Definitions and Overview
Cardiac monitoring in the emergency setting is continuous monitoring of a patient’s cardiac activity in order to identify conditions that may require emergent intervention. These conditions include certain arrhythmias, ischemia and infarction, and abnormal findings that could signal impending decompensation. This chapter focuses specifically on cardiac monitoring or electrocardiography; additional methods of continuous hemodynamic monitoring in the emergency department (ED) include pulse oximetry, end-tidal CO2 monitoring, central venous pressure monitoring, and continuous arterial blood pressure monitoring. Of note, telemetry is the ability to do cardiac monitoring from a remote location; in practice, this is often a centralized system that might be located at a nursing station where multiple patients can be monitored remotely.
Cardiac monitoring differs from a 12-lead electrocardiogram in that it is done continuously over a period of time rather than capturing one moment in time in a static image. The benefit of this is that it captures transient arrhythmias and ectopic beats or monitors for changes over time. A disadvantage of cardiac monitoring is that typically, only 2 leads are displayed instead of a full 12 leads, giving a less comprehensive view of the heart and limiting its utility for looking for anatomic patterns. For example, on the 12-lead EKG, ED practitioners usually group the inferior, anterior, and lateral leads when looking for ischemic or infarct patterns. These may be less evident on a monitor with only two leads. Additionally, the static EKG allows the ED physician to carefully study it for subtle findings, for example, to make measurements of intervals, whereas in real-time monitoring, this is very difficult. In practice, both modalities are commonly used in conjunction for many ED patients.
The American Heart Association (AHA) published a consensus document in 2004 establishing practice standards for electrocardiographic monitoring in hospital settings, which was updated in 2017 [1,2]. These comprehensive documents outline the indications for cardiac monitoring, the specific skills required of the practitioner for cardiac monitoring, and specific ECG abnormalities that the practitioner should recognize. The 2017 update addressed the overuse of arrhythmia monitoring among certain populations, appropriate use of ischemia and QT-internal monitoring among select populations, alarm management, and documentation in electronic health records [2].
Cardiac monitoring is essential for those patients who are at risk for an acute, life-threatening arrhythmia and can also be used to evaluate for developing ischemia, response to therapy, and as a diagnostic tool. The AHA guidelines divide indications for cardiac monitoring in the inpatient setting into four classes based on varying degrees (level A, B, C) of evidence. Cardiac monitoring is considered indicated in patients in Class I. In Class IIa, it “is reasonable to perform” cardiac monitoring, whereas in Class IIb, it “may be considered.” For Class III, cardiac monitoring is not indicated as there is no benefit or there may actually be harm. Newer guidelines tailor the recommendations based on specific patient populations and whether the cardiac monitoring is for arrhythmia or continuous ST-segment ischemic monitoring [2]. Specific patient populations that are considered include patients with:
- Chest pain or coronary artery disease.
- Major cardiac interventions such as open heart surgery.
- Arrhythmias.
- Syncope of suspected cardiac origin.
- After electrophysiology procedures/ablations.
- After pacemaker or ICD implantation procedures.
- Pre-existing rhythm devices.
- Other cardiac conditions (acute decompensated heart failure or infective endocarditis).
- Non-cardiac conditions (e.g., post-conscious sedation or post-non-cardiac surgery).
- Specific medical conditions (e.g., stroke, imbalance of potassium or magnesium, drug overdose, or hemodialysis).
- DNR/DNI status.
Table 1 lists Class I-III recommendations. The AHA Scientific Statement provides a more comprehensive and detailed list.
