A Novel Clinical Risk Prediction Model for Sudden Cardiac Death in Hypertrophic Cardiomyopathy (HCM Risk-SCD)
Can a new risk prediction model for sudden cardiac death (SCD) that provides individualized risk estimates be developed for hypertrophic cardiomyopathy (HCM) patients?
HCM is a leading cause of SCD, particularly in young adults. Current risk algorithms are insufficient and provide only a crude estimate of risk, making it difficult for patients and physicians to make informed decisions about treatment. The authors developed a prognostic model of SCD/appropriate shock from an implantable cardioverter-defibrillator (ICD) that was derived from a retrospective, multicenter longitudinal cohort study. The cohort study included patients from six large centers in Europe. The prognostic model was constructed from the entire data set using a Cox proportional hazards model and then internally validated using bootstrapping. Factors included in the model were obtained from the published literature.
The study population included 3,675 consecutive patients. During a follow-up period of 24,313 patient-years (median 5.7 years), 198 patients (5%) died suddenly or had an appropriate ICD shock. Of eight prespecified predictors, age, maximal left ventricular wall thickness, left atrial diameter, left ventricular outflow tract gradient, family history of SCD, nonsustained ventricular tachycardia, and unexplained syncope were associated with SCD/appropriate ICD shock at the 15% significance level. These predictors were included in the final model to estimate individual probabilities of SCD at 5 years with a c-index of 0.70 (95% confidence interval, 0.68-0.72). For every 16 ICDs implanted in patients with ≥4% 5-year SCD risk, potentially one patient will be saved from SCD at 5 years.
The authors noted that this is the first validated prognostic model for SCD among patients with HCM. It provides clinicians with the opportunity to discuss individualized estimates for these patients using readily collected clinical parameters.
HCM is a common inherited disorder and an important cause of SCD in young patients. Risk prediction is important, given that ICDs may be life-saving in appropriate cases, but could lead to complications and unnecessary procedures in low-risk individuals. This study provides a contemporary examination of factors that could lead to individualized risk prediction. However, clinicians do need to be cautious in its use for several reasons. Some high-risk patient subgroups (those with prior SCD) were appropriately excluded, and treatments such as surgical myectomy or septal ablation and beta-blockers were not considered. That said, this paper is an important step forward in understanding how outcomes vary in these patients. The collaborative effort of these six centers to better understand this condition, therefore, should be applauded.
Keywords: Prognosis, Defibrillators, Follow-Up Studies, Proportional Hazards Models, Death, Cardiomyopathies, Syncope, Europe, Tachycardia
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