Keck Institute for Space Studies

A cohort of 1472 patients who underwent both exercise stress testing and coronary angiography within six weeks was examined. The data indicated that a combination of exercise parameters is both diagnostically and prognostically important. Almost all patients (greater than 97%) who had positive exercise tests at Stage I or Stage II had significant coronary artery disease. More than half of these (greater than 60%) had three vessel disease and over 25% had significant narrowing (greater than 50%) of the left main coronary artery. Patients who achieved Stage IV or greater exercise durations with either negative or indeterminate ST-segment response had less than a 15% prevalence of three vessel disease and less than a 1% prevalence of left main coronary artery disease. A low risk subgroup (75% of all non-operated patients) was identified with a twelve month survival greater than 99%. A high risk subgroup (11% of all nonoperated patients) was identified with a twelve month survival of less than 85%. The exercise test is a noninvasive, reproducible method to assess the presence and extent of anatomic disease and the prognosis when significant disease has been defined. It should be used in conjunction with other noninvasive tests to determine optimal management in patients evaluated for ischemic heart disease.

Urban areas now house more than half the world's population, and are estimated to contribute over 70% of global energy‐related CO 2 emissions. Many cities have emission reduction policies in place, but lack objective, observation‐based methods for verifying their outcomes. Here we demonstrate the potential of satellite‐borne instruments to provide accurate global monitoring of megacity CO 2 emissions using GOSAT observations of column averaged CO 2 dry air mole fraction ( X CO 2 ) collected over Los Angeles and Mumbai. By differencing observations over the megacity with those in nearby background, we observe robust, statistically significant X CO 2 enhancements of 3.2 ± 1.5 ppm for Los Angeles and 2.4 ± 1.2 ppm for Mumbai, and find these enhancements can be exploited to track anthropogenic emission trends over time. We estimate that X CO 2 changes as small as 0.7 ppm in Los Angeles, corresponding to a 22% change in emissions, could be detected with GOSAT at the 95% confidence level.

Three-year survival for 163 consecutive medically treated patients with 50% or greater left main stenosis was 50%. Survival was significantly higher for patients with 50 to 70% left main stenosis (one and three-year survivals of 91% and 66%) than for patients with 70% or greater left main stenosis (one and three-year survivals of 72% and 41%). In fact, left main lesions of less than 70% were not associated with the increased risk usually attributed to patients with left main stenosis. A number of noninvasive and catheterization characteristics were significant predictors of survival for patients with 70% or greater left main stenosis. Noninvasive descriptors defined a low risk subgroup (one and three-year survivals of 97% and 74%) and a high risk subgroup (one- and three-year survivals of 59% and 25%). These observations have important implications both in assessing therapeutic interventions and in managing individual patients.

Eighty-seven patients with the clinical syndrome of infective endocarditis were examined by M-mode and two-dimensional echocardiography. Patients were divided into two groups based on the presence or absence of echocardiographically detected vegetative lesions. Group 1 consisted of 47 patients with one or more vegetations. Group 2 consisted of 40 patients without evidence of vegetations. Group 1 patients had a higher rate of complications: emboli, congestive heart failure and the need for surgical intervention. Analysis of morphologic characteristics of the vegetations in group 1 was of no predictive value for complications in individual patients. Two-thirds of the vegetations persisted unaltered well beyond the period of bacteriologic cure without significant complications. No characteristic alteration of the vegetations predicted the efficacy of medical therapy. Although the detection of vegetations by echocardiography in patients with the clinical syndrome of endocarditis clearly identifies a subgroup at risk for complications, decisions regarding clinical management made solely on the basis of the presence or absence of vegetative lesions are hazardous. Management of such patients must continue to be based on the clinical integration of multiple factors.

