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

Does continuous ST-segment monitoring add prognostic information to the TIMI, PURSUIT, and GRACE risk scores?

BACKGROUND

Recurrent ischemia is frequent in patients with non-ST-elevation acute coronary syndromes (NST-ACS), and portends a worse prognosis. Continuous ST-segment monitoring (CSTM) reflects the dynamic nature of ischemia and allows the detection of silent episodes. The aim of this study is to investigate whether CSTM adds prognostic information to the risk scores (RS) currently used.

METHODS

We studied 234 patients with NST-ACS in whom CSTM was performed in the first 24 hours after admission. An ST episode was defined as a transient ST-segment deviation in ≥1 lead of ≥ 0.1 mV, and persisting ≥1 minute. Three RS were calculated: Thrombolysis in Myocardial Infarction (TIMI; for NST-ACS), Platelet glycoprotein IIb/IIIa in Unstable angina: Receptor Supression Using Integrilin (PURSUIT; death/MI model), and Global Registry of Acute Coronary Events (GRACE). The end point was defined as death or nonfatal myocardial infarction (MI), during 1-year follow-up.

RESULTS

ST episodes were detected in 54 patients (23.1%) and associated with worse 1-year outcome: 25.9% end point rate versus 12.2% (Odds Ratio [OR]= 2.51; 95% Confidence Interval [CI], 1.18-5, 35; P = 0.026). All three RS predicted 1-year outcome, but the GRACE (c-statistic = 0.755; 95% CI, 0.695-0.809) was superior to both TIMI (c-statistic = 0.632; 95% CI, 0.567-0.694) and PURSUIT (c-statistic = 0.644; 95% CI: 0.579-0.706). A GRACE RS > 124 showed the highest accuracy for predicting end point. The presence of ST episodes added independent prognostic information the TIMI RS (hazard ratio [HR]= 2.23; 95% CI, 1.13-4.38) and to PURSUIT RS (HR = 2.03; 95% CI, 1.03-3.98), but not to the GRACE RS.

CONCLUSIONS

CSTM provides incremental prognostic information beyond the TIMI and PURSUIT RS, but not the GRACE risk score. Hence, the GRACE risk score should be the preferred stratification model in daily practice.

Long-term prognostic value and therapeutic implications of continuous ST-segment monitoring in acute coronary syndrome

BACKGROUND

In patients with acute coronary syndromes (ACS), recurrent ischemia detected by continuous electrocardiographic monitoring portends a poor outcome. We sought to investigate (1) the additional long-term prognostic value of ST-segment monitoring beyond the validated Global Registry of Acute Coronary Events (GRACE) risk score in ACS and (2) whether ST-segment monitoring can identify patients who benefit from early revascularization.

METHODS

We determined the GRACE risk score (a validated predictor of inhospital mortality) in 681 non-ST-elevation ACS patients enrolled in the Integrilin and Enoxaparin Randomized Assessment of Acute Coronary Syndrome Treatment trial. Continuous ST-segment monitoring in the first 48 hours was analyzed by an automated algorithm and reviewed by a blinded cardiologist. Clinical outcomes were centrally adjudicated in a blinded fashion.

RESULTS

ST-segment shifts were present in 19.1% of 681 patients. After a median follow-up of 30 months, patients with ST-segment shifts had a higher risk of death (17.7% vs 5.8%, log-rank P < .001) and death or myocardial infarction (MI) (24.6% vs 11.1%, log-rank P < .001). In multivariable analysis adjusting for GRACE risk score, the presence of ST-segment shifts remained an independent predictor of death (adjusted hazard ratio = 2.37, 95% CI 1.38-4.09, P = .002) and death/MI (adjusted hazard ratio = 1.93, 95% CI 1.25-3.00, P = .003). Inhospital revascularization was independently associated with a lower risk of death/MI among patients with ST-segment shifts but not among those without (P for interaction = .02).

CONCLUSIONS

Continuous ST-segment monitoring provides incremental prognostic information beyond the validated GRACE risk score determined on presentation and identifies high-risk patients who benefit from early revascularization. This simple and valuable clinical tool may be useful in the routine management of ACS.

Computerized vectorcardiography telemetry: a new device for continuous multilead ST-segment monitoring of ambulatory patients. A preliminary report

BACKGROUND

Continuous vectorcardiography ST-segment monitoring has become a well-established method in the surveillance of patients with acute myocardial ischemia. However, immobility of the vectorcardiography technique prevents monitoring of patients during ambulatory activities. Computerized vectorcardiography telemetry (CVT) with the capacity of real-time ST-segment analysis has been developed in an attempt to overcome this shortcoming. Recent data, however, indicate that changes in body position occasionally lead to pseudo-ischemic ST-segment changes during continuous ST-segment monitoring.

