Day: March 21, 2022

What Are Potential Physical Examination Findings for Patients with Atrioventricular Canal Defects?

Patient Presentation
A 7-day-old male came to clinic for routine followup. He had Trisomy 21 with an atrioventricular canal heart defect. Additional evaluations during the newborn stay did not identify other congenital anomalies including no heterotaxia. He had been bottle feeding well without cyanosis or tachypnea, and taking the bottle within 15 minutes.

The pertinent physical exam showed a well-appearing male with Trisomy 21 facial features. His weight was down 3% from birthweight and was 15% on the Trisomy 21 growth chart. His lungs were clear and his heart had a normal S1, S2 but with a systolic murmur heard best toward the left sternal border to the apex. He had no hepatosplenomegaly. Femoral pulses were strong. He had mild hypotonia.

The diagnosis of a patient with Trisomy 21 and atrioventricular canal defect was confirmed. His mother asked good questions about how to continue monitoring him at home. The patient’s clinical course the following week showed he had passed birth weight but was decreasing in weight gain per day. The mother was instructed to increase the calories per ounce of formula. At return the following week the infant still was not showing signs of fatigue or difficulties with feeding but weight gain per day continued to decline. Cardiology was called and arranged to have him be seen the following day, where they began diuretic therapy. Over time he needed more ionotropic support before he had successful surgical correction at 4 months of age.

Discussion
Atrioventricular canal defects (AVCD) are a heterogeneous range of congenital heart defects (CHD) arising from malformations of intracardiac septal development. Essentially the location where the 4 corners of the 2 atria and 2 ventricula meet is abnormally formed. There is partial or complete fusion of the mitral and tricuspid valves along with atrial (ASD) and ventricular septal defects (VSD). Fusion of the endocardial cushions occurs around 4-5 weeks gestation. The anatomy for an individual is bespoke as the variations of the valve leaflets, chordal attachments and variations in ASD and VSD are numerous. This pathology causes fluid overload and left-to-right shunting and resulting pulmonary overcirculation.

AVCDs occur in ~3-7% of CHD patients or in about 3.5/10,000 live births. Patients with AVCDs often have extracardiac anomalies (75%). AVCDs are common in patients with Trisomy 21 (40-45% of Trisomy 21 patients have AVCD) but also with heterotaxy (15%). Non-syndrome patients are observed in about 25% of AVCD patients. Other genetic syndromes associated with AVCD include “CHARGE,…, Ellis-van-Creveld, Ivemark, Kaufman McKusick, Ritscher-Schinzel, Smith-Lemli-Opitz, and 3p.”

Patients are often identified prenatally on prenatal ultrasound or karyotype. Others are identified soon after birth with abnormal physical examination. Others may not present until 1-2 months of life when pulmonary overcirculation occurs. Diagnosis is made by echocardiogram.

In 1955, Dr. Walton Lillehei of the University of Minnesota successfully surgically treated a patient with AVCD. Patients are surgically treated usually between 3-6 months before pulmonary overcirculation is severe. Presurgery this includes proper weight management but also may need diuretics, angiotensin-converting enzyme inhibitor, angiotension 2 receptor blockers and/or digoxin. The surgical technique involves patches to vertically separate the ventricles and the atria along with creating separate mitral and tricuspid valves horizontally. Because of the location the main potential post-procedure problems include heart block as the coronary sinus is located close to this area, and valvular competence and adequacy. Intraoperative mortality is cited at ~3% and 10-year survival rate is ~90%. Re-operation occurs in about 5-10% of people usually because of mitral regurgitation.

Learning Point
In patients with suspected AVCD, the general physical examination should look for dysmorphic features especially those associated with Trisomy 21, but also evaluation of other mid-line defects such as cleft lip/palate and musculoskeletal abnormalities. Signs of heterotaxy should also be looked for. Signs and symptoms of AVCD are usually associated with congestive heart failure including increased work of breathing, sweating with activities such as eating, sleepiness and lethargy. Tachypnea, tachycardia, wheezing and poor weight gain can be noted. Patients may also have pulmonary rales, hepatomegaly, jugular venous distention and apical displacement of the apical impulse. Generally AVCD is acyanotic as it is has left-to-right shunting, but during crying or other circumstances can cause right-to-left shunting and cyanosis for a period of time. Auscultation may show a wide split S2 because of the left-to-right shunting, and an S3 gallop again because of increased flow. There may be a holosystolic murmur that is best at the apex or a mid-diastolic murmur because of valvular regurgitation.

Questions for Further Discussion
1. What are the 5 “C’s” of cyanotic congenital heart disease? A review can be found here
2. What are common acyanotic congenital heart diseases? A review can be found here
3. What other extracardiac problems are common in patients with Trisomy 21?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for this topic: Congenital Heart Defects

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Malik M, Khalid Nuri M. Surgical Considerations in Atrioventricular Canal Defects. Semin Cardiothorac Vasc Anesth. 2017;21(3):229-234. doi:10.1177/1089253217708622

Digilio M C., Pugnaloni F, De Luca A, et al. Atrioventricular canal defect and genetic syndromes: The unifying role of sonic hedgehog. Clinical Genetics. 2019;95(2):268-276. doi:10.1111/cge.13375

Knatterud M. C. Walton Lillehei, PhD, MD. Medical School – University of Minnesota. Published November 24, 2020. Accessed November 16, 2021. https://med.umn.edu/lhi/about/c-walton-lillehei

Rigby M. Atrioventricular Septal Defect: What Is in a Name? J Cardiovasc Dev Dis. 2021;8(2):19. doi:10.3390/jcdd8020019

Umapathi KK, Agasthi P. Atrioventricular Canal Defects. In: StatPearls. StatPearls Publishing; 2021. Accessed November 15, 2021. http://www.ncbi.nlm.nih.gov/books/NBK557511/

Author
Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa