Download Murmurs Dr. Jason Waechter June/2004 A murmur is a sound

Murmurs
Dr. Jason Waechter
June/2004
A murmur is a sound caused by vibration due to turbulent flow of blood. It can occur in the heart
or in vascular structures close to the heart. They can occur in states of disease, but can also occur
in a structurally normal heart.
This handout will outline briefly, the mechanisms of some common murmurs with the aim to help
make murmur classification more easily understood.
The following diagram shows the necessary physical layout for most murmurs:
High(er) pressure
Low(er) pressure
Narrowing
The simplified diagram shows 2 chambers connected by a segment that is narrowed. Blood flows
from the chamber of higher pressure to the chamber of lower pressure. As a consequence of this
physical arrangement, blood flow is fast through the narrowing, but then becomes turbulent (as
opposed to laminar) in the receiving chamber. Turbulent flow causes vibrations against the
chamber wall and this produces sound. Note that a “chamber” does not need to be a cardiac
chamber, but can also be a large blood vessel.
Turbulent flow
When this same phenomenon occurs at a site distant to the heart, the sound is called a bruit
(pronounced brew-ee). Bruits are described in the carotid, abdominal aortic, renal, and femoral
arteries, to name a few locations. In this situation, the 2 “chambers” are the artery before and after
the narrowing. Bruits and murmurs are essentially the same thing, but in different locations.
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Describing Murmurs
Murmurs can be described a number of different ways:
• timing:
 cardiac cycle: systolic, diastolic, or both
 early, middle, late or throughout (pan- or holo-) the cardiac cycle
• mid systolic is also called “diamond shaped” and “crescendo/decrescendo”
• intensity: 6 point scale (denoted in roman numerals)
 Grade I/VI: very quiet, maybe requires special manouvres to hear
 Grade II/VI: quiet to moderate volume
 Grade III/VI: loud volume, easy to hear for beginners
 Grade IV/VI: has a thrill (palpable vibration accompanies the sound)
 Grade V/VI: can be heard with edge of stethoscope on patient. Very loud.
 Grade VI/VI: can be heard with stethoscope OFF patient. Very loud.
• note: grades V and VI can have, but do not require, a thrill
• location:
 where is the murmur the loudest
 where does the murmur radiate to (other locations it can be heard)
• quality:
 what does the actual sound resemble
• “musical”, “machinery”, high pitched, low pitched
• requires some experience to be able to describe
Understanding Patterns of Murmurs
A little common sense and logic will help you understand and remember what types of murmurs
are associated with which lesions:
• think about which chamber has high pressure and which has low pressure and how this is
determined by the cardiac cycle
• understand that regurgitation means “leaking backward” and is the same as insufficiency
• understand that stenosis means narrowing
For example, if you think about aortic valve stenosis, can you predict which part of the cardiac
cycle the murmur will occur in?
Answer:
• during systole, blood flows through the narrowed aortic valve from the high pressure left
ventricle to the lower pressure aorta
• during diastole, there is no blood flow through the aortic valve (valve is closed)
• thus, the murmur will be a systolic murmur
• high pressure chamber = left ventricle, low pressure chamber = aorta
What about aortic regurgitation?
Answer:
• during systole, blood flows through the (normal sized) aortic valve
• during diastole, blood flow does occur in a backward direction from the high pressure aorta
into the low pressure diastolic left ventricle
• leakage during diastole occurs through a “partly opened” valve which produces a functional
narrowing of the valve and the murmur will be diastolic
• high pressure chamber = aorta, low pressure chamber = left ventricle
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Can you predict the cardiac cycle(s) of the following murmurs? (answers at bottom)
1.
Aortic regurgitation/insufficiency
2.
Aortic stenosis
3.
Mitral regurgitation/insufficiency
4.
Mitral stenosis
5.
Patent ductus arteriosus (PDA)
6.
Ventricular Septal Defect (VSD)
7.
Pulmonary stenosis
8.
Tricuspid regurgitation
Hints:
• what are the 2 “chambers” being considered
• what is the pressure relationship between these 2 chambers during the cardiac cycles
Try to fill in your answers before looking at the answers provided.
“Normal” murmurs:
Murmurs can occur in a structurally normal heart with normal valves. Note that a normal valve
creates a slight narrowing. Thus, during conditions where flow rates are very high through a
normal valve, a murmur can be created. Names for these murmurs include flow murmurs or
physiological murmurs. They are usually mid-systolic and can occur in:
• children
• pregnancy
• pathological “high output” states
 hyperthyroidism
 fever
 sepsis
Further reading:
• Bates' Guide to Physical Examination & History Taking
• Cecil Essentials of Medicine
• Cecil Medicine (MDConsult textbook listed under “Internal Medicine”)
• Braunwald’s “Heart” (MDConsult textbook listed under “Cardiology”)
• Website with very detailed information: http://www2.umdnj.edu/~shindler/abc.html
Answers to table:
1-diastolic, 2-systolic, 3-systolic, 4-diastolic, 5-both, 6-systolic, 7-systolic, 8-systolic
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