Improvement of cardiac conduction after hyperventilation in tricyclic antidepressant overdose.

Three patients wtih severe cardiotoxicity secondary to tricyclic antidepressant (TCA) overdosage were treated with induced mechanical hyperventilation. All three demonstrated marked QRS narrowing, reflecting improved intracardiac conduction, after hyperventilation therapy. Such therapy may help to prevent or abolish ventricular dysrhythmias, often a feature of life-threatening TCA overdoses.