Refractory angina

Article written and reviewed by Dr Luca Moretti

Refractory angina is a chronic condition in which angina or equivalents attributable to ischemia persist despite maximally tolerated anti-ischemic therapy and indicated, genuinely feasible revascularization. The traditional definition required epicardial disease and more than three months' duration; a contemporary proposal broadens the concept to obstructive and nonobstructive mechanisms and suggests at least six months. It is neither simply frequent angina nor synonymous with no options. Before applying the label, ischemia must be demonstrated, mechanisms identified, and treatment truly optimized.

Many patients have diffuse multivessel disease, chronic occlusions, small vessels, degenerated grafts, or previous interventions that make another procedure difficult. Others have unrecognized microvascular disease, vasospasm, or myocardial bridging; these may coexist with stenoses and explain symptoms after technically successful PCI. Some patients deemed unsuitable for revascularization at one center become candidates after expert review. Refractoriness therefore requires a structured second review, not a hasty diagnosis of exclusion.
The dominant problem is often quality of life: daily pain, CCS class III-IV limitation, fear of exertion, loss of work, depression, and repeated admissions. Mortality is not necessarily proportional to pain frequency and depends mainly on ventricular function, anatomy, and comorbidities; this does not make symptoms secondary, because disability and healthcare use are important outcomes. Treatment seeks to restore activity and independence as well as prevent events.

Optimal care is provided by an Angina Heart Team integrating clinical cardiology, imaging, physiology, interventional cardiology, cardiac surgery, rehabilitation, pain medicine, and psychology. The team confirms diagnosis, identifies targets, removes ineffective drugs, and selects advanced therapies with transparent evidence and risks; patient participation defines realistic goals. Fewer episodes, more steps, return to work, or sleeping without fear may matter more than an isolated test result.

Etiology, risk factors, pathogenesis, and pathophysiology

The obstructive form often results from diffuse coronary disease with small distal segments, chronic occlusions, or multiple stenoses. Focal PCI does not correct a distributed gradient, and bypass may lack adequate distal targets. Calcification, bifurcations, and previous stents increase complexity; perfusion depends on collaterals and pressure, while anemia or tachycardia further lowers the threshold. Physiological reassessment distinguishes a correctable lesion from a vascular bed without one target.
After PCI, persistent angina may result from incomplete revascularization, underexpansion, restenosis, progression, or ischemia unrelated to the stent. Intracoronary imaging and physiology identify mechanical problems and residual lesions; successful PCI may nevertheless leave microvascular dysfunction and vasospasm. Repeating intervention on pain alone without anatomical and physiological concordance increases the risk of more stents and persistent symptoms.

After bypass, vein grafts may degenerate, anastomoses narrow, and native vessels progress. Competitive flow and mammary graft patency alter the choice among native-vessel PCI, graft PCI, and repeat bypass; review requires previous angiograms, the operative report, and updated imaging. Repeat surgery carries greater risk and is proposed only when expected benefit exceeds alternatives and medical therapy.
Microvascular dysfunction reduces CFR and may result from remodeling, rarefaction, or impaired vasodilation. Epicardial or microvascular spasm causes dynamic ischemia; both may coexist with obstructive atherosclerosis and explain post-revascularization angina; CFR, resistance, and acetylcholine testing identify the endotype. Phenotype-based treatment may transform a supposedly refractory patient into one who was previously underdiagnosed.

Myocardial bridging may cause systolic compression and diastolic compromise during tachycardia; nitrates may accentuate some hemodynamic features. Diagnosis requires anatomy and provoked physiology, not bridge presence alone; hypertrophic cardiomyopathy, aortic stenosis, and hypertension cause microvascular ischemia and high demand. Treating the structural condition may reduce angina more than another coronary intervention.
Chronic pain alters attention, expectation, and central sensitization; this does not deny ischemia: repeated signals, fear, and depression may amplify disability while ischemic burden remains stable. Placebo and context affect procedural and drug outcomes, as sham-controlled studies show; psychological and pain therapy is added, not substituted for cardiac diagnosis. The goal is to reduce suffering without invalidating the patient's experience.

