Electrophysiologic effects of ischemic preconditioning on QT dispersion during coronary angioplasty.
OBJECTIVE
The aim of this study was to examine the effect of ischemic preconditioning on the manner of ventricular repolarization by assessing the change in QT dispersion during coronary angioplasty.


BACKGROUND
QT interval dispersion reflects regional variations in ventricular repolarization and cardiac electrical instability. Previous studies have suggested that increased QT dispersion is associated with an increased incidence of malignant ventricular arrhythmias, whereas brief episodes of myocardial ischemia can render the heart more resistant to subsequent ischemic episodes, a phenomenon called ischemic preconditioning.


METHODS
To assess the effects of ischemic preconditioning on myocardial repolarization by examining the change in QT dispersion during coronary angioplasty, we studied 47 consecutive patients (39 men and 8 women; mean age 57 +/- 16 years). QT dispersion was measured after each balloon inflation during coronary angioplasty. Statistical analysis was performed by using repeated measurement of analysis of variance.


RESULTS
There were significant differences in QT dispersion as the number of balloon inflations increased (mean +/- SD 52 +/- 14, 42 +/- 11, 36 +/- 9, 31 +/- 10 and 29 +/- 11 ms, respectively [p < 0.01], for the first, second, third, fourth and fifth balloon inflations). The magnitude of decrease in QT dispersion was significant in the first and second balloon inflations, then became insignificant with later inflations.


CONCLUSIONS
These data indicate that the gradual decrease in QT dispersion provoked by coronary artery occlusion and reperfusion during coronary angioplasty may be associated with electrophysiologic effects of ischemic preconditioning on myocardium in the human heart.
Okishige
K
K
Cardiac Electrophysiology Laboratory, Yokohama Red Cross Hospital, Japan.
Yamashita
K
K
Yoshinaga
H
H
Azegami
K
K
Satoh
T
T
Goseki
Y
Y
Fujii
S
S
Ohira
H
H
Satake
S
S
D015906:Angioplasty, Balloon, Coronary; D001145:Arrhythmias, Cardiac / Q000517:prevention & control; D003327:Coronary Disease / Q000503:physiopathology / Q000628:therapy*; D004562:Electrocardiography; D004594:Electrophysiology; D005260:Female; D006321:Heart / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000503:physiopathology*; D015428:Myocardial Reperfusion Injury / Q000517:prevention & control