Rhythm Challenge #4

How would you describe this heart rhythm? Lead II is on top and lead V1 is on bottom.


  • NSR at a rate of about 80 with LBBB for underlined rhythm. Multifocal PACs. One focus very close to underlined pacemaker, and one probably conducting through a bundle of kent-like accessory pathway (short PR-interval & delta wave present with PAC).That's all I got on this one. Very interesting though.

  • Tom B says:

    Good observation, Adam! I also considered the possibility of an accessory pathway on those beats, but I think a fusion complex is more likely, just going with the odds.Also, if you look at the rhythm strip I uploaded to the facebook fan page, it shows one additional cardiac cycle at the very beginning of the strip which shows a fusion complex at the same interval.Tom

  • Christopher says:

    NSR w/ multifocal PACs. I didn't notice the AP-features, but am taking a second look.

  • Tom B says:

    Christopher – Check out the comments on the facebook fan page. Since the aberrantly conducted beats conincide with a long-short cycle, it could be Ashman's phenomenon!Tom

  • Christopher says:

    I see a long-short-long cycle before the Ashman beats, but not long-short. It looks like the normal beat comes through prior to the different morphology PAC comes through.

  • 3 underlying SR beats with LBBB, 1 PAC/PJC with the same pathway, 1 underlying SR beat with compensatory pause, and then 1 complex with a different pathway but initiated by the same or similar underlying atrial impulse.god, it's been a while since someone's mentioned ashman's.

  • Terry says:

    Isn't Ashman's a rate dependent BBB? I agree with the PAC's and LBBB. Does look like some fusion beats too.

  • Tom B says:

    Christopher -The Ashman's beat would be the short cycle! Tom

  • Tom B says:

    burned-out-medic and Terry -I will probably write a follow-up post about Ashman's phenomenon.Tom

  • tal says:

    there is a regular NSR, with regulary irregular ventricular response. the RBBB pattern beat is always preceded by a normal LBBB one and a short RR one, probably a premature junctional complex. that led me to think about an accessory pathway, possibly hidden in the left side, who turned refractory by the JPC, allowing it to skip the P wave and conduct it's beat later on.

  • Brown Frown says:

    Why are people calling the premature beats PAC's? Am I missing something? They look like PJC's to me. Just curious. In any rate, there is a repeating pattern in the rhythm. The first complex aside, there is a "run" of 3 wide sinus complexes followed by a PJC (PAC) then a pause of sorts, an "odd" looking sinus complex (for this rhythm, and repeat. I just plotted out the P waves. They're regular and fall in the midst of the PJC's

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