| Modern device therapy for treating atrial fibrillation (AF) is inadequate because patients poorly tolerate the high-energy shocks required to terminate AF. Recently, a low-energy defibrillation alternative called anti-tachycardia pacing (ATP) has been considered. In-vivo experimental studies of ATP on AF have been limited by the lack of an effective research tool. This work describes the design, implementation, and evaluation of an implantable cardiac telemetry system developed for the long-term study of AF and ATP in conscious and ambulatory animals. By building a pacing and sensing system with remote interrogation and real-time transmission of atrial electrograms (AEGs), this system yields valuable results that cannot be obtained in an acute surgical setting or by using commercial implantable cardioverter-defibrillators.; This novel system was designed to provide the following capabilities for AF research in conscious, untethered animals: (1) chronic rapid atrial pacing for AF induction; (2) programmable stimuli for atrial effective refractory period (AERP) measurements; (3) conventional ATP; (4) real-time telemetry of 4 channels of AEGs. The resulting system consisted of an implantable unit that paced and sensed from the atria and an external communication unit with a graphical user interface that remotely controlled the pacer and displayed AEGs.; The device's usefulness was demonstrated in-vivo. One pacer was implanted in a sheep for 3 months, during which time AF was successfully induced by rapid pacing. AEGs and AERPs were recorded throughout the course of AF induction. A decrease of AERP was documented, confirming the progression of the electrical remodeling process in the atria. Another pacer was implanted for 32 days. During this study AF was induced and ATP was delivered. Immediately after each ATP trial, AEGs were acquired to examine the direct effect of the ATP. The pacer battery was also recharged in-vivo. All data was collected remotely using a wireless network connection, eliminating the need to remain in close proximity of the animal. These studies demonstrated that the implantable cardiac telemetry system can be used to collect unique and comprehensive in-vivo data from a conscious animal for an extended period of time, making this system a useful research tool. |
