Myocardial Infarction Flashcards
Which anatomical structures are affected in myocardial infarction?
The left coronary artery and its branches - left anterior descending (LAD), circumflex and left main stem
Right coronary artery - posterior descending artery
What is the usual physiology of the coronary arteries?
They deliver blood carrying oxygen and nutrients to the myocardial tissues
Which structural abnormalities can lead to myocardial infarction?
Narrowing of the arteries as a result of coronary atheroma
Coronary thrombosis
What is coronary thrombosis?
Blockage of an artery due to a blood clot
What physiological abnormalities occur as a result of myocardial infarction?
Ischaemia which eventually leads to necrosis of myocardium
Impaired contraction of myocardium
Abnormal electrical activity of heart cells
In which groups of people is myocardial infarction more common?
More common in men and the elderly
Family history is usually present
What are the risk factors for myocardial infarction?
- smoking
- high blood pressure
- high cholesterol
- high blood sugar/diabetes
- low exercise
- obesity
What symptoms are experienced during a myocardial infarction?
Severe crushing central chest pain which is sudden in onset
The pain radiates to arm or neck
Associated nausea, vomiting, sweating and breathlessness
What are the clinical signs of a patient with myocardial infarction?
Patient clearly distressed due to pain
Low blood pressure and fast heart rate
Breathlessness
What clinical signs may be observed relating to the lungs?
Fluid may be heard on the lungs during inspiration
This is due to pulmonary oedema (fluid in alveoli)
What will an ECG look like in a patient with MI?
It shows “ST elevation” if the coronary artery is completely blocked
What will a blood test show in a patient with MI?
Raised levels of the heart protein troponin
What will an echocardiogram of a patient with MI show?
Reduced contraction of the affected area
What is a coronary angiogram and what may it show in a patient with MI?
X-ray of the heart arteries
Shows an artery blocked by atheromatous stenosis and by a blood clot (thrombosis)
What immediate medical treatment is used to treat an MI patient?
- morphine for pain relief
- high-flow oxygen
- oral aspirin treatment
What have thrombolytic drugs been replaced by in treatment of MI?
Primary percutaneous intervention
What is involved in primary percutaneous intervention?
a thin tube is inserted into the arm or leg to remove the clot
a small balloon is used to open the narrowed artery and a metal stent is placed there to hold the artery open
What is the focus of primary and secondary prevention of MI?
Treatment or avoidance of risk factors
Why is aspirin used to prevent MI?
It has antiplatelet action to prevent blood clots
Why is clopidogrel used to prevent MI?
It has antiplatelet action to prevent blood clots, especially when a coronary stent is present
Why are beta-blockers used to prevent MI?
They lower the heart rate and blood pressure through blocking the effects of adrenaline and noradrenaline
Why are statins used to prevent MI?
They are HMG-CoA reductase inhibitors that lower blood cholesterol
Why are ACE inhibitors used to treat MI?
They block angiotensin converting enzyme to prevent production of angiotensin II
