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OBJECTIVE: The purpose of this study is to introduce an efficient method for the optimization of iterative reconstruction CT protocols based on phantom image analysis and the comparison of obtained results with actual patient data. MATERIALS AND METHODS: We considered chest, abdomen, and pelvis CT examinations before the installation of an iterative reconstruction algorithm (iDose4) to define the exposure parameters used in clinical routine with filtered back projection (FBP). The body area of a CT phantom was subsequently scanned with various tube voltages and tube currents-exposure time products, and acquired data were reconstructed with FBP and different levels of iDose4. The contrast-to-noise ratio (CNR) for FBP with the original exposure parameters was calculated to define the minimum acceptable CNR value for each tube voltage. Then, an optimum tube current-exposure time products for each tube voltage and level of iterative reconstruction was estimated. We also compared findings derived by the phantom with real patient data by assessing dosimetric and image quality indexes from a patient cohort scanned with exposure parameters gradually adjusted during 1 year of adoption of iDose4. RESULTS: By use of the proposed phantom method, dose reduction up to 75% was achievable, whereas for an intermediate level of iteration (level 4), the dose reduction ranged between 50% and 60%, depending on the tube voltage. For comparison, with the gradual adjustment of exposure settings, the corresponding dose reduction for the same level of iteration was about 35%. CONCLUSION: The proposed method provides rapid and efficient optimization of CT protocols and could be used as the first step in the optimization process.
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Algoritmos , Dosis de Radiación , Protección Radiológica/métodos , Intensificación de Imagen Radiográfica/métodos , Interpretación de Imagen Radiográfica Asistida por Computador/métodos , Tomografía Computarizada por Rayos X/métodos , Humanos , Fantasmas de Imagen , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Tomografía Computarizada por Rayos X/instrumentaciónRESUMEN
OBJECTIVES: The aims of this study were to compare a commercially available reconstruction algorithm (iDose4) with filtered back projection (FBP) in terms of image quality (IQ) for both retrospective electrocardiographically gated and prospective electrocardiographically triggered cardiac computed tomographic angiography (CCTA) protocols and to evaluate the achievable radiation dose reduction. METHODS: A total cohort of 58 patients underwent either prospective CTCA or retrospective CTCA with full or reduced tube current-time product (in milliampere-second) protocol on a 64-slice multidetector computed tomographic scanner. All images were reconstructed with FBP, whereas the reduced milliampere-second images were also reconstructed using 2 levels (levels 4 and 6) of iDose4. Subjective and objective IQ was evaluated. RESULTS: Dose reductions of 43% in the retrospective CCTA protocol and 27% in the prospective CCTA protocol were achieved without compromising IQ. In the prospective CCTA protocol, the reduced-dose images were highly scored; thus, additional reduction of exposure settings is feasible. In the retrospective acquisition, dose reduction has led to similar IQ scores between the reduced-dose iDose4 images and the full-dose FBP images. Considering different reconstructions (FBP, iDose-L4 and -L6) of the same acquisition data, increase in iDose4 level resulted in less noisy images. A slight improvement was also noticed in all IQ indices; however, this improvement was not statistically significant for both acquisition protocols. CONCLUSIONS: This study demonstrated that the application of iDose at CCTA facilitates significant radiation dose reduction by maintaining diagnostic quality. The combination of iDose4 with prospective acquisition is able to significantly reduce effective dose associated with CTCA at values of approximately 2 mSv and even lower.
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Algoritmos , Angiografía Coronaria/métodos , Angiografía Coronaria/normas , Electrocardiografía/métodos , Dosis de Radiación , Tomografía Computarizada por Rayos X , Humanos , Persona de Mediana Edad , Tomografía Computarizada Multidetector , Estudios Prospectivos , Estudios RetrospectivosRESUMEN
The ongoing evolution of computer technology has made the use of iterative reconstruction (IR) algorithms clinically applicable. We reviewed current literature on the clinical use of IR against filtered back projection algorithms in terms of image quality and radiation dose. Iterative reconstruction algorithms provide equal or better image quality compared with filtered back projection, with dose reduction ranging from 25% to 98.6%. However, several studies have reported that the superior results of IR regarding objective evaluation are not always favorably interpreted by radiologists. Further clinical evaluation is needed to certify the optimal tradeoff between imaging quality and radiation dose, and radiologists need to become more familiar with the new appearance of computed tomographic images.
