Atrioventricular in India = an overview

Atrioventricular in India = an overview Introduction Background

Endocardial cushion defects, more commonly known as Atrioventricular (ATRIOVENTRICULAR) canal or septal defects, include a range of defects characterized by involvement of the atrial septum, the ventricular septum, and one or both of the ATRIOVENTRICULAR valves.

These defects can be classified by several methods. A distinction generally is made between partial and complete defects. A complete Atrioventricular septal defect indicates the presence of both atrial and ventricular septal defects with a common Atrioventricular valve. A partial defect indicates atrial septal involvement with separate mitral and tricuspid valve orifices.

Atrioventricular canal defects arise from abnormal development of the endocardial cushions. In these patients, the superior and inferior cushions do not close completely. An interatrial communication is left at the lower part of the atrial septum. This is called an ostium primum defect. The failure of the endocardial cushions to fuse results in an abnormally low position of the Atrioventricular valves and an abnormally high position of the aortic valve. A part of the ATRIOVENTRICULAR valves originates from the endocardial cushions, and their improper fusion results in anterior and posterior components to the mitral valve leaflet.

Pathophysiology

Predominant left-to-right shunting of blood through the heart occurs in these patients. In patients with partial defects, this occurs through the ostium primum atrial septal defect. When a complete endocardial cushion defect is present, a large ventricular septal defect as well as valvular insufficiency may develop, resulting in volume overload of both the left and right ventricles associated with heart failure in early life. In patients with long-standing pulmonary overload, pulmonary vascular disease may develop and congestive heart failure (CHF) symptoms may improve. This improvement is a poor prognostic indicator because it heralds the development of right-to-left shunting and irreversible pulmonary hypertension (ie, Eisenmenger syndrome).

Frequency

United States

The frequency rate is about 3% of children with congenital heart disease. Sixty to seventy percent of these defects are of the complete form. More than half of those affected with the complete form hAtrioventriculare Down syndrome.

International

The frequency rate is about 3% of children who hAtrioventriculare congenital heart disease.

Mortality/Morbidity

Patients with only ostium primum atrial septal defect and minimal insufficiency of the left Atrioventricular valve (ie, mitral valve) do well without treatment during infancy, childhood, and adolescence. During adulthood, these patients develop symptoms of CHF and atrial arrhythmia.

Patients with septal defects and mitral valve insufficiency develop CHF early in life, with high rates of morbidity and mortality if the valvular insufficiency is pronounced. Patients with a complete defect develop CHF in infancy, with frequent respiratory infections and poor weight gain.

Race

No racial predilection is apparent.

Sex

Girls are affected slightly more frequently than boys.

Age

Endocardial cushion defect is a congenital defect present at birth. The severity of the symptom complex and presentation is dependent directly upon the severity of the defect and the presence of mitral insufficiency.

Clinical History

An infant may be relatively asymptomatic. In severe cases, patients hAtrioventriculare a history of poor feeding, chronic upper respiratory tract infections, pneumonia, and poor growth. The mother may notice difficulty with crying, frequent pauses during feeding, and nasal flaring. As the child grows older, the more common manifestations of CHF may develop, including Atrioventricularersion to activity and play, simple fatigability, dyspnea, and edema.

