A comparison of myocardial magnetic resonance extracellular volume mapping at 3 T against histology of tissue collagen in severe aortic valve stenosis and obstructive hypertrophic cardiomyopathy

Fig. 1. Myocardial T1 and ECV mapping at 3 T. A four-chamber native T1 map (A) was acquired with a 5 s (3 s) 3 s MOLLI sequence, while 12 min after administration of 0.1 mmol/kg body weight gadobutrol a 4 s (1 s) 3 s (1 s) 2 s MOLLI sequence was used (B). The extracellular volume fraction (ECV; C) was calculated using blood T1 estimated from a region of interest (ROI) drawn in the left ventricular blood pool (dotted line) and blood hematocrit determined in a venous blood sample obtained just prior to MR examination. This case is a 61-year-old male (body mass index, 25.8 kg/m2) with obstructive hypertrophic cardiomyopathy scheduled for septal myectomy. Native T1 in the septal ROI (solid line) was 1206 ± 29 ms, and 1933 ± 30 ms for the blood pool. After contrast agent administration, T1 values were 615 ± 16 ms and 474 ± 12 ms, respectively. With hematocrit at 0.43 L/L, septal ECV was calculated at 28.1% ± 1.9%

Fig. 2. Histology of myocardial interstitial fibrosis. Images of picrosirius red-stained myocardial tissue samples were obtained at 40 × magnification (A, C), from which the myocardial collagen content was determined by isolating the picrosirius red-stained surface area (B, D) from the original images. Myocardial collagen content in these sections was 3.2% (A, B) and 9.2% (C, D)

Fig. 3. Regression analyses of the native longitudinal relaxation rate R1 of left ventricular blood with blood hematocrit (A), and of in vivo myocardial native T1 and extracellular volume fraction (ECV) measured with quantitative magnetic resonance imaging (MRI) at 3 T (B) against ex vivo myocardial collagen content determined histologically with picrosirius red staining of myocardial tissue samples obtained from the same patients (C, D, respectively). Dashed lines indicate the 95% confidence intervals of the linear model fits (solid lines). AS aortic valve stenosis, HCM hypertrophic cardiomyopathy, Hct hematocrit