Cardiac magnetic resonance radiomics for prediction of incident heart failure: a feasibility study in the UK Biobank Imaging cohort

Background

Cardiac magnetic resonance (CMR) radiomics is a novel image quantification technique with the potential to improve image-based disease diagnosis and prediction.

Purpose

In this proof-of-concept study, we aimed to evaluate the utility of CMR radiomics in the prediction of incident heart failure (HF).

Methods

We studied 32,121 UK Biobank participants with CMR. Incident HF was defined from linked Hospital Episode Statistics. To create a balanced cohort, we identified as comparators an equal number of randomly selected subjects who did not develop the outcome of interest during this period. Radiomics shape, first-order and texture features were extracted from short-axis cine images (left and right ventricle, left ventricular myocardium) using the Pyradiomics toolbox. Vascular risk factors (VRFs) were considered as additional predictors. Feature selection was conducted using the sequential forward selection technique and modelling was performed using Support Vector Machine (SVM) methods with 5-fold cross-validation. Models were developed using 1) VRFs alone, 2) radiomics alone, and 3) VRFs and radiomics. We determined model performance using receiver operating characteristic (ROC) curve and area under the curve (AUC) scores.

Results

Over average follow-up time of 3.7 (±1.3) years, 209 participants experienced incident HF. Among vascular risk factors, age, body size, hypertension, diabetes, high cholesterol were chosen for the incident HF predictive model (Accuracy: 0.66, AUC: 0.73) by the SVM methods. The model based on radiomics features reached a marginal improvement compared to vascular risk factors alone (Accuracy: 0.71, AUC: 0.75). The combination of VRFs and radiomics features significantly improved the performance of the model to predict incident HF compared to VRFs alone (Accuracy: 0.77; AUC: 0.83; p<0.05)

Conclusion

We demonstrate the feasibility of CMR radomics features to predict incident HF and illustrate their added value over vascular risk factors.

Funding Acknowledgement

Type of funding sources: Public grant(s) – EU funding.

Timeline of Adverse Events during Immune Checkpoint Inhibitors for Advanced Melanoma and Their Impacts on Survival

Immune-related adverse events (irAEs) are frequent and could be associated with improved response to immune checkpoint inhibitors (ICIs). A prospective cohort of advanced melanoma patients receiving ICI as first-line therapy was retrospectively reviewed (January 2011−February 2019). A total of 116 of 153 patients presented with at least one irAE (75.8%). The most frequent irAEs were dermatological (derm irAEs, 50%), asthenia (38%), and gastrointestinal (29%). Most irAEs appeared within the first 90 days, while 11.2% appeared after discontinuation of the therapy. Mild grade 1−2 derm irAEs tended to appear within the first 2 months of therapy with a median time of 65.5 days (IQR 26-139.25), while grade 3−4 derm irAEs appeared later (median 114 days; IQR 69-218) and could be detected at any time during therapy. Only derm irAE occurrence was related to improved survival (HR 6.46). Patients presenting derm irAEs showed better 5-year overall survival compared to those with no derm irAEs (53.1% versus 24.9%; p < 0.001). However, the difference was not significant when adjusting for the duration of therapy. In conclusion: the timeline of immune-related-AEs differs according to the organ involved. The (apparent) improved survival of patients who present derm AEs during immunotherapy could be partially explained by longer times under treatment.

P14.12 Gyriform infiltration as imaging biomarker for adult diffuse astrocytic glioma, IDH wildtype, with molecular features of glioblastoma

BACKGROUND

Diffuse astrocytic gliomas, IDH wildtype, with molecular features of glioblastoma (molecular glioblastomas) are associated with a poor prognosis. We previously found that these tumors frequently display gyriform infiltration, defined as areas of elective cortical hypersignal on MRI FLAIR sequence. The objective of the present study was to assess the diagnostic value of gyriform infiltration as an imaging marker for these tumors.

MATERIAL AND METHODS

MRI scans from 430 patients with newly diagnosed glioma (molecular glioblastoma n = 31, IDH wildtype glioblastoma n = 298, IDH-mutant astrocytoma n = 50, IDH-mutant and 1p19q codeleted oligodendroglioma n= 51) were evaluated for the presence of a gyriform infiltration by 2 independent reviewers. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated to assess the performance of the presence of a gyriform infiltration for identifying molecular glioblastoma.

