Cardiopulmonary Exercise Test and Sudden Cardiac Death Risk in Hypertrophic Cardiomyopathy
Are parameters during cardiopulmonary exercise testing predictive of sudden cardiac death (SCD) among patients with hypertrophic cardiomyopathy (HCM)?
In a prospective multicenter study, 623 consecutive outpatients with HCM at five tertiary Italian centers were recruited and followed from September 2007 to April 2015. The study composite endpoint was SCD, aborted SCD, and appropriate implantable cardioverter-defibrillator (ICD) interventions.
During a median follow-up of 3.7 years (interquartile range, 2.2-5.1 years), 25 patients reached an endpoint at 5 years (three SCD, four aborted SCD, 18 appropriate ICD interventions). At multivariate analysis, ventilation versus carbon dioxide relation during exercise (VE/VCO2 slope) remained independently associated with the study endpoint, either with the 2011 American College of Cardiology Foundation/American Heart Association guideline-derived score (c-index 0.748) or with the 2014 European Society of Cardiology guideline-derived score (c-index 0.750). A VE/VCO2 slope cut-off value of 31 showed the best accuracy in predicting a SCD endpoint within the entire HCM study cohort (sensitivity 64%, specificity 72%, area under the curve 0.72).
The authors concluded that the VE/VCO2 slope might improve SCD risk stratification, particularly in those HCM categories classified at low-intermediate SCD risk according to contemporary guidelines. They propose further larger studies, possibly on independent cohorts, to confirm these preliminary findings.
Established risk factors for SCD among patients with HCM include family history (SCD in a first-degree relative, or SCD in any relative ≤50 years old), marked left ventricular hypertrophy (≥30 mm thickness), Holter monitor evidence of nonsustained supraventricular tachycardia ≥3 and consecutive beats ≥120 min-1, unexplained syncope within 5 years, and failure to increase systolic blood pressure by ≥20 mm Hg from rest to peak exercise. These data suggest that the relationship between ventilation and carbon dioxide during exercise might have added predictive value.
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