Josephson Clinical Cardiac Electrophysiology

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Chapter 6: Ectopic Rhythms and Premature Depolarizations ■

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aVR

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FIGURE 6.16 Concealed His extrasystole producing multilevel block. RBBB and LAH are present with 3:1 block. The first block occurs below the recorded His. A His extrasystole retrogradely conceals in the A-V node resulting in the next sinus beat to block in the A-V node. The preexcitation of the subnodal structures gives enough time to recover so the subsequent sinus beat conducts. This was the mechanism of 3:1 block. A-V, atrio ventricular; d, distal; LAH, left anterior hemiblock; p, proximal; RBBB, right bundle branch block.

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HBEd

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HBEp

FIGURE 6.17 Junctional tachycardia post aortic valve replacement. Following aortic valve replacement for aortic stenosis, incessant bursts of junc tional tachycardia were observed. Note there is no retrograde conduction to the atrium, but there is concealed conduction in the atrioventricular node. This rhythm was able to be reproducibly initiated by ventricular pacing and was catecholamine sensitive, suggesting a triggered mechanism due to delayed afterdepolarizations. d, distal; HBE, His bundle electrogram; p, proximal.