RESULTS

A gyriform infiltration was observed in 16/31 (52%) patients with a molecular glioblastoma, 40/298 (13%) patients with an IDH-wildtype glioblastoma but in none of the patients with an IDH-mutant astrocytomas or an IDH-mutant and 1p19q codeleted oligodendroglioma. Among the 56 patients with a gyriform infiltration, 54 patients had an IDH wildtype pTERT mutant glioma and 2 an IDH wildtype pTERT wildtype glioma. Interrater agreement was good (κ= 0.68, P &lt; 0.001). Specificity, sensitivity, PPV and NPV of the presence of a gyriform infiltration for the diagnosis of molecular glioblastoma were 90%, 29%, 52% and 96% and for the diagnosis of an IDHwt pTERT mutant glioma were 97%, 15%, 96% and 20%. The presence of a gyriform infiltration was associated with a worse prognosis in the entire cohort (13.6 months vs 29.3 months, P = .001).

CONCLUSION

Gyriform infiltration is a specific imaging marker of molecular glioblastomas and IDH wildtype pTERT mutant diffuse gliomas.

Long-term impact of temozolomide on 1p/19q-codeleted low-grade glioma growth kinetics

Although upfront temozolomide (TMZ) has been widely-used to treat 1p/19q-codeleted diffuse low-grade gliomas (LGG), its long-term impact on the growth kinetics of these tumors has not been determined. Based on serial magnetic resonance images we retrospectively evaluated the evolution of the mean tumor diameter (MTD) in 36 progressive 1p/19q-codeleted LGG treated with upfront TMZ. After TMZ onset, all but two patients (94.4%) presented a progressive MTD decrease that lasted for a median duration of 23 months (range 3-114). In 10 patients (27%) MTD regrowth occurred during TMZ treatment and in 22 patients (66%) after TMZ discontinuation. In these patients, median time to MTD regrowth after TMZ discontinuation was 12 months (range 1-88). The rate of MTD regrowth at 3 and 5 years after TMZ onset was 77 and 94%, respectively. Time to tumor progression (TTP) based on volumetric analysis was shorter than TTP based on Response Assessment in Neuro-Oncology (RANO) bidimensional criteria (23 vs. 35 months, p = 0.05) and shorter than time to next oncological treatment (23 vs. 46 months, p = 0.001). In 10 patients (27%), absence of volumetric analysis led to continue TMZ for a median of 10 cycles after MTD had started to regrow. Volumetric analysis is important to precisely assess chemotherapy efficacy in 1p/19q-codeleted LGG, identify early tumor progression and avoid futile chemotherapy continuation. In the present series, although some long-lasting volumetric responses were observed, most tumors resumed their growth within 3 years after TMZ onset.

Use of mobile technologies in patients with psychosis: A systematic review

There is a growing interest in mobile Health interventions (m-Health) in patients with psychosis. The aim of this study is to conduct a systematic review in order to analysethe current state of research in this area. The search of articles was carried out following the PRISMA criteria, focusing on those studies that used mobile technologies in patients with psychosis during the period from 1990 to 2016. A total of 20 articles were selected from the 431 studies found. Three types of studies are distinguished: 1) Analysis of quality and usability, 2) Improving treatment adherence and reducing hospital admissions, and 3) Analysisof patient symptoms.

CONCLUSIONS

m-Health interventions are feasible, and are easy to use for patients with psychosis. They evaluate the evolution of psychotic symptoms more efficiently, and improve adherence to treatment, as well as symptoms and hospital admissions. However, a particular strategy does not stand out over the rest, because differences in methodology make them difficult to compare.

External ophthalmomyiasis: a case series

Oestrus ovis or 'sheep botfly' causes common ophthalmomyiasis in warm climates. It is a self-limited infestation with symptoms such as foreign body sensation and/or tearing. The larvae can be observed in the conjunctiva and should be extracted with forceps. The development of larvae beyond the first stage does not occur in healthy humans, although they may penetrate the ocular globe, causing so-called internal myiasis. External ophthalmomyiasis is typical of rural areas, but it may be observed occasionally in urban environments.

