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Biomedical subjects

G A van Es

Publications and source records attributed to G A van Es.

At least 19 recordsLinked to original sources
PubMed1999

Continuous ST-segment monitoring associated with infarct size and left ventricular function in the GUSTO-I trial.

BACKGROUND: The aim of this study was to evaluate whether in patients with myocardial infarction, the intensity and duration of myocardial ischemia as measured by continuous ST monitoring are associated with infarct size and residual left ventricular function. METHODS AND RESULTS: The analyses included patients with myocardial infarction, receiving thrombolytic therapy, who were enrolled in the electrocardiographic substudy of GUSTO-I, monitored by a vector-derived 12-lead electrocardiographic recording system, and in whom either infarct size (defined as cumulative release of alpha-hydroxybutyrate dehydrogenase activity per liter of plasma over a 72-hour period [Q(72)]) or left ventricular ejection fraction (LVEF) was determined. With the use of linear regression analysis, we investigated the association of various ST-trend characteristics with Q(72) (206 patients) and with LVEF (180 patients). A higher area under the ST trend since thrombolysis until 50% ST recovery and a higher area under recurrent ischemic episodes (ST reelevations) were significantly associated with a higher Q(72), whereas only a higher area under recurrent ischemic episodes was significantly associated with a lower LVEF. These associations remained after adjusting for other patient characteristics such as age, sex, infarct location, and time to treatment. CONCLUSIONS: These findings support the physiologic hypothesis that both the intensity and duration of myocardial ischemia (both reflected by the estimated areas under the ST-trend curve) determine myocardial damage and thus are associated with infarct size and ejection fraction in patients with acute myocardial infarction who receive thrombolytic therapy.

Aged↗
PubMed1999

A randomized placebo-controlled trial of fluvastatin for prevention of restenosis after successful coronary balloon angioplasty; final results of the fluvastatin angiographic restenosis (FLARE) trial.

BACKGROUND: The 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors competitively inhibit biosynthesis of mevalonate, a precursor of non-sterol compounds involved in cell proliferation. Experimental evidence suggests that fluvastatin may, independent of any lipid lowering action, exert a greater direct inhibitory effect on proliferating vascular myocytes than other statins. The FLARE (Fluvastatin Angioplasty Restenosis) Trial was conceived to evaluate the ability of fluvastatin 40 mg twice daily to reduce restenosis after successful coronary balloon angioplasty (PTCA). METHODS: Patients were randomized to either placebo or fluvastatin 40 mg twice daily beginning 2-4 weeks prior to planned PTCA and continuing after a successful PTCA (without the use of a stent), to follow-up angiography at 26+/-2 weeks. Clinical follow-up was completed at 40 weeks. The primary end-point was angiographic restenosis, measured by quantitative coronary angiography at a core laboratory, as the loss in minimal luminal diameter during follow-up. Clinical end-points were death, myocardial infarction, coronary artery bypass graft surgery or re-intervention, up to 40 weeks after PTCA. RESULTS: Of 1054 patients randomized, 526 were allocated to fluvastatin and 528 to placebo. Among these, 409 in the fluvastatin group and 427 in the placebo group were included in the intention-to-treat analysis, having undergone a successful PTCA after a minimum of 2 weeks of pre-treatment. At the time of PTCA, fluvastatin had reduced LDL cholesterol by 37% and this was maintained at 33% at 26 weeks. There was no difference in the primary end-point between the treatment groups (fluvastatin 0.23+/-0.49 mm vs placebo 0.23+/-0.52 mm, P=0.95) or in the angiographic restenosis rate (fluvastatin 28%, placebo 31%, chi-square P=0.42), or in the incidence of the composite clinical end-point at 40 weeks (22.4% vs 23.3%; logrank P=0.74). However, a significantly lower incidence of total death and myocardial infarction was observed in six patients (1.4%) in the fluvastatin group and 17 (4.0%) in the placebo group (log rank P=0.025). CONCLUSION: Treatment with fluvastatin 80 mg daily did not affect the process of restenosis and is therefore not indicated for this purpose. However, the observed reduction in mortality and myocardial infarction 40 weeks after PTCA in the fluvastatin treated group has not been previously reported with statin therapy. Accordingly, a priori investigation of this finding is indicated and a new clinical trial with this intention is already underway.

