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Left ventricular ejection times during exercise testing with scintigraphy. Their use in the detection of ischemic
Insights
Normal subjects exhibit shorter left ventricular ejection times (LVETs) during and after exercise compared to individuals with coronary artery disease. This difference may reflect altered cardiac function and ejection rates in response to exercise and post-exercise recovery.
Area of Science:
- Cardiology
- Exercise Physiology
- Diagnostic Imaging
Background:
- Left ventricular ejection time (LVET) is a measure of cardiac function.
- Assessing LVET during exercise can provide insights into cardiovascular health.
- Coronary artery disease (CAD) may affect cardiac response to physical stress.
Purpose of the Study:
- To compare LVETs in healthy individuals and patients with suspected CAD during and after maximal treadmill exercise.
- To establish regression equations for correcting LVETs based on heart rate during exercise and post-exercise recovery.
- To investigate potential differences in ejection dynamics between groups.
Main Methods:
- LVETs and heart rates (HRs) were measured in 20 control subjects and 31 patients with suspected CAD using the Bruce protocol.
- Data were collected at rest, during exercise, and for 8 minutes post-exercise.
- Linear regression analysis was used to derive correction factors for LVET based on HR.
Main Results:
- Control subjects had higher HRs and shorter LVETs at peak exercise compared to the CAD group.
- LVETs in controls remained significantly shorter than in the CAD group up to 5 minutes post-exercise.
- Subjects with CAD demonstrated longer post-exercise LVETs, suggesting slower ejection rates.
Conclusions:
- Individuals with presumptive coronary artery disease exhibit prolonged left ventricular ejection times post-exercise compared to healthy controls.
- This finding may be linked to altered cardiac output and venous pooling effects in CAD patients.
- LVET, corrected for heart rate, can differentiate between healthy individuals and those with coronary artery disease during recovery from exercise.
Abstract:
Left ventricular ejection times ( LVETs ) were obtained in a group of 20 control subjects (group 1) during maximal treadmill exercise testing, using a Bruce protocol, and in conjunction with myocardial scintigraphy. Heart rates (HRs) and LVETs were recorded during standing rest, each minute of exercise, and for eight minutes in the postexercise period. A linear regression equation was constructed and separate correction factors of 1.04 X HR + observed LVET (correlation coefficient, -.86) for the exercise period and 0.73 X HR + LVET (correlation coefficient, -.71) for the postexercise period were derived. The LVETs were also recorded in 31 subjects with positive ECGs and defects on myocardial scanning with thallous chloride TL201 (group 2) during a similar exercise protocol. Comparison of groups 1 and 2 disclosed that the former had a higher HR and shorter LVET than the latter at peak effort (consonant with the significantly longer duration of exercise achieved by the control subjects). The LVETs in group 1 remained significantly shorter than that of group 2 through the fifth minute postexercise. In the postexercise period, the LVET indexes were significantly shorter in group 1 than group 2 at 1, 3, and 5 minutes. Subjects with presumptive coronary disease (positive ECG and defects on thallium 201 scanning) not only have a decreased exercise tolerance and HR, but after exercise, their ejection times are substantially longer than in normal subjects. This may be attributed to a slower rate of ejection in patients with coronary disease when venous pooling on quiet standing after exercise delivers a smaller volume to the heart. In normal subjects, the lesser volume may be ejected more rapidly.