Biomedical subjects

K B Schechtman

Publications and source records attributed to K B Schechtman.

At least 19 recordsLinked to original sources

PubMed1996

Gender-related differences in left ventricular filling dynamics in older subjects after endurance exercise training.

The present study was designed to determine if gender affects the adaptive response to endurance exercise training of left ventricular filling dynamics in older individuals. Recently, it was shown that gender influences the cardiovascular responses to endurance exercise training in older subjects. Older men improve left ventricular systolic performance and increase maximal cardiac output in response to endurance exercise training, whereas older women do not. Twelve men (65 +/- 1 years old; mean +/- SE) and 10 women (64 +/- 1) were studied before and after 9 months of endurance exercise training. Maximal O2 uptake was determined during treadmill exercise. Left ventricular filling dynamics and ejection fraction (EF) at rest and during supine exercise were assessed by Tc-99m radionuclide ventriculography. When expressed relative to body weight, maximal O2 uptake (VO2 max) was increased by 24% (27.3 +/- 1.5 to 34.0 +/- 1.5 ml/kg/min; p < .01) in men and 27% (21.9 +/- 1.0 to 27.8 +/- 1.0 ml/kg/min; p < .01) in women in response to endurance exercise training. In men, the time-to-peak filling rate (TPFR) decreased (-19.8 +/- 6.7 ms; p < .05) during exercise at a comparable heart rate in response to training. In contrast, the change in TPFR in women (+2.7 +/- 6.0 ms) was small and insignificant. Peak filling rate (PFR) at rest and during exercise was similar before and after training in men and women. The change in left ventricular systolic reserve at a comparable heart rate from pre-to posttraining improved in men (delta EF 4 +/- 3%; p < .05), but not in women (-2 +/- 3%). The results indicate that the adaptive response of left ventricular filling dynamics to endurance exercise training is influenced by gender in older subjects. Older men show improvement in left ventricular filling dynamics, whereas older women do not.

Aged↗

PubMed1995

Myocardial injury in critically ill patients. A frequently unrecognized complication.

OBJECTIVE: To determine the incidence and effect of unrecognized cardiac injury in critically ill patients. DESIGN: Prospective, blinded, single-center study. SETTING: The medical and respiratory intensive care unit of an academic health center. PATIENTS: Two hundred nine patients (224 admissions). MAIN OUTCOME MEASURES: Daily measurement of levels of cardiac troponin I, a sensitive, highly specific, and long-lived marker of myocardial injury. Concurrently, signs and symptoms potentially related to myocardial ischemia were tabulated by blinded investigators. All clinical evaluation and management decisions were made by the physicians responsible for the care of the patient. RESULTS: Thirty-two (15%) of the 209 patients had evidence of myocardial damage based on elevated levels of cardiac troponin I. Only 12 (37%) of these 32 patients were diagnosed as having acute myocardial infarction by the intensive care unit staff. Cardiac damage was unrecognized in the other 20 (63%). Unrecognized cardiac injury was more common in young patients and in blacks. Mortality in patients with myocardial injury that was recognized (42%) or unrecognized (40%) was higher than in those without myocardial injury (15%) (P < .001). Patients with cardiac injury were more frequently hypotensive (75% vs 50%; P = .007) and in need of mechanical ventilation (66% vs 27%; P < .001) and had longer intensive care unit stays (5.3 vs 3.1 days; P < .007) than patients without cardiac injury. CONCLUSION: The incidence of myocardial injury defined by elevated levels of cardiac troponin I was unexpectedly high and associated with increased morbidity and mortality. Clinically, it was often unrecognized.

Adult↗

PubMed1995

Quantitative assessment of myocardial ultrasound tissue characterization through receiver operating characteristic analysis of Bayesian classifiers.

