Paradoxical Splitting of the Second Sound
The normal or "physiological" splitting of the second heart sound (see physiological splitting podcast) increases so as to be recognizable after inspiration but inaudible after expiration. Paradoxical splitting or the "unexpected" observation is the presence of splitting at rest with a return to normal or a single second sound during expiration. Since this is the opposite of the normal or "physiological" finding, it is termed paradoxical splitting of the second sound.
This finding is most often present in the setting of left bundle branch block or ventricular pacing but it may also be seen in left ventricular failure; with volume lesions of the left ventricle such as patent ductus arteriosus; in patients with severe aortic valve stenosis, or uncontrolled hypertension; and with premature closure of the pulmonary valve as seen in severe tricuspid valve stenosis.
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Updated July 2010