Rhythm-based Management in Cardiac Arrest
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Article at a Glance
- Clinicians should be able to readily recognize the four rhythms associated with cardiac arrest: ventricular fibrillation, pulseless ventricular tachycardia, pulseless electrical activity, and asystole.
- Clinicians must minimize any interruptions in CPR when treating a patient with cardiac arrest rhythms.
- Administering electrical therapy as early as possible to patients with shockable rhythms increases the rate of successful return of spontaneous circulation.
- Clinicians should treat nonshockable rhythms with CPR and the drug epinephrine, which improves blood flow to the heart and brain.
Cardiac arrest features four electrocardiographic rhythms of interest, including (1) ventricular fibrillation (VF), (2) pulseless ventricular tachycardia (pVT), (3) pulseless electrical activity (PEA), and (4) asystole.
These electrocardiographic rhythms do not produce sufficient blood flow to sustain perfusion. VF is characterized by disorganized electrical activity, while pVT produces organized electrical activity.
Likewise, PEA is an organized electrical rhythm lacking sufficient mechanical ventricular activity to produce a detectable pulse.
Asystole is an absence of ventricular electrical activity with or without atrial electrical activity.
Survival rates decrease if there is a delay in defibrillation, especially for patients with shockable rhythms (VF and pVT).1 It is paramount for healthcare institutions to institute policies reducing the time to diagnose cardiac arrest and deliver rapid defibrillation. Fewer interruptions in chest compression also improve outcomes.
A clinician’s cardiopulmonary resuscitation (CPR) interruptions should be as brief as possible; the clinician should stop only to assess the rhythm, shock VF or pulseless VT, perform a pulse check when an organized rhythm is achieved, or to place an advanced airway. Intravenous or intraosseous access to drugs and fluids can be achieved without stopping CPR.
The clinician’s execution of rhythm-based management determines the patient’s outcome in cardiac arrest.
In reality, there are many more unsuccessful resuscitative efforts than successful ones, posing a question: are clinicians really managing their patients properly?
A patient’s arrest rhythms can change during advanced cardiac life support (ACLS). Interventions are adjusted based on the cardiac monitor’s rhythm. Early in its progression, ventricular fibrillation features coarse waveforms that become finer if the clinician does not intervene or if poor technique is used. Eventually, fine VF becomes asystole. Early defibrillation is necessary for VF because, once it deteriorates into asystole, the treatment options are limited to CPR with medications. Asystole is a nonshockable rhythm.2 Alternatively, a clinician’s effective ACLS strategies can “improve” nonshockable rhythms such as PEA and asystole into VF and pVT, which can then be treated with electrical therapy. Healthcare clinicians should be ready to shock at any time.Change in Rhythms During ACLS
To terminate VF, the recommended shock dose for biphasic defibrillators depends on manufacturer recommendations. If the clinician does not know this information, they may use the highest dose the system provides. Subsequent shocks should be delivered using the same or higher dose than the previous dose. For monophasic defibrillators, a dose of 360 joules (J) is recommended for all brands. The same dose is used for subsequent shocks. If VF recurs after successful termination, the clinician administers the same shock dose that previously terminated the rhythm. Multimodal defibrillators in manual mode reduce the length of time of interrupted CPR; however, there is an increase in the inappropriate shock frequency. Defibrillators deliver electrical shocks to restore the heart rhythm.Defibrillators
The key to managing shockable rhythms is rapid defibrillation. In the prehospital setting, the rescuer commonly uses an automated external defibrillator (AED) during cardiac arrest. As soon as the AED arrives, the clinician applies the pads to the patient while CPR is being performed. Once the rescuer places the AED pads and connects the cable to the AED, CPR is interrupted to allow the AED to analyze the rhythm. If the AED diagnoses a shockable rhythm, it charges before shocking. While the AED is charging, the clinician continues CPR. Once it is fully charged, everyone must clear the patient before the AED operator pushes the shock button on the AED. On a manual defibrillator, the clinician continues CPR while a second rescuer charges the defibrillator. Once charged, CPR is paused to “clear” the patient. The shock is delivered, and CPR is resumed immediately, beginning with chest compressions, and continued for another two minutes. The CPR/shock cycle is repeated while the patient remains in a shockable rhythm. Rhythm and pulse checks are performed in less than 10 seconds to minimize interruptions in CPR.3 Ventricular Fibrillation Pulseless Ventricular Tachycardia Read: Narrow Complex TachycardiasShocking VF and PVT
Related Video – One Quick Question: Should You Choose CPR or Defibrillation?
