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Biomedical subjects

C R Thompson

Publications and source records attributed to C R Thompson.

At least 55 records · Page 3Linked to original sources
PubMed1994

Juxtacardiac pleural pressure during positive end-expiratory pressure ventilation: an intraoperative study in patients with open pericardium.

OBJECTIVES: This study was conducted to measure the cardiac constraining effect of the lungs during positive end-expiratory pressure and relate extracardiac pleural pressure (radial stress) to airway pressure, right atrial pressure and left ventricular filling. BACKGROUND: During positive end-expiratory pressure ventilation, the extracardiac pressure is elevated, and therefore intracavitary filling pressure does not reflect ventricular preload. Estimates of this pressure might be useful clinically to assess left ventricular preload. METHODS: In eight patients who had undergone coronary or valvular surgery and whose pericardium was left widely open, a flat pleural balloon transducer was placed over the anterolateral left ventricular wall. We recorded pulmonary capillary wedge pressure, right atrial pressure and left ventricular short-axis end-diastolic area by transesophageal echocardiography. Incremental positive end-expiratory pressure was applied. RESULTS: Extracardiac pleural pressure increased (p < 0.01) from 0.6 +/- 1.8 (+/- SD) to 2.4 +/- 1.8, 5.3 +/- 1.5 and 8.2 +/- 1.5 mm Hg at a positive end-expiratory pressure of 5, 10 and 15 cm H2O, respectively. The slope relating extracardiac pleural pressure to positive end-expiratory pressure (in mm Hg) was 0.70 +/- 0.10, and the intercept was zero. Increasing extracardiac pleural pressure was associated with a progressive increase in pulmonary capillary wedge pressure and a decrease in left ventricular end-diastolic area. Consequently, although pulmonary capillary wedge pressure and left ventricular area changed in opposite directions, the value of pulmonary capillary wedge pressure minus extracardiac pleural pressure correlated positively with left ventricular area (r = 0.95, p < 0.001). Changes in right atrial pressure (Pra) correlated with changes in extracardiac pleural pressure (Ppleural): delta Pra = -0.3 + 0.56. delta Ppleural (r = 0.89, p < 0.001). CONCLUSIONS: In postoperative patients with open pericardium, pulmonary capillary wedge pressure minus extracardiac pleural pressure predicts left ventricular end-diastolic area during positive end-expiratory pressure. Further studies should be done to determine whether the observed relations between airway pressure and extracardiac pleural pressure and between right atrial pressure and extracardiac pleural pressure may give clinically useful estimates of left ventricular preload during positive end-expiratory pressure.

Aged↗
PubMed1994

Effect of lung inflation and sternotomy direction on pleural space violation.

Patients often are disconnected temporarily from the ventilator before sternotomy to avoid entering the pleural space with the sternal saw. Although this practice is widespread, it is based on questionable physiologic principles. To evaluate the efficacy of this maneuver in reducing the incidence of pleural space violation with first-time sternotomy, 126 cardiac patients were randomized prospectively to either lungs inflated or deflated during sternotomy with the surgeon blinded to the particular assignment. The incidence of pleural space violation overall was 12%, occurring in 15% of patients with deflated lungs and in 9% of those with inflated lungs (p = 0.455 by chi 2 test). Examining the effect of the direction of sternotomy on pleural space entry revealed a 4% incidence with sternotomy starting at the xiphoid versus a 21% incidence with sternotomy starting at the sternal notch (p = 0.009 by chi 2 test). Preexisting hyperinflation of the lungs as evaluated by chest radiograms did not influence the incidence of pleural space violation. To reduce pleural space violation, sternotomy should be performed from the xiphoid to the sternal notch. More importantly, disconnecting the patient from the ventilator does not reduce pleural space violation with sternotomy and its further use is not indicated. These findings are discussed in the context of relevant heart-lung pathophysiology.

Cardiac Surgical Procedures↗
PubMed1994

The Drosophila tissue-specific factor Grainyhead contains novel DNA-binding and dimerization domains which are conserved in the human protein CP2.

We have mapped the regions in the Drosophila melanogaster tissue-specific transcription factor Grainyhead that are required for DNA binding and dimerization. These functional domains correspond to regions conserved between Grainyhead and the vertebrate transcription factor CP2, which we show has similar activities. The identified DNA-binding domain is large (263 amino acids) but contains a smaller core that is able to interact with DNA at approximately 400-fold lower affinity. The major dimerization domain is located in a separate region of the protein and is required to stabilize the interactions with DNA. Our data also suggest that Grainyhead activity can be modulated by an N-terminal inhibitory domain.

