Introduction

Stable angina is a common presentation of Coronary Heart disease РCHD (aka Ischaemic Heart disease РIHD)

  • Stable angina, (aka ‚ÄėAngina pectoris‚Äô, and colloquially “Angina“) is a syndrome which causes exertional chest pain, relieved by rest or the use of nitrates
  • Stable angina is a clinical syndrome rather than a disease – and represents a clinical manifestation of underlying coronary artery disease
  • It occurs when there is insufficient oxygen supply to the heart to meet demand i.e. when there is¬†myocardial ischaemia¬†without infarct
  • This inability typically occurs as a result of narrowing of the coronary arteries. This narrowing can be due to:
    • Atherosclerosis
    • Arterial spasm
    • (Blood clot – which is the mechanism seen in acute coronary syndromes)
  • Angina typically presents as central or left sided chest pain, with or without radiation to the neck, arm or jaw, and is generally transient, most commonly occurring on exertion, but can also be triggered by emotion
  • Acute attacks are treated with nitrites (e.g. sublingual GTN spray)
  • It is diagnosed with a combination of history, ECG and myocardial imagining – typically an angiogram
  • Long-term management involves the use of beta-blockers, calcium-channel blockers, aspirin and statins

It is¬†extremely¬†important to different stable angina from ACS –¬†acute coronary syndrome¬†(unstable angina, NSTEMI and STEMI) – whereby there is an acute narrowing or complete occlusion of the coronary artery due to blood clot – as the treatment is very different. Acute coronary syndrome result in infarction of myocardial tissue, not just ischaemia. However, the presenting symptom – chest pain – often feels identical to that of ACS – as the mechanism of the pain is essentially the same –¬†lack of oxygen to the heart muscle.¬†

Typical presentation

  • Central or left sided chest discomfort
    • May radiated to jaw, arm epigastrium – like ACS pain
  • Can vary from mild to severe
  • Usually described as a “tight” or “crushing” sensation
  • Dyspnoea may or may not be present
  • Usually result from exertion
  • Symptoms relieved by rest
  • Symptoms typically of several minutes duration – shorter acting symptoms of a few seconds only are unlikely to be ischaemia related
  • Patient may get frequent symptoms (several times daily) or only rarely (months between episodes)
    • This does not necessarily correspond to the severity of the disease
  • Crescendo angina¬†is said to occur when attacks are increasing in frequency and / or severity and is correlated to high risk of severe ACS
  • Any changes to a patient’s usual pattern of symptoms should be considered a significant risk for ACS and investigated as such

Differentiating angina and ACS

  • If the pain doesn’t resolve within 5 minutes of cessation of activity, and/or with use of GTN spray, treat as ACS
  • Angina is typically exertional
  • Suspicion of ACS should be increased if the symptoms have occurred at rest

MI causes permanent heart muscle damage (infarct), stable angina does not. They have similar symptoms, although the pain of MI is often greater than angina. Any diagnosis of sudden onset chest pain should be treated as ACS until proven otherwise (unless the pain does resolve as above and the patient already has a diagnosis of stable angina)

Causes

  • Atheroma¬†seen in coronary artery disease – this accounts for the vast majority of cases
  • Aortic valve disease
  • Hypertrophic cardiomyopathy

Classifying causes by oxygen supply and demand

  • Oxygen demand factors ‚Äď heart rate, blood pressure, left ventricular hypertrophy (more muscle to supply!), valve disease ‚Äď e.g. aortic stenosis ‚Äď so the heart has to work hard to pump
  • Oxygen supply ‚Äď duration of diastole (needs to be long enough to allow sufficient blood to flow to the heart), coronary vasomotor tone, haemoglobin levels, oxygen saturation.

