Search

In order to better understand the attenuation characteristics in the crust of the central and western Tien Shan orogenic belt, we investigate both Qp and Qs values by applying the extended coda-normalization method. We estimate the frequency-dependent attenuation of both P and S waves in the frequency band of 1.0–20.0 Hz using data from local networks. The average frequency relations of Qp and Qs have been derived as Qp = (61 ± 9) × f(1.21±0.08) and Qs = (77 ± 6) × f(1.11±0.04) by fitting a power-law frequency dependence model for the study region. The low Q0 and high η values indicate that the central and western Tien Shan is a tectonically and seismically active region. We also find lateral variations of both Qp,s and Qs/Qp values, reflecting complex tectonic structures in the study area. In general, the relatively high-attenuation areas corresponding to tectonically active regions are found beneath mountainous ranges in the central Tien Shan whereas the relatively low-attenuation areas are associated with stable regions, such as Fergana Basin and Issyk-Kul Lake. Besides, regions in the central Tien Shan with Qs/Qp > 1 are likely partially saturated with fluids or rich in scattering heterogeneities, whereas regions in the western Tien Shan display Qs/Qp < 1, possibly suggesting almost complete fluid saturation. [ABSTRACT FROM AUTHOR]

Background Optimizing systemic oxygen delivery ( DO2) and hemodynamics in children with hypoplastic left heart syndrome ( HLHS) is a clinical challenge. Mathematical modeling of the HLHS circulation has been used to determine the relationship between oxygen kinetic parameters and DO2 and to determine how DO2 might be optimized. The model demonstrates that neither arterial oxygen saturation (SaO2) nor mixed venous oxygen saturation (SvO2) alone accurately predicts DO2. Objectives Oxygen delivery kinetics predicted by previously described mathematical modeling were compared with actual patients' hemodynamic data. We sought to determine which patient derived parameters correlated best with DO2. Methods Patients with HLHS who underwent cardiac catheterization prior to surgery to create a superior cavopulmonary anastomosis from 2007 to 2011 were identified. Hemodynamic data obtained were compared with the data derived from the mathematical model. Correlations between SaO2, SvO2, SaO2-SvO2, SaO2/(SaO2-SvO2), pulmonary-to-systemic blood flow ratio ( Qp/ Qs), and DO2 were evaluated using both linear and nonlinear analyses, and R2 was calculated. Results/Conclusions Patients' data fit most aspects of the mathematical model. DO2 had the best correlation with SaO2/(SaO2-SvO2; R2 = 0.8755) followed by SaO2-SvO2 ( R2 = 0.8063), while SaO2 or SvO2 alone did not demonstrate a significant correlation as predicated by the mathematical model ( R2 = 0.09564 and 0.4831, respectively). SaO2/(SaO2-SvO2) would be useful clinically to track changes in DO2 that occur with changes in patient condition or with interventions. [ABSTRACT FROM AUTHOR]

Purpose: Phase-contrast Cardiovascular Magnetic Resonance Imaging (CMR) generally requires the analysis of stationary tissue adjacent to a blood vessel to serve as a baseline reference for zero velocity. However, for the heart and great vessels, there is often no stationary tissue immediately adjacent to the vessel. Consequently, uncorrected velocity offsets may introduce substantial errors in flow quantification. The purpose of this study was to assess the magnitude of these flow errors and to validate a clinically applicable method for their correction. Materials and Methods: In 10 normal volunteers, phase-contrast CMR was used to quantify blood flow in the main pulmonary artery (Qp) and the aorta (Qs). Following image acquisition, phase contrast CMR was performed on a stationary phantom using identical acquisition parameters so as to provide a baseline reference for zero velocity. Aortic and pulmonary blood flow was then corrected using the offset values from the phantom. Results: The mean difference between pulmonary and aortic flow was 26 ± 21 mL before correction and 7.1 ± 6.6 mL after correction (p = 0.002). The measured Qp/Qs was 1.25 ± 0.20 before correction and 1.05 ± 0.07 after correction (p = 0.001). Conclusion: Phase-contrast CMR can have substantial errors in great vessel flow quantification if there is no correction for velocity offset errors. The proposed method of correction is clinically applicable and provides a more accurate measurement of blood flow. [ABSTRACT FROM AUTHOR]