Physical Partial defects present with the physical findings common to atrial septal defects. The second heart sound is widely split without respiratory variations. A systolic ejection murmur may be heart at the upper left sternal border. A low-pitched early diastolic rumble may be heart at the lower left sternal border and is related to increased tricuspid valve flow. A murmur of mitral insufficiency may or may not be present. Additional findings in complete endocardial cushion defects relate to the ventricular septal defect and valvular insufficiency. Poor physical development, hyperinflated thorax, bulging precordium, Harrison grooves, mild or intermittent cyanosis, and stigmata of Down syndrome (eg, oblique palpebral fissures, large protuberant tongue, small and broad hands, simian crease, inner epicanthic skin fold) Arterial and jugular venous pulse – Water hammer pulse, dominant v wAtrioventriculare in the jugular venous pulse Precordial movement and palpation – Systolic thrill, palpable impulse in the second and third intercostal space representing a dilated pulmonary artery, prominent heAtrioventriculare at the left sternal border Auscultation A single first heart sound is heard, which may be a relatively soft fixed splitting of the second heart sound. A systolic murmur of a ventricular septal defect can be heard as well as the systolic murmur of mitral insufficiency. Pulmonary hypertension is associated with a loud pulmonic component of the second heart sound. Causes Genetics The characteristic pattern of the malformation has been attributed to trisomy 21 and Down syndrome in some cases. Some evidence exists that a critical region of chromosome band 21q22 may contribute particularly to the cardiac malformation in this syndrome. Other chromosomal abnormalities also can result in Atrioventricular septal defects, in particular, deletion of 8p, partial 10q monosomy, partial 13q monosomy, ring 22 14 q+, and 1p+3p-. In most cases of significant chromosomal aberration, Atrioventricular  septal defects are associated with other noncardiac congenital defects. But, isolated ATRIOVENTRICULAR septal defects can be transmitted in families as an autosomal dominant trait. Linkage analyses hAtrioventriculare suggested a locus for autosomal dominant Atrioventricular septal defects on chromosome 1p but no specific gene defect has yet been identified. Growth factor aberrations: In the developing fetus, cardiac tissue formation is dependent upon appropriate growth factor stimulation including transforming growth factor beta and platelet-derived growth factor. Alterations in the concentration or efficacy of these factors during embryogenesis can contribute to the cardiac malformations. Differential Diagnoses

Atrial Septal Defect
Mitral Regurgitation
Ventricular Septal Defect

Workup Laboratory Studies CBC count: Blood tests determine the presence of polycythemia in a potentially cyanotic condition. Prothrombin time/activated partial thromboplastin time (PT/aPTT): In children with cyanotic heart disease, the coagulation profile may be abnormal because of associated polycythemia. Electrolytes: This test detects any abnormalities incurred with treatment of CHF. Imaging Studies Chest radiography This test is a excellent general screening that shows cardiac enlargement, particularly of the right atrium and ventricle. The main pulmonary artery usually is prominent with increased pulmonary vascular markings. After pulmonary hypertension develops, a reduction in pulmonary vascular markings is observed. Echocardiography M-mode shows diastolic movement of the mitral valve with enlarged right ventricle and paradoxical motion of the interventricular septum. Two-dimensional echocardiography is highly reliable in identification of septal defects. Echocardiography identifies the absence of the interventricular septum. Findings may include right ventricular dilatation and paradoxical motion of the interventricular septum. The extent of septal defects as well as the left-to-right shunting and degree of valvular insufficiency can be determined as well as an estimate of pulmonary artery pressure. Lack of displacement of the left and right Atrioventricular valves is a characteristic finding in this condition. Prolonged diastolic contact between the anterior mitral leaflet and the interventricular septum also may be noted. Associated defects that may require attention also can be detected. Abnormalities in the Atrioventricular valves can be identified reliably. Transesophageal echocardiography clearly identifies Atrioventricular valve morphology. MRI: This test readily visualizes the deficiency in the ventricular septum as well as Atrioventricular valve morphology. Cardiac catheterization: This test is indicated when clinically significant questions remain unanswered after a comprehensive noninvasive evaluation. If other lesions are suspected or if operative plotting cannot be performed adequately after noninvasive testing, then catheterization should be undertaken. Left ventricular angiography in the frontal plane shows an elongated left ventricular outflow tract, called a “gooseneck deformity,” which is characteristic of this condition. Catheterization should involve quantitation of the shunts and valvular insufficiency and calculation of pulmonary vascular resistance. Aortography may be performed to determine whether a patent ductus arteriosus is present. Other Tests Electrocardiography The typical ECG in patients with partial Atrioventricular septal defects shows first-degree Atrioventricular block and left axis deviation (because of late left anterior fascicular depolarization). Patients with right ventricular dilatation usually hAtrioventriculare partial or complete right bundle-branch block. Complete Atrioventricular block and atrial fibrillation commonly occur in older patients. See Medscape’s Atrial Fibrillation Resource Center. A prolonged PR interval accompanied by biventricular or left ventricular hypertrophy also may be seen. Treatment Medical Care

Medical treatment is designed to relieve the symptoms of CHF until operative correction is feasible. The objective of therapy is to Atrioventricularoid development of pulmonary vascular obstructive disease. When heart failure and associated pulmonary congestion are present, diuretics and digoxin are indicated.

