Paroxysmal tachycardia is a heart condition defined by episodes of an abnormally rapid heart rhythm that begin and end suddenly. Tachycardia refers to a heart rate exceeding 100 beats per minute (bpm), and “paroxysmal” means these rapid rhythms occur intermittently in sudden bursts. This unpredictable, episodic nature is the defining feature, distinguishing it from a consistently fast heart rate. While the abrupt onset can be alarming, paroxysmal tachycardia is generally considered a manageable condition.
Understanding the Nature of Paroxysmal Tachycardia
Paroxysmal tachycardia (PT) represents an electrical malfunction in the heart’s conduction system, causing the heart rate to dramatically increase, often to 150 to 250 bpm. This sustained, rapid rhythm is not a normal physiological response to physical exertion or stress.
Most commonly, PT is identified as Paroxysmal Supraventricular Tachycardia (PSVT), meaning the rapid rhythm originates in the upper chambers of the heart (atria) or the atrioventricular (AV) node. The heart’s normal rhythm is governed by the sinoatrial (SA) node, the natural pacemaker. In PSVT, an electrical short circuit develops above the lower chambers, overriding the SA node’s signal and causing the heart to contract rapidly.
The hallmark of PT is the spontaneous and abrupt nature of its onset and cessation. Episodes can last from a few seconds to many hours before the heart spontaneously reverts to its normal rhythm.
The Experience of an Episode
During a paroxysmal tachycardia episode, the symptoms experienced can be intense and often mimic a severe anxiety or panic attack. The most common sensation is palpitations, described as the heart racing, pounding, or fluttering uncomfortably in the chest. The heart rate is regular but extremely fast, often between 120 and 230 beats per minute.
The rapid heart rate impairs the heart’s ability to efficiently fill with blood between beats, leading to a temporary reduction in blood flow to the body. This can cause lightheadedness, dizziness, or a feeling of being faint. Individuals may also experience shortness of breath (dyspnea) or mild chest discomfort.
The duration of these symptoms is highly variable. The rapid rhythm may stop as suddenly as it started, leaving the person immediately feeling better, although sometimes fatigued. While uncomfortable, these episodes are generally not life-threatening for individuals with an otherwise healthy heart structure.
Electrical Pathways and Common Triggers
The underlying cause of paroxysmal tachycardia is typically an abnormal electrical circuit within the heart, usually a congenital anomaly. The most frequent form is Atrioventricular Nodal Re-entrant Tachycardia (AVNRT), where an extra, small pathway exists near the AV node, creating a loop for the electrical signal to rapidly circle. Another common mechanism is Atrioventricular Re-entrant Tachycardia (AVRT), which involves an accessory pathway connecting the upper and lower heart chambers, as seen in Wolff-Parkinson-White (WPW) syndrome.
These short-circuit mechanisms are present from birth but only cause symptoms when a premature electrical impulse triggers the rapid, circular rhythm, or re-entry. PSVT is the term used for rhythms originating above the ventricles, including AVNRT and AVRT. Paroxysmal Ventricular Tachycardia (PVT), which originates in the lower chambers, is less common and often associated with underlying structural heart disease, making it a more serious condition.
While the structural anomaly is the prerequisite, external factors often serve as non-physiological triggers that initiate the rapid rhythm.
Common Triggers
- Excessive consumption of stimulants like caffeine, which increases the heart’s electrical excitability.
- High levels of emotional stress or anxiety, due to the release of adrenaline.
- Consuming alcohol, particularly in excess.
- The use of nicotine or illicit stimulant drugs.
- Certain over-the-counter medications, such as cold remedies containing decongestants.
- Factors that place physiological stress on the body, including intense exercise, dehydration, or a lack of sleep.
Diagnosis and Management Options
The first step in diagnosing paroxysmal tachycardia is documenting the rapid heart rhythm during an active episode. Since the episodes are intermittent, an Electrocardiogram (EKG) performed in a doctor’s office often appears normal between events. To capture the paroxysmal nature of the condition, physicians use ambulatory monitoring devices, such as a Holter monitor worn for one to seven days, or an event recorder, which can be manually or automatically activated during a symptomatic episode.
Once a PT episode is confirmed, management options depend on the frequency and severity of symptoms. For immediate termination, patients may be taught vagal maneuvers, such as bearing down (the Valsalva maneuver) or coughing. These physical actions stimulate the vagus nerve to slow the heart rate and are often a highly effective first-line intervention.
Long-term management focuses on preventing future episodes, starting with lifestyle modifications like trigger avoidance. Medications are common for recurrent cases; beta-blockers and calcium channel blockers are frequently prescribed to slow the heart rate. For individuals with highly symptomatic or frequent episodes, catheter ablation may be recommended. This procedure is potentially curative, using heat or cold energy to intentionally destroy the abnormal electrical pathway responsible for the short circuit.