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Arrhythmias and Cardiac Emergencies, Lecture notes of Nursing

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Arrhythmias and Cardiac Emergencies
Sandra Goldsworthy, David Waters
CHAPTER ELEVEN
}
LEARNING OUTCOMES
After completing this chapter you will be able to:
Systematically interpret sinus, atrial, junctional, ventricular and
heart block rhythms.
Describe nursing implications and treatment for sinus, atrial,
junctional, ventricular and heart block rhythms.
Describe priority treatment for key cardiac emergencies such
as cardiac arrest.
Test your knowledge with practice questions and a case study
at the conclusion of the chapter.
INTRODUCTION
Arrhythmia interpretation and care of patients experiencing acute
cardiac events is a foundational competency required of registered
nurses working in critical care. The aim of this chapter is to provide
a resource for critical care nurses internationally that will assist
with recognition of key characteristics of sinus, atrial, junctional,
ventricular arrhythmias and atrio-ventricular (AV) blocks. In addition,
evidence-based care will be discussed in relation to symptomatic
arrhythmias and cardiac emergencies such as myocardial infarction
and cardiac arrest.
The chapter will conclude with practice questions and a case
study. Helpful websites and further resources will also be provided.
The intention of the chapter is to provide an overview of the key
components of basic arrhythmias and a summary of treatment. The
chapter is designed to accommodate learners that have a good
understanding of cardiac anatomy and physiology in addition to an
introductory level of understanding of cardiac arrhythmias.
Arrhythmia interpretation: where to start
The first part of accurately interpreting arrhythmias is to use a
systematic approach (see Table 1). However, before you begin to
analyze the rhythm strip, ALWAYS check the patient first and ensure
they are stable.
Normal sinus rhythm
In order to analyze cardiac rhythms, it is essential to have an
understanding of the ‘benchmark’ rhythm or hemodynamically
perfect rhythm; which is referred to as normal sinus rhythm (see
Figure 1) and sometimes abbreviated to NSR.
Figure 1. Normal sinus rhythm
In order to be considered normal sinus rhythm, the rhythm must have
the following characteristics:
Steps Explanation
1. Regularity Assess whether the rhythm is
regular or irregular
2. Rate Calculate ventricular and atrial rate
3. Assess p waves Are the p waves: rounded,
symmetrical, one for every QRS,
all look the same?
4. Calculate pr interval Normal =.12 to .20 seconds
5. Calculate QRS interval Normal = .06 to .10 seconds
6. Assess ST segment The ST segment should be on the
baseline or ‘isoelectric’ line. If it
is elevated or depressed it could
mean cardiac injury or ischemia
and requires urgent further
assessment.
In addition, the physician should
be notified immediately since
this could indicate that the
patient could be experiencing a
myocardial infarction.
7. Interpret the arrhythmia Name the arrhythmia based on the
characteristics above (i.e. atrial
fibrillation)
8. Nursing intervention/
treatment required
Determine what intervention is
required.
Is the patient stable or unstable?
Should the physician be notified?
Table 1. Systematic approach to arrhythmia interpretation
Rhythm: regular
Rate: 60 to 100/minute
p waves: present, upright, symmetrical, one before every QRS
pr interval: .12 to .20 seconds
QRS length: .06 to .10 seconds
If the rhythm has all of the above characteristics but the ST segment
is elevated, it would be referred to as sinus rhythm with an elevated
ST segment versus ‘normal’ sinus rhythm.
Sinus rhythms
In the next section, arrhythmias originating in the sino-atrial (SA)node
will be explored. The characteristics, causes, nursing implications
and treatment required for sinus bradycardia, sinus tachycardia,
sinus arrhythmia and wandering atrial pacemaker will be presented.
Slow rhythms: sinus bradycardia
A patient is considered to be bradycardic when their heart rate drops
below 60 beats per minute. Generally, a person often becomes
symptomatic when their heart rate drops below 50 beats/minute,
(see Figure 2) however slower heart rates can be observed in fit
and athletic individuals, who will often remain asymptomatic. As a
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Arrhythmias and Cardiac Emergencies

