ST Change Vector Magnitude Research Articles

Novel technique for ST-T interval characterization in patients with acute myocardial ischemia

BackgroundThe novel signal processing techniques have allowed and improved the use of vectorcardiography (VCG) to diagnose and characterize myocardial ischemia. Herein, we studied vectorcardiographic dynamic changes of ventricular repolarization in 80 patients before (control) and during Percutaneous Transluminal Coronary Angioplasty (PTCA). MethodsWe propose four vectorcardiographic ST-T parameters, i.e., (a) ST Vector Magnitude Area (aSTVM); (b) T-wave Vector Magnitude Area (aTVM); (c) ST-T Vector Magnitude Difference (ST-TVD), and (d) T-wave Vector Magnitude Difference (TVD). For comparison, the conventional ST-Change Vector Magnitude (STCVM) and Spatial Ventricular Gradient (SVG) were also calculated. ResultsOur results indicate that several vectorcardiographic parameters show significant differences (p-value<0.05) before starting and during PTCA. Statistical minute-by-minute PTCA comparison against the control situation showed that ischemic monitoring reached a sensitivity=90.5% and a specificity=92.6% at the 5th minute of the PTCA, when aSTVM and ST-TVD were used as classifiers. ConclusionsWe conclude that the sensitivity and specificity for acute ischemia monitoring could be increased with the use of only two vectorcardiographic parameters. Hence, the proposed technique based on vectorcardiography could be used in addition to the conventional ST-T analysis for better monitoring of ischemic patients.

Analysis of vectorcardiographic dynamic changes in patients with acute myocardial ischemia

This work evaluates the vectorcardiographic dynamic changes in ischemic patients before and during Percutaneous Transluminal Coronary Angioplasty (PTCA). Four vectorcardiographic parameters were computed in 51 ischemic and 52 healthy subjects with the objective of assessing the differences between both groups: ST Vector Magnitude Area (STVMa), T Vector Magnitude Area (TVMa), ST Vector Difference (STVD), and T Vector Difference (TVD). The conventional ST-Change Vector Magnitude (STCVM) and Spatial Ventricular Gradient (SVG) were also calculated. Results indicate that the most of them show significant differences between healthy and ischemic subjects. Since, the statistical minute-by-minute PTCA comparison against a healthy population shows that ischemic patients monitoring reached values of Sensitivity = 99.5% and Specificity = 99.4%, when STVD, TVD and SVG were used in the classification. In conclusion the sensitivity and specificity for acute ischemia monitoring could be increase with the used of only three vectorcardiographic parameters.

Acute myocardial ischemia monitoring before and during angioplasty by a novel vectorcardiographic parameter set

BackgroundThis work evaluates the vectorcardiographic dynamic changes in ischemic patients before and during Percutaneous Transluminal Coronary Angioplasty (PTCA). MethodsFour QRS-loop parameters were computed in 51 ischemic and 52 healthy subjects with the objective of assessing the vectorcardiographic differences between both groups: maximum vector magnitude (QRSmVM), planar area (QRSPA), maximum distance between centroid and loop (QRSmDCL) and perimeter (QRSP).The conventional ST-change vector magnitude (STCVM), QRS-vector difference (QRSVD) and spatial ventricular gradient (SVG) were also calculated. ResultsStatistical minute-by-minute PTCA comparison against a healthy population showed that ischemic patients monitoring is greatly enhanced when all the QRS-loop parameters, in combination with the standard STCVM, QRSVD and SVG indexes, are used in the classification. Sensitivity and Specificity, in turn, reached rather high values, 95.4% and 95.2%, respectively. ConclusionsThese new vectorcardiographic set of complementary QRS-loop parameters, when combined with the classics STCVM, QRSVD and SVG indexes, increase sensitivity and specificity for acute ischemia monitoring.

