Heart Murmurs and Valvular Disease
How a Physician Suspects Particular Types of Cardiac Valve Problems
Heart murmurs are often a sign of diseased heart valves or other cardiac disease. What does a physician hear when evaluating murmurs?
Heart murmurs are abnormal heart sounds related to blood flow, generally detected by listening with a stethoscope. People with murmurs may not know about them until they have a checkup with a doctor. Once they are found, it becomes a matter of further exploration.
Normal Heart Sounds
The heart is divided into a right side and a left side. Blood returning from the body flows into the right atrium, through the tricuspid valve to the right ventricle, and through the pulmonic valve into the pulmonary arteries. After passing through the lungs, blood travels into the left atrium, through the mitral valve to the left ventricle, and through the aortic valve into the aorta. Blood is pumped to all tissues before returning to the heart once again.
Each cardiac cycle has two phases: systole and diastole.
- Systole: During the systolic phase, the ventricles contract. The mitral and tricuspid valves are pushed closed by the blood so that blood does not flow back into the atria. Instead, it travels only through the aortic and pulmonic valves.
- Diastole: The diastolic phase is when the ventricles relax and the atria contract. Blood from the atria flow into the ventricles through the mitral and tricuspid valves. Meanwhile, the aortic and pulmonic valves close.
A normal sound is produced during both phases. The closing of the mitral and tricuspid valves during systole produce one sound (S1, or "lub") and the closing of the aortic and pulmonic valves during diastole produce another (S2, or "dub"). Together, they form the two-component heartbeat sound that people are familiar with.
Physicians generally listen to the heart over four key areas, each corresponding to the heart valve that is heard best: the upper right chest for the aortic valve, the upper left chest for the pulmonic valve, the lower left chest towards the midline (medial) for the tricuspid valve, and the lower left chest towards the side (lateral) for the mitral valve. In addition to rate and rhythm, they listen for S1 and S2 plus any extra abnormal sounds.
Murmurs and Valvular Disease
Heart murmurs are continuous but brief sounds that may be described as a harsh blowing sound. If present, the physician must find where on the chest it is heard the loudest. This suggests the heart valve that is involved.
The next step is to characterize the murmur. Abnormal heart valves generally have one or both of the following problems: narrowing (stenosis) that limits forward flow and incomplete closure that allows backflow (regurgitation). The physician listens for S1 and S2, sometimes feeling a pulse simultaneously as a guide, and determines when the murmur occurs. This and the valve most likely involved narrow the diagnosis.
For example, a physician hears a murmur loudest over the upper right chest, suggesting the aortic valve is affected. Further listening reveals that the murmur is after S1 and before S2. In other words, the mitral and tricuspid valves close at S1, the murmur from the aortic valve occurs, and the aortic and pulmonic valves close at S2. The murmur would have to be created by a narrow aortic valve. Therefore, the likely diagnosis is aortic stenosis. If, however, the murmur is loudest over the aortic valve and occurs after S2, when the aortic and pulmonic valves are supposed to close, then the sound is coming from backflow through the aortic valve, characteristic of aortic regurgitation.
The mitral valve is also prone to stenosis or regurgitation. With mitral stenosis, the murmur is loudest over the lower left lateral chest and after S2 when the mitral valve is supposed to open. A murmur in the same location but after S1, when the mitral valve should close, suggests mitral regurgitation. The same steps can apply to the tricuspid and pulmonic valves, although disease of these two valves is less common.
Even with the stethoscope, the definitive method of diagnosing and evaluating a heart murmur is an echocardiogram, or ultrasound of the heart. This imaging test allows one to see the valves as they open and close and the direction of blood flow. It confirms the suspected valve problem and also assesses the severity by measuring the size of the valve opening. This information will guide a cardiologist towards the best treatment.
Final Words
This is only a basic explanation of how murmurs and valvular disease work. There are many additional nuances with the heart exam plus other abnormal heart sounds and conditions that are beyond the scope here. Any concerns about one's own heart should be discussed with a personal physician.
