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Biomedical subjects

D Massel

Publications and source records attributed to D Massel.

At least 19 recordsLinked to original sources
PubMed2005

Ejection fraction velocity ratio as an indicator of aortic stenosis severity.

BACKGROUND: Despite the widespread use of the continuity equation in the estimation of aortic valve area (AVA) in patients with aortic stenosis, it is subject to errors, time consuming, and can be technically demanding. As such, simpler methods of assessing aortic stenosis severity have been pursued. METHODS: The ejection fraction velocity ratio [EFVR = ejection fraction (%) / maximal aortic velocity (m/sec)] was compared to AVA determined with the continuity equation in 857 patients with aortic stenosis and varying degrees of LV systolic dysfunction. Severe aortic stenosis was defined as an AVA < 1.0 cm2. RESULTS: There was good to excellent correlation between our index and aortic valve area (P < 0.001 for each ejection fraction subgroup). Receiver operating characteristic analysis showed that the EFVR functioned well with areas under the curve between 0.893 and 0.938. CONCLUSION: The EFVR is a simple noninvasive method for screening patients for an AVA of 1.0 cm2. It could be used as a screening test or in lieu of the continuity equation particularly when there is problematic measurement of either the LVOT diameter or velocity.

Aged↗
PubMed2005

Patient reperfusion preferences in acute myocardial infarction: mortality versus stroke, benefits versus costs, high technology versus drugs.

BACKGROUND: Reperfusion therapy, thrombolysis and primary percutaneous coronary intervention (PCI) decrease mortality in ST elevation acute myocardial infarction. Tissue plasminogen activator (tPA) reduces the risk of death but at an increased risk of stroke and cost compared with streptokinase (SK). PCI reduces the risk of death and stroke compared with tPA, but at increased costs. The authors explored patient preferences for the various reperfusion strategies. PATIENTS AND METHODS: Among patients hospitalized with an acute coronary syndrome, preferences for tPA or SK were determined using a questionnaire based on Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries (GUSTO-1) trial data including risk of death, stroke and the combination of the two. The impact of cost was assessed under the assumption of government or patient payment. Overall, the societal preference was solicited based on all the data. A similar survey was conducted comparing primary PCI with tPA using outcome data from a Cochrane review. RESULTS: When viewed in the context of net clinical benefit (NCB), 66.7% of patients chose tPA over SK. The preference for tPA diminished under the scenario of patient payment compared with government payment. However, as a societal strategy, the preference for tPA was 40.5% (P<0.001 versus NCB). Preference for primary PCI over tPA was strong whether based on risk of death (78.5%), stroke (88.1%) or NCB (95.4%). Cost considerations resulted in a slight fall in PCI preference (87.7%). As an overall societal strategy, 81.0% chose primary PCI over tPA (P=0.016 versus NCB). The preference for PCI was twice that for the most effective, but perhaps riskier, thrombolytic agent (tPA) (P<0.0001). CONCLUSIONS: Preference for the potentially inferior thrombolytic agent appears to depend on the lesser risk of stroke and the lower cost. Primary PCI was preferred by patients likely due to the lower risk of death and stroke, despite the increased cost. The preferences appeared to be influenced by societal costs. In addition, the allure and heightened expectations of high technology may play a role.

Age Factors↗
PubMed2004

Precision and accuracy of the bedside examination in detecting an ejection fraction of less than 40% following acute myocardial infarction.

