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Serial Electrocardiography and ST Segment Trend Monitoring
Chapter 70
Serial Electrocardiography and ST Segment Trend Monitoring J. Lee Garvey
A single, static electrocardiogram (ECG) contains information demonstrating cardiac electrical activity during approximately 10 seconds of cardiac function. Contrast that to the course of coronary artery disease (months to years) and acute coronary syndrome (ACS; minutes to hours). Optimally, the timing of ECG sampling performed when patients present with symptoms should match the time domain of the underlying pathologic process. Repeated sampling of the 10-second standard ECG during the time period of ACS of minutes to hours supplies additional diagnostic and prognostic information. This can be accomplished manually or automatically by using hardware and software devices. ACS results in derangement of the electrical function of the heart, most often reflected by an alteration of the ST segment. Dynamic changes in ST segment elevation or depression have been documented in the course of ischemia and acute myocardial infarction (AMI).1–5 The typical course probably reflects varying degrees of elevation or depression, spontaneously occurring and resolving because of the underlying pathophysiologic process.6 Because each of these processes changes over time, and also with therapeutic interventions, the resulting ST segment amplitude will show corresponding changes over a similar time frame—minute to minute, for a period of hours to days. ST segment trend monitoring systems usually display information using typical ECG presentations. A set of up to 10 electrode wires is attached to the patient in the usual manner. Signal processing techniques are used to reduce artifactual signal and atypical beats (e.g., premature ventricular contractions). Most systems require an electrode set to be physically connected to the monitoring equipment, but telemetric systems impose fewer physical limitations on patients. Radiolucent electrode systems do not interfere with cardiac catheterization imaging. The ST segment monitor samples typical (static) 12-lead ECGs repeatedly at a frequency of one per minute. At this rate, 1440 ECGs may be collected in a 24-hour period. Obviously, real-time human review of this number of ECGs is prohibitive. Automated analysis of ST segment amplitude of each lead for such a number of samples is a trivial task for 342
today’s microprocessors. This rate is sufficient to capture changes in the underlying pathophysiologic processes of ischemia, and may be visually shown as a trend of ST segment change over time. ST segment trend data may be displayed for each of the 12 leads (Fig. 70-1), or as the absolute value of a summation of ST changes (Fig. 70-2). Automated visual and auditory alarm systems call attention to situations in which ST segment changes have exceeded preset limits. Typical limits for ST segment trend analysis alarms are a change (increase or decrease) of 200 μV in a single lead, or 100 μV of change in two or more electrically contiguous leads occurring for two or three consecutive samples. This implies that the baseline ECG is compared with subsequent ECGs. Systems that use a Frank lead set (x, y, z) of orthogonal electrodes calculate and display ST segment changes as the ST vector magnitude (ST⫺VM) = (STx2 + STy2 + STz2)1/2 over time (Fig. 70-2). A reversible increase in ST⫺VM of greater than 50 μV from baseline is considered abnormal.7
FIGURE 70-1 • Normal trend of ST segment amplitude in each of 12 standard ECG leads over 12 hours. Arrow denotes minor changes in ST segment amplitude (<100 mV) resulting from change in body position.
CHAPTER 70: Serial Electrocardiography and ST Segment Trend Monitoring
343
560 480
Microvolts
400 320 240 180 80 0 00:00
02:00
04:00
06:00
08:00
10:00
12:00
FIGURE 70-2 • Trend of ST segment vector magnitude recorded over 12 hours. Arrows indicate periods of cardiac ischemia. (Adapted from Dellborg M, Andersen K: Key factors in the identification of the high-risk patient with unstable coronary artery disease: Clinical findings, resting 12-lead electrocardiogram, and continuous electrocardiographic monitoring. Am J Cardiol 1997;80:35E, with permission.)
