Myocardial Infarction Flashcards
How would you define an MI?
A myocardial infarction occurs when blood flow to (a part of) the heart stops or decreases
- Cardiac muscle gets damaged
- Often occurs in coronary artery
- Leads to cell death, which will release troponin
What symptoms are associated with an MI?
- Pain
- Sweating, nausea, vomiting
- Breathlessness, weakness, fatigue
- Loss of consciousness
What sort of chest pain characterises an MI?
Tightness, pressure and squeezing. Can also be knife-like, tearing or burning
Pain may radiate to left arm, lower jaw, neck, shoulder
What is Levine’s sign? As seen in an MI?
person localises chest pain by clenching one or both fists over their sternum (historical, but not necessarily accurate)
What percentage of MIs are silent?
22-64%
What are risk factors for getting an MI?
- Old age
- Actively smoking
- High blood pressure
- Diabetes Mellitus
- Total cholesterol, low HDL, high LDL and high triglycerides
Other risk factors include male sex, obesity, alcohol use
What happens if cardiac myocytes are not supplied with sufficient oxygen?
If the impaired blood flow is sustained, an ischemic cascade is triggered:
- Heart cells in the territory of the blocked coronary artery die and do not grow back
- Collagen scar replaces heart tissue
- Apoptosis of affected cells
What are the two types of MIs, as described by their location in the cardiac wall?
Ischemia first affects the subendocardial region, which will begin to die within 15-30 minutes after blood loss
- This is just below the inner surface of the heart
- Most susceptible to damage
- Subendocardial infarction
When the MI persists, a transmural infarction can arise
What are the risks after an MI?
Post-MI, there is myocardial scarring which leads to an alteration in the conduction pathway, putting someone at risk for:
- Arrhythmias
- Heart block
- Aneurysm of the heart ventricles
- Inflammation of heart wall
What is often the cause of an MI?
Atherosclerotic plaques can rupture, leading to the formation of blood clots that block the (coronary) artery
How is an MI diagnosed?
An MI is defined by increased troponin, as well as one of the following:
- Symptoms relating to ischemia
- Changes on ECG
- Changes in the motion of the heart wall
- Demonstration of a thrombus
Blood tests will show elevated troponon I and troponin T
What are patients who experience a STEMI at risk of?
Patients experiencing acute STEMI are at risk for developing life-threatening arrhythmias like ventricular fibrillation which causes sudden cardiac arrest, sometimes referred to as a “massive heart attack”.
How do you treat a STEMI?
CPR and defibrillation
What is characteristic of a NSTEMI?
No elevation of the ST interval - potential depression, as seen on an ECG
Often subendocardial
What is angina?
Angina is a type of chest pain that results from reduced blood flow to the heart