|The Art of Auscultation|
Despite advances in noninvasive cardiac diagnostics, auscultation remains a pivotal component of the adult physical examination. This time-honored art plays an important clinical role and is critical for ensuring the cost-effective use of technology.
In 1816, the French physician Rene Theophile Hyacinthe Laennec was trying to examine the heart of a relatively obese woman. Unable to employ direct auscultation because of the patient's sex and body size, Laennec rolled a quire of thick paper into a cylinder and applied one end to the apex of the patient's heart and the other end to his own ear. With this simple device, Laennec had invented the monaural stethoscope, which was later made from a straight wooden tube with a small flattened bell at one end. In the early 1900s, the monaural stethoscope was modified and supplanted by the binaural stethoscope, a device consisting of two flexible rubber tubes connected at one end to earpieces and at the other end to a chest piece. The Stethoscope became the doctor's badge and an indispensable tool for auscultation of the heart.
During the last 20 or 30 years, however, technological advances have spurred the development of a multitude of sophisticated cardiac diagnostic techniques that have upstaged the stethoscope. Many physicians rely on echocardiography, for example, as the standard for routine cardiac evaluations practice that has important cost implications. Although still seen as the symbol of a distinguished past, the stethoscope-often draped conspicuously around the physician's neck or over the shoulder-seems to have taken a backseat to current technologies. But applied auscultation, in the context of the entire cardiovascular physical examination, is, and will remain, an important diagnostic tool.
The history and physical examination are essential for uncovering clues to cardiac disease. The physical examination of the heart and auscultation often lead to a diagnosis. Even negative findings are important. For example, if the cardiac physical examination is otherwise normal in a healthy 5-year-old male, a murmur is likely to be benign. Similarly, an echocardiographic diagnosis of "mitral valve prolapse" is probably incorrect in a 20-year-old woman in whom auscultation is normal. A thorough cardiovascular examination is also cost-effective. The potential cost savings of selective use of expensive diagnostic tests can be enormous. Consider that at least 20% of the echocardiograms ordered by general physicians during a 2- to 3-year period at a hospital where one of the consultants for this article works could have been avoided if skilled cardiac examinations had been performed first.
Finally, in contrast to medical technology, which is usually impersonal, cardiac auscultation establishes a connection between the physician and the patient that enhances trust. There are few things more reassuring to a patient than having the physician personally take the history and do a careful physical examination.
The cardiovascular physical examination is an amalgamation of visible, palpable, and audible information that in the context of the patient's medical history-can provide insights that often identify a specific cardiac disorder. The examination begins with an assessment of the general and detailed physical appearance, and observations of the arterial and jugular venous pulses follow.
A tall jugular venous V wave reflects tricuspid insufficiency. Wide pulse pressure is a common feature of aortic insufficiency, whereas a slow rising pulse suggests aortic stenosis.
Palpation is useful for identifying the topography of the heart, thereby allowing a more refined use of the stethoscope. Palpation of the apex provides a sense of the size of the left ventricle and the quality of its contraction (see Figure 1). The presence of a palpable murmur, or thrill, indicates that the murmur is at least grade 3 or more. Thrills are best detected using the distal metacarpals. The clinical significance of a thrill depends on its timing during the cardiac cycle (systolic, diastolic, continuous), as well as its location, duration, and direction of radiation.
Precordial and abdominal percussion aid in establishing the situs of major organs - the heart, stomach, and liver. Percussion on the chest provides evidence of lung consolidation or pleural effusion.
The art of cardiac auscultation is a difficult skill requiring refined acoustic perception, including the ability to discriminate subtle differences in intensity, pitch, location, radiation, duration, timing, and intervals of heart sounds. These characteristics provide valuable clinical clues. For example, a diminished first heart sound is common when the PR interval is prolonged. An accentuated first heart sound is characteristic of mitral stenosis. Splitting of the second heart sound may be normal or abnormally wide, fixed, or paradoxical (see Figure 2). In atrial septal defect, the splitting is fixed; splitting is wide with right bundle-branch block and paradoxical in left bundle-branch block. Splitting is best heard at the left base or third left intercostal space.
