Continuous 12-lead ST-segment Monitoring Research Articles

Updated Practice Standards for ECG Monitoring: Impact at the Bedside

Any trigger for notifying the health care provider depends on the patient, as well as the expectations for a given setting. Patients vary in their responses to arrhythmias. A consistent message is that any hemodynamically unstable patient should have continuous electrocardiographic (ECG) monitoring. Each unit should consider having preset default heart rate parameters to guide provider notification. These decisions are based on discussion with all stakeholders, including providers and nurses.Consider why your patient may have an elevated cardiac troponin level and no chest pain. Does the patient have neuropathy and, therefore, may not sense angina? Is the patient unable to communicate because of impaired mental status, a language barrier, intubation, or sedation? If the answer to any of these questions is yes, your patient may benefit from continuous ST-segment monitoring. The current highest recommendation for continuous ST-segment monitoring is a IIa (ie, it is reasonable to perform the procedure, but more evidence is needed) in selected patients in a nursing unit with technology for continuous 12-lead ST-segment monitoring and related education and protocols that facilitate reduction of false and nonactionable alarm signals.Because the QT interval can often be measured successfully in all leads, prioritize monitoring the ST segment in the lead with known ST-segment depression or elevation. For example, if the patient had ST-segment changes in a particular lead during a myocardial infarction or balloon inflation during percutaneous coronary intervention, choose that lead; if the patient returns after a successful revascularization, select the lead in which the patient had previously demonstrated ST changes. If the patient is having wide QRS tachycardia, monitor lead V1 to distinguish ventricular tachycardia from supraventricular tachycardia with aberrancy.Dispelling this belief requires a change in unit culture. This change includes considering other types of monitoring such as continuous pulse oximetry instead of ECG monitoring using telemetry. Also consider changing the name of a unit from telemetry unit to progressive care unit or step-down unit. Patients may not need telemetry monitoring on these units, but still need qualified nurses who can provide care for complex airway issues and vascular procedures.

Estimation performance of a reduced lead system during continuous 12-lead ECG ST-segment monitoring

BackgroundReduced 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. MethodA 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. ResultsFor 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). ConclusionThe 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.

Cardiovascular Effects of Cocaine

The use of cocaine has evolved from chewing the leaves of the Erythroxylon coca bush thousands of years ago, to purification of cocaine hydrochloride over 100 years ago and its use in tonics and elixirs (at one time in popular cola drinks), to insufflating and injecting the fine, white, water-soluble, powder form, to a smokable freebase form called “crack,” which became popular in the 1980s.1 In 2007, 2.1 million Americans had recent cocaine use; 1.6 million met criteria for cocaine dependence or abuse.1 Cocaine accounted for 31% of all visits to the emergency department related to drug misuse or abuse.1 From 1971 to 1987, the incidence of deaths caused by cocaine overdose increased 20-fold in Dade County, Florida.2 In a consecutive series of 233 emergency visits by cocaine-using patients, 56% presented with cardiovascular complaints, including 40% with chest pain.3 A minority of these patients have acute myocardial infarction (MI) (≈6%),4,–,7 and overall mortality is low (<1%).3,–,5,8,–,10 However, cocaine is associated with a number of cardiovascular diseases, including MI, heart failure, cardiomyopathies, arrhythmias, aortic dissection, and endocarditis. Identifying patients with acute disease is challenging. This review describes the relationship between cocaine and various cardiovascular diseases, as well as appropriate diagnostic evaluation and therapies. ### Molecular Cocaine stimulates the sympathetic nervous system by inhibiting catecholamine reuptake at sympathetic nerve terminals,11,12 stimulating central sympathetic outflow,11 and increasing the sensitivity of adrenergic nerve endings to norepinephrine (Figure 1).12 Cocaine also acts like a class I antiarrhythmic agent (local anesthetic) by blocking sodium and potassium channels, which depresses cardiovascular parameters.13 Of these 2 primary, opposing actions, enhanced sympathetic activity predominates at low cocaine doses, whereas the local anesthetic actions …

Utilization of ST-Segment Deviation Sum and Change Score to Identify High Risk Emergency Department Chest Pain Patient with Acute Coronary Syndromes

Background: No information is currently available regarding optimal cutoff values of the ST-segment deviation sum (STDsum) score for predicting acute myocardial infarction (AMI) and ST-segment deviation change (STDchange) score for predicting adverse outcome (AO) in emergency department (ED) chest pain patients undergoing continuous 12-lead ST-segment monitoring.

