Classical Wenckebach

Report:

Sinus rhythm 82 – 86/min

Second degree AV block, Möbitz 1

Left atrial abnormality (LAA)

Recent inferior infarction

Comment:

Most clinically observed Wenckebach periods are in some way atypical; the long ones are so as a rule. The commonest atypical feature, so common that atypical is a misnomer, is failure of the ventricles to accelerate smoothly or at all before the pause. Here the distal chamber accelerates through both 4:3 and 5:4 conduction. This is, as expected, because the increments in PR interval are progressively smaller.

Below (Fig 88a) is an earlier trace, in equally classic escape-capture bigeminy. The junctional escapes are slightly larger in V1 than the conducted sinus beats, a manifestation of non-phasic aberrant conduction.

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