High-Density Lignin-Derived Carbon Nanofiber Supercapacitors with Enhanced Volumetric Energy Density

Supercapacitors are increasingly used in short-distance electric transportation due to their long lifetime (≈15 years) and fast charging capability (>10 A g-1 ). To improve their market penetration, while minimizing onboard weight and maximizing space-efficiency, materials costs must be reduced (<10 $ kg-1 ) and the volumetric energy-density increased (>8 Wh L-1 ). Carbon nanofibers display good gravimetric capacitance, yet their marketability is hindered by their low density (0.05-0.1 g cm-3 ). Here, the authors increase the packing density of low-cost, free-standing carbon nanofiber mats (from 0.1 to 0.6 g cm-3 ) through uniaxial compression. X-ray computed tomography reveals that densification occurs by reducing the inter-fiber pore size (from 1-5 µm to 0.2-0.5 µm), which are not involved in double-layer capacitance. The improved packing density is directly proportional to the volumetric performances of the device, which reaches a volumetric capacitance of 130 F cm-3 and energy density of 6 Wh L-1 at 0.1 A g-1 using a loading of 3 mg cm-2 . The results outperform most commercial and lab-scale porous carbons synthesized from bioresources (50-100 F cm-3 , 1-3 Wh L-1 using 10 mg cm-2 ) and contribute to the scalable design of sustainable electrodes with minimal 'dead volume' for efficient supercapacitors.

Operando Bragg Coherent Diffraction Imaging of LiNi0.8Mn0.1Co0.1O2 Primary Particles within Commercially Printed NMC811 Electrode Sheets

Due to complex degradation mechanisms, disparities between the theoretical and practical capacities of lithium-ion battery cathode materials persist. Specifically, Ni-rich chemistries such as LiNi_0.8Mn_0.1Co_0.1O₂ (or NMC811) are one of the most promising choices for automotive applications; however, they continue to suffer severe degradation during operation that is poorly understood, thus challenging to mitigate. Here we use operando Bragg coherent diffraction imaging for 4D analysis of these mechanisms by inspecting the individual crystals within primary particles at various states of charge (SoC). Although some crystals were relatively homogeneous, we consistently observed non-uniform distributions of inter- and intracrystal strain at all measured SoC. Pristine structures may already possess heterogeneities capable of triggering crystal splitting and subsequently particle cracking. During low-voltage charging (2.7-3.5 V), crystal splitting may still occur even during minimal bulk deintercalation activity; and during discharging, rotational effects within parallel domains appear to be the precursor for the nucleation of screw dislocations at the crystal core. Ultimately, this discovery of the central role of crystal grain splitting in the charge/discharge dynamics may have ramifications across length scales that affect macroscopic performance loss during real-world battery operation.

X-ray micro-computed tomography as a non-destructive tool for imaging the uptake of metal nanoparticles by graphene-based 3D carbon structures

Graphene-based carbon sponges can be used in different applications in a large number of fields including microelectronics, energy harvesting and storage, antimicrobial activity and environmental remediation. The functionality and scope of their applications can be broadened considerably by the introduction of metallic nanoparticles into the carbon matrix during preparation or post-synthesis. Here, we report on the use of X-ray micro-computed tomography (CT) as a method of imaging graphene sponges after the uptake of metal (silver and iron) nanoparticles. The technique can be used to visualize the inner structure of the graphene sponge in 3D in a non-destructive fashion by providing information on the nanoparticles deposited on the sponge surfaces, both internal and external. Other deposited materials can be imaged in a similar manner providing they return a high enough contrast to the carbon microstructure, which is facilitated by the low atomic mass of carbon.

Identifying the Cause of Rupture of Li-Ion Batteries during Thermal Runaway

As the energy density of lithium-ion cells and batteries increases, controlling the outcomes of thermal runaway becomes more challenging. If the high rate of gas generation during thermal runaway is not adequately vented, commercial cell designs can rupture and explode, presenting serious safety concerns. Here, ultra-high-speed synchrotron X-ray imaging is used at >20 000 frames per second to characterize the venting processes of six different 18650 cell designs undergoing thermal runaway. For the first time, the mechanisms that lead to the most catastrophic type of cell failure, rupture, and explosion are identified and elucidated in detail. The practical application of the technique is highlighted by evaluating a novel 18650 cell design with a second vent at the base, which is shown to avoid the critical stages that lead to rupture. The insights yielded in this study shed new light on battery failure and are expected to guide the development of safer commercial cell designs.

