Four-dimensional flow magnetic resonance imaging study to explain high prevalence of pulmonary vein stump thrombus after left upper lobectomy

Figure 1. Four-dimensional-flow magnetic resonance imaging of blood flow (arrows) in the left atrium from pulmonary veins in a preoperative patient (A). After lobectomy, five characteristic flow patterns were observed in the left atrium, as shown by representative cases: multidirectional flow (arrows) in a patient undergoing left upper lobectomy with pulmonary vein stapling (B), ascending flow (arrows) in a patient undergoing left upper lobectomy with pulmonary vein ligation (C), recurrent flow (arrows) in a patient undergoing left lower lobectomy with pulmonary vein stapling (D), retracting flow (arrows) in a patient undergoing right lower lobectomy with pulmonary vein stapling (E), and blowout flow (arrows) in a patient undergoing right lower lobectomy with pulmonary vein stapling (F).

Video 1. A representative blood flow pattern in the left atrium in a preoperative patient on four-dimensional-flow magnetic resonance image. Blood flows from the right superior and inferior PV (blue) go smoothly to the left ventricle. Likewise, the blood flow from the left superior PV (green) comes into contact with the flows from the right PVs (blue) in the left atrium and subsequently goes smoothly to the left ventricle. In contrast, blood flow from the left inferior PV (red) goes cranially, forming an eddy stream in the atrium before going into the ventricle.

Video 2. Five characteristic flow patterns in the left atrium are found after lobectomy, as shown by representative cases: (I) multidirectional flow (to-and-fro static blood movement near the pulmonary vein stump) in a patient undergoing left upper lobectomy with pulmonary vein stapling, (II) ascending flow (head on collision with two venous flows, forming small coil-like flows near the pulmonary vein stump) in a patient undergoing left upper lobectomy with pulmonary vein ligation, (III) recurrent flow (large eddy blood stream without turbulence in the left atrium) in a patient undergoing left lower lobectomy with pulmonary vein stapling, (IV) retracting flow [antegrade movement (washout) of the blood around the vein stump that is accompanied by the neighboring pulmonary venous flow] in a patient undergoing right lower lobectomy with pulmonary vein stapling, and (V) blowout flow (blowout of the venous stump by blood streams derived from the diagonally located pulmonary vein) in a patient undergoing right lower lobectomy with pulmonary vein stapling.

Figure 2. Dynamic change in the blood flow velocity (mL/s) near the pulmonary venous stump during a single stroke (R-R interval) in patients who underwent left upper lobectomy (LUL) (A), left lower lobectomy (LLL) (B), right upper lobectomy (RUL) (C), and right lower lobectomy (RLL) (D). The blood flow velocity near the stump appears to change extensively after LUL, suggesting the development of blood turbulence within the remaining left superior venous conduit (A). According to a quantitative analysis, the standard deviation of the blood flow velocity near the venous stump in patients who underwent LUL is significantly higher than that in each of the other lobectomy groups (E).

Figure 3. The length of the remaining pulmonary venous conduit after lobectomy according to the types of lobectomy. The length of the remaining venous conduit was longest in patients who had undergone left upper lobectomy (LUL) with statistically significant differences from each of the other lobectomy groups. LLL, left lower lobectomy; RUR, right upper lobectomy; RLL, right lower lobectomy.

Figure 4. Significant relationship between the length of the remaining venous conduit and the standard deviation of the blood flow velocity near the venous stump (r=0.671, P<0.0001). Solid circles; patients who underwent left upper lobectomy, Open circles; patients who underwent lobectomy other than left upper lobectomy, Arrow head; patients who developed pulmonary venous thrombus after lobectomy

Figure 5. Correlation among patients who underwent left upper lobectomy with division of the left superior pulmonary vein using ligation after stapling, patients who underwent left upper lobectomy with division of the left superior pulmonary vein using stapling alone, and patients who underwent other types of lobectomy with division of the pulmonary vein using stapling alone, with regard to the length of the remaining pulmonary venous conduit after division of the pulmonary vein (A) and the standard deviation of the blood flow velocity near the left superior pulmonary venous stump (B).