Stable angina

Article written and reviewed by Dr Luca Moretti

Stable angina is a clinical syndrome in which chest discomfort or an equivalent occurs at a relatively predictable threshold of exertion or stress and resolves with rest or nitrate. The word stable describes the reproducibility of the clinical pattern over the recent period, not the biological stability of the plaque or the absence of risk. Rapid worsening, onset at rest, or unusual duration changes the clinical question and requires exclusion of acute coronary syndrome. The diagnosis cannot be based on a single adjective used to describe the pain.
The classic mechanism is an atherosclerotic stenosis that limits the increase in blood flow, but angina may result from diffuse disease, microvascular dysfunction, vasospasm, or combinations of these. Coronary angiography without obstructions therefore does not exclude an ischemic origin; conversely, a visible stenosis does not prove that the pain is caused by it. Anatomy and physiology must be consistent with the territory and symptom. Assessment distinguishes anginal pain, demonstrable ischemia, and prognosis, three related but non-equivalent dimensions.

Symptom severity is measured through episode frequency, avoided activities, nitrate use, and instruments such as the Seattle Angina Questionnaire. The CCS class describes limitation during activities but does not quantify atherosclerotic burden or myocardial infarction risk; a person who has stopped walking may report few episodes despite severe limitation. History-taking and follow-up must therefore ask not only “how often,” but also which activities have been abandoned.
Treatment simultaneously aims to reduce episodes, restore function, and prevent events. Nitrates, beta-blockers, calcium channel blockers, and other antianginal agents are selected according to the hemodynamic profile; statins, risk-factor control, and antithrombotic therapy address risk; PCI or bypass surgery is used when the symptomatic or prognostic benefit justifies the procedure. Revascularization treats an anatomical target, not the entirety of atherosclerosis. The best decision is the one that links mechanism, objective, and patient preferences.

Etiology, risk factors, pathogenesis, and pathophysiology

In obstructive angina, a stenosis produces resistance to flow that increases during hyperemia. At rest, the arterioles dilate and compensate; during exercise, reserve is insufficient and subendocardial perfusion falls. Length, minimum area, pressure, collateral vessels, and serial lesions modify the effect beyond the visual percentage. A 70% stenosis may not be functionally significant, whereas a less conspicuous lesion in diffuse disease may contribute. FFR and iFR improve patient selection for PCI.
Diffuse atherosclerosis gradually reduces pressure along the vessel and may not present a focal site suitable for stenting. Physiological pullback distinguishes diffuse and focal patterns; in the former, the hemodynamic gain from isolated PCI may be modest. Plaque burden continues to confer event risk even when angina is controlled. Statin therapy and intensive prevention are therefore necessary regardless of whether a revascularizable lesion exists.

Microvascular dysfunction reduces CFR through structural or vasomotor abnormalities; microvascular spasm causes ischemia with patent epicardial arteries. Symptoms may occur during or after exertion, last longer, and respond variably to nitrates; epicardial vasospasm typically occurs at rest, although mixed patterns exist. Persistence after PCI should prompt investigation of these mechanisms before the pain is attributed to residual stenoses or psychological causes.
Heart rate, contractility, and blood pressure determine oxygen demand. Climbing, cold, wind, meals, and stress increase cardiac work; tachycardia shortens diastole. Anemia, hypoxemia, and reduced perfusion pressure decrease supply; a worsening threshold may therefore result from fever, hyperthyroidism, arrhythmia, or blood loss without anatomical progression. Correcting the precipitant is part of anti-ischemic therapy.

Pain arises from metabolite accumulation and activation of cardiac afferents, but perception is modulated by neuropathy, the autonomic nervous system, and central processing. Diabetes and previous myocardial infarction may attenuate the signal; anxiety and hypervigilance may amplify it without making it imaginary; ischemia and pain do not coincide in every episode. Effective therapy assesses both perfusion and the symptomatic experience, avoiding the use of either as the sole proof of the other.
Atherosclerotic factors include LDL, smoking, hypertension, diabetes, kidney disease, age, family history, and lipoprotein(a). The presence of angina signals a possible ischemic mechanism, but future risk depends on their control and on the extent of disease; obesity and physical inactivity increase demand and deconditioning as well as metabolic risk. Depression, isolation, and medication costs reduce adherence and must be addressed as clinical determinants.

