Effects of atrioventricular conduction delay on the outcome of cardiac resynchronization therapy

Abstract Background and purpose First-degree atrioventricular (AV) block in relation to the outcome of cardiac resynchronization therapy (CRT) has not been well examined. Methods Patients who received a CRT defibrillator or pacemaker between January 2002 and September 2010 at Mayo Clinic were classified into 2 groups: normal PR interval and prolonged PR interval. Standard sensed (100 milliseconds) and paced (130 milliseconds) AV delay was programmed after CRT. Clinical presentations and echocardiography were assessed before CRT and at a median of 6 months after CRT. Results The normal PR interval group (n = 199) had greater improvements in heart failure functional class (mean [SD], 0.7 [0.8] vs 0.5 [0.9]; P = .03) and left ventricular ejection fraction (9.4% [12.4%] vs 5.9% [9.5%]; P = .007) than the prolonged PR group (n = 204). Conclusion Compared with prolonged PR interval, the presence of normal PR interval was associated with a greater improvement in heart failure.