Evaluation of electrocardiographic criteria for right atrial enlargement by quantitative two-dimensional echocardiography.

OBJECTIVES: This study was conducted to evaluate the sensitivity and specificity of traditional electrocardiographic (ECG) criteria for right atrial enlargement and identify improve criteria, using quantitative two-dimensional echocardiography. BACKGROUND: Traditional ECG criteria for right atrial enlargement, such as P pulmonale, have been increasingly criticized as insensitive and nonspecific. Quantitative two-dimensional echo-cardiography has been shown to be a useful method for evaluating atrial size. METHODS: Hospitalized patients with mild, moderate and severe right atrial enlargement were selected from our laboratory's data base and compared with age- and gender-correlated hospitalized control subjects. After exclusions, 100 patients with right atrial enlargement and 25 control patients remained. Planimetric measurement of right atrial volumes was accomplished by two independent observers using the single-plane method of discs algorithm. Electrocardiograms were independently evaluated for current and newly proposed right atrial enlargement criteria. RESULTS: Fifty-two patients (52%) were in sinus rhythm, 41 were in atrial fibrillation, 5 were in atrial flutter, and 2 were in ectopic atrial rhythm. All control subjects were in sinus rhythm. The right atrial volume for the control group was 35.0 +/- 7.4 ml (mean +/- SD), with a narrow, roughly normal distribution. The right atrial volume for the patient group was 147.6 +/- 69.1 ml (median 127.2) in a wide, skewed distribution. The difference of mean values was highly significant (p = 0.0001). Right ventricular enlargement was found to some degree in all patients with right atrial enlargement. The most powerful predictors of right atrial enlargement were a QRS axis > 90 degrees, a P wave height in lead V2 > 1.5 mm and an R/S ratio > 1 in lead V1 in the absence of complete right bundle branch block. The combined sensitivity of these three criteria was 49%, with preservation of 100% specificity. P pulmonale detected only 6% of patients with right atrial enlargement. CONCLUSIONS: Using quantitative two-dimensional echocardiography, we found that most previously reported ECG criteria for right atrial enlargement have low predictive power. The best predictors of right atrial enlargement were a P wave height > 1.5 mm in lead V2 and, as new criteria, a QRS axis > 90 degrees and an R/S ratio > 1 in lead V1 in the absence of complete right bundle branch block. The combined sensitivity of these three criteria was 49%, with preservation of 100% specificity. Further studies are needed to prospectively validate these findings.

Left ventricular function immediately after intravenous cocaine: a quantitative two-dimensional echocardiographic study.

OBJECTIVES: We tested the hypothesis that intravenous cocaine, in doses commonly self-administered in nonmedical settings, causes acute myocardial ischemia and left ventricular dysfunction. BACKGROUND: Cocaine-induced cardiac complications are responsible for a growing number of deaths in young people, but the mechanism by which cocaine induces these complications is unclear. METHODS: We performed 12-lead electrocardiography and quantitative two-dimensional echocardiography in 20 subjects before and after single intravenous doses of high dose cocaine (1.2 mg/kg body weight), low dose cocaine (0.6 mg/kg) and placebo. RESULTS: At 2 to 7 min after cocaine administration, the rate-pressure product was increased significantly from baseline (high dose 73%, low dose 63%, placebo 8%, p < 0.001 for either dose vs. placebo). During this time, electrocardiography demonstrated dose-related nonspecific changes (high dose in 14 of 20 subjects, low dose in 9 of 20 subjects, placebo in 2 of 20 subjects, p < 0.002 for either dose vs. placebo). In contrast, echocardiography showed that the frequency of hyperdynamic left ventricular wall segments doubled after high dose cocaine compared with placebo (34% [108 of 318] vs. 16% [51 of 319], respectively, p = 0.0001) but that there was no change in either left ventricular ejection fraction (high dose 66 +/- 9%, placebo 67 +/- 6%, p = NS) or wall motion score index (high dose 0.67 +/- 0.44, placebo 0.85 +/- 0.30, p = NS). CONCLUSIONS: We conclude that intravenous cocaine, in doses commonly self-administered in nonmedical settings, does not cause acute myocardial ischemia or left ventricular dysfunction. We speculate that cocaine-induced cardiac complications are caused by idiosyncratic coronary artery vasospasm, by exceptionally high dosages or by cocaine-induced coronary artery thrombosis.

