Exercise Doppler Echocardiography

Summary Doppler echocardiography is a promising technique for evaluating left ventricular performance during exercise. The method is inexpensive and relatively simple to perform and analyze. Studies of reasonable quality can be performed even at high workloads. Peak velocity of blood flow, acceleration, and stroke volume are parameters clearly related to the function of the left ventricle and can be used to show changes due to ischemia induced by exercise. A number of potential problems exist in applying Doppler echo to the assessment of left ventricular function. It is assumed that the interrogating beam of ultrasound is parallel to flow, and that the flow profile is relatively flat. Neither of these assumptions may be true, however, and the orientation of the ultrasound beam and flow could change during exercise. Problems exist in measuring aortic area. Deterioration of signal quality during exercise may make determination of the onset and termination of flow difficult, and outlining the flow velocity integral may be inaccurate. Despite these potential limitations, the method appears to work remarkably well. The ability to accurately detect changes in function as opposed to absolute function may be the best way to apply this method. Further work needs to be done to establish the precise determinates of ascending aortic blood flow and their relationship to preload, afterload, and contractility. Just as ejection fraction is not a pure indicator of left ventricular contractility, neither is aortic blood flow. In particular, afterload appears to have a major influence on blood flow velocity. Further study is clearly warranted to place the results of exercise Doppler measurements of ascending aortic blood flow into clinical perspective.