BACKGROUND: Left ventricular function is the most important determinant of prognosis following myocardial infarction. METHODS: A prospective analytical cohort study of 33 cardiac care unit survivors of acute myocardial infarction was performed to assess the accuracy, reproducibility and observer variation of the bedside Valsalva response in predicting an ejection fraction (EF) less than 40%. RESULTS: Agreement between physicians for the clinical Valsalva response was excellent (kappa coefficient 0.75), as was the comparison between physicians' clinical response to the Finapres (Ohmeda, USA) hemodynamic response (weighted kappa=0.85). The EF was significantly higher among patients with a normal Valsalva response (56.9%) than in patients with either an absent overshoot (48.4%) or a square wave (28.3%) response (P<0.001). Physicians were very accurate at estimating whether the EF was greater or less than 40%. In 40 of 66 situations, the clinicians were confident, based on the clinical examination and the Valsalva response, that the EF was either greater or less than 40%. In these situations, agreement (95.0%) and kappa (0.89) were both excellent. When all patients were considered, the degree of agreement (90.8%) and kappa (0.80) diminished slightly. A square wave response had poor sensitivity (37.5%) but excellent specificity (92.7%), whereas any abnormal response had excellent sensitivity (91.7%) but poor specificity (54.8%). CONCLUSION: Compared with many other aspects of the clinical examination, the bedside Valsalva manoeuvre has acceptable degrees of interobserver variability. A normal response tends to rule in an EF of greater than 40%, whereas a square wave response rules out an EF of greater than 40%. This simple bedside manoeuvre may be useful in predicting low EF following acute myocardial infarction.

Adult↗
PubMed2003

The number needed to harm: is it too optimistic?

The number needed to treat (NNT) to prevent one adverse outcome event is a useful measure of clinical trial results and represents the therapeutic effort required to realize a specific clinical benefit. With many therapies, there are both positive and negative consequences. Analogous to the NNT, there is the number needed to harm (NNH), which is the reciprocal of the absolute risk increase in situations where the experimental treatment harms more patients then the control treatment. The NNH is the number of patients who, if they received the experimental treatment, would lead to one additional person being harmed compared with patients who receive the control treatment. The NNH may, however, provide an optimistic measure of the true risks caused by therapy.

Clinical Trials as Topic↗
PubMed2002

The number remaining at risk: an adjunct to the number needed to treat.

Although the number of patients needed to treat (NNT) to prevent an adverse clinical event is of great clinical value to practising physicians, it is limited in that it fails to provide a measure of prognosis among patients not achieving benefit. For example, if the NNT is 100, what is likely to happen to the other 99? The number remaining at risk (NRR), which is an index that enhances the value of the NNT, is described. The NRR is the ratio of the residual event rate among treated patients and the absolute reduction in outcome events (NRR = experimental event rate [EER]/control event rate [CER]-EER), where EER and CER are the event rates among experimental and control groups, respectively. This index represents the number of events likely to occur among the NNT, or the odds of experiencing an adverse outcome event as opposed to deriving benefit from therapy. The NRR is a simple index that can easily be calculated from the published results of a clinical trial. As an adjunct to the NNT, it provides a measure of the impact of therapy and the average prognosis of remaining patients.

Data Interpretation, Statistical↗
PubMed2001

Risks and benefits of adding anti-platelet therapy to warfarin among patients with prosthetic heart valves: a meta-analysis.

OBJECTIVES: The objective of this study was to compare the effectiveness and safety of adding dipyridamole or aspirin to warfarin among patients with prosthetic heart valves using meta-analytic techniques. BACKGROUND: Patients with prosthetic heart valves are at increased risk for valve thrombosis and arterial thromboembolism. Oral anticoagulation alone, or the addition of antiplatelet drugs, has been used to minimize this risk. An important issue is the effectiveness and safety of the latter strategy. METHODS: A combined MEDLINE and manual search was made for relevant articles from 1966 to November 1999. Standard meta-analysis techniques were used. RESULTS: Ten studies involving 2,199 subjects met the inclusion criteria. Compared with anticoagulation alone, the addition of an antiplatelet agent reduced the risk of thromboembolic events (odds ratio [OR]: 0.41, p < 0.001) and total mortality (OR: 0.49, p < 0.001). The risk of major bleeding was increased when antiplatelet agents were added (OR: 1.50, p = 0.033). For major bleeding, the comparison of trials performed before and after 1990 (OR: 2.23 and 0.88, respectively) showed that the chi-square test for heterogeneity was significant (p = 0.025). The latter trials used low-dose aspirin, suggesting that the risk of bleeding may be lower with contemporary low-dose (100 mg daily) aspirin. CONCLUSIONS: Adding antiplatelet therapy, especially low-dose aspirin, to warfarin decreases the risk of systemic embolism or death among patients with prosthetic heart valves. The risk of major bleeding is slightly increased with antiplatelet therapy. Nonetheless, the risk of bleeding appears to have diminished with the lower doses of aspirin used in the more recent trials, resulting in a favorable risk-to-benefit profile.