Comparison of a vectorcardiographically derived 12-lead electrocardiogram with the conventional electrocardiogram during wide QRS complex tachycardia, and its potential application for continuous bedside monitoring.

Previous investigators published conflicting reports comparing a vectorcardiographically derived electrocardiogram (ECGD) with the conventional 12-lead one (ECG). Prior comparisons were obtained in adults during sinus rhythm, but never in patients with wide QRS complex tachycardia. The ECGD was evaluated during baseline rhythms in patients with varying cardiac diagnoses, and the diagnostic accuracy of the 2 methods was compared during 64 episodes of wide QRS complex tachycardia in 49 patients during cardiac electrophysiologic study. All leads of the 12-lead ECGD closely resembled the conventional ECG in baseline and tachycardia tracings, except leads V3 and V4. QRS voltages were less in the ECGD, resulting in an inability to detect left ventricular hypertrophy in one third of patients with that diagnosis. There was excellent agreement between the ECGD and ECG in diagnosing prior myocardial infarction (92%), ventricular preexcitation patterns (100%), bundle branch and fascicular blocks (100%), and axis deviation. The ECGD was equally as valuable as the ECG in the diagnosis of wide QRS complex tachycardia. There was perfect agreement between the 2 lead systems in application of the morphologic criteria differentiating supraventricular tachycardia with aberration from ventricular tachycardia in leads V1, V2 and V6, and for criteria requiring axis determination and measurement of RS intervals in the precordial leads. The ECGD tracings contained less muscle artifact during body movements (e.g., after direct-current defibrillation). In conclusion, the ECGD's close correlation with the ECG, and its technical superiority and simple 5 torso-positioned electrode configuration make it worth pursuing as an option for continuous bedside monitoring.

The diagnosis of pericardial effusion and cardiac tamponade by 12-lead ECG. A technology assessment.

OBJECTIVE: This study was designed to determine the diagnostic value of 12-lead ECG for pericardial effusion and cardiac tamponade. DESIGN: Cross-sectional study. SETTING: University hospital. PATIENTS: Hospitalized patients with and without pericardial effusion and cardiac tamponade. MEASUREMENTS AND RESULTS: In a blinded manner, we reviewed 12-lead ECGs from 136 patients with echocardiographically diagnosed pericardial effusions (12 of whom had cardiac tamponade) and from 19 control subjects without effusions. We examined the diagnostic value of three ECG signs: low voltage, PR segment depression, and electrical alternans. We found that all three ECG signs were specific but not sensitive for pericardial effusion (specificity, 89 to 100%; sensitivity, 1 to 17%) and cardiac tamponade (specificity, 86 to 99%; sensitivity, 0 to 42%). None of the ECG signs were associated with pericardial effusions of all sizes, but low voltage was associated with large and moderate pericardial effusions (odds ratio = 2.5; 95% confidence interval [CI] = 0.9 to 6.5; p = 0.06) and with cardiac tamponade (odds ratio = 4.7; 95% CI = 1.1 to 21.0; p = 0.004). In contrast, PR segment depression was associated only with cardiac tamponade (odds ratio = 2.0; 95% CI = 1.0 to 4.0; p = 0.05), while electrical alternans was not associated with either pericardial effusion or cardiac tamponade. CONCLUSIONS: Low voltage and PR segment depression are ECG signs that are suggestive, but not diagnostic, of pericardial effusion and cardiac tamponade. Because these ECG findings cannot reliably identify these conditions, we conclude that 12-lead ECG is poorly diagnostic of pericardial effusion and cardiac tamponade.

Letter: Case of the "missing strings".

PIP: A method of removing an IUD whose strings may be lost is discussed. Having identified the intrauterine location of the IUD by touch with probe, a second Lippes loop was placed and the long strings not trimmed at all. When the patient returned later the most recently placed loop was removed and the strings of the first loop became visible; the extraction of the loop was very easy. The author feels that the above method is innocuous and entails a minimum of discomfort and expense. If this method were to be used in the case of loops with lost strings instead of surgery, the savings in hospital costs would be a minimum of a half million dollars.^ieng

Effective separation of forces in a mode coupling theory of self-diffusion.

