Josephson Clinical Cardiac Electrophysiology

146

■ Josephson’s Clinical Cardiac Electrophysiology

1

V1

A

A

HRA

A

A

CS

V

V

A

A

H

H

V

Hr

HBE

100

135

T

80

20

80

FIGURE 5.1 Retrograde concealed conduction by a fascicular extrasystole. From top to bottom, tracings represent standard leads 1 and V1 and high right atrium (HRA), coronary sinus (CS), His bundle electrogram (HBE), and time lines (T) at 10 and 100 msec. The first beat is a conducted sinus beat, with an A-H = 100 msec, H-V = 80 msec, and a right bundle branch block configuration. The second beat is a fascicular extrasystole, with an “Hr-V” = 20 msec. Note that there is no manifest conduction above the atrioventricular (A-V) junction (ie, no atrial electrogram). Note, however, in the next sinus beat that the A-H interval is prolonged to 135 msec, indicating that the retrograde wavefront from the preceding beat partially penetrated (concealed) in the A-V node, rendering it relatively refractory to the next sinus impulse. A, atrial deflection; H, His bundle deflec tion; Hr, retrograde His deflection; V, ventricular deflection.

1

aVF

V1

A

A

A

HRA

A

A

A

H

H

H

H

V

V

HBE

T

300

Copyright © 2023 Wolters Kluwer, Inc. Unauthorized reproduction of the content is prohibited. FIGURE 5.2 Retrograde concealed conduction by a junctional (His bundle) escape rhythm during intra-His complete heart block. Atrioventricular (A-V) dissociation is present, and there is no retrograde activation of the atria by the His bundle escape rhythm. There are three sinus depolar izations, as evidenced by early high right atrial (HRA) activation. The first sinus impulse is blocked above the proximal His bundle (ie, in the A-V node); the second conducts to the proximal His bundle with a short A-H interval, and it is then blocked; and the third conducts to the proximal His bundle with a longer A-H interval. The A-V nodal block in the first beat and the A-V nodal delay in the third beat are due to concealed retrograde conduction of the His bundle beats into the A-V node. Thus, despite antegrade intra-His block, the distal His bundle escape rhythm can conduct retrogradely and affect antegrade conduction (ie, unidirectional antegrade block is present).