Angioplasty, Balloon, Coronary↗
PubMed1999

Redundancy of single diagnostic test evaluation.

Diagnostic research and diagnostic practice frequently do not cohere. Studies commonly evaluate whether a single test discriminates between disease presence and absence, whereas in practice a test is always judged in the context of other information. This study illustrates drawbacks of single-test evaluation and discusses principles of diagnostic research. We used data on 140 patients suspected of pulmonary embolism who had an inconclusive ventilation-perfusion lung scan. We evaluated three tests: partial pressure of oxygen in arterial blood (PaO2), x-ray film of the thorax, and leg ultrasound. On the basis of single-test evaluations, ultrasound was most informative. Given a prior probability of 0.27, it had a much better combination of positive and negative predictive value (0.71 and 0.21, respectively) relative to thorax x-ray (0.33 and 0.11) and PaO2 (0.35 and 0.27). The combination of positive and negative likelihood ratio was also more promising for ultrasound (7.3 and 0.7) than for thorax x-ray (1.3 and 0.3) and PaO2 (1.3 and 0.9). As the tests are always performed after the history and physical, we judged their added value using multivariable logistic modeling with receiver operating characteristic (ROC) analyses. The ROC areas of the model, including history and physical, with additional PaO2, thorax x-ray, or ultrasound, were 0.75, 0.77, 0.81, and 0.81, respectively, which indicated similar added value of thorax x-ray and ultrasound. Application of the models to patient subgroups also yielded added predictive value for thorax x-ray film. Thus, the results of single-test evaluations may be very misleading. As no diagnosis is based on one test, single-test evaluations have limited value in diagnostic research and only have relevance in the context of screening and the initial phase of test development. Diagnostic research should always apply an approach of constructing, extending, and validating diagnostic models in agreement with routine clinical work-up using logistic regression analyses.

Analysis of Variance↗
PubMed1998

Intravascular ultrasound-guided optimized stent deployment. Immediate and 6 months clinical and angiographic results from the Multicenter Ultrasound Stenting in Coronaries Study (MUSIC Study)

OBJECTIVES: A study was set up to validate the safety and feasibility of intravascular ultrasound-guided stenting without subsequent anticoagulation, and its impact on the 6 months restenosis rate. METHODS: The study was designed to be multicentred, prospective, and observational. RESULTS: One hundred and sixty-one patients with stable angina and a de novo coronary artery lesion were enrolled. In four patients, the implantation of a Palmaz-Schatz (with spiral bridge) stent had failed. One of these four patients died 3 days following bypass surgery. In two other patients, intravascular ultrasound assessment was not performed. One hundred and twenty-five of the remaining 155 patients (81%) were treated with aspirin (100 mg x day(-1)), because all three criteria for optimized stent expansion were met. Twenty-two of the remaining 38 patients (25%), in whom at least one criterion was not met were treated with aspirin and acenocoumarol (3 months, INR 2.5-3.5), while 16 patients only received aspirin. Stent thrombosis was documented in two patients (1.3%) for which repeat angioplasty was performed. During the hospital stay, there were no deaths or Q-wave myocardial infarctions. Five patients (3.2%) sustained a non-Q-wave myocardial infarction. During the follow-up period (198+/-38 days, complete for all patients, except one), one patient (0.6%) sustained a Q-wave myocardial infarction, one (0.6%) underwent bypass surgery, and repeat angioplasty was performed in nine patients (5.7%). In two of the nine patients, repeat angioplasty involved another lesion. Therefore, the target lesion revascularization rate during follow-up was 4.5% (seven patients). At quantitative coronary angiography, the minimal lumen diameter (mean+/-SD) increased from 1.12+/-0.34 mm before to 2.89+/-0.35 mm after stenting. Repeat angiography at 6 months was performed in 144 patients (92%). The minimal lumen diameter at follow-up was 2.12+/-0.67 mm. Restenosis (diameter stenosis of 50% or more) was documented in 12 patients or 8.3%. When the two patients with documented stent thrombosis are included, the restenosis rate amounts to 97%. CONCLUSIONS: These data confirm that, in selected patients, stents can safely be implanted without the use of systemic anticoagulation, provided optimal stent expansion is achieved. The exact role of intravascular ultrasound in the achievement of these results needs to be established by appropriately designed studies. In the meantime, intravascular ultrasound coupled with the Palmaz-Schatz stent incorporating a spiral bridge, may have contributed considerably to the immediate angiographic outcome, which in turn may explain the favourable clinical and angiographic outcome at 6 months.

