ECG Review-VT With No Heart Disease?
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Clinical Scenario: The wide-complex tachycardia (WCT) shown in the Figure was obtained from a 40-year-old man with schizophrenia, but no other medical problems. He had no other evidence of heart disease. What is the rhythm likely to be? Is there anything special about this type of WCT?
Interpretation: The rhythm in the Figure is regular at a rate of 160/minute. Atrial activity is absent. The QRS complex is wide, although not markedly so. The differential diagnosis includes ventricular tachycardia (VT) vs. supraventricular tachycardia with QRS widening resulting from either preexisting bundle branch block or aberrant conduction. Subtle morphologic clues in favor of VT as the diagnosis include the atypical right bundle branch block (RBBB) configuration of the QRS complex in lead V1 (slurring of the initial r wave in this lead) and the predominant, negative deflection (S wave) in lead V6. That said, definitive diagnosis of the etiology of this arrhythmia was not forthcoming until electrophysiologic study, which demonstrated fascicular VT arising from the left posterior hemifascicle.
Two distinct patterns of VT are commonly seen in patients without heart disease. One pattern manifests a left bundle branch block (LBBB) morphology with an inferior axis; the other simulates bifascicular block (RBBB and left anterior hemiblock). The latter form is the type seen here. These two forms of ventricular outflow tract VT occur most often in relatively younger adults, and are frequently precipitated by exercise. Despite symptoms of palpitations and/or presyncope, long-term prognosis is usually surprisingly good. The important therapeutic feature unique to these forms of VT is their generally favorable response to treatment with calcium channel blockers (verapamil/diltiazem) and beta-blockers, which often allows ambulatory management of these patients with minimal morbidity or impingement on lifestyle.
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