Turbulence due to a temporary increase in blood flow causes this murmur. Predisposing conditions include anemia, pregnancy, fever, and hyperthyroidism.
Stenosis of the pulmonic valve impairs flow across the valve, increasing afterload on the right ventricle. It is congenital and most often found in children. Pathologically increased flow across the pulmonic valve may mimic the murmur of pulmonic stenosis. The systolic murmur of an atrial septal defect originates from this flow, not the defect itself.
murs tend to peak near midsystole and usually stop before St. The crescendo-decrescendo or "diamond" shape is not always audible, but the gap between the murmur and S2 helps to distinguish midsystolic from pansystolic murmurs.
Location. 2nd to 4th left interspaces between the left sternal border and the apex
Intensity. Grade 1 to 2, possibly 3
None: normal splitting, no ejection sounds, no diastolic murmurs, and no palpable evidence of ventricular enlargement. Occasionally, a patient has both an innocent murmur and another kind of murmur.
Similar to innocent murmurs
Possible signs of a likely cause
Location. 2nd and 3rd left interspaces
Radiation. If loud, toward the left shoulder and neck
Intensity. Soft to loud; if loud, associated with a thrill
Quality. Often harsh
In severe stenosis, S2 is widely split and P2 is diminished. When P2 is inaudible, no splitting is heard.
An early pulmonic ejection sound is common.
A right-sided S4 may be present. The right ventricular impulse is often increased in amplitude and may be prolonged.
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TABLE 7-6 ■ Midsystolic Murmurs (Continued)
May be decreased
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