OBJECTIVES: This work proposes a self-consistent assessment methodology for quantitative evaluation of any combination of diagnostic features, with the immediate goal of quantitatively assessing the discriminating power in diabetic patients of features derived from ultrasound backscatter from myocardium. BACKGROUND: Four features from analysis of left ventricular myocardial ultrasound backscatter have previously been shown to be sensitive to potentially cardiomyopathic changes in patients with insulin-dependent diabetes mellitus who have no overt heart disease. The measured features were significantly different between such patients and normal control subjects, as well as among groups of such patients with and without systemic complications of the disease. The quantitative discriminating potential of the features was not assessed. METHODS: Multivariate classifier functions were constructed and analyzed by using the methodology of the receiver operating characteristic curve, which allows quantitative assessment of the discriminating power of these features, alone or in combination. The area under the receiver operating characteristic curve--the true positive rate averaged over all false positive rates--was used as a summary measure of performance. RESULTS: In distinguishing patients with insulin-dependent diabetes mellitus from normal control subjects, the most discriminating combination of ultrasound features for the detection of such changes in these patients yielded receiver operating characteristic curves with area measures of approximately 0.80; for such patients with retinopathy the measure increased to 0.90. This performance is comparable to that of many commonly used diagnostic tests. CONCLUSIONS: A self-consistent set of evaluation methodologies has quantitatively demonstrated the sensitivity of four ultrasound backscatter features to otherwise latent changes in myocardial structure that accompany the evolution of insulin-dependent diabetes mellitus. The results are remarkable in themselves and suggest the potential of the features for the general field of cardiac ultrasound tissue characterization.

Bayes Theorem↗

PubMed1995

Transabdominal versus retroperitoneal incision for abdominal aortic surgery: report of a prospective randomized trial.

PURPOSE: The purpose of this study was to perform a randomized, prospective trial that compares the transabdominal with the retroperitoneal approach to the aorta for routine infrarenal aortic reconstruction. METHODS: From August 1990 through November 1993, patients undergoing surgery for abdominal aortic aneurysm (AAA) disease or aortoiliac occlusive disease (AIOD) were asked to participate in a randomized trial comparing the transabdominal incision (TAI) to the retroperitoneal incision (RPI) for aortic surgery. One hundred forty-five patients were randomized, with 75 (41 with AAA and 34 with AIOD) in the TAI group and 70 (40 with AAA and 30 with AIOD) in the RPI group. There were no significant differences between the groups in terms of age, sex, postoperative pain control (epidural vs patient-controlled analgesia), or comorbid conditions, except for a higher incidence of chronic obstructive pulmonary disease in the TAI group (21 vs 8 patients). RESULTS: The incidence of intraoperative complications was similar for both groups. After surgery, the incidence of prolonged ileus (p = 0.013) and small bowel obstruction (p = 0.05) was higher in the TAI group. Overall, the RPI group had significantly fewer complications (p < 0.0001). The overall postoperative mortality rate (two deaths) was 1.4%, with both occurring in the TAI group (p = 0.507). The RPI group also had significantly shorter stays in the intensive care unit (p = 0.006), a trend toward shorter hospitalization (p = 0.10), lower total hospital charges (p = 0.019), and lower total hospital costs (p = 0.017). There was no difference in pulmonary complications (p = 0.71). In long-term follow-up (mean 23 months), the RPI group reported more incisional pain (p = 0.056), but no difference was found in incisional hernias or bulges (p = 0.297). CONCLUSIONS: We conclude that the RPI approach for abdominal aortic surgery is associated with fewer postoperative complications, shorter stays in the hospital and intensive care unit, and lower cost. There is, however, an increase in long-term incisional pain. Current methods of postoperative pain control seem to decrease the incidence of pulmonary complications.

Abdomen↗

PubMed1995

Methodological and statistical problems in sleep apnea research: the literature on uvulopalatopharyngoplasty.

