Atrioventricular Septal Defect (AVSD)

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 Fibrous Fibrocystic Change ring to which valve leaflets attach
• Ostium primum Ostium Primum Atrial Septal Defect (ASD): 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 (ASD) located near the AVVs

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) ( ASD ASD Autism spectrum disorder (ASD) is a neurodevelopmental disorder marked by poor social skills, restricted interests/social interactions, and repetitive/stereotyped behaviors. The condition is termed a “spectrum” because of the wide variability in the severity of symptoms exhibited. Autism Spectrum Disorder) + single AVV annulus with separate tricuspid/ mitral valve Mitral valve The valve between the left atrium and left ventricle of the heart. Heart: Anatomy openings
• Complete: ASD ASD Autism spectrum disorder (ASD) is a neurodevelopmental disorder marked by poor social skills, restricted interests/social interactions, and repetitive/stereotyped behaviors. The condition is termed a “spectrum” because of the wide variability in the severity of symptoms exhibited. Autism Spectrum Disorder + VSD + single/fused mitral and tricuspid annulus and openings
• Intermediate or transitional: ASD ASD Autism spectrum disorder (ASD) is a neurodevelopmental disorder marked by poor social skills, restricted interests/social interactions, and repetitive/stereotyped behaviors. The condition is termed a “spectrum” because of the wide variability in the severity of symptoms exhibited. Autism Spectrum Disorder + small VSD Small VSD Ventricular Septal Defect (VSD) + usually a single mitral and tricuspid annulus 
• Unbalanced: hypoplasia Hypoplasia Hypoplastic Left Heart Syndrome (HLHS) of one ventricle + single/fused mitral and tricuspid annulus opening mainly into the other ventricle

Epidemiology

• 5%–8% of all congenital heart defects
• Prevalence Prevalence The total number of cases of a given disease in a specified population at a designated time. It is differentiated from incidence, which refers to the number of new cases in the population at a given time. Measures of Disease Frequency: 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 ASD Autism spectrum disorder (ASD) is a neurodevelopmental disorder marked by poor social skills, restricted interests/social interactions, and repetitive/stereotyped behaviors. The condition is termed a “spectrum” because of the wide variability in the severity of symptoms exhibited. Autism Spectrum Disorder in AVSD involves most inferior part of atrial septum ( ostium primum Ostium Primum Atrial Septal Defect (ASD) defect).

Pathophysiology

Symptoms of AVSD ( cyanosis Cyanosis A bluish or purplish discoloration of the skin and mucous membranes due to an increase in the amount of deoxygenated hemoglobin in the blood or a structural defect in the hemoglobin molecule. Pulmonary Examination, heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR), 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 Blood flow Blood flow refers to the movement of a certain volume of blood through the vasculature over a given unit of time (e.g., mL per minute). Vascular Resistance, Flow, and Mean Arterial Pressure in the pulmonary system.

Partial AVSD

• Left-to-right shunt through ostium primum Ostium Primum Atrial Septal Defect (ASD) defect (usually significant) + regurgitation Regurgitation Gastroesophageal Reflux Disease (GERD) through mitral and/or tricuspid valve Tricuspid valve The valve consisting of three cusps situated between the right atrium and right ventricle of the heart. Heart: Anatomy defects (usually moderate) + minimal to no pulmonary vascular resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing
• With large defects, mixing of right and left atrial blood causes cyanosis Cyanosis A bluish or purplish discoloration of the skin and mucous membranes due to an increase in the amount of deoxygenated hemoglobin in the blood or a structural defect in the hemoglobin molecule. Pulmonary Examination.
• Usually, symptoms are not evident until adulthood because of the low pulmonary pressure.
• Gerbode defect: Mitral regurgitation Regurgitation Gastroesophageal Reflux Disease (GERD) often occurs through the mitral valve Mitral valve The valve between the left atrium and left ventricle of the heart. Heart: Anatomy 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 Regurgitation Gastroesophageal Reflux Disease (GERD) with development of heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR)
• Progressive pulmonary vascular disease and higher pulmonary vascular resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing (PVR)
• Symptoms arise within the 1st year of life.
• Eisenmenger physiology Eisenmenger Physiology Truncus Arteriosus: Gradual increase in right-to-left shunt causes central cyanosis Central Cyanosis Tricuspid Valve Atresia (TVA).

