[Tachycardia with wide ventricular complexes and alternating QRS complexes and RR intervals]

A patient with sustained monomorphic ventricular tachycardia developed a second tachycardia of incessant character with alternating RR-interval and alternating QRS-complexes after treatment with amiodarone. A retrograde His bundle deflection was recorded during the latter arrhythmia, that was induced as well with atrial as with ventricular stimulation. The "alternating" tachycardia could be explained by alternating bundle branch reentry and alternating conduction in the myocardium. This view is supported by the finding of an alternating mid-diastolic potential. This case report introduces a new electrocardiographic entity in the spectrum of wide QRS-tachycardias.