The goal of this observational study is to learn more about the diagnosis of coronary endothelium function and coronary vasospasm using a dedicated invasive protocol in patients who has angina without obstruction in their main heart arteries. The main question it aims to answer is the feasibility, reproducibility, and safety of this invasive protocol:
Does this invasive protocol diagnose coronary endothelial dysfunction and vasospasm without issues?
Participants already having invasive coronary angiogram and physiological studies will undergo additional physiological measurements during the same procedure.
Participants will enrol in a symptoms and quality of life questionnaire using dedicated questionnaires and a mobile application to assess the burden of their symptoms before and after the invasive procedure and up to 12 months follow up.
A subset of participants will undergo a repeat set of these measurements to assess reproducibility of the invasive protocol.
A subset of the participants will also undergo a cardiac MRI to assess correlation with the invasive protocol measurements.
Patients with symptoms suggestive of angina.
Evidence of unobstructed coronary arteries on invasive or non-invasive coronary angiography (coronary stenosis <50% and /or FFR >0.80).
Above the age of 18.
The subject has been informed of the nature of the study, agrees to its provisions and has signed written informed consent.
Pregnancy.
Contraindication to angiography and/or physiological assessment with adenosine or acetylcholine.
Previous coronary artery bypass graft (CABG).
Moderate to severe valvular heart disease.
Single group
Invasive coronary physiological measurements
Procedure/SurgeryInvasive assessment of changes in coronary blood flow, resistance, and distal pressure in response to acetylcholine infusion. These will be measured during a clinical indicated invasive coronary angiogram procedure and physiological studies using a standard coronary pressure wire and a dedicated infusion catheter.
Feasibility outcome
Proportion of patients in whom the full invasive protocol (baseline and post-stimulation measurements) is successfully completed without major technical issues or protocol deviations.
Reproducibility outcome
Intra- and inter-operator variability of measurements quantified using intraclass correlation coefficients and Bland-Altman plots in a predefined reproducibility subset.
Safety outcome
Incidence of adverse events related to the procedure or medications.
Correlation between invasive and non-invasive measures of endothelial-dependent coronary microvascular dysfunction.
Strength of correlation (unit of measure = correlation coefficient, r) between invasive indices of endothelial-dependent coronary microvascular function obtained during the study protocol (absolute coronary blood flow and absolute microvascular resistance measured by continuous thermodilution during intracoronary acetylcholine testing) and non-invasive measures of myocardial perfusion (myocardial perfusion reserve obtained from cardiac stress perfusion imaging). Diagnostic agreement for identifying endothelial-dependent microvascular dysfunction will also be assessed (unit of measure = area under ROC curve, sensitivity, and specificity), using the invasive assessment as the reference standard.
Correlation between invasive physiological indices of coronary microvascular function and symptom burden at baseline.
The strength of correlation (Pearson or Spearman correlation coefficient; unit of measure = correlation coefficient, r) between invasive physiological measurements of coronary microvascular function obtained during the study protocol (e.g., absolute coronary blood flow and absolute microvascular resistance derived by continuous thermodilution during acetylcholine testing) and patient-reported symptom burden assessed at baseline using validated questionnaires (Seattle Angina Questionnaire-7 \[SAQ-7\] and EQ-5D-5L scores).
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