Abstract 4843: New Stratification for the Risk of Ventricular Tachycardia in Subjects with Hypertrophic Cardiomyopathy Using Focal Myocardial Fibrosis Detected by Multislice CT
Purpose: To predict ventricular tachycardia (VT) in subjects with hypertrophic cardiomyopathy (HCM), we evaluated focal myocardial fibrosis (MF) as early defects in the early phase and abnormal enhancement in the late phase in electrocardiogram (ECG)-gated multislice computed tomography (MSCT) and examined their relationship using transthoracic echocardiogram (TTE), and Holter ECG or 24 hour ECG monitoring.
Material and methods: 52 subjects (37 males, 15 females, 62±15 years) with HCM by TTE were recruited. Subjects with myocardial hypertrophy by hypertension or valvular diseases or with myocardial infarction were excluded. Enhanced ECG-gated MSCT (Light Speed Ultra 16, GE) was performed at 30 seconds and 8 minutes after contrast injection. Holter ECG or 24 hour ECG monitoring were used to evaluate the risk of VT. VT was defined as more than three continuous ventricular premature beat.
Result: MF was detected in 27 subjects: of whom 19 (70.3%) had VT. A significantly lower percentage of the 25 subjects without MF, 8 (32.0%) had VT (p=0.003). In 14 subjects with hypertrophic obstructed cardiomyopathy, 7 had MF, of whom 4 had VT. In the 7 without MF only 2 had VT. In a logistic model using data from 52 subjects, MF by MSCT and male sex were associated with increased incidence of VT (relative risk and 95% confidential intervals 4.2, 1.1~16.4 and 6.0, 1.05~34.4, respectively). We divided all 52 subjects into 4 based on lesion of hypertrophy: septal type (Group 1, n=23), apical type (Group 2, n=12), diffuse type (Group 3, n=15), and others (Group 4, n=2). MF occurred less frequently in apical type than in septal type and diffuse type (p=0.022, 0.015, respectively). But VT occurrence rates were not significantly different in those 4 groups. Maximum LV wall thickness in Group 2 was significantly smaller than in Groups 1 and 3 (p=0.004, 0.04, respectively).
Conclusion: The incidence of VT was significantly higher in subjects with MF than in those without MF by MSCT. In apical hypertrophy the rate of Mf and maximum LV wall thickness were less than in septal and diffuse type hypertrophy. The detection of focal MF by MSCT may be useful to predict the risk of VT in subjects with HCM. Apical hypertrophy might have less MF than septal and diffuse types in HCM.