We are in danger of losing our clinical heritage and pinning too much faith in figures thrown up by machines. Medicine will suffer if this tendency is not checked. —Paul Wood1
Physician assistants (PAs) learn heart sounds and murmurs during their education, but whether these skills are retained or perfected beyond the cardiac block of instruction is not known. However, documentation shows that many physicians, residents, and medical students have poor auscultation skills that often diminish further after they enter clinical practice.2,3 With the advances in echocardiography, the cardiac examination using physiologic maneuvers has been called irrelevant.4 In medicine, however, the cardiac examination remains a cost-effective, sensitive, and specific screening tool for cardiac disease.5 Recognizing pathologic cardiac conditions that generate murmurs requires careful attention to S1 and S2 heart sounds to identify their timing and characteristics in order to detect possible causes.
This article reviews basic murmur characteristics and the typical effects of physiologic maneuvers on cardiac murmurs. These maneuvers can assist clinicians in developing a differential diagnosis for a murmur of uncertain origin, especially in patients with undiagnosed hypertrophic obstructive cardiomyopathy and aortic stenosis.6
A STEPWISE PROCESS
Clinicians must have a logical process in mind while listening to patient heart sounds and murmurs. Having a solid understanding of the anatomy and pathophysiology of heart sounds and murmurs is critical to knowing what is being heard.7 Reviewing heart sound and murmur diagrams in physical diagnosis textbooks can help clinicians get a mental picture of what they are hearing. Follow these steps to properly describe any murmur that is detected:8
- Identify murmur timing: systolic, diastolic, or continuous. For practical purposes, a diastolic murmur is always pathologic.
- Determine the murmur's intensity: Murmurs typically are graded using the Levine scale and are assigned a value from I to VI. The most important distinction is to identify the presence of a palpable thrill. An easily heard murmur with a palpable thrill is designated grade IV to VI. A thrill associated with a murmur represents significant turbulence and is always pathologic.9
- Determine the location of maximum intensity: aortic (second right intercostal space), pulmonic (second left intercostal space), Erb point (second pulmonic to third left intercostal space), tricuspid (fourth left intercostal space), or mitral (fifth left intercostal space, midclavicular line)
- Radiation: carotids, left axilla, left sternal border, and apex
- Quality: soft, blowing, harsh, or rumbling
- Shape: crescendo-decrescendo, crescendo, decrescendo, continuous.
BASIC CHARACTERISTICS OF COMMON HEART MURMURS
There are many kinds of heart murmurs and ways to organize the sounds. For simplicity, we use mnemonics based on the causes of the murmurs: HAPI for midsystolic murmurs (hypertrophic cardiomyopathy, aortic stenosis, pulmonic stenosis, or innocent, Table 1); MTV for holosystolic murmurs (mitral regurgitation, tricuspid regurgitation, or ventricular septal defect, Table 2); and ArMs for diastolic murmurs (aortic regurgitation or mitral stenosis, Table 3). Up to 50% of patients age 65 years or older present with a systolic murmur. The most common pathology is aortic stenosis and mitral regurgitation.10
Midsystolic (systolic ejection) murmurs
The midsystolic murmurs start after S1, peak in midsystole, and end before S2. Aortic stenosis often is not diagnosed until patients are symptomatic, when morbidity and mortality are much worse. The prevalence of aortic valve disease is increasing with an aging population and many patients are not diagnosed until they have symptoms of shortness of breath, syncope, or chest pain.11 Performing cardiac auscultation in older adults is key to early identification of aortic stenosis; patients who are symptomatic on presentation have a much higher cardiac morbidity and mortality.11
Holosystolic (valvular regurgitation) murmurs
These murmurs are caused by retrograde blood flow across an incompetent valve, which causes a pansystolic murmur that starts at S1 and ends at S2.
All diastolic murmurs should be considered pathologic. Aortic regurgitation is high-pitched, and best heard with the diaphragm of the stethoscope. Mitral stenosis is low-pitched and best heard with the bell.12
Pathologic continuous murmurs are a result of rapid blood flow or an abnormal communication between a high-pressure arterial compartment and a low-pressure venous compartment. Reasons for continuous murmurs caused by high-to-low pressure shunts include patent ductus arteriosus and arteriovenous fistulas of the coronary or pulmonary vessels. An example of a high-flow continuous murmur is a mammary souffle of pregnancy.13 These murmurs generally are unaffected by physiologic maneuvers and will not be covered in this article.