Community-acquired pneumonia in immunocompromised older patients: incidence, causative organisms and outcome

The number of elderly patients in the community with immunosuppressive conditions has increased progressively over recent decades. We sought to determine the incidence, causative organisms and outcome of community-acquired pneumonia (CAP) occurring in immunocompromised older patients. We prospectively compared cases of CAP in immunocompromised and non-immunocompromised patients admitted to five public hospitals in three Spanish regions. Of 320 cases studied, 115 (36%) occurred in immunocompromised patients, including: solid or hematological malignancy (97), corticosteroids or other immunosuppressive drugs (44), solid organ or stem cell transplant (five), and other conditions (eight). The etiology was established in 44% of immunocompromised patients vs. 32% of non-immunocompromised patients (p 0.03). Streptococcus pneumoniae was the most common causative organism in both groups (29% vs. 21%; p 0.08), followed by Legionella pneumophila (3% vs. 6%; p 0.01). Gram-negative bacilli were more frequent among immunocompromised patients (5% vs. 0.5%; p <0.01), particularly Pseudomonas aeruginosa (3% vs. 0%; p 0.04). Nocardiosis was only observed in immunocompromised patients (two cases). Bacteremia occurred similarly in the two groups. No significant differences were found with respect to ICU admission (8%, in both groups) or the length of stay (12.5 vs. 10.4 days). The early (<48 h) (3.5 vs. 0.5%; p 0.04) and overall case-fatality rates (12% vs. 3%; p <0.01) were higher in immunocompromised patients. In conclusion, a substantial number of older patients hospitalized for CAP are immunocompromised. Although relatively uncommon, CAP due to gram-negative bacilli, including P. aeruginosa, is more frequent among these patients. CAP occurring in immunocompromised patients causes significant morbidity and mortality.

Effectiveness of the pneumococcal polysaccharide vaccine in preventing pneumonia in the elderly

The objective of our study was to evaluate the effectiveness of the 23-valent pneumococcal polysaccharide vaccine (PPV) in preventing hospital admission for community-acquired pneumonia (CAP) in people ≥65 yrs of age. We conducted a matched case-control study in patients with CAP admitted to five Spanish hospitals. Cases were persons aged ≥65 yrs admitted to hospital through the emergency department, who presented a clinical and radiological pattern compatible with pneumonia, assessed using established criteria. We matched each case with three control subjects by sex, age (±5 yrs), date of hospitalisation (±30 days) and underlying disease. The study period was May 1, 2005 to January 31, 2007. The PPV immunisation status of cases and controls was investigated. Adjusted ORs for vaccination were calculated using logistic regression analysis. A total of 489 cases and 1,467 controls were included in the final analysis. The overall adjusted vaccination effectiveness for all patients was 23.6% (95% CI 0.9-41.0). The adjusted vaccination effectiveness for immunosuppressed patients was 21.0% (95% CI -18.7-47.5). Our results suggest that the PPV may potentially reduce hospitalisations for pneumonia in the elderly and supports vaccination programmes in this age group.

Rotavirus y adenovirus 40–41 como causantes de gastroenteritis infantil

Introducción

El rotavirus es la principal causa de diarrea grave en niños menores de 5 años, y ocasiona una elevada morbilidad y mortalidad a escala mundial. El objetivo de este trabajo ha sido conocer la epidemiología de los virus entéricos que se declaran en el Sistema de Notificación Microbiológica de Cataluña (SNMC), rotavirus y adenovirus 40-41, y valorar la importancia que tienen en el contexto de la enfermedad entérica.

Material y métodos

Se han revisado retrospectivamente las declaraciones que realizan los laboratorios de los hospitales que participan en el SNMC durante los años 1995-2002. Los casos de gastroenteritis aguda se han diagnosticado por detección de antígeno en heces. Las variables analizadas han sido: edad, sexo, mes y año de aislamiento. Como métodos estadísticos se han utilizado el test de la ?2 y test de Fisher; las proporciones se han comparado utilizando la prueba binomial y el nivel de significación estadística se ha establecido en 0,05.

Resultados

Se han detectado 6.708 (94,3%) rotavirus y 409 (5,7%) adenovirus 40-41. Las gastroenteritis agudas virales han presentado mayor morbilidad en niños pequeños menores de 2 años: el 76 y el 68% de rotavirus y adenovirus, respectivamente, se han concentrado en este grupo de edad. El rotavirus se ha aislado principalmente en invierno (68%), mientras que el adenovirus, aunque se ha presentado estable en todas las estaciones, ha sido más frecuente en otoño (35,2%). Respecto a las enteritis, bacterianas y virales, vigiladas en el SNMC, el rotavirus y el adenovirus han supuesto la segunda y la cuarta causa etiológica, respectivamente, en los niños menores de 5 años, después de Campylobacter y Salmonella.

