Supraventricular tachycardia

In most cases, supraventricular tachycardias occur in an otherwise structurally normal heart. These are referred to as “SVTs on a healthy heart.” However, several factors may be involved in their onset or triggering, especially in specific forms such as Bouveret’s tachycardia or junctional tachycardia, which are linked to well-identified rhythmology mechanisms.

Predisposing factors

• Congenital factors: some people are born with an anatomical predisposition to supraventricular tachycardias, such as the presence of an accessory pathway (Wolff–Parkinson–White syndrome) or the presence of two conduction pathways in the atrioventricular node (the substrate for AV nodal reentry, which causes Bouveret’s tachycardia);
• Structural heart abnormalities: although less common, certain heart diseases can promote the onset of supraventricular tachycardias:
  • Valvular disease (particularly mitral valve disease);
  • Congenital heart disease;
  • Atrial enlargement;
  • After-effects of cardiac surgery.

Triggering factors

Several triggers can precipitate an episode of supraventricular tachycardia in predisposed individuals:

• Stress and anxiety: some people experience what is known as stress-related tachycardia, often occurring at rest. While benign, it can be mistaken for a pathological arrhythmia;
• Fatigue;
• Excessive intake of stimulants (caffeine, alcohol, nicotine);
• Intense physical activity;
• Hormonal changes (pregnancy, menstruation);
• Medications (sympathomimetics, theophylline);
• Hyperthyroidism;
• Imbalances in blood electrolytes (potassium, magnesium).

It is also common to observe resting tachycardia in anxious or fatigued individuals, often due to a physiological sinus tachycardia, sometimes referred to as *sinus tachycardia* in the English-language literature.

It is important to note that most patients with supraventricular tachycardias have no identifiable underlying heart disease. Nonetheless, a basic cardiac work-up, including at least an echocardiogram, is systematically recommended to rule out any possible structural abnormality.

The clinical manifestations of supraventricular tachycardias vary greatly from one patient to another, depending on the type of tachycardia, its rate, its duration, and the possible presence of underlying heart disease.

Common symptoms

• Palpitations: sensation of rapid, regular or irregular heartbeats, often with sudden onset and termination;
• Shortness of breath (dyspnea), especially during prolonged episodes;
• Chest tightness or discomfort;
• Fatigue;
• Dizziness or lightheadedness;
• Anxiety, often linked to awareness of the palpitations;
• Polyuria (increased urine output during or after the episode);
• Syncope (loss of consciousness), rare but possible in cases of very rapid rates or abrupt termination of the tachycardia.

Episode characteristics

Supraventricular tachycardia episodes have several features that can help distinguish them from other rhythm disorders:

• Sudden onset: episodes often start abruptly, “as if a switch had been flipped”;
• Equally abrupt ending: the episode may stop spontaneously or after vagal maneuvers;
• Regular rhythm: in most SVTs (except atrial fibrillation), the rhythm is very regular;
• High rate: generally between 150 and 250 beats per minute;
• Variable duration: from a few seconds to several hours, or even days in some cases.

Symptoms may worsen if the tachycardia persists for a long time due to cardiac muscle fatigue. A prolonged episode can sometimes trigger transient heart failure, presenting with more pronounced shortness of breath and swelling (edema).

Supraventricular tachycardias are generally benign arrhythmias that do not directly threaten life, especially when they occur in a structurally normal heart. However, they can lead to certain complications:

• Reduced quality of life: the discomfort caused by palpitations and the associated anxiety can have a significant impact on daily life, particularly when episodes are frequent or prolonged;
• Faintness or syncope: episodes of lightheadedness or even loss of consciousness can occur during an episode (due to decreased cardiac output) or upon its abrupt termination (due to a transient sinus pause);
• Heart failure: prolonged tachycardia may cause shortness of breath linked to transient heart failure, usually reversible once the episode stops;
• Thromboembolic complications: certain supraventricular tachycardias—particularly atrial fibrillation, atrial flutter, and some atrial tachycardias—can promote the formation of clots in the atria, with a risk of systemic embolism (notably stroke). This risk mainly concerns patients with other cardiovascular risk factors (advanced age, hypertension, diabetes, etc.);
• Tachycardia-induced cardiomyopathy: very rarely, frequent and prolonged supraventricular tachycardias can lead to impaired left ventricular function, which is generally reversible after the arrhythmia is controlled.

