What is the clinical evidence from this study?

Study design: Observational. Population: Stable angina (n=39). Intervention: Afternoon exercise testing (1600 hours) vs. Morning exercise testing (0800 hours). Primary outcome: Heart rate and ST segment displacement.

August 1, 1982Open Access

Diurnal variation in exercise responses in angina pectoris.

MJM JoyLourdes Hospital CPCharlotte PollardUniversity of Manchester TNT O NunanThe University of Adelaide

Key Result

Afternoon exercise testing (1600 hours) elicited significantly greater ST segment displacement than morning testing (0800 hours) in patients with stable angina.

Study Design

Type

Observational (n=39)

Structured PICO

Does the time of day affect exercise electrocardiography responses (heart rate and ST segment displacement) in patients with stable angina?

Population

39 Caucasian males, including 30 with stable angina and 9 normal controls, evaluated for diurnal variation in exercise electrocardiography responses.

Exposure

Symptom-limited exercise electrocardiography performed at different times of day (0800, 1200, and 1600 hours), with some patients receiving propranolol 40 mg four times a day and others on no treatment.

Comparator

Intra-subject comparison of morning (0800 hours) versus afternoon (1600 hours) exercise responses, and comparison against normal control subjects.

Outcome

Heart rate and ST segment displacement during exercise electrocardiography.surrogate

Exercise electrocardiography responses in angina patients exhibit significant diurnal variation, with greater ST segment displacement and heart rates in the afternoon compared to the morning, which should be accounted for in clinical assessments.

Abstract

Thirty caucasian male patients with stable angina were investigated in two groups of nine and one group of 12. Nine normal subjects were also studied. Patients in the first group (on no treatment) underwent symptom-limited exercise electrocardiography at 0800, 1200, and 1600 hours on the same day. Their heart rates and ST segment displacements at 1600 hours were significantly greater than at 0800 hours and the same phenomenon was seen in the second group who had been receiving propranolol 40 mg four times a day. A similar effect was noted for ST segment displacement but not for heart rate in the third group (on no treatment) tested at 0800 hours and 1600 hours on separate days, two to three weeks apart. Normal control subjects showed no diurnal variation in heart rate and their heart rate responses at 1600 hours were reduced by propranolol. The observations show a circadian variation in the ST segment response to exercise in patients with angina and a possible training effect on heart rate with multiple exercise testing on the same day. This variation is associated with a reduction in vagal parasympathetic tone to the heart and should be taken into account in the assessment of patients with angina and in particular when comparing responses to treatment.

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