When there are holes in the septum that divide the four chambers of the heart the oxygen-rich blood and oxygen-poor blood mix this creates more stress on the heart to pump blood to where oxygen is needed. As a result, you get enlargement of the heart, heart failure (being unable to adequately supply body with needed oxygen, pulmonary hypertension, and pneumonia.

The development of pulmonary hypertension is very serious. And this because the left ventricle is weakened due to its overuse. When this happens, the pressure backs up into the pulmonary veins and the lungs. This type of damage is irreversible which is why immediate treatment is recommended after diagnosis.

Treatment is surgical and involves closure of the atrial and ventricular septal defects and restoration of a competent left AV valve as far as is possible. Open surgical procedures require a heart-lung machine and are done with a median sternotomy. Surgical mortality for uncomplicated ostium primum defects in experienced centers is 2%; for uncomplicated cases of complete atrioventricular canal, 4% or less. Certain complications such as tetralogy of Fallot or highly unbalanced flow across the common AV valve can increase risk significantly.

Infants born with AVSD are generally in sufficient health to not require immediate corrective surgery. If surgery is not required immediately after birth, the newborn will be closely monitored for the next several months, and the operation held-off until the first signs of lung distress or heart failure. This gives the infant time to grow, increasing the size of, and thereby the ease of operation on, the heart, as well as the ease of recovery. Infants will generally require surgery within three to six months, however, they may be able to go up to two years before the operation becomes necessary, depending on the severity of the defect.

A device, known as the Amplatzer muscular VSD occluder, may be used to close certain VSDs. It was initially approved in 2009. It appears to work well and be safe. The cost is also lower than having open heart surgery. The device is placed through a small incision in the groin.

The Amplatzer septal occluder was shown to have full closure of the ventricular defect within the 24 hours of placement. It has a low risk of embolism after implantation. Some tricuspid valve regurgitation was shown after the procedure that could possibly be due from the right ventricular disc. There have been some reports that the Amplatzer septal occluder may cause life-threatening erosion of the tissue inside the heart. This occurs in one percent of people implanted with the device and requires immediate open-heart surgery. This erosion occurs due to improper sizing of the device resulting with it being too large for the defect, causing rubbing of the septal tissue and erosion.

Most cases do not need treatment and heal at the first years of life. Treatment is either conservative or surgical. Smaller congenital VSDs often close on their own, as the heart grows, and in such cases may be treated conservatively.

Some cases may necessitate surgical intervention, i.e. with the following indications:

1. Failure of congestive cardiac failure to respond to medications

2. VSD with pulmonic stenosis

3. Large VSD with pulmonary hypertension

4. VSD with aortic regurgitation

For the surgical procedure, a heart-lung machine is required and a median sternotomy is performed. Percutaneous endovascular procedures are less invasive and can be done on a beating heart, but are only suitable for certain patients. Repair of most VSDs is complicated by the fact that the conducting system of the heart is in the immediate vicinity.

Ventricular septum defect in infants is initially treated medically with cardiac glycosides (e.g., digoxin 10-20 µg/kg per day), loop diuretics (e.g., furosemide 1–3 mg/kg per day) and ACE inhibitors (e.g., captopril 0.5–2 mg/kg per day).

Heart septal defect refers to a congenital heart defect of one of the septa of the heart.

- Atrial septal defect

- Atrioventricular septal defect

- Ventricular septal defect

Although aortopulmonary septal defects are defects of the aorticopulmonary septum, which is not technically part of the heart, they are sometimes grouped with the heart septal defects.

Tricuspid atresia is a form of congenital heart disease whereby there is a complete absence of the tricuspid valve. Therefore, there is an absence of right atrioventricular connection. This leads to a hypoplastic (undersized) or absent right ventricle.

This defect is contracted during prenatal development, when the heart does not finish developing. It causes the heart to be unable to properly oxygenate the rest of the blood in the body. Because of this, the body does not have enough oxygen to live, so other defects must occur to maintain blood flow.

Because of the lack of an A-V connection, an atrial septal defect (ASD) must be present to fill the left ventricle with blood. Also, since there is a lack of a right ventricle there must be a way to pump blood into the pulmonary arteries, and this is accomplished by a ventricular septal defect (VSD).

The causes of Tricupsid atresia are unknown.

An atrial septal defect (ASD) and a ventricular septal defect (VSD) must both be present to maintain blood flow-from the right atrium, the blood must flow through the ASD to the left atrium to the left ventricle and through the VSD to the right ventricle to allow access to the lungs

A defect in the ostium primum is occasionally classified as an atrial septal defect, but it is more commonly classified as an atrioventricular septal defect

The ostium primum atrial septal defect (also known as an endocardial cushion defect) is a defect in the atrial septum at the level of the tricuspid and mitral valves. This is sometimes known as an endocardial cushion defect because it often involves the endocardial cushion, which is the portion of the heart where the atrial septum meets the ventricular septum and the mitral valve meets the tricuspid valve.

