Paroxysmal tachycardia is a common heart rhythm disorder characterized by episodes where the heart suddenly begins beating very rapidly and then abruptly returns to a normal rhythm. Tachycardia means a fast heart rate, generally over 100 beats per minute, while the “paroxysmal” distinction refers to the sudden, temporary nature of the event. This condition affects the heart’s electrical system, causing a temporary malfunction.
Understanding Paroxysmal Tachycardia
Paroxysmal Tachycardia involves an accelerated heart rate originating from an electrical issue above the heart’s lower chambers, often called Paroxysmal Supraventricular Tachycardia (PSVT). During an episode, the heart rate typically ranges from 150 to 250 beats per minute, significantly exceeding the normal resting rate of 60 to 100 beats per minute. This rapid beating is caused by an electrical “short circuit” within the heart’s upper chambers.
The most common form, Atrioventricular Nodal Re-entrant Tachycardia (AVNRT), involves an extra electrical pathway near the atrioventricular (AV) node. This node acts as the electrical bridge between the upper and lower heart chambers. This extra path allows the electrical signal to loop repeatedly, creating a rapid, self-sustaining circuit. Another type, Atrioventricular Re-entrant Tachycardia (AVRT), often involves an abnormal muscle fiber connecting the upper and lower chambers, commonly seen in Wolff-Parkinson-White syndrome.
The symptoms experienced during an episode can be intense and often mimic an anxiety attack. Common physical sensations include palpitations, such as a racing or pounding in the chest, along with shortness of breath. A person may also experience lightheadedness, dizziness, or chest discomfort due to the heart’s reduced efficiency in pumping blood. These episodes can last for a few seconds, several minutes, or occasionally for hours.
Immediate Response: Stopping an Episode
When an episode begins, the first-line, non-prescription approach involves performing specific physical actions known as vagal maneuvers. These maneuvers stimulate the vagus nerve, a major component of the parasympathetic nervous system that controls heart rate. Stimulating this nerve sends a signal that can help interrupt the short circuit and potentially restore a normal rhythm.
One of the most effective techniques is the Valsalva maneuver, which involves bearing down. A modified version requires the individual to sit or lie down, take a deep breath, and exhale forcefully against a closed mouth and pinched nose for about 15 seconds. Immediately after, the person is laid flat with their legs elevated to about a 45-degree angle for another 15 seconds. Other simple maneuvers include coughing forcefully and repeatedly or immersing the face in ice-cold water, which triggers the diving reflex.
While these techniques can successfully terminate an episode, it is important to know when to seek professional medical help. Emergency attention is required if the rapid heart rate is accompanied by severe symptoms like chest pain, fainting spells, or severe dizziness. If an episode lasts longer than usual or does not stop after several attempts at vagal maneuvers, medical intervention may be necessary to restore the heart’s normal rhythm.
Identifying the Underlying Electrical Issue
Accurately diagnosing the specific type of electrical short circuit is necessary for effective long-term management. Since paroxysmal tachycardia episodes are intermittent, the main diagnostic challenge lies in capturing the heart’s rhythm during a symptomatic event. A standard 12-lead Electrocardiogram (ECG) performed in a clinic is often normal between episodes, so specialized monitoring devices are necessary.
The initial step often involves using ambulatory monitoring devices, which record the heart’s electrical activity over a longer period. A Holter monitor records the ECG continuously for 24 to 48 hours, which is helpful if episodes occur frequently. For individuals whose episodes are less common, an event recorder or a mobile cardiac outpatient telemetry device is used. These devices can be worn for several weeks and are activated by the patient when symptoms begin.
If episodes are extremely rare, an Implantable Loop Recorder (ILR) may be placed just under the skin for continuous monitoring over several years, ensuring even infrequent events are captured. Analyzing the ECG tracing during an episode allows the cardiologist to determine the exact origin and mechanism of the tachycardia, such as whether it is an AVNRT or AVRT.
Common Triggers
Identifying and avoiding personal triggers plays a role in management. Common non-structural triggers include stress, anxiety, excessive consumption of caffeine or alcohol, and lack of sleep. Certain over-the-counter cold medications containing stimulants like pseudoephedrine can also provoke an episode.
Long-Term Management and Treatment Options
Once the underlying electrical problem has been identified, treatment focuses on preventing future episodes. For patients with infrequent or mild symptoms, observation and lifestyle modifications, such as managing stress and limiting stimulants, may be sufficient. For more symptomatic individuals, medical therapy or a procedural intervention is recommended.
Medication management commonly involves using rate-controlling drugs like beta-blockers and calcium channel blockers. Beta-blockers work by blocking the effects of adrenaline, slowing the heart rate and reducing the force of contractions. Calcium channel blockers, such as verapamil or diltiazem, act primarily on the AV node to slow the conduction of electrical impulses, preventing the rapid cycling that sustains the tachycardia. Antiarrhythmic agents may also be used, but they are reserved for cases where first-line medications are ineffective or not tolerated.
The most definitive treatment for many forms of paroxysmal tachycardia is catheter ablation. This procedure is considered a curative option, especially for Supraventricular Tachycardia (SVT) types. Catheter ablation involves threading thin, flexible wires through blood vessels, usually from the groin, up to the heart. Once the specific short-circuit pathway is located, radiofrequency energy or cryotherapy is applied to a small area of heart tissue to eliminate the faulty electrical connection. This prevents the electrical loop from forming again, with success rates often reported between 94% and 98.5%.