Cross sectional echocardiographic assessment of the extent of the atrial septum relative to the atrioventricular junction in atrioventricular septal defect

Common Atrium or Atrioventricular Septal Defect: What Is in a Name?

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Common atrium is characterized by complete/near-complete absence of IAS.

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Common atrium frequently accompanies AVSD, although it can occur as an isolated entity.

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Most AVSDs with an atrial communication have normal to near-normal atrial septal lengths.

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Partial AVSD with near-complete absence of IAS is an uncommonly reported heart condition.

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With many echo features present, it is difficult to apply one diagnostic label to complex CHD.

Complete atrioventricular canal in a dog

This report details a case of complete, type A atrioventricular (AV) canal, also called complete endocardial cushion defect, in a young dog. Complete AV canal is classified as three types: A, B or C depending on the degree of linkage between common AV valve and ventricular chambers. Despite the defect this dog, which did not undergo surgical treatment, remains in ISACHC class Ib 19 months after the initial diagnosis.

Electrophysiologic and anatomical relationships studied in primum atrioventricular septal defect

Anatomy and pattern of electrical activation predict the function and contraction pattern of the heart. Patients with primum atrioventricular septal defect (primum AVSD) present with abnormality of both anatomical arrangements and electric activation and serve therefore as an interesting population for studying electro-anatomic relationships in the heart. Understanding the relationships between anatomic and electrophysiologic abnormality is appropriate not only for diagnosis, therapy, and prognosis in patients with primum AVSD but also for understanding the developmental relationship between the conduction system and heart structures, in general. This article presents a review of the anatomical and electrophysiologic characteristics of patients with primum AVSD and provides recent knowledge of electroanatomical relationships of the heart.

Understanding atrioventricular septal defect: anatomoechocardiographic correlation

OBJECTIVE

Correlate the anatomic features of atrioventricular septal defect with echocardiographic images.

MATERIALS AND METHODS

Sixty specimen hearts were studied by sequential segmental analysis. Echocardiograms were performed on 34 patients. Specimen hearts with findings equivalent to those of echocardiographic images were selected in order to establish an anatomo-echocardiographic correlation.

RESULTS

Thirty-three specimen hearts were in situs solitus, 19 showed dextroisomerism, 6 were in situs inversus and 2 levoisomerism. Fifty-eight had a common atrioventricular valve and 2 had two atrioventricular valves. Rastelli types were determined in 21 hearts. Nine were type A, 2 intermediate between A and B, 1 mixed between A and B, 4 type B and 5 type C. Associated anomalies included pulmonary stenosis, pulmonary atresia atrial septal defect, patent ductus arteriosus and anomalous connection of pulmonary veins. Echocardiograms revealed dextroisomerism in 12 patients, situs solitus in 11, levoisomerism in 7 and situs inversus in 4. Thirty-one patients had common atrioventricular valves and three two atrioventricular valves. Rastelli types were established in all cases with common atrioventricular valves; 17 had type A canal defects, 10 type B, 3 intermediate between A and B, 1 mixed between A and B and 3 type C. Associated anomalies included regurgitation of the atrioventricular valve, pulmonary stenosis, anomalous connection of pulmonary veins, pulmonary hypertension and pulmonary atresia.

CONCLUSION

Anatomo-echocardiographic correlation demonstrated a high degree of diagnostic precision with echocardiography.

Echo-morphological correlates in patients with atrioventricular septal defect and common atrioventricular junction

It is now well recognized that patients fulfilling the diagnostic criterions for the group of hearts usually described as atrioventricular canal malformations, or atrioventricular septal defects, can present with shunting at atrial level, at both atrial and ventricular levels, and on occasion, with shunting only at ventricular level.1,2It is also well recognized that, in most instances, the patients with shunting exclusively at atrial level have separate atrioventricular valvar orifices for the right and left ventricles, this arrangement often described as the “ostium primum” variant of atrial septal defect.3Morphological and echocardiographic studies, however, have shown that, in this variant presumed to represent deficient atrial septation, it is the atrioventricular septal structures, rather than the atrial septum, which are deficient, the phenotypic feature being the presence of a common atrioventricular junction.4,5In this review, we will show how, using modern day echocardiographic techniques, particularly the newly developed potential for three-dimensional display, it is an easy matter to identify the presence or absence of the common atrioventricular junction, and then to demonstrate the various relationships between the valvar leaflets, the septal structures, and the common junction itself which determine the options for clinical presentation within the group.

Complete atrioventricular canal

Complete atrioventricular canal (CAVC), also referred to as complete atrioventricular septal defect, is characterised by an ostium primum atrial septal defect, a common atrioventricular valve and a variable deficiency of the ventricular septum inflow. CAVC is an uncommon congenital heart disease, accounting for about 3% of cardiac malformations. Atrioventricular canal occurs in two out of every 10,000 live births. Both sexes are equally affected and a striking association with Down syndrome was found. Depending on the morphology of the superior leaflet of the common atrioventricular valve, 3 types of CAVC have been delineated (type A, B and C, according to Rastelli's classification). CAVC results in a significant interatrial and interventricular systemic-to-pulmonary shunt, thus inducing right ventricular pressure and volume overload and pulmonary hypertension. It becomes symptomatic in infancy due to congestive heart failure and failure to thrive. Diagnosis of CAVC might be suspected from electrocardiographic and chest X-ray findings. Echocardiography confirms it and gives anatomical details. Over time, pulmonary hypertension becomes irreversible, thus precluding the surgical therapy. This is the reason why cardiac catheterisation is not mandatory in infants (less than 6 months) but is indicated in older patients if irreversible pulmonary hypertension is suspected. Medical treatment (digitalis, diuretics, vasodilators) plays a role only as a bridge toward surgery, usually performed between the 3rd and 6th month of life.

