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The Stethoscope: Uses and Limitations

Stethoscope-Uses-and-LimitationsWith the stethoscope, you can detect irregularities, known as murmurs, between the heart’s two phases of contraction. Dubbed “S1” and “S2,” these primary heart sounds are said to sound like a “lub” and “dub”, respectively. S1 occurs as the mitral valve closes, while S2 is the result of the atrial valve closing. Ideally, the heart should be silent between these two events.

A murmur is characterized as a whooshing or clicking sound between S1 and S2, and may be the result of a hole in the heart wall or a rough edge on a valve. You will typically use the stethoscope’s bell to listen to the lower-frequency sounds produced in the mitral valve, and the diaphragm to listen to the higher-frequency sounds produced elsewhere in the chest. Not all irregular heart sounds are the result of a heart defect, but if you detect irregularities while exterior symptoms of heart issues are present, you should follow up immediately with additional testing.

Exterior Symptoms

• Dyspnea

Dyspnea is defined as the symptom of breathlessness or the impression that your patient has to focus on their breathing. Another term for this condition is “air hunger.” Air hunger is normal in times of great exertion, such as when running, and is a common symptom of asthma and pneumonia. Outside of these circumstances, however, it is typically indicative of a heart issue such as congestive heart failure or cardiac ischemia. It is also present in cases of interstitial lung disease and chronic obstructive pulmonary disease.

• Edema

Edema, formerly known as hydropsy, is the accumulation of fluid directly beneath the skin or within body cavities. You can readily detect the condition when present by examining the ankles. Those with edema may exhibit a “galloping” or thready pulse. If the condition is related to the heart, it is likely that one or several of the blood vessels of the leg are clotted.

• Cyanosis

Cyanosis occurs when blood in the extremities is not replenished with oxygen. This condition causes the fingers and toes to take on a purple or bluish tint. Cyanosis occurs when at least 5.0 g/dL of deoxyhemoglobin builds up in the tissues and can be indicative of heart failure.

• Cachexia

Cachexia, or “wasting,” is described as a sudden loss of weight that cannot be attributed to diet and exercise. Cachexia is typically a side effect of many autoimmune diseases, such as AIDS, and it is also seen during the course of cancer treatment. Cachexia generally entails a loss of appetite and muscle atrophy as well. If the above disease processes are not present, the possibility of congestive heart failure should be considered.

What the Stethoscope Can Detect

Generally, the stethoscope can detect any number of issues with the heart valves themselves. However, it is important to note that a heart murmur—or an extra sound between S1 and S2— is not necessarily indicative of a heart valve issue. Many children exhibit murmurs as they grow. If you detect a murmur, it is standard practice to check the lungs for fluid buildup with the stethoscope. If fluid buildup is present, you should follow up with an ECG, checking for congenital heart defects. In adults, these symptoms are often indicative of acquired heart valve disease. This condition is generally caused by any combination of aging, infection, and other diseases such as rheumatic fever.

If you detect a whooshing or “warbling” sound before S2, or a generalized “galloping” sound, the patient may be suffering heart failure. In heart failure, the heart muscle has become too weak to effectively pump blood throughout the body. Thready pulse can occur innocently in children and young adults, but it is never considered innocent in those over 30.

A soft lub or pulse before S1 may indicate high blood pressure or a stiff heart muscle. In this instance, the heart muscle has trouble constricting completely, and the extra sound produced is quite faint. An echoing S1 can also indicate heart calcification, mitral regurgitation and left bundle branch block.

What the Stethoscope Can’t Detect

There are several congenital heart defects that escape detection with a stethoscope. Many of the sounds produced by these conditions are so faint that most practitioners miss them. The most commonly missed condition is atrial fibrillation. Atrial fibrillation presents as a type of arrhythmia in which the heart beats too fast and irregularly. Specifically, the atria twitch instead of contract. Patients can go years without symptoms, but they may present at any time with extreme nausea, fatigue and shortness of breath. While many congenital heart defects are impossible to detect with a stethoscope, they are readily apparent on an ECG. In an atrial fibrillation ECG result, the S1 peak is often split into two. This indicates that the heart’s pacing is off, causing the right ventricle to close before the mitral valve.

Heart defects such as these are relatively rare. AF affects roughly 2 in every 100 people. However, early detection is essential as the presence of AF greatly increases the likelihood of stroke. When in doubt, an ECG is the logical next step in most cases.

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