Coronary abnormalities seen in patients with Kawasaki disease include perivascular brightness, a lack of distal tapering of the coronaries, diffuse dilation (typically referred to as ectasia [Fig. 14-2]), and aneurysmal dilation (Figs. 14-3 and 14-4) of the coronary arteries. Aneurysms are rarely seen before 10 days into the illness. Coronary scarring, calcification, and stenosis are typically seen in later phases of the illness. Thrombosis of the coronary arteries can occur at any time during the illness. Aneurysms can be classified as saccular with equal lateral and axial dimensions giving the appearance of a round bead, fusiform with proximal and distal tapering of the aneurysm giving a more tubelike appearance, or giant where the aneurysm measures more than 8 mm in size (Box 14-4).

Figure 14-2 Diffuse dilation (ectasia) of the left main coronary artery (LMCA), left anterior descending artery (LAD), and circumflex coronary artery (Cx).

Figure 14-3 Saccular aneurysm of the LAD.

Figure 14-4 Aneurysm of the proximal right coronary artery (RCA).

Acquisition

Initial echocardiogram is used as a baseline and should be a complete study.

Step 1: Complete Transthoracic Echocardiogram

• Although the focus of the echocardiogram is looking for coronary artery abnormalities, patients should be assessed for structural cardiac disease.

• A complete echocardiogram should be performed including 2D imaging, pulsed wave (PW), and color Doppler.

Step 2: Assess Coronary Arteries

• Image all major coronary arteries (left main [LMCA], left anterior descending [LAD], circumflex [Cx], right coronary [RCA], and posterior descending [PDA]).

• Coronary arteries should be measured, and the values for the LMCA, LAD, and RCA should be compared with normal values (Figs. 14-5 and 14-6).

• Avoid measuring near branch points because this may cause an overestimation of size.

• Coronary arteries may be diffusely dilated (ectasia) and may not appear to taper normally.

• Aneurysms may be present, and the number and location of aneurysms should be documented.

• If an aneurysm is present, make sure to evaluate for possible thrombus within the aneurysm or the presence of stenosis.

• Flow in the coronary arteries should be demonstrated; using color Doppler with a low Nyquist limit is helpful.

• Use the highest frequency transducer possible.

• A slight clockwise rotation of the transducer in parasternal short axis views may help to visualize RCA and LMCA (see Fig. 14-1).

• Coronary artery visualization (Box 14-5).

• In the parasternal long axis, a right-to-left sweep may demonstrate the LMCA, LAD, and Cx (Fig. 14-7).

• The apical four-chamber (4C) view with anterior angulation will show the distal Cx in the anterior atrioventricular groove (Fig. 14-8).

• The proximal RCA can be seen from an apical 4C view with anterior angulation in the anterior atrioventricular groove or from a subcostal coronal view (Fig. 14-9).

• The middle RCA can be seen in cross section in the parasternal long axis angled toward the tricuspid valve (TV) and lateral atrioventricular groove.

• The distal RCA and posterior descending coronary artery can be seen in the apical 4C view with posterior angulation in the posterior atrioventricular groove or from the subcostal frontal view with posterior angulation.

Figure 14-5 Coronary artery measurements.

Figure 14-6 Mean and prediction limits for 2 and 3 standard deviations for size of the LAD (A), proximal RCA (B), and LMCA (C) according to body surface area for children 18 years old. LMCA Z scores should not be based on dimension at orifice and immediate vicinity; enlargement of LMCA secondary to Kawasaki disease usually is associated with ectasia of the LAD, Cx, or both.

(From Newburger JW, Takahashi M, Gerber MA, et al. Diagnosis, treatment, and long-term management of Kawasaki disease: A statement for health professionals from the Committee on Rheumatic Fever, Endocarditis, and Kawasaki Disease, Council on Cardiovascular Disease in the Young. American Heart Association. Pediatrics. 2004;114:1708–1733.)

