Acute Coronary Syndrome (ACS)

• Acute coronary syndrome (ACS) includes STEMI, NSTEMI, and unstable angina pectoris (UAP)
• Differential diagnosis depends on biomarkers detectable only after several hours
• Treatment is dependent on clinical signs at presentation

ECG Characteristics

• Absence or presence of ST elevation differentiates STEMI from NSTEMI-ACS
• NSTEMI-ACS may show ST segment depression, nonspecific wave abnormalities, or normal ECG
• Increase in cardiac biomarkers (Troponin T or I) indicates NSTEMI if there is no ST elevation
• If troponin remains negative without ST elevation, it is UAP

ACS Causes and Therapeutic Goals

• ACS often leads to malignant arrhythmias and sudden cardiac death
• Treatment goals include treating life-threatening conditions, preserving left ventricular function, and preventing heart failure by minimizing myocardial damage

Signs and Symptoms

• Chest pain often radiates to other areas of the upper body
• Dyspnea, sweating, nausea, vomiting, and syncope also often occur
• Atypical symptoms are more common in the elderly, females, and diabetics
• Signs and symptoms of ACS cannot be used alone for diagnosis

Investigations

• Key investigation is a 12-lead ECG to assess ACS; Prehospital ECG helps in treatment decisions
• In STEMI cases, immediate reperfusion therapy is needed, either Percutaneous coronary intervention (PCI) or Prehospital fibrinolysis
• Biomarkers such as troponin T and I characterize non-STEMI and distinguish it from STEMI and unstable angina in the absence of ST Elevation on ECG

Early Discharge and Chest Pain Protocols

• Decision rules for early discharge that include history, clinical examinations, biomarkers, ECG criteria, and risk scores are unreliable
• Chest pain (observation) units for patients presenting to the ED with a history suggestive of ACS, but normal initial workup may be a safe and effective strategy for evaluating patients
• Chest pain observation units (CPUs) identify those patients who require admission for invasive procedures using examiniations, an ECG, and biomarker testing

Treatment and Symptoms of ACS

• Glyceryl trinitrate treats ischaemic chest pain and has beneficial haemodynamic effects, such as dilation of the venous capacitance vessels, dilation of the coronary arteries
• Glyceryl trinitrate should only be adminsitered if the SBP is > 90mmHg & patient has ongoing ischaemic chest pain or useful in the treatment of acute pulmonary congestion.
• Nitrates should not be used in patients with hypotension (SBP ≤90mmHg) specifically with Bradycardia, Inferior infarction & RV involvement
• Morphine (initial doses: 3-5mg IV) is an analgesic of choice for nitrate-refractory pain, also calming effects
• Morphine is dilator of venous vessels, benefit in patients with pulmonary congestion; avoid NSAIDs for analgesia because of their pro-thrombotic effects
• Monitor arterial oxygen saturation (SaO2) with pulse oximetry to determine oxygen need; administer only if hypoxaemic
• Aim for oxygen saturation of 94-98%, or 88-92% if at risk of hypercapnic respiratory failure

Antiplatelet Treatment

• Inhibition of platelet aggregation is of primary importance for initial ACS treatment and secondary prevention
• ASA should be given as soon as possible to all those suspected of having ACS because it decreases mortality; initial dose is 160-325 mg
• ADP receptor inhibitors include thienopyridines (clopidogrel, prasugrel) and ticagrelor, which irreversibly inhibit the ADP receptor
• Clopidogrel should be given early to non-STEMI-ACS patients along with ASA and an antithrombin
• When a conservative approach is selected loading dose of clopidogrel should be 300 mg; If a planned PCI approach initial dose of 600mg
• STEMI patients with fibrinolysis should be treated with clopidogrel, 300mg loading dose if >75 years of age, in addition to ASA + an antithrombin
• Glycoprotein (Gp) IIB/IIIA inhibitors ends in reversible inhibition of the Gp IIB/IIIA; lack data to support in STEMI or non-STEMI-ACS
• Unfractionated heparin (UFH) is an indirect thrombin inhibitor used with ASA as adjunct with fibrinolytic therapy or primary PCI (PPCI) and for unstable angina & STEMI
• Enoxaparin and fondaparinux are alternative antithrombins
• Enoxaparin reduces mortality, myocardial infarction, and need for urgent revascularisation if given within 24-36 h of non-STEMI-ACS onset versus UFH
• Fondaparinux & enoxaparin are reasonable alternatives to UFH for patients undergoing conservative management
• Fondaparinux or bivalirudin are preferred with increased bleeding risk because they cause less bleeding, or with planned invasive approach

Strategies and Systems of Care

• Systematic strategies improve out-of-hospital care for ACS patients
• Strategies intended to identify STEMI patients and shorten reperfusion treatment delay
• Specific decisions during the initial care relate to reperfusion strategy and bypassing non-PCI hospitals

Reperfusion Strategy in STEMI

• Reperfusion must be initiated ASAP for patients presenting with STEMI within 12 hours of symptom onset
• Fibrinolysis is most effective in the first 2-3 hours after symptom onset and is beneficial if fibrinolytics are administered out-of-hospital
• Primary PCI (coronary angioplasty) is the preferential treatment for STEMI
• Combinations of Fibrinolysis and PCI include facilitated PCI, pharmaco-invasive strategy refers to PCI performed routinely 3-24 hours after fibrinolysis, and rescue PCI which is defined as PCI performed for a failed reperfusion
• Pharmaco-invasive' strategy includes early transfer for angiography and PCI if necessary after fibrinolytic treatment
• Fibrinolysis is preferred immediately if there is inappropriate delay to PCI or with No contraindication
• PCI is preferred if it is timely and available, or there is a contraindication for fibrinolysis or cardiogenic shock

Triage and Transfer for PCI

• Death, reinfarction, or stroke risk is reduced if STEMI patients are transferred to tertiary care facilities for PPCI

Reperfusion after CPR

• CHD is the most frequent cause of out-of hospital cardiac arrest
• In patients with STEMI or new LBBB, perform immediate angiography and PCI or fibrinolysis
• It is reasonable to perform immediate angiography and PCI in selected patients despite the lack of ST elevation on the ECG or prior clinical findings

Primary and Secondary Prevention

• Preventive interventions in patients presenting with ACS should be initiated
• Preventive measures improve prognosis by reducing the number of major adverse events
• Prevention includes beta-blockers, ACE inhibitors/angiotensin receptor blockers, statins, ASA, and thienopyridines (if indicated)