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Angina is chest discomfort that happens when the heart muscle is not getting enough blood. In stable angina it is predictable — it comes on with a certain amount of effort and settles with rest. Unstable angina is the same pain behaving differently: coming on at rest, lasting longer, or appearing with much less effort than before. That change usually means a fatty deposit inside a coronary artery has cracked and a clot is forming on it. Unlike a heart attack, the muscle has not yet been damaged — which is exactly why it is worth acting on quickly.
Definition
Unstable angina belongs to the group of conditions called acute coronary syndromes, alongside the two types of heart attack.1,2 It is defined by symptoms of myocardial ischaemia occurring at rest, with new onset, or in a worsening pattern, in the absence of a rise in cardiac troponin — the blood marker that indicates heart muscle damage.2,3
The distinction from a heart attack is precisely that: in unstable angina the blood supply is compromised but the muscle has not yet died. The original classification of the condition dates from 1989 and is still referenced.4
The diagnosis has become considerably less common, for a technical reason worth understanding. Modern high-sensitivity troponin assays detect very small amounts of muscle injury that older tests missed. Many patients who would once have been labelled "unstable angina" are now correctly diagnosed with a small non-ST-elevation myocardial infarction.3,9 If a relative was given this diagnosis twenty years ago, the same presentation today might be named differently.
Pathophysiology
The plaque, and what changes
Atherosclerotic plaque builds within the artery wall over years. In stable angina the plaque is fixed: it limits flow when demand rises, and the pain is predictable. Instability occurs when the fibrous cap over a plaque erodes or ruptures, exposing its contents to the blood.1,2
Clot formation
Platelets aggregate at the site and a thrombus forms. If it occludes the vessel completely, the result is a heart attack. If it narrows the vessel severely but intermittently, the result is unstable angina — ischaemia at rest, variable through the day, and capable of progressing within hours.1,2
Other contributors
Coronary spasm, arterial dissection, and increased demand from severe anaemia, infection or arrhythmia can each produce the same picture, and management differs accordingly.1,2
Symptoms
- Chest discomfort — pressure, tightness or heaviness rather than sharp pain, often described with a fist rather than a fingertip.
- Radiation to the arm, jaw, neck or back.
- Breathlessness, sweating, nausea or a sense of dread.
- Occurring at rest, or with much less exertion than previously, or lasting longer than usual episodes.1
Presentation is frequently atypical in women, people with diabetes and older adults — breathlessness, fatigue or upper abdominal discomfort without prominent chest pain. This is a recognised reason for delayed presentation and delayed diagnosis.1,5
Chest pain at rest, or angina that has changed its pattern, is a same-day emergency assessment. Call 000. Do not drive yourself and do not wait to see whether it settles.1,6
Diagnosis
- ECG, repeated, since changes can be intermittent. ST depression or T wave inversion supports the diagnosis; a normal ECG does not exclude it.1,2
- High-sensitivity troponin on arrival and repeated after an interval, using a rapid rule-in/rule-out protocol. A rise identifies infarction rather than unstable angina.2,3
- Risk scoring — the GRACE score estimates six-month risk and guides how urgently invasive assessment is offered.12
- Coronary angiography, timed according to risk, with CT coronary angiography used in lower-risk presentations.2
Management
Initial treatment is in hospital and aims to stop the clot progressing while assessing the coronary anatomy.2,6,10
- Antiplatelet therapy — aspirin immediately, usually with a second agent.2
- Anticoagulation during the acute phase.2
- Anti-anginal treatment — nitrates and beta blockers.2,5
- High-intensity statin, started early and continued long term.2,6
- Revascularisation — angioplasty with a stent, or bypass surgery, with timing determined by risk.2,12
- Cardiac rehabilitation and secondary prevention, which is where the long-term benefit is won and is discussed below.7,8
Co-morbidities and complications
- Progression to myocardial infarction, the immediate risk and the reason for urgency.1,12
- Arrhythmia during the acute phase.2
- Heart failure, where ischaemia is extensive or recurrent.2
- Diabetes, chronic kidney disease, hypertension and smoking, which cluster with coronary disease and worsen outcome.6,12
- Depression and anxiety after an acute coronary event, which independently predict poorer outcomes and lower rehabilitation attendance.11
Medications
Listed so that the purpose of each is clear. Prescribing sits with the cardiology team and the GP.
- Aspirin, usually lifelong.2
- A second antiplatelet (ticagrelor, prasugrel or clopidogrel), typically for twelve months after a stent.2
- Statin at high intensity, for plaque stabilisation as much as for cholesterol.2,6
- Beta blocker, reducing cardiac workload.2,5
- ACE inhibitor, particularly with diabetes, hypertension or impaired ventricular function.2,6
- Glyceryl trinitrate spray for symptom relief, with clear instruction on when to use it and when to call 000.5,6
Prognosis
Outcome depends on the extent of coronary disease, ventricular function, and how completely secondary prevention is implemented.12 Treated promptly, most people do well, and many return to full activity.