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Algoritmos , Carga Corporal (Radioterapia) , Dosis de Radiación , Protección Radiológica/métodos , Intensificación de Imagen Radiográfica/métodos , Interpretación de Imagen Radiográfica Asistida por Computador/métodos , Tomografía Computarizada por Rayos X/métodos , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
This paper reviews the history of surgical procedures developed for eradication of atrial fibrillation (AF) during cardiac surgery for structural heart disease, and in patients with AF without other indication for cardiac surgery. Current evidence indicates that, despite their proven efficacy, the Cox-Maze procedure and its modifications require cardiopulmonary bypass and cannot be easily justified in the case of AF without other indication for cardiac surgery. In patients undergoing cardiac surgery for mitral valve disease, concomitant ablation techniques using modifications of the Maze and alternative energy sources appear to be safe and effective in treating AF, especially in non-rheumatic disease. Minimally invasive epicardial ablation has been recently developed and can be performed on a beating heart through small access incision ports. Various techniques combining pulmonary vein isolation, ganglionated plexi ablation, and left atrial lines have been tried. Initial results are promising but further clinical experience is required to establish ideal lesion sets, appropriate energy sources, and the benefit-risk ratio of such an approach in patients without other indication for cardiac surgery. The role of surgical ablation in the current management of AF is under investigation.
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Fibrilación Atrial/cirugía , Procedimientos Quirúrgicos Cardíacos , Ablación por Catéter , Enfermedades de las Válvulas Cardíacas/cirugía , Fibrilación Atrial/complicaciones , Fibrilación Atrial/historia , Procedimientos Quirúrgicos Cardíacos/efectos adversos , Procedimientos Quirúrgicos Cardíacos/historia , Procedimientos Quirúrgicos Cardíacos/normas , Ablación por Catéter/efectos adversos , Ablación por Catéter/historia , Ablación por Catéter/normas , Enfermedades de las Válvulas Cardíacas/complicaciones , Enfermedades de las Válvulas Cardíacas/historia , Historia del Siglo XX , Historia del Siglo XXI , Humanos , Guías de Práctica Clínica como Asunto , Recurrencia , Resultado del TratamientoRESUMEN
The impact of the anatomic characteristics of coronary stenoses on the development of future coronary thrombosis has been controversial. This study aimed at identifying the anatomic and flow characteristics of left anterior descending (LAD) coronary artery stenoses that predispose to myocardial infarction, by examining angiograms obtained before the index event. We identified 90 patients with anterior ST-elevation myocardial infarction (STEMI) for whom coronary angiograms and their reconstruction in the three-dimensional space were available at 6 to 12 months before the STEMI, and at the revascularization procedure. The majority of culprit lesions responsible for STEMI occurred between 20 and 40 mm from the LAD ostium, whereas the majority of stable lesions not associated with STEMI were found in distances >60 mm (p < 0.001). Culprit lesions were significantly more stenosed (diameter stenosis 68.6 ± 14.2% vs 44.0 ± 10.4%, p < 0.001), and significantly longer than stable ones (15.3 ± 5.4 mm vs 9.2 ± 2.5 mm, p < 0.001). Bifurcations at culprit lesions were significantly more frequent (88.8%) compared with stable lesions (34.4%, p < 0.001). Computational fluid dynamics simulations demonstrated that hemodynamic conditions in the vicinity of culprit lesions promote coronary thrombosis due to flow recirculation. A multiple logistic regression model with diameter stenosis, lesion length, distance from the LAD ostium, distance from bifurcation, and lesion symmetry, showed excellent accuracy in predicting the development of a culprit lesion (AUC: 0.993 [95% CI: 0.969 to 1.000], p < 0.0001). In conclusion, specific anatomic and hemodynamic characteristics of LAD stenoses identified on coronary angiograms may assist risk stratification of patients by predicting sites of future myocardial infarction.
