8.2 Ischaemic Heart Disease & Anticoagulation

8.2 Ischaemic Heart Disease & Anticoagulation

Quick Answer: In ischaemic heart disease (IHD), pharmacists support antiplatelet therapy, statins for secondary prevention, nitrates for angina symptoms, risk-factor medicines (e.g. antihypertensives, antianginals), and lifestyle reinforcement. For atrial fibrillation and venous thromboembolism, know warfarin (INR, interactions) versus DOACs (apixaban, rivaroxaban, dabigatran—counselling, renal awareness, bleeding risk). Dual antiplatelet duration is protocol-defined. Suspected acute coronary syndrome (ACS) is emergency care, not pharmacy observation.

This section integrates Standard 3.2 (implementing antiplatelet/anticoagulant plans safely) and 3.3 (monitoring INR, bleeding, adherence, and clinical deterioration).

Antiplatelets in IHD

Aspirin

Low-dose aspirin remains a foundation of secondary prevention after MI, ACS, or established atherosclerotic disease when indicated. Counselling points:

• Take as directed (often with food if gastric irritation).
• Watch for bleeding (GI, bruising, black stools, haematemesis).
• Do not add other NSAIDs casually—increased bleeding and CV risk concerns.
• Enteric-coated products do not eliminate serious GI bleed risk.

Primary prevention aspirin is more nuanced and not a default “everyone over 50” community message—defer to guideline/prescriber decisions for primary prevention.

P2Y12 inhibitors

Clopidogrel, prasugrel, and ticagrelor are used with aspirin as dual antiplatelet therapy (DAPT) after ACS and/or coronary stenting according to cardiology protocols. Exam-level points:

Duration concepts: DAPT length depends on ACS vs elective stenting, stent type era, bleeding risk, and cardiologist plan—commonly measured in months, not “forever by default,” but never stop early because the patient “feels fine” or has a dental appointment without checking the cardiology plan. Premature cessation after stenting risks stent thrombosis.

After DAPT completes, many patients continue single antiplatelet therapy long-term unless anticoagulation supersedes the plan (complex dual/triple therapy is specialist-managed).

Nitrates

Glyceryl trinitrate (GTN) spray or tablets are used for acute angina relief; longer-acting nitrates (e.g. isosorbide mononitrate) for prophylaxis with nitrate-free intervals to limit tolerance.

Counselling (GTN):

• Sit down before use (hypotension/dizziness).
• Follow the patient’s action plan for dose repeats and when to call an ambulance if pain persists (classic teaching often links unresolved pain after GTN doses to emergency activation—use the written plan).
• Store spray correctly; check expiry.
• Drug interaction: avoid with PDE5 inhibitors (sildenafil, tadalafil, etc.)—severe hypotension risk. Separate timing rules are strict; when in doubt, do not combine.

Statins in secondary prevention

After ACS or established atherosclerotic CVD, high-intensity statin therapy concepts are central (e.g. atorvastatin or rosuvastatin at secondary-prevention intensities as prescribed). Goals are risk reduction, not only a laboratory LDL number in isolation. Counsel on adherence (often lifelong), muscle symptoms (see Section 8.4), and not stopping after “good cholesterol results” without medical advice.

Warfarin — INR monitoring and interactions

Warfarin remains relevant for mechanical heart valves, some antiphospholipid syndromes, and selected AF/VTE cases.

INR principles

• Target INR range is indication-specific (commonly around 2–3 for many indications; mechanical mitral valves often higher—confirm the individual target).
• Dose adjusts to INR, not to a fixed “standard tablet forever.”
• Missed doses, binge alcohol, acute illness, and diet shifts can swing INR.

Interactions (high-yield)

Warfarin is interaction-dense. Pharmacists must check:

• Antibiotics and antifungals (e.g. metronidazole, some macrolides, azoles) that potentiate effect
• Amiodarone, many anti-inflammatories, and other CYP/protein-binding interacting drugs
• Herbal products (e.g. St John’s wort decreasing effect; others increasing bleed risk)
• Vitamin K intake consistency (not necessarily zero green vegetables—consistent intake)

Any new medicine, including OTC, should trigger “do you take warfarin?” and interaction/INR plan thinking.

Counselling

• Bleeding and bruising vigilance; medical care for major bleeding.
• Tablet strength colours/strengths must match the current dose plan—dispensing errors are high risk.
• Keep anticoagulant book/clinic contact details available.

DOACs — apixaban, rivaroxaban, dabigatran

Direct oral anticoagulants simplified monitoring versus warfarin for many AF and VTE indications but require disciplined counselling.

Apixaban/rivaroxaban/dabigatran are not interchangeable unit-for-unit; indication, dose, and renal criteria differ. Switching between anticoagulants follows defined schemes.

When to refer for suspected ACS

Community red flags for possible ACS include:

• Crushing central chest pain or pressure ± radiation to arm, neck, jaw
• Associated sweating, nausea, dyspnoea, syncope
• Pain at rest or lasting longer than typical stable angina
• Failure of usual GTN response per action plan
• Known IHD with accelerating symptoms (unstable pattern)

Action: activate emergency services / urgent medical assessment. Do not delay for antacids, “wait and see,” or routine GP next week. Aspirin may be part of emergency first-aid protocols in some settings when not contraindicated—but emergency pathway is the priority decision for the Intern Written exam when the vignette is clearly ACS-like.

Bleeding risk and dual/triple therapy

Patients may temporarily receive combinations of antiplatelet(s) plus anticoagulant after stents with AF—bleeding risk is high. Intern role: recognise the complexity, reinforce adherence to the exact cardiology plan, avoid adding NSAIDs, counsel on bleed signs, and escalate confusion about duration rather than guessing.

Exam mindset

Expect questions on: DAPT not stopped early post-stent; GTN + PDE5 inhibitor contraindication; warfarin–antibiotic interaction and INR; DOAC renal dose awareness; rivaroxaban food/counselling nuances; and chest pain needing emergency care. Correct answers protect thrombotic risk after ACS/stents and bleeding risk on anticoagulants simultaneously—two sides of the same therapeutic coin.