Hisatsune Ootsubo

Tissue edema and loss of tracer microspheres in infarcted myocardium

SummaryMicrosphere loss from the ischemic myocardium was studied in a canine model after 2 and 7 days coronary occlusion. 10 million tracer microspheres (TM) of 7–10 μm diameter were injected into the left atrium before and 15 minutes after left anterior descending coronary artery (LAD) occlusion. To determine the tissue water content, dried tissue weight was measured after desiccation. TM content in the nonoccluded left circumflex coronary artery (LCX) area was unchanged before and after coronary occlusion. In the infarcted area, microsphere loss was maximum at the low flow endocardial region averaging 27% and 42% in 2 and 7 days occlusion, respectively. An inverse linear correlation between TM loss and regional blood flow in 2 (r=−0.82, p<0.05) and 7 (r=−0.96, p<0.01) days coronary occlusion was noted. Water content was increased in the ischemic endocardium by 4.1 and 5.7% in 2 and 7 days occlusion, thus approximately 17% of TM loss was attributed to tissue edema. These results suggest that there is an ischemia-dependent reduction of TM in the ischemic myocardium and that microsphere migration participates in the major part of TM loss. Thus flow measurements by TM may be invalid when this compound is injected during the active phase of microsphere migration or during water content alterations.

Linear relationship between perfusion area and infarct size

SummaryThe purpose of this study was to develop a technique measuring the perfusion area of the coronary artery preocclusively and to study the relationship between the perfusion are aand infarct size.125I tracer microspheres were selectively injected into the left circumflex coronary artery (LCX) preocclusively, and then the LCX was ligated 48 hours later the heart was removed, rapidly frozen, and 50-μ transverse sections were obtained from base, middle and apex of the canine left ventricle, and used for autoradiography to measure perfusion area and for tetrazolium staining to measure infarct size. Dogs were divided into 2 groups: group 1 in which the main trunk of the LCX was occluded to produce large infarct (n=10) and group 2 in which the distal branch of the LCX was occluded to produce small infarct (n=10). There was a linear correlation between the perfused and infarcted area regardless of a size or location of the perfusion area involved. These results indicate that the extent of infarction is directly proportional to the perfusion area and is not altered by the location in the ventricle.

Constriction of the epicardial coronary artery induced by α-adrenergic stimulation

SummaryEffects of alpha adrenergic stimulation on diameter change of the epicardial coronary artery were studied in in-situ canine heart. The diameter of the left circumflex coronary artery (LCX) was continuously measured by 10 MHz PZT crystals applied to the external wall of the LCX. Aortic pressure was measured using high fidelity catheter-tip manometer.Enhanced activity of alpha adrenergic receptor by humoral and/or somatic nerve stimulations caused a reduction of the LCX diameter despite of the systemic pressure rise.