Computer methods for myocardial contrast two-dimensional echocardiography

Two computer-aided videodensitometric methods that may be used in conjunction with two-dimensional contrast echocardiography were examined to quantify the time course of echographic opacification in the myocardium after experimental injections of contrast agents (hand-agitated Renografin-saline and sonicated sorbitol 70% solutions) into the left main coronary artery. Echographic studies of myocardial cross sections were digitized with an image processing computer using a 128 × 128 resolution matrix. Both stop frame and continuous cycle modes of acquisition were performed. A set of computer programs was developed to extract and analyze time-intensity curves from the digitized images. These included cardiac outline delineation, segmental division, regional intensity computation and exponential curve analysis. The stop frame method was applied to experimental studies in 17 closed chest dogs during control states and after coronary occlusions. Significant differences were found in the decay half-lives of echo intensity between normal (24 ± 8 seconds) and acutely ischemic (293 ± 165 seconds; p < 0.001) myocardium for the Renografinsaline solution. Interobserver reproducibility of the measured half-lives was r = 0.91 and standard error of the estimate = 5 seconds. The continuous cycle method of analysis was examined in five closed chest dogs (with up to six injections per dog), applying the sonicated sorbitol 70% solution in only the control state. The mean halflife was 4.2 ±1.1 seconds.These computer-based videodensitometric methods might be applied to a wide variety of experimental studies in two-dimensional contrast echocardiography that attempt to quantify myocardial perfusion and function

Effects of pressure-controlled intermittent coronary sinus occlusion on regional ischemic myocardial function

Pressure-controlled intermittent coronary sinus occlusion has been reported to reduce infarct size in dogs with coronary artery occlusion, possibly because of increased ischemic zone perfusion and washout of toxic metabolites. The influence of this intervention on regional myocardial function was investigated in open and closed chest dogs. In six open chest dogs with severe stenosis of the left anterior descending coronary artery and subsequent total occlusion, a 10 minute application of intermittent coronary sinus occlusion increased ischemic myocardial segment shortening from 5.5 ± 1.2 to 8.2 ± 2.6% (NS) and from −0.1 ± 2.1 to 2.3 ± 1.2% (NS), respectively.In eight closed chest anesthetized dogs, intermittent coronary sinus occlusion was applied for 2.5 hours between 30 minutes and 3 hours of intravascular balloon occlusion of the proximal left anterior descending coronary artery. Standardized two-dimensional echocardio-graphic measurements of left ventricular function were performed to derive systolic sectional and segmental fractional area changes in five short-axis cross sections of the left ventricle. Fractional area change in all the severely ischemic segments (< 5% systolic wall thickening) was −4.0 ± 4.7% at 30 minutes after occlusion, and increased with subsequent 60 and 150 minutes of treatment to 13.1 ± 3.3 and 7.0 ± 3.3%, respectively (p < 0.05). At the most extensively involved low papillary muscle level of the ventricle, regional ischemic fractional area change was increased by intermittent coronary sinus occlusion between 30 and 180 minutes of coronary occlusion from −0.4 ± 0.1 to 14.4 ± 4% (p < 0.05), whereas a further deterioration was noted in untreated dogs with coronary occlusion.Continuous arterial and coronary venous blood density measurements were performed in seven open chest dogs to determine the influence of pressure-controlled intermittent coronary sinus occlusion on ischemic myocardial washout. The arteriovenous density gradient was 0.16 ± 0.05 g/Iiter during coronary artery occlusion, and decreased to 0.05 ± 0.08 g/liter (p < 0.05) as a result of the intervention, suggesting a significant fluid washout from the myocardium. It is concluded that pressure-controlled intermittent coronary sinus occlusion provides recovery of cardiac function and that this benefit might be associated with enhanced ischemic zone washout