Provocation of obstruction in a patient with left ventricular hypertrophy without obstruction catheterized by the author in 1962. (A) Baseline pressure; (B) 16 cardiac cycles following isoproterenol bolus; dashed lines show increases in left ventricle and reductions in brachial artery systolic pressures. (C) Maximal effect = 90 mmHg gradient. B.A., brachial artery; L.V., left ventricle. Reproduced from Ref.²