Ischemic ST-segment episodes during the initial 24 hours of ST elevation myocardial infarction predict prognosis at 1 and 5 years

Objectives The aims of the study were to assess the prognostic value of recurrent ischemic episodes during the first 24 hours in ST elevation myocardial infarction (STEMI) treated with thrombolysis and to explore those episodes as a part of a low-risk prognostic feature. Design Two hundred twenty patients with STEMI treated with thrombolysis were monitored for 24 hours with continuous online vectorcardiography assessing ST vector changes to record recurrent ischemic events. Results Ischemic events measured as an increase in ST-change vector magnitude (STC-VM) more than 50 μV for at least 2 minutes during 4- to 24-hour predicted mortality in a 5-year follow-up based on a multivariable analysis (hazard ratio, 1.18/episode; confidence interval, 1.01-1.37). The more episodes there were, the worse the prognosis. A low-risk group with a 1-year mortality of 1.9% could be identified. Conclusion Continuous ST-segment monitoring during the first 24 hours of a myocardial infarction is a valuable tool for identifying high- and low-risk patients. The STC-VM events during 4 to 24 hours of the first day of a myocardial infarction predict mortality within 5 years.

Signs of myocardial ischaemia after injection of oxytocin: a randomized double-blind comparison of oxytocin and methylergometrine during Caesarean section

BackgroundECG changes, similar to those seen during myocardial ischaemia, together with symptoms of chest pain, are common during Caesarean section (CS). We hypothesized that oxytocin administration has cardiovascular effects leading to these symptoms and ECG changes. MethodsForty women undergoing elective CS under spinal anaesthesia were given an i.v. bolus of either 10 IU of oxytocin (Group OXY-CS, n=20) or 0.2 mg of methylergometrine (Group MET-CS, n=20), in a double-blind, randomized fashion after delivery. Ten healthy, non-pregnant, non-anaesthetized women were used as normal controls (Group OXY-NC, n=10) and were given 10 IU of oxytocin i.v. Twelve-lead ECG, on-line, computerized vectorcardiography (VCG), and invasive arterial pressure were recorded. ResultsOxytocin produced a significant increase in heart rate, +28 (sd 4) and +52 (3) beats min−1 [mean (sem); P<0.001], decreases in mean arterial pressure, −33 (2) and −30 (3) mm Hg (P<0.001), and increases in the spatial ST-change vector magnitude (STC-VM), +77 (12) and +114 (8) μV (P<0.001), in CS patients and controls, respectively. Symptoms of chest pain and subjective discomfort were simultaneously present. Methylergometrine produced mild hypertension and no significant ECG changes. ConclusionsOxytocin administered as an i.v. bolus of 10 IU induces chest pain, transient profound tachycardia, hypotension, and concomitant signs of myocardial ischaemia according to marked ECG and STC-VM changes. The effects are related to oxytocin administration and not to pregnancy, surgical procedure, delivery, or sympathetic block from spinal anaesthesia.

Contributions of myocardial ischemia and heart rate to ST segment changes in patients with or without coronary artery disease

ST changes related to ischemia at different heart rates (HRs) have not been well described. We aimed to analyze ST dynamic changes by vectorcardiography (VCG) during pacing-induced HR changes for subjects with proven coronary artery disease (CAD) and without (non-CAD). Symptomatic CAD patients scheduled for elective surgery were enrolled along with a non-CAD group. During anesthesia, both groups were placed at multiple ascending levels. VCG ST data, and in particular in ST change vector magnitude (STC-VM) from baseline, along with arterial and great coronary artery vein (GCV) blood samples were collected to determine regional myocardial lactate production. A total of 35 CAD and 10 non-CAD patients were studied over six incremental 10 beat/min HR increases. STC-VM mean levels increased in the CAD group from 9+/-5 to 131+/-37 microV (standard deviation) compared with non-CAD subjects with 8+/-3-76+/-34 microV. Myocardial ischemia (lactate production) was noted at higher HRs and the positive predictive value for STC-VM to detect ischemia was 58% with the negative predictive value being 88%. STC-VM at 54 microV showed a sensitivity of 88% and a specificity of 75% for identification of ischemia. Both HR and ischemia at higher HRs contribute to VCG ST elevation. Established ST ischemia detection concerning HR levels is suboptimal, and further attention to the effects of HR on ST segments is needed to improve electrocardiographic ischemia criteria.

