# Josephson Clinical Cardiac Electrophysiology

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■ Josephson’s Clinical Cardiac Electrophysiology

PCL 600

1

aVF

V1

S1–S2 560 560

A

A2

A1 A1–A2

A1

HRA

S1

S2

S1

625

H1–H2

A2 H2

A1

A1 H1

A1 H V 110 90

H1

V1

V1

HBE

A

220

1

aVF

V1

A1–A2 S1–S2

550 550

A

A1

A2

A1

HRA

S2

S1

S1

H1–H2

645

A2

A1

A1

A

H V

H1 V1

H1 V1

H2 V2 100

HBE

B

250

1

aVF

V1

A1–A2 S1–S2

510 510

A

A1

A2

A1

HRA

S1

S2

S1

H1–H2610

A1

A1

A2

A

H

V

H2

H1

V1

H1

V1

HBE

C

240

1

aVF

V1

A1–A2 S1–S2

500 500

A

A2

A1

A1

HRA

S1

S1

S2

H1–H2810

A1

4

A1

A2

V

H2 V2 90

A

H

V1

H1 V1

H1

HBE

450

D

TL

Copyright © 2023 Wolters Kluwer, Inc. Unauthorized reproduction of the content is prohibited. FIGURE 5.13 Multiple levels of conduction delay associated with gaps in the atrioventricular (A-V) conducting system. A to D. From top to bot tom, leads 1, aVF, and V1, and electrograms from the high right atrium (HRA) and His bundle (HBE). In each panel, the atrium is paced at a con stant paced cycle length (PCL) of 600 msec, and progressively premature atrial extrastimuli (A2) are delivered. A. A1-A2 is 560 msec; A2 blocks below the His bundle. The effective refractory period (ERP) of the His-Purkinje system is defined as an H1-H2 of 625 msec. B. At a shorter coupled A2 delay in both the A-V node and the proximal His-Purkinje system allows recovery of the initial site of block. C. At a shorter coupling interval, not enough delay is produced in the A-V node or proximal His-Purkinje system to allow conduction to occur. D. At a 10-msec shorter coupling interval, however, dual A-V nodal pathway producing a marked jump in the A2-H2 interval to 450 msec allows the initial site of block to recover. Thus, multiple levels of conduction delay and block are present, all of which contribute to gap phenomena. See text for discussion. TL, time line.

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