AIMS

This report describes the technical features of the CVT system, presents clinical examples using CVT, and assesses the influence of changes in body position on ST-vector magnitude (ST-VM) during CVT, respectively.

METHODS

Clinical cases involving CVT are presented. The influence of changing body position during CVT monitoring was evaluated on 24 patients with suspected acute coronary syndromes, i.e., unstable angina or acute myocardial infarction. Each patient performed a specific body positional schedule.

RESULTS

We present three discrete clinical cases where CVT provided early and valuable evidence of ongoing myocardial ischemia. The consequences of different recumbent and ambulatory body positions on ST-VM during CVT monitoring appear to be limited.

CONCLUSION

Computerized vectorcardiography telemetry is a promising new tool for disclosing residual myocardial ischemic activity during the mobilization phase of patients with acute coronary syndromes. The clinical value of CVT needs further investigation in future trials.

A phase of increased ST elevation during coronary occlusion following ischemic preconditioning

ATP-sensitive potassium channels are opened during the course of ischemic preconditioning (IP). As experimental data suggest that opening of sarcolemmal ATP-sensitive potassium channels underlie ST elevation during myocardial ischemia, one would expect to observe increased ST elevation during ischemia following IP. However, clinical studies have reported IP to attenuate ST elevation during repeated brief coronary occlusions. The objective of this study was to characterize the temporal course of ST elevation during coronary occlusion following IP. Twenty-eight closed-chest pigs were subject to catheter-based left anterior descending coronary artery occlusion/ reperfusion for 45/120 minutes. Thirteen animals were preconditioned by two occlusion/reperfusion cycles of 10/30 minutes. Fifteen pigs served as controls. The electrocardiographic ST vector magnitude was continuously monitored. IP reduced the infarct size normalized for area at risk (IP 9.6 +/- 15.8%; control 71.2 +/- 14.7%; p < 0.001). IP increased the time between coronary artery occlusion and appearance of significant rise in ST vector magnitude from 51 +/- 17 to 94 +/- 33 seconds (p < 0.01). IP reduced the rise in ST vector magnitude after 120 seconds of occlusion from 202 +/- 85 microV to 68 +/- 28 microV (p < 0.001) and increased the rise in ST vector magnitude after 600 seconds from 265 +/- 106 microV to 427 +/- 232 microV (p < 0.001).

CONCLUSION

Ischemic preconditioning reduced and delayed early ST elevation during subsequent coronary artery occlusion, but increased late ST elevation. Thus, ischemic preconditioning causes a dynamic and critically time-dependent biphasic pattern of ST elevation during repeated coronary occlusions.

Long term risk stratification of patients with acute coronary syndromes: characteristics of troponin T testing and continuous ST segment monitoring

OBJECTIVE

To examine the long term prognostic characteristics of troponin T testing and continuous multi-lead ST segment monitoring in combination with clinical and 12 lead ECG risk indicators in patients with acute coronary syndromes (ACS).

PATIENTS AND DESIGN

Patients with suspected ACS (n = 213) were studied. Troponin T was analysed in blood samples collected during the first 12 hours after admission. Continuous vectorcardiography ST segment monitoring was performed for 24 hours and the number of ST vector magnitude episodes was registered. Patients were followed up for a median of 28 months. The end point was a composite of cardiac death and acute myocardial infarction.

RESULTS

Thirty eight (18%) patients reached the composite end point. The median (interquartile range) time from study inclusion to the time of the composite end point was longer for patients predicted to be at risk by troponin T testing (n = 27) than for those predicted to be at risk by ST segment monitoring (n = 20) (8.4 (0.2-15) months v 0.3 (0.1-4.3) months, p = 0.04). Significant univariate predictors of the composite end point were age > or = 65 years, diabetes, previous myocardial infarction, congestive heart failure, use of beta blockers or diuretics at admission, 12 lead ECG ST segment depression at admission, troponin T concentration > or = 0.10 microg/l, and > or = 1 ST vector magnitude episodes. Age > or = 65 years, previous myocardial infarction, and troponin T concentration > or = 0.10 microg/l provided independent prognostic information after multivariate analysis of potential risk variables. The prognostic value of transient ischaemic episodes in ACS seems to be confined to the short term.

CONCLUSIONS

Both biochemical and continuous ECG markers reflect an increased risk for patients with ACS; however, the methods exhibit different temporal risk characteristics.