Conclusiones

De los diferentes virus que pueden causar gastroenteritis aguda, hay otros virus con frecuencias elevadas, como calici-virus y astrovirus, que no se buscan sistemáticamente, por lo que hay que valorar las frecuencias con prudencia. A pesar de esto, el rotavirus es la principal causa de la gastroenteritis viral, y afecta principalmente a edades tempranas de la vida, sobre todo a niños de 1 a 11 meses, con un claro predominio en invierno. Respecto al adenovirus 40-41, se ha presentado preferentemente en niños menores de 2 años y con mayor frecuencia en otoño. La vacunación contra el rotavirus es prioritaria para poder disminuir el alto índice de morbilidad y mortalidad que ocasiona esta enfermedad.

Prevalence of Neisseria meningitidis carriers in the school population of Catalonia, Spain

The aim of this study was to determine the prevalence of healthy Neisseria meningitidis pharyngeal carriers in a representative sample of the Catalonian school population, as well as its associated factors. The sample was divided into age groups: < or = 5, 6-7 and 13-14 years old. Parents were given a questionnaire to collect information on sociodemographic and epidemiological variables. Oropharyngeal swabs were collected with a cotton-tipped swab in an Amies transport medium and cultured on Thayer Martin plates at 35 degrees C in 5% CO2. The isolates were serogrouped and sero/subtyped. Of the 1406 children studied, 75 (5.34%) meningococcal carriers were detected: 63 B (4.5%), 9 non groupable (0.7%), 2 29E (0.1%) and 1X (0.07%). No serogroup C meningococci were found in this study, probably due to the high A+C vaccination coverage of up to 68.9% in children 6-7 years old. Bivariate analysis identified six statistically significant risk factors for meningococcal carriage: increasing age, recent upper respiratory tract infection, previous antibiotic treatment, number of students in the class, size of the classroom and social class. Multivariate analysis found that only age and previous antibiotic treatment remained statistically significant when the other factors were controlled.

[Etiology of enteritis in a university general hospital in Barcelona (1992-1995)]

BACKGROUND

The aim of the study was to describe the etiology of enteropathogenic agents over a four-year period (1992-1995) in a University Hospital in Barcelona.

METHODS

We studied 12,793 stool samples, 4519 were obtained from patients under 15 years and 8274 were obtained from patients over 14 years. The specimens were examined for bacteriological, parasitological and virological enteropathogens.

RESULTS

In 3380 specimens of 12,793 stool samples studied were identified an enteropathogen (26.4%). Polymicrobial associations were observed in the 6.8% of the cases. Pathogens were identified in 45% of children samples and 16.3% of adults samples. The etiological enteritis agents more frequently detected in the paediatric patients were Campylobacter (13.5%), rotavirus (11.3%) and Salmonella (10.2%); and Salmonella (4.9%), Campylobacter (3.1%) and Giardia intestinalis (2.1%) in adults. Cryptosporidium (13.5%) was the most frequent cause of gastrointestinal tract infections in HIV-infected subjects. In the children with stools positives, the presence of red and white blood cells were more frequent than the adults with stools positives (73% versus 26.6%).

CONCLUSIONS

The enteropathogenic agents such as Campylobacter, Salmonella, and Giardia were the most frequent cause of gastroenteritis in our environment. In the children, rotavirus infections predominated during the cold months. The most frequent cause of gastroenteritis in HIV-infected patients was Cryptosporidium followed by Campylobacter.

[Traumatic asphyxia and continuous venovenous hemofiltration. Report of a case]

A 32-year-old man was admitted with traumatic asphyxia, with aspiration to the bronchi after being buried under sand. The condition progressed to respiratory distress syndrome and systemic inflammatory response. Because ventilatory and hemodynamic deterioration was rapid and severe, in spite of mechanical ventilation and vasoactive drugs, we instated early continuous arteriovenous hemofiltration, which also allowed us to meet the patient's full nutritional needs. We believe that the patient's very satisfactory progress can be attributed to the early use of this procedure, along with appropriate specific treatment.