Combining baseline clinical descriptors and real-time response to therapy: the incremental prognostic value of continuous ST-segment monitoring in acute myocardial infarction

Background Clinical descriptors and ST-segment recovery variables hold prognostic information for clinical outcome after thrombolysis for acute myocardial infarction (MI). We sought to define the incremental prognostic value of continuous 12-lead ST-segment monitoring variables to clinical risk descriptors identified by the Global Utilization of Streptokinase and TPA (alteplase) for Occluded Coronary Arteries (GUSTO-I) trial 30-day mortality analysis. Methods Of 1,777 patients enrolled in continuous ST-segment substudies from the Thrombolysis and Angioplasty in Myocardial Infarction (TAMI-9), GUSTO-I, Duke University Clinical Cardiology Study (DUCCS-II), Integrilin to manage Platelet Aggregation to Combat Thrombus in Acute Myocardial Infarction (IMPACT-AMI), Promotion of Reperfusion by Inhibition of Thrombin During Myocardial Infarction Evolution (PRIME), and Platelet Aggregation Receptor Antagonist Dose Investigation and Reperfusion Gain in Myocardial Infarction (PARADIGM) trials, 825 patients qualified for assessment of time to recovery. ST recovery variables analyzed were time to stable ST-recovery and late ST elevation. Patients who were at low clinical risk (n = 261) had no high-risk descriptors, and patients at high clinical risk (n = 564) had at least 1 of these high-risk descriptors: age ≥70 years, systolic blood pressure ≤110 mm Hg, heart rate ≥90 beats/min, anterior MI, or previous MI. High (n = 90), moderate (n = 318), and low (n =417) ST-risk groups were defined by the presence of both slow ST recovery and late ST elevation, one or the other, or neither, respectively. End points analyzed were inhospital death and combined death, reinfarction, or congestive heart failure. Results There was a trend toward increased mortality rate in the high-clinical/high-ST-risk group. For the composite end point, ST subgrouping resulted in significant event stratification in both patients at low and high clinical risk. In multivariable analysis, age and heart rate were independent predictors of both mortality and the composite end point. Late ST elevation added incremental prognostic information. Conclusion Age, heart rate, and late ST elevation are powerful, independent predictors of adverse clinical outcome. Continuous monitoring allows noninvasive assessment of the response to therapy. Consequently, this technique will enhance the potential to risk-stratify individual patients in a real-time setting.

Early Definition of Treatment Outcomes After Reperfusion Therapy for Myocardial Infarction

Aims. Early definition of treatment outcomes, including coronary patency and infarct size, after reperfusion therapy for myocardial infarction (MI) is desirable to identify patients requiring further intervention. Methods and Results. Patients receiving reperfusion therapy for a first MI had continuous 12-lead ST segment monitoring to document reperfusion and ischaemia time. Infarct size was measured by 12-lead QRS score and radionuclide scintigraphy ( 201 Tl single-photon emission computed tomography, SPECT) at 1 week, and left ventricular function by echocardiography at 1 week and 1 month. Resolution of ST elevation accurately detected TIMI 2 or 3 reperfusion (predictive accuracy 93%) in 55 patients undergoing immediate angioplasty, but ST recovery was delayed (17±14 min) after angiographic reperfusion. A multivariate model, including risk region and ischaemia time, accurately predicted MI size ( R 2=0.80, P<0.00001) in these patients. The same model, prospectively applied on Day 1 to 154 patients receiving thrombolytic therapy, accurately predicted MI size, measured by QRS score ( R 2=0.88, P<0.0000001) and 201 Tl SPECT ( R 2=0.75, P<0.000001) at 1 week for individual patients. Regional myocardial wall motion at 1 month was directly correlated with MI size predicted by the model on Day 1 ( r=0.73, P<0.0001). Conclusions. Use of ST segment monitoring during reperfusion therapy facilitates early prediction of treatment outcomes, including coronary reperfusion, infarct size and ventricular function.