A comprehensive review of the literature on the surgical treatment of sleep apnea found 37 appropriate papers (total n = 992) on uvulopalatopharyngoplasty (UPPP). Methodological and statistical problems in these papers included the following: 1) There were no randomized studies and few (n = 4) with control groups. 2) Median sample size was only 21.5; thus statistical power was low and clinically important associations were routinely classified as "not statistically significant". 3) Only one paper presented the confidence bounds that might distinguish between statistical and clinical significance. 4) Because of short follow-up time and infrequent repeat follow-ups, little is known about whether UPPP results deteriorate with time. 5) In at least 15 papers, bias caused by retrospective designs and nonrandom loss to follow-up raised questions about the generalizability of results. 6) Few papers associated polysomnographic data with patient-based quality of life measures. 7) Missing data and missing and inconsistent definitions were common. 8) Baseline measures were often biased because the same assessment was inappropriately but routinely used for both screening and baseline. We conclude that because of these and other problems, there is much that is needlessly unknown about UPPP. It is the responsibility of the research and professional communities to define training, editorial and review procedures that will raise the methodological and statistical quality of published research.

Humans↗

PubMed1995

Relationship between physical performance and self-perceived physical function.

OBJECTIVE: The objective of this study was to compare two methods of measuring physical function in subjects with a broad range of abilities and to evaluate the effects of cognitive, social, educational, and age factors on the relationship between the two methods. DESIGN: Multiple regression analysis was used to compare self-perceived (dependent variables) with performance measures (independent variables). Covariates included age, gender, Mini-Mental State Exam score, education, living status, and depression score. SETTING: Five community-dwelling and two nursing home sites. PARTICIPANTS: 417 community-dwelling subjects and 200 nursing home residents aged 62-98 years. MEASUREMENTS: Self-perceived physical function was assessed with the physical dimension summary score of the Sickness Impact Profile, which comprises three subscales: ambulation, mobility, and body care and movement. Physical performance was evaluated by self-selected gait speed, chair-stand time, maximal grip strength, and a balance score. RESULTS: Nursing home residents and community-dwellers were significantly different (P < .0001) in all variables except age and gender. Self-perceived and performance-based measures were moderately correlated, with a range from r = -.194 to r = -.625 (P < .05). Gait speed was the strongest independent predictor of self-perceived physical function in both groups. Symptoms of depression were also an independent predictor of self-perceived function in nursing home residents; subjects who had such symptoms report more self-perceived dysfunction than would be predicted based on performance tests. CONCLUSIONS: Self-selected gait speed is a global indicator of self-perceived physical function over a broad range of abilities. External determinants (depressive symptoms, cognitive function, marital status, etc.) affect self-perceived function in both groups, but gait speed is the greatest single predictor of self-perceived function. In nursing home residents depressive symptomatology is related to self-perceived.

Activities of Daily Living↗

PubMed1994

The effect of poor compliance and treatment side effects on sample size requirements in randomized clinical trials.

Treatment side effects and associated noncompliance have methodological implications vital to the testing of new drugs. In this paper, we quantify the impact of these factors on sample size requirements in clinical trials. In the Lipid Research Clinics Trial, side effects caused treatment group compliance (50.8%) to be lower than placebo compliance (67.3%). Cholesterol reduction among treatment noncompliers was 35.2% of the reduction among compliers. Had treatment group compliance been as high as placebo compliance, 41% fewer patients would have been required to achieve the same statistical power and an expected 31% more coronary events would have been prevented. We conclude: Because they discourage patient compliance, treatment side effects can (1) cause large sample size increases, (2) lead to underestimates of true efficacy, and (3) contribute to potentially invalid negative conclusions in clinical trials. The impact of side effects goes well beyond the complications and patient discomforts with which they are associated.

Cholestyramine Resin↗

PubMed1994

Older adults' perceptions of their health and functioning in relation to sleep disturbance, falling, and urinary incontinence.FICSIT Group.

