Permanent Pacing for Drug-refractory Symptomatic Patients With Obstructive Hypertrophic Cardiomyopathy. (PACE-OHCM)

Inclusion Criteria: unequivocal diagnosis of HCM, on the basis of 2-dimensional echocardiographic demonstration of a hypertrophied (wall thickness >15 mm or > 13 mm in familial HOCM) and non dilated LV in the absence of another cardiac or systemic disease capable of producing the same magnitude of hypertrophy; patients in whom coronary disease has been excluded; presence of severe refractory symptoms (NYHA class II-IV), as evidenced by moderate-to-severe functional disability resulting from exertional dyspnea or chest pain sufficient to support a desire for alternative treatment modalities, following administration (in standard dosages) of beta-blocker and either disopyramide or verapamil, independently or in association; peak instantaneous LV outflow tract gradient > 50 mm Hg (resting or provoked), estimated by continuous wave Doppler; Exclusion Criteria: end-stage phase of HCM (unless CRT therapy is considered); ejection fraction <50% (unless CRT therapy is considered); severe mitral valve disease (+++) not related to systolic anterior movement and/or papillary muscle abnormalities; age below 18 years.