Paroxysmal Supraventricular Tachycardia (PSVT)

How PSVT happens

Normally, each heartbeat begins in the sinus node and passes once through the AV node to the ventricles. In PSVT, an extra electrical pathway creates a loop. A well-timed extra beat can set off a signal that circles around the loop repeatedly, driving the heart at a fast, fixed rate. When the loop is interrupted, the rhythm stops as suddenly as it started.

Types

Symptoms

• sudden onset of a rapid, regular heartbeat, like a switch being flipped
• pounding in the chest or a pulsing feeling in the neck
• lightheadedness or dizziness
• breathlessness and chest tightness
• anxiety
• sweating
• needing to pass urine after an episode
• sudden stop, sometimes after a pause
• fainting, uncommon

Episodes can last a few seconds or many hours. Some people have them a few times a year, others several times a week.

Triggers

• caffeine and energy drinks
• alcohol
• lack of sleep
• stress
• exercise, or bending and straightening
• decongestants and stimulants
• an overactive thyroid (hyperthyroidism)

Often there is no trigger.

PSVT vs anxiety and sinus tachycardia

Many people with PSVT are first told they have panic attacks, so an ECG during an episode is valuable. See panic attack.

Diagnosis

• ECG during an episode: the best way to confirm PSVT. Go to urgent care or an ER while it is happening if possible.
• Smartwatch or handheld ECG recordings, which can capture brief episodes.
• Holter or event monitor for intermittent episodes.
• Resting ECG between episodes, which may show a delta wave in WPW.
• Echocardiogram to check heart structure.
• Blood tests for thyroid function and electrolytes.
• Electrophysiology study to map the circuit, usually combined with ablation.

Treatment

Stopping an episode yourself: vagal maneuvers

Vagal maneuvers stimulate the vagus nerve, slowing conduction through the AV node.

Modified Valsalva maneuver (shown in the REVERT trial to work in about 4 in 10 people):

1. Sit upright.
2. Blow into a 10 ml syringe hard enough to move the plunger, or strain as if having a bowel movement, for 15 seconds.
3. Immediately lie flat and have someone raise your legs to 45 degrees for 15 seconds.
4. Sit back up and check your pulse. Repeat once if needed.

Other options include splashing ice-cold water on the face. Never press on your eyeballs. Carotid massage should only be done by a clinician.

In the ER

• adenosine given rapidly into a vein, which briefly stops the heart's electrical activity and resets the rhythm. It causes a few seconds of chest discomfort or flushing
• IV calcium channel blockers (verapamil, diltiazem) or beta-blockers
• electrical cardioversion if the person is unstable

Long-term options

• No treatment for infrequent, brief, well-tolerated episodes, using vagal maneuvers.
• "Pill in the pocket": a single dose of medicine taken during an episode, prescribed by a cardiologist.
• Daily medicines: beta-blockers or calcium channel blockers, and sometimes flecainide.
• Catheter ablation: thin catheters are passed through a vein in the groin to the heart, and the extra pathway is destroyed with heat or cold. Success rates are around 95% for AVNRT and AVRT, with a small risk (under about 1%) of damaging normal conduction and needing a pacemaker. Guidelines support ablation as a first-line option for recurrent symptomatic PSVT.

Outlook

PSVT is rarely life-threatening in people with structurally normal hearts. Wolff-Parkinson-White syndrome carries a small risk of dangerous rhythms if atrial fibrillation develops, so ablation is often recommended. After successful ablation, most people never have another episode. Pregnancy can make episodes more frequent; treatment options are chosen carefully.

Frequently asked questions

What is PSVT?

PSVT, or paroxysmal supraventricular tachycardia, is a condition causing sudden episodes of a very fast, regular heartbeat that start and stop abruptly. It is caused by an extra electrical circuit above the heart's lower chambers and is usually not dangerous.

How do you stop an SVT episode?

Try the modified Valsalva maneuver: strain or blow into a syringe for 15 seconds, then lie flat with your legs raised. Splashing ice-cold water on your face can also work. If the episode continues beyond 15 to 30 minutes or you feel unwell, go to the ER.

Is PSVT dangerous?

In most people with a normal heart, PSVT is not life-threatening, though episodes can be frightening and disruptive. It is more concerning with fainting, heart disease or Wolff-Parkinson-White syndrome, which should be assessed by a cardiologist.

Can SVT be cured?

Yes. Catheter ablation cures about 95% of common types of SVT by destroying the extra electrical pathway. Many people choose it to avoid lifelong medicines or recurrent episodes.

How do I know if it is SVT or anxiety?

SVT usually starts and stops abruptly, with a very fast, fixed rate of 150 or more. Anxiety-related fast heartbeat builds and settles gradually. An ECG recorded during an episode, including from some smartwatches, is the best way to tell the difference.