Absolute pulse energy measurements of soft x-rays at the Linac Coherent Light Source.

This paper reports novel measurements of x-ray optical radiation on an absolute scale from the intense and ultra-short radiation generated in the soft x-ray regime of a free electron laser. We give a brief description of the detection principle for radiation measurements which was specifically adapted for this photon energy range. We present data characterizing the soft x-ray instrument at the Linac Coherent Light Source (LCLS) with respect to the radiant power output and transmission by using an absolute detector temporarily placed at the downstream end of the instrument. This provides an estimation of the reflectivity of all x-ray optical elements in the beamline and provides the absolute photon number per bandwidth per pulse. This parameter is important for many experiments that need to understand the trade-offs between high energy resolution and high flux, such as experiments focused on studying materials via resonant processes. Furthermore, the results are compared with the LCLS diagnostic gas detectors to test the limits of linearity, and observations are reported on radiation contamination from spontaneous undulator radiation and higher harmonic content.

Temporal cross-correlation of x-ray free electron and optical lasers using soft x-ray pulse induced transient reflectivity.

The recent development of x-ray free electron lasers providing coherent, femtosecond-long pulses of high brilliance and variable energy opens new areas of scientific research in a variety of disciplines such as physics, chemistry, and biology. Pump-probe experimental techniques which observe the temporal evolution of systems after optical or x-ray pulse excitation are one of the main experimental schemes currently in use for ultrafast studies. The key challenge in these experiments is to reliably achieve temporal and spatial overlap of the x-ray and optical pulses. Here we present measurements of the x-ray pulse induced transient change of optical reflectivity from a variety of materials covering the soft x-ray photon energy range from 500eV to 2000eV and outline the use of this technique to establish and characterize temporal synchronization of the optical-laser and FEL x-ray pulses.

The soft x-ray instrument for materials studies at the linac coherent light source x-ray free-electron laser.

The soft x-ray materials science instrument is the second operational beamline at the linac coherent light source x-ray free electron laser. The instrument operates with a photon energy range of 480-2000 eV and features a grating monochromator as well as bendable refocusing mirrors. A broad range of experimental stations may be installed to study diverse scientific topics such as: ultrafast chemistry, surface science, highly correlated electron systems, matter under extreme conditions, and laboratory astrophysics. Preliminary commissioning results are presented including the first soft x-ray single-shot energy spectrum from a free electron laser.

Effects of exercise on left ventricular performance determined by echocardiography in chronic, severe mitral regurgitation secondary to mitral valve prolapse.

Data on the effects of exercise on left ventricular (LV) volumes and ejection performance in patients with severe mitral regurgitation (MR) are limited. With use of a matched-pairs design, 10 asymptomatic patients with chronic, severe MR and normal LV systolic function who were not receiving vasodilator therapy (group 1) and 10 matched normal control subjects with no structural heart disease (group 2) performed symptom-limited upright bicycle ergometry with quantitative echocardiographic analysis. An additional 8 patients with severe, chronic MR and normal LV systolic function who were receiving vasodilator therapy at the time of testing (group 3) were studied for comparison. The 3 cohorts exercised for similar periods of time. Group 1 and 3 patients had similar end-diastolic volumes at rest, both of which were significantly greater than those of normal controls. Although resting LV end-systolic volume was greater in groups 1 and 3 than in normal controls, the 3 groups had similar relative percent reductions in end-systolic volume during exercise (30 +/- 12%, 32 +/- 13%, and 30 +/- 24%; p = NS). A similar percent increase in LV ejection fraction was also observed in all 3 cohorts (18 +/- 9%, 15 +/- 9%, and 14 +/- 6%; p = NS). Forward stroke volume increased significantly in group 1 (59 +/- 21 and 71 +/- 18 ml; p <0.001) and in group 3 (59 +/- 17 and 68 +/- 13 ml; p < 0.05). Thus, in asymptomatic patients with chronic, severe MR and normal LV ejection fraction at rest, there is an improvement in LV ejection fraction and an increase in forward stroke volume during exercise. These effects are comparable to those observed in normal controls. Directional differences in the cohort receiving no activity therapy were indistinguishable from either patients receiving vasodilator therapy or normal control subjects.

Prognostic value of normal technetium-99m-sestamibi cardiac imaging.