Biodistribution of 99mTc-MAA on SPECT/CT performed for 90Y radioembolization therapy planning: a pictorial review

Purpose

To evaluate the frequency of 99mTc-MAA uptake in extrahepatic organs during 90Y radioembolization therapy planning.

Methods

This retrospective case series of 70 subjects who underwent 99mTc-MAA hepatic artery perfusion studies between January 2014 and July 2016 for 90Y radioembolization therapy planning at our institution involved direct image review for all subjects, with endpoints recorded: lung shunt fraction, extrahepatic radiotracer uptake, time from MAA injection to imaging.

Results

Combined planar and SPECT/CT imaging findings in the 70 subjects demonstrated lung shunt fraction measurements of less than 10% in 53 (76%) subjects and greater than 10% in 17 (24%) subjects. All patients demonstrated renal cortical uptake, 23 (33%) demonstrated salivary gland uptake, 23 (33%) demonstrated thyroid uptake, and 32 (46%) demonstrated gastric mucosal uptake, with significant overlap between these groups. The range of elapsed times between MAA injection and initial imaging was 41-138 min, with a mean of 92 min. There was no correlation between time to imaging and the presence of extrahepatic radiotracer uptake at any site.

Conclusions

During hepatic artery perfusion scanning for 90Y radioembolization therapy planning, extrahepatic uptake is common, particularly in the kidney, salivary gland, thyroid and gastric mucosa, and is hypothesized to result from breakdown of 99mTc-MAA over time. Given the breakdown to smaller aggregates and ultimately pertechnetate, this should not be a contraindication to actual Y-90 microsphere therapy. Although we found no correlation between time to imaging and extrahepatic uptake, most of our injection to imaging times were relatively short.

Laser-preparation of geometrically optimised samples for X-ray nano-CT

A robust and versatile sample preparation technique for the fabrication of cylindrical pillars for imaging by X‐ray nano‐computed tomography (nano‐CT) is presented. The procedure employs simple, cost‐effective laser micro‐machining coupled with focused‐ion beam (FIB) milling, when required, to yield mechanically robust samples at the micrometre length‐scale to match the field‐of‐view (FOV) for nano‐CT imaging. A variety of energy and geological materials are exhibited as case studies, demonstrating the procedure can be applied to a variety of materials to provide geometrically optimised samples whose size and shape are tailored to the attenuation coefficients of the constituent phases. The procedure can be implemented for the bespoke preparation of pillars for both lab‐ and synchrotron‐based X‐ray nano‐CT investigations of a wide range of samples.

Antiproton stopping power data for radiation therapy simulations

Stopping powers of H, He, H₂, and H₂O targets for antiprotons have been calculated using a convergent close-coupling method. For He and H₂ targets electron-electron correlations are fully accounted for using a multiconfiguration approximation. Two-electron processes are included using an independent-event model. The water molecule is described using a neon-like structure model with a pseudo-spherical potential. Results are tabulated for the purpose of Monte Carlo simulations to model antiproton transport through matter for radiation therapy.

Endoscopic full-thickness resection of gastric tumors using a novel grasp-and-snare technique: feasibility in ex vivo and in vivo porcine models

BACKGROUND AND STUDY AIMS

Endoscopic full-thickness resection (EFTR) is a less-invasive method of en bloc removal of gastrointestinal tract tumors. The aim of this study was to evaluate the feasibility of a grasp-and-snare EFTR technique using a novel tissue-lifting device that provides more secure tissue anchoring and manipulation.

METHODS

EFTR of normal gastric tissue and model stomach tumors was performed using a double-channel therapeutic endoscope with a prototype tissue-lifting device through one channel and a prototype hexagonal snare through the other. The lifting device was advanced through the open snare and anchored to the gastric wall immediately adjacent the model tumor. The tissue-lifting device was then partially retracted into the endoscope, causing the target tissue, including tumor, to evert into the gastric lumen. The open snare was then placed distal to the tumor around uninvolved gastric tissue. Resection was performed with a blended electrosurgical current through the snare. In the live pigs, EFTR was followed by laparotomy to asses for complications.

RESULTS

24 EFTRs were performed -- 14 in explanted stomachs and 10 in live pigs. In total, 23/24 resections resulted in full-thickness gastric defects. Resection specimens measured up to 5.0 cm when stretched and pinned on a histology stage. Gross margins were negative in 17/20 model tumor resections. Two resections were complicated by gastric mural bleeding. There was no evidence of adjacent organ injury.

