Acute Coronary Syndrome
Acute Coronary Syndrome (ACS) is a medical condition characterised by a sudden reduction in blood flow to the heart muscle, causing the muscle to function improperly or die. This is primarily due to the blockage of the coronary arteries. The most common symptom is centrally located chest pain, which can radiate to the left shoulder or jaw and is often associated with nausea and sweating. Symptoms can vary, particularly in women, older adults, and individuals with diabetes mellitus.
Classification
ACS is categorised into three types based on electrocardiogram (ECG) changes and cardiac biomarkers:
- ST Elevation Myocardial Infarction (STEMI): Complete blockage of a coronary artery with ST elevation on ECG.
- Non-ST Elevation Myocardial Infarction (NSTEMI): Partial blockage without ST elevation but with elevated cardiac biomarkers.
- Unstable Angina: Ischaemia without cell injury or necrosis and no elevation in cardiac biomarkers.
Signs and Symptoms
The hallmark symptom of ACS is chest pain, experienced as tightness, pressure, or burning, often radiating to the arm, shoulder, neck, back, upper abdomen, or jaw. This may be accompanied by sweating, nausea, and shortness of breath. Unlike stable angina, which occurs during physical activity and resolves at rest, unstable angina can occur suddenly and at rest, lasting longer and being resistant to rest or medication.
Pathophysiology
ACS primarily results from the rupture of an atheromatous plaque in the coronary artery, leading to thrombus formation and arterial blockage. Plaque rupture is more common in STEMI, whereas plaque erosion is more common in NSTEMI. Once the artery is unblocked, there is a risk of reperfusion injury due to the spread of inflammatory mediators.
Other causes include spontaneous coronary artery dissection, ischaemia without obstructive coronary artery disease, and myocardial infarction without obstructive coronary artery disease.
Diagnosis
Electrocardiogram
The ECG is very important in differentiating between various causes of acute chest pain. Changes indicating heart damage include ST elevation, new left bundle branch block, and ST depression. An absence of ECG changes does not immediately rule out NSTEMI or unstable angina.
Blood Tests
Cardiac biomarkers like troponin I and T are elevated in myocardial infarction (both STEMI and NSTEMI) but not in unstable angina.
Prediction Scores
Risk scores such as the HEART score and TIMI score, combined with cardiac biomarkers, help assess the likelihood of myocardial infarction in emergency settings.
Prevention
Preventing ACS involves controlling risk factors for atherosclerosis: healthy eating, regular exercise, managing hypertension and diabetes, avoiding smoking, and controlling cholesterol levels. Aspirin is beneficial for high-risk individuals. Secondary prevention strategies are similar to those for myocardial infarction. Notably, smoking bans have been associated with significant reductions in hospital admissions for ACS.
Treatment
Initial Management
Patients with presumed ACS are typically administered aspirin, clopidogrel or ticagrelor, nitroglycerin, and morphine if chest discomfort persists. Angiography is recommended for new ST elevation or new bundle branch blocks. Additional oxygen is not beneficial unless the patient has low oxygen levels.
STEMI
For STEMI, thrombolytics or percutaneous coronary intervention (PCI) may be performed. Thrombolytics stimulate fibrinolysis to destroy clots, while PCI involves mechanically opening blocked arteries using angioplasty and stent deployment. Rapid treatment is essential, with guidelines recommending thrombolytics within 30 minutes and PCI within 90 minutes.
NSTEMI and NSTE-ACS
Management includes aspirin, a second antiplatelet agent, and heparin, with IV nitroglycerin and opioids if pain persists. Fondaparinux is preferred over enoxaparin. Delaying angioplasty until the next morning is not inferior to immediate intervention. Early statin use reduces the risk of further ACS.
Cocaine-associated ACS should be managed similarly, but beta blockers should be avoided, and benzodiazepines should be used early.
Prognosis
Prediction Scores
The TIMI and GRACE risk scores help identify high-risk patients and estimate mortality risk after a heart attack, considering clinical and medical history factors.
Biomarkers
Markers like natriuretic peptides and monocyte chemoattractive protein can predict death and heart failure risk post-ACS.
Day of Admission
Weekend admissions are associated with higher mortality and lower utilisation of invasive procedures, a phenomenon known as the weekend effect.
Self-assessment MCQs (single best answer)
What is the primary cause of Acute Coronary Syndrome (ACS)?
Which type of ACS is characterised by complete blockage of a coronary artery with ST elevation on ECG?
What is the hallmark symptom of ACS?
Which cardiac biomarker is elevated in both STEMI and NSTEMI?
What is the immediate initial management treatment for presumed ACS?
What is the recommended time frame for performing PCI in STEMI patients?
Which drug should be avoided in the management of cocaine-associated ACS?
What is the primary goal of thrombolytic therapy in STEMI?
What is a common risk factor for developing ACS?
According to the text, which day of admission is associated with higher mortality and lower utilisation of invasive procedures?
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