A mode coupling theory (MCT) expression for the self-diffusion coefficient follows simply when the soft fluctuating intermolecular forces are projected along a collective densitylike variable. The projected forces separate into two parts: from the gradient of the direct correlation function (dcf), and from the short range forces. The time correlation function of the dcf-derived forces is related to the excess entropy, as shown by Ali [J. Chem. Phys. 124, 144504 (2006)], and this relationship is evaluated for two variations of MCT. As for hard spheres, the derivation of an analogous MCT is beset by a number of singularities that kinetic theory could not remove. A justifiable MCT for hard sphere fluids may not exist.

The freezing transition of a hard sphere fluid subject to the Percus-Yevick approximation.

A classical density functional theory is applied to the calculation of the fluid-solid transition for hard spheres, using the Percus-Yevick (PY) direct correlation function. Three algebraic conditions are established for the coexistence densities and the Lindemann parameter. The terms neglected in the present analysis are small and the present theory, in our eyes, is essentially an exact solution given the PY approximation. No fluid-solid transition is found for the bcc lattice, whereas for expanded fcc lattices, the agreement with previous density functional theory-based theories is good.

Stokes-Einstein relations for a square-well fluid.

A Stokes-Einstein relation, relating the shear viscosity eta to the self-diffusion coefficient D, is constructed for a classical fluid subject to an effective two-body intermolecular force, derived from a square-well potential, undergoing dynamics as described by a Smoluchowski equation for pair diffusion. The time correlation functions for eta and 1D are separated into contributions from delta function, hard-sphere forces, and from delta function, square-well soft forces. Furthermore, D is separated into its two- and three-body time correlation functions, and eta into its two- to four-body terms. D shows activated diffusion, as in Arrhenius behavior, and on the level of two-body dynamics, the Deta product adheres to the Stokes-Einstein relation, subject to a small correction for potential softness. Three-body time correlation functions increase D, whereas three- and four-body correlation functions in eta are partially offsetting. The deviation of Deta product from the Stokes-Einstein law arises from the three-body time correlations functions in D.

APPLICATION OF A MODEL OF CATEGORIZING BEHAVIOR.

A model for Latent Partition Analysis is proposed and two applications to data arising from sorting tasks are described. The model is based on a possible strategy which subjects might use in sorting a large number of stimuli. The first application is concerned with a judgmental classification of semantic differential scales in conhast to the usual type uf analysis based on responding with the scales to particular concepts. The second application is concerned with the classification by university students of a selection of student behaviors.

FACTOR ANALYTICAL TREATMENT OF GROWTH DATA.

This paper presents a limited linear factor analysis model for the analysis of repeated measures of several traits on the same subjects. Attention is drawn to the problem of analysing growth in mean scores, and an analytical resolution of this problem, together with an appropriate method of analysis, is presented for the case of independent error terms. A special condition, expected to hold for some data, is discussed, and the corresponding rotational procedures derived. Data from an artificial experiment satisfying the model are analysed to illustrate the methods evolved.

SOME DIFFERENCES IN COGNITIVE ABILITIES BETWEEN SELECTED CANADIAN AND FILIPINO STUDENTS.

This study was designed to compare both profiles of mean performance and relationships between performances on cognitive tasks in groups of children and adolescents in Canada and The Philippines with similar educational experience. A battery of eighteen tests, including the Raven's Progressive Matrices (1968), the SRA Primary Mental Abilities Tests, and selected tests from the ETS kit, was used. The samples included 219 students from an urban centre in Ontario, boys, and girls in grades 6 and 8 from private, public, and Catholic schools, and 203 students in Manila from similar sources. The results demonstrate the existence of two general factors of intellectual funotioning, one concerned with conceptual or relational thinking and the other with forming associations. There was a marked difference between the profiles of mean factor scores for the Canadian and Filipino groups, but an equally marked similarity within groups.

Adolescents' self-perceptions of competence in life skill areas.

