Meij, S.

Simultaneous comparison of 3 derived 12-lead electrocardiograms with standard electrocardiogram at rest and during percutaneous coronary occlusion (Article)

2008-05-01T00:00:00Z

Aim: The aim of the study was to simultaneously test the EASI lead system and two other derived ECG methods against the standard 12-lead ECG during percutaneous coronary intervention (PCI). Methods: During 44 percutaneous coronary interventions, a simultaneously recorded 12-lead and EASI ECG were marked at the start of the PCI (baseline) and at known ischemia caused by balloon inflation (peak). ST deviations were measured 60 ms after the J point at baseline and peak in all leads and were summated (SUMST) to assess overall changes. For regional changes, the lead with the highest ST deviation (PEAKST) was marked. For each patient, derived 12-lead ECGs were computed from the EASI leads and a lead subset using patient-specific coefficients (PS) and coefficients based on a patient population (GEN). Absolute differences were computed between each derived and routine ECG for SUMST and PEAKST. Results: SUMST was at baseline 567 μV (range: 150-1707) and increased at peak to 871 μV (range: 350-2101). SUMST difference at peak was for EASI: 163 μV (CI: 90-236, P <.001), GEN: 46 μV (CI: 2-91, P = .40), and PS: 16 μV (CI: 3-30, P = .15). PEAKST difference at peak was for EASI: 49 μV (CI: 19-220, P = .02), GEN: 48 μV (CI: -43-154, P = .26), and PS: 20 μV (CI: -51-32, P = .65). Conclusion: Simultaneous direct comparison of three derived ECG methods shows overall and regional differences in accuracy across PS, GEN, and EASI. Median SUMST and PEAKST differences for PS are lower than for GEN and EASI, and show a more accurate reconstruction.

Auctioning Bulk Mobile Messages (Research Paper)

2003-03-04T00:00:00Z

The search for enablers of continued growth of SMS traffic, as well as the take-off of the more diversified MMS message contents, open up for enterprises the potential of bulk use of mobile messaging , instead of essentially one-by-one use. In parallel, such enterprises or value added services needing mobile messaging in bulk - for spot use or for use over a prescribed period of time - want to minimize total acquisition costs, from a set of technically approved providers of messaging capacity. This leads naturally to the evaluation of auctioning for bulk SMS or MMS messaging capacity, with the intrinsic advantages therein such as reduction in acquisition costs, allocation efficiency, and optimality. The paper shows, with extensive results as evidence from simulations carried out in the Rotterdam School of Management e-Auction room, how multi-attribute reverse auctions perform for the enterprise-buyer, as well as for the messaging capacity-sellers. We compare 1- and 5-round auctions, to show the learning effect and the benefits thereof to the various parties. The sensitivity will be reported to changes in the enterprise's and the capacity providers utilities and priorities between message attributes (such as price, size, security, and delivery delay). At the organizational level, the paper also considers alternate organizational deployment schemes and properties for an off-line or spot bulk messaging capacity market, subject to technical and regulatory constraints.

Recurrent ischaemia during continuous multilead ST-segment monitoring identifies patients with acute coronary syndromes at high risk of adverse cardiac events; meta- analysis of three studies involving 995 patients. (Article)

2001-12-06T00:00:00Z

AIMS: Recurrent ischaemia, detected by continuous ECG monitoring, in patients with unstable angina increases the risk of unfavourable outcome. Studies that evaluated this relationship have been limited by the small series of patients. By combining data from three studies, the present analysis aims to provide an accurate assessment of the impact of recurrent ischaemia detected by multilead ECG-ischaemia monitoring on the occurrence of death and myocardial infarction in patients with acute coronary syndromes. METHODS AND RESULTS: Data were obtained from CAPTURE, PURSUIT and FROST, three trials evaluating glycoprotein IIb/IIIa blockers in patients with non-ST-elevation acute coronary syndromes. Patients were monitored for 24 h after enrollment with a computer-assisted 12-lead or a vectorcardiographic ECG-ischaemia monitoring device. In a retrospective blinded analysis, recurrent ischaemic episodes were identified by a computer algorithm. The number of ischaemic episodes was normalized to 24 h. Ischaemic episodes were detected in 271 (27%) of 995 patients. There was a direct proportional relationship between the number of ischaemic episodes per 24 h and the probability of cardiac events at 5 and 30 days. The 30-day composite of death and myocardial infarction occurred in 5.7% of patients without episodes and increased to 19.7% in patients with >/=5 episodes. After adjustment for baseline predictors of adverse outcome, the relative risk of death or myocardial infarction at 5 and 30 days increased by 25% for each additional ischaemic episode per 24 h. CONCLUSIONS: This analysis emphasizes the need for integration of multilead ECG-ischaemia monitoring systems in coronary care units and emergency wards to improve early risk stratification in patients with acute coronary syndromes.

