes were attached to the tip of a catheter to facilitate intracardiac positioning at pacing sites. In six safety studies (five treatment and one sham), ultrasound energy was transmitted to both chest walls, and histopathologic examinations were performed to evaluate bioeffects due to ultrasound energy transmission.
Results: In five feasibility studies, direct and ultrasound-mediated electrical pacing was demonstrated at 30 sites in the right atrium, right ventricle, and left ventricle, at direct electrical pacing outputs of 1.4 +/- 0.6 V and ultrasound-mediated electrical pacing outputs of 1.8 +/- 0.9 V. The mechanical index was 0.6 +/- 0.4 at the receiver site during ultrasound-mediated pacing at a depth of 11.2 +/- 2.4 cm from the chest wall. Using two receiver-electrode catheters, biventricular pacing was demonstrated in all studies. In five safety study treatment animals at a similar depth, the peak mechanical index was 2.3, and the thermal index was 0.4. Microscopic evaluation revealed no evidence of mechanical or thermal bioeffects.
Conclusion: The feasibility and safety of this novel technology for pacing without leads has been demonstrated acutely in animals.