Prevalence and clinical impact of latent obstruction in hypertrophic cardiomyopathy

Abstract Funding Acknowledgements Type of funding sources: None. BACKGROUND Hypertrophic cardiomyopathy (HCM) is characterized by varying degrees of left ventricular outflow tract obstruction (LVOTobs). We aim to define the prevalence, clinical profile and impact of LVOTobs under physiological exercise in HCM patients (pts). METHODS Single center retrospective study of consecutive HCM pts without LVOTobs at rest (resting gradient <30mmHg), referred for exercise stress echocardiogram (ESE) between 2015 and 2019. Significative latent obstruction was defined as a LVOT gradient ≥50 mmHg during exercise or at early recuperation. RESULTS A total of 56 pts were included (64% men, mean age 57 ± 11 years, 61% septal HCM). The majority of pts (47; 84%) were in NYHA I functional class, 20 (36%) had history of syncope or pre-syncope (S/pS) and 7 (13%) had an implantable cardioverter defibrillator (ICD). Twelve (21%) pts had systolic anterior motion (SAM) of the mitral valve at rest. Thirty-five (63%) pts performed ESE under beta-blocker (BB) therapy. Mean exercise time was 8 ± 3 min. During ESE, 2 (4%) pts developed a LVOT gradient between 30 to 50 mmHg and 17 pts (30%) developed a significative LVOTobs gradient (mean 85 ± 18 mmHg). Pts with significative latent LVOTobs had more previous complaints of S/pS (59% vs 26%, p=.017), a tendency for a higher NYHA functional class (p=.082) and were more frequently on BB therapy (82% vs 18%, p=.043). Mean septum thickness was similar between groups (17 ± 0.7 vs 16 ± 0.6 mm, p=.536). The presence of SAM at rest was more frequent in the significative latent LVOTobs pts (p<.001). No differences were noted in exercise tolerance (p=.526). During a median follow-up of 43 (IQR 15-53) months, 7 (41%) pts with significative latent LVOTobs had a pre-syncope, 3 (18%) were diagnosed with atrial fibrillation and 2 (12%) had a cardiovascular admission . There was up-titration/initiation of BB therapy in 5 (29%) pts, referral for septal myectomy in 3 (18%) and ICD implantation for primary prevention in 3 (18%) pts. No proper ICD shocks, sustained ventricular arrythmias or deaths occurred. Comparing significative latent to non LVOTobs pts, the first ones had more ICD implantation (log rank p =.04) and performed a surgical myectomy more frequently (log rank p= .018) during the follow-up. CONCLUSION In our study, significative latent LVOTobs was observed in 30% of pts. Its presence can have clinical implications in HCM pts approach and should be suspected in more symptomatic pts and when SAM is present at rest.