Antidromic atrioventricular reentrant tachycardia mimicking ventricular tachycardia in the setting of previous myocardial infarction

The differentiation between ventricular tachycardia and broad-complex supra ventricular tachycardia can be extremely difficult, particularly in emergen cy situations. We report a case of hemodynamically compromising broad-compl ex tachycardia in a 63-year-old man. The patient had previously sustained a n anteroseptal myocardial infarction and had subsequently undergone coronar y artery bypass surgery because of triple-vessel coronary artery disease. I ntravenous treatment with ajmalin terminated the tachycardia and revealed p reexcited QRS complexes compatible with the presence of a left-sided atriov entricular accessory pathway. An antidromic atrioventricular reentrant tach ycardia (identical to the clinical tachycardia) was induced during an elect rophysiologic study. In conclusion, there are several causes of broad-compl ex tachycardia, even in patients with previous myocardial infarction, and, where doubt exists, electrophysiologic studies should be performed.