What Is Pulseless Electrical Activity?

Overview

Pulseless electrical activity (PEA) is a type of irregular heart rhythm (i.e., arrhythmia). It is a clinical condition where the heart’s electrical system is malfunctioning given that ventricular electrical activity is insufficient or undetectable therefore meaningful ventricular mechanical activity (i.e., maintaining a heartbeat which pumps blood around the body) can’t take place.

Consequently, this arrhythmia results in a lack of a palpable pulse and the eventual stopping of the heart (i.e., cardiac arrest). Ultimately, PEA is thought to be a precursor to sudden cardiac death, therefore immediate medical attention should be paid to its symptoms given that lack of treatment can result in sudden cardiac death.¹

Previously, pulseless electrical activity was termed electromechanical dissociation (EMD).²

What is pulseless electrical activity?

The cardiac conduction system (i.e., the heart’s electrical system) is a network of nodes, cells and signals that control one’s heartbeat. For regular pumping of the heart, specialised heart muscle cells send electrical signals to the different heart muscles instructing them when to contract (squeeze) and expand. It is this expansion and contraction that controls the blood flow through the heart and the entire body.

There are several different conditions that affect the cardiac conduction system and result in heart rhythm disorders. Arrhythmia, is of particular note here, given that it refers to abnormal heart rhythms that can vary from mild, relatively harmless changes to severe, life-threatening changes.³ Again, pulseless electrical activity is a type of abnormal heart rhythm.

How well the cardiac conduction system works can be illustrated using electrocardiogram (ECG or EKG) – a diagnostic test used by medical professionals operating on the detection of electrical currents in the heart. In regard to PEA, the heart does indeed have a detectable electrical current, however, this current is weak or insufficient to yield the necessary cardiac mechanical output.⁴ In other words, crucially the heart isn’t strong enough to pump blood through the body.

Forms of pulseless electrical activity

Pulseless electrical activity (PEA) comes in two different forms:

• Pseudo-PEA – A type of PEA where the heart’s electrical activity causes the heart muscles to contract but does so very weakly. This negligible cardiac mechanical output does move some blood, yet it is not enough to prompt a sufficient heartbeat capable of pumping blood effectively through the body to satisfy the body’s demands. Consequently, there is no detectable pulse.
• True PEA – Type of PEA where the heart’s electrical activity is present but considerably faint. The heart muscles don’t react to it therefore there is no cardiac mechanical output. Consequently, blood isn’t being pumped through the heart or body so there is no pulse that can be detected.

Difference between PEA and asystole

Pulseless electrical activity (PEA) refers to weak or undetectable electrical activity that prevents the heart from effectively pumping blood around the body.

Asystole refers to the shutting down of the heart’s electrical system (i.e., ‘flat-lining’ – as depicted on ECG/EKG) therefore there is no heartbeat or any meaningful cardiac output.

Whilst both these cardiac rhythms can lead to cardiac arrest (i.e., ‘clinical death’), the crucial difference between the two stems from PEA having some detectable electrical activity albeit negligible compared to no detectable electrical in asystole.

Consequences of PEA – stages of death

Given that PEA results in severe loss of cardiac output, the blood supply to the heart, brain and rest of the body is interrupted. Because of this interruption, the body is unable to function as it normally would and without correction, it can lead to devastating consequences, notably death. There are different types of death that include…

• Clinical death – When the heart stops (i.e., cardiac arrest), you stop breathing and the heart stops pumping blood around. Essentially, the body is shutting down since the lack of blood flow to the brain and other vital organs hinders their functionality and recoverability. Due to the cardiac arrest, you are perceived as ‘clinically dead’.
• Brain death – When the heart stops, the blood supply (which supplies oxygen) to the brain is interrupted. Given that the brain is considerably oxygen-dependent and highly sensitive to a lack of oxygen, this disruption results in brain hypoxia (i.e., death of cells in the brain) should the lack of oxygen persist beyond 5 minutes. Once these cells start to die, it becomes increasingly impossible to revive you as the brain has essentially died.

Given the seriousness of these consequences and the finite window of action for recovery, the need for adequate treatment is vital.

Causes of pulseless electrical activity

The causes of pulseless electrical activity (PEA) fall into two dichotomous categories.

