Behavior of leadless atrioventricular synchronous pacing during exercise

The leadless Micra AV pacemaker is designed to provide atrioventricular (AV) synchronous tracking by detecting atrial contraction. Detection of the mechanical atrial signals can become challenging at a fast sinus rate.

The purpose of the study was to evaluate the AV synchronous performance during exercise in outpatients implanted with a Micra AV pacemaker.

Patients were enrolled at least 1 month after Micra AV implantation and underwent a cycle test protocol. Serial device interrogations (each minute) and continuous electrocardiograms were collected to measure AV synchrony and determine maximum achieved sinus and ventricular rates for each patient. In addition, the A1, A2, A3, and A4 accelerometer signal amplitudes were measured at the start and peak of exercise.

Thirty-five patients (mean age 75.6 ± 13.4 years; 28 (80%) male) were enrolled in the study; 22 (64%) were predominantly ventricular paced (>90%) during exercise. Mean AV synchrony was 90.4% in the entire cohort and 84.7% in patients with high-degree AV block. The mean amplitude of the accelerometer signals increased significantly from the start to the peak of exercise: A1, 4.1-6.3 m/s²; A2, 2.4-3.8 m/s²; and A4, 4.5-7.6 m/s² (P < .01 for all). The time from the ventricular ecvent (VS/VP) to A2 showed a decrease of 25 ms for each 100 ms decrease of the R-R interval.

Maintaining AV synchrony during maximal exercise in elderly patients is achievable by adequate detection of atrial contraction at fast sinus rates by the leadless Micra AV pacemaker. All components of the accelerometer signal increased, likely because of increased contractility related to exercise.