Incident Atrial Fibrillation and Flutter in Patients With Pulmonary Arterial Hypertension: Influence of Right Ventricular Dilatation and Reduced Right Atrial Function

BACKGROUND: The relationship between right atrial (RA) structural and functional remodeling and risk of incident atrial fibrilla-tion/flutter (AF/AFL) in pulmonary arterial hypertension remains poorly defined. METHODS: In a multicenter observational cohort study of 326 patients with pulmonary arterial hypertension, we evaluated associations between RA structure and function, as determined by echocardiography, and incident AF/AFL. Incidence rates were calculated using time-to-event analysis. Cox proportional hazards models identified factors associated with incident AF/ AFL, and Harrell's C-statistics compared predictive performance. Survival decision tree and restricted cubic spline analyses identified thresholds associated with increased risk of AF/AFL. RESULTS: The mean age was 51±15 years, 79% were women, and the mean REVEAL (Registry to Evaluate Early and LongTerm Outcomes in Pulmonary Arterial Hypertension) Lite score was 7.4±2.9. Over a median follow-up of 6.1 years, 56 patients (17.1%) developed AF/AFL, corresponding to an incidence rate of 25.3 cases (95% CI, 19.5-32.8) per 1000 person-years. Each 5% decrease in RA emptying fraction (hazard ratio [HR], 1.38 [95% CI, 1.03-1.86]; P=0.03) and each 1-cm increase in right ventricular basal diameter (HR, 1.55 [95% CI, 1.18-2.05]; P=0.002) were independently associated with 38% and 55% higher hazards of incident AF/AFL, respectively. The C-statistics for predicting incident AF/AFL were 0.62 for RA emptying fraction and 0.65 for right ventricular basal diameter. Survival decision tree and restricted cubic spline analyses identified thresholds for right ventricular basal diameter (>5.4 cm) and RA emptying fraction (<17% and <45%) associated with increased AF/AFL risk. CONCLUSIONS: Larger right ventricular basal diameter and lower RA emptying fraction are associated with increased risk of incident AF/AFL in patients with pulmonary arterial hypertension and may help identify individuals at higher risk.