Transthoracic Assessment of Coronary Flow Velocity Reserve: A Practical Approach to Diagnostic Testing in Patients with Angina and No Obstructive Coronary Artery Disease
Table 1
Noninvasive assessment of coronary microvascular function by transthoracic Doppler echocardiography.
Summary of noninvasive assessment of coronary microvascular function by transthoracic Doppler echocardiography
Physiological pathway: nonendothelial dependent
Preferred coronary artery: left anterior descending artery
Measurement: coronary flow velocity reserve (CFVR) ratio of hyperemic to resting coronary flow velocities (m/s); continuous scale
Cutoff for coronary microvascular dysfunction: CFR <2.0
Common vasodilators: adenosine (0.14 mg/kg/minute; intravenous infusion); dipyridamole (0.84 mg/kg; intravenous infusion); and regadenoson (0.4 mg; intravenous injection)
Patient preparation: absence from methylxanthines and medications affecting myocardial perfusion or myocardial metabolic activity; breathing exercises
Examination steps:
(i) Identification of the coronary flow signal using a 2D color Doppler or intravenous contrast enhancement in case of poor visualization
(ii) Alignment of the coronary flow signal of the ultrasound beam as parallel to the coronary flow as possible
(iii) Maintenance of probe position and measuring angle throughout the examination
(iv) Documentation of characteristic flow curves during rest and hyperemia
