Coronary artery assessment by multidetector computed tomography in patients with prosthetic heart valves

Objectives Patients with prosthetic heart valves may require assessment for coronary artery disease. We assessed whether valve artefacts hamper coronary artery assessment by multidetector CT. Methods ECG-gated or -triggered CT angiograms were selected from our PACS archive based on the presence of prosthetic heart valves. The best systolic and diastolic axial reconstructions were selected for coronary assessment. Each present coronary segment was scored for the presence of valve-related artefacts prohibiting coronary artery assessment. Scoring was performed in consensus by two observers. Results Eighty-two CT angiograms were performed on a 64-slice ( = 27) or 256-slice ( = 55) multidetector CT. Eighty-nine valves and five annuloplasty rings were present. Forty-three out of 1160 (3.7%) present coronary artery segments were non-diagnostic due to valve artefacts (14/82 patients). Valve artefacts were located in right coronary artery (15/43; 35%), left anterior descending artery (2/43; 5%), circumflex artery (14/43; 32%) and marginal obtuse (12/43; 28%) segments. All cobalt-chrome containing valves caused artefacts prohibiting coronary assessment. Biological and titanium-containing valves did not cause artefacts except for three specific valve types. Conclusions Most commonly implanted prosthetic heart valves do not hamper coronary assessment on multidetector CT. Cobalt-chrome containing prosthetic heart valves preclude complete coronary artery assessment because of severe valve artefacts. Key Points Most commonly implanted prosthetic heart valves do not hamper coronary artery assessment Prosthetic heart valve composition determines the occurrence of prosthetic heart valve-related artefacts Bjork-Shiley and Sorin tilting disc valves preclude diagnostic coronary artery segment assessmen

Binary Population Synthesis: Methods, Normalization, and Surprises

In this paper we present a brief overview of population synthesis methods with a discussion of their main advantages and disadvantages. In the second part, we present some recent results from synthesis models of close binary compact objects with emphasis on the predicted rates, their uncertainties, and the model input parameters the rates are most sensitive to. We also report on a new evolutionary path leading to the formation of close double neutron stars (NS), with the unique characteristic that none of the two NS ever had the chance to be recycled by accretion. Their formation rates turn out to be comparable to or maybe even higher than those of recycled NS-NS binaries (like the ones observed), but their detection probability as binary pulsars is much smaller because of their short lifetimes. We discuss the implications of such a population for gravitational-wave detection of NS-NS inspiral events, and possibly for gamma-ray bursts and their host galaxies.Comment: 15 pages, 1 figure, to appear in the proceedings ``The influence of binaries on stellar population studies'', Brussels, August 2000 (Kluwer Academic Publishers), ed. D.Vanbevere

Muscle Fiber Type-Dependent Differences in the Regulation of Protein Synthesis

This study examined fiber type-dependent differences in the regulation of protein synthesis in individual muscle fibers found within the same whole muscle. Specifically, the in vivo SUrface SEnsing of Translation (SUnSET) methodology was used to measure protein synthesis in type 1, 2A, 2X and 2B fibers of the mouse plantaris muscle, in response to food deprivation (FD), and mechanical overload induced by synergist ablation (SA). The results show that 48 h of FD induced a greater decrease in protein synthesis in type 2X and 2B fibers compared to type 1 and 2A fibers. Type 2X and 2B fibers also had the largest FD-induced decrease in total S6 protein and Ser240/244 S6 phosphorylation, respectively. Moreover, only type 2X and 2B fibers displayed a FD-induced decrease in cross-sectional area (CSA). Ten days of SA also induced fiber type-dependent responses, with type 2B fibers having the smallest SA-induced increases in protein synthesis, CSA and Ser240/244 S6 phosphorylation, but the largest increase in total S6 protein. Embryonic myosin heavy chain (MHCEmb) positive fibers were also found in SA muscles and the protein synthesis rates, levels of S6 Ser240/244 phosphorylation, and total S6 protein content, were 3.6-, 6.1- and 2.9-fold greater than that found in fibers from control muscles, respectively. Overall, these results reveal differential responses in the regulation of protein synthesis and fiber size between fiber types found within the same whole muscle. Moreover, these findings demonstrate that changes found at the whole muscle level do not necessarily reflect changes in individual fiber types