Serial exercise testing in patients with effort angina: Variable tolerance, fixed threshold

• Published in: Journal of the American College of Cardiology 1985-11, Vol.6 (5), p.1011-1015
• Main Authors: Waters, David D., Mccans, John L., Crean, Peter A.
• Format: Article
• Language: English
• Subjects: Adult; Aged; Angina Pectoris - physiopathology; Biological and medical sciences; Blood Pressure; Cardiology. Vascular system; Coronary heart disease; Electrocardiography; Exercise Test; Female; Heart; Heart Rate; Humans; Male; Medical sciences; Middle Aged
• ISSN: 0735-1097; 1558-3597
• DOI: 10.1016/S0735-1097(85)80302-8

To investigate the frequency and mechanism of variable threshold angina, seven treadmill exercise tests were performed in each of 28 patients with stable effort angina and exercise-induced ST segment depression. Each patient had tests at 8 amon 4 days within a 2 week period and on 1 of these days had three additional tests at 9 am, 11 amand 4 pm. Time to 1 mm ST depression increased from 277 ± 172 seconds on day 1 to 319 ± 186 seconds on dqy 2, 352 ± 213 seconds on day 3 and 356 ± 207 seconds on day 4 (p < 0.05). Rate-pressure product at 1 mm ST depression remained constant. Similarly, time to 1 mm ST depression increased from 333 ± 197 seconds at 8 amto 371 ± 201 seconds at 9 amand to 401 ± 207 seconds at 11 amand decreased to 371 ± 189 seconds at 4 pm(p < 0.01). Again, ratepressure product at 1 mm ST depression remained constant. The standard deviation for time to 1 mm ST depression, calculated as a percent of the mean for each patient's seven tests and then averaged for the entire group, was 22 ± 11 %. The standard deviation for rate-pressure product at 1 mm ST depression, calculated in the same way, was significantly less at 8.4 ± 2.8% (p < 0.001). In 78 (40%) of the 196 tests, time to 1 mm ST depression was less than 80% or greater than 120% of the patient's mean; in contrast, rate-pressure product at 1 mm ST depression was less than 80% or greater than 120% of the patient's mean in only 3 tests (1.5%). Thus, considerable variability in exercise tolerance occurs in patients with effort angina, even when ratepressure product at the onset of ischemia remains fixed. A history of variable threshold angina does not necessarily imply variations in coronary tone.