Continuous ST-Segment Monitoring: Protocol for Practice

The purpose of continuous ST-segment monitoring is to provide an alert for potential ischemia.In 1999, Drew et al1 published consensus guidelines recommending use of continuous ST-segment monitoring for specific cardiac patients. However, these guidelines have not yet uniformly become the standard of practice.To aid in implementing consensus guidelines, we describe a nurse-directed hospital-wide protocol with interdisciplinary agreement on continuous ST-segment monitoring. We begin with a review of current guidelines for continuous ST-segment monitoring among hospitalized patients. Results of a brief survey of hospital use of continuous ST-segment monitoring in our community are provided to facilitate discussion of the extent of implementation of the guidelines into practice. We also review research studies and discuss current limitations of continuous ST-segment monitoring. Finally, we present implications for further research to clarify best-practice use of continuous ST-segment monitoring.Although the 12-lead electrocardiogram (ECG) is a standard for detecting ischemic coronary events, it provides a static snapshot rather than the continuous recording of dynamic changes that may be visualized by using continuous ST-segment monitoring.2 Continuous ST-segment monitoring has been available since the mid-1980s,3 but only about half of critical care units use this technology.4In light of the newly published consensus guidelines for universal definition of myocardial infarction by experts from the American Heart Association (AHA), American College of Cardiology, and other relevant organizations,5 more continuous and accurate ST-segment monitoring is needed. The consensus guidelines5 describe ECG manifestations of acute myocardial ischemia (in absence of left ventricular hypertrophy and left bundle branch block) as new ST-segment elevation at the J-point in 2 contiguous leads, with the cutoff points of more than 2 mm in men or more than 1.5 mm in women in leads V2 and V3 and/or more than 1 mm in other leads. The J-point is located at the point where the QRS segment ends. Contiguous leads that provide information on surface areas of the heart are found in Table 1.5–8 The guidelines also describe acute myocardial ischemia as ST-segment depression of greater than 0.5 mm in 2 contiguous leads and/or T-wave inversion greater than 1 mm in 2 contiguous leads with a prominent R wave.In 1999, a consensus statement1 of practical clinical guidelines for optimal use of ST-segment monitoring was published by an international interdisciplinary work group consisting of physicians, nurses, and a cardiac monitoring engineering expert. The group recommended that continuous ST-segment monitoring be included in (but not limited to) monitoring for a minimum of 24 to 48 hours in patients who were experiencing acute myocardial infarction or acute coronary syndrome (ACS) and in patients after coronary artery intervention to detect patency after thrombolytic therapy or primary angioplasty. Recommendations were based largely on expert opinion and case reports because few randomized clinical trials of continuous ST-segment monitoring had been done.In 2001, Patton and Funk4 reported on the uniformity of continuous ST-segment monitoring as a standard of practice in the United States. A random sample (n=192) of clinical nurse specialists and nurse managers were surveyed by US mail. Only 54.2% of respondents indicated that their departments used continuous ST-segment monitoring to detect ischemia in patients with ACS.In 2004, a scientific statement of practice standards for ECG monitoring in the hospital was published by the AHA and endorsed by the American Association of Critical-Care Nurses (AACN) and the International Society of Computerized Electrocardiology.3 The comprehensive best-practice standards were created to facilitate safe and effective monitoring for cardiac dysrhythmias, QT-segment monitoring, and ischemia monitoring and included guidelines for continuous ST-segment monitoring in certain patients.The task force writers of the scientific statement on practice standards for ECG monitoring3 developed a rating system (Table 2)9–15 based on research evidence and expert opinion to make recommendations about which patients should have continuous ST-segment monitoring.In 2004, AACN published a practice alert6 recommending that the standard of practice include continuous ST-segment monitoring of patients in the early phases of ACS who arrive in the emergency department with chest pain or anginal-equivalent syndromes, who have undergone a percutaneous coronary intervention with suboptimal results, or who may have a variant angina (eg, angina caused by vasospasm rather than by occlusion). The