Imaging Coronary Microvascular Dysfunction (CMD) Study

All patients will be consented and will undergo Rb-82 rest-stress myocardial perfusion imaging PET with flow quantitation using vasodilator (regadenoson preferred) stressor and cold pressor test and an exercise treadmill test according to standard modified Bruce protocol (if able to exercise).

Only the patients who do not have a recent coronary CT angiography will be consented for undergoing a coronary CT angiography for measurement of plaque burden and quantification of extent and degree of epicardial stenosis.

A small subset of patients who have abnormal flow parameters on PET will be invited to participate in the invasive angiographic validation cohort and will undergo an invasive functional angiography with measurement of FFR, CFR, IMR and Ach-vasoreactivity testing to obtain validation data for PET-guided diagnosis of CMD. A short questionnaire of symptom, suspected diagnosis and planned management will be administered to the treating physician prior to and post-study enrollment.

Patient risk factors, symptoms, health status, medications will be collected using standardized data collection form on study enrollment.

For Aim 2, the cardiac PET findings will be made available to the treating clinician.

A positive PET result for endothelial-independent CMD will be defined as global MBFR <2. A positive PET result for endothelial-dependent CMD will be defined as MBF with cold-pressor test <=40%.

If there was evidence of CMD on cardiac PET, specific treatment recommendations will be made available to the treating physician. These recommendations will include consideration of aspirin, statin and ACE-inhibitors in all patients, beta-blockers (eg: carvedilol 6.25 mg BID with uptitration) as first line, non-dihydropyridine calcium channel blockers (cardizem and verapamil) as second line, and amlodipine (in combination with beta-blocker) or ranolazine as third-line therapy.

Patient symptoms and health status and downstream resource utilization (ER admissions for chest pain, use of other invasive or non-invasive diagnostic procedures for CAD) will be collected at 3 months.

Invasive physiology measurements will be made available to the treating clinician along with recommended management based on INOCA endotype (corMICA trial treatment algorithm) at completion of 3 months.

Inclusion criteria

• Patients with symptoms of exertional angina and/or dyspnea (confirmed on Seattle Angina Questionnaire and Rose Dyspnea Questionnaire)
• Evidence of non-obstructive CAD on CCTA or coronary angiography (no stenosis >50% and/or FFR if performed >0.80)

Exclusion criteria

• Patients with reduced LVEF (<50%) or diagnosis of cardiomyopathy
• Patients with co-existent moderate or severe valve disease
• Patients with eGFR <30 ml/min/m2
• History of prior coronary revascularization
• Non-coronary indication for CCTA or coronary angiogram determining eligibility
• Contraindications to regadenoson (severe asthma/chronic obstructive pulmonary disease, brady-arrhythmias, or systolic blood pressure <90 mm Hg)
• Inability to provide informed consent
• Pregnancy