Perfusion local myocardial

An important feature of the distributed model is the stress and pressure distribution within the LV wall, Figure 6, which is an important factor in the determination of the local myocardial perfusion. Note that the strain rate affects the stress distribution when the flow is high, Figure 6b. Note also the change in the sarcomere length distribution from the beginning to the end of systole, Figure 6d. 

Technetium-99m tetrafosmin ( Tc-(V)02 (l,2-bis(bis(2-ethoxyethyl)phosphino)ethane) (see Fig. 3d)) is a myocardial perfusion agent. It is used as an adjunct in the diagnosis and localization of myocardial ischemia and/or infarction. 

Apart from echocardiography, another promising clinical application of synthetic microbubbles is the ultrasonic monitoring of local blood flow in the abdomen (analogous to the earlier use of gas microbubbles to monitor myocardial perfusion (ref. 443)). Such refined ultrasonic blood flow measurements, utilizing injected... 

Oxygen deprivation follows when blood flow is compromised by a local, temporary circulatory blockade that may occur naturally as a result of stenosis, stroke, or a myocardial infarction (heart attack) or may accompany therapeutic interventions, such as percutaneous transluminal coronary angioplasty (PTCA). Packed RBCs are not useful for restoration of oxygen delivery in these situations, because they are too large to traverse the constricted vessels or too viscous and fragile to be pumped through a perfusion balloon catheter. A number of preclinical studies in this area are summarized below. 

In conclusion, the Folts model of cyclic coronary blood flow variations clearly involves platelet microembolization. However, the role of physical obstruction versus microvascular constriction in the impaired myocardial perfusion is not entirely clear. Platelet-endothelium and platelet-leukocyte interactions may also contribute to the local inflammatory response37. 

Thallium scanning with the aid of computer analysis segregates the images into anatomic regions and specifically localizes areas of dead or necrotic myocardial tissue. In conjunction with ECHO or SPECT, thallium scans can correlate areas of abnormal wall motion with areas of poor perfusion. Sensitivity and specificity of thallium scanning to detect IHD disease are comparable with those of ET (75% and 80%, respectively). When used in conjunction with exercise ECG, sensitivity increases to about 80%. Thallium scanning also can be used in conjunction with ET to allow detection of lower levels of ischemia than may be determined from ECG abnormalities or patient... 

Diagnosis of reduced regional perfusion and localization of myocardial infarction... 

Cardiac scintigraphy can be used to obtain parameters of cardiac perfusion and function. 99mTc-pyrophosphate can be used to assess acute myocardial infarction. In the case of myocardial infarction the agent localizes in the area of necrotic tissue, forming an intense spot of radioactivity. Global uptake of activity in the ventricular myocardium usually represents some other cardiac disease. 

It is the purpose of the present study to develop a general model of the LV which relates the mechanical determinants of cardiac contraction to the spatial myocardial energetics and the local coronary perfusion during the cardiac cycle. It is hoped that the model will help in the understanding and the quantification of... 

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