Acute Coronary Syndrome (ACS)

Written By Danial Mirza

Definition

Acute Coronary Syndrome (ACS) is a clinical term encompassing a spectrum of life-threatening conditions caused by a sudden, severe reduction in blood flow to the heart muscle (myocardium) (15). It represents the most urgent manifestation of coronary artery disease and is diagnosed based on a constellation of symptoms indicative of acute myocardial ischemia (1, 15). The classification and management in Malaysia are guided by the national Clinical Practice Guidelines (CPGs) for ST-Elevation Myocardial Infarction (STEMI) and Non-ST-Elevation ACS (NSTE-ACS) (2).

Epidemiology

Coronary artery disease is the leading cause of death in Malaysia, making ACS a significant national health burden (9, 15). The National Cardiovascular Disease (NCVD) registry reports an approximate ACS incidence of 141 per 100,000 population per year (12). A uniquely challenging aspect in Malaysia is the young age of onset; the mean age for ACS presentation is 58.5 years, which is substantially younger than in Western countries (10, 15). Alarmingly, 25.6% of all ACS patients are under 50, with this figure rising to 31.4% for those with the most severe form, STEMI (10). This premature onset in the nation's most productive individuals poses a profound socioeconomic challenge (10, 16).

The disease shows a strong male predominance (4:1 ratio) (12). There are also notable ethnic variations, with individuals of Indian ethnicity being consistently over-represented in ACS cohorts relative to the general population, indicating a higher per-capita risk (10). The majority of patients (94.2%) have at least one major cardiovascular risk factor, with hypertension (62.1%), diabetes mellitus (44.6%), dyslipidemia (40.6%), and current smoking (37.0%) being the most prevalent (10).

Pathophysiology

The underlying cause of nearly all ACS events is the disruption of an atherosclerotic plaque within a coronary artery (4, 15). This process involves a chronic, inflammatory buildup of lipids and fibrous tissue in the artery wall (15). When a "vulnerable" plaque ruptures or erodes, it exposes its highly thrombogenic core to the blood, triggering an aggressive clotting cascade (15). This leads to the formation of an intracoronary thrombus that obstructs blood flow (4, 15). The clinical presentation—ranging from unstable angina to a full-thickness myocardial infarction—is a direct consequence of the size of this thrombus and the duration of the resulting ischemia (4, 15).

Classification

The initial 12-lead ECG is the critical tool for classification, which dictates the immediate management pathway (13).

  • ST-Elevation Myocardial Infarction (STEMI): This is the most urgent form of ACS, characterized by symptoms of myocardial ischemia combined with persistent ST-segment elevation on the ECG (2). It typically signifies a complete and persistent thrombotic occlusion of a coronary artery, causing transmural ischemia (2, 15). Without immediate reperfusion, this leads to irreversible necrosis of the heart muscle, confirmed by a subsequent rise in cardiac biomarkers like troponin (2, 15). The guiding principle is "time is muscle," and the goal is immediate reperfusion (2).

  • Non-ST-Elevation Acute Coronary Syndrome (NSTE-ACS): This is a broader category that includes Unstable Angina (UA) and Non-ST-Elevation Myocardial Infarction (NSTEMI) (3). NSTE-ACS is the more common presentation in Malaysia (15).

    • Unstable Angina (UA): Patients present with ischemic symptoms, but crucially, there is no elevation in cardiac biomarkers (4). This indicates that the ischemia was not severe or prolonged enough to cause detectable cardiomyocyte death (4).

    • NSTEMI: The clinical presentation is similar to UA, but it is defined by the presence of elevated cardiac biomarkers (troponin), confirming that myocardial necrosis has occurred (4). This is usually caused by a partially occlusive thrombus or a transient complete occlusion (4).

Clinical Presentation

The classic presentation of ACS is retrosternal chest pain, often described as a pressure, tightness, or heaviness, which may radiate to the jaw, neck, or left arm (15).

  • Diagnostic Clues: The Killip classification is a simple, powerful tool used at the bedside to assess for signs of acute heart failure, which strongly predicts mortality (15).

  • Common Symptoms (>50%):

    • Retrosternal chest pain or discomfort

    • Shortness of breath (dyspnea) (15)

    • Sweating (diaphoresis) (15)

    • Nausea (15)

  • Less Common Symptoms (10-50%):

    • Atypical presentations are more common in women, the elderly, and patients with diabetes (15). These can include isolated epigastric pain, indigestion, or unexplained fatigue (15).