Aged↗
PubMed1997

Effect of acadesine on myocardial ischaemia in patients with coronary artery disease.

Acadesine, an adenosine regulating agent, attenuates the adverse effects of ischaemia on ventricular function in animals. This study examined its influence on pacing-induced ischaemia in 47 patients undergoing coronary angiography. After 15 min of recovery from control pacing, an infusion of acadesine (5, 10, 20, 50 mg/kg i.v.) was commenced and after a further 15 min the protocol was repeated with the infusion continued. At higher doses, minor beneficial effects on ejection fraction and myocardial lactate metabolism were observed. Haemodynamics were unaffected. Systemic lactate rose in relation to acadesine, up to 60% (P < 0.001 versus placebo). The data may indicate that acadesine stimulates anaerobic glycolysis in man.

Adult↗
PubMed1997

Efficiency optimization of the selection period in therapeutic trials.

To determine eligibility for a (randomized) clinical trial, measuring the inclusion and exclusion criteria can be extended over a period of time. During this period, known as the selection period, a patient is repeatedly examined at certain time intervals. This study describes an approach for optimizing the efficiency of the selection period. Efficiency is defined as the costs of randomizing one patient. The objective is to construct prediction models based on data obtained early in the selection period to predict subsequent exclusions. A prediction model increases the efficiency if after its application the costs per randomization are lower. The approach is illustrated using data from the selection period of the Rotterdam Cardiovascular Risk Intervention (ROCARI) trial which was composed of five consecutive patient visits. At each visit, data to determine eligibility was obtained. We found that logistic regression models based on data of the first and second visit could predict exclusions during the third visit. Application of the prediction models suggested that in this particular trial the costs per randomization would decrease by $52. As the initial costs per randomization were $1444, there would be a 3.6% (52/1444) savings in recruitment costs under the prediction models, accounting for a savings of more than $450,000. We conclude that the use of data obtained early in a selection period can predict subsequent exclusions, and therefore could increase the efficiency of such a period. The approach could be applied to data obtained in a pilot study as well as data obtained in the beginning of a prolonged intake period.

Cost Savings↗
PubMed1997

Limitations of sensitivity, specificity, likelihood ratio, and bayes' theorem in assessing diagnostic probabilities: a clinical example.

We evaluated the extent to which the sensitivity, specificity, and likelihood ratio of the exercise test to diagnose coronary artery disease vary across subgroups of a certain patient population. Among 295 patients suspected of coronary artery disease, as independently determined by coronary angiography, we assessed variation in sensitivity and specificity according to patient history, physical examination, exercise test results, and disease severity in 207 patients with and 88 patients without coronary artery disease, respectively. The sensitivity varied substantially according to sex (women 30% and men 64%), systolic blood pressure at baseline (53% to 65%), expected workload (50% to 64%), systolic blood pressure at peak exercise (50% to 67%), relative workload (33% to 68%), and number of diseased vessels (39% to 77%). The specificity varied across subgroups of sex (men 89% and women 97%) and relative workload (85% to 98%). The likelihood ratio varied (3.8 to 17.0) across the same patient subgroups, as did the sensitivity. As each population tends to be heterogeneous with respect to patient characteristics, no single level of these parameters can be given that is adequate for all subgroups. Use of these parameters as a basis for calculating diagnostic probabilities in individual patients using Bayes' theorem has serious limitations.

