Cardiac Views

THE SPECIAL CASE OF THE RIGHT HEART

The right heart is divided into an INFLOW region (right atrium, tricuspid valve, and beginning of RV) and an OUTFLOW region (right ventricular outflow tract (RVOT), pulmonic valve, and main pulmonary artery) and different views are needed to evaluate each region.

RV INFLOW abnormalities are frequent in our patients, so we routinely obtain RV INFLOW views in the three heart windows. RV OUTFLOW views are covered in the Advanced Right Heart Disease chapter and are only performed in response to some abnormalities in the RV INFLOW.

PARASTERNAL WINDOW

This is traditionally the first window to be imaged. Although the parasternal window is not the best to evaluate every aspect of the heart, we attempt three routine views in this window in case the apical and subcostal windows are suboptimal.

Some structures may be better seen in the more cephalad part of the window (e.g., ascending aorta), while others are better in a more caudad interspace (e.g., mid-LV). We try to begin in the cephalad part of the window.

After the patient is positioned in the left lateral decubitus position, identify the left edge of the sternum halfway between the suprasternal notch and the xiphoid. This will be the cephalad part of the window in most patients.

Fully load the phased array probe with gel (like an ice cream cone), carefully keep it horizontal, and bring it to the patient’s chest. Dump the gel on the previously identified target area and spread it caudad.

PLAX: The parasternal long axis is the first view. Examiner fingers should be near the bottom of the probe with the thumb on the indicator end and the third/fourth fingers on the opposite end. Position the probe with the thumb pointing to the patient’s right shoulder and the arm resting on the patient to maintain a relaxed wrist and hand. The probe may need rotation, fanning, or tilting to get a good view, as shown in the following:

The default depth for our heart preset is deliberately several centimeters greater than needed for most hearts so that pleural and pericardial fluid will be identified. After this fluid assessment, the depth must be moved closer to the pericardium. We study the PLAX clockwise, beginning at the top with the proximal RVOT and progressing through the ascending aorta (AA), the aortic valve (AV), the left atrium (LA), the mitral valve (MV), and the basal portions of the left ventricle (LV).

The short axis descending aorta is below the left atrium in the PLAX. Another nearby vascular structure, the coronary sinus, may be seen in the PLAX right underneath the posterior mitral valve. This vein collects the venous blood from the myocardium and returns it to the RA. It runs on the posterior heart in between the atria and the ventricles. It enlarges beyond 1 cm when RA pressure is chronically increased or in a congenital abnormality discussed more in the Atria Size and Function chapter. Here is a dilated coronary sinus in a patient with various abnormalities that we ignore for now.

PLAXR: This is the first RV INFLOW view. From the standard PLAX position, fan the probe modestly to look under the caudad sternum. In most patients, this will feel like you are pushing the top of the probe towards the patient’s left shoulder. Here is a good PLAXR.

On the screen, the RA is at the bottom, the tricuspid valve (TV) is in the middle, the inflow part of the RV is above, and the view should be studied following the blood flow. In the RA, the IVC enters at the bottom left, with the coronary sinus entry a notch above the IVC.

PSAX: The parasternal short axis view is achieved from the PLAX with a 90-degree clockwise rotation of the probe (indicator toward the left ventricle). The rotation can be more accurate if the right hand anchors the probe while the left rotates. The PSAX can’t be a better view than the PLAX because they use the same window. If a good PLAX and PLAXR have been obtained, the PSAX is routinely helpful for only two things (covered in subsequent chapters): the left ventricular “doughnut” and the cross-section of the aortic valve leaflets.

APICAL WINDOW

The apical window in the left lateral decubitus position is typically described as about two intercostal spaces caudad of the PLAX window at the anterior axillary line. Very obese patients may have more horizontal hearts with an apical window almost straight lateral from the PLAX. The line created by the probe in the PLAX position points the way to the apex. Beginning ultrasonographers and even advanced users with difficult-to-image patients should get the best PLAX using a good amount of gel. Then, slide the probe on the chest to follow the line of the PLAX. The apical window should be found, but the view will be the apical3 (discussed below). To get to the apical4 view, rotate the probe counterclockwise 90 degrees using two hands.

