Symptom-limited vs heart-rate-limited exercise testing soon after myocardial infarction
Insights
Early exercise testing after myocardial infarction using either heart-rate-limited or symptom-limited protocols showed similar results for detecting exercise-induced ST-segment depression. Neither protocol predicted future cardiac events, but ischemic responses did.
Area of Science:
- Cardiology
- Exercise Physiology
- Clinical Medicine
Background:
- Guidelines for exercise testing post-myocardial infarction are crucial for patient management.
- Previous studies have explored various exercise testing protocols, but direct comparisons soon after an uncomplicated event are limited.
Purpose of the Study:
- To compare the effectiveness of heart-rate-limited (HRL) and symptom-limited (SXL) exercise testing protocols in detecting abnormalities soon after uncomplicated myocardial infarction.
- To assess the predictive value of exercise-induced findings for early cardiac events.
Main Methods:
- 93 men underwent HRL testing and 107 underwent SXL testing at 3 weeks post-myocardial infarction.
- Protocols differed in termination criteria (fixed heart rate vs. symptom/limit attainment).
- Exercise-induced ST-segment depression, ventricular ectopic activity, and subsequent cardiac events were monitored.
Main Results:
- Both HRL and SXL protocols revealed similar prevalence of exercise-induced ST-segment depression and ventricular ectopic activity.
- SXL protocol achieved higher peak heart rate and workload.
- Ischemic ST-segment responses predicted early cardiac events (15% vs. 3%), while arrhythmias did not.
Conclusions:
- Symptom-limited and heart-rate-limited exercise tests are comparable for detecting ischemic ST-segment depression and ventricular ectopic activity early after uncomplicated myocardial infarction.
- Ischemic ST-segment changes during early post-infarction exercise testing are more indicative of future cardiac events than ventricular arrhythmias.
Abstract:
To develop guidelines for exercise testing soon after uncomplicated myocardial infarction, 93 men completed a heart-rate-limited (HRL) protocol and 107 completed a symptom-limited (SXL) protocol 3 weeks after the acute event. In the HRL protocol, effort terminated at a heart rate of 130 beats/min in the absence of a limiting symptom, exertional hypotension or ventricular tachycardia. Peak heart rate was not an end point in the SXL protocol. Despite a higher peak heart rate and work load in patients who completed the SXL protocol, the prevalence of exercise-induced ischemic ST-segment depression and ventricular ectopic activity was similar in the two groups. No complications occurred with either protocol. Twelve patients (6%) had cardiac events within the next 2 months. Regardless of the test protocol used, early events were more common in patients with ischemic ST-segment responses (15%) than in patients without ischemic responses (3%) (p less than 0.01). In contrast, exercise-induced ventricular arrhythmias were not predictive of early events. Eleven weeks after infarction, when all tests were SXL, the prevalence of exercise-induced ischemic ST-segment depression and premature ventricular complexes was similar to that at 3 weeks. We conclude that SXL and HRL exercise test protocols reveal a similar prevalence of ischemic ST-segment depression and ventricular ectopic activity soon after uncomplicated myocardial infarction.
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