Clinicians must remember that ST segment amplitude is rarely isoelectric in all leads at baseline. Subsequent further changes of less than 100 μV may occur and render an ECG “diagnostic” for ACS before being detected by a system that is set to detect changes of voltage. Similarly, subtle changes in ST segment amplitude of less than 100 μV may truly reflect active ischemia. This degree of change is very difficult to detect visually, and is usually excluded from automated systems’ alarm settings to increase specificity. Changes in body position may be reflected as a change in the ST segment amplitude, particularly in the precordial leads.8 The underlying 12-lead ECGs generally continue to show a consistent overall pattern, but QRS voltage and subsequent repolarization voltage (ST segment/T wave) may be changed. This is usually of small magnitude, but may be noticed during continuous ST segment trend monitoring (Fig. 70-1). Alarm violations may occur when electrical noise contaminates the signal. Meticulous attention to skin preparation and lead positioning minimizes this risk. When alarms occur, trained staff should examine the ST segment trend and specific underlying 12-lead ECGs to determine the pathophysiologic or artifactual cause.
ST Segment Monitoring in the Emergency Department It is intuitive that application of a tool (ischemia monitoring) that captures transient diagnostic changes (ST elevation or depression) that otherwise could be missed should improve the time to definitive treatment, and thus improve outcomes in ACS. The ST segment trend for a patient with “atypical symptoms” who demonstrated acute ischemia is presented in Figure 70-3. The dynamic nature of the underlying coronary artery disease is reflected in the time course of ECG changes for this patient. In a series of 1000 patients, Fesmire et al.9 showed that ST segment trend monitoring is useful for patients with chest
pain in the emergency department (ED). In their series, ST segment magnitudes were measured every 20 seconds for at least 1 hour, and automated serial ECGs were obtained at least every 20 minutes. This cohort included the entire spectrum of patients with chest pain in the ED—from ST segment elevation AMI through those at low likelihood for ACS. This monitoring technique improved sensitivity in identifying AMI and ACS compared with the initial presentation ECG (68% versus 55% for AMI; 34% versus 27% for ACS). ACS diagnostic sensitivity improved (99.4% versus 97.1%). This monitoring technique was also used to identify patients requiring intensive anti-ischemic therapy, intensive care unit admission, and emergent cardiac catheterization; as well as to assess reperfusion therapy. ST segment monitoring is also used as a means of surveillance for ischemia in patients in the ED considered to be at low risk for ACS.10–12 A consensus panel8 suggests that a total of 8 to 12 hours of continuous ST segment monitoring, in conjunction with serial sampling of blood for markers of myocardial necrosis and provocative testing for ischemia, may be an effective way to evaluate patients with chest pain in the ED. However, although protocols for the rapid evaluation have been published,13,14 no specific study evaluating the cost effectiveness of ST segment monitoring of patients at low risk for ACS has been reported. Moreover, because a normal or nondiagnostic ECG obtained on presentation does not exclude AMI or the presence of coronary artery disease, serial ECGs and ST segment monitoring likewise cannot be the sole means to exclude potential ACS.
Use in Assessing Coronary Artery Patency During elective coronary angioplasty procedures, Krucoff et al.15 studied the relation between balloon inflation and dynamic ST segment movement. ST segment changes were typically detectable in an anterior lead set with inflation in the left anterior descending artery, or in an inferior lead set with
SECTION IV: ADVANCED TECHNIQUES AND TECHNOLOGIES
200 μV
344
40 min
A 2500
Heart Rate (bpm) 88 100
III
2000 1500 1000 500 0 −500 −1000 −1500 −2000
STM (uV) 24 214
−2500 0
100
QRS Diff. 1.7 8.4 200
300
400
500
600
700
800
900
1000
1100 1200
B FIGURE 70-3 • ST segment trending. A, ST segment trend from a 62-year-old woman with “atypical” symptoms for cardiac ischemia. A cluster of spikes at the base of each panel notes recurrent, brief episodes of abnormal, dynamic ST segment changes documenting ischemia. B, Individual composite beats from lead III showing baseline ECG, and ECG at time of maximal ST segment elevation. (Continued)
CHAPTER 70: Serial Electrocardiography and ST Segment Trend Monitoring
345
11:09
C 11:18
D
11:21
E FIGURE 70-3—cont’d • ST segment trending. C, Twelve-lead ECG (time = 11:09 AM) shows nondiagnostic ST segment findings only. D, Twelve-lead ECG (time = 11:18 AM) is now diagnostic for ST segment elevation in inferior and lateral leads. E, Twelve-lead ECG (time = 11:21 AM) shows resolution of ST segment abnormalities within 3 minutes.
inflation in the right coronary artery or circumflex. Similarly, ST segment monitoring has also been used to predict infarct artery patency after pharmacologic reperfusion therapy.16–18 To investigate the association between early recovery from ST segment elevation and long-term mortality in patients with AMI, French et al.17 followed 766 patients treated with fibrinolytic therapy. They found that ST segment recovery in the lead with initial maximum ST segment elevation was a predictor of long-term survival (2.5 to 10 years, P = 0.03 to 0.0005), but ST segment recovery, measured as the sum of all leads with ST segment changes (or elevation), was not.
