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CLINICAL RESEARCH: DIABETES AND CARDIOVASCULAR DISEASE

Paradoxical Increase in Ventricular Torsion and Systolic Torsion Rate in Type I Diabetic Patients Under Tight Glycemic Control

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 and Samuel A. Wickline, MD, FACC^_*,,_*

^_* Cardiovascular Magnetic Resonance Laboratories, Washington University School of Medicine, St. Louis, Missouri
Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri
Department of Biomedical Engineering, Washington University School of Medicine, St. Louis, Missouri
Philips Medical Systems, Best, the Netherlands.

Manuscript received March 18, 2005; revised manuscript received July 27, 2005, accepted August 22, 2005.

^_* Reprint requests and correspondence: Dr. Samuel A. Wickline, Division of Cardiology, Washington University School of Medicine, Box 8086, 660 South Euclid Avenue, St. Louis, Missouri 63110. (Email: saw{at}wuphys.wustl.edu).

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.

Abbreviations and Acronyms   DCM = diabetic cardiomyopathy   ES = duration from end-diastole to end-systole   HbA1c = hemoglobin A1c   HR = heart rate   LV = left ventricle/ventricular   MRI = magnetic resonance imaging   TR-r = maximal torsion rate during recoil   TR-s = maximal torsion rate during systole   TTE = transthoracic echocardiography

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