The Surgical Implantation of Novel Epicardial Pacemakers in Rodents

OBJECTIVES: Rodent hearts have been used as models of cardiac disease for many years in the investigation of cardiovascular physiology. Chronic pacing has been used to induce heart failure or arrhythmia in the past. However, the size and durability of the devices, as well as the viability of the animals following the implantation, have been some of the many challenges. In this study, we present a new technique for the successful implantation of wireless cardiac pacemakers in rat hearts. METHODS: We present two novel wireless and battery-free pacemakers that are currently under development. One model is completely biodegradable, while the other is not. Anesthesia is induced in the isofluorane chamber and the rats are intubated using standard technique and connected to the ventilator. A left thoracotomy is performed, the lung is mobilized posteriorly, and the pericardium is opened. The pacemaker electrode is sutured to the epicardium using 6-0 monofilament non-absorbable sutures. The receiver portion of the pacemaker is placed in a subcutaneous pocket. After the chest is closed, the rats are extubated and monitored until sternal recumbency is regained. Afterwards, the rats are placed in a cage with radiofrequency (RF) wireless control stimulator and the data was recorded using a standard small animal electrocardiogram (EKG) recording device. RESULTS: A total of five functioning pacemakers have been implanted. The rats had unremarkable post-operative course and showed long-term survival. The devices were activated and we were able to observe the change of EKG from normal sinus rhythm at 300 to 340 bpm to 400 to 500 ventricular rhythms with wide QRS. Once the remote signal was turned off, we observed a return of cardiac rhythm to normal sinus rhythm. Conclusion: The surgical technique we have developed is an effective and reproducible approach for the implantation of wireless epicardial pacemakers in rats. This will lead to the expanded use of wireless pacemakers in rats that will help recreate human disease patterns in animals