Surgical Care Infants with partial Atrioventricular septal defects that are symptomatic are referred for corrective surgery, which includes mitral valvuloplasty and closure of the atrial septal defect. Asymptomatic patients with an ostium primum defect are referred for elective repair after infancy. Patients with complete ATRIOVENTRICULAR septal defects who do not hAtrioventriculare associated right ventricular outflow obstruction generally hAtrioventriculare pulmonary artery pressures near systemic levels. These patients will develop pulmonary vascular disease after the first year of life and usually are referred for corrective surgery in infancy. Historically, children were treated with pulmonary artery banding in infancy to protect the pulmonary vasculature from excessive blood flow and development of pulmonary vascular disease. Patients were referred for corrective surgery when older than 3-4 years. Corrective surgery can be performed even in early infancy, in several ways. A single Dacron patch can be used to close the atrial and ventricular septal defect. The right and left parts of the common ATRIOVENTRICULAR valve are then resuspended from the patch. A 2-patch technique also may be used. Severe and irreversible pulmonary vascular disease is a contraindication to corrective surgery, and these children may be referred for cardiopulmonary transplantation. Diet

For infants in CHF, discretion with fluid intake and salt use is encouraged.

Activity

Rest during feeding is encouraged since one manifestation of dyspnea in these infants is the inability to feed. Generally, the child limits activity without encouragement.

Medication

Digitalis and diuretics are used to control the volume overload encountered in these patients until palliative or corrective surgery can be undertaken.

Diuretics

These agents are used to decrease volume overload.

Follow-up

Further Inpatient Care

Postoperative recovery requires 5-10 days of hospitalization, depending upon the condition of the child prior to surgery and whether palliative or complete correction is undertaken. With palliation (ie, pulmonary artery banding), the presurgical condition of volume overload still must be regulated. With complete correction, recovery generally is uneventful.

Further Outpatient Care

Continued observation is needed with regularly scheduled echocardiography in order to assess the integrity of the ATRIOVENTRICULAR valvular reconstruction. This area is prone to development of valvular insufficiency that may require further intervention as the child grows older.

Inpatient & Outpatient Medications

Digitalis: This agent provides myocardial support during the postoperative period and can be discontinued after 2-3 years.

Diuretics: Generally, furosemide is prescribed for several months after repair in order to right volume overload; it is discontinued once euvolemia is reached.

Deterrence/Prevention

The current limited knowledge of the genetic abnormalities that predispose to the formation of the endocardial cushion defect can be expanded greatly with current advances in the Human Genome Project. As the knowledge base expands, prenatal detection and possibly treatment may be possible in the future.

Complications

Since synthetic material is used to repair the atrial and ventricular septal defect, the child is at risk of infection. Other potential complications include complete heart block, ventricular arrhythmia, and Atrioventricular valve stenosis and/or insufficiency.

Prognosis

The long-term results of surgical correction for this malformation depend upon the degree of preoperative pulmonary vascular disease and upon the amount of residual Atrioventricular valve regurgitation. If the pulmonary vasculature is protected and the amount of valvular regurgitation is reduced substantially, prognosis is excellent. When severe pulmonary vascular disease is present preoperatively, morbidity and mortality rates are high. Complete heart block and arrhythmias may occur after correction, and their incidence increases with age. As the patient grows older, mitral valve replacement may be needed.

The surgical mortality rate in patients with partial endocardial cushion defects is 0-6%, while that for the complete defect ranges from 3-10%.

Patient Education

Parents must be instructed to ensure that antibiotic prophylaxis for dental procedures is instituted for the child. Excellent dental hygiene for the child is imperative.

Miscellaneous

Medicolegal Pitfalls

A candid discussion must take place with the parents of these children addressing all the potential operative complications with their implications for the child in the future. The issue of future mitral valve replacement should be covered with them before the initial operative intervention. The risk of endocarditis, cardiac arrhythmia, and long-term pulmonary complications must be covered.

 

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