Cardiac resynchronization therapy for the treatment of heart failure in patients with ventricular tachyarrhythmias - Cardiac resynchronization therapy for the treatment of heart failure
The goal of the study was to assess the safety and effectiveness of cardiac resynchronization therapy (CRT) when combined with an implantable cardioverter defibrillator (ICD) versus no CRT in patients with symptomatic heart failure (HF), intraventricular conduction delay, and malignant ventricular tachyarrhythmias.
Treatment with CRT and ICD therapy will be associated with a reduction in progression of HF compared with ICD therapy alone.
Patients Enrolled: 490
NYHA Class: NYHA class II/III/IV (%): 32/60/8 in CRT arm and 33/57/10 in control arm
Mean Follow Up: 3-6 months
Mean Patient Age: mean age 66 years
Mean Ejection Fraction: Mean baseline LVEF 21% in CRT arm and 22% in control arm
NYHA class II-IV, LVEF ≤35%, QRS interval ≥120 ms, and conventional indications for implant of an ICD
Atrial tachyarrhythmias or conventional indications for a permanent pacemaker
Progression of HF, defined as all-cause mortality, hospitalization for HF, and ventricular tachycardia/ventricular fibrillation requiring device intervention
Peak oxygen consumption (VO2), six-minute walk, NYHA class, QOL, and echocardiographic analysis
Patients with symptomatic HF, intraventricular conduction delay, and malignant ventricular tachyarrhythmias requiring therapy from an ICD were implanted with a device capable of providing both CRT and ICD therapy. Patients were randomized to CRT (n=245) or control (no CRT, n=245) for up to six months. The randomized therapy was programmed after 30 days without CRT.
Patients were treated for 30 days with medical therapy following the implantation of the ICD, but before programming CRT.
Although all patients were in New York Heart Association (NYHA) class II-IV at study entry, 40% of the patients who presented in NYHA class III/IV improved to NYHA class I or II, and 19% NYHA class II patients worsened to NYHA class III/IV during the 30-day medical therapy period.
The primary endpoint of HF progression did not differ significantly in the CRT versus the no CRT arm (relative 15% decrease with CRT, p=0.35). The secondary endpoints of peak VO2 (0.8 ml/kg/min vs. 0.0 ml/kg/min, p=0.030) and six-minute walking test (35 m vs. 15 m, p=0.043) were significantly improved in the CRT arm versus the no CRT arm.
There was no difference in changes in NYHA class (p=0.10) or quality of life (QOL) (p=0.40) between the treatment arms. Ventricular dimensions were improved in the CRT arm (left ventricular [LV] internal diameter in diastole, -3.4 mm vs. -0.3 mm, p<0.001; LV internal diameter in systole, -4.0 mm vs. -0.7 mm, p<0.001), as was LV ejection fraction (EF) (5.1% vs. 2.8%, p=0.020). In a subgroup analysis, CRT therapy was associated with improvements in the secondary endpoints of peak VO2, six-minute walking test, NYHA class, QOL, and LVEF in patients with advanced HF (NYHA class III/IV).
Among patients with symptomatic HF, intraventricular conduction delay, and malignant ventricular tachyarrhythmias, treatment with ICD therapy with CRT was not associated with an improvement in the primary endpoint of progression of HF compared with ICD therapy without CRT therapy, but was associated with improvements in many of the secondary endpoints of functional status.
CRT therapy was also associated with improvements in functional status, but not mortality in both the MIRACLE and MIRACLE ICD studies. The present study was underpowered to detect a significant difference in the primary endpoint because the actual event rate observed was approximately half that expected in the original study design.
Higgins SL, Hummel JD, Niazi IK, et al. Cardiac resynchronization therapy for the treatment of heart failure in patients with intraventricular conduction delay and malignant ventricular tachyarrhythmias. J Am Coll Cardiol 2003;42:1454-9.
Clinical Topics: Arrhythmias and Clinical EP, Diabetes and Cardiometabolic Disease, Heart Failure and Cardiomyopathies, Prevention, Implantable Devices, SCD/Ventricular Arrhythmias, Acute Heart Failure, Exercise
Keywords: Walking, Tachycardia, Ventricular, Quality of Life, Heart Conduction System, Ventricular Fibrillation, Heart Failure, Defibrillators, Implantable, Cardiac Resynchronization Therapy
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