Endocardial cushion defects are associated with abnormalities of the atrioventricular valves (the mitral valve and the tricuspid valve). These include the cleft mitral valve, and the single atrioventricular valve (a single large, deformed valve that flows into both the right ventricle and the left ventricle).

Endocardial cushion defects are the most common congenital heart defect that is associated with Down's syndrome.

Cor triatriatum (or triatrial heart) is a congenital heart defect where the left atrium (cor triatriatum sinistrum) or right atrium (cor triatriatum dextrum) is subdivided by a thin membrane, resulting in three atrial chambers (hence the name).

Cor triatriatum represents 0.1% of all congenital cardiac malformations and may be associated with other cardiac defects in as many as 50% of cases. The membrane may be complete or may contain one or more fenestrations of varying size.

Cor triatrium sinistrum is more common. In this defect there is typically a proximal chamber that receives the pulmonic veins and a distal (true) chamber located more anteriorly where it empties into the mitral valve. The membrane that separates the atrium into two parts varies significantly in size and shape. It may appear similar to a diaphragm or be funnel-shaped, bandlike, entirely intact (imperforate) or contain one or more openings (fenestrations) ranging from small, restrictive-type to large and widely open.

In the pediatric population, this anomaly may be associated with major congenital cardiac lesions such as tetralogy of Fallot, double outlet right ventricle, coarctation of the aorta, partial anomalous pulmonary venous connection, persistent left superior vena cava with unroofed coronary sinus, ventricular septal defect, atrioventricular septal (endocardial cushion) defect, and common atrioventricular canal. Rarely, asplenia or polysplenia has been reported in these patients.

In the adult, cor triatriatum is frequently an isolated finding.

Cor triatriatum dextrum is extremely rare and results from the complete persistence of the right sinus valve of the embryonic heart. The membrane divides the right atrium into a proximal (upper) and a distal (lower) chamber. The upper chamber receives the venous blood from both vena cavae and the lower chamber is in contact with the tricuspid valve and the right atrial appendage.

The natural history of this defect depends on the size of the communicating orifice between the upper and lower atrial chambers. If the communicating orifice is small, the patient is critically ill and may succumb at a young age (usually during infancy) to congestive heart failure and pulmonary edema. If the connection is larger, patients may present in childhood or young adulthood with a clinical picture similar to that of mitral stenosis. Cor triatriatum may also be an incidental finding when it is nonobstructive.

The disorder can be treated surgically by removing the membrane dividing the atrium.

An acyanotic heart defect, also known as non-cyanotic heart defect, is a class of congenital heart defects. In these, blood is shunted (flows) from the left side of the heart to the right side of the heart due to a structural defect (hole) in the interventricular septum. People often retain normal levels of oxyhemoglobin saturation in systemic circulation.

This term is outdated, because a person with an acyanotic heart defect may show cyanosis (turn blue due to insufficient oxygen in the blood).

Ventricular inversion, also known as atrioventricular discordance, is a condition in which the anatomic right ventricle of the heart is on the left side of the interventricular septum and the anatomic left ventricle is on the right.

Left to right shunting heart defects include:

- Ventricular septal defect (VSD) (30% of all congenital heart defects)

- Atrial septal defect (ASD)

- Atrioventricular septal defect (AVSD)

- Patent ductus arteriosus (PDA)

- Previously, Patent ductus arteriosus (PDA) was listed as acyanotic but in actuality it can be cyanotic due to pulmonary hypertension resulting from the high pressure aorta pumping blood into the pulmonary trunk, which then results in damage to the lungs which can then result in pulmonary hypertension as well as shunting of blood back to the right ventricle. This consequently results in less oxygenation of blood due to alveolar damage as well as oxygenated blood shunting back to the right side of the heart, not allowing the oxygenated blood to pass through the pulmonary vein and back to the left atrium.

- (Edit - this is called Eisenmenger's syndrome and can occur with Atrial septal defect and ventricular septal defect as well (actually more common in ASD and VSD) therefore PDA can still be listed as acyanotic as, acutely, it is)

Others:

- levo-Transposition of the great arteries (l-TGA)

Acyanotic heart defects without shunting include:

- Pulmonary stenosis (a narrowing of the pulmonary valve)

- Aortic stenosis

- Coarctation of the aorta

In PLSVC, the left brachiocephalic vein does not develop fully and the left upper limb and head & neck drain into the right atrium via the coronary sinus.

The variation, in isolation, is considered benign, but is very frequently associated with cardiac abnormalities (e.g. ventricular septal defect, atrioventricular septal defect) that have a significant mortality and morbidity. It is more frequent in patients with congenital heart defects.

CXR : decreased pulmonary blood flow and oligemic lung field

ECG : left axis deviation

In anatomy, a persistent left superior vena cava (PLSVC) is the most common variation of the thoracic venous system, is prevalent in 0.3% of the population, and an embryologic remnant that results from a failure to involute.

Recent studies suggest that cardiac resynchronization therapy can reduce the incidence of ventricular dyssynchrony and thus increase cardiac efficiency.

