Cardiology Medical News about heart failure;implantable cardioverter-defibrillator

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Maximizing Survival Benefit With Primary Prevention Implantable Cardioverter-Defibrillator Therapy in a Heart Failure Population
Circulation, 08/27/09

Levy WC et al. – A clinical risk prediction model identified subsets of moderately symptomatic heart failure patients in SCD–HeFT in whom single–lead ICD therapy was of no benefit and other subsets in which benefit was substantial.

Exclusive Author Commentary
Wayne C. Levy, 08/27/09

There has been considerable debate about which heart failure patients should receive a primary prevention ICD. We used a variant (SHFM-D) of the widely validated Seattle Heart Failure Model (SHFM - Http://SeattleHeartFailureModel.org) and applied it prospectively to the Sudden Cardiac Death Heart Failure Trial (SCD-HeFT). This was a trial of primary prevention single lead ICDs in NYHA 2 or 3 heart failure patients with an ejection fraction of ?35%. We have previously shown that low risk patients by the SHFM have a higher proportion of deaths due to sudden death (and thus likely more benefit from an ICD) while higher risk patients have a higher proportion of deaths due to progressive heart failure, where an ICD may not alter total mortality (Circulation 2007). Within the SCD-HeFT trial, the lower risk patients with a ~2.5-4.5% annual mortality had an ~90% reduction in sudden death and an ~50% reduction in all cause mortality. This translated into ~2 years of additional total lifespan for each ICD placed. It is likely these patients may require 2 or 3 ICDs over their lifetime. Thus, an ICD approach is anticipated to add 4-6 years of total life expectancy in these lower risk patients. In NYHA 2 or 3 patients who had an estimated annual mortality of ~20%, the ICD failed to reduce all cause mortality and prevented only ~25% of sudden deaths. Thus, many of the events adjudicated by the blinded event committee as sudden death, were unable to be prevented by an ICD either due to other causes of sudden death (i.e. pulseless electrical alternans, pulmonary embolus, pump failure, etc.) or the ICD failed to terminate the event (VT storm or intractable VF). In this analysis, NYHA 2-3 patients with a ~20-25% annual mortality (i.e. high risk) had no mortality benefit from a primary prevention ICD. Most NYHA 2 patients will not be in this high risk group (~2% of all NYHA 2 patients) whereas ~15% of NYHA 3 patients may be in this high group who had no benefit from a primary prevention ICD. Thus, it is likely use of risk stratification using the SHFM-D will be most effective in NYHA 3 patients. A caution is that this analysis only applies to primary prevention ICDs and not secondary prevention ICDs. Further research is necessary to identify which patients derive the most benefit from a secondary prevention ICD. At this time, we have not developed an interactive version of the new simplified model, SHFM-D. You can use the current SHFM at Http://SeattleHeartFailureModel.org or in the Epocrates Tool Kit (Pocket PC and Palm) to estimate annual mortality. If the estimated mortality is >20-25%/year than a primary prevention ICD will likely have no benefit based on the results of this research (please note the interactive model has not been modified to reflect this new research). We hope to have an interactive version of the SHFM-D available in the future.

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