CONCLUSIONS

EFTR of gastric tumors using the grasp-and-snare technique is feasible in pigs. This technique is advantageous in that eversion of the gastric wall avoids injury to external organs, continuous luminal insufflation is not required, and the involved techniques are familiar to endoscopists. Additional research is necessary to further evaluate safety and reliable closure.

Utility of current risk stratification tests for predicting major arrhythmic events after myocardial infarction

OBJECTIVES

We surveyed the literature to estimate prediction values for five common tests for risk of major arrhythmic events (MAEs) after myocardial infarction. We then determined feasibility of a staged risk stratification using combinations of noninvasive tests, reserving an electrophysiologic study (EPS) as the final test.

BACKGROUND

Improved approaches are needed for identifying those patients at highest risk for subsequent MAE and candidates for implantable cardioverter-defibrillators.

METHODS

We located 44 reports for which values of MAE incidence and predictive accuracy could be inferred: signal-averaged electrocardiography; heart rate variability; severe ventricular arrhythmia on ambulatory electrocardiography; left ventricular ejection fraction; and EPS. A meta-analysis of reports used receiver-operating characteristic curves to estimate mean values for sensitivity and specificity for each test and 95% confidence limits. We then simulated a clinical situation in which risk was estimated by combining tests in three stages.

RESULTS

Test sensitivities ranged from 42.8% to 62.4%; specificities from 77.4% to 85.8%. A three-stage stratification yielded a low-risk group (80.0% with a two-year MAE risk of 2.9%), a high-risk group (11.8% with a 41.4% risk) and an unstratified group (8.2% with an 8.9% risk equivalent to a two-year incidence of 7.9%).

CONCLUSIONS

Sensitivities and specificities for the five tests were relatively similar. No one test was satisfactory alone for predicting risk. Combinations of tests in stages allowed us to stratify 91.8% of patients as either high-risk or low-risk. These data suggest that a large prospective study to develop a robust prediction model is feasible and desirable.

Dysrhythmia hazard after hospitalization for myocardial infarction: two ECG prognostic methods compared

We retrieved reports of heart rate variability and signal-averaged electrocardiograms (SAECG) used to predict risk of a dysrhythmic event. From each report the number of cases with and without events was extracted to establish accurate values for true positive rate (tpr = sensitivity) and false positive rate (fpr = 1 minus specificity). For all the heart rate variability reports, these values were collected and tpr values were plotted versus fpr. The (fpr,tpr) data were summarized by a meta ROC graph using the method of Moses and Shapiro. A composite weighted mean value and 95% confidence interval were also derived. A summary meta-ROC curve for the SAECG reports was similarly obtained., Meta-ROC analysis of multiple reports better summarizes the performances of different prognostic methods and allows the effect of combining tests for a larger population to be simulated.

Neurally mediated cardiac syncope: autonomic modulation after normal saline infusion

OBJECTIVES

This study assessed the heart variability response to orthostatic stress during tilt table testing before and after normal saline administration.

BACKGROUND

The efficacy of sodium chloride and mineralocortoid in the treatment of neurally mediated cardiac syncope is attributed to intravascular volume expansion; however, their modulation of autonomic nervous system activity has not been evaluated.

METHODS

Heart rate variability analysis was performed on 12 adolescents with a history of syncope or presyncope (mean age 15.2+/-0.7 years) during tilt table testing. Subjects were upright 80 degrees for 30 min or until syncope. After normal saline administration, the patient was returned upright for 30 min. Heart rate variability analysis data were analyzed by an autoregression model (Burg method).

RESULTS

All subjects reproducibly developed syncope during control tilt table testing; median time to syncope was 9.4+/-2.1 min. After normal saline infusion, none of the subjects developed syncope after 30 min upright. In the control tilt, there was an initial increase followed by a progressive decrease in low frequency power until syncope. Repeat tilt after normal saline administration demonstrates that low frequency power increased but the magnitude of initial change was blunted when compared with control. In addition, low frequency power increased during normal saline tilt sequence compared with the control tilt, during which it decreased.

CONCLUSIONS

Normal saline blunted low frequency power stimulation and prevented paradoxical low frequency power (sympathetic) withdrawal. Increasing intravascular volume with normal saline alters autonomic responses that may trigger neurally mediated syncope reflexes.