People normally experience angina as exertional chest pain that is relieved by rest.
People may also experience myocardial ischaemia as shortness of breath or without symptoms (silent ischaemia)

Other precipitating factors

  • Cold weather
  • Heavy meals
  • Intense emotion

Diagnosing Stable Angina

  • This is mainly based on clinical history ‚Äď and patients will usually present in the Primary care (GP) setting
  • Chest Pain – ¬†is ‚Äėtight‚Äô, heavy‚Äô, or ‚Äėgripping‚Äô.
    • The pain is usually felt behind the sternum and can radiate to the neck, jaw, arms, and sometimes back.
  • Shortness of breath (SOB)
  • Both pain and SOB brought on by exertion, and relieved by rest
  • Symptoms typically last several minutes after the precipitating event has stopped (e.g. exercise or stress)
  • Classically relieved by GTN

The likelihood of a diagnosis of angina increases when there are risk factors for cardiovascular disease present:

Investigations

  • ECG ‚Äď will often be normal ‚Äď a normal ECG does not exclude a diagnosis of angina or ACS!¬†If performed during an episode of angina (e.g. during an exercise tolerance test – aka stress test) then typical changes on an ECG might include:
    • ST-depression
    • Ventricular ectopics
    • Bundle branch abnormalities
  • ETT –¬†Exercise tolerance test
    • Assess for symptoms and ECG changes when the heart is stressed
    • Has sensitivity of about 905 but a specificity of only about 70%
  • Echocardiogram
  • Angiogram –¬†is the most accurate diagnostic test for coronary artery disease (and therefore for stable angina), But it is relatively expensive, and not without risk, and not necessary for the diagnosis.
    • Its main indication is to assess the extent of coronary artery lesions when revascularisation therapies (e.g. stenting (PCI) or bypass) are being considered. As such it is typically reserved for the most symptomatic patients, although its use is increasing.
    • Coronary artery narrowing is considered significant when the luminal diameter is reduced by >70%
  • Blood tests – for screening of risk factors – cholesterol, fasting glucose
  • Echocardiograph –¬†may be considered to establish the level of left ventricular function

Echocardiography

Echo gives information about left ventricular function and ventricular and atrial wall motion defects – which are typically secondary to previous myocardial infarction.

  • Left-ventricular ejection fraction (LVEF) is a strong predictor of long-term outcome
    • LVEF >50% – 12 year survival = 75%
    • LVEF 35-49% – 12 year survival = 55%
    • LVEF <35% – 12 year survival = 21%

Stress test

The stress test (aka exercise stress test or exercise tolerance test) is useful for patients with a normal resting ECG, who are physically able to exercise – usually on a treadmill but occasionally also available on a bicycle.

  • Patients with an abnormal resting ECG – e.g. atrial fibrillation, left ventricular hypertrophy or other ECG changes are more likely to have false positives and may not be appropriate for a stress test

Exercise increases cardiac load and can provoke myocardial ischaemia – which manifests as chest pain, dyspnoea and ECG changes.

Exercise echocardiography is also performed for individuals with difficult to interpret ECGs (e.g. due to pacing or left bundle branch block).

Pharmacological stress testing can be performed in individuals who cannot exercise. In this instance, medication is given to increase cardiac output Рplacing similar stresses on the heart as exercise.

Coronary Artery Imaging

Usually, this is in the form of angiography. Plain CT scan of the arteries can be performed to assess the level of calcification Рbut these result correlate poorly to the level of arterial narrowing.

In some lower risk patients, a contrast CT can be performed, but in the majority of cases, and angiogram is the imaging modality of choice.

This gives exact information on the level of narrowing of the coronary arteries, and which vessels are affected. It is particularly useful to help determine if revascularisation is necessary. With medical treatment only (without revascularisation), 12-year survival rates are:

  • Single vessel disease – 75%
  • Two vessel disease – 59%
  • Triple vessel disease – 50%

In particular, proximal narrowing of the left main coronary artery and the left anterior descending artery is associated with a poor prognosis.