Improved speed and stability of st-segment recovery with reduced-dose tenecteplase and eptifibatide compared with full-dose tenecteplase for acute st-segment elevation myocardial infarction

ObjectivesThis sub-study of the Integrilin and Tenecteplase in Acute Myocardial Infarction (INTEGRITI) trial evaluated of the impact of combination reperfusion therapy with reduced-dose tenecteplase plus eptifibatide on continuous ST-segment recovery and angiographic results. BackgroundCombination therapy with reduced-dose fibrinolytics and glycoprotein IIb/IIIa inhibitors for ST-segment elevation myocardial infarction improves biomarkers of reperfusion success but has not reduced mortality when compared with full-dose fibrinolytics. MethodsWe evaluated 140 patients enrolled in the INTEGRITI trial with 24-h continuous 12-lead ST-segment monitoring and angiography at 60 min. The dose-combination regimen of 50% of standard-dose tenecteplase (0.27 μg/kg) plus high-dose eptifibatide (2 boluses of 180 μg/kg separated by 10 min, 2.0 μg/kg/min infusion) was compared with full-dose tenecteplase (0.53 μg/kg). ResultsThe dose-confirmation regimen of reduced-dose tenecteplase plus high-dose eptifibatide was associated with a faster median time to stable ST-segment recovery (55 vs. 98 min, p = 0.06), improved stable ST-segment recovery by 2 h (89.6% vs. 67.7%, p = 0.02), and less recurrent ischemia (34.0% vs. 57.1%, p = 0.05) when compared with full-dose tenecteplase. Continuously updated ST-segment recovery analyses demonstrated a modest trend toward greater ST-segment recovery at 30 min (57.7% vs. 40.6%, p = 0.13) and 60 min (82.7% vs. 65.6%, p = 0.08) with this regimen. These findings correlated with improved angiographic results at 60 min. ConclusionsCombination therapy with reduced-dose tenecteplase and eptifibatide leads to faster, more stable ST-segment recovery and improved angiographic flow patterns, compared with full-dose tenecteplase. These findings question the relationship between biomarkers of reperfusion success and clinical outcomes.

2-D echocardiography prediction of adverse events in ED patients with chest pain

The objective of this study was to establish the efficacy of two-dimensional (2-D) echocardiography (echo) in predicting adverse cardiac events in patients presenting to the ED with possible acute coronary syndrome (ACS). Patients 25 years of age or older having symptoms consistent with ACS and a non-diagnostic electrocardiogram (ECG) were evaluated with 0-, 3-, 6-, and 9-hour creatine kinase -MB (CK-MB) assays and continuous 12-lead ECG ST-segment monitoring. Patients with normal serial CK-MB assays and no ECG changes after 9 hours had a resting 2-D transthoracic echo performed. A positive 2-D echo was defined as segmental or global wall motion abnormalities. Patients were followed up after 6 months to identify adverse events resulting from ACS. Of the 1112 patients receiving an echo, 18 had positive studies. None had adverse events on follow-up. Of the 1094 patients with a negative 2-D echo, 15 had adverse events (2 acute myocardial infarctions, 2 coronary artery bypass graftings, and 11 percutaneous transluminal coronary angioplasties). Resting 2-D echo did not predict cardiac adverse events in patients with possible ACS and non-diagnostic serial 12-lead ECG and normal serial CK-MB at the end of a 9-hour evaluation. (Am J Emerg Med 2003;21:106-110. Copyright 2003, Elsevier Science (USA). All rights reserved.)

Transient myocardial ischemia is an independent predictor of adverse in-hospital outcomes in patients with acute coronary syndromes treated in the telemetry unit

Objective: The purpose of this study was to determine whether transient myocardial ischemia (TMI) is predictive of adverse in-hospital outcomes among patients admitted to a telemetry unit with acute coronary syndrome (ACS). Design and Setting: The study was designed as a prospective clinical trial in a telemetry unit of a large, urban, university medical center. Sample: The sample was comprised of adult patients admitted to the telemetry unit for treatment of acute myocardial infarction, unstable angina, or coronary artery disease warranting cardiac catheterization or percutaneous coronary intervention. Methods: Continuous 12-lead electrocardiographic (ECG) ST-segment monitoring was initiated in patients admitted to the telemetry unit. TMI was defined as a change in ST amplitude of ≥ 100 μV (elevation or depression) in ≥ 1 ECG lead lasting ≥ 60 seconds, comparing a baseline 12-lead ECG with an event ECG. Frequencies, measurements of central tendency, t test, χ2 test, and logistic regression analysis were used for data analysis. A P value of <.05 was adopted as the critical value to determine statistical significance. Results: In 237 telemetry unit patients, 39 patients (17%) had ischemia. Overall, 46% of the patients with ischemia had in-hospital complications compared with 10% of the group without ischemia (P <.001). After controlling for other predictors of adverse outcomes (eg, age, gender, Norris prognostic indicator), patients with TMI were 8.5 times more likely to have in-hospital complications (95% CI, 3.71 to 19.71). Conclusion: TMI is an independent predictor of in-hospital complications among patients with ACS treated in the telemetry unit setting. Continuous 12-lead ECG ST-segment monitoring provides prognostic information for risk stratification of patients admitted to the hospital for treatment of ACS. (Heart Lung® 2003;32:71-78.)

