Atrial Rhythms

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    71 year old male with heart palpitations.

    31 year old male who is asymptomatic and has a history of cardiomyopathy.

    Questions

    Question 1: How do you know the premature beats are PACs? 

    Question 2: Why do the PACs aberrate?

    Key Findings

    -Sinus rhythm with atrial bigeminy

    Coding for Boards

    -Sinus rhythm

    -Premature atrial complexes

    -Abberant conduction

    Answers

    Question 1: Careful inspection of the T waves after each sinus beat reveals a P wave imbedded within. This is especially evident when compared with the T waves after the last 3 sinus beats.

    Question 2: These beats occur relatively earlier and fall in the relative refractory period of the His-Purkinje system. This results in phase 3 block, or rate dependent aberration.