Time from symptom onset to treatment and outcomes after thrombolytic therapy. GUSTO-1 Investigators

OBJECTIVES

This study sought to examine the relations among patient characteristics, time to thrombolysis and outcomes in the international GUSTO-I trial.

BACKGROUND

Studies have shown better left ventricular function and decreased infarct size as well as increased survival with earlier thrombolysis, but the relative benefits of various thrombolytic agents with earlier administration are uncertain.

METHODS

We evaluated the relations of baseline characteristics to three prospectively defined time variables: symptom onset to treatment, symptom onset to hospital arrival (presentation delay) and hospital arrival to treatment (treatment delay). We also examined the relations of delays to clinical outcomes and to the relative 30-day mortality benefit with accelerated tissue-type plasminogen activator (t-PA) versus streptokinase.

RESULTS

Female, elderly, diabetic and hypertensive patients had longer delays at all stages. Previous infarction or bypass surgery was an additional risk factor for treatment delay. Early thrombolysis was associated with lower overall mortality rate (< 2 h, 5.5%; > 4 h, 9.0%), but no additional relative benefit resulted from earlier treatment with accelerated t-PA versus streptokinase (p = 0.38). Longer presentation and treatment delays were both associated with increased mortality rate (presentation delay < 1 h, 5.6% and > 4 h, 8.6%; treatment delay < 1 h, 5.4%, and > 90 min, 8.1%). As time to treatment increased, the incidence of recurrent ischemia or reinfarction decreased, but the rates of shock, heart failure and stroke increased.

CONCLUSIONS

Earlier treatment resulted in better outcomes, regardless of thrombolytic strategy. Elderly, female and diabetic patients were treated later, adding to their already substantial risk.

Tuning the equilibrium ion affinity and selectivity of the EF-hand calcium binding motif: substitutions at the gateway position

The ion binding parameters of the EF-hand Ca2+ binding motif are carefully tuned for different biological applications. The present study examines the contribution of the ninth position of the Ca2+-coordinating EF-loop to the tuning of Ca2+ affinity and selectivity, using the model EF-loop of the Escherichia coli galactose binding protein. Eight side chains, representing the entire set of side chains commonly observed in natural EF-loop sequences, are tested at the ninth position of the model EF-loop to determine their effects on equilibrium ion binding parameters. Using the spherical metal ions of groups Ia, IIa, and IIIa and the lanthanides as probes, both the Ca2+ affinities and ionic selectivities of the engineered sites are quantitated. Neutral side chains of different size at the ninth EF-loop position [Gln (wild type), Asn, Thr, Ser, Ala, Gly] are observed to yield similar Ca2+ affinities and retain the native ability to exclude the physiological competing metal cations Na+, K+, and Mg2+. Acidic gateway side chains (Glu, Asp) are found to reduce Ca2+ affinity and shift the ionic charge selectivity as much as 10(3)-fold toward trivalent cations. Relative to the native Gln, all engineered side chains cause a partial loss of ionic size selectivity, stemming from enhanced affinities for nonphysiological large ions. Overall, the results have implications for the molecular mechanisms used by the EF-loop to control both (i) charge selectivity, which is proposed to stem from the electrostatic repulsion between the coordinating oxygens, and (ii) size selectivity, which is theorized to involve complex interactions between multiple coordinating side chains. Finally, it has recently been shown that the ninth EF-loop position serves as a "gateway" to modulate the kinetics of Tb3+ binding and release without shifting the equilibrium affinity of this ion [Drake, S. K., & Falke, J. J. (1996) Biochemistry 35, 1753-1760]. The present results confirm that isoelectric substitutions at the gateway position have little effect on Ca2+ affinity, thereby supporting the hypothesis that the gateway side chain provides kinetic tuning of Ca2+ signaling proteins independently of their Ca2+ activation thresholds.

