Surgical Management of Hearts with Isomeric Atrial Appendages

Background and aim: On the basis of previously published accounts, coupled with our own experience, we have assessed the surgical approaches to patients with isomeric atrial appendages. Methods: We reviewed pertinent published studies on surgical treatment of individuals with isomeric atrial appendages, with the pertinent surgical details provided by most of the manuscripts. Results: Half of patients with right isomerism, and two-thirds of those with left isomerism have bilateral superior caval veins. Azygos extension of the inferior caval vein is reported in three-quarters of those with left isomerism. The coronary sinus is universally absent in right isomerism, along with totally anomalous pulmonary venous connection, and is absent in two-fifths of those with left isomerism.. Univentricular atrioventricular connections are expected in up to three-quarters of those with right isomerism. Atrioventricular septal defect is reported in up to four-fifths, more frequently in right isomerism, with such patients typically having discordant ventriculoatrial connections or double outlet right ventricle. Reported mortalities extend to 85% for those with right, and 50% for those with left isomerism. In right isomerism, mortality is up to 54% for systemic-to-pulmonary arterial shunting, up to 75% for univentricular repair, and up to 95% for repair of totally anomalous pulmonary venous connection itself. No more than one-quarter had undergone Fontan completion, with reported mortalities of 21%. Conclusion: Early surgical results are satisfactory in patients with left isomerism, but disappointing for those with right. Recent advances in cardiac and liver transplantation may offer improved survival.

Primary central pulmonary artery plasty for right atrial isomerism with pulmonary coarctation

Objective Patients with unbalanced pulmonary artery growth resulting from pulmonary coarctation are considered unsuitable candidates for the Fontan procedure. Particularly, patients with right isomerism pose a challenge. We aimed to investigate the use of primary central pulmonary artery plasty at initial palliation in patients with right isomerism. Methods We recruited 34 right isomerism patients with pulmonary atresia and pulmonary coarctation who underwent modified Blalock-Taussig shunt with or without primary central pulmonary artery plasty between 1998 and 2014. We classified them into the primary central pulmonary artery plasty (group P) and no primary central pulmonary artery plasty (group N) groups. We retrospectively analyzed reintervention for pulmonary artery after initial palliation, difference in size between the left and right pulmonary arteries, overall survival, success of the Fontan procedure. Results The group P and group N included 25 and 9 patients, respectively. Five (20%) and six (67%) patients in group P and group N, respectively, required reintervention for pulmonary artery after initial palliation ( p = 0.017). No patient underwent reintervention for the pulmonary artery before bidirectional cavopulmonary shunt in group P. There was a significant difference in the bilateral pulmonary artery size balance between the groups before bidirectional cavopulmonary shunt ( p = 0.041). The two-lung Fontan procedure was successful in 14 (56%) and 1 (11%) patient in group P and group N. Conclusion Primary central pulmonary artery plasty may contribute toward improving the balance in the size of the PA and preclude the need for reintervention for PA.

Fetal Ultrasonic Evaluation of Bronchial Morphology in Fetuses with Isomerism

<b><i>Objective:</i></b> The aim of the study was to evaluate whether fetal ultrasound could determine bronchial isomerism and distinguish left isomerism from right isomerism. <b><i>Methods:</i></b> We identified 110 healthy fetuses and 28 fetuses with isomerism. The outer angle between the tracheal midline and the inner margin of the bronchus is measured. The bronchial angles and the ratio of left/right bronchial angle were used to differentiate bronchial morphology and confirm the presence of bronchial isomerism in pathological cases. <b><i>Results:</i></b> The normal angles of the left and right bronchi were 146.98° (95% CI, 145.15–147.81°) and 167.37° (95% CI, 166.30–168.44°), separately. The cutoff bronchial angle of 156.5° was used to distinguish left bronchus from right bronchus. The bronchial isomerism could be identified in all pathological cases by autopsy and bronchial-atrial concordance occurred in 27 pathological cases (96.4%). In 21 pathological cases, the bilateral bronchial angle was &#x3c;156.5 versus &#x3e;156.5 differentiated left from right isomerism, respectively. The ratio of the left/right bronchial angle of &#x3e;0.935 identified 92.9% (26/28) of all pathological cases, with a sensitivity of 89.7%. <b><i>Conclusions:</i></b> Fetal ultrasound can detect the bronchial morphology and the presence of bronchial isomerism in fetuses with isomerism according to bronchial angles and the ratio of left/right bronchial angle.

Pitx controls amphioxus asymmetric morphogenesis by promoting left-side development and repressing right-side formation

Background Left-right (LR) asymmetry is an essential feature of bilateral animals. Studies in vertebrates show that LR asymmetry formation comprises three major steps: symmetry breaking, asymmetric gene expression, and LR morphogenesis. Although much progress has been made in the first two events, mechanisms underlying asymmetric morphogenesis remain largely unknown due to the complex developmental processes deployed by vertebrate organs. Results We here addressed this question by studying Pitx gene function in the basal chordate amphioxus whose asymmetric organogenesis, unlike that in vertebrates, occurs essentially in situ and does not rely on cell migration. Pitx null mutation in amphioxus causes loss of all left-sided organs and incomplete ectopic formation of all right-sided organs on the left side, whereas Pitx partial loss-of-function leads to milder phenotypes with only some LR organs lost or ectopically formed. At the N1 to N3 stages, Pitx expression is gradually expanded from the dorsal anterior domain to surrounding regions. This leads to activation of genes like Lhx3 and/or Prop1 and Pit, which are essential for left-side organs, and downregulation of genes like Hex and/or Nkx2.1 and FoxE4, which are required for right-side organs to form ectopically on the left side. In Pitx mutants, the left-side expressed genes are not activated, while the right-side genes fail to decrease expression on the left side. In contrast, in embryos overexpressing Pitx genes, the left-side genes are induced ectopically on the right side, and the right-side genes are inhibited. Several Pitx binding sites are identified in the upstream sequences of the left-side and right-side genes which are essential for activation of the former and repression of the latter by Pitx. Conclusions Our results demonstrate that (1) Pitx is a major (although not the only) determinant of asymmetric morphogenesis in amphioxus, (2) the development of different LR organs have distinct requirements for Pitx activity, and (3) Pitx controls amphioxus LR morphogenesis probably through inducing left-side organs and inhibiting right-side organs directly. These findings show much more dependence of LR organogenesis on Pitx in amphioxus than in vertebrates. They also provide insight into the molecular developmental mechanism of some vertebrate LR organs like the lungs and atria, since they show a right-isomerism phenotype in Pitx2 knockout mice like right-sided organs in Pitx mutant amphioxus. Our results also explain why some organs like the adenohypophysis are asymmetrically located in amphioxus but symmetrically positioned in vertebrates.

Retrograde sharp potential resembling the his-bundle electrogram: is this a case of atrioventricular re-entrant tachycardia involving twin atrioventricular nodes with the anterior node exhibiting only retrograde conduction?

A 2-year-old male with right isomerism was referred for supraventricular tachycardias. Atrial pacing study revealed that anterograde conduction was only through the posterior atrioventricular node. During the mapping of ventriculoatrial conduction, we identified a sharp potential resembling a His-bundle electrogram with a decremental property at the anterior wall of the common atrium. Catheter ablation for the potential eliminated the anterior ventriculoatrial conduction, thereby indicating retrograde activation of the possible anterior atrioventricular node.