OBJECTIVE: To investigate variation in older adults' perceived health and functioning that is associated with self-reported sleep disturbance, falling, and urinary incontinence, controlling for self-reported depression, ambulation difficulty, number of chronic conditions, and subjects' sociodemographic characteristics. DESIGN: Multicenter prospective study (FICSIT). SETTING: Persons age 70 and older living in the community evaluated at baseline. PARTICIPANTS: 239 women, 113 men; mean age = 77. MEASUREMENTS: Sleep disturbance score based on EPESE questions, recent falls history (Y/N), incontinent episodes (Y/N), CES-D score, SIP Ambulation score, and 4 MOS SF-36 scale scores. RESULTS: Women were significantly more likely than men to report multiple conditions (sleep disturbance, falling, incontinence) and to report lower levels of functioning as measured by 3 of 4 SF-36 scales. In regression analyses, sleep disturbance and urinary incontinence were significant predictors of perceived limitations in usual role activities because of physical health problems. Depression and ambulation measures significantly predicted scores on all 4 SF-36 scales. CONCLUSIONS: Our analysis suggests that it is important to address depressive symptomatology and ambulation difficulty--which in turn are related to sleep disturbance, falling, and urinary incontinence--in efforts to enhance older adults' perceived health and functioning.

Accidental Falls↗

PubMed1994

Enhanced left ventricular performance in endurance trained older men.

BACKGROUND: The age-associated decline in aerobic exercise capacity is partially reversible by endurance exercise training. Moderate-intensity endurance exercise training increases aerobic exercise capacity mediated, in part, by improvement of stroke volume and left ventricular performance in older men. The present study was designed to characterize the nature of cardiovascular adaptations to strenuous endurance exercise of long duration and to delineate the mechanisms underlying increased stroke volume and cardiac output in highly trained older endurance athletes. METHODS AND RESULTS: Nine male master athletes (MA: 64 +/- 2 years old, mean +/- SEM) and 9 older sedentary healthy men (controls: 63 +/- 1 year) were studied. Left ventricular systolic function was evaluated with the use of cardiac blood pool imaging and echocardiography. Maximal O2 uptake (VO2max) was 50.4 +/- 1.7 mL.kg-1 x min-1 in the MA and 29.6 +/- 1.4 mL.kg-1 x min-1 (P = .0001) in controls. Systolic and mean blood pressures at rest and during exercise were not different in the two groups. Left ventricular systolic function at peak exercise was higher in the MA than in sedentary controls as evidenced by (1) a higher left ventricular functional reserve (delta EF: 12.4 +/- 2 versus 5.6 +/- 2.5, P = .05), (2) a large decrease in end-systolic volume during exercise (MA: 56 +/- 4 mL at rest and 42 +/- 5 mL at peak exercise, P = .007; controls: 43 +/- 2 mL at rest and 42 +/- 6 mL at peak exercise, P = .35) with no differences in systolic blood pressure, (3) a higher left ventricular fractional shortening at peak exercise (MA: 52 +/- 2.6%; controls: 45 +/- 1%, P = .046) at comparable values for end-systolic wall stress (MA: 56 +/- 12 g/cm2; controls: 53 +/- 7 g/cm2, P = .50), and (4) a greater decrease in end-systolic diameter at peak exercise in the MA than in controls (MA: -1.2 +/- 0.16 cm versus -0.57 +/- 0.13 cm, P = .014) despite no significant differences between the changes in end-systolic wall stress during exercise (MA: -15.5 +/- 7.5 g/cm2, controls: -11.0 +/- 9.0 g/cm2, P = .6). MA had a larger end-diastolic volume at rest (153 +/- 6 versus 132 +/- 4 mL, P = .009) with a normal wall thickness-to-radius ratio (0.34 +/- 0.02). Peak exercise stroke volume was higher (P = .023) in the MA (132 +/- 6 mL/min) than in the sedentary controls (111 +/- 6 mL/min). Changes in stroke volume correlated strongly with changes in ejection fraction in the MA (r = .80, P = .010) but not in sedentary controls (r = .59, P = .097). Further, changes in stroke volume from rest to exercise correlated strongly with changes in end-diastolic volume in both MA (r = .78, P = .013) and sedentary controls (r = .73, P = .026), suggestive of reliance of stroke volume on end-diastolic volume and preload. However, for a given increase in end-diastolic volume, the rise in stroke volume during exercise was significantly larger in the MA than in controls, which, in the absence of differences in mean blood pressures, indicates that enhanced left ventricular systolic function independent of preload plays an additional role in maintaining a higher stroke volume at peak exercise in the highly trained older men. CONCLUSIONS: Cardiac adaptations in older endurance trained men are characterized by volume-overload left ventricular hypertrophy and enhancement of left ventricular systolic performance at peak exercise. These adaptive responses contribute to enhanced stroke volume at peak exercise in older endurance trained men.