Spectrum of electrophysiologic and electropharmacologic characteristics of verapamil-sensitive ventricular tachycardia in patients without structural heart disease

Verapamil-sensitive ventricular tachycardia (VT) is a well-recognized clinical entity that some authorities believe may result from triggered activity. Despite its uniform response to verapamil, however, there is evidence that this uncommon form of VT may not be as homogeneous as first believed. Standard intracardiac electrophysiologic techniques were used to study verapamil-sensitive VT in 32 patients (aged 38 years +/- 20 years) without evidence of structural heart disease. More than half of these patients (69%) exhibited VT with a right bundle branch block-type QRS pattern, with the remainder (31%) displaying VT with a left bundle branch block pattern. In 31% of the patients the VT could be induced by fixed-cycle length atrial pacing, whereas in 59% of patients fixed-cycle length ventricular pacing was necessary. A critical range of cycle lengths for VT induction was required in 66% of the patients. Ventricular tachycardia was initiated with single atrial premature extrastimuli in 16% of patients, single ventricular extrastimuli in 50% of patients, and double ventricular premature extrastimuli in 9% of patients. Ventricular tachycardia displaying cycle-length alternans was observed in 28% of patients. In only 19% of patients was it possible to entrain VT during pacing from the right ventricular apex. Isoproterenol infusion was required for tachycardia induction in 50% of patients, 44% of whom had VT with a left bundle branch block QRS pattern, with the remaining 56% exhibiting VT with a right bundle branch block pattern. Beta-adrenergic blockers suppressed 53% of verapamil-sensitive VT in patients tested, whereas adenosine terminated VT in 50% of patients, with 81% of these patients exhibiting either a left bundle branch block QRS pattern or isoproterenol dependence. Ventricular tachycardia exhibiting a left bundle branch block pattern was more likely to be isoproterenol dependent (p <0.05) and adenosine sensitive (p <0.001). However, verapamil-sensitive, catecholamine-dependent VT was no more likely to be adenosine sensitive than the catecholamine-independent form of the arrhythmia (p >0.5). Verapamil-sensitive VT exhibits properties expected of both a reentrant and triggered arrhythmia, and it is inconsistently dependent on both exogenous catecholamines for induction and intravenous adenosine for termination. Verapamil-sensitive VT encompasses a heterogeneous group of tachycardias that may result from multiple cellular electrophysiologic mechanisms.

Activated partial thromboplastin time and outcome after thrombolytic therapy for acute myocardial infarction: results from the GUSTO-I trial

BACKGROUND

Although intravenous heparin is commonly used after thrombolytic therapy, few reports have addressed the relationship between the degree of anticoagulation and clinical outcomes. We examined the activated partial thromboplastin time (aPTT) in 29,656 patients in the Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries (GUSTO-I) trial and analyzed the relationship between the aPTT and both baseline patient characteristics and clinical outcomes.

METHODS AND RESULTS

Intravenous heparin was administered as a 5000-U bolus followed by an initial infusion of 1000 U/h, with dose adjustment to achieve a target aPTT of 60 to 85 seconds. aPTTs were collected 6, 12, and 24 hours after thrombolytic administration. Higher aPTT at 24 hours was strongly related to lower patient weight (P < .00001) as well as older age, female sex, and lack of cigarette smoking (all PT< .0001). At 12 hours, the aPTT associated with the lowest 30-day mortality, stroke, and bleeding rates was 50 to 70 seconds. There was an unexpected direct relationship between the aPTT and the risk of subsequent reinfarction. There was a clustering of reinfarction in the first 10 hours after discontinuation of intravenous heparin.

CONCLUSIONS

Although the relationship between aPTT and clinical outcome was confounded to some degree by the influence of baseline prognostic characteristics, aPTTs higher than 70 seconds were found to be associated with higher likelihood of mortality, stroke, bleeding, and reinfarction. These findings suggest that until proven otherwise, we should consider the aPTT range of 50 to 70 seconds as optimal with intravenous heparin after thrombolytic therapy.

Multivariable prognostic models: issues in developing models, evaluating assumptions and adequacy, and measuring and reducing errors

Multivariable regression models are powerful tools that are used frequently in studies of clinical outcomes. These models can use a mixture of categorical and continuous variables and can handle partially observed (censored) responses. However, uncritical application of modelling techniques can result in models that poorly fit the dataset at hand, or, even more likely, inaccurately predict outcomes on new subjects. One must know how to measure qualities of a model's fit in order to avoid poorly fitted or overfitted models. Measurement of predictive accuracy can be difficult for survival time data in the presence of censoring. We discuss an easily interpretable index of predictive discrimination as well as methods for assessing calibration of predicted survival probabilities. Both types of predictive accuracy should be unbiasedly validated using bootstrapping or cross-validation, before using predictions in a new data series. We discuss some of the hazards of poorly fitted and overfitted regression models and present one modelling strategy that avoids many of the problems discussed. The methods described are applicable to all regression models, but are particularly needed for binary, ordinal, and time-to-event outcomes. Methods are illustrated with a survival analysis in prostate cancer using Cox regression.