Anticoagulant properties, clinical efficacy and safety of efegatran, a direct thrombin inhibitor, in patients with unstable angina. (Article)

1999-08-01T00:00:00Z

AIMS: Thrombin plays a key role in the clinical syndrome of unstable angina. We investigated the safety and efficacy of five dose levels of efegatran sulphate, a direct thrombin inhibitor, compared to heparin in patients with unstable angina. METHODS: Four hundred and thirty-two patients with unstable angina were enrolled. Five dose levels of efegatran were studied sequentially, ranging from 0.105 mg. kg(-1). h(-1)to 1.2 mg. kg(-1). h(-1)over 48 h. Safety was assessed clinically, with reference to bleeding and by measuring clinical laboratory parameters. Efficacy was assessed by the number of patients experiencing any episode of recurrent ischaemia as measured by computer-assisted continuous ECG ischaemia monitoring. Clinical end-points were: episodes of recurrent angina, myocardial infarction, coronary intervention (PTCA or CABG), and death. RESULTS: Efegatran demonstrated dose dependent ex-vivo anticoagulant activity with the highest dose level of 1.2 mg. kg(-1). h(-1)resulting in steady state mean activated partial thromboplastin time values of approximately three times baseline. Thrombin time was also increased. Neither of the efegatran doses studied were able to suppress myocardial ischaemia during continuous ECG ischaemia monitoring to a greater extent than that seen with heparin. There were no statistically significant differences in clinical outcome or major bleeding between the efegatran and heparin groups. Minor bleeding and thrombophlebitis occurred more frequently in the efegatran treated patients. CONCLUSION: Administration of efegatran sulphate at levels of at least 0.63 mg. kg(-1). h(-1)provided an anti-thrombotic effect which is at least comparable to an activated partial thromboplastin time adjusted heparin infusion. There was no excess of major bleeding. The level of thrombin inhibition by efegatran, as measured by activated partial thromboplastin time, appeared to be more stable than with heparin. Thus, like other thrombin inhibitors, efegatran sulphate is easier to administer than heparin. However, no clinical benefits of efegatran over heparin were apparent.

Reduction of Recurrent Ischemia With Abciximab During Continuous ECG Ischemia Monitoring in Patients With Unstable Angina Refractory to Standard Treatment (CAPTURE) (Article)

1998-01-01T00:00:00Z

Background—In the CAPTURE (c7E3 Fab Anti Platelet Therapy in Unstable REfractory angina) trial, 1265 patients with refractory unstable angina were treated with abciximab or placebo, in addition to standard treatment from 16 to 24 hours preceding coronary intervention through 1 hour after intervention. To investigate the incidence of recurrent ischemia and the ischemic burden, a subset of 332 patients (26%) underwent continuous vector-derived 12-lead ECG-ischemia monitoring. Methods and Results—Patients were monitored from start of treatment through 6 hours after coronary intervention. Ischemic episodes were detected in 31 (18%) of the 169 abciximab and in 37 (23%) of the 163 placebo patients (NS). Only 9 (5%) of abciximab versus 22 (14%) of placebo patients had 2 ST episodes (P<0.01). In patients with ischemia, abciximab significantly reduced total ischemic burden (P<0.02), which was calculated alternatively as the total duration of ST episodes per patient, the area under the curve of the ST vector magnitude during episodes, or the sum of the areas under the curves of 12 leads during episodes. Twenty-one patients (6%) suffered a myocardial infarction (MI) (18) or died (3) within 5 days of treatment. The presence of asymptomatic and symptomatic ST episodes during the monitoring period preceding coronary intervention was associated with an increased relative risk of these events of 3.2 (95% CI 1.4, 7.4) and 4.1 (95% CI 1.4, 12.2), respectively. Conclusions—Recurrent ischemia predicts MI or death within 5 days of follow-up. Treatment with abciximab is associated with a reduction of frequent ischemia and a reduction of total ischemic burden in patients with refractory unstable angina. As such, patients with ischemia derive particularly high benefit from abciximab.

