Overview
Definitions
- Atrioventricular septal defects (AVSDs): a spectrum of congenital cardiac malformations involving the atrioventricular septum and atrioventricular valves
- Atrioventricular septum: a layer of tissue that separates the atria from the ventricles, composed of cardiac tissues
- Atrioventricular valves (AVVs): mitral and tricuspid valves
- Atrioventricular valve annulus: fibrous ring to which valve leaflets attach
- Ostium primum: a kind of atrial septal defect Atrial Septal Defect Atrial septal defects (ASDs) are benign acyanotic congenital heart defects characterized by an opening in the interatrial septum that causes blood to flow from the left atrium (LA) to the right atrium (RA) (left-to-right shunt). Atrial Septal Defect located near the AVVs
Complete atrioventricular septal defect: Notice the simultaneous flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure of blood from the left atrium and ventricle to their right counterparts.
Image by Lecturio.Classification
Classification of AVSD is based on anatomy of defect:
- Partial: atrial septal defect Atrial Septal Defect Atrial septal defects (ASDs) are benign acyanotic congenital heart defects characterized by an opening in the interatrial septum that causes blood to flow from the left atrium (LA) to the right atrium (RA) (left-to-right shunt). Atrial Septal Defect (ASD) + single AVV annulus with separate tricuspid/mitral valve openings
- Complete: ASD + VSD + single/fused mitral and tricuspid annulus and openings
- Intermediate or transitional: ASD + small VSD + usually a single mitral and tricuspid annulus
- Unbalanced: hypoplasia of one ventricle + single/fused mitral and tricuspid annulus opening mainly into the other ventricle
Forms of atrioventricular septal defect
Image by Lecturio.Epidemiology
- 5%–8% of all congenital heart defects
- Prevalence: 1 out of 3,000–4,000 live births
- Strong association with Down’s syndrome, especially the complete type
Etiology
- Normally, endocardial cushions close off atrial and ventricular septa during fetal cardiac development.
- Underlying genetic defects → abnormal development of endocardial cushions → AVSD
- ASD in AVSD involves most inferior part of atrial septum (ostium primum defect).
Pathophysiology
Symptoms of AVSD (cyanosis, heart failure, and pulmonary hypertension Pulmonary Hypertension Pulmonary hypertension (PH) or pulmonary arterial hypertension (PAH) is characterized by elevated pulmonary arterial pressure, which can lead to chronic progressive right heart failure. Pulmonary hypertension is grouped into 5 categories based on etiology, which include primary PAH, and PH due to cardiac disease, lung or hypoxic disease, chronic thromboembolic disease, and multifactorial or unclear etiologies. Pulmonary Hypertension) are due to excessive blood flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure in the pulmonary system.
Partial AVSD
- Left-to-right shunt through ostium primum defect (usually significant) + regurgitation through mitral and/or tricuspid valve defects (usually moderate) + minimal to no pulmonary vascular resistance Vascular Resistance Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Vascular resistance is directly related to the diameter of the vessel (smaller vessels have higher resistance). Vascular Resistance, Flow, and Mean Arterial Pressure
- With large defects, mixing of right and left atrial blood causes cyanosis.
- Usually, symptoms are not evident until adulthood because of the low pulmonary pressure.
- Gerbode defect: Mitral regurgitation Mitral regurgitation Mitral regurgitation (MR) is the backflow of blood from the left ventricle (LV) to the left atrium (LA) during systole. Mitral regurgitation may be acute (myocardial infarction) or chronic (myxomatous degeneration). Acute and decompensated chronic MR can lead to pulmonary venous congestion, resulting in symptoms of dyspnea, orthopnea, and fatigue. Mitral Regurgitation often occurs through the mitral valve cleft directly into the right atrium (RA), causing RA enlargement.
Complete AVSD
- Significant left-to-right shunt through both atrial and ventricular septal defects
- Some degree of right-to-left shunt with larger defects
- Significant AVV regurgitation with development of congestive heart failure Congestive heart failure Congestive heart failure refers to the inability of the heart to supply the body with normal cardiac output to meet metabolic needs. Echocardiography can confirm the diagnosis and give information about the ejection fraction. Congestive Heart Failure
- Progressive pulmonary vascular disease and higher pulmonary vascular resistance Vascular Resistance Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Vascular resistance is directly related to the diameter of the vessel (smaller vessels have higher resistance). Vascular Resistance, Flow, and Mean Arterial Pressure (PVR)
- Symptoms arise within the 1st year of life.
- Eisenmenger physiology: Gradual increase in right-to-left shunt causes central cyanosis.
Anatomy of the atrioventricular septation complex in a human 4-chambered heart with normal anatomy and in hearts with AVSDs.
