Paroxysmal tachycardia

Overview

Paroxysmal tachycardia is a condition characterized by sudden, brief episodes of abnormally fast heart rate (tachycardia) that begin and end abruptly. The term "paroxysmal" refers to the intermittent and sudden nature of the episodes. Paroxysmal tachycardia can arise from the atria (supraventricular) or the ventricles (ventricular), and while some episodes may be harmless, others can be serious and require medical attention. Common forms include paroxysmal supraventricular tachycardia (PSVT) and paroxysmal ventricular tachycardia (PVT). The condition is seen in both healthy individuals and those with underlying heart disease.

Causes

Paroxysmal tachycardia is caused by abnormal electrical signaling in the heart that leads to rapid heart rhythms. The specific cause depends on the type of tachycardia:

Paroxysmal Supraventricular Tachycardia (PSVT)

• Atrioventricular nodal reentrant tachycardia (AVNRT): The most common form of PSVT, involving a reentry circuit near the AV node.

• Atrioventricular reentrant tachycardia (AVRT): Often associated with accessory pathways, such as in Wolff-Parkinson-White syndrome.

• Atrial tachycardia: Originates from an ectopic focus in the atria.

Paroxysmal Ventricular Tachycardia (PVT)

• Coronary artery disease or prior myocardial infarction: Damaged heart tissue can lead to abnormal electrical circuits.

• Cardiomyopathy or heart failure: Structural changes increase the risk of arrhythmias.

• Electrolyte imbalances: Particularly low potassium or magnesium levels.

• Drug toxicity: Especially with medications like digoxin or antiarrhythmic drugs.

General Triggers

• Stress or anxiety

• Caffeine, alcohol, or stimulant use

• Hyperthyroidism

• Fever or infections

Symptoms

Symptoms of paroxysmal tachycardia can vary in severity and duration. Episodes may last seconds to hours and can occur sporadically or frequently. Common symptoms include:

• Palpitations: A sensation of rapid or pounding heartbeat

• Dizziness or lightheadedness: Due to reduced blood flow to the brain

• Shortness of breath

• Chest discomfort or pain: Especially in individuals with coronary artery disease

• Fatigue or weakness

• Fainting (syncope): In more severe or prolonged episodes

• Anxiety or panic: Common during acute episodes

Diagnosis

Diagnosis of paroxysmal tachycardia involves confirming the arrhythmia during an episode and identifying its type and underlying cause. Diagnostic steps include:

Initial Evaluation

• Medical history and physical exam: Focused on frequency, duration, and triggers of episodes

• Electrocardiogram (ECG): May capture an episode if it occurs during the test

Monitoring and Imaging

• Holter monitor: A 24–48 hour portable ECG recording to capture intermittent episodes

• Event monitor or loop recorder: Longer-term monitoring for infrequent symptoms

• Echocardiogram: Evaluates heart structure and function

• Exercise stress test: Assesses response to exertion and identifies exercise-induced arrhythmias

Electrophysiology Study (EPS)

• A specialized test using intracardiac electrodes to map electrical pathways and identify arrhythmia mechanisms, often used before catheter ablation

Treatment

Treatment depends on the type, frequency, and severity of paroxysmal tachycardia episodes. The main goals are to stop acute episodes, prevent recurrences, and treat any underlying causes.

1. Acute Episode Management

• Vagal maneuvers: Techniques such as the Valsalva maneuver or carotid sinus massage can terminate PSVT episodes

• Medications: Intravenous adenosine, beta-blockers, or calcium channel blockers are used to terminate PSVT

• Cardioversion: In cases of unstable or refractory tachycardia, especially in PVT

2. Long-term Management

• Medications:

  • Beta-blockers (e.g., metoprolol)

  • Calcium channel blockers (e.g., verapamil)

  • Antiarrhythmics (e.g., flecainide, amiodarone)

• Catheter ablation: A curative procedure that destroys the abnormal electrical pathway, especially effective for PSVT and AVRT

• Implantable cardioverter-defibrillator (ICD): For patients with life-threatening ventricular tachycardia or those at high risk of sudden cardiac arrest

• Lifestyle modifications: Avoiding triggers like caffeine, stress, and stimulants

Prognosis

The prognosis for paroxysmal tachycardia depends on the type and underlying cause:

Paroxysmal Supraventricular Tachycardia (PSVT)

Generally has an excellent prognosis. While uncomfortable, episodes are usually not life-threatening. Catheter ablation offers a high cure rate, and many patients live normal lives with little or no medication after treatment.

Paroxysmal Ventricular Tachycardia (PVT)

Can be serious, particularly in individuals with structural heart disease. It may lead to ventricular fibrillation and sudden cardiac arrest if untreated. Prognosis improves significantly with early diagnosis, appropriate medication, and use of an ICD when necessary.

With proper management and follow-up, most patients with paroxysmal tachycardia can achieve good symptom control and maintain a high quality of life. Regular cardiac evaluations and lifestyle adjustments play a key role in long-term outcomes.