Table 1 – Select Indications for Cardiac Monitoring
Class I Indications | Early phase ACS or after MI |
| After open-heart surgery or mechanical circulatory support |
| Atrial tachyarrhythmias |
| Symptomatic sinus bradycardia |
| 2nd or 3rd degree AV block (exception as noted below for asymptomatic Wenckebach) |
| Congenital or genetic arrhythmic syndrome (e.g. WPW, Brugada, LQTS) |
| After stroke |
| With moderate to severe imbalance of potassium or magnesium |
| After drug overdose |
Class IIa and IIb Indications | Non-sustained VT |
| Asymptomatic, significant bradycardia with negative chronotropic medications initiated |
| After non-cardiac major thoracic surgery |
| Chronic hemodialysis patients without other indications (e.g. hyperkalemia, arrhythmia) |
Class III Indications | After non-urgent PCI without complications or after routine diagnostic coronary angiography |
| Patients with chronic atrial fibrillation, sinus bradycardia, or asymptomatic Wenckebach who are hemodynamically stable and admitted for other indications |
| Asymptomatic post-operative patients after non-cardiac surgery |
| DNR/DNI patients when the data will not be acted on and comfort-focused care is the goal |
Ischemia Monitoring
Continuous ST-Segment Ischemia Monitoring was highlighted in the 2017 AHA guidelines as a specific indication for cardiac monitoring for patients most at risk for ischemia. Older monitors may not have this capability, but more modern monitors are programmed with automated ischemia monitoring that identifies abnormal ST-segment elevation or depression; manufacturers do not automatically enable this capability, and it may be turned on or off. To reduce unnecessary alarms, it is recommended (IIa level) to enable this function only in high-risk patients in the early phase of ACS and to individualize which lead should be prioritized based on the coronary artery suspected to be affected by an ischemic process. High-risk patients would include those being evaluated for vasospastic angina, those presenting with MI, post-MI patients without revascularization or with residual ischemic lesions, and newly diagnosed patients with a high-risk lesion such as a left main blockage.
QTc Monitoring
QTc monitoring aims to assess the safety of QT-prolonging medications and avoid Torsade de Pointes (TdP). Most hospitals do not have fully automated continuous QTc monitoring, so QTc monitoring and measurements may need to be performed manually or semi-automated with digital calipers. Regardless of the method, in general, recommendations for QTc monitoring are for patients with specific risk factors for TdP who are started on anti-arrhythmic drugs with a known risk for TdP (e.g., dofetilide, sotalol, procainamide, quinidine, and others), patients with a history of prolonged QTc started on non-anti-arrhythmic drugs with risk for TdP, those undergoing targeted temperature management, specific electrolyte derangements, and select drug overdoses. As with ischemic monitoring, QTc monitoring is not universally recommended for all patients, so consulting the 2017 guidelines for select patient scenarios is best.
Rhythm Interpretation
One of the most critical skills of an ED physician is in interpreting both static EKGs and interpreting arrhythmias on a cardiac monitor. A skilled practitioner must be able to diagnose common arrhythmias and be well-versed in the management of acute arrhythmias, recognizing which arrhythmias necessitate immediate action and which are less worrisome. Table 2 from the 2004 AHA guidelines lists the specific arrhythmias that the ED physician must be able to recognize. How and whether to treat an arrhythmia depends on many factors. The AHA has established algorithms for specific rhythms, including ventricular fibrillation (v-fib)/pulseless ventricular tachycardia (v-tach) and pulseless electrical activity (PEA)/asystole, as well as for non-specific rhythm categories such as bradycardia and tachycardia [3]. Additionally, they have published algorithms for clinical scenarios, including cardiac arrest, acute coronary syndrome, and suspected stroke.
The first step in the assessment of any rhythm is a clinical assessment of the patient. The premier issue of concern is if the patient is perfusing vital organs. A quick survey of the patient assessing mental status and pulses is essential to determining management. The management of a patient with v-tach will be substantially different if the patient is unresponsive and pulseless versus if the patient is awake with good pulses. As another example, the physician can quickly distinguish artifact from v-fib on the cardiac monitor by assessing the patient, as v-fib is not a perfusing rhythm.