Aging↗

PubMed1994

Atherosclerosis of the ascending aorta. Prevalence and role as an independent predictor of cerebrovascular events in cardiac patients.

BACKGROUND AND PURPOSE: The cause of cerebral and peripheral embolism remains undetermined in a significant number of patients. An atherosclerotic thoracic aorta has thus far been considered to be an uncommon one. METHODS: To define the potential role of the ascending thoracic aorta as an embolic source, intraoperative ultrasonic aortic imaging was performed in 1200 of 1334 consecutive patients aged 50 years and older who were undergoing cardiac surgery. Patients were divided into two groups according to the results of the ultrasound study in terms of presence or absence of atherosclerotic disease. The prevalence of previous neurological events in the two groups was characterized and compared. RESULTS: Ascending aortic atherosclerosis was present in 231 (19.3%) of the patients studied. Patients in this category were older (P < .0001). A higher percentage of them were smokers (P < .0001) compared with patients with less severe disease. Coronary artery disease was more extensive (P = .012), and a higher percentage of these patients had a history of peripheral vascular disease (P < .0001). Univariate analysis of the subjects with (n = 158) and without (n = 1042) previous neurological events indicated that age, body mass index, atrial fibrillation, hypertension, and atherosclerosis of the ascending aorta were associated significantly with previous occurrence of a cerebrovascular accident. For the group as a whole, multiple logistic regression analysis demonstrated that hypertension (odds ratio, 1.81; P = .002), atherosclerosis of the ascending aorta (odds ratio, 1.65; P = .013), and atrial fibrillation (odds ratio, 1.54; P = .060) were significantly and independently associated with the occurrence of previous neurological events. CONCLUSIONS: Atherosclerosis of the ascending aorta is an independent risk factor for cerebrovascular events. An atherosclerotic ascending aorta may represent a potential source of emboli or may be a marker of generalized atherosclerosis.

Age Factors↗

PubMed1994

Does topical antibiotic prophylaxis reduce post-tympanostomy tube otorrhea?

Purulent otorrhea is the most common complication of tympanostomy tube (TT) insertion. It may occur in the postoperative period or at any time during the sojourn of the tube. The efficacy of topical antimicrobial prophylaxis against purulent postoperative otorrhea (PPO) has been examined in 5 prospective, randomized studies; all demonstrated a reduction in PPO from topical antimicrobial prophylaxis, but in only 1 study was the difference statistically significant. Because the 5 studies used 2 different experimental designs--by-patient, and by-ear--a single meta-analysis could not be done. However, the by-patient studies met the criteria for meta-analysis, which demonstrated a combined odds ratio of 0.12 (95% confidence interval 0.04 to 0.37, p = .0002). This represents an 85% reduction in otorrhea, which is judged to be clinically as well as statistically significant. We conclude from the available evidence that prophylactic use of topical antimicrobial agents following TT insertion consistently reduces the rate of PPO. However, the low incidence of PPO and the heterogeneity of the published studies prevent making a final judgment for or against the continued use of these agents. Therefore, given that these potentially ototoxic agents are frequently administered to prevent postoperative otorrhea, further study of this subject is warranted. In the meantime, we recommend judicious use of these agents following TT insertion in those cases at higher risk for PPO, namely those with mucoid or purulent effusion.

