The effect of acute myocardial ischemia on the myocardial elastic modulus has been a matter of controversy. To evaluate this question, diastolic elastic modulus was assessed by finite element analysis of left ventricular geometry using three-dimensional echocardiographic reconstructions and right and left ventricular pressure recordings. Elastic properties were estimated before and after coronary occlusion in 6 open-chest dogs. Elastic modulus values were derived by means of a computer program that determined the global elastic modulus that best predicted the diastolic changes in left ventricular geometry. In the finite element analysis after coronary occlusion, two analyses were performed: one utilizing the control elastic modulus for all segments of the left ventricle and one in which ischemic (dyskinetic) segments were assigned a higher elastic modulus. Results showed that the control elastic modulus was a poor predictor of diastolic left ventricular expansion after coronary occlusion. The finite element analysis in which the ischemic segments were assigned a higher elastic modulus better predicted ischemic diastolic wall motion patterns. Error values (difference between predicted and actual left ventricular segmental diastolic motion) were: control, 1.9 +/- 0.3 mm (mean +/- SD), ischemia, 2.9 +/- 0.5 mm, and 2.2 +/- 0.4 mm using the stiffer elastic modulus for ischemic segments. Error values were significantly higher (p less than 0.05) under ischemic conditions when the control elastic modulus was uniformly applied compared with control and ischemia with dyskinetic segments assigned a higher elastic modulus. From these data, it is concluded that the myocardial diastolic elastic modulus is increased by ischemia and that this approach may allow clinical assessment of intrinsic muscle stiffness.
Cine computed tomography is capable of providing accurate, quantitative assessment of regional myocardial perfusion over a broad range of perfusion states. This method, if extended to the study of humans, could enhance the understanding of disorders of the coronary circulation in human cardiovascular disease states.
Recent world-wide statistical data show that. tanker spills generally amount to about 160 barrels. of oil per million barrels shipped, of which between 40-70 barrels are spilled at the receiving port. This historical data base can be adapted to proposed deepwater ports in. order t9_ calcul~ate the spill expectation at those ports. The methodology takes into account conditions existing at the proposed ports that afford~enefits_not occurring at the data base ports. By taking credit for these conditions, expected tanker spillage at two proposed deepwater ports (SEADOCK and LOOP) is demonstrated to range between 0.2 and 2 ppm of throughput, a much lower rate than that experienced at conventional ports.
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