CORonary MICrovascular Angina (CorMicA) (CorMicA)

Angina is form of chest pain that is due to a lack of blood to the heart muscle. Angina is commonly triggered by stress and exertion, and is a common health problem worldwide. The diagnosis and treatment of angina is usually focused on detection of blockages in heart arteries, and relief of this problem with drugs, stents or bypass surgery. However, about one third of all invasive angiograms that are performed in patients with angina do not reveal any blockages. Many of such patients may have symptoms due to narrowings in the very small micro vessels (too small to be seen on an angiogram). The purpose of this research is to undertake a 'proof-of-concept' clinical trial to gather information as to whether routine tests of small vessel function in the heart might help identify patients with a stable coronary syndrome due to a disorder of coronary function (vasospastic or microvascular angina), and appropriately rule out this problem in patients with normal test results. The diagnostic strategy enables stratification of patient sub-groups to optimized therapy (personalised medicine). Evidence of patient benefits in this study would support the plan for a larger study that would be designed to impact on healthcare costs and patient reported outcome measures (PROMS).

Background: Patients with a stable coronary syndromes include those with obstructive coronary artery disease (CAD) or ischaemia with no obstructive CAD (INOCA). Disorders of coronary vasomotion leading to microvascular and vasospastic angina are debilitating, prognostically important health problems. Use of coronary function tests with thresholds (normal/abnormal) that are linked to evidence-based treatment (start/stop) could be useful to diagnose (rule-in/rule-out) these conditions, but, evidence is lacking. Design: (1) A proof-of-concept, randomised controlled stratified medicine trial of a clinical strategy informed by invasive tests of coronary function and linked guideline-based treatment decisions vs. standard care using angiography only in 150 patients; (2) A nested observational imaging sub-study using quantitative stress perfusion cardiac magnetic resonance (CMR). CONSORT guidelines will be followed. Objectives: (1) To assess whether a diagnostic strategy involving tests of coronary function changes the diagnosis and treatment and improves health and economic outcomes; (2) To assess the diagnostic accuracy of novel MRI methods for abnormal perfusion due to microvascular disease. Methods: Patients undergoing invasive coronary angiography for the investigation of known or suspected angina and who do not have either structural heart disease or a systemic health problem that would explain those symptoms will be invited to participate. Written informed consent is required for participation. Eligibility is further confirmed at the time of the coronary angiogram by exclusion of obstructive (>50% stenosis, fractional flow reserve <=0.80) coronary artery disease (CAD). After the angiogram, eligible participants will be randomised immediately in the catheter laboratory to test disclosure (intervention group) or measurement without disclosure (control group). Coronary function will be assessed using a diagnostic guidewire and intra-coronary infusions of acetylcholine (10-6M, 10-5M, -10-4M) and a bolus of glyceryl trinitrate (300 micrograms). The guidewire-derived parameters include fractional flow reserve (FFR), coronary flow reserve (CFR), index of microvascular resistance (IMR) and the resistance reserve ratio (RRR). Participants who are enrolled but not randomised will enter a follow-up registry. The endotypes (diagnostic strata) are: obstructive CAD, coronary vasospastic angina, microvascular angina, endothelial dysfunction (no angina), normal (non-cardiac, normal coronary function results, no angina). Thus, a diagnosis may be ruled-in or ruled-out based on the test results. Microvascular disease will be characterised as structural (abnormal IMR) and/or functional (abnormal CFR, RRR). Primary outcome: Between-group difference in Seattle Angina Questionnaire (SAQ) scores at 6 months; Secondary: Reclassification of the treatment decision; certainty of the diagnosis; health status (EQ-5D, Illness Perception, Treatment Satisfaction & Patient Health questionnaires); angina medication and adherence; health economics; reference clinical decisions as evaluated by an independent expert panel of clinicians. Follow-up will continue in the longer term, including through electronic health record linkage. Value: To our knowledge, the study is the first to assess the clinical value of invasive management guided by routine use of adjunctive tests of coronary function in appropriately selected patients. The study will provide new insights into disease mechanisms and provide pilot data to inform the rationale and design of a larger clinical trial. The CMR substudy will provide information on the diagnostic utility of quantitative non-invasive imaging methods in this patient population. Should our hypotheses be confirmed, the research will bring new knowledge with potential benefits to patients and healthcare providers.