practice alert provides short, specific guidelines for monitoring based on the AHA/AACN consensus guidelines, including an audit tool for ST-segment monitoring.16In 2006, we conducted a brief community survey of 17 hospitals in and around the local St Paul/Minneapolis and Rochester, Minnesota, areas to determine use of continuous ST-segment monitoring in emergency department and inpatient areas. Of 17 hospitals surveyed, routine continuous ST-segment monitoring was used in 47% of progressive care units and 41% of intensive care units (ICUs). In hospitals in which patients were routinely monitored in an emergency department or observational unit to rule out acute myocardial infarction, only 29% of hospitals used continuous ST-segment monitoring as part of their “rule out” protocol in these departments. One small regional hospital used continuous ST-segment monitoring as a standard of practice to help determine which patients qualified for immediate transfer to a level I facility for immediate intervention (with confirmation of ST-segment changes by 12-lead ECG). Overall, use of continuous ST-segment monitoring did not appear to be related to hospital size. Results of this Midwest survey may reflect a lack of improvement in use of this type of monitoring by hospitals since the national survey in 2001.4 However, we used a convenience sample and surveyed only a single area of the United States; thus, the results may not be generalizable.Why is continuous ST-segment monitoring not a consistent standard of practice across hospitals? Probable reasons include a lack of awareness of the consensus guidelines or a published protocol, lack of acceptance by physician and nurse leaders who may be awaiting the results of clinical trials to support a stronger level of evidence, and lack of education for nurses about what to do when findings on continuous ST-segment monitoring are abnormal.More clinical trials and awareness of existing trials are needed to strengthen the perceived level of evidence for continuous ST-segment monitoring. The level of evidence for use of this type of monitoring in hospitalized patients was initially based largely on expert opinion, case reports, and consensus guidelines. No controlled, randomized clinical trial has definitively indicated that patients who receive continuous ST-segment monitoring have better outcomes than do patients who do not have the monitoring. However, strong descriptive and comparative studies with prospective designs have been published.Jernberg et al17 found that use of multilead ST-segment monitoring in patients with ACS allowed prospective identification of patients who had the best response to longer treatment with low-molecular-weight heparin, thus resulting in lower rates of mortality, myocardial infarction, and revascularization (35.3% vs 53.4%; relative risk reduction, 34%; P=.01). Researchers in a substudy18 of the Global Utilization of Streptokinase and TPA for Occluded Coronary Arteries (GUSTO-I) trial concluded that recurrent ST-segment elevation as detected via continuous ST-segment monitoring was an independent predictor of mortality, even after consideration of multiple clinical risk factors in the GUSTO mortality model.In a multisite, prospective, comparative study of 1777 patients, Maas et al19 found that age, heart rate, and late ST-segment elevation were independent risk factors for adverse clinical outcomes. ST subgroupings resulted in significant stratification for both low- and high-risk patients for the composite end points (in-hospital death and combined death, reinfarction, or congestive heart failure). Maas et al concluded that continuous ST-segment monitoring is helpful in assessing response to therapy, especially in high-risk patients more than 70 years old.In patients with ACS, transient myocardial ischemia is an independent predictor of worse outcomes. In a study20 conducted at various sites in Canada, 681 patients admitted with non–ST-elevation ACS were randomly assigned to receive either enoxaparin or intravenous unfractionated heparin. At 30 months, patients with ST-segment shifts were more likely to die (17.7% vs 5.8%; P<.001) and to reach the composite end point for worse outcomes (24.6% vs 11.1%; P < .001) than were patients without such shifts. After adjustments for risk scores, the presence of ST-segment shifts on continuous ECGs was a stronger independent predictor of mortality than were the findings on admission 12-lead ECGs.20 Several other investigators reported that using continuous ST-segment monitoring helped to predict patients’ severity of disease at a variety of time points: during hospitalization,19,21,22 after discharge,23 and in long-term follow-up.24In the first study involving a comprehensive evaluation of ST-segment changes