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

BACKGROUND: Heart rate control in atrial fibrillation (AF) is typically assessed by 24-hour electrocardiography (ECG). There are scarce data on the use of 24-hour ECG parameters to predict mortality in AF.

AIMS: We aimed to identify 24-hour ECG parameters that predict mortality in AF.

METHODS: We enrolled 280 ambulatory patients (mean [SD] age, 72.0 [8.7] years; 57.9% men) with permanent or persistent AF. Data on mortality and pacemaker or defibrillator implantation during follow-up were collected. Predictors of mortality were assessed using the Cox proportional hazards model and C-statistic.

RESULTS: Compared with survivors, 78 (28%) patients who died were older, more often had comorbidities, left bundle branch block (LBBB), reduced left ventricular ejection fraction, lower maximum heart rate, a higher number of ventricular extrasystoles, and the longest R-R interval below 2 seconds. Univariate analysis revealed higher mortality in patients with the longest R-R intervals below 2 seconds compared with those with the R-R 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 R-R intervals of at least 2 seconds. The area under curve (AUC) for mortality prediction increased after inclusion of ECG parameters 0.748 [95% CI, 0.686-0.810] vs 0.688 [95% CI, 0.618-0.758]; P = 0.02).

CONCLUSIONS: A high number of R-R intervals longer than 2 seconds or their absence on 24-hour ECG may predict mortality in AF.