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A 74 year old female was admitted to our hospital because of bradycardia caused by digitalis intoxication. The patient had undergone percutaneous transvenous mitral commissurotomy four years ago. The left atrial pressure decreased to 12 mm Hg at the end of the procedure and no continuous murmur was heard. On physical examination a grade 3/6 continuous murmur was heard over the fifth intercostal space at the right sternal border besides an apical diastolic rumbling murmur. The peak intensity of the murmur was around the S2 and was barely heard around the S1.
Transoesophageal echocardiography revealed a tiny hole in the atrial septum and a continuous flow signal was seen from left atrium to right atrium through the hole with a peak velocity of 2 m/s (top). The continuous murmur disappeared when a 7 NIH catheter crossed the hole and was placed in the left atrium during cardiac catheterisation. Mean left and right atrial pressures were 24 mm Hg and 5 mm Hg, respectively, and the calculated mitral valve area was 1.2 cm2 (bottom).
The maximal echo Doppler velocity during a cardiac cycle coincided with the maximal intensity of the continuous murmur. The diameter of a 7 French catheter was sufficient to stop the left to right shunt. Although an uncomplicated atrial septal defect itself does not produce any murmur and the velocity is usually less than 1 m/s, the murmur in this patient was caused by an increased flow velocity through the hole implying increased left atrial pressure.