Adult↗
PubMed1996

Cost effectiveness of stent implantation versus PTCA: the BENESTENT experience.

The aim of this paper is to assess the costs and effects of stent implantation versus percutaneous transluminal coronary angioplasty (PTCA). Data have been taken from both the BENESTENT-I and BENESTENT-II pilot study. Effects are expressed in terms of event-free survival and costs include those of the initial hospitalization and those during follow-up. The costs per additional event-free survivor after 7 months are estimated at Dfl 88,315, Dfl 28,127 and Dfl 6747 using respectively the results from the BENSTENT-I study, the BENESTENT-II pilot study and phase IV of the BENESTENT-II pilot study. Significant decreases in complications and ischaemic events have made stent implantation not only the most favourable in terms of event-free survival but also in terms of cost effectiveness.

Angioplasty, Balloon, Coronary↗
PubMed1994

Recoil following Wiktor stent implantation for restenotic lesions of coronary arteries.

The purpose of this study was to determine acute recoil of the vessel wall immediately after Wiktor stent implantation in native coronary arteries of 77 consecutive patients and to assess whether there was compression or "late recoil" of the stent itself at long-term follow-up. Furthermore, the relationship between recoil and a number of clinical, angiographic, and procedural variables was studied in addition to the relation between acute recoil renarrowing or restenosis was assessed. All angiograms were analyzed with the Cardiovascular Angiography Analysis System using automated edge detection. Acute recoil was defined by the difference between the mean diameter of the fully expanded balloon on which the stent was mounted and the mean diameter of the stented segment. Late recoil was calculated by comparing the mean diameter of the stent itself immediately after implantation and at follow-up without opacification of the vessel. Acute recoil amounted to 0.25 +/- 0.32 mm or 8.2%. Multivariate analysis identified sex (coefficient = -0.20, p = 0.04) and stent/artery ratio (coefficient = 0.99, p = 0.0001) as the only independent predictors of acute recoil. "Late recoil" of the stent itself was not observed. The overall difference between the mean diameter of the stent itself immediately after implantation and at follow-up was -0.15 +/- 0.33 mm, suggesting an overall increase in diameter of 5.0%. There was no relation between acute recoil and late restenosis. On the contrary, there was a trend towards a greater degree of recoil in patients without restenosis. Moreover, linear regression analysis disclosed a weak but negative correlation between acute recoil and a loss in minimal luminal diameter (coefficient: -0.55, p = 0.04). The Wiktor stent effectively scaffolds the instrumented vessel. Only a minimal amount of acute recoil was noted, which did not contribute to late luminal renarrowing or restenosis. In addition, no late compression of the stent itself was observed. These data suggest that tissue ingrowth into the lumen of the stented segment is the main cause of late luminal renarrowing after stent implantation.

Aged↗
PubMed1994

Reproducibility of carotid vessel wall thickness measurements. The Rotterdam Study.

We studied the reproducibility of measurement of ultrasonographically assessed common carotid intima-media thickness and assessed whether measurement error of intima-media thickness occurred randomly or was associated with potential determinants of atherosclerosis. Eighty participants of the Rotterdam Study underwent a second ultrasound scan of both carotid arteries within 3 months of the first scan. The replicate measurements involved the posterior intima-media thickness of the distal common carotid artery. Mean differences (SD) in intima-media thickness of the right common carotid artery between paired measurements of sonographers, readers and visits were -0.004 mm (0.10), 0.066 mm (0.07), and -0.013 mm (0.13), respectively. Similar results were obtained for the left common carotid artery. Measurement error of intima-media thickness, i.e. the absolute difference in measurements between two subsequent visits, increased significantly with increasing common carotid intima-media thickness. This association disappeared after logarithmical transformation of the intima-media thickness data. Age, sex, smoking, body mass index, serum lipids, fibrinogen, and systolic and diastolic blood pressure were not significantly associated with the measurement error of intima-media thickness. Our findings indicate that measurements of common carotid intima-media thickness are highly reproducible. Measurement error of intima-media thickness is small and appears to be proportional with the level of intima-media thickness and is not significantly associated with most risk factors for atherosclerotic vessel wall disease.

