The Prognostic Implication of Late Gadolinium Enhancement Quantification and Syncope in Hypertrophic Cardiomyopathy

<b>Background:</b> Risk stratification for sudden cardiac death in hypertrophic cardiomyopathy (HCM) remains challenging. Late gadolinium enhancement (LGE) on cardiac MRI signifies myocardial fibrosis and is linked to adverse outcomes in HCM. However, the threshold of LGE that is clinically significant remains a subject of debate. We hypothesized that even small amounts of LGE (≥ 5%) or a history of syncope are associated with worse outcomes. <b>Methods</b>: Between May 2018 and June 2023, HCM patients were prospectively enrolled at the Medical University of Vienna, Austria, a tertiary referral center. The primary endpoint was a composite of new-onset ventricular tachycardia, appropriate ICD therapy, and all-cause mortality. <b>Results</b>: In total, 230 patients were included. The median age of patients was 56 (IQR 44, 64) years, 40% (<i>n</i> = 94) were female, and 43% (<i>n</i> = 84) had significant left ventricular outflow tract obstruction (LVOTO). Over a median follow-up of 3.2 years, 29 patients (13%) met the composite endpoint. While the ESC HCM risk score was not associated with the primary endpoint, both LGE > 5% (Adj. HR 6.16) and a history of at least one syncope (Adj. HR 3.40) were independently associated with the primary endpoint. These associations were consistent across patients with and without LVOTO. <b>Conclusions:</b> In conclusion, our findings indicate that the combination of a history of syncope together with small amounts of LGE (≥ 5%) in cardiac MRI are associated with unfavorable clinical outcomes in HCM patients.