12.3 Angina, Myocardial Infarction and Antiplatelet Therapy

3. Ischaemic Heart Disease: Angina Pectoris and Myocardial Infarction

Ischaemic heart disease (IHD), or coronary artery disease (CAD), results from atherosclerotic narrowing of the coronary arteries, restricting blood flow and oxygen delivery to the myocardium.

Angina Pectoris: Stable vs Unstable Angina

Angina pectoris is the clinical manifestation of transient myocardial ischaemia without myocyte necrosis. It is vital to differentiate between stable and unstable angina in the clinical setting:

Chairside Protocol for Angina Pectoris

1. Pre-procedure Verification: Confirm the patient has brought their own prescribed glyceryl trinitrate (GTN) sublingual spray (400 mcg/dose). Inspect the expiry date and place the canister directly on the bracket table before commencing any treatment.
2. Stress Reduction Protocol: Schedule short morning appointments. Ensure profound local anaesthesia. Maintain effective communication and consider conscious sedation (inhalation sedation with nitrous oxide/oxygen) for highly anxious patients.
3. Management of an Acute Anginal Attack in the Dental Chair:
   • Step 1: Stop dental treatment immediately. Remove all instruments, rubber dam, and materials from the mouth.
   • Step 2: Position the patient comfortably, typically sitting upright (lying flat increases venous return and cardiac preload, aggravating myocardial work).
   • Step 3: Administer one or two sprays of sublingual GTN (400–800 mcg) under the tongue (or one sublingual tablet). Ensure the patient does not inhale during spray activation.
   • Step 4: Reassure the patient and administer oxygen (10–15 L/min via non-rebreather mask if SpO2 < 94% or if patient is in respiratory distress).
   • Step 5: Monitor vital signs (pulse, blood pressure, oxygen saturation). Normal response: chest pain resolves within 2 to 5 minutes. A common side effect is a throbbing vascular headache and transient hypotension.
   • Step 6 (The 5-Minute Rule): If chest pain persists after 5 minutes, administer a second dose of GTN (one spray).
   • Step 7 (Suspected Myocardial Infarction): If pain persists after 10 to 15 minutes, or does not respond to two doses of GTN, or if pain is severe and accompanied by nausea, cold diaphoresis, dyspnoea, or radiation to the jaw, neck, or back, assume an acute myocardial infarction:
     • Immediately call 999 for an emergency ambulance.
     • Administer a single 300 mg dispersible aspirin tablet orally (instruct patient to chew or dissolve it before swallowing to accelerate absorption), provided there is no known allergy or active bleeding.
     • Prepare the automated external defibrillator (AED) and emergency medical kit.

Myocardial Infarction (MI): Elective Care Deferral Windows

An acute myocardial infarction involves irreversible ischaemic necrosis of a portion of the myocardium resulting from acute coronary artery occlusion.

• The 6-Month Window: Traditional UK clinical dental guidance recommends deferring all elective dental care for 6 months following an acute myocardial infarction. The risk of recurrent infarction, life-threatening ventricular arrhythmias (ventricular tachycardia, ventricular fibrillation), and sudden cardiac arrest is highest during the first 30 to 90 days, remaining significantly elevated until 6 months when collateral circulation and myocardial scar maturation have established.
• Contemporary Interventional Cardiology (3 Months): In patients who have undergone successful early primary percutaneous coronary intervention (PCI / coronary stenting) with complete revascularisation and who remain entirely asymptomatic without residual left ventricular dysfunction, elective dental treatment may proceed after 3 months, provided formal liaison and clearance have been obtained from the patient's treating cardiologist.
• Emergency Dental Care Within the Deferral Window: If emergency treatment is necessary for severe odontogenic pain, spreading cellulitis, or trauma within the post-MI deferral period, it must be performed in a hospital dental department in consultation with cardiology, utilizing minimal intervention, non-pharmacological temporisation, or treatment under continuous haemodynamic monitoring.

Post-Stent Management and Antiplatelet Therapy

Following coronary artery stent implantation, patients are placed on Dual Antiplatelet Therapy (DAPT)—typically combining Aspirin (75 mg daily) with a P2Y12 adenosine diphosphate (ADP) receptor antagonist (such as Clopidogrel 75 mg daily, Ticagrelor 90 mg twice daily, or Prasugrel 10 mg daily):

• Duration: DAPT is prescribed for 1 month following a Bare-Metal Stent (BMS), and for 6 to 12 months following a Drug-Eluting Stent (DES) or acute coronary syndrome.
• Clinical Rule: NEVER stop or interrupt dual antiplatelet therapy for dental procedures without explicit written authorization from the patient's cardiologist. Stopping DAPT abruptly within the first 6 to 12 months results in catastrophic acute stent thrombosis, precipitating a massive, frequently fatal transmural myocardial infarction.
• Haemostasis: Dental extractions and minor oral surgery can be safely executed on single or dual antiplatelet therapy using meticulous local haemostatic measures (resorbable sutures, gelatin/collagen sponges, oxidized cellulose, and pressure packs).