Amino Acid Sequence↗
PubMed1993

The diagnostic utility of contrast echocardiography in patients with refractory hypoxemia.

Three illustrative cases of refractory hypoxemia in adults are presented. In two cases contrast echocardiography was invaluable in establishing the diagnosis of a true anatomic right to left shunt, as well as in localizing the shunt to an intracardiac or extracardiac site. In the third case true anatomic right to left shunt was excluded by means of contrast echocardiography. The pathophysiology of hypoxemia is discussed with emphasis on the potential diagnostic utility of contrast echocardiology in patients with refractory hypoxemia. A diagnostic flow chart is proposed.

Adult↗
PubMed1993

Heart rate variability in healthy term newborns: the contribution of respiratory sinus arrhythmia.

Cardiorespiratory interactions in healthy full term newborns were investigated. Spectral analysis was used on heart rate and breathing data from 22 neonates 2-5 days old to reveal coincident frequencies in the breathing and heart rate variability (HRV) spectra, thus identifying respiratory sinus arrhythmia (RSA). The spectral description of HRV in healthy term newborns revealed a consistent and distinct RSA feature, with a mean contribution of over 30%. The contribution of RSA to HRV was dependent on breathing frequency and absolute RSA power. The mechanisms that produce this cardiorespiratory interaction are considered to be functionally active in the healthy term neonate.

Arrhythmia, Sinus↗
PubMed1993

Comparison of short-time Fourier, wavelet and time-domain analyses of intracardiac sounds.

Heart sounds provide clinicians with valuable diagnostic and prognostic information. They are repetitive in nature, but reflect complex mechano-acoustical events which have been inadequately described by traditional digital signal processing methods. In this study, left ventricular and aortic intravascular phonocardiograms were obtained from six patients by catheter-mounted piezoelectric transducers. Phonocardiograms (PCGs) were bandpass filtered (50-500 Hz), digitized at 4kHz and analyzed by three separate techniques: (1) Short-Time Fourier Transform (STFT), (2) Fast Wavelet Transform (FWT), and (3) a pulse-counting time-domain method based on an Order Statistic (OS) filter. The resulting time-frequency distributions were employed to examine intra-patient and inter-patient acoustic variability. Results suggest that STFT and FWT provide comparable temporal and frequency resolution of cardiac acoustical events. However, the time-varying and multicomponent nature of heart sounds was poorly characterized by the OS technique employed in this study. This study suggests that improved localization of acoustic events during the cardiac cycle may prove useful in the development of automated auscultation devices.

Adult↗
PubMed1992

Synthesis of unusual thick pili by Escherichia coli of EPEC serogroup O119.

Unique very thick pili were found in varying numbers on cells of five out of 11 clinical isolates of enteropathogenic Escherichia coli belonging to the classic EPEC serogroup O119. They were approximately 12.5 nm in diameter, which is thicker than any other known E. coli pilus type. Analysis of the plasmid profiles of the O119 isolates showed that one strain was plasmid-free while the remainder contained numerous plasmids with a wide range of sizes. The thick pilus determinants were located on a 140-kb non-transferrable plasmid. They were not associated with adherence or a putative 90-kb enteroadherence factor plasmid.

Bacterial Adhesion↗
PubMed1992

Histamine decreases left ventricular contractility in normal human subjects.

To determine whether histamine alters human left ventricular contractility we measured heart rate, calibrated carotid arterial pressure, and left ventricular dimensions (echocardiogram) in nine healthy volunteers. We assessed baseline contractility using the end-systolic pressure-dimension relationship and the end-systolic meridional wall stress-rate-corrected velocity of circumferential fiber shortening relationship determined over a wide range of afterloads using phenylephrine and nitroprusside infusions. We then infused histamine for 3-5 min at a dose predetermined to decrease mean arterial pressure by 20%, both before and after H1 receptor antagonist pretreatment (diphenhydramine 50 mg i.v.). Histamine decreased end-systolic pressure but, unlike an equally hypotensive infusion of nitroprusside, did not decrease end-systolic dimension or increase fractional shortening. Histamine also decreased velocity of circumferential fiber shortening at the same end-systolic meridional wall stress as controls (P < 0.05). These effects of histamine were inhibited by H1 antagonist pretreatment. We conclude that the dominant effect of histamine on the human heart is to decrease left ventricular contractility and that this decrease in contractility is dependent, at least partially, on H1-receptor activation.

Adult↗
PubMed1989

Importance of effective, early and sustained reperfusion during acute myocardial infarction.