Sandra Goldsworthy, David Waters

CHAPTER ELEVEN

LEARNING OUTCOMES

After completing this chapter you will be able to:

  • Systematically interpret sinus, atrial, junctional, ventricular and heart block rhythms.
  • Describe nursing implications and treatment for sinus, atrial, junctional, ventricular and heart block rhythms.
  • Describe priority treatment for key cardiac emergencies such as cardiac arrest.
  • Test your knowledge with practice questions and a case study at the conclusion of the chapter. INTRODUCTION Arrhythmia interpretation and care of patients experiencing acute cardiac events is a foundational competency required of registered nurses working in critical care. The aim of this chapter is to provide a resource for critical care nurses internationally that will assist with recognition of key characteristics of sinus, atrial, junctional, ventricular arrhythmias and atrio-ventricular (AV) blocks. In addition, evidence-based care will be discussed in relation to symptomatic arrhythmias and cardiac emergencies such as myocardial infarction and cardiac arrest. The chapter will conclude with practice questions and a case study. Helpful websites and further resources will also be provided. The intention of the chapter is to provide an overview of the key components of basic arrhythmias and a summary of treatment. The chapter is designed to accommodate learners that have a good understanding of cardiac anatomy and physiology in addition to an introductory level of understanding of cardiac arrhythmias. Arrhythmia interpretation: where to start The first part of accurately interpreting arrhythmias is to use a systematic approach (see Table 1). However, before you begin to analyze the rhythm strip, ALWAYS check the patient first and ensure they are stable. Normal sinus rhythm In order to analyze cardiac rhythms, it is essential to have an understanding of the ‘benchmark’ rhythm or hemodynamically perfect rhythm; which is referred to as normal sinus rhythm (see Figure 1) and sometimes abbreviated to NSR. Figure 1. Normal sinus rhythm In order to be considered normal sinus rhythm, the rhythm must have the following characteristics: Steps Explanation
  1. Regularity Assess whether the rhythm is regular or irregular
  2. Rate Calculate ventricular and atrial rate
  3. Assess p waves Are the p waves: rounded, symmetrical, one for every QRS, all look the same?
  4. Calculate pr interval Normal =.12 to .20 seconds
  5. Calculate QRS interval Normal = .06 to .10 seconds
  6. Assess ST segment The ST segment should be on the baseline or ‘isoelectric’ line. If it is elevated or depressed it could mean cardiac injury or ischemia and requires urgent further assessment. In addition, the physician should be notified immediately since this could indicate that the patient could be experiencing a myocardial infarction.
  7. Interpret the arrhythmia Name the arrhythmia based on the characteristics above (i.e. atrial fibrillation)
  8. Nursing intervention/ treatment required Determine what intervention is required. Is the patient stable or unstable? Should the physician be notified? Table 1. Systematic approach to arrhythmia interpretation
  • Rhythm: regular
  • Rate: 60 to 100/minute
  • p waves: present, upright, symmetrical, one before every QRS
  • pr interval: .12 to .20 seconds
  • QRS length: .06 to .10 seconds If the rhythm has all of the above characteristics but the ST segment is elevated, it would be referred to as sinus rhythm with an elevated ST segment versus ‘normal’ sinus rhythm. Sinus rhythms In the next section, arrhythmias originating in the sino-atrial (SA)node will be explored. The characteristics, causes, nursing implications and treatment required for sinus bradycardia, sinus tachycardia, sinus arrhythmia and wandering atrial pacemaker will be presented. Slow rhythms: sinus bradycardia A patient is considered to be bradycardic when their heart rate drops below 60 beats per minute. Generally, a person often becomes symptomatic when their heart rate drops below 50 beats/minute, (see Figure 2) however slower heart rates can be observed in fit and athletic individuals, who will often remain asymptomatic. As a

general rule, when a patient’s heart rate is less than 60/minute critical care nurses should be prepared to immediately assess for signs of decreased cardiac output (i.e. decreased level of consciousness, hypotension, chest pain). The characteristics of sinus bradycardia are:

