The iCorMicA study is a multicentre, prospective, randomised, double-blind, sham-controlled, parallel-group, end-point trial and registry. The investigators seek to determine whether stratified medical therapy guided by an adjunctive interventional diagnostic procedure (IDP) during the invasive management of patients with known or suspected angina but no obstructive coronary artery disease improves symptoms, wellbeing, cardiovascular risk and clinical outcomes.

Ischaemic heart disease (IHD) includes coronary artery disease (or 'coronary heart disease 'CHD') and ischaemic with no obstructive coronary arteries (INOCA). Coronary angiography is standard care for the evaluation of symptomatic patients and known or suspected coronary artery disease. A considerable proportion e.g. >1 in 3, of patients undergoing invasive coronary angiography for known or suspected angina do not have obstructive epicardial coronary artery disease.

The CorMicA pilot study involved prospective enrolment of patients referred for clinically indicated coronary angiography during a 12-month period (2016-2017) in the West of Scotland). 391 patients were enrolled, 185 (47%) had no obstructive coronary disease and 151 were randomised in a clinical trial of stratified medicine based on invasive tests of coronary vascular function. A high proportion (~4 in 5) of these patients had a diagnosis of INOCA due to a disorder of coronary vasomotion including microvascular- and/or vasospastic angina. The trial provided preliminary evidence that stratified medicine, as an adjunct to standard angiography-guided management, has potential to improve symptoms and quality of life. The mechanisms involved changes in diagnosis, treatment and lifestyle measures.

The CorMicA investigators were the first group to introduce stratified medicine for the management of ischaemic heart disease. Limitations of the CorMicA study included the setting (mainly single centre), partial blinding, short-term follow-up (primary outcome at 6 months) and the sample size. Acetylcholine reactivity testing was used to assess the susceptibility to coronary spasm (microvascular and/or macrovascular). Although acetylcholine is a naturally occurring substance, current formulations are not licensed for parenteral administration. Further, clinicians should have training and experience before implementing acetylcholine coronary reactivity testing. These considerations present a barrier to adoption in daily practice, which becomes all the more relevant given INOCA is generally under-recognised. A diagnostic coronary guidewire is already widely used in standard care and, unlike reactivity testing using acetylcholine, a guidewire has transferable potential to support stratified medicine during routine practice. This is especially the case for ad-hoc follow-on testing when obstructive coronary artery disease is excluded.

The vasoactive responses to acetylcholine reflect endothelial and vascular smooth muscle cell effects, which may overlap with the vasoactive responses to adenosine (non-endothelial dependent). Calcium channel blocker therapy is indicated for the functional endotypes associated with impaired vasodilatation and/or vasoconstriction. This raises the possibility that acetylcholine testing may not be routinely required as an adjunctive test to coronary angiography and instead could be reserved for selected cases, or in specialist centres. Instead, the diagnostic guidewire approach may be sufficient as a routine, first line test for the evaluation of INOCA during daily practice.

Anatomical imaging using coronary angiography is the standard of care and clinicians may determine any diagnosis based on all of the available information and their clinical judgement. This approach avoids the need for additional tests. With this approach, the patient's symptoms in response to empirical therapy can be assessed during follow-up and the treatment can be revised as clinically appropriate. In daily practice, adoption of adjunctive tests of coronary function is very low and, in the absence of large, multicentre trials, coronary angiography with or without adjunctive tests of coronary vascular function may be considered reasonable, reflecting equipoise.

iCorMicA is a multicentre, prospective, randomised, double-blind, sham-controlled, parallel-group, end-point (patient reported outcome measures (PROMS), health outcomes, health economics) trial and registry. The investigators aim to determine whether stratified medical therapy, guided by a guidewire-based interventional diagnostic procedure (IDP) at the time of invasive coronary angiography (i.e. functional angiography), improves outcomes in patients with known or suspected angina but no obstructive coronary artery disease. Symptoms of angina or angina-equivalent are determined according to the Rose and/or Seattle Angina questionnaires. The IDP utilises principles of thermodilution to measure coronary vascular function (IMR, CFR, RRR), which aid clinicians in establishing a diagnosis of microvascular angina, vasospastic angina, mixed (both), or none, as per Coronary Vasomotion Disorders International Study Group (COVADIS) criteria. The feasibility, safety, efficacy and effect on healthcare resource utilisation of stratified medicine will be tested in multiple hospitals in different countries in Europe.

Participants with no obstructive epicardial coronary artery disease (coronary stenosis <50% and/or FFR >0.80) are eligible for randomisation (1:1) to either the intervention (IDP-guided, results disclosed) or blinded control (IDP undertaken but results not disclosed, standard of care) group. Medical therapy will be informed according to the clinical diagnosis (endotype). Patients in the intervention group with abnormal coronary vascular function may undergo repeated evaluations to assess the response to intracoronary therapy e.g. calcium channel blocker, enabling a personalised treatment plan. Patients who are ineligible for randomisation (e.g. obstructive coronary artery disease) may be entered into a prospective clinical registry, with individuals from each site invited to undergo similar follow-up assessments as the randomised participants.

Trial participants will be blinded to treatment group. The clinicians responsible for on-going care will also be blinded. Following invasive management, patients and clinicians will be advised of the diagnosis (endotype) but not the randomised group. The endotype will be informed by the IDP in the intervention group but not in the control group (sham procedure). Medical therapy and lifestyle measures are linked to the endotype and informed by contemporary practice guidelines. Therefore, optimal guideline-directed medical care according to the endotype is intended to be the same, regardless of the group allocation.

The sample size is 1500 randomised participants. The minimum follow-up duration is 12 months from the last participant recruitment. Follow-up will continued in the longer term including, where feasible, electronic case record linkage. The primary outcome measure is the Summary Score of the Seattle Angina Questionnaire at 12 months. Secondary outcomes include other Patient Reported Outcome Measures (PROMS) to describe other aspects of health and wellbeing. These include EQ-5D-5L, Illness perception (Brief IPQ), Treatment satisfaction (TSQM), Duke Activity Status Index (DASI), the International Physical Activity Questionnaire (IPAQ-SF) short-form and a pain questionnaire.

Additional objectives include the wider evaluation of the safety and diagnostic utility of the IDP in a multicentre, multinational setting, and the effects of stratified medicine on the rates of major adverse cardiovascular events by randomised group. The registry will represent a parallel control group. Scientific analyses of circulating biomarkers will be performed to better understand the pathophysiology of INOCA.

Inclusion Criteria:

1. Age ≥18 years.
2. A clinical plan for invasive coronary angiography.
3. Symptoms of angina (typical or atypical) according to the Rose- and/or Seattle Angina questionnaires.
4. Able to comply with study procedures.
5. Able to provide informed consent.

Exclusion Criteria:

1. A non-coronary primary indication for invasive angiography (e.g. valve disease, heart failure).
2. History of coronary artery bypass surgery.
3. Presence of obstructive disease evident in a main coronary artery (diameter >2.5 mm), i.e. a coronary stenosis >50% and/or a fractional flow reserve (FFR) ≤0.80*.
4. Logistical reason*. *These patients will enter a follow-up registry.

After the study has completed

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Patients and clinicians responsible for downstream (post-catheter laboratory) care are blinded to the randomisation allocation group (i.e. are blinded to whether the patient was in the intervention or blinded/control group).