Clinical Presentation

Partial AVSD

• Often asymptomatic until later in childhood or adulthood
• Mild shunt with minimal AVV regurgitation Regurgitation Gastroesophageal Reflux Disease (GERD): asymptomatic; discovered during a general physical exam later in life
• Large shunt and severe AVV regurgitation Regurgitation Gastroesophageal Reflux Disease (GERD):
  • 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 Splitting Defense Mechanisms 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 Holosystolic Murmur Tricuspid Valve Atresia (TVA) 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: Anatomy due to mitral regurgitation Regurgitation Gastroesophageal Reflux Disease (GERD)

Complete AVSD

• Usually presents within the first year of life 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, 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, and heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR)
• 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: Anatomy enlargement, a precordial bulge, and a palpable systolic thrill Systolic Thrill Ventricular Septal Defect (VSD) at the 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 Cyanosis A bluish or purplish discoloration of the skin and mucous membranes due to an increase in the amount of deoxygenated hemoglobin in the blood or a structural defect in the hemoglobin molecule. Pulmonary Examination later during childhood or adolescence.

Diagnosis

Chest X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests

Severe partial or complete atherosclerotic cardiovascular disease (ASCVD): large cardiac silhouette with a prominent pulmonary artery Pulmonary artery The short wide vessel arising from the conus arteriosus of the right ventricle and conveying unaerated blood to the lungs. Lungs: Anatomy 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. Electrocardiogram (ECG)

Significant changes seen with complete ASCVD:

• Left axis deviation (negative QRS complex QRS complex Electrocardiogram (ECG) in inferior leads) or superior axis deviation (negative QRS complex QRS complex Electrocardiogram (ECG) in inferior leads plus Q waves in I and aVL)
• Biventricular or isolated right ventricular hypertrophy Right Ventricular Hypertrophy Tetralogy of Fallot
• Right ventricular conduction delay
• Tall P waves
• Prolongation of PR interval PR interval Electrocardiogram (ECG)

Echocardiography Echocardiography Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues. The standard approach is transthoracic. Tricuspid Valve Atresia (TVA)

• Confirms the diagnosis: performed either prenatally or soon after birth
• Findings:
  • RV enlargement
  • Abnormally low AVVs with “gooseneck” deformity Deformity Examination of the Upper Limbs of LV outflow tract
  • Tricuspid valve Tricuspid valve The valve consisting of three cusps situated between the right atrium and right ventricle of the heart. Heart: Anatomy is at same level as mitral valve Mitral valve The valve between the left atrium and left ventricle of the heart. Heart: Anatomy instead of normal, more apical insertion.
  • A VSD and a single AVV is seen in complete AVSD.
• Doppler Doppler Ultrasonography applying the doppler effect, with frequency-shifted ultrasound reflections produced by moving targets (usually red blood cells) in the bloodstream along the ultrasound axis in direct proportion to the velocity of movement of the targets, to determine both direction and velocity of blood flow. Ultrasound (Sonography): used to detect blood flow Blood flow Blood flow refers to the movement of a certain volume of blood through the vasculature over a given unit of time (e.g., mL per minute). 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 Regurgitation Gastroesophageal Reflux Disease (GERD)
• May show associated anomalies such as patent ductus arteriosus Ductus arteriosus A fetal blood vessel connecting the pulmonary artery with the descending aorta. Patent Ductus Arteriosus (PDA) or coarctation of aorta Aorta The main trunk of the systemic arteries. Mediastinum and Great Vessels: Anatomy

Management

Partial and Transitional AVSD

• Surgery is performed through a right atrial incision and is highly successful.
• Surgical repair in childhood is advised to prevent complications (e.g., arrhythmias, heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR), 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).

Complete AVSD

• Surgery is more complicated, but still highly successful.
• Surgical repair is generally recommended by 6 months of age to prevent irreversible 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.

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 Regurgitation Gastroesophageal Reflux Disease (GERD)

Prognosis Prognosis A prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas

• Most patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with mild partial AVSD are asymptomatic and only develop symptoms in the 3rd or 4th decade of life.
• Complete AVSD has a high mortality Mortality All deaths reported in a given population. Measures of Health Status rate during infancy without corrective surgery.