Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
Functional murmurs
Practicing cardiology remains a powerful experience for the clinician. The ability to look, feel, and listen remains the most highly rewarding foundation of the diagnostic capability, nowhere more evident than in the assessment of subjects with congenital heart disease. The stethoscope is a lasting symbol of healing professions. Invented in 1816 by Laënnec in France, the word “stethoscope” originates from the Greek “stethos,” meaning “chest,” and “scope,” meaning “to look.” The original meaning of this classic tool has withstood the test of time, as primary diagnosis for cardiovascular disease has evolved with the stethoscope, the phonocardiogram, and cardiac ultrasound, all modalities that are discussed throughout this book.
Sounds produced by mechanical processes in the heart can be correlated with the presence or absence of disease. Most normal heart sounds occur during the closing of heart valves. Pathological murmurs occur where flow is made turbulent by the presence of abnormal pressure gradients between vascular structures, cardiac chambers and/or heart valves as they open and close. The timing, duration, pitch, intensity, location, and changes with hemodynamic maneuvers relate to the characteristics of the pressure changes from which they originate. In this chapter as in others, signal processing techniques, such as phonocardiogram recording, are used to illustrate heart sounds and murmurs.
Murmurs that occur in the absence of either morphologic or physiologic abnormalities of the heart or circulation have been called normal, innocent, functional, physiologic, or benign. These murmurs are common in children. The ability to differentiate functional from pathological murmurs is more consistent in children than in adults. The index of suspicion is the murmur itself in light of an otherwise normal auscultation, physical examination, and electrocardiogram.
Functional systolic and continuous murmurs unassociated with pathology are described below and shown in Box 2.1 . Functional murmurs are never solely diastolic, with one exception: the transient left basal holodiastolic or middiastolic ductus arteriosus murmur sometimes heard during the first 3 or 4 days of life, where a valve-like structure at the pulmonary arterial end of the ductus (see Chapter 17 ) is held responsible for selective diastolic flow. ,
BOX 2.1
Functional Murmurs
- A.
Systolic
- 1.
The vibratory systolic murmur of Still
- 2.
The pulmonary artery systolic murmur
- 3.
The branch pulmonary artery systolic murmur
- 4.
The supraclavicular systolic murmur
- 5.
The systolic mammary souffle
- 6.
The aortic sclerotic systolic murmur
- 7.
The cardiorespiratory systolic murmur
- 1.
- B.
Continuous
- 1.
The venous hum
- 2.
The continuous mammary souffle
- 3.
The cephalic continuous murmur
- 1.
Functional systolic murmurs
The vibratory systolic murmur
The normal vibratory midsystolic murmur was described by George F. Still in 1909 ( Figs. 2.1 and 2.2 ). Still wrote, “It is heard usually just below the level of the nipple, and about halfway between the left margin of the sternum and the vertical nipple line....Its characteristic feature is a twanging sound very like that made by twanging a piece of tense string....Whatever may be its origin, I think it is clearly functional, that is to say, not due to any organic disease either congenital or acquired.”
Still’s murmur is seldom heard in infants but is prevalent after 3 years of age with diminishing frequency toward adolescence. The murmur ranges from grade 1 to 3/6 and is loudest between the apex and lower left sternal edge in the supine position. , During exercise, excitement, or fever, the murmur intensifies (see Fig. 2.1 ). The quality is distinctive , —vibratory or buzzing with a uniform, medium, pure frequency (70 to 130 cycles per second) requiring the stethoscopic bell for best assessment. The closest acoustic analogy is Still’s twanging of a taut rubber band or string (see earlier). The murmur begins shortly after the first heart sound and is typically confined to the first half of systole with a relatively long gap between the end of the murmur and the second heart sound (see Figs. 2.1 and 2.2 ).
