Atrial Rhythms

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    81 year old male with heart palpitations and a history of regular supraventricular tachycardia(SVT).

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

    Questions

    Question 1: Why do some beats aberrate? 

    Question 2: Careful inspection of this tracings suggests 2 populations of RR intervals. What is the significance of this finding?

    Question 3: What type of regular SVT does this patient likely have?

    Key Findings

    -Atrial fibrillation with rapid ventricular response

    Coding for Boards

    -Atrial fibrillation

    -Non-specific ST and/or T wave abnormalities

    -Aberrant conduction

    Answers

    Question 1: 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.

    Question2: The presence of two distinct populations of RR intervals during atrial fibrillation suggests the presence of dual AV nodal physiology. Some of the atrial impulses conduct down the slow pathway, while others conduct down the fast pathway.

    Question 3:  The presence of dual AV nodal physiology makes AVNRT the most likely type of regular SVT for this patient.