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Heart Valve Diseases

Heart valve disease refers to a group of conditions affecting the mobility and closure of the heart's four valves. Anatomically, the heart is divided into four chambers. Deoxygenated blood returns from the periphery of our body through the inferior and superior vena cava into the right atrium. The tricuspid valve serves as the gateway from the right atrium into the right ventricle. The pulmonic valve, in turn, regulates the flux of the blood from the right ventricle into the pulmonary arteries. Blood then enters the pulmonary circulation for oxygenation, and return to the left atrium. From the left atrium, blood transverses the mitral valve to reach the left ventricle, and ultimately is pumped to the aorta leading to our systemic circulation through the aortic valve.

Heart valve diseases arise as a result of congenital abnormalities or acquired conditions such as infections or degenerative processes, which in turn change the hemodynamic blood patterns that flow through the heart valves. These abnormalities often lead to narrowing or stenosis, or it can also lead to leakage, which is also called regurgitation. Valvular murmurs can often be picked up through auscultation, and the degree of severity is formally quantified by the use of transthoracic echocardiogram. Below is a review of the most common valvular conditions.

Aortic Valve Stenosis

Aortic stenosis occurs from a narrowing of the aortic valve, often caused by either progressive calcification of the valve or rheumatic heart disease. It is important to note that rheumatic aortic valve is often accompanied by mitral valve disease as well. There are also congenital conditions such as unicuspid and most commonly bicuspid aortic valve which changes the properties of the valve and predisposes it to early narrowing.

The natural history of aortic stenosis is characterized by asymptomatic progression until the valve area is narrowed enough to elicit the classical symptoms of angina, syncope, and exertional dyspnea. Severe aortic stenosis is suggested by an aortic jet velocity greater than 4 m/s, a mean transvalvular gradient greater than 50 mmHg, and an aortic valve area of less than 1 cm2. Severe aortic stenosis warrants surgical intervention with aortic valve replacement. In Heyde's syndrome, a subgroup of patients with aortic stenosis are also found to have concomitant gastrointestinal bleeding. This is thought to be due to defective von Willebrand factors from disruptive passage across the narrow valve in the background of arteriovenous malformations.

Aortic Valve Insufficiency

Aortic valve insufficiency may occur from an abnormality of the aortic valve or a dilatation of the aortic root, causing diastolic regurgitant flow from the aorta back into the left ventricle. This backflow of blood causes increased left ventricular pressure, dilatation, and hypertrophy. Causes for this dilatation include bicuspid aortic valve, aortic aneurysms, and Marfan's syndrome. Of importance, patients with aortic insufficiency who develop severe left ventricular dilatation are at increased risk of sudden cardiac death (SCD), and serial annual echocardiograms are warranted in order to monitor the progression of disease. Medical therapy with afterload reducers such as nifedipine or angiotensin-converting enzyme (ACE) inhibitors can delay the progression of aortic insufficiency. Surgical replacement of the aortic valve should be considered when the left ventricular end-systolic diameter reaches 55 mm or if the ejection fraction is less than 60 percent.

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