Bicuspid aortic valves are the most common cardiac valvular anomaly, occurring in 1–2% of the general population. It is twice as common in males as in females.

Bicuspid aortic valve is a heritable condition, with a demonstrated association with mutations in the NOTCH1 gene. Its heritability (formula_1) is as high as 89%. Both familial clustering and isolated valve defects have been documented. The incidence of bicuspid aortic valve can be as high as 10% in families affected with the valve problem..Recent studies suggest that BAV is an autosomal dominant condition with incomplete penetrance. Other congenital heart defects are associated with bicuspid aortic valve at various frequencies, including coarctation of the aorta.

Individuals with MVP are at higher risk of bacterial infection of the heart, called infective endocarditis. This risk is approximately three- to eightfold the risk of infective endocarditis in the general population. Until 2007, the American Heart Association recommended prescribing antibiotics before invasive procedures, including those in dental surgery. Thereafter, they concluded that "prophylaxis for dental procedures should be recommended only for patients with underlying cardiac conditions associated with the highest risk of adverse outcome from infective endocarditis."

Many organisms responsible for endocarditis are slow-growing and may not be easily identified on routine blood cultures (these fastidious organisms require special culture media to grow). These include the HACEK organisms, which are part of the normal oropharyngeal flora and are responsible for perhaps 5 to 10% of infective endocarditis affecting native valves. It is important when considering endocarditis to keep these organisms in mind.

The following table includes the main types of valvular stenosis and regurgitation. Major types of valvular heart disease not included in the table include mitral valve prolapse, rheumatic heart disease and endocarditis.

Inflammation of the heart valves due to any cause is called valvular endocarditis; this is usually due to bacterial infection but may also be due to cancer (marantic endocarditis), certain autoimmune conditions (Libman-Sacks endocarditis, seen in systemic lupus erythematosus) and hypereosinophilic syndrome (Loeffler endocarditis). Certain medications have been associated with valvular heart disease, most prominently ergotamine derivatives pergolide and cabergoline.

Valvular heart disease resulting from rheumatic fever is referred to as "rheumatic heart disease". Damage to the heart valves follows infection with beta-hemolytic bacteria, such as typically of the respiratory tract. Pathogenesis is dependent on cross reaction of M proteins produced by bacteria with the myocardium. This results in generalized inflammation in the heart, this manifests in the mitral valve as vegetations, and thickening or fusion of the leaflets, leading to a severely compromised buttonhole valve.

Rheumatic heart disease typically only involves the mitral valve (70% of cases), though in some cases the aortic and mitral valves are both involved (25%). Involvement of other heart valves without damage to the mitral are exceedingly rare.

While developed countries once had a significant burden of rheumatic fever and rheumatic heart disease, medical advances and improved social conditions have dramatically reduced their incidence. Many developing countries, as well as indigenous populations within developed countries, still carry a significant burden of rheumatic fever and rheumatic heart disease and there has been a resurgence in efforts to eradicate the diseases in these populations.

Prior to the strict criteria for the diagnosis of mitral valve prolapse, as described above, the incidence of mitral valve prolapse in the general population varied greatly. Some studies estimated the incidence of mitral valve prolapse at 5 to 15 percent or even higher. One study suggested MVP in up to 35% of healthy teenagers.

Recent elucidation of mitral valve anatomy and the development of three-dimensional echocardiography have resulted in improved diagnostic criteria, and the true prevalence of MVP based on these criteria is estimated at 2-3%. As part of the Framingham Heart Study, for example, the prevalence of mitral valve prolapse in Framingham, MA was estimated at 2.4%. There was a near-even split between classic and nonclassic MVP, with no significant age or sex discrimination. MVP is observed in 7% of autopsies in the United States.

Bicuspid aortic valve abnormality is seen in 1 to 2 percent of all live births. It is associated with a number of mutations affecting Notch signalling pathway.

There is no exact mechanism for Lutembacher's syndrome but instead a combination of disorders as the result of Atrial septal defect (ASD) and/or Mitral valve stenosis.