Aspirin↗
PubMed2001

Reducing bedrest following arterial puncture for coronary interventional procedures--impact on vascular complications: the BAC Trial.

BACKGROUND: The optimal time for ambulating patients following femoral arterial puncture for percutaneous coronary intervention is unknown. This study was designed to test the hypothesis that reducing time to ambulation from 6 hours to 2 hours would not increase vascular complications. METHODS: In this randomized, controlled, single-center trial, patients were randomly assigned to receive either 2, 4 or 6 hours (control group) of bedrest after hemostasis was achieved at the femoral arterial puncture site. A total of 354 patients, enrolled from March 1997 to October 1998, participated in the study with 299 completing the full protocol. The primary endpoint was the incidence of vascular complications and any resulting interventions or outcomes including surgery, blood transfusion, prolonged length of stay or ultrasound compression. RESULTS: The 2 hour and 4 hour experimental groups were comprised of 99 patients each, while the 6 hour control group was comprised of 101 patients. There were no differences in vascular complications between the groups. A subgroup analysis of patients who received abciximab (n = 43) did not reveal any differences between groups. Only one patient developed a pseudoaneurysm (p = 0.36), requiring surgical repair and a prolonged length of stay. CONCLUSIONS: Patients undergoing femoral arterial puncture for coronary interventional procedures can safely ambulate 2 hours after hemostasis of the puncture site. Patients receiving abciximab as part of their coronary procedure may be able to ambulate as early as 2 hours following hemostasis.

Adult↗
PubMed2000

Strict reliance on a computer algorithm or measurable ST segment criteria may lead to errors in thrombolytic therapy eligibility.

BACKGROUND: There is accumulating evidence that thrombolytic therapy is underused among eligible patients with acute myocardial infarction. We sought to determine whether potential errors in electrocardiographic diagnosis might be a contributing factor. METHODS: Seventy-five electrocardiograms were interpreted on 2 separate occasions by 3 cardiologists. Two criteria were compared for thrombolysis eligibility: (1) measurement of > or =1 mm ST-segment elevation in 2 contiguous leads (measured) and (2) criterion 1 plus the subjective opinion that the changes represented acute transmural injury (interpretive). The results were compared with computerized interpretations by the Marquette 12SL system. RESULTS: Raw agreement and agreement corrected for chance between raters for both criteria were excellent and tended to be better for interpretive compared with measured criteria (kappa = 0.89 vs 0.78, respectively). Strict reliance on measured electrocardiographic criteria alone would have resulted in overuse of thrombolysis among all 3 raters. Based on the consensus opinion, the absolute overuse of thrombolysis would have been approximately 15% (P <.0034). The computer algorithm had a specificity of 100% and a sensitivity of 61.5%. Reliance on the computerized interpretation alone would have lead to underuse of thrombolytic therapy compared with consensus opinion (21.3% vs 34. 6%; P <.005). CONCLUSION: Agreement for suspected acute myocardial infarction tended to be better when the appearance of the ST segments was added to measurable ST elevation criteria. Strict reliance on measurable criteria may lead to the inappropriate overuse of thrombolysis. Although the Marquette 12SL system has excellent specificity, it has poor sensitivity for the diagnosis of thrombolysis-eligible AMI. Reliance on computerized electrocardiographic interpretation would lead to the inappropriate underuse of thrombolytic therapy in situations in which qualifying electrocardiographic criteria are actually met.

Algorithms↗
PubMed2000

Greater expectations in a cancer trial: absolute more than relative survival increases, community more than academic clinicians.

