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Objective The aim of this study was to determine whether resting ST-T wave abnormalities (ST-Ta) provide incremental prognostic information in patients with no history of coronary artery disease undergoing dobutamine stress echocardiography (DSE). Methods We evaluated 1308 consecutive patients without previous myocardial infarction (MI) or revascularization who underwent DSE. Ischemia was defined as new or worsening wall motion abnormalities. End points during follow-up were all-cause death and cardiac death/nonfatal MI. Results ST-Ta were detected in 162 (12%) patients. The incidence of ischemia was higher in patients with baseline ST-Ta than patients without [74 (46%) vs. 327 (28%), P = 0.00001]. During a follow-up of 4.6 +/- 3 years, cardiac death/nonfatal MI occurred in 42 (26%) patients with resting ST-Ta and in 157 (14%) patients without resting ST-Ta (P < 0.001). Patients with ST-Ta had a higher annual cardiac death/nonfatal MI rate compared with patients without, both in the presence of normal DSE (3.2 vs. 1.4%, P = 0.01) as well as abnormal DSE (5.3 vs. 3%, P < 0.001). In a Cox proportional modeling, resting ST-Ta added incremental value over clinical and stress echocardiographic data for the prediction of death (global chi(2) 125, 140, 150, respectively; P < 0.05) and cardiac death/nonfatal MI (global chi(2) 79, 100, 111, respectively; P < 0.05). Conclusion Baseline ST-Ta are associated with an increased risk of cardiac death/nonfatal MI and all-cause mortality, incremental to clinical data and DSE results. The associated risk is persistent among patients with normal DSE. Coron Artery Dis 22:559-564 (C) 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins.

Objective To investigate the association between (cardiac) mortality and spatial QRS-T angle in patients undergoing dobutamine - atropine stress echocardiography (DSE) for evaluation of known or suspected coronary disease. Methods Between 1990 and 2003, 2347 patients underwent DSE for evaluation of coronary disease at the Erasmus Medical Center. Echocardiographic images were analyzed offline using a 16-segment, 5-point scoring model for regional function. Twelve-lead resting ECGs were analyzed and patients were grouped in three categories according to their spatial QRS-T angle: normal (0-105 degrees), borderline (105-135 degrees), and abnormal (135-180 degrees). Results Mean age was 61 +/- 13 years, 66% were male, 32% had hypertension, 26% had hypercholesterolemia, 28% were smokers, and 12% were diabetic. During a mean follow-up of 7 +/- 3.4 years, 26.5% (623) of the patients died; 15.3% (359) died due to a cardiac cause. Abnormal QRS-T angle (135-180 degrees) was present in 21% of the patients. Abnormal QRS-T angle was a predictor of cardiac death [ hazard ratio: 3.2 (2.6-4.1)] and all-cause mortality [hazard ratio: 2.2 (1.8-2.6)]. After multivariate analysis abnormal and borderline QRS-T angle, peak wall motion score, age, male sex, history of diabetes, history of heart failure, smoking, and hypertension were independent predictors of (cardiac) death. Conclusion Abnormal QRS-T angle is an independent predictor of (cardiac) death in patients undergoing DSE. Abnormal QRS-T angle should be considered as a risk factor in stable patients evaluated for coronary disease. Coron Artery Dis 21:26-32 (C) 2010 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT center dot A large number of drugs can prolong the QTc interval on the electrocardiogram (ECG). center dot Clinical decision support systems may generate drug safety alerts on QTc prolongation. center dot Drug safety alerts are frequently overridden. WHAT THIS STUDY ADDS center dot QTc alert overriding does rarely result in ECG recordings. center dot ECGs before and after QTc overrides reveal clinically relevant QTc prolongation. To investigate whether, in patients in whom drug-drug interaction (DDI) alerts on QTc prolongation were overridden, the physician had requested an electrocardiogram (ECG), and if these ECGs showed clinically relevant QTc prolongation. For all patients with overridden DDI alerts on QTc prolongation during 6 months, data on risk factors for QT prolongation, drug class and ECGs were collected from the medical record. Patients with ventricular pacemakers, patients treated on an outpatient basis, and patients using the low-risk combination of cotrimoxazole and tacrolimus were excluded. The magnitude of the effect on the QTc interval was calculated if ECGs before and after overriding were available. Changes of the QTc interval in these cases were compared with those of a control group using one QTc-prolonging drug. In 33% of all patients with overridden QTc alerts an ECG was recorded within 1 month. ECGs were more often recorded in patients with more risk factors for QTc prolongation and with more QTc overrides. ECGs before and after the QTc override were available in 29% of patients. Thirty-one percent of patients in this group showed clinically relevant QTc prolongation with increased risk of torsades de pointes or ventricular arrhythmias. The average change in QTc interval was +31 ms for cases and -4 ms for controls. Overriding the high-level DDI alerts on QTc prolongation rarely resulted in the preferred approach to subsequently record an ECG. If ECGs were recorded before and after QTc overrides, clinically relevant QTc prolongation was found in one-third of cases. ECG recording after overriding QTc alerts should be encouraged to prevent adverse events.

