Symptom-limited versus low level exercise testing before hospital discharge after myocardial infarction.
OBJECTIVE
This study was undertaken to compare a low level and a symptom-limited test performed before hospital discharge after an uncomplicated myocardial infarction.


BACKGROUND
Exercise testing after myocardial infarction provides useful prognostic information. Usually either a low level test is performed before hospital discharge or a symptom-limited test is performed at 3 weeks.


METHODS
The study group comprised 202 patients with an uncomplicated myocardial infarction; 58 patients had a non-Q wave infarction and 115 patients had received thrombolytic therapy. Both a low level and a symptom-limited exercise test were performed in 200 of the 202 study patients in randomized order on consecutive days, a mean of 7.4 +/- 2.3 days after infarction.


RESULTS
The symptom-limited test required a considerably greater effort than the low level test: exercise duration was 554 +/- 209 versus 389 +/- 125 s (p less than 0.0001), and peak work load was 5.7 +/- 1.8 versus 4.2 +/- 1.1 METs (p less than 0.0001). The peak heart rate was higher during the symptom-limited test (121 +/- 20 vs. 108 +/- 14 beats/min, p less than 0.0001), as was the rate-pressure product. The number of patients who developed ST segment depression greater than or equal to 1 mm increased from 56 during the low level test to 89 during the symptom-limited test (p less than 0.0001). ST segment depression greater than or equal to 2 mm occurred in 22 patients during the low level test and in 41 patients during the symptom-limited test, an 86% increase (p less than 0.0001). The number of patients with either angina or ST depression greater than or equal to 1 mm increased from 66 to 105 (p less than 0.0001) with the symptom-limited test. Exercise test results were similar for patients with a Q wave or a non-Q wave infarction. Exercise duration was longer and exercise-induced ST depression less frequent in patients who had received thrombolytic therapy.


CONCLUSIONS
A symptom-limited exercise test performed before hospital discharge after uncomplicated myocardial infarction provides a significantly greater cardiovascular stress than does a low level test and is associated with an ischemic response nearly twice as frequently. The prognostic significance of a positive response at higher work loads has not been defined.
Juneau
M
M
Department of Medicine, Montreal Heart Institute, Quebec, Canada.
Colles
P
P
Théroux
P
P
de Guise
P
P
Pelletier
G
G
Lam
J
J
Waters
D
D
D000787:Angina Pectoris / Q000175:diagnosis; D001794:Blood Pressure / Q000502:physiology; D004562:Electrocardiography; D005069:Evaluation Studies as Topic; D015444:Exercise / Q000502:physiology; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis* / Q000188:drug therapy / Q000453:epidemiology; D010351:Patient Discharge; D011379:Prognosis; D015912:Thrombolytic Therapy; D013997:Time Factors