Intensive insulin treatment reduces transient ischaemic episodes during acute coronary events in diabetic patients

Objectives — This study tested the impact of intensive metabolic treatment with insulin on transient myocardial ischaemia detected with continuous 12-lead ST-segment monitoring during non-ST segment elevation acute coronary syndromes in type 2 diabetic patients.Methods and results — The study included 57 type 2 diabetic patients with non-ST segment elevation acute coronary syndromes.Twenty-eight patients randomized to conventional treatment plus intensive insulin therapy (group A) and twenty-nine to conventional therapy only (group B). Group A patients received insulin by infusion for 48 hours according to a predefined protocol aiming to maintain normoglycaemia. Group B patients received standard coronary care unit treatment. The ST-segment monitoring was performed for 48 hours in the coronary care unit.The two groups were comparable in terms of medical history, clinical and biochemical data.Three patients from both groups were excluded from the analysis because there was objective evidence for evolution in persistent ST-segment elevation acute myocardial infarction. Six patients (24%) from group A vs. twelve from group B (46.2%) had evidence of transient ischaemia (p=0.098). Group A patients showed significantly lower values in the mean number [group A vs. group B: 0.4 ± 0.8 vs. 2 ± 3.1, p<0.01] and total duration of ST-episodes [group A vs. group B: 2.4 ± 5.1 vs. 21.2 ± 31 min, p<0.01]. Multivariate analysis revealed that the mean plasma glucose during the study period was a powerful predictor of the presence (b: 0.377, p<0.01), the number (b: 0.523, p<0.001) and the total duration (b: 0.686, p<0.001) of ST-episodes, respectively.Conclusions — Intensive insulin treatment considerably decreases the number and the total duration of ST-episodes in type 2 diabetic patients suffering from non-ST segment elevation acute coronary syndromes.

Continuous 12-lead ST-segment monitoring improves identification of low-risk patients with chest pain and a worse in-hospital outcome.

Various strategies have been proposed to improve diagnosis and triage of patients with chest pain at low risk, but uncertainty still exists on the optimal combination of diagnostic tools that should be used in this subset of patients. The aim of this study was to evaluate the incremental benefit of continuous 12-lead ST-segment monitoring over that provided by conventional diagnostic tools in patients with chest pain. Of 232 consecutive patients referred because of chest pain, 52 were classified as low-risk according to the Agency for Health Care Policy and Research unstable angina guidelines and observed for 12 h with serial cardiac enzymes and electrocardiograms (ECG) (every 3 h). All patients also underwent both echocardiography at entry and continuous 12-lead ST-segment monitoring during the observation period. During a mean hospital stay of 3.7 days (range 1-14 days), a benign outcome was observed in 37 patients (71%), whereas 15 patients (29%) had major cardiac events or recurrence of chest pain of ischemic origin. Addition of ST-segment monitoring findings to baseline clinical data as well as to serial enzymes and ECG features added significant incremental prognostic value (p < 0.001). Multivariate analysis showed reproduction of pain by chest pressure (p < 0.05) and presence of ST-segment changes (> or = 0.1 mV) during 12-lead ST-segment monitoring (p < 0.001) as independent predictors of a benign or unfavorable outcome. In low-risk patients with chest pain, continuous 12-lead ST-segment monitoring provides significant incremental diagnostic and prognostic information to currently used clinical, enzymatic, and ECG data, and is helpful in identifying the subset of patients with a worse in-hospital outcome.

Which chest pain patients potentially benefit from continuous 12-lead ST-segment monitoring with automated serial ECG?