Aged↗
PubMed1990

Myocardial protection by intravenous diltiazem during angioplasty of single-vessel coronary artery disease.

The possible cardioprotective effect of diltiazem during ischemia caused by percutaneous transluminal coronary angioplasty was tested. Electrocardiograms and myocardial lactate, hypoxanthine and urate production were determined in 26 patients with a stenosis in the left anterior descending artery without angiographically demonstrable collaterals. Measurements took place before angioplasty, after each of 4 occlusions and 15 minutes after the last balloon inflation. Patients were randomly given placebo or DL-diltiazem (0.4 mg/kg as a bolus intravenously, followed by an infusion of 15 mg/hr). During angioplasty the ST-segment elevation for the anterior wall leads V2, V4 and V6, and the intracoronary lead was similar for both groups, as was lactate release. Diltiazem significantly reduced cardiac hypoxanthine release immediately after angioplasty from 63 to 88% (p less than 0.05). The drug diminished urate production after the last dilatation by 82% (p less than 0.05). In conclusion, intravenous infusion of diltiazem reduced cardiac adenosine triphosphate breakdown during angioplasty as shown by diminished hypoxanthine and urate production. In contrast, diltiazem was unable to attenuate ST-segment elevation and lactate release.

Adenosine Triphosphate↗
PubMed1989

Increased serum levels of fibrinogen degradation products due to treatment with recombinant tissue-type plasminogen activator for acute myocardial infarction are related to bleeding complications, but not to coronary patency. European Co-operative Study Groups for rt-PA.

The association of increasing serum levels of fibrinogen degradation products after recombinant tissue-type plasminogen activator (rt-PA) therapy with bleeding and early coronary patency was assessed in 242 patients with acute myocardial infarction. After administration of 5,000 IU heparin, a median of 40 mg (range 35 to 60) of double chain rt-PA was given intravenously in 90 min. Bleeding occurred in 62 patients; in 73% of patients it was observed within the 1st 24 h and 84% of events consisted of hematoma or prolonged bleeding, or both, at puncture sites. Bleeding events occurred 2.12 times as often in patients with serum levels of fibrinogen degradation products greater than 85 mg/liter as in patients with serum levels less than 22 mg/liter (95% confidence interval 1.01 to 4.43). The infarct-related coronary vessel was patent in 65% of patients at 90 min after the start of rt-PA infusion. In patients with high serum levels of fibrin(ogen) degradation products, coronary patency at 90 min after the start of rt-PA infusion was not better (13% less, 95% confidence interval - 33%, 13%) than in patients with low serum levels. This uncoupling of thrombolytic effect in terms of coronary patency and systemic fibrinogenolysis confirms the experimentally demonstrated fibrin specificity of double chain rt-PA in human subjects. Because fibrin specificity of single chain rt-PA is at least similar to that of double chain rt-PA, the observations in this analysis most likely hold also for single chain rt-PA.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Serum potassium values in relation to the use of diuretics in patients with unstable angina pectoris.

