Development of a hybrid decision support model for optimal ventricular assist device weaning.

BACKGROUND: Despite the small but promising body of evidence for cardiac recovery in patients that have received ventricular assist device (VAD) support, the criteria for identifying and selecting candidates who might be weaned from a VAD have not been established. METHODS: A clinical decision support system was developed based on a Bayesian Belief Network that combined expert knowledge with multivariate statistical analysis. Expert knowledge was derived from interviews of 11 members of the Artificial Heart Program at the University of Pittsburgh Medical Center. This was supplemented by retrospective clinical data from the 19 VAD patients considered for weaning between 1996 and 2004. Artificial Neural Networks and Natural Language Processing were used to mine these data and extract sensitive variables. RESULTS: Three decision support models were compared. The model exclusively based on expert-derived knowledge was the least accurate and most conservative. It underestimated the incidence of heart recovery, incorrectly identifying 4 of the successfully weaned patients as transplant candidates. The model derived exclusively from clinical data performed better but misidentified 2 patients: 1 weaned successfully, and 1 that needed a cardiac transplant ultimately. An expert-data hybrid model performed best, with 94.74% accuracy and 75.37% to 99.07% confidence interval, misidentifying only 1 patient weaned from support. CONCLUSIONS: A clinical decision support system may facilitate and improve the identification of VAD patients who are candidates for cardiac recovery and may benefit from VAD removal. It could be potentially used to translate success of active centers to those less established and thereby expand use of VAD therapy.

Relative contributions of age and atherosclerosis to vascular stiffness.

To determine the relative contributions of aging and atherosclerosis to vascular stiffness, we studied aortic stiffness, plaque, and elastin in 8-, 16-, 25-, and 34-week-old male ApoE-KO and C57BL/6J control mice (N = 48). Stiffness increased gradually in both strains up to 25 weeks (p < 0.05), and dramatically between 25 and 34 weeks in ApoE-KO (p < 0.001). Aging ApoE-KO demonstrated increased plaque (p = 0.02), medial thickening (p < 0.001), and severe elastin fragmentation (p < 0.001). We conclude that the contribution of aging to vascular stiffness is relatively minor compared with the influence of atherosclerosis. However, the effect of atherosclerosis on stiffness is significant only with advanced stages of plaque formation.