A New Multiparameter Approach to Computational Simulation for Fontan Assessment and Redesign

Introduction. Despite an abundance of prior Fontan simulation articles, there have been relatively few clinical advances that are a direct result of computational methods. We address a few key limitations of previous Fontan simulations as a step towards increasing clinical relevance. Previous simulations have been limited in scope because they have primarily focused on a single energy loss parameter. We present a multi-parameter approach to Fontan modeling that establishes a platform for clinical decision making and comprehensive evaluation of proposed interventions. Methods. Time-dependent, 3-D blood flow simulations were performed on six patient-specific Fontan models. Key modeling advances include detailed pulmonary anatomy, catheterization-derived pressures, and MRI-derived flow with respiration. The following performance parameters were used to rank patients at rest and simulated exercise from best to worst performing: energy efficiency, inferior and superior vena cava (IVC, SVC) pressures, wall shear stress, and IVC flow distribution. Results. Simulated pressures were well matched to catheterization data, but low Fontan pressure did not correlate with high efficiency. Efficiency varied from 74% to 96% at rest, and from 63% to 91% with exercise. Distribution of IVC flow ranged from 88%/12% (LPA/RPA) to 53%/47%. A “transcatheter” virtual intervention demonstrates the utility of computation in evaluating interventional strategies, and is shown to result in increased energy efficiency. Conclusions. A multiparameter approach demonstrates that each parameter results in a different ranking of Fontan performance. Ranking patients using energy efficiency does not correlate with the ranking using other parameters of presumed clinical importance. As such, current simulation methods that evaluate energy dissipation alone are not sufficient for a comprehensive evaluation of new Fontan designs.     

Risk of Pregnancy-Related Hypertension Within 5 Years of Exposure to Drinking Water Contaminated With Escherichia coli O157:H7

J Clin Hypertens(Greenwich). 2010;12:613–620. © 2010 Wiley Periodicals, Inc. The authors evaluated the risk for pregnancy-related hypertension among previously healthy women who conceived within 5 years of exposure to drinking water contaminated with Escherichia coli O157.H7 in Walkerton, Canada (2000). Chronic hypertension was defined as systolic/diastolic blood pressure ≥140/90 mm Hg before 20 weeks gestation; gestational hypertension was defined as new onset systolic/diastolic blood pressure ≥140/90 mm Hg ≥20 weeks gestation. The incidence of hypertension was compared between women who were asymptomatic during the outbreak to those who experienced acute gastroenteritis. Blood pressure data were available for 135 of 148 eligible pregnancies. The adjusted relative risks for chronic and gestational hypertension were 1.5 (95% confidence interval [CI]: 0.3–7.7) and 1.0 (95% CI: 0.4–2.5), respectively. Mean arterial pressure before 20 weeks gestation was 2.7 mm Hg higher in women who had acute gastroenteritis (95% CI: 0.05–5.4). A trend toward higher chronic hypertension and mean arterial pressure in early pregnancy was observed among women who experienced gastroenteritis after exposure to bacterially-contaminated drinking water.     

The Poor Outcome of Ischemic Stroke in Very Old People: A Cohort Study of Its Determinants

OBJECTIVES: To assess how much of the excess risk of poor outcome from stroke in people aged 80 and older aging per se explains, independent of other prognostic determinants.
DESIGN: Cohort, observational.
SETTING: University hospital.
PARTICIPANTS: One thousand five hundred fifty-five patients with first-ever ischemic stroke consecutively referred to an in-hospital Clinical Pathway program were studied.
MEASUREMENTS: The relationship between age and 1-month outcome (death, disability (modified Rankin Scale 3–5), and poor outcome (modified Rankin Scale 3–6)) was assessed, with adjustment for several prognostic factors.
RESULTS: Six hundred twelve patients aged 80 and older showed worse outcome after 1 month than those who were younger, in terms of mortality (19% vs 5%, hazard ratio (HR)=3.85, 95% confidence interval (CI)=2.8–5.4) and disability (51% vs 33%, odds ratio (OR)=3.16, 95% CI=2.5–4.0), although in multivariate models, the adjusted HR for mortality decreased to 1.47 (95% CI=1.0–2.16) and the ORs for disability and poor outcome decreased to 1.76 (95% CI=1.32–2.3.) and 1.83 (95% CI=137–2.43), respectively. Stroke severity, the occurrence of at least one medical complication, and premorbid disability explained most of the risk excess in the oldest-old.
CONCLUSION: Stroke outcome is definitely worse in very old people, and most of the excess risk of death and disability is attributable to the higher occurrences of the most-severe clinical stroke syndromes and of medical complications in the acute phase. These represent potential targets for preventive and therapeutical strategies specifically for elderly people.