Electrical storm is an independent predictor of adverse long-term outcome in the era of implantable defibrillator therapy.

AIMS: Electrical storm (ES) is a life-threatening arrhythmia complication affecting patients treated with an implantable cardioverter defibrillator (ICD). Despite its increasing importance, existing data on prognosis and management of ICD patients affected by ES are limited and conflicting. METHODS: We prospectively studied 169 consecutive patients receiving an ICD. Thirty-two patients presented with at least one episode of ES during the period of observation (33+/-26 months). ES patients were older (64+/-9 vs. 59+/-13 years, P=0.013) with more advanced congestive heart failure (CHF) but a similar incidence of an underlying organic heart disease. RESULTS: Long-term total and cardiac mortality were both increased among ES patients. Seventeen of the 32 ES patients died as opposed to 19 of the 137 ICD patients without ES (53 vs. 14%, P<0.001). In multivariate Cox regression analysis adjusted for the main confounders, history of ES was significantly and independently associated with total and cardiac mortality (risk ratio (RR)=2.13, P=0.031 and RR=2.59, P=0.019, respectively). CONCLUSION: ES is a relatively frequent complication affecting ICD patients treated for secondary prevention of sudden cardiac death (SCD). Although the acute management of this serious arrhythmia complication is usually successful, occurrence of ES is a strong independent predictor of poor outcome in ICD patients.

Differences in the morphology and duration between premature P waves and the preceding sinus complexes in patients with a history of paroxysmal atrial fibrillation.

BACKGROUND: Atrial fibrillation (AF) is the most common arrhythmia encountered in clinical practice. Experimental and human mapping studies have demonstrated that perpetuation of AF is due to the presence of multiple reentrant wavelets with various sizes in the right and left atria. HYPOTHESIS: Atrial fibrillation may be induced by atrial ectopic beats originating in the pulmonary veins, and premature P-wave (PPW) patterns may help to identify the source of firing. METHODS: To evaluate the morphology and duration of PPWs, 12-lead digital electrocardiogram (ECG) strips containing clearly definable PPWs not merging with the preceding T waves were obtained in 25 patients with AF history (9 men, mean age 59.5 +/- 2.2 years) and 25 subjects without any previous AF history (11 men, mean age 53.6 +/- 25 years). The polarity of PPWs was evaluated in all 12 ECG leads. Previously described indices, such as P maximum, P dispersion (= P maximum-P minimum), P mean, and P standard deviation were also calculated. RESULTS: Premature P-wave patterns were characterized by more positive P waves in lead V1. All P-wave analysis indices were significantly higher in patients with AF than in controls when calculated in the sinus beat, whereas they did not differ between the two groups when calculated in the PPW. P-wave indices did not differ between the PPW and the sinus either patients with AF or controls, except for P mean, which was significantly higher in the sinus (110.1 +/- 1.7 ms) than in the PPW (100 +/- 2 ms) only in patients with AF (p = 0.001). CONCLUSION: The evaluation of PPW patterns is only feasible in a small percentage of short-lasting digital 12-lead ECG recordings containing ectopic atrial beats. Premature P wave patterns characterized by more positive P waves in lead V1, which indicates a left atrial origin in the ectopic foci. The observed differences in P-wave analysis indices between patients with AF and controls and between sinus beats and PPWs may be attributed to the presence of electrophysiologic changes in the atrial substrate.