The initial assessment of tachyarrhythmias (heart rate > 100) is to determine if the rhythm is “narrow-complex” (i.e., a QRS duration < 0.12s) or “wide-complex” (i.e., a QRS duration of 0.12s or greater). A narrow complex rhythm is considered a supraventricular rhythm (originating above the ventricles). Supraventricular tachycardia is a generic term encompassing any narrow-complex tachycardias originating above the AV node. Colloquially, when many practitioners refer to “SVT,” however, they are referring to a specific subcategory of supraventricular tachycardia called AV nodal re-entrant tachycardia (AVNRT). Wide complex tachycardias either originate in the ventricles or could originate in the atria and have an associated bundle branch block. Different criteria have been developed to help the practitioner distinguish between ventricular tachycardia and an SVT “with aberrancy” (i.e., aberrant conduction either due to an accessory path such as in Wolff-Parkinson-White or with a bundle branch block), the most well known of which are the Brugada criteria [4,5]. Practically speaking, many ED practitioners will assume the more dangerous and potentially unstable rhythm (v-tach) until proven otherwise; of course, the clinical picture and the patient’s vital signs are of utmost importance in determining the management of these patients. An excellent summary of this issue with rhythm strip examples is provided on the FOAM site “Life in the Fast Lane” [6].
Table 2 – Specific Arrythmias (adapted from AHA Scientific Statement [1])
Normal rhythms |
| |
| Normal sinus rhythm | |
| Sinus bradycardia | |
| Sinus arrhythmia | |
| Sinus tachycardia | |
Intraventricular conduction defects |
| |
| Right and left bundle-branch block | |
| Aberrant ventricular conduction | |
Bradyarrhythmias |
| |
| Inappropriate sinus bradycardia | |
| Sinus node pause or arrest | |
| Non-conducted atrial premature beats | |
| Junctional rhythm | |
AV blocks |
| |
| 1st degree | |
| 2nd degree Mobitz I (Wenckebach) or Mobitz II | |
| 3rd degree (complete heart block) | |
Asystole |
| |
Pulseless electrical activity (PEA) |
| |
Tachyarrhythmias |
| |
| Supraventricular | Paroxysmal supraventricular tachycardia (AV nodal reentrant, AV reentrant) |
Atrial fibrillation | ||
Atrial flutter | ||
Multifocal atrial tachycardia | ||
Junctional ectopic tachycardia | ||
Accelerated ventricular rhythm | ||
Ventricular | Monomorphic and polymorphic ventricular tachycardia | |
Torsades de pointes | ||
Ventricular fibrillation | ||
Premature complexes |
| |
| Supraventricular (atrial, junctional) | |
| Ventricular | |
Pacemaker electrocardiography |
| |
| Failure to sense | |
| Failure to capture | |
| Failure to pace | |
ECG abnormalities of acute myocardial ischemia |
| |
| ST-segment elevation, depression | |
| T-wave inversion | |
Muscle or other artifacts simulating arrhythmias |
| |
While each rhythm has distinctive management, it is worth noting for the novice learner that only v-fib and pulseless v-tach warrant asynchronized mechanical defibrillation (i.e. “shocking” the patient). Many students are stunned upon observing an asystolic cardiac arrest code to learn that shocking a “flatline” (i.e., asystolic) patient is an inappropriate treatment perpetuated by fictitious TV shows and movies. For unstable patients with arrhythmias but still have palpable pulses, synchronized cardioversion may be used.
Regarding medications, for certain rhythms and clinical scenarios, only vasopressor types of medications are used (e.g., epinephrine for asystole). For other rhythms and scenarios, antiarrhythmic medications are used (e.g., amiodarone for v-tach). Atrioventricular (AV) nodal blocking agents are often necessary for supraventricular tachyarrhythmias. One author suggests using a five “As” approach to treating emergency arrhythmias, keeping in mind the medications adenosine, amiodarone, adrenaline (epinephrine), atropine, and ajmaline [7]. Ajmaline is an antiarrhythmic that is not commonly used in English-speaking countries where procainamide is more common as an alternative to amiodarone for unstable v-tach.