  • ⚠️ Red Flag Signs & Symptoms:

    • Severe, persistent chest pain unresponsive to nitrates.

    • Signs of acute heart failure (Killip Class II-IV): This includes lung crackles, an S3 gallop, elevated jugular venous pressure, or frank pulmonary edema (15).

    • Cardiogenic shock (Killip Class IV): Defined by hypotension (systolic BP <90 mmHg) with evidence of end-organ hypoperfusion (e.g., cool peripheries, altered mental state, low urine output) (15). This is the most feared complication, occurring in about 10.6% of STEMI cases in Malaysia, with extremely high mortality (15, 22).

    • Life-threatening arrhythmias (e.g., Ventricular Tachycardia, Ventricular Fibrillation) (15).

Complications

  • Acute (in-hospital):

    • Arrhythmias: Life-threatening ventricular arrhythmias (VT/VF) are a major risk in the first 48 hours (15). Bradyarrhythmias and AV block are also common, particularly in inferior STEMI (15).

    • Heart Failure & Cardiogenic Shock: Acute left ventricular dysfunction is the strongest predictor of mortality (15).

    • Mechanical Complications: Though rare, these are often fatal and include rupture of the ventricular free wall, interventricular septum, or a papillary muscle (15).

    • Right Ventricular (RV) Infarction: This complicates up to 50% of inferior STEMIs and carries a high risk of hypotension and death (2).

  • Long-term:

    • Recurrent myocardial infarction

    • Chronic heart failure

    • Stroke

    • Increased risk of all-cause mortality

Prognosis

Overall in-hospital mortality for ACS in Malaysia was 7.7% during the 2020-2021 period, with one-year all-cause mortality at 18.9% (10). A critical finding from the NCVD registry is the "NSTEMI prognostic paradox": while STEMI patients have higher acute mortality, NSTEMI patients exhibit poorer outcomes at one year (10, 15). This is likely due to the NSTEMI cohort being older with more comorbidities, and suggests a potential "complacency gap" in their long-term management after the less dramatic initial event (15).

Differential Diagnosis

  • Aortic Dissection: This is a key differential due to the shared feature of severe chest pain. However, the pain is often described as tearing or ripping, may radiate to the back, and can be associated with unequal blood pressures in the arms or neurological deficits, features less common in ACS. A widened mediastinum on chest X-ray and definitive imaging (CT aortogram) are distinguishing.

  • Pulmonary Embolism: Consider this especially if the patient presents with pleuritic chest pain, dyspnea, and hypoxia. The presence of risk factors for venous thromboembolism (e.g., recent surgery, immobility, malignancy) and specific ECG changes (like S1Q3T3) may point towards this diagnosis, which is confirmed with a CT pulmonary angiogram.

  • Pericarditis: This can also present with sharp, central chest pain. However, the pain is typically pleuritic (worse on inspiration) and relieved by sitting forward. The ECG classically shows widespread concave ST elevation and PR depression, which differs from the localized, convex ST elevation of STEMI.

Investigations

Immediate & Bedside Tests

  • 12-Lead ECG: This is the single most important immediate test, mandatory within 10 minutes of first medical contact (2, 15). Its purpose is to rapidly stratify the patient into STEMI or NSTE-ACS pathways (the action), as this distinction dictates the entire subsequent management strategy, particularly the need for emergency reperfusion (the rationale) (15).

Diagnostic Workup

  • First-Line Investigations:

    • High-Sensitivity Cardiac Troponin (hs-cTn): The initial test of choice for suspected ACS without ST elevation. It is highly sensitive for detecting myocardial necrosis (the rationale) and is essential to differentiate NSTEMI from unstable angina, confirming the need for anti-thrombotic therapy and risk stratification (the action) (3, 15). The Malaysian CPGs advocate for rapid 0- and 1-hour or 0- and 2-hour rule-in/rule-out algorithms (3).

  • Gold Standard:

    • Invasive Coronary Angiography: This is the definitive gold standard test as it directly visualizes the coronary arteries, identifying the precise location and severity of the culprit lesion (the rationale) (15). This leaves no room for diagnostic doubt and directly guides revascularization with PCI or bypass surgery (the action) (15).