Lutembacher is caused indirectly as the result of heart damage or disorders and not something that is necessarily infectious. Lutembacher's syndrome is caused by either birth defects where the heart fails to close all holes in the walls between the atria or from an episode of rheumatic fever where damage is done to the heart valves such as the mitral valve and resultant in an opening of heart wall between atria. With Lutembacher's syndrome, a fetus or infant is usually seen to have a hole in their heart wall (interatrial) separating their right and left atria. Normally during fetal development, blood bypasses the lungs and is oxygenated from the placenta. Blood passes from the umbilical cord and flows into the left atrium through an opening called the foramen ovale; the formaen ovale is a hole between the two atria. Once a baby is born and the lungs begin to fill with air and the blood flow of the heart changes, a tissue flap (somewhat like a trap door) called the septum primium closes the foramen ovale or hole between the two atria and becomes part of the atrial wall. The failure of the hole between the two atria to close after birth leads to a disorder called ASD primium. The most common problems with an opening found in the heart with Lutembacher's syndrome is Ostium Secundum. Ostium Secundum is a hole that is found within the flap of tissue (septum primium) that will eventually close the hole between the two atria after birth. With either type of ASD, ASD will usually cause the blood flow from the right atrium to skip going to the right ventricle and instead flow to the left atrium. If mitral stenosis (the hardening of flap of tissue known as a valve which opens and closes between the left atrium and ventricle to control blood flow) is also present, blood will flow into the right atrium through the hole between the atria wall instead of flowing into the left ventricle and systemic circulation. Eventually this leads to other problems such as the right ventricle failing and a reduced blood flow to the left ventricle.

In addition to the ASD, acquired MS can be present either from an episode of rheumatic fever (the mother has or had rheumatic fever during the pregnancy) or the child being born with the disorder (congenital MS). With the combination of both ASD and MS, the heart can be under severe strain as it tries to move blood throughout the heart and lungs.

Significant mitral valve regurgitation has a prevalence of approximately 2% of the population, affecting males and females equally. It is one of the two most common valvular heart diseases in the elderly.

There are several potential challenges associated with routine screening for HCM in the United States. First, the U.S. athlete population of 15 million is almost twice as large as Italy's estimated athlete population. Second, these events are rare, with fewer than 100 deaths in the U.S. due to HCM in competitive athletes per year, or about 1 death per 220,000 athletes. Lastly, genetic testing would provide a definitive diagnosis; however, due to the numerous HCM-causing mutations, this method of screening is complex and is not cost-effective. Therefore, genetic testing in the United States is limited to individuals who exhibit clear symptoms of HCM, and their family members. This ensures that the test is not wasted on detecting other causes of ventricular hypertrophy (due to its low sensitivity), and that family members of the individual are educated on the potential risk of being carriers of the mutant gene(s).

Aortic stenosis in the Rottweiler appears to be true subvalvular aortic stenosis (SAS), similar to that in the Newfoundland dog, as opposed to the valvular form (seen more in boxer dogs) or the supravalvular form sometimes seen in people.

Almost all cases of mitral stenosis are due to disease in the heart secondary to rheumatic fever and the consequent rheumatic heart disease. Uncommon causes of mitral stenosis are calcification of the mitral valve leaflets, and as a form of congenital heart disease. However, there are primary causes of mitral stenosis that emanate from a cleft mitral valve. It is the most common valvular heart disease in pregnancy.

Other causes include infective endocarditis where the vegetations may favor increase risk of stenosis. Other rare causes include mitral annular calcification, endomyocardial fibroelastosis, malignant carcinoid syndrome, systemic lupus erythematosus, whipple disease, fabry disease, and rheumatoid arthritis. hurler' disease, hunter's disease, amyloidosis.

The natural history of mitral stenosis secondary to rheumatic fever (the most common cause) is an asymptomatic latent phase following the initial episode of rheumatic fever. This latent period lasts an average of 16.3 ± 5.2 years. Once symptoms of mitral stenosis begin to develop, progression to severe disability takes 9.2 ± 4.3 years.

In individuals having been offered mitral valve surgery but refused, "survival" with medical therapy alone was 44 ± 6% at 5 years, and 32 ± 8% at 10 years after they were offered correction.

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.

Indications for surgery for chronic MI include signs of left ventricular dysfunction with ejection fraction less than 60%, severe pulmonary hypertension with pulmonary artery systolic pressure greater than 50 mmHg at rest or 60 mmHg during activity, and new onset atrial fibrillation.

Canadian genetic testing guidelines and recommendations for individuals diagnosed with HCM are as follows:

- The main purpose of genetic testing is for screening family members.

- According to the results, at-risk relatives may be encouraged to undergo extensive testing.

- Genetic testing is not meant for confirming a diagnosis.

- If the diagnosed individual has no relatives that are at risk, then genetic testing is not required.

- Genetic testing is not intended for risk assessment or treatment decisions.

- Evidence only supports clinical testing in predicting the progression and risk of developing complications of HCM.

For individuals "suspected" of having HCM:

- Genetic testing is not recommended for determining other causes of left ventricular hypertrophy (such as "athlete's heart", hypertension, and cardiac amyloidosis).

- HCM may be differentiated from other hypertrophy-causing conditions using clinical history and clinical testing.