A real-time, phased-array, two-dimensional echocardiography system was used to assess mitral valve motion in 30 catheterized patients with pure mitral stenosis. Suitable images for analysis of mitral valve motion were obtained in 25 patients. The valve leaflets were most thickened and immobile at the leaflet tips while maximum mobility was at the leaflet body. Diastolic movement of anterior mitral leaflet toward the septum pulled the posterior mitral leaflet mid-portion inferiorly. Systolic bulging of the mid-portion of the anterior mitral leaflet into the left atrium was seen in 40% (10 of 25). Movement of the anterior mitral leaflet in diastole is primarily due to movement of the whole mitral apparatus in patients with mitral stenosis. The anterior mitral leaflet E to F slopes did not correlate (r=0.38) with the mitral valve area determined at catheterization. Planimetry of the mitral valve area directly from the videotape images compared favorably to the valve area determined at catheterization (r=0.95). Thus, mitral valve area determined by this technique is an accurate noninvasive method for assessing the severity of mitral stenosis.¿

In order to define baseline descriptive criteria for the diagnosis of mitral valve prolapse with cross-sectional echocardiography, 49 patients undergoing catheterization were examined by a real-time, two-dimensional phased array echocardiographic imaging system. Angiography was used to separate patients into two distinct groups: 15 with normal mitral valve function and 34 with definite mitral valve prolapse. Systolic mitral leaflet and annulus motion were then observed in each patient and similarities and differences were noted between the two groups of patients. Correlative M-mode echocardiographic data were available in 37 patients. Certain two-dimensional echocardiographic findings restricted to the angiographically proven mitral valve prolapse group were defined: 1) posteriorly displaced coaptation of the leaflets, 2) systolic superior movement of one or both mitral leaflets above the level of the mitral ring, and 3) a systolic curling motion of the posterior mitral ring on its adjacent myocardium. One or more of these abnormalities were found in all 34 patients with angiographic mitral valve prolapse. When mitral valve prolapse does occur, the results of two-dimensional echocardiography would suggest that both leaflets are usually involved.

Left ventricular wall motion was assessed in 105 consecutive patients both invasively, using biplane cineangiography, and noninvasively, by a real-time, phased-array, two-dimensional echocardiography system. Ventricular wall motion in five anatomic areas of the ventricle (anterolateral, posterolateral, apical, septal, and inferior) was analyzed by both methods in a double-blind manner. Two-dimensional echocardiographic images were deemed adequate for analysis in 82% of the regions (430 of 525). Fifty-five discrepancies were noted in the comparison of the remaining 430 regions. The reasons for discrepancies in interpretation between the two methods were established for 54 during retrospective review: 33 were due to echocardiography (inadequate target visualization, observer error, or tangential echo views). Fifteen were related to angiography (overlay of silhouettes or observer error), and six were due to other reasons including definition problems or spatial orientation difficulties. Both real-time, two-dimensional echocardiography and cineangiography have advantages and disadvantages. The techniques used together could provide more complete information concerning ventricular wall movement than is now currently available.

We use historical and new atmospheric trace gas observations to refine the estimated source of methane (CH(4)) emitted into California's South Coast Air Basin (the larger Los Angeles metropolitan region). Referenced to the California Air Resources Board (CARB) CO emissions inventory, total CH(4) emissions are 0.44 ± 0.15 Tg each year. To investigate the possible contribution of fossil fuel emissions, we use ambient air observations of methane (CH(4)), ethane (C(2)H(6)), and carbon monoxide (CO), together with measured C(2)H(6) to CH(4) enhancement ratios in the Los Angeles natural gas supply. The observed atmospheric C(2)H(6) to CH(4) ratio during the ARCTAS (2008) and CalNex (2010) aircraft campaigns is similar to the ratio of these gases in the natural gas supplied to the basin during both these campaigns. Thus, at the upper limit (assuming that the only major source of atmospheric C(2)H(6) is fugitive emissions from the natural gas infrastructure) these data are consistent with the attribution of most (0.39 ± 0.15 Tg yr(-1)) of the excess CH(4) in the basin to uncombusted losses from the natural gas system (approximately 2.5-6% of natural gas delivered to basin customers). However, there are other sources of C(2)H(6) in the region. In particular, emissions of C(2)H(6) (and CH(4)) from natural gas seeps as well as those associated with petroleum production, both of which are poorly known, will reduce the inferred contribution of the natural gas infrastructure to the total CH(4) emissions, potentially significantly. This study highlights both the value and challenges associated with the use of ethane as a tracer for fugitive emissions from the natural gas production and distribution system.