Additional interventions may include pacemaker placement for symptomatic heart blocks. In many cases, the ED practitioner must also determine the underlying precipitant of the arrhythmia and tailor treatment to that cause. The emergency physician must familiarize himself with each rhythm and its unique management in any given clinical scenario.
At the end of this chapter, some good internet resources for the ED practitioner to practice interpreting EKGs and cardiac rhythms are provided.
Case Example
A 44-year-old male patient with a history of hypertension and end-stage renal disease on hemodialysis presents with shortness of breath after missing dialysis for 6 days. He reports gradual onset shortness of breath associated with orthopnea and increased lower extremity edema. He denies chest pain or palpitations. He does not have any cough or fever. On physical exam, he is in no distress, afebrile with a heart rate of 60, respiratory rate of 20, blood pressure of 140/78 mmHg, and oxygen saturation of 98% on room air. He has a regular rate and rhythm without murmurs and has crackles bilaterally to the inferior 1/3 of the lung bases and 1+ pitting edema of the bilateral lower extremities.
You decide to get an EKG, which shows the following:
You send a blood chemistry test, place the patient on a cardiac monitor, and one hour later note the following on the monitor:
What are the indications for cardiac monitoring in this patient? What EKG abnormalities do you see? What does the rhythm strip show? What is the treatment?
Case Discussion
The ED practitioner should recognize potentially life-threatening conditions that a patient who has missed hemodialysis is at risk for are fluid overload (leading to pulmonary edema) and hyperkalemia. This patient could be considered to meet the Class I monitoring criteria for “needing intensive care” and possibly with “pulmonary edema”; however, even if the patient had no symptoms, the patient is indeed at risk for an acute life-threatening arrhythmia that would necessitate cardiac monitoring.
The EKG demonstrates peaked T waves indicative of acute hyperkalemia. Given the clinical picture of missed dialysis and the peaked Ts on the EKG, the ED physician should immediately initiate treatment for acute hyperkalemia without waiting for a confirmatory blood test (unless immediate point-of-care tests are available). If the patient’s hyperkalemia progressed, the patient could develop QRS widening with the morphology as shown on the rhythm strip called a “sine wave.” This dangerous finding could precipitously deteriorate into a life-threatening arrhythmia such as pulseless v-tach with cardiac arrest and should prompt immediate action. It is important to note that hyperkalemia can manifest in a variety of different EKG findings and does not always follow a consistent pattern from peaked Ts to QRS widening to sine waves; therefore, the patient should be treated at the first indication of any hyperkalemia-related EKG changes.
Conclusions
Cardiac monitoring is an important tool to monitor patients at risk for acute arrhythmias (including those at risk specifically for TdP) and acute or worsening cardiac ischemia. It can be helpful to immediately identify patients with life-threatening arrhythmias who need immediate intervention, to assess the response to medications for arrhythmias, and to help exclude arrhythmias as a likely etiology of a patient’s symptoms (e.g., a patient with syncope) [9]. Given the limited resources and the lack of benefits for many patients, the purpose and duration of cardiac monitoring should be carefully considered. Overuse can not only waste resources but can also contribute to alarm hazards, including “alarm fatigue,” where clinicians are barraged by so many false or nonactionable alarm signals that they become desensitized and do not respond to real events. Therefore, appropriate use and staff education are critical to maximizing the benefits of cardiac monitoring.
Author
Stacey Chamberlain
Dr. Stacey Chamberlain is a board certified emergency physician who is a Professor in the Department of Emergency Medicine at the University of Illinois at Chicago (UIC). She also serves as the Director of the Global Emergency Medicine Fellowship Program and the Co-Director of the Social Emergency Medicine Fellowship Program. In addition to her work in Emergency Medicine, she is the Director of Academic Programs at the UIC Center for Global Health. In this role, she oversees the Global Medicine (GMED) Program for UIC medical students and the graduate global health certificate programs. Dr. Chamberlain has done clinical, educational, public-health, disaster-response, and emergency medicine development work, including working with several globally-focused NGOs, spanning five continents. Her global health work focuses on capacity building in emergency care in Uganda.