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Estenosis Coronaria/diagnóstico por imagen , Trombosis Coronaria/diagnóstico por imagen , Hemodinámica , Infarto del Miocardio con Elevación del ST/diagnóstico por imagen , Anciano , Angiografía Coronaria , Estenosis Coronaria/complicaciones , Estenosis Coronaria/fisiopatología , Trombosis Coronaria/etiología , Trombosis Coronaria/fisiopatología , Trombosis Coronaria/cirugía , Femenino , Humanos , Imagenología Tridimensional , Masculino , Persona de Mediana Edad , Infarto del Miocardio/diagnóstico por imagen , Infarto del Miocardio/etiología , Infarto del Miocardio/fisiopatología , Infarto del Miocardio/cirugía , Revascularización Miocárdica , Modelación Específica para el Paciente , Estudios Retrospectivos , Infarto del Miocardio con Elevación del ST/etiología , Infarto del Miocardio con Elevación del ST/fisiopatología , Infarto del Miocardio con Elevación del ST/cirugía , Índice de Severidad de la EnfermedadRESUMEN
In patients with stable coronary artery disease (CAD) blood hypercoagulability figures among factors leading to thrombosis. Tissue factor (TF) exposure at ruptured plaque initiates blood coagulation and hypercoagulability is responsible for thrombus formation. Early identification of patients eligible for angiography is a challenging issue for effective prevention of ACS. This pilot study aimed to identify biomarkers of hypercoagulability that can be prospectively used in risk assessment tools for the evaluation of CAD severity. Biomarkers of hypercoagulability could be a used for the evaluation of CAD severity. Platelet-poor plasma from 66 patients who were referred to coronary angiography was assessed for thrombin generation, phospholipid-dependent clotting time (Procoag-PPL ® ) and D-Dimers, and evaluated against atherosclerotic burden. Patients with CAD, as compared to controls, showed attenuated thrombin generation lag time: 4.7 (3.8-5.4) min versus 2.5 (2.1-2.9) min; p < 0.0001, shorter Procoag-PPL® clotting time 55.0(32-66) s versus 62.8 (42-85) s; p = 0.001), and higher D-Dimer levels 0.509 (0.27-2.58) µg/ml versus 0.309 (0.23-0.39) µg/ml; p = 0.038. Multivariate logistic regression model showed excellent discriminatory value in predicting CAD severity. The ROADMAP-CAD study showed that the Procoag-PPL® clotting time and thrombin Peak are informative for the the burden of the coronary atherosclerotic disease. The clinical relevance of this observation in the development of a new clinic-biological risk assessment model for early diagnosis of severe CAD has to be examined in a prospective study.
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Enfermedad de la Arteria Coronaria/sangre , Trombofilia/sangre , Anciano , Biomarcadores/sangre , Coagulación Sanguínea , Pruebas de Coagulación Sanguínea , Enfermedad de la Arteria Coronaria/diagnóstico , Femenino , Productos de Degradación de Fibrina-Fibrinógeno/análisis , Humanos , Masculino , Persona de Mediana Edad , Proyectos Piloto , Estudios Prospectivos , Medición de Riesgo , Trombofilia/diagnósticoRESUMEN
People in their everyday lives are exposed to radiation. Natural radiation is emitted from space, subsoil, and various materials which contain radioactive materials. Humans are also exposed to radiation from medical and industrial applications that use radioactive sources with artificial radioactive materials. Such radioactive sources may nevertheless get out of the control system and become orphan sources. Because these radiation sources are usually contained within metal shields such as lead and iron, the shields can end up as scrap metal being used in the metallurgical industry as raw material. Incidents have been recorded around the world, and several are reported in the literature and described here, where orphan sources have caused direct radiation exposure and/or environmental and personal contamination when the sources leaked. Timely and prompt recognition of an orphan radioactive source or device is crucial in order to minimize the radiological risk and its implications for the general population.