Two-dimensional echocardiography (2-D echo) was used with peripherally injected contrast material to detect interatrial shunts in 33 patients. Group 1 consisted of 11 patients having classic clinical findings of atrial septal defect. Group 2 consisted of 12 patients with problems requiring that atrial shunting be excluded. Group 3 (control group) consisted of 10 patients undergoing cardiac catheterization for chest pain. Confirmation of the 2-D echo findings was provided by cardiac catheterization in 32 patients and postmortem examination in one. Right-to-left atrial shunts were detected in all 11 patients in group 1, although seven had no right-to-left shunt calculable by oximetry. Four patients in Group 2 had right-to-left atrial shunts. None of the patients in Group 3 had atrial shunts. In the 15 patients with atrial shunts, the degree of right-to-left shunting could be qualitatively assessed as small, moderate, or large. There were no false-negative or false-positive results by contrast 2-D echo.

A new two-dimensional ultrasound imaging system capable of producing high resolution tomographic images of the heart in real time has been developed. This system relies on phased array principles to rapidly steer the ultrasound beam through the structures under investigation. A hand-held linear array of 16 ultrasound transducers with overall dimensions of 14 mm at the site of contanct may be readily manipulated to image various cardiac structures. The resulting images are displayed in a circular sector format, 60 degrees in azimuth and typically 15 cm in range. At his maximum range, image frames consisting of 256 lines are generated at the rate of 20 frames/second. High azimuthal resolution throughout the field of view is assured by a focused transmit beam and by sweeping the focus of the receiver is synchrony with the range of returning echoes. Azimuthal resolution varies from 2 to 5 mm throughout the field of view while range resolution is 1.5 mm. This imaging system has proven particularly useful for the delineation of left ventricular spatial geometry by the identification of endocardium, myocardium, papillary muscles and interventricular septum. High quality images of anterior and posterior mitral leaflets, aortic root and aortic leaflets as well as left atrium and other cardiac structures have been obtained.

The capability of a pulsed Doppler flowmeter combined with a phased-array imaging system to measure volume flow was tested in vitro and in patients undergoing cardiac catheterization. The Doppler-phased-array system (DPA) was used to determine vessel diameter and a superimposed cursor was used to locate the range and angle of the Doppler sample volume. DPA estimates of continuous flow through tubing in a water tank correlated strongly (r = 0.99) with measured flow corresponding to physiologic ranges from 3-12 l/min. For pulsatile flow in a water tank, a correlation of r = 0.86 with measured flow was obtained, whereas DPA estimates of cardiac outputs compared with Fick estimates in the 11 patients produced a correlation of r = 0.83. These data indicate that estimates of cardiac output are possible using the DPA approach.

Real-time, two-dimensional echocardiography was used to document the presence and assess the size and location of vegetative lesions of the cardiac valves and chambers in seven patients with bacterial endocarditis. Anatomic correlation (surgical or autopsy) was accurate in all patients. Two-dimensional echocardiography was shown to be of particular value in determining morphologic characteristics of the lesions since this technique provides spatial information concerning moving cardiac structures. The results of two-dimensional echocardiography were most helpful in determining selected aspects of the clinical care provided for each patient. These data demonstrate that real-time, two-dimensional echocardiography, in combination with M-mode imaging techniques, may be of great potential value in the detection of vegetative endocarditis. Furthermore, reliable assessment of lesion size and location may, in time, become a valuable method for following the morphologic changes that occur in vegetative lesions, and thus determine the efficacy of antibiotic therapy. This information may also provide a means for evaluating certain patients for surgical intervention.

