12 Left Heart Anomalies

Brian D. Soriano, David S. Owens

Background

• Left heart anomalies include lesions of the mitral valve (MV), left ventricular outflow tract (LVOT), aortic valve (AV), coronary arteries, and aorta (Ao). Within each of these structures there is a wide spectrum of both congenital and acquired diseases.

• Certain genetic lesions are associated with left heart lesions (Table 12-1).

TABLE 12-1 SYNDROMES AND DISEASES ASSOCIATED WITH LEFT HEART LESIONS

Left Heart Disease	Association
Coarctation of the aorta	Turner syndrome
	Bicuspid AV
	Unicuspid AV
Supravalvular aortic stenosis	Williams syndrome
Dilated aorta	Bicuspid AV
	Marfan syndrome
	Loeys-Dietz syndrome
	Ehlers-Danlos syndrome
	Shprintzen-Goldberg syndrome
	Turner Syndrome
Simultaneous left heart obstructions: mitral stenosis, aortic stenosis, coarctation	Shone syndrome
	Hypoplastic left heart syndrome

This list is intended to summarize more commonly associated syndromes and is not all-inclusive.

Overview of Echocardiographic Approach

• Any abnormality that is detected by echocardiography (echo) should trigger the detailed evaluation of structures both upstream and downstream of the lesion. For example, if coarctation of the aorta is diagnosed, both the AV and MV should be carefully evaluated to rule out associated functional or structural abnormalities (Box 12-1).

• Evaluation of lesions by two-dimensional (2D) echo should be performed via all available acoustic windows because subtle diagnostic or anatomic clues can be gleaned. A single en face view of the MV, for example, would not be able to determine whether there are problems with the submitral apparatus or whether there are signs of supramitral obstruction.

• Fine-tune 2D images to maximize resolution. Use the highest frequency transducer that windows will permit. Eliminate unnecessarily wide views by narrowing the 2D sector angle or by zooming into a region of interest. Consider changing line density if higher frame rates take priority over spatial resolution.

• Doppler imaging is critical to evaluate the hemodynamic impact of the anomaly. The regions immediately adjacent to an identified anomaly should be carefully performed to determine whether problems exist in series. Color Doppler complements spectral Doppler and can help visualize the location and degree of stenosis or regurgitation and the presence or absence of turbulence.

• Nyquist limits are inversely related to transducer frequency; if color Doppler maps or pulsed wave (PW) Doppler scales are limited, consider switching to a lower frequency setting or switch to a lower frequency transducer.

• A good-quality color Doppler map is best predicted by the quality of the 2D image and the acoustic windows. If the acoustic window or the 2D image is poor, the color Doppler maps are unlikely to be useful.

• A surprisingly good spectral Doppler tracing, however, can frequently be obtained even if 2D images are suboptimal.

• If necessary, intravenous contrast can enhance spectral Doppler images.

Box 12-1

Suggested Echocardiographic Approach for Left Heart Lesions

Left Heart Obstruction

• Detailed evaluation of anatomy by 2D from multiple windows

• PW Doppler evaluation both upstream and downstream of region

• Spectral Doppler and color Doppler map of the region

• Evaluate for left ventricular hypertrophy or dysfunction

• Evaluate for the presence or absence of pulmonary hypertension

AV Regurgitation

• Detailed 2D views of valvular and subvalvular regions

• Evaluate lesion with PW Doppler across the LVOT and supravalvular area, CW Doppler across region, and color Doppler

• Evaluate LV: size, function, and mass

MV Regurgitation

• Detailed 2D views of valve, chordae, and papillary muscles

• Color Doppler of regurgitant jet

• Evaluate left atrial size

• Evaluate for the presence or absence of pulmonary hypertension

Coronary Artery Lesions

• Evaluate right and left ventricular function

• If acoustic windows allow, the origins of coronary arteries must be evaluated

• Use low Nyquist color Doppler (≤40 cm/s) to fill the imaged vessels

Left Atrial Anomalies

Cor Triatriatum

• Can be either obstructive or widely patent.

• Typically seen as an “extra” atrial septum that partially divides the left atrium (LA) into a pulmonary venous chamber and the true left atrial chamber.

Anatomic and Physiologic Imaging

• The true left atrial chamber can be identified by locating the left atrial appendage orifice.

