Merck Manual

Please confirm that you are a health care professional

honeypot link

Cardiac Auscultation


Jessica I. Gupta

, MD, University of Michigan Health;

Michael J. Shea

, MD, Michigan Medicine at the University of Michigan

Reviewed/Revised Mar 2023
Topic Resources

Auscultation of the heart requires excellent hearing and the ability to distinguish subtle differences in pitch and timing. Hearing-impaired health care practitioners can use amplified stethoscopes. High-pitched sounds are best heard with the diaphragm of the stethoscope. Low-pitched sounds are best heard with the bell. Very little pressure should be exerted when using the bell. Excessive pressure converts the underlying skin into a diaphragm and eliminates very low-pitched sounds.

The entire precordium is examined systematically, typically beginning over the apical impulse with the patient in the left lateral decubitus position. The patient rolls supine, and auscultation continues at the lower left sternal border, proceeds cephalad with auscultation of each interspace, then caudad from the right upper sternal border. The clinician also listens over the left axilla and above the clavicles. The patient sits upright for auscultation of the back, then leans forward to aid auscultation of aortic and pulmonic diastolic murmurs or pericardial friction rub.

Major auscultatory findings include

  • Heart sounds

  • Murmurs

  • Rubs

Heart sounds are brief, transient sounds produced by valve opening and closure; they are divided into systolic and diastolic sounds.

Murmurs are produced by blood flow turbulence and are more prolonged than heart sounds; they may be systolic, diastolic, or continuous. They are graded by intensity and are described by their location and when they occur within the cardiac cycle. Murmurs are graded in intensity on a scale of 1 to 6 (see table Heart Murmur Intensity Heart Murmur Intensity Heart Murmur Intensity ).


Rubs are high-pitched, scratchy sounds often with 2 or 3 separate components, which may vary according to body position; during tachycardia, the sound may be almost continuous.

The clinician focuses attention sequentially on each phase of the cardiac cycle, noting each heart sound and murmur. Intensity, pitch, duration, and timing of the sounds and the intervals between them are analyzed, often providing an accurate diagnosis. Historically, a diagram of the major auscultatory and palpatory findings Palpation Complete examination of all systems is essential to detect peripheral and systemic effects of cardiac disorders and evidence of noncardiac disorders that might affect the heart. Examination... read more Palpation of the precordium was drawn in the patient’s chart each time the patient’s cardiovascular system was examined (see figure Diagram of physical findings Diagram of physical findings in a patient with aortic stenosis and mitral regurgitation Diagram of physical findings in a patient with aortic stenosis and mitral regurgitation ). With such diagrams, findings from each examination could be compared. Subsequent examination findings should be interpreted in the context of available imaging results (including echocardiogram and cardiac MRI) to diagnose and monitor valvular abnormalities.

Diagram of physical findings in a patient with aortic stenosis and mitral regurgitation

Murmur, character, intensity, and radiation are depicted. Sound of pulmonic closure exceeds that of aortic closure. Left ventricular (LV) thrust and right ventricular (RV) lift (heavy arrows) are identified. A 4th heart sound (S4) and systolic thrill (TS) are present. a = aortic closure sound; p = pulmonic closure sound; S1 = 1st heart sound; S2 = 2nd heart sound; 3/6 = grade of crescendo-diminuendo murmur (radiates to both sides of neck); 2/6 =grade of pansystolic apical crescendo murmur; 1+ = mild precordial lift of RV hypertrophy (arrow shows direction of lift); 2+ = moderate LV thrust (arrow shows direction of thrust).

Diagram of physical findings in a patient with aortic stenosis and mitral regurgitation

Systolic heart sounds

Systolic sounds include the following:

  • 1st heart sound (S1)

  • Clicks

S1 and the 2nd heart sound (S2, a diastolic heart sound) are normal components of the cardiac cycle, the familiar “lub-dub” sounds.

S1 occurs just after the beginning of systole and is predominantly due to mitral closure but may also include tricuspid closure components. It is often split and has a high pitch. S1 is loud in mitral stenosis Mitral Stenosis Mitral stenosis is narrowing of the mitral orifice that impedes blood flow from the left atrium to the left ventricle. The usual cause is rheumatic fever. Common complications are pulmonary... read more . It may be soft or absent in mitral regurgitation Mitral Regurgitation Mitral regurgitation (MR) is incompetency of the mitral valve causing flow from the left ventricle (LV) into the left atrium during ventricular systole. MR can be primary (common causes are... read more Mitral Regurgitation due to valve leaflet sclerosis and rigidity but is often distinctly heard in mitral regurgitation due to myxomatous degeneration of the mitral apparatus or due to ventricular myocardial abnormality (eg, papillary muscle dysfunction, ventricular dilation). S1 is often soft or absent in first-degree atrioventricular block as the atrioventricular valve leaflets (mitral and tricuspid) drift to a nearly closed position prior to ventricular systole.

Clicks occur only during systole; they are distinguished from S1 and S2 by their higher pitch and briefer duration. Some clicks occur at different times during systole as hemodynamics change. Clicks may be single or multiple.

