Josephson Clinical Cardiac Electrophysiology

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■ Josephson’s Clinical Cardiac Electrophysiology

1 2 3

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Ar

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HRA

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H*

AH V

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HBE

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T

FIGURE 6.14 Multiple manifestations of His bundle depolarizations in one patient. Three His bundle depolarizations (H*) are recorded. The first H* has no manifestation on the surface electrocardiogram (ECG) and appears as an isolated His spike without affecting subsequent atrioven tricular conduction. The second H* blocks within the His-Purkinje system but conducts retrogradely to the atrium to be manifested as a blocked atrial premature depolarization. This resets the sinus node and allows the third H* to arise as an escape rhythm during the sinus pause. HBE, His bundle electrogram; HRA, high right atrium;

patterns due to multilevel block ( Figure 6.16 ). The pattern of 3:1 block should suggest multilevel block, and in this case, block in the more proximal structure (A-V node) was due to a His extrasystole. Junctional tachycardia can occur as a primary arrhythmia (usually in children, junctional ectopic tachycardia or JET), secondary to digitalis intoxication, or in the setting of injury to the His bundle (ie, valve surgery, ab scess, sarcoidosis, etc) ( Figure 6.17 ). Triggered activity due to

isolated His bundle spikes that do not affect subsequent events. Frequently, multiple manifestations of His bundle ex trasystoles may be recorded in one patient ( Figure 6.14 ). 36 In such a patient, the presence of conducted His bundle extrasys toles on the ECG is an important clue to the diagnosis. Complex conduction problems including “gap” phenomena (see Chap ter 5) may be observed with His extrasystoles ( Figure 6.15 ). 36 His extrasystoles can also produce unusual conduction

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Ar

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Ar

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955

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930

HRA

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H V

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H-H* 540

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H-H* 410

HBE

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935

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895

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H-H* 350

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HBE

HBE

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FIGURE 6.15 Conduction patterns of spontaneously occurring His extrasystoles. A to D. Each panel shows the simultaneous recording from top to bottom of surface leads 1, 2, and 3, followed by high right atrium (HRA) and His bundle electrogram (HBE) deflections. Time lines (T) on the bottom of each frame record 100 msec per large spike. The basic rhythm is sinus with similar cycle lengths (895-955 msec) in each frame. A. A His extrasystole (H*) with coupling interval (H-H*) of 540 msec conducts antegrade with normal H*V time (48 msec), as well as retrograde. Note the reversal of the intra-atrial conduction pattern of the retrograde atrial depolarization (Ar) in this and subsequent panels. B. A His extrasystole with shorter coupling interval (H-H* = 460 msec) conducts to the ventricle with prolonged infranodal conduction (72 msec) and an RBBB pattern. Ar is clearly seen in the HRA and is partially buried within the ventricular depolarization in the HBE. C. Further prematurity of the His extrasystole (H-H* = 410 msec) causes block within the His-Purkinje system, and no ventricular depolarization occurs. D. With even greater prematurity (H H* = 350 msec), infranodal conduction resumes, but with marked prolongation (H*V = 172 msec) and the development of an LBBB pattern. LBBB, left bundle branch block; RBBB, right bundle branch block. (Reprinted from Bonow RO, Josephson ME. Spontaneous gap phenomenon in atrioventricular conduction produced by concealed His bundle extrasystoles. J Electrocardiol . 1977;10:263, with permission from Elsevier.)

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