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eComment: Biventricular pacing improves cardiac function compared to univenticular pacing alone in postoperative patients

Cardiothoracic Surgery Department of University Hospital of Patras, Rion Patras, Greece

Does biventricular pacing provide a superior cardiac output compared to univentricular pacing wires after cardiac surgery?

Several studies have recently suggested that atrio-biventricular (RA-BiV) pacing or cardiac resynchronization therapy (CRT) may improve hemodynamics in post-cardiac surgery patients, as you mentioned in your very well-structured article [1]. Routinely, in cardiac surgical procedures, epicardial pacing leads are placed on the right atrium (RA) and right ventricle (RV) in case of significant bradycardia or development of atrioventricular block. However, it has been reported previously that atrio-RV (RA-RV) pacing may induce LV dyssynchrony and hemodynamic compromise compared with atrial pacing (RA) alone [2].

In a recent prospective observational study, Cannesson et al. studied the impact of atrio-biventricular pacing on hemodynamics and left ventricular dyssynchrony compared with atrio-right ventricular pacing alone in the postoperative period after coronary artery bypass grafting (CABG), confirming the beneficial effect of biventricular pacing even in postoperative patients [3]. Especially, 25 consecutive patients undergoing CABG surgery (9 off pump and 16 using cardiopulmonary bypass) were studied during atrial, RA-RV, and RA-BiV pacing. Patients with cardiac arrhythmias, preoperative left bundle-branch block, postoperative inotropic support, and intracardiac shunt were excluded. It is notable that preoperative left ventricular ejection fraction (LVEF) was between 30% and 70% (mean LVEF 54±11%), while QRS duration was <120 milliseconds in all patients. Cardiac output (CO) calculated by using the velocity-time integral obtained by transthoracic echocardiography and left ventricular dyssynchrony using tissue Doppler imaging (TDI) were assessed at each step [3].

Interestingly, the above study revealed that RA-RV pacing induces a decrease in CO compared with RA pacing, and that RA-BiV pacing significantly improves CO compared with RA-RV pacing in the postoperative period after CABG surgery [3]. This improvement is related to the restoration of LV synchronicity. Especially, the benefits of CRT are stemed from a) the acute resynchronization of regional LV mechanics, b) the notable decrease in mitral regurgitation, and c) the reverse remodeling that is a long-term effect of CRT [3]. Moreover, CRT is able to improve contractility while decreasing myocardial oxygen consumption [4].

In chronic heart failure (HF) patients, RV pacing has even been shown to increase the risk of death or acute HF hospitalization. Several studies suggest that biventricular pacing has the ability to reverse the abnormal activation pattern induced by RV pacing and to restore hemodynamics [5]. Cannesson et al. support this hypothesis by describing the acute deleterious effect of RV pacing on CO. This effect seems to be related only to LV dyssynchrony induced by this pacing mode. By performing RA-BiV pacing, the authors were able to restore LV synchronicity and significantly increase CO. Thus they found that RA-BiV pacing was able to weakly but significantly increase CO compared with RA pacing alone [3].

In conclusion, the well-documented observation that BiV pacing significantly improves CO compared with RA-RV pacing after CABG surgery by restoring LV synchronicity, renders cardiac resynchronization therapy as the most optimal pacing mode even in postoperative patients.

	References

Top References

 

1. Vaughan P, Bhatti F, Hunter S, Dunning J. Does biventricular pacing provide a superior cardiac output compared to univentricular pacing wires after cardiac surgery. Interact CardioVasc Thorac Surg 2009;8:673–679.[Abstract/Free Full Text]
2. Pham PP, Balaji S, Shen I, Ungerleider R, Li X, Sahn DJ. Impact of conventional versus biventricular pacing on hemodynamics and tissue Doppler imaging indexes of resynchronization postoperatively in children with congenital heart disease. J Am Coll Cardiol 2005;46:2284–2289.[Abstract/Free Full Text]
3. Cannesson M, Farhat F, Scarlata M, Cassar E, Lehot J. The impact of atrio-biventricular pacing on hemodynamics and left ventricular dyssynchrony compared with atrio-right ventricular pacing alone in the postoperative period after cardiac surgery. J Cardiothorac Vasc Anesth 2009 Feb 11, [Epub ahead of print].
4. Nelson GS, Berger RD, Fetics BJ, Talbot M, Spinelli JC, Hare JM, Kass DA. Left ventricular or biventricular pacing improves cardiac function at diminished energy cost in patients with dilated cardiomyopathy and left bundle-branch block. Circulation 2000;102:3053–3059.[Abstract/Free Full Text]
5. Kindermann M, Hennen B, Jung J, Geisel J, Böhm M, Fröhlig G. Biventricular versus conventional right ventricular stimulation for patients with standard pacing indication and left ventricular dysfunction: the Homburg Biventricular Pacing Evaluation (HOBIPACE). J Am Coll Cardiol 2006;47:1927–1937.[Abstract/Free Full Text]

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