Table 1.

Summary of the non-invasive diagnostic modalities for the evaluation of coronary microcirculation.

Imaging modality	Technique	Material	Threshold	Advantages	Disadvantages
Transthoracic Doppler echocardiography	Pulsed wave Doppler of the LAD	Vasodilators	CFRV < 2	•Widely available •Low cost •No radiation	•Limited to LAD •Technically difficult to reproduce & not widely available •Obstructive disease requires pre-evaluation
Myocardial contrast echocardiography	Microbubble velocity & myocardial blood volume	Microbubble contrast agent	MBF < 2	•Widely available •Low cost •No radiation	•Technically difficult to reproduce & not widely available •Obstructive disease requires pre-evaluation •CMD lacks validation
Positron emission tomography	Rest & stress perfusion imaging	Radioisotope agent & vasodilators	MPR < 2	•Reference for noninvasive imaging •All territories evaluated	•Radiation •Time consuming •Expensive •Obstructive disease requires pre-evaluation
Cardiac magnetic resonance	Rest & stress perfusion imaging	Gadolinium contrast & vasodilators	MPRI < 2	•No radiation •All territories evaluated •Excellent spatial resolution	•Limited availability •Time consuming •Expensive •Obstructive disease requires pre-evaluation
Contrast enhanced cardiac computed tomography	Rest & stress perfusion imaging	Iodine contrast & vasodilators	MPR < 2	•Combined epicardial & microvascular system assessed •All territories evaluated	•Limited availability •Radiation •Limited quantification of MBF

LAD: Left anterior descending artery; CFRV: Coronary flow reserve velocity; MBF: Myocardial blood flow; CMD: Coronary microvascular dysfunction; MPR: Myocardial perfusion reserve; MPRI: Myocardial perfusion reserve index. The most validated imaging modalities are Positron Emission Tomography and Cardiac Magnetic Resonance. Other non-invasive tests have limited data on the exact percentage of accuracy, sensitivity and specificity compared to invasive testing.