A randomized trial of the effect of automated ventricular capture on device longevity and threshold measurement in pacemaker patients.

BACKGROUND: An automatic capture (AC) algorithm adjusts ventricular pacing output to capture the ventricle while optimizing output to 0.5 V above threshold. AC maintains this output and confirms capture on a beat-to-beat basis in bipolar and unipolar pacing and sensing. OBJECTIVE: To assess the AC algorithm and its impact on device longevity. METHODS: Patients implanted with a pacemaker were randomized 1:1 to have the AC feature on or off for 12 months. Two threshold tests were conducted at each visit- automatic threshold and manual threshold. Average ventricular voltage output and projected device longevity were compared between AC on and off using nonparametric tests. RESULTS: Nine hundred ten patients were enrolled and underwent device implantation. Average ventricular voltage output was 1.6 V for the AC on arm (n = 444) and 3.1 V for the AC off arm (n = 446) (P < 0.001). Projected device longevity was 10.3 years for AC on and 8.9 years for AC off (P < 0.0001), or a 16% increase in longevity for AC on. The proportion of patients in whom there was a difference between automatic threshold and manual threshold of

Pacing in the middle cardiac vein in a patient with tricuspid prosthesis.

A man with acute endocarditis developed complete heart block several days after the tricuspid and aortic valve replacement. Several weeks after implantation, his epimyocardial pacing leads developed a high threshold and failed to capture the ventricle at the maximal pulse width and output of the pacemaker. An angled-tip lead was placed in the middle cardiac vein for ventricular pacing. The pacing and sensing thresholds of this lead were within the expected range during follow-up. Therefore, in patients with prosthetic tricuspid valve, pacing in the middle cardiac vein should be considered before open-chest placement of the epimyocardial lead.