MYOCARDIAL INFARCTION Flashcards
signs and symptoms of a myocardial infarction
In general and for Mike
In general:
- pallor/ pale peripheries
- chest pain or discomfort- not relieved and severe
- shortness of breath
- nausea/vomitting
- increased heart rate
- pain/ discomfort in shoulder, neck, arm or jaw
- abnormal heart rate
- ECG changes
- hypertension
- sweating
For Mike:
- indigestion pain that developed into chest pain (main one)
- sweating
- pale peripheries and face
- sore arm
- tingling sensation in arm/ hand
risk factors of a myocardial infarction
In general and for Mike
In general:
- atherosclerosis
- older adult age
- family history
- family history
- males
- hypertension
- obesity
- inactivity
- tobacco use
- hyperlipidemia
- hypercholesteremia
- hyperglycaemia/ diabetes
For Mike:
- smoking
- family history
- male
- atherosclerosis
- hyperlipidemia
- hypercholestremia
pathophysiology of a myocardial infarction
Myocardial infarction occurs when there is sustained myocardial ischemia due to the blockage of the cononary artery. This most commonly occurs when a thrombus forms after an atherosclerotic plaque in the coronary artery ruptures. Atherosclerosis is the thickening/ hardening of arterial walls due to plaque formation. When it ruptures, a thrombus forms which further restricts the artery. This leads to hypoxic injury (decreased oxygen) which increases lactic acid production and inflammation which leads to myocardial necrosis (tissue death) and their cell membrane (sarcolemma) breaks down and their cellular contents (proteins) are leaked into the surrounding body fluids and blood.
what happens to neighbouring cells affected by inflammation;
1. stunning- temporary loss of contraction
2. hibernation- stop contracting to preserve life when there is sustained ischemia
3. remodelling- permanent loss of contracting
There can be STEMI and NSTEMI myocardial infarctions
NSTEMI- no S-T elevation on ECG, patrial thickness necrosis from severe coronary artery narrowing
STEMI- S-T segment elevation on ECG, full thickness necrosis. complete and prolonged occlusion of an epicardial blood vessel. This is what Mike had
complications of a myocardial infarction
decreased cardiac output/ heart functionality leads to;
- angina/ re-infarct/ infarct extension
- arrythmias- life threatening- ventricular fibrillation
- valvular incompetence
- cardiogenic shock
- left ventricular aneurysm
- ventricular rupture
- pericarditis (inflammation of pericardium
- heart failure
collapse and cardiac arrest:
After the ECG confirmed Mike had suffered a MI, he was administered thrombolytic drugs. Shortly after this, Mike collapsed as his heart went into ventricular fibrillation (ventricle quiver so no cardiac output) cardiac arrest. Mike was then defibrillated and he returned to NSR (normal sinus rhythm) post resuscitation.
arrhythmias and further ischemic injury:
Mike experienced atrial fibrillation (atrial quiver) and shortly after developed chest pain, with some pain in his left limb. His ECGs over his time at the hospital show atrial fibrillation and S-T segment elevation. Arrhythmias are alterations in the cardiac conduction and atrial fibrillation is the most common (blood pools in the atria which can lead to clot formation which can turn into an embolism and block blood flow). Life threatening ones are ventricle tachycardia (rapid conduction of ventricles increasing HR). ventricle fibrillation which Mike had (ventricle quiver so no cardiac output) and asystole (no contraction- flat line).
comparison to similar conditions (coronary artery disease and atherosclerosis)
coronary artery disease;
- Narrowing and/or blockage of coronary arteries (deliver blood supply to the heart)- leads to ischemia which leads to;
1. Angina (chest pain) oxygen demand is greater than oxygen supply
- Stable, predictable (with exercise)
- Unstable, unpredictable (strong indicator for
myocardial infarction)
2. Myocardial infarction (heart attack)
- It is most commonly due to atherosclerosis (narrowing of the arteries)
atherosclerosis;
- Thickening/ hardening of arterial walls due to plaque formation
- LDL= bad cholesterol
- HDL= good cholesterol
- Plaque narrows arterial wall
- Plaque becomes susceptible to rupture
- If it rupture than a thrombus forms which further restricts the artery
coronary artery disease- vacsular conditions
atherosclerosis- vascular conditions
patient tests or assessments for myocardial infarction
In general and for Mike
expected labratory tests;
- full blood count
- cardiac enzymes
- urea and electrolytes
- thyroid function tests
- blood glucose
expected investigations
- chest x-ray
- ECG
- angiogram
management of a myocardial infarction. What is Mona and perfusion therapy
Immediate management has the following goals
- decrease heart workload
- increase oxygen delivery to body tissues
- re-perfuse the heart wall
MONA- drugs
M- Morphine- to relieve chest pain if the chest pain doesn’t resolve with sublingual or I.V. nitroglycerin
O- oxygen- given if the patients 02 saturation level is below 92% to ensure adequate oxygen delivery
N- nitroglycerin- given to reduce chest pain. Is a potent vasodilator, decreases myocardial oxygen consumption and cardiac workload
A- aspirin- slows platelet aggregation, reducing the risk of further occlusion or re-occlusion of the coronary artery or the recurrent ischemic event
perfusion therapy is a medical treatment to restore blood flow either through or around blocked ateries. Mike received thrombolysis drugs as perfusion therapy after his initial hospital admission in the local hospital with the following
-Enoxaparin (Clexane): helps prevent the original arterial clot from expanding and allows it to break down, opening up the vessel and inhibiting new clot formation. Clexane is administered as a subcutaneous injection, as well as an IV bolus in the acute setting.
