ACS Flashcards
What is the main cause of cardiovascular disease (CVD)?
Cardiovascular disease (CVD) is generally due to reduced blood flow to the heart, brain or body caused by atheroma or thrombosis.
It is increasingly common after the age of 60, but rare below the age of 30.
Plaques (plates) of fatty atheroma build up in different arteries during adult life. These can eventually cause narrowing of the arteries, or trigger a local thrombosis (blood clot) which completely blocks the blood flow
What are the main types of CVD?
The main types of CVD are: coronary heart disease (CHD), stroke and peripheral arterial disease (PVD).
Risk factors for CVD
In more than 90% of cases, the risk of a first heart attack is related to nine potentially modifiable risk factors:
- smoking/tobacco use
- poor diet
- high blood cholesterol
- high blood pressure
- insufficient physical activity
- overweight/obesity
- diabetes
- psychosocial stress (linked to people’s ability to influence the potentially stressful environments in which they live)
- excess alcohol consumption.
Who is a typical patient with ACS?
Middle-aged (man) or elderly (either sex) patient, often with FH of CHD and one or more of the major reversible risk factors.
In many patients, there is no preceding history of angina.
What are the signs and symptoms of ACS?
Central chest pain often describes as heaviness or tightness with radiation to neck, jaw or arms.
Dyspnoea
Autonomic disturbances- nausea, sweating (diaphoresis) and vomiting
Tachycardia (anterior MI), bradycardia (inferior MI).
Pulmonary oedema with large infarcts.
Atypical presentations are common over 75
years of age.
What are the sub-types of ACS?
There are 3 sub-types of ACS.
ST-elevation MI (STEMI)
Non-STEMI (NSTEMI)
Unstable angina
What is STEMI?
ECG shows persistent ST-segment elevation in 2 or more anatomically contiguous leads.
Atherosclerosis with plaque rupture and thrombus formation is the underlying aetiology for STEMI.
Probable proximal occlusion of a major coronary artery.
STEMI is usually associated with a relatively large amount of damage to the myocardium (heart muscle) caused by a major blockage in the coronary artery
What is unstable angina?
Defined by the absence of myocardial necrosis.
Prolonged (>20 minutes) angina at rest.
ECG typically shows ST-segment depression and T-wave inversion but may be normal.
What is the initial treatment of presumed MI?
Oxygen (if needed) should be >90%
Aspirin in addition with ticagrelor or clopidogrel.
Beta-blocker
What is NSTEMI?
An acute ischaemic event causing myocyte necrosis.
ECG may show ST-segment depression or T wave inversion.
The distinction from unstable angina is based on cardiac biomarkers.
History and cardiac markers are the most useful diagnostic tools in NSTEMI.
NSTEMI is often associated with relatively less damage to the myocardium, caused by either partial blockage of the coronary artery or blockage of a smaller artery.
ECG changes in MI
1) Pathological Q waves usually indicate current or prior myocardial infarction. Q waves are considered pathological if:
> 40 ms (1 mm) wide
> 2 mm deep
> 25% of the depth of QRS complex
Seen in leads V1-3
2) Left bundle branch block (LBBB). ECG characteristics of LBBB are:
Broad QRS (>3small square/0.12sec) and
Deep S wave in V1 and
No Q wave in V5/V6
3) ST-segment (STEMI) and T wave abnormalities (e.g. ST-segment depression or T wave flattening or inversion-inversion due to changes in ventricular depolarisation (NSTEMI or Unstable angina)
Does a normal ECG exclude MI?
NICE guidance is clear that a normal ECG does not exclude ACS.
ECG may be difficult to interpret if there is a bundle branch block or previous MI.
Diagnosis of MI
ECG.
Cardiac biomarkers- troponins and creatine kinase
FBC- may indicate anaemia or thrombocytopenia
Electrolytes- may be deranged
Blood sugar and lipids to rule out diabetes and high cholesterol
Which tool is used to predict the likelihood of future CHD events?
Using the GRACE risk score, eight factors independently predict the risk of heart attack and/or death: age heart rate systolic blood pressure renal function congestive heart failure ST-segment deviation cardiac arrest elevated biomarkers
Based on the risk stratification of ACS, what should be done?
High risk- Echocardiogram (could be stress) Coronary angiography Low risk- Perfusion imaging using adenosine, dipyridamole or dobutamine
How do you assess troponin in an ACS setting?
Cardiac troponin I and cardiac troponin T are biological markers of cardiomyocyte necrosis.
They are released into the circulation when damage to cardiac muscle has occurred.
Troponins (>99%) are raised in STEMI and NSTEMI but not in unstable angina.
The higher the levels of troponin, the higher the mortality.
Levels of troponin increase within 3-6 hours, peak at 36 hours and is elevated for 2 weeks.
Conditions other than acute MI that may cause troponin levels to be raised include myocarditis, congestive heart failure, severe infections, musculoskeletal conditions and renal disease.
Why are troponins preferred to creatine kinase?
Raised troponins are more specific than creatine kinase.
Creatine kinase can be released from any damaged muscle in the body.
When is myocardial necrosis irreversible?
After 30 minutes.
What is the coronary sinus?
The venous drainage from the heart is via the coronary sinus.
The coronary sinus is a collection of veins joined together to form a large vessel that collects blood from the myocardium.
It delivers deoxygenated blood to the right atrium.
The coronary sinus may be readily cannulated by the cardiologist.
What are the key branches of the right and left coronary artery?
The key branches of the right (Right marginal and posterior descending) and left (Left anterior descending, left marginal and left circumflex) main coronary vessels.
The coronary arteries originate from the aortic sinuses.
What does tachycardia do to the heart?
Tachycardia increases myocardial oxygen demand (as the heart has to beat faster and hence do more work) and decreases coronary blood flow (as the duration of diastole is shortened considerably).
How do you monitor patients with acute chest pain?
Monitor people with acute chest pain, using clinical judgement to decide how often this should be done, until a firm diagnosis is made. This should include:
• exacerbations of pain and/or other symptoms
• pulse and blood pressure
• heart rhythm
• oxygen saturation by pulse oximetry
• repeated resting 12-lead ECGs
• checking pain relief is effective.
How could the ECG be normal in ACS?
Ischaemia in circumflex territory
• Isolated RV ischaemia
• (these are detected using V7-V9 and V3R and V4R leads)
• transient episodes of bundle branch block
(either RBBB or LBBB)
Management of NSTEMI?
NSTEMI is more common than STEMI.
GTN is initial treatment. (N)
Analgesia and IV opioid used for pain that doesn’t settle with nitrate. (M)
Oxygen if sats is below 94% (normal) or 88% (COPD)- oxygen avoided if there is no hypoxaemia. (O)
Loading dose of aspirin (300 mg OD) and clopidogrel (300mg OD) for a year then clopidogrel stopped after a year. (A)
MONA
Beta-blocker is the first choice of anti-anginal treatment and can reduce subsequent ischaemic events. Calcium-channel blocker used if beta-blocker is CI.
THEN assess needs for an invasive or conservative approach.
People with NSTEMI and Unstable angina should be investigated with coronary angiography (with PCI if indicated) within 72 hours of admission unless the patient has serious comorbidities including cancer or end-stage liver disease.