It is important to note that the risk of sudden death from supraventricular tachycardias is extremely low, unlike certain ventricular tachycardias. However, in patients with Wolff–Parkinson–White syndrome, the presence of a rapidly conducting accessory pathway can, in rare cases, cause excessive acceleration of the ventricular rate during atrial fibrillation, with a potential risk of ventricular fibrillation.

Main diagnostic methods

A definitive diagnosis of supraventricular tachycardia relies primarily on electrocardiographic recording during an episode. Several methods can be used to obtain this recording:

• Standard 12-lead electrocardiogram (ECG): the basic test which, if performed during an episode, allows the precise type of supraventricular tachycardia to be identified. Between episodes, the ECG is often normal but may sometimes reveal diagnostic clues (ventricular pre-excitation in Wolff–Parkinson–White syndrome, abnormal P waves in certain atrial tachycardias);
• Holter ECG: continuous recording of heart activity for 24 to 48 hours, enabling detection of tachycardia episodes occurring during that time. Particularly useful for frequent arrhythmias;
• Event recorder: a device worn by the patient for several weeks, allowing ECG recording during symptoms by pressing a button. Useful for infrequent episodes;
• Exercise ECG: recording heart activity during standardized physical exercise. Can be helpful if episodes are triggered by exertion;
• Implantable loop recorder: a small device implanted under the skin of the chest, capable of recording heart activity for several years. Indicated in rare but severe symptoms such as unexplained syncope.

These diagnostic tests can be performed at the various Rythmopôle Paris centers, including Cardiopôle Yvart (Paris 15th) and Centre Damrémont (Paris 18th).

Electrophysiological study

In certain cases, particularly when ablation is being considered or when the diagnosis remains uncertain despite non-invasive tests, an intracardiac electrophysiological study (EPS) may be recommended:

• This is a procedure performed in the operating room, usually under local anesthesia, involving the insertion of recording catheters into the heart via a venous puncture in the groin;
• These catheters record the heart’s internal electrical activity and allow programmed cardiac stimulation to try to induce and analyze the tachycardia;
• EPS provides an accurate diagnosis of the mechanism and location of the tachycardia, and can be immediately followed by an ablation procedure if indicated.

Electrophysiological studies are performed at Institut Mutualiste Montsouris (Paris 14th) by the electrophysiologists of Rythmopôle Paris.

Basic cardiac assessment

In addition to tests aimed at documenting the tachycardia, a basic cardiac work-up is generally recommended:

• Echocardiography: to evaluate heart structure and function and detect any associated cardiac abnormalities;
• Blood tests: including an electrolyte panel (potassium, magnesium, calcium) and a thyroid function test.

The management of supraventricular tachycardias relies on two complementary strategies: treating the acute episode and preventing recurrences.

Management of an acute episode

Several approaches can be used to stop an ongoing episode of supraventricular tachycardia:

• Vagal maneuvers: these techniques stimulate the vagus nerve, slowing conduction through the atrioventricular node and potentially stopping certain tachycardias (notably AV nodal reentrant tachycardia). They include:
  • Valsalva maneuver (forced exhalation against resistance);
  • Carotid sinus massage (to be performed only by a physician);
  • Immersing the face in cold water;
  • Forceful coughing.
• Emergency drug treatment:
  • Intravenous adenosine: first-line hospital treatment for reentrant tachycardias;
  • Other intravenous antiarrhythmics: beta-blockers, calcium channel blockers, amiodarone, depending on the type of tachycardia and clinical context.
• Electrical cardioversion: external electric shock, reserved for cases resistant to other treatments or in situations of hemodynamic instability.