Administration, Topical↗

PubMed1994

Comparable detection of acute myocardial infarction by creatine kinase MB isoenzyme and cardiac troponin I.

Although measurement of cardiac troponin I (cTnI) is, in some situations, more specific for detection of cardiac injury than is measurement of the MB isoenzyme of creatine kinase (MBCK), its sensitivity and specificity relative to MBCK for detection of myocardial infarction has not been established. Accordingly, we studied prospectively 199 consecutive patients admitted to the coronary care unit. Values of MBCK and cTnI mass were determined in all samples. Of the 188 patients admitted with a suspicion of acute myocardial ischemia, 89 were diagnosed as having an acute myocardial infarction on the basis of the patterns of MBCK values. Eighty-six of these patients also had increased cTnI (concordance, 96.6%); three did not. Of the patients diagnosed as without infarction, five with unstable angina and symptoms in the day(s) prior to admission had increased cTnI, for a cTnI specificity of 94.9%. Receiver operating characteristic curve analysis indicated that cTnI and MBCK had statistically indistinguishable diagnostic accuracies for the detection of acute myocardial infarction.

Aged↗

PubMed1993

Comparison of carbon-11-acetate with fluorine-18-fluorodeoxyglucose for delineating viable myocardium by positron emission tomography.

OBJECTIVES: This study was designed to determine in patients with advanced coronary disease whether prediction of recovery of mechanical function after coronary revascularization could be accomplished more effectively by positron emission tomography (PET) with carbon-11 (11C)-acetate than by PET with fluorine-18 (18F)-fluorodeoxyglucose. BACKGROUND: Results of previous studies have demonstrated that preservation of myocardial oxidative metabolism (measured by PET with 11C-acetate) is necessary for recovery of systolic function after coronary revascularization. METHODS: Myocardial oxidative metabolism was quantified before revascularization in 34 patients by the analysis of the rate of myocardial clearance of 11C-acetate. Metabolism of glucose was assessed by analysis of uptake of 18F-fluorodeoxyglucose. Receiver operating characteristic curves for predicting functional recovery were derived for the measurements of oxidative metabolism and glucose metabolism. In addition, criteria for prediction of recovery of function based on measurements of oxidative metabolism and glucose metabolism were developed and compared. RESULTS: Analysis of receiver operating characteristic curves indicated that estimates of oxidative metabolism were more robust in predicting functional recovery than were estimates of glucose metabolism (p < 0.02). Moreover, threshold criteria with 11C-acetate exhibited superior positive and negative predictive values (67% and 89%, respectively) than did the criteria with 18F-fluorodeoxyglucose (52% and 81%, respectively), p < 0.01. In segments with initially severe dysfunction, estimates of oxidative metabolism tended to be more robust than estimates of glucose metabolism in predicting functional recovery. Moreover, in such segments, the threshold criteria with 11C-acetate tended to exhibit superior positive and negative predictive values (85% and 87%, respectively) than did the criteria with 18F-fluorodeoxyglucose (72% and 82%, respectively), although statistical significance was not achieved. CONCLUSIONS: In patients with advanced coronary artery disease, the extent to which functional recovery can be anticipated after coronary revascularization can be delineated accurately by quantification of regional oxidative metabolism by PET with 11C-acetate.

Acetates↗

PubMed1993

Dobutamine stress echocardiography predicts surgical outcome in patients with an aortic aneurysm and peripheral vascular disease.

