ADDITIONAL VALUE OF QUANTIFICATION OF MYOCARDIAL FIBROSIS BY CONTRAST-ENHANCED MRI TO IDENTIFY SUBJECTS WITH HYPERTROPHIC CARDIOMYOPATHY AND SUDDEN CARDIAC DEATH RISK

Background. A 5-year sudden cardiac death risk model in line with ESC-2014 (HCM Risk-SCD score) Guidelines assesses the risk of sudden cardiac death in individuals with hypertrophic cardiomyopathy using clinical parameters without taking into account magnetic resonance imaging indices including myocardial fibrosis. Aim. To compare subjects with low, moderate, and high sudden cardiac death risks, identified based on HCM Risk-SCD score, with delayed enhancement magnetic resonance imaging-evidenced fibrosis and to assess the role of fibrosis in identification of patients with sudden cardiac death risk. Material and Methods. A total of 98 patients with hypertrophic cardiomyopathy underwent an integrative examination including cardiac echocardiography, 24-h electrocardiography monitoring, delayed gadolinium-enhanced magnetic resonance imaging, and an assessment of a 5-year sudden cardiac death risk by HCM Risk-SCD score. Results and Discussion. Out of 98 patients, 45 (46%) patients had low risk of sudden cardiac death, 26 (26%) patients had intermediate risk, and 27 (28%) patients had high sudden cardiac death risk by HCM Risk-SCD score. During the follow-up period, (mean 41 months; 25 to 58 months), 16 adverse events were registered: sudden cardiac death occurred in 9 patients while 7 patients had been successfully resuscitated and implanted with implantable cardioverter defibrillator for secondary prevention of sudden cardiac death. The risk assessment using HCM Risk-SCD score showed high risk in 8 out of 16 (50%) patients; 2 (12.5%) patients had moderate risk, while 6 (37.5%) patients had low risk. High-risk patients demonstrated significantly (p<0.001) larger fibrosis (mean 28.5%; quartiles 21.9%; 44.1%) compared to those with moderate risk (mean 17.6%; quartiles 8.0%; 22.5%) and low risk of sudden cardiac death (mean 11.7%; quartiles 5.8%; 17.6%). The volume of fibrosis by delayed contrast-enhanced magnetic resonance imaging was associated with the adverse outcomes rate, which was 15%. A Log rank test in the KaplanMeier survival analysis showed statistically significant differences (p=0,002) in groups with fibrosis <15% and≥15%. The regression analysis showed that myocardial fibrosis was more significant factor associated with sudden cardiac death (OR 12; 95% CI 1.6–91) compared to SCD ESC-2014 score (OR 2.8 95% CI 1.1–7.5). Conclusion. Therefore, based on regression analysis, patients with hypertrophic cardiomyopathy who had myocardial fibrosis volume ≥15% were identified as a group with risk of sudden cardiac death and adverse arrhythmic events.