P5683Incremental hazard associated with the degree of advanced intaratrial block in cardiac resynchronization therapy treated heart failure patients

Abstract Background Advanced Inter Atrial Block (aIAB) reflects a disruption of the electrical signal between the atria and develops gradually. It has been predictive of atrial fibrillation and death in patients with Cardiac Resynchronization Therapy (CRT). A higher number of inferior ECG leads demonstrating biphasic P waves was proposed as a measure of aIAB severity, however its prognostic importance has not been proven. Purpose To assess if aIAB is associated with poor prognosis in CRT recipients and to see if there is a dose-response relationship between the aIAB severity and the outcome. Methods CRT recipients with sinus rhythm on digitally stored preoperative ECG were included (n=565, median age 70 years, 82% male, 55% ischemic heart failure [HF] etiology, 54% CRT-P, 70% left bundle branch block [LBBB]). Automated analysis of P-wave duration [PWD] and morphology in leads II, aVF and III assessed as positive, negative or biphasic +/− was performed and patients classified as having either No IAB (PWD <120ms), Partial IAB (pIAB, PWD ≥120 ms, positive P-waves in inferior leads), aIAB (PWD ≥120 ms and biphasic p-waves in one of the inferior leads). aIAB patients were further stratified by the presence of biphasic P waves in only one (aIAB-1) or more (aIAB-2) inferior leads. Extreme aIAB was defined as biphasic P waves in lead II and negative in leads III and aVF. Cox regression analyses adjusted for age, gender, NYHA class, ischemic HF etiology, left ventricular ejection fraction, LBBB, CRT-P versus CRT-D and PWD were performed to assess the impact of aIAB and its types on the endpoint hospitalization for HF or death at 5 years of follow up. Results Advanced IAB was observed in 65 patients (10 with aIAB-1, 53 with aIAB-2 and 2 with extreme aIAB) and pIAB in 151. No clinically relevant significant differences in baseline characteristics were observed between groups. Compared to the NoIAB group, aIAB-2 and extreme aIAB independently predicted the combined endpoint with adjusted HR=1.82 (95% CI 1.14–2.90, p-value 0.012) and HR=4.70 (95% CI 1.10–20.16, p-value 0.037), respectively. Conclusion Advanced IAB is associated with HF admissions or death from any cause in HF patients treated with CRT. Our findings indicate dose-response relationship between the severity of aIAB and the outcome.