Ken Nagao, MD; Kazuyoshi Satou, MD; Ken Arima, MD; Ikuyoshi Watanabe, MD; Makoto Yamashita, MD; Katsuo Kanmatsuse, MD

Abstract
This study was conducted in an attempt to clarify whether preinfarction angina has an ischemic preconditioning effect. The subjects of this study were Killip class I patients who had suffered a first acute myocardial infarction (MI) as a result of total occlusion of the proximal left anterior descending coronary artery without development of collateral vessels and multivessel coronary artery disease. All subjects achieved successful reperfusion [thrombolysis in myocardial infarction (TIMI) flow grade 3] through intracoronary thrombolysis with single-chain urokinase-type plasminogen activator (SCU-PA). Subsequently, they received the same drug therapy and remained free of reocclusion. The patients were divided into those who experienced a new onset of prodromal angina within 24 h before the onset of acute MI [PA(+) group] and those who had a sudden onset of acute MI without the preceding angina [PA(-) group]. They were further divided according to the time interval from the onset of acute MI to reperfusion (within 1 h, 1-2 h, 2-3 h, 3-4 h, and 4-7 h). In addition, the left ventricular ejection fraction (LVEF), left ventricular end-diastolic volume index (LVEDVI), and the amount of creatine kinase (CK) released (sigmaCK) were compared in these 2 groups at reperfusion time. The results of this study showed that sigmaCK was significantly lower in the PA(+) group than in the PA(-) group (1,850 mIU vs 3,583 mIU) when reperfusion was induced within 1 h after the onset of acute MI. When reperfusion was induced 1-2 h after the onset of acute MI, sigmaCK tended to be lower in the PA(+) group than in the PA(-) group (3,677 mIU vs 5,261 mIU). Once the time to reperfusion exceeded 2 h, there was no significant difference in sigmaCK between these 2 groups. On the other hand, there were no significant differences in LVEF and LVEDVI between these 2 groups at any reperfusion time. In conclusion, preinfarction angina had a preconditioning effect (reduction in sigmaCK), but this effect was lost once the time interval from the onset of acute MI to reperfusion exceeded 2 h.
(Jpn Circ J 1997; 61: 843-849)

Key Words: Ischemic preconditioning; Preinfarction angina; Acute myocardial infarction; Infarction size; Thrombolytic therapy

Mailing address: Ken Nagao, MD, Surugadai Nihon University Hospital, 1-8-113, Kanda Surugadai, Chiyoda-chu, Tokyo, Japan