Silent mitral stenosis

Silent mitral stenosis


When the mitral diastolic murmur is not audible despite the presence of severe mitral stenosis, it is called silent mitral stenosis (MS).

Mechanism and causes of silent MS

Right ventricular hypertrophy causes clockwise rotation of the heart so that the left ventricle becomes more posterior and the apex is formed by the right ventricle. Hence the mitral diastolic murmur is not heard at the apex. Another reason is the decreased flow across the mitral valve in very severe mitral stenosis diminishing the intensity of the murmur. The decreased mobility of the thick and calcified mitral leaflets in severe calcific mitral stenosis may contribute to the decrease in intensity of the mitral diastolic murmur.

Lutembacher syndrome [1], pulmonary emphysema, and obesity are other possible causes for silent MS. Severe tricuspid stenosis is another cause of silent mitral stenosis [2]. In this case even the transmitral gradient may be low despite having severe mitral stenosis.

Transmitral gradient may be lower than that expected for the severity of mitral stenosis in Lutembacher syndrome. Due to the associated large atrial septal defect, gradient between left and right atria is reduced. Hence the left atrial pressure is lowered and consequently the transmitral gradient. But the left to right shunt across the ASD will be high.

In emphysema and obesity, the murmur of mitral stenosis may be inaudible due to poor transmission from the heart to stethoscope. In emphysema air intervenes while adipose tissue intervenes in obesity. Murmur audibility may improve on auscultation in held expiration in the left lateral position.

Silent MS can present as pulmonary hypertension with right heart failure [3] or with Ortner’s syndrome due to compression of the left recurrent laryngeal nerve by massively dilated left atrium or pulmonary artery [4]. Ortner’s syndrome presents with hoarseness of voice.

References

  1. El-Sherif N, El-Mallah S, El-Ramli ZM, Sorour AH. The acquired Lutembacher’s syndrome a cause for “Silent” MS. J Egypt Med Assoc. 1968;51(9):723-36.
  2. Sheikhzadeh A, Moghbeli H, Ghabussi P, Tarbiat S. Severe tricuspid valve stenosis. A cause of silent MS. Jpn Heart J. 1983 Jul;24(4):563-70.
  3. Lenkin ML, Shugoll GI. Silent MS presenting as pulmonary hypertension with right heart failure. Med Ann Dist Columbia. 1967 Oct;36(10):594-8.
  4. Agrawal JK, Agrawal BV. Silent MS with Ortner’s syndrome. J Assoc Physicians India. 1973 Apr;21(4):387-90.

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