Pressures on the NHS throughout the UK have been widely publicised lately, as it becomes increasingly difficult to access health services, with excessive waiting times.
Many patients are waiting several months to discuss their symptoms of chest pain, palpitations, breathlessness, etc with a Cardiologist. Or even if they have, there is now a significant wait to have the appropriate tests to investigate things further.
This page is designed as an educational resource to give patients some helpful information about some cardiac conditions and will be updated every few weeks.
SUPRAVENTRICULAR TACHYCARDIA (SVT):
To understand SVTs, we need to first understand what happens normally. Normally, a single electrical impulse originates at the top of the right atrium (specifically from the Sino-Atrial or SA node) and passes through the AV node in the middle of the heart, causing the 2 ventricles below the AV node to pump blood all around the body. This event occurs roughly once every second, resulting in a normal heart rate of approximately 60 beats per minute, though in reality a heart rate of 60-100 is considered normal.
Supraventricular Tachycardias (SVT) are fast heart rhythm disturbances which originate above or inside the AV node. By contrast, fast heart rhythm disturbances originating below the AV node are called Ventricular Tachycardia (VT).
There are a number of different types of SVT such as Atrial Fibrillation and Atrial Flutter but the most common type is AtrioVentricular Node Re-entry Tachycardia or AVNRT. In AVNRT, a random impulse (called an ectopic beat) arising from the ventricles can meet the AV node at the same time as a normal impulse from the SA node, causing a circuit to spin around the AV node rapidly in a circular fashion. This causes the ventricles to beat at double or triple speed, resulting in a patient’s pulse suddenly jumping to 150-200bpm (see figure 2).
Patients with AVNRT would typically experience intermittent palpitations, chest pain or breathlessness, often occurring with no obvious trigger and could last anywhere from a few seconds to several hours. It is not possible to determine whether such symptoms are due to SVT or VT without having an ECG at the time of the event. In severe cases, this is done in A&E where urgent treatment can be given.
But most often, tests are done as an outpatient. The main tests in this situation are:
- Portable or ambulatory ECG monitors for patients to wear under their clothes for a few days (up to 2 weeks) to try and capture the heart’s ECG when the palpitations happen
- Echocardiogram in order to confirm that the heart is structurally normal and ensure there is no underlying problem driving the SVT, for example a leaky / narrowed heart valve.
- In some patients, it may be necessary to have cardiac CT and / or MRI as well.
Once the diagnosis has been made, treatment is usually either one or both of the following:
- Medical therapy – tablets such as β-blockers to settle the SVT
- Ablation therapy – an interventional procedure to eliminate the SVT (AVNRT)
Because SVTs are generally a benign problem, many patients can simply be reassured that there is no risk of a heart attack or stroke or sudden death occurring, if the heart is structurally normal on the echo scan. And in such cases, no treatment may be necessary at all, just an acceptance that palpitations will occur from time to time and if they are not too troublesome for the patient, they can simply let it pass off, especially if short-lived in duration.
But in other cases, the symptoms are too frequent and patients prefer some medications to settle the uncomfortable feelings of palpitations or chest pains down. Bisoprolol is usually the first tablet prescribed as it is generally a well-tolerated, once daily treatment. There are additional tablets (e.g. Amiodarone or Flecainide) that can be given in more resistant cases.
Ablations are day-case procedures that are only performed at specialist cardiac hospitals. These involve small tubes and wires being passed through the groin into the heart under sedation in a theatre. With the help of mobile X-ray scanners, the wires are guided into the correct chambers in the heart where the SVT originates and the rhythm is ablated. Put simply, ablation is burning out part of the circular circuit in the AV node that the SVT spins around, thereby eradicating the problem. If you would like to book in for an appointment to discuss anything you have read above or to have some tests, then please get in touch either by phone or email.
