12-lead ST-segment Research Articles

Frequency, duration, magnitude, and consequences of myocardial ischemia during intracoronary ultrasonography

To determine the frequency, duration, magnitude, and possible adverse effects of ischemia during intracoronary ultrasonography, real-time standard 12-lead electrocardiograms were recorded before, during, and after ultrasonography. Ischemia was defined as new-onset ST segment deviation of ≥1 mm in one or more leads, measured at J + 80 msec. The magnitude of ischemia was expressed as the sum of absolute ST segment deviations across 12 leads. Eighteen (67%) of 27 patients had ischemia during intracoronary ultrasonography. The electrocardiogram resembled the characteristic pattern observed with occlusion of the vessel under study, involving ST segment elevation in contiguous leads in 89% of patients. A higher proportion of women (88%) had ischemia than men (58%), and women had smaller arterial lumenal areas compared with men (6.3 vs 9.1 mm 2 ; p < 0.05). Individuals with ischemia were smaller than those without ischemia (body surface area = 1.99 vs 1.79 m 2 ; p = 0.01). The mean duration of ischemia was 4 minutes and the mean 12-lead ST segment deviation score was 8.5 mm (maximum 20.5 mm). No patient with ischemia during ultrasonography had complications. Ischemia is common during intracoronary ultrasonography, particularly in women and individuals with smaller vessels; however, no adverse outcomes occur as a result. (Am Heart J 1997;134:474-8.)

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.

ST segment monitoring with a derived 12-lead electrocardiogram is superior to routine cardiac care unit monitoring

Prior studies have shown that a derived 12-lead electrocardiogram with a simple electrode configuration is comparable with the standard electrocardiogram for arrhythmia analysis. A prospective, comparative, within subjects design was used to compare the value of the derived 12-lead electrocardiogram with that of routine monitoring of leads V1 and II for detection of transient myocardial ischemia in 250 patients treated for unstable angina or myocardial infarction. During 11,532 hours of derived 12-lead ST segment monitoring, 55 (22%) of 250 patients had 176 episodes of ischemia. Of the 55 patients with ischemia, 75% reported no chest pain and 64% had no ischemic ST changes with routine monitoring leads. All five patients who developed angiographically confirmed abrupt reocclusion after percutaneous transluminal coronary angioplasty had ischemic ST changes with the derived electrocardiogram (sensitivity, 100%), compared with only two patients with routine monitoring (sensitivity, 40%). Serious complications occurred in 17% of angina patients with ischemic events compared to 3% of those without ischemia. Length of stay in the cardiac care unit was twice as long in angina patients who had ischemic events. In patients with acute myocardial infarction, ischemic events were not associated with a more complicated hospital course; however, length of stay in the cardiac care unit was longer in patients with recurrent ischemia. The findings show that derived 12-lead ST monitoring is superior to routine monitoring of leads V1 and II for detecting transient myocardial ischemia. ST monitoring of the derived 12-lead electrocardiogram may identify high-risk patients with unstable angina and provide prognostic information that would not be otherwise available from the usual clinical measures.

Continuous 12-lead St segment monitoring: An adjunct to identifying silent ischemia and infarct in the emergency department

The presence of myocardial ischemia or infarct may be unnoticed by ED staff when conventional dysrhythmia monitors and static 12-lead EKGs are used. The inherent problem with static EKGs is their insensitivity to the dynamic flow changes that occur in subtotal occlusions. 1 Although many emergency departments now have dysrhythmia monitors with threeqead ST segment monitoring capabilities, the staff chooses which three leads to monitor. This decision is less complicated if the 12-lead EKG reading is diagnostic for ischemia or infarct. However, it is estimated that 10% to 15% of myocardial infarctions are clinically silent. 2 Patients with atypical chest pain, nondiagnostic initial EKGs, and normal enzyme concentrations are particularly at risk for misdiagnosis. Combining continuous 12dead ST segment monitoring with an observation protocol that includes dysrhythmia monitoring in conjunction with serial measurements of enzyme concentrations and EKGs should reduce the incidence of inappropriate dispositions in this population. ST segment changes noted with continuous 12lead ST segment monitoring has been shown to correlate closely with coronary artery patency during reperfusion therapy. Continuous 12-lead ST segment monitoring can detect the dynamic flow changes in subtotal occlusion with 90% sensitivity and 92% specificity when compared with the angiography standard. 3 Changes in blood flow through the coronary vessels, which can be missed by a static, 12-lead EKG, occur during both infarct and ischemia. This is particularly true if the patient is not experiencing pain at the time.

Ischemia monitoring during reperfusion therapy using combined frequent CK-MB, troponin T, myoglobin and continuous 12-lead ST segment analysis

Ischemia monitoring during reperfusion therapy using combined frequent CK-MB, troponin T, myoglobin and continuous 12-lead ST segment analysis

Continuous 12-lead ST-segment recovery analysis in the TAMI 7 study. Performance of a noninvasive method for real-time detection of failed myocardial reperfusion.

