Relation of perfusion defects observed with myocardial contrast echocardiography to the severity of coronary stenosis: correlation with thallium-201 single-photon emission tomography.

It has been previously shown that myocardial contrast echocardiography is a valuable technique for delineating regions of myocardial underperfusion secondary to coronary occlusion and to critical coronary stenoses in the presence of hyperemic stimulation. The aim of this study was to determine whether myocardial contrast echocardiography performed with a stable solution of sonicated albumin could detect regions of myocardial underperfusion resulting from various degrees of coronary stenosis. The perfusion defect produced in 16 open chest dogs was compared with the anatomic area at risk measured by the postmortem dual-perfusion technique and with thallium-201 single-photon emission tomography (SPECT). During a transient (20-s) coronary occlusion, a perfusion defect was observed with contrast echocardiography in 14 of the 15 dogs in which the occlusion was produced. The perfusion defect correlated significantly with the anatomic area at risk (r = 0.74; p less than 0.002). During dipyridamole-induced hyperemia, 12 of the 16 dogs with a partial coronary stenosis had a visible area of hypoperfusion by contrast echocardiography. The four dogs without a perfusion defect had a stenosis that resulted in a mild (0% to 50%) reduction in dipyridamole-induced hyperemia. The size of the perfusion defect during stenosis correlated significantly with the anatomic area at risk (r = 0.61; p = 0.02). Thallium-201 SPECT demonstrated a perfusion defect in all 14 dogs analyzed during dipyridamole-induced hyperemia; the size of the perfusion defect correlated with the anatomic area at risk (r = 0.58; p less than 0.03) and with the perfusion defect by contrast echocardiography (r = 0.58; p less than 0.03). Thus, myocardial contrast echocardiography can be used to visualize and quantitate the amount of jeopardized myocardium during moderate to severe degrees of coronary stenosis. The results obtained show a correlation with the anatomic area at risk similar to that obtained with thallium-201 SPECT.

Safety and efficacy of a new transpulmonary ultrasound contrast agent: initial multicenter clinical results.

Myocardial contrast echocardiography has been found to be a safe and useful technique for evaluating relative changes in myocardial perfusion and delineating areas at risk. Although earlier contrast agents required direct delivery into the coronary arteries or aortic root, a new echocardiographic contrast agent, sonicated albumin microspheres (Albunex), has been found to cross the pulmonary circulation in experimental models. To determine the safety and preliminary efficacy of intravenous injections of Albunex in humans, 71 patients at three independent medical institutions underwent two-dimensional echocardiographic examination before, during and after the administration of three intravenous doses of Albunex, ranging from 0.01 to 0.12 ml/kg body weight. All patients provided a complete history and underwent physical and neurologic examination and laboratory and electrocardiographic evaluation before the injections; all evaluations (except for the history) were repeated at 2 h and 3 days after the injections of Albunex. The efficacy of the injections was qualitatively assessed by two independent blinded observers using a grading system of 0 to +3, with 0 indicating an absence of contrast effect and +3 indicating full opacification of the cavities examined. All injections were well tolerated and no serious side effects were noted in any of the patients. Irrespective of dose group, a cavity opacification greater than or equal to +2 was seen in the right ventricle in 212 (88%) of 240 injections and in the left ventricle in 151 (63%) of 240 injections as judged by the independent observers. The degree of ventricular cavity opacification appeared to be dose and concentration related.(ABSTRACT TRUNCATED AT 250 WORDS)

Doppler echocardiography: application to the assessment of successful thrombolysis of prosthetic valve thrombosis.

Prosthetic valve thrombosis remains a significant problem despite anticoagulation therapy and advances in valve design. Thrombolytic therapy offers an alternative approach to valve replacement in patients with high surgical risk. In this article we discuss three cases in which Doppler echocardiography was used to confirm the diagnosis of prosthetic mitral valve obstruction and serially monitor the response of valvular hemodynamic measurements to thrombolysis with intravenous streptokinase. These cases illustrate how the Doppler technique, in addition to allowing the noninvasive diagnosis of prosthetic valve obstruction, is presently the ideal tool to follow serially the effect of thrombolytic therapy on prosthetic valve function.

Assessment of regional myocardial perfusion with myocardial contrast echocardiography in a canine model of varying degrees of coronary stenosis.

Previous studies showed that myocardial contrast echocardiography can be used to detect relative regional underperfusion in a canine model of critical coronary stenoses. The aim of this study was to determine if myocardial contrast echocardiography performed with a sterile sonicated human serum albumin preparation (Albunex, Molecular Biosystems, San Diego, Calif.) could detect the presence of coronary stenoses of variable degrees of severity. The results were compared with myocardial blood flow as assessed by radiolabeled microspheres in 16 open-chest dogs during baseline, following the creation of a coronary stenosis of variable severity and at the peak of dipyridamole-induced hyperemia. When flow ratios (that is, flow in the control area/ischemic area) were examined, a good correlation was observed between the area under the time-intensity curve and radioactive microsphere blood flow (r = 0.94, p < 0.0001), which allowed distinction of mild from severe stenosis. However, a consistent underestimation of the dipyridamole-induced hyperemia by myocardial contrast echo was seen in the control zone. This could be partially explained by a simultaneous increase in coronary blood flow and blood volume with dipyridamole and by attenuation of the ultrasound signal because of the high concentration of microbubbles at high flows. Myocardial contrast echocardiography can quantitate the amount of jeopardized myocardium during various degrees of coronary stenoses.