Acute Coronary Syndrome: From Symptoms to Treatment

Acute Coronary Syndrome: From Symptoms to Treatment

Acute coronary syndrome (ACS) is a life-threatening cardiovascular emergency that occurs when the blood flow to the heart is suddenly blocked. This article will provide information on the characteristics, diagnosis, treatment, and management of ACS, focusing specifically on ST-segment elevation myocardial infarction (STEMI).

# Characteristics of Acute Coronary Syndrome

Unstable Angina:

• New-onset angina that occurs within 48 hours.

• Angina that occurs at rest.

• Increasing angina: chest pain that is more intense, lasts longer, or occurs more frequently than previous episodes.

Typical Angina Symptoms:

• Sudden onset.

• Location: pain behind the breastbone or radiating to the left side.

• Radiation: to the neck, left shoulder, arm, and 4th and 5th fingers.

• Quality: crushing, squeezing.

• Duration: several minutes to hours.

• Relief with rest and nitroglycerin is minimal.

Systolic Murmur:

• Pansystolic: myocardial infarction causing rupture of the papillary muscle of the mitral valve, leading to mitral regurgitation.

• Systolic + murmur: ventricular septal defect.

Killip Classification:

• Class I: No signs of heart failure.

• Class II: Mild to moderate heart failure signs (S3 gallop, rales < 1/2 lung, elevated jugular venous pressure).

• Class III: Pulmonary edema.

• Class IV: Cardiogenic shock.

# Diagnosis of Acute Coronary Syndrome

Diagnostic Criteria for ST-Segment Elevation Myocardial Infarction (STEMI) on ECG:

• ST elevation ? 1mm in at least 2 contiguous leads D2, D3, aVF, V1-V6, D1, aVL.

• Presence of left bundle branch block/ischemia.

• Presence of Q waves in at least 2 contiguous leads with width > 30ms and depth > 1mm or QS pattern; in V2, V3, only needs to be > 20ms wide.

Suspect Inferior Wall Myocardial Infarction, ECG:

• Add V3R, V4R (ST elevation ? 0.5mm for women or men > 40 years old).

Suspect Lateral Wall, ECG:

• Add V7-V9 (only need ? 0.5mm).

Repeat ECG:

• 90 minutes after fibrinolytic therapy.

• Immediately after percutaneous coronary intervention (PCI) in patients with ST elevation.

Localization of Coronary Artery Occlusion:

• Anterior wall: ST elevation in V1-V4 (anterior wall) or from V1-V6 (extensive wall).

• Inferior wall: elevation in DII, DIII, aVF.

• Lateral wall: DI, aVL, V5-V6.

Coronary Artery Occlusion is Considered Successful Reperfusion When:

• ST elevation decreases by at least 50% compared to before intervention or fibrinolytic therapy.

# Supporting Tests

Troponin:

• Changes within 1-4 hours after myocardial infarction.

• Peaks at 24-48 hours and remains elevated for 7-14 days.

• Difficult to detect re-infarction.

CK/CKMB:

• Rises 3-12 hours after infarction, peaks in 24 hours, and returns to normal after 48-72 hours.

• Can be used to monitor the effectiveness of intervention.

Echocardiography:

• Demonstrates regional wall motion abnormalities: hypokinesis, akinesis, dyskinesis, and aneurysm formation.

# Differential Diagnoses

• Acute Aortic Syndrome: severe chest pain radiating to the back, mismatch between clinical presentation and ECG and cardiac enzyme findings, blood pressure differences, pulse pressure difference between the two upper extremities, widened mediastinum on X-ray, ultrasound: shows aortic dissection, CT scan, etc.

• Pulmonary Embolism: chest pain, shortness of breath, hemoptysis, but no pulmonary edema, blood gas: reduced PaO2 and PaCO2, ECG: S1Q3, MSCT scan to confirm.

• Pericarditis: sharp, stabbing pain, pain worsens with positional changes, worsens while lying flat, ECG: ST elevation concordant in the anterior precordial leads without reciprocal changes.

• Acute Myocarditis: difficult to distinguish, previous signs of infection, ultrasound: reduced global contractility.

# Risk Stratification

TIMI (STEMI) Risk Score:

• > 75 years old: 3 points.

• 65-74 years old: 2 points.

• Diabetes, Hypertension, Angina: 1 point.

