Supraventricular Tachycardia (SVT) is a condition where the heart beats abnormally fast due to a fault in the electrical system located in the upper chambers, or “supraventricular” region, of the heart. This rapid rhythm is a type of arrhythmia, caused by electrical signals misfiring or traveling through an extra pathway. The physical experience of an SVT episode can be unsettling, often manifesting as an intense awareness of the heart’s activity. Understanding the specific physical sensations associated with SVT helps individuals recognize the condition and know what to expect.
The Primary Sensation of a Racing Heart
The most immediate and characteristic sensation of SVT is a racing heart, known medically as palpitations. During an episode, the heart rate typically accelerates dramatically, often reaching speeds between 150 and 250 beats per minute, which is far faster than a typical heart rate increase from exertion. This rapid, sustained pace causes the unique feeling in the chest.
People often describe this sensation as a forceful “pounding” or “thumping” against the chest wall, feeling as though the heart is working against a powerful resistance. Others may feel a rapid “fluttering” or “quivering” deep within the chest cavity. This is not a gradual increase like during exercise, but an almost instantaneous shift from a normal resting rhythm to a runaway pace.
The sensation of the heart pounding can sometimes be felt not just in the chest, but also as a distinct, forceful pulsing in the neck. This arises because the atria (upper chambers) contract so rapidly that they may not be timed perfectly with the ventricles (lower chambers). This inefficient pumping causes blood to briefly back up into the veins of the neck, creating the noticeable throbbing sensation.
Unlike the controlled, rhythmic acceleration during exercise, the SVT rhythm feels erratic or disorganized, even if the electrical pattern is regular. This rapid, uncontrolled acceleration creates a sense of mechanical failure. This feeling contributes significantly to the anxiety many people experience during an episode.
Systemic Effects During an Episode
The rapid heart rate of SVT significantly impacts the body’s overall function because the heart does not have enough time to refill completely with blood between beats. When the chambers contract too quickly, the volume of blood pumped out (cardiac output) decreases. This reduced blood flow is responsible for physical symptoms felt throughout the body, separate from the direct heart sensation.
One of the most common systemic effects is lightheadedness or dizziness. This occurs because the brain temporarily receives less oxygenated blood due to the heart’s inefficient pumping, which can make an individual feel unsteady or detached from their surroundings.
Shortness of breath (dyspnea) is another frequent symptom, stemming from the body’s reduced ability to circulate oxygen. Even while resting, the individual may feel they cannot take a satisfying breath, as the circulatory system struggles to meet oxygen demands. This can be compounded by weakness or fatigue that quickly sets in.
Some people also report discomfort or pressure in the chest area, which is often distinct from the sharp pain associated with other heart conditions. This tightness is thought to be related to the heart muscle working intensely fast without adequate rest or blood flow.
The Distinct Pattern of Onset and Cessation
A defining feature of the SVT experience is its paroxysmal nature, meaning the episodes typically begin and end with abruptness, often described as an “on/off switch.” The transition from a normal heart rate to a rapid one is immediate, frequently happening without any warning or apparent trigger. This sudden onset is a primary identifier of the condition.
The rapid heart rate may start instantly while resting, reading a book, or waking from sleep, making it feel unpredictable and out of control. This lack of a clear preceding event, such as a physical stressor, contributes to the anxiety and panic that frequently accompanies the episode.
Equally characteristic is the sudden cessation of the episode, where the heart rate snaps back to normal just as quickly as it began. This immediate return to a regular rhythm often brings relief, but it can be followed by a feeling of being “washed out” or fatigued. Even a short episode can leave the individual feeling exhausted.
This post-episode fatigue can linger for hours or even days, depending on the duration and speed of the tachycardia, reflecting the physiological strain endured. The sudden, unpredictable nature of the episodes, coupled with the lingering exhaustion, makes the SVT experience disruptive to daily life.
Warning Signs Requiring Immediate Medical Attention
While many SVT episodes resolve spontaneously and are generally not life-threatening, certain accompanying symptoms indicate a severe reduction in cardiac output and necessitate immediate medical attention. These signs suggest that the body’s vital organs are not tolerating the rapid heart rate.
The most concerning symptom is syncope (fainting), which signifies a momentary but significant loss of blood flow to the brain. Any episode of actual loss of consciousness or near-fainting must be treated as an emergency.
Crushing chest pain that feels like angina is a serious warning sign, suggesting that the heart muscle is being deprived of sufficient oxygen. This discomfort, especially if it persists, requires immediate evaluation.
Difficulty breathing that is more severe than simple shortness of breath, or the feeling of physical collapse, warrants an emergency call. These symptoms, including sudden weakness or a feeling of impending doom, indicate a potentially unstable medical situation.