Jina Chung, MD; Paul Abraszewski, MD; Xin Yu, ScD; Wei Liu, ScD; Andrew J. Krainik, MD, MPH; Marvin Ashford, MD; Shelton D. Caruthers, PhD; Janet B. McGill, MD; Samuel A. Wickline, MD
Clinical Research | January 2006

Objectives This study sought to characterize the early features of diabetic cardiomyopathy by magnetic resonance imaging (MRI) tagging.
Background The earliest manifestations of diabetic cardiomyopathy have not been well established, especially under tight glycemic management. We hypothesized that torsion measurements would identify subclinical contractile alterations in type I diabetics with normal left ventricular ejection fraction, mass, blood pressure, and aggressive glycemic control. We also sought to characterize the influence of elevated resting heart rates (HRs) of diabetics on torsion.
Methods Sixteen patients with type I diabetes and 10 control patients underwent cine and tagged MRI with a 1.5-T scanner. Torsion, strain, and their rates were measured. To quantify the influence of chronotropic and inotropic stimulation on torsion, nine healthy volunteers underwent MRI tagging at rest, after atropine injection, and after exercise.
Results Diabetic patients (hemoglobin A1c, 6.8 ± 0.4%) had a higher resting HR (77.0 ± 12.4 beats/min vs. 59.0 ± 5.6 beats/min; p < 0.01), higher maximal torsion by 23% (3.5 ± 0.9°/cm vs. 2.7 ± 0.4°/cm; p < 0.01) and higher maximal systolic torsion rate (TR-s) by 25% (0.013 ± 0.003°/cm/s vs. 0.010 ± 0.002°/cm/s, p = 0.01). Torsion did not significantly change with chronotropic stimulation (p = 0.30).
Conclusions In diabetics under tight glycemic control, we observed a surprising increase in torsion and TR-s unrelated to chronotropic influences of HR. We propose that increased torsion and TR-s could represent early predictive markers of the propensity to cardiac dysfunction in asymptomatic type I diabetics. Furthermore, these findings seem fundamental to the diabetic state itself and unaccounted for by other comorbidities.

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