NHLBI workshop on the utilization of ECG databases: preservation and use of existing ECG databases and development of future resources

Baseline examinations and periodic reexaminations in longitudinal population studies, together with ongoing surveillance for morbidity and mortality, provide unique opportunities for seeking ways to enhance the value of the electrocardiogram (ECG) recorded with digital technology as an inexpensive and noninvasive tool for prognosis and diagnosis. Clinicians, epidemiologists, and engineers from industry, government, and academic medical centers gathered at a workshop sponsored by the National Heart, Lung, and Blood Institute (NHLBI) on June 11-12, 1997, to discuss the research potential of ECG databases, their preservation and accession, and standards for recording and storage. Databases considered were those acquired in ongoing and future NHLBI-funded studies and in clinical settings in which the ECG continues to provide valuable information for evaluation and treatment. The accessibility of existing databases, the quality of their data, and the availability of ancillary demographic and clinical information were major themes. Also discussed were appropriate statistical methodologies to be used with these data for developing and testing ECG algorithms. The workshop participants affirmed the value of these databases and urged the establishment of an ECG advisory and review group to (1) resolve technical and proprietary issues for the utilization of currently existing databases; (2) develop standards for recording, storage, and utilization of ECGs in future NHLBI-supported studies; (3) oversee the creation of a national ECG database resource, consisting of an archive of ECG databases from past and ongoing NHLBI-supported studies, and a registry of ECG databases that would eventually include digital ECGs from populations currently underrepresented in the demographic spectrum of the NHLBI databases.

Panoramic display of the orderly sequenced 12-lead ECG

The standard 12-lead electrocardiogram (ECG) has been developed over many years. The ECG has had a long and successful history of providing diagnostic information in clinical medicine. Cardiac arrhythmias have been elucidated by deductive reasoning from continuous ECG recordings with confirmation from electrophysiologic studies. Recently, there has been renewed interest in the morphology of the QRS complex, ST-segment, and T wave, which raises the important question of considering whether the usual method of display provides maximal diagnostic capabilities. The conventional display provides a logical visualization of precordial lead recordings representing the horizontal plane, but does not provide a logical visualization of the limb lead recordings representing the frontal plane. Many clinical problems require the consideration of serial ECGs necessitating the comparison of separate pages. An alternate format presenting serial recordings on a single page would be advantageous. Some automated ECG analysis systems already include the capability for multiple display formats, but these have not yet been widely used in clinical practice. This point of view paper introduces a new display format for the standard 12-lead ECG that includes: (1) a presentation of an orderly sequence of leads to facilitate scanning through different points in space and (2) a presentation of recordings of 12-lead sequences to facilitate scanning through different points in time. This display format could either replace or supplement the conventional ECG format.

Specialist outreach clinics in general practice

OBJECTIVES

To establish the extent and nature of specialist outreach clinics in primary care and to describe specialists' and general practitioners' views on outreach clinics.

DESIGN

Telephone interviews with hospital managers. Postal questionnaire surveys of specialists and general practitioners.

SETTING

50 hospitals in England and Wales.

SUBJECTS

50 hospital managers, all of whom responded. 96 specialists and 88 general practitioners involved in outreach clinics in general practice, of whom 69 (72%) and 46 (52%) respectively completed questionnaires. 122 additional general practitioner fundholders, of whom 72 (59%) completed questionnaires.

MAIN OUTCOME MEASURES

Number of specialist outreach clinics; organisation and referral mechanism; waiting times; perceived benefits and problems.

RESULTS

28 of the hospitals had a total of 96 outreach clinics, and 32 fundholders identified a further 61 clinics. These clinics covered psychiatry (43), medical specialties (38), and surgical specialties (76). Patients were seen by the consultant in 96% (107) of clinics and general practitioners attended at only six clinics. 61 outreach clinics had shorter waiting times for first outpatient appointment than hospital clinics. The most commonly reported benefits for patients were ease of access and shorter waiting times.

CONCLUSIONS

Specialist outreach clinics cover a wide range of specialties and are popular, especially in fundholding practices. These clinics do not seem to have increased the interaction between general practitioners and specialists.

Improved detection of echocardiographic left ventricular hypertrophy using a new electrocardiographic algorithm

OBJECTIVES

The purpose of this study was to use the Framingham data base to devise and test an improvement in an electrocardiographic (ECG) voltage criterion for detecting left ventricular hypertrophy that is gender specific and adjusts for age and obesity.

