IVCD & ST/T Alternans: Tricyclic Overdose

Report:

Broad complex tachycardia of uncertain origin

QRS 0.28”

Probable atrial ? sinus tachycardia

ST/T alternans

Comment:

The patient was in coma, but not fitting; in shock, but not circulatory collapse; the QRS was well over 0.16”, but there were as yet no malignant ventricular arrhythmias; hypoventilating and hypercarbic, but still breathing spontaneously. The logical first step was to intubate him and optimise intravascular volume1. That done, the alternans became hardly noticeable on 12-lead ECG (Fig 4a below).

Although QRS prolongation over 0.16” is a marker of serious morbidity2, its potential causes and mechanisms are many and the patients whose prolongation is due to tricyclics almost always have other, more obvious, reasons for being in the ICU3.

The arrhythmia recorded appears to have atrial waves in front of the broad complexes; they appear biphasic and may even be of sinus origin. Retrograde conduction from the ventricles, however, cannot be completely dismissed. A 12-lead ECG would have - as always - helped; but I wanted to ventilate the patient first4. The 12-lead ECG, once taken as the patient was improving (below), supported the diagnosis of probable sinus tachycardia.

Repolarisation alternans is an ominous sign of impending arrhythmias.

Fig 4a. 12-lead ECG at a later time. Repolarisation alternans is still visible in V1-2.

Fig 5. 59 year old man in pulmonary œdema.