Aim: The aim of the study was to simultaneously test the EASI lead system and two other derived ECG methods against the standard 12-lead ECG during percutaneous coronary intervention (PCI). Methods: During 44 percutaneous coronary interventions, a simultaneously recorded 12-lead and EASI ECG were marked at the start of the PCI (baseline) and at known ischemia caused by balloon inflation (peak). ST deviations were measured 60 ms after the J point at baseline and peak in all leads and were summated (SUMST) to assess overall changes. For regional changes, the lead with the highest ST deviation (PEAKST) was marked. For each patient, derived 12-lead ECGs were computed from the EASI leads and a lead subset using patient-specific coefficients (PS) and coefficients based on a patient population (GEN). Absolute differences were computed between each derived and routine ECG for SUMST and PEAKST. Results: SUMST was at baseline 567 mu V (range: 150-1707) and increased at peak to 871 mu V (range: 350-2101). SUMST difference at peak was for EASI: 163 mu V (CI: 90-236, P

In clinical practice, continuous recording of all leads of the 12-lead electrocardiogram (ECG) is often not possible. We wanted to assess how well absent, noisy, or defective leads can be reconstructed from different lead subsets and how well lead reconstruction performs over time. A data set of 234 24-hour ECG recordings was divided into an equally sized training and test set. Precordial leads were systematically removed, and for all lead subsets including both limb leads and at least one precordial lead, the absent leads were reconstructed using general and patient-specific reconstruction templates. Reconstruction performance was measured by correlation between the original and reconstructed leads over the QRS and T waves, by average and maximum absolute ST differences, and by agreement when a clinical decision rule was applied. Reconstruction performance over time was evaluated at baseline, at 20 minutes, and 1, 6, 12 and 24 hours after the start of each recording. Reconstruction accuracy was high (correlationor =0.932, average ST differenceor =30 microV, agreementor =94.9%) with general reconstruction for lead sets with 1 or 2 precordial leads removed but was less satisfactory when more leads were missing. Patient-specific reconstruction performed well when up to 4 precordial leads were removed (correlationor =0.967, average ST differenceor =26 microV, agreementor =95.7%). Patient-specific reconstruction performance initially slightly decreased and then stabilized over time but remained much better than general reconstruction after 24 hours. Accurate reconstruction of the 12-lead ECG from lead subsets is possible over time. General reconstruction allows reconstruction of 1 or 2 precordial leads, whereas up to 4 leads can be reconstructed well using patient-specific reconstruction.

