Acute Coronary Syndrome

Acute Coronary Syndrome (ACS) represents a spectrum of clinical conditions associated with acute myocardial ischemia and/or infarction due to abrupt reduction in coronary blood flow. It is a major cause of morbidity and mortality worldwide and requires rapid diagnosis and intervention. ACS encompasses three primary entities: unstable angina (UA), non-ST-elevation myocardial infarction (NSTEMI), and ST-elevation myocardial infarction (STEMI). Each presents with distinct clinical, electrocardiographic, and laboratory features, yet shares a common underlying pathophysiological mechanism—plaque disruption and subsequent thrombosis in coronary arteries.

Pathophysiology

The heart receives its oxygen supply via the coronary arteries. The pathogenesis of ACS typically begins with atherosclerotic plaque formation within these vessels. Over time, plaques may become unstable and rupture, exposing subendothelial elements and promoting platelet aggregation and thrombus formation. This thrombus may partially or completely occlude the vessel, leading to myocardial ischemia and, if not reversed promptly, infarction.

Atherosclerosis and Plaque Instability

Atherosclerosis is a chronic inflammatory process involving the deposition of lipids and fibrous elements in the arterial wall. Risk factors such as hypertension, hyperlipidemia, diabetes mellitus, smoking, and family history accelerate plaque formation. The most dangerous plaques are those with a lipid-rich core and a thin fibrous cap, as these are more prone to rupture.

Thrombus Formation

When a plaque ruptures, the body’s coagulation cascade is triggered. Platelets adhere to the exposed collagen and release pro-inflammatory mediators, leading to further platelet recruitment and activation of clotting factors. The resulting thrombus may cause complete or partial obstruction, resulting in varying degrees of myocardial damage.

Clinical Presentation

Patients with ACS typically present with chest pain or discomfort, often described as pressure, tightness, or heaviness. The pain may radiate to the arms, neck, jaw, or back and is usually associated with diaphoresis, nausea, dyspnea, and palpitations. However, atypical presentations are common, especially in elderly, female, and diabetic patients, who may experience minimal or no chest pain.

Unstable Angina

Unstable angina is characterized by chest pain at rest or with minimal exertion, or by new-onset severe angina. Unlike myocardial infarction, unstable angina does not cause detectable elevations in cardiac biomarkers.

NSTEMI

Non-ST-elevation myocardial infarction presents similarly to unstable angina but is distinguished by a rise in cardiac biomarkers (troponin, CK-MB) indicating myocardial necrosis. Electrocardiogram (ECG) findings may show ST-segment depression or T-wave inversions.

STEMI

ST-elevation myocardial infarction is defined by persistent chest pain and characteristic ECG changes: ST-segment elevation in contiguous leads. Biomarkers are also elevated. STEMI is associated with complete coronary occlusion and typically results in transmural (full-thickness) infarction.

Diagnosis

The diagnosis of ACS relies on a combination of clinical assessment, ECG, and measurement of cardiac biomarkers.

• Electrocardiogram (ECG): This is the first-line diagnostic tool. STEMI is confirmed by ST-segment elevations, while NSTEMI and UA may show ST-segment depressions, T-wave inversions, or be non-specific.
• Cardiac Biomarkers: Troponin I and T are highly sensitive and specific for myocardial injury. Creatine kinase-MB (CK-MB) is less specific but may be useful for detecting reinfarction.
• Imaging: Echocardiography, coronary angiography, and cardiac MRI may be used to assess ventricular function and visualize coronary anatomy.

Risk Stratification

Early risk assessment guides management decisions in ACS. Tools like the TIMI (Thrombolysis In Myocardial Infarction) and GRACE (Global Registry of Acute Coronary Events) scores estimate short-term mortality risk and assist in identifying patients who would benefit from aggressive interventions.

Management

The management of ACS revolves around restoring coronary blood flow, preventing further clot formation, and minimizing myocardial damage.

Initial Treatment

Upon presentation, patients should receive:

• Oxygen therapy: If hypoxic.
• Aspirin: To inhibit platelet aggregation.
• Nitroglycerin: To relieve chest pain and reduce cardiac preload.
• Morphine: For refractory pain (use with caution).
• Beta-blockers: Unless contraindicated, to reduce myocardial oxygen demand.
• Statins: To stabilize plaques and reduce cholesterol.

Antithrombotic Therapy

Antiplatelet agents (such as clopidogrel, prasugrel, or ticagrelor) and anticoagulants (like heparin or enoxaparin) are administered to reduce further thrombus formation.

Reperfusion Strategies

For STEMI, prompt reperfusion is essential:

• Primary Percutaneous Coronary Intervention (PCI): The preferred method, ideally within 90 minutes of first medical contact.
• Thrombolytic therapy: Used when PCI is unavailable within the recommended time window.

For NSTEMI and unstable angina, early invasive strategies may be considered for high-risk patients, while others may be managed conservatively.

Long-Term Management

Following stabilization, secondary prevention strategies are critical:

• Lifestyle modification: Smoking cessation, dietary changes, regular exercise, weight management.
• Pharmacotherapy: Continued use of antiplatelet agents, beta-blockers, ACE inhibitors, and statins.
• Cardiac rehabilitation: Supervised exercise and education program to improve outcomes.