If a practical, reliable, noninvasive marker of failed reperfusion was available in real time, the benefits of further therapy in this patient subgroup could be tested. We developed a method of 12-lead ST-segment recovery analysis using continuously updated reference points to provide such a marker. In this study, our method was prospectively tested in 144 patients given thrombolytic therapy early in myocardial infarction. All patients had 12-lead continuous ST-segment monitoring and acute angiography, each analyzed in an independent, blinded core laboratory. ST-segment recovery and re-elevation were analyzed up to the moment of angiography, at which time patency was predicted. Predictions were correlated to angiographic infarct artery flow, with TIMI flow 0 to 1 as occluded and TIMI flow 2 to 3 as patent. Infarct artery occlusion was seen on first injection in 27% of patients. The positive predictive value of incomplete ST recovery or ST re-elevation by our method was 71%, negative predictive value 87%, with 90% specificity and 64% sensitivity for coronary occlusion. ST recovery analysis predicted patency in 94% of patients with TIMI 3 flow versus 81% of patients with TIMI 2 flow and predicted occlusion in 57% of patients with collateralized occlusion versus 72% of patients with non-collateralized occlusion. In a regression model including other noninvasive clinical descriptors, ST recovery alone contained the vast majority of predictive information about patency. In a blinded, prospective, angiographically correlated study design, 12-lead continuous ST-segment recovery analysis shows promise as a practical noninvasive marker of failed reperfusion that may contribute substantially to currently available bedside assessment. Our data also suggest that patients with TIMI 2 flow or with collateralized occlusions may represent a physiological spectrum definable with ST-segment recovery analysis.

Continuously updated 12-lead ST-segment recovery analysis for myocardial infarct artery patency assessment and its correlation with multiple simultaneous early angiographic observations

Early angiography may not adequately subgroup patients with myocardial infarction if cyclic changes in coronary flow occur frequently. From a pilot experience using a new 12-lead ST-segment monitor, a continuously updated, self-referenced ST-recovery analysis method was developed to quantify both instantaneous recovery, as a noninvasive marker of patency, and cumulative ST recovery over time, as a marker of the speed, stability and duration of reperfusion. In 22 patients with acute infarction in whom 44 observations of unique angiographic patency were noted within 6 hours of presentation, serial patency assessments simultaneous with all angiographic observations predicted coronary occlusion with 90% sensitivity and 92% specificity. Of the 22 patients, 11 (50%) had multiple ST trend transitions suggesting cyclic changes in coronary flow before catheterization. Speed, stability and duration of ST-segment recovery were defined by the time to first 50% ST recovery, total number of ST-trend transitions and patent physiology index (percentage of monitoring period showing ST recovery), respectively. Subgrouped angiographically, the median (interquartile range) for cumulative ST parameters with patent (n = 8) versus occluded (n = 14) arteries were, respectively — time to 50% recovery, 1.57 (1.16, 1.70) versus 0.17 (−0.47, 0.32) hours; number of reelevation/recovery events, 1.5 (1, 3) versus 3 (1, 3); and patent physiology index, 52 (47, 59) versus 50 (5, 73). Thus, continuous ST-segment recovery analysis appears to predict simultaneous angiographic patency over serial assessments, whereas cumulative parameters appear to contain independent information, probably because of patency changes before or after angiography.

Continuous 12-lead electrocardiograph monitoring in the emergency department

Many patients presenting to the emergency department with suspected acute myocardial infarction have an initial electrocardiogram (ECG) nondiagnostic for acute injury or ischemia. Continuous ST segment monitoring devices have been used by physicians in the past to diagnose ischemia in the ambulatory outpatient population and to identify coronary occlusion in postthrombolytic and postsurgical patients. We report three patients with suspected acute myocardial infarction who underwent real-time continuous 12-lead ST segment monitoring with frequent serial ECGs on a microprocessor-controlled device during their initial emergency department evaluation. Continuous 12-lead ECG monitoring revealed significant changes on the ECG in all three cases presented, with a resultant change in emergency department therapy. Interestingly, all of these patients had significant ECG changes in the absence of recurrence of chest pain. We believe real-time continuous 12-lead ST segment monitoring with frequent serial ECGs can identify patients with an initially nondiagnostic or atypical ECG who may benefit from early interventional therapy.

Unstable infarct artery

Range of TREP (0-360 min) and %REC (0-99%) showed considerable overlap across infarct artery patency groups. Thus, (1) continuous 12-lead ST trend flux correlated well with simultaneous angiographic patency of the infarct artery and (2) quantified ST activity was highly variable within groups defined by angiographic patency and may provide insight into the heterogenous physiologic outcomes within such subgroups. Within a population defined by angiographic infarct artery patency, early, late, or unstable reperfusion may provide physiologically unique outcomes. An index for quantification of very early and dynamic infarct artery activity was developed using continuous 12-lead digital ST-segment monitoring in 35 patients presenting with myocardial infarction of <6 hours, treated with thrombolytics or primary percutaneous transluminal coronary angioplasty (PICA). All patients underwent angiography. From trends of ST level versus time, marked peaks and troughs of trend activity were used to noninvasively define: (1) moment-moment coronary patency; (2) time to first evidence of reperfusion (TREP, minutes), and (3) summed periods of recovery (versus worsening) as a percentage of the total recording time (%REC). ST interpretation correlated with angiographic infarct artery patency in 31 of 34 (91%)

Tues 1545 Changes in coronary patency with continuous 12-lead ST segment monitoring during transport and early management of acute myocardial infarction patients

Tues 1545 Changes in coronary patency with continuous 12-lead ST segment monitoring during transport and early management of acute myocardial infarction patients

Tues 1615 The use of digital real-time 12-lead ST segment trends in the management of acute myocardial infarction patients during helicopter transport and early hospitalization

Tues 1615 The use of digital real-time 12-lead ST segment trends in the management of acute myocardial infarction patients during helicopter transport and early hospitalization