Opening Snap of Mitral Valve Stenosis
You can hear the opening snap near the cardiac apex, but more easily appreciate it along the lower left sternal border. Its proximity to aortic valve closure may create confusion with a widely split second sound. You may find the sound less confusing if you inch upward along the left sternal border and note a decline in the intensity of the early diastolic sound in conjunction with audible splitting of the second sound with inspiration.
It is important to listen carefully to a mitral opening snap so you can identify a still mobile mitral valve and estimate the severity of mitral stenosis. As the severity of mitral stenosis increases, left atrial pressure rises. Rising left atrial pressure results in the mitral valve opening at earlier time points along the decline of left ventricular pressure during relaxation. Therefore, the time from aortic valve closure sound to opening snap (often referred to as the A2-OS) offers us a method for estimating the severity of the disease. Consider also that A2/OS may be influenced by heart rate, impaired left ventricular relaxation, and concurrent mitral regurgitation.
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Updated August 2009