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Am J Physiol Heart Circ Physiol 294: H867-H874, 2008. First published November 30, 2007; doi:10.1152/ajpheart.00573.2007
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Temporal changes in cardiac force- and flow-generation capacity, loading conditions, and mechanical efficiency in streptozotocin-induced diabetic rats

Dong-Feng Yeih,1,2 Lian-Yu Lin,2 Hung-I Yeh,3 Yu-Jun Lai,3 Fu-Tien Chiang,2 Chuen-Den Tseng,2 Shu-Hsun Chu,1 and Yung-Zu Tseng2,4

1Department of Cardiology, Far Eastern Memorial Hospital, Pan-Chiao, Taipei; 3Departments of Internal Medicine and Medical Research, Mackay Memorial Hospital; Mackay Medicine, Nursing and Management College, Taipei Medical University, Taipei; 2Department of Internal Medicine, National Taiwan University Hospital, Taipei; and 4Department of Cardiology, Show Chwan Memorial Hospital, Chang-Hua, Taiwan

Submitted 17 May 2007 ; accepted in final form 24 November 2007

Diabetes mellitus may result in impaired cardiac contractility, but the underlying mechanisms remain unclear. We aimed to investigate the temporal alterations in cardiac force- and flow-generation capacity and loading conditions as well as mechanical efficiency in the evolution of systolic dysfunction in streptozotocin (STZ)-induced diabetic rats. Adult male Wistar rats were randomized into control and STZ-induced diabetic groups. Invasive hemodynamic studies were done at 8, 16, and 22 wk post-STZ injection. Maximal systolic elastance (Emax) and maximum theoretical flow (Qmax) were assessed by curve-fitting techniques, and ventriculoarterial coupling and mechanical efficiency were assessed by a single-beat estimation technique. In contrast to early occurring and persistently depressed Emax, Qmax progressively increased with time but was decreased at 22 wk post-STZ injection, which temporally correlated with the changes in cardiac output. The favorable loading conditions enhanced stroke volume and Qmax, whereas ventriculoarterial uncoupling attenuated the cardiac mechanical efficiency in diabetic animals. The changes in Emax and Qmax are discordant during the progression of contractile dysfunction in the diabetic heart. In conclusion, our study showed that depressed Qmax and cardiac mechanical efficiency, occurring preceding overt systolic heart failure, are two major determinants of deteriorating cardiac performance in diabetic rats.

diabetes; contractile function; hemodynamics; mechanical efficiency; ventriculoarterial coupling


Address for reprint requests and other correspondence: Y.-Z. Tseng, Dept. of Internal Medicine, National Taiwan Univ. Hospital, 7, Chung-Shan South Road, Taipei, 10016 Taiwan, Republic of China (e-mail: yztseng{at}ntu.edu.tw)






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