USING PHYSIOLOGIC MANEUVERS
Physiologic maneuvers, also called dynamic auscultation, can be used to help clinicians arrive at a diagnosis when a murmur is heard but the cause is difficult to ascertain.14 In patients with suspected hypertrophic obstructive cardiomyopathy, dynamic auscultation is required to correctly evaluate the murmur.6 For murmurs in general, and depending on the heart valve involved, certain physiologic maneuvers are used to either increase or decrease the intensity of the murmur being examined. In general, physiologic maneuvers seek to alter one of two hemodynamic parameters, preload or afterload.
In simple terms, preload refers to the amount of blood returning to the heart from the systemic circulation, and the volume of blood in the heart at the end of diastole.15 Increasing preload also increases the amount of blood that must transit the heart with each systolic beat. This upsurge in blood flow generally increases the intensity of lesions, such as a stenotic valve, that obstruct forward blood flow. Increasing the amount of blood returning to the heart also can change the character of a murmur by altering the contour of the left ventricle.
Several simple maneuvers can be used to temporarily alter preload:
- In a Valsalva maneuver, the patient bears down against a closed glottis. The conventional theory is that the maneuver causes increased intrathoracic and intra-abdominal pressure and reduces venous return to the right side of the heart. In recent research on left ventricular filling during Valsalva, Zhang and colleagues found that the increased intrathoracic pressure also causes increased vascular resistance in the left side of the heart and the pulmonary venous system. This reduces intraluminal pressure in the pulmonary vessels and reduces left ventricular filling.16 Decreased right-sided preload causes decreased left-sided preload, and with less blood in the left ventricle, a murmur such as aortic stenosis will decrease.
- Squatting increases venous return to the right side of the heart with compression of the veins in the lower extremities and has the opposite effect to the Valsalva maneuver. With increased right-sided preload, and thus increased left-sided preload, the aortic stenosis murmur will be amplified.12
- Standing from a squatting position causes the column of blood to pool in the lower extremities and decreases right-sided preload and decreased left ventricular end-diastolic pressure, left ventricular size and decreases stroke volume. Because of less volume in the left ventricle, an aortic stenosis murmur will decrease. Standing from a supine position also decreases an innocent murmur of childhood.17
The pressure in the systemic circuit against which the heart must pump to eject blood is called afterload.15 In general, this increased back pressure on the heart boosts the intensity of murmurs that lead to retrograde blood flow (such as mitral regurgitation). It is also relatively simple to temporarily increase afterload.
- Handgrip increases afterload by increasing systemic vascular resistance. This increase in pressure causes a delay in left ventricular emptying, and with less flow, a murmur of aortic stenosis will decrease. However, with increased left ventricular pressure the mitral regurgitation murmur will increase.12
Through clinical experience, we have found that the effects of the maneuvers described above only last for several heartbeats. The body very quickly adjusts to the altered hemodynamics to reestablish homeostasis. Clinicians should be sure their stethoscopes are in place and listen carefully as they perform the maneuver.
THE VENTILATORY CYCLE
Changes in intrathoracic pressure associated with breathing also can alter the characteristics of a murmur and assist with identification. Inspiration increases right-sided heart murmurs (tricuspid and pulmonary valves) and expiration increases left-sided murmurs (mitral and aortic valves). Use the mnemonic RILE: Right-Inspiration, Left-Expiration.14,15
Inspiration creates negative intrathoracic pressure and increases venous return to the right side of the heart. With this increase in preload, right-sided heart murmurs such as tricuspid regurgitation and pulmonic stenosis are increased.18 This change in the character of this murmur is sometimes referred to as Carvallo sign.4
Expiration increases intrathoracic pressure, reduces venous return to the right side of the heart, and forces blood out of the lungs to the left atrium. The increase of preload to the left side of the heart increases left-sided murmurs such as mitral regurgitation and aortic stenosis.12
CHOICE AND TIMING OF MANEUVERS
For patients with midsystolic murmurs:
- If the cause is hypertrophic cardiomyopathy, standing and Valsalva maneuvers increase the murmur; squatting and handgrip maneuvers decrease it.