Patient records in 36 consecutively identified patients with typical echocardiographic findings of atrial septal aneurysm were reviewed. Ten of the 36 (28%) had cerebrovascular events. Of these 10, 5 had completed strokes of definite embolic origin on the basis of clinical, angiographic, and computed tomographic findings; 2 had transient ischemic attacks of probable embolic origin. One of the 36 patients had a definite peripheral vascular embolus. Thus, 6 of 36 consecutively identified patients with atrial septal aneurysm (17%) had definite embolic events and 8 of 36 (22%) had definite or possible embolic events. The cause of the association between atrial septal aneurysm and emboli is unknown. While aneurysm-associated thrombus has been suggested, the high proportion (90%) of patients with interatrial shunting demonstrated by contrast echocardiography in this study suggests paradoxical embolization as a potential cause. Whatever its mechanism, the high prevalence of embolic events in this series strongly supports the premise that atrial septal aneurysm is a cardiac abnormality with embolic potential.

"Contrast echocardiography", utilizing a two-dimensional ultrasound system and peripheral venous injections, was used for the detection of tricuspid regurgitation in 30 patients. The appearance of contrast in the inferior vena cava and the back and forth movement of contrast across the tricuspid valve were considered evidence for tricuspid regurgitation. Echocardiographic findings were correlated with clinical and angiographic data. Patients were assigned on the basis of clinical data to one of three groups. Group I included five patients whose clinical findings were diagnostic for tricuspid regurgitation. Group II included patients (15) whose clinical findings were equivocal for tricuspid regurgitation and patients whose recognized primary problem is frequently associated with tricuspid regurgitation. Group III contained ten patients serving as controls. All group I patients had positive echocardiographic studies for tricuspid regurgitation, while all group III patients had negative studies, suggesting that this technique may be specific for tricuspid regurgitation. Among the group II patients were three who had positive echocardiographic studies despite the absence of specific clinical findings of tricuspid regurgitation, suggesting that this technique may be more sensitive than the methods in common use.

The contemporary global carbon cycle is dominated by perturbations from anthropogenic CO 2 emissions. One approach to identify, quantify, and monitor anthropogenic emissions is to focus on intensely emitting urban areas. In this study, we compare the ability of different CO 2 observing systems to constrain anthropogenic flux estimates in the Los Angeles megacity. We consider different observing system configurations based on existing observations and realistic near‐term extensions of the current ad hoc network. We use a high‐resolution regional model (Stochastic Time‐Inverted Lagrangian Transport‐Weather Research and Forecasting) to simulate different observations and observational network designs within and downwind of the Los Angeles (LA) basin. A Bayesian inverse method is employed to quantify the relative ability of each network to improve constraints on flux estimates. Ground‐based column CO 2 observations provide useful complementary information to surface observations due to lower sensitivity to localized dynamics, but column CO 2 observations from a single site do not appear to provide sensitivity to emissions from the entire LA megacity. Surface observations from remote, downwind sites contain weak, sporadic urban signals and are complicated by other source/sink impacts, limiting their usefulness for quantifying urban fluxes in LA. We find a network of eight optimally located in‐city surface observation sites provides the minimum sampling required for accurate monitoring of CO 2 emissions in LA, and present a recommended baseline network design. We estimate that this network can distinguish fluxes on 8 week time scales and 10 km spatial scales to within ~12 g C m –2 d –1 (~10% of average peak fossil CO 2 flux in the LA domain).

According to the thoracic pump model of cardiopulmonary resuscitation (CPR), the heart serves as a passive conduit for blood flow from the pulmonary to the systemic vasculature, necessitating an open mitral valve and anterograde transmitral blood flow during chest compression. To assess the applicability of this model to manual CPR techniques, two-dimensional echocardiograms were recorded from the right chest wall and/or the esophagus in nine dogs (18 to 26 kg) during manual CPR. The aortic valve opened with chest compression and closed with release, while the pulmonary and tricuspid valve leaflets closed with compression and opened during release. The mitral valve remained open during ventilation alone and during abdominal compressions. With the onset of brief, high-velocity (high-impulse) chest compressions, the mitral valve closed rapidly and the left ventricle was deformed, whether compressions were applied to the sternum or the left mid-chest wall. The mitral valve reopened with release of each compression. Left atrial echocardiographic contrast injections confirmed the absence of anterograde transmitral blood flow during high-impulse compression and its presence during release. Failure of mitral leaflet approximation during chest compression was observed only when a very low-velocity, prolonged (low-impulse) compression technique was used, or when regions that did not directly overlie the heart were compressed. Consistent with these observations, simultaneous recordings of the left ventricular and left atrial pressures during high-impulse sternal compressions in five dogs (19 to 25 kg) demonstrated peak and mean left ventriculoatrial pressure gradients of 38.5 +/- 4.0 and 13.5 +/- 2.9 mm Hg, respectively, and these pressure gradients declined with less impulsive compressions. The observations made during all but low-impulse chest compressions are inconsistent with the thoracic pump model, and support direct cardiac compression as the primary mechanism of forward blood flow with more impulsive manual chest compression techniques.

