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Post myocardial infarction stratification and the signal-averaged electrocardiogram.
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Neurochemical stratification in the inner plexiform layer of the vertebrate retina.
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High-risk metastatic gestational trophoblastic disease: further stratification into two clinical entities.
Forty-two of sixty-seven patients (62.7%) treated for high-risk metastatic trophoblastic disease achieved and maintained complete remissions. The survival rate was significantly improved in those patients with scores lower than 8 according to a modification of the World Health Organization (WHO) prognostic scoring system. A low score was associated with a higher probability of response to single-agent therapy, although the difference was not statistically significant. The score, however, was significantly associated with response to multiagent chemotherapy with methotrexate, actinomycin D, and cyclophosphamide (P = 0.0004). Therefore, future trials of new combinations of chemotherapy in high-risk patients should be stratified according to the patients' prognostic scores.
Time course of stratification of the dendritic fields of ganglion cells in the retina of the cat.
The inner plexiform layer (IPL) of the retina has been shown by previous workers to comprise a number of sublayers (sublaminae or strata), each containing a distinct component of its circuitry. Using horseradish peroxidase applied to cultured whole retinas, we have observed the segregation of the dendrites of ganglion cells of the cat retina into two sublayers of the IPL. These sublayers appear to correspond to the a and b sublaminae described in studies of the adult IPL. As the dendritic fields of ganglion cells form, in mid-gestation, they are diffuse, spreading through the ganglion cell and inner plexiform layers. A few weeks before birth the dendrites become restricted to the IPL, but it is not until after birth, between P(postnatal day)2 and P5, that they segregate into inner and outer sublayers of the IPL. The process of segregation may involve the loss or 'pruning' of excess dendrites formed in 'wrong' sublayers. The segregation of dendrites into sublayers occurs concurrently with the formation of synapses by bipolar cells and may be induced by contacts made by bipolar cells onto the dendrites of ganglion cells.
Risk stratification by early exercise testing after an episode of unstable coronary artery disease. The RISC Study Group.
After stabilization of symptoms by medication a predischarge exercise test was performed in 855 men admitted with suspected unstable angina (54%) or non-Q-wave myocardial infarction (46%). Multiple logistic regression analysis demonstrated that the number of leads with ST-depression at exercise, low maximal work load, increasing age and ST-elevation in electrocardiogram at rest had independent prognostic value concerning the risk of myocardial infarction or death during the following year. Therefore a combination of extension of ST-depression and peak work load was used to define 'high and low risk response' at the exercise test. After 1 year the mortality in patients with 'high risk' compared to 'low risk' exercise response was 3.6% and 0% (P < 0.001) and the risk of either myocardial infarction or death was 15.4% and 3.9% (P < 0.0001), respectively. ST-depression, occurrence of angina and low peak load at exercise were independent predictors of future severe angina. After 1 year 29.5% of patients with any of these indicators at exercise had incapacitating symptoms that necessitated referral for coronary angiography compared to 4.8% in the group without these findings (P < 0.0001). The predictive value of the exercise test remained high in subgroups based on inclusion diagnosis, age or findings in electrocardiogram at rest and independently of treatment with beta-blockade, other antianginal medication or aspirin at the time of the exercise test.
Early risk stratification of patients with a first inferior wall acute myocardial infarction. SPRINT Study Group.
A prognostic index based on admission characteristics of patients with inferior acute myocardial infarction was developed to predict mortality and other major complications during hospitalization. The study sample included 1841 consecutive patients with a first inferior wall acute myocardial infarction, hospitalized in 13 out of 21 operating coronary care units in Israel. Age, angina in the past, congestive heart failure and blood glucose level > 180 mg/dl were independently associated with higher in-hospital mortality and morbidity. The prognostic weights of these risk factors were determined in a study group which comprised two thirds of the patients (n = 1210) who were randomly selected from the 1841 participants. A prognostic score (range, 0-15) was calculated as the sum of the prognostic weights of the above four risk factors for each patient. These scores were determined in both the study group and in a validation group (the remaining one third of the patients, n = 592). In-hospital mortality in the study group ranged from no death for 102 patients with a prognostic score of 0, to a 37% mortality rate in 106 patients whose prognostic score was > 8. Accordingly, the study group was divided into groups of low-risk (score 0-5), intermediate-risk (score 6-8) and high-risk (score > 8), with in-hospital mortality of 3, 13 and 37%, respectively. In-hospital mortality among patients in the validation group determined to be at low-, intermediate- and high-risk was 3, 13 and 44%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Comparison of dobutamine infusion and exercise during radionuclide ventriculography in the risk stratification after acute myocardial infarction.