A prospective observational study was performed in 678 chest pain patients with suspected acute coronary ischemic syndrome (ACS) and absence of clinical and ECG criteria for emergent reperfusion therapy on presentation to determine how often continuous 12-lead ST-segment monitoring with automated serial ECG (SECG) results in a significant change in therapy during the initial emergency department (ED) evaluation in typical high- and low-risk chest pain patients. After initial history, physical, and ECG were obtained, patients were grouped into high and low risk subgroups based on ED physician's assessment of likelihood of ACS. Significant change in therapy was defined as thrombolytic drug administration, emergent percutaneous coronary angioplasty (PTCA), and intensive anti-ischemic therapy with intravenous heparin and/or intravenous nitroglycerin. SECG monitoring was continued until either the patient was taken for emergent PTCA or until 2-hour serum markers measurements were obtained. A total of 26 patients therapy was changed secondary to SECG monitoring which represented 14.6% of high-risk patients and 1.1% of low-risk patients. New injury (21 patients) and new ischemia (4 patients) were the only SECG findings that led to a change in therapy. SECG monitoring had a 15.2 times increased odds of changing therapy in the high risk patients as compared with the low risk patients ( P < .0001; 95% CI 6.1 to 38.2). Chest pain evaluation protocols that exclude these high risk ED patients from SECG monitoring should be reevaluated. Our data also suggests that researchers designing randomized studies to show utility of SECG monitoring should focus on the high-risk patients. (Am J Emerg Med 2000;18:773-778.

A rapid protocol to identify and exclude acute myocardial infarction: Continuous 12-lead ECG monitoring with 2-hour delta CK-MB

A prospective observational study was performed in 706 chest pain patients who underwent our chest pain evaluation protocol which consists of continuous 12-lead ST-segment monitoring with automated serial ECG (SECG) and a 2-hour delta (Δ) CK-MB level determination before ED physician making final disposition decision to determine the incremental value of our 2-hour protocol for identifying myocardial infarction (MI) as compared with the initial ECG in combination with a baseline CK-MB. The initial ECG was obtained on presentation and considered positive if it revealed injury or ischemia. SECGs were obtained at least every 10 minutes and considered positive if it revealed new injury or ischemia. The baseline CK-MB value was considered positive if it was ≥12 ng/mL and index ≥4%. ΔCK-MB was defined as a difference between the 2 hour and baseline CK-MB and was considered positive if the value was ≥+1.5 ng/mL. MI was defined as acute myocardial infarction (AMI) or recent AMI (ie, AMI patients presenting on falling curve of CK-MB). The incremental value of the 2 hour protocol (ie, SECG in conjunction with ΔCK-MB) was more sensitive for identification of MI than the baseline protocol (ie, initial ECG in conjunction with the baseline CK-MB) (94.0% versus 55.4%; P < .0001) and reliably both identified (+LR = 14.6) and excluded MI (−LR = 0.06). SECG monitoring in conjunction with the 2 hour ΔCK-MB allows for early identification and exclusion of MI, and can assist the ED physician in making appropriate treatment and disposition decisions. (Am J Emerg Med 2000;18:698-702.

Real-time application of continuous 12-lead ST-segment monitoring: 3 case studies

Real-time application of continuous 12-lead ST-segment monitoring: 3 case studies

Myocardial ischemia correlates with reduced fibrinolytic activity following peripheral vascular surgery

Study Objectives: To evaluate the relationship between perioperative ischemia and serial concentrations of D-dimer, which is a sensitive and specific marker of fibrinolytic activity. Myocardial ischemia and infarction are well-recognized complications of peripheral vascular surgery. We hypothesized that patients at increased risk of perioperative myocardial ischemia might be identified preoperatively by abnormal hemostatic indices. Design: Prospective clinical outcomes study. Setting: A 1,124-bed tertiary care medical center. Patients: 42 ASA physical status II, III, and IV patients undergoing peripheral vascular surgery. Interventions: Serial D-dimer concentrations were measured preoperatively, and at 24 and 72 hours postoperatively. Continuous 12-lead ST-segment monitoring (Mortara Instrument, Inc., Milwaukee, WI) was performed with the acquisition of a 12-lead ECG every 20 seconds for 72 hours. Measurements and Main Results: D-dimer measurements were performed in duplicate using the Dimer Gold assay (American Diagnostica, Greenwich CT). Ischemic episodes, as defined by continuous 12-lead ST-segment monitoring, occurred in 49% of patients. There were no demographic differences between ischemic and nonischemic groups. Although baseline D-dimer concentrations were not statistically significantly different between groups, patients experiencing perioperative myocardial ischemia generated significantly less D-dimer during the perioperative period ( p = 0.014). Conclusions: Patients with an impaired fibrinolytic response, as defined by reduced generation of D-dimer, experienced an increased incidence of perioperative myocardial ischemia.