• Systolic blood pressure < 100 mmHg: 3 points.

• Heart rate > 100 bpm: 2 points.

• Killip Class II-IV: 2 points.

• Weight < 67kg: 1 point.

• Anterior wall myocardial infarction or left bundle branch block: 1 point.

• Time to coronary reperfusion > 4 hours: 1 point.

CADILLAC Risk Score:

• Assesses the risk of mortality during percutaneous coronary intervention (PCI).

• Less effective before intervention due to the use of left ventricular functional parameters.

• LVEF < 40%: 4 points.

• Killip 2/3: 3 points.

• Renal insufficiency (eGFR < 60): 3 points.

• Post-intervention TIMI flow 0-2: 2 points.

• > 65 years old: 2 points.

• Anemia (HCT < 0.39 male, < 0.36 female): 2 points.

• Triple vessel coronary artery disease: 2 points.

CRUSADE Risk Score:

• Assesses the risk of bleeding during the use of anticoagulants and antiplatelet agents after PCI.

• Gender, heart rate, blood pressure, creatinine, GFR, HCT, history of diabetes, peripheral artery disease.

# Timing of Angiography and PCI

Urgent (< 2 hours):

• Chest pain unresponsive to treatment.

• Severe heart failure, new or worsening wheezing or cough.

• Cardiogenic shock.

• Life-threatening arrhythmia (sustained ventricular tachycardia or ventricular fibrillation).

Early within 24 hours:

• Significant increase/decrease in troponin over time.

• ST/T wave changes.

• Diabetes.

• GFR < 60%; LVEF < 40%.

• Recent coronary reperfusion (6 months after PCI).

• History of previous myocardial infarction.

• GRACE > 140 but no high-risk features.

If GRACE 109/140, consider performing within 24/72 hours.

# Indications for Coronary Reperfusion

• All patients with new-onset ST elevation or left bundle branch block within 12 hours of symptom onset.

• Acute myocardial infarction presenting later than 12 hours but with ongoing signs of necrosis/ischemia, PCI is preferred.

• Consider reperfusion for stable patients presenting 12-24 hours after symptom onset.

• Patients presenting > 24 hours with stable symptoms are not routinely treated with reperfusion.

# Treatment of Acute Coronary Syndrome

Pain Relief:

• Morphine sulfate intravenous injection 2-5mg, repeat after 5-10 minutes, is the first-line treatment.

• Sublingual nitroglycerin 0.4mg. Be cautious of hypotension (avoid for 24 hours with sildenafil and 48 hours with tadalafil).

Thrombolysis:

• Prefer using fibrin-specific drugs (tenecteplase is preferred due to reduced risk and easier administration as a single-dose injection).

Anticoagulation and Antiplatelet Therapy:

• Continue immediately and after thrombolytic therapy.

Anticoagulation:

• Heparin if PCI is planned: bolus 60-70 units/kg followed by 12 units/kg maintenance, maintaining aPTT at 50-70 seconds or 1.5-2 times the control group.

• Enoxaparin is preferred if PCI is not planned.

• Fondaparinux can be used as a 2.5mg intravenous injection or 2.5mg subcutaneous injection.

Antiplatelet Therapy:

• Aspirin loading dose 162-325mg + clopidogrel loading dose 300mg < 75 years old or 75mg > 75 years old.

Duration of Dual Antiplatelet Therapy:

• Minimum of 1 year if no bleeding complications.

If the patient is at high risk of stent thrombosis or has poor post-intervention flow:

• Continue enoxaparin for 1-5 days (maximum 8 days).

In cases of atrial fibrillation or chamber thrombosis:

• Oral anticoagulation (vitamin K antagonists or NOACs).

If the patient has heart failure or left ventricular dysfunction after myocardial infarction:

• Use beta-blockers long-term if no contraindications.

• Use ACE inhibitors within 24 hours after reperfusion if the patient also has diabetes or anterior wall myocardial infarction, use long-term.

• Use angiotensin II receptor blockers instead of ACE inhibitors if the patient is intolerant.

• Use aldosterone antagonists if heart failure with EF < 40% or diabetes if not accompanied by renal insufficiency or increased potassium.

Treatment Differences between STEMI and NSTEMI:

• Do not use thrombolytic therapy for NSTEMI.