Aortic stenosis, hypertrophy, hypertrophic cardiomyopathy, and hypertension may cause angina with or without coronary artery disease. Myocardial bridging and coronary anomalies are selected causes; reflux and chest-wall disorders mimic the symptom without ischemia. Two causes commonly coexist, especially in older adults. An accurate diagnosis assigns weight to each mechanism and does not force every episode into a single explanation.
The ischemic threshold also depends on perfusion pressure. Hypotension due to dehydration or medication may trigger angina despite reducing cardiac work, whereas hypertension increases wall tension and demand. An excessively short diastole during tachycardia particularly compromises the left ventricle; heart rate and blood pressure during symptoms are therefore recorded. Therapy that is effective at rest may prove insufficient or excessive during real-life activities.

Collateral vessels may delay ischemia and limit necrosis, but they do not ensure adequate flow during exertion. Exercise training improves peripheral efficiency and endothelial function, reducing heart rate at a given workload; it does not dissolve a stenosis. The warm-up phenomenon may involve vasodilation and preconditioning, but it does not justify ignoring new symptoms. Exercise prescription uses adaptation within a defined safety range.

Pathological anatomy, classification, and progression

Traditional classification defines angina as typical when characteristic discomfort, provocation by exertion or stress, and relief with rest or nitrate coexist; two elements make the presentation less typical, and one or none makes it nonanginal. This terminology guides probability but does not exclude disease; contemporary guidelines emphasize description and probability rather than rigid labels. Age, sex, and risk factors modify the meaning of the same symptom.

Functional classification of angina according to the Canadian Cardiovascular Society

• Class I: ordinary activities do not cause angina; symptoms occur with strenuous, rapid, or prolonged exertion.
• Class II: slight limitation of ordinary activities, with angina when walking rapidly, uphill, in the cold, after meals, or under stress.
• Class III: marked limitation of ordinary activities, with angina when walking short distances or climbing one flight of stairs at a normal pace.
• Class IV: inability to perform any physical activity without discomfort; angina may also be present at rest.

The CCS class is assigned according to real life, taking the activity actually performed into account. An apparently low class in a sedentary person may conceal severe limitation; tests and questionnaires clarify capacity. Class IV may be chronic, but new or changed pain at rest is an acute warning sign. A change in class over time is a treatment outcome, not a sufficient measure of prognosis.
Anatomically, disease may involve one vessel, multiple vessels, the left main coronary artery, or present as diffuse atherosclerosis. The myocardial mass supplied, coronary dominance, and collateral vessels influence ischemia; chronic occlusions may be compensated at rest and symptomatic under stress. Complexity affects the choice between PCI and bypass surgery. In the absence of obstructions, microvascular, vasospastic, mixed, or indeterminate endotypes are classified through functional testing.

Angina may remain stable for years, improve with treatment, or become unstable. Plaque progression increases limitation, whereas rupture or erosion causes acute thrombosis even without prior worsening; restenosis after PCI tends to cause a gradual return of symptoms, whereas stent thrombosis is a sudden event. After bypass surgery, grafts and native vessels evolve separately, making anatomical reconstruction necessary when symptoms recur.
Repeated ischemia may cause stunning and contribute to ventricular dysfunction; a silent myocardial infarction may leave a scar. Angina itself, however, does not imply necrosis, and stable troponin elevation is not part of it. In a chronic presentation, mildly elevated troponin may reflect structural injury and prognosis, but an acute change requires exclusion of myocardial infarction. Echocardiography and CMR distinguish scar, function, and alternative diagnoses.

Event risk and symptom burden follow different trajectories. Plaque stabilization may reduce myocardial infarctions without eliminating angina, whereas PCI may improve angina without changing the risk from remote plaques. This explains why preventive therapy continues even when the patient is asymptomatic and why symptomatic therapy is titrated even with a favorable prognosis. The objectives must be stated before every intervention.
Angina due to vasospasm is classified separately because it often occurs at rest and shows circadian variation, but it may overlap with a stable exertional form. Microvascular dysfunction may produce prolonged symptoms and an incomplete response to nitrates; describing all these presentations as “stable angina” without an endotype reduces therapeutic precision. Temporal stability is therefore considered alongside mechanistic classification.

Chronic occlusions may be associated with predictable angina, dyspnea, or no symptoms because of adaptation. Viability and ischemia in the territory, limitation, and complexity guide recanalization; an anatomical occlusion alone does not mandate PCI. When the distal vessel is small or disease is diffuse, the probability of symptomatic benefit may be lower than the procedural risk.