Diabetes, kidney disease, peripheral vascular disease, and reduced ejection fraction increase complex anatomy and limit drugs or access. Frailty and hypotension reduce tolerated doses; bradycardia prevents some combinations; nonadherence may arise from cost, adverse effects, and complexity rather than refusal. Before calling treatment maximal, clinicians verify adequate dose, duration, use, and mechanism.
Subendocardial perfusion is the target of many mechanisms and advanced treatments. Controlled coronary sinus narrowing may raise venous pressure and redistribute flow toward the subendocardium; the actual effect varies with anatomy and territory. EECP raises diastolic pressure and lowers afterload during sessions, with possible later vascular adaptation; plausible rationales do not replace controlled clinical endpoints.

Cardiac nociception travels through sympathetic and vagal afferents and is modulated spinally and centrally. Spinal cord stimulation may alter transmission and autonomic control; less pain does not necessarily mean elimination of ischemia, so patients are taught to recognize equivalents and changes. Pain therapy is integrated with event prevention and is not used to permit dangerous exertion without assessment.

Pathological anatomy, classification, and progression

The conventional definition requires demonstrated reversible ischemia and chronic symptoms uncontrolled by drugs, PCI, or bypass. A contemporary concept includes ANOCA/INOCA and multiple mechanisms if investigated and treated. A minimum duration avoids labeling during initial titration or after a recent event. The proposed six months is not yet universal. Reports should state the definition applied.

Elements required before defining refractory angina

• Persistent, clinically limiting anginal symptoms or equivalents.
• Credible demonstration of ischemia or a coronary mechanism capable of producing it.
• Review of epicardial anatomy, previous stents and grafts, and revascularization feasibility.
• Assessment of microvascular disease, vasospasm, and other mechanisms when anatomy does not explain symptoms.
• Stratified drug therapy that is taken and titrated to the maximum tolerated dose.
• Exclusion or treatment of noncardiac causes and factors amplifying disability.

Patients are described as no-option when conventional revascularization is not feasible, but the category is time-dependent and varies with expertise and technology. Dedicated centers may treat previously unsuitable chronic occlusions; new grafts are not always possible; periodic review may change options, but high-risk procedures are not offered merely because technically possible. Expected benefit must be meaningful to the patient.
Phenotypes may be obstructive epicardial, microvascular, vasospastic, mixed, or post-revascularization. Classification guides beta-blockers, calcium channel blockers, nitrates, ranolazine, and devices. A coronary sinus reducer is studied mainly for left-territory ischemia and corrects neither stenosis nor spasm. Counterpulsation acts on hemodynamics and adaptation. Neuromodulation acts on pain and perhaps autonomic balance, with different evidence.

Disease may remain symptomatic for years. Contemporary studies show better survival than older perceptions, but admissions and depression remain high. Some improve through education and rehabilitation without anatomical change; others worsen from progression or heart failure; trajectory is measured with SAQ, CCS class, activity, and nitrate use. A composite focused only on death or infarction misses the main expected benefit of advanced antianginal therapies.
Chronic ischemia may contribute to stunning and dysfunction, but frequent pain does not prove continuous necrosis. Stable elevated troponin in renal disease or cardiomyopathy does not count episodes; an acute change requires infarction assessment; CMR quantifies scar and function, PET flow and reserve. Follow-up separates prognostic progression from persistent symptoms to avoid alarm and untargeted procedures.

Selection for advanced therapies requires reproducible criteria. A one-class CCS reduction may matter but is placebo-sensitive; sham-controlled trials are particularly necessary for devices. Perfusion, exercise, and SAQ measure different dimensions; symptom improvement without perfusion change may still matter, but mechanism and duration must be stated. Survival benefit is not claimed without evidence.
Classification by ischemic territory distinguishes left, right, or global ischemia and affects devices and revascularization. A reducer may have less effect in the right territory because of venous drainage, whereas EECP is not territorial; a chronic occlusion with a large viable territory differs from diffuse microvascular disease. Treatment is linked to anatomical compartment, not CCS class alone.

