Single site left ventricular pacing induced dyssynchrony and cardiomyopathy.

Single site left ventricular (LV) pacing in the absence of intrinsic ventricular activity can be as detrimental to LV function as right ventricular apical pacing. This report describes a patient with complete heart block who developed significant dyssynchrony and cardiomyopathy secondary to single site lateral LV pacing. The process was reversed by placement of a second anterior LV lead.

The effect of bipole tip-to-ring distance in atrial electrodes upon atrial tachyarrhythmia sensing capability in modern dual-chamber pacemakers.

INTRODUCTION: Accurate atrial arrhythmia discrimination is important for dual chamber pacemakers and defibrillators. The aim was to assess the accuracy of atrial arrhythmia recording using modern devices and relate this to atrial tip-to-ring (TTR) distance. METHODS: One hundred eighty-two patients (72 + or - 9 years, 55% male) with paroxysmal atrial fibrillation were enrolled and were included in the study if they had an atrial fibrillation (AF) burden of 1-50% during a monitoring phase. Seventy-nine patients fulfilled these criteria and were followed for at least 5 months. Electrodes were classified as having short (<10 mm), medium (10-12), or long (13-18) atrial TTR spacing. RESULTS: Two thousand eight hundred eighty-three detailed onset reports were analyzed; 730 (25%) demonstrated aberrant sensing. Six percent were due to farfield R wave oversensing (FFRWO) and 19% due to undersensing, sometimes occurring in the same patient and study phase. FFRWO was significantly reduced with short TTR electrodes (P < 0.05). Undersensing due to sensitivity fallout was 18% (short), 24% (medium), and 17% (long) (P = ns). Undersensing due to pacemaker blanking was 11% (short), 11% (medium), and 12% (long) (P = ns). Active fixation electrodes did not show any difference from passive fixation. CONCLUSION: Atrial electrodes with a short TTR (<10 mm) significantly reduce FFRWO without increasing undersensing and should be used routinely in patients with paroxysmal atrial tachyarrhythmias. However, 20% of atrial tachyarrythmia episodes were incorrectly classified as terminated by these modern devices due to undersensing. Clinicians should be wary of using device-derived endpoints that rely on AF episode number or duration as these may be falsely increased or reduced, respectively.

The use of atrial overdrive and ventricular rate stabilization pacing algorithms for the prevention and treatment of paroxysmal atrial fibrillation: the Pacemaker Atrial Fibrillation Suppression (PAFS) study.

AIMS: The PAFS study is a randomized, multicentre investigation of the effects of third generation anti-atrial fibrillation pacemaker algorithms in patients with paroxysmal atrial fibrillation (PAF). METHODS AND RESULTS: 182 patients (72 +/- 9 years, 55% male) with at least three symptomatic episodes of PAF within prior 3 months resistant to two anti-arrhythmics were enrolled. A pacemaker-derived atrial fibrillation (AF) burden of 1-50% was required in the initial induction phase. Seventy-nine patients fulfilled these criteria and were randomized to four, month-long phases in a crossover design. Algorithm phases were 'rate soothing' on, 'ventricular rate stabilization' on, and 'All on', which included these two algorithms plus post-AF response. The algorithm phases were compared to 'All off' dual chamber universal mode (DDD 60) for the analysis. Forty-two percent of patients enrolled in the monitoring phase had no AF. The percentage of AF induced by premature atrial contractions (PACs) was significantly reduced by rate soothing from 25 to 17% (P < 0.05). There was no significant change in AF burden, AF episode number, quality of life, or symptoms with any algorithm (P = ns). CONCLUSION: The rate-soothing algorithm by atrial overdrive pacing reduced PAC-initiated PAF. However, there was no overall change in AF burden, PAF episodes, patient symptoms, or quality of life. Forty-two percent of PAF patients did not show any AF after enrollment, suggesting that bradycardia pacing alone eliminates AF.

Temporal changes in atrial refractoriness following DC cardioversion of persistent atrial fibrillation in man.

AIMS: Studies have demonstrated shortening of the atrial effective refractory period (ERP) after episodes of atrial fibrillation (AF). This is termed atrial remodelling. It is unclear whether restoration of SR after persistent AF in patients with a clinical substrate results in reversal of this shortening and whether this is maintained long term. METHODS AND RESULTS: The ERP was determined at mid-lateral right atrial wall (MLRA) and right atrial appendage (RAA) at 600 ms and 400 ms drive cycle lengths and at basic sinus cycle length in 81 patients with persistent AF immediately, 24 h and 2 weeks following external DC cardioversion. All atrially active drugs were stopped for at least 5 half lives. (1) Prolongation of the ERP was observed at both atrial sites and all cycle lengths up to 24 h post cardioversion (p < 0.0001). (2) However, between 24 h and 2 weeks a subsequent shortening occurred in the ERP returning it to near post cardioversion levels. (3) The ERP was significantly longer at 24 h post cardioversion in patients who remained in SR for 2 weeks or longer compared with those who reverted to AF. CONCLUSION: Prolongation of the atrial ERP occurred following restoration of SR in persistent AF patients but was not maintained and displayed a biphasic pattern such that by 2 weeks the ERP had returned to baseline values. Despite this finding, a longer ERP at 24 h post cardioversion was associated with maintenance of SR in the medium-term.

Does sinus rhythm beget sinus rhythm? Long-term follow-up of the patient activated atrial defibrillator.

The aim of this study was to determine the effect of early patient activated cardioversion of atrial fibrillation (AF) using the atrial defibrillator on recurrence of AF. Fifteen patients, mean age 63 +/- 14 years, 80% men, with drug-resistant persistent AF were implanted with the Jewel AF atrial defibrillator. All patients performed self-administered cardioversion for AF recurrences. Over a 2 year follow-up, 238 patient-activated cardioversions were performed in 14 patients. Sinus rhythm was restored on every occasion with 96% of episodes terminating with a single shock. The median time from AF onset to patient awareness of symptoms was 2.5 hours. The median time from onset of symptoms to cardioversion was 3.5 hours. Comparison of the first and second six month period following implant showed a nonsignificant increase in mean total AF duration (75.7 +/- 107.8 hours vs 146.6 +/- 194.1 hours, P = 0.28). Two patients (13%) had a decreasing frequency of AF recurrences. The majority continued to have regular recurrences of AF. The atrial defibrillator is an extremely effective method of restoring sinus rhythm in patients with persistent AF. Regular early use of the atrial defibrillator, increased the duration of sinus rhythm in a minority of patients during long-term follow-up. Most patients had regular recurrences of AF requiring patient-activated cardioversion.