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.

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.

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.

If untreated, severe symptomatic aortic stenosis carries a poor prognosis with a 2-year mortality rate of 50-60% and a 3-year survival rate of less than 30%. Prognosis after aortic valve replacement for people who are younger than 65 is about five years less than that of the general population; for people older than 65 it is about the same.

In Heyde's syndrome, aortic stenosis is associated with gastrointestinal bleeding due to angiodysplasia of the colon. Recent research has shown that the stenosis causes a form of von Willebrand disease by breaking down its associated coagulation factor (factor VIII-associated antigen, also called von Willebrand factor), due to increased turbulence around the stenotic valve.

The epidemiology of pulmonary valve stenosis can be summed up by the congenital aspect which is the majority of cases, in broad terms PVS is rare in the general population.

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.

Tetralogy of Fallot occurs approximately 400 times per million live births and accounts for 7 to 10% of all congenital heart abnormalities.

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.

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.

In a retrospective analysis of over 1,300 newborns (born between 1996 and 2006) from 24 children’s hospitals in the United States, researchers at Cincinnati Children’s Hospital in Ohio found that babies with HLHS were more likely to be born in summer months, suggesting that seasonality and environmental factors may play a significant role in causation.

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.

Presence of a cystic hygroma increases the risk of HLHS in a fetus.

Its cause is thought to be due to environmental or genetic factors or a combination. It is associated with chromosome 22 deletions and DiGeorge syndrome.

Specific genetic associations include:

- JAG1

- NKX2-5

- ZFPM2

- VEGF

Embryology studies show that it is a result of anterior malalignment of the aorticopulmonary septum, resulting in the clinical combination of a VSD, pulmonary stenosis, and an overriding aorta. Right ventricular hypertrophy develops progressively from resistance to blood flow through the right ventricular outflow tract.

A left ventricular outflow tract obstruction (LVOTO) may be due to a defect in the aortic valve, or a defect located at the subvalvar or supravalvar level.

- Aortic valve stenosis

- Supravalvar aortic stenosis

- Coarctation of the aorta

- Hypoplastic left heart syndrome

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.

The pathophysiology of pulmonary valve stenosis consists of the valve leaflets becoming too thick (therefore not separate one from another), which can cause high pulmonary pressure, and pulmonary hypertension. This however, does not mean the cause is always congenital.

The left ventricle can be changed physically, these changes are a direct result of right ventricular hypertrophy. Once the obstruction is subdued, it (the left ventricle) can return to normal.

The mitral valve apparatus comprises two valve leaflets, the mitral valve annulus, which forms a ring around the valve leaflets, and the papillary muscles, which tether the valve leaflets to the left ventricle and prevent them from prolapsing into the left atrium. The "chordae tendineae" are also present and connect the valve leaflets to the papillary muscles. Dysfunction of any of these portions of the mitral valve apparatus can cause regurgitation.

The most common cause of MI in developing countries is mitral valve prolapse (MVP). and is the most common cause of primary mitral regurgitation in the United States, causing about 50% of cases. Myxomatous degeneration of the mitral valve is more common in women as well as with advancing age, which causes a stretching of the leaflets of the valve and the chordae tendineae. Such elongation prevents the valve leaflets from fully coming together when the valve closes, causing the valve leaflets to prolapse into the left atrium, thereby causing MI.

Ischemic heart disease causes MI by the combination of ischemic dysfunction of the papillary muscles, and the dilatation of the left ventricle. This can lead to the subsequent displacement of the papillary muscles and the dilatation of the mitral valve annulus.

Rheumatic fever and Marfan's syndrome are other typical causes. MI and mitral valve prolapse are also common in Ehlers Danlos Syndrome.

Secondary mitral insufficiency is due to the dilatation of the left ventricle that causes stretching of the mitral valve annulus and displacement of the papillary muscles. This dilatation of the left ventricle can be due to any cause of dilated cardiomyopathy including aortic insufficiency, nonischemic dilated cardiomyopathy, and Noncompaction cardiomyopathy. Because the papillary muscles, chordae, and valve leaflets are usually normal in such conditions, it is also called functional mitral insufficiency.

Acute MI is most often caused by endocarditis, mainly "S. aureus". Rupture or dysfunction of the papillary muscle are also common causes in acute cases, dysfunction, which can include mitral valve prolapse.

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.

Known environmental factors include certain infections during pregnancy such as Rubella, drugs (alcohol, hydantoin, lithium and thalidomide) and maternal illness (diabetes mellitus, phenylketonuria, and systemic lupus erythematosus).

Being overweight or obese increases the risk of congenital heart disease. Additionally, as maternal obesity increases, the risk of heart defects also increases. A distinct physiological mechanism has not been identified to explain the link between maternal obesity and CHD, but both prepregnancy folate deficiency and diabetes have been implicated in some studies.

A right ventricular outflow tract obstruction (RVOTO) may be due to a defect in the pulmonic valve, the supravalvar region, the infundibulum, or the pulmonary artery.

- Pulmonary atresia

- Pulmonary valve stenosis

- Hypoplastic right heart syndrome

- Tetralogy of Fallot

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.

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.

As Lutembacher's syndrome is known for ASD and MS, most of the symptoms experienced will be associated with ASD and MS. For most people, they will remain asymptomatic (experience no symptoms) but when symptoms are shown, they are due mainly to ASD and will vary depending on the size of the hole in the atria. If the patient has a large ASD, pulmonary congestion (blood or fluid buildup in the lungs) will happen later but if the patient has a small ASD, symptoms will appear early in the disorder. In general, unless the ASD and mitral stenosis causing Lutembacher's syndrome is severe, symptoms may not appear until the second and third decade of the patient's life. As many of the symptoms are asymptomic and may not appear until later in life, the duration or frequency of the symptoms varies. For symptoms such as palipitations, ventricular overload, heart failure, and pulmonary congenstion, these symptoms may be sudden and not that frequent as they are very severe symptoms. For symptoms such as loud mitral S1, pulmonary S2, mid-diastolic murmur, fatigue, reduced exercise tolerance, weight gain, ankle edema, and right upper quadrant pain, and ascities, these symptoms may be less frequent and severe; their duration may be only a few seconds, minutes, or even months.