<Li> Split during inspiration: normal . (See above) </Li> <Li> Wide splitting: seen in conditions that delay RV emptying (pulmonic stenosis, RBBB). Delay in RV emptying causes delayed pulmonic sound (regardless of breath); it is an exaggeration of normal splitting sounds . </Li> <Li> Split during expiration: Reverse splitting indicates pathology . Aortic stenosis, hypertrophic cardiomyopathy, left bundle branch block (LBBB), and a ventricular pacemaker could all cause a reverse splitting of the second heart sound . </Li> <Li> Split during both inspiration and expiration: <Ul> <Li> If splitting does not vary with inspiration, it is termed a "fixed split S" and is usually due to a septal defect, such as an atrial septal defect (ASD). The ASD creates a left to right shunt that increases the blood flow to the right side of the heart, thereby causing the pulmonary valve to close later than the aortic valve independent of inspiration / expiration . </Li> <Li> A bundle branch block either LBBB or RBBB, (although RBBB is known to be associated only with S1 split), will produce continuous splitting but the degree of splitting will still vary with respiration . </Li> </Ul> </Li>

Causes of reverse splitting of second heart sound