Myocardial extracellular volume fraction from T1 measurements in healthy volunteers and mice: relationship to aging and cardiac dimensions.

OBJECTIVES: This study aimed to test the characteristics of the myocardial extracellular volume fraction (ECV) derived from pre- and post-contrast T1 measurements among healthy volunteers. BACKGROUND: Cardiac magnetic resonance (CMR) T1 measurements of myocardium and blood before and after contrast allow quantification of the ECV, a tissue parameter that has been shown to change in proportion to the connective tissue fraction. METHODS: Healthy volunteers underwent standard CMR imaging with administration of gadolinium. T1 measurements were performed with a Look-Locker sequence followed by gradient-echo acquisition. We tested the segmental, interslice, inter-, intra-, and test-retest characteristics of the ECV, as well as the association of the ECV with other variables. Juvenile and aged mice underwent a similar protocol, and cardiac sections were harvested for measurement of fibrosis. RESULTS: In healthy volunteers (N = 32, 56% female; age 21 to 72 years), the ECV averaged 0.28 ± 0.03 (range 0.23 to 0.33). The intraclass coefficients for the intraobserver, interobserver, and test-retest absolute agreements of the ECV were 0.94 (95% confidence interval: 0.84 to 0.98), 0.93 (95% confidence interval: 0.80 to 0.98), and 0.95 (95% confidence interval: 0.52 to 0.99), respectively. In volunteers, the ECV was associated with age (r = 0.74, p < 0.001), maximal left atrial volume index (r = 0.67, p < 0.001), and indexed left ventricular mass. There were no differences in the ECV between segments in a slice or between slices. In mice (N = 12), the myocardial ECV ranged from 0.20 to 0.32 and increased with age (0.22 ± 0.02 vs. 0.30 ± 0.02, juvenile vs. aged mice, p < 0.001). In mice, the ECV correlated with the extent of myocardial fibrosis (r = 0.94, p < 0.001). CONCLUSIONS: In healthy volunteers, the myocardial ECV ranges from 0.23 to 0.33, has acceptable test characteristics, and is associated with age, left atrial volume, and left ventricular mass. In mice, the ECV also increases with age and strongly correlates with the extent of myocardial fibrosis.

Myocardial extracellular volume by cardiac magnetic resonance imaging in patients treated with anthracycline-based chemotherapy.

We aimed to determine whether the myocardial extracellular volume (ECV), measured using T1 measurements obtained during cardiac magnetic resonance imaging were increased in patients treated with anthracyclines. We performed cardiac magnetic resonance imaging and echocardiography and measured the ECV in 42 patients treated with anthracyclines. The data from the cardiac magnetic resonance study were compared to those from healthy volunteers. The anthracycline-treated cohort consisted of 21 men and 21 women with a mean age of 55 ± 17 years, who presented a median of 84 months after chemotherapy with a cumulative anthracycline exposure of 282 ± 65 mg/m(2) and a mean left ventricular ejection fraction of 52 ± 12%. The ECV was elevated in the anthracycline-treated patients compared to the age- and gender-matched controls (0.36 ± 0.03 vs 0.28 ± 0.02, p <0.001). A positive association was found between the ECV and left atrial volume (ECV vs indexed left atrial volume, r = 0.65, p <0.001), and negative association was found between the ECV and diastolic function (E' lateral, r = -0.64, p <0.001). In conclusion, the myocardial ECV is elevated in patients with previous anthracycline treatment and is associated with the diastolic function and increased atrial volumes.