To the Editor: Lobstein et al. (N Engl J Med 289:127–131, 1973) accurately describe the effects that vasoactive maneuvers may have on the systolic click and murmur in patients with the mitral click-murmur syndrome. However, their statement that the murmur of rheumatic mitral regurgitation is unaltered by these maneuvers requires comment. After amyl nitrite inhalation or during the strain phase of Valsalva's maneuver, the systolic murmur of rheumatic mitral regurgitation usually is appreciably reduced in intensity and may shorten in duration. Elevating afterload with phenylephrine, squatting, or the overshoot phase of Valsalva's maneuver is frequently associated with a concomitant increase.
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