Multivariable prognostic models: issues in developing models, evaluating assumptions and adequacy, and measuring and reducing errors

Multivariable regression models are powerful tools that are used frequently in studies of clinical outcomes. These models can use a mixture of categorical and continuous variables and can handle partially observed (censored) responses. However, uncritical application of modelling techniques can result in models that poorly fit the dataset at hand, or, even more likely, inaccurately predict outcomes on new subjects. One must know how to measure qualities of a model's fit in order to avoid poorly fitted or overfitted models. Measurement of predictive accuracy can be difficult for survival time data in the presence of censoring. We discuss an easily interpretable index of predictive discrimination as well as methods for assessing calibration of predicted survival probabilities. Both types of predictive accuracy should be unbiasedly validated using bootstrapping or cross-validation, before using predictions in a new data series. We discuss some of the hazards of poorly fitted and overfitted regression models and present one modelling strategy that avoids many of the problems discussed. The methods described are applicable to all regression models, but are particularly needed for binary, ordinal, and time-to-event outcomes. Methods are illustrated with a survival analysis in prostate cancer using Cox regression.

The gene for the human architectural transcription factor HMGI-C consists of five exons each coding for a distinct functional element

The gene on chromosome 12 coding for the human protein HMGI-C has been cloned and partially sequenced. It consists of five exons, the first and last of which include long untranslated regions. The 5' UTR includes a (CA/T)n tract and a polymorphic (CT)n tract. Exons II, III and IV (87, 51 and 33 bp) are dispersed over > 30 kb. Exons I-III separately encode the three basic DNA binding domains ('A-T hooks'), exon IV encodes an 11 amino acid sequence characteristic of HMGI-C and absent from the human HMGI(Y) gene [Friedmann, M., Holth, L. T., Zoghbi, H. Y. and Reeves, R. (1993) Nucleic Acids Res., 21, 4259-4267], whilst exon V encodes the acidic C-terminal domain, which is subject to multiple phosphorylation. The HMGI-C gene is thus a striking example of the separation of functional protein elements into different coding exons.

Job strain and the prevalence and outcome of coronary artery disease

BACKGROUND

It has been hypothesized that jobs that have both high psychological demands and low decision latitude ("job strain") can lead to coronary disease. The objective of this study was to test whether job strain was correlated with the presence of coronary disease at angiography or with long-term outcome in patients with angiographic coronary disease.

METHODS AND RESULTS

Employed patients under the age of 65 years undergoing diagnostic coronary angiography completed a self-administered questionnaire about their job duties and work environment. Job strain was measured by the method of Karasek. Patients were separated into three groups, based on extent of coronary disease: significant disease (> or = 75% stenosis), insignificant disease (> 0% but < 75% stenosis), and normal coronary arteries. Statistical analyses were performed using logistic regression and the Cox proportional hazards model. The 1489 patients enrolled had a median age of 52 years; 76% were male and 88% were white. By design, all patients were employed, 60% in white-collar jobs and only 16% in jobs requiring heavy labor. Traditional cardiac risk factors were most prevalent in the 922 patients with significant coronary artery disease, at intermediate levels in the 204 patients with insignificant disease, and least prevalent in the 363 patients with normal coronary arteries (all P < .01). Job strain was actually more common in patients with normal coronary arteries (35%) than in patients with insignificant (26%) or significant disease (25%, P < .002). In a multivariate analysis, job strain was not significantly correlated with the presence of coronary disease. Job strain was not correlated with angina frequency at the time of angiography. Job strain was not a predictor of cardiac events (cardiac death or nonfatal myocardial infarction) during follow-up.

CONCLUSIONS

Job strain was not correlated with the prevalence or severity of coronary artery disease in a cohort of patients undergoing coronary angiography. The outcome of patients with angiographically defined coronary disease was not affected by the level of job strain as measured by the method of Karasek.

Hand ischaemia following radial artery cannulation

Digital ischaemia following radial arterial cannulation is uncommon. It is usually the result of thrombotic occlusion of a dominant radial artery. However, factors other than arterial thrombosis per se may operate in the critically ill patient to produce digital ischaemia. The following case presentation includes a review of possible mechanisms of digital ischaemia following radial artery cannulation and discusses the therapeutic options available.