Can atrioventricular septal defects exist with intact septal structures?

The hallmark of an atrioventricular septal defect (AVSD) is a common atrioventricular junction, giving rise to a trileaflet left atrioventricular valve. AVSDs have the potential for interatrial shunting alone, interventricular shunting alone, or both. AVSDs without interatrial or interventricular communications have been identified at postmortem examination, but there are no reports of AVSDs with intact septal structures diagnosed in life. Six patients are described with AVSD and intact atrial and ventricular septa diagnosed echocardiographically. This report shows that AVSDs can exist without interatrial or interventricular communications and that the characteristic feature of this condition, the common atrioventricular junction with a trileaflet left atrioventricular valve, can be diagnosed in life by using cross sectional echocardiography. AVSDs with intact septal structures may be more common than previously described.

Increased cardiac atrial-to-ventricular length ratio in the fetal four-chamber view: a new marker for atrioventricular septal defects

OBJECTIVES

Atrioventricular septal defects (AVSDs) are the most common cardiac abnormality in fetuses with numerical chromosomal aberrations, in particular trisomy 21. The majority of AVSDs are not detected by routine ultrasound examination in pregnancy. We report two simple cardiac measurements that may substantially improve antenatal detection of AVSDs.

METHODS

Cross-sectional ultrasound images through the fetal thorax demonstrating the four-chamber plane of the heart were obtained in 123 normal fetuses between 10 and 38 weeks of gestation. Heart length was measured at the level of interventricular septum by placing the calipers on the epicardium at the apex of the heart and on the endocardium at the top of the atrium. Ventricular length was measured by shifting the atrial caliper to the crossing point of the ventricular septum and mitral valve. Atrial length was calculated as the difference between the heart length and ventricular length. Based on these measurements, the atrial-to-ventricular length (AVL) ratio was calculated. Data were compared to measurements from 29 consecutive fetuses with AVSD between 13 and 39 weeks of gestation.

RESULTS

In normal fetuses, the AVL ratio did not change with gestation and the mean AVL ratio was 0.47 (95% prediction interval 0.35 to 0.63). In the AVSD group, the mean AVL ratio was 0.77 (range, 0.59-0.99). If a cut-off value for the AVL ratio of 0.6 was chosen, the detection rate of AVSD was 86.2% at a 5.7% false-positive rate. For a 100% detection rate, the false-positive rate was 7.3%.

CONCLUSIONS

The AVL ratio can accurately discriminate between hearts with AVSDs and normal cardiac anatomy. Incorporation of the AVL ratio measurement into routine antenatal ultrasonography may substantially improve the ability to diagnose AVSDs antenatally.

Deficiency of the vestibular spine in atrioventricular septal defects in human fetuses with down syndrome

Data on the morphogenesis of atrioventricular septal defect (AVSD) in Down syndrome are lacking to support molecular studies on Down syndrome heart critical region. Therefore, we studied the development of complete AVSD in human embryos and fetuses with trisomy 21 using 3-dimensional graphic reconstructions and immunohistochemical markers. Eight trisomic hearts with AVSD and 10 normal hearts, ranging from 5 to 16 weeks' gestation, were examined. In AVSD, the muscular septum primum and venous valves develop normally, and the size and histology of the nonfused endocardial cushions also appear normal. However, the mass of extracardiac mesenchyme (vestibular spine), located at the dorsal mesocardium, is reduced and does not protrude ventrally along the right wall of the common pulmonary vein. As a result of this, the muscular septum primum and the right pulmonary ridge are seen as 2 separate septa that attach to the inferior endocardial cushion. Both the muscular septum primum and the superiorly fused venous valves (septum spurium) converge and are capped by a small rim of mesenchyme, which forms the roof of the persisting ostium primum and connects to cushions and the reduced vestibular spine. At 7 weeks, ventricular septation in AVSD is comparable to 5 to 6 weeks of normal cardiac development. At later stages, the septum spurium forms the anterosuperior limbus of the septum secundum and the mesenchymal cap becomes the bridging tendon that connects the bridging leaflets. Therefore, reduced expansion of the vestibular spine derived from the dorsal mesocardium appears to play an important role in the development of AVSD in Down syndrome.

The anatomy of interatrial communications--what does the interventionist need to know?

Increasingly, the interventional cardiologist is seeking to close interatrial communications by inserting devices by means of catheterisation. So as to optimise these procedures, it is advantageous to have a firm grasp of the anatomy of the normal atrial septal structures, this then providing the basis to understand the morphology of the holes which can exist between the chambers, not all of which are true septal defects. A true septal structure can be removed without exiting from the cavities of the heart. It is the flap valve of the oval fossa, along with the anterior rim of the fossa, which fulfill this criterion. The remainder of the extensive rim of the normal fossa is no more than an infolding between the walls of the right and left atria and their venous tributaries, and has different dimensions at various points around the circumference. The so-called muscular atrioventricular "septum" is a sandwich incorporating a layer of epicardial fibro-adipose tissue. True defects of the atrial septum, therefore, exist because of deficiency, perforation, or absence of the flap valve. Most of these defects will prove suitable for interventional closure, but potential caveats include multiple defects, aneurysm of the flap valve, or adjacency of the fossa to the venous orifices. The other interatrial communications, namely the sinus venosus, coronary sinus, and "ostium primum" defects are outside the confines of the oval fossa. Recognition of this feature is the key to their diagnosis, and their differentiation from true atrial septal defects. Of these defects, only the coronary sinus defect is likely to be suitable for device closure, and then only in the very rare circumstances when it is seen in isolation.