Distinguishing between normal and abnormal third and fourth heart sounds, which are typically soft and low-frequency, is challenging but critical, particularly since a third heart sound in an older person may be the only clue to abnormal left ventricular function. Low-pitched sounds are best heard with the bell of the stethoscope, whereas high-pitched sounds are best heard with the diaphragm. It's helpful to remember that a normal third heart sound is commonly heard over the left ventricular impulse in children and young adults. After ages 35 to 40, however, the presence of a third heart sound is usually abnormal. Early third heart sounds are heard in patients with mitral regurgitation.
Normal fourth heart sounds are common in older adults, implying an age-related decrease in left ventricular compliance. In contrast, a fourth heart sound is almost always abnormal in children. Abnormal fourth heart sounds are features of aortic stenosis, systemic hypertension, and ischemic heart disease. Third and fourth heart sounds may coincide-summate-and increase in prominence.
Third and fourth heart sounds are best heard when the bell of the stethoscope is placed over the left or right ventricular impulse with the application of just enough pressure to create a skin seal. Firm pressure and the use of the diaphragm of the stethoscope should be avoided since both can reduce or eliminate low-frequency third and fourth heart sounds.
To further improve the audibility of third heart sounds, have the patient perform isotonic exercises such as sit-ups, which increase venous return and induce or augment left ventricular filling sounds. Passive leg raising with the patient in the supine position is also effective. Inspiration increases the audibility of right ventricular third and fourth heart sounds. Note that you will not hear third or fourth heart sounds if there is an atrioventricular valve obstruction that retards ventricular filling.
Cardiac murmurs fall into 3 categories - systolic, diastolic, and continuous. Normal or "functional" systolic murmurs are benign and must be distinguished from abnormal systolic murmurs (see Figure 3, page 42). Innocent, or normal, murmurs are systolic except for the venous hum and mammary soufflé. Normal murmurs are ubiquitous in children, especially the innocent vibratory systolic Still's murmur.*
The clinical significance of a murmur depends on several key characteristics, including timing, pitch, duration, configuration, intensity, location, and radiation. Murmurs are best categorized according to where in the cardiac cycle they occur.
A key component of skilled auscultation is positioning of the patient. There are 3 basic positions in which auscultation should be performed-supine, left lateral decubitus, and sitting. In addition, several physical maneuvers may also have various effects on murmurs that help identify them:
The following sections highlight auscultatory findings and other physical signs associated with various types of heart disease. Careful auscultation can detect functionally abnormal valves in the majority of patients with significant valvular heart disease, including mitral stenosis, mitral insufficiency, aortic stenosis, and aortic insufficiency (see Table 1, page 46). Mitral stenosis is usually characterized by a prominent first heart sound and an opening snap in early diastole that is widely distributed over the chest. A diminished first heart sound suggests first-degree heart block or a calcified, immobile neutral valve. The murmur associated with mitral stenosis is typically a localized, mid-diastolic, low-pitched, apical rumble with presystolic accentuation. In atrial fibrillation, its duration varies with heart rate and the severity of the stenosis. A delayed opening snap and a short diastolic murmur suggest mild mitral stenosis.
Evidence of mitral stenosis is elicited by placing the bell of the stethoscope over the left ventricular impulse with the patient in the left lateral decubitus position. In fact, this may be the only position in which you will hear the murmur of mitral stenosis. Isotonic exercises or repetitive cough increase the heart rate and help accentuate the murmur.
Mitral insufficiency, or regurgitation, is usually characterized by a holosystolic murmur at the cardiac apex that often radiates to the axilla. The murmur may also radiate to the back or to the lower left sternal border. The murmur is high-frequency and may be accompanied by a prominent third heart sound. In acute severe mitral regurgitation, the murmur is typically early systolic. In mitral valve prolapse, the murmur of mitral regurgitation is late systolic. In ischemic heart disease, the regurgitant murmur may be midsystolic.
Mitral valve prolapse, or myxomatous mitral valve, is characterized by mid- to late systolic clicks followed by a late systolic murmur. Squatting decreases venous return and softens the murmur of mitral valve prolapse. Prompt standing has the opposite effect. Calcific aortic stenosis of a trileaflet valve is characterized by a midsystolic murmur that has a pure frequency at the apex and an impure frequency at the right base, with transmissions into the neck. A soft or absent aortic second sound reflects a calcified, immobile valve.
