Wide Splitting of the Second Sound
Normally, during expiration, the second heart sound becomes single. Failure to do so represents abnormal or wide splitting of the second sound. Should the normal ventilatory variation be recognized (see normal splitting of the second sound), the descriptive terminology is "wide splitting of the second sound with physiological variation".
The most common cause of wide splitting with physiological variation is electrical delay of right ventricular activation or right bundle branch block (RBBB). Other causes include pulmonary hypertension, pulmonary valve stenosis, partial anomalous insertion of pulmonary veins and sources of early aortic valve closure such as severe mitral regurgitation and ventricular septal defect.
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Updated September 2010