OBJECTIVES: This study was conducted to assess the utility of dobutamine stress echocardiography for determining the presence of significant coronary artery disease and for predicting surgical outcome and long-term prognosis in patients scheduled to undergo peripheral vascular or aortic aneurysm surgery. BACKGROUND: Assessment of coronary artery disease in patients scheduled to undergo peripheral vascular surgery can avoid perioperative complications. METHODS: Dobutamine stress echocardiography was performed in 98 consecutive patients scheduled to undergo aortic or peripheral vascular surgery. Intravenous dobutamine was infused in a graded fashion, with two-dimensional digital echocardiographic monitoring of ventricular function and segmental wall motion. Group 1 (n = 70) consisted of patients who exhibited a normal response to dobutamine infusion (negative dobutamine study); group 2 (n = 23) comprised those patients with an abnormal response to dobutamine, characterized by the development of new or worsening wall motion abnormalities at rest, indicating the presence of myocardial ischemia (positive dobutamine study). Five patients with an inconclusive dobutamine study (because of inadequate heart rate) were excluded from analysis. RESULTS: No major adverse effects occurred with testing in any patient. Sixty-eight of 70 patients with a negative study had peripheral vascular or aortic surgery performed without perioperative cardiac events (2 patients refused surgery). Nineteen of 23 patients with a positive study underwent coronary angiography and all had > 50% lumen narrowing in one or more major coronary artery distributions; 13 underwent coronary artery bypass grafting or angioplasty before peripheral vascular or aortic surgery and all had an uneventful perioperative period. Four of the 10 patients from group 2 who did not undergo coronary revascularization had a perioperative cardiac event (myocardial infarction in 2, an ischemic episode requiring urgent coronary bypass grafting in 1 and congestive heart failure in 1). CONCLUSIONS: Positive and negative dobutamine study results are significant predictors of the presence or absence of perioperative events (20% vs. 0%, p = 0.003). A positive test warrants coronary angiography and further medical or surgical intervention, or both, but a negative test indicates a low likelihood of perioperative cardiac complications of aortic or peripheral vascular surgery. During the long-term follow-up period in this study (group 1 mean, 24 months; group 2 mean, 15 months), two patients (3%) from group 1 and three (15%) from group 2 developed cardiac complications (p = 0.038). Thus, dobutamine stress echocardiography is safe and can predict surgical outcome in patients undergoing aortic aneurysm repair or surgery for occlusive disease of the peripheral arteries. In addition, a negative test result is a strong predictor of decreased perioperative and long-term cardiac morbidity and mortality.

Aged↗

PubMed1993

A comprehensive algorithm for determining whether a run-in strategy will be a cost-effective design modification in a randomized clinical trial.

In randomized clinical trials, poor compliance and treatment intolerance lead to reduced between-group differences, increased sample size requirements, and increased cost. A run-in strategy is intended to reduce these problems. In this paper, we develop a comprehensive set of measures specifically sensitive to the effect of a run-in on cost and sample size requirements, both before and after randomization. Using these measures, we describe a step-by-step algorithm through which one can estimate the cost-effectiveness of a potential run-in. Because the cost-effectiveness of a run-in is partly mediated by its effect on sample size, we begin by discussing the likely impact of a planned run-in on the required number of randomized, eligible, and screened subjects. Run-in strategies are most likely to be cost-effective when: (1) per patient costs during the post-randomization as compared to the screening period are high; (2) poor compliance is associated with a substantial reduction in response to treatment; (3) the number of screened patients needed to identify a single eligible patient is small; (4) the run-in is inexpensive; (5) for most patients, the run-in compliance status is maintained following randomization and, most importantly, (6) many subjects excluded by the run-in are treatment intolerant or non-compliant to the extent that we expect little or no treatment response. Our analysis suggests that conditions for the cost-effectiveness of run-in strategies are stringent. In particular, if the only purpose of a run-in is to exclude ordinary partial compliers, the run-in will frequently add to the cost of the trial. Often, the cost-effectiveness of a run-in requires that one can identify and exclude a substantial number of treatment intolerant or otherwise unresponsive subjects.

Algorithms↗

PubMed1993

Strategy for the reduction of stroke incidence in cardiac surgical patients.