Related Video – How to Use an Automated External Defibrillator (AED) Safely
Related Video – ECG Rhythm Review – Ventricular Fibrillation
Related Video – ECG Rhythm Review – Polymorphic Ventricular Tachycardia (Torsades de Pointes)
Epinephrine is the drug of choice to improve myocardial blood flow during CPR.4 The clinician administers epinephrine after the second shock attempt while CPR is in progress. If epinephrine is given after a shock has successfully terminated the cardiac arrest rhythm, it can have a detrimental effect on cardiovascular activity. Epinephrine 1 mg/10 mL syringeDrug Therapy in VF and pVT
Related Video – Epinephrine – ACLS Drugs
PEA and asystole are NONSHOCKABLE rhythms. The clinician administers epinephrine as soon as PEA or asystole is recognized and again every 3–5 minutes.5 Epinephrine is given via an intravenous bolus, followed by a normal saline flush. Epinephrine increases myocardial and cerebral blood flow during CPR. High-quality CPR and early epinephrine are the interventions of choice. The clinician performs intermittent pulse and rhythm checks every five CPR cycles (or approximately two minutes). This cycle continues until the patient develops a shockable rhythm or a definite pulse is felt. If a patient’s pulse is present after five CPR cycles, post-cardiac arrest care is started. If CPR is ineffective, the clinician must review possible reversible causes (see Hs and Ts) of PEA or asystole and treat them promptly. For example, in the case of hypoxemia, the clinician should prioritize advanced airway placement. In patients with volume loss or sepsis, intravenous or intraosseous administration of crystalloid fluids will benefit the patient; when a patient has had significant blood loss, blood transfusion is necessary. Clinicians should consider fibrinolytic therapy in patients who are believed to have experienced cardiac arrest as a result of a pulmonary embolism or myocardial infarction. Needle decompression should be performed in patients with tension pneumothorax. The rescuer must diagnose and treat a patient’s cardiac arrest according to their cardiac rhythm. Shockable rhythms include VF and pVT, and the clinician should defibrillate as quickly as possible following diagnosis. Nonshockable rhythms include PEA and asystole, and the clinician should begin CPR and administer epinephrine as soon as possible.Nonshockable Cardiac Arrest Rhythms
Related Video – Introduction to the Hs and T
There are four rhythms associated with cardiac arrest: ventricular fibrillation, pulseless ventricular tachycardia, pulseless electrical activity, and asystole. It is imperative a clinician identify which of these rhythms is present before continuing care. High-quality CPR is not delayed, however, while the clinician gets information about the patient’s rhythm. Shockable rhythms are treated with electrical therapy as early as possible, while patients with nonshockable rhythms are treated with epinephrine and CPR until the patient has a return of spontaneous circulation or develops a shockable rhythm.Conclusion
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Editorial Sources
ACLS Certification Association (ACA) uses only high-quality medical resources and peer-reviewed studies to support the facts within our articles. Explore our editorial process to learn how our content reflects clinical accuracy and the latest best practices in medicine. As an ACA Authorized Training Center, all content is reviewed for medical accuracy by the ACA Medical Review Board.
1. M Holmberg, S Holmberg, J Herlitz. Incidence, duration and survival of ventricular fibrillation in out-of-hospital cardiac arrest patients in Sweden. Resuscitation. 2000.
2. American Heart Association. Management of Cardiac Arrest. 2005.
3. Jesse Borke, MD, FACEP, FAAEM; Chief Editor: Kirsten A Bechtel, MD. Cardiopulmonary Resuscitation (CPR). Medscape. 2021.
4. Callaway CW. Epinephrine for cardiac arrest. Curr Opin Cardiol. 2013.
5. Tony I. Oliver; Usama Sadiq; Shamai A. Grossman. Pulseless Electrical Activity. National Library of Medicine. 2022.
6. McGuff Medical Products. Epinephrine. 2021.
More to Learn
Explore third-degree complete heart block and its ECG strip interpretation in our article. Gain insights into diagnosing and understanding this cardiac condition.
Learn about premature junctional contractions (PJCs) and their criteria in our article. Understand these premature beats that arise from the atrioventricular (AV) junction of the heart.