Variations in right atrial flow patterns in the normal heart a potential contributor to cryptogenic stroke in the setting of patent foramen ovale

Background Patent foramen ovale (PFO) occurs in a quarter of the population but half of those with cryptogenic stroke (CS). Difficulty in identifying the pathogenic PFO versus the innocent bystander has contributed to controversy surrounding outcomes following PFO closure. We aimed to investigate whether right atrial flow patterns could help define the mechanism for CS in the setting of PFO. Methods 4D flow cardiac magnetic resonance (CMR) was performed in 10 subjects (age 43±6 years, 4 male) with proven PFO and CS and in 10 controls (age 42±7years, 4 male) with normal trans-thoracic echocardiograms. CMR was performed at 3T (Achieva; Philips) with a 6-channel cardiac array. A retrospectively ECG-gated and respiratory-gated TFE sequence (TE/TR/flip:3.7/6.3ms/8°, VENC:150m/s, FOV:240mm(AP)x240mm(FH)x142mm (LR), spatial resolution:3mm 3 , temporal resolution:5055ms, 20 phases, SENSE, factor 2) was used. Analysis was performed with GTflow v2.0 (Gyrotools). Contours were placed manually in the superior vena cava (SVC) and inferior vena cava (IVC) in the axial plane at the junction with the right atrium. Net flow was assessed at these points. The relative position of the SVC and IVC at these points was measured. A pathline analysis of atrial flow was performed (SVC:red, IVC:green). Results