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"Abnormal" Responses of Ejection Fraction to Exercise, in Healthy Subjects, Caused by Region-of-Interest Selection

Seattle Veterans Administration Hospital and University of Washington, Seattle, Washington
The University of Texas Health Science Center, San Antonio, Texas

Correspondence: For reprints contact: Sherman G. Sorensen, MD, Dept. of Medicine, Div. of Nuclear Medicine, Univ. of Texas Health Science Ctr. at San Antonio, 7703 Floyd Curl Dr., San Antonio, TX 78284.

ABSTRACT

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 exercise RNA may occur due to the method of region-of-interest selection in normal subjects with normal or high ejection fractions.