: ObjectivesThis study sought to analyze the safety, efficacy, and follow-up results of percutaneous closure of secundum atrial septal defect (ASD) in young children.: BackgroundResults of ASD transcatheter closure in adults are widely reported but there are no large published series concerning young children.: MethodsBetween December 1996 and February 2002, 48 of 553 patients percutaneously treated at our institution were children age ≤5 years. Indications for closure were: elective closure in 32 patients; frequent respiratory infections in 8; failure to thrive in 2; liver transplantation in 5; and a fenestrated Fontan in 1. The procedure was carried out under general anesthesia with fluoroscopy and transesophageal control. Two different devices were used: 1) the CardioSEAL/StarFLEX (CS/SF) and 2) the Amplatzer septal occluder (ASO). Basal physical examinations and echocardiograms were performed prior to the procedure and at follow-ups (1, 6, and 12 months, and yearly thereafter).: ResultsThe mean age at closure was 3.6 ± 1.3 years. A CS/SF was used in 10 subjects; an ASO was used in 38 patients. No deaths or immediate major complications occurred. The total occlusion rate was 87% at procedure, rising to 94% at discharge. The mean follow-up was 18 ± 14 months. No midterm major or minor complications occurred. The occlusion rate rose to 100% at 12 months of follow-up. Symptomatic patients improved significantly.: ConclusionsIn the current era and in experienced hands, ASD closure can be performed safely and successfully, even in very young children. [Copyright &y& Elsevier]

: ObjectivesThe purpose of the study was to assess the long-term outcome of patients with small ventricular septal defects (VSDs) considered not to require surgical closure during childhood.: BackgroundAlthough patients with small VSDs have generally been considered not to require surgery, more recent data suggest that a significant percentage of these patients develop serious problems during adult life.: MethodsA total of 229 consecutive patients (115 females) with a VSD considered too small to require surgery during childhood as defined by normal pulmonary artery pressure, less than 50% shunt, pulmonary vascular resistance ≤200 dynes·s·cm−5, no VSD-related aortic regurgitation (AR), and no symptoms and who had no additional hemodynamically relevant heart defect were followed in an adult congenital heart disease program. Physical examination, electrocardiography, and echocardiography were performed in all patients in one- to three-year intervals; exercise tests and Holter monitoring were performed in 140 and 127 patients, respectively.: ResultsFollow-up was completed in 222 patients (97%). Mean age at last visit was 30 ± 10 years. Spontaneous VSD closure was observed in 14 patients (6%). No patients died, four patients (1.8%) had an episode of endocarditis, of whom two required aortic valve replacement, and one additional patient (0.4%) had surgical closure for hemodynamic reasons. For 118 patients who entered the study between 1993 and 1996 and were prospectively followed for 7.4 ± 1.2 years, event-free survival with end points defined as death, endocarditis or heart surgery was 99.1 ± 0.8% at three years, 96.5 ± 1.7% at six years and 95.5 ± 1.9% at eight years. At last visit, 94.6% of all patients studied were symptom free. Left ventricular (LV) size by echocardiography was normal in 198 (89%) patients, borderline in 23 patients and definitely enlarged in only one patient. None had systolic LV dysfunction, and pulmonary artery pressure (PAP) was normal in all patients. Mean exercise capacity was 92 ± 21% of expected, and 87% of patients had no arrhythmias on Holter monitoring, with the remainder showing benign rhythm disorders.: ConclusionsOutcome in well-selected patients with a small VSD is good. Surgical closure does not appear to be required during childhood as long as left-to-right shunt is <50% and signs of LV volume overload are absent, when PAP is not elevated, and no VSD-related AR or symptoms are present. [Copyright &y& Elsevier]