Table 1.

Landmark CRT Trials

Study	n	Inclusion Criteria	QRS (ms)	Design	Blinding	Control	Intervention	Follow-Up (months)	Primary End Point	Results
MIRACLE (4)	453	NYHA functional class III  or IV, LVEF ≤ 35%,  LVEDD ≥ 55 mm, SR	≥130	Parallel	Double  blind	CRT-Off	CRT-On	6	6MWD, NYHA functional  class, MLHFQ score	↑ 6MWD (p = 0.005), improved  NYHA functional class (p < 0.001),  ↓ MLHFQ score (p = 0.001)
MIRACLE-ICD (5)	369	NYHA functional class III  or IV, LVEF ≤ 35%,  LVEDD ≥ 55 mm,  ICD indicated, SR	≥130	Parallel	Double  blind	CRT-D  (CRT-Off)	CRT-D (CRT-On)	6	Peak VO2, NYHA  class, MLHFQ score	↑ 6MWD (p = 0.36), improved  NYHA functional class (p = 0.007),  ↓ MLHFQ score (p = 0.02)
Contak CD (6)	490	NYHA functional class  II–IV, LVEF ≤ 35%,  ICD indicated, SR	≥120	Parallel	Double  blind	CRT-D  (CRT-Off)	CRT-D (CRT-On)	6	Composite: all-cause mortality,  HF hospitalization, VT/VF  requiring intervention	RRR 15% (p = 0.35)
COMPANION (1)	1,520	NYHA functional class III  or IV, LVEF ≤ 35%,  LVEDD ≥ 60 mm, SR	≥120	1:2:2	—	Medical  therapy	CRT-P, CRT-D	16.2 (median)	All-cause mortality or  hospitalization	CRT-P HR: 0.81 (95% CI: 0.69−0.96;  p = 0.014); CRT-D HR: 0.80  (95% CI: 0.68–0.95; p = 0.010)
CARE-HF (3)	813	NYHA functional  class III or IV, LVEF ≤  35%, SR	≥150, 120−150 +  echocardiographic  dyssynchrony	Parallel	—	Medical  therapy	CRT-P	29.4 (mean)	All-cause mortality or CV  hospitalization	HR: 0.63 (95% CI: 0.51−0.77;  p < 0.001)
CARE-HF  Extended (2)								37.4	All-cause mortality	HR: 0.60 (95% CI: 0.47−0.77;  p < 0.0001)

CARE-HF = Cardiac Resynchronization–Heart Failure; CI = confidence interval; COMPANION = Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure; CRT = cardiac resynchronization therapy; CRT-D = cardiac resynchronization therapy with defibrillator; CRT-P = cardiac resynchronization therapy only; HF = heart failure; HR = hazard ratio; ICD = implantable cardioverter-defibrillator; LVEDD = left ventricular end-diastolic dimension; LVEF = left ventricular ejection fraction; MIRACLE = Multicenter InSync Randomized Clinical Evaluation; MIRACLE-ICD = Multicenter InSync ICD Randomized Clinical Evaluation; MLHFQ = Minnesota Living With Heart Failure Questionnaire; NYHA = New York Heart Association; RRR = relative risk ratio; 6MWD = 6-minute walk distance; SR = sinus rhythm; VF = ventricular fibrillation; VO₂ = oxygen consumption; VT = ventricular tachycardia; ↑ = increased; ↓ = decreased.