- If the cause is aortic stenosis, squatting and leg raises increase the murmur; standing, Valsalva, and handgrip maneuvers decrease it.
- If the cause is pulmonic stenosis, inspiration increases the murmur.
- If the murmur is innocent, standing for 1 minute from a supine position will decrease it.6,12,14 Physiologic innocent murmurs in children are midsystolic murmurs heard along the left sternal border when the patient is supine. In one study, 65% to 85% of young schoolage children had innocent murmurs.17 Lefort and colleagues found that a reliable clinical tool for ruling out pathologic heart murmurs was the murmur disappearing when the child stood up from a supine position.17
Although this is a useful physical examination pearl to identify a possibly innocent murmur, a study conducted by Khushu and colleagues found that 20% of children with asymptomatic murmurs had some form of congenital heart disease.19 These researchers support the current recommendation that all children with heart murmurs be referred for cardiology consultation and echocardiography.19
For holosystolic murmurs:
- If the cause is mitral regurgitation, squatting and handgrip maneuvers increase the murmur; standing and Valsalva maneuvers decrease it.
- If the cause is tricuspid regurgitation, inspiration increases the murmur.
- If the cause is a ventricular septal defect, squatting and handgrip maneuvers increase the murmur; standing decreases it.12
For diastolic murmurs:
- If the cause is aortic regurgitation, squatting, leg raise, and handgrip maneuvers increase the murmur; standing and Valsalva maneuvers decrease it.
- If the cause is mitral stenosis, the murmur increases with the handgrip maneuver, or when the patient is placed in the left lateral decubitus position with his or her breath held in exhalation.12
Importance of auscultation in patients after acute coronary syndrome (ACS)
In patients who have had ACS, cardiac auscultation for murmurs is important to determine if complications are developing. Any systolic murmur that develops after ACS is a red flag.
- Ventricular septal rupture may develop after an anteroseptal infarction. The patient will exhibit respiratory distress and acute heart failure. Auscultation will reveal a loud, harsh, holosystolic murmur with a palpable thrill.
- Left ventricular dilation secondary to ischemia or heart failure can cause mitral regurgitation and a holosystolic, high-pitched murmur. An isometric handgrip or leg raising will increase the murmur's intensity.
- Chordae tendinae rupture, papillary muscle rupture, and papillary muscle dysfunction are complications of ACS and can cause acute mitral regurgitation and a new holosystolic harsh murmur. Another complication after ACS is a reactive pericarditis (Dressler syndrome) that can cause a pericardial friction rub.20
CLINICAL AUSCULTATION PEARLS
- Diastolic murmurs and murmurs associated with a palpable thrill are almost always pathologic.
- Inspiration increases right-sided murmurs (tricuspid stenosis and pulmonic stenosis) and exhalation increases left-sided murmurs (aortic stenosis, mitral stenosis, mitral regurgitation).
- The murmur of aortic regurgitation is best heard at the second and third left intercostal space due to the angle of the regurgitant flow through the aortic valve toward the left side of the heart.
- A mitral regurgitation murmur will radiate to the left axilla.
- Differentiate an aortic stenosis murmur from hypertrophic cardiomyopathy by having the patient perform maneuvers that increase the venous return to the heart. Squatting or passive leg raising (increased venous return) decreases the midsystolic murmur of hypertrophic cardiomyopathy because increased volume in the left ventricle pushes the hypertrophic septum away from the ventricular outflow tract. Conversely, these maneuvers increase murmurs caused by aortic stenosis. Also, a murmur secondary to aortic stenosis will radiate to the neck through the carotids.
- Standing from a supine position has a 98% positive predictive value for decreasing the intensity of physiologic innocent murmurs in children.
Physical examination skills such as auscultation are in danger of becoming obsolete because of the availability of bedside and pocket echocardiography. However, combining new technologies such as pocket ultrasound devices with good auscultation skills improves diagnostic accuracy and patient care.9 Cardiac examination remains a cost-effective, sensitive, and specific method to identify cardiac disease. Clinicians can use physiologic maneuvers during the cardiac examination to help differentiate difficult cardiac murmurs and guide patients to appropriate care.
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