Box 14-5

Echocardiographic Views for Coronary Arteries

LMCA:

Parasternal short axis at the AV level

Parasternal long axis of the left ventricle (LV)

Subcostal left ventricular long axis

LAD:

Parasternal short axis at level of the AV

Parasternal long axis of the LV

Parasternal short axis of the LV

Left Cx:

Parasternal short axis at level of AV

Apical 4C

RCA, proximal:

Parasternal short axis at the AV level

Parasternal long axis of the LV

Subcostal coronal projection of the RVOT

Subcostal short axis at the level of the atrioventricular groove

RCA, middle segment:

Parasternal long axis inferior tangential of the LV

Apical 4C

Subcostal left ventricular long axis

Subcostal short axis at the level of the atrioventricular groove

RCA distal segment:

Apical 4C

Subcostal atrial long axis

PDA:

Apical 4C

Subcostal atrial long axis

Parasternal long axis imaging of the posterior interventricular groove

Figure 14-7 LAD seen in the parasternal long axis.

Figure 14-8 Cx seen from the apical four-chamber (4C) view with anterior angulation in the anterior atrioventricular groove.

Figure 14-9 RCA seen from the apical 4C view with anterior angulation in the anterior atrioventricular groove.

Step 3: Assess Valve Function

• All valves should be assessed for the presence and degree of regurgitation using both PW and color Doppler.

• MV regurgitation occurs in about 25% of patients with Kawasaki disease but is usually trivial to mild. TV regurgitation may also be present.

• Aortic valve (AV) regurgitation occurs less frequently than MV regurgitation and is usually trivial.

Step 4: Assess Ventricular Function

• Myocarditis may be present in the acute phase of the illness, and mildly depressed ventricular function may be noted.

• An assessment of global ventricular function should be performed and may be done by M-mode with calculation of a shortening fraction or apical imaging to calculate an ejection fraction.

• Patients with coronary abnormalities should be assessed for RWMAs that would suggest coronary ischemia or infarct. Views including parasternal long axis, parasternal short axis, and apical 4C and two-chamber are useful for imaging the 16 (or 17) standard myocardial segments useful in describing the location of wall motion abnormalities and determining the specific coronary artery distribution affected.

Step 5: Assess Aortic Root

• The aortic root should be imaged in the parasternal long axis view and measured during systole (per pediatric convention).

• Measurements should be compared with normal values for BSA (Z scores).

Step 6: Assess for Pericardial Effusion

• A transient pericardial effusion may be present in the acute phase of Kawasaki disease and is usually not hemodynamically significant.

• Size and location of the effusion should be noted.

Follow-up echocardiograms can be limited to evaluation of ventricular function and coronary arteries. If there is a history of valve regurgitation or other abnormalities, this should be reevaluated.

Pitfalls

• Using a low-frequency transducer may make imaging of coronary arteries difficult. It is best to use the highest frequency transducer possible.

• Optimize imaging by decreasing the gain and dynamic range (compression).

• If the patient has poor transthoracic images, transesophageal echo may need to be performed to assess the proximal LMCA and RCA.

• Recording images in a dynamic imaging format or digital cine format allows for better assessment of structures than a still-frame image.

Analysis

Coronary Artery Measurements

• Coronary arteries should be measured from inner edge to inner edge.

• Measurements should not be performed near branching points because this may overestimate the size of the coronary artery.

• Reference Z scores available for LMCA, LAD, and proximal RCA based on BSA (see Fig. 14-6).

• Coronary arteries are thought to be dilated if the measurement is a Z score greater than 2.5.

• Aneurysm size:

• Small to medium, larger than 3 mm but smaller than 6 mm (coronary Z score +3 to +7, based on a “typical” BSA for a 5 year old).

• Large: 6 mm or greater.

• Giant: 8 mm or greater (Fig. 14-10).

Figure 14-10 Giant aneurysm of the RCA.

Alternate Approaches

• Dobutamine stress echo may be used to assess for segmental wall motion abnormalities.

• Magnetic resonance imaging/magnetic resonance angiography is an alternative method to image coronary arteries and assess for aneurysms, coronary occlusions, and coronary stenosis.

• Computed tomography has been demonstrated to be useful for imaging proximal aneurysms.

• Cardiac catheterization allows for assessment of both proximal and distal aneurysms along with assessing for coronary stenosis (Fig. 14-11).

• Transesophageal echo may allow assessment of the proximal RCA and LMCA in patients with limited echo windows.

Figure 14-11 Angiogram of aneurysms in the RCA.