Doppler color flow mapping of epicardial coronary arteries: initial observations.

OBJECTIVES: We addressed the hypothesis that blood flow could be imaged by Doppler color flow mapping of the coronary arteries and characteristic patterns described in normal and diseased vessels. BACKGROUND: Echocardiographic imaging of the epicardial coronary arteries has been suggested as a useful adjunct to their intraoperative evaluation. Addition of Doppler color flow mapping could potentially enhance this evaluation by displaying the flow disturbance produced by anatomic lesions whose physiologic significance may otherwise be uncertain. In experimental models, such displays could also potentially provide insights into the pathophysiology of coronary blood flow and stenosis. METHODS: Epicardial coronary arteries were examined with a high resolution 7-MHz linear phased-array transducer both in vivo and in vitro. 1) The coronary arteries were studied in the beating hearts of 10 open chest dogs in which experimental stenoses were also created; the maximal extent of the arterial tree in which flow could be seen in the most ideal setting was also examined in four additional excised perfused canine hearts. 2) Six excised human coronary arteries were perfused in a pulsatile manner to determine whether abnormal flow patterns could be prospectively identified and subsequently correlated with pathologic evidence of stenosis. RESULTS: All normal coronary artery segments studied showed homogeneous flow without evidence of flow disturbance. In the excised heart, flow could be visualized to the distal extent of the epicardial vessels; in the open chest model, visualization of the proximal 5 to 6 cm was comparable, although surrounding structures limited access to the terminal portions of the vessels. The stenotic lesions created in the canine hearts (n = 9) showed recognizable alterations in the flow pattern: localized aliasing, proximal blood flow acceleration, distal flow disturbance and recirculatory flow. In the excised human arteries, these features identified 12 lesions, all of which corresponded to areas of > or = 50% lumen narrowing by pathologic examination. CONCLUSION: Blood flow in the epicardial coronary arteries can be imaged by Doppler color flow mapping and characteristic flow patterns described in normal and diseased vessels.

Variation in the color Doppler area of a regurgitant jet with changes in the absolute chamber pressure: an in vitro study.

The color Doppler appearance of a regurgitant jet depends on jet momentum, determined in part by the pressure difference between the two chambers. However, it is not clear if absolute chamber pressure has an independent effect on jet area. To test this question, an in vitro experiment was performed in which dynamically decaying jets were created with identical initial pressure gradients but five different levels of absolute chamber pressures. At every level of chamber pressure, color Doppler images were recorded with two different transducers (3.5 and 5.0 MHz) and jet areas were measured at four different flow rates (0 to 9.9 cm3/sec). A multilinear regression model was created with jet area as the dependent variable and jet flow rate, transducer frequency, and absolute chamber pressure as independent parameters. Jet area was most strongly predicted by flow rate (univariate r = 0.90) and transducer frequency (r = 0.32). Even after adjusting for these effects, however, a small but significant (p less than 0.0001) effect of absolute chamber pressure on jet area was seen with jet area rising by 0.89 cm2 for each 10 mm Hg increase in absolute chamber pressure (multivariate r = 0.96, p less than 0.0001). We conclude that the color Doppler area of a regurgitant jet is dependent not only on the relative pressure and flow between the two chambers but also on the absolute chamber pressure.