Occurrence of significant long PR intervals in patients implanted for sinus node dysfunction and monitored with SafeR™: The PRECISE study.

BACKGROUND: Long PR intervals may increase cardiovascular complications, including atrial fibrillation. In pacemakers, the SafeR™ mode monitors PR intervals, switching from AAI to DDD when criteria for atrioventricular block are met. AIMS: The PRECISE study evaluated the incidence and predictors of long PR intervals and their association with incident atrial fibrillation after 1 year in patients implanted for sinus node dysfunction and free from significant conduction disorders at baseline. METHODS: This French, prospective, multicentre, observational trial enrolled patients implanted with a REPLY™ dual-chamber pacemaker. Pacemaker memory recorded long PR intervals (defined as first-degree atrioventricular block mode switches occurring after six consecutive PR/AR intervals≥350/450ms) and atrial fibrillation incidence (fallback mode switch>1minute/day). Predictors were identified from baseline variables (age, sex, AR and PR intervals, atrial rhythm disorder and medication) using logistic regression. RESULTS: Of 291 patients with sinus node dysfunction enrolled, 214 were free from significant conduction disorders at baseline (mean age 79±8 years; 44% men; PR/AR intervals<350/450ms). After 1 year, long PR intervals had occurred in 116 patients (54%) and atrial fibrillation in 63 patients (30%). Amiodarone was the only independent predictor of long PR interval occurrence (odds ratio 2.50, 95% confidence interval 1.20-5.21; P=0.014). There was a strong trend towards an association between long PR interval and atrial fibrillation incidence (odds ratio 1.86, 95% confidence interval 0.97-3.61; P=0.051). CONCLUSIONS: Half of the patients with pure sinus node dysfunction developed long PR intervals in the year following pacemaker implantation. Amiodarone was the only independent predictor of long PR intervals. There was a strong trend towards an association between long PR intervals and incident atrial fibrillation.

Frequency of atrial tachyarrhythmias in patients treated by cardiac resynchronization (from the Prospective, Multicenter Mona Lisa Study).

The continuous measurement of sustained atrial tachyarrhythmia (AT) is now possible with some permanently implanted devices. Data on this subject remain controversial. The aim of this study was to evaluate the incidence of sustained AT in patients treated with cardiac resynchronization therapy using pacemakers without backup defibrillators (CRT-P), within the first year after implantation, using strict definition criteria for sustained AT and a systematic review of all high-quality electrographically recorded episodes. The Mona Lisa study was a prospective, multicenter, cohort study carried out from February 2004 to February 2006, with a 12-month follow-up period. Sustained AT was defined as an episode lasting > or =5 minutes; episodes were confirmed by a systematic review of electrograms in the whole study population. Of the 198 patients who underwent CRT-P device implantation and were enrolled in the study, 173 were in stable sinus rhythm at baseline and were included in the analysis (mean age 70 +/- 9 years, 66% men, 91% in New York Heart Association class III, mean QRS duration 164 +/- 26 ms, mean left ventricular ejection fraction 25 +/- 7%). During a mean follow-up period of 9.9 +/- 3.6 months, 34 patients experienced > or =1 episode of sustained AT, for an incidence rate of 27.5% (95% confidence interval 18.2 to 36.7). Only a history of AT was independently associated with the occurrence of sustained AT within the 12 months after CRT-P device implantation (hazard ratio 2.3, 95% confidence interval 1.2 to 4.4, p = 0.02). In conclusion, this first prospective electrogram-based evaluation of AT incidence demonstrated that 27% of patients developed > or =1 episode of sustained AT lasting > or =5 minutes in the 12 months after CRT-P device implantation.

The usefulness of surface 12-lead electrocardiogram to predict intra-atrial conduction block after successful atrial flutter ablation.

Intraatrial conduction block at the inferior vena cava-tricuspid annulus isthmus was shown to predict successful atrial flutter ablation. However, its demonstration requires the use of several electrode catheters. Thus, a simple approach using surface 12-lead ECG to prove the conduction block would be valuable. Twenty-two patients were prospectively studied during low septal and low lateral atrial pacing before and after successful atrial flutter ablation. Creation of the conduction block was confirmed by comparing the sequence of atrial activation using 3 multipolar catheters during atrial pacing before and after ablation. During low septal pacing, there was no significant difference before and after ablation in P-wave width, axis, or morphology. During low lateral atrial pacing, there was a significant P-wave axis rotation towards the right (from -67 +/- 27 degrees to +13 +/- 35 degrees, P <.001), and P-wave polarity in limb lead II changed from predominantly negative to predominantly positive in 21 of 22 patients. There was also an increase in P-wave width (from 136 +/- 32 to 169 +/- 36 ms, P <.001) and stimulus-to-QRS interval (from 268 +/- 61 ms to 343 +/- 95 ms, P <.001) during low lateral pacing that was not observed during low septal pacing. We conclude that creation of a conduction block in the inferior vena cava-tricuspid annulus isthmus modifies surface 12-lead ECG during low lateral atrial pacing only. We also suggest that P-wave polarity in limb lead II during low lateral pacing could be used as a noninvasive marker of unidirectional counter-clockwise conduction block during atrial flutter ablation.