In recent years, the trend towards the performance maximization of modern internal combustion engines has led to the creation of accurate simulation models to optimize the engine design and operating ...conditions. Temperature management is crucial to achieve the performance goals of an internal combustion engine without affecting the component’s reliability. Formula 1 mandates that only a limited number of experimental tests can be performed, which leads to the necessity of simulators capable of substituting empirical tests. Furthermore, the requirement of adapting the vehicle setup before each race weekend to maximize the performance on each circuit layout necessitates short computational time. To address this, the development of a zero-dimensional model of the thermal flows within an engine is presented in this paper. This model allows to precisely compute the dynamic variations of all the heat flows inside the combustion engine, excluding only the radiative ones and the engine components’ temperatures. The new simulation approach has been developed and validated on a Formula 1 engine and shown to be precise and fast. The results demonstrate the value of the proposed model with an average engine fluid temperature error of less than 1 °C for a computational cost comparable with on-board applications.
Abstract Objectives This study explored whether cardiac magnetic resonance (CMR) could help select patients who could benefit from revascularization by identifying inducible myocardial ischemia and ...viability in the perfusion territory of the artery with chronic total occlusion (CTO). Background The benefit of revascularization using percutaneous coronary intervention (PCI) in CTO is controversial. CMR offers incomparable left ventricular (LV) systolic function assessment in addition to potent ischemic burden quantification and reliable myocardial viability analysis. Whether CMR guided CTO revascularization would be helpful to such patients has not yet been explored fully. Methods A prospective study of 50 consecutive CTO patients was conducted. Of 50 patients undergoing baseline stress CMR, 32 (64%) were selected for recanalization based on the presence of significant inducible perfusion deficit and myocardial viability within the CTO arterial territory. Patients were rescanned 3 months after successful CTO recanalization. Results At baseline, myocardial perfusion reserve (MPR) in the CTO territory was significantly reduced compared with the remote region (1.8 ± 0.72 vs. 2.2 ± 0.7; p = 0.01). MPR in the CTO region improved significantly after PCI (to 2.3 ± 0.9; p = 0.02 vs. baseline) with complete or near-complete resolution of CTO related perfusion defect in 90% of patients. Remote territory MPR was unchanged after PCI (2.5 ± 1.2; p = NS vs. baseline). The LV ejection fraction increased from 63 ± 13% to 67 ± 12% (p < 0.0001) and end-systolic volume decreased from 65 ± 38 to 56 ± 38 ml (p < 0.001) 3 months after CTO PCI. Importantly, despite minimal post-procedural infarction due to distal embolization and side branch occlusion in 8 of 32 patients (25%), the total Seattle Angina Questionnaire score improved from a median of 54 (range 45 to 74) at baseline to 89 (range 77 to 98) after CTO recanalization (p < 0.0001). Conclusions In this small group of patients showing CMR evidence of significant myocardial inducible perfusion defect and viability, CTO recanalization reduces ischemic burden, favors reverse remodeling, and ameliorates quality of life.
Transient loss of consciousness initially diagnosed as epileptic seizures and then documented as paroxysmal atrioventricular block. Cardiac resynchronization and defibrillator therapy guided by a ...multimodality approach.
Transient loss of consciousness initially diagnosed as epileptic seizures and then documented as paroxysmal atrioventricular block. Cardiac resynchronization and defibrillator therapy guided by a multimodality approach.
Vagus nerve stimulation (VNS) is a useful tool for drug-resistant epilepsy, but it induces known laryngeal side effects, with a significant role on patients’ quality of life. VNS patients may show ...persistent left vocal fold (LVF) palsy at rest and/or recurrent LVF adduction during stimulation. This study aims at electromyographically evaluating laryngeal muscles abnormalities in VNS patients. We compared endoscopic laryngeal evaluation data in six VNS patients with laryngeal muscle electromyography (LMEMG) carried out on the thyroarytenoid, cricothyroid, posterior cricoarytenoid, and cricopharyngeal muscles. Endoscopy showed LVF palsy at rest in 3/6 patients in whom LMEMG documented a tonic spastic activity with reduced phasic modulation. In four out of six patients with recurrent LVF adduction during VNS activation, LMEMG showed a compound muscle action potential persisting for the whole stimulation. This is the first LMEMG report of VNS-induced motor unit activation via recurrent laryngeal nerve and upper laryngeal nerve stimulation. LMEMG data were could, therefore, be considered consistent with the endoscopic laryngeal examination in all patient.
Abstract Background The incidence and predictors of contrast-induced nephropathy (CIN) after percutaneous coronary intervention (PCI) of chronic total occlusions (CTO) have not been specifically ...reported. Methods This retrospective analysis included all consecutive patients referred for PCI of CTO between April 2003 and March 2008, with baseline and 24 h postprocedural available creatinine levels. CIN was defined as 24 h postprocedural increase of baseline creatinine levels ≥ 0.5 mg/dl (CIN05 ) or ≥ 25% (CIN25 ). Severe renal dysfunction (SRD) was defined as acute renal failure requiring dialysis, or an increase in baseline creatinine levels ≥ 2.0 mg/dl (SRD2 ) or ≥ 50% (SRD%). Patients were classified into risk categories for CIN, according to the validated Mehran risk score. Results A total of 227 patients were included, mean age of 64 ± 10 years, the majority being at low risk for CIN (55% with ≤ 5 points in the Mehran score). CIN25 occurred in 6.16% (14/227) patients and CIN05 in 0.88% (2/227). The incidence of SRD2 or SDR% was 0% (0/227) and 0.9% (2/227), respectively, with no patient requiring dialysis. Patients who developed CIN25 received a higher contrast volume than those who did not (312 ml (210–400) vs 260 ml (200–345), p = 0.14), but the difference was not statistically significant. Conclusions In this consecutive cohort of patients, the incidence of CIN following PCI for CTO was low despite the administration of moderate to large volumes of contrast media. Attempts at revascularization of CTO should not be discouraged or be prematurely interrupted because of the fear of CIN.