The first weeks carry the highest risk, which is why early invasive assessment is offered to higher-risk patients.2,12 Beyond that, the trajectory is largely determined by modifiable factors — smoking, blood pressure, lipids, glucose, weight and physical activity.6,11
Living with it
Two things dominate the months afterwards, and only one of them is medical.
The first is the medication routine, which is larger than most people expect and matters most in the year after a stent.
The second is confidence. A great many people leave hospital physically able to exert themselves and psychologically unwilling to. Left alone, that fear becomes deconditioning, and deconditioning worsens both symptoms and risk. Attending cardiac rehabilitation is the single most useful thing most people can do in this period, and it remains substantially under-attended.8,11
Role of the physiotherapist
Acute unstable angina is treated in hospital. Our role begins afterwards, and it is the part with the strongest evidence behind it of anything on this page.
Exercise-based cardiac rehabilitation after an acute coronary syndrome reduces cardiovascular mortality and hospital readmission and improves quality of life, in Cochrane reviews spanning dozens of randomised trials.7,8 Few interventions in the whole of cardiology carry that weight of evidence, and it is delivered largely by physiotherapists and exercise physiologists.
What that looks like here:
- Assessment before exercise — current symptoms, medications, revascularisation status, and any exercise test results from the cardiology team.
- An individually prescribed exercise programme, aerobic and resistance, progressed by symptoms and heart rate response.7,8
- Teaching the difference between safe exertion and warning symptoms, including when to use GTN and when to call 000. This is the part that restores confidence.
- Supporting secondary prevention — activity, smoking cessation referral, and adherence conversations, alongside the GP.6,11
- A home or telehealth-supported programme where attending in person is not practical, which has been shown to produce comparable outcomes and matters in Central Queensland.11
We work alongside your cardiologist and GP. Bring your discharge summary and current medication list to a first appointment.
- Cardiorespiratory Rehabilitation — the intervention with the strongest evidence after an acute coronary syndrome
- Physiotherapy Assessment — a full assessment before starting, including what your discharge summary means for exercise
- Lifestyle Changes — the secondary prevention that determines the next ten years
The hospital treats the acute event; what happens over the following months decides the next ten years. Exercise-based cardiac rehabilitation reduces cardiovascular death and readmission, and most people never attend one. We assess you, prescribe exercise you can actually do, and teach the difference between safe exertion and a warning symptom — which is usually what gets confidence back.
Part 1 · References
- Collet JP, Thiele H, Barbato E, et al. 2020 ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation. Eur Heart J 2021;42(14):1289–1367.
- Byrne RA, Rossello X, Coughlan JJ, et al. 2023 ESC Guidelines for the management of acute coronary syndromes. Eur Heart J 2023;44(38):3720–3826.
- Thygesen K, Alpert JS, Jaffe AS, et al. Fourth universal definition of myocardial infarction (2018). Eur Heart J 2019;40(3):237–269.
- Braunwald E. Unstable angina: a classification. Circulation 1989;80(2):410–414.
- Amsterdam EA, Wenger NK, Brindis RG, et al. 2014 AHA/ACC guideline for the management of patients with non-ST-elevation acute coronary syndromes. Circulation 2014;130(25):e344–e426.
- Chew DP, Scott IA, Cullen L, et al. National Heart Foundation of Australia and Cardiac Society of Australia and New Zealand: Australian clinical guidelines for the management of acute coronary syndromes 2016. Heart Lung Circ 2016;25(9):895–951.
- Anderson L, Oldridge N, Thompson DR, et al. Exercise-based cardiac rehabilitation for coronary heart disease: Cochrane systematic review and meta-analysis. J Am Coll Cardiol 2016;67(1):1–12.
- Dibben G, Faulkner J, Oldridge N, et al. Exercise-based cardiac rehabilitation for coronary heart disease. Cochrane Database Syst Rev 2021;11:CD001800.
- Braunwald E, Morrow DA. Unstable angina: is it time for a requiem? Circulation 2013;127(24):2452–2457.
- Roffi M, Patrono C, Collet JP, et al. 2015 ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation. Eur Heart J 2016;37(3):267–315.
- Taylor RS, Dalal HM, McDonagh STJ. The role of cardiac rehabilitation in improving cardiovascular outcomes. Nat Rev Cardiol 2022;19(3):180–194.
- Fox KAA, Dabbous OH, Goldberg RJ, et al. Prediction of risk of death and myocardial infarction in the six months after presentation with acute coronary syndrome (GRACE). BMJ 2006;333(7578):1091.
Clinical evidence
Part 1 covers the same condition without the technical detail. What follows is the evidence base behind it, written for clinicians — the literature, the reasoning and the gaps.
For clinicians: this summary supports clinical reasoning and is not a protocol. Check current guidelines and local policy before applying it, and read it alongside the key references and guidelines directory.
