What is Pulseless ventricular tachycardia?

The heart is made up of four chambers. The upper two small chambers are called atria, and the lower two large chambers are called ventricles. Blood flows downwards from the atria into the ventricles. The ventricles are responsible for contracting and pushing the blood out of the heart into the lungs and the rest of the body.

In ventricular tachycardia, the ventricles contracting at a fast pace to function adequately. This rapid contraction prevents the ventricles from filling sufficiently with blood, resulting in inadequate blood supply to the lungs and the rest of the body. Consequently, the blood supply can become too poor to sustain life. Without blood being pumped around the body, a person will have no pulse, leading to the condition known as pulseless ventricular tachycardia. 

This is a life-threatening condition and treatment must be started immediately to attempt to restore the normal function of the heart. Prompt identification and initiation of treatment can reduce the irreversible damage to tissues and organs, significantly improving the chances of survival.

Recognition and diagnosis

The normal range for a resting heartbeat is between 60-100 beats per minute. In ventricular tachycardia, the heart rate is often over 100 beats per minute. It is important to note that ventricular tachycardia is not always pulseless and the severity of this arrhythmia is dependent on how fast the heart is beating, how long it occurs(duration) and how often(frequency). 

Clinical presentation

Individuals experiencing ventricular tachycardia (VT) may present with symptoms of chest pain, shortness of breath, palpitations or lightheadedness that could also lead to syncope (fainting). They may have low blood pressure and show signs of lack of oxygen such as a bluish discolouration of the lips. If episodes of VT continue, this could lead to the person collapsing and becoming unconscious causing pulseless VT and eventually cardiac arrest. If treatment is not commenced immediately the chances of survival are very low and could lead to death within minutes.¹

Diagnostic criteria

Diagnosis of pulseless VT is made based on the clinical presentation and review of an electrocardiogram (ECG). An ECG is a test used to examine the electrical signals that make the heartbeat. Electrode stickers are placed across the chest to detect these signals and this records a 10-second snapshot of how these signals are moving through the heart's muscle. This test can give an insight of where the heartbeat is originating and if there are any irregularities in its path through the heart muscle.

Here is what a normal ECG looks like:

Each signal picked up is labelled with a letter from P to T which creates a complex. These signals represent different segments of the heartbeat(cardiac cycle) cycle. The first wave i.e, the P wave, represents the initiation of the cycle and the contraction of the atria. The QRS corresponds to the ventricle’s contraction. The T wave corresponds to the relaxation of the ventricles after a contraction.

In comparison, here is what VT can look like on an ECG:

The ECG criteria for diagnosing VT is >3 consecutive complexes with ventricular beats over 100 beats per minute and a QRS duration of >0.12 seconds.¹ It is important to note that there are different types of VT which can present as variations in the shape of the complex.²

Pulseless VT can be identified by the absence of a pulse. This can be checked by feeling for a pulse on the neck (carotid artery).

Immediate actions in pulseless VT

The first action after identifying someone with pulseless VT is to call for help. This initial step is key in starting the chain of survival algorithms set out by resuscitation guidelines worldwide. Prompt identification of the emergency and activating the emergency response system whether that be calling an ambulance or alerting a medical professional can have an impact on the chance of survival. As previously mentioned, if untreated, pulseless VT can quickly progress to cardiac arrest. For each minute that a person is without a pulse, their chances of survival to hospital discharge is reduced by 10%.³

The next step would be to start assessing the individual, using an ABCDE algorithm. The first step is to assess the airway by checking if the person is breathing. This can be done by leaning your head over the person's nose and mouth, listening for breath sounds, feeling for breath on your cheek and looking to see if the chest is rising or falling. If any of these are absent, one should call for a defibrillator and start cardiopulmonary resuscitation (CPR) as soon as possible.

Advanced cardiac life support (ACLS) algorithm for pulseless ventricular tachycardia

There are guidelines set out by resuscitation councils across the world on how to manage these emergency situations, so it is important to keep up to date and review these regularly. Prompt response to these situations is key for survival of the individual and early intervention of defibrillation and CPR are the two key factors influencing the outcome.

Defibrillation

A defibrillator is an equipment used to examine the heart rhythm and to deliver a jolt of energy. The energy is sent through two large pads in an attempt to restart the heart when it has stopped or to shock it to return to its normal beating pattern. The pads are applied to the chest and the machine is switched on. Anyone can use a defibrillator and there are a number of defibrillators in the community for public use in an emergency.

