Ventricular tachycardia (VT)

What is ventricular tachycardia (VT)?

The term tachycardia comes from the Greek words for “swift” and “heart”. That’s a helpful description of what the condition involves. In ventricular tachycardia, the heartbeat becomes faster than normal – at least 100 beats per minute (bpm) and sometimes much faster than that (a normal heartbeat at rest is usually between 60 and 100 bpm).

The word ventricular refers to the lower chambers of the heart – the ventricles – which is where this rhythm problem originates. One of the problems with VT is that the ventricles can start to contract so quickly they don’t have enough time to fill the heart properly with blood. This means the heart isn’t functioning as efficiently as it should and isn’t able to pump enough oxygen around the body.

Serious cases of VT can lead to Ventricular fibrillation (VF or VFib), a dangerous rhythm condition that causes the lower heart chambers to “fibrillate” (quiver) and stop pumping blood around the body (cardiac arrest).

However, VT can also result in a cardiac arrest if the rhythm is very fast, particularly if the heart is also reduced in function, for instance, from previous damage by a myocardial infarction.

Ventricular tachycardia shouldn’t be confused with supraventricular tachycardia (SVT), an arrhythmia that originates ‘supra’ (above) the ventricles, in the atria.

What causes ventricular tachycardia?

VT is rooted in an abnormal electrical pathway that starts in the ventricles. In a normal situation, the electrical signals that help your heart to beat correctly travel first across the upper chambers (the atria), then down into the atrioventricular node (a kind of bridge between the upper and lower chambers) and on to the ventricles. This enables the heart muscle to contract in a regular and coordinated way, and to pump blood efficiently around your body.

In VT, however, the signals within the ventricles become faulty, causing those lower chambers to contract too quickly. Why does this happen in the first place? The most common factor is an underlying heart condition. Many cases of VT are related to coronary artery disease, for example, where the arteries become blocked, preventing the heart muscle from receiving blood and oxygen, damaging the heart permanently by causing scar tissue. But it can also be caused by prior damage to the heart, for instance due to:

• scars in the heart tissue from other causes (which can cause interference with the normal flow of electrical signals)
• heart failure
• heart valve disease
• myocarditis (inflammation of the heart muscle, commonly from virus infection)

Structural problems in the heart aren’t the only potential causes of ventricular tachycardia, however. VT can sometimes be triggered by certain types of medication, using stimulants like cocaine or methamphetamines, or by significant changes in electrolyte levels (such as potassium, sodium and calcium).

Genetics can play a role too; you may be more susceptible to VT if you have a family history of tachycardia or other arrhythmias, or if you’ve inherited a condition like Long QT syndrome, which causes fast, chaotic heartbeats, or Brugada syndrome, a rare genetic condition that affects the heart’s electrical activity.

What does ventricular tachycardia feel like?

It often comes down to how the irregular rhythm is presenting in your heart. Broadly speaking, there are two main ways that VT can impact the heart. Non-sustained VT (known as NSVT) is when the irregular rhythm starts and stops on its own within 30 seconds; this type of episode may not cause any noticeable symptoms, though you might notice a brief fluttering or palpitation.

Sustained VT is when the abnormal rhythm lasts for longer than 30 seconds. Because sustained VT can reduce oxygen flow throughout the body, it can trigger a range of adverse symptoms. These include:

• Fatigue
• Dizziness or light-headedness
• Shortness of breath
• Sweating or nausea
• Feeling faint, collapse or losing consciousness
• Falling blood pressure
• Chest pains, and even cardiac arrest

Sustained VT that doesn’t stop on its own is a medical emergency and needs to be treated as quickly as possible.

Who gets ventricular tachycardia?

Ventricular tachycardia becomes more common with age. But as we mentioned above (What causes ventricular tachycardia), the biggest risk factor for VT is prior heart damage, for example, from a heart attack, coronary artery disease, or heart muscle inflammation. You’re also at higher risk if you already have an underlying heart condition or if you have a family history of heart rhythm problems.

But VT can also affect people with structurally normal hearts or with no other underlying heart problems. We call this idiopathic ventricular tachycardia. Idiopathic VT often arises from an “irritable focus,” in which a group of cells in the ventricles begins to generate abnormal electrical impulses. This type of VT is usually easier to treat

How do you diagnose ventricular tachycardia?

The standard way to diagnose VT is with an electrocardiogram (ECG). This is a simple test that uses sticky electrode patches to record the electrical activity in your heart; it can either be done while you rest on a bed in the clinic, or while you walk or run on a treadmill (an exercise ECG or cardiac stress test).

Some types of ECG – such as an ambulatory ECG, a Holter monitor or an event monitor – can also be done at home. This can help us obtain a clearer picture of the activity and any anomalies occurring in your heart over a longer period. In rare cases, we recommend an implantable loop recorder, a small device placed under the skin of the chest that continuously records the heartbeat for up to three years.

Other types of tests we might recommend include an Electrophysiology Study (EPS) or imaging tests such as an X-ray, CT scan, MRI scan, or an echocardiogram (an ultrasound test that shows your heart in real time).

Alongside the tests, we will also talk to you in detail about any symptoms you’ve been experiencing, the medicines you might be taking, and your family history. This will help us to build a complete picture of what’s happening in your heart before we take the next steps.

What happens next?

There are several effective treatments for ventricular tachycardia. As a rule of thumb, you would need treatment for VT if you a) have symptoms or b) have the VT rhythm for more than 30 seconds (with or without symptoms).

In VT treatment, our main goals are to 1) stop the VT and slow your rapid heartbeat and 2) reduce the symptoms you’ve been getting and prevent dangerous complications now or in the future.

Short term – Depending on your diagnosis, we can use anti-arrhythmic medicines (such as beta blockers, calcium-channel blockers and amiodarone) to bring down the rapid heartbeat and stabilise your heart rhythm. We may also recommend a procedure called cardioversion, a short operation that uses electrical energy to return the heart to its natural (‘sinus’) rhythm

Longer term – Some VT cases need to be managed over a longer time period. As well as anti-arrhythmic medicines, we might also recommend a treatment called a cardiac ablation. This is an operation that uses catheters (small, flexible tubes) and electrical energy to target the heart tissue that’s causing the rogue electrical signals and restore the heart’s natural rhythm.

Some patients with VT can also benefit from an internal defibrillator (also known as an implantable cardioverter defibrillator or ICD). This is a tiny pacemaker device that sits underneath the skin of your chest and constantly monitors your heart rate and rhythm as you go about your normal activities. If it detects a serious rhythm problem, it can deliver a lifesaving electrical treatment to your heart.

Lifestyle – Making changes to your activities and lifestyle can sometimes reduce the risk of further VT episodes. These might include avoiding smoking, alcohol and highly caffeinated drinks, and avoiding strenuous exercise until your symptoms are under control. We’ll discuss these options with you when we discuss your treatment plan.