Permanent Pacing for Drug-refractory Symptomatic Patients With Obstructive Hypertrophic Cardiomyopathy.

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.