Abstract
AIMS: Patients with first-degree atrioventricular (AV) block and mechanical AV dyssynchrony can present with heart failure (HF)-like symptoms. AV-optimized conduction system pacing (CSP) can improve haemodynamics and symptoms, but selection criteria remain uncertain. We aimed to identify electrocardiographic and echocardiographic predictors of an acute haemodynamic response to AV-optimized CSP in symptomatic first-degree AV block. METHODS AND RESULTS: Nineteen patients (mean age 60.5 ± 21.1 years; 37% female) with symptomatic first-degree AV block underwent baseline electrocardiography and echocardiography followed by AV-optimized conduction system pacing and repeat echocardiographic assessment. Electrocardiographic parameters (PR interval, P wave duration/PR interval ratio) and echocardiographic indices (E/A wave confluence, A-Q interval, and DFT/RR ratio) were tested for association with change in left ventricular stroke volume (LVSV).The mean PR interval was 395 ± 61 ms, the mean A-Q interval 155 ± 65 ms, and the mean DFT/RR ratio 0.34 ± 0.1. E/A wave confluence was present in 15 patients (79%). AV-optimized pacing increased LVSV by 7.8 ± 3.9 ml, corresponding to an 11.8 ± 5.7% relative increase (P < .01). Echocardiographic parameters were associated with LVSV response, including A-Q interval (r = 0.63, P = .004), DFT/RR ratio (r = -0.59, P = .008), and E/A wave confluence (r = 0.57, P = .01). Electrocardiographic parameters were not associated with LVSV change. CONCLUSIONS: Echocardiographically assessed mechanical AV dyssynchrony, rather than electrocardiographic parameters, is associated with an acute haemodynamic response to pacing. Echocardiographic evaluation may help identify patients with prolonged PR interval who could benefit from AV-optimized CSP.