Stable Angina
Stable angina is chest pain or discomfort caused by predictable myocardial ischaemia, usually triggered by exertion or emotional stress and relieved by rest or nitrates.
This page covers the definition, causes, risk factors, symptoms, investigations, diagnosis, ECG findings, management, pharmacological treatment, revascularisation, complications, and prognosis of stable angina.
The content is based primarily on NICE guideline [CG95] Recent-onset chest pain of suspected cardiac origin: assessment and diagnosis and [CG126] Stable Angina: Management.
Background Information
Definition
Stable angina is the most common clinical manifestation of stable CADCoronary artery disease:
- Defined as pain / constricting discomfort in the chest / neck / shoulder / jaw / arm caused by insufficient myocardial perfusion
CADCoronary artery disease can manifest clinically as either stable angina or as ACS:
| CAD manifestation | Pathophysiology | Clinical presentation |
|---|---|---|
| Stable angina | Stable, fixed coronary artery stenosis causing ischaemia on exertion | Predictable symptoms on exertion and relieved by rest or nitrates |
| ACS | Plaque rupture + acute thrombosis causing sudden reduction of myocardial perfusion | Sudden onset symptoms at rest, or symptoms that do not improve with rest or nitrates |
Be aware that stable angina is NOT the same as unstable angina. Unstable angina falls under the category of ACS.
Pathophysiology
Stable angina is caused by myocardial ischaemia resulting from an imbalance between myocardial oxygen supply and demand. [ref]
Factors reducing oxygen supply: [ref]
- Coronary artery atherosclerosis – most common
- Coronary artery vasospasm (classically caused by cocaine use)
- ↑ Heart rate
- Anaemia
Factors increasing oxygen demand: [ref]
- ↑ Heart rate (e.g. physical exertion, emotional stress)
- ↑ Afterload (e.g. hypertension)
Risk Factors
Major risk factors (for developing CADCoronary artery disease, thus stable angina): [ref]
- Old age
- Male
- Smoking
- Hypertension
- Hyperlipidaemia (esp. ↑ LDL and ↓ HDL)
- Diabetes mellitus
- Obesity (esp. central obesity)
- Family history of premature CAD (defined as 1st degree relative with CAD at <55 y/o if male / <65 y/o if female)
Complications
Main complications are:
- ACSAcute coronary syndrome
- Heart failure
- Increased overall risk of cardiovascular death
Diagnosis
To evaluate and diagnose stable angina, first perform a clinical assessment, then carry out diagnostic tests.
1. Clinical Assessment
Typical History of Stable Angina
Stable angina presents as repetitive and reversible attacks
Characteristic features:
- Constricting discomfort in the front of the chest, or in the neck, shoulders, jaw or arms
- Brought on by physical exertion
- Relieved by rest or GTNGlyceryl trinitrate within ~5 min
Other common accompanying clinical features:
- Dyspnoea
- Diaphoresis
- Nausea and vomiting
Additional factors to take into consideration:
| Factors that make stable angina more likely | Factors that make stable angina unlikely |
|---|---|
|
Chest pain / discomfort that is:
Consider GI causes (e.g. GORD, peptic ulcer disease) or MSK pain (e.g. costochondritis, rib fracture) |
Clinical Diagnosis
Make a clinical diagnosis based on how many of the characteristic stable angina features are present:
- 3 features → typical angina
- 2 features → atypical angina
- 1 / 0 features → non-anginal chest pain
The 3 stable angina characteristic features (as described above) are:
- Constricting discomfort in the front of the chest, or in the neck, shoulders, jaw or arms
- Brought on by physical exertion
- Relieved by rest or GTNGlyceryl trinitrate within ~5 min
2. Investigation and Diagnosis
Chest pain that occurs at rest or does not improve with rest / GTN is suggestive of unstable chest pain.
- These patients should be assessed immediately with a resting ECG to exclude ACS
- If ECG shows acute changes (e.g. ST elevation) → follow the ACS pathway (see this article)
If there is typical / atypical angina (diagnosed clinically) → perform the following diagnostic tests (on an outpatient basis).
Choice of diagnostic tests (to evaluate for CADCoronary artery disease):
- 1st line: CT coronary angiography (CTCA)
- 2nd line: non-invasive functional imaging
- Stress echocardiography (dobutamine / exercise)Supportive findings include regional wall motion abnormalities (e.g. hypokinesia, akinesia)
- Cardiac MRI
- Nuclear perfusion imaging (myocardial perfusion scintigraphy)
- 3rd line: invasive coronary angiography
NICE also recommends testing for anaemia, which is a known exacerbating factor of stable angina.