Echocardiographic and cardiac catheterization findings were compared in 61 patients with mitral stenosis without other significant lesions in an attempt to determine the clinical usefulness of echocardiography in the assessment of such patients. There was a poor correlation between the E-F slope on the echocardiogram and the calculated mitral valve area (r = 0.51). A review of reported data relating the E-F slope to mitral valve area indicated that echocardiographic assessment of mitral valve area had low sensitivity and specificity. The amplitude of excursion of the anterior leaflet did not differ significantly in patients undergoing valvotomy and those undergoind valve replacement. The data obtained suggest that while the echocardiogram is a reliable method of diagnosing mitral stenosis, the E-F slope is an unreliable index of the severity of the lesion.

Two-dimensional echocardiographic findings in a group of 24 patients with atrial septal defects were correlated with findings obtained by cardiac catheterization and M-mode echocardiography. The prevalence of mitral prolapse was 95% by two-dimensional echocardiography and 59% by angiography in patients with secundum and sinus venosus atrial septal defects. The majority of the group with echocardiographic prolapse manifested a distinctive pattern of prolapse, with predominant involvement of the anterior mitral leaflet. Thirty-eight percent of the patients in this series manifested paradoxical septal motion by M-mode and/or two-dimensional echocardiography. In the patients with abnormal septal motion, the net systolic anterior movement of the septum was caused by an exaggerated systolic anterior movement of the main body of the left ventricle. The atrial septal defect could be visualized with confidence by two-dimensional echocardiography only in the two patients with ostium primum atrial septal defects. Cleft anterior mitral leaflets were also clearly demonstrated in these two patients.

Nanocrystalline WO 3 films were produced by advanced reactive gas deposition onto alumina substrates. The as‐deposited films had a tetragonal crystal structure and a mean grain size of around 6 nm, as found by X‐ray diffraction and electron microscopy. Sintering at a temperature τ s > 770 K yielded monoclinic films. We investigated the gas‐sensing properties of films sintered up to 870 K. After an initial “activation” at τ s = 750 K, the nanocrystalline WO 3 films showed excellent gas‐sensing properties, even at room temperature, on exposure to low concentrations of H 2 S in air. As little as 10 ppm of H 2 S made the conductance increase by a factor of about 10 3 within 10 min. The initial properties could be restored by heating the films to 530 K for 1 min.

The effects of etomidate and thiopental on myocardial contractility were compared in 10 experiments on isolated papillary muscle preparation perfused by a conscious donor dog. Equianesthetic doses of etomidate (1.4 mg/kg) and thiopental (15.5 mg/kg) were determined separately in conscious dogs. Tension developed by the papillary muscle decreased significantly less after etomidate (17 ± 2%) than after thiopental (33 ± 3%) (P < 0.002) when injected intravenously in equianesthetic doses in donor dogs. When added to arterial blood perfusing the papillary muscle, etomidate had 4–5 times more negative inotropic effect than thiopental. At the same time, the anesthetic potency of etomidate was approximately 11 times greater than that of thiopental. We conclude that both etomidate and thiopental produce a dose-dependent direct negative inotropic effect but that in equianesthetic doses, etomidate causes less pronounced depression of myocardial contractility than thiopental.