Clinical demonstration of functional wave front of the intramyocardial ischemic region in patients with coronary stenosis

In experimental studies, deterioration of the transmural myocardial contractility occurs heterogeneously in coronary hypoperfusion. That is, the subendocardium is the first layer to become vulnerable to the ischemia in the acute reduction of the coronary flow according to J. I. Hoffman (1987), K. A. Reimer and R. B. Jennings (1979) and P. Colonna et al. (1999). With a longer period of ischemia, necrosis progresses heterogeneously from the endocardium to the epicardium (the wavefront phenomenon) by K. A. Reimer and R. B. Jennings (1979). After the release of 15 min coronary occlusion, the ischemic myocardium progressively recovers its contractility. This post-ischemic recovery in contractility has also been demonstrated to be heterogeneous along the myocardial wall, but is much quicker at the subepicardial side than at the subendocardium, with a "subendocardial post ischemic stunning" according to R. Boli et al. (1989). However, at present, there is still a serious deficiency in the clinical information concerning the transmyocardial functional heterogeneity across the human ventricular wall. The "phased tracking method", adopted in this study, has advantages over the conventional clinical diagnostic methods because of its higher spatial and temporal resolution together with its ease of handling for repetitive use according to H. Kanai et al. (1997) and H. Kanai and Y. Koiwa (2001). In this preliminary clinical study, we examined whether the transmural systolic function obtained by the phased tracking method is capable of supplying new information about the ischemic myocardium under ischemia and after coronary reperfusion.