November 12, 2015 by dailybolusoflr
By: Erin Kane, MD
How do you know you need one?
• Reciprocal changes in anteroseptal leads V1-3 – deep, horizontal ST depression
What is the relevant anatomy?
• Isolated posterior MI is 3-11% of infarcts
• Posterior infarction is present in 15-20% of STEMIs, often in context of lateral or inferior infarction
• Usually caused by occlusion of PDA (which is a branch of the RCA in 80% of individuals, otherwise may be via LCx or co-supplied by both – right dominant circulation versus left dominant or codominant)
How do you place the leads to get it?
• Leads V7-9 are placed on posterior chest wall
How do you read it?
• 0.5mm ST segment elevation makes diagnosis of posterior MI
Anatomical relationship of leads
• Inferior wall – Leads II, III, and aVF
• Anterior wall – leads V1 to V4
• Lateral wall – Leads I, aVL, V5, V6
• Posterior wall – Leads V7 to V9
• Right ventricle – stayed tuned for tomorrow’s MM