Wenckebach Conduction of Sinus Tachycardia
Report:
Sinus tachycardia 116/min
SVEB
Second degree AV block, Möbitz 1
Comment:
Some of the blocked P waves look different in shape from others, due to their position on the preceding T wave. Their timing easily distinguishes them from blocked SVEBs.
The fifth group in the lower strip shows a Wenckebach sequence with prolonging, then shortened PR intervals; the atrial rate is also irregular. A reentry beat is suggested by the apparent mirror-image P wave associated with shorter PR interval (the fourth in the group), but this is merely due to its superimposition on an earlier part of the T wave. The shorter PR interval and R-R cycle are most likely due to the early QRS being a dissociated (P waves are all on time) junctional beat. It neednât be that, ether: Wenckebach conduction can shorten spontaneously in the middle of a sequence, but this is quite uncommon.
Even large P waves can be âburiedâ in sinus tachycardia and their detection (and differentiation from other atrial activity) is only possible by mapping them out.
Fig 136a. Wenckebach trigeminy due to 4:3 conduction of sinus tachycardia. Fig 137. 62 year old woman with acute anterior infarct and new LBBB, on isoprenaline infusion in the X-ray Department.
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