A racing heartbeat has many possible causes, and the great majority are harmless. Most of the time it is the body responding normally to something, such as exercise, caffeine, stress, anxiety, alcohol, dehydration or a fever, and the fast heart rate settles once the trigger passes. In some cases, though, a racing heartbeat is caused by a genuine rhythm disorder, where the heart’s electrical system produces an abnormally fast rate on its own. The two can feel remarkably similar, which is why a racing heartbeat that is sudden, prolonged, recurrent or associated with other symptoms is worth having properly assessed rather than simply explained away.
The medical term for a fast heart rate is tachycardia, generally defined as a resting rate above 100 beats per minute. Over more than 20 years as a Consultant Cardiologist at Kingston Hospital, much of that as Clinical Lead of the department, and with a longstanding interest in rhythm assessment across my private clinics at Parkside, The New Victoria, Cleveland Clinic London and Heartsure, I would say that the single most useful thing I can offer patients with a racing heartbeat is a clear answer as to which category theirs falls into. Distinguishing a normal physiological response from a true arrhythmia is the whole task, and it is usually achievable once the rhythm is captured during an episode.
When a racing heartbeat is completely normal
The heart is designed to speed up. It is meant to respond to the body’s changing demands, and a fast rate is often exactly the right response rather than a fault. During exercise, the heart rate rises to deliver more oxygen to working muscles. During fear or excitement, adrenaline drives it up as part of the body’s natural alarm response. This is normal, healthy function, and it would be a problem if it did not happen.
Several everyday factors push the heart rate up in the same way. Caffeine, nicotine and alcohol are common stimulants of a fast heartbeat, as are dehydration, a missed meal, a hot environment and lack of sleep. A fever reliably raises the heart rate, roughly ten beats per minute for each degree of temperature. What I have found across many years of practice is that identifying and removing a patient’s personal triggers works better than any medication for this kind of racing heartbeat, because when the fast rate is a normal response to caffeine, poor sleep or stress, the answer lies in the trigger rather than in treating the heart itself.
Anxiety and the racing heart
Anxiety deserves particular mention, because it is one of the most common causes of a racing heartbeat and one of the most distressing. When anxiety or a panic attack strikes, the body releases adrenaline, which drives the heart rate up sharply. The racing heart is then often noticed and interpreted as a sign of danger, which increases the anxiety further, which drives the heart rate higher still. It is a genuine physical response, not something imagined, and the sensation can be frightening.
The difficulty is that the symptoms of a panic attack and those of a true rhythm disorder can overlap considerably, with both producing a fast heartbeat, breathlessness and chest discomfort. This is one reason I am cautious about attributing a racing heartbeat to anxiety without first making sure there is no underlying rhythm problem. What I emphasise to patients is that anxiety and a heart rhythm disorder are not mutually exclusive, and confirming the heart rhythm is normal during an episode is often profoundly reassuring in its own right, sometimes reducing the anxiety that was driving the symptom.
The rhythm disorders that cause a racing heart
When a racing heartbeat comes from a fault in the heart’s electrical system rather than a normal response, it is called a tachyarrhythmia, and there are several distinct types. Supraventricular tachycardia, or SVT, is one of the most common. It produces sudden episodes of a very fast, regular heartbeat that start and stop abruptly, often in younger people with structurally normal hearts, and patients frequently describe the heart suddenly switching into a fast rate and later switching back just as suddenly.
Atrial fibrillation is the most common sustained arrhythmia and produces a racing heartbeat that is both fast and irregular. It is important because it raises the risk of stroke, and it is one of the key diagnoses I am always seeking to identify or exclude. Atrial flutter produces a fast but more regular rhythm and is closely related. These conditions sit within the broader family of irregular heartbeats, and distinguishing between them is essential because the right treatment differs for each. Less commonly, a racing heartbeat originates in the lower chambers of the heart as a ventricular arrhythmia, which can be more serious, particularly in someone with underlying heart disease, and always warrants prompt specialist assessment.
The underlying causes that drive a fast heart rate
Sometimes a racing heartbeat is a sign of a condition elsewhere in the body rather than a primary fault in the heart. An overactive thyroid is a classic example, raising the heart rate through excess thyroid hormone, and it is easily missed without a blood test. Anaemia causes the heart to beat faster to compensate for the reduced oxygen-carrying capacity of the blood. These are exactly the kind of causes that blood tests reveal, which is why I check thyroid function and a full blood count in most patients presenting with a persistently fast heart rate.
Other underlying drivers include a high temperature from infection, low blood sugar, and the effects of various medications and recreational drugs. Some asthma inhalers, decongestants and thyroid medications can raise the heart rate, as can stimulant drugs. Alcohol is a particularly common and underestimated cause, both directly and through its disruption of sleep, and the wider impact of alcohol on heart health reaches well beyond a temporarily fast pulse. This is why a thorough history of medications, lifestyle and general health matters as much as examining the heart itself.
