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Pediatric Partial and Intermediate Atrioventricular Septal Defects Clinical Presentation

  • Author: M Silvana Horenstein, MD; Chief Editor: P Syamasundar Rao, MD  more...
 
Updated: Mar 27, 2014
 

History

In the absence of moderate to severe mitral regurgitation (MR) and other associated congenital heart disease (CHD), partial atrioventricular septal defect (AVSD) is often discovered later in childhood when the patient is referred for evaluation of a heart murmur. Also, partial AVSD is less common in Down syndrome than in complete AVSD.

Note the following:

  • The clinical presentation of patients with partial AVSD depends on the degree of MR and on the associated cardiac defects.
  • Other cardiac anomalies that may be associated with partial AVSD include secundum atrial septal defect (ASD), persistent left superior vena cava draining to the coronary sinus, pulmonary stenosis, discrete subaortic stenosis, tricuspid stenosis, tricuspid atresia, coarctation of the aorta, patent ductus arteriosus (PDA), perimembranous ventricular septal defect (VSD), and hypoplastic left ventricle (LV).
  • Children with atrioventricular valve competence usually exhibit no significant symptoms. They are usually referred to a pediatric cardiologist if a heart murmur is detected during routine examination.
  • Substantial left-to-right shunting may exacerbate pulmonary disease and cause frequent lower respiratory infections in some patients. These patients may present with tachypnea, respiratory distress, and inadequate weight gain.
  • Infants with severe MR often demonstrate poor feeding, tachypnea, and labored breathing. Rarely, respiratory distress may be so severe as to require mechanical ventilation.
  • Progressive cardiac enlargement and LV dysfunction cause shocklike symptoms and eventually lead to mortality.
  • Adolescents and young adults may note progressive exercise intolerance.
  • Palpitations caused by atrial arrhythmia become more common in young adulthood, and sustained supraventricular tachycardia, atrial flutter, or atrial fibrillation may trigger the onset of congestive heart failure (CHF) in older patients with AVSD.
  • Hypervolemia of pregnancy may trigger CHF symptoms and complicate pregnancy.
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Physical

General appearance

Most children with partial AVSD and minimal MR appear healthy. Patients who have Down syndrome exhibit features typical of the condition.

Patients with severe MR in infancy can manifest tachypnea, retractions, and diaphoresis, especially during and immediately after feeding. Poor caloric intake and excessive metabolic demands lead to growth failure. Older children and adolescents with severe MR may display a prominent left chest as well as a slim (asthenic) build.

Pulmonary and cardiovascular examination

Palpation and auscultatory findings depend on the severity of the left-to-right shunt, the presence of MR, and associated defects (eg, LV outflow obstruction, PDA).

Fine rales or rhonchi, or both, may be heard in the lung fields of older patients with severe MR but are rare in infants.

The partial AVSD provides auscultatory findings that are indistinguishable from those created by any other large ASD. A prominent impulse along the right sternal border, consistent with a right ventricle (RV) lift, may be present. Alternatively, severe MR can cause a prominent apical impulse or thrill.

The classic auscultatory finding associated with an ASD is a constant or fixed splitting of the second heart sound (S2), frequently accompanied by a pulmonary ejection murmur audible at the upper left sternal border.

A large AVSD with substantial left-to-right shunting creates a mid-diastolic rumbling murmur, audible along the lower left sternal border. This often occurs in association with a prominent third heart sound (S3) in that location. These sounds are attributed to an abnormally high flow across the tricuspid component of the atrioventricular valve.

The apical murmur of MR occurs even with a small cleft in the atrioventricular valve. This murmur has a blowing quality and must be differentiated from the murmur caused by a VSD. However, when it occurs with a fixed split S2, this murmur is helpful in differentiating a partial AVSD from a secundum ASD.

Severe MR can also cause a diastolic murmur audible over the apical area, which, in association with the systolic murmur, produces a to-and-fro quality.

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Causes

AVSDs are presumed to occur secondary to extracellular matrix abnormalities that produce faulty development of the endocardial cushions and the atrioventricular septum. It has been recently described that yet another structure, the dorsal mesenchymal protrusion, which derives from the second heart field, should also fully develop in order to have an intact 4-chambered heart; otherwise, an ASD or an AVSD occurs.[2]

More detailed scientific theories interpret the normal development of the human heart as an orderly coordination of transcriptional programs. Therefore, the variety and range of anatomic malformations in CHD are believed to be caused by a faulty mechanism that disrupts the above.

