Related Experiment Videos
Sequence of mechanical and electrical changes during myocardial ischemia: assessment by an ambulatory left
1Second Department of Internal Medicine, Nihon University School of Medicine, Tokyo.
Insights
Left ventricular dysfunction appears before electrical changes during exercise-induced myocardial ischemia and resolves sooner. This temporal sequence also applies to recovery from ischemia.
Area of Science:
- Cardiology
- Nuclear Medicine
- Exercise Physiology
Background:
- Myocardial ischemia during exercise can affect both cardiac function and electrical activity.
- Understanding the temporal relationship between these changes is crucial for diagnosing and managing coronary artery disease.
Purpose of the Study:
- To investigate the relationship between left ventricular (LV) function and electrocardiogram (ECG) changes during exercise-induced myocardial ischemia.
- To determine the temporal sequence of LV dysfunction and electrical changes during and after exercise.
Main Methods:
- Ambulatory left ventricular function monitoring using a cadmium telluride (CdTe) radionuclide probe was performed during ergometer exercise tests in 14 patients with coronary artery disease.
- Continuous recording of LV time-activity curves, with calculation of end-systolic count, end-diastolic count, and ejection fraction.
- Simultaneous ECG recording to assess ST depression.
Main Results:
- Left ventricular dysfunction (increased end-systolic count, decreased ejection fraction) and ST depression were observed in 15 of 28 tests.
- Left ventricular dysfunction occurred earlier than ST depression (97 ± 19 sec difference).
- LV function recovered faster (33 ± 8.5 sec) than ST depression (which persisted for an additional 85 ± 18.5 sec).
Conclusions:
- Left ventricular dysfunction precedes electrical changes during exercise-induced ischemia.
- Left ventricular function recovers earlier than electrical changes after exercise cessation.
- The same temporal sequence is observed during the restoration from myocardial ischemia.
Abstract:
To investigate the relationship between left ventricular function and electrical changes during myocardial ischemia, ambulatory left ventricular function monitoring and ECG recording were made during the ergometer exercise test in 14 patients with coronary artery disease. An ambulatory ventricular function monitor consists of a small cadmium telluride (CdTe) radionuclide probe (250 g) affixed to the patient's chest wall, a preamplifer (10 g), and a portable data acquisition unit (600 g). Left ventricular time-activity curves were recorded continuously using this monitor, and the end-systolic count (volume), end-diastolic count (volume) and ejection fraction were calculated after background subtraction. Twenty-eight exercise tests were performed in the supine and upright positions. In 15 tests, left ventricular dysfunction, i.e., an increase in the end-systolic count (greater than or equal to 10%) and a decrease in ejection fraction (greater than or equal to 5%), and ST depression (greater than or equal to 0.1 mV) were observed. In these 15 tests, exercise duration was 362 +/- 27 sec. Left ventricular dysfunction occurred earlier than ST depression and the time difference was 97 +/- 19 sec. Left ventricular function recovered 33 +/- 8.5 sec after discontinuation of exercise, while ST depression continued for the additional 85 +/- 18.5 sec after recovery of left ventricular function. In conclusion, 1) left ventricular dysfunction occurs earlier than electrical changes during exercise-induced ischemia; 2) left ventricular dysfunction improves earlier than electrical changes after exercise; and 3) the same temporal sequence exists in the restoration from myocardial ischemia.