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
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