Acute Coronary Syndromes and Acute myocardial Infarction - Presentation And Investigation Flashcards
What are the different incidences of caridac chest pain?
New excertional angina?
Unstable angina?
Acute MI?
Sudden Cardiac Death?
New exertional angina - 52%
Unstable angina - 13%
Acute MI - 22%
Sudden cardiac death - 13%
What is Stable Angina defined as?
Myocardial blood flow does not meet demand - ischaemia
Central chest tightness, often radiation to neck and/ or arms.
Aggravated by exertion & stress.
Relief by stopping activity & rapid improvement with sublingual nitrate.
What are the different acute coronary syndromes?
Unstable angina
NSTEMI- Non-ST-segment elevation MI
STEMI
How does atherothrombosis formation (the pathogenesis of all acute coronary syndromes) occur?
Plaque disruption
Why do plaques rupture?
Inflammation and sheer stress
What is the main difference between acute coronary syndromes and ACS?
ACS symptoms will almost always give symptoms at rest in contrast to stable angina which is only on exertion.
What are the non-modifiable risk factors for Acute Coronary Syndromes?
Age, gender, creed, family history & genetic factors.
Previous angina, cardiac events or interventions.
What are the modifiable risk factors for Acute Coronary Syndromes?
Smoking
Diabetes mellitus
Hyperlipidaemia
Hypertension
Lifestyle- exercise & diet
What is a typical history of unstable angina Pectoris (UAP)?
Angina on effort
Progressive increasing severity and frequency
Often provoked by less exertion and/or then at rest
What is a typical history for those with NSTEMI?
More often start with myocardial ischaemic symptoms occurring at rest.
What is the pain like in acute coronary syndromes?
Site - retrosternal
Character - often tight band/pressure/heaviness
Radiation - neck and/or into jaw, down arms
Aggravating factors - with exertion, emotional stress
Relieving factors: relieving factors e.g. incomplete improvement with GTN, or physical rest; and/or ongoing
What must you ensure to check for on examination for unstable angina and NSTEMI?
HR, BP
Listen for murmurs, crackles in chest
May look very unwell
May look completely fine
Often no specific features to find
What are the possible investigations for unstable angina and NSTEMI?
Electrocardiogram and Biomarkers
What are common results of ECG in UAP and NSTEMI?
Often normal ECG results
Commonly ST-segment depression, transient ST-segment elevation and/or T-wave inversion
More often in UAP changes resolve after pain, and in NSTEMI they tend to persist (but not always);
serial ECGs to detect delayed changes essential
Why is the difference in infarction between STEMI and NSTEMI?
STEMI - transmural
NSTEMI - sub endocardial infarct
How do you differentiate between NSTEMI and unstable angina?
Biomarkers - troponin and CKMB
Here is why there is a rise in ST segment in STEMI
Rise in ST segment because:
Infarcted tissue loses the ability to maintain resting potential of -90mv. Sodium potassium pumps no longer work, so it is partially depolarised. Normally true baseline of an ECG is zero because there is no difference in voltage. However the positve vector of depolarisation travels away from the electrode - negative deflection of baseline – so it shifts lower. ST segment now appears elevated because the ST segment is where there is complete depolarisation – so the ST segment is on the true baseline. In comparison to original baseline, ST segment is higher up.
Here is why there is ST depression in NSTEMI
NSTEMI – depolarisation vector travels towards the detector, shift of baseline upwards. ST segment refers to the point where there is complete depolarisation. ST segment now appears lower. ST segment returns to normal because of fibrosis. Fibrotic tissue doesn’t have the ionic leakage of necrotic tissue.
When is there likely going to be an atypical ACS presentation?
In women; the elderly or diabetics, influenced by reduced pain sensation.
What are the symptoms of angina and NSTEMI?
Breathlessness alone +/- signs of heart failure
Nausea & vomiting +/- other autonomic symptoms
Epigastric pain +/- recent onset indigestion
What does elevated cTn (cardiac troponin) suggest?
High risk of adverse events
Beware, not all troponin elevations are a ACS and caused by atherothrombosis
What does elevation of cardiac troponin indicate?
Elevated with compromise of myocyte integrity.
Sensitive and specific marker of cardiac myocyte damage
What do the levels of biomarkers indicate?
Characteristic rise and fall of cTn with ischaemic damage
Different pattern for acute myocardial infarction to unstable angina pectoris
What is the immediate treatment for UAP and NSTEMI?
First ABCDE approach, then MONA
Morphine (or diamorphine)
Oxygen
Nitroglycerine (GTN spray or tablet)
Aspirin 300 mg orally (crush/chew)
What does antiplatelet therapy for UAP and NSTEMI event consist of?
Usually dual anti-platelet therapy (Aspirin & ADP receptor blocker) for one year following ACS event (look at McClays pharmacology treatment of ACS and AMI for further details)
What does antithrombotic therapy for UAP and NSTEMI consist of?
Intravenous unfractionated heparin (UFH) or s/c low molecular weight heparin (LMWH)
What is other medical therapy for unstable angina and NSTEMI that isn’t anti-platelet therapy or antithrombotic therapy?
β-blockers are recommended in ACS in the absence of contraindications (asthma, acute left ventricular dysfunction, impaired AV nodal conduction); target heart rate should be between 50 and 60 bpm.
Statins both acutely & chronically reduce further events.
