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.

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.

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.

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.

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.

Since the valve does not open properly in aortic stenosis, there is a decrease in the forward movement of blood into the aorta. Fetal aortic stenosis impairs left ventricular development, which can lead to hypoplastic left heart syndrome. If untreated, HLHS is lethal, as a result of the inability of the left heart to pump enough blood to sustain normal organ function. In fetal life, this is condition is manageable because the ductus arteriosus acts as a bypass, and supports the delivery of oxygenated blood to the systemic circulation. However, the ductus arteriosus closes during the first few days of life, resulting in systemic circulation failure in babies born with aortic valve stenosis.

Hypertension is defined when a patient's blood pressure in the arm exceeds 140/90 mmHg under normal conditions. This is a severe problem for the heart and can cause many other complications. In a study of 120 coarctation repair recipients done in Groningen, The Netherlands, twenty-nine patients (25%) experienced hypertension in the later years of life due to the repair. While hypertension has many different factors that lead to this stage of blood pressure, people who have had a coarctation repair — regardless of the age at which the operation was performed — are at much higher risk than the general public of hypertension later in life. Undetected chronic hypertension can lead to sudden death among coarctation repair patients, at higher rates as time progresses.

Angioplasty is a procedure done to dilate an abnormally narrow section of a blood vessel to allow better blood flow. This is done in a cardiac catheterization laboratory. Typically taking two to three hours, the procedure may take longer but usually patients are able to leave the hospital the same day. After a coarctation repair 20-60% of infant patients may experience reoccurring stenosis at the site of the original operation. This can be fixed by either another coarctectomy.

Coronary artery disease (CAD) is a major issue for patients who have undergone a coarctation repair. Many years after the procedure is done, heart disease not only has an increased chance of affecting coarctation patients, but also progresses through the levels of severity at an alarmingly increased rate. In a study conducted by Mare Cohen, MD, et al., one fourth of the patients who experienced a coarctation died of heart disease, some at a relatively young age.

Clinical criteria are used in most studies when defining recurrence of coarctation (recoarctation) when blood pressure is at a difference of >20 mmHg between the lower and upper limbs. This procedure is most common in infant patients and is uncommon in adult patients. In a study conducted by Koller et al., 10.8% of infant patients underwent recoarctations at less than two years of age while another 3.1% of older children received a recoarctation.

People who have had a coarctation of the aorta are likely to have bicuspid aortic valve disease. Between 20% and 85% of patients are affected with this disease. Bicuspid aortic valve disease is a big contributor to cardiac failure, which in turn makes up roughly 20% of late deaths to coarctation patients.

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.

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 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

Unfortunately, coarctations can not be prevented because they are usually present at birth. The best thing for patients who are affected by coarctations is early detection. Some signs that can lead to a coarctation have been linked to pathologies such as Turner syndrome, bicuspid aortic valve, and other family heart conditions.

Supravalvular aortic stenosis is associated with genetic damage at the Elastin gene locus on chromosome 7q11.23. Fluorescent in situ hybridisation techniques have revealed that 96% of patients with Williams syndrome, where supravalvular aortic stenosis is characteristic, have a hemizygous deletion of the Elastin gene. Further studies have shown that patients with less extensive deletions featuring the Elastin gene also tend to develop supravalvular aortic stenosis

Fetal aortic stenosis is a disorder that occurs when the fetus’ aortic valve does not fully open during development. The aortic valve is a one way valve that is located between the left ventricle and the aorta, keeping blood from leaking back into the ventricle. It has three leaflets that separate when the ventricle contracts to allow blood to move from the ventricle to the aorta. These leaflets come together when the ventricle relaxes.

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.

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.

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

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.

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.

When pulmonic stenosis (PS) is present, resistance to blood flow causes right ventricular hypertrophy. If right ventricular failure develops, right atrial pressure will increase, and this may result in a persistent opening of the foramen ovale, shunting of unoxygenated blood from the right atrium into the left atrium, and systemic cyanosis. If pulmonary stenosis is severe, congestive heart failure occurs, and systemic venous engorgement will be noted. An associated defect such as a patent ductus arteriosus partially compensates for the obstruction by shunting blood from the left ventricle to the aorta then back to the pulmonary artery (as a result of the higher pressure in the left ventricle) and back into the lungs.

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 treatment of choice is percutaneous balloon valvuloplasty and is done when a resting peak gradient is seen to be >60mm Hg or a mean >40mm Hg is observed.

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.