Circadian variation of exercise test response and diagnostic significance of non-pharmacological provocation tests in patients with vasospastic angina

Yun, Kyung Ho; Oh, Seok Kyu; Jeong, Jin Won; Park, Yang Kyu

Abstract

BACKGROUND: Exercise tests (ET), hyperventilation tests (HVT) and cold pressor tests (CPT) have been used to induce coronary artery spasm. However their diagnostic significance and the circadian variation of exercise test response in patients with vasospastic angina are still uncertain.
METHODS
To elucidate the circadian variation of ET response and to evaluate the diagnostic significance of non-pharmacological provocation tests, 21 consecutive patients with pure vasospastic angina were studied. Six ETs were performed in the early morning, late morning, and late afternoon in consecutive days, 2 HVTs and 2 CPTs in the early morning. The circadian distribution and types of angina (at rest, on physical activity, or both) from before admission to after discharge (mean follow-up periods 19+/-9 months) were evaluated by clinical history, clinical records and Holter recordings. Circadian distribution of anginal attacks recorded through the all observation periods were classified into 3 patterns (morning and night : MN, morning and afternoon or evening : M+F/E, morning, night and afternoon and/or evening : MN+F/E).
RESULTS
One hundred and eleven ETs (39 early morning, 38 late morning, 34 late afternoon tests), 35 HVTs and 33 CPTs were performed. ETs showed 14 positive responses (36%) in the early morning, 14 (37%) in the late morning and 12 (35%) in the late afternoon without any circadian variation. Among the 11 patients who underwent all 6 exercise tests, 3 patients (27%) showed at least one positive response in the early morning, 4 (36%) in the late morning and 4 (36%) in the late afternoon. Subgroups of the subjects according to the types and activity of angina and the numbers of spastic artery also failed to show any circadian variation in ET response, but M+F/E group of circadian pattern of angina showed a peak of positive response in the early morning (p<0.05). HVTs showed significantly higher positive response (23/35, 66%, p<0.05) than ETs (14/39, 36%) and CPTs showed significantly lower positive response (2/33, 6%, p<0.01) than ETs in the early morning. Double tests with more than 1 positive response couldn't increase the positive response in ETs (9/19, 47%), and CPTs (2/14, 14%) but increased significantly in HVTs(15/16, 94%, p<0.05), particularly in the group with low activity (7/8, 86%, p<0.01). ETs showed ST segment elevation in 29 (72%) and depression in 11 (28%) of the 40 positive tests, HVTs in 21 (91%) and 2 (9%) of the 23 positive tests and CPTs in 2 (100%) and 0 (0%) of the 2 positive tests. The ST segment elevation was significantly higher in HVTs than in ET (p<0.05).
CONCLUSION
These findings suggest that the exercise test in the early morning do not increase positive response and is not a sensitive diagnostic test associated with occasional depression of ST segment, but hyperventilation test, especially if repeated, is a very sensitive test with predominant elevation of ST segment in patients with vasospastic angina.