Effects of critical coronary stenosis on global systolic left ventricular function quantified by pressure-volume relations during dobutamine stress in the canine heart

AbstractObjectives. In this study we quantified the effects of a critical coronary stenosis on global systolic function using pressure-volume relations at baseline and during incremental dobutamine stress.Background. The effects of coronary stenosis have previously been analyzed mainly in terms of regional (dys)function. Global hemodynamics are generally considered normal until coronary flow is substantially reduced. However, pressure-volume analysis might reveal mechanisms not fully exposed by potentially load-dependent single-beat parameters. Moreover, no systematic analysis by pressure-volume relations of the effects of dobutamine over a wide dose range has previously been presented.Methods. In 14 dogs left ventricular volume and pressure were measured by conductance and micromanometer catheters, and left circumflex coronary flow by Doppler probes. Measurements in control and with left circumflex stenosis were performed at baseline and at five levels of dobutamine (2.5 to 20 μg/kg/min). The end-systolic pressure-volume relation (ESPVR) dP/dtMAX− vs. end-diastolic volume (dP/dtMAX− VED) and the relation between stroke work and end-diastolic volume (preload recruitable stroke work [PRSW]) were derived from data obtained during gradual caval occlusion.Results. In control, dobutamine gradually increased heart rate up to 20 μg/kg/min, the inotropic effect blunted at 15 μg/kg/min. With stenosis, the chronotropic effect was similar, however, contractile state was optimal at approximately 10 μg/kg/min and tended to go down at higher levels. At baseline, the positions of ESPVR and PRSW, but not of dP/dtMAX− VED, showed a significant decrease in function with stenosis. No differences between control and stenosis were present at 2.5 μg/kg/min; the differences were largest at 15 μg/kg/min.Conclusions. Pressure-volume relations and incremental dobutamine may be used to quantify the effects of critical coronary stenosis. The positions of these relations are more consistent and more useful indices than the slopes. The positions of the ESPVR and PRSW show a reduced systolic function at baseline, normalization at 2.5 μg/kg/min and a consistent significant difference between control and stenosis at dobutamine levels of 5 μg/kg/min and higher

Impact of cognitive radio on radio astronomy

The introduction of new communication techniques requires an increase in the efficiency of spectrum usage. Cognitive radio is one of the new techniques that fosters spectrum efficiency by using unoccupied frequency spectrum for communications. However, cognitive radio will increase the transmission power density and cause an increasing level of Radio Frequency Interference (RFI), which may impact other services and particularly passive users of the spectrum. In this paper we present the principles of cognitive radio and introduce a model for its impact on radio astronomy

Der Heiland lebt : de drie vroegste Paascantates van Johann Sebastian Bach : een theologisch-muzikale analyse

In dit onderzoek vraagt van de te bespreken drie vroegste Paascantates van Johann Sebastian Bach, BWV 4, BWV 31 en BWV 66, allereerst de koraaltekst de aandacht. Daarbij worden theologische lijnen, Bijbelse beelden, metaforen en sleutelwoorden naar voren gehaald en in onderling verband geplaatst. Daarna volgt een muzikale analyse met aandacht voor muzikaal-retorische figuren, inzet van instrumenten en stemmen, maatsoorten, toonsoorten en andere muzikale middelen waarvan Bach zich bediende. Ten slotte worden tekst en muziek betrokken in een onderlinge exegese, waarin wordt nagegaan welke Bijbels-theologische elementen uit de cantateteksten door Bach in de muziek zijn benadrukt. Van belang daarbij is de vraag in welke mate Bach in zijn muziek uiting heeft gegeven aan zijn geestelijke opvattingen, alsmede in hoeverre hij daarbij aansluiting vond bij theologische uitgangspunten van het lutheranisme. Gebruik is gemaakt van voor Bach belangrijke auteurs, zoals Abraham Calov, Martin Luther, Heinrich Müller, Erdmann Neumeister en August Pfeiffer, van wie werken in Bachs bibliotheek aanwezig waren en die ten behoeve van dit onderzoek zijn bestudeerd. Onderzoek heeft aangetoond dat Bach veel waardering had voor genoemde auteurs en hun werken, zoals onder meer blijkt uit zijn aantekeningen in de Calov-commentaar, het verklanken van teksten van Müller en het feit dat opvattingen van Pfeiffer in zijn oeuvre worden weerspiegeld. In deze studie zal Bach worden geplaatst in de geestelijke context van zijn tijd, teneinde zijn intenties te kunnen beschrijven. Dit onderzoek draagt de titel: “Der Heiland lebt”. Deze woorden, genomen uit het eerste Recitativo van BWV 66, vatten de inhoud van de drie besproken Paascantates kernachtig samen

