Accept/decline decision module for the liver simulated allocation model.

Simulated allocation models (SAMs) are used to evaluate organ allocation policies. An important component of SAMs is a module that decides whether each potential recipient will accept an offered organ. The objective of this study was to develop and test accept-or-decline classifiers based on several machine-learning methods in an effort to improve the SAM for liver allocation. Feature selection and imbalance correction methods were tested and best approaches identified for application to organ transplant data. Then, we used 2011 liver match-run data to compare classifiers based on logistic regression, support vector machines, boosting, classification and regression trees, and Random Forests. Finally, because the accept-or-decline module will be embedded in a simulation model, we also developed an evaluation tool for comparing performance of predictors, which we call sample-path accuracy. The Random Forest method resulted in the smallest overall error rate, and boosting techniques had greater accuracy when both sensitivity and specificity were simultaneously considered important. Our comparisons show that no method dominates all others on all performance measures of interest. A logistic regression-based classifier is easy to implement and allows for pinpointing the contribution of each feature toward the probability of acceptance. Other methods we tested did not have a similar interpretation. The Scientific Registry of Transplant Recipients decided to use the logistic regression-based accept-decline decision module in the next generation of liver SAM.

Cases of hemolytic anemia with periprosthetic leaks evaluated by real-time 3-dimensional transesophageal echocardiography.

Hemolytic anemia is recognized as a rare complication of mitral valve replacement or repair. We report on a 44-year-old man with shortness of breath and hemolytic anemia, 23 years after mitral valve replacement (Hall-Kaster), and a 63-year-old woman diagnosed of hemolytic anemia, 4 years after mitral and tricuspid annuloplasty (Tailor ring, An-core ring). Routine 2-dimensional transthoracic echocardiography revealed paravalvular leakage around the prosthesis. Subsequent real-time 3-dimensional (3D)transesophageal echocardiography helped the perceptional appreciation of the leakage and the measuring of the regurgitant orifice area using the anatomically correct plane. Surgical findings of each case fit those of 3D volumetric images.

Fusiform aneurysm presenting with cervical radiculopathy in ehlers-danlos syndrome.

Ehlers-Danlos syndrome (EDS) type IV is characterized by its clinical manifestations, which are easy bruising, thin skin with visible veins, and rupture of arteries, uterus, or intestines. Arterial complications are the leading cause of death in vascular EDS because they are unpredictable and surgical repair is difficult due to tissue fragility. The authors report a case presented with cervical radiculopathy due to a segmental fusiform aneurysm of the cervical vertebral artery. Transfemoral cerebral angiography (TFCA) was done to verify the aneurysmal dilatation. However, during TFCA, bleeding at the puncture site was not controlled, skin and underlying muscle was disrupted and profound bleeding occurred during manual compression after femoral catheter removal. Accordingly, surgical repair of the injured femoral artery was performed. At this time it was possible to diagnose it as an EDS with fusiform aneurysm on cervical vertebral artery. Particularly, cervical fusiform aneurysm is rare condition, and therefore, connective tissue disorder must be considered in such cases. If connective tissue disorder is suspected, the authors suggest that a noninvasive imaging modality, such as, high quality computed tomography angiography, be used to evaluate the vascular lesion to avoid potential arterial complications.