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Introduction Whether obesity, a modifiable risk factor in patients with hypertrophic cardiomyopathy (HCM), can influence coronary microvascular dysfunction (CMD) is unknown. Objective To assess the relationship between body weight and CMD measured with myocardial blood flow (MBF) at positron emission tomography (PET) in patients with HCM. Methods All consecutive patients with HCM referred to PET scan from 2010 to 2020 were reviewed. Only patients with PET and cardiac magnetic resonance (CMR) analysis, Patients were classified into three groups according to baseline BMI: BMI30 kg/m2. Results Of 1512 patients with HCM, 134 (8.9%) had been referred to a PET scan and 79 (5.2%) met the inclusion criteria (29% were women, median age was 44 [28-53] years). Overall, 52% had a BMI30 kg/m2. At PET, average MBF was 2.08 [1.52-2.40] ml/min/g and was similar among BMI groups (p=0.288) irrespective of fibrosis at CMR. Prevalence of severe microvascular dysfunction was similar (MBF Conclusions Obesity is not associated with worsening of CMD in HCM patients. These findings support the hypothesis that the worse symptomatic profile in obese HCM patients is due to increased prevalence of obstruction rather than accentuation of structural phenotype. Thus, the symptomatic handicap associated with obesity may be reversible following appropriate weight-reduction strategies

Background Current understanding of the lifetime mortality of patients with hypertrophic cardiomyopathy (HCM) has been extrapolated from cohorts with 8–10 years follow-up. Real survival rates and long-term burden of HCM are largely unresolved. Objective To describe HCM lifetime mortality over 28-years of observation. Methods We analyzed clinical/instrumental data of the historic cohort of 202 patients diagnosed from 1970s. ECG, echocardiographic, clinical records until last follow-up were recorded. Reasons for death were classified as HCM related (Sudden Death (SD), Heart Failure related (HF)) and non-HCM related deaths. Results Patients were followed-up for 28±6 years (41±17 to 69±14 years), 63% were males. Patients progressively dilated the Left Atrium (40±6 to 50±9mm, p Conclusions HCM-related mortality at 10 years significantly underestimated the lifetime rates of HF death, which doubled in the second/third decade of observation. Conversely, SD rates remained constantly low. Real burden of HCM is time dependent and can be appreciated only after prolonged exposure to the disease. Funding Acknowledgement Type of funding source: None

Introduction The presence of sarcomere mutations is a powerful predictor of heart failure-related outcomes in Hypertrophic Cardiomyopathy (HCM). However, whether the prevalence of left ventricular (LV) dysfunction differs in patients with mutations in the two most prevalent HCM-associated genes (i.e. MYBPC3 and MYH7) is unclear. Purpose To ascertain lifetime trends in prevalence of LV dysfunction in HCM associated with pathogenic or likely-pathogenic MYBPC3 versus MYH7 mutations. Methods Clinical and instrumental records of 402 HCM patients with MYBPC3 (N=251) or MYH7 (N=151) mutations were retrospectively reviewed. Presence of systolic dysfunction (ejection fraction [EF] Results Patients were diagnosed at a mean age of 39±17 years and 63% were men. At first evaluation MYBPC3-HCM patients were less frequently obstructive (15% vs 26% in MYH7; p=0.005) and had lower LVEF (61±11% vs 64±9%; p=0.01). Prevalence of diastolic dysfunction increased with age and was lowest in MYBPC3 patients No significant differences were observed in terms of NYHA class change, atrial fibrillation, stroke, heart failure, appropriate ICD intervention or cardiovascular death. However, prevalence of NSVT was higher for MYBPC3 (39% vs 14% in MYH7, p In vitro cross-sectional evaluation of myocardial samples taken during septal myectomy at different ages showed a decline in contraction-relaxation properties after age 40 in MYPBC3 carriers, but preserved function in MYH7 patients (Figure). Kinetic of myosin cross-bridges Conclusions In HCM patients, mutations in the MYBPC3 gene and early diagnosis are associated with slowly progressing systolic impairment leading to overt dysfunction in 15% compared to 5% in MYH7-HCM. However, outcome was similar in the two subsets. These differences in lifetime myocardial performance between the two most common HCM-associated genes suggest diverse pathways of disease progression, potentially amenable to requiring different molecular approaches.