Measurement of cardiac valve and aortic blood flow velocities in stroke patients: a comparison of 4D flow MRI and echocardiography.

4D flow MRI is an emerging technique that allows quantification of 3D blood flow in vivo. However, comparisons with methods of blood velocity quantification used in clinical routine are sparse. Therefore, we compared velocity quantification using 4D flow MRI with transthoracic and transesophageal echocardiography at the mitral and aortic valves and the aorta. Forty-eight stroke patients (age 67.3 ± 15.0 years) were examined by 4D flow MRI. Blood flow velocities were assessed using standardized 2D analysis planes positioned in the mitral valve (MV), aortic valve (AV), ascending aorta (AAo), and descending aorta (DAo) and were compared with echocardiography. MRI showed moderate-high correlations of systolic velocity values for the MV (r = 0.67, p < 0.001), AV (r = 0.77, p < 0.001), AAo (r = 0.93, p < 0.001), and DAo (r = 0.76, p < 0.001) along with moderate-high intraclass-correlation-coefficients: MV 0.79 (95% CI 0.62, 0.88), AV 0.86 (95% CI 0.75, 0.92), AAo 0.96 (95% CI 0.93, 0.98), and DAo 0.83 (95% CI 0.70, 0.90). However, MRI underestimated absolute systolic blood flow velocities compared with echocardiography by 8.6% for the MV (p = 0.07), 3.1% for the AV (p = 0.48), 10.7% for the AAo (p = 0.09), and 15.0% for the DAo (p = 0.01). Blood flow velocities obtained using 4D flow MRI and echocardiography at the MV, AV, and the ascending and DAo showed moderate to high correlations. Underestimation of absolute velocity values by MRI was low. Thus, 4D flow MRI seems ideally suited to comprehensively assess cardiac and aortic pathologies and related hemodynamic changes in future studies.