Use in Perioperative and Intraoperative Settings Cardiovascular monitoring is a cornerstone of management in the perioperative setting. Application of ST segment monitoring in an attempt to identify episodes of ischemia has been used in this setting as well.19–21 This area is not without its own controversy and discussion.22–24 Discordance may exist between ST segment changes (electrical) and transesophageal echocardiography (mechanical) as detectors of perioperative ischemia. In a comparison with post hoc analysis of intraoperative Holter recordings, various real-time ST segment
346
SECTION IV: ADVANCED TECHNIQUES AND TECHNOLOGIES
monitors were found to be of moderate sensitivity (60% to 78%) and specificity (69% to 89%) in detecting ischemia in patients undergoing coronary artery bypass surgery.25
References 1. Velez J, Brady WJ, Perron AD, Garvey L: Serial electrocardiography. Am J Emerg Med 2002;20:43. 2. Fesmire FM, Smith EE: Continuous 12-lead electrocardiograph monitoring in the emergency department. Am J Emerg Med 1993;11:54. 3. Krucoff MW, Croll MA, Pope JE, et al: Continuously updated 12-lead ST-segment recovery analysis for myocardial infarct artery patency assessment and its correlation with multiple simultaneous early angiographic observations. Am J Cardiol 1993;71:145. 4. Cohn PF, Sodums MT, Lawson WE, et al: Frequent episodes of silent myocardial ischemia after apparently uncomplicated myocardial infarction. J Am Coll Cardiol 1986;8:982. 5. Klootwijk P, Cobbaert C, Fioretti P, et al: Noninvasive assessment of reperfusion and reocclusion after thrombolysis in acute myocardial infarction. Am J Cardiol 1993;72:75G. 6. Patel DJ, Knight CJ, Holdright DR, et al: Pathophysiology of transient myocardial ischemia in acute coronary syndromes: Characterization by continuous ST-segment monitoring. Circulation 1997;95:1185. 7. Dellborg M, Andersen K: Key factors in the identification of the highrisk patient with unstable coronary artery disease: Clinical findings, resting 12-lead electrocardiogram, and continuous electrocardiographic monitoring. Am J Cardiol 1997;80:35E. 8. Drew BJ, Krucoff MW: Multilead ST-segment monitoring in patients with acute coronary syndromes: A consensus statement for healthcare professionals: ST-Segment Monitoring Practice Guideline International Working Group. Am J Crit Care 1999;8:372. 9. Fesmire FM, Percy RF, Bardoner JB, et al: Usefulness of automated serial 12-lead ECG monitoring during the initial emergency department evaluation of patients with chest pain. Ann Emerg Med 1998;31:3. 10. Gibler WB, Sayre MR, Levy RC, et al: Serial 12-lead electrocardiographic monitoring in patients presenting to the emergency department with chest pain. J Electrocardiol 1993;26(Suppl):238. 11. Garvey JL: Can ST segment monitoring beat static twelve-lead ECG? In Gibler WB (ed): Pushing the Therapeutic Envelope for Emergency Cardiac Medicine: Acute Coronary Syndromes and Beyond. New York, Health Science Communications, 2001, p. 2.