BACKGROUND

Electrocardiographic detection of left ventricular hypertrophy has been receiving increasing attention. The "Cornell" ECG voltage, defined as the sum of voltages for the R wave of lead aVL and S wave of lead V3, has been shown to correlate strongly with echocardiographically estimated left ventricular mass. Because the magnitude of this voltage varies with both age and obesity, we have proposed a simple formula for its adjustment for these two variables.

METHODS

Using linear regression, the adjustment formula was estimated from data on 1,468 men and 1,883 women from the Framingham Heart Study cohort who were free of myocardial infarction and who had both an ECG and an echocardiogram recorded during the same clinic examination. A modified receiver operating characteristic curve method was used to compare sensitivities at the same specificity levels. The adjustment formula was estimated from one randomly chosen half of the study cohort and applied to the other half for evaluation.

RESULTS

Significant improvement in sensitivity for the detection of left ventricular hypertrophy was realized at all levels of specificity. At a specificity level of 98%, the adjustment increased the sensitivity of the Cornell voltage from 10% to 17% in men and from 12% to 22% in women. For severe hypertrophy, defined as a left ventricular mass > 3 SD above the gender-specific mean, the sensitivity increased from 23% to 38% for men and from 22% to 55% for women at a specificity level of 95%.

CONCLUSIONS

This approach can substantially enhance the utility of the ECG for the detection of left ventricular hypertrophy. If these results are validated in other population groups, this approach may prove valuable in the screening of hypertensive populations and for the monitoring of patients undergoing treatment for hypertension.

A kinetic model of CD4+ lymphocytes with the human immunodeficiency virus (HIV)

This report describes a kinetic model of in vitro cytopathology involving interactions of human immunodeficiency virus (HIV) with CD4+ helper T lymphocytes. The model uses nonlinearly coupled, ordinary differential equations to simulate the dynamics of infected and uninfected cells and free virions. It is assumed that resting cells are more readily infected than activated cells, but once infected, only activated cells produce more virus. Resting cells can be activated by some appropriate stimulus (e.g. phytohemagglutinin, soluble antigen). The model predicts that the initial inoculum of virus is taken up by resting cells and without stimulation the system comes to a steady state of two populations, namely infected and uninfected cells. Stimulation of this system produces two additional populations, namely infected and uninfected activated cells which, along with the previous populations, exhibit cyclic behavior of growth, viral expression/release, and death. Additional stimuli enhance or diminish the cyclic behavior depending upon their occurrence in time. These simulations suggest a similar dynamics in human HIV infection and may explain a major factor responsible for the widely varying depletion rate of (CD4+) helper T cells in AIDS patients.

A filter to suppress ECG baseline wander and preserve ST-segment accuracy in a real-time environment

Accurate monitoring of the ST-segment displacements in real-time environments can be distorted by the nonlinear phase response of a baseline filter such as the single-pole, high-pass (0.5 Hz) filter that is standard in the industry today. The authors have previously constructed a four-pole null phase (1.0 Hz) filter that is nearly ideal in suppressing baseline wander while preserving ST-segment accuracy; however, this foreward/backward filter requires capture of a large ECG segment before filtering, thereby producing a delay that is unacceptable in a real-time environment. As a practical compromise, a two-pole, phase-compensated (1.0 Hz) filter was constructed while introducing a small time delay (160 ms). It performs much better than the "standard filter" and almost as well as the "ideal" filter in several tests, namely (1) suppression of baseline wander in a series of ECGs, (2) suppression of artificial baseline, (3) response to a triangular impulse wave (American Heart Association test), and (4) J-point displacement in several ECGs.

Suppression of baseline wander in the ECG using a bilinearly transformed, null-phase filter

The purpose of this study was to design and test a bilinearly transformed, null-phase (BLT/NP) filter for removing baseline wander and to compare it with the cubic spline for performance. For this purpose, the ECG data were filtered to remove high-frequency noise and low-frequency baseline wander to form a set of "clean" ECGs. Artificial low-frequency noise mimicking typical baseline wander was constructed from sine and cosine waves at 0.20 and 0.45 Hz and with amplitudes of 400 and 300 microV, respectively, and added to the "clean" ECGs to form the "test" ECGs. The BLT/NP filter and the cubic spline method each were applied to a "test" ECG to form a "restored" ECG. The measure of performance was the root mean square difference (RMSD) between the "restored" ECG and the initial "clean" ECG. RMSD values showed that on the average the BLT/NP filter performed as well as the cubic spline method and has the advantage that accurate determination of the QRS onset is not required.