[Evaluation of chromogenic medium CPS ID2 (bioMérieux) in urine cultures]

BACKGROUND

The aim of the study was to evaluate the chromogenic agar plate CPS ID2 (bioMérieux) and determine its cost-benefit ratio.

METHODS

A total of 2,193 urinary sediments were processed. The urine culture was carried out in CPS ID2 agar and in cystine-lactose electrolyte deficient (CLED) agar, when needed. Identification of the microorganisms was performed following standard microbiologic procedures through biochemical tests prepared in our laboratory. The identification, from CPS ID2 agar, by direct detection in medium of four metabolic activities: beta-glucuronidase, beta-glucosidase, deaminase, and indol production, was performed following to manufacturer's instructions.

RESULTS

A total of 289 urine cultures were positive, 18 were negative and 34 were contaminated samples. The identification, directly performed from the colonies detected in CPS ID2 agar, was correct in 96% of 166 Escherichia coli, in 92% of 24 Proteus mirabilis and in 97% of 38 enterococci. CPS ID2 agar exhibited 94% and 100% sensitivity and specificity, respectively in E. coli identification, 92% and 100% in P. mirabilis and 97% and 99% in Enterococcus. The use of this new media, CPS ID2, in our laboratory, implies a budgetary increment. However, if commercial galleries are used for routine identification, the cost will be reduced using this new media.

CONCLUSIONS

The CPS ID2 agar allows the isolation and direct identification of the most frequent urinary tract pathogens: E. coli, P. mirabilis and Enterococcus in primary isolation medium. Using this medium, bacteriologists will be able to save time and reagents when identifying the most common uropathogens. Furthermore, the use of this medium would reduce costs in some laboratories.

US and color Doppler imaging of ocular and orbital disease in the pediatric age group

Ultrasonography (US) is a rapid, accurate, noninvasive method of evaluating ocular and orbital disease. A wide spectrum of pediatric ocular and orbital disorders can be demonstrated with US: ocular congenital malformations, vitreoretinal disorders, primary and metastatic ocular and orbital neoplasms, inflammatory and congestive disease (focal or systemic), cystic disease, trauma, and foreign bodies. US may be the method of choice for studying ocular congenital anomalies and vitreoretinal disorders owing to its high definition and noninvasiveness. In ocular neoplasms, US demonstrates the morphology of the lesion, its solid or liquid nature, and the presence of calcifications. Its use is limited when the tumor extends outside the globe; computed tomography (CT) or magnetic resonance (MR) imaging must then be performed. In ocular trauma, US precisely demonstrates the presence of hemorrhage, retinal and choroidal detachment, and foreign bodies. CT and MR imaging are superior in evaluation of orbital disease. Color Doppler US often allows differential diagnosis of vascular, inflammatory, and neoplastic disease.

Effect of kappa-casein split peptides on platelet aggregation and on thrombus formation in the guinea-pig

An undecapeptide (residues 106-116 of cow kappa-casein) is known to inhibit human platelet aggregation and fibrinogen binding through inhibition of the interaction between the fibrinogen gamma-chain C-terminus and alphaIIbbeta3. This was due to structural homologies with the fibrinogen gamma-chain C-terminal dodecapeptide. We have therefore compared in this work the in vitro anti-aggregating activity of kappa-casein split peptides and their in vivo potential antithrombotic activity in a model of arterial thrombosis triggered by laser-induced intimal injury in the guinea-pig. Caseinoglycopeptide (residues 106-169), the undecapeptide (residues 106-116) and the pentapeptide KNQDK (residues 112-116) from cow kappa-casein, were anti-aggregating peptides and exerted a significant antithrombotic activity in the guinea-pig. Caseinoglycopeptides from three species (cow, ewe and human) were also antithrombotic and the most potent being the human one. The antithrombotic activity was achieved in vivo for doses less than the one suspected from in vitro data and for which, ex vivo platelet aggregation was not decreased. In conclusion, the relative involvement of the fibrinogen gamma-chain C-terminal dodecapeptide could be much more important in in vivo thrombosis process than in in vitro platelet aggregation. Its specificity and activity in vivo unveiled an interesting potential way for inhibition of arterial thrombosis if alternative molecular presentation (i.e. peptidomimetics) and alternative route (i.e. per os) can be developed.