The symptoms that raise the priority
Certain features accompanying a racing heartbeat make proper assessment more urgent. A racing heartbeat associated with chest pain, significant breathlessness, dizziness or fainting needs prompt evaluation, as these suggest the fast rate may be affecting the heart’s ability to pump effectively. A racing heartbeat that comes on very suddenly, that lasts a long time, or that is happening more and more often is also more likely to represent a defined rhythm disorder.
Context matters too. A racing heartbeat in someone with known heart disease, a weakened heart muscle or a family history of sudden cardiac death is treated with considerably more caution than the same symptom in an otherwise healthy young person. What I stress to patients is that the sensation alone cannot reliably separate a benign cause from a significant one, which is precisely why recording the heart’s electrical activity during an episode is so valuable.
How I assess a racing heartbeat in clinic
The central challenge is that a racing heartbeat usually comes and goes, so the goal of assessment is to capture the heart’s electrical activity during an actual episode. It typically begins with a resting ECG, although this only records a brief moment and will often appear normal if the patient is not experiencing symptoms at that time. Blood tests to check thyroid function, a full blood count and electrolytes are routine, and an echocardiogram assesses whether there is any structural cause within the heart.
The decisive step is usually prolonged monitoring, and the choice of test matters a great deal. A 24-hour or 48-hour monitor suits frequent symptoms, but for episodes that occur only every week or two it will often miss them entirely. Drawing on the many rhythm assessments I have arranged over the years, a ZIO patch worn for up to 14 days works better than a standard 24-hour monitor for intermittent symptoms, because the longer recording window greatly increases the chance of capturing an episode that a shorter test would miss. Capturing the rhythm during a racing episode is what converts uncertainty into a precise diagnosis, because it shows exactly what the heart is doing at the moment the patient feels it.
How a racing heartbeat is treated
Treatment depends entirely on the cause, which is why diagnosis comes first. A racing heartbeat driven by lifestyle factors usually needs nothing more than attention to caffeine, alcohol, sleep and stress, alongside reassurance once a rhythm disorder has been excluded. Where an underlying condition such as an overactive thyroid or anaemia is found, treating that condition resolves the fast heart rate.
When a true arrhythmia is responsible, effective treatments exist and many are highly successful. Supraventricular tachycardia and atrial flutter often respond very well to catheter ablation, a procedure that targets the small area of heart tissue responsible for the abnormal circuit, and for these patients I work closely with my colleague Dr Para Dhillon. Atrial fibrillation is managed with a combination of rate or rhythm control and, in most patients, anticoagulation to reduce stroke risk. Certain medications, particularly beta-blockers, can slow the heart rate and reduce the frequency of episodes across a range of conditions. The reassuring reality is that most causes of a racing heartbeat are treatable, and many can be resolved entirely once correctly identified.
When to seek urgent help
Most episodes of a racing heartbeat are not emergencies, but some require immediate attention. A racing heartbeat that does not stop, that is accompanied by chest pain, severe breathlessness or fainting, or that occurs alongside symptoms of a heart attack needs emergency assessment, so call 999. A single episode of feeling faint with a racing heart, or a blackout associated with a fast heartbeat, should also be assessed promptly rather than ignored.
For recurrent but self-limiting episodes that stop on their own, urgent care is not usually needed, but these still warrant a proper outpatient assessment to establish the cause. The distinction is between a racing heartbeat that is compromising you in the moment, which is an emergency, and one that comes and goes without other symptoms, which needs investigation but not panic.
When to seek a cardiology opinion
A specialist assessment is worth arranging if you have episodes of a racing heartbeat that are sudden, recurrent, prolonged or worsening, or that come with breathlessness, chest discomfort, dizziness or fainting. It is also worth arranging if you have been told your pulse is fast or irregular, if you have a family history of rhythm problems or sudden cardiac death, or if you have an overactive thyroid or other condition alongside a persistently fast heart rate.
You can read verified feedback from patients I’ve seen if it helps you decide whether a private cardiology opinion is the right step for you.
Conclusion
A racing heartbeat is one of the most common symptoms I assess, and in the majority of people it turns out to be a normal response to an everyday trigger such as exercise, caffeine, stress, anxiety or alcohol. In a minority, it reflects a genuine rhythm disorder such as supraventricular tachycardia or atrial fibrillation, which is important to identify because effective and often curative treatment is available. Because the harmless and the significant can feel so alike, the sensible course is neither to panic nor to dismiss it, but to have the rhythm recorded during an episode so that the cause is known and the right action, if any, can be taken.
If you are experiencing a racing heartbeat, or you have been told your pulse is fast or irregular, you can contact me, Dr Arvind Vasudeva, on 020 8977 4826 to arrange a rhythm assessment. I consult at Parkside Hospital in Wimbledon, The New Victoria Hospital in Kingston, Cleveland Clinic London and the Heartsure Clinic, and you can book a convenient appointment here through my secretary Hannah.