Abstract 4683: Risk Stratification in Hypertrophic Cardiomyopathy: Evidence that Syncope is a Marker for Sudden Death

Abstract

Risk stratification and identification of those patients with hypertrophic cardiomyopathy (HCM) at the highest risk for sudden death is a major issue for patient management, given the effective option of the implantable defibrillator in this disease. For example, the prognostic significance of syncope has not been investigated systematically in large HCM cohorts, and therefore treatment strategies related to this symptom have been based largely on intuition and experience. We assessed the relationship between syncope and sudden death in 1511 consecutive HCM patients. Unexplained (n=153) or neurally-mediated (n=52) syncope occurred in 205 (14%) of patients. Over a 5.6±5.2 year follow-up, 74 patients died suddenly. Relative risk of sudden death was 1.78 (95% CI 0.88 –3.51; p=0.08) in patients with unexplained syncope, and 0.91 (95% CI 0.00 –3.83; p=1.0) in those with neurally-mediated syncope, compared to patients without syncope. However, the time interval between unexplained syncope and initial patient evaluation proved to have a strong impact on sudden death risk. Patients with recent syncope (≤6 months from initial evaluation) showed a 5-fold increase in risk compared to patients without syncope (adjusted HR=4.89; CI 2.19 –10.94; p=0.006), a relationship maintained throughout all age groups (<18, 18 –39 and ≥40 years). Conversely, adult patients (18 –39 and ≥40 years) with remote syncope (>6 months from evaluation) showed no increase in sudden death rate (4.8; 95% CI 0.1–26.7 and 3.2; 95% CI 0.1–17.8 per 1000 person-years, respectively), compared to patients of similar age without syncope (11.8; 95% CI 7.6 –17.6 and 5.7%; 95% CI 3.8 – 8.3 per 1000 person-years). Left ventricular outflow obstruction was not associated with sudden death risk (p=0.29). In this large HCM cohort, unexplained syncope proved to be a risk factor for sudden death. In addition, the temporal proximity of syncopal events to patient evaluation is of clinical relevance. Recent unexplained syncope is associated with an increased risk for sudden death in all age groups, while remote syncopal events do not convey increased risk to adult patients.