The Q-T Ratio as a Guide to the Exercise Test in the Digitalized Subject

¹ Associate Professor of Medicine, Electrocardiographic Laboratory, Division of Cardiology, Department of Internal Medicine, Temple University Health Sciences Center, Philadelphia, Pennsylvania
² Cardiovascular Clinical Research Grant, Temple University Health Sciences Center
³ Professor of Medicine and Chairman, Division of Cardiology, Department of Internal Medicine, Temple University Health Sciences Center

Ten normal digitalized subjects and six patients with ischemic heart disease taking digitalis were studied to determine the utility of the Q-T ratio as a possible guide to differentiating a positive and negative exercise test in the presence of digitalis. A striking decrease in the Q-T ratio in normal digitalized subjects was seen with exercise. Digitalized patients with ischemic heart disease, however, responded with a uniform lengthening of the Q-T ratio with exercise. Thus, in this small group of patients, it appears that shortening of the Q-T ratio, in the presence of ST segment changes with exercise in the digitalized subject favors a false positive test due to the drug, whereas lengthening of the Q-T ratio favors a truly positive test unrelated to the drug.