Coronary sinus flow measurement. The coronary sinus was identified in the atrio-ventricular groove, on the basal slices of the short-axis stack (panel a). the plane for flow measurement was prescribed parallel to the long-axis of the heart on the 4-chamber view and perpendicular to the direction of flow in the coronary sinus, approximately 0.5 cm from the ostium (green line, panels a and b). the proximal coronary sinus was seen in cross-section on the phase contrast images (panels c and d). flow vs time curves were generated by drawing a region of interest around the coronary sinus to calculate through-plane flow (panel e).