Effect of pharmacological wash-out in patients undergoing exercise testing after acute myocardial infarction

Pharmacological therapy can reduce diagnostic and prognostic accuracy of exercise stress testing. However, the risk of withdrawing drugs early after myocardial infarction (MI) has not been established. We assessed safety and clinical implications of drug withdrawal in patients undergoing stress testing after uncomplicated MI.

A total of 362 MI patients underwent ECG Holter 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 were evaluated for reproducibility using kappa statistics and Bland-Altman method.

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 therapy. A mean heart rate increase of 8 beats/min (agreement range -8 to +14 beats/min) and a five-fold increase in VPB/h (agreement range -141 to +151) were observed 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.

The withdrawal of therapy is well tolerated soon after uncomplicated MI; however, a generic but not individual risk of ventricular arrhythmias and/or transient myocardial ischemia has to be taken into account.