Cardiology Teaching Package
A Beginners Guide to Normal Heart Function, Sinus Rhythm & Common Cardiac Arrhythmias
Definition of Myocardial Infarction
Prior to 2001, 2 categories existed:
- Acute myocardial infarction (AMI)
- Unstable angina, subdivided into high and low risk
Now Myocardial infarction is defined if the following criteria are satisfied:
- Rise and gradual fall of Troponin T and/or
- A more rapid rise and fall of Creatinine Kinase
And at least one of the following:
- Typical ischaemic chest pain
- Pathological Q waves on ECG
- ST elevation or depression on ECG
- Coronary occlusion on angiography
Q waves can occur naturally on an ECG where they appear as a small downward deflection following the P wave, no more than 2 small squares in depth. Pathological Q waves are greater than 2 small squares in depth. They are often followed by a reduced R wave and are indicators of myocardial tissue death.
