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Interact CardioVasc Thorac Surg 2009;8:673-678. doi:10.1510/icvts.2008.201350 © 2009 European Association of Cardio-Thoracic Surgery
Does biventricular pacing provide a superior cardiac output compared to univentricular pacing wires after cardiac surgery?
a Department of Cardiothoracic Surgery, Morriston Hospital, Swansea, Wales, UK Received 23 December 2008; received in revised form 11 March 2009; accepted 13 March 2009
*Corresponding author. Tel./fax: +447801548122.
A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether biventricular pacing provides a superior cardiac output compared to univentricular pacing wires after cardiac surgery. Using the reported search, 439 papers were found from which 13 papers represented the best evidence on the subject. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes and results are tabulated. We conclude that in 9 of the 13 papers presented, significant increases in the cardiac index and mean arterial pressure were found with biventricular pacing. In the four negative studies, which included an experimental study, the patients tended to have normal or better ejection fractions and narrow QRS complexes. Up to a 22% increase in Cardiac Index was reported in the positive studies. Exact pacing wire placement varies and some studies caution that if in the wrong place, the index can actually drop. Transoesophageal flow volume loops have been used to guide placement. Benefits seem greatest in patients with a poor ejection fraction and a wide QRS complex.
Key Words: Thoracic surgery; Biventricular pacing; Cardiac surgery
A best evidence topic was constructed according to a structured protocol. This protocol is fully described in the ICVTS [1].
You are in theatre assisting with a patient who has just undergone an aortic and mitral valve replacement. The left ventricular function was impaired and the consultant asks for biventricular epicardial pacing leads. You have not seen these before and ask your consultant if this helps the cardiac index. He suggests that you look it up and answer the question for yourself.
For (patients after cardiac surgery) do (biventricular pacing wires compared to right ventricular wires alone) provide a (superior cardiac output)?
Medline 1950 to Dec 2008 using the Ovid SP interface (left ventri$.mp or biventricular.mp) AND (exp Pacemaker, Artificial/OR Cardiac Pacing/or pacing.mp) AND (exp Thoracic Surgery/OR Cardiovascular Surgical Procedures/OR exp Cardiac Surgical Procedures/OR CABG.mp OR cardiac surgery.mp).
Four hundred and thirty-nine papers were found from which 13 represented the best evidence papers. These are documented in Table 1.
Epicardial pacing is commonly indicated in cardiac surgical patients and this is conventionally performed using right ventricular (RV) and right atrial (RA) pacing wires. RV pacing wires are usually used due to ease of application to the anterior wall of the RV. In the non-cardiac surgical literature, cardiac resynchronization therapy (CRT) is known to benefit patients in heart failure. The Pacing Therapies for Congestive Heart Failure [PATH-CHF] study [2, 3] has demonstrated the advantageous haemodynamics of CRT in patient with severe LV dysfunction. Similarly, the Multisite Stimulation Cardiomyopathy [MUSTIC] study [4] demonstrated a significant improvement in LV ejection fraction (EF) and patient symptoms after 12 months of biventricular pacing in 131 heart failure patients. In patients after cardiac surgery, Flynn et al. [5] studied the effect of atrio-monoventricular pacing with active lead placement on the right ventricle (control), the anterior left ventricle and the posterior left ventricle. In the 25 patients studied, pacing with the active lead placed posteriorly on the left ventricle increased cardiac index from 2.74 to 3.08 l/min/m2 (P=0.019). Significant increases in mean arterial pressure were also observed (67.88 mmHg to 71.12 mmHg, P=0.02) with the use of this pacing mode. There were no complications relating to application or removal of the left ventricle pacing leads. Foster et al. [6] studied the effects of atrio-biventricular pacing in comparison to atrio-monoventricular pacing in 18 elective coronary artery bypass patients of whom 14 had LV ejection fractions (LVEF) of over 40%. They found that biventricular pacing was associated with a significant increase in cardiac index (CI) relative to all other pacing modes studied and decreased systemic vascular resistance. Weisse et al. [7] studied the effect of atrio-biventricular pacing in 22 patients with poor left ventricular function (EF 29.8±4.8) who underwent CABG. Temporary epicardial pacing electrodes were placed on the right atrium and the paraseptal region of the left and right ventricle. The study showed that in patients with left bundle branch block, atrio-biventricular (and also atrio-left ventricular) pacing increased cardiac index and decreased wedge pressure compared with atrial (and atrio-right ventricular) pacing. Tanaka et al. [8] studied the effect of biventricular pacing in four patients with severe left ventricular dysfunction and dilatation with intraventricular conduction delay. They found that in the acute post-surgical period, biventricular pacing increased mean systemic blood pressure by 11% and mean LV stroke work index by 19% and also reduced mitral regurgitation. Dekker et al. [10] studied 11 patients, who had been referred for surgical LV lead placement after failed coronary sinus lead implantation using pressure-volume loops created by a conductance catheter to select the optimal site. They found that biventricular pacing with an optimal LV lead position significantly increased stroke volume (51–71 ml, P=0.01), and ejection fraction (27–35%, P=0.007). Biventricular pacing at a suboptimal site did not significantly change left ventricular function and even worsened it in some cases. Schmidt et al. [11] reported that neither cardiac index nor pulmonary artery pressure or pulmonary capillary wedge pressure showed any significant difference during the various pacing configurations in a study of 26 patients including both CABG and valve procedures. They conclude that biventricular pacing after heart surgery does not improve parameters of regional and global LV systolic function. Healy et al. [13] looked at coronary conduit flow as well as cardiac index in patients after first-time CABG with either DDD RV pacing or DDD biventricular pacing. They found no differences between these modes but all of their patients had LVEF above 30% and narrow QRS complexes. Berberian et al. [14] observed a 22% increase in the cardiac index in eight patients having DDD RV pacing compared to DDD biventricular pacing. These patients were all undergoing valve replacement or already had a conduction block and five had a QRS interval of more than 150 ms. Dzemali et al. [15] showed in 54 patients with ejection fractions <30% undergoing cardiac surgery that many of these patients could have their cardiac index significantly improved with biventricular pacing. Kleine et al. [16] reported a single patient with a 170 ms QRS who only successfully weaned from bypass after biventricular pacing was instituted. Raichlen in 1984 investigated the effect of LV or RV pacing in elective CABG patients but found no difference in these patients with good LV function [17]. Muehlschlegel et al. [18] in ten patients with poor LV function found a 44% increase in cardiac index compared to pre-operatively, and 13% better than a univentricular lead. They place their lead on the obtuse margin of the LV next to the first obtuse marginal artery. One animal-based study by Tomioka et al. [9] showed that biventricular pacing in pigs actually disrupts the natural sequence of shortening of the myocardial band and results in impaired LV function but they found that high septal pacing preserves the sequential shortening pattern of the myocardial band and LV function.
In nine of the 13 papers presented, significant increases in the cardiac index and mean arterial pressure were found with biventricular pacing. In the four negative studies, which included an experimental study, the patients tended to have normal or better ejection fractions and narrow QRS complexes. Up to a 22% increase in Cardiac Index was reported in the positive studies. Exact placement varies and some studies caution that if in the wrong place, the index can actually drop. Transoesophageal flow volume loops have been used to guide placement. Benefits seem greatest in patients with a poor ejection fraction and a wide QRS complex.
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Abstract
1. Introduction
