Dynamic on-line vectorcardiography improves and simplifies in-hospital ischemia monitoring of patients with unstable angina

The protective effects of uric acid against myocardial ischemia via the Nrf2 pathway

Uric acid (UA) possesses both pro- and anti-oxidative properties in ischemic heart disease, but the underlying mechanism remains unclear. We aimed to investigate UA's protective effect on myocardial ischemia by examining its effects on ECG Ischemic Alterations (EIA) and H2O2-induced oxidative stress in H9C2 myocardial cells. The incidence of EIA decreased over time and was more prevalent among women than men. A U-shaped relationship was observed between UA levels and EIA incidence, with the third quartile exhibiting a protective association. Addition of 237.9 μmol/L UA improved cellular damage and oxidative stress in H2O2-treated H9C2 cells, as determined by cell viability, LDH release, ROS levels, and total antioxidant capacity assays. UA activated the Nrf2 pathway, evidenced by increased expression of Nrf2, GCLC, and HO-1 proteins. By reversing cell cycle blockage, promoting wound healing ability, improving colony-forming capacity, and increasing angiogenesis in H2O2-treated cells, UA exhibited positive effects on cardiomyocyte growth characteristics. Additionally, use of Nrf2 inhibitor ML385 confirmed the involvement of the Nrf2 pathway by negating UA's effects on oxidatively damaged cardiomyocytes. Our findings suggest that UA induces downstream antioxidant factors to ameliorate oxidative stress by activating the Nrf2 pathway, which could be one of the targets responsible for UA's beneficial effects in myocardial ischemia.

Review of Processing Pathological Vectorcardiographic Records for the Detection of Heart Disease

Vectorcardiography (VCG) is another useful method that provides us with useful spatial information about the electrical activity of the heart. The use of vectorcardiography in clinical practice is not common nowadays, mainly due to the well-established 12-lead ECG system. However, VCG leads can be derived from standard 12-lead ECG systems using mathematical transformations. These derived or directly measured VCG records have proven to be a useful tool for diagnosing various heart diseases such as myocardial infarction, ventricular hypertrophy, myocardial scars, long QT syndrome, etc., where standard ECG does not achieve reliable accuracy within automated detection. With the development of computer technology in recent years, vectorcardiography is beginning to come to the forefront again. In this review we highlight the analysis of VCG records within the extraction of functional parameters for the detection of heart disease. We focus on methods of processing VCG functionalities and their use in given pathologies. Improving or combining current or developing new advanced signal processing methods can contribute to better and earlier detection of heart disease. We also focus on the most commonly used methods to derive a VCG from 12-lead ECG.

Identification of Patients with Myocardial Infarction. Vectorcardiographic and Electrocardiographic Analysis

BACKGROUND

The largest morbidity and mortality group worldwide continues to be that suffering Myocardial Infarction (MI). The use of vectorcardiography (VCG) and electrocardiography (ECG) has improved the diagnosis and characterization of this cardiac condition.

OBJECTIVES

Herein, we applied a novel ECG-VCG combination technique to identifying 95 patients with MI and to differentiating them from 52 healthy reference subjects. Subsequently, and with a similar method, the location of the infarcted area permitted patient classification.

METHODS

We analyzed five depolarization and four repolarization indexes, say: a) volume; b) planar area; c) QRS loop perimeter; d) QRS vector difference; e - g) Area under the QRS complex, ST segment and T-wave in the (X, Y, Z) leads; h) ST-T Vector Magnitude Difference; i) T-wave Vector Magnitude Difference; and j) the spatial angle between the QRS complex and the T-wave. For classification, patients were divided into two groups according to the infarcted area, that is, anterior or inferior sectors (MI-ant and MI-inf, respectively).

RESULTS

Our results indicate that several ECG and VCG parameters show significant differences (p-value<0.05) between Healthy and MI subjects, and between MI-ant and MI-inf. Moreover, combining five parameters, it was possible to classify the MI and healthy subjects with a sensitivity = 95.8%, a specificity = 94.2%, and an accuracy = 95.2%, after applying a linear discriminant classifier method. Similarly, combining eight indexes, we could separate out the MI patients in MI-ant vs MI-inf with a sensitivity = 89.8%, 84.8%, respectively, and an accuracy = 89.8%.