Abstract Background The introduction of optical coherence tomography (OCT) as an intracoronary imaging modality has allowed accurate assessment of strut apposition and neointimal tissue coverage. ...This study set out to assess the inter and intraobserver variability of measurements of acute stent apposition and strut tissue coverage using OCT. Methods Thirty patients were studied (14 immediately after stent implantation and 16 during follow-up angiography mean of 4.7 ±2.8 months) using OCT (LightLab, Westford, Massachusetts, US). Data analysis was performed by 2 experienced observers. Struts were classified as “embedded", “protruding" or “malapposed" to the vessel well and recorded as percentage of total struts. Intimal coverage at follow-up was measured as the thickness of tissue covering each strut expressed in μm. Intra and interobserver variability was assessed by Bland-Altman plots and by calculation of the intraclass correlation coefficient (ICC). Results An average of 3967 struts was examined by each observer and, overall, 53.7% of struts was embedded, 36.4% protruding and 9.9% malapposed. Low intraobserver variability for all measures of strut apposition was found, with repeatability coefficients that ranged between 5.1% and 9.3% and ICC exceeding 95% in all cases. Interobserver variability was also low (repeatability coefficients 6.6–10.8 and ICC > 91.3%). Mean intimal thickness in the follow-up group was 172.5 µm. Bland-Altman plots demonstrated a low intraobserver and interobserver variability for intimal thickness, with repeatability coefficients 26.7 μm and 24.1 μm, respectively and ICC exceeding 98.6% for both. Conclusions Low intra and interobserver variability can be expected when analyzing OCT data for stent apposition and tissue coverage. This supports the validity of OCT as a clinical and research tool in the setting of intracoronary stent imaging.
Although the rate of procedural complications during transcatheter aortic valve implantation has decreased because of technological advancement and increased operator experience, device embolization ...remains a rare but potentially fatal complication, even with new generation devices. We report, to our knowledge, the first case of Portico valve (St Jude Medical, Minneapolis, MN) migration despite apparent optimal initial implantation depth, which was retrieved using a novel strategy after failure of a traditional retrieval technique. We also describe a mechanism of left coronary artery systolic perfusion with diastolic backflow, which led to myocardial ischemia.
Bien que les avancées technologiques et la plus grande expérience des opérateurs aient fait diminuer le taux de complications liées à l’intervention durant l’implantation valvulaire aortique par cathéter, l’embolisation liée au dispositif demeure une complication rare, mais potentiellement fatale, même avec des dispositifs de nouvelle génération. En dépit de la profondeur optimale apparente de l’implantation initiale, c’est à notre connaissance le premier cas de migration de la prothèse valvulaire Portico (St Jude Medical, Minneapolis, MN), qui a pu être récupérée selon une nouvelle stratégie après l’échec de la technique de récupération traditionnelle. Nous décrivons également un mécanisme de perfusion de l’artère coronaire gauche en systole accompagnée d’un reflux en diastole qui a mené à l’ischémie myocardique.
Abstract Drug-eluting stents (DES) have made a tremendous impact on the practice of percutaneous coronary intervention. Recently however, long-term DES failures have become a focal point, ...particularly with restenosis and thrombosis. An uncommon, yet important cause of DES failure is stent fracture. Of the two established first generation DES, the sirolimus-eluting stent (SES) has been particularly linked to cases of stent fracture, likely as a result of its closed cell design compared with other DES employing an open cell system. We present 2 cases of SES fracture confirmed using high-resolution intravascular optical coherence tomography giving unique insights into the in-vivo appearance of this complication.
The 2-dimensional silhouette image provided by coronary angiography has well-recognized limitations. Angiographic images do not accurately represent the true complexity of the luminal morphology in ...coronary disease and give no indication of the functional influence of luminal changes on coronary blood flow. These limitations are more pronounced in angiographically intermediate stenoses and in patients in whom there is a clear discrepancy between the clinical picture and angiographic findings. In such cases there is often poor concordance between the estimated percentage angiographic stenosis and the corresponding intravascular ultrasound image or noninvasive functional data. The validation and clinical availability of robust and accurate physiologic indices, which can be used as an adjunct to diagnostic angiography in the cardiac catheterization laboratory, have been pivotal in promoting ischemia-driven coronary revascularization. Deferral or revascularization based on such physiologic indices is associated with improved clinical outcome as well as more favorable health economic data. Although there are several clinical indices, fractional flow reserve remains the "gold standard," with indications for physiologic assessment of angiographic intermediate stenoses, including left main stem stenoses and ostial disease as well as serial lesions. The availability of such indices is an important step in streamlining management of patients undergoing cardiac catheterization by allowing routine provision of an "all-in-one" ischemia-driven revascularization service.
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