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Exposición a la Radiación/efectos adversos , Traumatismos por Radiación/prevención & control , Liberación de Radiactividad Peligrosa/estadística & datos numéricos , Humanos , Exposición a la Radiación/análisis , Traumatismos por Radiación/etiologíaRESUMEN
OBJECTIVE: To develop and implement a method for three-dimensional (3D) reconstruction of coronary arteries from conventional monoplane angiograms. BACKGROUND: 3D reconstruction of conventional coronary angiograms is a promising imaging modality for both diagnostic and interventional purposes. METHODS: Our method combines image enhancement, automatic edge detection, an iterative method to reconstruct the centerline of the artery and reconstruction of the diameter of the vessel by taking into consideration foreshortening effects. The X-Ray-based 3D coronary trees were compared against phantom data from a virtual arterial tree projected into two planes as well as computed tomography (CT)-based coronary artery reconstructions in patients subjected to coronary angiography. RESULTS: Comparison against the phantom arterial tree demonstrated perfect agreement with the developed algorithm. Visual comparison against the CT-based reconstruction was performed in the 3D space, in terms of the direction angle along the centerline length of the left anterior descending and circumflex arteries relative to the main stem, and location and take-off angle of sample bifurcation branches from the main coronary arteries. Only minimal differences were detected between the two methods. Inter- and intraobserver variability of our method was low (intra-class correlation coefficients > 0.8). CONCLUSION: The developed method for coronary artery reconstruction from conventional angiography images provides the geometry of coronary arteries in the 3D space.
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Angiografía Coronaria/métodos , Procesamiento de Imagen Asistido por Computador/métodos , Imagenología Tridimensional , Tomografía Computarizada por Rayos X/métodos , Algoritmos , Humanos , Variaciones Dependientes del Observador , Fantasmas de ImagenRESUMEN
OBJECTIVE: This study aimed at comparing three-dimensional (3-D) reconstruction with two-dimensional coronary angiograms with respect to anatomical parameters that might affect plaque formation and rupture. METHODS: Sixty patients with stable left anterior descending (LAD) lesions and 60 patients with an anteroseptal myocardial infarction and recanalized LAD were studied. RESULTS: Conventional angiography significantly underestimated the distance of the stenosis from the ostium of the LAD, 29.4+/-14.5 versus 35.3+/-18.5 mm, P<0.001. Vessel curvature at the site of the lesion was overestimated by conventional angiography compared with 3-D reconstruction, 147.6+/-30.6 degrees versus 162.3+/-11.2 degrees , P<0.001, as was axial bending of the LAD owing to ventricular contraction (17.8+/-7.78 degrees vs. 8.9+/-8.9 degrees , P<0.001). No agreement was observed between two-dimensional and 3-D analysis for either curvature on lesion or axial bending assessment, with intraclass correlation coefficient values 0.155 (-0.009, 0.315) and -0.022 (-0.183, 0.174), respectively. No significant agreement was found between the two methods in the detection of on-stenosis bifurcations (1.7%, kappa=0.086, P=0.349). CONCLUSION: Conventional coronary angiography cannot provide accurate estimates of anatomical parameters, such as distance of a coronary stenosis from the ostium of the vessel, coronary artery curvature at the site of stenosis, axial deformity and bending because of ventricular contraction, and classification of bifurcations. Reconstruction of the coronary tree in 3-D space is necessary for such estimations.
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Angiografía Coronaria/métodos , Estenosis Coronaria/diagnóstico por imagen , Procesamiento de Imagen Asistido por Computador/métodos , Infarto del Miocardio/diagnóstico por imagen , Anciano , Estenosis Coronaria/patología , Vasos Coronarios/patología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Infarto del Miocardio/patologíaRESUMEN
INTRODUCTION: There is growing evidence that atherosclerosis, as well as endothelial biology, depend on arterial wall shear stress (WSS). Several methods of WSS calculation with varying degrees of complexity have been proposed. This study aimed at investigating whether the most straightforward and easier to apply of these methods give comparable results in clinical practice. METHODS: Complete velocity encoding measurements using phase contrast magnetic resonance imaging were performed in 20 patients at a level perpendicular to the long axis of the ascending aorta approximately 2cm above the aortic valve. WSS was calculated at this location on maximum systole. MR imaging was accomplished on a 1.5T scanner. Four methods were applied to calculate WSS; three of them are based on the predictions of Poiseuille's theory of flow, while the last one is based on calculations resulting by the application of the definition of WSS. RESULTS: WSS calculated with the above mentioned methods was found to be in the range 4.2+/-1.8 to 3.5+/-1.7dynes/m(2). The velocity profile at the site of measurements can be described with a parabolic equation of the form u=ar(2)+br+c with an average r(2)=0.83, which is in good agreement with Poiseuille's theory of flow. Comparison of the results shows no statistically significant differences between WSS measurements calculated with these methods. DISCUSSION: The four methods are equivalent in calculating WSS at the ascending aorta when blood flow velocities have a good parabolic distribution.