  • Monitoring & Staging:

    • Transthoracic Echocardiography: This is performed to identify regional wall motion abnormalities that support the diagnosis (the action) and, crucially, to assess overall left ventricular ejection fraction, a powerful determinant of prognosis (the rationale) (5, 15).

Management

Management Principles

The management of ACS focuses on rapid diagnosis, immediate risk stratification, restoration of coronary blood flow, prevention of recurrent thrombosis, and long-term secondary prevention (15).

Acute Stabilisation (The First Hour)

  • Airway/Breathing: Administer high-flow oxygen via a non-rebreather mask only if oxygen saturation is <95% (the action), which is crucial to prevent exacerbating myocardial injury in non-hypoxic patients while correcting tissue hypoxia when present (the rationale) (2).

  • Circulation: Secure two large-bore IV cannulas and administer a loading dose of Aspirin 300 mg (soluble or chewable) to rapidly inhibit platelet aggregation (the action), which is critical for preventing thrombus propagation (the rationale) (2).

  • Disability/Exposure:

    • Administer intravenous opioids (e.g., Morphine 2.5-5 mg IV, titrated) to alleviate severe chest pain and reduce sympathetic drive (the action), which decreases myocardial oxygen demand (the rationale) (2).

    • Administer a loading dose of a P2Y12 inhibitor (e.g., Ticagrelor 180 mg or Clopidogrel 300-600 mg) in addition to aspirin to provide more potent and comprehensive platelet inhibition (the action), further reducing the risk of coronary artery re-occlusion (the rationale) (2).

Definitive Therapy

For STEMI:

The goal is immediate reperfusion. The choice is dictated by geography and logistics (15).

  • First-Line (Preferred): Primary Percutaneous Coronary Intervention (PCI): This is the gold standard if it can be performed within 120 minutes of first medical contact (2, 15). It involves immediate angiography and stenting of the blocked artery, leading to superior outcomes (2, 15).

  • Alternative: Fibrinolytic Therapy: This is a crucial life-saving therapy when timely PCI is unavailable (2, 15). It involves administering a "clot-busting" drug (e.g., Tenecteplase, given as a weight-adjusted IV bolus) to dissolve the thrombus (2). The target door-to-needle time is less than 30 minutes (2).

  • Pharmaco-invasive Strategy: A hybrid approach for non-PCI capable hospitals. It involves immediate fibrinolysis followed by urgent transfer to a PCI-capable "hub" for angiography within 3-24 hours (15). This strategy provides the benefit of early chemical reperfusion while ensuring definitive invasive management (15).

For NSTE-ACS:

Management is guided by risk stratification using tools like the GRACE score (3, 15).

  • Very High/High-Risk Patients: (e.g., refractory pain, hemodynamic instability, dynamic ECG changes, GRACE score >140). An early invasive strategy is mandated (3). Angiography should be performed immediately (<2 hours for very high risk) or within 24 hours (for high risk) (3).

  • Low/Intermediate-Risk Patients: May be managed with an initial conservative strategy, with angiography performed within 72 hours for intermediate-risk patients (3). Medical therapy is optimized, and non-invasive stress testing may be used to guide the need for later angiography (4).

  • Medical Therapy: All patients receive Dual Antiplatelet Therapy (DAPT) and anticoagulation (e.g., with Fondaparinux or Enoxaparin) (3).

Supportive & Symptomatic Care

  • High-intensity statin: (e.g., Atorvastatin 80 mg) should be started early.

  • Beta-blockers: (e.g., Metoprolol) should be initiated within 24 hours if no contraindications exist.

  • ACE inhibitors or ARBs: Should be started, especially in patients with LV dysfunction, heart failure, or diabetes.

Key Nursing & Monitoring Instructions

  • Strict hourly input/output chart monitoring to assess fluid status and renal perfusion.

  • Continuous cardiac monitoring for the first 24-48 hours to detect arrhythmias.

  • Regular neurological observations, especially post-fibrinolysis, to screen for intracranial hemorrhage.

  • Inform medical staff if systolic BP drops below 90 mmHg, urine output is <0.5mL/kg/hr, or if the patient develops new or worsening chest pain.

Long-Term Plan & Patient Education

Discharge planning starts on admission. The focus is on lifelong secondary prevention (15).