before, during, and after percutaneous coronary intervention, Terkelsen et al25 performed continuous ST-segment monitoring in 92 patients with ST-elevation myocardial infarction, from ambulance through the percutaneous procedure until 90 minutes after the procedure. The results indicated that a prespecified ST-monitoring classification was useful for stratifying patients at the time of percutaneous coronary intervention into groups at low, intermediate, and high risk. Terkelsen et al25 recommended use of continuous ST-segment monitoring for an early indication of the degree of reperfusion after percutaneous intervention.Akkerhuis et al26 performed a meta-analysis of 3 prospective clinical trials (n=995) with retrospective blinded analysis of recordings of continuous monitoring done in a core laboratory. They found that the number of ischemic episodes in 24 hours was directly proportionate to the probability of cardiac events at 5 and 30 days. After known baseline predictors of worse outcomes were controlled for, each transient ischemic event was predictive of a 25% increase in the risk of death or myocardial infarction at 5 and 30 days. Akkerhuis et al26 concluded that integration of continuous ST-segment monitoring via a 12-lead ECG system was warranted in the emergency and coronary care departments to enable early identification of patients who may benefit from early revascularization.Finally, in an ongoing study, Drew et al27 are investigating whether prehospital ST-segment monitoring with telephone transmission of ST events to the target hospital can improve hospital time-to-treatment in patients with ACS. Results from this study will add to the body of literature and may provide support for the use of continuous ST-segment monitoring in a prehospital environment.Patients with silent or unrecognized ischemia may benefit from continuous ST-segment monitoring. Reported rates of silent ischemia among hospitalized patients vary, from 21% to 77%, depending on the type of patient, hours of monitoring, and method of continuous ST-segment monitoring.17,28–30 Gunnarsson et al31 reported that continuous, real-time multilead ST-segment monitoring was as accurate as or more accurate than standard 12-lead ECG monitoring.Kress et al15 used continuous 3-lead Holter monitors with blinded ST-segment analysis by a cardiologist to detect myocardial ischemia in ICU patients receiving mechanical ventilation who had risk factors for coronary artery disease. Ischemia was defined as ST-segment elevation or depression of more than 0.1 mV from baseline. Myocardial ischemia was detected among 24% of patients, who subsequently had a longer ICU stay (mean, 17.4 days; SD, 17.5 vs mean, 9.6 days; SD, 6.7; P=.04) than did patients without ischemia. The study involved patients receiving continuous ST-segment monitoring to detect ischemia while being awakened from sedation. Continuous ST-segment monitoring was a more helpful end point than troponin T level for detecting myocardial ischemia because many patients had preexisting troponin leaks that could not be “undone” and because continuous ST-segment monitoring provided real-time data (rather than a static troponin marker).Certain populations of patients with coronary ischemia, such as women and patients with diabetes mellitus, may have atypical anginal symptoms. In a large study20 of patients with myocardial infarction, 33% did not have chest pain on arrival at the hospital. Patients without chest pain, compared with patients with chest pain, were significantly more likely to be women, have diabetes, or have prior heart failure. Additionally, patients with myocardial infarction without chest pain had a longer delay before going to a hospital (mean, 7.9 vs 5.3 hours); were less likely to have a diagnosis of confirmed myocardial infarction at the time of admission (22.2% vs 50.3%); and were less likely to receive thrombolysis or primary angioplasty (25.3% vs 74.0%), aspirin (60.4% vs 84.5%), β-blockers (28.0% vs 48.0%), or heparin (53.4% vs 83.2%).In another study,32 patients with myocardial infarction without chest pain had a 23.3% in-hospital mortality rate compared with a rate of 9.3% among patients with chest pain. Pope et al33 also reported that failure to hospitalize patients who had acute myocardial infarction or unstable angina (missed diagnoses) was significantly related to the absence of typical features of cardiac ischemia.Less well-recognized populations of patients vulnerable to silent ischemia may include patients with confusion and patients who cannot communicate effectively (eg, patients who are sedated and intubated, mentally impaired, or experiencing acute delirium). Continuous ST-segment monitoring may be helpful in detecting silent ischemia. Once ischemia is detected, interventions