Progress on the CSE diagnostic study. Application of McNemar's test revisited

The authors describe an extension of McNemar's test that can be used to compare diagnostic performance when multiple statements are obtained from computer analysis or visual interpretation of the ECG. If two or more diagnostic statements are made, by definition only one can be correct for the cases in the CSE pilot database, which were selected for single, clinically well documented, abnormalities. If one statement stood out from others as being made with the highest degree of certainty, that was accepted as the single interpretation, right or wrong. However, when two or more statements were made with the same degree of certainty and only one statement was correct, then in the previous application of McNemar's test that interpretation was given credit for being correct. In the extension of the method presented in this article, such an interpretation is given partial credit for the one correct statement and partial discredit for any incorrect statement, thereby reporting the results more properly in the sensitivity and specificity statistics for the different diagnostic categories.

Nonparametric comparison of entire ROC curves for computerized ECG left ventricular hypertrophy algorithms using data from the Framingham Heart Study

A computer program may be capable of several different statements for left ventricular hypertrophy (eg, possible LVH, probable LVH, consistent with LVH), but such statements resulting from discretized levels of sensitivity/specificity would represent only isolated points on a receiver-operating characteristic (ROC) curve, which is a plot of all levels of sensitivity versus specificity. Even if two algorithms use the same discrete scales, their performances may not readily be compared. The authors present a comparison methodology for ROC curves using ROC area as a nonparametric measure of the ability of the algorithm to separate the two populations; the ROC area ranges from 0.5 (no ability) to 1.0 (perfect separation) and is unbiased if the normal versus abnormal populations have no common values for the measurement. The methodology compares the performance of ECG algorithms on the same population of cases by testing for significant differences of ROC areas and incorporating correlation of the algorithms in a nonparametric way. To illustrate this methodology, they use ECG and echocardiographic data from the Framingham Heart Study.

Studies of Trypanosoma cruzi clones in inbred mice. III. Histopathological and electrocardiographical responses to chronic infection

Histopathological and electrocardiographical (ECG) changes occur in the heart of C3H/HeN and C57BL/6 mice infected for 1 year with Trypanosoma cruzi clones Sylvio-X10/4 (X10/4), Miranda/78 (M/78), or Miranda/80 (M/80). Heart parasitism and a variable degree of inflammation occurred following infection with clones X10/4 or M/78 but not with M/80. Clone X10/4 caused more extensive myocardial inflammation and fibrosis than clone M/78. Myocardial fibrosis was more extensive in C3H than in C57 mice infected with clone X10/4. The normal ECG pattern of C3H mice is distinctly different from C57 mice. The PR intervals of mice infected with clone X10/4 greater than M/78 greater than M/80 approximately equal to controls. ECG abnormalities occurred more frequently in mice infected with clone X10/4 than in controls or mice infected with either M/78 or M/80 regardless of strain or sex and were generally more severe in C57 than in C3H infected with X10/4. First degree atrioventricular block occurred more frequently in C3H mice infected with clone X10/4 or M/78 and C57 mice infected with X10/4 than in all other groups. Complete atrioventricular dissociation occurred frequently in C57 mice infected with X10/4 and rarely in other mice. These results demonstrate that the myocardial response of mice to T. cruzi infection, both histological and electrophysiological, is modulated by both the mouse strain and the parasite isolate used.

The emerging prominence of computer electrocardiography in large population-based surveys