Characterization of an antithrombotic peptide from kappa-casein in newborn plasma after milk ingestion

Bovine and human kappa-caseinoglycopeptides, two antithrombotic peptides derived from the corresponding kappa-caseins, were detected in physiologically active concentrations in the plasma of 5-d-old newborn infants after ingestion of cow's-milk-based formula or human milk respectively. It is suggested that these two bioactive peptides are released from milk proteins during digestion.

In search of a correlation between the electron affinity and the radiosensitizing activity of some glyoxylic compounds

The electron affinity of some glyoxylic compounds with radiosensitizing properties was evaluated using different approaches. The half-wave reduction potentials were measured by polarography, and the molecular structures in solution were determined by NMR spectroscopy. The electron affinity of the unhydrated and hydrated molecules was theoretically evaluated by means of a semi-empirical quantum mechanical procedure, the MNDO. The possible correlations between these values and the radiosensitizing efficiency of these glyoxylic compounds is discussed.

Kinetic study of the enzyme NADPH cytochrome-C (P-450) reductase: non-Michaelian behaviour

1. Contrary to what has been accepted until now, the enzyme exhibits non-Michaelian kinetics both against NADPH and against cytochrome-c as substrates; deviations were detected that have led to the proposition of a rate equation of minimum degree 2:2. 2. A general mechanism is proposed that includes, apart from the binding of the enzyme to NADPH, the formation of an enzyme-cytochrome-c complex, both routes leading to the formation of a ternary-complex NADPH-enzyme-acceptor. 3. From the latter, a series of intermediate steps finally leads to the release of the enzyme in conditions to start a new catalytic cycle. 4. Application of the King-Altman method to this mechanism yields a kinetic equation of degree 2:2 with respect to the cytochrome-c and NADPH, in accordance with our experimental results.

The non-Michaelian action of thrombin on peptide p-nitroanilide substrates

1. v([S]) kinetic data were obtained for the hydrolysis of the chromogenic substrates H-D-Phe-L-Pip-L-Arg-pNA (S-2238), H-D-Ile-L-Pro-L-Arg-pNA (S-2288), Tos-Gly-L-Pro-L-Arg-pNA (Tos-Ch-TH) and Cbz-Gly-L-Pro-L-Arg-pNA (Cbz-Ch-TH) by native human thrombin under different experimental conditions (Pip is pipecolyl, pNA is p-nitroanilide, Tos is tosyl and Cbz is benzyloxycarbonyl). 2. The data were fitted to rational functions of order 1:1, 2:2 and 3:3 by using non-linear regression. Discrimination between equations of different degree was made using the F-test. 3. In all, 24 curves were fitted. In 17 cases degree 2:2 was significantly better than degree 1:1 at a confidence level of 95%. In no case was any further significant improvement found with functions of degree 3:3. 3. Our results allow us to assert that native human thrombin is an enzyme that does not allow Michaelian kinetic behaviour when acting on chromogenic substrates. Instead, the empirically obtained steady-state data require mechanisms whose rate equation is at least of degree 2:2.

Kinetic study of the inhibition of the amidolytic activity of thrombin by benzamidine and N-dansyl-(p-guanidino)-phenylalanine-piperidide (I-2581)

1. v([I]) data were obtained for the hydrolysis of the chromogenic substrate H-D-Phe-L-Pip-L-Arg-pNA (S-2238) by native human thrombin in the presence of the synthetic inhibitors Benzamidine and N-dansyl-(p-guanidino)-phenylalanine-piperidide (I-2581). v([S]) data were also obtained in the absence and presence of fixed concentrations of each of the inhibitors. 2. Analysis of the kinetic data was based on the numerical fitting to rate equations of the polynomial quotient type of degree n:m using nonlinear regression methods. The discrimination between rate equations with different degrees was performed by application of the statistical F test. 3. Of eight v([I]) curves fitted, in six cases it was found that degree 1:2 was significantly better than degree 1:1 at a confidence level of 95% or higher; in no case was a significant improvement found with rate equations with a higher number of parameters. For the v([S]) data, of eleven curves fitted it was found that in nine cases degree 2:2 significantly improved degree 1:1 at confidence levels 99% and in one case at a level of 95%; no significant improvement was found with rate equations of higher degree for these data either. 4. Our findings allow us to propose that inhibition of the amidolytic activity of native human thrombin by benzamidine and I-2581 may be accounted for by mechanisms whose v([I]) rate equation will be a minimum of degree 1:2, thus implying a pure inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of infarct size in acute canine myocardial infarction by single-photon emission computed tomography with technetium-99m pyrophosphate

