Clinical Example:  Heart Sounds and Valve Disorders

The heart sounds are due to the closing of the valves.  As the valve leaflets (cusps) snap shut, vibations occur in the valves and surrounding structures, creating sounds that can be heard through a stethoscope placed on the chest. 

The first heart sound, S1 or "lub", is due to the closing of the AV valves, which occurs at the beginning of systole (when the ventricles begin to contract).  The second heart sound, S2 or "dup", is due to the closing of the aortic and pulmonary valves, and occurs at the beginning of diastole (when the ventricles begin to relax).

Valve disorders occur when there is damage to the valve leaflets or to the chordae tendineae.  There are two general kinds of valve disorders:

• stenosis The valve opening is narrowed, causing resistance to flow through the valve when it is open.


• insufficiency The doesn't close properly, causing regurgitation of blood.

Both types of valve disorders cause turbulent flow of blood, which makes a noise called a murmur. A useful exercise in studying the cardiac cycle is to determine whether a murmur due to a defective valve should be systolic or diastolic.  Be sure you can fill out the table below.

Valve disorders can be diagnosed by careful listening to determine the timing and location of a murmur.  This technique is referred to as auscultation.  The figure shows the locations that are best for hearing listening to each particular valve. Note that the positions for best listening to the aortic and pulmonary valves are opposite to what you might think they would be based on which side of the heart the vessel leaves. As we discuss in lecture, echocardiography is an extremely useful modern technique that uses ultrasound to image the heart and valves.

For fun, you can listen to different types of heart sounds by going to this page from the UW Department of Medicine.

Clinical Example: Transcatheter Aortic Valve Replacement (TAVR) for the Treatment of Aortic Stenosis

Aortic stenosis is a narrowing of the aortic valve.  In the United States, most patients with aortic stenosis have a degenerative disease in which the valve stiffens and calcium deposits form on the valve leaflets.  Aortic stenosis can also be caused by a congenital malformation where there are two valve leaflets (bicuspid aortic valve) instead of the normal three (tricuspid aortic valve).  Aortic stenosis may also occur as a consequence of rheumatic fever, but this is more common in the developing world.

Aortic stenosis causes symptoms when the narrowing of the valve starts to affect blood flow. A patient with severe aortic stenosis may experience dyspnea (shortness of breath) upon exertion, dizziness or syncope (fainting), and angina (chest pain).  These symptoms are not specific to valve disorders, but are general symptoms that occur in heart failure or coronary artery disease.

Severe aortic stenosis that causes symptoms needs to be surgically treated with valve replacement, because without treatment, symptoms worsen and mortality is quite high.  Valve replacement was traditionally done by open heart surgery, but in the last 20 years, minimally invasive procedures have been developed.  In transcatheter aortic valve replacement (TAVR), a catheter is used to guide an expandable prosthetic (replacement) valve into position.  Usually, a balloon is inflated to cause the prosthetic valve to expand.  The prosthetic valve crushes the damaged valve against the walls of the aorta, and the tissue of the damaged, replaced valve serves to hold the prosthetic valve in place.  The femoral artery is often used as an entry point for the catheter because it is easily accessed through the skin of the upper thigh.