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Aorta/patología , Aorta/fisiopatología , Interpretación de Imagen Asistida por Computador/métodos , Imagen por Resonancia Magnética/métodos , Modelos Cardiovasculares , Adulto , Anciano , Velocidad del Flujo Sanguíneo , Presión Sanguínea , Simulación por Computador , Módulo de Elasticidad , Femenino , Humanos , Masculino , Persona de Mediana Edad , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Resistencia al Corte , Estrés Mecánico , Adulto JovenRESUMEN
PURPOSE: Wall shear stress (WSS) appears to contribute significantly in the initiation and progression of atherosclerotic disease. The purpose of this work is to present in vivo systolic and diastolic WSS calculations in the human ascending aorta by the application of three straightforward methodologies based on Poiseuille's theory of flow. MATERIALS AND METHODS: Blood flow measurements were performed retrospectively in the ascending aorta of 20 non-atherosclerotic patients using phase-contrast MRI. WSS calculations were performed assuming Poiseuille's theory of flow based on average flow volume, average flow velocity and maximum flow velocity. Systolic and diastolic WSS values were calculated and compared with the calculated maximum and minimum values of WSS throughout the cardiac cycle. RESULTS: Systolic WSS values calculated by average flow volume, average flow velocity and maximum flow velocity were similar (0.4+/-0.2N/m(2), 0.4+/-0.3N/m(2)and 0.4+/-0.2N/m(2), respectively). Diastolic WSS values calculated by maximum flow velocity were significantly higher (11.6+/-7.0x10(-2)N/m(2)) compared to values calculated by average flow volume (0.3+/-0.9x10(-2)N/m(2)) and average flow velocity (0.3+/-1.0x10(-2)N/m(2)). Comparison of systolic and diastolic WSS values with maximum and minimum WSS values showed that time instances of maximum and minimum blood flow velocities do not coincide with time instances of maximum and minimum blood flow volume. CONCLUSION: In vivo calculation of WSS in the ascending aorta is feasible by phase-contrast MRI flow measurements and straightforward methodologies based on Poiseuille's theory of flow. However, measurements based on maximum flow velocity show larger deviations compared to measurements based on mean flow volume or mean flow velocity.
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Aorta/fisiología , Velocidad del Flujo Sanguíneo/fisiología , Diástole/fisiología , Interpretación de Imagen Asistida por Computador/métodos , Imagen por Resonancia Magnética/métodos , Modelos Cardiovasculares , Sístole/fisiología , Adulto , Anciano , Simulación por Computador , Módulo de Elasticidad , Femenino , Humanos , Masculino , Persona de Mediana Edad , Resistencia al Corte , Adulto JovenRESUMEN
BACKGROUND: One approach to improve ablation for atrial fibrillation (AF) is to focus on physiological targets including focal or rotational sources or ganglionic plexi (GP). However, the spatial relationship between these potential mechanisms has never been studied. We tested the hypothesis that rotors and focal sources for AF may co-localize with ganglionated plexi (GP). METHODS: We prospectively identified locations of AF rotors and focal sources, and correlated these to GP sites in 97 consecutive patients (age 59.9±11.4, 73% persistent AF). AF was recorded with 64-pole catheters with activation/phase mapping, and related to anatomic GP sites on electroanatomic maps. RESULTS: AF sources arose in 96/97 (99%) patients for 2.6±1.4 sources per patient (left atrium: 1.7±0.9 right atrium: 1.1±0.8), each with an area of 2-3cm2. On area analyses, the probability of an AF source randomly overlapping a GP area was 26%. Left atrial sources were seen in 94 (97%) patients, in whom ≥1 source co-localized with GP in 75 patients (80%; p<0.05). AF sources were more likely to colocalize with left vs right GPs (p<0.05), and colocalization was more likely in patients with higher CHADS2VASc scores (age>65, diabetes; p<0.05). CONCLUSIONS: This is the first study to demonstrate that clinically detected AF focal and rotational sources in the left atrium often colocalize with regions of autonomic innervation. Studies should define if the role of AF sources differs by their anatomical location.
