Study objectives: Pharmacological therapy can reduce diagnostic and prognostic accuracy of exercise stress testing. However, the risk of withdrawing drugs ear ly after myocardial infarction (MI) has not been established. We assessed safety and clinical implications of drug withdrawal in patients undergoing stress test ing after uncomplicated MI. Methods: A total of 362 MI patients underwent ECG Ho lter recording before and after withdrawing beta blockers, calcium antagonists and nitrates. QRS(QRS/h) and ventricular premature beats(VPB/h) count per hour, repetitive ventricular arrhythmias, ST segment changes and patient complaints w ere evaluated for reproducibility using kappa statistics and Bland Altman metho d. Results: No major complications occurred. Forty three patients complained of >1 symptom on and 37 off therapy. QRS/h and VPB/h count were significantly(p< 0 .0001) higher off therapy but correlated with the corresponding values on therap y. A mean heart rate increase of 8 beats/min (agreement range -8 to +14 beats/ min) and a fivefold increase in VPB/h(agreement range -141 to +151) were obser ved after withdrawing therapy. Repetitive ventricular arrhythmias and ST changes were also more frequent off therapy but intra patient reproducibility was poor : kappa 0.12(95%confidence interval(CI)-0.01 to 0.25) for arrhythmias, -0.02( 95%CI-0.46 to 0.39) for ST depression and -0.01(95%CI-0.66 to 0.64) for ST elevation. Conclusions: The withdrawal of therapy is well tolerated soon after u ncomplicated MI; however, a generic but not individual risk of ventricular arrhy thmias and/or transient myocardial ischemia has to be taken into account.
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