The machine will show you where to place the pads and talk you through as to how to use it. Once attached, the machine will interpret the heart's rhythm and tell you whether it is a rhythm that can be shocked, in the hope of resetting the heartbeat back to normal. Pulseless VT is a shockable rhythm. Early defibrillation (within 3-5 minutes) has shown to improve the chance of survival by 50-70%.³ So, this step is vital in the process.

CPR

Cardiopulmonary resuscitation or CPR is a term given to the interventions to restore breathing and pumping of the heart during a cardiac arrest. Chest compressions are the manual compression of the chest to mimic the heart's job of pumping blood around the body. When using a defibrillator, it will alert you when to stop chest compressions in order to assess the rhythm of the heart.

To start chest compressions, follow these steps:

• Interlock the fingers together, with hands stacked on top of each other, palms facing down(dominant hand above the other)
• Place your hands in the centre of the chest
• Keeping arms straight, push down through the heel of your hand firmly at a rate of 2 compressions per second

The aim is to push down a third of the chest (approximately 5-6cm). So, it is better to be too firm than too soft.
You can do compressions either continuously or at 30 compressions to 2 rescue breaths (if possible). The administration of breaths will depend on the circumstances; If you are willing to give the person a mouth-to-mouth breath or if in a hospital, it will depend on the type of assistance there is with the airway and the method of delivering breaths.

Establishing an airway

It is important to check if the airway is clear by looking in the mouth and checking if there is anything causing an obstruction. If clear, and you are not aware of a neck or head injury, then a head tilt, chin lift can be performed. By placing two fingers on the forehead and two fingers under the chin, the head can be tilted back, and the airway opened by lifting the chin.

If a head or neck injury is suspected, then a jaw thrust can be performed. This involves placing fingers behind the angle of the jaw bilaterally and thrusting the jaw forward to safely open the airway.

A temporary airway can be placed to maintain this position to support breathing during resuscitation. This is called oropharyngeal airways when placed in the mouth. Advanced airways include a supraglottic airway or endotracheal airway. These are placed by well-trained individuals. Once an airway is secured, a method of delivering oxygen can be commenced.

Generally, this is done using a bag valve mask(BVM)/device. A BVM is an airway system for delivering high-flow oxygen and forcing air into the lungs to encourage the intake of oxygen that we naturally do when breathing normally. When in cardiac arrest, breathing ceases so the BVM takes on this role.

Administration of medications

As part of the algorithm for managing pulseless VT, the administration of different medications can assist in returning the heart to normal pacing.

Vasopressors

Vasopressors are a potent type of medication that constricts the arteries and overall increases pressure in the vessels. This can help to improve blood circulation from the peripheries (arms and legs) to the vital centrally located organs. Epinephrine (Adrenaline) has been used in cardiac arrests for over 30 years and is the most widely used medication in cardiac arrests involving pulseless VT. A study of over 8,000 patients found that those given epinephrine for cardiac arrests had a significantly higher rate of 30-day survival.⁴

Antiarrhythmic drugs

Antiarrhythmic drugs are used to chemically regulate the heart rhythm. Two of these types of drugs standardly used are amiodarone and lidocaine. Amiodarone is licensed specifically for life-threatening ventricular arrhythmias such as pulseless VT. Both can be administered as a part of the ACLS algorithm in an attempt to support the restoration of spontaneous circulation.

Post-resuscitation care and management

Once circulation has been restored, it is crucial to transfer the individual to an advanced care facility, such as a critical care unit or intensive care unit at a hospital. This is important to monitor the individual closely and attempt to find the cause of the pulseless VT.

Post-event testing

There are various tests that can be performed to determine the cause of the arrhythmia These include blood tests to check the levels of minerals such as potassium and sodium which are essential for the conduction system of the heart.

An ECG can identify any potential damage that occurred due to the loss of oxygenated blood during the cardiac arrest. If any damage is suspected, a procedure called an angiogram may be performed, which can examine the coronary arteries and determine if a lesion within these may have been the cause.

A CT scan of the head or chest may be required, especially if there is evidence of a neurological defect – such as confusion.

Once the cause has been identified, it can be monitored and treated appropriately.

Summary

Pulseless VT is a life-threatening condition that requires prompt and immediate treatment. Initial interventions can be commenced by anyone in the form of calling for help, starting chest compressions and early defibrillation. Referral to healthcare professionals is key, for initiation of the advanced cardiac life support algorithm including advanced techniques for airway management and administration of medications in an attempt to return the heartbeat to its normal rhythm.