-Tenecteplase: a fibrinolytic which binds to fibrin and converts plasminogen into plasmin, which then degrades fibrin. It is administered intravenously and should be given as soon as possible after MI, if primary PCI is not available.
what does an ECG do and what were the results of Mikes ECG
It can diagnose ischemia or an MI because impaired blood supply to the heart affects cardiac conduction which can be seen as characteristic changes in the ECG recording. The specific changes that occur depend on where the infarction is located, the size of the area affected and the duration of the infarct.
An ECG measures the electrical activity of the heart. The deflections on the ECG waveform reflect repolarisation and depolarisation occurring throughout the cardiac cycle. There are 12 leads that attach to the patient
Mikes ECG showed S-T elevation areas which suggest transmural infarction and S-T depression areas which suggest subendocardial ischemia or infarction. Changes in the S-T segment reflect damage to the ventricular walls of the heart.
why are blood tests important- cardiac enzymes and what did Mikes blood tests show
- Due to the breakdown of the myocardial cell membrane (sarcolemma), proteins leak out of the myocytes and become detectible in blood. Elevated cardiac enzymes are significant markers for cardiac injury/MI.
-Troponin T is a contractile protein that is only released from myocytes when necrosis has occurred, and thus it is highly sensitive, and specific, to cardiac muscle cell damage.
Mikes blood tests show he has elevated troponin T levels, indicating myocardial necrosis. He also had evelated triglyceride levels, decreased HDL levels and a higher than normal cholesterol/ HDL ratio.
what is PCI (angiogram and angioplasty)
PCI involves the use of coronary angiograms to visualise and assess the damage associated with coronary ischemia. Once the problem is located angioplasty can be performed to open up the affected vessels.
angiogram:
It is performed by injecting a contrast agent into the bloodstream, which makes the blood vessels surrounding the heart visible on an x-ray. This is to show nay blockages or narrowing of the arteries.
Mikes angiogram revealed stenosis and thrombosis n the right coronary artery, so he underwent a right coronary artery angioplasty
Angioplasty, with stent This is a technique used to widen a narrowed or obstructed artery. In the procedure, a collapsed metal tube (stent) surrounding a collapsed balloon is passed into the vascular system using a guide wire (catheter). The balloon is positioned in the narrowed area and then inflated. This squashes the deposits causing the narrowing and expands the stent, thus opening the blood vessel. The balloon is then deflated and removed, while the stent remains to keep the artery open, thus allowing the return of normal blood flow.
management of an MI on discharge- medications prescribed and changes to lifestyle factors
medications prescribed are;
1. aspirin- blocks cox enzyme and prevents platelet aggregation, therefore helping to prevent blood clots
2. anti-coagulants- they act on different sites of the coagulation cascade to prevent clot formation
3. beta blockers- block the effects of the hormone epinephrine, causing the heart to beat more slowly and with less force which lowers blood pressure. Also help widen veins and arteries to improve blood flow
4. nitroglycerine- activates guanylate cyclase which increases blood flow to the myocardium and reduces cardiac preload and afterload
5. cholesterol lowering medications- inhibit HMG-CoA to lower cholesterol
Mike was prescribed:
1. Aspirin- a nonsteroidal anti-inflammatory drug (NSAID) which prevents platelet aggregation, therefore helping to prevent blood clotting.
2. Clopidogrel- inhibits platelet activation and aggregation; often used in combination with aspirin to prevent thrombosis after angioplasty.
3. Glyceryl trinitrate (GTN) spray: relaxes smooth muscle (potent vasodilator) & decreases cardiac workload; best used as required for angina or MI.
4. Metoprolol: beta blocker which reduces heart rate (HR), cardiac output (CO) and blood pressure (BP) through inhibition of catecholamines.
5. Simvastatin: inhibits cholesterol synthesis to lower cholesterol
Dietary and lifestyle factors;
- smoking cessation
- dietary changes such as a low fat, low salt diet with plenty of fruit and vegetables
- mike was prescribed nicotine patches
