Preconditioning by Hypoventilation Increases Ventricular
Arrhythmia Threshold in Wistar Rats
P. ŠVORC, I. BRAČOKOVÁ
Department of Physiology, Medical Faculty, Šafárik
University, Košice, Slovak Republic
Received
April 25, 2002
Accepted August 4, 2002
Summary
Hypoventilation, as one of ventilatory disorders, decreases the
electrical stability of the heart similarly as ischemia. If
preconditioning by short cycles of ischemia has a
cardioprotective effect against harmful influences of a
prolonged ischemic period, then preconditioning by
hypoventilation (HPC) can also have a similar effect.
Anesthetized rats (ketamine 100 mg/kg + xylasine 15 mg/kg i.m.,
open chest experiments) were subjected to 20 min of
hypoventilation followed by 20 min of reoxygenation (control
group). The preconditioning (PC) was induced by one (1PC), two
(2PC) or three (3PC) cycles of 5-min hypoventilation followed by
5-min reoxygenation. The electrical stability of the heart was
measured by a ventricular arrhythmia threshold (VAT) tested by
electrical stimulation of the right ventricle. Twenty-minute
hypoventilation significantly decreased the VAT in the control
and 1PC groups (p<0.05) and non-significantly in 2PC vs. the
initial values. Reoxygenation reversed the VAT values to the
initial level only in the control group. In 3PC, the VAT was
increased from 2.32±0.69
mA to 4.251.31 mA. during hypoventilation (p<0.001) and to 4.37±1.99
mA during reoxygenation (p<0.001). It is concluded that
cardioprotection against the hypoventilation/ reoxygenation-induced
decrease of VAT proved to be effective only after three cycles
of HPC.
Key
words
Hypoventilation • Cardioprotection • Preconditioning •
Ventricular arrhythmia • Rats
Reprint
requests
P. Švorc, Department of
Physiology, Medical Faculty, Šafárik University, Tr. SNP 1, 040
66 Košice, Slovak Republic. E-mail:
psvorc@central.medic.upjs.sk
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