The determinants of myocardial salvage after thrombolytic therapy during acute myocardial infarction (AMI) have not been clearly defined. In 1984, a prospective randomized trial was undertaken to define the relations between delay to treatment and effectiveness of perfusion to salvage of myocardium. Patients presenting within 2 hours of symptom onset received intravenous streptokinase immediately (group 1, 20 patients) or 5 hours after symptom onset (group 2, 16 patients). Effective perfusion (less than or equal to 90% residual stenosis with rapid distal runoff) occurred in 63% of patients in both groups. Five patients, all in group 1, had recurrent AMI; 4 of the 5 had effective perfusion. There was no group difference in left ventricular ejection fraction at baseline or before discharge. However, group 1 patients with effective perfusion tended to have a greater predischarge mean ejection fraction than those in group 1 with ineffective perfusion (53 +/- 13 vs 44 +/- 16%, p less than 0.10) and had a greater mean value than those in group 2 with ineffective perfusion (53 +/- 13 vs 38 +/- 17%, p less than 0.03). The ejection fraction did not change significantly between admission and discharge in either group, but it increased significantly in group 1 patients with effective perfusion and no recurrent AMI (delta EF = +6 +/- 8%, p less than 0.04). Group 1 patients with ineffective perfusion had a significant decrease in ejection fraction (delta EF = -4 +/- 4%, p less than 0.04). In group 2 patients the ejection fraction did not change, regardless of the state of perfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

Usefulness of early positive technetium-99m stannous pyrophosphate scan in predicting reperfusion after thrombolytic therapy for acute myocardial infarction.

To test the hypothesis that scans with technetium-99m pyrophosphate (Tc-99m-PPi) are positive when performed early after successful thrombolytic therapy for acute myocardial infarction (AMI), 16 consecutive patients with AMI who received thrombolytic therapy within 5 hours after the onset of chest pain were studied. Patients were included if chest pain lasted for greater than 30 minutes, was unresponsive to sublingual nitroglycerin and was associated with at least 0.2 mV ST-segment elevation in at least 2 contiguous electrocardiographic leads. All patients received 1.5 million IU of streptokinase intravenously, a mean of 195 +/- 99 minutes after onset of chest pain. Tc-99m-PPi scans and coronary cineangiograms were recorded 491 +/- 156 minutes and 518 +/- 202 minutes, respectively, after the onset of symptoms. Effective reperfusion was present in 10 patients, 6 of whom had positive Tc-99m-PPi scans (sensitivity of 60% to detect reperfusion). Of the 6 patients without effective reperfusion, 3 had positive Tc-99m-PPi scans (specificity of 50%, p greater than 0.05). Analysis of the data using various definitions of effective reperfusion or artery patency yielded similar results. Thus, our findings indicate that early AMI scanning with Tc-99m-PPi does not accurately detect the presence or absence of reperfusion in patients with AMI after treatment with intravenous streptokinase. At this time, coronary cineangiography is the only reliable method to detect reperfusion promptly after thrombolytic therapy.

Aged↗
PubMed1988

Crop loss assessment for California: modeling losses with different ozone standard scenarios.

Crop yield losses were estimated for ambient O3 concentrations and for a series of potential O3 air quality standards for California, including the current statewide 1-h oxidant (O3) standard of 0.10 ppm (196 microg m(-3)), 12-h growing season averages, and other models. A model for statewide losses was developed using hourly O3 data for all sites in the State, county crop productivity data, and available O3 concentration-yield loss equations to determine potential yield losses for each crop in each county in California for 1984. Losses were based on comparison to an estimated background filtered air concentration of 0.025 or 0.027 ppm, for 12 or 7 h, respectively. Potential losses due to ambient air in 1984 were estimated at 19% to 25% for dry beans, cotton, grapes, lemons, onions, and oranges. Losses of 5% to 9% were estimated for alfalfa and sweet corn. Losses of 4% or less were estimated for barley, field corn, lettuce, grain sorghum, rice, corn silage, spinach, strawberries, sugar beets, fresh tomatoes, processing tomatoes, and wheat. Implementation of either a modified rollback to meet the current 1 h California O3 standard (0.10 ppm) or a three-month, 12-h growing season average of 0.045 ppm was necessary to produce large reductions in potential crop losses.

Journal Article↗
PubMed1987

Nonuniformity of pericardial surface pressure in dogs.

