Role of cardiac MRI in diabetes

Abstract

Diabetes and insulin resistance have a variety of detrimental effects on cardiovascular health and outcomes. Cardiac magnetic resonance offers a non-invasive means to obtain many layers of information at a tissue level, including fibrosis, edema, intramyocardial motion, triglyceride content, and myocardial energetics. The role of cardiovascular magnetic resonance is particularly important in the evaluation of recognized and unrecognized coronary artery disease. In this review, we address the current state-of-the-art in cardiac magnetic resonance imaging - for both clinical and investigational use - as it applies to diabetic cardiovascular disease.

Figure 1

A 50 year-old diabetic female with no known history of coronary artery disease underwent research imaging studies. A cardiac stress PET study did not reveal any significant perfusion defect. First-pass perfusion imaging in short axis (left panel) demonstrating an infero-septal perfusion defect. Matching short-axis late gadolinium enhancement (LGE) imaging reveals a subendocardial scar suggestive of prior infarct. Collectively these finding are consistent with unrecognized infarction with peri-infarct ischemia in the right coronary territory. A severe coronary stenosis in the mid right coronary artery was confirmed on x-ray coronary angiography.

Figure 2

Kaplan-Meier estimates of all-cause mortality in 187 patients with T2D undergoing CMR. At a median follow-up of 17 months there was a 4-fold increased hazard of major adverse cardiovascular events and over a 7-fold increased hazard of all-cause mortality in patients with LGE. (From: Kwong RY, Sattar H, Wu H, et al., Incidence and prognostic implication of unrecognized myocardial scar characterized by cardiac magnetic resonance in diabetic patients without clinical evidence of myocardial infarction. (From: Kwong RY, Sattar H, Wu H et al. Incidence and prognostic implication of unrecognized myocardial scar characterized by cardiac magnetic resonance in diabetic patients without clinical evidence of myocardial infarction. Circulation 2008;118:1011–20) [29••].

Figure 3

Adenosine stress perfusion imaging (left) reveals a defect in the basal and mid inferior, inferoseptal and inferolateral walls. Phase-sensitive late gadolinium enhancement (LGE) imaging shows accumulation of gadolinium in the basal inferolateral and basal inferior segment to suggest prior infarct.

Figure 4

³¹P-spectroscopy allows for the study of myocardial energetics by identifying the spectra that represent high-energy phosphate availability. In a study of 21 patients with T2D, cardiac phosphocreatine-to-ATP ratio was lower in T2D than in healthy volunteers.

Figure 5

Estimating diffuse fibrosis by T1 mapping. Gadolinium distributes differentially based on the amount of extracellular volume relative to the volume taken up by pure cardiomyocytes. By quantifying the relaxation times (R1=1/T1) of the myocardium versus the blood pool, the amount of extracellular volume can be estimated. (From Ho CY, Abbasi SA, Neilan TG, et al.: T1 measurements identify extracellular volume expansion in hypertrophic cardiomyopathy sarcomere mutation carriers with and without left ventricular hypertrophy. (From: Ho CY, Abbasi SA, Neilan TG, et al.: T1 measurements identify extracellular volume expansion in hypertrophic cardiomyopathy sarcomere mutation carriers with and without left ventricular hypertrophy. Circ Cardiovasc Imaging 2013, 6:415–422) [78].

Figure 6

T1 mapping using an inversion pulse and a Look-Locker sequence and a GRE readout. This is done once before and thrice after the administration of gadolinium, and ultimately results in a reproducible, histologically validated estimation of the extracellular volume (ECV) fraction.

Figure 7

T1 mapping demonstrates a significant difference in extracellular volume (ECV) fraction between patients with Type 2 diabetes (right) and normal controls (left), despite the lack of any evidence of coronary artery disease, diastolic dysfunction, or ventricular hypertrophy. (Reprinted with permission from: Rao AD, Shah RV, Garg R, et al.: Aldosterone and myocardial extracellular matrix expansion in type 2 diabetes mellitus. Am J Cardiol 2013, 112(1):73–8) [79].

Figure 8

Correlation of endogenous aldosterone production and extracellular volume (ECV) fraction by T1-mapping in 21 patients with Type-2 diabetes. (Reprinted with permission from: Rao AD, Shah RV, Garg R, et al.: Aldosterone and myocardial extracellular matrix expansion in type 2 diabetes mellitus. Am J Cardiol 2013, 112(1):73–8) [79].