Monophasic Action Potential(MAP) recording using contact electrode is very sensitive method to detect the ischemic changes of myocardium. The purpose of this study were to investigate changes of MAP during percutaneous transluminal coronary angioplasty(PTCA) and to evaluate through MAP whether or not a brief episode of ischemia influenced on subsequent ischemic episode during PTCA.

MAPs using endocardial contact electrode were recorded dbefore, during the fitst and second inflation and 3 min after PTCA in 7 patients undergoing PTCA.

1) MAP amplitude significantly decreased to 79.1±11.0% during the first inflation(p<0.05) and to 86.3±9.0% during the second inflation(p<0.05) and recovered to 92.7±3.7% at 3 min after PTCA.

2) MAP duration to 90% repolarization(MAPD 90) significantly decreased to 91.4±5.1% during the first inflation(p<0.05) and to 95.3±3.5% dudring second inflation(p<0.05) and recovered to 97.3±2.8% at 3 min after PTCA.

3) Double prodducts showed no significant difference between the first and second inflation.

4) The changes of MAP amplitude and MAP duration during the second inflation was significantly lower than that recorded during the first inflation.

MAP recording using endocardial contact electode may be safe and very sensitive method to detect the ischemic changes of human endocardium and the lessened MAP changes during the second inflation supports the concept of preconditioning ischemia.