Prevention of recurrences

Two strategies can be considered to prevent recurrent episodes of supraventricular tachycardia:

• “Palliative” strategy: aims to control symptoms without eliminating the arrhythmia substrate.
  • No active treatment and patient education: for rare, well-tolerated episodes, simply informing the patient about maneuvers to perform during a crisis may be sufficient;
  • “Pill-in-the-pocket” approach: taking medication only during an episode, to attempt to stop it;
  • Long-term preventive drug treatment: daily use of antiarrhythmics (beta-blockers, calcium channel blockers, flecainide, etc.) to reduce the frequency of episodes. This strategy carries a risk of medication side effects and is not effective in 100% of cases.
• “Curative” strategy: aims to permanently eliminate the arrhythmia substrate via catheter ablation.

The choice between these strategies depends on the type of tachycardia, the frequency and tolerance of episodes, the patient’s age and comorbidities, and personal preferences. This decision is made jointly by the patient and their electrophysiologist at Rythmopôle Paris, taking all these factors into account.

Principle of ablation

Catheter ablation is an interventional procedure designed to permanently eliminate the arrhythmia substrate responsible for supraventricular tachycardia. Despite its name, nothing is physically “removed” during the procedure; rather, targeted lesions are created using micro-burns to interrupt abnormal electrical circuits or neutralize ectopic foci.

Two techniques can be used to create these lesions:

• Radiofrequency ablation: uses thermal energy (heat) to create localized lesions;
• Cryoablation: uses extreme cold to create lesions. This technique is sometimes preferred when the target area is close to sensitive structures (such as the atrioventricular node), as it allows the effect of the lesion to be tested reversibly before making it permanent.

Procedure steps

Catheter ablation for supraventricular tachycardia generally proceeds as follows:

• Hospitalization: most often on an outpatient basis (admission in the morning, discharge the same evening);
• Anesthesia: usually local at the puncture site, sometimes combined with light sedation. General anesthesia may be required in certain complex cases;
• Access: puncture of the femoral vein (in the groin), rarely the femoral artery or other vessels;
• Catheter positioning: under X-ray guidance, electrode catheters are introduced into the heart;
• Mapping: precise identification of the arrhythmia circuit or ectopic focus using intracardiac electrical recordings and sometimes three-dimensional mapping systems;
• Ablation: application of energy (radiofrequency or cryotherapy) to create targeted lesions;
• Verification: tests to ensure that the tachycardia can no longer be induced;
• Catheter removal and puncture site compression;
• Post-procedure monitoring for a few hours.

This procedure is performed at Institut Mutualiste Montsouris by the electrophysiologists of Rythmopôle Paris.

Results and risks

Catheter ablation for supraventricular tachycardia generally achieves excellent results:

• High success rate: over 90–95% for AV nodal reentrant tachycardia (Bouveret’s disease), accessory pathway reentry (Wolff–Parkinson–White syndrome), and typical atrial flutter; slightly lower for other types of tachycardia;
• Usually definitive result, allowing antiarrhythmic medication to be discontinued;
• Low recurrence rate, generally below 5%, with the possibility of a second procedure if necessary.

However, like all interventional procedures, ablation carries certain risks:

• Groin hematoma: the most common complication, occurring in about 2% of cases, usually mild;
• Atrioventricular block requiring pacemaker implantation: very rare (around 0.5% of cases), mainly during ablation of AV nodal reentry or accessory pathways close to the AV node (parahisian pathways);
• Pericardial effusion: extremely rare (less than 0.1% of cases);
• Anesthesia-related complications;
• Other rare complications: vascular injury, infection, thromboembolic events.

These risks are always discussed with the patient before the procedure, weighing them against the expected benefits and available therapeutic alternatives.

Rythmopôle Paris offers comprehensive expertise in the management of supraventricular tachycardias:

• A team of electrophysiologists specializing in the diagnosis and treatment of heart rhythm disorders;
• State-of-the-art facilities for performing all necessary diagnostic tests (ECG, Holter ECG, event recorders);
• Expertise in catheter ablation procedures, with access to the most advanced technologies (three-dimensional mapping, cryoablation) at Institut Mutualiste Montsouris;
• A personalized approach, taking into account each patient’s symptoms, preferences, and risk profile;
• Tailored follow-up care provided at multiple centers in the Île-de-France region, ensuring easier access to treatment;
• Extensive experience, with several hundred ablation procedures performed each year.