Acute Coronary Syndrome (ACS)

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CLINICAL DESCRIPTION

This is a term that describes symptoms resulting from severe acute myocardial ischemia. The ischemia may, or may not, lead to myocardial infarction (heart attack). ACS is classified as ST segment elevation on an electrocardiogram (ST-segment elevation myocardial infarction - STEMI) or a non-ST-segment elevation myocardial infarction (NSTEMI) and unstable angina (an ACS without elevation of cardiac enzymes). Atherosclerosis or obstruction of coronary blood vessels lead to reduction in blood supply to the heart muscle.

Risk Factors

  • The risk factors for ACS are identical to those for, and include previous episodes of stable angina pectoris.
  • Risk factors for this condition include:
    • obesity
    • diabetes mellitus
    • hypertension
    • smoking
    • hyperlipidemia

CLINICAL FEATURES

SIGNS AND SYMPTOMS

  • Chest pain (Sudden onset)
  • Varying degree but often severe and described as tightness, heaviness or constrictive in nature 
  • Symptoms persist for more than 30 minutes) and may not be relieved by rest or glyceryl trinitrate
  • Chest pain May radiate to the left arm, the neck or jaw
  • Nausea, Vomiting.
  • Shortness of breath or fatigue (this may be the only presentation in diabetics and the elderly)
  • Loss of consciousness
  • Restlessness and apprehension
  • Excessive sweating
  • Peripheral or central cyanosis
  • Pulse may be thready, fast, irregular, slow or normal
  • Blood pressure may be high, low, or unrecordable (following extensive damage to heart muscle)
  • Bilateral crepitations in the chest (with left ventricular failure)
  • Presence of a third or fourth heart sound (suggests heart failure)
  • Confusion in the elderly

INVESTIGATIONS

  • Standard 12 lead ECG, cardiac enzymes: CK-MB, CK, AST, LDH, troponins, serum lipid profile, random blood sugar, FBC, Urea, creatinine, and electrolytes, echocardiography and coronary angiography.

TREATMENT

Treatment objectives 

  • To relieve distress and pain
  • To limit infarct size
  • To prevent and treat complications
  • To reverse cardiac remodeling
  • To prevent re-infarction
  • To identify and manage modifiable risk factors
  • To improve quality of life

NON-PHARMACOLOGICAL 

  • Admit patient
  • Reassure patient and encourage bed rest in the first 48 hours
  • Encourage cessation of smoking
  • Ensure weight reduction (in overweight and obese individuals) in the long term

PHARMACOLOGICAL

  • Oxygen, intranasal, by face mask or nasal cannula
  • Aspirin, oral (chewable), 300 mg STAT and Clopidogrel, oral, 300 mg STAT.
  • Glyceryl trinitrate, sublingual, 500 microgram stat.
  • Morphine, IV, 5-10 mg STAT.
  • Metoclopramide, IV, 10 mg STAT (to prevent vomiting induced by morphine)

Maintenance treatment following immediately after initial treatment 

  • Aspirin, oral, 75mg-indefinitely; Clopidogrel, oral, 75 mg daily (patients who receive revascularization therapy will require treatment for up to 12 months)
  • Anticoagulation: Enoxaparin, SC, 1 mg/kg 12 hourly
  • Prevention of cardiac arrhythmias and reduction of myocardial workload: Atenolol, oral, 25-100 mg daily (avoid only if beta-blockers are contraindicated) or carvedilol 3.125mg bd (escalate dose gradually to maximum dose) or Bisoprolol, oral, 5-20 mg daily Or Metoprolol, oral, 50-100 mg 8-12 hourly
  • Prevention of infarcted area remodeling: ACE inhibitor e.g., enalapril 5-10mg or Lisinopril, oral, 2.5-20 mg daily Or ARBs e.g., Losartan, oral, 25-50 mg daily Or Telmisartan 40-80mg daily 
  • STEMI: Fibrinolytic agents (streptokinase or rTPA) may be given as reperfusion therapy in patients presenting with STEMI under specialist care
  • Manage acute complications such as pulmonary oedema, cardiogenic shock, and cardiac arrhythmias
  • Manage hyperglycemia with insulin
  • Change diabetic patients previously on oral hypoglycemic agents to insulin during the acute phase of Myocardial infarction

Long-term treatment (secondary prevention):

  • Aspirin, oral, 75-150 mg daily indefinitely
  • Atenolol, oral, 25-100 mg daily (avoid only if beta-blockers are contraindicated)

Or 

  • Carvedilol 3.125mg bd po or Bisoprolol, oral, 5-20 mg daily Or Metoprolol, oral, 50100 mg 8-12 hourly
  • To prevent cardiac remodeling and improve survival:
  • enalapril 5-20mg daily or Lisinopril, oral, 2.5-20 mg daily

Or 

  • Losartan, oral, 25-50 mg daily

Or 

  • Telmisartan 40-80mg daily (Note Avoid ACE inhibitors and Angiotensin receptor blockers in patients with BP < 100 mmHg)
  • To stabilize the clot and reduce blood cholesterol levels:
  • Atorvastatin, oral, 20-40 mg daily

Or 

  • Rosuvastatin, oral, 10-20 mg daily

Or  

  • Simvastatin, oral, 40-80 mg daily.

Statins are indicated irrespective of lipid levels

To improve coronary dilatation and reduce myocardial workload: 

  • Isosorbide dinitrate, oral, 10 mg 8-12 hourly
  • Control of hypertension and hyperglycemia if present

Referral Criteria 

All patients with suspected ACS require an urgent ECG. If ECG is not available or cannot be interpreted, refer immediately to a higher facility.

Patients with confirmed STEMI in any facility should be referred urgently to a Physician Specialist or Cardiologist (after an initial oral dose of 300 mg of aspirin). Other patients with N-STEMI and unstable angina should be referred to a physician specialist or cardiologist after the initial management above.