Canadian Cardiovascular Society Angina Classification

This is sometimes used to class the severity of Angina from I-IV. It is very similar to the NYHA classification of Heart Failure

  • Class I ‚Äď ‚ÄėOrdinary Activity‚Äô (e.g. walking or climbing stairs) does not precipitate angina
  • Class II ‚Äď Angina precipitated by walking upstairs, cold weather, or meals
  • Class III ‚Äď marked limitation of normal physical activity
  • Class IV ‚Äď Symptoms present at rest, unable to carry out many normal physical activities

Risk Stratification

The presence of angina indicates underlying coronary artery disease. The next step is to evaluate the severity of this underlying cardiac disease, for the purposes of assessing future risk of myocardial infarction Рand in particular whether or not revascularisation (e.g. coronary artery stenting, or coronary artery bypass graft РCABG) is indicated. Prognostic indicators include:

  • Left ventricular function
  • Stress testing (e.g. treadmill or pharmacological stress test)
  • Coronary artery disease extent as seen on angiogram
  • Age
  • Diabetes
  • Hypertension
  • Hypercholesterolaemia
  • Heart failure

Prognosis

  • If stable angina is present, without history of MI, and with normal resting ECG and normal BP, then annual mortality is about 1.5%
  • If risk factors are present, then annual mortality greatly increases:
    • Abnormal ECG – 8.4%
    • Hypertension – 7.5%
    • Both – 12%
    • T2DM – quoted above risks doubled

Management of stable Angina

This can be divided into lifestyle modifications, pharmacological interventions, and revascularisation. 

Lifestyle

  • Diet advice – plant-based whole foods diet (e.g. mediterranean diet) has been shown to improve long term outcomes
  • Smoking cessation
    • After 2 years, risk of MI is same as for those who have never smoked
  • Control hypertension
  • Treat hyperlipidaemia
  • Alcohol – within safe drinking limits
    • No more than 2 standard drinks on any single day, and two days per week with no alcohol intake
  • Weight – aim for BMI <=25
  • Regular exercise – 150 minutes per week of moderate intensity exercise – reduces cardiovascular risk regardless of weight loss, by up to 30%

Pharmacological

There are two main mechanisms used to relieve the symptoms of angina:

  • Increasing blood flow to the heart muscle (by dilating coronary arteries) – e.g. wth¬†GTN¬†(Glycerytrinitrate)
  • Decreasing the workload on the heart (e.g. with beta-blocker or calcium channel blocker long term)

First line treatment

  • Beta-blocker (e.g. atenolol)
    • Proven to reduce MI and sudden death risk
    • Decrease heart rate, contractility, and cardiac output – which reduces cardiac O2 demand
  • Calcium channel blocker (e.g. verapamil, diltiazem)
    • These two agents are preferred due to their negative chronotropic events
    • Typically reserved for patients who are unable to tolerate beta-blockers or whose symptoms are incompletely controlled with beta-blockers
  • Nitrates
    • Patients will also likely carry GTN spray or pills with them at all times to relieve acute episodes.
    • Nitrates cause vasodilation
    • Can cause hypotension
    • Provide quick relief – within a couple of minutes, and lasts for up to 30 minutes
  • Aspirin (or another anti platelet drug – such as clopidogrel or ticagrelor)
      • Reduced the risk of thrombus formation and thus ACS

Second line treatment

Consider adding…

  • Long acting nitrate
    • e.g. isosorbide mononitritae or dinitrate
    • Typically effect lasts for 4-6 hours
  • Nicorandil
  • Ivabradine
  • Ranolazine

Third line treatment

  • Consider PCI (cardiac stent, balloon angioplasty)
    • Typically both balloon agionplasty and stunning are performed simultanesouly
    • The procedure carries a 1-3% mortality, and 5% risk of MI
    • There is¬†no evidence¬†that angioplasty (+/- stent) improves survival or reduces risk of ACS. It may however reduce symptoms of stable angina
  • CABG – Coronary arty bypass graft
    • Similar risks as PCI (above)
    • Completely eliminates symptoms in about 85% of patients
    • Does¬†not¬†appear to improve survival for those with class I or II disease (see above)
    • Modest improvement in survival for those with left main coronary artery disease or triple vessel disease
    • Patients with T2DM have better outcomes with CABG than PCI

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