Type 1 diabetes (T1DM) may lead to changes in left ventricular (LV) function and cardiomyopathy in the absence of coronary artery disease (CAD) or hypertension.^1,2 This suggests that diabetes has direct effects on the heart, which can contribute to the development of cardiomyopathy and LV dysfunction, possibly due to alterations in sympathetic innervation and myocardial oxidative metabolism and efficiency.³ These factors may lead to subsequent changes in the LV contractile patterns such as torsion and strain, which have emerged as earlier indicators of myocardial dysfunction.4 The primary aim of this study is to evaluate the association between MRI-derived parameters of cardiac function (both systolic (global and regional) and diastolic) and the presence of T1DM at baseline and 3-years follow-up. The secondary aim of the study is to assess the differences in the MRI-derived cardiac parameters between T1DM male and female patients.

Forty-five T1DM patients (24 females and 21 males; age=34±13 years), and 9 matched healthy controls (HC; 4 females and 5 males; age=34±13 years) with normal glucose tolerance, blood pressure, and lipid profile were studied with MRI. The main inclusion criteria for the diabetic subjects were: T1DM diagnosis, age 18-65 years, diabetes duration 5-10 years, and no signs of microvascular complications. All T1DM subjects were followed up for 3 years, while adhering to the current standard of care, and 27 of the T1DM subjects (15 females and 12 males; age=35±13 years) underwent a follow-up MRI exam at 3 years. All subjects had normal resting electrocardiograms (ECG) and normal exercise treadmill test results before enrolling in the study.

The MRI exam consisted of cine images (one four-chamber image and a stack of parallel short-axis images covering the heart); myocardial grid-tagged images (three short-axis images at the basal, mid-ventricular, and apical levels); and transmitral velocity-encoded flow images for measuring the LV ejection fraction (EF) and mass ratio (LVMR=LV mass/LV end-diastolic volume); myocardial strain and apical-to-basal torsion; and mitral early-to-atrial filling ratio (E/A), respectively, as measures of global; regional; and diastolic heart function, respectively. The cine and flow images were analyzed using Medis Q-mass and Q-flow packages, respectively, while the tagged images were analyzed using the Diagnosoft HARP software. Student’s t-test was conducted between the patients at baseline and follow-up, between the female and male patients, and between the patients and HC (P<0.05 was considered significant).

The T1DM subjects were relatively young, with mean age of 34±13 years, diabetes duration of 14±6 years, and 60% were females. The majority (87%) were Caucasian, with 7% African Americans and 7% Hispanics. Seventy-eight percent of the diabetic subjects were non-smokers, 18% were former smokers and 4% were current smokers. None had clinical evidence of chronic complications or CAD at baseline. The cardiac parameters of systolic function were within normal ranges in the T1DM subjects, and there were no differences between T1DM and HC at baseline in any of the measured variables, as shown in Table 1 and Figure 1. In the patient group, only LVMR and basal circumferential strain significantly decreased from baseline to follow-up. Mitral E/A increased and apical torsion decreased from baseline to follow-up, although these differences were not significant. Among the parameters that showed differences between baseline and follow-up, only LVMR showed significant difference between female and male patients, both at baseline (0.69±0.13 vs. 0.62±0.11, P=0.05) and follow-up (0.53±0.10 vs. 0.68±0.07, P=0.0001). The natural history and mechanisms of myocardial dysfunction in T1DM are not well understood. Several studies have reported that LV dysfunction may occur in T1DM in the absence of ischemic heart disease or hypertension.⁵ The results of this study demonstrated that at baseline, T1DM shows no significant differences compared to HC. At 3-years follow-up, the LV mass (especially in male patients), apical-to-basal torsion, and diastolic function (represented by the E/A ratio) normalize toward the measurement ranges in HC, and are accompanied by decreased basal LV strain. The results suggest that diabetes has direct effects on the heart, which can contribute to the development of cardiomyopathy and LV dysfunction in the absence of large vessel disease. These results have immediate relevance in understanding the pathophysiology and natural history of myocardial contractile dysfunction and enhanced risk of cardiovascular disease in T1DM. In conclusion, MRI is a valuable technique for evaluating global and regional cardiac function in T1DM patients and for following measurements’ changes over time. Larger studies with longer follow-up time are needed to better understand the nature of ventricular remodeling in T1DM.