Inverted U-Shaped Relation Between the Risk of Sudden Cardiac Death and Maximal Left Ventricular Wall Thickness in Hypertrophic Cardiomyopathy

Abstract

H ypertrophic cardiomyopathy (HCM) is an inherited myocardial disorder characterized by increased left ventricular wall thickness, which is not solely explained by abnormal loading conditions. 1 The clinical perception is that the more severe the hypertrophy, the higher is the risk of sudden cardiac death (SCD) 2 and left ventricular maximal wall thickness (MWT) is one of several clinical features used to guide prophylactic implantable cardioverter defibrillator (ICD) therapy. [1][2][3] However, patients at the most severe end of the hypertrophy spectrum are under-represented in clinical studies 4,5 and their assumed highrisk status is based on extrapolation of data from other patient subgroups. A recent multicenter study reported that patients with left MWT ≥35 mm were not at higher risk of SCD compared with patients with lesser hypertrophy, 6 echoing the findings of an earlier cohort study. 7 The aim of this study was to examine the relation between MWT and the risk of SCD. Methods Study Design and OverviewThis is a retrospective, multicenter, longitudinal cohort study conducted by the Hypertrophic Cardiomyopathy Outcomes Investigators (http://www.HCMRisk.org). The relation of SCD risk and MWT was © 2016 American Heart Association, Inc.

Relationship Between Maximal Left Ventricular Wall Thickness and Sudden Cardiac Death in Childhood Onset Hypertrophic Cardiomyopathy

“…This finding is in keeping with recent reports from other independent pediatric populations, which have described a nonlinear association between interventricular septal thickness and left ventricular posterior wall thickness Z scores and SCD risk, plateauing at a Z score of 20 using the Boston normative data. 18,29,30 It is also in keeping with the results of a large adult HCM study (n=3673) 20 and suggests that the relationship between LVH and MLVWT is similar in adult and pediatric patients. The mechanism underlying these observations is unknown, but possible explanations include competing causes of death in those with severe LVH or alternative molecular arrhythmogenic pathways in those with milder hypertrophy.…”

Extreme Left Ventricular Hypertrophy in Pediatric Hypertrophic Cardiomyopathy: Good News or Bad News?

“…This study follows the findings of an inverted U-shaped relationship between the risk of SCD and MLVWT in adults (≥16 years) by O’Mahony et al 6 The inverted U-shape of this relation implies that the estimated risk of SCD increases with worsening hypertrophy to reach plateau and declines thereafter. O’Mahony et al 6 had shown that in adult patients, the cumulative incidence of SCD risk increased with 5 mm increments in MLVWT, but beyond MLVWT ≥35 mm the risk of SCD was not greater than the baseline HCM group with MLVWT≤14 mm. Similarly, Norrish et al 5 have shown that estimated risk of SCD at 5 years peaked at an MLVWT Z score of +23; beyond which no further increase in risk was seen, and instead, there was a fall in the estimated risk of SCD.…”

Role of echocardiography in the diagnosis and management of hypertrophic cardiomyopathy

“…Maximal WT has long been considered a key aspect of SCD risk stratification and is included in all stratification scores 1 15 30 40. Different studies reported an increased risk of SCD in patients with a maximal WT of ≥30 mm, although few data are available with extreme LVH (≥35 mm)41 and a paradoxical reduction in SCD risk has been reported recently in individuals with LVH ≥35 mm 42…”