DOPPLER ECHOCARDIOGRAPHY
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| Plate 3-13 PRINCIPLES OF DOPPLER ECHOCARDIOGRAPHY |
Echocardiography with Doppler ultrasound is based on the principle of estimating velocity and direction of blood flow by using moving red blood cells as a target (see Plate 3-13). There are two types of Doppler US: continuous wave and pulse wave. With the continuous wave technique the transducer can be aimed along the long axis of the ventricle of the aorta and can record all flow patterns encountered. The pulse wave technique allows simultaneous recording of the Doppler and 2D echocardiography. The pulsed technique allows the localization of a Doppler sample in the area of interest (e.g., mitral and aortic valves). Using these Doppler techniques, a transvalvular gradient across the aortic or mitral valves can be derived, as well as estimation of the pressure and severity of mitral, aortic, and tricuspid valve regurgitations.
Doppler color
flow imaging techniques allow noninvasive imaging of blood flow through the
heart and the display of flow data on the 2D echocardiogram. Color flow imaging
can provide the approximate size and direction of any abnormal flow velocity
within the heart, including mitral or aortic insufficiency and ventricular
septal defect. Doppler echocardiography is extremely sensitive and will detect
even the slightest amount of tricuspid regurgitation, even in patients with no
evidence of cardiac disease.
The accepted
indications of cardiac US include the following:
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Valvular heart disease (native cardiac valve, pros- thetic cardiac valve),
suspected or proven infective endocarditis.
•
Ischemic heart disease (i.e., myocardial infarction), when the physician
asks a specific question that can be answered by cardiac US.
•
Heart muscle disease, to establish the morphologic diagnosis and
hemodynamic assessment of patients with cardiomyopathy, systemic illness
associated with cardiac involvement and clinical symptoms, and exposure to
cardiotoxic agents.
•
Pericardial disease, to evaluate clinical manifestations or suspicion of
pericardial disease.
•
Cardiac masses, to evaluate patients with suspected cardiac masses.
•
Cardiac murmurs, to evaluate an organic murmur in a patient with
cardiorespiratory symptoms or a murmur in an asymptomatic patient if clinical
features indicate at least moderate probability that the murmur is organic.