Image: “Anatomy of the atrioventricular septation complex” by US National Library of Medicine. License: CC BY 4.0
(A) shows a properly septated heart with a complete atrial and ventricular septum;
(B) depicts a heart with an incomplete AVSD; and in
(C) a heart with a complete AVSD is shown.
Note that when a primary atrial septal defect Atrial Septal Defect Atrial septal defects (ASDs) are benign acyanotic congenital heart defects characterized by an opening in the interatrial septum that causes blood to flow from the left atrium (LA) to the right atrium (RA) (left-to-right shunt). Atrial Septal Defect is observed, the muscular rim at the base of the atrial septum is missing.
IVS = interventricular septum,
pAS = primary atrial septum,
pASD = primary atrial septal defect Atrial Septal Defect Atrial septal defects (ASDs) are benign acyanotic congenital heart defects characterized by an opening in the interatrial septum that causes blood to flow from the left atrium (LA) to the right atrium (RA) (left-to-right shunt). Atrial Septal Defect,
LA = left atrium,
LV = left ventricle,
RA = right atrium,
RV = right ventricle,
VSD = ventricular septal defect.
Clinical Presentation
Partial AVSD
- Mild shunt with minimal AVV regurgitation: asymptomatic; discovered during a general physical exam later in life
- Large shunt and severe AVV regurgitation:
- History of exercise intolerance, easy fatigability, and/or recurrent pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia
- Physical examination:
- Moderate to severe cardiac enlargement
- Hyperdynamic precordium
- Accentuated 1st heart sound, wide-fixed splitting of 2nd heart sound, a pulmonary systolic ejection murmur, mid-diastolic rumble at lower left sternal border due to increased flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure through the AVVs, and an apical holosystolic murmur radiating to the axilla Axilla The axilla is a pyramid-shaped space located between the upper thorax and the arm. The axilla has a base, an apex, and 4 walls (anterior, medial, lateral, posterior). The base of the pyramid is made up of the axillary skin. The apex is the axillary inlet, located between the 1st rib, superior border of the scapula, and clavicle. Axilla and Brachial Plexus due to mitral regurgitation
Complete AVSD
- Usually presents during infancy with failure to thrive Failure to Thrive Failure to thrive (FTT), or faltering growth, describes suboptimal weight gain and growth in children. The majority of cases are due to inadequate caloric intake; however, genetic, infectious, and oncological etiologies are also common. Failure to Thrive and history of recurrent pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia
- Physical examination:
- Cardiac and liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver enlargement, a precordial bulge, and a palpable systolic thrill at lower left sternal border
- Heart sounds Heart sounds Heart sounds are brief, transient sounds produced by valve opening and closure and by movement of blood in the heart. They are divided into systolic and diastolic sounds. In most cases, only the first (S1) and second (S2) heart sounds are heard. These are high-frequency sounds and arise from aortic and pulmonary valve closure (S1), as well as mitral and tricuspid valve closure (S2). Heart Sounds are similar to those in severe forms of partial AVSD.
- Milder cases may occasionally present with cyanosis later during childhood or adolescence.
Diagnosis
Chest X-ray
Severe partial or complete atherosclerotic cardiovascular disease (ASCVD): large cardiac silhouette with a prominent pulmonary artery arch and increased pulmonary vascularity
Electrocardiogram Electrocardiogram An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Normal Electrocardiogram (ECG)
Significant changes seen with complete ASCVD:
- Left axis deviation (negative QRS complex in inferior leads) or superior axis deviation (negative QRS complex in inferior leads plus Q waves in I and aVL)
- Biventricular or isolated right ventricular hypertrophy
- Right ventricular conduction delay
- Tall P waves
- Prolongation of PR interval
Echocardiography
- Confirms the diagnosis: performed either prenatally or soon after birth
- Findings:
- RV enlargement
- Abnormally low AVVs with “gooseneck” deformity of LV outflow tract
- Tricuspid valve is at same level as mitral valve instead of normal, more apical insertion.
- A VSD and a single AVV is seen in complete AVSD.
- Doppler: used to detect blood
flow
Flow
Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls.
Vascular Resistance, Flow, and Mean Arterial Pressure in the defect
- Left-to-right shunt at atrial, ventricular, and/or LV-to-right atrial levels
- Degree of AV regurgitation
- May show associated anomalies such as patent ductus arteriosus Patent ductus arteriosus The ductus arteriosus (DA) allows blood to bypass pulmonary circulation. After birth, the DA remains open for up to 72 hours and then constricts and involutes, becoming the ligamentum arteriosum. Failure of this process to occur results in patent ductus arteriosus (PDA), a condition that causes up to 10% of congenital heart defects. Patent Ductus Arteriosus (PDA) or coarctation of aorta
An apical 4-chamber 3-D echocardiogram in a patient with AVSD. Arrowheads mark the hinges of the common atrioventricular junction. The bridging leaflets divide the defect into an interatrial (ASD) and interventricular (VSD) component. Note the posterior location of the inferior vena caval orifice ( IVC IVC The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs. Mediastinum and Great Vessels) relative to the septal structures. L, left; S, superior.
