Abstract 15916: Improvement of Cardiac Function with Increasing Stimulus Strength during Left Ventricular Pacing in Cardiac Resynchronization Therapy
Introduction. Cardiac resynchronization therapy (CRT) has become an established option for reducing the risk of mortality as well as improving symptoms in patients with severe heart failure. However, 20% to 30% of patients fail to obtain benefit from CRT. Previous electrophysiology studies have shown that increasing stimulus strength (SS) during pacing captures an enlarged myocardial area and could provide more rapid electrical conduction compared with baseline. During CRT, increasing SS during left ventricular (LV) pacing seems to reduce QRS duration on electrocardiogram.
Hypothesis. This study aimed to investigate whether the increasing SS during LV pacing improves mechanical dyssynchrony and cardiac function in patients treated with CRT.
Methods. Twenty-six patients (67±13 years, 20 males) with CRT were enrolled. We changed their pacing SS of LV lead into three condition of off, 2.5V (LSS: low stimulus strength condition) and 5V (HSS: high stimulus strength condition). QRS duration, various mechanical dyssynchrony and cardiac functional parameters were measured in each condition.
Results. QRS duration decreased significantly with increasing SS (138.6±21.4ms in LSS to 126.8±23.1ms in HSS, p<0.001), and the standard deviation of time from QRS to peak systolic velocity for 12 left ventricular segments decreased significantly (69.6±21.8 in LSS to 55.6±19.4 in HSS, p<0.001). Furthermore, LV ejection fraction and stroke volume increased significantly by HSS (29.4±10.6% in LSS to 33.4±11.6% in HSS, p=0.005, 50.7±15.5ml in LSS to 63.8±18.3ml in HSS, p<0.001, respectively).
Conclusions. Increasing SS during LV pacing may improve mechanical dyssynchrony and cardiac function. LV pacing SS should be taken into account for the optimization of CRT.
- © 2012 by American Heart Association, Inc.