ABSTRACT
OBJECTIVE: Transcatheter aortic valve replacement (TAVR) has been established as an alternative therapy for patients with severe aortic stenosis who are unfit for the surgical aortic valve replacements. Pre and periprocedural imaging for the TAVR procedure is the key to procedural success. Currently transesophageal echocardiography (TOE), including real-time three-dimensional (RT-3D) imaging TOE, has been used for peri-interventional monitoring and guidance for TAVR. We describe our initial experience with real-time three-dimensional intracardiac echocardiography (RT-3DICE), imaging technology for the use in the TAVR procedure. METHODS: We used RT-3DICE using an ACUSON SC2000 2.0v (Siemens Medical Solution), and a 10F AcuNav V catheter (Siemens-Acuson, Inc, Mountain View, California, USA) in addition to preoperative multislice CT (MSCT) in total of five patients undergoing TAVR procedure. RESULTS: Aortic annulus and sinus of valsalva diameters were measured using RT-3DICE. Aortic valve measurements obtained using RT-3DICE are comparable to those obtained using MSCT with no significant difference in our patients. CONCLUSIONS: This small study of five patients shows the safe use of RT-3DICE in TAVR Procedure and may help the procedures performed under local anaesthesia without the need for TOE.
ABSTRACT
UNLABELLED: The use of echocardiography, whilst well established in cardiology, is a relatively new concept in critical care medicine. However, in recent years echocardiography's potential as both a diagnostic tool and a form of advanced monitoring in the critically ill patient has been increasingly recognised. In this series of Critical Care Echo Rounds, we explore the role of echocardiography in critical illness, beginning here with haemodynamic instability. We discuss the pathophysiology of the shock state, the techniques available to manage haemodynamic compromise, and the unique role which echocardiography plays in this complex process. CASE: A 69-year-old female presents to the emergency department with a fever, confusion and pain on urinating. Her blood pressure on arrival was 70/40, with heart rate of 117âbpm Despite 3âl of i.v. fluid she remained hypotensive. A central venous catheter was inserted and noradrenaline infusion commenced, and she was admitted to the intensive care unit for management of her shock state. At 6âh post admission, she was on high dose of noradrenaline (0.7âµg/kg per min) but blood pressure remained problematic. An echocardiogram was requested to better determine her haemodynamic state.
ABSTRACT
We report a systematic molecular dynamics study of the isochoric equilibration of hard-sphere fluids in their metastable regime close to the glass transition. The thermalization process starts with the system prepared in a nonequilibrium state with the desired final volume fraction Ï for which we can obtain a well-defined nonequilibrium static structure factor S(0)(k;Ï). The evolution of the α-relaxation time τ(α)(k) and long-time self-diffusion coefficient D(L) as a function of the evolution time t(w) is then monitored for an array of volume fractions. For a given waiting time the plot of τ(α)(k;Ï,t(w)) as a function of Ï exhibits two regimes corresponding to samples that have fully equilibrated within this waiting time [Ï≤Ï(c)(t(w))] and to samples for which equilibration is not yet complete [Ï≥Ï(c)(t(w))]. The crossover volume fraction Ï(c)(t(w)) increases with t(w) but seems to saturate to a value Ï(a)≡Ï(c)(t(w)â∞)≈0.582. We also find that the waiting time t(w)(eq)(Ï) required to equilibrate a system grows faster than the corresponding equilibrium relaxation time, t(w)(eq)(Ï)≈0.27[τ(α)(eq)(k;Ï)](1.43), and that both characteristic times increase strongly as Ï approaches Ï(a), thus suggesting that the measurement of equilibrium properties at and above Ï(a) is experimentally impossible.
