Table 1

Classification of angina by pathophysiology

Angina with obstructive CAD
Obstructive CAD Flow limiting epicardial coronary artery disease*
  • >90% stenosis in a major coronary vessel

  • Fractional flow reserve ≤0.80 or NHPR<0.90

  • Intermediate coronary stenosis in single major vessel with documented ischaemia

Symptoms and/or signs of ischaemia but no obstructive CAD (INOCA)
Microvascular angina†17 1. Symptoms of myocardial ischaemia
  • Effort and/or rest angina

  • Angina equivalents (ie, shortness of breath)

2. Absence of obstructive CAD*
  • FFR>0.80

  • NHPR>0.89

  • Absence of flush ostial branch vessel occlusions

3. Objective evidence of myocardial ischaemia
  • Ischaemic ECG changes during an episode of chest pain

  • Stress-induced chest pain and/or ischaemic ECG changes in the presence or absence of transient/reversible abnormal myocardial perfusion and/or wall motion abnormality

4. Coronary microvascular dysfunction
  • Impaired CFR (≤2.0 or≤2.5 depending on methods used)

  • Increased coronary microvascular resistance (eg, IMR>25, HMR≥2.5 mm Hg cm–1 s)

  • Coronary microvascular spasm, defined as reproduction of symptoms, ischaemic ECG shifts but no epicardial spasm during acetylcholine testing.

  • Coronary slow flow phenomenon, defined as TIMI frame count >25

Vasospastic angina‡42 Nitrate-responsive angina At least one of:
  • Rest angina—especially between night and early morning

  • Marked diurnal variation in exercise tolerance—reduced in morning

  • Precipitated by hyperventilation

  • Calcium channel blockers (but not β-blockers) suppress episodes

Ischaemic ECG changes During spontaneous episode, any one of the following in at least two contiguous leads:
  • ST segment elevation ≥0.1 mV

  • ST segment depression ≥0.1 mV

  • New negative U waves

Coronary artery spasm Either spontaneously or in response to provocation (eg, acetylcholine):
  • Transient total or subtotal coronary artery occlusion (>90% constriction)

  • Reproduction of angina symptoms

  • Ischaemic ECG changes

  • *The finding of obstructive epicardial disease does not exclude other important contributors to ischaemia (microvascular dysfunction and/or vasospasm). The physiological ischaemic lesion thresholds are drawn from 2018 ESC guidelines for myocardial revascularisation and randomised trials; however, the authors acknowledge that majority of lesions with grey-zone physiology values (eg, FFR 0.75–0.82) are not associated with downstream myocardial ischaemia (NCT02425969—Dr B Hennigan, Personal Correspondence).

  • †Definitive MVA is only diagnosed if all four criteria are present. Suspected MVA is diagnosed if criteria 1 and 2 are met but only one of the final two criteria are met (either objective evidence of ischaemia (criterion 3) or evidence of coronary microvascular dysfunction (criterion 4).

  • ‡'Definitive vasospastic angina’ is diagnosed if nitrate-responsive angina is evident during spontaneous episodes and either the transient ischaemic ECG changes during the spontaneous episodes or coronary artery spasm criteria are fulfilled. ‘Suspected vasospastic angina’ is diagnosed if nitrate-responsive angina is evident during spontaneous episodes but transient ischaemic ECG changes are equivocal or unavailable and coronary artery spasm criteria are equivocal. NHPR (eg, iwFR, dPR).

  • CAD, coronary artery disease; CFR, coronary flow reserve; CFR, coronary flow reserve; dPR, diastolic pressure ratio; FFR, fractional flow reserve; HMR, hyperaemic microvascular resistance; IMR, index of microcirculatory resistance; MVA, microvascular angina; NHPR, non-hyperaemic pressure ratio.