Differential diagnosis of tachycardia with a typical left bundle branch block morphology.

The evaluation of wide QRS complex tachycardias (WCT) remains a common dilemma for clinicians. Numerous algorithms exist to aid in arriving at the correct diagnosis. Unfortunately, these algorithms are difficult to remember, and overreliance on them may prevent cardiologists from understanding the mechanisms underlying these arrhythmias.

Magnesium sensitive, adenosine resistant, repetitive monomorphic ventricular tachycardia.

Repetitive monomorphic ventricular tachycardia (RMVT) is characterized by episodes of ventricular ectopy and nonsustained VT exacerbated by catecholamines. Because this arrhythmia is frequently adenosine sensitive, its mechanism is believed to be cyclic adenosine monophosphate-mediated triggered activity due to delayed afterdepolarizations. We present a case of RMVT associated with significant hypomagnesemia (serum level = 1.