The location and extent of myocardial infarction (MI) are important predictors of patient course. The current study tests the hypothesis that MI size could be measured accurately using rotating gamma camera single-photon emission computed tomography ( SPECT ) and technetium-99m pyrophosphate (PPi) and that the accuracy of these measurements was independent of MI location and transmural or nontransmural distribution. SPECT was performed in 38 dogs 48 hours after ligation of the left anterior descending coronary artery (14 dogs) or left circumflex coronary artery (LC) (24 dogs) at the mid-level or below. Projection images were corrected for center-of-rotation and field nonuniformity and processed with a 1-dimensional low-pass filter to diminish rib activity. Sixteen 0.5-cm-thick transverse sections, including the entire left ventricle, were reconstructed by filtered backprojection , low-pass filtered, contrast enhanced and processed with a 3-dimensional boundary enhancement operator. The boundary of PPi uptake in each slice was marked automatically using an algorithm that combined a directional derivative and a threshold, and required continuity of the boundary in 3 dimensions. The total number of volume elements that showed abnormal tracer uptake were summed, corrected to absolute volume, and multiplied by the specific weight of cardiac muscle. Scintigraphic MI weight was compared with pathologic MI weight. There was an excellent correlation between scintigraphic and pathologic MI weight. The poorer correlation for nontransmural compared with transmural MIs is most likely a function of size alone, since MIs that weighed less than 10 g (n = 12, range 1.3 to 9.5 g), both transmural and nontransmural, showed a similar correlation: S = 1.07 X P + 0.56 (r = 0.81, standard error of the slope = 0.245).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of inotropic and chronotropic stimuli on acute myocardial ischemic injury. III. Influence of basal heart rate

The influence of basal heart rate (HR) on the effects of inotropic (dobutamine infusion) and chronotropic (atrial pacing) stimuli during acute myocardial ischemia was assessed by measurement of intramural carbon dioxide partial pressure (PCO2) in open-chest dogs undergoing transient 10-minute left anterior descending coronary artery occlusions. In protocol I, in 5 dogs anesthetized with pentobarbital alone, HR increased from 153 +/- 10 to 182 +/- 7 beats/min between experimental coronary occlusions, but the increase in ischemic zone intramural carbon dioxide tension (delta PmCO2) was not altered by this significant increase in HR. In protocols II to V, dogs were anesthetized with combinations of morphine, thiamylal and pentobarbital and had a basal average HR of 81 beats/min. Atrial pacing in protocol II (13 dogs) increased HR from 76 +/- 21 to 134 +/- 19 beats/min (p less than 0.001); left ventricular (LV) myocardial oxygen consumption (MVO2) rose from 3.9 +/- 1.6 to 4.9 +/- 1.4 ml/min/100 g (p less than 0.05), and delta PmCO2 rose from 42 +/- 14 to 50 +/- 15 mm Hg (p less than 0.01), indicating more severe ischemic injury during the second experimental coronary occlusion. In protocol III, 11 dogs received 20 micrograms/kg/min of dobutamine before the second experimental occlusion, which significantly (p less than 0.02) increased HR, LV dP/dt and MVO2; delta PmCO2 increased from 46 +/- 13 to 63 +/- 18 mm Hg (p less than 0.01). The 7 dogs in protocol IV received 3.9 +/- 1.9 micrograms/kg/min of dobutamine, titrated such that HR was unchanged (84 +/- 10 vs 81 +/- 15 beats/min), but LV dP/dt increased by 92% (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

A mechanism for fibrin monomer aggregation based on a kinetic study

A kinetic study was carried out of the aggregation of fibrin monomers under different reaction conditions. At either acid or base pH values, second-order kinetic processes were observed throughout the concentration range studied. At neutral pH (6.8 less than or equal to pH less than or equal to 7.3) the kinetics were of second order at fibrin monomer concentrations of less than 0.3-0.4 mg/ml, while at higher concentrations they changed to first order. Both the second order rate constants and the opacity of the fibrin gels are highly dependent on pH, ionic strength, the concentration of calcium ions and on temperature. A three-step reaction mechanism is proposed for the aggregation of fibrin monomers to explain the kinetic behaviour observed in the different reaction media.