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Congenital obstruction to left atrial flow: Mitral stenosis, cor triatriatum, pulmonary vein stenosis


Congenital obstruction to left atrial flow can originate at or near the junction of pulmonary veins and left atrium (pulmonary vein stenosis), within the left atrium (cor triatriatum), immediately above the mitral valve (supravalvular stenosing ring), or within the mitral apparatus (mitral stenosis) ( Fig. 9.1 and Box 9.1 ). Pure or relatively pure forms of each defect are emphasized in this chapter, although a variety of anomalies often coexist with a wide range of anomalies. , Pulmonary veno-occlusive disease and total anomalous pulmonary venous connection with obstruction are covered in Chapter 12 and hypoplastic left heart with a hypoplastic mitral orifice is covered in Chapter 28 .

Fig. 9.1
(A) Illustration of congenital obstruction to left atrial flow involving the mitral apparatus or immediately above or contiguous with the mitral annulus. (B) Illustration of typical cor triatriatum. A fibrous or fibromuscular diaphragm partitions the left atrium. The proximal compartment receives the pulmonary veins and is a high-pressure zone. The distal compartment contains the fossa ovalis and the left atrial appendage (LAA) and is a low-pressure zone. (C) Illustration of pulmonary vein stenosis in which one or more pulmonary veins are narrowed near their left atrial junction. Ao, Aorta; LA, left atrium; LPV, left pulmonary veins; LV, left ventricle; RPV, right pulmonary veins.

BOX 9.1
Congenital Obstruction to Left Atrial Flow With a Functionally Adequate Left Ventricle

Congenital mitral stenosis

  • Obstruction within the mitral apparatus: short chordae tendineae with decreased interpapillary muscle distance and reduced or obliterated interchordal spaces.

  • Parachute mitral valve

  • Anomalous mitral arcade

  • Accessory mitral valve tissue

  • Anomalous left ventricular muscle bundles or obstructing papillary muscles

  • Double-orifice mitral valve

  • Supravalvular stenosing ring

Cor triatriatum

Pulmonary vein stenosis

Congenital mitral stenosis

Congenital mitral stenosis involves the annulus, the zone immediately above and contiguous with the annulus, the leaflets, the chordae tendineae, and the papillary muscles. The physiologic consequences of congenital mitral stenosis are analogous to acquired mitral stenosis.

Incidence has been estimated at 0.6% of necropsy cases of congenital heart disease, and 0.21% to 0.42% of clinical cases. Congenital mitral stenosis with a functionally adequate left ventricle includes the following malformations in approximate order of frequency (see Box 9.1 ) :

  • 1.

    Short chordae tendineae with a reduction in or obliteration of interchordal spaces and a decrease in interpapillary muscle distance ( Fig. 9.2 A).

    Fig. 9.2, Illustrations of three anatomic types of congenital mitral stenosis involving the mitral apparatus. (A) The typical form is characterized by decreased interpapillary muscle distance and a reduction in interchordal spaces. (B) Parachute mitral valve with a single eccentric papillary muscle. (C) Supravalvular stenosing mitral ring.

  • 2.

    Parachute mitral valve which consists of a single eccentric papillary muscle (absence of one papillary muscle or fusion of the two papillary muscles) into which all chordae tendineae from both leaflets insert ( Fig. 9.3 , and see Fig. 9.2 B).

    Fig. 9.3, (A) Left ventriculogram from an 8-year-old girl with a parachute mitral valve identified by the single papillary muscle (wedge of negative contrast, arrow ). (B) Echocardiogram (apical four-chamber) from a 10-year-old boy with Shone complex consisting of a supravalvular stenosing ring, a parachute mitral valve, and an eccentric single papillary muscle with all chordae (single chordae). (C) Necropsy specimen from a 14-year-old boy with a parachute mitral valve (upper right arrow) , obstructing interchordal slits, and insertion into a single eccentric papillary muscle (PM) . A supravalvular ring is identified by the upper left arrow . AO, Ascending aorta; LA, left atrium; LV, left ventricle; MV, mitral valve.

  • 3.

    Anomalous mitral arcade is characterized by a band of fibrous tissue that runs adjacent to the free margins of the mitral leaflets with short or absent chordae tendineae and multiple contiguous papillary muscles. The arcade can permit normal function or can render the valve mechanism incompetent when the chordae tendineae are well formed. , Rarely, an anomalous mitral arcade coexists with a tricuspid arcade and incompetence of both atrioventricular valves. A supravalvular stenosing ring consists of a circumferential diaphragm at the base of the atrial surfaces of the mitral leaflets (see Fig. 9.2 C). , , , , Rarely, a supravalvular ring occurs as an isolated obstructive lesion, or coexists with mitral regurgitation.