Vectorcardiographic ST deviations related to increased heart rate in the absence of ischemia in an experimental pig model

The electrocardiographic ST segment may change when heart rate (HR) increases. We aimed to analyze vectorcardiographic ST relation and myocardial conditions during controlled HR increases in anesthetized pigs. The relative parameters ST change vector magnitude and ST change vector angle were calculated at paced HRs ranging from 85 to 175 beats per minute. ST change vector magnitude increased from baseline 6.3 ± 1.3 to 26.0 ± 3.1 μV ( P < .01; range, 4-50 μV) at HR 175 beats per minute with similar changes in ST change vector angle, whereas the absolute parameter ST vector magnitude demonstrated a heterogeneous pattern without any systematic relation to HR changes. Microdialysis results from left ventricular wall, with analysis of glucose, lactate, and pyruvate, showed no sign of ischemia during pacing. Potassium concentrations did not change during pacing. We conclude that significant HR-related ST vector changes can occur in the absence of myocardial ischemia.

ST‐segment deviations during pacing‐induced increased heart rate in patients without coronary artery disease

In order to interpret ST-segment changes as an indicator of ischemia in patients with higher heart rates (HRs), the relation between ST-segment levels and HR needs to be well defined in subjects without coronary artery disease. Eighteen patients with normal ECGs in the catheterization laboratory, after radiofrequency ablation of AV nodal re-entry tachycardia or an accessory pathway were included. Computerized online vectorcardiography (VCG) was performed during step-wise atrial pacing-induced increases in HR up to 150 beats min(-1) (bpm). The ST-vector magnitude (ST-VM) and the relative ST change vector magnitude (STC-VM) were analysed at the J point, J + 20 and J + 60 ms. There was no divergence in the course of ST-VM or STC-VM based on J point + 0, 20, or 60 ms during increasing HR. The STC-VM mean values increased progressively during increases in HR above 100 bpm, with an average increase in STC-VM of 15-20 microV per 10 bpm increases in HR. The ST-VM response during HR increases showed a heterogeneous and unpredictable pattern. The STC-VM increases linearly with rising HRs above 100 bpm. The STC-VM can exceed widely recognized ischemic thresholds during higher HRs in the absence of ischemia. The choice of J point time to ST-VM measurements as tested here is not important for the STC-VM relation to HR at these HR levels. Further clinical testing is needed to improve the diagnostic specificity of STC-VM measurements during increased HRs.

Isolated ultrafiltration affects dynamic vectorcardiographic ischemia monitoring parameters

The present study was undertaken to assess the role of isolated ultrafiltration (UF phase) and hemodialysis with minimal ultrafiltration (HD phase) in changes in parameters reflecting myocardial ischemia: QRS vector difference (QRS-VD), ST change vector magnitude (STC-VM) and ST vector magnitude (ST-VM6) registered by MIDA (myocardial infarction dynamic analysis). Twelve patients on maintenance hemodialysis were first ultrafiltrated for 2.5 h without dialysis (UF) followed by a 2.5-hour session of hemodialysis with minimal ultrafiltration (HD). Computerized vectorcardiography (VCG) was used for on-line dynamic analysis of ST segment and QRS complex changes. Blood volume (BV) changes were monitored non-invasively and continuously with the CRIT-LINE instrument. Whole-body bioelectric impedance analysis (BIA) was used for extracellular water (ECW) estimation. During the UF phase QRS-VD and STC-VM showed a statistically significant increasing linear trend (time effect for both QRS-VD and STC-VM p < 0.0001, while no changes were noted in ST-VM6; time effect p = 0.986). During the HD phase none of these parameters changed (time effect for QRS-VD p = 0.855, for STC-VM p = 0.275 and for ST-VM6 p = 0.976). During the UF, phase changes in QRS-VD were in close relation to those in ECW. Isolated ultrafiltration leads to an increase in the VCG ischemia monitoring parameters QRS-VD and STC-VM. The increase of QRS-VD is related to changes in ECW. Hemodialysis with minimal ultrafiltration has no effect on VCG ischemia monitoring parameters.

Assessment of Myocardium at Risk with Computerized Vectorcardiography and Technetium-99m-Sestamibi-Single Photon Emission Computed Tomography during Coronary Angioplasty

Objective - To compare the myocardium at risk (MAR) as estimated by computerized vectorcardiography (cVCG) with MAR determined by Tc-99m-sestamibi-SPECT using coronary angioplasty as the model for transient transmural ischemia in humans. Methods and results - In 37 patients with stable angina pectoris, cVCG was recorded continuously during coronary angioplasty. The scintigraphic defect was quantified using an automated software program (CEqual). The ST vector magnitude (ST-VM) and the ST change vector magnitude (STC-VM) correlated well with MAR estimated by scintigraphy, ST-VM ( r = 0.71, p < 0.001) and STC-VM ( r = 0.84, p < 0.001). All patients with STC-VM <50 w V during occlusion had defects of less than 10% of the left ventricle. Conclusion - 1) ST-VM and STC-VM give a reasonable useful estimate of MAR size during transient coronary occlusion. 2) STC-VM <50 w V is a reliable limit to identify patients with MAR size less than 10%. 3) ST-VM does not add information to STC-VM with respect to detection of ischemia. 4) The existence of collateral vessels has great impact on both ST-vector changes and scintigraphic imaging of myocardial ischemia.

