Heart Murmurs

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Chapter 12 Heart Murmurs

Introduction and Basic Issues

Table 12-2 Classification of Murmurs Described in This Chapter*

A. Functional (27–65) B. Systolic (66–194) C. Diastolic (197–258)
Systolic Semilunar Ejection Atrioventricular Stenosis
• Still’s murmur (46–50) • Aortic stenosis • Mitral stenosis (197–209)
     • Valvular (82–115)
   • Subvalvular hyper-trophic (116–128)
   • Subvalvular “fixed” (129)
   • Supravalvular (130)
• Pulmonary systolic ejection murmur (51) • Pulmonic stenosis (132–133) • Mitral diastolic flow murmur (210)
• Supraclavicular arterial bruit (52) • Ventricular septal defect (134–138) • Tricuspid stenosis (211–212)
• Aortic sclerosis (56–65)   • Tricuspid diastolic flow murmur (213–215)
Continuous AV Regurgitation Semilunar Regurgitation
• Venous hum (53) • Mitral regurgitation (142–170) • Aortic regurgitation (216–251)
• Mammary soufflé (54) • Mitral valve prolapse(171–184) • Pulmonic regurgitation (252–258)
  • Tricuspid regurgitation (185–194)  
Diastolic    
• Very rare, and always associated with either S3 or a diastolic rumble (33–34)    

* Not including continuous extracardiac murmurs like that of patent ductus arteriosus. The numbers in parentheses refer to the pertinent questions.

Cardiac auscultation is the centerpiece of physical diagnosis, and recognizing murmurs is its most challenging aspect. It requires the identification of sounds jam-packed in less than 0.8 second, often overlapping, and not infrequently at the threshold of audibility. Stethoscopy is like learning a musical instrument and similarly rewarding. Hence, despite being as old as the battle of Waterloo, this little tool and its skillful use still occupy an important role in 21st-century medicine.

1 What are the auscultatory areas of murmurs?

The classic ones are shown in Fig. 12-1 and Table 12-1. Auscultation typically starts in the aortic area, continuing in clockwise fashion: first over the pulmonic, then the mitral (or apical), and finally the tricuspid areas. Since murmurs may radiate widely, they often become audible in areas outside those historically assigned to them. Hence, “inching” the stethoscope (i.e., slowly dragging it from site to site) can be the best way not to miss important findings.

5 What, then, should be the approach to a newly detected murmur?

The first step should be to use the cardiovascular exam to separate pathologic from functional murmurs (see below, questions 2833). This is essential to avoid expensive and possibly dangerous laboratory tests. Then, if the murmur is identified as organic, the physical examination should provide clues to its site of origin, its hemodynamic cause, and, possibly, its severity.

Classification

10 How are murmurs classified?

The first (and most important) separation is purely clinical: pathologic versus functional. The real classification, however, is based on the phase of the cardiac cycle where the murmur is located. Accordingly, murmurs are divided into systolic, diastolic, and continuous. This is clinically relevant, since diastolic and continuous murmurs are (almost) always pathologic, whereas systolic murmurs are often functional (Fig. 12-2).

image

Figure 12-2 Phonocardiographic description of pathologic cardiac murmurs.

(From James EC, Corry RJ, Perry JF: Principles of Basic Surgical Practice. Philadelphia, Hanley & Belfus, 1987.)

Systolic murmurs are then further classified into ejection and regurgitant. This division, first proposed by Leatham in 1958, is based on the murmur’s length and relationship to S2. It defines ejection murmurs as forward flowing, crescendo-decrescendo, early to mid systolic, and ending always before S2. Conversely, it defines regurgitant murmurs as backward flowing, plateau shaped, spanning throughout systole, and always incorporating S2. Still, regurgitant murmurs also may be limited to late systole. In fact, they may even last beyond S2. Yet, their hallmark remains the extension into the S2. Although clinically valuable (regurgitant murmurs tend to be pathologic, whereas ejection murmurs are often functional), Leatham’s classification is impractical since some regurgitant murmurs may have an ejection quality. Moreover, it relies on the bedside identification of S2, which is not always easy. Hence, today’s preference is for separating murmurs only on the basis of systolic timing (early, mid, late, and holo) and by using as reference points both S1 and S2. Accordingly:

14 Once the phase of the cardiac cycle has been identified, which other characteristics of a murmur should be analyzed and described?

1. The timing: Murmurs can span throughout systole (holosystolic) or diastole (holodiastolic), or they may occur only in the early, mid, or late phases of each interval:

