Left Heart Anomalies - Clinical Tree

Left-sided anomalies are prevalent among adults with congenital heart disease. They can occur in isolation or with associated defects ( Fig. 42.1 ). Patients usually require lifelong monitoring because native lesions may progress and postintervention complications may develop. Echocardiography is essential for diagnosis, management, and long-term follow-up, and it increasingly plays a role in understanding the physiologic changes of left-sided anomalies and the timing for intervention. We review left heart congenital anomalies, including those of the left atrium (LA), mitral valve, left ventricle (LV), left ventricular outflow tract (LVOT), aorta, and coronary arteries.

Cor Triatriatum

Cor triatriatum sinister is a rare diagnosis, accounting for only 0.1% to 0.4% of all congenital heart disease. ^, The incidence is similar for men and women, and no related genetic disorders have been described.

Cor triatriatum (i.e., triatrial heart) results when the atrium is divided by a membrane into a posterior pulmonary venous chamber and an anterior anatomic LA chamber that contains the left atrial appendage (LAA) and the true atrial septum that bears the fossa ovalis. The membrane can vary significantly in size and shape. It may appear similar to a diaphragm or be funnel shaped, bandlike, or imperforate and can contain one or more fenestrations of various sizes. Classically, the posterior portion of this condition should be distinguished from a supramitral ring, in which the LAA is located proximal to the membrane.

Atrial septal defects (ASDs) are common, with about 70% of patients having a patent foramen ovale or ASD. The ASD allows communication between the right atrium and the pulmonary venous chamber or the distal LA chamber. Associated anomalous pulmonary venous connections can occur, and cor triatriatum sometimes involves veins from only one lung. Other associations include a persistent left superior vena cava to the coronary sinus and coarctation of the aorta (CoA).

Cor triatriatum in adults has been diagnosed incidentally or in the setting of atrial arrhythmias. There may also be chronic pulmonary venous hypertension leading to heart failure and the development of secondary pulmonary arterial hypertension.

Echocardiographic imaging of cor triatriatum with two-dimensional (2D) transthoracic echocardiography (TTE) is often best demonstrated in apical views. It is seen as a curvilinear membrane in the midportion of the LA. The membrane is often thin and may move in response to changes in atrial pressures. The membrane also can be seen in the parasternal long-axis view as a vertical linear structure within the LA that is perpendicular to the ascending aorta. Color Doppler imaging is used to assess turbulent diastolic flow, and spectral Doppler can document any gradient across the membrane ( Fig. 42.2 ).

The relationship between the LAA and the membrane is most easily seen in parasternal short-axis views. The position of the septum primum should also be assessed because malattachment of the septum primum can be confused with cor triatriatum in some views. All four pulmonary venous connections are assessed from high parasternal short-axis views, and the atrial septum is carefully evaluated from subxiphoid, parasternal short-axis, and high right parasternal views. Evaluation also includes measurement of the coronary sinus size, assessment for left-sided superior vena cava, and acquisition of suprasternal notch views of the aortic arch with Doppler for CoA. RV pressures should be carefully assessed. Three-dimensional (3D) reconstruction of echocardiographic images can improve definition of the accessory membrane, detection of fenestrations, and characterization of the membrane’s relationship with surrounding structures.

Congenital Mitral Valve Disease

Congenital mitral valve disease (excluding mitral valve prolapse) is rare, but it is associated with increased morbidity and mortality rates due to mitral stenosis, regurgitation, or both. Mitral valve anomalies can involve one or more of its components, including the mitral annulus, valve leaflets, chordae tendineae, and papillary muscles. Congenital mitral valve disease commonly occurs in conjunction with other left heart obstructive lesions, including the Shone complex (i.e., supravalvular mitral ring, parachute mitral valve, subvalvular aortic stenosis, and CoA). 3D evaluation often can provide added insight to assess complex mitral morphology for surgical or percutaneous intervention.

Cleft Mitral Valve

A cleft mitral valve is a cleft (split) of the anterior leaflet into two separate leaflet components, with each attached to a separate papillary muscle group ( Fig. 42.3 ). Cleft mitral valves are most commonly encountered in atrioventricular septal defects (AVSDs), in which the cleft represents the deficiency of atrioventricular valve tissue where the superior and inferior bridging leaflets meet at the ventricular septum. In this setting, the cleft is oriented toward the mid-interventricular septum.

An isolated cleft mitral valve is not associated with an AVSD. Isolated clefts are typically oriented toward the LVOT. This is an uncommon congenital anomaly that can occasionally be associated with ventricular septal defects (VSDs) or conotruncal anomalies.

