Effect of acute subendocardial ischemia on ventricular refractory periods.
OBJECTIVE
To investigate the impact of acute subendocardial ischemia on the dispersion of ventricular refractory periods.


METHODS
Acute subendocardial ischemia was induced in sheep by partial ligation of the left circumflex coronary artery and rapid pacing of the left atrium. The ventricular effective refractory period (ERP) was measured in five areas of the left ventricle by a programmed premature stimulation technique.


RESULTS
The average ERP and ERP dispersion remained unchanged in the control group (n=5, P>0.05). In the study group (n=5), the ERP was shortened following subendocardial ischemia. ERP dispersion decreased significantly from 48+/-9 ms to 36+/-13 ms 30 min after the ischemia (P=0.02). There was neither spontaneous nor stimulation-induced ventricular arrhythmia after ischemia.


CONCLUSIONS
Acute subendocardial ischemia leads to a homogenous reduction of ventricular ERP. This may partially explain why subendocardial ischemia is associated with a low incidence of ventricular arrhythmia.
Ma
Longle
L
Department of Cardiology, Liaocheng City People's Hospital, Shandong Province, People's Republic of China.
Wang
Lexin
L