AVSDs are often associated with genetic syndromes such as trisomy 21 or Down syndrome;Holt-Oram syndrome, which results from mutations in the TBX5 gene; and heterotaxy syndromes, which result from mutations in genes such as PITX2, SHH, and NODAL. A newly described CRELD1 gene is likely to be an AVSD-susceptibility gene, and CRELD1 mutations may increase the risk of developing a heart defect[3] ; this mutation is believed to be associated with the 3p deletion syndrome[4] characterized by low birth weight, varying degrees of mental retardation, ptosis, and micrognathia.[5]

Genetic mutations may be also associated with nonsyndromic cardiac defects. For example, one of the most important factors for the differentiation of mesodermal progenitor cells is the homeobox protein Nkx-2.5. In humans, 28 germline Nkx-2.5 mutations have been associated with CHD. Studies have shown that mutations in the gene Nkx-2.5 are associated specifically with AVSDs and VSDs.[6] Mutations in the GATA4 transcriptional factor may also cause AVSDs by disrupting its role during different stages in cardiogenesis.[7]

To date, approximately 100 CHD "risk genes" have been described. Of these, 6 subphenotypes have been shown to be linked to partial AVSDs. Of note, these genes have also been linked to aortic valve stenosis, subaortic stenosis, AVSDs associated with tetralogy of Fallot, tetralogy of Fallot, and truncus arteriosus.[8]

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Contributor Information and Disclosures
Author

M Silvana Horenstein, MD Assistant Professor, Department of Pediatrics, University of Texas Medical School at Houston; Medical Doctor Consultant, Legacy Department, Best Doctors, Inc

M Silvana Horenstein, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American Medical Association

Disclosure: Nothing to disclose.

Coauthor(s)

Michael A Portman, MD, MD Professor, Department of Pediatrics, University of Washington School of Medicine; Director of Research, Division of Cardiology, Seattle Children's Hospital; Attending Physician, Seattle Children's Heart Center; Attending Physician, Cardiology Clinic, Providence Everett Medical Center

Michael A Portman, MD, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American Heart Association, American Physiological Society, Society for Pediatric Research

Disclosure: Nothing to disclose.

Specialty Editor Board

Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

Alvin J Chin, MD Emeritus Professor of Pediatrics, University of Pennsylvania School of Medicine

Alvin J Chin, MD is a member of the following medical societies: American Association for the Advancement of Science, Society for Developmental Biology, American Heart Association

Disclosure: Nothing to disclose.

Chief Editor

P Syamasundar Rao, MD Professor of Pediatrics and Medicine, Division of Cardiology, Emeritus Chief of Pediatric Cardiology, University of Texas Medical School at Houston and Children's Memorial Hermann Hospital

P Syamasundar Rao, MD is a member of the following medical societies: American Academy of Pediatrics, American Pediatric Society, American College of Cardiology, American Heart Association, Society for Cardiovascular Angiography and Interventions, Society for Pediatric Research

Disclosure: Nothing to disclose.

Additional Contributors

Paul M Seib, MD Associate Professor of Pediatrics, University of Arkansas for Medical Sciences; Medical Director, Cardiac Catheterization Laboratory, Co-Medical Director, Cardiovascular Intensive Care Unit, Arkansas Children's Hospital

Paul M Seib, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American Heart Association, Arkansas Medical Society, International Society for Heart and Lung Transplantation, Society for Cardiovascular Angiography and Interventions

Disclosure: Nothing to disclose.

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Partial atrioventricular septal defect (AVSD): The mitral and tricuspid annuli are separate. The cleft in the mitral leaflet is in the anterior position. This type of anatomy is usually associated with a primum atrial septal defect (ASD). Partial AVSD is more common than intermediate AVSD.
Intermediate atrioventricular septal defect (AVSD): A single valve annulus is present. The anterior and posterior bridging leaflets are fused (whereas in complete AVSD the anterior and posterior bridging leaflets are not fused). Therefore, the atrioventricular valve has a tricuspid and a mitral component. Intermediate AVSD is the least common type of AVSD.
Echocardiogram of the apical 4-chamber view demonstrating a partial atrioventricular septal defect (AVSD). Chambers are denoted by RA (right atrium), RV (right ventricle), and LV (left ventricle).
Echocardiogram with subcostal view demonstrates an atrioventricular septal defect (AVSD). A portion of the ostium secundum atrial septum is also missing, just superior to the ostium primum defect.
Color Doppler demonstrates left-to-right shunting through the partial atrioventricular septal defect (AVSD) shown in the following images.
Left superior axis deviation in the frontal plane and rR' pattern in right precordial leads.
 
 
 
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