Factors associated with deferred lesion failure following fractional flow reserve assessment in patients with diabetes mellitus

Objective: To explore the predictors of deferred lesion failure (DLF) in patients with diabetes mellitus (DM) and lesions with a fractional flow reserve (FFR) >0.80 and to examine whether a predictive relationship between negative FFR values (>0.80\u20131.00) and DLF exists. Background: DM is associated with rapidly progressive atherosclerosis and predictors of DLF in FFR negative lesions in this high-risk group are unknown. Methods: All DM patients who underwent FFR-assessment between 1/01/2010 and 31/12/2013 were included, and followed until 1/7/2015. Patients carrying 651 FFR negative lesion(s) were assessed for DLF, and multivariate models used to identify independent factors associated with DLF. Results: A total of 205 patients with 252 FFR >0.80 lesions were identified. At a mean follow-up of 3.1 \ub1 1.4 years, DLF occurred in 29/205 (14.1%) patients, 31/252 (12.3%) lesions. Using marginal Cox regression multivariate analysis, insulin requiring DM [HR 2.24 (95%CI; 1.01\u20134.95), P = 0.046] and prior revascularization [HR 2.70 (95%CI 1.21\u20136.01), P = 0.015] were identified as being associated with a higher incidence of DLF. Absolute FFR values in FFR negative lesions in DM patients are not predictive of DLF (receiver operating characteristics curve analysis: area under the curve: 0.57 \ub1 0.06, 95%CI 0.46\u20130.69). Conclusions: In DM patients with FFR negative lesions, insulin requiring DM and prior revascularization are predictors for DLF. In contrast to non-DM patients, no predictive relationship between absolute negative FFR values (ranging >0.80\u20131.00) and the risk of DLF exists in DM patients

Temperature-Induced Increase in Methane Release from Peat Bogs: A Mesocosm Experiment

Peat bogs are primarily situated at mid to high latitudes and future climatic change projections indicate that these areas may become increasingly wetter and warmer. Methane emissions from peat bogs are reduced by symbiotic methane oxidizing bacteria (methanotrophs). Higher temperatures and increasing water levels will enhance methane production, but also methane oxidation. To unravel the temperature effect on methane and carbon cycling, a set of mesocosm experiments were executed, where intact peat cores containing actively growing Sphagnum were incubated at 5, 10, 15, 20, and 25°C. After two months of incubation, methane flux measurements indicated that, at increasing temperatures, methanotrophs are not able to fully compensate for the increasing methane production by methanogens. Net methane fluxes showed a strong temperature-dependence, with higher methane fluxes at higher temperatures. After removal of Sphagnum, methane fluxes were higher, increasing with increasing temperature. This indicates that the methanotrophs associated with Sphagnum plants play an important role in limiting the net methane flux from peat. Methanotrophs appear to consume almost all methane transported through diffusion between 5 and 15°C. Still, even though methane consumption increased with increasing temperature, the higher fluxes from the methane producing microbes could not be balanced by methanotrophic activity. The efficiency of the Sphagnum-methanotroph consortium as a filter for methane escape thus decreases with increasing temperature. Whereas 98% of the produced methane is retained at 5°C, this drops to approximately 50% at 25°C. This implies that warming at the mid to high latitudes may be enhanced through increased methane release from peat bogs

Carbon exchange in Western Siberian watershed mires and implication for the greenhouse effect : A spatial temporal modeling approach

The vast watershed mires of Western Siberia formed a significant sink of carbon during the Holocene. Because of their large area these mires might play an important role in the carbon exchange between terrestrial ecosystems and the atmosphere. However, estimation of the Holocene and future carbon balance of whole Western Siberian mires is hampered by the lack of spatially resolved models. The main objective was to assess the carbon exchange fluxes of the mires using a 3-D dynamic approach. These exchange fluxes comprise the sequestration of carbon dioxide (CO2) by peat growth, the emission of methane (CH4) by anaerobic peat decay and the emission of CO2 by aerobic peat decay. From the detailed analysis of peat cores from different sites in the southern taiga of Western Siberia, it emerged that Holocene peat growth and carbon accumulation had different trends, caused by variations in vegetation succession. These differences were strongly influenced by the position in the landscape. Therefore, the effect of climatic change on mire development varied spatially. The indirect effects of climate change through local hydrology appeared to be more important than direct influences of changes in precipitation and temperature. Mire development is closely connected to hydrological dynamics. In the thesis a 3-D dynamic modeling approach is described that makes use of groundwater modeling. In successive timesteps peat growth and decay as well as mire type distribution were calculated, depending on hydrological conditions. The model was forced with a paleo-precipitation record to include variable climatic input. The model results show the Holocene development of a watershed mire from a few small spots to a contiguous mire landscape. As hydrology is the major limiting factor, the mire development is most sensitive to precipitation and evapotranspiration. Under unchanged conditions the mire will grow further, eventually reaching its maximum peat thickness around 11400 yr A.D. Under wetter climatic conditions the mire growth could continue much longer, whereas under dryer conditions an earlier termination will occur. Mire drainage leads to aerobic decay of peat and thus to CO2 emission instead of uptake. In a modeling study in a mire catchment containing both drained and undrained parts, the effect of drainage was quantified. The results show that the water table drawdown not only affected the drained mire part, but also influenced the undrained part over a zone of 1-1.5 km. In this zone peat growth and carbon accumulation were decreased. The contribution of a mire system to the greenhouse effect is depending on the exchange of the greenhouse gases CO2 and CH4. CH4 is a much stronger greenhouse gas than CO2, but has a much shorter atmospheric lifetime. With a stocks-and-flows approach the radiative forcing of both gases could be calculated. This approach has been applied in two cases: (1) the northward shift of bioclimatic zones in Western Siberia under 21st century warming and (2) the carbon exchange in a Western Siberian mire resulting from the 3-D dynamic model. The results show that Western Siberian mires form a sink of greenhouse gases at present and have therefore a negative contribution to the greenhouse effect. Under 21st century warming or drainage conditions the mires will turn into a source of greenhouse gases, thus enhancing the greenhouse effect. However, in the case of warming the increase in CH4 emission will be overruled by the increase in CO2 uptake on the long term, thus leading to a negative contribution again

Health economics: economic history, modelling, and public policy, in the New Zealand health care system

The focus of this thesis is health economics and the interface between the public and private hospital sectors within the New Zealand health care system. It summarises the distinctive elements which characterise consumer demand for health care; prices, time costs, third parties, real incomes, quality, environment, agency. Various models of supply of hospital care are considered encompassing the differing incentive structures to the major market participants. An economic history of the New Zealand hospital sector dates back to the early settlers, and helps explain the evolution of the current system. The thesis then introduces a theoretical model of the New Zealand hospital sector; specifically the area of non-acute or elective surgery which is most relevant for the interaction between the public and private hospital market. The elements of demand for health care are incorporated into the model which encompasses three specific sectors: public hospitals; private hospitals; and health insurance. Output and pricing policies and derived from the simultaneous interaction between the private and public sectors. The thesis considers the evolution of health insurance and the reasons behind the rapid growth in private health insurance membership during the 1960's and 1970's. The establishment of a major public accident insurance scheme was also introduced in New Zealand in the early 1970's. An empirical microeconometric study estimating the association between the major health variables lends weight to the hypothesis that public and private non-acute surgical treatment are close substitutes. Recent public policy changes in health care in New Zealand, are analysed, with emphasis on causes of market failure and an explanation why extensive government intervention is common to health care systems around the world