1. Primary pulseless electrical activity – Associated with cardiac arrest (i.e., endogenous/internal) where there is a problem with the heart itself.

• Decreased preload – Refers to the stretching of cardiac myocytes (heart muscle) prior to contraction.⁵ The heart can only pump out the volume it contains so decreased preload effectively means less blood available to be pumped out therefore there’s decreased cardiac output.
• Increased afterload – Refers to the ‘load or face’ against which the heart has to contract to eject blood.⁶ So increased afterload results effectively mean it’s harder for the heart to pump out blood so there’s decreased cardiac output.
• Decreased contractility (i.e., a condition called myocardial failure) – Impairs the pumping ability of one or both ventricles (chambers of the heart that collect and expel blood) meaning it’s harder for the heart to pump out blood so there’s decreased cardiac output.

2. Secondary pulseless electrical activity – Associated with outside causes (i.e., exogenous/external) as opposed to problems with the heart itself. Causes of secondary PEA include…

• Hypovolemia – The body loses fluid (e.g., blood or water), or dehydration.⁷
• Hypoxia – Lack of oxygen therefore affecting body tissue.⁸
• Hydrogen ion (acidosis) – When acid builds up in the blood and other body tissues.⁹
• Hypothermia – Prolonged exposure to extremely cold temperatures.¹⁰
• Hypokalcemia – Low potassium levels.¹¹
• Hyperkalcemia – High potassium levels.¹²
• Tension pneumothorax – Accumulation and entrapment of air/gas within the cavity between the lungs and chest wall which causes the lung to collapse.¹³
• Tamponade – The fluid sac (pericardial) surrounding the heart fills abnormal amounts of blood or other fluid and compresses the heart.¹⁴
• Thromboembolism – Myocardial infarction (MI)(heart attack)  caused by decreased or complete cessation of blood flow to the heart. Pulmonary embolism (PE) when a blood clot blocks a blood vessel in the lungs.¹⁵
• Toxins – Prescription or recreational drugs and other toxic substances affect the heart.

In the context of secondary PEA, treatment should focus on directly addressing the underlying causes which are impeding the heart/body from operating as it should be. Typically, such rectification will result in the successful resuscitation of the individual.

Signs & symptoms of pulseless electrical activity

The signs and symptoms that an individual with pulseless electrical activity may display include…

• Absence of a palpable pulse.
• Apnoea – When you stop breathing or have no airflow then blood oxygen levels drop.
• Cyanosis – Decreased oxygen in blood results in discolouration of blood tissue to a bluish-purple hue.¹⁶
• Respiratory acidosis – Decreased ventilation prohibits the lungs from removing carbon dioxide (CO₂) so this excess CO₂ in the blood causes acidity of blood and other bodily fluids.¹⁷
• Hypothermia – Prolonged exposure to extremely cold temperatures uses up the body’s stored energy leading to lower body temperatures therefore affecting the brain.
• Electrolyte imbalance (such as hypo- or hyper-kalemia) – Certain mineral levels (notably potassium) in the blood get either too high or too low.
• Blood loss/haemorrhage¹⁸ (resulting in hypovolemia) – Loss of blood from a damaged blood vessel causes decreased blood pressure and dizziness.
• Pallor – A paleness in appearance due to lack of oxygen.
• Jugular venous distention – Swelling of the vein that runs down the right side of the neck, thereby preventing normal blood flow and increased jugular vein pressure (a sign of heart failure).¹⁹
• Tracheal deviation – Abnormal pressure in the chest cavity or neck causes the trachea to be pushed to one side of the neck, thereby indicating unequal pressure within the chest cavity.

Treatment for pulseless electrical activity

Pulseless electrical activity (PEA) is a heart rhythm disturbance (arrhythmia) that is fatal unless the underlying cause can be identified and treated at once.

Firstly, the only way to definitively identify whether a stopped heart involves PEA is with an electrocardiogram (ECG/EKG) which measures the electrical activity of the heart. Critically, this machinery isn’t readily available outside of a hospital environment so until emergency services or first responders arrive the following initial treatment should be offered regardless of whether or not PEA is involved.

Notably, cardiopulmonary resuscitation (CPR) should be administered as a matter of urgency whenever a cardiac arrest happens, even more so when outside of a hospital or medical setting. Here, because the heart either stops beating or beats too ineffectively during a cardiac arrest, externally applying sporadic pressure to the heart will keep blood and oxygen circulating to the brain and other vital organs. This technique doesn’t restart the heart however it should be continued until the emergency services, or first responders arrive.

