The absence of the apical first heart sound in patients with aortic incompetence should raise suspicion for premature mitral valve closure, which is associated with rapidly developing severe aortic regurgitation and a grave prognosis.
Absent apical S1 may flag premature mitral closure in severe AI; case report leaves open its independent prognostic value.
The phenomenon of premature mitral valve closure is described in three patients with severe aortic insufficiency and related to absence of the first heart sound. The occurrence of premature mitral closure is favored by severe aortic regurgitation probably with increased impedance to left ventricular filling. Available evidence suggests that this phenomenon usually occurs in the more rapidly developing forms of aortic incompetence (bacterial endocarditis, post surgical, and traumatic rupture of the valve), that it is uncommon, and that it often implies a grave prognosis. It should be suspected when the apical first heart sound is absent in aortic incompetence.
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Meadows et al. (1963) studied this question.