Twelve-lead ST-segment monitoring is a widely used tool for capturing focal ischemia and transient intermittent episodes. However, continuous registration of all 10 electrodes is impractical in clinical settings. This study investigated the accuracy of 2 derived 12-lead strategies that required 6 electrodes, including all limb leads, and 2 precordial leads by using population-based (generalized) and individualized (patient-specific) reconstruction coefficients to derive the additional 4 chest leads. A total of 26,880 simultaneous digital conventional 12-lead generalized and patient-specific electrocardiograms were monitored over 112 hours in 39 patients during percutaneous coronary intervention, including 159 balloon occlusions in 63 arteries, to test accuracy at rest and during ischemia. Occlusion duration was 78 seconds (range 42 to 96) in the left main coronary in 2 patients, the left anterior descending artery in 15, the right coronary artery in 10, the circumflex artery in 2, and graft segments in 5 patients. Average summated 12-lead ST deviation over the study population at baseline was 377 microV (range 104 to 1,718), which increased at peak ischemia to an average of 1,086 microV (range 282 to 4,099). Median absolute differences at peak ischemic ST deviation were 25 microV in lead V(1), 0 microV in lead V(2), 35 microV in lead V(3), 34 microV in lead V(4), 0 microV in lead V(5), 11 microV in lead V(6), and 114 microV for summated 12-lead ST deviation with the generalized method and 7 microV in lead V(1), 4 microV in lead V(2), 1 muV in lead V(3), 5 microV in lead V(4), 4 microV in lead V(5), 9 microV in lead V(6), and 83 microV for the summated 12-lead ST deviation with the patient-specific method. Limb leads (I, II, III, aVR, aVL, and aVF) were identical in all patients. Thus, generalized and patient-specific methods derived from 12-lead electrocardiography using actual limb and 2 precordial electrodes accurately derived the additional chest leads at rest and during ischemia. These approaches appear to be more practical than conventional 10-electrode monitoring but preserve high accuracy.

It may not always be possible to record all precordial leads of the standard 12-lead electrocardiogram (ECG). Especially in monitoring situations, a minimal lead set from which the 12-lead ECG can be reconstructed, would be valuable. This article assesses how well missing precordial leads could be synthesized from the remaining leads of the 12-lead ECG. A total of 2,372 diagnostic 12-lead ECG recordings were obtained from subjects with chest pain suggestive for acute myocardial infarction. Representative average beats were computed from the digital 12-lead ECG recordings with our Modular ECG Analysis System. The recordings were divided into a learning set and a test set. We considered all lead sets with one or more precordial leads removed, but always including limb leads I and II. By using the learning set, general reconstruction coefficients were computed to synthesize the missing precordial leads to each lead set. Performance of the synthesis was assessed by cross correlation between the original and the reconstructed leads. Also, patient-specific reconstruction coefficients were derived for each ECG in the test set and correlations were determined. High correlation coefficients were found with both reconstruction techniques. For different sizes of lead sets, the best patient-specific reconstructions had higher correlation values than the general reconstructions. For example, when 2 precordial leads were excluded, the best patient-specific median correlation was 0.994 compared to 0.963 for the best general reconstruction correlation. General reconstruction allows synthesis of 2 or 3 excluded precordial leads in good approximation. When patient-specific reconstruction can be applied, a minimal lead set including the limb leads and only 2 precordial leads suffices.