The perceptions of a sample of 1061 adolescents of their own competence in a number of life-skill areas were assessed. Three sets of scales were used-those concerned with competence viewed as efficacy in various life areas and situations, those concerned with competence as the satisfaction of goals based on Maslow's hierarchy of needs, and assessments of the structural complexity of performance on a short essay task. In addition to comparisons among self-perceptions for different areas, a number of major comtextual and personal variables was studied for differences in self-perceptions-course type, school type, state, career aspirations and expectations, major life concerns, age, and gender. There were strong gender differences that suggested that females generally underrated their own competence. The major educational or work contexts reflected important differences in patterns of self perceptions of skill. Differences between those with different major life concerns and career hopes and expectations aligned with course type differences. Finally, there were strong indications that the self-perceptions of competence that were reported formed a strong general factor, favoring the notion of generic over domain specific self-perceptions.

Mechanization of library procedures in the medium-sized medical library. XII. An information retrieval system: a combination of a manual selective dissemination of information, and a personal file indexing system by computer.

The introduction of a manual selective dissemination of information system with a computer-based personal index service into a Medical School Library is described. An account is given of the selection of participants, the development and maintenance of search profiles, the daily procedures, the forms and outputs of the system, and the computer index maintenance system. The costs of both the manual citation selection system and the computer index maintenance system are reported.

Prospective study of angiotensin II response to positional change in pregnancy-induced hypertension.

The response of endogenous angiotensin II levels to positional change, lateral to supine recumbency, was investigated in a prospective study of 55 primigravid patients during the last half of pregnancy. Blood samples were obtained in the lateral and supine recumbent positions. The mean supine angiotensin II level was significantly higher between 29 and 34 weeks' gestation in those patients destined to develop pregnancy-induced hypertension than in those who remained normotensive (P less than 0.05). As gestation advanced, the mean per cent relative change of angiotensin II from the lateral to the supine position altered from negative to positive in those patients destined to develop pregnancy-induced hypertension, whereas it remained negative in those patients who remained normotensive. These findings are discussed in relation to pathophysiologic alterations in the development of pregnancy-induced hypertension.

Traumatic acute pericardial tamponade.

Pericardial tamponade should always be suspected in the clinical setting of any penetrating wound to the thorax or upper abdomen. The most reliable diagnostic criterion is the triad of hypotension, tachycardia and an elevated central venous pressure. Pericardiocentesis should be performed as a temporizing measure until definitive surgical therapy can be carried out. If the patient suddenly decompensates or arrests in the emergency department, immediate thoractomy with evacuation of the pericardial clot and open chest cardiac massage should be performed. Four case reports are presented. The pathophysiology and treatment are reviewed in detail.

Should the electrocardiogram be used to guide therapy for patients with left bundle-branch block and suspected myocardial infarction?

CONTEXT: Recently, an algorithm based on the electrocardiogram (ECG) was reported to predict myocardial infarction (MI) in patients with left bundle-branch block (LBBB), but the clinical impact of this testing strategy is unknown. OBJECTIVE: To determine the diagnostic test characteristics and clinical utility of this ECG algorithm for patients with suspected MI. DESIGN: Retrospective cohort study to which an algorithm was applied, followed by decision analysis regarding thrombolysis made with or without the algorithm. SETTING: University emergency department, 1994 through 1997. PATIENTS: Eighty-three patients with LBBB who presented 103 times with symptoms suggestive of MI. MAIN OUTCOME MEASURES: Myocardial infarction determined by serial cardiac enzyme analyses and stroke-free survival. RESULTS: Of 9 ECG findings assessed, none effectively distinguished the 30% of patients with MI from those with other diagnoses. The ECG algorithm indicated positive findings in only 3% of presentations and had a sensitivity of 10% (95% confidence interval, 2%-26%). The decision analysis showed that among 1000 patients with LBBB and chest pain, 929 would survive without major stroke if all received thrombolysis compared with 918 if the ECG algorithm was used as a screening test. CONCLUSIONS: The ECG is a poor predictor of MI in a community-based cohort of patients with LBBB and acute cardiopulmonary symptoms. Acute thrombolytic therapy should be considered for all patients with LBBB who have symptoms consistent with MI.