12. Sarko J, Pollack CV Jr: Beyond the twelve-lead electrocardiogram: Diagnostic tests in the evaluation for suspected acute myocardial infarction in the emergency department, part I. J Emerg Med 1997;15:839. 13. Graff L, Joseph T, Andelman R, et al: American College of Emergency Physicians Information Paper: Chest pain units in emergency departments—a report from the Short-Term Observation Services Section. Am J Cardiol 1995;76:1036. 14. Gomez MA, Anderson JL, Karagounis LA, et al: An emergency department-based protocol for rapidly ruling out myocardial ischemia reduces hospital time and expense: Results of a randomized study (ROMIO). J Am Coll Cardiol 1996;28:25. 15. Krucoff MW, Loeffler KA, Haisty WKJ, et al: Simultaneous ST-segment measurements using standard and monitoring-compatible torso limb lead placements at rest and during coronary occlusion. Am J Cardiol 1994;74:997. 16. Pasceri V, Andreotti F, Maseri A: Clinical markers of thrombolytic success. Eur Heart J 1996;17(Suppl E):35. 17. French JK, Andrews J, Manda SOM, et al: Early ST-segment recovery, infarct artery blood flow, and long-term outcome after acute myocardial infarction. Am Heart J 2002;143:265. 18. Krucoff MW, Green CE, Satler LF, et al: Noninvasive detection of coronary artery patency using continuous ST-segment monitoring. Am J Cardiol 1986;57:916. 19. Slogoff S, Keats AS, David Y, Igo SR: Incidence of perioperative myocardial ischemia detected by different electrocardiographic systems. Anesthesiology 1990;73:1074. 20. McDermott MM, Lefevre F, Arron M, et al: ST segment depression detected by continuous electrocardiography in patients with acute ischemic stroke or transient ischemic attack. Stroke 1994;25:1820. 21. Kotrly KJ, Kotter GS, Mortara D, Kampine JP: Intraoperative detection of myocardial ischemia with an ST segment trend monitoring system. Anesth Analg 1984;63:343. 22. Jopling MW: Pro: Automated electrocardiogram ST-segment monitoring should be used in the monitoring of cardiac surgical patients. J Cardiothorac Vasc Anesth 1996;10:678. 23. Proctor LT, Kingsley CP: Con: ST-segment analysis—who needs it? J Cardiothorac Vasc Anesth 1996;10:681. 24. Selbst J, Comunale ME: Myocardial ischemia monitoring. Int Anesthesiol Clin 2002;40:133. 25. Leung JM, Voskanian A, Bellows WH, Pastor D: Automated electrocardiograph ST segment trending monitors: Accuracy in detecting myocardial ischemia. Anesth Analg 1998;87:4.
Serial Electrocardiography and ST Segment Trend Monitoring J. Lee Garvey
A single, static electrocardiogram (ECG) contains information demonstrating cardiac electrical activity during approximately 10 seconds of cardiac function. Contrast that to the course of coronary artery disease (months to years) and acute coronary syndrome (ACS; minutes to hours). Optimally, the timing of ECG sampling performed when patients present with symptoms should match the time domain of the underlying pathologic process. Repeated sampling of the 10-second standard ECG during the time period of ACS of minutes to hours supplies additional diagnostic and prognostic information. This can be accomplished manually or automatically by using hardware and software devices. ACS results in derangement of the electrical function of the heart, most often reflected by an alteration of the ST segment. Dynamic changes in ST segment elevation or depression have been documented in the course of ischemia and acute myocardial infarction (AMI).1–5 The typical course probably reflects varying degrees of elevation or depression, spontaneously occurring and resolving because of the underlying pathophysiologic process.6 Because each of these processes changes over time, and also with therapeutic interventions, the resulting ST segment amplitude will show corresponding changes over a similar time frame—minute to minute, for a period of hours to days. ST segment trend monitoring systems usually display information using typical ECG presentations. A set of up to 10 electrode wires is attached to the patient in the usual manner. Signal processing techniques are used to reduce artifactual signal and atypical beats (e.g., premature ventricular contractions). Most systems require an electrode set to be physically connected to the monitoring equipment, but telemetric systems impose fewer physical limitations on patients. Radiolucent electrode systems do not interfere with cardiac catheterization imaging. The ST segment monitor samples typical (static) 12-lead ECGs repeatedly at a frequency of one per minute. At this rate, 1440 ECGs may be collected in a 24-hour period. Obviously, real-time human review of this number of ECGs is prohibitive. Automated analysis of ST segment amplitude of each lead for such a number of samples is a trivial task for 342
today’s microprocessors. This rate is sufficient to capture changes in the underlying pathophysiologic processes of ischemia, and may be visually shown as a trend of ST segment change over time. ST segment trend data may be displayed for each of the 12 leads (Fig. 70-1), or as the absolute value of a summation of ST changes (Fig. 70-2). Automated visual and auditory alarm systems call attention to situations in which ST segment changes have exceeded preset limits. Typical limits for ST segment trend analysis alarms are a change (increase or decrease) of 200 μV in a single lead, or 100 μV of change in two or more electrically contiguous leads occurring for two or three consecutive samples. This implies that the baseline ECG is compared with subsequent ECGs. Systems that use a Frank lead set (x, y, z) of orthogonal electrodes calculate and display ST segment changes as the ST vector magnitude (ST⫺VM) = (STx2 + STy2 + STz2)1/2 over time (Fig. 70-2). A reversible increase in ST⫺VM of greater than 50 μV from baseline is considered abnormal.7
FIGURE 70-1 • Normal trend of ST segment amplitude in each of 12 standard ECG leads over 12 hours. Arrow denotes minor changes in ST segment amplitude (<100 mV) resulting from change in body position.
