MARVEL

Abstract
BACKGROUND: Micra TPS© is a leadless VVI mode pacemaker that is implanted in the right ventricle and provides rate response via a 3-axis accelerometer (ACC). New software was developed to detect atrial contraction using the ACC enabling AV synchronous pacing to get VDD pacing mode.
OBJECTIVE: To sense atrial contractions from the Micra ACC signal and provide AV
synchronous pacing.

METHODS: The MASS/MASS2 early feasibility studies showed intracardiac accelerations
related to atrial contraction can be measured via ACC in the Micra leadless pacemaker.
MARVEL was a prospective multicenter study designed to characterize the closed-loop
performance of an AV synchronous algorithm downloaded into previously implanted Micra
devices.

RESULTS: A total of 64 patients completed the MARVEL study procedure at 12 centers in 9
countries. Patients were implanted with a Micra for a median of 6.0 months (range: 0–41.4).
High-degree AV block was present in 33 patients while 31 had predominantly intrinsic
conduction during the study. Average AVS during AV algorithm pacing was 87.0% (CI: 81.8%-
90.9%); 80.0% in high-degree block patients and 94.4% in patients with intrinsic conduction. AVS was significantly greater (P<0.001) during AV algorithm pacing compared to VVI in high degree block patients while AVS was maintained in patients with intrinsic conduction. In our center 6 patients (4 M/2W) were enrolled with high degree AV block in 4 and lower degree AV block in 2. In our cohort VDD response was similar compared to all study patients.

CONCLUSION: Accelerometer-based atrial sensing is feasible and significantly improves AV
synchrony in patients with AV block and a single-chamber leadless pacemaker implanted in the
right ventricle.