A low-pressure phenotype limits nitrates and vasodilators; bradycardia limits beta-blockers and nondihydropyridines; long QT limits ranolazine. Hemodynamic classification makes maximal therapy relative to actual tolerance; the same dose is not maximal for everyone. Ambulatory measurements and orthostatic symptoms distinguish true, temporary, and correctable intolerance.

Clinical manifestations

Angina is often daily, CCS class III or IV, with a very low threshold. Walking at home, dressing, or emotional stress may cause pressure; dyspnea or fatigue may predominate. Duration is generally minutes, but recovery may be slower in diffuse or microvascular disease; continuous pain for hours requires alternative diagnoses and acute assessment. Frequency is documented without assuming every episode shares one mechanism.
Variability gives clues: nocturnal and resting episodes with circadian rhythm suggest spasm; predictable exertional symptoms suggest stenosis or microvascular disease; post-exertional pain may accompany microvascular dysfunction. A threshold changing with anemia or tachycardia indicates a correctable modifier; drug response helps but does not prove diagnosis. A diary of activity, heart rate, pressure, and drugs improves review.

After PCI, pain may be unchanged, different, or recurrent after an interval. Unchanged pain suggests a wrong target or additional mechanism; gradual recurrence may indicate restenosis or progression; acute pain requires exclusion of thrombosis; after bypass, time from surgery and territory guide imaging. No clinical pattern replaces assessment when instability or troponin elevation appears.
Examination seeks heart failure, valve disease, arrhythmias, anemia, hyperthyroidism, and iatrogenic hypotension. Pressure and rate limit further doses; edema may reflect calcium channel blockade or congestion. Reduced pulses affect EECP and interventional access; examination may be normal despite severe symptoms. Frailty is measured because deconditioning and fall risk alter rehabilitation and polypharmacy.

Limitation causes job loss, dependence, and withdrawal from sexual and social life. Depression and anxiety are frequent and may reduce adherence; fear of infarction leads to avoidance of all exertion; these outcomes are assessed through instruments and interview; psychotherapy is not a declaration of noncardiac origin. Rehabilitation gradually restores activity and redefines safe and dangerous signals.
True instability may overlap chronic symptoms. Different, longer, resting pain with sweating, syncope, acute dyspnea, or lack of response requires ECG and troponin. Frequent-pain patients risk normalizing every episode as usual; emergency instructions must be simple and individualized. Neuromodulation or other pain treatments do not remove the need to recognize new equivalents.

Success is a clinically meaningful change: fewer episodes, more activity, less nitrate, better SAQ, or fewer visits. Complete freedom from pain is not always realistic; goals such as walking for 20 minutes or returning to a specific activity make progress verifiable. Assessment includes adverse effects and treatment burden because improvement with hypotension or sedation is unsatisfactory.
Patients may develop nitrate tolerance and increase doses independently, causing headache and hypotension. A diary identifies actual frequency and prophylactic use; a nitrate-free interval is restored without leaving the most symptomatic hours uncovered; increasing use signals worsening or an uncontrolled mechanism. The plan distinguishes usual use from episodes requiring emergency care.

Dyspnea may dominate when ischemia raises filling pressures or heart failure coexists. A cardiopulmonary exercise test may distinguish circulatory, ventilatory, and deconditioning limits in complex cases but does not localize ischemia alone; rehabilitation uses this information for workload. Rapid worsening first requires exclusion of congestion, anemia, arrhythmia, and an acute event.

Investigations and diagnosis

Review begins with angiograms, PCI films, operative reports, tests, CMR, medications, and response. A new reading may find overlooked lesions, underexpanded stents, grafts, collaterals, or an unevaluated territory. Reports alone are insufficient when images exist; reasons PCI or bypass was excluded are reconstructed. Experienced operators confirm the judgment of no feasible revascularization.
Stress CMR, PET, SPECT, or echocardiography demonstrates ischemia according to the case. PET quantifies global flow, CMR perfusion and scar; regional tests may underestimate balanced ischemia. Extent helps define risk and targets but is insufficient for a procedure; a years-old test does not describe current status. Repetition is chosen if it changes decisions or if quality and presentation conflict.

