"Fixed" splitting of the second heart sound in ventricular septal defect.

Abstract

Eleven cases of catheter proven ventricular septal defect with left-to-right shunting in the absence of pulmonary hypertension were studied by phonocardiography. All showed wide and relatively fixed splitting of the second heart sound. Reasons for the relative fixation of the split are suggested, and the point is made that such fixed splitting is not necessarily a sign of atrial septal defect.The wide and fixed splitting of the two components of the second heart sound in patients with atrial septal defect is well established and is regarded as an important clue to the diagnosis of this condition (Aygen and Braunwald, I962; Dexter, I956). In one study of II5 patients with atrial septal defect, 87 showed no respiratory variation of these two components while in 28 there was an average increase of only o0oi sec an inspiration (Johnston, I957). The second heart sound in patients with ventricular septal defects, on the other hand, though recognized as being widely split, is generally thought to show normal movement with respiration. Leatham investigated 23 patients with ventricular septal defects of varying size, and found that in 17 of these subjects the second heart sound was widely split. On inspiration the width of the splitting increased 'normally' -that is, the split was wide but not fixed. However, the average amount of increase in splitting on inspiration in these patients was only 0eo2 sec (from an average of 0X045 sec in expiration to an average of o-o65 in inspiration) (Leatham and Gray, I956 Because it was our clinical impression that the respiratory variation of the A2-P2 interval in patients with ventricular septal defect was less than normal, we undertook the following study. Subjects and methodsPatients with ventricular septal defect were studied by phonocardiography. The criteria used for patient selection were:i Presence of a ventricular septal defect with left-to-right shunt confirmed by cardiac catheterization. 2 Absence of additional cardiac defects (for example, atrial septal defect, pulmonary stenosis, etc). 3 Absence of complete right or left bundlebranch block. 4 Absence of pulmonary hypertension due to raised pulmonary vascular resistance. Two patients with modestly raised pulmonary artery pressures associated with large left-to-right shunts were included. 5 Patient age sufficient to allow co-operation during sound recordings.Phonocardiograms were recorded at the pulmonary valve area and at the left sternal edge during and after held expiration and inspiration and during a prolonged period of exaggerated respiration. Valsalva manoeuvre was avoided. All recordings were made on a Cambridge Multichannel Recorder (Type 72II2) using mid-frequency filters and paper speeds of 75 and I00 mm/sec. All tracings were then measured to determine the minimum and maximum splitting