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.

Novel MYO1D Missense Variant Identified Through Whole Exome Sequencing and Computational Biology Analysis Expands the Spectrum of Causal Genes of Laterality Defects

Laterality defects (LDs) or asymmetrically positioned organs are a group of rare developmental disorders caused by environmental and/or genetic factors. However, the exact molecular pathophysiology of LD is not yet fully characterised. In this context, studying Arab population presents an ideal opportunity to discover the novel molecular basis of diseases owing to the high rate of consanguinity and genetic disorders. Therefore, in the present study, we studied the molecular basis of LD in Arab patients, using next-generation sequencing method. We discovered an extremely rare novel missense variant in MYO1D gene (Pro765Ser) presenting with visceral heterotaxy and left isomerism with polysplenia syndrome. The proband in this index family has inherited this homozygous variant from her heterozygous parents following the autosomal recessive pattern. This is the first report to show MYO1D genetic variant causing left–right axis defects in humans, besides previous known evidence from zebrafish, frog and Drosophila models. Moreover, our multilevel bioinformatics-based structural (protein variant structural modelling, divergence, and stability) analysis has suggested that Ser765 causes minor structural drifts and stability changes, potentially affecting the biophysical and functional properties of MYO1D protein like calmodulin binding and microfilament motor activities. Functional bioinformatics analysis has shown that MYO1D is ubiquitously expressed across several human tissues and is reported to induce severe phenotypes in knockout mouse models. In conclusion, our findings show the expanded genetic spectrum of LD, which could potentially pave way for the novel drug target identification and development of personalised medicine for high-risk families.

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.

Balloon atrial septostomy through azygos vein in two cases of D-TGA with left atrial isomerism

Balloon atrial septostomy is a palliative procedure that is performed in D-transposition of great arteries when surgery is not immediately available. Although D-TGA and left isomerism association are rare, it is an important condition as the BAS procedure approach is unique. In this case report, we present two cases of D-TGA with left isomerism where BAS was performed due to restrictive atrial septal defect and lack of immediate availability of the paediatric cardiac surgeon.

Temporary pacemaker implantation through umbilical vein in a low birth weight neonate with congenital complete heart block

Congenital heart block is a rare and lethal condition in paediatric population associated with maternal connective tissue disorders and rarely with structural cardiac disease like atrioventricular canal defects with or without left isomerism and congenitally corrected transposition of great arteries. Pacing in neonate if indicated is generally accomplished by epicardial pacing systems. However, in cases of significant bradycardia and haemodynamic instability, temporary pacemaker implantation via transvenous approach remains as a suitable option. Despite the advances in percutaneous catheter interventions, use of transvenous pacing in newborn is extremely challenging due to inadvertent risk of vessel injury, thrombus formation and mortality, and most of the time technical inability to place the lead within the right ventricular cavity. We report a case of congenital complete atrioventricular block in a premature male with birth weight of 1.51 kg who was managed with temporary pacemaker implantation through umbilical vein.