Prolonging the atrioventricular delay at increased heart rates during CRT improved LVOT-VTI (+0.146 cm/s per 10 bpm heart rate increase per 20 ms increase of AVD after exercise, P=0.013).
Does prolonging the atrioventricular delay (AVD) at increased heart rates improve cardiac performance (LVOT VTI) in patients with cardiac resynchronization therapy?
In patients with cardiac resynchronization therapy, the relatively short baseline atrioventricular delay should be prolonged at increased heart rates to optimize systolic performance.
Effect estimate: LVOT-VTI +0.146 cm/s per 10 bpm HR increase per 20 ms AVD increase
p-value: p=0.013
BACKGROUND: During cardiac resynchronization therapy (CRT), cardiac performance is dependent on an optimized atrioventricular delay (AVD). However, the optimal AVD at different heart rates has not been defined yet during CRT. METHOD: The effects of an increase in heart rate by pacing or physical exercise on optimal AVD were studied in 36 patients with biventricular pacemakers/defibrillators. The velocity time integral (VTI) in the left ventricular outflow tract (LVOT) was measured with pulsed Doppler either at three different paced heart rates in the supine position or in seated position before and after physical exercise. RESULTS: The baseline AVD was optimized to 99 +/- 19 ms in the supine and 84 +/- 22 ms in the seated position. When the heart rate was increased by DDD pacing, there was a positive linear relationship between an increase in heart rate, in AVD and in VTI (LVOT-VTI + 0.047 cm/s per 10 beats per minute (bpm) heart rate increase per 20 ms increase in AVD, P = 0.007). A similar but more pronounced relationship was found after physical exercise in the seated position (LVOT-VTI + 0.146 cm/s per 10 bpm heart rate increase per 20 ms increase of AVD, P = 0.013). This effect was observed in patients with and without AV block and mitral regurgitation. CONCLUSIONS: In conclusion, the systolic performance of the dilated ventricle, which depends on an elevated preload, is critically affected by the appropriate timing of the AVD during exercise. In contrast to normal pacemaker patients, in CRT the relatively short baseline AVD should be prolonged at increased heart rates. Further studies with other means of measuring exercise cardiac performance are needed to confirm these unexpected findings.
Scharf et al. (Fri,) conducted a other in Cardiac resynchronization therapy (n=36). Prolongation of atrioventricular delay at increased heart rates vs. Baseline atrioventricular delay was evaluated on Velocity time integral (VTI) in the left ventricular outflow tract (LVOT) (LVOT-VTI +0.146 cm/s per 10 bpm HR increase per 20 ms AVD increase, p=0.013). Prolonging the atrioventricular delay at increased heart rates during CRT improved LVOT-VTI (+0.146 cm/s per 10 bpm heart rate increase per 20 ms increase of AVD after exercise, P=0.013).