Supplementary Material for: Interatrial Block Predicts Atrial Fibrillation and Total Mortality in Patients with Cardiac Resynchronization Therapy

<b><i>Background:</i></b> Interatrial block (IAB) and abnormal P-wave terminal force in lead V₁ (PTFV₁) are electrocardiographic (ECG) abnormalities that have been shown to be associated with new-onset atrial fibrillation (AF) and death. However, their prognostic importance has not been proven in cardiac resynchronization therapy (CRT) recipients. <b><i>Objective:</i></b> To assess if IAB and abnormal PTFV₁ are associated with new-onset AF or death in CRT recipients. <b><i>Methods:</i></b> CRT recipients with sinus rhythm ECG at CRT implantation and no AF history were included (<i>n</i> = 210). Automated analysis of P-wave duration (PWD) and morphology classified patients as having either no IAB (PWD &lt;120 ms), partial IAB (pIAB: PWD ≥120 ms, positive P waves in leads II and aVF), or advanced IAB (aIAB: PWD ≥120 ms and biphasic or negative P wave in leads II or aVF). PTFV₁ &gt;0.04 mm•s was considered abnormal. Adjusted Cox regression analyses were performed to assess the impact of IAB and abnormal PTFV₁ on the primary endpoint new-onset AF, death, or heart transplant (HTx) and the secondary endpoint death or HTx at 5 years of follow-up. <b><i>Results:</i></b> IAB was found in 45% of all patients and independently predicted the primary endpoint with HR 1.9 (95% CI 1.2–2.9, <i>p</i> = 0.004) and the secondary endpoint with HR 2.1 (95% CI 1.2–3.4, <i>p</i> = 0.006). Abnormal PTFV₁ was not associated with the endpoints. <b><i>Conclusions:</i></b> IAB is associated with new-onset AF and death in CRT recipients and may be helpful in the risk stratification in the context of heart failure management. Abnormal PTFV₁ did not demonstrate any prognostic value.