Findings Rate: 84/min Atrial rhythm P wave axis - 90 P ‘ – L II , L III, aVF ,V2 to V6 P --L I, aVR , a VL, V1 QRS axis normal T inversion L II , L III, aVF ST depression L III, aVF Findings of ectopic atrial rhythm
Repeat ECG taken for the patient reverted back to sinus rhythm and was similar to ECG 1
To differentiate rightatrial from left atrial rhythm
P wave morphology is useful in differentiating left from right atrial foci.
This is a function of the anatomical relationship of the atria, with the left atrium being a more posterior and leftward structure than the right atrium.
As such, leads V1 and aVL are useful discriminators.
Left atrial Right atrial
A positive or biphasic P wave in aVL has a positive predictive accuracy of 83% and negative predictive value of 85% for a right atrial focus.
In contrast, a positive P wave in V1 is a feature of left atrial foci. It has a sensitivity and specificity of 93% and 88% respectively.
Right Atrial Rhythm In right atrial rhythm the depolarization begins in the right atrium and spreads posteriorly and superiorly towards the left atrium (towards aVL). This inscribes a positive deflection (p wave) in aVL.
In left atrial rhythm the depolarization of atria begins in the left atria and spreads anteriorly towards right atrium(in the direction of V1). This inscribes a positive deflection (p wave) in lead V1.
The exceptions to the above criteria are ectopic foci with origin at the high crista terminalis (right atrial - near SA node) and impulse originating near the atrial septum.
In our patient a positive p wave in V1 with a negative p in V6 is suggestive of a left atrial rhythm.