Bidirectional tachycardia during long-term treatment with digitalis and methyl-xanthine: The efficacy of mexiletine

We report a case of bidirectional tachycardia detected in a patient affected by postinfarction dilated cardiomyopathy; he was on theophylline and showed high serum levels of digoxin, but no clinical evidence of digitalis intoxication. Electrocardiographic monitoring allowed the detection of frequent ventricular ectopic beats, several episodes of non sustained ventricular tachycardia and repeated episodes of bidirectional tachycardia. Digitalis and theophylline withdrawal together with mexiletine administration determined the suppression of all detected arrhythmias. This case supports the view that particular caution should be employed when digitalis and theophylline are administered in combination to patients with a depressed left ventricular function; moreover, mexiletine should be considered the antiarrhythmic drug of choice in this particular clinical setting.