ABC | Volume 115, Nº2, August 2020

Original Article Mattos BP et al. Sudden death in hypertrophic cardiomyopathy Arq Bras Cardiol. 2020; 115(2):197-204 history of SCD and NSVT added to LVOT obstruction, was associated to a decrease of device recommendations with the ESC risk score, reaching an ICDunwarranted in 55%of the cases. Our results suggest that the downgrade in ICD recommendations provided by the ESC model is mainly related to cases in which the recommendationwith theNorth American guideline is based on the presence of a single predictor associated or not with a modifying risk factor. These findings are justified by the fact that the European model defines primary prevention on the basis of a set of risk factors and not on the presence of a single marker. The ESC HCM risk-SCD score has been independently validated in the populations of three continents in observational studies mostly showing that the new model contributes to the improvement of risk stratification and clinical decision-making. 24-28 Other studies point out the sensitivity of low score for the recognition of high-risk patients, the capacity to identify cases with an ICD unwarranted and the similar event rates observed in the three risk levels. 29-32 Our study supports these findings demonstrating that the European model decreases the ICD recommendations compared to the North American guideline, leaves all patients with SCDor appropriate shock unprotected and establishes major agreement in cases not requiring implantation. Nevertheless, themetanalysis of six studies conductedwith 7,291 patients demonstrates that in most cases, the five-year SCD risk is properly estimated with the ESC score. 33 The European score settles the stratification for SCD using a rigid statistical model in a complex disease with unpredictable course. Methodological limitations may depend on left atrial evaluation with diameter, LVOT obstruction with Valsalva maneuver, and on exclusion of myocardial ischemia, late gadolinium enhancement and LV apical aneurysm. Although restrictions may be admitted to its performance, particularly in high-risk patients, the European score should be assimilated in clinical practice as a validated tool to guide therapeutic decisions. The assessment of the percentages achieved by the variables in the formula in each case may contribute to the interpretation of results in clinical practice. In the present study, the North American approach would protect a higher number of individuals than the European criteria, although it could result in unnecessary implants and could expose these populations to device complications such as infections and inappropriate shocks. 4,15,17 Prospective studies equally validated in lower risk populations are necessary to identify new predisposing factors that may improve the indications of primary prevention ICD. Study limitations The present study is based on the evaluation of a well- documented single-center HCM cohort comprising a less selected and older population. The clinical characteristics and the reduced event rates show the low-risk profile of the study patients, who differ from those included in the majority of the validation cohorts. These aspects may limit our conclusions to populations presenting the same characteristics. However, the study cases are as representative of the disease as those selected in referral centers with higher risk and more prone to complications. Conclusions In the study of an older low-risk HCM cohort, we found low agreement between the SCD primary prevention criteria established by the 2011 ACCF/AHA and the 2014 ESC guidelines. The ESC HCM risk-SCD score has decreased the ICD recommendation in the study population, especially in those with class IIa under the North American system and left all patients presenting SCD or appropriate shock in the period unprotected. The major contribution for the score calculation of the risk predictors not included in the 2011 ACCF/AHA strategy may justify in some way the discrepancy between the two guidelines. Author contributions Conception and design of the research, Acquisition of data, Analysis and interpretation of the data and Writing of the manuscript: PMattos BP, Scolari FL, Garbin HI; Statistical analysis and Critical revision of the manuscript for intellectual content: Mattos BP, Scolari FL. Potential Conflict of Interest No potential conflict of interest relevant to this article was reported. Sources of Funding There were no external funding sources for this study. Study Association This study is not associatedwith any thesis or dissertationwork. 1. SemsarianC , InglesJ, MaronMS, MaronBJ.Newperspectivesontheprevalence of hypertrophic cardiomyopathy. J AmColl Cardiol. 2015;65(12):1249-54. 2. Mattos BP. Sudden death risk stratification in hypertrophic cardiomyopathy: genetic and clinical bases. Arq Bras Cardiol. 2006;87(3):391-9. 3. 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