The Effect of Time of Day on Ischemic Response, and Exercise Test Indexes in Persons with Symptoms of Chronic Stable Angina

The aim of the present study was to investigate the effect of time of day on ischemic response, and exercise test indexes in persons with symptoms of chronic stable angina.

We selected 24 volunteers with symptoms of chronic stable angina aged 45 to 65 years with average age of 55.4 ± 6.2. All the participants performed exercise test with treadmill (Bruce protocol) at two times, morning (8-10 am) and evening (3-5 pm) with interval of 96 hours. Considering individual ischemic responses (rate of ST segment depression during recovery and testing, starting stage of changes, and the number of leads with ST segment depression), the risk of developing coronary artery disease (CAD) was graded as negative, and low-risk and high-risk positive, and eventually the risk of CAD development and change of exercise test indexes [metabolic equivalents (METs), heart rate, blood pressure, rate-pressure product (RPP), time, distance, and rate of perceived exertion] were compared between morning and evening exercise tests. Findings: The subjects developed more intense ischemic response in the evening exercise test (rise of ST segment depression, the start of ST segment depression at earlier stage, and increasing number of leads) (P < 0.5). But exercise test indexes did not show any significant change between morning and evening exercise test (P > 0.5).

Ischemia response is considered as the most important achievement of exercise test, subject to the time of exercise test, but it is not clear enough that which test (morning or evening) is well indicative of coronary artery stenosis, so it needs to be investigated further.