CHAPTER 70: Serial Electrocardiography and ST Segment Trend Monitoring
343
560 480
Microvolts
400 320 240 180 80 0 00:00
02:00
04:00
06:00
08:00
10:00
12:00
FIGURE 70-2 • Trend of ST segment vector magnitude recorded over 12 hours. Arrows indicate periods of cardiac ischemia. (Adapted from Dellborg M, Andersen K: Key factors in the identification of the high-risk patient with unstable coronary artery disease: Clinical findings, resting 12-lead electrocardiogram, and continuous electrocardiographic monitoring. Am J Cardiol 1997;80:35E, with permission.)
Clinicians must remember that ST segment amplitude is rarely isoelectric in all leads at baseline. Subsequent further changes of less than 100 μV may occur and render an ECG “diagnostic” for ACS before being detected by a system that is set to detect changes of voltage. Similarly, subtle changes in ST segment amplitude of less than 100 μV may truly reflect active ischemia. This degree of change is very difficult to detect visually, and is usually excluded from automated systems’ alarm settings to increase specificity. Changes in body position may be reflected as a change in the ST segment amplitude, particularly in the precordial leads.8 The underlying 12-lead ECGs generally continue to show a consistent overall pattern, but QRS voltage and subsequent repolarization voltage (ST segment/T wave) may be changed. This is usually of small magnitude, but may be noticed during continuous ST segment trend monitoring (Fig. 70-1). Alarm violations may occur when electrical noise contaminates the signal. Meticulous attention to skin preparation and lead positioning minimizes this risk. When alarms occur, trained staff should examine the ST segment trend and specific underlying 12-lead ECGs to determine the pathophysiologic or artifactual cause.
ST Segment Monitoring in the Emergency Department It is intuitive that application of a tool (ischemia monitoring) that captures transient diagnostic changes (ST elevation or depression) that otherwise could be missed should improve the time to definitive treatment, and thus improve outcomes in ACS. The ST segment trend for a patient with “atypical symptoms” who demonstrated acute ischemia is presented in Figure 70-3. The dynamic nature of the underlying coronary artery disease is reflected in the time course of ECG changes for this patient. In a series of 1000 patients, Fesmire et al.9 showed that ST segment trend monitoring is useful for patients with chest
pain in the emergency department (ED). In their series, ST segment magnitudes were measured every 20 seconds for at least 1 hour, and automated serial ECGs were obtained at least every 20 minutes. This cohort included the entire spectrum of patients with chest pain in the ED—from ST segment elevation AMI through those at low likelihood for ACS. This monitoring technique improved sensitivity in identifying AMI and ACS compared with the initial presentation ECG (68% versus 55% for AMI; 34% versus 27% for ACS). ACS diagnostic sensitivity improved (99.4% versus 97.1%). This monitoring technique was also used to identify patients requiring intensive anti-ischemic therapy, intensive care unit admission, and emergent cardiac catheterization; as well as to assess reperfusion therapy. ST segment monitoring is also used as a means of surveillance for ischemia in patients in the ED considered to be at low risk for ACS.10–12 A consensus panel8 suggests that a total of 8 to 12 hours of continuous ST segment monitoring, in conjunction with serial sampling of blood for markers of myocardial necrosis and provocative testing for ischemia, may be an effective way to evaluate patients with chest pain in the ED. However, although protocols for the rapid evaluation have been published,13,14 no specific study evaluating the cost effectiveness of ST segment monitoring of patients at low risk for ACS has been reported. Moreover, because a normal or nondiagnostic ECG obtained on presentation does not exclude AMI or the presence of coronary artery disease, serial ECGs and ST segment monitoring likewise cannot be the sole means to exclude potential ACS.