Clinical manifestations

Discomfort is described as pressure, heaviness, squeezing, burning, or difficulty breathing, most often retrosternal and diffuse. Patients frequently indicate the area with the palm rather than one finger. Radiation may extend to one or both arms, the jaw, back, or epigastrium. Intensity does not necessarily correlate with the ischemic mass. Instantaneous stabbing pain or continuous pain lasting hours without relation to exertion is less typical, but assessment considers the context.
Provocation is the most useful feature: brisk walking, climbing, cold, a headwind, emotion, or a large meal produces a reproducible threshold. The symptom generally resolves within minutes as demand falls. A warm-up phenomenon, with better tolerance of a second effort, may result from vascular and metabolic adaptation. Marked variability at rest suggests vasospasm or mixed mechanisms and requires a more detailed history.

Dyspnea may be an anginal equivalent, but it is less specific. Transient ischemia raises filling pressures; chronic heart failure, lung disease, anemia, and obesity produce similar symptoms. Fatigue, nausea, and sweating may accompany the pain. In patients with neuropathy or communication difficulties, a reduction in activity observed by family members may be more informative than denial of the symptom.
The history records the number of episodes, duration, nitrate use, activities interrupted, and temporal pattern. A chest diagram and a diary reduce ambiguity. The response to nitrate supports the hypothesis but is not specific, because nitrate also acts on the esophagus and spontaneous resolution is common; reproducibility during a test adds evidence. Patients should describe the symptom before suggestive words are offered to them.

The examination is often normal between episodes. High blood pressure increases demand; hypotension limits treatment and perfusion. An aortic murmur, third heart sound, crackles, and vascular signs modify risk and diagnosis. Reproduction of pain by palpation suggests a chest-wall cause but does not exclude coexisting coronary artery disease. During pain, ST changes, arrhythmias, or dynamic mitral regurgitation support a cardiac origin.
The distinction between stable and unstable depends on change. Severe new-onset angina, episodes at rest, rapid crescendo, duration beyond usual, syncope, or autonomic symptoms require urgent assessment. Patients must not use repeated nitrates to delay seeking help during an unusual episode. A written plan specifies when to stop activity, take the prescribed dose, and call emergency services.

Chronic limitation promotes deconditioning, fear, depression, and loss of autonomy. Patients may avoid sexual activity, work, or travel because of fear even after ischemia is controlled; rehabilitation and communication correct excessive restrictions and verify the response under supervision. Patient-reported outcomes are measured as seriously as blood pressure and LDL.
Angina may be more difficult to recognize in patients with language barriers, cognitive impairment, or different concepts of pain. Interpreters and caregivers help without replacing the patient’s voice. Questions about activities and concrete sensations are more reliable than a list of adjectives; inequalities in access affect delays and treatment. Standardized assessment reduces the risk that sex, ethnicity, or social status will influence diagnosis.

Pain during sexual activity is managed like any other physical workload, assessing stability and capacity. Fear and erectile dysfunction are common and rarely raised spontaneously. Nitrates and PDE5 inhibitors must not be combined; the patient receives an interval and instructions appropriate to the molecule. Resumption of activity is not prohibited generically. Counseling reduces anxiety and dangerous medication practices.

Investigations and diagnosis

ECG and echocardiography form the foundation, together with a complete blood count and assessment of kidney function, glucose, and lipids. ECG may show scar, ST-T abnormalities, conduction block, or hypertrophy; a normal tracing does not exclude angina. Echocardiography assesses regional dysfunction, ejection fraction, valves, and other heart disease; troponin is indicated if the history suggests an acute phase. A chronic diagnosis is not made with isolated biomarkers.
Clinical probability guides the choice. With very low probability and a nonsuggestive history, investigation of other causes may suffice; with low or intermediate probability, CCTA identifies or excludes plaque and stenosis. Extensive calcium, arrhythmia, and kidney disease may limit it; with known disease or a need to quantify ischemia, stress imaging is often more informative. The chosen test must answer a question formulated before it is performed.

Exercise ECG records symptoms, workload, heart rate, blood pressure, arrhythmias, and ST changes. It has prognostic and functional value but lower diagnostic sensitivity and specificity than imaging; baseline abnormalities or inability to exercise make it unsuitable for ischemia assessment. A negative test can be interpreted only if a sufficient workload is reached and it is not limited by medication or extracardiac factors. The Duke treadmill score integrates exercise, ST changes, and angina in appropriate patients.
Stress echocardiography, CMR, SPECT, and PET identify ischemia through wall motion or perfusion. PET quantifies absolute flow and CFR; CMR combines perfusion, function, and scar without radiation; SPECT is widely available but uses relative comparison; echocardiography depends on the acoustic window and operator. The choice considers probability, availability, and contraindications. A small defect and extensive ischemia do not have the same therapeutic implications.