can be initiated that increase chances for maintaining viable myocardial tissue. In this era of widespread interventional capability, nurses caring for cardiac patients should examine available technology that alerts caregivers to changes in cardiac status.Nurse leaders and biomedical engineers must carefully consider continuous ST-segment monitoring preferences and alarm levels based on published recommendations. Number and volume of audible alarms should be designated to avoid “nuisance alarms.”34 Too many false-positive alarms may reduce the sensitivity of nurses and thus their response, as well as physicians’ responses.In addition to concerns about continuous ST-segment monitoring, general bedside ECG monitoring has concerns related to quality assurance that must be addressed. Drew et al35 identified several weaknesses of ECG monitoring, including lack of skin preparation before ECG patches are applied and inaccurate placement of ECG leads. If the lead that overlies the current of injury is not the one selected for continuous ST-segment monitoring, a sense of false assurance may result, with potential for missed ischemia.Even when ECG patches are and by nurses, certain limitations in current bedside ST-segment monitoring. current in-hospital monitors do not detect T-wave which may be the only of ischemia in patients. or patients may that false that ST monitoring be that do not become to ST alarms and to patients from being with of nurses for ECG monitoring to be ongoing and evidence Results of a in which to ischemic from ECG was were only of nurses were to the presence or absence of ischemia in However, et found that after the of critical care nurses in their sample a on and bedside of ST were to done in a core education must be by ongoing of and placement based on the monitoring of each are a core education level of education may more than a single to ECG monitoring. may also unit that monitoring lead to the of patients Additionally, of lead placement may of or nurses, who may be or quality assurance are needed to the lead placement of a sample of critical care nurses for not using ST monitoring was the lack of by that practice changes in cardiac monitoring interdisciplinary are not of the consensus guidelines for cardiac monitoring. interdisciplinary discussion and agreement on ECG monitoring is a in about ECG monitoring heart rates and is needed to the current of The in cardiac has from of a of myocardial and to and intervention when ST-segment changes that may ischemia are intervention, of an left may death of the and thus of heart Nurses in hospitals without an physician their on ST on the 12-lead ST-segment results whether or not a level I hospital is for transfer of a with ACS. and accurate identification of ischemia that acute care nurses use critical about a monitoring the leads selected for monitoring a may be based on or a unit protocol rather than a critical about the for monitoring. patients who have undergone cardiac lead is used to avoid a lead the lead is helpful for and ventricular and However, may not be the best lead for depending on the artery that was Table a were the coronary artery and the left the best leads be and V2 or units have to only 1 lead and 1 lead and have routinely used or and for monitoring these leads may provide ECG may be depending on the primary a nurse to for of a ventricular use of a standard lead may be the is to for of the selected lead may be However, the for monitoring a who has had revascularization of the left the nurse may only leads and are selected for monitoring. The nurse more a lead that monitors the surface of the heart or nurses should lead on the monitoring of each this it more than an in ECG monitoring. Nurses for cardiac monitoring should receive the ongoing education to critical about lead to a and the of continuous ST-segment monitoring to or for accurate ST lack of practice and lack of consensus by about the for continuous ST-segment monitoring. The provided for nurse leaders implementation of ST-segment monitoring A included clinical education of nurses, physicians, and who should be to leads and changes in the ST segment elevation vs after a coronary intervention, false and patients’ and with a in to better the clinical of changes in the ST for for continuous ST-segment monitoring have been by Drew and and A of nurses have published clinical continuous ST-segment monitoring is used in their One of the reports from nurses in who the of use of this technology and who used 2 case studies to continuous ST-segment monitoring via 12-lead ECG provided information in a who emergency percutaneous intervention during a myocardial infarction and a who thrombolytic therapy for an myocardial In the patient, continuous ST-segment monitoring provided early of the was