  • Medications: Ensure patient understands the importance of adherence to DAPT (typically for 12 months), statins, beta-blockers, and ACE inhibitors (4, 15).

  • Lifestyle: Provide aggressive counseling on smoking cessation, a heart-healthy diet, regular physical activity, and weight management (15).

  • Cardiac Rehabilitation: Strongly recommend and refer the patient to a structured cardiac rehabilitation program to improve functional capacity and reduce mortality (15, 26).

When to Escalate

Call Your Senior (MO/Specialist) if:

  • The patient's diagnosis is unclear, or they present with atypical features.

  • The patient develops any Red Flag signs: hemodynamic instability, signs of cardiogenic shock, acute heart failure, or life-threatening arrhythmias (3).

  • There is a failure of reperfusion after fibrinolysis (e.g., persistent chest pain and minimal ST-segment resolution).

  • The patient develops complications from therapy (e.g., major bleeding, neurological changes).

Referral Criteria:

  • Immediate discussion with the on-call Cardiologist: For all patients with STEMI to decide on the reperfusion strategy (PCI vs. Fibrinolysis vs. Pharmaco-invasive).

  • Referral to the Cardiology team: For all patients with confirmed NSTE-ACS for risk stratification and to determine the timing of angiography.

  • Referral to Cardiothoracic Surgery: For patients with complex multi-vessel disease, mechanical complications, or failed PCI.

References

  1. Acute Coronary Syndromes w/out Persistent ST-Segment Elevation: Disease Summary | MIMS Malaysia. (n.d.). Retrieved July 7, 2025, from https://www.mims.com/malaysia/disease/acute-coronary-syndromes-w-out-persistent-st-segment-elevation/disease-summary

  2. Ministry of Health Malaysia. (2019). Clinical Practice Guidelines: Management of Acute ST-Elevation Myocardial Infarction (4th Edition). Putrajaya: MOH. Retrieved from https://www.moh.gov.my/moh/resources/penerbitan/CPG/CPG%20STEMI%202019.pdf

  3. Ministry of Health Malaysia. (2021). Clinical Practice Guidelines: Management of Non-ST Elevation Acute Coronary Syndrome (3rd Edition). Putrajaya: MOH. Retrieved from https://www.moh.gov.my/moh/resources/Penerbitan/CPG/CARDIOVASCULAR/CPG%20Management%20of%20NSTE-ACS%203rd%20Edition%202021.pdf

  4. Ministry of Health Malaysia. (2011). Management of Unstable Angina / Non-ST Elevation Myocardial Infarction. Putrajaya: MOH. Retrieved from https://www.moh.gov.my/moh/resources/Penerbitan/CPG/CARDIOVASCULAR/12.pdf

  5. Byrne, R. A., Rossello, X., Coughlan, J. J., Barbato, E., Berry, C., Chieffo, A., ... & ESC Scientific Document Group. (2023). 2023 ESC Guidelines for the management of acute coronary syndromes. European Heart Journal, 44(38), 3720-3826. https://doi.org/10.1093/eurheartj/ehad191

  6. Management of Acute ST Segment Elevation Myocardial Infarction (STEMI) 2019. (2019). National Heart Association of Malaysia. Retrieved from https://www.malaysianheart.org/publication/clinical-practice-guidelines/p/management-of-acute-st-segment-elevation-myocardial-infarction-stemi-2019

  7. Management of Non-ST Elevation Myocardial Infarction (NSTE-ACS). (2021). National Heart Association of Malaysia. Retrieved from https://www.malaysianheart.org/publication/clinical-practice-guidelines/p/management-of-non-st-elevation-myocardial-infarction-nste-acs

  8. Management of Acute ST-Elevation Myocardial Infarction [Malaysia Clinical Practice Guideline (MCPG)] 4th Edition. (2019). ResearchGate. Retrieved from https://www.researchgate.net/publication/335675881_Management_of_Acute_ST-Elevation_Myocardial_Infarction_Malaysia_Clinical_Practice_Guideline_MCPG_4th_Edition

  9. A Review of Coronary Artery Disease Research in Malaysia. (2016). The Medical Journal of Malaysia, 71(Suppl 1), 50-55. Retrieved from https://www.e-mjm.org/2016/v71s1/coronary-artery-disease-research.pdf

  10. National Heart Association of Malaysia. (2022). Annual Report of the NCVD-ACS Registry 2020-2021. Kuala Lumpur: NHAM. Retrieved from http://www.acrm.org.my/ncvd/documents/report/ACS%20Report%202020-2021%20Final.pdf

  11. NCVD Annual Reports. (n.d.). National Heart Association of Malaysia. Retrieved July 7, 2025, from https://www.malaysianheart.org/publication/ncvd-annual-reports

  12. Wan Azman, W. A., et al. (2012). Malaysian National Cardiovascular Disease Database (NCVD)--Acute Coronary Syndrome (ACS) registry: how are we different?. Medical Journal of Malaysia, 67(4), 369-374.

