Electrocardiographic patterns and long-term clinical outcome in cardiac resynchronization therapy

The present study aims to identify the predictive value of electrocardiographic (ECG) patterns on long-term clinical and echocardiographic outcome in patients treated with cardiac resynchronization therapy (CRT).

Clinical information including a standard 12-lead ECG was collected from patient files in consecutive patients treated with CRT from 1997 to 2007. Symptomatic response was defined as improvement in New York Heart Association class (> or =1) and echocardiographic response as improvement in left ventricular ejection fraction of > or =5% absolute. We included 659 patients [median age 66 years, 526 (80%) male]. There was a higher all-cause and cardiac mortality in patients with left bundle branch block (LBBB), prolonged PR interval, right-axis deviation combined with LBBB in the pre-implant ECG, and no QRS reduction after CRT. Patients with right bundle branch block and patients with an intermediate QRS duration (150-200 ms) had a higher chance of symptomatic improvement, and patients with normal PR interval and normal axis in LBBB had a higher chance of echocardiographic improvement.

Cardiac resynchronization therapy does not change the predictive value of ECG patterns in heart failure patients with bundle branch block, where LBBB, a prolonged PR, and an abnormal axis in LBBB are signs of a more severe degree of myocardial disease, and therefore a worse outcome. Lack of electrical resynchronization defined as an unchanged or prolonged QRS duration is associated with higher all-cause and cardiac mortality in patients treated with CRT.