Clicks due to myxomatous degeneration of valves may occur any time during systole but move toward S1 during maneuvers that transiently decrease ventricular filling volume (eg, standing, Valsalva maneuver). If ventricular filling volume is increased (eg, by lying supine), clicks move toward S2, particularly in mitral valve prolapse. For unknown reasons, characteristics of the clicks may vary greatly between examinations, and clicks may come and go.

Systolic Heart Sounds

Diastolic heart sounds

Diastolic sounds include the following:

  • 2nd, 3rd, and 4th heart sounds (S2, S3, and S4)

  • Diastolic knocks

  • Mitral valve sounds

Unlike systolic sounds, diastolic sounds are low-pitched; they are softer in intensity and longer in duration. Except for S2, these sounds are usually abnormal in adults, although an S3 may be physiologic up to age 40 and during pregnancy.

S2 occurs at the beginning of diastole, due to aortic and pulmonic valve closure. Aortic valve closure (A2) normally precedes pulmonic valve closure (P2) unless the former is late or the latter is early. Aortic valve closure is late in left bundle branch block or aortic stenosis; pulmonic valve closure is early in some forms of preexcitation phenomena. Delayed pulmonic valve closure may result from increased blood flow through the right ventricle (eg, in atrial septal defect Atrial Septal Defect (ASD) An atrial septal defect (ASD) is an opening in the interatrial septum, causing a left-to-right shunt and volume overload of the right atrium and right ventricle. Children are rarely symptomatic... read more of the common secundum variety) or complete right bundle branch block Bundle Branch Block and Fascicular Block Bundle branch block is partial or complete interruption of impulse conduction in a bundle branch; fascicular block is similar interruption in a hemifascicle of the left bundle. The disorders... read more . Increased right ventricular flow in atrial septal defect also abolishes the normal respiratory variation in aortic and pulmonic valve closure, producing a fixed split S2. Left-to-right shunts with normal right ventricular volume flow (eg, in membranous ventricular septal defects Ventricular Septal Defect (VSD) A ventricular septal defect (VSD) is an opening in the interventricular septum, causing a shunt between ventricles. Large defects result in a significant left-to-right shunt and cause dyspnea... read more Ventricular Septal Defect (VSD) ) do not cause fixed splitting. A single S2 may occur when the aortic valve is regurgitant, severely stenotic, or atretic (in truncus arteriosus when there is a common valve).

Diastolic Heart Sounds

S3 occurs in early diastole, when the ventricle is dilated and noncompliant. It occurs during passive diastolic ventricular filling and usually indicates serious ventricular dysfunction in adults; in children, it can be normal, sometimes persisting even to age 40. S3 also may be normal during pregnancy. Right ventricular S3 is heard best (sometimes only) during inspiration (because negative intrathoracic pressure augments right ventricular filling volume) with the patient supine. Left ventricular S3 is best heard during expiration (because the heart is nearer the chest wall) with the patient in the left lateral decubitus position.

S4 is produced by augmented ventricular filling, caused by atrial contraction, near the end of diastole. It is similar to S3 and heard best or only with the bell of the stethoscope. During inspiration, right ventricular S4 increases and left ventricular S4 decreases. S4 is heard much more often than S3 and indicates a lesser degree of ventricular dysfunction, usually diastolic. S4 is absent in atrial fibrillation (because the atria do not contract) but is almost always present in active myocardial ischemia or soon after myocardial infarction Acute Myocardial Infarction (MI) Acute myocardial infarction is myocardial necrosis resulting from acute obstruction of a coronary artery. Symptoms include chest discomfort with or without dyspnea, nausea, and/or diaphoresis... read more Acute Myocardial Infarction (MI) .

S3, with or without S4, is usual in significant systolic left ventricular dysfunction; S4 without S3 is usual in diastolic left ventricular dysfunction.

A summation gallop occurs when S3 and S4 are present in a patient with tachycardia, which shortens diastole so that the 2 sounds merge. Loud S3 and S4 may be palpable at the apex when the patient is in the left lateral decubitus position.

A diastolic knock occurs at the same time as S3, in early diastole. It is not accompanied by S4 and is a louder, thudding sound, which indicates abrupt arrest of ventricular filling by a noncompliant, constricting pericardium.

An opening snap (OS) may occur in early diastole in mitral stenosis Mitral Stenosis Mitral stenosis is narrowing of the mitral orifice that impedes blood flow from the left atrium to the left ventricle. The usual cause is rheumatic fever. Common complications are pulmonary... read more or, rarely, in tricuspid stenosis Tricuspid Stenosis Tricuspid stenosis (TS) is narrowing of the tricuspid orifice that obstructs blood flow from the right atrium to the right ventricle. Almost all cases result from rheumatic fever. Symptoms include... read more . Mitral opening snap is very high pitched, brief, and heard best with the diaphragm of the stethoscope. The more severe mitral stenosis is (ie, the higher the left atrial pressure), the closer the opening snap is to the pulmonic component of S2. Intensity is related to the compliance of the valve leaflets: The snap sounds loud when leaflets remain elastic, but it gradually softens and ultimately disappears as sclerosis, fibrosis, and calcification of the valve develop. Mitral opening snap, although sometimes heard at the apex, is often heard best or only at the lower left sternal border.