  13. Malaysia-ACute CORonary syndromes Descriptive study (ACCORD): evaluation of compliance with existing guidelines in patients with acute coronary syndrome. (2011). PubMed. Retrieved from https://pubmed.ncbi.nlm.nih.gov/21808962/

  14. Abidin, I. Z., et al. (2023). The prevalence of young ST-elevation myocardial infarction, the risk factors, and the pattern of coronary artery involvement in the Serdang PPCI Registry over 7 years. European Heart Journal, 44(Supplement_2), ehad655.1506. https://doi.org/10.1093/eurheartj/ehad655.1506

  15. This article synthesizes information from the provided document "Coronary Artery Syndrome Malaysia.pdf", which contains consolidated data from various Malaysian CPGs, NCVD reports, and research papers.

  16. Ramli, A. N. M., et al. (2016). Acute coronary syndrome in young adults from a Malaysian tertiary care centre. Singapore Medical Journal, 57(9), 513–517. https://doi.org/10.11622/smedj.2016029

  17. National Cardiovascular Disease Database. (n.d.). Association for Clinical Research Malaysia. Retrieved July 7, 2025, from https://www.acrm.org.my/ncvd/reports_annual%20Reports.php

  18. Annual Report of the NCVD-PCI Registry Year 2019-2020. (2021). National Heart Association of Malaysia. Retrieved from https://www.malaysianheart.org/news-updates/highlights/p/annual-report-of-the-ncvd-pci-registry-year-2019-2020

  19. Annual Report of the NCVD-ACS Registry Year 2020-2021. (2022). National Heart Association of Malaysia. Retrieved from https://www.malaysianheart.org/publication/ncvd-annual-reports/p/annual-report-of-the-ncvd-acs-registry-year-2020-2021

  20. Highlights of the first Malaysian National Cardiovascular Disease Database (NCVD): Percutaneous Coronary Intervention (PCI) Registry. (2012). ResearchGate. Retrieved from https://www.researchgate.net/publication/229110224_Highlights_of_the_first_Malaysian_National_Cardiovascular_Disease_Database_NCVD_Percutaneous_Coronary_Intervention_PCI_Registry

  21. The Foundation of NCVD PCI Registry: The Malaysia's First Multi-Centre Interventional Cardiology Project. (n.d.). Association for Clinical Research Malaysia. Retrieved July 7, 2025, from http://www.acrm.org.my/ncvd/documents/article/pciRegistry%20article.pdf

  22. Yeoh, K. C., et al. (2019). In-hospital mortality of cardiogenic shock complicating ST-elevation myocardial infarction in Malaysia: a retrospective analysis of the Malaysian National Cardiovascular Database (NCVD) registry. BMJ Open, 9(5), e025734. https://doi.org/10.1136/bmjopen-2018-025734

  23. Strengthening acute coronary syndrome referral network: Insights from initiatives of Penang General Hospital cardiology centre. (2019). Medical Journal of Malaysia, 74(4), 343-348. Retrieved from https://www.e-mjm.org/2019/v74n4/acute-coronary-syndrome.pdf

  24. Primary percutaneous coronary intervention services in Ministry of Health hospitals. (2015). Ministry of Health Malaysia. Retrieved from https://www.moh.gov.my/index.php/database_stores/attach_download/347/310

  25. MySTEMI Foundation. (n.d.). MySTEMI Network. Retrieved July 7, 2025, from https://www.mystemifoundation.org.my/mystemi-network

  26. Sivaraman, S., et al. (2022). Quality of life among Patients with Acute Coronary Syndrome in Malaysia. Value in Health Regional Issues, 30, 1-7. https://doi.org/10.1016/j.vhri.2022.04.002

Danial Mirza
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