The year 1987 marks the centennial of electrocardiography. As Beamish reminds us, it was the first and foremost technical aid to the cardiologist. During the history of cardiovascular epidemiology, which dates back roughly forty years, electrocardiography has played a central role as a relatively specific marker for coronary and hypertensive heart disease. The lack of sensitivity of electrocardiography and the advent of new technologies such as ultrasonography for assessment of such heart disease in cardiology and cardiovascular epidemiology has raised questions as to whether electrocardiography might be replaced in the next century. Recent developments in computer electrocardiography have rendered suggestions of the decreased importance of electrocardiography premature. Use of computer analysis of electrocardiograms in epidemiologic studies, which dates back less than three decades, has renewed interest in and expanded the role of electrocardiography in cardiology in general and cardiovascular epidemiology in particular. The computer analysis of electrocardiograms has allowed the processing and analysis of large numbers of electrocardiograms in a rapid, efficient, systematic and consistent manner. This has led to new, more sensitive criteria for detection of left ventricular hypertrophy as a discrete variable. In addition, the numerous waveform amplitude and duration measurements by computer have allowed the development of mathematical models to express the likelihood of coronary heart disease (myocardial infarction) and degree of left ventricular hypertrophy (estimates of left ventricular mass) on continuous scales. These developments have contributed substantially to the potential of electrocardiography (and particularly computer electrocardiography) in future studies and clinical applications.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrocardiographic changes with advancing age. A cross-sectional study of the association of age with QRS axis, duration and voltage

In order to examine the electrocardiographic (ECG) changes which occur with advancing age we defined an apparently healthy reference population derived from prospectively followed subjects of the Framingham Heart Study. Healthy subjects were clinically free of hypertension, coronary artery disease, congestive heart failure and valve disease and were not taking antihypertensive or other cardiac medications. ECG tracings were analyzed by the IBM Bonner (V2) program. Mean values and correlations with age for PR duration, QRS duration and axis, S wave voltage V1 and R wave voltage V5 are presented. With advancing age in men there is a narrowing of QRS, a leftward QRS axis shift, and a loss of S V1 and R V5 amplitude. In women only a leftward QRS axis shift is associated with advancing age. These changes should be considered in defining normal age- and sex-specific reference values. These findings underscore theoretical limitations of commonly-used criteria for the ECG diagnosis of conditions such as left ventricular hypertrophy.

Use of functional maps in renal scintigraphy to detect segmental arterial lesions

Renography using a gamma camera, a minicomputer, [123I]orthoiodohippurate ([123I]OIH), and a canine model was employed to evaluate computer-generated maps of regional renal function. Renograms were obtained before and after ligations of the right renal arterial branch in four dogs, with subsequent angiographic and histologic confirmation of the lesions. Postoperative time-activity curves were normal. Washout and persistence index in three of four right kidneys showed regional abnormality. Functional renal mapping may provide a clinical technique for evaluating human renal vascular hypertension.

Comparative evaluation of the IBM (12-lead) and Royal Infirmary (orthogonal three-lead) ECG computer programs

A comparison of two computer programs for ECG interpretation was undertaken. Twelve-lead ECGs from 300 patients with various clinical abnormalities were interpreted at the National Institutes of Health using version 1 of the IBM program and corresponding orthogonal three-lead ECGs were analyzed by the Glasgow Royal Infirmary (GRI) program. Interpretations were compared with respect to the clinical documentation, wherever possible, and with each other directly in the case of diagnostic statements for which non-ECG documentation was not available. The two programs had a similar performance in determining abnormalities such as myocardial infarction and ventricular hypertrophy. However, with respect to conduction defects and ST-T-wave statements, certain discrepancies between the two program performances were revealed. There were 222 disagreements between various diagnostic statements. GRI was judged correct in 119 of these disagreements and IBM in 70. In these 189 cases the disagreement could most often be accounted for by different criteria and/or algorithms in the two programs or by the use of different ECG lead sets. The remaining 33 disagreements had to be classified as inconclusive.

A comparison of simultaneous measurements of systolic function in the baboon by electromagnetic flowmeter and high frame rate ECG-gated blood pool scintigraphy

Left ventricular (LV) systolic timing and relative volume variations were simultaneously measured by electromagnetic flowmeter (EMF) and high frame rate ECG-gated blood pool scintigraphy in five baboons. No significant differences (p greater than 0.1, paired t test) were observed in the time (from R wave) to peak aortic flow (maximum LV ejection rate), time to cessation of aortic flow (end-systole) or in the duration of aortic flow (LV ejection time). A small (approximately 15 msec) but significant systematic difference (p less than 0.02) was noted in the time to onset of aortic flow. The shape of each scintigraphic time-activity curve during systole was compared to an equivalent curve synthesized from 10 EMF flow profiles obtained in the same baboon. Comparison of these paired curves over systolic ejection yielded an average correlation or r = 0.95 (range 0.90--0.99). The ratio of peak flow to stroke volume determined from these data did not differ significantly (p greater than 0.05). In the baboon, quantitative high temporal resolution ECG-gated scintigraphy appears to reflect closely the detailed timing and relative magnitude variation of LV volume during the entire period of systolic ejection. We conclude that the assumptions underlying the scintigraphic method are valid in the baboon during the ejection interval.

