BACKGROUND: Despite many advantages, leadless pacemakers are currently only capable of single-chamber ventricular pacing.
METHODS: The prospective MARVEL 2 (Micra Atrial tRacking using a Ventricular accELerometer 2) study assessed the performance of an automated, enhanced accelerometer-based algorithm downloaded to the Micra leadless pacemaker for up to 5 h in patients with AV block. The primary efficacy objective was to demonstrate the superiority of the algorithm to provide AV synchronous (VDD) pacing versus VVI-50 pacing in patients with sinus rhythm and complete AV block. The primary safety objective was to demonstrate that the algorithm did not result in pauses or heart rates of >100 beats/min.
RESULTS: Overall, 75 patients from 12 centers were enrolled; an accelerometer-based algorithm was downloaded to their leadless pacemakers. Among the 40 patients with sinus rhythm and complete AV block included in the primary efficacy objective analysis, the proportion of patients with ≥70% AV synchrony at rest was significantly greater with VDD pacing than with VVI pacing (95% vs. 0%; p
BACKGROUND: Leadless pacemakers may be preferred in patients with limited vascular access and high-infection risk, such as patients on hemodialysis.
METHODS: Patients on hemodialysis at the time of Micra implantation attempt (n = 201 of 2,819; 7%) from the Micra Transcatheter Pacing Study investigational device exemption trial, Micra Transcatheter Pacing System Continued Access Study Protocol, and Micra Transcatheter Pacing System Post-Approval Registry were included in the analysis. Baseline characteristics, periprocedural outcomes, and intermediate-term follow-up were summarized.
RESULTS: Patients on hemodialysis at the time of Micra implantation attempt were on average 70.5 ± 13.5 years of age and 59.2% were male. The dialysis patients commonly had hypertension (80%), diabetes (61%), coronary artery disease (39%), and congestive heart failure (27%), and 72% had a condition that the implanting physician felt precluded the use of a transvenous pacemaker. Micra was successfully implanted in 197 patients (98.0%). Reasons for unsuccessful implantation included inadequate thresholds (n = 2) and pericardial effusion (n = 2). The median implantation time was 27 min (interquartile range: 20 to 39 min). There were 3 procedure-related deaths: 1 due to metabolic acidosis following a prolonged procedure duration in a patient undergoing concomitant atrioventricular nodal ablation and 2 deaths occurred in patients who needed surgical repair after perforation. Average follow-up was 6.2 months (range 0 to 26.7 months). No patients had a device-related infection or required device removal because of bacteremia.
CONCLUSIONS: Leadless pacemakers represent an effective pacing option in this challenging patient population on chronic hemodialysis. The risk of infection appears low with an acceptable safety profile. (Micra Transcatheter Pacing Study; NCT02004873; Micra Transcatheter Pacing System Continued Access Study Protocol; NCT02488681; Micra Transcatheter Pacing System Post-Approval Registry; NCT02536118).