  • Rhythm: regular
  • Rate: < 60/minute
  • p waves: present, upright, symmetrical, one before every QRS
  • pr interval: .12 to .20 seconds
  • QRS length: .06 to .10 seconds
  • Cause: parasympathetic stimulation (i.e. medications, vomiting, suctioning, bearing down); hypoxemia
  • Treatment: only treated if patient is symptomatic. If symptomatic, Atropine administered IV bolus is the treatment of choice. If the patient becomes unstable (i.e. exhibits symptoms of chest pain, heart failure, syncope or a reduced level of consciousness) an intravenous chronotrope infusion (such as epinephrine or dopamine) or external transcutaneous pacing should be considered. Figure 2. Sinus bradycardia Fast rhythms: sinus tachycardia A patient is considered tachycardic when their heart rate rises above 100/minute, although typically individuals do not experience symptoms until the heart rate climbs above 150/minute (see Figure 3). It is best practice for a critical care nurse to assess for signs and symptoms of decreased cardiac output (i.e. hypotension, decreased level of consciousness) when the heart rate is greater than 100/ minute since this could result in patients developing cardiac ischemia, angina or even a myocardial infarction. Characteristics of sinus tachycardia are:
  • Rhythm: regular
  • Rate: >100/minute
  • p waves: present, upright, symmetrical, one before every QRS
  • pr interval: .12 to .20 seconds
  • QRS length: .06 to .10 seconds
  • Cause: sympathetic stimulation (i.e. medications, pain, fever, anxiety, shock); hypoxemia. Typically gradual in onset versus paroxysmal
  • Treatment: aimed at treating the underlying cause (i.e. intravenous fluids for hypovolaemia or analgesics for acute pain). Figure 3. Sinus tachycardia Irregular rhythms: sinus arrhythmia and wandering atrial pacemaker The next two arrhythmias, sinus arrhythmia (see Figure 4) and wandering atrial pacemaker (see Figure 5) are typically benign and do not require treatment. The characteristics of sinus arrhythmia are:
    • Rhythm: irregular
    • Rate: 60-100/minute
    • p waves: present, upright, symmetrical, one before every QRS
    • pr interval: .12 to .20 seconds
    • QRS length: .06 to .10 seconds
    • Cause: can be a normal aberration; seen in children and also in mechanically ventilated patients
    • Treatment: no treatment required; observe for further arrhythmia development. The characteristics of wandering atrial pacemaker are:
    • Rhythm: regular or slightly irregular
    • Rate: 60-100/minute
    • p waves: vary in shape and size
    • pr interval: .12 to .20 seconds
    • QRS length: .06 to .10 seconds
    • Cause: can be a normal aberration; ischemia
    • Treatment: no treatment required. Figure 4. Sinus arrhythmia Figure 5. Wandering atrial pacemaker Atrial rhythms In the next section, rhythms originating in the atria will be explored. These arrhythmias include: premature atrial contractions (PAC: see Figure 6), atrial flutter (see Figure 7), atrial fibrillation (see Figure 8) and supraventricular tachycardia (see Figure 9). Key characteristics of these rhythms will be identified along with nursing implications and helpful tips to assist critical care nurses in accurately interpreting atrial arrhythmias. Thecharacteristics of premature atrial contractions are:
    • Rhythm: early beat (PAC) causes rhythm to be irregular
    • Rate: underlying rhythm usually 60-100/minute
    • p waves: have different configuration than underlying rhythm
    • pr interval: .12 to .20 seconds in underlying rhythm
    • QRS length: .06 to .10 seconds in underlying rhythm
    • Cause: can be a normal aberration; ischemia; or a signal of atrial irritability - can lead to more serious atrial rhythms
    • Treatment: no treatment required for isolated PACs. Assess for increasing PACs since this indicates increasing atrial irritability and underlying cause (i.e. hypovolemia, hypervolemia or electrolyte imbalance) needs to be treated.