Vectorcardiography risk stratifies emergency department chest pain patients with left ventricular hypertrophy on the initial 12-lead ECG

BACKGROUND

Vectorcardiographic (VCG) measurements of ST-vector magnitude (VM) and QRS-vector difference (VD) have been demonstrated to be independent predictors of adverse outcome (AO) and acute myocardial infarction (AMI) in emergency department (ED) chest pain patients with absence of bundle branch block or left ventricular hypertrophy (LVH) on the initial 12-lead electrocardiogram (ECG). The prognostic value of ST-VM and QRS-VD in ED chest pain patients with LVH on the initial 12-lead ECG has not been previously investigated.

METHODS

A prospective observational study was performed in 196 consecutive ED chest pain patients with suspected AMI and presence of voltage criteria for LVH on initial ECG who underwent continuous VCG monitoring during the initial evaluation. The optimal baseline ST-VM value and 2-hour QRS-VD value were defined as the most accurate value on the receiver operator characteristic curve (value with lowest false-negative and false-positive rate). Thirty-day AO was defined as AMI, percutaneous coronary intervention, coronary artery bypass grafting (CABG), or cardiac death occurring within 30 days of initial ED visit.

RESULTS

Fourteen patients (7.1%) were diagnosed as 24-hour AMI and 28 patients (14.3%) experienced 30-day AO. The optimal cut-off value for predicting 30-day AO was > 124 microV for ST-VM and > 21.7 microV for QRS-VD. Patients with either a positive ST-VM or a positive QRS-VD had 8.8 times increased odds of AMI (95% confidence interval, CI, 1.9-40.3; P = 0.003); 4.3 times increased odds of 30-day PTCA/CABG (95% CI 1.3-13.8; P = 0.019); and 3.8 times increased odds of 30-day AO (95% CI 1.6-9.3; P = 0.003).

CONCLUSIONS

Baseline ST-VM and 2-hour QRS-VD risk stratifies ED chest pain patients with LVH voltage criteria on the initial 12-lead ECG.

ST-segment monitoring in patients with acute coronary syndromes

ST-segment analyses from electrocardiograms during acute coronary syndromes (ACS) have repeatedly shown strong mechanistic links to coronary artery patency and myocardial reperfusion. In these patients, such analyses have also consistently been reported to have close correlations with outcome--correlations superior even to those reported for invasive coronary flow measurements and outcome. Continuous multilead ST-monitoring of patients with ACS provides accurate and noninvasive information on the dynamics of the myocardial reperfusion process over time. This information can be used for improved early diagnostic accuracy, evaluation of treatment efficacy, early risk-stratification, and can be supportive in clinical decision making regarding these patients. Continuous multilead ST-monitoring during ACS is no longer a cumbersome source of more nuisance than benefit, but can be an accurate and useful tool in multicenter clinical trials, as well as in clinical medicine.

Use of baseline ST-vector magnitude to identify electrocardiographic injury in patients with suspected acute myocardial infarction

No information is currently available regarding optimal cut-off values of the ST-vector magnitude (ST-VM) for predicting acute myocardial infarction (AMI) in emergency department (ED) chest pain patients undergoing vectorcardiographic (VCG) monitoring. A prospective observational study was performed in 1,722 chest pain patients with suspected acute coronary syndrome and absence of bundle branch block (BBB) and left ventricular hypertrophy (LVH) on initial ECG who underwent continuous VCG ST-segment monitoring during the initial ED evaluation. Three cut-off values for baseline ST-VM are reported and represent the smallest values in which the positive likelihood ratio (+LR) for AMI is greater than 5, 10, and 20, respectively. AMI occurred in 158 of 1,722 patients (9.2%) without BBB or LVH on initial ECG. Optimal cut-off values at the predetermined +LR values of 5, 10, and 20, were 121 microV (sensitivity, 41.8%; specificity, 92.0%), 151 microV (sensitivity, 29.1%; specificity, 97.1%), and 175 microV (sensitivity, 25.9%; specificity, 98.7%), respectively. Combining the earlier-mentioned cut-off values with physician judgment of initial pretest probability (high, intermediate, or low, respectively) resulted in a relative increase in identification of injury of 37.5% as compared with the ED physician's interpretation of initial ECG (41.8% v 30.4%; P <.0001), and 65.2% as compared with the official ECG interpretation (41.8% v 25.3%; P <.0001). Increasing ST-VM results in increasing likelihood of AMI. Clinical studies need to be performed to determine if ST-VM cut-off values of 121, 151, and 175 microV in conjunction with physician pretest probability of AMI can be used as criterion for emergent reperfusion therapy in patients without LVH or BBB on the initial ECG.

