Cardiac Murmurs:

Despite impressive recent advances in noninvasive cardiac testing, the physical examination remains the cornerstone of any cardiac evaluation. Auscultation of the heart can provide important clues to the diagnosis of valvular heart disease, congestive heart failure, congenital heart lesions, and other cardiac abnormalities.

Here I provide a concise guide to the distinguishing auscultatory features of common heart murmurs (Table). I also review the relationship between these findings and specific cardiac problems.

AUSCULTATION OF MURMURS: A BRIEF REVIEW

For best results, minimize ambient noise during auscultation and use a stethoscope equipped with a dia- phragm and a bell. The diaphragm detects high-frequency sounds, such as systolic ejection murmurs, while the bell detects low-frequency sounds, such as the rumble of mitral stenosis.

Use a systematic approach when listening to the heart.¹ First, auscultate at the right upper sternal border, next at the left upper sternal border; then proceed down the left sternal border. The final point of auscultation is the apex. The reverse sequence is also appropriate. Each point of auscultation correlates with one of the cardiac valves (Figure 1).

If you have difficulty in distinguishing between the first and second heart sounds at the apex, listen carefully at the left upper sternal border, where the second heart sound splits on inspiration and is usually louder than the first. Then, while keeping your focus on the rhythm of the heart, move the stethoscope slowly toward the lower left sternal border. This process is known as "inching."²

Descriptions of heart murmurs include identification of the following features:

Intensity.

Frequency.

Quality.

Configuration.

Timing.

Duration.

Location and radiation.

Intensity (loudness). This is graded on a 6-point scale. Grade 1 murmurs are very faint and heard only after you focus on the sound. Grade 2 murmurs are faint but heard as soon as you place the stethoscope on the precordium. Grade 3 murmurs are moderately loud. Grade 4 murmurs are loud. Grade 5 murmurs are very loud and can be heard with the stethoscope partly off the precordium. Grade 6 murmurs can be heard with the stethoscope slightlyoff the precordium.

Frequency. Murmurs are described as high-pitched (eg, the murmur of aortic regurgitation) or low-pitched (eg, the rumble of mitral stenosis).

Quality. A description of the quality of the sound heard helps further identify a murmur. For example, the murmur of mitral stenosis is frequently described as a rumble, and that of mitral regurgitation as "blowing."

Configuration, timing, and duration. These features are best described by means of diagrams. For example, a diagram of the murmur of aortic stenosis-a crescendo-decrescendo murmur-depicts its configuration as a diamond shape (Figure 2). Although a few murmurs are continuous, most murmurs are either systolic or diastolic. A diagram of the murmur of mitral prolapse-a late systolic murmur-uses a line graph to show when, relative to S₁ and S₂, the murmur begins.

Location and radiation. Murmurs associated with valvular stenosis are most audible at the point of auscultation that correlates with the affected cardiac valve (see Figure 1). The murmur of aortic stenosis is heard best at the second right intercostal space parasternally. The murmur of pulmonary stenosis is most audible at the second or third intercostal space parasternally. The murmur of tricuspid stenosis is heard best along the lower left sternal border. Finally, the murmur of mitral stenosis is most audible at the apex.

Murmurs of regurgitation can radiate far from the point of origin. The murmur of aortic regurgitation originates over the aortic area but radiates to the apex. The murmur of mitral regurgitation originates at the apex and radiates to the axilla.

SYSTOLIC MURMURS

Systolic ejection murmurs. These are described as crescendo- decrescendo murmurs; their intensity peaks in early or mid systole(see Figure 2). Ejection murmurs result from some type of outflow obstruction. Important causes include aortic stenosis, pulmonary stenosis, and hypertrophic obstructive cardiomyopathy. Systolic ejection murmurs can also occur in conditions of high cardiac output, such as anemia and thyrotoxicosis.

Innocent murmur.This is the most common murmur in school-aged children.³ The innocent murmur is a crescendo-decrescendo early systolic murmur that isheard best at the left lower sternal border. The murmur does not radiate and is usually grade 1 or 2. Although there is some controversy about the origin of innocent murmurs, one widely held opinion is that they result from turbulent blood flow generated by left ventricular ejection of blood. When an innocent murmur is heard in an older patient, evaluate for anemia, which causes high cardiac output and can thus generate a flow murmur.

Aortic stenosis. The murmur of mildaortic stenosis is an ejection murmur that peaks early in systole. It is harsh in quality and medium-pitched. It is heard best at the second right intercostal space and often radiates to the neck. As the severity of the stenosis worsens, the murmur peaks later in systole, and the A₂ component of the second heart sound decreases in intensity and is delayed. This delay results in paradoxical (reversed) splitting of S₂ and the merging of A₂ and P₂ on inspiration (Figure 3). Causes of aortic stenosis include congenital bicuspid aortic valve, rheumatic fever, and aortic sclerosis.