  • 4.

    Accessory mitral valve tissue.

  • 5.

    Anomalous left ventricular muscle bundles or anomalous obstructing papillary muscles. ,

  • 6.

    Double-orifice mitral valve which can be stenotic, incompetent, or functionally normal.

Flow across a normal mitral orifice is between the leaflets (interleaflet) and between the chordae tendineae (interchordal). In a parachute mitral valve, all chordae tendineae insert into a single papillary muscle, and the interchordal spaces are reduced or obliterated, so flow cannot be interchordal (see Figs. 9.2 B and 9.3 ).

A parachute mitral valve is usually one of the components of Shone’s complex, a developmental combination of four obstructive lesions, namely, supravalvular stenosing ring, parachute mitral valve, subaortic stenosis, and coarctation of the aorta ( Figs. 9.3 and 9.4 ). , , , All four lesions are not always present, and if present, may not be functionally significant. , , The supravalvular mitral ring can be rudimentary (see Fig. 9.3 C) or can bridge the mitral orifice as a stenosing diaphragm (see Fig. 9.3 B). , ,

The history

There is a male predilection in congenital mitral stenosis in contrast to rheumatic mitral stenosis which has a female predilection. Familial recurrence has not been reported. If the stenosis is severe, symptoms begin shortly after birth when pulmonary blood flow commences and suddenly enters the obstructed left atrium. Fifty percent of symptomatic infants die within 6 months, but an occasional infant is asymptomatic, and a few remain relatively free of symptoms for years. With a parachute mitral valve or a supravalvular mitral ring, longevity is better (median 10 years and 5.5 years, respectively), but short chordae tendineae and obliterated interchordal spaces result in death at a median age of 6 months. , Anomalous mitral arcade or double-orifice mitral valve permits adult survival when the mitral apparatus functions normally or is purely regurgitant. ,

Orthopnea, dyspnea, tachypnea, and paroxysmal cough are the result of pulmonary edema that is punctuated by lower respiratory infections. , , , Congenital mitral stenosis is occasionally associated with syncope but seldom with hemoptysis. Aphonia has been attributed to compression of the recurrent laryngeal nerve by a dilated hypertensive pulmonary trunk, analogous to hoarseness in adults with pulmonary hypertension and rheumatic mitral stenosis. Infective endocarditis is rare.

Physical appearance

Mild cyanosis coincides with congestive heart failure. , Recurrent lower respiratory infections and the catabolic effects of heart failure account for physical underdevelopment. ,

The arterial pulse, the jugular venous pulse, precordial movement, and palpation

The arterial pulse is normal and confirms normal sinus rhythm, which is the rule in congenital mitral stenosis. The jugular venous pulse has an increased A wave because of pulmonary hypertension ( Fig. 9.5 ). A precordial bulge is common, and a right ventricular impulse is palpable at the lower left sternal border and subxiphoid area. ,

Fig. 9.5, Right atrial pressure pulse (RA) showing a prominent A wave in a 3-year-old girl with congenital mitral stenosis.

Auscultation

Neither a loud first heart sound nor an opening snap are heard; the necessary preconditions for an opening snap and loud first heart sound are abrupt opening and closing movements of the belly of a mobile anterior mitral leaflet—these are not features of congenital mitral stenosis ( Figs. 9.6 and 9.7 ).

Fig. 9.6, Phonocardiogram from a 2-year-old girl with Shone complex (supravalvular stenosing ring, parachute mitral valve, coarctation of the aorta) and a patent ductus arteriosus with pulmonary vascular disease and reversed shunt. The first heart sound (S1) is soft, and there is no opening snap. There is a soft mid-diastolic murmur (DM) . S2, Second heart sound.

Fig. 9.7, Phonocardiogram from the 3-year-old girl with congenital mitral stenosis referred to in Fig. 9.5 . The first heart sound (S1) is loud, but there is no opening snap. A soft mid-diastolic murmur (DM) is followed by presystolic accentuation.

In the presence of a parachute mitral valve or a supravalvular ring, a holosystolic murmur at the apex or lower left sternal edge is due to mitral regurgitation or pulmonary hypertensive tricuspid regurgitation. An apical mid-diastolic murmur with presystolic accentuation (see Figs. 9.6 and 9.7 ) is exceptional because the rapid heart rate in infants shortens diastole and because a dilated hypertensive right ventricle displaces the left ventricle from the apex. , The pulmonary component of the second heart sound is loud because of pulmonary hypertension that sets the stage for the Graham Steell murmur of high-pressure pulmonary regurgitation.

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