to percutaneous coronary et used case studies to nurses in the coronary care unit at monitored ST via a real-time 12-lead The a risk stratification of patients with ST-segment monitoring for to use during for ACS. A specific protocol was not we found of a protocol that is in use a we provide our ST-monitoring protocol, with to perceived limitations of continuous ST-segment monitoring.In Heart of the United continuous ST-segment monitoring was in the early a ECG lead is nurse on the ICU or progressive care unit is to a cardiac Nurses new to cardiac monitoring receive a into 3 a of to 2 by of on the clinical and ECG hours are but are not only on ST-segment monitoring is provided in the cardiac new nurses receive further from the nurse on their units on the protocol for use of continuous ST-segment monitoring. to for patients who do not benefit from continuous ST-segment monitoring. nurses are to the alarm and to and alarm and are of the of 12-lead agreement was that the standard practice for using continuous ST-segment monitoring be by cardiac and A by the interdisciplinary group was that that the ST alarm must be the for patients. nurses must ST alarms to for patients who (Table a physician about an ST the nurse first that the patches are and that the alarm is not to an an caused by of the for in the ST segment for minutes (with or without or the nurse an 12-lead ECG to that ST changes are The is to findings on the 12-lead ECG of ischemia before the physician is this protocol, we are to reduce the number of telephone for false ECG is because nurses continuous ST-segment monitoring alarms when a admitted to rule out ACS for for cardiac are and ST changes are will have continuous ST-segment monitoring after a physician a diagnosis of for a who has further intervention but to have alarms on ST-segment monitoring, the nurse can an from a physician to increase alarm to to the protocol were after case studies of patients were studies provided to patients’ and interdisciplinary studies may also provide a for discussion among for to consensus guidelines into practice. will be published in in which case studies are used to practical of a protocol and related education for continuous ST-segment use of chest pain units for ACS patients should whether continuous ST-segment monitoring is used and should consider of units to receive or not receive continuous ST-segment monitoring that the of this monitoring can be further to be implementation of continuous ST-segment monitoring in patients being because of chest pain may include evaluation of whether continuous ST-segment monitoring can be used with cardiac to detect study could include a in the number of inpatient a in the number of missed of myocardial and of in treatment based on the results of continuous ST-segment monitoring. of an outcomes before and after implementation of continuous ST-segment monitoring could include whether continuous ST-segment monitoring provided of ischemia, and the time to cardiac in patients at risk for silent ischemia. and of are needed to interventions when alarms during continuous ST-segment research is needed to better clarify which populations of patients will benefit from continuous ST-segment monitoring, as well as the of time monitoring should be analysis of based on changes in the ST segment is study is needed on in the ST segment after cardiac Finally, the bedside monitoring that with the of is and is may improve use of this and should consider whether nurses in the and progressive care units have education in ECG monitoring. A discussion of education is for implementing for continuous ST-segment monitoring. The level of critical in technology to be by ongoing and to with nurses in the of continuous ECG monitoring used in hospitals where the patients. If continuous ST-segment monitoring is initiated as a new in a nurse leaders in education and practice should consider outcomes before and after the Nurses to from each especially about for alarm and when to an guidelines for use of continuous ST-segment monitoring. hospitals have not guidelines for this type of monitoring, and practice has been limited by lack of published on to the guidelines of the guidelines interdisciplinary discussion among nurse and biomedical engineers for alarm before monitoring and standards of practice for to our we the use of continuous ST-segment monitoring with a protocol developed by a clinical nurse and by an interdisciplinary The protocol included to of continuous ST-segment monitoring alarms and to a 12-lead ECG before a thus telephone for false-positive of consensus guidelines into practice work was performed at Heart United We the involved with cardiac monitoring at United of United the ECG and of the Heart

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