2. The intensity (or loudness): Traditionally graded by the Levine system from 1/6 to 6/6:

19 What is the effect of respiration on murmurs?

It depends. Initially noted by Pierre Potain in 1866 (and then rediscovered by Carvallo in 1946 and Leatham in 1954), respiration has important effects on murmurs’ intensity (not to mention on the splitting of S2) because of its associated swings in intrathoracic pressure and venous return. As a result, all right-sided findings (with the exception of the pulmonic ejection sound) get louder on inspiration (because of greater venous return to the right ventricle). Conversely, all left-sided findings either soften or stay the same (because of decreased left-sided venous return, caused by lung pooling—or, alternatively, because of the inspiratory interposition of the pulmonary appendage between the cardiac apex and chest wall). This physiologic principle provides the basis for the Rivero-Carvallo sign/maneuver: an increase in intensity of the holosystolic murmur of TR during (or at the end of) a deep inspiration—a highly specific (100%) but not too sensitive (60%) tool for the bedside separation of TR from MR. In a study by Cha et al. of 35 patients with valvular disease, all 19 with Rivero-Carvallo had TR on ventriculography. Yet, of the 16 without Rivero-Carvallo, only five had normal ventriculography; five had 1+ regurgitation, and six had 3+/4+ regurgitation. Hence, Rivero-Carvallo is a reliable indicator of TR, but its absence does not exclude it. Since it may be difficult to hear the changes in murmur intensity during normal respiration, auscultation should always be carried out in two phases: first at the end of a deep inspiration (while the patient is in post inspiratory apnea [i.e., holding breath for 3 to 5   seconds]) and then at the end of a deep expiration (while the patient is in post expiratory apnea for 3–5   seconds). The loudness of the systolic murmur should then be compared between the two phases, remembering that TR will get louder in held-inspiration (and, possibly, higher pitched, too), whereas MR will remain unchanged or soften. Held exhalation is also useful when searching for either a pericardial rub, the soft murmur of aortic regurgitation, or the faint pulmonic mid-systolic murmur of a patient with loss of thoracic kyphosis (i.e., straight back syndrome murmur).

22 What is the effect of Valsalva on sounds and murmurs?

Valsalva not only has important hemodynamic effects (that can be used for the recognition of congestive heart failure—see Chapter 2, questions 121–127), but may also elicit a diagnostic auscultatory response in patients with HOCM or mitral valve prolapse (MVP). This is mediated by a reduction in left ventricular diameter (caused by the strain), which in turn increases the left ventricular gradient of HOCM, thus intensifying its subvalvular systolic ejection murmur. This is the opposite of what happens to other murmurs of left ventricular outflow obstruction (such as, for example, valvular AS or PS), which instead soften with Valsalva (because of decreased venous return, with a resulting decrease in transvalvular gradients). The strain phase of Valsalva also anticipates the prolapse of a floppy mitral valve (by making the ventricle smaller, and thus “loosening up” the chordae tendineae). As a result, the click will occur earlier, and the murmur will lengthen. Hence, only two murmurs get enhanced by the straining phase of Valsalva: HOCM and MVP. In HOCM, the murmur gets louder, whereas in MVP it gets longer. Note that the release period of Valsalva may have opposite effects, based on the site of origin of the acoustic event being examined: right-sided murmurs will generally revert to their baseline intensity within 2–3 cardiac cycles, whereas left-sided murmurs will instead take a little longer (up to 5–10 cardiac cycles).

26 What about variations in cardiac cycle?

They also modify murmur intensity. For example, a longer diastolic pause (such as that following a premature beat) intensifies the murmur of AS because of lower systemic vascular resistances (due to the longer time available for aortic run-off into peripheral arteries) and higher left ventricular volume. This, in turn, increases contractility through Starling physiology, eventually resulting in higher transvalvular pressure gradients and thus a louder murmur. This triple phenomenon (lower afterload, higher preload, and increased contractility) also can be observed in situations of atrial fibrillation, where long and short cardiac cycles alternate randomly. Conversely, a murmur of atrioventricular regurgitation (like MR) tends to remain constant after a premature beat because the ejecting chamber has two available outlets: a normal forward/ejection one (large vessel) and an abnormal backwards/regurgitant one (atrium). This offsets the increase in ventricular contractility induced by a long diastole and thus keeps unchanged the intensity of a regurgitant murmur—even after a long diastolic phase. For instance, in the case of MR, the left ventricle can discharge into the left atrium (low pressure bed) or the aorta (high pressure bed). The percentage of blood ejected into each of these outlets depends on their relative resistance. After a long diastole (such as that following a premature beat), aortic resistance is decreased proportionally more than the atrial one (because even though the left atrium keeps filling during a long diastole, the aorta keeps emptying). As a result, although left ventricular volume is indeed higher after a premature beat (and so is contractility), proportionally more blood will be ejected into the aorta than into the atrium. This means that the regurgitant volume (and the intensity of the accompanying mitral murmur) will stay the same.

A. Functional Murmurs

28 How can physical examination help differentiate functional from pathologic murmurs?

There are two golden and three silver rules.

These silver rules are rooted in the pathogenesis of cardiac murmurs, which, in turn, relates to intracardiac pressure gradients and blood flow velocity. These are both maximal in early systole while tapering off during late systole and diastole. Hence, murmurs should never be generated during late systole or diastole. In fact, they should never touch the S2. If so, they reflect a high pressure gradient and thus a structural cardiac abnormality. This is also why benign systolic murmurs should always be “ejection” (i.e., with a crescendo-decrescendo shape) and not holosystolic (i.e., starting with S1 and ending with S2—in plateau fashion). Hence, pay close attention to S2, both in regard to intensity (with soft or absent S2 arguing in favor of pathology) and in regard to its relation of the murmur (with murmurs that incorporate S2 being more likely pathologic).

55 What can one do to sort out functional murmurs from pathologic ones?

1. Start with history, specifically:

2. Then continue with the physical examination, looking for clubbing and cyanosis and any abnormalities in the following areas of the cardiovascular exam:

3. Then carefully evaluate the murmur in its main characteristics, especially:

4. Finally, gather simple laboratory tests (such as an electrocardiogram or a chest x-ray), and look for any associated “bad company.”

B. Systolic Murmurs

(1) Systolic Ejection Murmurs