Paroxysmal Supraventricular Tachycardia (commonly known as PSVT) is a form of arrhythmia or heart rhythm disturbance that causes sudden episodes of a rapid, regular racing of the heart. The normal heart rate at rest is generally 60 to 80 beats per minute (BPM). During PSVT, the heart rate is generally above 120 BPM and more commonly can be as high as 150 to 220 BPM. The episodes can last from minutes to days, and usually it stops as abruptly as it started.
Fortunately, most episodes last a maximum of a couple of hours before stopping on their own. However, at times the rapid heartbeat won’t stop and patients have to go to an emergency room where they can receive medications directly into a vein to get the arrhythmia to stop.
PSVT can be seen in children and adults of all ages, although it is less common over age 65 (as those patients are more likely to suffer from atrial flutter or fibrillation). It may start occurring as a teenager and occur sporadically throughout a person’s whole life. However, some patients will not have their first episode until they are older (in their 30s or 40s).
Symptoms of PSVT
PSVT symptoms are rapid, regular palpitations often occur suddenly and are unrelated to any specific stimulus such as exercise or an adrenaline rush. In some cases, patients can even wake up with the symptoms. Less often, the arrhythmia can be triggered when the person is active, such as with exercise or emotional stress.
The rapid palpitations may be associated with other symptoms such as lightheadedness, weakness, shortness of breath, or a general feeling of chest discomfort and anxiety. For this reason, it is sometimes misdiagnosed as a panic attack. Rarely the condition may be asymptomatic (with no symptoms at all).
Infrequently, people can experience sudden loss of consciousness (“syncope” or fainting) due to a dramatic drop in blood pressure at the onset of the tachycardia. The drop in blood pressure leads to a decrease in blood flow to the brain. With inadequate blood flow to the brain, essential nutrients and oxygen are not delivered and the brain quickly shuts off, It only takes about 5-6 seconds of reduced blood flow to cause syncope. Loss of consciousness usually lasts for just a few seconds, until the brain compensates for the low blood pressure, or the patient falls over (thus restoring blood flow to the head).
Causes of PSVT
The heart has an electrical system that controls the heart’s rhythm. Any rhythm disturbance (“arrhythmia”) arises from abnormal functioning of the electrical circuits of the heart.
Each normal heartbeat starts in a structure called the Sinus Node, located at the top of the right atrium. It “fires” or generates an electrical signal that starts the heartbeat. That electrical signal spreads across the top chambers and stimulates the atria to contract. The electrical signal of the atrium then passes through an electrical connection between the top and bottom chambers. This connection is called the AV (atrioventricular) Node. The AV node allows the top and bottom chambers to work together and maintains efficient pumping of the blood.
Most patients with PSVT have an AV node with multiple electrical pathways. This can allow the electrical signal that controls the heart to get “stuck” going round and round in a “short circuit” within the region of the AV node. This arrhythmia is referred to as “AV Nodal Reentry Tachycardia,” also known as AVNRT. Less commonly, people can be born with an extra electrical connection that bridges the heart’s upper and lower chambers. Sometimes that extra connection, known as an “Accessory Pathway,” causes the electrical signals of the heart to look abnormal all of the time. We can see this very characteristic abnormality on an electrocardiogram (ECG or EKG) in patients with the Wolff Parkinson White (WPW) Syndrome. People with this extra pathway are prone to developing rapid heartbeats (PSVT) because the signal that controls the heart rhythm can get stuck chasing it’s own tail around and around in a circle, usually going down the AV node to the ventricles and then up the accessory pathway back to the atrium, which allows the signal to go back down the AV node again, thus completing the circuit. This specific type of PSVT is referred to as “AV Reentry Tachycardia” or “AV Reciprocating Tachycardia,” abbreviated AVRT. Sometimes the accessory pathway cannot pass the electrical signal from the atria to the ventricles and so the ECG may not look abnormal unless tachycardia is present. This is known as a “concealed” accessory pathway, but it can also cause AVRT.
Other less common electrical disturbances can arise from the top chambers and give rise to a rapid arrhythmia known as “Paroxysmal Atrial Tachycardia” or PAT. In that case, the AV node is not part of the circuit, like it is with the other two arrhythmias.
A person has to have an electrical “short circuit” for PSVT to occur. PSVT does not occur in people without an abnormal electrical pathway. However, in patients with an abnormal pathway, some things can “trigger” the PSVT to get started. Usually, PSVT starts because of a premature beat or series of rapid beats that set off the arrhythmia. Some lifestyle-related habits may increase the number of extra beats a person may have, so these factors could increase the chances of someone going into tachycardia. A few things that can trigger tachycardia are:
- Alcohol and caffeine consumption
- Illicit drug use
- Medication for other health problems.
