"Abnormal" responses of ejection fraction to exercise, in healthy subjects, caused by region-of-interest selection.

We performed serial exercise equilibrium radionuclide angiography in eight normal subjects with each subject executing three tests: control, after nitroglycerin, and after propranolol. The left-ventricular ejection fraction (EF) was calculated by two methods: (a) fixed region-of-interest (FROI) using a single end-diastolic ROI, and (b) variable region-of-interest (VROI) where an end-diastolic and end-systolic region of interest were used. Abnormal maximal EF responses occurred in five of eight subjects during control using FROI but in zero of eight employing VROI (p < 0.05). After nitroglycerin, three of eight subjects had abnormal responses by FROI, but zero of eight were abnormal by VROI (p < 0.05). After propranolol, blunted EF responses occurred in three of seven by both methods. Falsely abnormal EF responses to execrise RNA may occur due to the method of region-of-interest selection in normal subjects with normal or high ejection fractions.