Tachycardia refers to an abnormally fast heart rate. It can originate in either the atria or the ventricles. Here, we will focus on the latter condition: ventricular tachycardia.
The heart is an organ composed of four chambers: two atria and two ventricles, located on the left and right sides.
Each ventricle serves a specific function. The right ventricle contracts and pushes blood into the pulmonary arteries.
The left ventricle contracts and pushes blood into the aorta. The oxygen-rich blood is then delivered to the organs, muscles and tissues in the body.
The atria and ventricles contract in response to an electrical impulse. A resting heart rate for healthy people ranges between 60 and 100 beats per minute.
When the heart beats more than 100 beats per minute at rest, this is called tachycardia.
Ventricular tachycardia can be very brief. Sometimes the patient does not even feel it.
It can also persist over time and prevent the ventricles from filling properly and expelling blood. This leads to a low cardiac output and a risk of cardiovascular arrest.
Symptoms
When it is felt, which is not always the case, ventricular tachycardia causes palpitations, dizziness, difficulty breathing or even syncope (fainting with loss of consciousness).
It can lead to heart failure, ventricular fibrillation, or cardiac arrest.
These episodes may be very brief, lasting just a few seconds, or longer, lasting several hours.s.
Diagnosis
The electrocardiogram is the key test used to diagnose ventricular tachycardia. The diagnosis can also be established based on an ECG from a Holter monitor, a small device that records the patient’s heart rhythm for 24-48 hours. Finally, ventricular tachycardia can be observed on recordings from an insertable cardiac monitor, a small device placed under the skin to record cardiac activity for three years.
Once the diagnosis is confirmed, a complete assessment is carried out to determine the cause. A complete blood test is performed, as well as an echocardiogram. An angiogram is often performed to check for damage to the heart’s arteries (coronary arteries).
Other tests may also be prescribed, such as a stress test and cardiac MRI.
What is an electrocardiogram?
It is a test that records the heart’s electrical activity over a given period of time. It determines the speed at which the heart is beating (heart rate) and whether it is beating normally (heart rhythm). It is abbreviated as ECG or EKG.
Treatment
Treatment of ventricular tachycardia depends on the urgency of the situation.
Emergency treatment consists of cardiopulmonary resuscitation (CPR) combined with immediate defibrillation. In France, the witness must call the emergency services immediately by dialing 15. While waiting for their arrival, they should begin chest compressions and locate an automated external defibrillator (AED): there are websites and applications to locate one in seconds. If an AED is not available, the bystander must perform chest compressions until the emergency services arrive.
A quick response time is essential: for every minute that passes without CPR, a person in cardiac arrest loses 10% of their chance of survival!
How to perform CPR
Many organizations, such as the Red Cross (Croix-Rouge) and the Civil Defense (Protection Civile) provide CPR training. This is of course the best way to prepare for the possibility of intervening during an emergency situation.
If you witness a cardiac arrest, be prepared to intervene!
- Lay the person on a hard surface and kneel down right next to them by their side.
- Place your hands one on top of the other in the center of the chest, with your arms extended.
- Press down vertically with all your weight to apply strong compressions. Your hands should sink 5 to 6 centimeters and then rise to allow blood circulation. The compressions should ideally be performed at a rate of 100 per minute.
- After every 30 compressions, perform mouth-to-mouth if you have been trained to do so. Otherwise, continue the compressions until the emergency services arrive or until the defibrillator instructs you to stop.
What is an automated external defibrillator?
An automated external defibrillator is a device that emerged in the 1990s and which the French Ministry of Health made available to the general public in 2007. The device delivers an electric shock to restore the heart’s rhythm. In France, there are over 400,000 AEDs, not including those in hospitals.
There are two types.
- The semi-automatic, which delivers the shock when the user presses a button.
- And the automatic, which does not require this intervention.
In both cases, AEDs are equipped with voice guidance to help the user perform chest compressions and place the electrodes. The device also performs a diagnosis to decide whether or not to deliver an electric shock.
There are apps available to help locate the closest defibrillators, the most comprehensive being Stayin’ Alive.
If the ventricular fibrillation is caused by a reversible condition, it should be treated.
In most cases, when ventricular tachycardia occurs, it leads to the implantation of a defibrillator. This device monitors the heart’s electrical activity and delivers either anti-tachycardia stimulation or an electric shock if arrhythmia is detected.
What is an implantable cardioverter-defibrillator?
Implantable cardioverter-defibrillators are small devices connected to leads that are secured to the heart with screws or inserted under the skin. They should not be confused with automated external defibrillators.
Anti-arrhythmic medication can also be prescribed.
Finally, ventricular tachycardia ablation can be performed. In practice, this involves inserting a catheter into the ventricles through a vein or artery puncture in the groin and threading it through the blood vessels to the heart. A map of the ventricles is made to identify the affected areas, which are then ablated. Ablation refers to the targeted destruction of diseased heart tissue. Different types of energy can be used: radiofrequency, electroporation or cryoablation.
Reviewed and approved by Marine Arnaud, MD, Cardiologist at Bordeaux University Hospital (CHU)
