Exclusion criteria and pacemaker implantation technique have been reported previously.
All were in sinus rhythm and had been stable in NYHA Class III under optimized treatment for at least 1 month before inclusion. Entry criteria included an ejection fraction less than 35%, an end-diastolic diameter greater than 60mm, and QRS duration greater than 150ms. Sixty-seven patients were recruited into the study. 2.2 Patient selection and pacemaker implantation The Ethics Committee in participating centres approved the study protocol, and all patients gave their written informed consent before inclusion. at 9 and 12 months following randomization). Patients were restudied 3 and 6 months after completion of the crossover phase (i.e. The single-blind crossover phase (active vs inactive) was followed by a longitudinal period during which the pacing system was programmed according to the patient's preferred study period during the crossover phase.
In order to determine the effects of 3 months active A-BiV pacing, patients in active mode during the first arm of the crossover were combined with patients in active mode during the second arm of the crossover. Treatment order was decided according to a randomized block design, stratified per investigation centre. Two weeks after implantation, patients were randomized to receive either active A-BiV pacing for 3 months followed by a 3-month period during which the pacemaker was inactive, or a 3-month run-in period with the pacemaker inactive followed by a 3 months active A-BiV pacing. Baseline observations were made at this stage. Once satisfactory A-BiV performance had been confirmed, the pacing system was programmed inactive (ventricular inhibited pacing at 40beatsmin −1basic rate). Pacemaker implantation was performed after a 1-month observation period to verify clinical stability. Inclusion began in March 1998 and lasted 12 months.
#IVCD 3.3.3 TRIAL#
The MUSTIC trial 18 is a single-blind, randomized, controlled, crossover study, with patients recruited from 15 European centres. We therefore used echocardiography to correlate the haemodynamic effects of A-BiV pacing with changes in cavity size and exercise tolerance up to 12 months after the onset of pacing in a sub-study of patients participating in the MUSTIC study. However, the mechanisms by which A-BiV pacing improves mechanical LV function and exercise tolerance in the medium term are complex and not well understood. Short-term studies using atrio-biventricular (A-BiV) pacing in patients with severe congestive heart failure and IVCD report haemodynamic improvement by altering the ventricular activation sequence, 10–17 and recent results from the MUSTIC trial 18 suggest A-BiV pacing significantly improves exercise tolerance and quality of life in such patients. 9 Biventricular pacing has been proposed as a means of altering the electrical activation sequence in patients with heart failure and IVCD, with the aim of restoring synchronous LV contraction. 7,8 These effects become more marked during dobutamine stress. Septal minor and long axis contraction are delayed, 4,5 time to maximum rate of rise of ventricular pressure is prolonged, and the duration of mitral regurgitation 6 and isovolumic periods are increased, so that diastolic filling time at rest is reduced. Intra-ventricular conduction delay (IVCD) is common in patients with severe heart failure 1–3 and causes left ventricular (LV) asynchrony. Atrio-biventricular, Pacing, Dilated cardiomyopathy, Intra-ventricular conduction delay, Total isovolumic time, Ventricular asynchrony 1 Introduction
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