The characteristics of paroxysmal junctional tachycardia (PJT) are:

  • Rhythm: regular
  • Rate: 150 to 250/minute
  • p waves: inverted or absent (if seen)
  • pr interval: not applicable
  • QRS length: .06 to .10 seconds
  • Cause: ischemia
  • Treatment: see SVT Figure 10. Premature junctional contractions Figure 11. Junctional rhythm Figure 12. Accelerated junctional rhythm Figure 13. Paroxysmal junctional tachycardia Ventricular rhythms Ventricular rhythms are characterized by wide and bizarre QRS complexes. The rhythms that will be explored in this section include those caused by irritability which include: premature ventricular contractions (PVCs: see Figure 14), ventricular tachycardia (see Figure 15) and ventricular fibrillation (see Figure 16). In addition, ventricular rhythms that arise due to failure of higher level pacemakers (i.e. idioventricular, accelerated ventricular and aganol rhythms). It is important to distinguish between these two types of ventricular rhythms since the treatment and implications are very different (see Figures 17, 18 and 19). The characteristics of premature ventricular contractions (PVCs) are:
  • Rhythm: early beat (PVC) causes the rhythm to be irregular
  • Rate: 60 to 100/minute (underlying rhythm)
  • p waves: none (in PVC)
    • pr interval: none (in PVC)
    • QRS length: > .12 seconds (wide and bizzare)
    • Cause: ventricular irritability (e.g. hypoxemia, acid-base imbalance, medications, electrolyte imbalance)
    • Treatment: no treatment required for isolated PVCs; watch for an increase in PVCs (> 10/minute) since this indicates an increase in ventricular irritability. Note morphology and incidence of PVCs and escalate if required (PVCs could be multifocal, unifocal, couplets, bigeminal or trigeminal). The characteristics of ventricular tachycardia (VT) are:
  • Rhythm: regular
  • Rate: 150 to 250/min
  • p waves: none
  • pr interval: none
  • QRS length: > .12 seconds (wide and bizzare)
  • Cause: ventricular irritability (e.g. hypoxemia, acid-base imbalance, medications, electrolyte imbalance)
  • Treatment: confirm signs of life (i.e. presence of pulse and normal respiratory effort); obtain emergency assistance (i.e. cardiac arrest or rapid response team if available); if no signs of life (pulseless VT):
  • commence basic life support in accordance to national resuscitation guidelines (chest compressions and ventilation breaths)
  • defibrillate as per national resuscitation guidelines
  • secure intravenous access & administer Epinephrine & Amiodarone as per guidelines; if signs of life are noted (VT with a pulse):
  • administer oxygen as required
  • obtain intravenous access
  • administer intravenous Amiodarone
  • correct abnormal electrolytes. The characteristics of ventricular fibrillation (VF) are:
  • Rhythm: irregular and chaotic
  • Rate: cannot calculate
  • p waves: none
  • pr interval: none
  • QRS: none
  • Cause: ventricular irritability (e.g. hypoxemia, acid-base imbalance, medications, electrolyte imbalance)
  • Treatment: confirm signs of life (i.e. presence of pulse and normal respiratory effort); obtain emergency assistance (i.e. cardiac arrest or rapid response team if available); commence basic life support in accordance to national resuscitation guidelines (chest compressions and ventilation breaths); defibrillate as per national resuscitation guidelines; secure intravenous access and administer epinephrine and amiodarone as per guidelines. The characteristics of idioventricular rhythm are:
  • Rhythm: regular
  • Rate: < 40/minute
  • p waves: none
  • pr interval: none
  • QRS length: > .12 seconds (wide and bizarre)
  • Cause: ischemia, reperfusion post thrombolytics
  • Treatment: typically benign, transient; however if the patient exhibits signs of haemodynamic compromise, treat with interventions listed for bradycardia: atropine, chronotropic agents (intravenous infusion of Epinephrine), transcutaneous pacing.

