Supraventricular tachycardia (SVT) is a common heart rhythm disturbance which may occur in all age groups including young and otherwise healthy patients. It is characterised by a sudden and unpredictable development of heart palpitations which to the patient feel very fast and regular. It can last between a few minutes to several hours and subside almost as quickly as it came on. Occasionally it does not subside by itself and the patient has to go to hospital where medications are given to stop the SVT and get the patient back into a normal heart rhythm.
SVTs are generally not dangerous heart rhythm disturbances by which i mean that they don’t shorten lifespan but they can be bothersome, incapacitating and impact adversely on a patient’s quality of life. Often the symptoms of SVT (which are only manifest during the SVT) can, in addition to palpitations, include dizziness, near-blackouts, blackouts, nausea, anxiety, chest pain, and a feeling of impending doom.
Currently commonly available treatments include:
- Vagal manoeuvres: Activation of the vagus nerve can help slow the heart down and abort the SVT. Common manoeuvres which the patient can do themselves include straining down as if on the toilet, gentle massage of the carotid vessel and body in the neck and simply lying down and taking deep breaths in and out. These can work but the success rate is less than 30%
- Pill in the pocket: There are some medications such as beta-blockers (eg bisoprolol) or calcium antagonists (eg verapamil) or even Flecainide which can be taken when the SVT occurs and can help abort the SVT. Obviously the ideal pill in the pocket would be one which works instantly. Unfortunately most of the medications can have a slow onset of action and therefore their effectiveness is modest at most.
- The definitive treatment of SVT is an invasive procedure known as ablation. SVTs tend to occur because of the presence of extra electrical pathways within the heart. Usually the electrical impulses are generated in the god-given pacemaker that we are all born with (the SA node). The impulses then travel through to the ventricle via the normal electrical pathways. However an extra electrical pathways can provide a mechanism for the impulses to go back up to where they came from and a short-circuiting mechanism can ensue and this is responsible for the fast heart rates. A skilled cardiologist with experience in this field (otherwise known as an electrophysiologist) can identify the location of the abnormal electrical pathways and disrupt then during the ablation procedure. This often results in a cure from the SVT. Whilst it is the best course of action from the doctor’s perspective, patients are often understandably reluctant to undergo an invasive procedure which involves a small amount of associated risk.
There is therefore a real need for an effective treatment which is safe, convenient but also has a rapid onset of action and which the patient can take only when they have an SVT episode.
This is where Etripamil comes in. Etripamil is a potent and novel new medication which is a short acting calcium antagonist (with a half life of only 20 minutes) and comes in the form of a nasal spray which can be self-administered by the patient. It has a rapid onset of action and can be effective within 5 minutes of administration. It is short acting and metabolised quickly and therefore does not remain in the body too long to cause extra side effects. It is also highly effective. In one study by BS Stambler and colleagues, 104 patients were given this medication in an electrophysiology lab setting. In one study by BS Stambler and colleagues, 104 patients were given this medication in an electrophysiology lab setting. 4 doses were used – 35mg, 70 mg, 105mg and 140 mg.This was compared with placebo. Conversion rates were between 65 and 95% in the patients who were given the etripamil. The median time to conversion was less than 3 minutes. The main side effects were local irritation in the nose and patients who received the highest dose had a drop in their blood pressure.
The agent is produced by a company called Milestone pharmaceuticals and they have started their phase 3 studies where they are actively enrolling patients into a study called the NODE 303 study to assess whether this agent will be safe for patients to take without any medical supervision.
I hope you found this useful.
Tags: SVT; supraventricular tachycardia; Etripamil; Nasal spray for SVT