• The pulmonary venous chamber would not include the appendage orifice.

• PW Doppler and color Doppler should be used to determine whether any restriction across the cor membrane is present. Mean gradients greater that 3 mm Hg should be considered abnormal.

Key Points

• Cor triatriatum is a rare intra-atrial septation that requires careful anatomic and physiologic interrogation when suspected.

• When cor triatriatum occurs in the right atrium (cor triatriatum dextrum), it must be differentiated from prominent Eustacean and Thebesian valves.

Aortic Valve Anomalies

Congenital Anomalies

Bicuspid Aortic Valve

• Most common left-sided lesion.

• Typically fusion of the intercoronary commissure is present.

• The entire length of the commissure does not necessarily have to be fused; partial fusion can be present.

• Less common anatomic variants include unicuspid (Fig. 12-1) and quadricuspid AVs (Fig. 12-2).

• In truncus arteriosus, individuals are born with a single semilunar valve, which can be quadricuspid.

Figure 12-1 En face view of a unicuspid aortic valve (AV).

Figure 12-2 Quadricuspid AV.

Acquired Aortic Valve Disease

• Rheumatic aortic stenosis (AS) and regurgitation.

• Postinterventional regurgitation.

• AV prolapse.

• Usually associated with ventricular septal defects (VSDs), especially with subpulmonary (supracristal) defects.

Anatomic Imaging

• Leaflet thickness, position, and mobility are best evaluated in the parasternal long axis and short axis. M-mode cursors can evaluate motion with good temporal resolution. With modern-day ultrasound carts, however, temporal resolution of the 2D images is almost as fine.

• In adults, estimations of AV area can determined by using the continuity equation or, less frequently, by 2D planimetry.

• Valve areas are less frequently measured in pediatric patients due to the relative lack of precision in smaller patients as well as the low frequency of low-output AS for which the AV area would be diagnostically useful.

• Three-dimensional imaging of the AV can assist in evaluating both morphology and depth of the cusps.

Physiologic Data

• PW Doppler and continuous wave (CW) Doppler of the subaortic and supravalvular regions should be obtained to determine whether any additional obstruction exists (Fig. 12-3).

• Peak velocity and mean gradients can be obtained from the apical windows. The mean gradient from this view best correlates with peak-to-peak estimations by catheterization.

• Overestimation of pressure gradients can occur when velocities are obtained in the suprasternal notch (SSN) or high parasternal views. Pressure recovery phenomena may account for these discrepancies.

• Severity of AS can be underestimated when there is left ventricular systolic dysfunction.

• The degree of aortic regurgitation (AR) can be determined using both color Doppler and spectral Doppler.

• PW Doppler of the ascending and descending aorta should be obtained to evaluate the volume of regurgitation.

• Pressure half-time.

• Guidelines for assessing valve stenosis and regurgitation are outlined in Table 12-2.

Figure 12-3 Spectral Doppler tracing of subaortic stenosis.

TABLE 12-2 ECHOCARDIOGRAPHIC ASSESSMENT OF THE SEVERITY OF VALVE DISEASE IN ADULTS

Key Points

• Congenital AV disease is usually due to abnormalities in the number of valve leaflets and may result in AS and/or regurgitation.

• Assessment of valvular AS requires the integration of both 2D and Doppler data; when the valve appears to open well despite high transvalvular velocities, subaortic or supravalvular stenosis should be suspected.

• Congenital AV disease may be associated with an underlying connective disease disorder, and coarctation of the aorta and ascending aortic aneurysm are not uncommon associated findings.

Mitral Valve Anomalies

Congenital Anomalies

• MS variants include

• Supramitral ring (Figs. 12-4 and 12-5).

• Commissure fusion.

• Parachute valve (Figs. 12-6 12-7 12-8).

• Mitral arcade.

• Hypoplastic annulus.

• MV prolapse.

• Cleft MV.

• Can be isolated (Figs. 12-9 and 12-10).

• Is also present in other congenital diseases such as complete atrioventricular canal defects (see Chapter 6, Atrioventricular Septal Defect: Echocardiographic Assessment).

Figure 12-4 Apical view of a supramitral ring (arrows) in diastole. The mitral valve (MV) leaflets are tethered by the ring, leading to restricted mobility and a small orifice.

Figure 12-5 Parasternal long axis view of the supramitral ring (arrows).

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