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.

Fig 88a. Classic escape-capture bigeminy. Junctional escapes are very similar to conducted sinus beats, but slightly larger or smaller in most leads.

Fig 89. In the strip below, are there more QRS complexes of ventricular or of supraventricular origin?