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Circadian variation of total ischaemic burden and its alteration with anti-anginal agents
D Mulcahy1, J Keegan, D Cunningham
1National Heart Hospital, London.
Insights
Coronary artery disease patients experience frequent ischemic episodes, with 75% being silent. Atenolol medication altered the timing of these episodes, reducing morning occurrences.
Area of Science:
- Cardiology
- Circadian Rhythms
- Ischemic Heart Disease
Background:
- Coronary artery disease (CAD) is a leading cause of mortality.
- Ischemic episodes in CAD patients often occur without symptoms.
- Understanding the timing and patterns of ischemia is crucial for patient management.
Purpose of the Study:
- To investigate the circadian patterns of ischemic episodes in patients with coronary artery disease.
- To evaluate the effect of nifedipine and atenolol on these circadian patterns.
- To determine if silent (symptom-free) ischemic episodes follow similar temporal distributions.
Main Methods:
- Ambulatory ST segment monitoring was conducted on 150 patients with proven CAD.
- Patients were monitored for a total of 6264 hours off anti-anginal treatment.
- Double-blind controlled trials assessed 33 patients on nifedipine and 41 on atenolol.
Main Results:
- 598 ischemic episodes were detected, with 75% being silent.
- Most episodes (68%) occurred between 07:30 and 19:30, with morning and evening peaks.
- Atenolol abolished the morning peak, shifting peak incidence to the evening; nifedipine had no effect.
Conclusions:
- Ischemic episodes in CAD patients exhibit a distinct circadian pattern, with a significant proportion being silent.
- Atenolol effectively modifies this circadian pattern, suggesting a role in managing ischemic events.
- The findings suggest a link between the circadian distribution of ischemia and the timing of acute myocardial infarction and sudden death.
Abstract:
6264 hours of ambulatory ST segment monitoring of 150 unselected patients with proven coronary artery disease, who were off all routine anti-anginal treatments, showed 598 ischaemic episodes, of which 446 (75%) were silent (symptom-free). Most (68%) ischaemic episodes occurred between 0730 and 1930, with a peak in the morning and a lesser peak in the evening. Two subgroups were studied further in double-blind controlled trials: 33 patients had a total of 1313 hours of ST segment monitoring while treated with nifedipine; and 41 patients a total of 1581 hours while treated with atenolol. Nifedipine did not alter the circadian pattern of ischaemic episodes; atenolol abolished the morning peak, and the peak incidence of ischaemia then occurred in the evening. Circadian patterns for total duration of ischaemic episodes corresponded closely to those of episodes of ischaemia, and were similarly altered by treatment. The circadian pattern of silent ischaemic episodes and their total duration were very similar to those of total ischaemia for the group as a whole and the different subgroups. This circadian distribution of ischaemic episodes and the observed changes with treatment resemble the reported circadian variation of acute myocardial infarction and sudden death.