During angiography, FFR or iFR assesses intermediate lesions; pullback distinguishes focal from diffuse gradients. IVUS or OCT examines stents and anatomy. For chronic occlusions, length, calcium, proximal cap, collaterals, and distal vessel determine success and risk; a complex procedure needs plausible symptomatic benefit. Decisions include contrast, radiation, perforation, and potential collateral loss.
Without targets or with disproportionate symptoms, CFR, resistance, and acetylcholine assess microvascular disease and spasm; they may identify untried treatment. Pressure and rate distinguish hemodynamic limitation from drug intolerance; bridging requires mechanism-appropriate physiology and sometimes dobutamine. Refractoriness is suspended until a treatable endotype has been addressed.

Adherence is assessed through a nonjudgmental interview, regimen, prescriptions, and obstacles. Optimal treatment requires the correct drug, tolerated dose, duration, and actual use. Interactions may reduce levels or cause adverse effects leading to omissions; pressure, rate, ECG, renal and liver function define titration margins. Sequential trials are often more informative than adding many drugs together.
Alternatives include reflux, esophageal dysmotility, chest-wall disease, radiculopathy, pulmonary disease, and neuropathic pain. They may coexist with ischemia and explain the nonresponsive component. Targeted trials or consultations follow clinical signs; central sensitization is assessed without denying a cardiac component. The final diagnosis may be multiple, with a separate plan for each symptom generator.

Prognostic profiling includes ejection fraction, scar, arrhythmias, kidney disease, diabetes, and anatomy. Pain frequency alone does not indicate mortality; a very symptomatic patient with preserved function may have mainly quality-of-life goals; this distinction protects against high-risk procedures presented as lifesaving without evidence. Consent records the intended outcome and its probability.
Surgical review assesses distal targets, available conduits, graft patency, function, and resternotomy risk. Repeat bypass is neither excluded solely because of prior surgery nor offered when patency is unlikely. CT may map grafts and aorta before selected procedures. Comparison with complex PCI includes completeness and recovery potential.

Symptoms are measured with SAQ, CCS class, angina days, nitrate use, and activity. A patient-reported endpoint is vulnerable to placebo effects but clinically important; device trials therefore use sham procedures when possible; centers record baseline and follow-up with the same tool. A generic impression of improvement is insufficient to continue burdensome or risky treatment.

Treatment and prognosis

Prevention remains essential: statins and adjuncts, smoking cessation, blood pressure and diabetes control, activity, and antithrombotic therapy as indicated. Lowering LDL may not immediately relieve pain but prevents events; prevention is not abandoned because symptoms dominate; sublingual nitrate is retained with emergency instructions. Anemia, thyroid disease, hypoxia, and tachyarrhythmias are corrected to raise the threshold.
Antianginal therapy is stratified: beta-blockers for demand and tachycardia, calcium channel blockers for vasospasm or blood pressure, long-acting nitrates with a nitrate-free interval, ranolazine when pressure limits other options, and ivabradine in selected sinus rhythm; combinations consider bradycardia, QT, renal function, and interactions. Microvascular and spastic endotypes receive specific treatment; inadequate calcium channel blocker dosing does not prove refractoriness.

Revascularization is reconsidered for stenoses, chronic occlusions, grafts, or complex anatomy. CTO PCI may improve angina and quality of life in selected patients but carries risk and has no universal proven prognostic benefit; bypass is considered with suitable targets and acceptable risk. A procedure is not chosen merely because the patient wants something definitive; the objective and likelihood of relief are quantified.
The coronary sinus Reducer creates controlled coronary sinus stenosis. COSIRA showed improved angina class versus sham; ORBITA-COSMIC did not improve the main transmural perfusion endpoint, although some symptom outcomes improved. Response is not universal and no mortality or infarction benefit is proven. It is for selected patients with ischemia and refractory symptoms according to regulatory indications and availability. Sinus anatomy, right-territory ischemia, and comorbidities influence suitability.