Transient hypokalaemia may occur in acutely ill patients and is associated with an increased incidence of life-threatening arrhythmias. Therefore, we performed a retrospective analysis of the serum potassium values of 538 patients with unstable angina included in the Holland Interuniversity Nifedipine/metoprolol Trial in relation to the use of diuretics. On admission, 113 of these patients used diuretics. Potassium sparing diuretics had been used in 65 patients (group A) and non-potassium sparing diuretics in 48 patients (group B). From the 425 patients not on diuretics a random sample of 56 (group C) was drawn. Blood samples were taken routinely on admission to the coronary care unit. The serum potassium values found for group A, B and C were 3.77 +/- 0.55, 3.44 +/- 0.69 and 4.14 +/- 0.48, respectively, and the prevalence of hypokalaemia (less than 3.6 mmol) 40, 65 and 14% respectively. Rate ratio [95% confidence interval (CI)] for hypokalaemia when compared to group C was 2.6 (1.2-5.6) for group A and 4.9 (2.4-10.1) for group B. The prevalence of hypokalaemia was higher for women than for men (rate ratio, 95% CI: 1.4, 0.9-2.2). Patients already on beta-blocker therapy showed a 10% lower prevalence of hypokalaemia (rate ratio, 95% CI: 0.7, 0.5-1.1). These data were compared with serum potassium values of 104 patients with stable angina, who reported to the outpatient clinic. These patients were also divided into three groups according to the use of diuretics. Only in 15% of the patients using non-potassium sparing diuretics was hypokalaemia observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris↗
PubMed1988

Cost benefit analysis of early thrombolytic treatment with intracoronary streptokinase. Twelve month follow up report of the randomised multicentre trial conducted by the Interuniversity Cardiology Institute of The Netherlands.

The costs and benefits of early thrombolytic treatment with intracoronary streptokinase in acute myocardial infarction were compared in a randomised trial. All hospital admissions were recorded and the functional class was assessed at visits to the outpatient clinic during a 12 month follow up of 269 patients allocated to thrombolytic treatment and of 264 allocated to conventional treatment. Mean survival during the first year was calculated for patients with inferior and with anterior infarction and adjusted for impaired quality of life in cases where there were symptoms or hospital admission. In patients with inferior infarction mean survival was 337 days (out of a total follow up of 365 days) for patients allocated to thrombolytic treatment and 327 days for controls. Quality adjusted survival was seven days longer in the thrombolysis group (307 vs 300 days in controls). In patients with anterior infarction mean survival was significantly longer (35 days) in the thrombolysis group than in the control group as was quality adjusted survival (38 days) (304 vs 266 days in controls). The gain in life expectancy with thrombolytic treatment was 0.7 years for patients with inferior infarction, 2.4 years for patients with anterior infarction, and 3.6 years for the subset of patients with large anterior infarction who were admitted within two hours of the onset of symptoms. The costs of medical treatment, including medication, hospital stay, cardiac catheterisation, coronary angioplasty, and bypass surgery, in the first year follow up were higher inpatients allocated to thrombolytic treatment (an additional cost ofDfl 7000 in inferior and Dfl 9000in anterior infarction (1 pounds sterling approximately Dfl 3.3.)) than in conventionally treated patients. The additional costs per year of life gained were Dfl 10 000 in inferior infarction, Dfl 3 800 in anterior infarction, and only Dfl 1 900 in patients with large anterior infarction admitted within two hours of onset of symptoms. Intracoronary thrombolysis can be recommended as a cost effective treatment in patients with extensive anteroseptal infarction.

Clinical Trials as Topic↗
PubMed1988

Incidence of restenosis after successful coronary angioplasty: a time-related phenomenon. A quantitative angiographic study in 342 consecutive patients at 1, 2, 3, and 4 months.