Deterioration in peak systolic velocity is closely related to ischaemia during angioplasty: a vectorcardiographic and tissue Doppler imaging study.

We tested the hypothesis that the extent of signs of ischaemia detected by vectorcardiography (VCG) during elective coronary angioplasty (percutaneous transluminal coronary angioplasty; PTCA) is related to systolic and diastolic myocardial velocities, as determined by tissue Doppler echocardiography. A total of 15 patients undergoing PTCA (12 men/three women; age 61+/-9 years), without prior myocardial infarction and with an ejection fraction of >50%, were included. The balloon inflation was repeated three times, with minimum intervals of 2 min between inflations. Tissue Doppler echocardiography was performed, in an apical two- or four-chamber view, before and at the end of each inflation. Peak systolic velocity, time-to-peak systolic velocity (TTP), peak early (E(m)) and late (A(m)) diastolic velocities, the E(m)/A(m) ratio and isovolumic relaxation time were measured in the basal segments of the left ventricle. VCG recordings were carried out during the whole procedure. ST vector magnitude (ST-VM) and ST change vector magnitude (STC-VM) were monitored. The total duration and area of each VCG change during inflation were calculated for each patient. Isovolumic relaxation time, peak E(m) and A(m) values and the E(m)/A(m) ratio did not change significantly during inflation. Peak systolic velocity decreased (6.7+/-2.0 to 5.3+/-1.9 cm/s; P<0.001) and TTP increased (157+/-60 to 192+/-60 ms; P<0.01) during inflation. Both STC-VM time (r=-0.68, P<0.01) and STC-VM area (r=-0.68, P<0.01) were related to peak systolic velocity during inflation. STC-VM time was also related (r=0.55, P<0.05) to the difference in peak systolic velocity during compared with before inflation. ST-VM was less closely related to peak systolic velocity. Thus the duration and degree of ischaemia, as measured by VCG, are related to peak systolic velocity in the basal segments of the left ventricle.

Prognostic Value of Ischemia Monitoring with On-Line Vectorcardiography in Patients with Unstable Coronary Artery Disease

Aim: The aim of this study was to determine whether on-line vectorcardiography (VCG) gives independent prognostic information, regarding death, myocardial infarction (MI), and revascularization in patients with unstable coronary artery disease, i.e. unstable angina or non-Q-wave MI. Methods and Results: One hundred and fifty patients (mean age 69 ± 10), participating in a randomized study of low-molecular-weight heparin in unstable coronary artery disease, were studied with on-line VCG recordings for 24 h. During a 5–6-month follow-up, 11 patients died, 14 suffered a nonfatal MI and 31 were revascularized. Univariate predictors of death were diabetes mellitus (p < 0.01), maximum ST vector magnitude (ST-VM; p < 0.001), maximum ST change vector magnitude (STC-VM; p < 0.001), number of ST-VM (p < 0.01) and STC-VM episodes (p < 0.001). In multivariate analysis, the number of STC-VM episodes (p < 0.01) and diabetes mellitus (p < 0.02) each gave independent prognostic information regarding death. When all cardiovascular events were combined, the inhability to perform an exercise test (p < 0.05), maximum value of ST-VM (p < 0.01) and STC-VM (p < 0.001), the number of episodes of STC-VM (p < 0.001) and ST-VM (p < 0.001) all gave prognostic information. In multivariate analysis, the inability to perform an exercise test and the number of STC-VM episodes were independent predictors. Conclusion: VCG monitoring during the first 24 h of hospitalization for unstable coronary artery disease gives independent prognostic information.