Frequency of silent myocardial ischemia with 12-lead ST segment monitoring in the coronary care unit: Are there sex-related differences?

Background: Ischemia that occurs in the coronary care unit (CCU), whether symptomatic or silent, is associated with significant in-hospital and out-of-hospital complications. Studies have reported that more than 90% of ischemic episodes are silent in patients with unstable angina who are treated in the CCU with maximal medical therapy. Prior reports indicate that women complained more frequently of chest pain than men did. Purpose: The aim of this study was to compare the frequency of silent myocardial ischemia in men versus women with use of continuous 12-lead ST segment monitoring in the CCU. A secondary goal was to determine whether silent ischemia was associated with less ST segment deviation as compared with symptomatic ischemia. Method: Patients admitted for treatment of acute coronary syndrome in the CCU and who subsequently had 1 or more ischemic events during their monitoring period were selected for this analysis. All patients were continuously monitored (42.5 hours ± 37.6) in the CCU with the EASI (Zymed Medical Instruments, Camarillo, Calif) 12-lead electrocardiogram (ECG) system that derives 12 leads with use of 3 information channels and 5 electrodes. Results: Of 491 patients, 128 (91 men and 37 women) had at least 1 episode of transient myocardial ischemia. Men and women did not differ in their proportion of chest pain during ischemia (men 27% and women 21%, NS). For both men and women, ST segment deviation was significantly greater during symptomatic ischemia compared with silent ischemia. Conclusion: There are no sex-related differences in ischemic events in the CCU in regards to the variables of chest pain and ST magnitude. Therefore, because chest pain is not a reliable indicator of myocardial ischemia in the CCU, regardless of sex, patients should be adequately monitored for ischemic events. (Heart Lung® 1999;28:81-6)

Accuracy of the EASI 12-lead electrocardiogram compared to the standard 12-lead electrocardiogram for diagnosing multiple cardiac abnormalities

This study was performed to compare a derived 12-lead electrocardiogram (ECG) using a simple 5-electrode lead configuration (EASI 12-lead) with the standard ECG for multiple cardiac diagnoses. Accurate diagnosis of arrhythmias and ischemia often require analysis of multiple (ideally, 12) ECG leads; however, continuous 12-lead monitoring is impractical in hospital settings. EASI and standard ECGs were compared in 540 patients, 426 of whom also had continuous 12-lead ST segment monitoring with both lead methods. Independent standards relative to a correct diagnosis were used whenever possible, for example, echocardiographic data for chamber enlargement-hypertrophy, and troponin levels for acute infarction. Percent agreement between the 2 methods were: cardiac rhythm, 100%; chamber enlargement-hypertrophy, 84%–99%; right and left bundle branch block, 95% and 97%, respectively; left anterior and posterior fascicular block, 97% and 99%, respectively; prior anterior and inferior infarction, 95% and 92%, respectively. There was very little variation between the 2 lead methods in cardiac interval measurements; however, there was more variation in P, QRS, and T-wave axes. Of the 426 patients with ST monitoring, 138 patients had a total of 238 ST events (26, acute infarction; 62, angioplasty-induced ischemia; 150, spontaneous transient ischemia). There was 100% agreement between the 2 methods for acute infarction, 95% agreement for angioplastyinduced ischemia, and 89% agreement for transient ischemia. EASI and standard 12-lead ECGs are comparable for multiple cardiac diagnoses; however, serial ECG changes (eg, T-wave changes) should be assessed using one consistent 12-lead method.

