Powerlessness of a Number
Why Left Ventricular Ejection Fraction Matters Less for Sudden Cardiac Death Risk Assessment
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The national burden of sudden cardiac death (SCD) remains high at an annual incidence estimated at 183 000 and continues to account for a disproportionately elevated fraction of all cardiovascular deaths.1,2 Despite therapeutic advances in the treatment of coronary heart disease and heart failure and emphasis on SCD primary prevention with prophylactic implantable cardioverter defibrillators (ICDs), SCD accounts for 2.04 million or 40% to 50% of the potential years of life lost because of all premature cardiac death.2 SCD exceeds all noncardiac causes of death except overall cancer and accidents.2 However, it is well recognized that our current approach to SCD risk stratification that relies on a left ventricular ejection fraction (LVEF) <30% to 35% to identify primary prevention ICD candidates has limited overall societal impact. Particularly, among patients with nonischemic cardiomyopathy (NICM) with low LVEF, absolute SCD rates are declining in conjunction with comprehensive heart failure medical therapy and cardiac resynchronization therapy, as evidenced by the recently published DANISH trial (Danish Study to Assess the Efficacy of ICDs in Patients with Non-ischemic Systolic Heart Failure on Mortality).3,4 In contrast, individuals with LVEF >35% account for the highest absolute number of SCDs, comprising 70% to 80% of those who experience SCD.5,6
See Article by Pontone et al
LVEF is an inadequate surrogate for the underlying myocardial phenotype predisposing to SCD.7 The same LVEF can represent multiple cardiomyopathic derangements. Although a powerful predictor of total and non-SCD mortality, it has limited specificity for SCD. No LVEF cutoff discriminates between sudden and nonsudden modes of cardiac death.5,6,8 In fact, LVEF is not directly related to mechanisms of arrhythmia and can be subject to considerable spontaneous variability in individuals.5
Myocardial fibrosis is a major pathophysiologic determinant …