Cardiac Monitoring

by Stacey Chamberlain

Case Presentation

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 reported 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 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 (EKG from www.lifeinthefastlane.com):

https://i2.wp.com/lifeinthefastlane.com/wp-content/uploads/2011/02/ECG-Potassium-7-peaked-T-waves.jpg?ssl=1

You send a blood chemistry test, place the patient on a cardiac monitor and one hour later note the following on the monitor (EKG from www.lifeinthefastlane.com):

 

https://i0.wp.com/lifeinthefastlane.com/wp-content/uploads/2011/02/disappearance-p-waves-hyperk.jpg?ssl=1

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 is at the end of the chapter.

Introduction

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 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, of course, is for capturing transient arrhythmias, ectopic beats, or monitoring 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 to look 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 for 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. This comprehensive document outlines the indications for cardiac monitoring, the specific skills required of the practitioner for cardiac monitoring, and specific ECG abnormalities that the practitioner should recognize.

Cardiac monitoring is essential for those patients who are at risk for an acute, life-threatening arrhythmia. The AHA guidelines divide indications for cardiac monitoring in the inpatient setting into three classes. Cardiac monitoring is considered indicated in “most, if not all” patients in Class I, which includes 16 subcategories. In Class II, cardiac monitoring “may be of benefit in some patients but is not considered essential for all patients” and has 10 subcategories. For Class III, cardiac monitoring is not indicated.

Indications for Cardiac Monitoring

Adopted from AHA consensus document

Class I Indications

Cardiac monitoring is considered indicated in “most, if not all” patients in Class I

  1. Patients who have been resuscitated from cardiac arrest
  2. Patients in the early phase of acute coronary syndromes (ST-elevation or non–ST-elevation MI, unstable angina/“rule-out” MI)
  3. Patients with unstable coronary syndromes and newly diagnosed high-risk coronary lesions (for 24 hours)
  4. Adults or children who have undergone cardiac surgery
    (minimum of 48 to 72 hours)
  5. Patients who have undergone non-urgent percutaneous coronary intervention with complications
  6. Patients who have undergone implantation of an automatic defibrillator lead or a pacemaker lead and are considered pacemaker dependent
  7. Patients with a temporary pacemaker or transcutaneous pacing pads
  8. Patients with AV block
  9. Patients with arrhythmias complicating Wolff-Parkinson-White syndrome with rapid anterograde conduction over an accessory pathway
  10. Patients with long-QT syndrome and associated ventricular arrhythmias
  11. Patients receiving intra-aortic balloon counter-pulsation
  12. Patients with acute heart failure/pulmonary edema
  13. Patients with indications for intensive care
  14. Patients undergoing diagnostic/therapeutic procedures requiring conscious sedation or anesthesia
  15. Patients with any other hemodynamically unstable arrhythmia
  16. Diagnosis of arrhythmias in pediatric patients

Class II Indications

Cardiac monitoring “may be of benefit in some patients but is not considered essential for all patients.”

  1. Patients with post-acute MI (24 to 48 hours after admission)
  2. Patients with chest pain syndromes
  3. Patients who have undergone uncomplicated, non-urgent percutaneous coronary interventions
  4. Patients who are administered an antiarrhythmic drug or who require adjustment of drugs for rate control with chronic atrial tachyarrhythmias
  5. Patients who have undergone implantation of a pacemaker lead and are not pacemaker dependent
  6. Patients who have undergone uncomplicated ablation of an arrhythmia
  7. Patients who have undergone routine coronary angiography
  8. Patients with sub-acute heart failure
  9. Patients who are being evaluated for syncope
  10. Patients with do-not-resuscitate orders with arrhythmias that cause discomfort

Class III

Cardiac monitoring is not indicated

  1. Postoperative patients who are at low risk for cardiac arrhythmias (e.g. young patients without heart disease who undergo uncomplicated surgical procedures)
  2. Obstetric patients, unless heart disease is present
  3. Patients with permanent, rate-controlled atrial fibrillation
  4. Patients undergoing hemodialysis (unless they have a class I or II indication)
  5. Stable patients with chronic ventricular premature beats

“Must Know” Arrhythmias

One of the most critical skills of an ED physician is 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. AHA guidelines list the specific arrhythmias that the ED physician must be able to recognize.

Specific Arrhythmias (adopted from AHA Scientific Statement)

  • 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
  • Muscle or other artifacts simulating arrhythmias

Approach

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. 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., 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 from above the AV node. Colloquially, when many practitioners refer to “SVT” however, they are actually 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. 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 patient’s vital signs are of utmost importance in determining the management for these patients. A nice summary of this issue with rhythm strip examples is provided on the FOAM site “Life in the Fast Lane.”

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 perpetrated by fictitious TV shows and movies. For unstable patients with arrhythmias in patients who still have palpable pulses, synchronized cardioversion may be used.

In regards to medications, for certain rhythms and clinical scenarios, only vasopressor types of medications are used (e.g., epinephrine for asystole). For other rhythms and scenarios, anti-arrhythmic medications are used (e.g., amiodarone for v-tach). For supraventricular tachyarrhythmias, atrioventricular (AV) nodal blocking agents are often necessary. One author suggests using a five “As” approach to treating emergency arrhythmias, keeping in mind the medications adenosine, amiodarone, adrenaline (epinephrine), atropine and ajmaline. 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 and in many cases, determining the underlying precipitant of the arrhythmia and tailoring treatment to that cause. The emergency physician must familiarize himself with each rhythm and its unique management in any given clinical scenario.

Some useful internet resources for the ED practitioner are provided at the end of this chapter for practice interpreting EKGs and cardiac rhythms.

Case Discussion

The ED practitioner should recognize that the 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 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 an 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.

References and Further Reading

  • 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
  • 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. Heart 2001;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

Links To More Information

  • 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