Reduction of recurrent ischemia with abciximab during continuous ECG-ischemia monitoring in patients with unstable angina refractory to standard treatment (CAPTURE) (Article)

1998-01-01T00:00:00Z

BACKGROUND: In the CAPTURE (c7E3 Fab Anti Platelet Therapy in Unstable REfractory angina) trial, 1265 patients with refractory unstable angina were treated with abciximab or placebo, in addition to standard treatment from 16 to 24 hours preceding coronary intervention through 1 hour after intervention. To investigate the incidence of recurrent ischemia and the ischemic burden, a subset of 332 patients (26%) underwent continuous vector-derived 12-lead ECG-ischemia monitoring. METHODS and RESULTS: Patients were monitored from start of treatment through 6 hours after coronary intervention. Ischemic episodes were detected in 31 (18%) of the 169 abciximab and in 37 (23%) of the 163 placebo patients (NS). Only 9 (5%) of abciximab versus 22 (14%) of placebo patients had >/=2 ST episodes (P<0.01). In patients with ischemia, abciximab significantly reduced total ischemic burden (P<0.02), which was calculated alternatively as the total duration of ST episodes per patient, the area under the curve of the ST vector magnitude during episodes, or the sum of the areas under the curves of 12 leads during episodes. Twenty-one patients (6%) suffered a myocardial infarction (MI) (18) or died (3) within 5 days of treatment. The presence of asymptomatic and symptomatic ST episodes during the monitoring period preceding coronary intervention was associated with an increased relative risk of these events of 3.2 (95% CI 1.4, 7.4) and 4.1 (95% CI 1.4, 12.2), respectively. CONCLUSIONS: Recurrent ischemia predicts MI or death within 5 days of follow-up. Treatment with abciximab is associated with a reduction of frequent ischemia and a reduction of total ischemic burden in patients with refractory unstable angina. As such, patients with ischemia derive particularly high benefit from abciximab.

Comparison of usefulness of computer assisted continuous 48-h 3-lead with 12-lead ECG ischaemia monitoring for detection and quantitation of ischaemia in patients with unstable angina (Article)

1997-01-01T00:00:00Z

AIMS: The selection of ECG leads used for ST monitoring may influence detection and quantitation of ischaemia. METHODS: We compared on-line continuous 48-h 12-lead against 3-lead ST monitoring in 130 unstable angina patients (Mortara. ELI-100). Onset and offset of ST episodes were defined by the lead with the first > or = 100 microV ST change relative to baseline and the lead with the latest return to baseline ST level, respectively. ST episodes were calculated for 12 leads and 3 leads (V2, V5, III) separately. RESULTS: ST episodes were detected in 88 patients (77%) by 12-lead and in 71 patients (62%) by 3-lead ST monitoring (P < 0.02). The median number (25.75%) of episodes/patient was 1 (0.3) for 3-lead and 2 (1.6) for 12-lead (P < 0.0001). The total duration of ischaemia detected during 12-lead far exceeded 3-lead monitoring: 12.3 (1, 58.2) and 1.7 (0, 23.3) min respectively (P < 0.0001). The probability of recurrent ischaemia declined most during the first 24 h of monitoring. After a period without ST changes of 1, 12, 24 and 36 h, the probabilities of recurrent ischaemia were 63, 31, 14 and 9%, respectively. CONCLUSIONS: Continuous 12-lead ST monitoring increases detection rate and duration of ST episodes compared to 3-lead ST monitoring. The use of continuous 12-lead ECG monitoring devices on emergency wards and coronary care units is recommended.