There is no consensus on how the difference between control and experimental outcome rates, the clinically important difference, should be estimated when designing a clinical trial. We sought to determine whether community and academic clinicians had different perceptions as to what would constitute a clinically important increase in survival, when asked to respond in absolute or relative terms, before a trial was started rather than when the results were already known. A telephone survey of 25 practicing Canadian oncologists was performed. Questions were asked as to the importance of acceptable and minimally acceptable improvements in survival for a hypothetical trial of pancreatic cancer where the baseline survival was expected to be between 2 and 8 months. Responses were sought for absolute (additional months) or relative gains (percent improvement) in survival. The mean absolute additional survival expectations corresponded to at least a doubling of baseline survival and tended to be greatest when the prognosis was poorest (p = 0.06). Relative expectations for improved survival varied with baseline survival (p < 0.001). When improvement in survival was requested in relative terms, the median expected improvement was 25%. This is highly significantly different than when survival improvements were requested in absolute terms (p < 0.0001). Median absolute survival expectations were greater for community as compared with academically affiliated physicians (p = 0.046). We found that physicians are inconsistent in their interpretation of qualitative data. What constitutes a potentially clinically important treatment effect differs whether viewed in relative or absolute terms before the performance of a trial. Expectations were greatest when the prognosis was poorest and differed between community and academic physicians.

Adult↗
PubMed1999

Blood money.

Explore the source record for details and available documents.

Blood Banks↗
PubMed1999

Potential cost effectiveness of tissue plasminogen activator among patients previously treated with streptokinase.

BACKGROUND: A major limitation of streptokinase is the development and persistence of problematic neutralizing antibodies that have the potential to limit the effectiveness of repeat streptokinase therapy. Accordingly, tissue-type plasminogen activator (t-PA) is frequently administered to patients with recurrent infarction presenting more than four days from previous treatment with streptokinase. OBJECTIVE: To explore the marginal cost effectiveness of the use of t-PA among patients with resistance to streptokinase. MATERIALS AND METHODS: A model was developed incorporating short term (five- to six-week) costs and mortality data for various thrombolytic strategies. It was assumed that streptokinase would be clinically ineffective when administered to streptokinase-resistant patients. Sensitivity analyses were performed varying the baseline mortality, the proportion of patients resistant to streptokinase and the absolute survival benefit of t-PA compared with streptokinase. RESULTS: In the absence of streptokinase resistance, streptokinase is a cost effective strategy for patients with suspected myocardial infarction, even when the expected mortality is low. In the presence of streptokinase resistance, the combination of streptokinase and acetylsalicylic acid is most cost effective when rates of resistance are low ($16,389 per short run survivor with 5% resistance versus $21,306 with 50% resistance). t-PA is a cost effective alternative when rates of resistance are high ($54,158 per short run survivor with 50% resistance) assuming a 1% absolute risk reduction in mortality. As the level of resistance decreases, however, t-PA becomes a less cost effective choice ($203,092 per short run survivor with 5% resistance). However, t-PA is always more cost effective in the presence of any streptokinase resistance than when it is administered for an index myocardial infarction. CONCLUSIONS: This analysis shows that using t-PA in patients previously treated with streptokinase is a cost effective strategy. t-PA becomes less cost effective as the percentage of patients with streptokinase resistance decreases, particularly when the absolute risk reduction favouring t-PA over streptokinase is small. Nevertheless, if the early mortality advantage is sustained, very favourable cost effectiveness ratios are attained with t-PA even when the risk of resistance is low. t-PA used in the presence of streptokinase resistance is always more cost effective than when it is used for a first myocardial infarction.

Cost-Benefit Analysis↗
PubMed1999

Similar, the same or just not different: a guide for deciding whether treatments are clinically equivalent. [Dept. of Medicine, Division of Cardiology, Univ. of Western Ontario, London, Ontario].

