The Importance Of The Longest R-R Interval On 24-Hour Electrocardiography For 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 patients with AF.AIMS We aimed to identify 24-hour 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 follow-up 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 R-R interval below 2 seconds. Univariate analysis showed higher mortality in patients with the longest R-R intervals below 2 seconds compared with those with 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 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 R-R intervals longer than 2 seconds or their absence on 24-hour ECG may predict mortality in patients with AF.