Positional changes of spatial QRS- and ST-segment variables in normal subjects: Implications for continuous vectorcardiography monitoring during myocardial ischemia

Electrocardiographic QRS- and ST-segment changes are to beexpected during changes in body posture. We prospectively analyzed the influence of changes in body position on continuous vectorcardiography monitoring of QRS-vector difference (QRS-VD) and ST change-vector magnitude (STC-VM) according to the currently used criteria of myocardial ischemia in 21 normal subjects. Fifteen (71%)and 6 (29%) subjects had significant positional QRS-VD and STC-VM changes, respectively. Vectorcardiography changes were most frequent and pronounced in the left lateral position. An alternative to the existing criterion of ischemia is proposed to improve the specificity of STC-VM. Subjects with positional QRS-VD changes had higher mean STC-VM values as compared with those without such changes. Otherwise no characteristics among those with positional vectorcardiography changes could be identified. There was no statistically significant association between positional QRS-VD and STC-VM changes ( R = .13, P = .57). We conclude that the clinical use of QRS-VD in its present form for continuous vectorcardiography monitoring of myocardial ischemia seems to be of limited practical value, because of the presence of frequent “pseudo- ischemic” changes. STC-VM seems to have a significant potential of continuous vectorcardiography monitoring. However, an indicator of body position change or even an algorithm enabling on-line correction for positional vectorcardiography changes seems to be essential to improve the accuracy of this technique in identifying myocardial ischemia.

Prognostic value of maximum ST-vector magnitude during the first 24 h of vectorcardiographic monitoring in patients with unstable angina pectoris.

To assess the prognostic importance of alternate ways of quantifying myocardial ischaemia by continuous ST analysis, the maximum ST vector magnitude and the area under the ST vector magnitude trend curve during the first 24 h of continuous ST monitoring. During a 22-month period from 1991 to 1993, 195 patients admitted to our CCU with suspected unstable angina pectoris, were included in the study. During the first 24 h the patients were monitored for ischaemic episodes with computerized vectorcardiography, using a MIDA 1000 system. Twenty seven (14%) of the 195 patients died or had a non-fatal myocardial infarction within 1 year and the maximum ST vector magnitude among those patients was, on average, 201 microV compared with 118 microV in patients who survived 1 year free of myocardial infarction (P<0.01). The area under the ST vector magnitude trend curve was, on average, 1598 microVmin compared with 164 microVmin (P<0.01). By multivariate analysis, the maximum ST vector magnitude emerged as a superior predictor of death or myocardial infarction, compared with the area under the ST vector magnitude trend curve and the number of ST vector magnitude and ST change vector magnitude episodes. The maximum ST vector magnitude and age were independent predictors of death or non-fatal myocardial infarction within 1 year. Maximum ST vector magnitude during the first 24 h of vectorcardiographic monitoring seems to be a strong predictor of subsequent death or non-fatal myocardial infarction.

Relative contributions of a single-admission 12-lead electrocardiogram and early 24-hour continuous electrocardiographic monitoring for early risk stratification in patients with unstable coronary artery disease

Patients with unstable coronary syndromes are a heterogeneous group with varying degrees of ischemia and prognosis. The present study compares the prognostic value of a standard electrocardiogram (ECG) obtained at admission to the hospital with the information from 24-hour continuous electrocardiographic monitoring obtained immediately after admission. The admission ECGs and 24 hours of vectorcardiographic (VCG) monitoring from 308 patients admitted with unstable coronary artery disease were analyzed centrally regarding standard electrocardiographic ST-T changes, ST-vector magnitude (ST-VM), and ST change vector magnitude episodes. End points were death, acute myocardial infarction, and refractory angina pectoris within a 30-day follow-up period. ST-VM episodes (≥50 μV for ≥1 minute) during VCG monitoring was the only independent predictor of death or acute myocardial infarction by multivariate analysis. ST-VM episodes during vectorcardiography was associated with a relative risk of 12.7 for having a cardiac event, hypertension was associated with a relative risk of 1.7, and ST depression on the admission ECG was associated with a relative risk of 5.7. Patients with ST depression at admission had an event rate (death or acute myocardial infarction) of 17% at 30-day follow-up. Patients without ST depression could further be risk stratified by 24 hours of VCG monitoring into a subgroup with ST-VM episodes at similar (8%) risk and a subgroup without ST-VM episodes at low (1%) risk (p = 0.00005). Continuous VCG monitoring provides important information for evaluating patients with unstable coronary artery disease. It is recommended that patients not initially estimated at high risk based on the admission ECG are referred for 24 hours of VCG monitoring for further risk stratification.