Approach to murmurs

Timing of the murmur in the cardiac cycle correlates with the cause (see table Etiology of Murmurs by Timing Etiology of Murmurs by Timing Etiology of Murmurs by Timing ); auscultatory findings correlate with specific heart valve disorders. Various maneuvers (eg, inspiration, Valsalva, handgrip, squatting, amyl nitrate inhalation) can modify cardiac physiology slightly, making differentiation of causes of heart murmur possible (see table Maneuvers That Aid in Diagnosis of Murmurs Maneuvers That Aid in Diagnosis of Murmurs Maneuvers That Aid in Diagnosis of Murmurs ).


All patients with heart murmurs are evaluated by chest x-ray and electrocardiography (ECG). Echocardiography is required Echocardiography Echocardiography uses ultrasound waves to produce an image of the heart, the heart valves, and the great vessels. It helps assess heart wall thickness (eg, in hypertrophy or atrophy) and motion... read more Echocardiography to confirm the diagnosis, determine severity, and track severity over time. Usually, a cardiac consultation is obtained if significant disease is suspected.

Systolic murmurs

Systolic murmurs may be normal or abnormal. They may be early, mid, or late systolic, or holosystolic (pansystolic). Systolic murmurs may be divided into ejection, regurgitant, and shunt murmurs.

Ejection murmurs are due to turbulent forward flow through narrowed or irregular valves or outflow tracts (eg, due to aortic stenosis Aortic Stenosis Aortic stenosis (AS) is narrowing of the aortic valve, obstructing blood flow from the left ventricle to the ascending aorta during systole. Causes include a congenital bicuspid valve, idiopathic... read more Aortic Stenosis or pulmonic stenosis Pulmonic Stenosis Pulmonic stenosis (PS) is narrowing of the pulmonary outflow tract causing obstruction of blood flow from the right ventricle to the pulmonary artery during systole. Most cases are congenital... read more ). They are typically mid systolic and have a crescendo-diminuendo character that usually becomes louder and longer as flow becomes more obstructed. The greater the stenosis and turbulence, the longer the crescendo phase and the shorter the diminuendo phase.

Systolic ejection murmurs may occur without hemodynamically significant outflow tract obstruction and thus do not necessarily indicate a disorder. In normal infants and children, flow is often mildly turbulent, producing soft ejection murmurs. Older patients often have ejection murmurs due to valve and vessel sclerosis.

During pregnancy, many women have soft ejection murmurs at the 2nd intercostal space to the left or right of the sternum. The murmurs occur because a physiologic increase in blood volume and cardiac output increases flow velocity through normal structures. The murmurs may be greatly exaggerated if severe anemia complicates the pregnancy. These murmurs are distinct from the venous hum sometimes caused by engorged breast vessels during pregnancy (mammary souffle).

Systolic Murmurs

Diastolic murmurs

A mitral or tricuspid murmur due to an atrial tumor or thrombus may be evanescent and may vary with position and from one examination to the next because the position of the intracardiac mass changes.

Pearls & Pitfalls

  • Systolic murmurs may be normal or abnormal but diastolic murmurs are always abnormal.

Continuous murmurs

Continuous murmurs occur throughout the cardiac cycle. They are always abnormal, indicating a constant shunt flow throughout systole and diastole, hence remaining audible through S2. They may be due to various cardiac defects (see table Etiology of Murmurs by Timing Etiology of Murmurs by Timing Etiology of Murmurs by Timing ). Some defects produce a thrill; many are associated with signs of right ventricular hypertrophy and left ventricular hypertrophy. As pulmonary artery resistance increases in shunt lesions, the diastolic component gradually decreases. When pulmonary and systemic resistance equalize, the murmur may disappear.

When circulation is increased, as occurs during pregnancy, anemia, and hyperthyroidism Hyperthyroidism Hyperthyroidism is characterized by hypermetabolism and elevated serum levels of free thyroid hormones. Symptoms include palpitations, fatigue, weight loss, heat intolerance, anxiety, and tremor... read more Hyperthyroidism , a continuous venous hum is often heard in the right supraclavicular fossa; this venous hum also occurs normally in children. The sound generated by increased flow in a dilated internal mammary artery (mammary souffle), may be mistaken for a continuous cardiac murmur. Mammary souffle is typically heard best over the breast at the level of the right and/or left 2nd or 3rd intercostal space and, although often classified as continuous, is usually louder during systole.

Pericardial friction rub

A pericardial friction rub is caused by movement of inflammatory adhesions between visceral and parietal pericardial layers. It is a high-pitched or squeaking sound; it may be systolic, diastolic and systolic, or triphasic (when atrial contraction accentuates the diastolic component during late diastole). The rub sounds like pieces of leather squeaking as they are rubbed together. Rubs are best heard with the patient leaning forward or on hands and knees with breath held in expiration.

NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
quiz link

Test your knowledge

Take a Quiz!