Comparison of characteristics and outcomes of patients with obstructive vs. non-obstructive hypertrophic cardiomyopathy in a cohort from a referral center in colombia

Introduction Hypertrophic cardiomyopathy (HCM) is a common condition with a hereditary basis with two main phenotypes: obstructive and non-obstructive. There is limited data on this disease in Latin America and Colombia, with most research focusing on the obstructive phenotype. Additionally, treatment options for the non-obstructive form are scarce, leading to a gap in knowledge regarding this presentation of the disease. Purpose To characterize the HCM patient population in a referral center and compare characteristics, treatment, and outcomes—including hospitalizations for heart failure, transplantation, and mortality—between patients with the obstructive (left ventricular outflow tract gradient >30 mmHg) and non-obstructive (<30 mmHg) phenotypes. Materials and Methods A retrospective cohort study of HCM patients from 2000 to 2024 was conducted. Statistical analysis was performed to compare both groups. Results A total of 111 patients were included, 47 % (n=52) had a non-obstructive phenotype, while 53% (n=59) had an obstructive phenotype, of whom 51 patients had a gradient >50 mmHg. Systolic anterior motion of the mitral valve was reported in 48 patients (44 obstructive and 4 non-obstructive), with an average septal thickness of 18±5 mm. The most common variant was asymmetric septal hypertrophy (74.7%). Septal reduction therapy was required in 29 patients (26 underwent myectomy, and 3 received alcohol septal ablation). Only 9% were referred for genetic testing. In the comparative analysis, patients with obstructive phenotype had a higher prevalence of limitation in functional class (NYHA III-IV) (27% vs. 10%, p=0.034). Arrhythmias, including atrial fibrillation and ventricular tachycardia, were more frequent in the non-obstructive phenotype (23% vs. 8%, p=0.038), as were defibrillator implantation and cardiac resynchronization therapy. Patients with a non-obstructive phenotype had higher rates of hospitalization (25% vs. 12%, p=0.072) and need for transplantation (8% vs. 2%, p=0.184) compared with obstructive phenotype. All-cause mortality in this cohort was 23.4%, without a statistically significant difference (27% vs. 19%, p=0.32) (Table 1.) Conclusion Both phenotypes are common in this cohort. Obstructive patients had a worse NYHA functional class, whereas non-obstructive patients experienced higher rates of arrhythmias, hospitalizations, device implantation, and referral for transplantation. Mortality was similar between both groups. Referral for genetic testing was low. This analysis underscores the importance of focusing research on the non-obstructive phenotype and developing new treatment strategies to improve outcomes for these patients.