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A Guide To Performing
Complete Transthoracic Echocardiograms [continued] |
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| ICAEL DIVISION NEWS | Summer 2008 |
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One of the elements of study quality, as outlined in Part II, Section 3.1.2 of The Standards is definition of the endocardium. Optimize equipment capabilities for enhancing endocardial borders, and persevere in attempting to obtain the best possible images. Apical 2-chamber and apical long (apical 3-chamber) views are also required, and must display endocardial border definition as well as avoid foreshortening (see chart below).
Subcostal view - The required 4-chamber subcostal view is well-oriented for color interrogation of the atrial and ventricular septa. It is also an excellent view from which to align the Doppler cursor with a jet of tricuspid regurgitation that is directed toward the interatrial septum. The subcostal short axis is not a standard view, but should be acquired when a parasternal view is suboptimal or unattainable.
NOTE: The ICAEL Standards stipulate that all required views be attempted; any view that is unattainable must be documented as such.
Suprasternal notch view - The most current Standards state that this view is to be obtained "when indicated." For example, the aortic arch should be visualized in cases such as aortic stenosis, aortic dissection, bicuspid aortic valve, Marfan's Syndrome and any other cases in which it is appropriate to rule out coarctation, dilatation, malformation or damage.
Standard Doppler Views, Tips and Pitfalls
Color Doppler - Color interrogation of any regurgitation must be performed in two or more imaging planes. Optimize your machine settings to increase frame rate, improve color sensitivity and eliminate aliasing. While it is imperative that non-foreshortened, on-axis views be displayed in every study, be aware that non-standard views may also be used to better display color flow.
Spectral Doppler - The Standards require spectral waveforms of the forward flow for each valve. Part II, Section 3.1.2 directs that the Doppler beam must be properly aligned parallel to flow and that abnormal flows must be interrogated from multiple areas. Applicant laboratories often omit interrogation of the highest tricuspid velocity from multiple views. This velocity may be sought from the right ventricular inflow, parasternal short axis, apical and subcostal views. Again, a foreshortened apical view, possibly tilted to the right or left, may better visualize a jet of tricuspid regurgitation and improve the Doppler cursor alignment. Use precise placement of the cursor for both continuous and pulsed-wave Doppler, and enhance the visibility of the spectra by changing the speed, scale and other machine settings. Adjust the scan depth or Doppler scale to avoid inappropriate use of HPRF (high pulse repetition frequency) mode.
Failure to fully interrogate the highest aortic stenosis velocity is one of the most frequent reasons that applicant laboratories are delayed accreditation. The ICAEL Standards clearly state in Part II, Section 3.2.2.C that for aortic stenosis cases, the non-imaging continuous wave Doppler probe must be used from multiple areas to interrogate the highest aortic valve velocity. This probe must be utilized from at least two of these areas: apical, suprasternal notch and right parasternal border, and at least one good spectrum must be obtained. Scan areas should be labeled, and unsuccessful attempts to locate the flow should be documented.
2D/M-Mode Measurements, Tips and Pitfalls
The required left ventricular, aortic root and left atrial dimensions may be obtained in 2D or in M-Mode, provided that standard orthogonal planes are used for measurement. Due to the importance of a precise left ventricular outflow tract dimension [to the Continuity Equation], this measurement should be made in the parasternal long axis view, using the "zoom" feature. Note that because many laboratories now perform offline measurements, The Standards no longer require that the calipers be visible in a representative study. |
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AVOIDANCE OF FORESHORTENING
It is imperative that apical views are imaged in their proper orientation, with the transducer at the actual apex. In a "foreshortened" apical view, the transducer is placed at a point proximal to the true apex, and the apex is actually excluded from the image. This crucial error may hinder diagnosis of apical wall motion abnormalities or thrombi and can distort cardiac dimensions.
Look for these clues to an image that may be foreshortened. To be correct, scan lower and more laterally, utilize breathing techniques and reposition the patient.
- The apical endocardium appears to "dip down" toward the left ventricular cavity in systole
- The right ventricular apex appears to connect over the left ventricular apex rather than laterally to it
- The entire heart appears "round and bulbous" rather than elongated from apex to base
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FIGURE 3. In this foreshortened 4-chamber view the endocardium appears to "scrunch up" at the apex, and the cardiac shape is round. |
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FIGURE 4. The right ventricle appears enlarged and the right ventricular apex seems to attach over the left ventricle in this foreshortened view. |
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FIGURE 5. This well-oriented and non-foreshortened 4-chamber view displays the heart from true apex to base. The right ventricle is in fact of normal size, and the entire left ventricle and its endocardial border is visualized. |
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As laboratories strive to perform complete, quality diagnostic echocardiograms, The ICAEL Standards serve as a reference for ensuring day-to-day quality, in addition to preparing for accreditation itself.
Imaging examples created for this article by Ali Reese, RDCS.
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