Table 1: Invasive and Non-invasive Testing Approaches to Diagnose Microvascular Angina.

	Advantages	Disadvantages
Non-invasive Testing
Transthoracic Doppler, contrast echocardiography	Easy to perform Minimal risk No radiation Relatively inexpensive	Operator-dependent Difficult imaging and poor image quality Limited validation and poor correlation with PET
Cardiac PET	The most validated non-invasive tool to diagnose CMD Carries a prognostication value Accurate perfusion quantification Less likely to be affected by renal function Adding CT can allow anatomic assessment of the coronary arteries Not haematocrit-dependent Standard post-processing	Radiation exposure Expensive Not widely available Less spatial and temporal resolution compared to CT and CMR
CMR	Validated against invasive measurements and cardiac PET Myocardial perfusion semi-quantification No radiation exposure Excellent spatial and temporal resolution Allows tissue characterisation with the same study	Expensive Limited prognostication data Complex post processing Not widely available Requires frequent breath holds and longer exam duration Haematocrit-dependent Limited in patients with MRI non-compatible devices Limited in renal failure
Cardiac CT	Anatomic coronary data and perfusion data can be obtained in the same study Good spatial and temporal resolution compared to cardiac PET	High radiation exposure Higher risk for contrast-induced nephropathy Limited in renal failure Post-processing is complex Haematocrit-dependent Limited validation in patients with MVA Iodinated contrast can cause coronary vasodilation and overestimate myocardial perfusion
Invasive Testing
Coronary function test	Confirmatory test to diagnose CMD Accurately identifies different pathways contributing to MVA including CFR, CBF and coronary artery diameter change Provides assessment of other haemodynamic measures such as LVEDP and assesses degree of coronary artery stenosis Carries a prognostication value Standardised protocol	Radiation exposure Not widely available Risk of contrast-induced nephropathy in patients with renal failure Requires complex preparation and hospitalisation

CBF = coronary blood flow; CFR = coronary flow reserve; CMD = coronary microvascular dysfunction; CMR = cardiac magnetic resonance; LVEDP = left ventricular end diastolic pressure; MVA = microvascular angina.