Authors
Abraham WT, Young JB, Leon AR, et al.
Title
Effects of Cardiac Resynchronization on Disease Progression in Patients With Left Ventricular Systolic Dysfunction, an Indication for an Implantable Cardioverter-Defibrillator, and Mildly Symptomatic Chronic Heart Failure
References
Circulation 2004; 110: 2864-8
Background
Previous literature has shown that cardiac resynchronization improves quality of life, functional status, and exercise capacity in patients with moderate to severe systolic heart failure and a wide QRS complex with or without an indication for an ICD.
Purpose
To determine the safety and efficacy of CRT in patients with mildly symptomatic heart failure.
Design
Randomized, double-blind, parallel-controlled trial 186 patients with mildly symptomatic (NYHA class II) chronic heart failure, LVEF ≤ 35%, LV end-diastolic dimension ≥ 55 mm, QRS interval ≥ 130 ms, and an indication for an ICD. All patients on appropriate medical therapy including a diuretic, ACE inhibitor or ARB, digitalis, and a beta-blocker. Doses of the background medications were stable for ≥ 1 month (except for the beta-blocker, which was stable for 3 months).
Exclusion Criteria
Estimated survival < 6 months Baseline 6-minute walk test > 450 m Bradycardia requiring pacemaker Unstable angina, myocardial infarction, CABG, PTCA, cerebral vascular accident, or TIA within prior 3 months > 2 infusions of inotropic drug per week Systolic blood pressure <80 mmHg or > 170 mmHg Resting heart rate > 140 bpm Serum creatinine > 3 mg/dL (> 265 µmol/L) Hepatic enzymes > 3-fold upper normal values Severe lung disease Chronic atrial arrhythmias, or cardioversion or paroxysmal atrial fibrillation within previous 1 month Heart transplant recipient Severe valvular heart disease
Follow-Up
6 months
Treatment Regimen
Implantation of CRT/ICD device with a right atrial pacing lead, RV pacing/defibrillation lead, and an LV lead Random assignment to active CRT and active ICD therapy (CRT group) or active ICD therapy alone (control group) Evaluation at baseline, 1 month, 3 months, and 6 months after randomization
Results
Primary End Points: Change in peak oxygen consumption: CRT group (+ 0.5 mL/kg/min) vs control group (+ 0.2 mL/kg/min) (p = 0.87) Secondary End Points: Change in treadmill exercise duration: CRT group (+ 42 seconds) vs control group (+ 37 seconds) (p = 0.56) Change in ventilatory response to exercise (VE/VCO2): CRT group (- 1.8 mL/min) vs control group (+ 0.5 mL/min) (p = 0.01) Change in NYHA class: CRT group (- 0.18) vs control group (+ 0.01) (p = 0.05) Change in Quality of Life Questionnaire (Minnesota questionnaire – higher score, worse QOL): CRT group (- 13.3) vs control group (- 10.7) (p = 0.49) Change in six-minute hall walk distance: CRT group (+ 38 m) vs control group (+ 33 m) ( p = 0.59) Change in LV end-diastolic volume: CRT group (- 41 mL) vs control group (- 16 mL) (p = 0.04) Change in LV end-systolic volume: CRT group (- 42 mL) vs control group (- 14 mL) (p = 0.01) Change in LVEF: CRT group (+ 3.8%) vs control group (+ 0.8%) (p = 0.02) Composite clinical response – improvement (p = 0.01) Change in QRS duration: CRT group (-9 ms) vs control group (-9 ms) (p = 0.97) Occurrence of VF/VT: CRT group (22%) vs control group 26%) (p = 0.61)
Summary
In patients with mild heart failure symptoms (NYHA II) on optimal medical therapy with a wide QRS complex (≥ 130 ms) with an indication for an ICD, CRT did not alter exercise capacity but did result in significant improvement in cardiac structure and function.