Using patient-specific CT-derived anatomies, we demonstrated that increasing outflow graft inclination angle consistently produced elevated WSS on the LCC across all models. High WSS acting on the aortic valve is known to promote fibrotic remodeling around the commissures, potentially leading to restricted leaflet mobility and the development or progression of AI [5].

Previous studies using idealized aortic models have simulated the influence of graft position and angle. Gu et al. showed that graft implantation 2 cm from the STJ produced high WSS on the valve leaflets, and that azimuthal positioning altered which cusp received the greatest stress [6]. Wang et al., using fluid–structure interaction, reported substantial WSS on the cusp opposite the graft at an angle of 135° [7]. Iizuka et al. found that larger outflow graft-to-aorta (O-A) angles correlated with AI progression in LVAD patients [8], and their animal study demonstrated that obtuse angles worsened AI hemodynamics and reduced coronary flow [9].

Our results similarly demonstrate that greater outflow graft angles increase WSS, particularly on the LCC—located opposite the anastomosis when the azimuthal angle is fixed at 90°. Although shallow outflow graft angles may reduce adverse WSS, moving the anastomosis more distally is not always feasible in smaller-bodied patients, such as many in the Japanese population.

Surgical management of post-LVAD AI remains controversial. Park’s stitch—a coaptation stitch applied to the nodules of Arantius—has shown favorable outcomes [10, 11]. However, in cases where high WSS is chronically applied to the leaflets, the long-term durability of such repairs may be limited. Valve replacement may be required when leaflet preservation is not feasible. In our Case 1, the patient developed moderate-to-severe AI directed toward the anterior mitral leaflet, consistent with WSS elevation predicted at the LCC. Pathology revealed lymphocytic inflammation and degenerative changes consistent with mechanical stress induced by LVAD flow. During follow-up periods of 5 years (Case 2) and 4 years (Case 3), no coronary events, worsening of aortic insufficiency, or thromboembolic complications were observed. The clinically implanted outflow graft angles were 59.1° in Case 1, 50.4° in Case 2, and 50.8° in Case 3(Fig. 6). In Case 1, the outflow graft angle was the steepest among 3 cases, and aortic insufficiency requiring surgical intervention developed. In other 2 cases with shallower outflow graft angle, aortic insufficiency was not observed. Therefore, the variation of the outflow graft angle may have partly contributed to the different course in the real clinical setting. However, further studies are needed to derive optimal outflow graft angle by predicting the development of valve insufficiency using WSS on the valve cusp.

Coronary flow behavior in LVAD patients has been described in both clinical and large-animal studies [12,13,14], but CFD-based analyses remain scarce. In this study, shallower outflow graft angles reduced coronary flow and velocity. While reducing WSS on the aortic valve may be desirable, excessively shallow angles risk compromising coronary perfusion. We also clarified that actual coronary vascular resistance is influenced by ventricular pressure, coronary vascular bed resistance, and aortic valve opening and closure, and that the present findings should be interpreted within the context of the simplified modeling assumptions used in this study. Reduced root flow velocity may additionally increase the risk of aortic root thrombosis [15]. Although the present analysis was performed under simplified conditions, a shallower outflow graft angle may reduce coronary blood flow; however, it is uncertain whether such a reduction is sufficient to contribute to myocardial ischemia and coronary artery thrombosis.

Because CFD simulations based on preoperative CT can be performed with relative ease, such patient-specific analyses may help optimize graft angle selection and evaluate the need for prophylactic aortic valve procedures. Several reports have already begun to incorporate CFD into surgical planning [5, 6], suggesting that this approach may improve long-term outcomes in LVAD recipients.

All models assumed rigid arterial walls, and vessel compliance was not included.

The aortic valve was assumed to remain closed under continuous-flow conditions; pulsatile cases with partial valve opening were not evaluated.

Blood viscosity may differ from the values used due to anticoagulation therapy in LVAD patients. Another limitation of this study is the small sample size, consisting of only three cases. While incorporating dynamic aortic valve motion into CT-based CFD simulations remains technically challenging, this approach allows flexible geometric modification of static models and systematic evaluation under different conditions. However, the present model is simplified, and further analyses using a four-dimensional, time-dependent CFD framework would be warranted.