Reduced lead systems utilizing patient-specific transformation weights have been reported to achieve superior estimates than those utilizing population-based transformation weights. We report upon the effects of ischemic-type electrocardiographic changes on the estimation performance of a reduced lead system when utilizing patient-specific transformation weights and population-based transformation weights.A reduced lead system that used leads I, II, V2 and V5 to estimate leads V1, V3, V4, and V6 was investigated. Patient-specific transformation weights were developed on electrocardiograms containing no ischemic-type changes. Patient-specific and population-based transformations weights were assessed on 45 electrocardiograms with ischemic-type changes and 59 electrocardiograms without ischemic-type changes.For patient-specific transformation weights the estimation performance measured as median root mean squared error values (no ischemic-type changes vs. ischemic-type changes) was found to be (V1, 27.5 μV vs. 95.8 μV, P.001; V3, 33.9 µV vs. 65.2 µV, P.001; V4, 24.8 μV vs. 62.0 μV, P.001; V6, 11.7 μV vs. 51.5 μV, P.001). The median magnitude of ST-amplitude difference 60 ms after the J-point between patient-specific estimated leads and actual recorded leads (no ischemic-type changes vs. ischemic-type changes) was found to be (V1, 18.9 μV vs. 61.4 μV, P.001; V3, 14.3 μV vs. 61.1 μV, P.001; V4, 9.7 μV vs. 61.3 μV, P.001; V6, 5.9 μV vs. 46.0 μV, P.001).The estimation performance of patient-specific transformations weights can deteriorate when ischemic-type changes develop. Performance assessment of patient-specific transformation weights should be performed using electrocardiographic data that represent the monitoring situation for which the reduced lead system is targeted.

In this study, we assess the effects of electrode placement error on the EASI-derived 12-lead electrocardiogram (ECG). The study data set consisted of 744 body surface potential map (BSPM) recordings. The BSPMs, each of which was made up of 117 leads, were recorded from a mixture of healthy, myocardial infarction, and left ventricular hypertrophy subjects. The BSPMs were interpolated to increase the number of data points in the region of the EASI recording electrodes I, E, and A and the precordial leads. This facilitated 3 experiments. Firstly, recording sites I, E, and A were simultaneously moved +/- 5 cm vertically, in 0.5 cm increments, from their correct locations. Secondly, recording sites 1 and A were moved horizontally, again up to +/- 5 cm, in 0.5 cm increments. Finally, all 6 precordial leads were moved vertically in 0.5 cm increments up to +/- 5 cm. At each movement step, the resulting 12-lead ECG was compared with the original 12-lead ECG. Root mean square error was determined along with the absolute difference in J-point amplitude. Although the EASI leads were found to be less sensitive to electrode misplacement than the standard precordial leads, it was found that when precordial leads were moved up to +/- 3 cm vertically, the resulting 12-lead ECG more accurately resembled the original 12-lead ECG than a 12-lead ECG reconstructed from accurately positioned EASI leads. Further work is required to establish the effects of electrode misplacement beyond the +/- 5 cm limits assessed in this study. (C) 2010 Elsevier Inc. All rights reserved.

Patient monitoring with 12-lead ECG subsets typically uses the independent frontal leads I and II and any number of the six precordial leads to reconstruct the unrecorded ECG leads. However, variations of QRS amplitudes in leads I or II may have an effect on the signal to noise ratio of the reconstructed leads. The aim of this study was to develop and evaluate a dynamic frontal lead selection method (DFLS) to improve ECG reconstruction. We compared the DFLS method for general (GEN) and patient-specific (PS) reconstruction with a lead subset I, II, V2, and V5. For GEN reconstruction, a data set of 2372 diagnostic 12-lead ECGs obtained from subjects with chest pain suggestive of acute myocardial infarction was used. For PS, a data set of 71 continuous 12-lead PCI recordings was used. Reconstruction accuracy was assessed with correlation coefficients and root mean square errors. This study showed that the DFLS method increases GEN reconstruction performance in a subgroup with low QRS voltages. PS reconstruction shows a moderate overall performance increase.

In this study we evaluate limited lead sets for the reconstruction of 12-lead ECGs and body surface potential maps (BSPMs). For 12-lead ECG reconstruction, we focused on four available limited lead systems (V2, V1V5, V1V6, V2V5) to derive the standard 12-lead ECG and the EASI lead system as an alternative to the existing 12-lead ECG. We used a data set of 44 continuous 16-lead balloon inflation ECG registrations during percutaneous coronary interventions. For reconstruction of BSPMs an optimal lead selection algorithm was applied to a set of 744 BSPMs, consisting of recordings from subjects with myocardial infarction, left ventricular hypertrophy, and no apparent disease.Median root mean square (RMS) error for 12-lead ECG reconstruction were in decreasing order: V1V6: 165 muV, V2 131 muV, V1V5: 124 muV, EASI: 96 muV, and V2V5: 87 muV. In the BSPM reconstruction experiments, it was shown that by repositioning the six precordial leads the RMS error decreased from 35.4 muV to 26.7 muV. In summary, the results from this study have indicated that limited lead systems offer potential in all forms of cardiac monitoring and assessment, but certain lead sets show higher reconstruction errors.

