A case of junctional ectopic tachycardia with demonstration of both HA and HV dissociation during tachycardia

Figures

• 

  Figure 1. Baseline conduction intervals. A: During sinus rhythm. B: During tachycardia. Tachycardia was readily and reproducibly induced with burst pacing from the right ventricle. The AH and HV intervals in sinus rhythm were 160 and 51 ms, respectively. HV intervals in tachycardia were unchanged from those in sinus rhythm. The tachycardia cycle length was 300 ms. Note dissociation of His activation during tachycardia from atrial activation. CSp and CSd = proximal and distal coronary sinus electrogram; HISp and HISd = proximal and distal right-sided His/right bundle electrograms.

• 

  Figure 2. Entrainment during tachycardia from the right ventricle (RV; A) and left ventricle (LV; B). The tachycardia has a cycle length (CL) of 305 ms. A: Entrainment pacing was performed from the distal right-sided His/right bundle electrodes during tachycardia (pacing CL of 290 ms). Local ventricular electrograms showed a postpacing interval (PPI) of 480 ms. HV interval in tachycardia was 53 ms. However, the PPI to the local His electrogram was 400 ms. This shorter PPI would suggest that the His/right bundle was closer to the tachycardia source than the surrounding right ventricular myocardium. B: Entrainment pacing was performed from the left ventricular apex. The PPI at the site of pacing was 607 ms, considerably longer than the PPI when pacing from the right. Furthermore, the first tachycardia return beat had earlier His and local RV activation (489 and 549 ms, respectively) than the LV pacing site. These observations are consistent with retrograde left bundle branch block such that pacing from the LV could only penetrate the source of the tachycardia by propagating to the RV and up the right bundle. LVp and LVd were, respectively, proximal and distal electrode pairs on the pacing…

• 

  Figure 3. Catheter trauma to the right bundle during tachycardia resulted in dissociation of His activation from ventricular activation. During tachycardia, mechanical trauma to the right bundle resulted in variable HV conduction (3:2 pattern in this tracing) while the right- and left-sided His recordings remained in tachycardia. The left-sided His recording preceded the right-sided one by 30 ms, consistent with the source of the tachycardia being in the left-sided His-Purkinje system. LHp and LHd were, respectively, proximal and distal electrode pairs on the catheter recording from the upper left ventricular septum. The vertical line reveals the timing relationship between the left- and right-sided His activations.