Myocardial Infarctions Are HY for the USMLE

The formula for a Myocardial Infarction essentially is

Oxygen demand > (greater than) Oxygen supply

Myocardial tissue must therefore switch from aerobic to anerobic metabolism which generates only 2 ATP.

***AT REST THE HEART IS EXTRACTING ALMOST ALL OF THE O2 FROM ITS BLOOD SUPPLY***

therefore, for oxygen supply to increase, more blood must be pumped to the heart tissue (MOA of nitrates for ischemic chest pain). If supply cannot meet demand, the heart tissue may infarct.

Hacking Myocardial Infarctions on the EKG
The leads these changes are seen are listed in my drawing (see below)

• Peaked or Inverted T Waves - often earliest sign of ischemia
  
• ST segment
• Elevation
• Differential diagnosis: Prinzmetal's Angina
  
• a vasospasm of the smooth muscle of the artery
• Si/Sx: chest pain at rest
• cardiac enzymes = negative (differing it from an MI)
• Depressed in stable angina and subendocardial MI
  
• Deep Q waves
  
• These do not go away after the MI. Ever.
  
• therefore, deep Q waves indicats the patient may have suffered an MI