Background: Biventricular pacing improves left ventricular dysynchrony, leading to improvement in congestive heart failure symptoms. The extent of placebo effect, the predictors of response and the long term benefits are unknown.
Patients and methods: Forty-five patients with symptomatic congestive heart failure underwent implantation of a biventricular pacing system over a 30-month period (age 65 10 years, 37 men). Patients underwent implantation of a biventricular pacemaker or implantable defibrillator one month or longer after stabilization of congestive heart failure on maximal medical therapy, including angiotensin-converting enzyme inhibitors in 84% of patients and beta-blockers in 56% of patients. Three patients had New York Heart Association (NYHA) class II heart failure, 34 had NYHA class III and eight had NYHA class IV. Cardiomyopathy was ischemic in 31 patients, dilated in 12 and the result of other causes in two. The left ventricular ejection fraction was 19 5%.
Results: Implantation of the biventricular pacing system was successful in 38 of 45 patients (84%). Two patients had successful implantation with a second attempt, and one patient had an epicardial lead implant. Lead dislodgement occurred in four patients, with successful repositioning in all. During a mean follow-up of 10 7 months, the Minnesota Living with Heart Failure Questionnaire quality of life index score improved from 62 16 to 42 22 at one month (P<0.001), but subsequently returned to intermediate levels (55 26 at three months, 48 26 at six months and 56 34 at one year, P=0.50). In seven patients with deferred device activation, quality of life scores also improved by 10 15 points from baseline to one month with VDI 35 pacing, and improved a further 15 20 points with left ventricular lead activation. The mean NYHA class fell from 3.1 0.5 at baseline to 2.7 0.7 at one month (P=0.006) and remained stable thereafter (2.8 0.9 at three months, 2.8 0.9 at six months). Six patients died during follow-up, one patient had a cardiac transplantation and subsequently died, one patient had a successful cardiac transplantation and one patient underwent insertion of a left ventricular assist device. Death occurred due to progressive heart failure in five patients, sudden death occurred in one patient and a noncardiovascular cause resulted in the death of one patient. An analysis of NYHA responders (NYHA class improvement of 1 or more at last follow-up, 44% of patients) and quality of life responders (score improvement of 10 or more at last follow-up, 57% patients) did not show any difference in age, sex, heart failure etiology, QRS width, ejection fraction or baseline NYHA class.
Conclusions: Biventricular pacing improves quality of life and NYHA class in patients with advanced heart failure and intraventricular conduction delay. The attenuated benefit seen over time may be related to initial placebo effect or simple dual- chamber pacing, or the natural history of the underlying disease. Identification of patients most likely to respond to biventricular pacing was not possible.