Leadless pacing using induction technology: impact of pulse shape and geometric factors on pacing efficiency.

AIMS: Leadless pacing can be done by transmitting energy by an alternating magnetic field from a subcutaneous transmitter unit (TU) to an endocardial receiver unit (RU). Safety and energy consumption are key issues that determine the clinical feasibility of this new technique. The aims of the study were (i) to evaluate the stimulation characteristics of the non-rectangular pacing pulses induced by the alternating magnetic field, (ii) to determine the extent and impact of RU movement caused by the beating heart, and (iii) to evaluate the influence of the relative position between TU and RU on pacing efficiency and energy consumption. METHODS AND RESULTS: In the first step pacing efficiency and energy consumption for predefined positions were determined by bench testing. Subsequently, in a goat at five different ventricular sites (three in the right ventricle, two in the left ventricle) pacing thresholds using non-rectangular induction pulses were compared with conventional pulses. Relative position, defined by parallel distance, radial distance, and angulation between TU and RU, were determined in vivo by X-ray and an inclination angle measurement system. Bench testing showed that by magnetic induction for every alignment between TU and RU appropriate pulses can be produced up to a distance of 100 mm. In the animal experiment pacing thresholds were similar for non-rectangular pulses as compared with conventional pulse shapes. In all five positions with distances between 62 and 102 mm effective pacing was obtained in vivo. Variations in distance, displacement and angle caused by the beating heart did not cause loss of capture. At pacing threshold energy consumptions between 0.28 and 5.36 mJ were measured. Major determinants of energy consumption were distance and pacing threshold. CONCLUSION: For any given RU position up to a distance of 100 mm reliable pacing using induction can be obtained. In anatomically crucial distances, up to 60 mm energy consumption is within a reasonable range.

Leadless pacing of the heart using induction technology: a feasibility study.

OBJECTIVES: To develop a leadless pacemaker system based on induction technology and to investigate its feasibility and safety in the pig model. BACKGROUND: Despite tremendous technical advances during the last decades, cardiac pacing is still associated with a considerable rate of complications that can be primarily attributed to the leads. METHODS: The device consists of a transmitter unit implanted subcutaneously just above the heart and an endocardial receiver unit implanted in the apex of the right ventricle. The transmitter unit generates an alternating magnetic field that is converted into a voltage pulse by the receiver unit. In order to test feasibility, the receiver unit was attached to an electrophysiology catheter for signal recording and placed in the apex of the right ventricle of a pig. Subsequently, the receiver unit was implanted without external connection in the right ventricle. RESULTS: An alternating magnetic field of about 0.5 mT was generated by the transmitter unit in a distance of 3 cm. Voltage pulses with a duration of 0.4 ms and voltage amplitude of 0.6-1.0 V were generated. Using these pulse characteristics, a reliable stimulation of the heart could be achieved. A secure fixation of the receiver unit in the apex of the right ventricle could be obtained for the duration of this short-term study by using screw fixation. CONCLUSIONS: This study shows that induction technology is feasible for cardiac pacing. Typical voltage pulses could be generated by which an effectively stimulation in vivo could be achieved.