Physiol. Res. 49: 607-616, 2000

Susceptibility to Ischemia-Induced Arrhythmias and the Effect of Preconditioning in the Diabetic Rat Heart

T. Ravingerová, R. Štetka, D. Pancza, O. Uličná1, A. Ziegelhöffer, J. Styk
 

Institute for Heart Research, Slovak Academy of Sciences, and 1Pharmacobiochemical Laboratory of Medical Faculty, Comenius University, Bratislava, Slovak Republic

Received April 13, 2000
Accepted May 26, 2000


Summary
Diabetic heart is suggested to exhibit either increased or decreased resistance to ischemic injury. Ischemic preconditioning suppresses arrhythmias in the normal heart, whereas relatively little is known about its effects in the diseased myocardium. Our objective was to investigate whether development of diabetes mellitus modifies the susceptibility to ischemia-induced arrhythmias and affects preconditioning in the rat heart. Following 1 and 9 weeks of streptozotocin-induced (45 mg/kg, i.v.) diabetes, the hearts were Langendorff-perfused at constant pressure of 70 mm Hg and subjected to test ischemia induced by 30 min occlusion of the left anterior descending (LAD) coronary artery. Preconditioning consisted of one cycle of 5 min ischemia and 10 min reperfusion, prior to test ischemia. Susceptibility to ischemia-induced arrhythmias was lower in 1-week diabetics: only 42 % of diabetic hearts exhibited ventricular tachycardia (VT) and 16 % had short episodes of ventricular fibrillation (VF) as compared to VT 100 % and VF 70 % (including sustained VF 36 %) in the non-diabetics (P<0.05). Development of the disease was associated with an increased incidence of VT (VT 92 %, not significantly different from non-diabetics) and longer total duration of VT and VF at 9-weeks, as compared to 1-week diabetics. Preconditioning effectively suppressed arrhythmias in the normal hearts (VT 33 %, VF 0 %). However, it did not provide any additional antiarrhythmic protection in the acute diabetes. On the other hand, in the preconditioned 9-weeks diabetic hearts, the incidence of arrhythmias tended to decrease (VT 50 %, transient VF 10 %) and their severity was reduced. Diabetic rat hearts are thus less susceptible to ischemia-induced arrhythmias in the acute phase of the disease. Development of diabetes attenuates increased ischemic tolerance, however, diabetic hearts in the chronic phase can benefit more from ischemic preconditioning, due to its persisting influence.


Key words
Experimental diabetes · Myocardial ischemia · Preconditioning · Arrhythmias · Rat heart

Reprint requests
Dr. T. Ravingerová, Institute for Heart Research, Slovak Academy of Sciences, Dúbravská cesta 9, 842 33 Bratislava, Slovak Republic. e-mail: usrdravi@savba.sk


© 2000 by the Institute of Physiology, Czech Academy of Sciences