The Canadian Cardiovascular Society (CCS) recommends surgical intervention for these indications:

- Limited exercise capacity (NYHA III-IV)

- Increasing heart size (cardiothoracic ratio greater than 65%)

- Important cyanosis (resting oxygen saturation less than 90% - level B)

- Severe tricuspid regurgitation with symptoms

- Transient ischemic attack or stroke

The CCS further recommends patients who require operation for Ebstein's anomaly should be operated on by congenital heart surgeons who have substantial specific experience and success with this operation. Every effort should be made to preserve the native tricuspid valve.

Canine subvalvular aortic stenosis (SAS) is an abnormal, congenital heart murmur caused by subaortic stenosis (SAS). There is a high incidence of this condition among Rottweiler dogs.

There is very good evidence that it is heritable, passed on from generation to generation genetically. This genetic trait is what is called polygenic, so that the inheritance is complex. An animal might have the genes for SAS, yet have no actual sign of SAS. Also, an animal might have signs of subaortic stenosis, and yet offspring with signs of SAS may not be seen for a couple of generations. Any animal that has subaortic stenosis should not be bred, because they can definitely pass the defect on to future offspring. There is some controversy as to whether the parents of an animal with SAS should be bred again.

Heart murmurs are graded on a scale of 1 to 6, with one being very mild and six being very serious, with some animals dying before they reach this high stage due to a sudden leap in the grade or through long-term slowing down. Murmurs can exist due to a large number of heart problems (infection, trauma, anemia, etc.; some are innocent, with no cardiac pathology. Tests such as chest X-rays, echocardiography, and electrocardiography can be performed to evaluate the severity of the situation

The condition is usually detected during puppy visits to the veterinarian by hearing a heart murmur during physical examination. A heart murmur is the abnormal sound of blood rushing through one of the heart valves. Instead of just the heartbeat, a whistle of blood flow through a narrowed opening is heard. The puppy will most likely appear normal in all other respects. There is a possibility that the murmur may come and go, or it may develop slowly; this can be determined by frequent checks of a puppy's heart during its first few months. The chance for long-term survival of SAS is low.

Puppies and dogs diagnosed with subaortic stenosis can suffer from heart failure and sudden death. If a dog with SAS develops heart failure, medications can be prescribed to alleviate the clinical signs (sudden/strong lethargicism, continuous heavy panting, rise in temperature etc.)

The OFA has established a Congenital Heart Registry whose guidelines were established by veterinary cardiologists. A dog which auscultates normally at 12 months of age is considered to be free of congenital heart disease; upon confirmation of this, the OFA will issue a certificate.

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.

Ebstein's anomaly is a congenital heart defect in which the septal and posterior leaflets of the tricuspid valve are displaced towards the apex of the right ventricle of the heart. Its classified as a Critical congenital heart defect accounting for <1% of all congenital heart defects presenting in ≈1 per 200,000 live births.

Tricuspid valve stenosis itself usually doesn't require treatment. If stenosis is mild, monitoring the condition closely suffices. However, severe stenosis, or damage to other valves in the heart, may require surgical repair or replacement.

The treatment is usually by surgery (tricuspid valve replacement) or percutaneous balloon valvuloplasty. The resultant tricuspid regurgitation from percutaneous treatment is better tolerated than the insufficiency occurring during mitral valvuloplasty.

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

When treated early, that is, before the onset of pulmonary hypertension, a good outcome is possible in patients with Shone’s syndrome. However, other surgical methods can be employed depending upon the patient’s medical background. The single most important determinant of poor outcome during the surgical management of patients with Shone's syndrome is the degree of involvement of the mitral valve and the presence of secondary pulmonary hypertension.

A mild diastolic murmur can be heard during auscultation caused by the blood flow through the stenotic valve. It is best heard over the left sternal border with rumbling character and tricuspid opening snap with wide-splitting S1. It may increase in intensity with inspiration (Carvallo's sign). The diagnosis will typically be confirmed by an echocardiograph, which will also allow the physician to assess its severity.

Shone's syndrome (also called Shone's Complex, Shone's Anomaly)is a rare congenital heart disease described by Shone in 1963. In the complete form, four left-sided defects are present:

- Supravalvular mitral membrane (SVMM)

- Parachute mitral valve

- Subaortic stenosis (membranous or muscular)

- Coarctation of the aorta

Of these four defects, supravalvular mitral membrane (SVMM) is the first to occur, and triggers the development of the other three defects. Partial complexes, or form fruste, have also been described. The definition is often expanded to include lesions of the left side of the heart not originally ascribed to Shone's syndrome, including mitral and aortic valvular lesions and supravalvular aortic stenosis.

The term parachute mitral valve stems from the morphological appearance of the valve; that is to say, the mitral valve leaflets appear as the canopy of the parachute, the chordae as the strings and the papillary muscle as the harness.