UNLABELLED: The purpose of this study was to describe the clinical outcome of patients with a normal 99mTc-sestamibi cardiac imaging study. METHODS: One-day gated rest-stress planar dipyridamole (n = 112) and symptom-limited exercise (n = 122) 99mTc-sestamibi protocols were used. All patients (n = 234, mean age 55 +/- 12 yr, 127 males and 107 females) had normal perfusion and wall motion on qualitative analysis. Patients were followed for 6-16 mo (mean 10 +/- 2 mo). Cardiac events were defined as cardiac death or nonfatal myocardial infarction. RESULTS: ST-segment depression or chest pain occurred in 8 (7%) and 29 (26%) patients in the dipyridamole group, respectively, and 20 (16%) and 28 (22%) patients in the exercise group. Cardiac events occurred in only one patient. The annualized event rate was 0.5% per year. In addition, only two patients underwent coronary revascularization during the follow-up period. CONCLUSIONS: Our data confirm the benign outcome of patients with normal 99mTc-sestamibi cardiac imaging, at least over an intermediate follow-up period.

Mitral valve replacement versus mitral valve repair. A Doppler and quantitative stress echocardiographic study.

BACKGROUND: Standard mitral valve replacement (MVR) in patients with chronic mitral regurgitation results in consistent reductions in resting postoperative ejection fraction. This has been attributed to removal of the low-impedance ejection pathway into the left atrium or to disruption of the chordal apparatus. Mitral valve repair (MVP) does not reduce ejection fraction at rest. However, whether MVP confers any advantages with regard to dynamic left ventricular performance has not been investigated. The aim of this study was to directly compare standard MVR with MVP and to determine their respective influences on ventricular ejection performance during bicycle exercise. METHODS AND RESULTS: Ten consecutive patients with pure chronic mitral regurgitation who underwent MVP and 10 patients matched for age, sex, and preoperative ejection fraction who underwent standard MVR for pure chronic mitral regurgitation performed symptom-limited, graded upright bicycle exercise with simultaneous Doppler and quantitative two-dimensional echocardiography. Patients with MVP had significantly greater rest (55 +/- 12%) and exercise (63 +/- 11%) ejection fractions than matched patients with MVR (40 +/- 13% [P < .0001] and 42 +/- 17% [P < .005], respectively). End-systolic circumferential wall stress was significantly lower at rest (190 +/- 36 versus 244 +/- 46; P < .03) and at peak exercise (231 +/- 46 versus 300 +/- 52; P < .02) in patients with MVP. At peak exercise, left ventricular shape was significantly more spherical in patients with MVR than those with MVP (1.84 +/- 0.31 versus 2.45 +/- 0.59; P < .02). CONCLUSIONS: MVR with chordal transection resulted in significant reductions in rest and exercise ejection fraction. This was caused in part by a significant increase in end-systolic circumferential wall stress. MVP resulted in improved rest and exercise ejection indexes, primarily due to a marked reduction in end-systolic stress and maintenance of a more ellipsoidal chamber geometry.

Impact of antianginal medications, peak heart rate and stress level on the prognostic value of a normal exercise myocardial perfusion imaging study.

We sought to determine whether antianginal medications or the level of achieved stress affect the prognostic value of a normal exercise 201Tl study. We studied 261 patients with a normal exercise 201Tl study for 23 +/- 6 mo. Antianginal medications were taken at the time of stress testing in 128 patients. Peak heart rate ranged from 82 to 217 bpm; percent maximal predicted heart rate ranged from 42% to 136%. Chi-square analysis was used to determine the relationship of cardiac events to antianginal medications and stress indices. Primary cardiac events were defined as cardiac death or nonfatal myocardial infarction. Primary cardiac events occurred in six patients yielding an annual incidence of 1.2% per year. There was no significant relationship between cardiac event rate and antianginal medication use or any stress index, including Bruce stage, peak heart rate or blood pressure or percent maximal predicted heart rate achieved. The risk of cardiac death or nonfatal myocardial infarction in patients with a normal exercise 201Tl is low and is not affected by concurrent antianginal treatment or degree of stress achieved.

Extent of jeopardized viable myocardium determined by myocardial perfusion imaging best predicts perioperative cardiac events in patients undergoing noncardiac surgery.