Heart valve dysplasia is a congenital heart defect which affects the aortic, pulmonary, mitral, and tricuspid heart valves. Dysplasia of the mitral and tricuspid valves can cause leakage of blood or stenosis.

Dysplasia of the mitral and tricuspid valves - also known as the atrioventricular (AV) valves - can appear as thickened, shortened, or notched valves. The chordae tendinae can be fused or thickened. The papillary muscles can be enlarged or atrophied. The cause is unknown, but genetics play a large role. Dogs and cats with tricuspid valve dysplasia often also have an open foramen ovale, an atrial septal defect, or inflammation of the right atrial epicardium. In dogs, tricuspid valve dysplasia can be similar to Ebstein's anomaly in humans.

Mitral valve stenosis is one of the most common congenital heart defects in cats. In dogs, it is most commonly found in Great Danes, German Shepherd Dogs, Bull Terriers, Golden Retrievers, Newfoundlands, and Mastiffs. Tricuspid valve dysplasia is most common in the Old English Sheepdog, German Shepherd Dog, Weimaraner, Labrador Retriever, Great Pyrenees, and sometimes the Papillon. It is inherited in the Labrador Retriever.

The disease and symptoms are similar to progression of acquired valve disease in older dogs. Valve leakage leads to heart enlargement, arrhythmias, and congestive heart failure. Heart valve dysplasia can be tolerated for years or progress to heart failure in the first year of life. Diagnosis is with an echocardiogram. The prognosis is poor with significant heart enlargement.

Animal studies have shown that administration of the drugs vinblastine, streptonigrin, triparano, sulfonamide, tetracycline, antihistamines, and antitumor agents to pregnant mothers have resulted in offspring born with iniencephaly. The drug clomiphene, a drug commonly used for ovulation stimulation in fertility treatments, has also been seen to be associated with iniencephaly.

Treatment is aimed at slowing the rate by correcting acidosis, correcting electrolytes (especially magnesium and calcium), cooling the patient, and antiarrhythmic medications. Occasionally pacing of the atrium at a rate higher than the JET may allow improved cardiac function by allowing atrial and ventricular synchrony.

A 1994 study at the Adolph Basser Institute of Cardiology found that amiodarone, an antiarrhythmic agent, could be used safely and relatively effectively.

JET occurring after the first six months of life is somewhat more variable, but may still be difficult to control. Treatment of non-post-operative JET is typically with antiarrhythmic medications or a cardiac catheterization with ablation (removal of affected tissue). A cardiac catheterization may be performed to isolate and ablate (burn or freeze) the source of the arrhythmia. This can be curative in the majority of cases. The use of radiofrequency energy is infrequently associated with damage to the normal conduction due to the close proximity to the AV node, the normal conduction tissue. The use of cryotherapy (cold energy) appears to be somewhat safer, and can also be effective for the treatment of JET.

Normally, the atria and the ventricles are electrically isolated, and electrical contact between them exists only at the "atrioventricular node". In all pre-excitation syndromes, at least one more conductive pathway is present. Physiologically, the normal electrical depolarization wave is delayed at the atrioventricular node to allow the atria to contract before the ventricles. However, there is no such delay in the abnormal pathway, so the electrical stimulus passes to the ventricle by this tract faster than via normal atrioventricular/bundle of His system, and the ventricles are depolarized (excited) before (pre-) normal conduction system. This creates the ventricular pacemaker type of ectopic pacemaker.

The management includes identifying and correcting electrolyte imbalances and withholding any offending medications. This condition does not require admission unless there is an associated myocardial infarction. Even though it usually does not progress to higher forms of heart block, it may require outpatient follow-up and monitoring of the ECG, especially if there is a comorbid bundle branch block. If there is a need for treatment of an unrelated condition, care should be taken not to introduce any medication that may slow AV conduction. If this is not feasible, clinicians should be very cautious when introducing any drug that may slow conduction; and regular monitoring of the ECG is indicated.

An atrioventricular fistula is a fistula between an atrium and a ventricle of the heart.

Clinically, thrills can be felt on the arm of the patient if palpated at the fistula.

Pre-excitation syndrome is an abnormal heart rhythm in which the ventricles of the heart become depolarized too early, which leads to their partial premature contraction.

Isolated first-degree heart block has no direct clinical consequences. There are no symptoms or signs associated with it. It was originally thought of as having a benign prognosis. In the Framingham Heart Study, however, the presence of a prolonged PR interval or first degree AV block doubled the risk of developing atrial fibrillation (irregular heart beat), tripled the risk of requiring an artificial pacemaker, and was associated with a small increase in mortality. This risk was proportional to the degree of PR prolongation.

A subset of individuals with the triad of first-degree heart block, right bundle branch block, and either left anterior fascicular block or left posterior fascicular block (known as trifascicular block) may be at an increased risk of progression to complete heart block.

Studies have shown that obesity of the mother increases the risk of neural tube disorders such as iniencephaly by 1.7 fold while severe obesity increases the risk by over 3 fold.