From Ask Dr Wiki
The echocardiogram for many cardiologists has almost superseded the physical exam. Technologic advances have made this imaging modality so portable that bedside examination of a patient can be performed quickly. This ease of use can at times result in overuse of the modality. Either way, similar to the stethoscope and ECG, the transthoracic echocardiogram is a staple of clinical cardiology and an essential skill for a clinical cardiologist.
Echocardiography can provide imaging of all aspects of cardiovascular physiology and pathology including.
- Aortic, Mitral, Tricuspid and Pulmonic Valves including stenosis and regurgitation
- Left and Right Ventricular Function.
- Ischemic Ventricular Abnormalities
- Pericardial Disease
- Cardiac Tamponade
- Myocardial Restriction
- Systolic and Diastolic Heart Failure
- Pulmonary Embolism
- Intracardiac and Pulmonary Shunts
- Myocardial Tumors
- Acending Aortic Pathology
There are no frank contraindications to echocardiography. Certainly a patient needs to be cooperative to examination for optimal imaging. Other body factors including pulmonary pathology, decompensated heart failure, chest wall abnormalities and body habitus may interfere with image acquisition.
Positioning the patient in the left lateral decubitus position will bring the heart forward to the chest wall and closer to the transducer. Obtaining images at end expiration will also bring the heart closer to the chest wall, and may be particulary useful in patients with significant obstructive lung disease. Air trapping in these patients may make imaging especially difficult. In patients that are unable to lie in the decubitus position or in very obese patients, sometimes the only images that can be obtained are in the subxiphoid windows.
It is imperative to approach each study in a regimented fashion. While each operator or technologist may vary in their imaging steps, a set approach will ensure that all information is obtained from the patient. This is especially critical given that by the time that many studies are interpreted, the patient may no longer be available for further imaging.
A Comprehensive Echocardiographic Study
To begin a study, place the patient in a gown that will allow easy access to the various echo windows and explain in detail what will be involved in the study. It is important to always place ECG leads on a patient. Digital images are often gated to the surface ECG. If needed, timed clips may be obtained, but ECG information is important to correlate images to the cardiac cycle.
Three Orthogonal Planes:
- Long Axis - transects the heart from aortic root to the left ventricular apex
- Short Axis – runs from left mid clavicle to the right hip
- Four Chamber Axis – runs from apex to the base; perpendicular to other 2 axes
Position the patient in the left lateral decubitus position. The first two windows are taken in the PARASTERNAL window located between the 3rd-4th interconstal space.
- 1) Parasternal Long axis: This image is obtained with the transducer notch facing the right shoulder. In this position the Mitral and aortic valve should be imaged. Gross ventricular function should be determined and the posterior and interventricular septum should be examined for wall motion abnormalities. Pericardial effusions should be assessed. Measurements should be taken of the left ventricular cavity in both systole and diastole. The thickness of the posterior wall and the interventricular septum should be obtained. Often the ventricular apex is foreshortened in this view. Each of the valves should be examined for structural and motion abnormalities. M-Mode imaging should be used in the mid cavity, in the mitral leaflets and at the level of the aortic valve. Color Doppler imaging should be used to interrogate the mitral and aortic valves for the presence of signifcant regurgitation.
- 2) Parasternal short axis: Once the long axis is imaged, the echo probe should be rotated 90 degrees. In this position, the classic donut view of the left venticle is seen along with the right ventricle. Tilting the probe allows imaging of the left ventricle from the base to the apex. In each position, important aspects and cardiac structures are seen. Color should be applied through the short axis of the Aortic and mitral valves, the IAS and the tricuspid and pulmonic valves. Continuous wave doppler can be used across the Tricuspid Valve to assess RVSP.
Once the parasternal images are obtained, the probe should be laced along the left chest wall at the cardiac apex in the APICAL WINDOW. Often in patients with signficant lung disease or obesity, these images can be challenging. Shifting positions and imaging at end expiration can often assist in obtaining optimal images.
- 3) Apical 4-Chamber View: Shift the transducer to obtain all 4 chambers with the Left and Right ventricles in view. Image the mitral and tricuspid annulus and assess for RV and LV function and the presence of any wall motion abnormalities. Pericardial effusions should be assessed. Color Doppler should be placed accross the mitral and tricuspid valves to assess for regurgitation or stenosis. Zoomed images of regurgitation should be obtained. If significant regurgitation is present, it should be quantified as best as possible. Pulsed wave doppler (PW) should be obtained at the mitral leaflet tips to assess the mitral inflow pattern. If significant regurgitaiton is present, PW should be obtained in the Pulmonary veins to assess for blunting or reversal. Continuos wave doppler should be placed through the mitral valve and tricuspid valve to assess regurgitation and stenosis. RVSP may be estimated from CW through the tricuspid valve. Color doppler should be placed accross the intra-atrial septum to assess for PFO or ASD.Zoomed imaging of the setptum should be obtained in any situation concerning for itraatrial pathology.
After obtaining the Apical 4 chamber, the probe should be tilted anteriorly to open up the LVOT. This will facilitate the Apical 5 chamber view:
- 4) Apical 5-Chamber view: The aortic valve should be imaged and magnified to assess for sclerosis or stenosis. Significnat aortic stneosis is assessed with measurments taken in this view. CW should be placed directly accross the aortic valve to assess for aortic gradients. PW should be placed in the LVOT and immediately above the aortic valve. The LVOT should be measured. Aortic valve area can be calculated through these measuremnts.
In the Apical 4 chamber, the transduce should then be rotated 75-90 degrees counterclockwise to image the apical 2 chamber view:
- 5) Apical 2-Chamber View: LV function should be assessed as well as any wall motion abnormalities. Descending aortic size should be assessed as well as flow quality by color imaging.
Continued rotation of the transducer will open up the LVOT and form the Apical 3-Chamber View:
- 6) Apical 3-Chamber View: global function and Wall motion abnormaliteis should be assessef. Pericardial effusions should be assessed. Color doppler should be placed in the LVOT and accrross the aortic valve. CW should be placed accross the aortic valve to assess for aortic stenosis.
Once the Apical images are obtined, have the patient lie flat in the supine position and bend their knees to relax their abdominal musculature. The probe should then be placed under the xiphoid porcess and angles at the cardiac apex to show the SUBXIPHOID window . Many refer to the subxiphoid window as the fellows friend. It is a useful image as it can show a great deal of cardiac imaging even in difficult patients.
- 7) Sub-Costal or Sub-Xiphoid View: Start by locating the liver and moving the probe midline and angled anterior to bring the Left and right atria and ventricles into view. 2-D image the 4 chambers, assess for global LV fucntion, wall motion abnormalities, and pericardial effusions. Color, CW and PW accross the mitral and aortic valves. Assess the IVC and hepatic veins for collapse and inflow. PW hepatic veins. RA pressures should be estimated in this view. Rotating the probe 90 degrees will obtain a short axis view. Similar measuremnts should be assessed as in the parasternal short axis.
- 8) Suprasternal View: The probe should then be placed in the suprasternal notch angled down toward the ascending aorta. 2-D imaginf of the aorta and great vessels if visible to assess origin or dilitation. Color doppler and CW shoudl be used to assess for any flow abnormalities (regurgitaiton, coarct, PDA).