Juxtaposition of the atrial appendages describes the situation in which both appendages are found to the same side of the arterial pedicle. In most instances, the appendages are found to the left side of the pedicle.Reference Melhuish and Van Praagh 1 – Reference Anjos, Ho and Anderson 3 The arrangement in which the appendages are juxtaposed to the right side of the pedicle is much rarer. When seen thus far, to the best of our knowledge, the appendage arising from the left-sided atrium has always been positioned superiorly relative to the right-sided appendage, passing through the transverse pericardial sinus so as to reach the right side of the arterial pedicle. We have now encountered a most unusual heart, which has usual atrial arrangement, and in which the morphologically left appendage is juxtaposed in a rightward manner, but passes behind the heart rather than through the transverse sinus so as to reach its location inferior to the morphologically right appendage. The heart is also unusual in that there is an inter-atrial communication present between the cavities of the juxtaposed left appendage and the morphologically right atrium.
Description
The heart was from a 20-month-old girl, who was delivered normally after an uneventful pregnancy in the early 1960s, with a weight of 6 lbs 15 oz. Shortly after birth, the patient became cyanotic and was placed in an incubator for 10 days. She seemed to improve and was discharged from the hospital on the 12th day. During the next 2 months, the mother noticed that the baby became cyanotic when bathed, and developed cyanosis of the face and lips upon crying. She otherwise followed a normal developmental pattern, although hospitalised several times for acute upper respiratory tract infections. At the age of 6 months, she was admitted with the chief complaint of cough and severe cyanosis. A systolic murmur, graded at III to IV, was found in the left lower sternal border. The second component of the pulmonary sound was decreased, and no cardiac enlargement was evident. A cine-angiocardiogram yielded the diagnostic impression of “transposition complex with aorta in corrected position and a small pulmonary artery and large ventricular septal defect”. An electrocardiogram performed at this stage revealed combined ventricular hypertrophy and incomplete right bundle branch block. The patient was discharged 7 days after admission.
The final admission was at 20 months of age. The patient was hospitalized due to an increase in the number of cyanotic spells, particularly during the 2 months before admission, during which time she began to walk. She suffered these spells approximately once per week, and was found to squat to catch her breath. On physical examination, she was found to have a systolic murmur, again graded at 3 from 6, without cardiac enlargement; two days after admission, the right subclavian artery was anastomosed surgically to the right pulmonary artery. On the 4th post-operative day, the patient became comatose, a tracheostomy was performed, and she was started on a respirator. Her condition remained poor, and an electrocardiogram taken on the 5th post-operative day revealed complete right bundle branch block, first degree atrioventricular block, and elevated ST segments. The findings were interpreted as being indicative of ischaemia or strain of the heart. Although the patient appeared to be much improved on the 6th post-operative day, she subsequently deteriorated, and experienced cardiac arrest, with ventricular fibrillation confirmed by an electrocardiogram. Immediate cardiac massage and all other methods of resuscitation were of no avail and the patient was declared dead.
The heart was found in the Idriss archive of congenitally malformed hearts held at Ann & Robert H. Lurie Children’s Hospital of Chicago. The autopsy from which the clinical description was derived was performed in 1962. On viewing the anterior aspect of the heart, the morphologically left atrial appendage was seen forming the right border of the cardiac silhouette, lying to the right of, and inferior to, the normally located morphologically right atrial appendage (Fig 1a).
The anterior view of the heart ( a ) shows the left atrial appendage juxtaposed in a rightward manner but lying inferiorly relative to the morphologically right appendage. Opening the right atrium ( b ) shows an inter-atrial communication occupying the vestibular area, and lying immediately beneath the orifice of the coronary sinus. Note the expected location of the oval fossa, which is intact.
Opening the right atrium revealed the anticipated arrangement of the atrial septum, but with an unexpected inter-atrial communication between the atrial cavity and the juxtaposed left appendage. The opening between the atria deflected the coronary sinus in a cranial fashion, with the sinus itself occupying its expected position within the left atrioventricular groove (Fig 1b). The floor of the left atrium, however, was intact, with no evidence of a left-sided atrioventricular connection (Fig 2a). The pulmonary veins drained normally to the body of the morphologically left atrium. The oval fossa, which if patent would have communicated with the body of the left atrium, was intact.
