Narrow QRS tachycardia to wide QRS tachycardia with LBBB morphology. What is the mechanism?
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چکیده
A 42-year-old woman was referred for radiofrequency catheter ablation of narrow QRS tachycardia that was terminated with intravenous adenosine. Baseline twelve-lead ECG was normal during sinus rhythm and transthoracic echocardiography demonstrated no evidence of structural heart disease. The electrophysiological study showed a normal AH interval of 114 ms and HV interval of 37 ms during sinus rhythm. Atrial burst pacing reproducibly induced two tachycardia e 1) regular narrow QRS tachycardia and 2) wide QRS tachycardia with left bundle branch block (LBBB) morphology. Fig. 1 shows spontaneous transition of narrow QRS tachycardia to wide QRS tachycardia. What are the likely mechanisms of the tachycardia?
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