Importance of baseline functional and socioeconomic factors for participation in cardiac rehabilitation

Enrollment in cardiac rehabilitation has been reported to improve exercise capacity, psychological well-being, and survival. However, participation rates are low and the reasons for nonparticipation have not been adequately defined. The purpose of this study was to evaluate the major correlates of nonparticipation and to examine the level of participation of patients who stand to benefit most on the basis of preenrollment functional status and health behaviors. Three hundred ninety-three patients undergoing coronary artery bypass surgery (1) had baseline functional status and quality-of-life data collected, and (2) were recruited for participation in the Duke Center for Living comprehensive 3-week post-coronary bypass surgery rehabilitation program. Baseline demographic, clinical, catheterization, functional status, psychological status, and health behavior descriptors were analyzed to identify univariate and multivariable correlates of a patient's decision to participate in the program. At baseline, most clinical factors were similar in participants (n = 52) and nonparticipants (n = 341), but the nonparticipants were more often women (26% vs 12%, p = 0.02). Participants were also more likely to be employed (63% vs 45%, p = 0.02) and had a higher education and income distribution than nonparticipants (both p = 0.001). On 2 separate scales, nonparticipants had significantly more baseline functional impairment than participants (both p = 0.001). In multivariable analysis, the independent correlates of higher participation rates were: higher education (college graduates 71% more likely to participate than high school graduates) and better baseline Duke Activity Status Index (patients with mild functional impairment were at least 42% more likely to participate than patients with moderate impairment).(ABSTRACT TRUNCATED AT 250 WORDS)

Cost effectiveness of thrombolytic therapy with tissue plasminogen activator as compared with streptokinase for acute myocardial infarction

BACKGROUND

Patients with acute myocardial infarction who were treated with accelerated tissue plasminogen activator (t-PA) (given over a period of 1 1/2 hours rather than the conventional 3 hours, and with two thirds of the dose given in the first 30 minutes) had a 30-day mortality that was 15 percent lower than that of patients treated with streptokinase in the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries (GUSTO) study. This was equivalent to an absolute decrease of 1 percent in 30-day mortality. We sought to assess whether the use of t-PA, as compared with streptokinase, is cost effective.

METHODS

Our primary, or base-case, analysis of cost effectiveness used data from the GUSTO study and life expectancy projected on the basis of the records of survivors of myocardial infarction in the Duke Cardiovascular Disease Database. In the primary analysis, we assumed that there were no additional treatment costs due to the use of t-PA after the first year and that the comparative survival benefit of t-PA was still evident one year after enrollment.

RESULTS

One year after enrollment, patients who received t-PA had both higher costs ($2,845) and a higher survival rate (an increase of 1.1 percent, or 11 per 1000 patients treated) than streptokinase-treated patients. On the basis of the projected life expectancy of each treatment group, the incremental cost-effectiveness ratio--with both future costs and benefits discounted at 5 percent per year--was $32,678 per year of life saved. The use of t-PA was least cost effective in younger patients and most cost effective in older patients. At all ages, the use of t-PA in patients with anterior infarctions yielded more favorable cost-effectiveness values. In our secondary analyses, the cost-effectiveness values were most sensitive to a lowering of the projected long-term survival benefits of t-PA and to moderate or greater increases in the projected medical costs for patients in the t-PA group after the first year. In contrast, our results were not sensitive to even very unfavorable assumptions about the additional costs associated with the higher rate of disabling stroke that was noted in patients treated with t-PA in the GUSTO study.

CONCLUSIONS

The cost effectiveness of treatment with accelerated t-PA rather than streptokinase compares favorably with that of other therapies whose added medical benefit for dollars spent is judged by society to be worthwhile.

Variations in patient management and outcomes for acute myocardial infarction in the United States and other countries. Results from the GUSTO trial. Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries

OBJECTIVE

To examine differences in outcomes and patient management between patients in the United States and outside the United States undergoing thrombolysis for acute myocardial infarction.

DESIGN, SETTING, AND PATIENTS

Patients in the United States (n = 23,105) and 14 other countries (n = 17,916) were randomized to receive streptokinase plus either subcutaneous or intravenous (IV) heparin, accelerated recombinant tissue-type plasminogen activator (rt-PA) plus IV heparin, or combined streptokinase and rt-PA plus IV heparin.

