Plans support energy management.

A look at how three local Blue Cross and Blue Shield Plans have developed energy management programs illustrates certain similarities and differences based on the local environment.

Assessment of drug intervention on the ischemic myocardium: serial imaging and measurement with computerized tomography.

Computerized tomography was evaluated as a technique for imaging and measuring the effect of an intervention on acutely ischemic myocardium. Because cell edema occurs with acute myocardial ischemia and decreases the X-ray attenuation coefficients (tissue density) of myocardium, computerized tomographic images were used to quantitate the effect of hyperosmotic mannitol on ischemia-induced edema. Canine hearts were arrested and scanned after (1) temporary occlusion of the proximal circumflex artery followed by reflow of blood, or (2) continued occlusion of the distal left anterior descending coronary artery. X-ray attenuation values (Hounsfield units) were linearly related to tissue wet/dry weight ratios (r = 0.87, P less than 0.001). After 2 hours of occlusion of the left anterior descending coronary artery the hearts that received mannitol manifested a significant reduction (P less than 0.05) in the volume of left ventricular wall involved with edema. Although the area of edema measured with computerized tomography tended to be smaller in the hearts treated with mannitol than in untreated hearts subjected to a 6 hour occlusion of the left anterior descending coronary artery, the size of the lesion was variable and did not differ significantly from that in untreated hearts. With either short periods of circumflex arterial occlusion followed by blood reflow or with 2 or 6 hours of prolonged occlusion of the left anterior descending coronary artery, the difference in mean attenuation coefficients between the ischemic and nonischemic areas of myocardium in mannitol-treated and untreated hearts was significantly less. These results indicate that computerized tomography in the arrested heart can detect and quantitate the lesion of early acute myocardial ischemia and can quantitate the effect of drug intervention.

Right and left ventricular volumes and wall measurements: determination by computed tomography in arrested canine hearts.

Computed tomographic (CT) images of in vitro hearts filled with iodinated contrast medium have delineated right and left ventricular cavities, papillary muscles, major trabeculae, pulmonary artery, and the aorta. Because of relatively good structural definition, this study was undertaken to determine the potential use of CT in the measurement of cardiac dimensions and cavity volumes. Ten isolated arrested canine hearts were filled with an iodinated oil-paraffin mixture and scanned transversely from base to apex. Measurements of the thickness of the interventricular septum and of the left ventricular posterior wall (indexes of cardiac hypertrophy) had a high degree of correlation to similar measurements of corresponding heart specimens. Using serial tomographic images, the cavity volumes of individual tomographic scans were totaled. The volume of each scan of given thickness was obtained either by the use of planimetry or from a numerical computer printout. Both the planimetric and computer methods gave right and left ventricular volumes which correlated well (P less than .05) with the volumes of paraffin casts. Unlike other techniques widely used for ventricular volume measurement, the method described does not depend on an assumption that the chamber resembles a specific geometric model. This method of volume measurement is applicable to both the left ventricle, regardless of its shape, and to the concave irregularly shaped right ventricle.

Computerized tomography of ischemic myocardium: quantitation of extent and severity of edema in an in vitro canine model.

The capacity of computerized tomography to assess myocardial edema resulting from acute coronary occlusion was investigated in 19 arrested and 2 beating canine hearts. Edematous myocardium was consistently detected as areas of decreased attenuation values. The magnitude of the decrease in attenuation value was linearly related to the severity of the edema. The anatomic definition and tomographic information in the arrested hearts provided the capability for localization and quantitation of the extent of the lesion. The results of these in vitro investigations indicate that CT scanning is a technique which will contribute important pathophysiologic information about the evolution of myocardial ischemia.

Definition of cardiac structures using computerized tomography in isolated arrested and beating canine hearts.

Computerized axial tomography of the brain is a revolutionary noninvasive technique that has provided remarkable resolution of intracerebral structures. This study was undertaken to determine the potential of computerized tomography for defining the anatomy of 40 arrested and 9 beating (ejecting left heart preparation) canine hearts. Using an EMI cranial unit, scanning was performed in hearts under in vitro conditions with a lactated Ringer's interface. The tomographic scans obtained were later compared with comparable 8 mm thick sections of the heart. At physiologic levels of hematocrit (range 36 to 45%) external structures were well defined, but because of the lack of a differential between cavitary and myocardial densities, it was not possible to distinguish intracardiac structures. With very small amounts of iodinated contrast material (remotely administered in the case of the beating hearts) or with anemia (hematocrit less than 33%), the right and left ventricular cavities became clearly visible in both horizontal and longitudinal tomographic scans. It was possible to distinguish readily the boundaries of the ventricular and atrial cavities, the papillary muscles, the major trabeculae and the aorta. Rhythmic motion of the beating heart, suspended in its pericardium, did not eliminate structural definition. Thus, computerized tomography provides a new approach to the definition of cardiac structure with a relatively high degree of resolution. These observations point to the potential usefulness of this noninvasive technique for the evluation of both cardiac function and ventricular wall abnormalities.

Detection of edema associated with myocardial ischemia by computerized tomography in isolated, arrested canine hearts.

This study was undertaken to determine if computerized tomography (CT scanning) with an EMI cranial scanner could detect edema associated with myocardial ischemia in canine hearts. A localized area of decreased density in the posterior papillary muscle and surrounding myocardium was detected on serial 8 mm CT scan slices of each heart after 60 min of circumflex artery occlusion and 45 min of reflow of blood. The wet/dry weight ratios and previous electron microscope studies of the ischemic posterior papillary muscles revealed edema accumulation. After 1 hour of arterial occlusion and 12 hours of reflow (which produces extensive necrosis and a decrease in the wet/dry ratio) lesions were still discernible but were less consistently as severe. Permanent ligation of the left anterior descending coronary artery and major collateral arteries for 6 hours also resulted in a lesion of decreased density in the distribution of the occluded arteries. Thus, CT scanning can detect, and is a potential means for sequential noninvasive quantitation of myocardial edema associated with ischemia.

Computerized tomography of in vitro abdominal organs--effect of preservation methods on attenuation coefficient.

The effect of formalin, freezing, and refigeration on the attenuation coefficient of fresh abdominal tissue of rhesus monkeys and dogs was investigated over a 1-week period. These techniques were used individually and in combinations designed to simulate circumstances involved in future in vitro investigations of human specimens. Statistically significant alterations of attenuation coefficients were found to occur at all scanning times within the first week except for the first 48 hr of formalin storage. Refrigeration resulted in the largest alteration. The results indicate the attenuation coefficients of tissues preserved by these three methods may be altered and that the magnitude of the change will vary according to the preservation techniques, tissue, and duration between tissue death and scanning.

Intravenous cholangiography in the rhesus monkey. part I: Determination of optimal iodipamide dose during a one-hour infusion.

One-hour infusion intravenous cholangiography with iodipamide was performed in 3 rhesus monkeys with intact enterohepatic circulations. A series of four different doses including standard (0.3 ml/kg) and "double dose" (0.6 ml/kg) levels were compared. The 0.6 ml/kg dose resulted in significantly higher biliary iodine excretion and concentration than the lower two doses. A 1.2 ml/kg dose probably increased biliary iodine concentration a small amount when compared to the 0.6 ml/kg dose but did not increase iodine excretion. Peak iodine excretion and concentration occurred, on the average, at one hour. The excretion of iodine in the bile demonstrated no inhibitory effect on the concomitant excretion of bile salts.