Measurement of coronary flow velocity and coronary flow reserve during stress echocardiography in pediatric patients: A pilot study

BACKGROUND: Measuring coronary flow velocity (CFV) and coronary flow reserve (CFR) using transthoracic Doppler echocardiography represents a novel use of noninvasive imaging for the assessment of cardiac allograft vasculopathy (CAV) in adult heart transplant patients and coronary ischemia in several congenital heart lesions in children. OBJECTIVE: To determine the feasibility of using this technique to measure CFV and CFR during stress testing in pediatric cardiac transplant patients (PCTP). METHODS: Measurements of resting and peak CFV and CFR (peak CFV/resting CFV) were obtained from transthoracic Doppler echocardiograms performed during dobutamine stress echocardiography (n = 11) or semisupine cycle ergometry (n = 9) testing in 15 PCTP. A normal CFR value was defined as >= 2. RESULTS: CFV and CFR were measured in the left anterior descending (n = 4), left main (n = 12), right coronary (n = 4) and circumflex (n = 3) arteries. The median resting and peak CFV were 0.25 m/s (range 0.09 m/s to 0.50 m/s) and 0.65 m/s (range 0.22 m/s to 1.14 m/s), respectively. The median CFR was 2.35 (range 1.35 to 4.38). DISCUSSION: CFV and CFR can be measured in pediatric patients noninvasively using transthoracic echocardiography and without the need for contrast. The evaluation of CFR provides additional information to that obtained by regional wall motion analysis during stress echocardiography as well as left ventricular global physiological responses to stress. This combination could result in improved diagnostic accuracy of testing for CAV. The benefits of these integrated studies are that they are noninvasive, inexpensive and feasible, and do not require PCTP to undergo sedation or invasive procedures. CONCLUSIONS: The present pilot study showed that transthoracic CFR is feasible in pediatric patients. Additional studies are needed to determine its clinical utility as a noninvasive screening tool for CAV in PCTP and other pediatric conditions in which coronary artery disease is suspected.