Atherosclerosis of the ascending aorta (AAA) and severe carotid artery disease are risk factors for stroke in cardiac surgical patients. Twelve hundred of a consecutive series of 1,334 patients 50 years of age or older having a cardiac operation were screened for the presence of AAA by intraoperative ultrasonographic scanning and for the presence of carotid artery occlusive disease (791 of 798 patients > or = 65 years of age and younger symptomatic patients) by carotid duplex scanning. Coronary artery disease was present in 88% of the patients. Patients with moderate or severe AAA (n = 231; 19.3% of the total) were treated by ascending aortic replacement (n = 27) or by modified, less extensive techniques (n = 168) to avoid the atherosclerotic areas. Thirty-three patients had combined carotid endarterectomy and cardiac operation. Thirty-day mortality and stroke rates for the 1,200 patients were 4.0% and 1.6%, respectively. The stroke rate was low (1.1%) among the 969 patients with no or mild AAA. It was zero among 27 patients with moderate or severe AAA who had ascending aortic replacement and among the 33 patients who had carotid endarterectomy. The stroke rates were higher for 111 patients with moderate or severe ascending aortic disease who had only minor interventions (6.3%) and for 16 patients with severe carotid artery disease who did not have carotid endarterectomy (18.7%). Screening for AAA and carotid artery disease and aggressive surgical treatment of moderate or severe AAA and severe or symptomatic carotid artery disease appears to reduce the frequency of stroke in older cardiac surgical patients.

Aged↗

PubMed1993

Therapeutic end points for the treatment of atrioventricular node reentrant tachycardia by catheter-guided radiofrequency current.

OBJECTIVES: The purpose of this prospective study was to test the hypothesis that the elimination of inducible repetitive atrioventricular (AV) node reentry despite the persistence of slow AV pathway conduction is a valid end point for radiofrequency catheter ablation procedures in patients with supraventricular tachycardia due to AV node reentry. BACKGROUND: Although modification of AV node physiology by radiofrequency current can eliminate AV node reentrant tachycardia, therapeutic end points that are definitive of a satisfactory result in patients undergoing modification of the slow AV pathway have not been established. Applications of radiofrequency current at selected sites may eliminate all evidence of slow pathway conduction or sufficiently modify the refractory properties of the slow pathway to preclude sustained arrhythmias. Accordingly, total abolition of dual AV node physiology may not be necessary to prevent arrhythmia recurrence. METHODS: Radiofrequency catheter ablation of the slow AV pathway was attempted in 59 patients with typical AV node reentry. Tissue ablation was performed with a continuous wave of 500-kHz radiofrequency current. Twenty-five to 35 W was applied for 60 s at the site selected for tissue destruction. RESULTS: Dual AV node physiology was eliminated completely in 35 patients (59%), persisted without inducible AV node reentry in 13 patients (22%) and persisted with inducible single AV reentrant beats in 11 patients (19%). In patients with persistent dual AV node physiology, the maximal difference between the effective refractory period of the fast and slow pathways was reduced from 104 +/- 62 ms before the procedure to 37 +/- 37 ms after AV conduction had been modified (p < 0.001). During a mean follow-up interval of 15 months (range 4 to 28), only one patient (2%) had a recurrence of the tachycardia. CONCLUSIONS: Results demonstrate that when complete elimination of dual AV node physiology is difficult, modification of slow pathway conduction to the extent that repetitive AV node reentry cannot be induced is a definitive end point that portends a good prognosis.

Adolescent↗

PubMed1993

Frailty and injuries in later life: the FICSIT trials.

Physical frailty and fall-related injuries present two of the biggest threats to older people's functioning and quality of life. The Frailty and Injuries: Cooperative Studies of Intervention Techniques (FICSIT) trials represent a set of eight different clinical trials concerning physical frailty and injuries in later life. This report documents the history and organization of the trials and provides an overview of the measures being collected at multiple sites and the analytic strategies to be used for multi-site investigations.

Accidental Falls↗