APICAL4: We need to get lateral enough on the chest to be at the apex, where the LV should be bullet-shaped and not rounded unless the LV is dilated and abnormal.

Occasionally, a smaller patient has an apical4 with a vertical septum and full-size atria and ventricles with two leaflets of the mitral and tricuspid valves visible, as in the following:

For several reasons, a single apical4 cannot see all aspects of the heart equally well in many patients, so we divide the apical4 into left and right heart partitions and begin with the left. We study each side by following the blood flow, so the Atria are first. The probe requires rotation and fanning to optimize each side.

One adjustment is the RV-enhanced view, in which the probe is moved out lateral and cephalad around the apex so the septum on the screen leans toward the RV. While part of the lateral side of the LV may disappear, the lateral RV may be better seen, and the interventricular septum may be more defined because it is more perpendicular to the ultrasound beam. This clip shows an RV-enhanced apical4.

To obtain the LV-enhanced view, the probe is moved medially around the apex, angling toward the lateral wall of the LV. The septum tilts toward the LV on the screen, and the LV lateral wall is better seen. Here is an LV-enhanced apical4.

APICAL5: The apical 5-chamber view is achieved from the apical4 with a modest anterior fan that brings the AV and LV outflow tract (LVOT) into view.

APICAL2: The apical 2-chamber view is achieved from the apical4 with a slow probe rotation, so the indicator moves cephalad (counterclockwise) 45 degrees. It is important to stay over the LV, so start with the left heart near the center of the screen and rotate carefully, usually with two hands. During the rotation, the right side of the heart should disappear, and the LV will be seen above the LA. Analyze following the blood flow, so LA first. Here is a normal apical2.

APICAL3: The apical 3-chamber view will appear if the probe is rotated another 45 degrees counterclockwise from the apical2. This is also called the apical long axis because it is the same cut through the heart as the PLAX (same probe orientation as the PLAX), but now the view is from the apex (the PLAX gets tipped up). Notice that the apical3 is a 90-degree rotation from the apical4 just as the PLAX is 90 degrees away from the PSAX. If the apical3 is not achieved well with rotation, return to the PLAX and slide to the apex as described above in the apical window section. When the slide is impossible for a patient, get the PLAX view, lift your hand and arm up from the chest without changing the wrist or fingers, and move out to the apex. The aortic and mitral valves are more parallel to flow with the apical3 than the PLAX, and the LV apex is better seen. Study the apical3 following the blood flow. Here is a normal apical3.

APICAL3R: Just as the PLAX was easily modified to the PLAXR, the apical3 can be shifted with a fan to look under the sternum (cord tipped toward the left shoulder). This RV INFLOW view is parallel to flow through the tricuspid valve like the apical4 but has a different plane, so abnormalities may be better seen in some patients.

The view is like the PLAXR, with the RVOT heading off to the right on the screen. Study the structures following the blood flow.

SUBCOSTAL (SUBXIPHOID) WINDOW

SC4/5: The subcostal (SC) view is essential in many patients. It is best to obtain this while the patient remains in the left lateral position, which increases the chance that the liver will be down below the costal margin, giving a sonic window. The antrum of the stomach will be decompressed. Sometimes, the subcostal views are better when a patient stands.

Use your left fingers to find the costal margin immediately to your left of the xiphoid. Use an overhand grip, position the probe transverse below the rib, push in, and tilt/rock the probe toward the heart. A liver must be visible at the top of the screen, or the heart won’t be seen. Search with the probe along the costal margin for the best view.

The probe is usually farther away from the heart in the subcostal region, so increased depth is needed with most patients. The focus position may also need adjustment. The ultrasound beam must pass through a section of the liver thicker than the subcutaneous tissue of either the parasternal or apical windows, so increased gain improves the view in many patients.

As with the apical4, the right and left sides of the heart are rarely optimal simultaneously in a single plane, so the probe must be rotated and fanned to get the best views of each side. Here is a good SC4/5.

Study the right side of the heart first, following the blood flow, and then optimize the left heart and follow the blood flow.