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Fibrilación Atrial/fisiopatología , Fibrilación Atrial/cirugía , Ablación por Catéter/tendencias , Electrocardiografía/métodos , Ganglios Autónomos/fisiopatología , Adulto , Femenino , Humanos , Masculino , Estudios ProspectivosRESUMEN
The geometry of the coronary vessel network is believed to play a decisive role in the initiation, progression and outcome of coronary artery disease (CAD) and the occurrence of acute coronary syndromes (ACS). It also determines the flow field in the coronary artery which can be linked to CAD evolution. In this work geometric 3D models of left anterior descending (LAD) coronary arteries associated with either myocardial infarction (MI) or stable (STA) CAD were constructed. Transient numerical simulations of the flow for each model showed that specific flow patterns develop in different extent in the different groups examined. Recirculation zones, present distal the stenosis in all models, had larger extent and duration in MI cases. For mild stenosis (up to 50%) areas with low time averaged wall shear stress TAWSS (<0.15Pa) as well as areas with high TAWSS (>3Pa) appeared only in MI models; in moderate and severe stenosis (>50%) these areas were present in all models but were significantly larger for MI than STA models. These differentiations were expressed via numerical indices based on TAWSS, oscillating shear index (OSI) and relative residence time (RRT). Additionally we introduced the coagulation activation index (CAI), based on the threshold behaviour of coagulation initiation, which exceeded the suggested threshold only for MI models with intermediate stenosis (up to 50%). These results show that numerical simulations of flow can produce arithmetic indices linked with the risk of CAD complications.
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Simulación por Computador , Constricción Patológica/fisiopatología , Vasos Coronarios/fisiología , Hidrodinámica , Constricción Patológica/complicaciones , Vasos Coronarios/fisiopatología , Modelos Biológicos , Infarto del Miocardio/complicaciones , RiesgoRESUMEN
INTRODUCTION: The functional behavior and hemodynamic characteristics of percutaneously implanted bioprosthetic valves are not known. METHODS: We created aortic models after the simulated implantation of two of the most widely used bioprosthetic valves: the Edwards SAPIEN, and the Medtronic CoreValve. By using computational fluid dynamics analysis we sought to investigate variations in the aortic flow patterns induced by the two valve designs and their association with detrimental phenomena such as vascular remodeling, vascular wall damage and thrombosis. RESULTS: The simulated implantation of models that resemble the two valves resulted in different aortic flow conditions. Vortex formation in the upper ascending aorta was more persistent in the case of the simulated Medtronic valve. The ranges of average wall shear stress (WSS) values were 2.4-3.5 Pa for Edwards and 3.0-5.3 Pa for Medtronic; the calculated WSS values induced endothelial quiescence and an atheroprotective setting in both valves. The average shear stress on the simulated valve leaflets was low; however, hotspots were present in both valves (155.0 Pa for Edwards and 250.0 Pa for Medtronic) which would in theory be able to cause platelet activation and thus promote thrombosis. The pressure drops along the aorta were slightly lower for the Edwards compared to the Medtronic valve (198.0 Pa versus 218.0 Pa). CONCLUSIONS: The presented method allows the assessment of aortic flow conditions following the implantation of bioprosthetic valves. It may be useful in predicting detrimental flow phenomena, thus facilitating the selection of appropriate valve designs.
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Aorta/fisiología , Válvula Aórtica/cirugía , Bioprótesis , Modelos Cardiovasculares , Reemplazo de la Válvula Aórtica Transcatéter/métodos , Válvula Aórtica/fisiología , Velocidad del Flujo Sanguíneo , Simulación por Computador , Hemodinámica , HumanosRESUMEN
The assessment of functional severity of atherosclerotic stenoses in patients with coronary artery disease by invasive fractional flow reserve (FFR) measurement requires coronary artery cannulation, advancement of a wire and intravenous adenosine infusion with inherent procedure-related risk and costs. Coronary computed tomographic angiography (CCTA) and rotational coronary angiography (RA) have been recently used in conjunction with computational fluid dynamics (CFD) and image-based modelling for the determination of FFR without the need for additional imaging, modification of acquisition protocols or administration of medication. FFR derived from CCTA was demonstrated as superior to measures of CCTA stenosis severity for determination of lesion-specific ischaemia. Estimation of FFR from RA images and CFD provides a less invasive alternative to conventional FFR measurement while estimated values are in agreement with measured values. These new, combined anatomic-functional assessments have the potential to simplify the noninvasive diagnosis of coronary artery disease with a single study to identify patients with ischaemia-causing stenosis who may benefit from revascularisation.
