Visualizes heart in real time with ultrasound; Doppler recordings noninvasively assess hemodynamics and abnormal flow patterns (Table 114-1 and Fig. 114-1). Imaging may be compromised in pts with chronic obstructive lung disease, thick chest wall, or narrow intercostal spaces. Transesophageal echocardiography (TEE) is performed when higher resolution images of cardiac structures is required.
TABLE 114-1Clinical Uses of Echocardiography ||Download (.pdf) TABLE 114-1 Clinical Uses of Echocardiography
Cardiac chambers: size, hypertrophy, wall motion abnormalities
Valves: morphology and motion
Pericardium: effusion, tamponade
Aorta: aneurysm, dissection
Assess intracardiac masses
Valvular stenosis and regurgitation
Approximate intracardiac pressures
|Transesophageal Echocardiography |
Superior to 2-D echo to identify:
Cardiac source of embolism
Prosthetic valve dysfunction
Assess myocardial ischemia and viability
Two-dimensional echocardiographic still-frame images of a normal heart. Upper: Parasternal long axis view during systole and diastole (left) and systole (right). During systole, there is thickening of the myocardium and reduction in the size of the left ventricle (LV). The valve leaflets are thin and open widely. Lower: Parasternal short axis view during diastole (left) and systole (right) demonstrating a decrease in the left ventricular cavity size during systole as well as an increase in wall thickness. Ao, aorta. (Reproduced from Myerburg RJ: Harrison’s Principles of Internal Medicine, 12th ed, 1991.)
CHAMBER SIZE AND VENTRICULAR PERFORMANCE
Assessment of atrial and ventricular dimensions, global and regional systolic wall motion abnormalities (administration of IV echo contrast enhances myocardial border detection when needed), ventricular hypertrophy/infiltration, evaluation for pulmonary hypertension: RV systolic pressure (RVSP) is calculated from maximum velocity of tricuspid regurgitation (TR):
RVSP = 4 × (TR velocity)2 + RA pressure
(RA pressure is same as JVP estimated by physical examination.) In absence of RV outflow obstruction, RVSP = pulmonary artery systolic pressure.
LV diastolic function is assessed by transmitral spectral Doppler and Doppler tissue imaging, which measures velocity of myocardial relaxation (see Fig. 236-8, in HPIM-20).
Thickness, mobility, calcification, and regurgitation of each cardiac valve can be assessed. Severity of valvular stenosis is measured by Doppler (peak pressure gradient = 4 × [peak velocity]2); valve areas are calculated using additional Doppler techniques. Dobutamine echocardiography can clarify degree of aortic stenosis in pts who have poor contractile function or low-flow states. Structural lesions (e.g., flail leaflet, vegetation) resulting in regurgitation may be identified, and color flow and spectral Doppler (Fig. 114-2) estimate severity of regurgitation.
Schematic presentation of normal Doppler flow across the aortic (A) and mitral (B) valves. ...