Coronary angiography is performed for substantial symptoms, high risk, or when revascularization is anticipated. Visual assessment of intermediate lesions is imprecise; FFR or iFR identifies lesions that limit flow and improves PCI selection. Intracoronary imaging measures the vessel and plaque and optimizes stent implantation. If there are no stenoses, the pathway does not end when symptoms remain plausibly ischemic.
When microvascular or vasospastic angina is suspected, CFR, resistance, and acetylcholine identify endotypes. Criteria require symptoms, absence of obstruction, and consistent objective or functional evidence. PET and quantitative CMR can demonstrate reduced reserve noninvasively. An endotype-specific diagnosis supports beta-blockade or ranolazine in structural dysfunction and calcium channel blockers in spasm, avoiding empirical treatment.

The differential diagnosis includes reflux, esophageal spasm, costochondritis, radiculopathy, anxiety, pulmonary disease, aortic disease, and valvular disease. A therapeutic trial for an alternative cause is useful only when probability supports it; the final report describes the degree of certainty, mechanism, and risk. Unexplained pain is not defined as benign merely because one test is negative.
The technical quality of CCTA depends on heart rate, rhythm, breathing, and calcium. A non-evaluable segment is not negative; a stenosis overestimated by blooming is not automatically severe. High-risk plaques add information but do not by themselves indicate PCI; the report is integrated with probability and symptoms. A second test is selected when it resolves uncertainty with therapeutic consequences.

During pharmacological stress, vasodilators and dobutamine have different contraindications and profiles. Caffeine and medications interfere with some protocols; incorrect preparation reduces validity. Low global flow reserve may result from diffuse or microvascular disease even without regional defects. The report must distinguish a nondiagnostic test from a negative test. Communicating limitations prevents false reassurance and indiscriminate repeat testing.

Treatment and prognosis

Sublingual nitrate is taken while seated at symptom onset or before predictable exertion, as prescribed. It may cause headache and hypotension and must not be combined with phosphodiesterase-5 inhibitors or riociguat because of the risk of circulatory collapse. Pain that does not resolve rapidly or differs from usual requires emergency assistance. Nitrate treats the episode; it is not an alternative to assessing a clinical change.
Beta-blockers reduce heart rate and contractility; they are appropriate with tachycardia, ventricular dysfunction, certain arrhythmias, and in the post-infarction period, but may cause bradycardia, fatigue, and bronchospasm, especially in predisposed patients. Dihydropyridine calcium channel blockers reduce afterload, whereas verapamil and diltiazem slow atrioventricular nodal conduction and are unsuitable in significant systolic dysfunction. Combining agents, especially with verapamil or diltiazem, may cause excessive bradycardia or hypotension. Selection follows the profile, not a mandatory sequence.

Long-acting nitrates require a nitrate-free interval to limit tolerance. Ranolazine may be useful when blood pressure and heart rate limit other drugs, but requires attention to the QT interval, kidney and liver function, and interactions. Ivabradine can be used in sinus rhythm with an appropriate heart rate and selected indications; every addition is assessed after sufficient time against a measurable objective. Ineffective polypharmacy must not delay verification of adherence and mechanism.
Statin therapy, smoking cessation, blood pressure and diabetes control, and physical activity constitute prognostic therapy. Aspirin or an alternative is used in known atherosclerotic coronary disease according to risk; DAPT duration depends on PCI and events. An ACE inhibitor or angiotensin receptor blocker is indicated with hypertension, diabetes, kidney disease, ventricular dysfunction, or other conditions. Risk-factor control reduces events even if it does not immediately alter angina. Rehabilitation increases capacity and confidence during exertion.

PCI of a functionally significant stenosis can improve symptoms. Trials controlled with a placebo procedure show a contribution from the contextual effect, but also an antianginal benefit of PCI in selected patients, particularly evident in ORBITA-2 without background antianginal therapy. The individual benefit depends on severity, physiology, focal pattern, and expectations. PCI does not confer a benefit in death or myocardial infarction over contemporary medical therapy in all stable patients.
Bypass surgery is preferred for complex anatomy, multivessel disease with diabetes, left main disease, or other conditions according to the Heart Team. It offers more complete revascularization but entails surgery and recovery; PCI is less invasive but may require further procedures. The choice considers durability, risk, function, frailty, and preferences. If the symptom is inconsistent with the anatomy, revascularization without a plausible target reduces the probability of success.

