Residual viable myocardium after myocardial infarction may act as an unstable substrate for further events unless it is revascularized. Despite this association, age and left ventricular dysfunction remained the strongest predictors of cardiac death after myocardial infarction in these patients with a spectrum of left ventricular dysfunction.

The effect of different mAs settings on computed tomobraphy (CT) image quality was evaluated by a clinical study and phantom studies. In the clinical portion of this study, a number of CT images, obtained at various mAs settings, were reviewed by experienced CT interpreters. From these same images, graphs were charted of the root-mean-standard deviation (RMSD) vs. body size; there appeared to be a linear relationship between noise, as measured by RMSD, and body size. A performance phantom was used to evaluate the effect of the different mAs settings on resolution. There was some loss in low contrast resolution at 6 and 20 mAs; however, the resolution was identical at 40 and 100 mAs.

1. The maximum rates of left ventricular ejection and filling were derived (Fourier analysis) from the left ventricular volume curve (99m technetium-human serum albumin gated blood pool studies) in 12 normotensive subjects and 15 hypertensive patients of matched age groups. 2. Average values of cardiac output, ejection fraction, heart rate and left ventricular ejection rate were not significantly different in the two groups. 3. Hypertensive patients had a slower rate of left ventricular filling (P < 0.05), suggesting diminished left ventricular compliance in hypertension.

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SUMMARY The objectives were to study plasma and erythrocyte flow in an area of acute focal cerebral ischemia and define their relationship to developing microcirculatory obstruction as determined by morphological techniques. Eighteen adult cats, anesthetized with ketarnlne hydrochloride, had right middle cerebral artery (MCA) occlusion. Plasma flow was determined by measuring the transit of Iodine-131 ( l "I) albumin and erythrocyte flow was determined by measuring the transit of Technetium-99 ("Tc) labeled erythrocytes in the right Sylvian region. Transit studies were performed before and immediately after right MCA occlusion and at the end of the ischemic period, 1 hour, 3 hours, or 6 hours after occlusion. Intra-arterial perfusion with a buffered formaldehyde -colloidal carbon solution was carried out after completion of the isotope studies. Swelling of cerebral tissue and impaired carbon filling in the right MCA territory were seen initially after 3 hours occlusion and were more severe after 6 hours occlusion. Ischemic neuronal alterations, edema formation, and capillary luminal narrowing increased with longer periods of occlusion. '"I albumin transit time in the right Sylvian region was 8 ± 2 seconds before occlusion and 10 ± 2 seconds immediately after occlusion. "Tc erythrocyte transit time was 10 ± 2 seconds before occlusion and 12 ± 3 seconds immediately after occlusion. Transit times increased progressively with longer periods of occlusion in cats developing cortical ischemic changes. No evidence of complete microcirculatory obstruction to albumin and erythrocyte transit was seen in cats with 6 hours of occlusion despite the impaired filling of the cortical microcirculation with carbon. There were no findings to substantiate the hypothesis that plasmapheresis develops during the early phases of cerebral infarction. Stroke, Vo! 12, No 2, 1981MICROCIRCULATORY CHANGES may play an important role in the evolution of a cerebral infarct. Much of the information regarding these changes has been derived from morphological 1 " 7 and regional cerebral blood flow (rCBF) 8 " 1 ' studies. These studies, however, have not answered important questions regarding the possible development of microcirculatory obstruction to the passage of erythrocytes or the separation of plasma and erythrocyte flow (i.e., plasmapheresis) during the early phases of cerebral infarction. The objectives of this investigation were to study plasma and erythrocyte transit in an area of acute focal cerebral ischemia and define their relationship to developing microcirculatory obstruction as determined by morphological techniques. MethodsEighteen adult cats (mean weight 4.0 kg) were anesthetized with ketamine hydrochloride (40 mg/kg subcutaneously). Catheters were inserted into the right femoral artery and vein. A tracheostomy was performed through a longitudinal midline incision and mechanical ventilation instituted. Skeletal muscle paralysis was achieved with d-tubocurare (1.5 mg/ kg/IV). A small catheter was inserted into the right carotid art...