Hypertrophic cardiomyopathy.This condition leads to outflow obstruction at mid systole, as the mitral valve approximates the hypertrophied septum; the obstruction produces turbulent ejection of blood from the left ventricle. The resulting murmur is harsh and is heard best at the left lower sternal border. It typically becomes louder when the Valsalva maneuver is performed (because this maneuver worsens the obstruction by decreasing venous return and making the left ventricle smaller).⁴

Atrial septal defect. This produces left-to-right shunting in the atria, which in turn causes increased filling of the right ventricle and consequently, increased flow across the pulmonic valve. The increased flow producesa systolic ejection murmur that is heard best at the left sternal border across the pulmonic valve area. With large atrial septal defects, there is also excess blood flow across the tricuspid valve, which results in a mid-diastolic murmur at the left lower sternal border.³ S₂ is widely split and fixed.

Holosystolic murmurs. Holosystolic (pansystolic) murmurs (see Figure 2) result from retrograde flow out of a high-pressure chamber into a low-pressure chamber. Common causes of holosystolic murmurs include mitral insufficiency, tricuspid insufficiency, and ventricular septal defect.

Mitral regurgitation.The murmur of mitral regurgitation is generated when blood regurgitates from the left ventricle into the left atrium. This holosystolic murmur is a blowing sound that is heard best at the apex and radiates to the axilla. The first heart sound is often soft. Causes of mitral regurgitation include infective endocarditis, degenerative valvular disease (mitral valve prolapse), and rheumatic heart disease. If mitral valve prolapse is the cause, there may be a mid-systolic click followed by a late systolic murmur.

Tricuspid regurgitation.The murmur of tricuspid regurgitation is a holosystolic murmur of medium pitch that is heard best at the left lower sternal border and that may radiate to the right side of the sternum. The most common cause of tricuspid regurgitation is right ventricular failure, which results in chamber dilation and consequent enlargement of the tricuspid orifice.

Ventricular septal defect.This congenital lesion results in a persistent opening of the interventricular septum that allows blood to pass from the high-pressure left ventricle into the low-pressure right ventricle.⁵ The resulting murmur is a holosystolic murmur heard best along the left lower sternal border. When loud, it is harsh.

DIASTOLIC MURMURS

Diastolic regurgitant murmurs, which include aortic regurgitation murmurs and pulmonic valve regurgitation murmurs, result from retrograde flow across an incompetent valve. Diastolic filling murmurs, such as the murmur of mitral stenosis, result from turbulent flow across a valve (typically the mitral or tricuspid valve).

Aortic regurgitation. The murmur associated with aortic insufficiency occurs when the aortic valve fails to close completely and blood regurgitates from the aorta back into the left ventricle. It is a high-pitched decrescendo murmur that is heard best along the left lower sternal border and sternum.(Figure 4).

Two other murmurs may be associated with aortic regurgitation. The first of these is a systolic ejection murmur that results when volume overload of the left ventricle causes increased flow across the aortic valve. The second associated murmur is the Austin Flint murmur, a low-pitched mid-diastolic sound that is heard at the apex. Austin Flint murmurs are generated by impingement of the regurgitant flow on the anterior leaflet of the mitral valve.

Mitral stenosis. The murmur associated with mitral stenosis is a low-pitched diastolic rumbling sound with presystolic accentuation; it is usually preceded by an opening snap just after S₂ (see Figure 4). The murmur is located at the apex and is heard best with the bell. Rheumatic heart disease is the most common underlying cause.

CONTINUOUS MURMURS

Continuous murmurs begin in systole and continue through diastole. A classic example of a continuous murmur is that associated with patent ductus arteriosus. The murmur is caused by a continuous high-pressure shunt-blood flowing from the aorta through the patent ductus and into the pulmonary artery, during both systole and diastole. The murmur is heard over the second left intercostal space and is described as a continuous, rough, "machinery-type" sound.³ n

References:

REFERENCES:

1. Karnath B, Thornton W. Auscultation of the heart. Hosp Physician. 2002;38:39-43.

2. Harvey WP. Cardiac pearls. Dis Mon. 1994;40: 41-113.

3. Engle MA. Heart sounds and murmurs in diagnosis of heart disease. Pediatr Ann. 1981;10:84-93.

4. Stapleton J. Manipulating cardiac murmurs. Chest. 1982;81:135-136.

5. Moodie DS. Diagnosis and management of congenital heart disease in the adult. Cardiol Rev. 2001;9: 276-281.