Angina, Stable, Coronary Vasospasm, Coronary Circulation, Coronary Syndrome, Microvascular Angina, Coronary Disease

Participants are randomised to a 'Disclosed group' (Intervention group) or a 'Not disclosed group' (Standard Care). In the standard care group, coronary function parameters are measured but the results are not disclosed to the attending clinician or the participant.

In the intervention group, coronary function tests are measured and disclosed to the attending clinician permitting re-evaluation of the initial diagnosis and treatment as compared with initial angiography-guided decisions. The intervention involves measurement of CFR, IMR and RRR in a target, major coronary artery followed by coronary reactivity testing using incremental doses of acetylcholine (10-4M, 10-5M, 10-6M) to assess endothelial function, bolus infusion of ACh (10-4M) for vasospasm provocation testing, followed by administration of a bolus dose (300 micrograms) of glyceryl trinitrate. Endotypes are identified based on established criteria for abnormalities in coronary vasodilator function, vasospasm and microvascular resistance. The endotypes (diagnostic strata) are: obstructive CAD, coronary artery spasm, microvascular angina, endothelial dysfunction (no angina), normal (non-cardiac). A diagnosis may be ruled-in or ruled-out based on the test results.

Coronary function tests are measured but not disclosed to the attending clinician or the participant. The same coronary function tests are undertaken as in the intervention group. Masking is achieved by obscuring the catheter laboratory monitors from the attending clinician and participant. The effectiveness of masking is prospectively monitored.

Adjunctive tests of coronary artery function at the time of invasive coronary angiography. Diagnostic groups: stable coronary syndromes in patients with no-obstructive coronary artery disease including the following sub-groups (coronary artery vasospasm, microvascular spasm, impaired vasorelaxation due to (1) endothelial dysfunction and/or (2) non-endothelial dysfunction, or unaffected (normal test results). Medical management is linked to contemporary clinical guidelines for the management of patients with stable coronary artery disease (European Society of Cardiology (2013)).

Health status and symptoms will be assessed at baseline and again at 6 months using the Seattle Angina Questionnaire. The primary outcome is the within-subject change in SAQ score at 6 months from baseline.

Feasibility of the stratified medicine approach defined by protocol compliance as measured by deviations from the protocol.

Feasibility will be assessed in terms of enrolment rates and protocol compliance relating to enrolment, cross-over, integrity of blinding, adherence with therapy during follow-up, and compliance with follow up assessments

Diagnosis of endotypes (disease strata): obstructive CAD, coronary vasospastic angina, microvascular angina, endothelial dysfunction (no angina), normal (non-cardiac, normal coronary function results, no angina).

Impact of disclosure of the coronary function test results on the diagnosis and certainty of the diagnosis (diagnostic utility)

Impact of disclosure of the coronary function test results on medical decisions (including treatment and investigations), and to compare these decisions against a medical decisions formed by an independent panel of experts (reference dataset)

Assess the relationships between cardiovascular risk factors, reflected by validated risk scores (e.g. ASSIGN, JBS3), and parameters of coronary function, in medically managed patients.

Assess the participants' self-reported levels of anxiety and depression using the Patient Health Questionnaire-4 (PHQ-4)

Assess the participants' self-reported levels of treatment satisfaction using the Treatment Satisfaction Questionnaire for Medication (TSQM)

Assess the participants' perception of their illness using the brief Illness Perception Questionnaire

Assess the participants' general health status and self reported quality of life using the EQ5D questionnaire.

Health status and symptoms will be assessed at baseline and again at 6 months, 12 months and close-out using the Seattle Angina Questionnaire. The secondary outcome is the within-subject change in SAQ score over time.

Assess associations between circulating molecules that are implicated in the pathophysiology of disorders of coronary function.

Assess resource utilisation including primary and secondary care costs for tests, procedures and out-patient visits, and medicines, between the randomised groups

Assess the diagnostic accuracy of stress perfusion magnetic resonance imaging for identification of endotypes based on reference tests of coronary function.

Detection of clinically significant (actionable) incidental findings using magnetic resonance imaging. The incidental findings may be cardiac or non-cardiac.

Inclusion Criteria: A clinically-indicated plan for invasive coronary angiography. Symptoms of angina or angina-equivalent (according to the Rose- and Seattle Angina questionnaires). Exclusion Criteria: A non-coronary indication for invasive angiography e.g. valve disease During the angiogram: obstructive disease evident in a main coronary artery (diameter >2.5 mm), i.e. a coronary stenosis>50% or a fractional flow reserve (FFR) ≤0.80 Lack of informed consent.

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