Assessment of intravascular and extravascular mechanisms of myocardial perfusion abnormalities in obstructive hypertrophic cardiomyopathy by myocardial contrast echocardiography

Objectives: To assess mechanisms of myocardial perfusion impairment in patients with hypertrophic cardiomyopathy (HCM). Methods: Fourteen patients with obstructive HCM ( mean (SD) age 53 ( 10) years, 11 men) underwent intravenous adenosine myocardial contrast echocardiography (MCE), positron emission tomography ( PET) and cardiac catheterisation. Fourteen healthy volunteers ( mean age 31 ( 4) years, 11 men) served as controls. Relative myocardial blood volume (rBV), exchange flow velocity (beta), myocardial blood flow (MBF), MBF reserve (MFR) and endocardial-to-subepicardial (endo-to-epi) MBF ratio were measured from the steady state and contrast replenishment time-intensity curves. Results: Patients with HCM had lower rest MBF ( for LVRPP-corrected)-mean ( SD) (0.92 (0.12) vs 1.13 (0.25) ml/min/g, p, 0.01)-and hyperaemic MBF-(2.56 (0.49) vs 4.34 (0.78) ml/min/g, p, 0.01) than controls. Resting rBV was lower in patients with HCM (0.094 (0.016) vs 0.138 (0.014) ml/ml), and during hyperaemia (0.104 (0.018) ml/ml vs 0.185 (0.024) ml/ml) ( all p < 0.001) than in controls. b tended to be higher in HCM at rest (9.4 (4.6) vs 7.7 (4.2) ml/min) and during hyperaemia (25.8 (6.4) vs 23.1 (6.2) ml/min) than in controls. Septal endo-to-epi MBF decreased during hyperaemia ( 0.86 (0.15) to 0.64 (0.18), p < 0.01). rBV was inversely correlated with left ventricular (LV) mass index ( p < 0.05). Both hyperaemic and endo-to-epi MBF were inversely correlated with LV end-diastolic pressure, LV mass index, and LV outflow tract pressure gradient ( all p < 0.05). MCE-derived MBF correlated well with PET at rest (r = 0.84) and hyperaemia ( r = 0.87) ( all p < 0.001). Conclusions: In patients with HCM, LV end-diastolic pressure, LV outflow tract pressure gradient, and LV mass index are independent predictors of rBV and hyperaemic MBF.