A diagnosis of stable angina can be confirmed if:
- CTCA shows significant CAD (≥70% stenosis of at least 1 major artery segment or ≥50% stenosis of the left main coronary artery), or
- Non-invasive functional imaging shows reversible myocardial ischaemia
A resting ECG is NOT routinely required to diagnose stable angina:
- A normal resting 12-lead ECG cannot exclude the diagnosis of stable angina
- Possible ECG changes in stable angina include pathological Q wave / LBBB / ST or T wave abnormalities (indicative of ischaemia or previous infarction)
Management
All patients should all the following:
- Drugs to prevent/manage angina attacks
- Long-term medications
- Anti-anginal drugs
- Secondary prevention drugs
Last resort: revascularisation
Prevention and Management of Angina Attacks
Offer sublingual GTNGlyceryl trinitrate - a short-acting ntirate. Manages angina via 2 mechanisms: - Coronary artery vasodilation → improve myocardial perfusion - Peripheral vasodilation → reduce afterload → reduce myocardial oxygen demand as needed
- Use to manage acute attacks or as a preventive measureTo be taken before performing any activities that are known to bring on an attack (e.g. planned physical activity)
- Repeat dose after 5 minutes if pain persists
- If the pain is not relieved after 5 minutes after using the 2nd dose → call an ambulance
Long Term Management
Anti-Anginal Drugs
Anti-anginal drugs are taken long-term (daily), aiming to prevent angina attacks.
Step up accordingly if the existing step is not preventing angina effectively. However, do not routinely step up and add more drugs.
Step 1: monotherapy of beta blocker (atenolol / bisoprolol / metoprolol / propranolol) / rate-limiting CCB (verapamil / diltiazem)
Although not explicitly stated in the guidelines, it is sensible and good practice to titrate the first drug to the maximum tolerated dose before giving dual therapy.
Step 2 (either):
- Change to the other 1st line drug (into beta blocker OR rate-limiting CCB monotherapy), or
- Dual therapy of beta blocker + dihydropyridine CCB
e.g., Amlodipine, felodipine, nifedipine
Step 3: consider adding one of the additional drugs:
- Long-acting nitrate (e.g. isosorbide dinitrate, isosorbide mononitrate)
- Ivabradine (If funny channel blocker → reduces cardiac oxygen demand)
- Nicorandil (sodium channel blocker → reduces cardiac oxygen demand)
- Ranolazine (potassium channel activator → coronary vasodilation)
Key information that guides prescription and stepping up:
- Never combine a beta blocker with a rate-limiting CCB (i.e. verapamil and diltiazem), only with a dihydropyridine CCB
e.g., Amlodipine, felodipine, nifedipine
- Do not combine ivabradine with a rate-limiting CCB (i.e. verapamil and diltiazem), only with a dihydropyridine CCB
e.g., Amlodipine, felodipine, nifedipine
- In heart failure, beta blockers are preferred, rate-limiting CCB should be avoided
- Contraindications and cautions for both beta blockers and rate-limiting CCBs:
- Heart rate <50 bpm
- High-degree AV block (2nd / 3rd degree) without a pacemaker
- Sick sinus syndrome without a pacemaker
Nitrate Tolerance
- Continuous nitrate exposure, primarily with long-acting nitrate formulations (inc. oral isosorbide dinitrate/mononitrate), can result in drug tolerance.
- Tolerance is uncommon and clinically insignificant with short-acting formulations (e.g., sublingual glyceryl trinitrate used for angina attacks); unless used excessively or at frequent intervals
Prevention: nitrate-free intervals are recommended for the prevention of tolerance with long-acting nitrate formulations [Ref]
- Standard release formulations of isosorbide dinitrate/mononitrate are given in divided doses to maintain a nitrate-free interval of 10-14 hours per day
- Modified-release preparations: use a once-daily dose to maintain a nitrate-low period and thus minimise tolerance.
Secondary Prevention
All patients:
- Aspirin 75mg OD
- Atorvastatin 80 mg OD
Consider ACE inhibitors if there is concurrent diabetes mellitus.
NICE specifically states NOT to offer vitamin or fish oil supplements to treat stable angina due to the lack of evidence.
Revascularisation
Revascularisation should only be considered if symptoms are not controlled with optimal medical treatment.
2 main options of revascularisation:
- Percutaneous coronary intervention (PCI)
- Coronary artery bypass graft (CABG)
CABG is preferred over PCI if any of the following:
- >65 y/o
- Concurrent diabetes mellites
- Complex triple vessel disease +/- left main stem involvement
References
NICE Guideline: recent-onset chest pain of suspected cardiac origin: assessment and diagnosis
NICE Guideline: stable angina: management