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INTRODUCTION: The purpose of this study was to evaluate radiation dose reduction in coronary computerised tomography angiography (CCTA), using a commercially available iterative reconstruction (IR) algorithm as well as the behaviour of the image noise. METHODS: A total cohort of 47 patients underwent CCTA examination on a 64-slice multi-detector CT. They were divided into four groups according to the time when the examination was performed (before or after the installation of iDose) and the acquisition protocol followed (prospective or retrospective electrocardiography-ECG gated). The images acquired with reduced dose settings were reconstructed using two levels (L4 and L6) of the iDose4 algorithm. Image noise was measured in all cases. RESULTS: In retrospective acquisition, images acquired with a 46% lower radiation dose and reconstructed with iDose4 L6 provided noise comparable to that in the full-dose filtered back-projection images. For the prospective acquisition mode, a slight decrease (26%) in radiation dose resulted in noise improvement in low-dose images reconstructed with iDose4 L4 (16% noise removal) and L6 (30% noise removal). CONCLUSIONS: The fact that image quality is improved while radiation exposure is reduced indicates that there is room for a further reduction in exposure settings. Additionally, the combination of iDose4 with prospective acquisition is able to significantly reduce the radiation dose associated with CCTA at values of about 2 mSv and even lower.
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Angiografía Coronaria/métodos , Enfermedad Coronaria/diagnóstico por imagen , Procesamiento de Imagen Asistido por Computador , Dosis de Radiación , Intensificación de Imagen Radiográfica/métodos , Anciano , Algoritmos , Femenino , Humanos , Masculino , Persona de Mediana Edad , Tomografía Computarizada por Rayos X/métodosRESUMEN
INTRODUCTION: Renal sympathetic hyperactivity is vital for the maintenance and progression of essential hypertension. Catheter-based renal denervation is an evolving concept with favourable results regarding the control of hypertension; however, clinical experience is still limited. METHODS: We enrolled 15 patients with resistant hypertension who underwent percutaneous, catheter-based radiofrequency treatment for renal artery denervation. Patients were followed up for 4 to 13 months. RESULTS: Baseline mean blood pressure was 169/96 mmHg (SD 9/11), and patients were receiving a mean 3.9 ± 0.8 antihypertensive medications. Blood pressure values were reduced to 136/79 mmHg (SD 10/7), and antihypertensive medications to 2.9 ± 0.8 at 6.9 ± 3.4 months after the procedure. All procedures were uneventful and technically easy. The only drawbacks of the procedure are pain that the patient may feel during energy delivery, and the inability to obtain a sustained impedance reduction that allows completion of radiofrequency current delivery at some sites in the renal artery. CONCLUSIONS: Renal denervation facilitates control of resistant hypertension with reduction of medication, and appears to be a safe and technically easy procedure to accomplish.
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Ablación por Catéter/métodos , Hipertensión/cirugía , Arteria Renal/inervación , Arteria Renal/cirugía , Simpatectomía/métodos , Anciano , Femenino , Humanos , Masculino , Persona de Mediana Edad , Radiografía , Arteria Renal/diagnóstico por imagen , Resultado del TratamientoRESUMEN
The atrial sites associated with fractionated activity and/or high-frequency signals are commonly considered as targets of ablation for atrial fibrillation (AF); however, their temporal stability has not been established. A total of 21 patients with paroxysmal AF were studied. Left atrial (LA) ganglionated plexi (GP) were identified by high-frequency stimulation, and prolonged (3-minute) electrogram sampling from the GP and the posterior wall of the left atrium during AF was acquired. Fast Fourier transformation was used to determine the dominant frequencies (DFs) of the recorded electrogram signals and to study their temporal variability. The DF at the identified GP was 5.34 ± 0.78 Hz and at the posterior LA wall was 5.58 ± 0.87 Hz. Fractionation, expressed as electrograms exhibiting consecutive DFs deferring >20%, was detected at 21 of the studied GP (84%) and 7 of the posterior LA wall sites (44%). Fractionation, expressed as electrograms exhibiting DFs >8 Hz, was detected at 6 GP (24%) and 1 posterior LA wall site (6%). During the 3-minute recordings, the derived DFs were temporally variable, exhibiting an average coefficient of variation of 15.2 ± 12.0%. Fractionation, expressed by significant consecutive DF variability (>20%), was detected only for 18.0 ± 19.0% of the recording period at GP and for 12.7 ± 13.4% at the posterior LA wall. In conclusion, atrial electrograms are temporarily variable, and fractionation is transient at atrial sites associated with fractionated electrical activity during AF. Our results question the clinical validity of fractionated atrial electrograms for ablation purposes.