Non-invasive prediction of reperfusion and coronary artery patency by continuous ST segment monitoring in the GUSTO-I trial (Article)

1996-01-01T00:00:00Z

In the GUSTO-I ECG ischaemia monitoring substudy, 1067 patients underwent continuous ST segment monitoring, using vector-derived 12-lead (406 patients), 12-lead (373 patients) and 3-lead Holter (288 patients) ECG recording systems. Simultaneous angiograms at 90 or 180 min following thrombolytic therapy were performed as a part of the prospective study in 302 patients. Infarct vessel patency was established as TIMI perfusion grades 2 or 3 and occlusion as TIMI perfusion grades 0 or 1. Coronary artery patency was predicted from ST trends up to the time of angiography. Predictive values at 90 and 180 min after the start of thrombolysis were 70% and 82% for patency and 58% and 64% for occlusion, respectively. In retrospect, accuracy appeared greatest (79-100%) in patients with extensive ST segment elevation (> or = 400 microV), if both speed of ST recovery and extent of ST segment elevation were taken into account. Although the three recording systems differed considerably in signal processing, no significant difference in accuracy was demonstrated among these systems. We conclude that continuous ECG monitoring may help select high risk patients without apparent reperfusion who may benefit from additional reperfusion therapy. As ST recovery may occur early after the start of thrombolytics and accuracy of the test is related to peak ST levels, the use of on-line ECG monitoring devices on emergency wards and cardiac care units is recommended.

Epicardial wall motion and left ventricular function during coronary graft angioplasty in humans (Article)

1985-01-01T00:00:00Z

Epicardial wall motion and left ventricular function changes during temporary coronary artery occlusion were assessed in a patient at the time of percutaneous transluminal angioplasty performed on a previously placed stenotic coronary artery bypass graft. Epicardial wall motion was analyzed using biplane cineradiography with frame to frame measurements of distances between pairs of radiopaque epicardial markers placed at the time of previous cardiac surgery. Bypass graft occlusion after initial dilation led to the early onset of a biphasic epicardial late systolic lengthening and early diastolic shortening similar to the regional wall motion abnormality preceding the procedure.

Left ventricular performance, regional blood flow, wall motion, and lactate metabolism during transluminal angioplasty (Article)

1984-01-01T00:00:00Z

The response of left ventricular function, coronary blood flow, and myocardial lactate metabolism during percutaneous transluminal coronary angioplasty (PTCA) was studied in a series of patients undergoing the procedure. From four to six balloon inflation procedures per patient were performed with an average duration per occlusion of 51 +/- 12 sec (mean +/- SD) and a total occlusion time of 252 +/- 140 sec. Analysis of left ventricular hemodynamics in 19 patients showed that the relaxation parameters, peak negative rate of change in pressure, and early time constants of relaxation, responded earliest to short-term coronary occlusion (peak effect at 17 +/- 7 sec) while other parameters, such as peak pressure, left ventricular end-diastolic pressure, and peak positive rate of change in pressure, responded more gradually, suggesting a progressive depression of myocardial mechanics throughout the procedure. Left ventricular angiograms, available for 14 patients, indicated an early onset of asynchronous relaxation concurrent with the early response in peak negative dP/dt and the time constant of early relaxation. All hemodynamic functions fully recovered within minutes after the end of PTCA. Mean blood flow in the great cardiac vein and proximal coronary sinus and the hyperemic response were measured in 20 patients. Before PTCA mean flow in the great cardiac vein was 69 +/- 17 ml/min and in the coronary sinus it was 129 +/- 34 ml/min. Reactive hyperemia (great cardiac vein) was 55% after the first PTCA and 91% after the third. A more pronounced reaction was observed when the residual functional coronary stenosis was reduced in subsequent dilatations. Arteriovenous lactate difference appeared constant during the first two occlusions (control +0.11 mmol/liter, first PTCA -0.87 mmol/liter, and second PTCA -0.82 mmol/liter) and did not increase during subsequent occlusions. Within minutes after the procedure lactate balance was again positive, demonstrating the reversibility of the metabolic disturbances after repeated ischemia. The results of this study indicate that there is no permanent dysfunction of global or regional myocardial mechanics, myocardial blood flow, or lactate metabolism after PTCA with four to six coronary occlusions of 40 to 60 sec.

A model of asynchronous left ventricular relaxation predicting the bi-exponential pressure decay (Article)

1983-01-01T00:00:00Z

A new model for the pressure relaxation of the left ventricle is proposed. The model presumes that the myocardium relaxes asynchronously, but that when regions begin to relax, after a delay, the local wall stress decays as a mono-exponential process. This formulation results in an apparently bi-exponential process (two time constants) which has been previously reported. It is shown that the ratio of the two time constants (T2/T1) can be interpreted as the fraction of the myocardium which relaxes synchronously. Data are presented illustrating the Model during transient coronary occlusion in patients undergoing percutaneous transluminal coronary angioplasty.