Myocardial native-T1 times are elevated as a function of hypertrophy, HbA1c, and heart rate in diabetic adults without diffuse fibrosis

Purpose: Cardiac native-T1 times have correlated to extracellular volume fraction in patients with confirmed fibrosis. However, whether other factors that can occur either alongside or independently of fibrosis including increased intracellular water volume, altered magnetization transfer (MT), or glycation of hemoglobin, lengthen T1 times in the absence of fibrosis remains unclear. The current study examined whether native-T1 times are elevated in hypertrophic diabetics with elevated hemoglobin MC (HbA1c) without diffuse fibrosis. Methods: Native-T1 times were quantified in 27 diabetic and 10 healthy adults using a modified Look-Locker imaging (MOLLI) sequence at 1.5 T. The MT ratio (MTR) was quantified using dual flip angle cine balanced steady-state free precession. Gadolinium (0.2 mmol/kg Gd-DTPA) was administered as a bolus and post-contrast T1-times were quantified after 15 min. Means were compared using a two-tailed student's t-test, while correlations were assessed using Pearson's correlations. Results: While left ventricular volumes, ejection fraction, and cardiac output were similar between groups, left ventricular mass and mass-to-volume ratio (MVR) were significantly higher in diabetic adults. Mean ECV (0.25 +/- 0.02 Healthy vs. 0.25 +/- 0.03 Diabetic, P = 0.47) and MTR (125 +/- 16% Healthy vs. 125 +/- 9% Diabetic, P = 0.97) were similar, however native-T1 times were significantly higher in diabetics (1016 +/- 21 ms Healthy vs. 1056 31 ms Diabetic, P = 0.00051). Global native-T1 times correlated with MVR (rho = 0.43, P = 0.008) and plasma HbA1c levels (rho = 0.43, P = 0.0088) but not ECV (rho = 0.06, P = 0.73). Septal native-T1 times correlated with septal wall thickness (rho = 0.50, P = 0.001). Conclusion: In diabetic adults with normal ECV values, elevated native-T1 times may reflect increased intracellular water volume and changes secondary to increased hemoglobin glycation.