Forty-eight patients with acute myocardial infarction were subjected to radionuclide ventriculography during exercise and dobutamine infusion after a mean duration of 25 +/- 18 days following acute myocardial infarction. The results were compared and correlated with coronary angiography. Two patterns of abnormal response of radionuclide ventriculography were identified: (1) a worsening of the baseline wall motion abnormality confined to the infarcted area, and (2) fresh regional wall motion abnormalities in areas with normal motion at rest. Of 44 patients with significant coronary artery lesions (> or = 70% diameter stenosis), 18 had single vessel disease and 26 had multivessel disease. Dobutamine and exercise radionuclide ventriculography identified 23 and 21, respectively, of 26 multivessel disease patients yielding sensitivities of 88% and 80%. Seven of 18 single vessel disease patients showed a worsening of baseline wall motion abnormality of infarct area on dobutamine infusion radionuclide ventriculography. Subgroup analysis of coronary angiograms of single vessel disease revealed that 10 of 18 patients had subtotal occlusion of infarct-related artery supplying a hypokinetic area and the rest had a totally occluded coronary artery supplying an akinetic area. Dobutamine infusion and exercise radionuclide ventriculography detected 7 and 6 of these 10 patients implying the presence of jeopardized myocardium in infarcted/peri-infarct area. Dobutamine stress radionuclide ventriculography is an acceptable alternative to exercise testing to stratify risk following acute myocardial infarction.
Importance of stratification in later stages of clinical trials.
An erroneous assumption is often made in clinical trials that once patients achieve a remission on an early phase of a study, then they can be randomized to various arms of later phases of that trial without stratifying for induction therapy, the contention being that complete remissions imply a homogeneous sample with respect to therapy already received. This short article shows that this is not the case because induction therapies may be equal with respect to the percentage of complete remissions achieved but may differ in overall proportion of patients actually cured. Examples of clinical trials with this flaw are presented. A statistical explanation of the problem, which illustrates specific methodological points, is included.
Stratification in the design of a clinical trial.
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Symptoms, social stratification and self-responsibility for health in the United States and West Germany.
This study compares the responses of a sample of Americans in Illinois and West Germans in North-Rhine Westphalia on the basis of symptom perception, symptom experience, physician utilization and health-locus-of-control. The hypothesis that as socioeconomic status increases, the more likely the individual is to manifest and behavior favorable toward self-control and acceptance of personal responsibility in health care matters was tested. The hypothesis was supported by the American data, but not the West German. Possible trends in West German society accounting for a significant lack of socioeconomic variance in illness behavior are discussed.
Reaggregation of embryonic chick retina cells: pigment epithelial cells induce a high order of stratification.
We report here that, in comparison to aggregates from retinal cells alone, addition of pigmented epithelial cells to retinal cells in rotary culture results in a pronounced increase of spatial order. A particularly high level of organization is found in about 15-20% of the aggregates. In these 'retinoids' the main layers characteristic of developing in vivo retinae can be distinguished in correct sequential arrangement on the basis of morphological criteria and by using acetylcholinesterase histochemistry [5, 6, 15], peanut agglutinin-lectin binding [11] and Lucifer Yellow staining [7-9].
Comparison of pathologic and clinical evaluation of lymph nodes in prostate cancer: implications of RTOG data for patient management and trial design and stratification.
RTOG 77-06 and 75-06 were studies of nodal irradiation in prostate cancer, for which the status of nodes was determined by lymph node dissection (LND), lymphangiography (LAG), or computer assisted tomography (CT) based on investigator preference. Actuarial 5 year endpoints of survival, NED survival, local recurrence and distant metastasis have been determined by stage for 805 eligible patients with a comparison of pathologic vs clinical (imaging test) determined nodal status. Patients with pathologically negative lymph nodes show significantly improved 5 year survival (Stage T-2 (B) 84% vs 77%, Stage T-3,4 (C) 82% vs 65%) and NED survival (Stage T-2 (B) 72% vs 63%, Stage T-3,4 (C) 64% vs 44%) compared to patients clinically negative. Free of metastasis rates are increased in Stage T-3,4 (C) pathologic negative patients compared to imaging negative patients (75% vs 60%). A comparison of clinical positive versus clinical negative patients shows no difference in survival, NED survival or rate of metastasis, while a similar comparison of pathologic positive versus pathologic negative shows significant difference for all three endpoints (survival: Stage T-2 (B) 84% vs 61%, Stage T-3,4 (C) 82% vs 66%, NED survival: Stage T-2 (B) 72% vs 32%, Stage T-3,4 (C) 64% vs 32%; free of metastasis: Stage T-2 (B) 82% vs 64%, Stage T-3,4 (C) 75% vs 44%). The clinical determination of nodal status, therefore, has no prognostic value in contrast to pathologic determination and should not be used for stratifying patients in clinical trials. The CT scans often used to evaluate nodal status are more useful if delayed until they can be done as part of the treatment planning process where the CT has value. When imaging tests suggest positive lymph nodes in prostate cancer patients, the imaging finding is confirmed by biopsy.
DNA profile match probability calculation: how to allow for population stratification, relatedness, database selection and single bands.
In DNA profile analysis, uncertainty arises due to a number of factors such as sampling error, single bands and correlations within and between loci. One of the most important of these factors is kinship: criminal and innocent suspect may share one or more bands through identity by descent from a common ancestor. Ignoring this uncertainty is consistently unfair to innocent suspects. The effect is usually small, but may be important in some cases. The report of the US National Research Committee proposed a complicated, ad-hoc and overly-conservative method of dealing with some of these problems. We propose an alternative approach which addresses directly the effect of kinship. Whilst remaining conservative, it is simple, logically coherent and makes efficient use of the data.