Automatic aortic root landmark detection in CTA images for preprocedural planning of transcatheter aortic valve implantation

Transcatheter aortic valve implantation is currently a well-established minimal invasive treatment option for patients with severe aortic valve stenosis. CT Angiography is used for the pre-operative planning and sizing of the prosthesis. To reduce the inconsistency in sizing due to interobserver variability, we introduce and evaluate an automatic aortic root landmarks detection method to determine the sizing parameters. The proposed algorithm detects the sinotubular junction, two coronary ostia, and three valvular hinge points on a segmented aortic root surface. Using these aortic root landmarks, the automated method determines annulus radius, annulus orientation, and distance from annulus plane to right and left coronary ostia. Validation is performed by the comparison with manual measurements of two observers for 40 CTA image datasets. Detection of landmarks showed high accuracy where the mean distance between the automatically detected and reference landmarks was 2.81 ± 2.08 mm, comparable to the interobserver variation of 2.67 ± 2.52 mm. The mean annulus to coronary ostium distance was 16.9 ± 3.3 and 17.1 ± 3.3 mm for the automated and the reference manual measurements, respectively, with a mean paired difference of 1.89 ± 1.71 mm and interobserver mean paired difference of 1.38 ± 1.52 mm. Automated detection of aortic root landmarks enables automated sizing with good agreement with manual measurements, which suggests applicability of the presented method in current clinical practic

The link between market orientation and performance in the Australian public sector

Marketing academics and practitioners assume a direct link between market orientation and performance and argue that this applies to both business and non-business organisations. While this aspect has been studied in the business sector, this paper discusses the concepts of market orientation and performance and investigates this relationship in the Australian public sector. The conceptualization of market orientation used is that by Jaworski and Kohli (1993) on which basis MARKOR was developed. This instrument together with an instrument to measure the perceptions of performance of senior managers in the Australian public sector are used to investigate the hypothesized link. The findings confirm a positive relationship between market orientation and performance. The size and type of public sector organisation involved are also found to affect the levels of market orientation together with its components and performance. From the findings, implication are drawn and directions for future research discussed.peer-reviewe

Targeted versus universal prevention. a resource allocation model to prioritize cardiovascular prevention

<p>Abstract</p> <p>Background</p> <p>Diabetes mellitus brings an increased risk for cardiovascular complications and patients profit from prevention. This prevention also suits the general population. The question arises what is a better strategy: target the general population or diabetes patients.</p> <p>Methods</p> <p>A mathematical programming model was developed to calculate optimal allocations for the Dutch population of the following interventions: smoking cessation support, diet and exercise to reduce overweight, statins, and medication to reduce blood pressure. Outcomes were total lifetime health care costs and QALYs. Budget sizes were varied and the division of resources between the general population and diabetes patients was assessed.</p> <p>Results</p> <p>Full implementation of all interventions resulted in a gain of 560,000 QALY at a cost of €640 per capita, about €12,900 per QALY on average. The large majority of these QALY gains could be obtained at incremental costs below €20,000 per QALY. Low or high budgets (below €9 or above €100 per capita) were predominantly spent in the general population. Moderate budgets were mostly spent in diabetes patients.</p> <p>Conclusions</p> <p>Major health gains can be realized efficiently by offering prevention to both the general and the diabetic population. However, a priori setting a specific distribution of resources is suboptimal. Resource allocation models allow accounting for capacity constraints and program size in addition to efficiency.</p