To examine the role of systolic wall stress at rest in determining left ventricular performance during exercise in aortic regurgitation (AR), systolic wall stress (measured by M-mode echocardiography) was related to changes in left ventricular function during maximal exercise (evaluated by radionuclide ventriculography) in 30 patients with chronic aortic regurgitation. Of these 30 patients, 7 had a normal exercise response, defined as an absolute increase in ejection fraction of 5% or greater (Group I) and 23 had abnormal exercise response, defined as no change (less than 5% change) or a decline (less than or equal to 5%) in ejection fraction (Group II). Patients in Group I had a significantly lower radius/wall thickness ratio (2.5 +/- 0.2 versus 3.1 +/- 0.1, p less than 0.01) and lower peak systolic wall stress (123 +/- 11 versus 211 +/- 12 X 10(3) dynes/cm2, p less than 0.01) than patients in Group II. An increase in ejection fraction during exercise was seen in 6 of the 9 patients with normal systolic wall stress at rest (less than 150 X 10(3) dynes/cm2), but in only 1 of 21 patients with elevated systolic wall stress (p less than 0.001). Peak systolic wall stress at rest varied linearly, and inversely with changes in left ventricular ejection fraction during exercise (r = 0.60, p less than 0.001). Groups I and II did not differ in ejection fraction at rest, clinical symptoms or maximal work load achieved.(ABSTRACT TRUNCATED AT 250 WORDS)