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Figure 2 Survival curves, actual and projected. For the first 3.5 years, the two curves are the Kaplan-Meier estimates of the probability of survival in the implantable cardioverter-defibrillator (ICD) and conventional-therapy (CONV) arms, based on 1,095 patients in this cost study. From 3.5 years onward, the CONV survival curve has been projected assuming proportional hazards with an age- and gender-matched U.S. subpopulation, with a hazard ratio of 4.54. There are three projected ICD survival curves, ICD1 with hazard rates relative to CONV equal to 0.677 throughout, ICD2 with this hazard ratio increasing linearly to unity at 12 years, and ICD3 with the HR increasing to 1.44 at 12 years, reaching 1.0 at 7.1 years; see the text for rationales for these choices. Years-of-life saved are the areas between ICD and CONV curves.
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