The morphologically left atrium ( a ) has a muscular floor due to absence of the left-sided atrioventricular connection. It receives the pulmonary veins at its roof, and shows the flap valve of the oval fossa on its septal aspect. The orifice of the left appendage, however, is positioned posteriorly and inferiorly. The morphologically right atrium ( b ) is connected to a dominant left ventricle, with the junction guarded by a morphologically mitral valve. The aorta arises from the dominant left ventricle above a completely muscular infundibulum. A muscular ventricular septal defect communicates with the incomplete right ventricle, which is carried on the leftward and superior shoulder of the ventricular mass ( c ). It gives rise to the pulmonary trunk, with the pulmonary valve supported by a completely muscular infundibulum. The pulmonary trunk then ascends in a parallel manner as it exits from the pericardial cavity.
The cavity of the right atrium connected through a morphologically mitral valve with the dominant left ventricle, which gave rise to the aorta, the aortic valvar leaflets being supported by a completely muscular infundibulum (Fig 2b). The coronary arteries arose in the anticipated manner from the two aortic sinuses adjacent to the pulmonary trunk. The coronary artery arising from the left-hand sinus (#2) passed behind the aortic root to reach the left atrioventricular groove. A small muscular ventricular septal defect communicated with the incomplete right ventricle, which was carried on the anterior and leftward shoulder of the ventricular mass. The hypoplastic pulmonary trunk arose from the incomplete right ventricle, supported by a completely muscular subpulmonary infundibulum (Fig 2c). The pulmonary trunk itself extended from the base of the heart in a parallel manner relative to the aorta, the aortic root being positioned rightward and side-by-side relative to the pulmonary root.
Discussion
The heart examined in this study was unusual in several respects. In the first instance, the left atrial appendage was juxtaposed in a rightward manner so as to lie inferior to the right atrial appendage, but reached this position by passing behind the cardiac mass, rather than extending through the transverse pericardial sinus, as is the expected arrangement for rightward juxtaposition.Reference Anderson, Smith and Wilkinson 4 In the second instance, there was an inter-atrial communication between the juxtaposed atrial appendage and the cavity of the morphologically right atrium. The inter-atrial defect opened into the right atrium through the vestibule of the right atrioventricular valve, displacing cranially the opening of the coronary sinus. The walls of the coronary sinus itself were intact, and the sinus was normally positioned within the left atrioventricular groove. To the best of our knowledge, an inter-atrial communication of this kind has not been previously described. The oval fossa occupied its expected position and was intact. The third unusual feature of the heart devolves on the combination of atrioventricular and ventriculo-arterial connections. There was absence of the left atrioventricular connection, but with the morphologically right atrium connected to a dominant left ventricle. The incomplete right ventricle was carried on the anterior and leftward shoulder of the heart, so that, had a left-sided atrioventricular connection been formed, it would almost certainly have been guarded by a morphologically tricuspid valve. This arrangement, when seen, is itself usually associated with discordant ventriculo-arterial connections,Reference Tandon, Marín-García, Moller and Edwards 5 the heart being a “close-cousin” to congenitally corrected transposition. In the heart studied here, however, the ventriculo-arterial connections were concordant, but with the pulmonary trunk ascending in a left-sided and parallel manner relative to the aorta. The aorta arose from the dominant left ventricle, but with its valve supported by a completely muscular infundibulum. This is the arrangement initially considered to represent “anatomically corrected transposition”,Reference Van Praagh and Van Praagh 6 but now often described as “anatomically corrected malposition”.Reference Anderson, Becker, Losekoot and Gerlis 7 Our current preference is to describe this particular anatomy in terms of concordant ventriculo-arterial connections with parallel arterial trunks.Reference Bernasconi, Cavalle-Garrido, Perrin and Anderson 8 , Reference Cavalle-Garrido, Bernasconi, Perrin and Anderson 9 The combination of the various malformations, to the best of our knowledge, is unique. It is of interest that the pathologist providing the initial report described well the situation as representing a “functional single ventricle”. The complex anatomy is readily described on the basis of sequential segmental analysis.Reference Anderson and Ho 10
Acknowledgement
The authors are indebted to Dr Carl Backer for his ongoing support.
Financial Support
This research received no specific grant from any funding agency, commercial, or not-for-profit sectors.
Conflicts of Interest
None.