Use in Assessing Coronary Artery Patency During elective coronary angioplasty procedures, Krucoff et al.15 studied the relation between balloon inflation and dynamic ST segment movement. ST segment changes were typically detectable in an anterior lead set with inflation in the left anterior descending artery, or in an inferior lead set with
SECTION IV: ADVANCED TECHNIQUES AND TECHNOLOGIES
200 μV
344
40 min
A 2500
Heart Rate (bpm) 88 100
III
2000 1500 1000 500 0 −500 −1000 −1500 −2000
STM (uV) 24 214
−2500 0
100
QRS Diff. 1.7 8.4 200
300
400
500
600
700
800
900
1000
1100 1200
B FIGURE 70-3 • ST segment trending. A, ST segment trend from a 62-year-old woman with “atypical” symptoms for cardiac ischemia. A cluster of spikes at the base of each panel notes recurrent, brief episodes of abnormal, dynamic ST segment changes documenting ischemia. B, Individual composite beats from lead III showing baseline ECG, and ECG at time of maximal ST segment elevation. (Continued)
CHAPTER 70: Serial Electrocardiography and ST Segment Trend Monitoring
345
11:09
C 11:18
D
11:21
E FIGURE 70-3—cont’d • ST segment trending. C, Twelve-lead ECG (time = 11:09 AM) shows nondiagnostic ST segment findings only. D, Twelve-lead ECG (time = 11:18 AM) is now diagnostic for ST segment elevation in inferior and lateral leads. E, Twelve-lead ECG (time = 11:21 AM) shows resolution of ST segment abnormalities within 3 minutes.
inflation in the right coronary artery or circumflex. Similarly, ST segment monitoring has also been used to predict infarct artery patency after pharmacologic reperfusion therapy.16–18 To investigate the association between early recovery from ST segment elevation and long-term mortality in patients with AMI, French et al.17 followed 766 patients treated with fibrinolytic therapy. They found that ST segment recovery in the lead with initial maximum ST segment elevation was a predictor of long-term survival (2.5 to 10 years, P = 0.03 to 0.0005), but ST segment recovery, measured as the sum of all leads with ST segment changes (or elevation), was not.
Use in Perioperative and Intraoperative Settings Cardiovascular monitoring is a cornerstone of management in the perioperative setting. Application of ST segment monitoring in an attempt to identify episodes of ischemia has been used in this setting as well.19–21 This area is not without its own controversy and discussion.22–24 Discordance may exist between ST segment changes (electrical) and transesophageal echocardiography (mechanical) as detectors of perioperative ischemia. In a comparison with post hoc analysis of intraoperative Holter recordings, various real-time ST segment
346
SECTION IV: ADVANCED TECHNIQUES AND TECHNOLOGIES
monitors were found to be of moderate sensitivity (60% to 78%) and specificity (69% to 89%) in detecting ischemia in patients undergoing coronary artery bypass surgery.25
References 1. Velez J, Brady WJ, Perron AD, Garvey L: Serial electrocardiography. Am J Emerg Med 2002;20:43. 2. Fesmire FM, Smith EE: Continuous 12-lead electrocardiograph monitoring in the emergency department. Am J Emerg Med 1993;11:54. 3. Krucoff MW, Croll MA, Pope JE, et al: Continuously updated 12-lead ST-segment recovery analysis for myocardial infarct artery patency assessment and its correlation with multiple simultaneous early angiographic observations. Am J Cardiol 1993;71:145. 4. Cohn PF, Sodums MT, Lawson WE, et al: Frequent episodes of silent myocardial ischemia after apparently uncomplicated myocardial infarction. J Am Coll Cardiol 1986;8:982. 5. Klootwijk P, Cobbaert C, Fioretti P, et al: Noninvasive assessment of reperfusion and reocclusion after thrombolysis in acute myocardial infarction. Am J Cardiol 1993;72:75G. 6. Patel DJ, Knight CJ, Holdright DR, et al: Pathophysiology of transient myocardial ischemia in acute coronary syndromes: Characterization by continuous ST-segment monitoring. Circulation 1997;95:1185. 