Acute Coronary Syndrome

Acute coronary syndrome and thrombosis

Acute coronary syndrome (ACS) occurs when an atherosclerotic plaque ruptures, leading to thrombus formation within a coronary artery.⁵ Patients who develop symptoms consistent with ACS, such as chest pain and diaphoresis, require timely evaluation to determine the cause.^{9, 83} When ACS is diagnosed, further stratification into categories of ST-elevation myocardial infarction (STEMI), non-ST-elevation myocardial infarction (NSTEMI), and unstable angina guides therapeutic decision-making. Following recovery from an episode of ACS, patients continue to be at heightened risk of heart attack and stroke, for which a range of secondary preventive treatments are available.^{84, 85}

Three types of risk in ACS

There are three types of risk to consider in ACS.^{9, 83, 84}

• Physicians in the emergency care setting must assess the potential for acute, life-threatening disease when diagnosing the cause of chest pain or other symptoms that might indicate ACS
  
• After ACS is recognised, diagnostic acumen is required to stratify the patient as having either unstable angina, non-ST-elevation myocardial infarction (NSTEMI), or ST-elevation myocardial infarction (STEMI)
• Patients who survive an episode of ACS are at heightened risk of recurrent ACS and stroke

ECG showing NSTEMI

Risk assessment in ACS

Risk assessment is a key step in the emergency management of patients with ACS. Stratifying patients by likelihood of morbidity and mortality guides management decisions. A range of risk-scoring systems have been devised to enable clinicians to select the appropriate antithrombotic or fibrinolytic therapy.⁸⁶

Patients with complete occlusion of a coronary artery can often be identified by ST-segment elevation on electrocardiogram (ECG). This group, representing approximately one in three patients presenting with ACS, should receive prompt reperfusion treatment with fibrinolytic therapy or percutaneous coronary intervention (PCI). The remaining two thirds of ACS patients do not have ST-segment elevation on initial ECG and require further risk stratification.⁹

Serial evaluation of biomarkers, including troponin, C-reactive peptide, and B-type natriuretic peptide, provide independent, additive prognostic data to complement history and physical examination findings and ECG results.⁸⁶ These findings determine whether the problem is non-ST-elevation myocardial infarction (NSTEMI) or unstable angina; the urgency of treatment for these conditions varies depending on a patient’s specific clinical situation.

Coronary thrombosis, image 2 of 4

Long-term risks following ACS

The risk of cardiovascular death, recurrent myocardial infarction (MI), or progression to MI in patients initially presenting with unstable angina is greatest during the first two months after the acute event.⁸³ Subsequently, the clinical course of most patients with ACS is similar to that of patients with chronic stable coronary disease.

Because atherosclerotic plaque is often present throughout the arterial tree, patients who survive an episode of ACS live with an ongoing risk of a recurrent acute cardiovascular event, such as MI, sudden cardiac death, or stroke.⁸⁴ For patients who received a drug-eluting stent during revascularisation, there is an additional risk of late in-stent thrombosis.⁸⁷

A wide range of treatments are available to protect the heart and to decrease the propensity for recurrent atherothrombosis in survivors of ACS.⁸⁵