Enhanced external counterpulsation uses sequential cuffs synchronized with diastole to raise perfusion and reduce afterload. Repeated cycles may improve symptoms and capacity in some patients, but studies and access are limited; unsynchronizable arrhythmias, severe aortic regurgitation, uncontrolled hypertension, thrombosis, and severe vascular disease may limit treatment. Benefit is verified functionally without promising certain angiogenesis.
Spinal cord stimulation and other neuromodulation may reduce pain and nitrate use in selected patients, with less robust evidence and risks of implantation, infection, and malfunction. TENS may be tried selectively; sympathetic blocks have limited data; transmyocardial laser revascularization is not routinely recommended because efficacy is uncertain and risk exists. Cell, gene, shock-wave, and novel device therapies remain experimental outside trials or expert programs.

Gradual rehabilitation, CBT, education, and pain management reduce avoidance and amplification. The program uses activity goals, pacing, and safety without declaring pain psychogenic. Depression and sleep are treated; chronic opioids are avoided when possible because of tolerance and dependence; the team reassesses SAQ, class, episodes, adverse effects, and admissions. Prognosis is communicated by separating vital risk from symptom burden.
Cardiac rehabilitation is adapted to threshold and may use intervals, low-impact activity, and monitoring. Patients learn pacing without avoiding all effort; conditioning lowers heart rate and demand for the same activity; strength work is introduced gradually, considering pressure and vascular access. A home program maintains benefit and includes an exacerbation plan.

Psychological care may include cognitive behavioral therapy, structured mindfulness, and treatment of depression. The aim is to reduce fear, catastrophizing, and limitation, not challenge ischemia. Antidepressants are selected considering QT, pressure, and interactions; sleep and apnea are assessed because they modify pain and risk. Families learn to support activity without reinforcing avoidance.

Complications

The principal complication is chronic disability, with reduced activity, muscle loss, and metabolic worsening that further lower the threshold. Rehabilitation breaks the cycle with tolerable loads; functional assessment measures progress even if pain persists. Frailty and falls may result from disease and drug-induced hypotension.
Depression, anxiety, isolation, and suicidal ideation may occur with refractory pain and require direct assessment. Mental health affects quality of life and adherence, but support does not replace ischemia treatment; a crisis requires immediate risk-based intervention. With consent, family and caregivers support activity and event recognition.

Repeated admissions, angiograms, and procedures expose patients to bleeding, kidney injury, radiation, dissection, and stent complications. A shared plan reduces repetition of uninformative tests and defines urgent criteria; new symptoms are not ignored but compared with the usual phenotype. Available documentation prevents incomplete reconstruction at every visit.
Polypharmacy causes bradycardia, hypotension, edema, headache, long QT, and interactions. Adverse effects may mimic fatigue and reduce activity. Medication reconciliation identifies duplication and ineffective drugs; maximum tolerated therapy does not mean the greatest number of agents. Controlled withdrawal may show that a drug provided no benefit.

Infarction, heart failure, and arrhythmias remain possible according to substrate. Angina frequency does not distinguish an acute episode: new, longer, resting pain, syncope, or dyspnea requires assessment; neuromodulation requires specific instructions about equivalents. Reduced ejection fraction and scar receive prognostic drugs and devices independently of pain.
Advanced procedures have specific complications: reducer thrombosis or migration, venous complications, infection or stimulation-system problems, and skin or muscle injury with EECP. Selection and experience reduce risk; outcome registries assess durability and real-world safety. Therapy stops when burden exceeds measurable clinical benefit.

A patient labeled no-option may lose confidence and stop prevention. Communication must clarify that lack of a procedure does not mean lack of care: drugs, rehabilitation, risk control, and selected therapies remain active; prognosis is based on function and comorbidities, not fatalistic formulas. One care coordinator reduces fragmentation and uncoordinated visits.
Clinical trial participation provides access to experimental therapy but requires consent about evidence limitations, randomization, and possible sham. Cells, genes, and devices are not presented as established cures; negative or neutral outcomes matter as much as favorable ones. Patient protection includes avoiding unvalidated commercial offers and maintaining standard therapy during research.