Syncope in aortic valvular stenosis.

Simultaneous, continuous ambulatory recordings of systemic and pulmonary arterial pressure and heart rate were made in four patients with aortic valvular stenosis (AS) to explore the mechanisms of syncope in the disorder. When compared with six normal volunteers, patients with AS showed a subnormal systemic arterial pressure response to graded submaximal exercise. Three near-syncopal episodes, occurring during abrupt symptom-limited exercise, were associated with simultaneous acute falls in systemic and pulmonary arterial pressure in the absence of cardiac arrhythmia. Acute reflex peripheral arterial and venous vasodilatation, which may be mediated by the effects of sudden changes in left-ventricular pressure on ventricular baroreceptor activity, plays a central role in the exertion-induced syncope of aortic stenosis.