Continuous vectorcardiographic monitoring of ischemia during coronary angioplasty in patients with bundle-branch block.

Patients with the combination of bundle-branch block and ischemic heart disease have a poor outcome. There is no established criterion for detection of transient ischemia when bundle-branch block is present. To elucidate vectorcardiographic changes during coronary angioplasty of patients with bundle-branch block. The QRS complex and ST-segment changes of 29 patients with bundle-branch block were studied during elective coronary angioplasty using continuous vectorcardiography. Data for the patients with bundle-branch block were compared with data for narrow-QRS-complex controls, matched for the vessel dilated, sex, and age. Patients with bundle-branch block were found to have more pronounced changes in the QRS-vector difference as a response to coronary occlusion than did controls. ST-vector magnitude responded in a similar way during coronary occlusion of patients with and without bundle-branch block but from different baselines. ST change-vector magnitude was found to be the most sensitive parameter for detection of ischemia in patients with bundle-branch block as well as for controls. Monitoring of transient ischemia during coronary angioplasty for patients with bundle-branch block is feasible using continuous vectorcardiography. A change in ST vector magnitude > 100 microV is suggested to indicate significant ischemia in the presence of bundle-branch block.

Ischaemia monitoring with on‐line vectorcardiography during dobutamine stress echocardiography in patients after an episode of unstable coronary artery disease

Abstract. Lundin P, Eriksson SV, Andrén B, Lindahl B, Tornvall P, Melcher A (Danderyd Hospital, Danderyd, University Hospital, Uppsala, Karolinska Hospital, Stockholm, Sweden). Ischaemia monitoring with on‐line vectorcardiography during dobutamine stress echocardiography in patients after an episode of unstable coronary artery disease. J Intern Med 1998; 244: 61–70.ObjectivesThis study investigated the ability of on‐line vectorcardiography (VCG) to detect myocardial ischaemia as assessed by dobutamine stress echocardiography after an episode of unstable coronary artery disease.DesignDobutamine stress test (incrementally infused doses of 5, 10, 20, 30 and 40 μg kg−1 per minute) was performed during simultaneous VCG monitoring. QRS vector difference (QRS‐VD), ST vector magnitude (ST‐VM), ST change vector magnitude (STC‐VM) and T change vector magnitude (TC‐VM) were monitored. A new wall motion abnormality or worsening of abnormal wall motion was regarded as indicating a positive dobutamine stress test.SubjectsFifty‐five patients with unstable angina pectoris and 16 patients with an acute non‐Q‐wave myocardial infarction were studied 5–8 days after admission.ResultsA positive dobutamine stress test was observed in 37 patients (52%). The sensitivity, specificity and total accuracy of identifying patients with a positive dobutamine stress test by VCG were: 38%, 91% and 63% for QRS‐VD; 59%, 88% and 73% for ST‐VM; 84%, 79% and 82% for STC‐VM; and 86%, 23% and 56% for TC‐VM. Patients with a positive dobutamine stress test showed higher maximum VCG values than patients with a negative dobutamine stress test (QRS‐VD, P &lt; 0.01; ST‐VM, P &lt; 0.001; STC‐VM, P &lt; 0.001). The maximum VCG values were related to the number of segments showing new or worsening wall motion abnormality (QRS‐VD: r= 0.41, P &lt; 0.001; ST‐VM: r= 0.44, P &lt; 0.001; STC‐VM: r= 0.57, P &lt; 0.001).ConclusionSTC‐VM and ST‐VM seem to be the best VCG variables for detection of myocardial ischaemia as assessed by dobutamine stress echocardiography.

