A real-world experience of atrioventricular synchronous pacing with leadless ventricular pacemakers.

AIMS: The MicraTM transcatheter pacing system (TPS) (Medtronic) is the only leadless pacemaker that promotes atrioventricular (AV) synchrony via accelerometer-based atrial sensing. Data regarding the real-world experience with this novel system are scarce. We sought to characterize patients undergoing MicraTM -AV implants, describe percentage AV synchrony achieved, and analyze the causes for suboptimal AV synchrony. METHODS: In this retrospective cohort study, electronic medical records from 56 consecutive patients undergoing MicraTM -AV implants at the Mayo Clinic sites in Minnesota, Florida, and Arizona with a minimum follow-up of 3 months were reviewed. Demographic data, comorbidities, echocardiographic data, and clinical outcomes were compared among patients with and without atrial synchronous ventricular pacing (AsVP) ≥ 70%. RESULTS: Sixty-five percent of patients achieved AsVP ≥ 70%. Patients with adequate AsVP had smaller body mass indices, a lower proportion of congestive heart failure, and prior cardiac surgery. Echocardiographic parameters and procedural characteristics were similar across the two groups. Active device troubleshooting was associated with higher AsVP. The likely reasons for low AsVP were small A4-wave amplitude, high ventricular pacing burden, and inadequate device reprogramming. Importantly, in patients with low AsVP, subjective clinical worsening was not noted during follow-up. CONCLUSION: With the increasing popularity of leadless pacemakers, it is paramount for device implanting teams to be familiar with common predictors of AV synchrony and troubleshooting with MicraTM -AV devices.

Oversensing of transthoracic excitation stimuli in contemporary pacemakers.

BACKGROUND: Transthoracic impedance measurements (TIM) is primarily used for minute ventilation rate adaptive sensors in pacemakers. With elevated impedance, the TIM electrical signal itself is oversensed, causing device malfunction. OBJECTIVE: We report an increased incidence of TIM oversensing. METHOD: Retrospective chart review. We review existing records of 18 patients who have demonstrated device malfunction with TIM oversensing. RESULTS: We have found a 1.8% incidence of TIM-related oversensing in our patient population of 959 patients with contemporary Boston Scientific (Marlborough, MA, USA) pacemakers and cardiac resynchronization therapy pacemakers. One patient experienced a syncopal episode. CONCLUSION: Oversensing with pacing inhibition is apparent with the potential of adverse effects to patients.