The mechanism of Still’s murmur remains to be established. The pure medium frequency implies that a cardiac structure is set into periodic vibration during ventricular systole. Origin in the right side of the heart has been assigned to the pulmonary valve itself when “trigonoidation” of the leaflets results in periodic vibrations of the base of the cusps. A catheter across the pulmonary valve can tense the cusps and generate a transient pure-frequency midsystolic murmur ( Fig. 2.3 B). The relatively low right ventricular ejection pressure and velocity are believed to cause the attachments of the pulmonary cusps to vibrate at a low to medium frequency. A murmur produced by a vibrating semilunar valve at its arterial attachment tends to be transmitted into the cavity of the concordant ventricle, which could account for the thoracic location of Still’s murmur between the apex and lower left sternal edge (i.e., topographically over the right ventricle). In children with Still’s murmur, Doppler echocardiography has identified systolic vibrations in the aortic valve and higher maximum acceleration of flow in the left ventricular outflow tract. , However, a murmur originating in a vibrating aortic valve would be transmitted into the left ventricular cavity and heard best over the left ventricular impulse. Midsystolic murmurs in adults have been ascribed to high intraventricular velocities generated by vigorous left ventricular contraction associated with an increase in left ventricular mass. Origin of Still’s murmur has also been assigned to the left ventricular cavity , a location that is in accord with delayed response to the Valsalva maneuver. Left ventricular bands or false tendons (see Fig. 2.3 A) are believed to vibrate periodically during ventricular systole and transmit their vibrations to the chest wall. A high percentage of patients with Still’s murmur reportedly have left ventricular bands, especially in the outflow tract. However, the prevalence of Still’s murmur declines from childhood to adolescence, , whereas the prevalence of left ventricular bands is the same in children, adolescents, and adults. , , The incidence of Still’s murmur is believed to exceed the incidence of left ventricular bands, although incidence depends largely on the avidity with which bands are sought with echocardiography.
The pulmonary artery systolic murmur
A functional systolic murmur in the main pulmonary artery is most prevalent in children, adolescents, and young adults. , , The murmur is midsystolic with maximum intensity in the second left intercostal space next to the sternum ( Fig. 2.4 ), and ranges from barely audible to grade 3/6 in response to exercise, fever, or excitement. The frequency composition is medium-pitched and impure and best heard in the supine position with the stethoscopic diaphragm or moderate pressure of the bell during full held exhalation. , , The murmur represents normal ejection vibrations that reach the threshold of audibility from within the main pulmonary artery during right ventricular systole. The chest wall location is appropriate for origin in the pulmonary trunk, and intracardiac phonocardiograms record midsystolic murmurs within the pulmonary trunk in normal young subjects.
These murmurs are commonly heard during pregnancy and in subjects with anemia or hyperthyroidism. Loss of thoracic kyphosis increases proximity of the pulmonary trunk to the chest wall and increases the incidence of pulmonary systolic murmurs in the second left interspace.
The branch pulmonary artery systolic murmur
Branch pulmonary artery systolic murmurs are occasionally heard in normal neonates, especially premature neonates. , These murmurs are typically grade 1 to 2/6, are medium-pitched, and impure, but most importantly, are distributed to the left and right anterior chest, axillae, and back. The similarity of frequency composition to breath sounds, the rapid respiratory rate of infants, and the widespread thoracic locations of pulmonary artery systolic murmurs cause these murmurs to be overlooked. Audibility is improved if respiration is temporarily arrested by pinching the nostrils while the infant sucks a pacifier. Auscultation is best carried out by examining the infant in both supine and prone positions and by using the stethoscopic diaphragm applied to the right and left anterior chest, back, and axillae. The murmurs are typically confined to neonates, are usually absent at the first well-baby examination, and seldom persist beyond 3 to 6 months of age. , , The transient branch pulmonary artery systolic murmur in normal neonates is indistinguishable from the peripheral murmur of fixed stenosis of the pulmonary artery and its branches (see Chapter 10 ). The analogy sheds light on the mechanism of production. , , The pulmonary trunk in the fetus is a relatively dilated domed structure because it receives the output of the high-pressure right ventricle. Proximal right and left pulmonary arteries arise from the pulmonary trunk as comparatively small lateral branches that receive a paucity of intrauterine blood flow. When the lungs expand at birth, the difference in size between the pulmonary trunk and its right and left branches transiently persists, especially in premature infants ( Fig. 2.5 ). In addition to the disparity in size, the branches arise at relatively sharp angles from the inferior and posterior walls of the pulmonary trunk. These anatomic arrangements account for both the turbulence and the physiologic drop in systolic pressure from pulmonary trunk to proximal branches and for the branch pulmonary artery systolic murmur. ,
You're Reading a Preview
Become a Clinical Tree membership for Full access and enjoy Unlimited articles
If you are a member. Log in here
