The importance of the longest R-R interval on 24-hour electrocardiography for mortality prediction in patients with atrial fibrillation.

ABSTRACT

BACKGROUND: Heart rate control in atrial fibrillation (AF) is typically assessed by 24­hour electrocardiography (ECG). There are scarce data on the use of 24­hour ECG parameters to predict mortality in patients with AF. AIMS: We aimed to identify 24­hour ECG parameters that predict mortality in patients with AF. METHODS: We enrolled 280 ambulatory patients (mean [SD] age, 72 [8.7] years; 57.9% men) with permanent or persistent AF. Data on mortality and pacemaker or defibrillator implantation during follow­up were collected. Predictors of mortality were assessed using the Cox proportional hazards model and C statistic. RESULTS: Compared with survivors, 78 patients (28%) who died were older, more often had comorbidities, left bundle branch block (LBBB), reduced left ventricular ejection fraction, lower maximum heart rate, higher number of ventricular extrasystoles, and the longest R­R interval below 2 seconds. Univariate analysis showed higher mortality in patients with the longest R­R intervals below 2 seconds compared with those with R­R intervals of 2 seconds or longer (P <0.001). Independent mortality predictors in the regression model included older age, renal failure, history of coronary intervention, chronic obstructive pulmonary disease, LBBB, and a high number (≥770) or absence of R­R intervals of at least 2 seconds. The area under the curve for mortality prediction increased after including ECG parameters (0.748; 95% CI, 0.686-0.81; vs 0.688; 95% CI, 0.618-0.758; P = 0.02). CONCLUSIONS: A high number of R­R intervals longer than 2 seconds or their absence on 24­hour ECG may predict mortality in patients with AF.