Abstract 17538: Risk Stratification for Sudden Cardiac Arrest in Ischemic Cardiomyopathy Patients Eligible for a Primary Prevention ICD
Background: The LV ejection fraction (EF ≤ 35%) is currently the only parameter used to identify ICD candidates for the primary prevention of sudden cardiac arrest (SCA) yet many patients die from other causes or never have an arrhythmic event. We determined whether a model could be developed to more precisely predict event rates.
Methods: The PAREPET trial (Prediction of ARhythmic Events with Positron Emission Tomography) enrolled subjects (n=204) eligible for a primary prevention ICD with ischemic cardiomyopathy. Four independent risk factors for SCA were selected to construct a risk index: LV end diastolic volume index (LVEDV ml/m2 = V), creatinine (Cr), angiotensin inhibition therapy (A=1, if treated, or 0, if not), and volume of denervated myocardium (D=% of total heart volume). A risk index was developed from a parametric survival analysis of the time to an adjudicated SCA (T). The log-logistic distribution was assumed for T and the mean (μ) of Y=ln(T) was specified as a linear function of the four risk variables. The risk index was defined as a function of time since enrollment (t) where R(t) = the cumulative probability of SCA before time t as follows: R(t)=1-[1+(t/exp(μ))1/σ]-1. The method of Kim, et al (2006) was applied for follow-up descriptions of significant results, controlling for A and Cr.
Results: SCA was independent of EF (mean 27± 9%, SD). Age was 67±11 years, 90% had angiotensin inhibition therapy and mean Cr was 1.4 (range 0.6 to 8.0). Mean LVEDV was 89 ml/m2 (range 34-169) and 27% of the LV was denervated by PET (range 2.4-59%). Estimates of R(t) calculated from the fitted model μ=11.7-4.7D+2.0A-0.42Cr-0.03V and the estimate of σ=0.97 for combinations of LVEDV and denervation are shown in the Table.
Conclusion: The risk of SCA varies dramatically as the amount of denervation, LVEDV and Cr increase, while angiotensin inhibition therapy reduces it. This risk index, R(t), may allow better selection of patients with an LV EF ≤ 35% who would benefit from an ICD.
- Sudden cardiac death
- Risk factors
- Implantable cardioconvert defibrillator
- Epidemiologic methods
- Evidence-based medicine
- © 2013 by American Heart Association, Inc.