Previously, we have shown that pericardial constraint cannot be measured by true (hydrostatic) pressure except when an excess of pericardial fluid is present and that a device such as a balloon (which reflects radial contact stress as well as hydrostatic pressure) must be used. Since radial contact stress is the major component of the constraint exerted by the pericardium when little pericardial liquid is present, it follows that the pressure measured by the balloon might be different over different parts of the heart. In an attempt to test this hypothesis, in 11 anesthetized dogs we placed pericardial balloons over the right and left ventricular free walls, instrumented the animals to measure ventricular dimensions (sonomicrometry) and pressure, mounted pneumatic constrictors on the aortic and pulmonary artery, reapproximated the pericardium, and closed the chest under suction. We studied the transient effects of constrictions of the ascending aorta and pulmonary artery and of angiotensin infusion before and after intravenous saline infusion. Aortic constriction and, to a lesser degree, angiotensin increased pericardial pressure over the left ventricle more than over the right ventricle. Pulmonary artery occlusion increased pericardial pressure over the right ventricle but significantly decreased pericardial pressure over the left ventricle. We conclude that there are significant local differences in pericardial pressure (recorded by balloon) over the lateral ventricular surfaces during acute changes in afterload. These observations may be explained in part by decreased venous return to the contralateral ventricle, the tendency of the heart to resist lateral displacement, and the limited mobility of the pericardium.

Animals↗
PubMed1987

Transseptal pressure gradient and diastolic ventricular septal motion in patients with mitral stenosis.

Previous studies from our laboratory have shown that the position of the ventricular septum relative to the two ventricles at end-diastole is determined by the instantaneous transseptal pressure gradient (TSG) defined as left ventricular minus simultaneous right ventricular pressure. Since patients with mitral stenosis often have exaggerated leftward (paradoxic) motion of the ventricular septum during early diastole, we studied seven patients with mitral stenosis undergoing cardiac catheterization to determine if position (and therefore motion) of the ventricular septum was determined by TSG throughout diastole. M Mode echocardiograms derived from a two-dimensional parasternal short-axis view were recorded with simultaneous micromanometer measurements of left ventricular and right ventricular pressures. Six of seven patients demonstrated abnormal early diastolic leftward motion of the ventricular septum in at least one cardiac cycle. TSG measured at intervals throughout diastole ranged from -2.5 to +20 mm Hg, with abnormal TSG observed in most of the 40 cardiac cycles selected for analysis. The intracardiac position of the ventricular septum, defined as the distance from the right ventricular epicardium (RVEpi) to the left surface of the ventricular septum normalized for total cardiac dimension (RVEpi-VS), was plotted against left ventricular pressure, right ventricular pressure, and TSG. Linear regression of pooled data from all patients (164 observations) demonstrated a highly significant correlation between the instantaneous TSG and the relative intracardiac position of the ventricular septum (RVEpi-VS = 1.52 TSG + 42.7; r = .79, p less than .0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Oxidation of reduced menaquinone by the fumarate reductase complex in Escherichia coli requires the hydrophobic FrdD peptide.

Plasmids carrying cloned segments of the frd operon of Escherichia coli have been used in genetic complementation studies to identify two independent mutants defective in the frdD gene, which encodes the hydrophobic FrdD polypeptide of the fumarate reductase complex. Mutations in the frdA and frdB genes have also been mapped by this technique. One of the FrdD peptide mutants, DW109 (frdD-109), showed that fumarate reductase was not as tightly bound to the membrane in this mutant. In addition, the mutation in the FrdD peptide caused an almost total loss of the ability of the enzyme to oxidize either menaquinol-6, a physiological donor for fumarate reduction, or reduced benzyl viologen. However, the mutation did not impair the ability of the membrane-bound fumarate reductase complex to function with succinate as substrate, as evidenced by unchanged turnover numbers for phenazine methosulfate and 2,3-dimethoxy-5-methyl-6-pentyl-1,4-benzoquinone (a quinone analogue) reductase activities. These data establish the essential role of the FrdD polypeptide both in the interaction of the enzyme with reduced menaquinone and thus in anaerobic respiration with fumarate as electron acceptor, and in binding the enzyme to the membrane.

Benzoquinones↗
PubMed1985

M-mode and two-dimensional echocardiographic abnormalities in systemic lupus erythematosus.

A prospective clinical and echocardiographic study of 47 patients with systemic lupus erythematosus (SLE) and 46 age- and sex-matched controls showed an increased prevalence of echocardiographic abnormalities in the SLE group. Pericardial abnormalities were identified in ten patients with SLE and in no controls. Excluding mitral valve prolapse, valvular abnormalities were identified in ten patients with SLE (21%) and in three controls (7%). In the patients with SLE, abnormalities included mitral valve leaflet thickening in six, aortic valve thickening in five, and mitral annular calcification in two. The presence of valvular abnormalities correlated with duration but not with severity of SLE. The finding of systolic murmurs in 17 of 47 patients with SLE did not correlate with echocardiographic evidence of valvular disease. In six patients with SLE, valvular abnormalities detected by two-dimensional echocardiography were not seen on M-mode echocardiogram.

Adult↗