Is Doppler color-flow imaging a separate imaging technique from echocardiography?

Doppler imaging uses the direction and velocity of blood flow to evaluate cardiovascular hemodynamics, and color-flow imaging (CFI) provides real-time, two-dimensional imaging of blood flow. Echocardiography, Doppler imaging, and CFI are complementary rather than competitive; the best studies integrate the three techniques.

What are the major hemodynamic measurements and clinical applications of Doppler echocardiography?

Multiple hemodynamic measurements and analyses are possible with Doppler acquisition, but the major categories of application are ventricular performance, valvular function, and shunt lesions. Stroke volume can be obtained with measurements of the left ventricular outflow tract, blood flow into the ascending aorta, and flow velocities. Doppler evaluation of pulmonary artery flow allows measurement of right ventricular output. Measurement of time intervals aids in the evaluation of systolic and diastolic ventricular function. The differences in flow volumes can be used to calculate intracardiac shunts and regurgitant flows. One of the most valuable uses of Doppler is to evaluate valve function, especially pressure gradients, which can be used to calculate the area of the stenotic valve and maximal velocity across the valve. Flow disturbances (turbulence) are used to diagnose valvular regurgitation and to evaluate its severity.

What are the limitations to echocardiography and Doppler imaging?

The major limitation is the lack of anatomic quantitative measurements in echocardiography, which necessitates technical skill in performance and interpretation. Another limitation is the acquisition of total cardiac anatomic information, which is achieved in 80-90% of studies. Moreover the complexity of anatomic and hemodynamic information often leads to incorrect or incomplete interpretations by examiners who are not well versed or adequately experienced. In transesophageal echocardiography the images are frequently clear but should be interpreted only by an experienced cardiologist. Misinterpretation also may be due to technical limitations, misreading of artifacts, or extraneous echoes.

What are the clinically useful recommendations for echocardiography and Doppler imaging?

Evaluating ventricular systolic and diastolic performance

Estimating right-sided heart hemodynamics

Measuring pressure gradients and valvular orifice areas in stenotic valves or other discrete narrowings

Detecting valvular regurgitation and estimating its hemodynamic significance

Evaluating function of valvular prostheses

Establishing the presence and determining the significance of intracardiac shunts

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