Abstract

Prophylactic ICD: Review of main scores to predict survival benefit

Author(s): Moshe Rav-Acha, Ziv Dadon, Arik Wolak, Tal Hasin, Ilan Goldenberg, Michael Glikson

Current guidelines advocate prophylactic Implantable Cardioverter Defibrillator (ICD) for all symptomatic Heart Failure (HF) patients with Low Ejection Fraction (EF). As many patients will never use their device and some are prone to device-related complications, score delineating subgroups with differential ICD survival benefit is important to maximizing ICD benefits and mitigating complications. This review summarizes the main scores developed to predict the maximal or absence of ICD survival benefit, including The Madit-II-based Risk Stratification Score (MRSS) and the Seattle Heart Failure Model (SHFM), which were developed using randomized trials with a control group (medication only) and validated on large cohorts of ‘realworld’ HF patients with prophylactic ICDs, and other smaller models aiming to predict early mortality after ICD implant. Lastly, recent studies using cardiac MRI Cardiovascular Magnetic Resonance (CMR) to predict Ventricular Arrhythmia (VA) are mentioned. Most risk scores could not delineate sustained VA incidence, but rather overall mortality or mortality without prior appropriate ICD therapies, suggesting ICD nonbenefit. Multiple models have identified high-risk subgroups, consisting of 6%-20% of all prophylactic ICD candidates, who have an extremely high probability of early mortality after an ICD implant. On the other hand, low-risk subgroups were defined, in whom a high ratio of appropriate ICD therapy/death without prior appropriate ICD therapy was found, suggesting significant ICD survival benefit. Moreover, MRSS and SHFM models proved an actual ICD survival benefit in low- and medium-risk subgroups when compared with control patients, while no benefit was found in highrisk subgroups, consisting of 16%-20% of all ICD candidates. CMR reliably identified areas of myocardial scar and ‘channels’, with a remarkable ability to predict or exclude VA in those with or without a scar, respectively. To date, multiple scoring models exist that are capable of reliably predicting patient subgroups that would benefit or not from prophylactic ICD. Implementing these models into clinical practice may lead to an increase in the ICD benefit/non-benefit ratio, which is very low in current practice, based solely on EF evaluation. CMR is a potential technique which might help delineate patients with a low-versus high-risk for future VA, beyond EF alone.