- 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
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
- 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
- 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).
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 in the pulmonary system.
- 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
- 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.
- 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 (PVR)
- Symptoms arise within the 1st year of life.
- Eisenmenger physiology: Gradual increase in right-to-left shunt causes central cyanosis.
- 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 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
- 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.
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
- Confirms the diagnosis: performed either prenatally or soon after birth
- 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 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
Surgery is performed through a right atrial incision and is highly successful.
- 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
- Heart block
- Narrowed LV outflow tract
- Residual AVV regurgitation
- 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.
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