Listen to the chapter
2018 version of this topic – https://iem-student.org/cardiac-monitoring/
References
- Drew BJ, Califf RM, Funk M, Kaufman ES, Krucoff MW, et al. AHA Scientific Statement: Practice Standards for Electrocardiographic Monitoring in Hospital Settings. Circulation. 2004; 110: 2721-2746. doi: 10.1161/01.CIR.0000145144.56673.59
- Sandau KE, Funk M, Auerbach A, Barsness GW, Blum K, Cvach M, Lampert R, May JL, McDaniel GM, Perez MV, Sendelbach S, Sommargren CE, Wang PJ; American Heart Association Council on Cardiovascular and Stroke Nursing; Council on Clinical Cardiology; and Council on Cardiovascular Disease in the Young. Update to Practice Standards for Electrocardiographic Monitoring in Hospital Settings: A Scientific Statement From the American Heart Association. Circulation. 2017 Nov 7;136(19):e273-e344. doi: 10.1161/CIR.0000000000000527. Epub 2017 Oct 3. PMID: 28974521.
- ACLS Training Center. Algorithms for Advanced Cardiac Life Support 2015. Dec 2, 2015. Accessed at: https://www.acls.net/aclsalg.htm, Dec 10, 2015.
- Wellens HJJ. Ventricular tachycardia: diagnosis of broad QRS complex tachycardia. Heart2001;86:579-585 doi:10.1136/heart.86.5.579.
- Brugada P, Brugada J, Mont L, Smeets J, Andries EW. A new approach to the differential diagnosis of a regular tachycardia with a wide QRS complex. Circulation. 1991; 83: 1649-1659. doi: 10.1161/01.CIR.83.5.1649
- Burns E. VT versus SVT with aberrancy. Life in the Fast Lane. Accessed at: http://lifeinthefastlane.com/ecg-library/basics/vt_vs_svt/, Dec 10, 2015.
- Trappe H-J. Concept of the five ‘A’s for treating emergency arrhythmias. J Emerg Trauma Shock. 2010 Apr-Jun; 3(2): 129–136. doi: 10.4103/0974-2700.62111
- Ramzy M. Duration of Electrocardiographic Monitoring of Emergency Department Patients with Syncope. REBEL EM blog; June 13, 2019; Available at: https://rebelem.com/duration-of-electrocardiographic-monitoring-of-emergency-department-patients-with-syncope/.
Additional Online Resources
- Arrhythmias practice strips and skills http://www.practicalclinicalskills.com/arrhythmia.aspx
- ECG library. Life in the Fast Lane http://lifeinthefastlane.com/ecg-library/
- ECG examples. ECGPedia. http://en.ecgpedia.org
- FOAMEd summary of use of inpatient continuous electrocardiographic monitoring: Chief Corner: Continuous Electrocardiographic Monitoring; June 22, 2018; Accessed May 19, 2023 at: https://www.thesilverfridge.com/blog/2018/6/22/chief-corner-continuous-electrocardiographic-monitoring
Reviewed and Edited By
Arif Alper Cevik, MD, FEMAT, FIFEM
Prof Cevik is an Emergency Medicine academician at United Arab Emirates University, interested in international emergency medicine, emergency medicine education, medical education, point of care ultrasound and trauma. He is the founder and director of the International Emergency Medicine Education Project – iem-student.org, vice-chair of the International Federation for Emergency Medicine (IFEM) core curriculum and education committee and board member of the Asian Society for Emergency Medicine and Emirati Board of Emergency Medicine.