Prognosis depends more on ejection fraction, anatomy, ischemia, kidney disease, diabetes, and prevention than on angina class. Follow-up measures symptoms and targets, checks adverse effects, and updates the plan; a stable patient does not require automatic annual testing. A clinical change requires reassessment. Therapeutic success includes survival, freedom from events, the ability to perform meaningful activities, and reduced use of emergency resources.
Physical activity is prescribed after risk stratification and proceeds through warm-up, aerobic exercise, and cool-down. Patients learn to stop when symptoms occur, use nitrate according to the plan, and recognize an atypical episode. Strength training initially avoids maximal loads and prolonged straining; progression is based on tolerance rather than fear. Rehabilitation improves capacity, risk factors, and confidence even when some angina persists.

Drug titration requires home measurements and review of adherence, heart rate, and blood pressure. Irregular beta-blocker use may produce variability and rebound; continuous nitrate use without a drug-free interval causes tolerance. Formulations, schedules, and costs are adapted to the patient’s daily routine; success is reassessed after every change. If two or three consistent trials fail, the mechanism is revisited rather than additional drugs being accumulated.

Complications

Atherothrombotic destabilization causes unstable angina or myocardial infarction. New pain at rest, crescendo symptoms, prolonged duration, or autonomic symptoms require ECG and troponin testing. Patients must recognize this distinction and not attribute every episode to their stable condition; prevention reduces risk but does not eliminate it. The stenosis responsible for angina and the plaque responsible for myocardial infarction may be different lesions.
Ischemia and myocardial infarction may cause heart failure, mitral regurgitation, and remodeling. Progressive dyspnea, edema, or orthopnea requires echocardiography and specific therapy; disappearance of angina together with declining function is not improvement. In patients with reduced ejection fraction, revascularization, heart-failure medications, and devices are assessed according to dedicated criteria.

Arrhythmias may be triggered by ischemia or scar. Atrial fibrillation shortens diastolic time and may lower the anginal threshold, and may also require anticoagulation according to thromboembolic risk; ventricular tachycardia and syncope indicate higher risk. Antianginal drugs may cause bradycardia or conduction block. Monitoring is selected for palpitations, syncope, or findings and does not replace ischemia assessment.
Hypotension, headache, edema, fatigue, sexual dysfunction, QT prolongation, and interactions are complications of antianginal therapy. A prescription the patient cannot tolerate is not optimal therapy. Review includes noncardiac medications, alcohol, herbal products, and PDE5 inhibitor use; doses are reduced or drugs replaced while preserving the objective. Education prevents abrupt discontinuation and dangerous combinations.

Bleeding results from antiplatelet agents or anticoagulants and increases with age, kidney disease, anemia, and previous hemorrhage. Gastroprotection and proportionate duration reduce risk; therapy must not be discontinued autonomously after stent implantation. Hemorrhage requires a balance between hemostasis and thrombosis. The planned DAPT end date must be documented and updated after new events.
Refractory angina causes disability, depression, and repeated healthcare visits. Before diagnosis, adherence, stenoses, grafts, the microcirculation, spasm, and alternative causes are reassessed. A dedicated team can integrate medication, rehabilitation, advanced revascularization, and pain therapies. The objective is not merely to eliminate a signal, but to restore activity and autonomy without adding procedures that lack a target.

Revascularization may be complicated by kidney injury, bleeding, dissection, embolization, stroke, or procedural myocardial infarction. After PCI, underexpansion and nonadherence to antithrombotic therapy increase thrombosis; after bypass surgery, atrial fibrillation and infection affect recovery. Risk is compared with limitation and expected benefit. An elective procedure requires time for decision-making and preparation unless an acute change occurs.
Chronic nitrate use may cause tolerance and headache; beta-blockers may cause fatigue and sexual dysfunction; calcium channel blockers may cause edema or bradycardia; ranolazine may cause dizziness, interactions, and QT prolongation. These effects may reduce quality of life as much as angina. Assessment does not automatically attribute every symptom to coronary disease. Shared decision-making preserves useful drugs and replaces those with little net benefit.