OUTCOME MEASURES

Differences in 30-day mortality and patient management were compared among treatments and between US and non-US patients. Treatment-by-country interactions were assessed by logistic regression analyses. Expected mortality of US and non-US patients was estimated using a predictive model and was compared with observed mortality.

RESULTS

Mortality reduction with accelerated rt-PA vs streptokinase was greater in the United States (1.2% absolute decrease vs 0.7% elsewhere), but the test for treatment-by-country interaction against streptokinase was not significant (P = .30). Benefits of accelerated rt-PA over combination therapy were observed in the United States, but not in other countries (P = .02). Despite differences in base-line characteristics and patient management, 30-day mortality was not significantly different: 6.8% in the United States vs 7.2% elsewhere (P = .09). After adjustment for baseline differences, observed vs predicted outcomes were slightly better in the United States (6.8% vs 7.0%) than elsewhere (7.2% vs 7.0%), indicating that enrollment in the United States was a marginally significant predictor of better survival (P = .047).

CONCLUSIONS

No significant evidence for a differentially greater benefit of accelerated rt-PA over streptokinase was found in US vs non-US patients. However, increased procedure and treatment use in the United States was associated with only a small decrease in short-term mortality. Long-term follow-up is required to clarify the relationship between survival and the more intensive US management approach.

Production of fumonisins by Fusarium species of Taiwan

Twenty-nine Fusarium species isolated from various sources in different districts of Taiwan were tested for their ability to produce fumonisins in corn cultures. Only Fusarium moniliforme produced fumonisin B1 (FB1) and fumonisin B2 (FB2). The finding that the other 28 Fusarium species produced neither FB1 nor FB2 is preliminary because only one strain per species was studied. The detection of FB1 and FB2 in cultures of F. moniliforme was demonstrated by TLC and HPLC, and FB1 was further confirmed by mass spectrometry. In a separate experiment, in which 38 strains of F. moniliforme were tested for fumonisins, approximately 66% (25/38) produced FB1 and/or FB2. Of the 25 strains, 14 produced only FB1 and 11 produced both FB1 and FB2, and the amounts of FB1 and FB2 produced by different strains varied greatly. This is the first report that fumonisins are found in corn cultures experimentally infected with F. moniliforme strains from Taiwan. It is safe to assume that fumonisin producing strains of F. moniliforme are widely distributed among the economic crops such as corn, rice, sugarcane, and sorghum throughout the Island.

Significance of a coronary artery with thrombolysis in myocardial infarction grade 2 flow "patency" (outcome in the thrombolysis and angioplasty in myocardial infarction trials). Thrombolysis and Angioplasty in Myocardial Infarction Study Group

To determine whether pharmacologic reperfusion to Thrombolysis in Myocardial Infarction (TIMI) grade 2 flow during acute myocardial infarction confers the same clinical benefit as restoration of TIMI 3 flow, in-hospital clinical and angiographic outcomes in 1,229 patients prospectively enrolled in the Thrombolysis and Angioplasty in Myocardial Infarction trials were analyzed. Patients were treated with intravenous tissue plasminogen activator or urokinase, or both. Angiography of the infarct-related artery 90 minutes after initiation of thrombolytic therapy demonstrated TIMI grades 0, 1, 2, or 3 flow in 20%, 7%, 17%, and 55% of vessels, respectively. Rescue or adjunctive coronary angioplasty was performed in 80%, 27%, and 16% of patients with TIMI 0/1, 2, or 3 flow, respectively. Predischarge angiography was performed in 963 patients. A significant gradient of increasing mortality was seen in patients with lower TIMI flow (4.3%, 6.1%, and 10.1% with TIMI 3, 2, and 0/1 flow, respectively, p = 0.002). The incidence of congestive heart failure and recurrent ischemia was significantly higher in patients with TIMI 2 than with TIMI 3 perfusion (26% vs 19% for heart failure, p = 0.03; 23% vs 17% for recurrent ischemia, p = 0.05). Acute left ventricular ejection fraction and infarct zone regional wall motion were also significantly improved in patients with TIMI 3 than with TIMI 2 flow, with trends toward better improvement in global and regional function in the TIMI 3 group. These findings were not affected by the use of acute coronary angioplasty.(ABSTRACT TRUNCATED AT 250 WORDS)