Cleft mitral valves tend to be regurgitant. The mitral regurgitation jet typically originates from the anterior cleft and is directed posteriorly. The cleft is best visualized from a subxiphoid short-axis or parasternal short-axis view. It is important to determine whether the cleft attachments are contributing to LVOT obstruction. An isolated cleft can be diagnosed adequately by means of 2D echocardiography and Doppler interrogation or by 3D echocardiography.

Closure of the cleft improves coaptation, but there is a trade-off between coaptation and adequacy of the flow orifice, and mitral stenosis can sometimes occur. When the cleft mitral valve is the only defect, repair must be initiated on the basis of the usual clinical and echocardiographic criteria. If the degree of regurgitation is only mild to moderate, surgical repair is not urgent because the regurgitation does not progress over the intermediate term.

Supramitral Ring

A supramitral ring is an abnormal membranous tissue growth on the LA side of the mitral valve that appears as a shelf-like membrane located just above the mitral annulus but distal to the LAA, resulting in mitral inflow obstruction. The supramitral ring may be associated with other left-sided obstructive lesions. The ring, which is often circumferential, may encroach on the orifice of the mitral valve and adhere to the leaflets of the valve, restricting their movements.

An intramitral ring is located within the mitral tunnel, is closely adherent to the mitral leaflets, and occurs with a high incidence of structural mitral abnormalities, including restricted mobility of the mitral leaflets, reduced chordal length, reduced interpapillary muscle distance, single papillary muscle, and hypoplastic mitral annulus. The intramitral type is frequently part of the Shone complex.

Unlike rheumatic mitral disease, restriction occurs at the base of the leaflet, and the leaflet tips open freely in parallel and are unrestricted ( Fig. 42.4 ). The 4-chamber apical view provides an angle of interrogation perpendicular to the membrane. Color Doppler demonstrates flow acceleration beginning at the annular level, not at the leaflet tips. Parasternal long-axis views can also be helpful. If there is uncertainty after a thorough TTE, transesophageal echocardiography (TEE) should be performed.

Stenosis in the setting of a supramitral ring tends to increase over time. Surgical intervention should be considered for all patients with symptoms of obstruction, and it has an overall good outcome. ^, In all cases of supramitral obstruction and in one half of cases of intramitral obstruction, ring resection led to excellent long-term results.

Double-Orifice Mitral Valve

A double-orifice mitral valve (DOMV) occurs when there are two separate mitral valve orifices, and each is supported by its own chordae and papillary muscles. Orifices may be equal in size, or one may be significantly smaller than the other. DOMV is more common among patients with AVSD, but it can rarely be seen in isolation (7% of all DOMV cases).

When DOMV occurs in isolation, the valve typically functions well, and the defect is clinically insignificant. In the setting of DOMV associated with AVSD, regurgitation typically occurs through the posteromedial orifice. DOMV can be best seen from a short-axis view, which allows en face imaging of the double orifice and comparison of the size of each orifice. 3D echocardiography can provide additional detail to confirm orifice size and shape ( Fig. 42.5 ).

Parachute Mitral Valve

A true parachute mitral valve occurs when all chordae insert into a single papillary muscle, With a parachute-like mitral valve, the chordae are distributed unequally between two identifiable papillary muscles, but most converge on a dominant papillary muscle. This typically results in mitral stenosis due to restricted leaflet motion and restriction at the chordal apparatus. The other papillary muscle may be present without any chordal attachment, or it may be aberrant, small, or absent.

There is a strong correlation with other left-sided obstructive lesions. Parachute mitral valves associated with the Shone complex tend to connect to the posteromedial papillary muscles, whereas those associated with AVSDs tend to connect to the anterolateral papillary muscle. Abnormalities in papillary muscle formation can lead to a parachute mitral valve, likely because of underdeveloped space between the papillary muscles.

The diagnosis is made with parasternal short-axis imaging, which is used to assess the size and location of papillary muscles, mitral valve leaflets, and chordal attachments. Imaging must also carefully assess for other left-sided obstructive lesions, including LVOT obstruction and aortic arch imaging to rule out CoA ( Fig. 42.6 ).

Mitral Arcade

Mitral arcade is a rare entity that involves muscularization of the chordal apparatus, with the leaflets appearing to insert directly into the papillary muscles. Chordae are shortened or absent, and leaflets are often thickened. This is also known as a hammock valve, and it can result in mitral stenosis or regurgitation. This lesion often manifests early in life and has an overall poor outcome.

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