[Risk of syncope in hypertrophic cardiomyopathy: a multivariate analysis of prognostic variables]

Twenty-nine consecutive patients with symptomatic hypertrophic cardiomyopathy and a mean age of 44.8 +/- 12.2 years (range 21 to 63 years) underwent complex invasive and noninvasive testing in an attempt to identify a risk profile for syncope. Clinical, morphologic and electrophysiologic as well as functional parameters at rest and at symptom-limited pacing rate were analyzed for significant association with syncope. Exact stepwise logistic regression analysis identified three variables as significant independent predictors of syncope in hypertrophic cardiomyopathy: 1) age less than 30 years (beta = 4.803; p = 0.0007); 2) left ventricular end-diastolic volume index less than 60 ml/m2 (beta = 3.302; p = 0.006) and 3) non-sustained ventricular tachycardia on 72 h ambulatory ECG monitoring (beta = 2.5909; p = 0.03). The combined occurrence of all three variables had a 100% sensitivity and specificity to identify eight patients with syncopal events. Thus, the risk for syncope in hypertrophic cardiomyopathy is high in young patients with the combination of low left ventricular filling volume and episodes of non-sustained ventricular tachycardia. This finding might also explain the mechanism of syncope in hypertrophic cardiomyopathy as low-input-low-output failure induced by a sudden increase in heart rate in presence of a low filling volume.