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Lack of diurnal variation in the onset of non-Q wave infarction
N S Kleiman1, K B Schechtman, P M Young
1Department of Internal Medicine, Baylor College of Medicine, Houston, Texas.
Insights
This study found no clear diurnal pattern for non-Q wave myocardial infarction onset. Unlike Q-wave heart attacks, non-Q wave infarctions did not show a late morning peak, suggesting different underlying causes.
Area of Science:
- Cardiology
- Chronobiology
- Internal Medicine
Background:
- Myocardial infarction (MI) exhibits temporal patterns, with Q-wave MI showing a late morning peak.
- Non-Q wave MI is a distinct subtype of heart attack with potentially different pathophysiology.
- Understanding MI onset patterns may offer insights into disease mechanisms and prevention.
Purpose of the Study:
- To investigate the time of onset patterns for non-Q wave myocardial infarction.
- To compare circadian rhythms of non-Q wave MI with previously reported patterns for Q-wave MI.
- To explore potential differences in the pathogenesis of MI subtypes based on onset timing.
Main Methods:
- Analysis of onset times for 540 patients with confirmed non-Q wave MI from the Diltiazem Reinfarction Study.
- Inclusion of data from 627 screened but excluded patients for a total of 1,167 patients.
- Statistical analysis of onset data at 2-, 6-, and 8-hour intervals, examining subgroups including diabetics, women, and those with ST-segment elevation.
Main Results:
- No significant diurnal pattern in onset was observed for non-Q wave MI at 2- or 6-hour intervals across all patients.
- A statistically significant, though not predominant, occurrence of non-Q wave MI was noted between midnight and 8:00 AM (27%) at 8-hour intervals.
- Diabetics, women, and patients experiencing their first MI were more likely to have onset during afternoon hours; no late morning peak was observed.
Conclusions:
- The characteristic late morning preponderance seen in Q-wave MI is absent in non-Q wave MI.
- This divergence suggests potentially different pathophysiological mechanisms between Q-wave and non-Q wave myocardial infarction.
- The findings imply that the sustained thrombotic process in Q-wave MI may differ from the nonsustained process in non-Q wave MI.
Abstract:
Data concerning the time of onset of myocardial infarction were obtained for 540 of the 544 patients with creatinine kinase (CK)-MB-confirmed non-Q wave myocardial infarction enrolled in the multicenter Diltiazem Reinfarction Study. Data were also collected for 627 patients who were screened but excluded. Among the 1,167 patients, no diurnal pattern of onset could be found at either 2- or 6-hour intervals. Among the 540 patients enrolled in the trial, no pattern could be found at these intervals either, although at 8-hour intervals, 27% of infarctions occurred between midnight and 8:00 AM, compared with 37% between 8:00 AM and 4:00 PM and 36% between 4:00 PM and 12:00 AM (p = 0.02). In contrast to the patterns previously noted for Q wave myocardial infarction, there was no preponderance of non-Q wave infarction in the late morning. Circadian rhythm was also absent among patients not treated with beta-blockers as well as among patients presenting with ST segment elevation on their enrollment electrocardiograms. Diabetics, women, and patients with first infarction were more likely to present during the afternoon hours. We conclude that the late morning preponderance seen for Q-wave myocardial infarction is not discernable in patients with non-Q wave myocardial infarction. This observation suggests that the pathogenesis of these two infarct subtypes is different or that the process of thrombotic coronary occlusion in Q wave infarction (sustained) differs from that in non-Q wave infarction (nonsustained).