Effect of low body mass index in outcome of Micra leadless pacemaker implantation

Background Implantation of Micra transcatheter pacing system (TPS) requires introduction of a large caliber delivery catheter into patient’s venous system and right heart. While the investigational device exemption study population had a mean body mass index (BMI) of 27.6kg/m2, implantation outcome in patients with small body size requires further investigation. This study sort to evaluate the effect of low BMI in outcome of Micra TPS implantation Method Consecutive patients undergoing Micra TPS implantation between 19 September 2015 and 24 May 2018 in a single tertiary referral center were studied. Procedure efficacy outcome was defined as successful implantation with threshold being low (≤2.0V/0.24msec) and stable (increase in threshold of ≤1.5V / 0.24 msec) tested at implantation and all clinical follow up in the first year. Procedure safety outcome was defined as absence of major complications in the first year after implantation. A primary analysis was planned to identify factors affecting the composite procedure efficacy and safety outcome, with the hypothesis that low BMI would be associated with poor composite outcome. A secondary analysis was planned to study the effect of BMI on final implant position, number of device deployment and procedure time. Results 147 patients were included in the study. The mean BMI of the cohort was significantly lower than the investigational device exemption study (23.7±3.7kg/m2 vs 27.6±5.3 kg/m2, p Micra leadless pacemaker implantation in patients with low BMI was associated with an unfavorable composite efficacy and safety outcomes. Implantation in patients with low BMI was associated with a higher right ventricular implantation position, requirg more deployment attempts and longer procedure time. More data is needed to determine the optimal pacing approach for this high-risk group of patients.