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Leadless Pacemakers are a new generation of pacemakers, providing therapy for patients with bradyarrhythmias. Studies are performed to extend the existing single chamber pacing to dual chamber pacing system. For such a system, the implanted leadless pacemakers should be synchronized to provide atrium and ventricular co-ordination. Given size constraints from the first commercial products, the signal transmission efficiency has been investigated for varying distances between the two devices. The two devices are coupled thanks to electromagnetic inductive resonance. The energy consumed for providing synchronization is evaluated and is compared to available device battery capacity (220mAh), in order to test feasibility and estimate longevity. Device longevity plots for both simulation and experimental studies, for varying distances are analyzed, it is found that predicted longevity is less than 20 days (experimental study) for distances greater than 3mm.In this paper, electromagnetic resonance coupled load modulation technique is considered for providing synchronization and is tested for feasibility in simulation and experimental studies. In general, the results indicate that the load modulation technique is feasible to provide synchronization in between leadless pacemakers for small distances (< 15mm) with a decrease in system longevity. Keywords -Leadless pacemaker synchronization, inductive communication, load modulation in the leadless pacemaker, bio-circuits and systemI.

Dual chamber leadless pacemakers are multi-unit, battery-driven implants utilized for treating patients with bradyarrhythmias and sino-atrial dysfunctions. Establishing synchronization between the units provides coordination between the atrium and ventricular contraction, and this mechanism depletes battery energy. Due to implant size constraints, reducing the synchronization energy consumed to enhance the lifetime of the implant is crucial. In this paper, a set of strategies are proposed and evaluated to indicate the best strategy to enhance the lifetime of atrial unit based on the patient's heart condition. Beat selective pulse transmission is employed instead of pulse transmission on every beat to reduce energy consumption. The characteristics of interbeat contraction timing of the atrium and ventricle from the patient data is modeled as time series. The designed model is extended to model synchronization strategies with sufficient synchronization accuracy and reduction in energy consumption. It is found that the implant lifetime is dependent on the natural atrial contraction probability, which is patient specific. A relation between the transmission duty-cycle and natural atrial contraction probability is derived for all the strategies, and this analysis is used in a case study to quantify the longevity. The proposed strategies show improved lifetime in comparison to the reference strategy. In the case study, for natural atrial contraction probability of 0.1, longevity is increased by two orders in relation to the reference strategy with the longevity of 4 years. However, there is no one best strategy; instead, the most energy-efficient strategy is determined from patient's natural atrial contraction probability and tolerance to suboptimal coordination. INDEX TERMS Leadless pacemaker synchronization, improved atrial longevity, atrium and ventricle interbeat timing model, energy-efficient synchronization, interbeat time series equation.