- Exercise or emotional stress
Establishing a Diagnosis
The electrocardiogram is a recording of the electrical activity of the heart and will show the presence of PSVT. However, since PSVT occurs sporadically it’s often difficult to diagnose unless the patient is having an ECG recorded at the moment they have an episode.
A diagnosis of PSVT may be suspected based on the history of palpitations and the nature of the symptoms provided by the patient. WPW can be diagnosed with an ECG when the patient is not in tachycardia, but otherwise the doctor may have to order a heart monitor to wear for an extended period of time to try to catch an event. The most common monitor is called a Holter monitor, which records every single heartbeat for 24-48 hours. However, if the episodes don’t occur every day you may be required to wear a cardiac “event” monitor, which can monitor your heart’s activity for up to a month. Some patients with very infrequent symptoms can purchase an external heart monitor that can be used (along with a “smart phone”) to capture their ECG when they are having their next tachycardia event. Finally, a small implantable cardiac monitor (like a “chip”) can be inserted just under the skin to monitor patients for up to 3 years.
In patients who may have PSVT, it is recommended that they meet with a heart rhythm specialist (cardiac electrophysiologist), who will be highly experienced in diagnosing the cause of the tachycardic episodes. In some cases an invasive study known as an electrophysiologic study may be helpful to find the problem.
Prevention and Treatment
Even though the symptoms can be bothersome and at times scary, PSVT is not a life-threatening condition, and some patients can just live with it. The decision to treat PSVT has to do with the severity of the symptoms, the frequency and duration of the episodes, and how much the condition interferes with the patient’s quality of life. In rare cases, PSVT can cause fainting, and in that case it must be treated to avoid serious injury.
The ideal way to treat PSVT is to refer the patient to a cardiac electrophysiologist, who will likely recommend electrophysiologic (EP) testing. This procedure is like doing an ECG from the inside, through a vein, using multiple thin wire catheters. This painless procedure is done while the patient is sedated, so patients don’t remember much. Once the EP study demonstrates the location of the short circuit, catheter ablation can be performed to permanently cure the problem. During ablation, one of the wires is positioned right up against the source of the arrhythmia and is used to damage the abnormal pathway with electrical energy, thus eliminating the short circuit that is causing PSVT. Catheter ablation for PSVT has an extremely high success rate with a minimum of risk, and is regarded as “first-line therapy” to treat PSVT.
Some patients decide to turn down an ablation procedure and just live with the condition. Those patients may be able to alleviate the symptoms with short-term remedies that can get the tachycardia to stop once it gets started. These “vagal” maneuvers slow the signal down within the AV node and may be helpful in patients with brief, infrequent episodes. These maneuvers include bearing down while holding your breath (as if you are trying to have a bowel movement), splashing your face and neck with ice cold water, or coughing vigorously.
Medical therapy can be used as a temporary measure to reduce the frequency and severity of the PSVT attacks, but medications all have the potential for side effects. Besides that, they do not work all the time, so PSVT can still occur even on meds, and as soon as you stop the medication the problem comes right back.
Changes in daily habits and lifestyle can reduce the frequency and intensity of the episodes:
- Avoid the use of caffeine and alcohol – caffeine increases the premature beats that can trigger a tachycardia. Alcohol has a similar effect.
- Review your medications with your doctor to see if anything could be making it worse. For example, an electrolyte imbalance from the use of diuretic therapy for hypertension can trigger abnormal heartbeats and cause PSVT to start.
- Avoid situations that put a psychological strain on you – this refers to stressful conditions, situations of high anxiety and nervousness, and adrenaline rushes.
Keep in mind that every patient with PSVT has a short circuit, which is not likely to go away by itself. Patients can go for long periods in between tachycardia attacks, but the problem can still come back even after many years. If you want to learn more about your options to treat PSVT, speak to your doctor and ask to see an EP specialist who can provide you with expert advice.
Should I Worry?
PSVT does not put a high risk on your health, but it can cause significant symptoms and affect your quality of life. In addition, patients who experience fainting with rapid PSVT are at increased risk of driving a car or engaging in competitive sports. Depending on the severity of the condition, it can be a hard thing to live with. If you suspect you have PSVT, have yourself checked and follow the recommendation of the specialist. It’s better to be safe than sorry.