Heparin Is More Effective Than Inogatran, a Low-Molecular Weight Thrombin Inhibitor in Suppressing Ischemia and Recurrent Angina in Unstable Coronary Disease

Thrombin has been suggested as one of the main pharmacologic targets in unstable coronary syndromes. Electrocardiographic signs of ischemia during continuous monitoring convey prognostic information in these patients. This study assessed the anti-ischemic and clinical effects of the novel low-molecular weight thrombin inhibitor inogatran in patients with unstable angina and non–Q-wave infarction without persistent ST-segment elevation on hospital admission. Within 24 hours of the last episode of chest pain, 324 patients were randomized to 72 hours of treatment with inogatran or heparin. Continuous ST-segment analysis with computerized vectorcardiography was used to monitor ischemia for 24 hours. The occurrence of cardiac events during the first 7 days were studied and compared with ischemic episodes during the initial 24 hours. The heparin-treated patients had less episodes of ischemia (ST vector magnitude [ST-VM]: 1 ± 2.6 vs 2 ± 4.5, p <0.001 and ST change vector magnitude [STC-VM]: 3 ± 4.7 vs 6 ± 7.6, p <0.001) than the patients receiving inogatran. This was paralleled by a lower incidence of the combined end point of death, nonfatal infarction, refractory or recurrent angina during the first 7 days for the heparin-treated patients (35%) compared with the inogatran-treated patients (50%) (p <0.05). Patients who had episodes of ischemia in spite of anti-ischemic therapy were at increased risk of all events studied. Heparin is more effective than inogatran in suppressing myocardial ischemia and clinical events at short-term follow-up. Continuous ST-segment monitoring with vectorcardiography identifies nonresponders who are at an increased level of risk.

Reproducibility of on-line vectorcardiography measurements in patients with and without acute ischaemic heart disease.

The aim of the present study was to determine inter and intraobserver variations of measurements with on-line vectorcardiography (VCG). The VCG registrations were evaluated by two independent observers. One observer also evaluated the VCG registrations on two separate occasions. Monitored VCG variables were: ST vector magnitude (ST-VM), ST vector lead X (ST-X), ST change vector magnitude (STC-VM) and QRS vector difference (QRS-VD). On-line VCG was performed for 24 hours in 60 patients (10 with low probability of ischaemic heart disease, 25 with unstable angina pectoris and 25 with acute myocardial infarction). A close correlation between the two observers and small coefficients of variation were found regarding the ST-VM initial value (r = 0.99, 4.7), the ST-X maximum depression (r = 0.99, 3.2) and the QRS-VD end value (r = 0.98, 5.6). A less close correlation and higher coefficients of variation were found regarding the number of QRS-VD episodes (r = 0.94, 41.5), ST-VM episodes (r = 0.89, 37.8) and STC-VM episodes (r = 0.87, 35.1). Correlation coefficients and coefficients of variations for VCG measurements performed on two separate occasions by one observer ranged from 0.97 to 0.99 and from 18.1 to 1.8 respectively. Three (12%) of 25 patients with acute myocardial infarction did not meet the VCG infarction criterion (QRS-VD > or = 15 microVs) by both observers. In addition, five (20%) of the 25 patients with unstable angina pectoris met the VCG infarction criterion by both observers. The inter and intraobserver variation for VCG interpretations was low, but the number of QRS-VD, ST-VM and STC-VM episodes varied between the two observers. This finding suggests that additional training may improve the results. Caution is also recommended in using VCG to rule out or establish the diagnosis of acute myocardial infarction.

Non-invasive risk stratification within 48 h of hospital admission in patients with unstable coronary disease.

In this study we evaluated the prognostic value of three methods of early risk estimation in patients with unstable coronary disease. The methods evaluated were: clinical risk estimation at hospital admission, continuous ST analysis with computerized vectorcardiography for 24 h and serial measurements of creatinine kinase-MB for 48 h. Twenty-seven (14%) of the 195 patients died or had a non-fatal infarction within one year. Clinical risk evaluation correctly identified a subgroup of patients with low risk but did not otherwise predict outcome. Fifty-six (29%) patients had ST vector magnitude episodes on vectorcardiography, 70 (38%) had three or more episodes of ST change vector magnitude and 74 (38%) had a peak creatinine kinase-MB value of 6 microgram.l-1 or more. The even rate for patients with ST vector magnitude episodes (23%) was significantly higher than for those without (10%; P < 0.05). For patients with and without three or more episodes of ST change vector magnitude the event rate was 23% and 9% respectively (P < 0.05) and for patients with and without creatinine kinase-MB > or = 6 microgram.l-1 the event rate was 23% and 8% respectively (P < 0.01). The positive predictive value of having none, either one or both of the ST or creatinine kinase-MB markers positive was incremental. Continuous vectorcardiographic monitoring of ischaemia in combination with serial creatinine kinase-MB measurement considerably improves risk stratification in unstable coronary disease.