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J Thorac Cardiovasc Surg 2006;132:974-975
© 2006 The American Association for Thoracic Surgery
Brief Communication |
Washington University, Barnes Hospital, St Louis, Mo.
Received for publication August 27, 2005; accepted for publication April 14, 2006. * Address for reprints: Omid Hajiseyedjavadi, MD, MSc, 12513 E Lupine Ave, Scottsdale, AZ 85259. (Email: javadio{at}wustl.edu).
Biventricular pacing, or chronic resynchronization therapy (CRT), has been increasingly used in management of patients with class III to IV heart failure who have evidence of interventricular conduction delay. Despite the widespread use of this therapy, the endocardial procedure required for left ventricular (LV) lead placement can be labor intensive and fails in approximately 10% of patients.1,2
In fact, the LV lead placement in the Multicenter InSync Randomized Clinical Evaluation (MIRACLE) trial was associated with the highest rate of complication.1 Large number of patients undergoing cardiac surgery have some degree of systolic dysfunction in conjunction with interventricular conduction delay. Prophylactic epicardial LV lead placement in this setting may be beneficial and can be performed with ease. In the absence of any trials showing the beneficial effects of prophylactic LV lead placement during cardiac surgery, we sought to perform a subgroup analysis of the Multicenter InSync Implantable Cardioverter-Defibrillator (ICD) Randomized Clinical Evaluation (MIRACLE-ICD) trial to determine whether the beneficial effects of biventricular pacing continue to be evident in patients who had previously undergone coronary artery bypass grafting (CABG).
A review of the raw data from the MIRACLE-ICD trial was performed to determine the response to CRT of patients with coronary artery disease who received biventricular therapy long after CABG. A subgroup analysis from 363 patients with ischemic heart disease enrolled in the MIRACLE-ICD trial (New York Heart Association [NYHA] functional class III/IV symptoms, ejection fraction 
35%, QRS 
130 ms, and indication for ICD) revealed 222 (61%) with history of CABG. This subgroup formed the basis of this analysis. This group of patients had been prospectively randomly assigned 1:1 to 6 months of CRT versus no pacing. From this subset, clinical end points were analyzed with 2-sided Student t tests with mean ± SD changes from baseline to 6 months.
Mean age was 69 years, and 92% of the patients were male. Mean values were as follows: time from CABG to CRT, 9.2 years; number of vessels bypassed, 3.5; ejection fraction, 21.5%; and NYHA functional class, 2.8. Table 1 summarizes the outcomes.
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Biventricular pacing has been popularized as a new nonpharmacologic therapy for patients with chronic heart failure. In the 1980s, interest in pacing therapy for heart failure largely revolved around manipulation of the atrioventricular delay in patients with heart failure who were implanted with dual-chamber pacemakers that used right atrial and right ventricular leads.3 Shortening the atrioventricular delay appeared to be beneficial in patients with first-degree atrioventricular block and in those with Doppler evidence of presystolic mitral regurgitation.2,4 Early reports of biventricular pacing involved epicardial LV leads. In 1994, Cazeau and associates and later Foster and colleagues5 investigated pacing after CABG. Both groups found that maximal hemodynamic benefit was derived from a combination of atrial and biventricular pacing, especially when ventricles contracted sequentially and in synchrony. The underlying concept of CRT was that the efficiency of the heart as a pump would be increased if the start of systole could be synchronized by simultaneously pacing the two atria, followed by the ventricles.
In this subgroup analysis of a randomized, prospective trial, we demonstrated that patients who have previously undergone CABG derive benefits from CRT similar to those seen in the large cohort of patients in the MIRACLE-ICD trial. More specifically, the cohort of patients with NYHA class III or IV symptoms, ejection fraction no greater than 35%, QRS at least 130 ms, and indication for ICD demonstrated a predictable benefit from resynchronization. Although there may be other groups of patients with predictable benefit from an intraoperative lead placement, our data address the benefit for this particular cohort at this time. It is our contention that improvements in functional capacity of this subgroup of patients is a compelling argument in favor of prophylactic epicardial LV lead placement at the time of cardiac surgery. The potential difficulty of percutaneous lead placement—related to difficulties in cannulating the coronary sinus, variable anatomy, unsuitable target veins, diaphragmatic stimulation, and lead dislodgment—can be circumvented if these leads are placed during cardiac surgery.
Footnotes
Medtronic is the sponsor of the MIRACLE trial, which provided the data for this study. R.D. reports consulting and lecture fees from Medtronic. T.M. and K.H. report that they are employees of Medtronic and hold stock options in the company.
References
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