OBJECTIVES: This study was undertaken to test the hypothesis that the risk of perioperative cardiac events is not simply determined by the presence of myocardium at risk, but is directly related to the extent of myocardium at risk as reflected in thallium-201 myocardial imaging. BACKGROUND: The risk of perioperative cardiac events in patients undergoing noncardiac surgery has been related to the presence of transient defects on dipyridamole thallium-201 myocardial imaging, reflecting jeopardized viable myocardium. METHODS: The study cohort consisted of 231 consecutive patients who underwent noncardiac surgery and had a preoperative dipyridamole thallium-201 imaging study. Patients with vascular reconstruction or bypass constituted the largest surgical subgroup (n = 140). For thallium-201 imaging data, each of three planar projections was divided into three segments (total nine segments) and each segment was interpreted as normal or showing a transient or fixed defect. The ability of clinical and thallium-201 imaging data to predict perioperative cardiac events was compared with stepwise multivariate logistic regression analysis. RESULTS: Perioperative cardiac events occurred in 19 patients, including 5 with cardiac death, 7 with nonfatal myocardial infarction and 7 with unstable angina. For cardiac death or nonfatal myocardial infarction, the only significant multivariate predictors were the number of myocardial segments with transient thallium-201 defects (p < 0.0005) and a history of diabetes mellitus (p < 0.05). For all cardiac events, the only significant multivariate predictors were the number of myocardial segments with transient defects (p < 0.0001), diabetes mellitus (p < 0.05) and calcium channel blocker use (p < 0.05). CONCLUSIONS: The probability of important cardiac events in patients undergoing noncardiac surgery is best predicted by the extent of myocardium at risk as reflected on thallium-201 myocardial perfusion imaging. A history of diabetes mellitus also has a significant influence on perioperative risk.

Pulmonary hypertension in infants with bronchopulmonary dysplasia.

Seventeen children with oxygen-dependent bronchopulmonary dysplasia, right ventricular hypertrophy, and Doppler echocardiographic evidence of pulmonary hypertension were studied by cardiac catheterization. Fifteen of these patients had pulmonary hypertension when placed in room air; six of these 15 patients were shown to have large systemic-to-pulmonary collateral vessels. The hemodynamic responses to oxygen and hydralazine were evaluated. Five patients developed normal pulmonary artery pressure while receiving supplemental oxygen and were not studied further. Of the remaining ten patients, the six patients with large, hemodynamically significant collateral vessels all had deleterious reactions to hydralazine. Two of the four patients without collateral pulmonary circulation responded to hydralazine with further reductions in mean pulmonary artery pressure. Five of the ten patients who had persistent pulmonary hypertension while receiving oxygen have died. Cardiac catheterization and angiography may provide important diagnostic, therapeutic, and prognostic information in patients with pulmonary hypertension complicating bronchopulmonary dysplasia.

Percutaneous transluminal angioplasty of congenital coarctation of the aorta.

Two cases of successful dilatation of congenital coarctation of the aorta using the Grüntzig technique are reported. In a 3-week-old boy and an 11-month-old girl, systolic gradients across the narrowed areas were lowered from 50 to 8 mm Hg and from 23 to 8 mm Hg. Although the femoral pulses later disappeared in the younger patient, surgery was avoided. The second patient's gradient has remained minimal for 8 months and no surgery has been performed.

Pseudoaneurysm of the thoracic aorta: a late complication of umbilical artery catheterization.

Pseudoaneurysm of the thoracic aorta developed in an infant eight months following neonatal catheterization of the umbilical artery. Infection and placement of a stiff polyvinyl chloride catheter in the thoracic aorta appear to be the etiological factors. Preoperative diagnosis was posterior mediastinal tumor, and pseudoaneurysm was not included in the differential. Dacron graft patch angioplasty repair using partial cardiopulmonary bypass was successful. Postoperatively the patient has done well with no pressure gradient. Pseudoaneurysm should be suspected whenever a mediastinal mass appears in children who have had thoracic placement of umbilical artery catheters.

Diffuse pulmonary hemangiomatosis.

The authors describe three pediatric patients with diffuse pulmonary hemangiomatosis. Virtually identical clinical, radiographic, and pathologic findings were observed in each case. The combination of diffuse interstitial pulmonary infiltration and bloody pleural effusion in a child is pathognomonic. Early recognition of hemangiomatosis can allow more effective evaluation of therapeutic measures.

Cardiac death in mucocutaneous lymph node syndrome.

A 12 year old boy had 4 symptom-free years after hospitalization for acute febrile mucocutaneous lymph node syndrome before he died suddenly from extensive myocardial infarction. Current evidence suggests that many patients with this syndrome have coronary artery disease and that those with significant cardiac findings should be studied with coronary angiography. Serial studies are recommended because of the danger of sudden death.

Emphysematous gastritis in a leukemic child.

Emphysematous gastritis associated with gram-negative sepsis is described in a leukemic child on chemotherapy and steroids. Bubbly-appearing air and thickening of the gastric wall were radiographically demonstrated. This is analogous to the demonstration of air within the thickened bowel wall in necrotizing enterocolitis, which is not unusual in seriously ill leukemic children. Gastric involvement has not been previously reported.