Single-chamber leadless pacemaker for atrial synchronous or ventricular pacing

Feasibility of a novel atrial mechanical sensing method for leadless atrioventricular synchronous pacing

INTRODUCTION

Few studies have demonstrated a high degree of atrioventricular (AV) synchrony with a new leadless pacemaker called Micra AV. Our group previously reported a new and unique sensing method. We believe that this novel sensing method, "Simplified A3 method," might facilitate better AV synchrony than a conventional sensing method in almost all cases with Micra AV implantation.

METHODS

We conducted a non-randomized retrospective study comparing the two pacing methods at two centers. From December 1, 2021 to October 31, 2022, Micra AV was implanted for 32 patients at the two centers. Twenty of the 32 patients with sinus rhythm and complete AV block were included in this study. In Group 1, the conventional setting was programmed as follows: auto A3 threshold, auto A3 window-end (WE), and auto A4 threshold turned on during hospitalization. In Group 2, the "Simplified A3 method" was programmed as follows: auto A3 threshold and auto A3WE turned off. Instead, an intentionally prolonged A3WE (850-1000 ms) and low A3 threshold (A3 signal amplitude + 0.5-1.0 m/s2) were programmed.

RESULTS

Twenty patients were analyzed. In Group 2, AV synchrony (%AMVp) was significantly higher at the first outpatient clinic (63.0 ± 5.7% vs 81.0 ± 4.2%, p = .03). A3 threshold was significantly lower in Group 2 (5.9 ± 0.7 m/s2, p < .05 vs 2.3 ± 0.5 m/s2, p < .05).

CONCLUSION

Our novel sensing method might be a more feasible sensing method for obtaining higher AV synchrony than the conventional algorithm.

Association of leadless pacing with ventricular and valvular function

BACKGROUND

Traditional transvenous pacemakers are associated with worsening tricuspid valve function due to lead-related leaflet impingement, as well as ventricular dysfunction related to electromechanical dyssynchrony from chronic right ventricular (RV) pacing. The association of leadless pacing with ventricular and valvular function has not been well established. We aimed to assess the association of leadless pacemaker placement with changes in valvular regurgitation and ventricular function.

METHODS AND RESULTS

Echocardiographic features before and after leadless pacemaker implant were analyzed in consecutive patients who received a leadless pacemaker with pre- and postprocedure echocardiography at Duke University Hospital between November 2014 and November 2019. Valvular regurgitation was graded ordinally from 0 (none) to 3 (severe). Among 54 patients, the mean age was mean age was 70.1 ± 14.3 years, 24 (44%) were women, and the most frequent primary pacing indication was complete heart block in 24 (44%). The median RV pacing burden was 45.4 (interquartile range [IQR] 3.5-97.0). On echocardiogram performed 8.9 months (IQR 4.5-14.5) after implant, there was no change in the average severity of tricuspid regurgitation (mean change 0.07 ± 1.15, p = .64) from pre-procedure echocardiogram. We observed a decrease in the average left ventricular ejection fraction (LVEF) (52.3 ± 9.3 to 47.9 ± 12.1, p = .0019) and tricuspid annular plane systolic excursion (TAPSE) (1.8 ± 0.6 to 1.6 ± 0.4, p = .0437). Thirteen patients (24%) had absolute drop in LVEF of ≥10%.

CONCLUSION

We did not observe short term worsening valvular function in patients with leadless pacemakers. However, consistent with the pathophysiologic impact of RV pacing, leadless pacing was associated with a reduction in biventricular function.

Inappropriate rate response in a leadless pacemaker due to automatic rate profile optimization

A three-axis accelerometer sensor is incorporated in a leadless pacemaker (Micra^TM , Medtronic^Inc ) for rate adaptation. Three sensor setpoints at lower rate (LR), activity of daily living rate (ADLR), and upper rate (UR) are used to convert detected acceleration to a desired rate response. We describe inappropriate rate acceleration at rest and during chest physiotherapy in a sedentary elderly patient with leadless pacemaker. The underlying mechanism and various programming options are discussed.