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 microV 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 microV 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.

Risk stratification in non-ST segment elevation acute coronary syndromes with special focus on recent guidelines

Patients with unstable angina or non-ST segment elevation (non-Q-wave) myocardial infarction are a heterogeneous group with respect to their risk of developing clinically significant adverse events such as subsequent myocardial infarction and death. Recent guidelines promote risk stratification of these patients, targeting high-risk patients for maximal antithrombotic and antiischemic therapy and low-risk patients for early discharge. We reviewed current and future modalities for risk stratification of patients and the predictive value of these methods in context with available pharmacologic agents. Unfortunately, most of the data identifying a particular pharmacologic regimen as beneficial in high-risk patients are retrospectively derived from large trials. Until prospective studies that use markers to guide therapy are available, clinicians should be familiar with the use of these risk markers and their application to the role of a given management strategy, including pharmacologic therapy.

Comparison of continuous vectorcardiography and continuous 12-lead electrocardiography of patients with unstable coronary artery disease: do they identify the same population?

BACKGROUND

Continuous vectorcardiography (cVCG) and continuous 12-lead electrocardiography (c12ECG) are important tools for assessing patients with unstable coronary artery disease.

OBJECTIVE

To compare the incidences of ischemia detected by the two methods, and examine whether the patients identified belonged to the same population, with respect to various clinical variables.

METHODS

Within a randomized prospective trial (FRISC II) including patients with unstable coronary artery disease, ST-segment monitoring was performed either by cVCG or by c12ECG for 24 h after admission for 1016 patients.

RESULTS

cVCG and c12ECG were performed for 730 and 286 patients, respectively. Transient ischemic episodes in 253 (34.7%) patients were detected by cVCG and such episodes were detected in 91 (31.8%) patients by c12EGG. When patients in whom transient ischemic episodes had been detected by cVCG and c12ECG were compared, the groups were similar with respect to baseline characteristics, signs of myocardial damage (67.5 versus 70.5%), occurrence of exercise-induced ischemia (59.0 versus 60.0%), and presence of severe coronary lesions (57.0 versus 51.3%).

CONCLUSIONS

Results of this study suggest that these two methods identify the same high-risk population, and that these patients can be considered one group when results obtained using either system are analyzed in multicenter studies. This also implies that results concerning the occurrence of episodes of resting ischemia obtained using one system may also be applicable for the other.

Early assessment of long-term risk with continuous ST-segment monitoring among patients with unstable coronary syndromes. Results from 1-year follow-up in the TRIM study

A total of 323 patients who took part in the TRIM trial underwent an initial 24 h continuous electrocardiogram ST-segment monitoring. A ST vector magnitude (ST-VM) maximum > or = 144 microV predicted death or myocardial infarction within 1 year with a 78% specificity and a 52% sensitivity, an area under the ST-VM trend curve > or = 162 mu with a 86% specificity and a 42% sensitivity and presence of ST-VM episodes with a 70% specificity and a 68% sensitivity. Patients who had neither ST-VM episodes nor a ST-maximum > or = 144 microV had only a 4.5% incidence of death or myocardial infarction within one year as compared to 18% among those patients who met any of these criteria. ST-segment monitoring with continuous vectorcardiography is feasible for risk stratification at least up to 1 year after an episode of unstable coronary artery disease and several vectorcardiographic parameters may be used.

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 be expected 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.

ST-segment monitoring with continuous 12-lead ECG improves early risk stratification in patients with chest pain and ECG nondiagnostic of acute myocardial infarction

OBJECTIVES

The purpose of this study was to evaluate the prognostic importance of ischemic episodes detected by ST-segment monitoring with continuous 12-lead electrocardiography (ECG) in a nonselected coronary care unit (CCU) population with chest pain and ECG nondiagnostic of acute myocardial infarction (AMI).

BACKGROUND

Patients with chest pain and ECG nondiagnostic of AMI constitute a heterogeneous group concerning both diagnosis and prognosis. Continuous 12-lead ECG is a rather new method not thoroughly studied in this population.

METHODS

The ST-segment monitoring with continuous 12-lead ECG was performed for 12 h in 630 consecutive patients admitted to CCU due to chest pain and a nondiagnostic ECG, i.e., no ST-segment elevations. An ST-episode was defined as a transient ST-segment depression or elevation of at least 0.10 mV. The median follow-up time was six months.