High temporal resolution ECG-gated scintigraphic angiocardiography

The cardiac blood pool is visualized with high temporal resolution during a complete, average, cardiac cycle. The technique yields both qualitative and quantitative measures of cardiac performance.

A method for evaluating computer programs for electrocardiographic interpretation. II. Application to version D of the PHS program and the Mayo Clinic program of 1968

A previously described method for evaluating computer programs for electrocardiographic (ECG) interpretation was applied to Version D of the Public Health Service (PHS) program and to the Mayo Clinic program of 1968. Staff cardiologists found agreement with the results of the PHS program in 45.5% of 1150 unselected tracings. Clinically significant disagreements based strictly on application of different criteria occurred in 29%, while disagreements based on program errors were found in 25.5%. The corresponding results for the Mayo Clinic program are: agreement in 47%, disagreements due to criteria differences in 30.9%, and disagreements due to program errors in 22.1%.

Both programs had serious deficiencies, particularly in the diagnostic categories of myocardial infarction and cardiac arrhythmias. PHS program errors resulted primarily from mismeasurements and deficient program logic, while Mayo Clinic program errors more frequently resulted from pattern recognition failures. Neither program appears suitable for routine clinical use at the present time.

A method for evaluating computer programs for electrocardiographic interpretation. 3. Reproducibility testing and the sources of program errors

A simple method for testing reproducibility in ECG computer program performance results from using two digital representations of the same analog ECG tracing. Each digital representation is separated from the other by one millisecond in time. When the digital representations are processed by the Mayo Clinic program (1968), the diagnostic statements are identically reproduced in only 60% of 33 tracings. When the method is applied to version D of the PHS program and to the newly released IBM program of 1973, identical reproducibility is 43.3% and 76.0%, respectively, of 217 tracings. After analog filtering these figures are improved to 49.8% and 79.7%, respectively. These results show that reproducibility is most affected by a program's algorithms for pattern recognition, measurement, consistency checking, and noise handling. Reproducibility is less affected by attenuation of high frequency noise at the analog level. The relationship of reproducibility to program error rate in previous studies is discussed. Hence poor performance on this test obviates the need for a more time-consuming clinical evaluation. The need for human overview and quality checking is re-emphasized.

A method for evaluating computer programs for electrocardiographic interpretation. I. Application to the experimental IBM program of 1971

A method for evaluating computer programs for electrocardiographic interpretation is described. This method allows a clinician to judge the usefulness of a program for his specific setting and needs. The method requires a significant proportion and variety of abnormal tracings, the application of specific fixed criteria, and the separation of disagreements between the computer program and the clinician into those resulting from criteria differences and those resulting from programming errors, viz., pattern recognition failures, mismeasurements, and/or deficient program logic. When applied to the experimental IBM program 1971, staff cardiologists found essential agreement with the program's results in 76% of 1150 unselected tracings. Clinically significant disagreements based strictly on the application of different criteria occurred in 20% of the tracings, whereas disagreements based on program errors were found in only 4%. Although this program requires some system of human overview and quality checking, its potential for clinical implementation is worthy of consideration.

An automated method for the measurement of ventricular volume

Several important indices of myocardial performance depend upon accurate and frequent measurement of ventricular volume. Studies employing such measurements have been limited because of the difficulty of manually measuring and calculating volumes frequently enough to obtain meaningful data. We, therefore, have developed an automated method for determination of ventricular volume in man. Left ventricular cineangiograms taken in the right anterior oblique position at 60 frames/sec are projected with a flickerless projector onto a Plumbicon television camera. A second television camera is used by a skilled operator for masking out noncontributory portions of the film and for shading selected areas to facilitate accurate recognition of the opacified chamber. An electronic video-tracking device then simultaneously determines the area and the maximum length of the opacified chamber in each cine frame. These data are recorded as analog signals on magnetic tape. Volumes are calculated by computer and plotted against time. When volumes determined by this automated method are compared with those obtained by manual planimetry, the correlation coefficient is 0.96. Aluminum prolate spheroids, left ventricular casts, and left ventricular cineangiograms were studied. This automated technic permits rapid and accurate measurement of ventricular volume in patients having diagnostic left ventriculograms.