Within a hospital setting, the following treatments for PEA are evident:

• CPR – Again, these rescue breathing (mouth-to-mouth) chest compressions play a significant role in maintaining blood circulation so oxygen can be delivered to the brain and other vital organs.
• Epinephrine (chemical term for adrenaline) – Type of medication administered during CPR to reverse cardiac arrest and restore the heart to a normal rhythm.
• Directly treating the underlying cause of PEA – Secondary PEA implies there’s a specific cause behind this heart malfunction therefore correcting this cause will help return the heart back to its normal rhythm. Examples of specific treatments to treat such causes are as follows:

Shockable vs. Non-shockable rhythms

A shockable rhythm is one caused by abnormalities in the cardiac conduction system (i.e., abnormal electrical activity in the heart). These include:

• Ventricular tachycardia
• Ventricular fibrillation
• Supraventricular tachycardia

By addressing the cause of the PEA arrest, the heart can be returned to one of the shockable rhythms. Crucially, it’s vital healthcare and medical professions maintain vigilance for when a PEA or asystole converts back to a shockable rhythm. In these instances, a defibrillator can be used to shock the heart back to a normal rhythm.

For non-shockable rhythms, such as PEA and asystole, the heart is incapable of utilising the externally administered electrical shock to rectify the abnormality since the primary cause has yet to be addressed. Shocking a heart in these conditions would be of no benefit and instead, be likely to cause more damage.

Avoiding developing pulseless electrical activity?

Unfortunately, pulseless electrical activity (PEA) does not happen predictably as it is commonly viewed as an aspect of the normal dying process and can arise as a result of endogenous/internal (primary PEA) or exogenous/external (secondary PEA) factors. Because of this, PEA is not preventable and so there are few precautionary measures one can undertake beyond simply maintaining good cardiovascular health and treating any pre-existing heart condition(s).

FAQs

How is pulseless electrical activity diagnosed?

An electrocardiogram (ECG/EKG) is a medical device used to check the heart’s rhythm and electrical activity. This device is the only way to identify PEA and distinguish it from other causes of cardiac arrest.

Critically, the absence of a pulse indicates a clinical diagnosis of cardiac arrest, but additional tests may need to be conducted to identify the cause of the PEA.

Other medical/diagnostic tests medical professionals can utilise to diagnose PEA include:

• Arterial blood gas test – Measures the amount of oxygen (O₂) and carbon dioxide (CO₂) in the body. Also measures acid-base balance or pH level (i.e., acidity in the blood).
• Thermometer – Measures core body temperature.
• Echocardiogram – Test which uses sound waves to produce a detailed image of the heart.
• Serum electrolytes test – Blood test measuring the levels of electrolytes in the body (inc. sodium, chloride, potassium and bicarbonate).

Such tests and analyses are conducted to identify more specifically what the underlying cause behind PEA is – this is particularly important, especially for secondary PEA.

When should I see a doctor?

Given the nature of pulseless electrical activity and how life-threatening it is, the cardiac arrest the patient experiences is classified as a medical emergency that requires immediate medical attention. First and foremost, emergency services should be contacted, and CPR should be conducted until the first responders arrive.

The five tell-tale signs of a cardiac arrest you should start alert for include:

• Chest pain
• Dizziness/loss of consciousness/fainting
• Heart palpitations/lack of pulse
• Breathlessness
• Nausea or vomiting

Summary

Pulseless electrical activity (PEA) is a type of irregular heart rhythm (i.e., arrhythmia) where the heart’s electrical system is malfunctioning. More specifically, ventricular electrical activity is insufficient or undetectable therefore meaningful ventricular mechanical activity (i.e., maintaining a heartbeat which pumps blood around the body) can’t take place. Consequently, this arrhythmia results in a lack of a palpable pulse and the eventual stopping of the heart (i.e. cardiac arrest). Ultimately, PEA is thought to be a precursor to sudden cardiac death, therefore immediate medical attention should be paid to its symptoms given that lack of treatment can result in sudden cardiac death. Such treatment options include administering CPR, epinephrine, and correcting the direct cause of PEA.