SVT or VT?

Report:

Broad-complex tachycardia 154/min

Comment:

The tachycardia has unusual RAD, possibly a qR morphology in V1 and virtually concordant positive precordial pattern; yet it resembles RBBB and there appears to exist a 1:1 atrial activity (best seen as notching of the early part of T waves in V1-4). There may even be a tiny primary R wave in V1. There is a qRs morphology in V6, again favouring supraventricular origin. Still, ventricular arrhythmias are common and dangerous in this setting. Fortunately, there exist ECGs taken at other times, for comparison.

The same QRS features persist in sinus rhythm (Fig 49a) following cardioversion (with disopyramide 100 mg IV) and junctional rhythm (not shown) later. What looked like atrial activity was part of the notchy terminal QRS complex.

She had tetralogy of Fallot repaired at the ages of 9 and 18 years.

Patients with bizarre complexes are well advised to carry a copy of their ECG with them. In repaired tetralogy of Fallot patients, the risk of sudden death is related to the QRS complex width50. Knowledge of this fact and the bizarre QRS appearance often lead to misdiagnosis of VT in these patients.

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