Predictors of 30-day mortality in the era of reperfusion for acute myocardial infarction. Results from an international trial of 41,021 patients. GUSTO-I Investigators

BACKGROUND

Despite remarkable advances in the treatment of acute myocardial infarction, substantial early patient mortality remains. Appropriate choices among alternative therapies and the use of clinical resources depend on an estimate of the patient's risk. Individual patients reflect a combination of clinical features that influence prognosis, and these factors must be appropriately weighted to produce an accurate assessment of risk. Prior studies to define prognosis either were performed before widespread use of thrombolysis or were limited in sample size or spectrum of data. Using the large population of the GUSTO-I trial, we performed a comprehensive analysis of relations between baseline clinical data and 30-day mortality and developed a multivariable statistical model for risk assessment in candidates for thrombolytic therapy.

METHODS AND RESULTS

For the 41,021 patients enrolled in GUSTO-I, a randomized trial of four thrombolytic strategies, relations between clinical descriptors routinely collected at initial presentation, and death within 30 days (which occurred in 7% of the population) were examined with both univariable and multivariable analyses. Variables studied included demographics, history and risk factors, presenting characteristics, and treatment assignment. Risk modeling was performed with logistic multiple regression and validated with bootstrapping techniques. Multivariable analysis identified age as the most significant factor influencing 30-day mortality, with rates of 1.1% in the youngest decile (< 45 years) and 20.5% in patients > 75 (adjusted chi 2 = 717, P < .0001). Other factors most significantly associated with increased mortality were lower systolic blood pressure (chi 2 = 550, P < .0001), higher Killip class (chi 2 = 350, P < .0001), elevated heart rate (chi 2 = 275, P < .0001), and anterior infarction (chi 2 = 143, P < .0001). Together, these five characteristics contained 90% of the prognostic information in the baseline clinical data. Other significant though less important factors included previous myocardial infarction, height, time to treatment, diabetes, weight, smoking status, type of thrombolytic, previous bypass surgery, hypertension, and prior cerebrovascular disease. Combining prognostic variables through logistic regression, we produced a validated model that stratified patient risk and accurately estimated the likelihood of death.

CONCLUSIONS

The clinical determinants of mortality in patients treated with thrombolytic therapy within 6 hours of symptom onset are multifactorial and the relations complex. Although a few variables contain most of the prognostic information, many others contribute additional independent prognostic information. Through consideration of multiple characteristics, including age, medical history, physiological significance of the infarction, and medical treatment, the prognosis of an individual patient can be accurately estimated.

Determining VA physician requirements through empirically based models

OBJECTIVE

As part of a project to estimate physician requirements for the Department of Veterans Affairs, the Institute of Medicine (IOM) developed and tested empirically based models of physician staffing, by specialty, that could be applied to each VA facility.

DATA SOURCE/STUDY SETTING

These analyses used selected data on all patient encounters and all facilities in VA's management information systems for FY 1989.

STUDY DESIGN

Production functions (PFs), with patient workload dependent on physicians, other providers, and nonpersonnel factors, were estimated for each of 14 patient care areas in a VA medical center. Inverse production functions (IPFs), with physician staffing levels dependent on workload and other factors, were estimated for each of 11 specialty groupings. These models provide complementary approaches to deriving VA physician requirements for patient care and medical education.

DATA COLLECTION/EXTRACTION METHODS

All data were assembled by VA and put in analyzable SAS data sets containing FY 1989 workload and staffing variables used in the PFs and IPFs. All statistical analyses reported here were conducted by the IOM.

PRINCIPAL FINDINGS

Existing VA data can be used to develop statistically strong, clinically plausible, empirically based models for calculating physician requirements, by specialty. These models can (1) compare current physician staffing in a given setting with systemwide norms and (2) yield estimates of future staffing requirements conditional on future workload.

CONCLUSIONS

Empirically based models can play an important role in determining VA physician staffing requirements. VA should test, evaluate, and revise these models on an ongoing basis.