Angiotensin converting enzyme inhibitors: always if left ventricular dysfunction, controversial if normal function
Which UA/NSTEMI patients benefit from invasive strategy? (coronary revascularisation)
High risk patients
Give examples of invasive strategy/ coronary revascularisation
Coronary angiography and revascularisation by PCI
CABG
Typical Treatment Path for
Unstable angina & Non-ST elevation MI
Treatment path? (Not really in learning outcomes)
Most patients stay in hospital for 2-7 days.
Not all patients will have angiography, and not all who an angio. will need or have revascularisation.
Decisions more difficult in the elderly and/or those with important co-morbidities.
Many not reviewed after hospital discharge, some are for further decision making.
What is the result of coronary plaque rupture?
More complete, or complete thrombotic occlusion of coronary lumen and infarction of distal myocardium
Proximal occlusion of main artery causes greater damage
What can be the occlusion of distal or branch vessel cause?
if it supplies a critical structure - significant problems - rupture of papillary muscle, acute mitral regurgitation, occlusion of AV nodal artery – CHB (complete heart block)
What are the two forms of treatment for STEMI?
Fibrinolysis or primary PCI
What is the effect of removing an occlusive thrombus early?
nsooner occlusive thrombus is dissolved/removed, and vessel opened, the more myocardium will be salvaged.
Less LV damage results in better survival.
Why is PCI better than fibrinolytic therapy?
Superiority in terms of all-cause and cardiac mortality, recurrent MI; and, reduced risk of haemorrhagic stroke.
When is PCI most effective?
If delivered within 120-150 mins of the patient’s call for help (call to balloon time)
If door to balloon time is less than 90 minutes
If it has been over 3 hours of symptom onset
If there is cardiogenic shock, HF
High bleeding risk
If the diagnosis is uncertain
When is fibrinolysis the choice of treatment?
When PCI cannot be performed
Or when door to balloon (of PCI) is longer than 90 minutes
If the symptoms have been present for less than 3 hours (PCI most effective between 120-150 minutes)
If the difference in time between door to balloon is one or two hours greater than door to needle
When is the best time to initiate fibrinolysis?
Within 90 minutes of patient calling for help (call to needle) or within 30 minutes of hospital arrival
How can call to needle be reduced?
Prehospital fibrinolysis
What is the benefit of pre-hospital fibrinolysis?
Reduces early mortality by 15-20% in comparison to in-hospital fibrinolysis
What are the risks of fibrinolytic therapy?
Increased risk of bleeding and intra-cranial haemorrhage in some patients
Which patients have an increased risk of bleeding and intracranial haemorrhage?
Age > 75
Female sex
Previous stroke
Low body weight (F<65 kg, M<70 kg)
SBP > 160 mmHg
INR > 4 (international normalized ratio - tells you how fast the blood clots in patients receiving oral anticoagulant medication)
Chronic kidney disease & elevated creatinine
Not really in learning outcomes for this lecture, seen later in James McLay’s lecture
What investigation would you use for ST elevation myocardial infarction for in-patient investigations?
Echocardiography
What will echocardiography be used to see when examining a ST elevation myocardial infarction?
Size of wall motion and nature of wall motion
Overal contractility
Presence and degree of mitral regurgitation
Presence of mural thrombus
What are the most important determinants of MI survival?
Age and LV ejection fraction
What percentage of sudden cardiac deaths are resuscitated and survive?
about 2%
What is common in 80% of patients that are resuscitated & survive?
In resuscitated patients 80% had VT (ventricular tachcardia – life-threatening arrythmia) or VF (ventricular fibrillation)
Why does ACS result in ventricular arrythmia?
The atherothrombotic event causes acute myocardial ischaemia and subsequent electrical disturbance
Are all Sudden cardiac deaths ACS events?
NO
What does sudden cardiac death look like on an ECG?
What is the only effective treatment for VF arrest?
Defibrillation
How does sudden cardiac arrest differ from a heart attack?
Heart attacks occur when there is a blockage in one or more of the coronary arteries, preventing the heart from receiving enough oxygen-rich blood
In contrast, sudden cardiac arrest occurs when the electrical system to the heart malfunctions and suddenly becomes very irregular. The heart beats dangerously fast. The ventricles may flutter or quiver (ventricular fibrillation), and blood is not delivered to the body.
What does VF deteriorate into?
Asystole (a condition in which the heart ceases to beat.)
What is often proven to change the outcome of sudden cardiac death?
Bystander CPR
What are the mechanical complications of MI?
Free wall rupture
Septal Wall Rupture
Papillary Muscle Rupture
What are the ventricular arrythmia complications with MI?
VF
VT
Describe another complication associated with MI than isn’t a mechanical or an arrhythmic complication?
LV Thrombus
What is surgery for papillary muscle rupture or VSD?
Urgent surgery usually indicated.
Mitral valves are usually replaced rather than repaired.
VSD repair with pericardial or synthetic patch
Coronary artery bypass if needed & possible.
If survive acute episode long term prognosis is good
How do you diagnose VF from an ECG?
- P-waves and QRS complexes are not present
- Heart rhythm is highly irregular
- The heart rate is not defined (without QRS complexes)
When is LV thrombus usually found?
48 hours after infarction
What is treatment for LV thrombus?
Anticoagulation for 6/12 with warfarin and repeat echo