CONCLUSIONS

The new multivariable MI patient identification and localization technique, based on ECG and VCG combination indexes, offered excellent performance to differentiating populations with MI from healthy subjects. Furthermore, this technique might be applicable to estimating the infarcted area localization. In addition, the proposed method would be an alternative diagnostic technique in the emergency room.

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

BACKGROUND

This work evaluates the vectorcardiographic dynamic changes in ischemic patients before and during Percutaneous Transluminal Coronary Angioplasty (PTCA).

METHODS

Four 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 (QRS(mVM)), planar area (QRS(PA)), maximum distance between centroid and loop (QRS(mDCL)) and perimeter (QRS(P)).The conventional ST-change vector magnitude (STC(VM)), QRS-vector difference (QRS(VD)) and spatial ventricular gradient (SVG) were also calculated.

RESULTS

Statistical 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 STC(VM), QRS(VD) and SVG indexes, are used in the classification. Sensitivity and Specificity, in turn, reached rather high values, 95.4% and 95.2%, respectively.

CONCLUSIONS

These new vectorcardiographic set of complementary QRS-loop parameters, when combined with the classics STC(VM), QRS(VD) and SVG indexes, increase sensitivity and specificity for acute ischemia monitoring.

High prevalence of gastroesophageal reflux in patients with clinical unstable angina and known coronary artery disease

OBJECTIVES

Esophageal disease may mimic acute anginal pain. However, the prevalence of gastroesophageal reflux in the acute setting of patients with clinically unstable angina (UA) pectoris is not known. The aim of this study was to determine the co-existence of coronary artery disease (CAD) and gastroesophageal reflux in UA, and to study the feasibility of esophageal investigation in the chest pain unit.

DESIGN

22 patients with clinical UA and confirmed CAD were monitored by continuous vector cardiography and pH-measurement during 24 h of observation. Symptoms of chest pain and episodes of ischemia and reflux were recorded.

RESULTS

11 patients (50%) showed abnormal gastroesophageal reflux and another three (14%) had an increased number of reflux episodes. pH-measurements and esophageal manometry were well tolerated. Few chest pain episodes were recorded during the study period, and no association between chest pain, reflux, and ischemia could be shown.

CONCLUSION

Esophageal reflux is common in patients with UA and established CAD. As reflux-related chest pain may imitate angina pectoris, it is clinically important that gastroesophageal examination in patients with UA seems to be feasible and well tolerated in the 'acute setting'.

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.

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.

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.

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.

Vectorcardiographic changes as predictors of cardiac complications during major vascular surgery

OBJECTIVE

To elucidate the relation of changes in computerized vectorcardiographic trend parameters indicating perioperative myocardial ischemia with perioperative cardiac complications.

DESIGN

Prospective clinical study.

SETTING

A single university hospital.

PARTICIPANTS

Thirty-eight patients undergoing elective abdominal aortic surgery.

INTERVENTIONS

Computerized vectorcardiography recorded during surgery and for 48 hours postoperatively.

MEASUREMENTS AND MAIN RESULTS

Vectorcardiographic spatial alterations in the QRS complex (QRS-VD) and absolute (ST-VM) and spatial (STC-VM) ST-segment changes, previously used indicators of myocardial ischemia, were analyzed and related to the cardiac events detected clinically. In five patients with clearly ischemic (cardiac death, myocardial infarction, recurrent ischemia) and eight patients with possibly ischemic (congestive heart failure, arrhythmia) perioperative cardiac events, ST-VM and STC-VM were significantly increased intraoperatively. Postoperatively, these differences remained, but QRS-VD were also significantly increased. Intraoperative and postoperative changes indicating ischemia were strongly related (r = 0.83). The signs of ischemia were most pronounced during the postoperative 12 to 36 hours. The presence of 60 minutes of signs of ischemia during 2 hours revealed high sensitivity (85%), specificity (80%), and positive (69%) and negative (91%) predictive values for subsequent cardiac events. Traditional vector loop analysis showed signs of non-Q-wave infarctions in six patients, whereas only three of these were detected using standard clinical methods.

CONCLUSIONS

Vectorcardiographic signs of myocardial ischemia were significantly increased intraoperatively, but most pronounced postoperatively in the patients subsequently suffering cardiac events. The changes could be related to the individual cardiac morbidity with acceptable precision. Thus, continuous vectorcardiographic monitoring may be beneficial for patients at risk of developing perioperative ischemia.