Figure 14. Premature ventricular contractions Figure 15. Ventricular tachycardia Figure 16. Ventricular fibrillation Figure 17. Idioventricular rhythm Figure 18. Accelerated idioventricular rhythm Figure 19. Agonal rhythm The characteristics of accelerated idioventricular rhythm (AIVR) are:

  • Rhythm: regular
  • Rate: 40 to 100/minute
  • p waves: none
  • pr interval: none
  • QRS length: > .12 seconds (wide and bizarre)
  • Cause: drug toxicity, especially digoxin, cocaine and volatile anaesthetics such as desflurane; electrolyte abnormalities; cardiomyopathy; congenital heart disease; myocarditis; return of spontaneous circulation following cardiac arrest
  • Treatment: typically transient, no treatment required. The characteristics of aganol rhythm are:
    • Rhythm: very irregular
    • Rate: < 40/minute
    • p waves: none
    • pr interval: none
    • QRS length: > .12 seconds seconds
    • Cause: end stage cardiac disease
    • Treatment: this rhythm technically indicates a refractory end of life situation. AV Blocks Atrioventricular (AV) blocks are characterized by electrical conduction dysfunction through the myocardium. This is manifested as obstructed, delayed or variable electrical conduction through the AV node. Types of AV block include: 1st degree heart block (see Figure 20), 2nd degree heart block (Mobitz type 1 or Wenkebach: see Figure 21), 2nd degree heart block (Mobitz type 2: see Figure
    1. and 3rd degree heart block (complete heart block: see Figure 23). AV blocks can be associated with significant risk deterioration or haemodynamic compromise, so prompt identification and treatment is vital for the critical care nurse. Characteristics of each AV block will be explored, including nursing considerations and treatment options. The characteristics of first degree AV Block are:
    • Rhythm: regular
    • Rate: 60 to 100/minute
    • p waves: normal
    • pr interval: >.20 seconds
    • QRS length: .06 to .10 seconds
    • Cause: AV nodal disease; enhanced vagal tone (e.g. athletes); myocarditis; following myocardial infarction; electrolyte disturbances; medications (e.g. calcium channel blockers, beta blockers)
    • Treatment: no treatment required; observe for further block. The characteristics of second degree block Type I are:
    • Rhythm: regular or slightly irregular
    • Rate: 60 to 100/minute
    • p waves: normal
    • pr interval: progressively gets longer until a beat is dropped
    • QRS length: .06 to .10 seconds
    • Cause: ischemia
    • Treatment: usually benign, with no treatment required; if patient becomes haemodynamically compromised consider interventions for bradycardia; observe for worsening AV block. The characteristics of second degree AV block Type II are:
    • Rhythm: regular or irregular
    • Rate: varies
    • p waves: more p waves than QRS complexes
    • pr interval: constant
    • QRS length: .06 to .10 seconds or may be widened
    • Cause: ischemia; myocardial infarction
    • Treatment: if patient becomes haemodynamically compromised consider interventions for bradycardia; observe for worsening AV block; may require temporary or permanent pacing.

Answers

  1. c. Confirmation of cardiac arrest, cardiopulmonary resuscitation (CPR) and defibrillation. Artifact or patient movement can mimic ventricular fibrillation (VF), so it is vital that the healthcare professional confirms cardiac arrest prior to calling for assistance, commencing CPR or initiation of defibrillation. CPR should be initiated immediately to ensure that key organs remain perfused. Once a defibrillator is available, the patient should receive a shock, followed by further CPR.
  2. b. Ventricular fibrillation (VF) can be described as a complex, irregular and chaotic rhythm, which features no clear P waves and QRS complexes that have a random width and amplitude. VF is a cardiac arrest rhythm and warrants immediate CPR and defibrillation.
  3. c. Mr Ahmed’s rhythm deteriorated into sinus bradycardia. Treatment for symptomatic bradycardia includes administration of intravenous atropine. If atropine fails to achieve a satisfactory result, transcutaneous pacing can be implemented via a pacing enabled defibrillator.

FURTHER READING

Aehlert B (2018). ECGs Made Easy, 6th ed. Mosby: St. Louis, Missouri. Link M, Berkow L, Kudenchuk P et al. (2015). Update for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care, Part 7: Adult Advanced Cardiac Life Support. Circulation 132(18 Suppl 2): S444-64. Goldsworthy S (2012). Coronary Care 1 and 2 Manual. Durham College Continuing Education: Oshawa, Canada. Walraven G (2011). Basic Arrhythmias 7th ed. Pearson Publishers: Toronto, Ontario. Other helpful resources ECGlibrary.com. [for practice]. Available at: https://ecglibrary.com/ ecghome.php.

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