Regional heterogeneity of myocardial perfusion in healthy human myocardium: assessment with magnetic resonance perfusion imaging.

The knowledge of myocardial perfusion in healthy volunteers is fundamental for evaluation of patients with ischemic heart disease. The study was conducted to determine range, regional variability, and transmural gradient of myocardial perfusion in normal volunteers with Magnetic Resonance Perfusion Imaging (MRPI). Perfusion was assessed in 17 healthy volunteers (age: 20-47 yr, 11 males) at rest and adenosine-induced hyperemia using a 1.5 T MR scanner. Perfusion was quantified (mL/g/min) for the transmural myocardium and separately for the endo- and epimyocardium in the anterior, lateral, posterior, and septal left ventricular wall using the Fermi model for constrained deconvolution. Regional variabilities for resting, hyperemic perfusion, and perfusion reserve were 22 +/- 8%, 21 +/- 10%, and 35 +/- 18%. Mean resting, hyperemic perfusion, and perfusion reserve were 1.1 +/- 0.4 mL/g/min, 4.2 +/- 1.1 mL/g/min, and 4.1 +/- 1.4. Perfusion in the septum was higher at rest (1.3 +/- 0.3 mL/g/min vs. 1.0 +/- 0.3 mL/g/min, p < 0.05) and lower during hyperemia (3.6 +/- 0.8 mL/g/min vs. 4.5 +/- 1.1 mL/g/min, p < 0.03), resulting in a reduced perfusion reserve (PR) (3.2 +/- 0.9 vs. 4.5 +/- 1.4, p < 0.01) in the septum vs. the combined anterior, lateral, and posterior segments. Resting (0.9 +/- 0.3 mL/g/min vs. 1.4 +/- 0.5 mL/g/min, p < 0.01), but not hyperemic perfusion, was lower in the epi- vs. endomyocardium, resulting in a higher epimyocardial PR (4.8 +/- 1.8 vs. 3.5 +/- 1.4, p < 0.01) in all regions but the septum, where endo- and epimyocardial perfusion and perfusion reserve were not different. A considerable regional variability of myocardial perfusion was confirmed with MRPI. The exceptional anatomical position of the septum is reflected by the lack of a perfusion gradient, which was demonstrated in all other regions but the septum.