ECG of the week

Prof. P. Vijayaraghavan UnitA.Karthick Ramalingam

FIRST YEAR PGM 5

Background

60 year old Mrs. Ponnamma, known hypertensive presented with history suggestive of anginal type of chest pain, ECGwas taken.

ECG-1

Findings• Rate 88/min

• NSR

• P wave axis 60

• QRS axis Normal

• ST straightening LII ,LIII, aVF

• T inversion L III

ECG-2

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 right atrial from left atrialrhythm

• 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.

Right atrial

• A positive or biphasicP wave in aVL has apositive predictiveaccuracy of 83% andnegative predictivevalue of 85% for aright atrial focus.

Left atrial

• In contrast, a positiveP wave in V1 is afeature of left atrialfoci. It has asensitivity andspecificity of 93% and88% respectively.

Right Atrial Rhythm

In right atrial rhythm thedepolarization begins inthe right atrium andspreads posteriorly andsuperiorly towards theleft atrium (towardsaVL). This inscribes apositive deflection (pwave) in aVL.

• LEFT ATRIAL RHYTHM

• 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.

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