Framing. Unstable angina is defined by ischaemic symptoms without troponin elevation, and its boundaries have moved with assay sensitivity rather than with biology.3,9 Contemporary management follows the 2023 ESC acute coronary syndrome guideline, which now treats the NSTE-ACS spectrum as a continuum stratified by risk rather than as discrete diagnoses.2 The 1989 Braunwald classification and the 2014 AHA/ACC and 2015 ESC documents are the earlier framework against which that shift should be read, and older cohorts are defined by them.4,5,10
High-sensitivity troponin has reclassified much of the diagnosis
The fourth universal definition of myocardial infarction, combined with high-sensitivity assays, reclassifies a substantial proportion of patients formerly labelled unstable angina as small non-ST-elevation infarctions.3 Braunwald and Morrow set out the argument that the entity is becoming residual rather than central.9 The practical consequence for anyone reading older literature or an older discharge summary is that cohorts are not comparable across the assay transition, and event rates in pre-2010 unstable angina series describe a sicker, more heterogeneous population.3,9
The residual group — genuinely troponin-negative ischaemia — has a lower event rate than NSTEMI but is not benign, and guideline risk stratification still applies.2,12
Risk stratification drives timing, not diagnosis
GRACE scoring predicts six-month death and infarction and remains embedded in ESC and Australian guidance for determining the urgency of invasive assessment.6,12 Routine early invasive management benefits higher-risk patients; in lower-risk, troponin-negative presentations a selective strategy is appropriate, and CT coronary angiography has an established role.1,2
Cardiac rehabilitation: the strongest evidence on this page
The Cochrane review of exercise-based cardiac rehabilitation in coronary heart disease, updated in 2021 across dozens of randomised trials, found reductions in cardiovascular mortality and hospital admission with improved health-related quality of life.7,8 Effects on all-cause mortality have attenuated in contemporary trials, which is generally attributed to improvements in background medical therapy rather than to loss of benefit from exercise.8,11
The gap is delivery, not evidence. Participation rates remain low internationally, with access, travel and work the dominant barriers — a point of direct relevance to a regional Australian service.11 Home-based and telehealth-supported programmes achieve comparable outcomes to centre-based delivery in trial settings, which makes them the reasonable default where distance would otherwise mean no rehabilitation at all.11
Secondary prevention outweighs the acute intervention over time
Long-term outcome after an acute coronary syndrome is determined largely by lipid control, blood pressure, glycaemic management, smoking cessation and physical activity.2,6 Adherence to dual antiplatelet therapy in the first year after stenting is a specific and time-limited priority, and physiotherapy contact is often the most frequent clinical contact a patient has during that year.2,11
What we do not know
- Whether troponin-negative unstable angina warrants the same intensity of secondary prevention as NSTEMI. The evidence base is largely extrapolated from mixed ACS cohorts.3,9
- The optimal dose and modality of exercise after ACS; comparative trials of high-intensity interval versus moderate continuous training remain small.7,8
- How to raise participation. Interventions to improve rehabilitation uptake have produced modest and inconsistent effects.11
- Whether risk scores developed on pre-high-sensitivity cohorts retain their calibration in contemporary practice.12
References for the clinical evidence summary
- Collet JP, Thiele H, Barbato E, et al. 2020 ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation. Eur Heart J 2021;42(14):1289–1367.
- Byrne RA, Rossello X, Coughlan JJ, et al. 2023 ESC Guidelines for the management of acute coronary syndromes. Eur Heart J 2023;44(38):3720–3826.
- Thygesen K, Alpert JS, Jaffe AS, et al. Fourth universal definition of myocardial infarction (2018). Eur Heart J 2019;40(3):237–269.
- Braunwald E. Unstable angina: a classification. Circulation 1989;80(2):410–414.
- Amsterdam EA, Wenger NK, Brindis RG, et al. 2014 AHA/ACC guideline for the management of patients with non-ST-elevation acute coronary syndromes. Circulation 2014;130(25):e344–e426.
- Chew DP, Scott IA, Cullen L, et al. National Heart Foundation of Australia and Cardiac Society of Australia and New Zealand: Australian clinical guidelines for the management of acute coronary syndromes 2016. Heart Lung Circ 2016;25(9):895–951.
- Anderson L, Oldridge N, Thompson DR, et al. Exercise-based cardiac rehabilitation for coronary heart disease: Cochrane systematic review and meta-analysis. J Am Coll Cardiol 2016;67(1):1–12.
- Dibben G, Faulkner J, Oldridge N, et al. Exercise-based cardiac rehabilitation for coronary heart disease. Cochrane Database Syst Rev 2021;11:CD001800.
- Braunwald E, Morrow DA. Unstable angina: is it time for a requiem? Circulation 2013;127(24):2452–2457.
- Roffi M, Patrono C, Collet JP, et al. 2015 ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation. Eur Heart J 2016;37(3):267–315.
- Taylor RS, Dalal HM, McDonagh STJ. The role of cardiac rehabilitation in improving cardiovascular outcomes. Nat Rev Cardiol 2022;19(3):180–194.
- Fox KAA, Dabbous OH, Goldberg RJ, et al. Prediction of risk of death and myocardial infarction in the six months after presentation with acute coronary syndrome (GRACE). BMJ 2006;333(7578):1091.
Corrections: If something on this page is wrong, out of date or unclear, we want to know. Email reception@inspireclinic.au with the page name and what you believe is incorrect. Substantive corrections are made promptly, and the guide’s version and last-updated date are changed to reflect it.