HEART FAILURE AND CARDIOMYOPATHY

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

Osama I I Soliman¹, Paul Knaapen², Marcel L Geleijnse¹, Pieter A Dijkmans³, Ashraf M Anwar¹, Attila Nemes¹, Michelle Michels¹, Wim B Vletter¹, Adriaan A Lammertsma², Folkert J ten Cate¹

¹ Department of Cardiology, Thoraxcenter, Erasmus Medical Centre, Rotterdam, The Netherlands
² Department of Nuclear Medicine and Positron Emission Tomography, VU University Medical Centre, Amsterdam, The Netherlands
³ Department of Cardiology and Institute of Cardiovascular Research, VU University Medical Centre, Amsterdam, The Netherlands

Dr F J ten Cate, Department of Cardiology, Thoraxcentre, Erasmus Medical Centre Rotterdam, Dr Molewaterplein 40, 3015 GD, Room Ba304, Rotterdam, The Netherlands; f.j.tencate{at}erasmusmc.nl

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 (ß), 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. ß 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.

Abbreviations: endo-to-epi, endocardial-to-subepicardial; HCM, hypertrophic cardiomyopathy; LV, left ventricular; LVEDP, left ventricular end-diastolic pressure; LVMI, left ventricular mass index; LVOTG, left ventricular outflow tract gradient; LVRPP, left ventricular rate–pressure product; MBF, myocardial blood flow; MCE, myocardial contrast echocardiography; MFR, myocardial flow reserve; PET, positron emission tomography; rBV, relative blood volume; ROI, region of interest; RPP, rate–pressure product

Keywords: myocardial perfusion; hypertrophic obstructive cardiomyopathy; myocardial contrast echocardiography; positron emission tomography

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