RESULTS

A total of 176 ST-episodes occurred in 100 (15.9%) patients. The median duration and maximal ST-segment deviation in patients with ST-episodes were 80 min and 0.20 mV, respectively. Presence of ST-episodes predicted worse outcome concerning cardiac death and cardiac death or myocardial infarction (MI) (log-rank p < 0.001). At 30 day follow-up procedure, 10% versus 1.5% died from cardiac causes or had an MI in the group with and without ST-episodes, respectively. In a multivariate analysis, only troponin T > or = 0.10 microg/l and the presence of ST-episodes came out as independent predictors of cardiac death or MI.

CONCLUSIONS

Continuous 12-lead ECG monitoring provides prognostic information on-line and considerably improves early risk stratification in patients with ECG nondiagnostic of AMI and symptoms suggestive of acute coronary syndrome.

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

AIMS

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.

METHODS AND RESULTS

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.

CONCLUSION

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.

Admission risk assessment by cardiac troponin T in unstable coronary artery disease: additional prognostic information from continuous ST segment monitoring. TRIM study group. Thrombin Inhibition in Myocardial Ischemia

OBJECTIVES

We investigated whether the addition of 24 h of continuous vectorcardiography ST segment monitoring (cVST) for an early (within 24 h of the latest episode of angina) determination of cardiac troponin T (cTnT) could provide additional prognostic information in patients with unstable coronary artery disease (UCAD), i.e., unstable angina and non-Q wave myocardial infarction.

BACKGROUND

Determination of cTnT at admission and cVST are individually reported to be valuable techniques for the risk assessment of patients with UCAD.

METHODS

Two hundred and thirty-two patients suspected of UCAD were studied. Patients were followed for 30 days, and the occurrence of cardiac death or acute myocardial infarction (AMI) were registered.

RESULTS

One ST segment episode or more (relative risk [RR] 7.43, p = 0.012), a cTnT level > or = 0.20 microg/liter (RR 3.85, p = 0.036) or prestudy medication with calcium antagonists (RR 3.31, p = 0.041) were found to carry independent prognostic information after multivariate analysis of potential risk variables. By combining a cTnT determination and subsequent cVST for 24 h, subgroups of patients at high (25.8%) (n = 31), intermediate (3.1%) (n = 65) and low risk (1.7%) (n = 117) of death or AMI could be identified.

CONCLUSIONS

Twenty-four hours of cVST provides additional prognostic information to that of an early cTnT determination in patients suspected of having UCAD. The combination of biochemical and electrocardiographic methods provides powerful and accurate risk stratification in UCAD.

Temporal and positional variability of the ST segment during continuous vectorcardiography monitoring in healthy subjects

Continuous vectorcardiography ST-segment monitoring (cVST) is a well-established method in the diagnosis and risk evaluation of patients with acute myocardial ischemia. Previous investigations have demonstrated that electrocardiographic ST-segment changes are to be expected, during both repeated measurements and changes in body position. We prospectively analyzed the influence of spontaneous temporal variation (technical and biological noise) and changes in body position on the ST segment (ST-vector magnitude [ST-VM]) during cVST of 21 healthy human subjects. The 95% expectancy range of the spontaneous intraindividual ST-VM variation was found to be +/-8 microV for the error of measurement, and +/-14 and +/-24 microV during 24-hour and day-to-day cVST measurements, respectively. Positional ST-segment changes in the orthogonal leads were frequent, especially in leads X and Z, and in the left lateral position. Positional orthogonal ST-segment changes resulted in significant ST-VM changes in two of seven subjects. It is concluded that the low spontaneous temporal ST-VM variation must be considered as good reproducibility. Moreover, the present findings support currently used ST-VM ischemia criteria. However, the impact of positional changes on ST-VM seems to be of importance (with the possibility of false-positive results) and should be taken into account during cVST.

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 (> or = 50 microV for > or = 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.

Heparin is more effective than inogatran, a low-molecular weight thrombin inhibitor in suppressing ischemia and recurrent angina in unstable coronary disease. Thrombin Inhibition in Myocardial Ischemia (TRIM) Study Group

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.

Key factors in the identification of the high-risk patient with unstable coronary artery disease: clinical findings, resting 12-lead electrocardiogram, and continuous electrocardiographic monitoring

This article reviews a range of methods for identifying high-risk patients with unstable coronary artery disease, including clinical evaluation, the resting 12-lead electrocardiogram, continuous vectorcardiography, and a combined risk evaluation using continuous vectorcardiography and measurement of troponin-T. Clinical evaluation is not very accurate for identifying high-risk patients and modern techniques have not been fully validated in clinical trials. The combination of continuous vectorcardiography and biochemical monitoring is a very powerful method of identifying both very high- and very low-risk patients and may be increasingly used in the future.