Complications

ACS can lead to a variety of complications, both acute and chronic:

• Arrhythmias: Ventricular fibrillation, tachycardia, or bradyarrhythmias.
• Heart failure: Due to extensive myocardial damage.
• Cardiogenic shock: Severe impairment of cardiac output.
• Mechanical complications: Papillary muscle rupture, ventricular septal defect, free wall rupture.
• Recurrent ischemia: Further episodes of angina or infarction.

Prognosis

The prognosis of ACS depends on the extent of myocardial injury, adherence to therapy, and presence of comorbidities. Early intervention and optimal medical therapy have significantly improved survival rates. However, the risk of recurrent events remains substantial, emphasizing the need for ongoing preventive measures and patient education.

Prevention

Primary prevention involves addressing modifiable risk factors:

• Control of hypertension, diabetes, and hyperlipidemia
• Smoking cessation
• Healthy diet rich in fruits, vegetables, and whole grains
• Regular physical activity
• Maintenance of a healthy body weight

For secondary prevention, patients who have experienced ACS should adhere meticulously to medical therapy and lifestyle interventions.

Nursing Care of Patients with Acute Coronary Syndrome

Administering Emergency Interventions

• Oxygen Therapy: Administer supplemental oxygen as prescribed, especially if saturation is below 94%.
• Medication Administration: Give prescribed medications such as aspirin, nitroglycerin, morphine (for pain), antiplatelets, anticoagulants, beta-blockers, and statins following the doctor’s orders.
• IV Access: Establish and maintain intravenous access for medication and fluid administration.
• Pre-procedure Preparation: Prepare the patient for diagnostic procedures like ECG, cardiac enzymes evaluation, or coronary angiography as needed.

Ongoing Monitoring and Prevention of Complications

• Haemodynamic Stability: Watch for signs of shock, hypotension, or heart failure; report immediately to the medical team.
• Arrhythmia Surveillance: Be vigilant for arrhythmias such as ventricular tachycardia or fibrillation; keep resuscitation equipment ready.
• Monitor for Bleeding: Especially if the patient is on thrombolytics or anticoagulants, observe for signs of bleeding at puncture sites, in urine, stool, or gums.
• Fluid Balance: Maintain accurate intake and output records to prevent fluid overload or dehydration.

Patient Comfort and Support

• Pain Relief: Administer pain medications as per protocol, and provide a calm, reassuring environment to reduce anxiety.
• Positioning: Keep the patient in a semi-Fowler’s position to enhance comfort and facilitate breathing.
• Rest and Activity: Encourage bed rest during the acute phase, gradually increasing activity as tolerated and as per medical advice.
• Psychological Support: Offer emotional support, address fears, and involve family members in care and decision-making.

Education and Discharge Planning

• Medication Education: Teach the patient about the purpose, dosage, and possible side effects of prescribed medications.
• Lifestyle Modification: Advise on dietary changes, smoking cessation, regular exercise, weight management, and controlling risk factors like hypertension and diabetes.
• Warning Signs: Educate the patient and family on recognising symptoms of recurrent angina or complications and the importance of seeking immediate medical help.
• Follow-up Care: Ensure appointments for cardiac rehabilitation and follow-up with cardiologists are scheduled and understood.

Documentation

• Document all assessments, interventions, patient responses, and communication with the healthcare team accurately and promptly.

Cultural and Social Considerations in the Indian Context

• Respect patient beliefs and preferences regarding food, rest, and family involvement.
• Address language barriers and use interpreters if necessary to ensure effective communication.
• Involve family members in education and discharge planning, as family support is crucial in Indian society.

REFERENCES

1. American Heart Association. Acute Coronary Syndrome. https://www.heart.org/en/health-topics/heart-attack/about-heart-attacks/acute-coronary-syndrome. .
2. American Heart Association. What is a Heart Attack?. https://www.heart.org/en/health-topics/heart-attack/about-heart-attacks
3. Costello BT, Younis GA. Acute Coronary Syndrome in Women: An Overview. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7328082/. Tex Heart Inst J. 2020;47(2):128-129.
4. Varghese T, et al. Non-ST elevation acute coronary syndrome in women and the elderly: Recent updates and stones still left unturned. F1000 Research. 2020; doi:10.12688/f1000research.16492.1.
5. Merck Manual (Professional Version). Overview of Acute Coronary Syndromes (ACS). https://www.merckmanuals.com/professional/cardiovascular-disorders/coronary-artery-disease/overview-of-acute-coronary-syndromes-acs.
6. Singh A, Museedi AS, Grossman SA. Acute Coronary Syndrome. https://www.ncbi.nlm.nih.gov/books/NBK459157/. 2021 Jul 19. In: StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing; 2022 Jan-.
7. Lloyd-Jones DM, et al. Life’s essential 8: Updating and enhancing the American Heart Association’s construct of cardiovascular health: A presidential advisory from the American Heart Association. Circulation. 2022; doi:10.1161/CIR.0000000000001078.
8. Smith JN, Negrelli JM, Manek MB, Hawes EM, Viera AJ. Diagnosis and management of acute coronary syndrome: an evidence-based update. https://pubmed.ncbi.nlm.nih.gov/25748771/. J Am Board Fam Med. 2015;28(2):283-293.
9. Bergmark BA, et al. Acute coronary syndromes. The Lancet. 2022; doi:10.1016/S0140-6736(21)02391-6.

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