Why does inspiration cause splitting of s2

Split S2 The sound you are hearing now is a normal sinus rhythm with a splitting of S2. Because this sound is looped for playback, you are hearing only the split S2. If this were the actual sound pattern you heard when auscultating, this would be a fixed, split S2, which is not a normal condition and is associated with atrial septal defects. The venous return to the right ventricle RV increases during inspiration due to negative intrathoracic pressure and P2 is even more delayed, so it is normal for the split of the second heart sound to widen during inspiration and to narrow during expiration.

Clinically, this is more remarkable with slow heart rates. In that case, the split is usually wide and fixed with no change difference between inspiration and expiration due to fixed RV volume see ASD section.

In both conditions, the aortic valve A2 closes after the pulmonary valve P2. Since the respiration only affects P2, its effect in paradoxical splitting is the opposite of normal, i. The third heart sound S3 represents a transition from rapid to slow ventricular filling in early diastole. S3 may be heard in normal children. The fourth heart sound S4 is an abnormal late diastolic sound caused by forcible atrial contraction in the presence of decreased ventricular compliance.

A figure showing normal and abnormal splitting of the second heart sound. Started in , this collection now contains interlinked topic pages divided into a tree of 31 specialty books and chapters. Content is updated monthly with systematic literature reviews and conferences.

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