Original article
Cardiovascular
Optimized Biventricular Pacing in Atrioventricular Block After Cardiac Surgery

https://doi.org/10.1016/j.athoracsur.2005.03.111Get rights and content

Background

Temporary pacing is required after open-heart surgery for treatment of heart block. Atrioventricular delay and ventricular pacing site might be manipulated to increase cardiac output. We hypothesized that by optimizing both atrioventricular delay and ventricular pacing site a 10% improvement in cardiac output would be observed compared with a standard pacing protocol.

Methods

Seven patients in first or third degree heart block after valve replacement surgery had temporary wires sewn to the right atrium, right ventricle, and left ventricle. Cardiac output was measured by integrating flow velocity from an ultrasonic aortic flow probe. After optimization of atrioventricular delays during atrial synchronous right ventricular pacing, the effects of ventricular pacing site were tested at the optimum atrioventricular delay for 10-second intervals.

Results

Biventricular pacing was beneficial in all patients with a mean increase of 22% in cardiac index over right ventricular pacing (1.95 L/min/m2 ± 0.27 standard error of the mean (SEM) to 2.38 L/min/m2 ± 0.27 SEM, p = 0.0012) and 14% over left ventricular pacing (2.08 L/min/m2 ± 0.22 SEM to 2.38 L/min/m2 ± 0.27 SEM, p = 0.0133). Comparing optimized with standard pacing for 30-second intervals yielded a mean increase of 10% in cardiac index over three respiratory cycles (2.87 L/min/m2 ± 0.33 SEM to 2.60 L/min/m2 ± 0.37 SEM, p = 0.009) and 17% at the corresponding end-expiratory beats (2.76 L/min/m2 ± 0.33 SEM to 2.36 L/min/m2 ± 0.36 SEM, p = 0.011).

Conclusions

Biventricular pacing at optimum atrioventricular delay improves cardiac output in patients with postoperative heart block by at least 10% compared with standard pacing.

Section snippets

Patient Selection

This study was approved by the Western Institutional Review Board. With the consent of the attending surgeon, patients undergoing open-heart surgery with a high probability of postoperative AVB were approached to enroll in this study. All patients gave informed consent. Candidates included patients undergoing valve replacement surgery and patients with known first, second, or third degree block. Patients were excluded if the surgeon did not plan to dissect the aorta or pulmonary artery in case

Study Population

A total of 15 patients were enrolled in this study. Eight patients were excluded because they did not develop heart block. Upon separation from CPB, the protocol was initiated in 7 patients. Six patients developed complete heart block and one patient remained in first-degree heart block. Table 2 lists baseline clinical characteristics for these patients including primary pathologic lesions.

Preoperatively, 4 patients were in normal sinus rhythm and 3 patients were in first-degree heart block.

Comment

This study indicates that BiVP at optimum AVD significantly enhances CO in patients with AVB during open-heart surgery. Although optimum AVD setting was patient specific, in each case BiVP was associated with significant improvement in CO compared with RV or LV pacing. The present study systematically studies acute effects of pacing protocol modification at constant heart rate in patients who require pacing for AVB after CPB during open-heart surgery. In this study, we focused primarily on the

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