Supraventricular Tachycardia (SVT) is a common arrhythmia where the heart beats at an excessively fast rate due to an electrical malfunction originating above the lower chambers. This condition causes the heart rate to abruptly accelerate, often far exceeding the typical resting rate. For those experiencing an episode, the primary concern is the dramatic and startling subjective experience that accompanies this sudden change in rhythm. This is not merely a fast heart rate felt during exercise, but a chaotic physical sensation. Understanding the nature of this experience, from the core chest feeling to the body-wide effects, can help those who encounter this unsettling condition.
Defining the Core Sensation
The most immediate and defining symptom of an SVT episode is the sudden onset of intense palpitations felt directly in the chest. This sensation is often described as the heart instantly “switching on” to a rapid, disorganized pace, with no gradual build-up. The heart rate typically ranges from 150 to 250 beats per minute, a significant acceleration from a normal resting rate.
Many people describe the sensation as a violent fluttering or a frantic pounding against the ribcage. The feeling is frequently likened to a bird trapped in the chest or a drum rapidly hammering from within. This rapid action often prevents the heart from beating effectively, leading to a feeling of the heart “skipping beats” or having an irregular pattern even within the overall fast rhythm.
The forceful pounding can sometimes be felt not only in the chest but also distinctly in the neck. This results from the rapid, inefficient contractions of the upper heart chambers, which can cause the blood vessels in the neck to pulse visibly and strongly. Due to the surprising and abrupt nature of the onset, the core sensation is frequently accompanied by a profound and immediate sense of alarm or panic.
How Rapid Heart Rate Affects the Body
The intense speed of the heart during SVT episodes causes secondary symptoms throughout the body, driven by a reduction in cardiac output. When the heart beats too quickly, the chambers do not have enough time to fully refill with blood between contractions. This significantly lessens the amount of blood pumped out, starving the body’s tissues, particularly the brain, of necessary oxygen.
A consequence of this reduced blood flow to the brain is lightheadedness or dizziness. People may feel unsteady on their feet or have a sense of being on the verge of fainting, though complete loss of consciousness is less common. This is often accompanied by a sudden feeling of weakness or profound fatigue, even if the person was previously at rest.
The body’s attempt to compensate for the reduced output can manifest as mild shortness of breath or the need to take deeper breaths. Patients may also experience mild chest discomfort or pressure, which is usually a non-specific ache related to the rapid, forceful action rather than a sign of a heart attack. Sweating and a general feeling of unease or intense anxiety are common systemic responses to the body’s compromised state during the episode.
The Electrical Cause of the Symptoms
The dramatic physical symptoms of SVT are directly traceable to a fault in the heart’s electrical wiring system. The heart’s natural pacemaker is overridden by an abnormal electrical signal originating above the lower chambers. This can be visualized as an electrical short circuit that bypasses the normal, controlled pathway.
This malfunctioning circuit creates a rapid, repetitive loop of electrical activity, similar to a record skipping. The result is the sudden, chaotic firing that causes the heart muscle to contract excessively fast. The sudden onset and equally abrupt cessation of the episode are characteristic hallmarks of this electrical re-entry mechanism.
The electrical signal finds an extra or alternative pathway to travel back up and prematurely re-stimulate the upper chambers. This rapid, uncontrolled cycling of the electrical impulse drives the heart rate to high levels, which the patient perceives as violent pounding or fluttering.
Recognizing When SVT Requires Urgent Care
While many SVT episodes are brief and resolve spontaneously, certain symptoms signal a medical emergency requiring immediate professional help. Any instance of fainting or a near-fainting spell (syncope or pre-syncope) is a red flag indicating the heart is failing to pump sufficient blood to the brain, necessitating urgent evaluation.
It is also important to seek emergency care if a rapid heart rate is accompanied by severe chest pain, which could indicate a strain on the heart muscle. Immediate medical attention is warranted if difficulty breathing is pronounced or persistent, or if the episode lasts significantly longer than typical for the individual.
Patients should never attempt unprescribed self-treatment techniques, such as vagal maneuvers, without prior instruction and clearance from a healthcare professional. For those with a known history of heart disease, any sustained episode of SVT should be considered serious, regardless of the accompanying symptoms.