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Asymptomatic and electrically silent myocardial ischemia during upright leg cycle ergometry and treadmill exercise
K A Williams1, L A Taillon, J E Carter
1Department of Medicine (Cardiology), University of Chicago, Illinois 60637.
Insights
Clandestine myocardial ischemia, which is silent and asymptomatic, is more common during upright leg cycle ergometry (82%) than treadmill exercise (42%). Exercise type significantly impacts the detection of coronary artery disease.
Area of Science:
- Cardiology
- Exercise Physiology
Background:
- Myocardial ischemia can be "clandestine," meaning it is not detected by symptoms or electrocardiogram changes, but is visible on scintigraphy.
- Detecting all forms of ischemia is crucial for managing coronary artery disease (CAD).
Purpose of the Study:
- To compare the frequency of clandestine myocardial ischemia during treadmill exercise versus upright leg cycle ergometry in patients with CAD.
- To assess how different exercise modalities affect the symptomatic and electrocardiographic detection of ischemia.
Main Methods:
- 38 patients with CAD and reversible ischemia on thallium-201 scintigraphy underwent both treadmill and upright leg cycle ergometry.
- Peak double product, angina, electrocardiogram changes, and scintigraphic findings were recorded.
- Specificity of leg cycle testing was evaluated in patients without scintigraphic ischemia.
Main Results:
- Angina pectoris and positive exercise electrocardiograms were significantly more frequent during treadmill exercise than leg cycling.
- Leg cycle testing demonstrated higher specificity for detecting ischemia in patients without scintigraphic evidence.
- Clandestine ischemia was detected in 82% of leg cycle tests versus 42% of treadmill tests.
- Patients with prior coronary artery bypass surgery had a higher incidence of clandestine ischemia.
Conclusions:
- Upright leg cycle ergometry is more effective at revealing clandestine myocardial ischemia compared to treadmill exercise.
- The choice of exercise modality critically influences the symptomatic and electrical manifestations of exercise-induced ischemia.
- Leg cycle ergometry may be a valuable tool for uncovering silent ischemia in CAD patients, particularly those with prior bypass surgery.
Abstract:
The frequency of "clandestine" (electrically silent and asymptomatic, but scintigraphically evident) myocardial ischemia during treadmill and upright leg cycle ergometric studies was compared in 38 patients with coronary artery disease and reversible ischemia on both thallium-201 scintigraphy and exercise radionuclide angiography. A similar peak double product was attained in both studies. Angina pectoris was significantly more frequent with treadmill exercise than with leg cycling (29 vs 5%, p = 0.0079). An interpretable and positive exercise electrocardiogram occurred in 53% of treadmill tests, but in only 19% of leg cycle tests (p = 0.0025); in a group of 22 patients without scintigraphic ischemia, leg cycle testing had greater specificity (95 vs 64%, p = 0.0248). Ischemia was manifest by symptoms or an abnormal electrocardiogram in 59% of treadmill tests, but in only 18% of leg cycle tests (p = 0.0003). There were no differences between the exercise variables or the degree of scintigraphic abnormalities of the 22 patients with manifest ischemia and the 16 with clandestine ischemia. However, patients with previous coronary artery bypass surgery experienced clandestine ischemia more frequently than did those without bypass surgery (80 vs 33%, p = 0.0103). Thus, clandestine ischemia occurs more frequently during symptom-limited upright leg cycle ergometry (82%) than during treadmill exercise (42%). The symptomatic and electrical manifestations of exercise-induced ischemia have a critical dependence on the type of exercise used.