The syndrome of absent or faint second heart sound, rapid systole and forward collapsing pulse.
A syndrome consisting of an absent or faint second heart sound, prominent cardiac impulse and non-regurgitant or forward collapse of the pulse is described. There was, moreover, no second sound or flow murmur audible in either the aortic or the pulmonary area even though the impulse and collapsing pulse suggested a hyperdynamic circulation; the upstroke was sharp but without the full waterhammer knock. It is argued that the dominant cause of the collapsing pulse will usually be vasodilation, that absence or faintness of the second sound is due to a narrow angle of divergence between the ventricular and arterial pressure decay curves, and that in marked contrast to aortic regurgitation the quality of the impulse derives from rapid systole of lightly loaded ventricles. Although they described its separate elements, pre-homeostatic era clinicians may have overlooked the syndrome in the belief that the heart regulated a largely passive circulation, regarding only primary intracardiac events and the first heart sound as important. Sir William Stokes nevertheless foresaw that alterations in the second sound might be due to changes in vascular tone as well as in elasticity. Wider recognition, deeper understanding and appropriate correction of this syndrome may prove both useful and enlightening.