A high-frequency, musical midsystolic murmur originates from periodic vibrations of the bases of the thickened aortic leaflets and is transmitted into the left ventricle and heard best at the apex when the patient is turned into the left lateral decubitus position.
In patients with this form of aortic valve disease, it's often difficult to determine whether the valve is sclerotic or stenotic. Here, the echocardiogram is pivotal. If the left ventricular impulse is sustained in a patient without systemic hypertension, a stenotic aortic valve is likely.
Aortic regurgitation is characterized by an early diastolic, high-frequency murmur that is difficult to detect and when soft may be easily missed. The soft, high-pitched, decrescendo murmur of aortic regurgitation is best heard by applying the diaphragm of the stethoscope along the mid-left sternal border with firm pressure while the patient sits and leans forward and exhales completely. The murmur's loudness, duration, and radiation may reflect the severity of the leak. The degree of regurgitation is often reflected in a wide arterial pulse pressure and a laterally displaced prominent apical impulse.
In severe aortic regurgitation, a presystolic or late diastolic low-pitched mitral murmur (Austin Flint murmur) may be audible and is caused by partial closure of the anterior mitral leaflet.
Tricuspid stenosis is typically characterized by 2 features that differentiate the murmur of tricuspid stenosis from the murmur of mitral stenosis. First, the tricuspid murmur is presystolic and increases in loudness during inspiration. Second, the murmur is localized to the lower left sternal edge. Little or no mid-diastolic rumble is evident unless the patient is in atrial fibrillation.
High-pressure Bicuspid regurgitation is characterized by a high-frequency holosystolic murmur best detected at the left sternal border. Inspiration increases the intensity of the murmur, although this sign may be absent in patients with right ventricular failure. Other physical findings include a right ventricular pulsation. The height of the jugular V wave reflects the degree of tricuspid regurgitation.
Other forms of heart disease Hypertrophic obstructive cardiomyopathy is characterized by a sustained left ventricular impulse, a loud fourth heart sound, and an apical murmur that is usually midsystolic. Listening to the midsystolic murmur while the patient squeezes both fists together increases blood pressure and causes the outflow tract to widen, decreasing the intensity and duration of the murmur. Squatting has a similar effect, whereas standing does exactly the opposite-the blood pressure falls, increasing flow into the left ventricle and making the murmur louder. Valsalva's maneuver tends to accentuate the murmur of hypertrophic cardiomyopathy.
Atrial septal defect is accompanied by a relatively soft and unimpressive left basal midsystolic murmur that may be easily overlooked. Many patients reach adolescence and adulthood before a diagnosis is made. A palpable right ventricle suggests the diagnosis of atrial septal defect. Auscultatory findings include a relatively short, impure, midsystolic murmur at the second left interspace that is typically followed by fixed splitting of the second heart sound.
A bicuspid aortic valve occurs in about 2% of live births, much more frequently in males than in females. If the bicuspid aortic valve functions normally, the diagnosis is often overlooked. A typical aortic ejection sound, however, accompanies a mobile bicuspid aortic valve and is heard best at the apex. The sound is easily mistaken for a split first heart sound.
In general, patients with symptomatic murmurs or those in whom you suspect valvular heart disease should have an echocardiogram, a chest film, and an ECG. An ECG may suggest the presence of arrhythmia, cardiac hypertrophy, MI, and conduction abnormalities. The chest x-ray is useful for identifying cardiomegaly.
Overestimation of valvular regurgitation is a major problem with echocardiograms. The physical signs are also often more reliable, especially in patients who have aortic or tricuspid regurgitation.
Patients aged 50 or older may also be candidates for cardiac catheterization or angiography to assess the coronary arteries. Although MRI is useful for diagnosing congenital heart disease, it has little value in valvular or ischemic heart disease.
The following resources are available for physicians interested in fine tuning and practicing their auscultatory skills. These pages have audio files.
The Auscultation Assistant
First heart sound (S1)
Second heart sound (S2)
Extra heart sounds
|Adapted with permission from Alpert JS . Approach to the cardiac patient. In: Dale DC, Federman DD, eds. Scientific American Medicine. New York, NY: Scientific American Medicine, Inc. 1996. Copyright 1996. All rights reserved. Modified by the article consultants.|