Wide split fixed 2nd hea sound is heard in :March 2005

Ans. C: ASDFixed splitting denotes absence of significant variation of the splitting interval with respiration, such that the separation of A2, and P2, remains unchanged during inspiration and expiration.Atrial septal defect, with either normal or high pulmonary vascular resistance, is the classic example of fixed splitting of the second sound.The fixed nature of the split is due to approximately equal inspiratory delay of the aoic and pulmonic components, indicating that the two ventricles share a common venous reservoir. Respiratory splitting of the second sound immediately returns to normal following surgical repair of an atrial septa] defect, although the pulmonic closure sound may remain delayed for weeks or months.Severe right hea failure can lead to a relatively fixed split. This occurs because the right ventricle fails to respond to the increased volume produced by inspiration and because the lungs are so congested that impedance to forward flow from the right ventricle barely falls during inspiration.In anomalous pulmonary venous return without atrial septal defect, fixed splitting is not usually seen despite the simultaneous inspiratory delay in aoic and pulmonic closure