12-lead ST-segment monitoring vs single-lead maximum ST-segment monitoring for detecting ongoing ischemia in patients with unstable coronary syndromes

12-lead ECG monitoring of the ST segment is more sensitive than patients' symptoms for detecting ischemia after thrombolytic therapy or catheter-based interventions, but it is unclear whether monitoring of the single lead showing maximum ST deviation would be as efficacious. To determine whether monitoring all 12 ECG leads for changes in the ST segment is necessary to detect ongoing ischemia in patients with unstable coronary syndromes. Continuous 12-lead ST segment monitoring was performed in 422 patients from the onset of myocardial infarction or during balloon inflation in catheter-based interventions until the patient's discharge from the cardiac care unit. Computer-assisted techniques were used to determine (1) which lead showed the maximum ST deviation at the onset of myocardial infarction or during balloon inflation and (2) what proportion of later ischemic events were associated with ST deviation in this lead. The lead with the maximum ST deviation could be determined in 312 patients (74%). The remaining 110 (26%) had non-Q wave infarction without ST deviation or no ST changes during balloon inflation. During 18,394 hours of 12-lead ST monitoring, 118 (28%) of the 312 patients had a total of 463 ischemic events, 80% of which were silent. Of 377 ischemic events in which a maximum ST lead was detected, 159 (42%) did not show ST deviation in this lead (sensitivity, 58%; 95% CI, 53%-63%). Routine monitoring of leads V1 and II showed ST deviation in only 152 of the 463 events (sensitivity, 33%; 95% CI, 29%-37%). Monitoring of all 12 ECG leads for changes in the ST segment is necessary to detect ongoing ischemia in patients with unstable coronary syndromes.

Comparative Prognostic Significance of Simultaneous Versus Independent Resolution of ST Segment Depression Relative to ST Segment Elevation During Acute Myocardial Infarction

Objectives. We sought to determine the prognostic significance of simultaneous versus independent resolution of ST segment depression that occurs concomitant with ST segment elevation during acute myocardial infarction (AMI).Background. ST segment depression in leads other than those showing ST segment elevation during AMI is a common phenomenon. Whether this indicates adverse outcomes remains controversial. We hypothesized that the timing of ST segment depression resolution relative to ST segment elevation resolution might differentiate between a high risk group and a low risk group of patients.Methods. Continuous 12-lead ST segment monitoring was performed after thrombolytic therapy for AMI in 413 patients, 261 of whom met technical criteria for analysis. Blinded analysis of ST segment depression resolution patterns was used to group patients as follows: 1) no ST segment depression at any time (control group); 2) ST segment depression resolving simultaneously with ST segment elevation (simultaneous group); and 3) ST segment depression persisting after ST segment elevation resolution (independent group). These patterns were correlated with the outcomes—recurrent angina, reinfarction, heart failure and death—using chi-square analysis and the Fisher exact test for categoric variables and the Wilcoxon rank-sum test for continuous variables.Results. The incidence of recurrent angina, reinfarction and heart failure was similar among the three groups. In-hospital mortality, however, was significantly higher in the independent group (13%) than either the simultaneous group (1%, p < 0.001) or the control group (0%, p = 0.002).Conclusions. Continuous analysis of ST segment resolution identifies, among patients with AMI with concomitantly occurring ST segment elevation and depression, a subgroup with increased in-hospital mortality. The pathogenic mechanism of increased mortality is not currently known.

Comparison of standard and derived 12-lead electrocardiograms for diagnosis of coronary angioplasty-induced myocardial ischemia

To determine whether a derived 12-lead electrocardiogram (ECG) would demonstrate typical ST-segment changes of ischemia during percutaneous transluminal coronary angioplasty (PTCA), 207 patients were monitored with continuous 12-lead ST-segment monitoring during angioplasty. Additionally, to compare the derived and standard ECGs during known periods of ischemia with PTCA balloon inflation, 151 patients were recorded with both electrocardiographic methods during the procedure. Of the 207 patients recorded with the derived ECG, 171 (83%) had typical ischemic ST-segment changes during PTCA balloon inflation. The amplitudes of these ST deviations were similar to those observed during transient myocardial ischemia observed in clinical settings (median peak ST deviation, 225 μV). There was agreement regarding presence or absence of ischemia in 150 of the 151 patients recorded with both derived and standard electrocardiographic methods (>99% agreement). With use of the standard ECG as the “gold standard” for ischemia diagnosis, there were no false-positive results and only 1 false-negative result with the derived ECG. Furthermore, there was nearly perfect agreement between the two 12-lead methods in terms of anterior versus inferior wall patterns of ischemia. Future studies are required to determine whether continuous monitoring with a derived ECG would improve diagnosis and lead to better patient outcomes.