ABCDE Management for Patients with Acute Coronary Syndrome:

• A5: antiplatelet, anticoagulation, ACE, angiotensinogen blocker, aldosterone receptor blocker.

• B2: blood pressure, beta-blocker.

• C2: cigarette cessation, cholesterol.

• D2: diabetes, diet.

• E2: exercise, EF.

Absolute Contraindications to Thrombolytic Therapy:

• Previous history of stroke.

• Cerebral infarction within 6 months.

• Central nervous system lesions, cerebral vascular malformations.

• Severe head trauma within 3 weeks.

• Gastrointestinal bleeding within 1 month.

• Coagulation disorders.

• Aortic dissection.

• Recent puncture at sites where bleeding cannot be controlled within 24 hours.

# Silent Myocardial Infarction

• Silent symptoms such as fatigue, decreased exercise tolerance, no clear chest pain.

• Seen in patients with early postoperative complications, elderly, dementia, stroke sequelae, diabetes.

# Notes on Percutaneous Coronary Intervention (PCI)

• Mandatory use of 1 anticoagulant: bivalirudin, heparin, enoxaparin.

• Do not use fondaparinux for early intervention.

• May be discontinued after intervention if successful.

# Medications Used in Myocardial Infarction

Beta-Blockers:

• Should be started early within 24 hours after reperfusion.

• Used for patients with heart failure (except acute heart failure), left ventricular dysfunction, sinus tachycardia, arrhythmia.

• Can be used long-term if no contraindications.

ACE Inhibitors:

• Use early within 24 hours after reperfusion.

• Used for patients with heart failure, left ventricular dysfunction, diabetes, or anterior wall myocardial infarction.

Angiotensin II Receptor Blockers:

• When intolerant to ACE inhibitors.

Aldosterone Antagonists:

• Used in heart failure with EF < 40%.

• No renal insufficiency or increased potassium.

# Early Discharge

• When to discharge early within 72 hours after reperfusion?

• Successful coronary reperfusion.

• No intervention complications.

• Compensated left ventricular function, no heart failure.

• Completed cardiac rehabilitation.

# Lifestyle Modifications

• Limit activity if hemodynamics are unstable.

• Sedation.

• Well-balanced, easily digestible diet low in salt and cholesterol.

• Avoid constipation, use laxatives.

# LDL-C Control

• High-dose statin regardless of initial LDL-C value, except in cases of contraindications.

• Monitor after 4-6 weeks to reach target < 1.8.

# Heart Rate in Myocardial Infarction

• Increases in cases of left ventricular failure.

• Decreases in acute myocardial infarction with atrioventricular block.

# Pericardial Friction Rub

• Appears 24 hours or a few weeks after myocardial infarction.

• A consequence of an acute pericardial reaction following myocardial infarction or Dressler’s syndrome.

# Dressler’s Syndrome

• Pericarditis after myocardial infarction.

• Mechanism related to autoimmune response to antigens released from necrotic myocardial cells.

• Symptoms: fever, pericardial friction rub, elevated CRP, leukocytosis.

• Responds well to corticosteroids, colchicine.

# Fixed ST Elevation

• Also seen in:

• Left ventricular aneurysm.

• Left bundle branch block, W-P-W syndrome.

• Hypertrophic cardiomyopathy, left ventricular hypertrophy.

• Pacemaker placement.

• Premature repolarization.

# Non-Fixed ST Elevation

• Also seen in:

• Myocarditis, acute pericarditis.

• Hyperkalemia.

• Pulmonary embolism.

• Acute neurological injury.

# Coronary Blood Supply

• Left anterior descending artery: anterior wall, interventricular septum, apex, part of the lateral wall of the left ventricle.

• Left circumflex artery: posterior wall, part of the lateral wall and part of the inferior wall of the left ventricle.

• Right coronary artery: right ventricle, inferior wall of the left ventricle, part of the posterior wall of the left ventricle.

# Elevated Troponin Levels in Other Conditions

• Myocarditis, pericarditis.

• Acute coronary syndrome.

• Acute pulmonary edema.

• Takotsubo syndrome.

• Renal failure.

• Burns, severe trauma, rhabdomyolysis, etc.

# Reperfusion

• If the patient has no contraindications to dual antiplatelet therapy, use a drug-eluting stent.

Note: This article is for informational purposes only and does not replace the advice of a medical professional. Consult with a physician for proper diagnosis and treatment.