7. Dellborg M, Andersen K: Key factors in the identification of the highrisk patient with unstable coronary artery disease: Clinical findings, resting 12-lead electrocardiogram, and continuous electrocardiographic monitoring. Am J Cardiol 1997;80:35E. 8. Drew BJ, Krucoff MW: Multilead ST-segment monitoring in patients with acute coronary syndromes: A consensus statement for healthcare professionals: ST-Segment Monitoring Practice Guideline International Working Group. Am J Crit Care 1999;8:372. 9. Fesmire FM, Percy RF, Bardoner JB, et al: Usefulness of automated serial 12-lead ECG monitoring during the initial emergency department evaluation of patients with chest pain. Ann Emerg Med 1998;31:3. 10. Gibler WB, Sayre MR, Levy RC, et al: Serial 12-lead electrocardiographic monitoring in patients presenting to the emergency department with chest pain. J Electrocardiol 1993;26(Suppl):238. 11. Garvey JL: Can ST segment monitoring beat static twelve-lead ECG? In Gibler WB (ed): Pushing the Therapeutic Envelope for Emergency Cardiac Medicine: Acute Coronary Syndromes and Beyond. New York, Health Science Communications, 2001, p. 2.
12. Sarko J, Pollack CV Jr: Beyond the twelve-lead electrocardiogram: Diagnostic tests in the evaluation for suspected acute myocardial infarction in the emergency department, part I. J Emerg Med 1997;15:839. 13. Graff L, Joseph T, Andelman R, et al: American College of Emergency Physicians Information Paper: Chest pain units in emergency departments—a report from the Short-Term Observation Services Section. Am J Cardiol 1995;76:1036. 14. Gomez MA, Anderson JL, Karagounis LA, et al: An emergency department-based protocol for rapidly ruling out myocardial ischemia reduces hospital time and expense: Results of a randomized study (ROMIO). J Am Coll Cardiol 1996;28:25. 15. Krucoff MW, Loeffler KA, Haisty WKJ, et al: Simultaneous ST-segment measurements using standard and monitoring-compatible torso limb lead placements at rest and during coronary occlusion. Am J Cardiol 1994;74:997. 16. Pasceri V, Andreotti F, Maseri A: Clinical markers of thrombolytic success. Eur Heart J 1996;17(Suppl E):35. 17. French JK, Andrews J, Manda SOM, et al: Early ST-segment recovery, infarct artery blood flow, and long-term outcome after acute myocardial infarction. Am Heart J 2002;143:265. 18. Krucoff MW, Green CE, Satler LF, et al: Noninvasive detection of coronary artery patency using continuous ST-segment monitoring. Am J Cardiol 1986;57:916. 19. Slogoff S, Keats AS, David Y, Igo SR: Incidence of perioperative myocardial ischemia detected by different electrocardiographic systems. Anesthesiology 1990;73:1074. 20. McDermott MM, Lefevre F, Arron M, et al: ST segment depression detected by continuous electrocardiography in patients with acute ischemic stroke or transient ischemic attack. Stroke 1994;25:1820. 21. Kotrly KJ, Kotter GS, Mortara D, Kampine JP: Intraoperative detection of myocardial ischemia with an ST segment trend monitoring system. Anesth Analg 1984;63:343. 22. Jopling MW: Pro: Automated electrocardiogram ST-segment monitoring should be used in the monitoring of cardiac surgical patients. J Cardiothorac Vasc Anesth 1996;10:678. 23. Proctor LT, Kingsley CP: Con: ST-segment analysis—who needs it? J Cardiothorac Vasc Anesth 1996;10:681. 24. Selbst J, Comunale ME: Myocardial ischemia monitoring. Int Anesthesiol Clin 2002;40:133. 25. Leung JM, Voskanian A, Bellows WH, Pastor D: Automated electrocardiograph ST segment trending monitors: Accuracy in detecting myocardial ischemia. Anesth Analg 1998;87:4.