The exclusion of women from clinical trials of thrombolytic therapy: implications for developing the thrombolytic predictive instrument database

The thrombolytic predictive instrument (TPI) was developed to identify those patients most likely to benefit from thrombolytic therapy for acute myocardial infarction as well as to facilitate the earliest possible administration of this treatment. The TPI consists of predictive models derived from clinical data obtained from both clinical trials and data registries. These models are subject to potential bias due to combinations of primary data from different sources. The purpose of this investigation was to assess the influence of gender in developing the TPI database. In this database, there were 1,096 (22%) women and 3,826 (78%) men; only 38% of the women were enrolled in clinical trials, whereas 46% of the men were (p < 0.0001). Within clinical trials, there were few significant eligibility differences between women and men, as the vast majority of patients met eligibility standards for entry in these trials. However, within clinical registries, the women were older (p < 0.0001) and more often had elevated blood pressure on admission (p = 0.002). Multivariate logistic regression indicated that after adjustment for significant predictors of trial inclusion, women were 25% less likely to be included in clinical trials (odds ratio = 0.76, 95% confidence interval = 0.60, 0.96). In order to counter bias introduced by the exclusion of women from clinical trials, the TPI database included patients from non-trial settings. Carefully including patients from clinical registries or non-trial settings may be an important strategy in constructing generally applicable predictive instruments.

Revisit of MALDI for small proteins

Matrix-assisted laser desorption/ionization (MALDI) was used for several small proteins (such as insulin) and for peptides. It was found that the detection efficiencies of MALDI for the insulin B chain and the insulin A chain are drastically different. Similar phenomena were also observed for various types of peptides. The positive-ion signal of MALDI in detecting proteins or peptides was found to be greatly enhanced by the presence of a basic amino acid in their chains. The experimental results indicate that this enhancement may arise from proton transfer in solution by an acid-base reaction between the protein/peptide and matrix molecule. This pre-protonated mechanism provides a low energy barrier for the ionization of peptides in a MALDI process, and greatly reduces the energy threshold of MALDI. Matrix effects on the ionization mechanism are discussed.

Use of medical resources and quality of life after acute myocardial infarction in Canada and the United States

BACKGROUND

Much attention has been directed to the use of medical resources and to patients' outcomes in Canada as compared with the United States. We compared U.S. and Canadian patients with respect to their use of medical resources and their quality of life during the year after acute myocardial infarction.

METHODS

A total of 2600 U.S. and 400 Canadian patients were randomly selected from the Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries (GUSTO) trial. Base-line data from their initial hospitalizations were analyzed, and the patients were then interviewed by telephone 30 days, 6 months, and 1 year after myocardial infarction to determine their use of medical care and quality of life.

RESULTS

The Canadian patients typically stayed in the hospital one day longer (P = 0.009) than the U.S. patients but had a much lower rate of cardiac catheterization (25 percent vs. 72 percent, P < 0.001), coronary angioplasty (11 percent vs. 29 percent, P < 0.001), and coronary bypass surgery (3 percent vs. 14 percent, P < 0.001). At one year 24 percent of the Canadian and 53 percent of the U.S. patients had undergone angioplasty or bypass surgery at least once (P < 0.001). The Canadian had more visits to physicians during the follow-up year (P < 0.001), but fewer visits to specialists (P < 0.001). At 30 days, functional status was equivalent in the patients from the two countries. However, after one year the U.S. patients had substantially more improvement than the Canadian patients (P < 0.001). The prevalence of chest pain and dyspnea at one year was higher among the Canadian patients (34 percent vs. 21 percent and 45 percent vs. 29 percent, respectively; P < 0.001).

CONCLUSIONS

The Canadian patients had more cardiac symptoms and worse functional status one year after acute myocardial infarction than the U.S. patients. The Canadian patients also underwent fewer invasive cardiac procedures and had fewer visits to specialist physicians. These results suggest, but do not prove, that the more aggressive pattern of care in the United States may have been responsible for the better quality of life.

Adenosine in wide complex tachycardia: potential pitfalls in diagnostic value

Adenosine is an efficacious diagnostic and therapeutic agent in the acute management of wide complex tachycardias. Its potent negative dromotropic effect terminates supraventricular tachycardias involving the atrioventricular node, allowing differentiation from tachycardias of atrial and ventricular origin. Its extranodal actions, however, may lead to potential pitfalls in arrhythmia diagnosis. We report three unusual cases of patients with adenosine-sensitive tachycardias. One patient had idiopathic ventricular tachycardia originating from the right ventricular outflow tract, one had ectopic atrial tachycardia, and one had atrial fibrillation with rate-related intraventricular aberration. Recognition of the extranodal actions of adenosine and careful ECG evaluation before and after adenosine administration should maximize the diagnostic accuracy of adenosine in wide complex tachycardias.