Related Experiment Videos
Changes in myocardial ischemic threshold during daily activities
S Banai1, M Moriel, J Benhorin
1Heiden Department of Cardiology, Bikur Cholim Hospital, Jerusalem, Israel.
Insights
Myocardial ischemic threshold varies significantly during daily life in coronary artery disease patients. This variability, linked to heart rate changes, may indicate coronary artery vasomotor activity.
Area of Science:
- Cardiology
- Clinical Medicine
- Physiology
Background:
- Coronary artery disease (CAD) management often relies on understanding myocardial ischemic thresholds.
- Ischemic episodes in CAD patients can occur during various daily activities, not just exertion.
- Holter monitoring provides continuous electrocardiogram (ECG) data to detect these episodes.
Purpose of the Study:
- To assess the variability of myocardial ischemic threshold during daily activities.
- To correlate heart rate changes preceding ischemic episodes with the ischemic threshold.
- To explore the relationship between ischemic threshold variability and the frequency of ischemic events.
Main Methods:
- Studied 80 patients with known CAD and documented ischemic episodes on Holter monitoring.
- Determined the lowest and highest heart rate at the onset of ischemia for each patient.
- Analyzed 895 ischemic episodes to identify preceding heart rate changes.
Main Results:
- Mean lowest ischemic threshold was 85 beats/min; mean highest was 109 beats/min.
- Highest ischemic threshold matched values observed during exercise stress tests.
- 74% of ischemic episodes were preceded by a >10% heart rate increase.
- Ischemic threshold variability increased with the number of ischemic episodes (2-60%).
Conclusions:
- Significant variability exists in myocardial ischemic thresholds during daily activities in CAD patients.
- Heart rate increases often precede ischemic episodes, even during non-exertional activities.
- Ischemic threshold variability may serve as an indirect indicator of coronary artery vasomotor function.
Abstract:
This study assesses the variations in myocardial ischemic threshold (heart rate at the onset of ischemia) during daily activities in patients with ischemic episodes on Holter monitoring. Eighty patients with known coronary artery disease, positive treadmill stress test results and greater than or equal to 2 ischemic episodes during a 24-hour period of Holter monitoring were studied. The lowest and the highest ischemic thresholds were determined for each patient. The mean lowest ischemic threshold was 85 beats/min, and the mean highest ischemic threshold was 109 beats/min. The highest ischemic threshold was identical to ischemic threshold values noted during exercise. Of the 895 ischemic episodes, 654 (74%) were preceded by a moderate (greater than 10%) increase in heart rate. The variability of ischemic threshold (difference in percentage between the highest and lowest ischemic thresholds) increased with the number of ischemic episodes (range 2 to 60%). However, in different patients with a similar number of ischemic episodes, different variability was observed. These differences in ischemic thresholds are probably indirect indicators of the vasomotor activity of the coronary arteries in different patients.