Postinfarction risk stratification.
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Risk stratification before thrombolytic therapy in patients with acute myocardial infarction. The Thrombolysis in Myocardial Infarction (TIMI) Phase II Co-Investigators.
Several studies in the prethrombolytic era on the treatment of acute myocardial infarction identified selected variables from the patient's history, physical examination, chest roentgenogram and electrocardiogram that could be used to estimate mortality in patients with evolving infarction. To extend such assessment to patients receiving thrombolytic therapy, this study evaluated the prognostic utility of several risk factors in the 3,339 patients (2,742 men, 597 women, aged 24 to 78 years) enrolled in Phase II of the Thrombolysis in Myocardial Infarction (TIMI) trial. Before intravenous tissue plasminogen activator was given, the presence of each of eight risk factors was noted: age greater than or equal to 70 years, female gender, a history of diabetes mellitus or previous myocardial infarction, electrocardiographic evidence of evolving anterior infarction or atrial fibrillation, evidence on physical examination of mild pulmonary congestion or hypotension (systolic pressure less than 100 mm Hg) and sinus tachycardia (heart rate greater than 100 beats/min). Of the 3,339 patients, the 78 with pulmonary edema or cardiogenic shock were excluded because their risk was known to be high. Of the remaining 3,261, 864 (26%) had no risk factor (low risk); their mortality rate at 6 weeks was only 1.5%. In contrast, 2,397 (74%) had one or more risk factors (not low risk); of these, 5.3% died in 6 weeks (p less than 0.001). Among those with one or more risk factors, mortality at 6 weeks was related to the number of risk factors on admission; those with four or more had a mortality rate at 6 weeks of 17.2%. Thus, these eight risk factors can be easily remembered and assessed in patients with myocardial infarction who are candidates for thrombolytic therapy and can be used to estimate short-term mortality.
Prognostic significance of a predischarge exercise test in risk stratification after unstable angina pectoris.
The prognostic significance of exercise testing was compared with clinical and electrocardiographic (ECG) variables in a prospective study of 107 patients with unstable angina discharged from the hospital on medical therapy. During a follow-up period of 12.8 +/- 1.4 months, 10 patients (9%) had a nonfatal myocardial infarction (n = 8) or died (n = 2) and 22 (20%) were readmitted with recurrent unstable angina. The relation between 20 clinical, ECG and exercise test variables and the risk of adverse outcome (death, nonfatal myocardial infarction or recurrent unstable angina) was analyzed using both univariate and multivariate (logistic regression) analysis. Univariate predictors of adverse outcome included diabetes mellitus, evolutionary T wave changes, T wave changes on the preexercise ECG and low maximal rate-pressure product during exercise. Independent predictors of adverse outcome in multivariate analysis included diabetes mellitus, evolutionary T wave changes after admission, rest pain during hospitalization, ST depression during exercise and low maximal rate-pressure product. A predictive model constructed using the regression equation and all independent predictors stratified patients into high and low risk groups (41% and 5% risk of adverse outcome, respectively). The result of a predischarge exercise test adds independent prognostic information to clinical and ECG data in medically treated patients with unstable angina and could be used in combination with clinical and ECG data to identify patients at risk of adverse events.
Risk stratification for arrhythmic events in postinfarction patients based on heart rate variability, ambulatory electrocardiographic variables and the signal-averaged electrocardiogram.
The value of heart rate variability, ambulatory electrocardiographic (ECG) variables and the signal-averaged ECG in the prediction of arrhythmic events (sudden death or life-threatening ventricular arrhythmias) was assessed before hospital discharge in 416 consecutive survivors of acute myocardial infarction. During the follow-up period (range 1 to 1,112 days), there were 24 arrhythmic events and 47 deaths. The initial relation between several prognostic factors and arrhythmic events was explored with use of the Kaplan-Meier product limit estimates of survival function. Impaired heart rate variability less than 20 ms (p less than 0.0000), late potentials (p less than 0.0000), ventricular ectopic beat frequency (p less than 0.0000), repetitive ventricular forms (p less than 0.0000), left ventricular ejection fraction less than 40% (p less than 0.02) and Killip class (p less than 0.02) were identified as significant univariate predictors of arrhythmic events. When these variables were analyzed by using a stepwise Cox regression model, only impaired heart rate variability, followed by late potentials and repetitive ventricular forms remained independent predictors of arrhythmic events. The combination of impaired heart rate variability and late potentials had a sensitivity of 58%, a positive predictive accuracy of 33% and a relative risk of 18.5 for arrhythmic events and was superior to other combinations including those incorporating left ventricular function, exercise ECG, ventricular ectopic beat frequency and repetitive ventricular forms. These results suggest that a simple method of assessment based on heart rate variability and the signal-averaged ECG can select a small subgroup of survivors of myocardial infarction at high risk of future life-threatening arrhythmias and sudden death.