Hyper-synchronicity in Hypertrophic Cardiomyopathy (HCM) : Description, Mechanism and Origin With a Multi-imaging Approach to Predict Dual Chamber Pacing Response

Identification and Quantification of a Mechanical Hyper-synchronicity State in Hypertrophic Cardiomyopathy (HCM) With Left Outflow-tract Obstruction and Description of Its Electrical and Electro-mechanical Characteristics Thanks to an Innovative Multi-imaging Approach to Predict a Positive Response to Dual Chamber Pacing. The Hsync Study.

Hypertrophic cardiomyopathy (HCM) is a common genetic cardiovascular disease. Outflow-tract gradient of 30 mmHg or more under resting conditions is an independent determinant of symptoms of progressive heart failure and death.

The investigators hypothesize that the electrical approach by dual chamber pacing could improve symptoms and reduce outflow-tract obstruction in a specific sub-group of selected patients with a mechanical hyper-synchronicity. The aim of the study is to identify and describe this phenomenon in HCM with (O-HCM) and without (NO-HCM) outflow-tract obstruction thanks to innovative multi-imaging approach.

The concept of physiological ventricular desynchrony was described recently with technics of myocardial deformation analysis applied in animal models. Authors confirmed the existence of a time delay in the contraction of the apical walls before basal walls. In O-HCM, the outflow-tract obstruction could be explained by a mechanical hyper-synchronicity between apical and basal walls. This study aims to describe the possible hyper-synchronized contraction in O-HCM and NO-HCM patients unlike the physiological desynchrony observed in healthy volunteers (HV) For this purpose, three imaging tests will be used at baseline: echocardiography (TEE), magnetic resonance imaging (MRI) with gadolinium enhancement only in HCM, and 3-dimensional electrocardiographic mapping (ECM) combined with computed tomography-scan. No follow-up is planned for this study.

Inclusion Criteria:

• HCM: Adults aged more than 18 years with sarcomeric hypertrophic cardiomyopathy under optimal medical therapy, isolated septal hypertrophy, sinus rhythm, exploitable acoustic window. For women of childbearing age, effective contraception and required negative pregnancy test.
• O-HCM : outflow-tract gradient more than 30 mmHg at rest and during exercise
• NO-HCM : outflow-tract gradient less than 30 mmHg at rest and during exercise
• HV: Adults aged more than 18 years, without cardiovascular disease. For women of childbearing age, effective contraception and required negative pregnancy test.

Exclusion Criteria:

- HV: unusable acoustic window