Right atrial dilatation associates with conduction velocity, incidence of arrhythmias and clinical outcomes in pulmonary hypertension.

IntroductionThe mechanism, frequency and clinical impact of arrhythmias in pulmonary hypertension (PH) are unclear. We sought to clarify the electrophysiological mechanism in PH and correlate with arrhythmia incidence and clinical outcomes. MethodsInvasive (n=10) and non-invasive (n=30) electrophysiological mapping techniques determined myocardial conduction velocity, scar burden and atrioventricular (AV) nodal refractoriness, which were then related to cardiac structure and function. Implantable cardiac monitors (ICMs) were implanted into 80 patients with pulmonary arterial hypertension (PAH). Arrhythmia and clinical worsening episodes were prospectively assessed over 186 patient-years follow-up, and features associated with arrhythmia incidence were identified. Two cohorts encompassing all causes of PH (n=564 and n=3348) were interrogated to assess the relationship between defined arrhythmia risk variables and outcomes. ResultsRight atrial (RA) dilatation was associated with slower conduction velocity (R=0.52, p=0.01) and more prolonged AV nodal refractoriness (R=0.82, p=0.03). In the ICM study, 79 arrhythmia events were noted in 40% of participants. Only RA size was independently associated with significant arrhythmia (HR 1.03, 95% CI 1.01-1.06, p=0.01). Arrhythmia incidence associated with clinical worsening, and 20% of patients received ICM-uncovered targeted arrhythmia treatment. 69% of patients with treated arrhythmia were asymptomatic (median time-to-arrhythmia-detection 7 months). In both longitudinal PH cohorts, right atrial (RA) size was associated with worse survival independent of RA pressure and pulmonary vascular resistance. InterpretationThe dominant mechanism associated with disordered cardiac electrophysiology in pulmonary hypertension patients is RA enlargement. RA size was the only significant variable associated with longitudinal arrhythmias in PAH and in two large prospective cohorts with representative populations of all causes of pulmonary hypertension, RA size is predictive of outcomes independent of pulmonary vascular resistance. Randomised trials are needed to clarify if screening and treating arrhythmias in pulmonary hypertension improves outcomes.