Josephson Clinical Cardiac Electrophysiology

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Chapter 5: Miscellaneous Phenomena Related to Atrioventricular Conduction ■

CL 500

1 V1

1

V1

A

A1

A1

A1

A1

A2

HRA

HRA

A1 V1 V2

V1

AH

V

V1

V1 V2

A2

A1

A1

A1 H2

HBE

HBE

75

S1

S1 V1-V2 260 S2

S1 120

S1 V1-V2 270 50 120S2 130

35

T

T

B

A

1 V1

1 V1

A1

A

A2

A1

A1

A

HRA

HRA

V1

V1 V2

A1 V1 V2

V1

AH V

A1

A1 H2

A1

HBE

HBE

S1 S2 170 50 V1-V2 230

75

S1

S1

S1 V1-V2 210

S2

35

T

T

C

D

FIGURE 5.14 Type II retrograde gap in ventriculoatrial (V-A) conduction. The ventricular drive rate is constant at 500 msec. Note the low-to-high sequence of atrial activation. A. V2 encounters retrograde conduction delay below the His bundle. The S2-H2 interval is 130 msec, and retrograde activation of the atria occurs. B. V2 blocks within the His-Purkinje system (HPS) and neither H2 nor A2 is seen. C. With further prematurity of V2, conduction resumes with a S2-H2 of 170 msec as V2 encounters delay before the site of initial block, allowing sufficient time for recovery. D. The effective refractory period of the site of delay is reached, and V-A conduction is again interrupted.

1 2 3 V1

A1

A1

A2

900

HRA

365

A1

V1

A1 V1 A2

H1

H2

H1

HBE

H1-H2 400

S

T

1 2 3 V1

A1

930

A1 A1 V1 H1

Ae

320 A2

HRA

A2

V2

Ae

A1 V1 H1

H2

HBE

H1-H2 375

S

T

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FIGURE 5.15 “Pseudo-supernormal” conduction due to Type II atrioventricular (A-V) gap. In the top panel, an atrial extrastimulus (A2) that was introduced during sinus rhythm at a coupling interval (A1-A2) of 365 msec blocks below the His bundle deflection. In the bottom panel, an atrial extrastimulus (A2) that was introduced at a coupling interval of 320 msec is conducted despite a slightly longer preceding sinus cycle length that, if anything, would be expected to favor nonconduction. Note the strikingly long H2-V2 (235 msec) that has permitted the distal HPS to recover. The resultant beat is conducted with the left bundle branch block, and it is followed by an atrial echo (Ae).