Sino-Atrial Wenckebach

Report:

Sinus rhythm

Left atrial abnormality (LAA)

5:4 and 4:3 sino-atrial exit block, Möbitz 1

Normal QRS/T

Comment:

In each pause, an entire P-QRS-T sequence is missing; the pause itself is less long than two sinus cycles. There is slight acceleration of rate before the pause – opposite of what happens in respiratory sinus arrhythmia. No blocked SVEBs can be made out.

The patient also had runs of SVT (Fig 149a below) - a sick sinus syndrome. The LAA supports this diagnosis too, although it may only be a transient after-effect of the SVT itself..

The only proviso in making the diagnosis of SSS is exclusion of antiarrhythmic drugs likely to cause identical appearances.

Overpage (Fig 149b) is a long period of junctional rhythm 54/min with four sinus captures out of thin air. The preceding rhythm seems to have occurred during sinus arrest. The next ECG is normal, except, again, the junctional rhythm.

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