Josephson Clinical Cardiac Electrophysiology

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■ Josephson’s Clinical Cardiac Electrophysiology

1

aVF

V1

A

A

HRA MRA FO CSp CSm

A

A

A

A

A

A

A

A

A

A

CSd

A

A

HBE

H

V

H

V

H V

H

V

RV T

FIGURE 6.10 Junctional rhythm presenting as bigeminy secondary to (A-V) nodal reentry. Leads 1, aVF, and V1 are shown with electrograms from the high right atrium (HRA), midright atrium (MRA), fossa ovalis (FO), and proximal, mid-, and distal coronary sinus (CSp, CSm, CSd) as well as His bundle electrogram (HBE) and right ventricular (RV) electrogram. Junctional rhythm is present. Each junctional escape beat is followed by retrograde conduction to the A-V node. Retrograde conduction is by way of the slow A-V nodal pathway, which allows reexcitation of the His bundle over the fast pathway. Thus, retrograde dual A-V nodal pathways with reentry in the presence of a junctional rhythm can give rise to a bigeminal rhythm. A-V, atrioventricular; T, time line.

T L1 L2 V1 RA

A

A

H-V H-V

HB

UE

0.1 mV

DS 0.08-0.12 mV/sec H-H 820-860 msec

A

T L1 L2 V1 RA S S S 600 600 A A A

A

V

HV

H

A H A AH

1,440

1,390

HB

1,200

UE

0.005 mV/sec

0.01

DS 0.08-0.12. H-H 820-860.

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FIGURE 6.11 Effects of atrial pacing on the junctional rhythm and the junctional diastolic slope. A and B. Tracings are arranged as follows: T, time lines; L1, L2, V1, leads 1, 2, and V1 of the electrogram; RA, high right atrial electrogram; HB, bipolar His bundle electrogram; and UE, unipolar electrogram of the His bundle. The arrows indicate junctional diastolic slopes (DS). A, H, and V are electrograms of the atria, the His bundle, and the ventricles. S = stimulus artifact. Voltage calibration is for UE. A. Control. B. Atrial pacing at 600-msec cycle length for 30 seconds resulted in 2:1 conduction to the His bundle and the ventricles. After pacing, the junctional cycle length was prolonged from 820 to 860 msec in control to 1,440 msec, and the diastolic slope decreased from 0.08 to 0.12 mV/sec in control to 0.005 mV/sec. The junctional cycle length and the diastolic slope returned to control values after 2 beats. See text for details. (From Hariman RJ, Gomes JAG, El-Sherif N. Recording of diastolic slope with catheters during junctional rhythms in humans. Circ . 1984;69:485-491.)