Elsevier

Heart Rhythm

Volume 6, Issue 7, July 2009, Pages 1063-1065
Heart Rhythm

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Incessant tachycardia with wide and narrow QRS complexes: What is the mechanism?

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Case presentation

A 40-year-old man was referred for catheter ablation of an incessant wide QRS tachycardia. Twelve-lead ECG revealed a tachycardia with right bundle branch block (RBBB) pattern that spontaneously alternated with a tachycardia having a narrow QRS complex (Figure 1). During electrophysiologic study, the tachycardia was incessant at 168 bpm. QRS morphology showed an RBBB pattern with 1:1 VA conduction. Earliest atrial activation was recorded at the coronary sinus ostium. The tachycardia was

Commentary

The response to overdrive atrial pacing suggests a subatrial origin of the tachycardia. HV interval during tachycardia was shorter than that during normal sinus rhythm. Earliest HB activity during the RBBB form of tachycardia was localized in the left HB recording area or left septal subaortic region (HV, 22 ms). Right-side HB activity (HV, 10 ms) and the left bundle branch electrogram followed left subaortic HB activation. HV interval of the second tachycardia (with narrow QRS) was 45 ms,

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