Most clinical trials are designed to demonstrate superiority of one intervention over another. A less common goal is to show that any differences are sufficiently small to consider them interchangeable or clinically equivalent. Although similar to effectiveness trials, equivalence trials pose distinct methodological and interpretive challenges. Emphasis is placed on the distinction between a study designed to show 'equivalence' and a study designed to show 'superiority' that fails in its quest but in the end claims equivalence. Strategies used to minimize bias in superiority trials may actually increase the probability of showing no difference. Although there is no consensus as to the best statistical approach in describing the results of equivalence trials, an approach based on confidence intervals may be easier for clinicians to comprehend. A guide was developed to assist readers in determining whether claims of clinical equivalence are valid.

Cardiovascular Diseases↗
PubMed1999

Mediastinal irradiation: A risk factor for atherosclerosis of the internal thoracic arteries.

Previous radiotherapy to the thorax is a risk factor for coronary artery disease. Patients with radiation-induced atherosclerosis tend to be young and frequently have lesions involving the coronary ostia and left anterior descending artery. Bypass is often the most suitable method of revascularization, and given the young age of the patient, arterial conduits would be considered superior to vein grafts. However, the internal thoracic arteries can lie within the radiation field and may not be free of atherosclerosis. A 40-year-old man who required coronary artery bypass grafting for multivessel coronary artery disease 11 years following radiotherapy for Hodgkin's lymphoma is reported. Preoperative angiography showed that the right internal thoracic artery had significant atherosclerosis and was unsuitable as a conduit.

Adult↗
PubMed1999

Access to an outpatient cardiology consultation in southwestern Ontario.

OBJECTIVE: To determine whether there were differences in waiting time for a consultation for a nonurgent cardiology problem among specialists in an academic centre compared with those in community practice. DESIGN: Cross-sectional telephone survey. SETTING: Southwestern Ontario. PARTICIPANTS: Academically affiliated and community-based specialists in cardiology or internal medicine with an interest in cardiology. OUTCOME MEASURE: Waiting period in weeks for outpatient consultation. RESULTS: Among community specialists, those with cardiology training had significantly longer waiting times than those without for nonurgent cardiology consultation (median 8.6 versus 3.8 weeks, P=0.0077). Waiting times for consultation were significantly longer for academic specialists than for those in community practice (median 9.1 versus 4.1 weeks, P=0.0013). Significantly longer waiting times exist in communities with a population greater than 100,000 (median 9.1 versus 4.0 weeks, P=0.0005). CONCLUSIONS: Waiting times for consultation for a nonurgent cardiology problem are long. Waiting times are longer for physicians with certification in cardiology, in the academic medical centre and in larger communities.

Academic Medical Centers↗
PubMed1999

Evidence-based medicine and reteplase: inductive arguments over deductive reasoning.

Two trials of thrombolysis for acute myocardial infarction are contrasted and compared using a systematic approach developed for the interpretation of studies where equivalence is claimed. Reteplase has been compared with streptokinase in a true equivalence trial (International Joint Efficacy Comparison of Thrombolytics [INJECT] trial) and with tissue plasminogen activator in a failed superiority trial (Global Use of Strategies to Open Occluded Coronary Arteries [GUSTO] III). Important methodological distinctions and economic insights are highlighted. Using this approach one can conclude that the INJECT investigators have shown that reteplase is at least as effective as streptokinase and that the test for equivalence was satisfied. The point estimate of the treatment effect for the primary outcome event favours reteplase over streptokinase, and the confidence intervals essentially eliminate the possibility of streptokinase superiority. The GUSTO III primary outcome event, 30-day mortality, provides no convincing evidence that reteplase is equivalent to tissue plasminogen activator. Selective emphasis on one or two post hoc outcome event clusters, such as death and nonfatal stroke, or death and disabling stroke, provides some suggestive, but not conclusive, evidence for equivalence. Moreover, for some of the outcome events, and in particular the primary outcome event, the point estimate suggests that reteplase is, in fact, slightly less effective than tissue plasminogen activator.

Confidence Intervals↗