Determination of the Optimal Atrioventricular Interval in Sick Sinus Syndrome During DDD Pacing

AV timing in pacemaker patients with first-degree AV block: which is preferable, intrinsic AV conduction or pacing?

Some patients with pacemakers present with first-degree atrioventricular (AV) block. To avoid right ventricular (RV) pacing, preserving intrinsic AV conduction as much as possible is recommended. However, there is no clear cutoff AV interval to determine whether intrinsic AV conduction should be preserved or RV pacing should be delivered. This study aimed to compare a pacing mode-preserving, intrinsic AV conduction with the DDD mode delivering RV pacing in terms of echocardiographic parameters in patients with first-degree AV block and to investigate whether RV pacing induces heart failure (HF). Stroke volume (SV) was measured to determine the optimal AV delay with the intrinsic AV conduction rhythm and the DDD pacing delivering RV pacing. Echocardiographic evaluation was performed for 6-month follow-up period. Seventeen patients were studied. At baseline, mean intrinsic PQ interval was 250 ± 40 ms. SV was greater with RV pacing with optimal AV delay of 160 ms than with intrinsic AV conduction rhythm in all patients. Therefore, pacemakers were set to the DDD to deliver RV pacing. During follow-up, seven patients developed HF. Mean baseline E/E′ ratio in patients who developed HF (HF group) during RV pacing was higher than in patients without HF (non = HF group; 17.9 ± 8 versus 11.5 ± 2, P = 0.018) Even within HF group patients without a high baseline E/E′ ratio, it increased with RV pacing (22.2 ± 6 versus 11.6 ± 2; P < 0.001). In patients with pacemaker and first-degree AV block, RV pacing with the optimal AV delay of 160 ms increased SV. However, the risk of HF may be increased with RV pacing if the E/Eʹ ratio is > 15 during intrinsic AV conduction or RV pacing. RV pacing should be avoided in patients with high E/Eʹ ratio under intrinsic AV conduction or RV pacing.

Echocardiography for determining the optimal atrioventricular interval in patients with dual chamber pacemakers

BACKGROUND

We investigated the clinical value of Doppler echocardiography for determining the optimal setting of atrioventricular interval in patients with dual chamber pacemakers (DDD). In 38 patients with complete atrioventricular block and DDD pacemakers, the atrioventricular interval was prolonged in a stepwise fashion by 20 ms, from 90 to 250 ms, and cardiac stroke volume and transmitral flow were measured by pulsed Doppler echocardiography.

METHODS

The optimal atrioventricular interval at which the cardiac stroke volume was maximal was 168.9 +/- 15.6 ms. The atrioventricular interval was 178.4 +/- 23.4 ms when the end of the A wave coincided with complete closure of the mitral valve.

RESULTS

There was a significant linear relationship between the optimal atrioventricular interval and the predicted optimal atrioventricular interval (Y = 86.2 +/- 0.5X, r = 0.70, standard error of the estimate [SEE] = 11.5, P < 0.01).

CONCLUSION

The optimal atrioventricular interval setting for DDD pacing can be successfully determined using Doppler echocardiography, which is a noninvasive, repeatable, and simple approach.