Abstract 17333: Novel Evidence of the Coronary Microvascular Steal Phenomenon in Hypertrophic Cardiomyopathy - A Quantitative Stress Perfusion Cardiovascular Magnetic Resonance Study
Background: Hypertrophic cardiomyopathy (HCM) is associated with microvascular ischemia. Mechanisms include reduced coronary arteriolar density and intima-medial thickening, particularly in the endocardium. However, the severity and spatial distribution of ischemia are unclear. Our aim was to assess the pattern of microvascular ischemia quantitatively using stress perfusion cardiovascular magnetic resonance (CMR).
Methods: HCM patients (n=28, mean±SD age 57±14 years, 19 male) with no significant coronary disease were studied. First-pass CMR perfusion imaging was undertaken during adenosine-induced hyperemia (140µg/kg/min) and at rest using a hybrid echo-planar imaging sequence (3 slices). After image registration, a modified Fermi-constrained deconvolution algorithm was applied pixel-wise to calculate absolute blood flow (Fig 1). From these pixel maps, regions of interest (ROI) in hypoperfused and hyperemic myocardium were identified at stress and compared with corresponding areas at rest. The myocardium was also segmented into 16 AHA sectors split into epicardial and endocardial layers.
Results: Rest endocardial myocardial blood flow (MBF) [ml/g/min] was significantly higher than epicardial values (mean±SD: 1.25±0.32 vs 1.20±0.31; p<0.001). However, after hyperemia, this reversed and epicardial was significantly higher than endocardial MBF (2.38±0.69 vs 2.01±0.55, p<0.001). In ROI analysis, 16 patients (57%) had myocardial perfusion reserve (MPR=stress/rest MBF) in hypoperfused areas <50% of hyperemic areas (min/max MPR 0.35±0.11). Furthermore, 8 of these patients (29%) had stress MBF lower than resting values, suggesting marked microvascular steal (mean±SE MBF: 1.02±0.06 vs 1.17±0.06, p<0.001; and min/max MPR 0.29±0.10).
Conclusions: HCM is associated with significant coronary microvascular dysfunction, which particularly affects the endocardium, and in a subset of patients, gives rise to microvascular steal at stress.
- Perfusion imaging
- Magnetic resonance imaging
- Hypertrophic cardiomyopathy
- Cardiac hypertrophy
- Cardiac MRI
- © 2012 by American Heart Association, Inc.