Asunto(s)
Fibrilación Atrial/fisiopatología , Electrocardiografía , Atrios Cardíacos/fisiopatología , Algoritmos , Análisis de Varianza , Fibrilación Atrial/diagnóstico por imagen , Femenino , Análisis de Fourier , Humanos , Masculino , Persona de Mediana Edad , Venas Pulmonares/diagnóstico por imagen , Procesamiento de Señales Asistido por Computador , Estadísticas no Paramétricas , Factores de Tiempo , Tomografía Computarizada EspiralRESUMEN
BACKGROUND: The ideal bifurcation stenting technique is not established, and data on the hemodynamic characteristics at stented bifurcations are limited. METHODS AND RESULTS: We used computational fluid dynamics analysis to assess hemodynamic parameters known affect the risk of restenosis and thrombosis at coronary bifurcations after the use of various single- and double-stenting techniques. We assessed the distributions and surface integrals of the time averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and relative residence time (t(r)). Single main branch stenting without side branch balloon angioplasty or stenting provided the most favorable hemodynamic results (integrated values of TAWSS=4.13·10(-4) N, OSI=7.52·10(-6) m(2), t(r)=5.57·10(-4) m(2)/Pa) with bifurcational area subjected to OSI values >0.25, >0.35, and >0.45 calculated as 0.36 mm(2), 0.04 mm(2), and 0 mm(2), respectively. Extended bifurcation areas subjected to these OSI values were seen after T-stenting: 0.61 mm(2), 0.18 mm(2), and 0.02 mm(2), respectively. Among the considered double-stenting techniques, crush stenting (integrated values of TAWSS=1.18·10(-4) N, OSI=7.75·10(-6) m(2), t(r)=6.16·10(-4) m(2)/Pa) gave the most favorable results compared with T-stenting (TAWSS=0.78·10(-4) N, OSI=10.40·10(-6) m(2), t(r)=6.87·10(-4) m(2)/Pa) or the culotte technique (TAWSS=1.30· 10(-4) N, OSI=9.87·10(-6) m(2), t(r)=8.78·10(-4) m(2)/Pa). CONCLUSIONS: In the studied models of computer simulations, stenting of the main branch with our without balloon angioplasty of the side branch offers hemodynamic advantages over double stenting. When double stenting is considered, the crush technique with the use of a thin-strut stent may result in improved immediate hemodynamics compared with culotte or T-stenting.
Asunto(s)
Angioplastia Coronaria con Balón , Circulación Coronaria/fisiología , Stents Liberadores de Fármacos , Hidrodinámica , Modelos Cardiovasculares , Simulación por Computador , Enfermedad de la Arteria Coronaria/epidemiología , Enfermedad de la Arteria Coronaria/fisiopatología , Enfermedad de la Arteria Coronaria/terapia , Reestenosis Coronaria/epidemiología , Reestenosis Coronaria/fisiopatología , Vasos Coronarios/fisiología , Everolimus , Humanos , Inmunosupresores/uso terapéutico , Factores de Riesgo , Sirolimus/análogos & derivados , Sirolimus/uso terapéuticoRESUMEN
Catheter ablation is an established therapeutic option for certain patients with atrial fibrillation (AF), but the reported success rates of anatomically oriented ablation techniques are low compared with those for other ablation indications, particularly for persistent AF. Electrophysiologically oriented ablation techniques have emerged over the last decade that aim at modifying the arrhythmogenic substrate to the extent that it cannot maintain fibrillatory activity. Electrogram-guided ablation procedures are the most common substrate-targeted ablation approaches and can be broadly divided into procedures that target atrial sites with particular electrogram characteristics in either the time domain (complex fractionated electrograms) or frequency components in the frequency domain (dominant frequencies). The concept of electrogram-based catheter ablation of AF by identifying complex fractionated electrograms and dominant frequency sites is valid only if these sites are temporally stable.