Utilization of cardiac magnetic resonance imaging (cMRI) as an imaging modality in clinical practice is rapidly increasing. More evidence from randomized studies establishing clinical safety and performance of pacing systems in patients undergoing a cMRI scan is needed.

In our study cohort, the use of the VIP algorithm significantly reduced the %RVp, while the VAC algorithm reduced in-clinic time needed to collect device data.

Purpose: There are limited published data from controlled studies on pacemaker implanted patients who underwent a Cardiac MRI scan. The purpose of this prospective, international, multi-center, randomized study was to demonstrate safety and efficacy of the SJM MRI conditional pacing system in patients undergoing cardiac MRI scan. Methods: Patients (n = 283) indicated for dual chamber pacemaker implant were invited to provide voluntary consent at 15 centers across Asia and randomized either to the MRI scan group (SG; n = 140) or the Control group (CG; n = 143) post successful device implantation (Accent MRITM DDDR, Tendril MRITM lead, St. Jude Medical). Each patient in SG (within 9 – 12 weeks post-implant) underwent an elective, prespecificed, non-diagnostic cardiac MRI scan in a 1.5 Tesla horizontal cylindrical bore scanning machine with total magnet exposure time of approximately 60 minutes, maximized gradient slew rate of up to 200 T/m/s and whole body SAR < 4W/kg. Clinical evaluation and device interrogation were performed at baseline, pre and post MRI scan visit and 1-month post MRI for all enrolled patients. The primary endpoint for device safety was freedom from MRI-related complications. The primary endpoint for device efficacy was change in RA/RV capture threshold and sensing amplitude from the MRI visit to 1 month post-MRI visit. Summary of results: The study achieved both safety and efficacy endpoints with 118 patients completing the 1 month post MRI scan visit reporting 100% freedom from MRI scan related complications at the 1 Month post Cardiac MRI Scan follow-up visit (95% LCB: 97.4%). The study reported 12 SADEs & 28 SAEs all of which were found to be not related to MRI scan. No significant changes in device performance with respect to RA/RV capture threshold and RA/RV sensing amplitude from the MRI visit to 1 month post-MRI visit were observed between CG and SG groups (Table 1). Change in RA/RV lead efficacy parameters# #Minimum 113 subjects were required in each group to achieve more than 90% of power at a one sided significant level of 5% to show the non-inferiority with a margin of 10% *n - Number of subjects who experienced an increase in RA capture threshold @ 0.5 ms at 1 M post-MRI scan ≤ 0.5V compared to pre-MRI testing *n - Number of subjects who experienced a decrease in RA sensing amplitude ≤ 50% and ≥ 1.5 mV at 1 M post-MRI scan compared to pre-MRI testing Change in RA/RV lead efficacy parameters# #Minimum 113 subjects were required in each group to achieve more than 90% of power at a one sided significant level of 5% to show the non-inferiority with a margin of 10% *n - Number of subjects who experienced an increase in RA capture threshold @ 0.5 ms at 1 M post-MRI scan ≤ 0.5V compared to pre-MRI testing *n - Number of subjects who experienced a decrease in RA sensing amplitude ≤ 50% and ≥ 1.5 mV at 1 M post-MRI scan compared to pre-MRI testing Conclusions: This study of the St. Jude Medical Accent MRITM pacemaker system in patients undergoing 1.5T cardiac MRI scans at up to 4W/kg successfully met the safety and efficacy endpoints.

Background Several past clinical studies have demonstrated that frequent and unnecessary right ventricular pacing in patients with sick sinus syndrome and compromised atrio‐ventricular conduction (AVC) produces long‐term adverse effects. The safety and efficacy of two pacemaker algorithms, Ventricular Intrinsic Preference™ (VIP) and Ventricular AutoCapture (VAC), were evaluated in a multi‐center study in pacemaker patients. Methods We evaluated 80 patients across 10 centers in India. Patients were enrolled within 15 days of dual chamber pacemaker (DDDR) implantation, and within 45 days thereafter were classified to either a compromised AVC (cAVC) arm or an intact AVC (iAVC) arm based on intrinsic paced/sensed (AV/PV) delays. In each arm, patients were then randomized (1:1) into the following groups: VIP OFF and VAC OFF (Control group; CG), or VIP ON and VAC ON (Treatment Group; TG). Subsequently, the AV/PV delays in the CG groups were mandatorily programmed at 180/150 ms, and to up to 350 ms in the TG groups. The percentage of right ventricular pacing (%RVp) evaluated at 12‐month post‐implantation follow‐ups were compared between the two groups in each arm. Additionally, in‐clinic time required for collecting device data was compared between patients programmed with the automated AutoCapture algorithm activated (VAC ON) vs. the manually programmed method (VAC OFF). Results Patients randomized to the TG with the VIP algorithm activated exhibited a significantly lower %RVp at 12 months than those in the CG in both the cAVC arm (39±41% vs. 97±3%; p =0.0004) and the iAVC arm (15±25% vs. 68±39%; p =0.0067). In‐clinic time required to collect device data was less in patients with the VAC algorithm activated. No device‐related adverse events were reported during the year‐long study period. Conclusions In our study cohort, the use of the VIP algorithm significantly reduced the %RVp, while the VAC algorithm reduced in‐clinic time needed to collect device data.