Been a while since we did cardiology so I wanted to do a quick review on the normal deflections you should expect to find in each lead of an EKG

Limb Leads

Lead I – Looks across top of heart with positive electrode at left arm – so QRS complexes are upright but not that tall

Lead II – Follows normal electrical axis of heart, top right to bottom left . All complexes should be upright and tall.

Lead III – Looks from top left towards bottom left – at this angle P waves may be inverted but QRS should be upright (more than in lead I)

Lead aVR – Positive on right arm, so everything negatively deflected

Lead aVL – Positive on left arm – similar to Lead I but this lead looks down AND to the right so QRS are upright but very small

Lead aVF – Positive at left leg, looking at bottom of heart. Electricity is coming right at this lead so QRS should be upright and prominent.

 

Chest Leads

Leads V1-V6 – R wave starts very small and S wave is prominent. As the leads progress the R wave is more prominent and S wave is gone in V6. This is known as R wave progression.

  P Wave

P wave should be upright in Leads I and II as well as V3-V6

P wave always inverted in aVR

P wave usually upright in aVF and V3 but occasionally biphasic or flat

P wave is variable in leads III,  aVL, V1 and V2 (upright, inverted, biphasic)

Inverted P wave in II, III and aVF and upight in aVR is diagnostic for a Junctional or low ectopic atrial rythm.

Most people say that your best view of the P wave is in Lead II – others say V1. The truth is that every patient is different, find the best one on your patients EKG and study that one well.

 

See this page for some quick review and this page