Image: “Three dimensional echocardiography in congenital heart defects” by Department of Pediatrics, Medical University of South Carolina, USA. License: CC BY 2.0
Atrioventricular septal defect with 2 separate atrioventricular valves.
Image: “Understanding atrioventricular septal defect” by Echocardiography in Out Patients Clinic, Instituto Nacional de Cardiología Ignacio Chávez, Juan Badiano N degrees 1, Colonia Sección XVI, Mexico City, Mexico. License: CC BY 2.0
(A): Internal view of right chambers, left (1) and right (2) atrioventricular valves, ostium primum (asterisk), and arrow pointing to the insertion of the septal leaflets of the left valve in the crest of the interventricular septum. Note the confluence of the ostium primum with the atrioventricular septal defect (upper asterisk), the commissure that separates those leaflets, the ample commissure between the septal leaflets, and the anterior leaflet of the right atrioventricular valve (lower asterisk).
(B): The 2 separate atrioventricular valves (1 and 2) and the fusion of the septal leaflets to the crest of the interventricular septum that closes the ventricular septal defect (arrow) can be seen. IAS: interatrial septum.
Management
Partial AVSD
Surgery is performed through a right atrial incision and is highly successful.
Complete AVSD
- Surgery is more complicated, but still highly successful.
- Must be performed early (during infancy) due to higher risk of pulmonary hypertension Pulmonary Hypertension Pulmonary hypertension (PH) or pulmonary arterial hypertension (PAH) is characterized by elevated pulmonary arterial pressure, which can lead to chronic progressive right heart failure. Pulmonary hypertension is grouped into 5 categories based on etiology, which include primary PAH, and PH due to cardiac disease, lung or hypoxic disease, chronic thromboembolic disease, and multifactorial or unclear etiologies. Pulmonary Hypertension with delayed surgery
Surgical complications Surgical complications Surgical complications are conditions, disorders, or adverse events that occur following surgical procedures. The most common general surgical complications include bleeding, infections, injury to the surrounding organs, venous thromboembolic events, and complications from anesthesia. Surgical Complications
- Heart block
- Narrowed LV outflow tract
- Residual AVV regurgitation
Prognosis
- Most patients with mild partial AVSD are asymptomatic and only develop symptoms in the 3rd or 4th decade of life.
- Complete AVSD has a high mortality rate during infancy without corrective surgery.
References
- Yue, E. L., & Meckler, G. D. (2020). Congenital and acquired pediatric heart disease. In J. E. Tintinalli, O. J. Ma, D. M. Yealy, G. D. Meckler, J. S. Stapczynski, D. M. Cline & S. H. Thomas (Eds.), Tintinalli’s emergency medicine: A comprehensive study guide, 9e (). New York, NY: McGraw-Hill Education. accessmedicine.mhmedical.com/content.aspx?aid=1166594605
- Cunningham, F. G., Leveno, K. J., Bloom, S. L., Dashe, J. S., Hoffman, B. L., Casey, B. M., & Spong, C. Y. (2018). Fetal imaging. Williams Obstetrics. New York, NY: McGraw-Hill Education. accessmedicine.mhmedical.com/content.aspx?aid=1160773294
- Kliegman, R. M., M.D., St Geme, Joseph W., MD, Blum, N. J., M.D., Shah, Samir S., M.D., M.S.C.E., Tasker, Robert C., M.B.B.S., M.D., & Wilson, Karen M., M.D., M.P.H. (2020). Acyanotic congenital heart disease: Left-to-right shunt lesions. In R. M. Kliegman MD et al. Nelson textbook of pediatrics. https://www.clinicalkey.es/#!/content/3-s2.0-B9780323529501004533
- Park, Myung K., MD, F.A.A.P., F.A.C.C. (2015). Fisiopatología de las lesiones con cortocircuito izquierda-derecha. In Park, Myung K., MD, FAAP, FACC (Ed.), Cardiología pediátrica. https://www.clinicalkey.es/#!/content/3-s2.0-B9788490228333000096
- Davidson, M. A., M.D. (2008). Primary care for children and adolescents with down syndrome. Pediatric Clinics of North America, 55(5), 1099-1111. DOI:http://dx.doi.org/10.1016/j.pcl.2008.07.001