Data from experimental, clinical, and pathologic studies have suggested that the process of restenosis begins very early after coronary angioplasty. The present study was performed to determine prospectively the incidence of restenosis with use of the four National Heart, Lung, and Blood Institute and the 50% or greater diameter stenosis criteria, as well as a criterion based on a decrease of 0.72 mm or more in minimal luminal diameter. Patients were recatheterized at 30, 60, 90, or 120 days after successful percutaneous transluminal coronary angioplasty (PTCA). After PTCA all patients received 10 mg nifedipine three to six times a day and aspirin once a day until repeat angiography. Of 400 consecutive patients in whom PTCA was successful (less than 50% diameter stenosis), 342 underwent quantitative angiographic follow-up (86%) by use of an automated edge-detection technique. A wide variation in the incidence of restenosis was found dependent on the criterion applied. The incidence of restenosis proved to be progressive to at least the third month for all except NHLBI criterion II. At 4 months a further increase in the incidence of restenosis was observed when defined as a decrease of 0.72 mm or more in minimal luminal diameter, whereas the criteria based on percentage diameter stenosis showed a variable response. The lack of overlap between the different restenosis criteria applied affirms the arbitrary nature of angiographic definitions currently in use. Restenosis should be assessed by repeat angiography, and preferably ascertained according to the change in absolute quantitative measurements of the luminal diameter.

Adult↗
PubMed1988

Assessment of immediate and long-term functional results of percutaneous transluminal coronary angioplasty.

Assessment of the functional significance of coronary artery lesions during cardiac catheterization has recently become possible by calculating coronary flow reserve from both myocardial contrast appearance time and density in the resting and hyperemic states determined from digitized coronary cineangiograms. However, the interobserver and intraobserver variabilities, as well as the short-, medium-, and long-term variabilities of the coronary flow reserve measurements, have to be established before this technique becomes an acceptable means of assessing the immediate and long-term functional results of revascularization procedures such as percutaneous transluminal coronary angioplasty (PTCA). Variability was defined as the mean difference and standard deviation of the difference between duplicate determinations of coronary flow reserve. The intraobserver variability (mean difference +/- SD) in the measurement of coronary flow reserve was -0.01 +/- 0.07. Interobserver variability by two observers was +0.08 +/- 0.52. Short-term variability based on the analysis of two coronary cineangiograms taken 5 minutes apart was -0.02 +/- 0.26. Medium-term variability (coronary cineangiographies repeated 1-3 hours apart) was found to be -0.06 +/- 0.52. Long-term variability (coronary cineangiographies repeated 3-5 months apart) was 0.11 +/- 0.63. Having established the reproducibility of this radiographic method, we studied the prospective changes in coronary flow reserve in 25 patients undergoing PTCA for single vessel coronary artery disease. Coronary flow reserve measurements and quantitative coronary cineangiography were performed before, immediately after, and 3-5 months after PTCA. PTCA resulted in an immediate increase in coronary flow reserve from 1 +/- 0.3 to 2.3 +/- 0.6 with a concomitant increase in obstruction area from 0.9 +/- 0.3 to 3.3 +/- 0.7 mm2. Nine of the 25 patients developed restenosis defined as a diameter stenosis greater than 50% at follow-up. The other 16 patients had a coronary flow reserve of 3.3 +/- 0.6, which was measured 3-5 months after PTCA. Coronary flow reserve measurement from digitized coronary cineangiograms is a reproducible method for the assessment of the physiological importance of coronary artery obstructions. Short-, medium-, and long-term investigations of the functional results of interventions such as pharmacological therapy or revascularization can be performed reliably with this technique.

Adult↗
PubMed1987

Early termination of clinical trials with prolonged observation of individual patients: a case study.

Stopping rules for a placebo controlled clinical trial of anticoagulants after acute myocardial infarction were evaluated by means of computer simulation for the case of five interim analyses. The trial will be terminated and the null hypothesis of no treatment effect rejected when the one-sided P-value (logrank test) is lower than 0.005, 0.005, 0.005, 0.014, and 0.023 at the respective interim analyses, and 0.032 at final evaluation. This implies a total size alpha = 0.05 and a power close to that of fixed sample size testing. The trial will also be terminated, without rejecting the null hypothesis, when the one-sided P-value exceeds 0.95, 0.88, 0.81, 0.74, and 0.67 at the respective interim analyses. This modification hardly affects size and power.

Anticoagulants↗