Morphological considerations pertaining to recognition of atrial isomerism. Consequences for sequential chamber localisation.

Abstract

SUMMARYThe atrial morphology and venous connections were assessed "blind" in 51 necropsy specimens from patients with visceral heterotaxy. This was compared with bronchial morphology as established by dissection. Six specimens were found to have both atria and bronchi in situs solitus or inversus, and were rejected. In the remainder, atrial isomerism was diagnosed, though this required minor revision of the atrial assessment in two patients. Thirty-four patients had isomeric right atria and bronchi, while 11 had isomeric left atria and bronchi.In seven cases, splenic status was unknown, but in seven of the remaining 38 (1844%) atrial isomerism was not associated with either asplenia or polysplenia. Nevertheless, right isomerism was strongly associated with total anomalous pulmonary venous drainage (as is asplenia) and left isomerism was likewise associated with interruption of the inferior vena cava (as is polysplenia). Bilateral superior venae cavae and hepatic veins, and absence of the coronary sinus, were frequent in both forms of isomerism (as they are in asplenia and polysplenia).These findings suggest that atrial situs can be defined as solitus inversus, right isomerism, and left isomerism. This determination of atrial situs is quite independent of any other abnormalities of visceral situs. The high incidence of anomalies of both venous return and common atrium resulted in presumed complete mixing of blood at atrial level in all but one patient (97-8%), making the haemodynamic connection between atria and ventricles almost always ambiguous. To describe this anatomical connection as ambiguous when there are two ventricles present is therefore no more than a recognition of anatomical and haemodynamic reality. To investigate these questions we have studied visceral situs, atrial morphology, and venous connections in 45 patients in whom the diagnosis of visceral heterotaxy was made or confirmed at necropsy.

Pediatric Cardiology and Cardiovascular Surgery: 1950-2000

“…Eschewing a "deductive" approach to segmental analysis, Dr Robert Anderson and his colleagues from the United Kingdom, using a segmental approach, advocated a sequential "connections" approach. [22][23][24] This approach did not focus on infundibular anatomy, and their initial approach did not use the concept of ventricular loops, nor did their approach incorporate the bracketed shortcut alphabet nomenclature. These 2 schools of cardiac nomenclature were initially quite polarized, and although they share many similarities, their differences have not been completely resolved.…”

“…[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] With their clinical colleagues, they compiled clinicopathological correlations and published extensively on specimens that constituted their cardiac registries. Collectively, they described and characterized the entire spectrum of congenitally malformed hearts and produced a number of classifications of various cardiac anomalies, including tricuspid atresia, interruption of the aortic arch, truncus arteriosus, ventricular septal defect, double-inlet ventricle, and double-outlet right ventricle.…”

Efficacy of MRI in Complicated Congenital Heart Disease with Visceral Heterotaxy Syndrome

“…The identification of cardiac situs is the first step in the analysis and diagnosis of complex CHD (2). Some still doubt the presence of isomerism in subsets of visceral heterotaxy (8).…”

“…Splenic abnormality was not always accompanied by isomerism (14); 13% to 18% of cases showed splenic anomaly independent of the cardiac situs (2,15). The survival rate with right isomerism is poor compared to that with left isomerism, in part because of the increased severity and complexity of CHD and the increased risk for sepsis in the absence of the spleen (16).…”

“…Atrial isomerism is a subset of situs ambiguous and is a condition in which the right-sided and left-sided atria are morphologically similar (1). The associated cardiovascular anomaly is generally complicated, and its incidence is different in right and left isomerisms (1)(2)(3). Although the prognosis of congenital heart disease (CHD) with situs ambiguous is poor, successful operation is possible only if the surgeon knows with precision the associated anatomic arrangements.…”