Table 2

Primary Effectiveness End Points

Study DesignInSync (Medtronic)InSync ICD (Medtronic)Contak CD (Guidant)Contak TR (Guidant)Epic HF (St. Jude)
Year study began19981999199820002002
Year device approved20012002200220042004
Type of deviceCRT-PCRT-DCRT-DCRT-PCRT-D
ComparisonCRT on vs. offCRT on vs. offCRT on vs. offCRT on vs. offCRT on vs. off
Follow-up1, 3, 6 months1, 3, 6 months0, 3, 6 months0, 3, 6 months0, 1, 3, 6 months
BlindingDoubleDoubleDoubleUnblindedDouble
Primary effectiveness end pointNYHA functional class, 6-min walk, QOLNYHA functional class, 6-min walk, QOLComposite index (mortality, HF hospitalizations, therapy for VT/VF)Peak Vo2, 6-min walkPeak Vo2
Additional effectiveness end pointsMortality, peak Vo2, QRS, hospitalization, echo measures, neurohormonesMortality, peak Vo2, QRS, hospitalization, echo measures, neurohormonesPeak Vo2, QOL, 6-min walk, NYHA functional class, echo measures, norepinephrine, heart rateQOL and NYHA functional class6-min walk, QOL, NYHA functional class, echo measures
Sample size (total randomized)532555490448178

CRT = cardiac resyncronization therapy; HF = heart failure; NYHA = New York Heart Association; QOL = quality of life; VT/VF = ventricular tachycardia/ventricular fibrillation; Vo2= oxygen consumption.

  • The trial design defined success as occurring if any one of the three end points was statistically significant at alpha = 0.0167, if any two were significant at alpha = 0.025, or if all three were significant at alpha = 0.05.

  • The trial design defined success as occurring if: 1) peak Vo2improved >0.7 ml/kg/min (p < 0.05) and 6-MWD improvement resulted in p < 0.10; or 2) peak Vo2improved >0.5 ml/kg/min (p < 0.10) and 6-MWD improvement resulted in p < 0.05.