A Far-Reaching Interpolation

Report:

Sinus rhythm.

VEBs, frequent, two interpolated.

Comment:

The concealed retrograde conduction governing the PR interval after an intercalated VEB rarely affects more than one cycle. In the top and middle strips, the first VEB is intercalated and prolongs the PR interval of two subsequent sinus cycles. This is uncommon26.

Note also the short R-R intervals following the intercalated cycle; this is even more pronounced in the additional examples below (Fig 35a). The second beat following the interpolated VEB mimics a premature atrial beat - a sinus extrasystole - except that its P wave is “on time”.

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