In emergency care situations, recording all leads of the 12-lead ECG is often not possible due io technical and organizational restrictions. The recording of a subset of leads and subsequent synthesis of rhe absent leads might be a solution to these problems. The goal of this study was to evaluate the efficacy of a reduced lead set, consisting of leads I, 11, V2, and V5. The lead subset was derived from a data set of 12-lead ECGs recorded from parients with a suspected acute myocardial infarction prior to hospitalization. Performance was evaluated by comparing the originally recorded leads and reconstructed leads using correlation coeflcients and STdigerences. Several clinically important decision rules for detection and pre-hospital treatment were evaluated on the original and reconstructed 12-lead ECGs and accuracy was determined. This study shows that high agreement, correlation coeflcients and small STdifferences can be obtained between the original and reconstructed leads.

Objective: To investigate whether the orientation of the electrical T-axis and the spatial QRS-T angle provide independent diagnostic and prognostic information in patients presenting with acute chest pain. Methods: Patients with symptoms suggestive of acute cardiac pathology, who were seen by a general practitioner and for whom a prehospital electrocardiogram (ECG) was recorded by the ambulance service between 1992 and 1994 were investigated. The ECGs (n = 2,261) for our study population were stored for off-line analysis by the Modular ECG Analysis System. QRS- and T-axes were computed from the reconstructed vectorcardiographic X, Y and Z leads. During the year 2000, a follow-up of the entire cohort was performed, and the vital status of the patients was determined via the civil registrar’s office. Cox multivariable regression analyses were performed to evaluate the relation between the orientation of the T-axis, the spatial QRS-T angle and long-term mortality. Results: An abnormal orientation of the T-axis and the spatial QRS-T angle were associated with an increased likelihood of cardiac diseases and an increased risk of all-cause mortality during short- and long-term follow-up. Conclusions: We conclude that the frontal T-axis and the spatial QRS-T angle are important determinants of diagnosis and prognosis in patients presenting with acute chest pain. The reintroduction of vectorcardiography in routine clinical practice might therefore be reconsidered.

Electrode positions for continuous monitoring of 12-lead ECG are different from those for recording a standard 12-lead ECG. To reduce noise and to minimize false alarms, proximal placement of the limb leads is preferred over the standard location at the wrists and ankles. These differences are often associated with apparent frontal QRS-axis shifts, disappearing Q-waves in the inferior leads and marked changes of R-amplitudes in leads I and II. These changes make it difficult to compare ECGs. This study presents a general and patient-specific method to correct for these changes.

It is well known that changes in the body position (BPC) can have marked changes on the electrical axis of the heart. This may cause ST-segment shifts and/or T-wave inversions, triggering false alarms during continuous ECG monitoring. To investigate the effects in the CCU setting, a body position test (BPT) has been set up to measure the effect during controlled BPC. The ECG obtained in the supine position was used as reference. A scalar and spatial approaches were used. The scalar approach uses linear regression analysis, the supine position being the reference mapping all measurements to the supine position. The spatial approach uses the derived VCG by applying the inverse Dower transformation. This paper describes the results of the first 54 patients done so far. Marked ST-changes (>100 /spl mu/V) were observed in 11 patients out of the 54 when turning to their left side. Other positions appear to have much less effect. A concomitant axis shift in the frontal plane of more than 15 degrees was present in 5 of these 11 patients with ST-changes. Two patients showed T-wave inversion when turning from supine to the left side.