Tachycardia refers to a fast resting heart rate, usually over 100 beats per minute. Tachycardia can be dangerous, depending on its underlying cause and on how hard the heart has to work.
Some people with tachycardia may have no symptoms or complications. However, tachycardia significantly increases the risk of stroke, sudden cardiac arrest, and death.
Tachycardia refers to a high resting heart rate.
In general, a resting adult heart beats between 60 and 100 times per minute. When an individual has tachycardia, the upper or lower chambers of the heart beat significantly faster.
When the heart beats too rapidly, it pumps less efficiently and blood flow to the rest of the body, including the heart itself, is reduced.
Because the heart is beating quicker, the muscles of the heart, or myocardium, need more oxygen. If this persists, oxygen-starved myocardial cells can die, leading to a heart attack.
Atria, ventricles, and the electrical circuitry of the heart
The human heart consists of four chambers:
- Atria: These are the two upper chambers.
- Ventricles: These are the two lower chambers
There are left and right atria and ventricles.
The heart has a natural pacemaker called the sinus node. It is located in the right atrium. The sinus node produces electrical impulses. Each one triggers an individual heartbeat.
The electrical impulses leave the sinus node and go across the atria, making the atria muscles contract. This atria muscle contraction pushes blood into the ventricles.
The electrical impulses continue to the atrioventricular (AV) node, a cluster of cells. The AV node slows down the electrical signals, and then sends them on to the ventricles.
By delaying the electrical signals, the AV node is able to give the ventricles time to fill with blood first. When the ventricle muscles receive the electrical signals, they contract, pumping blood either to the lungs or the rest of the body.
When there is a problem with the electrical signals resulting in a faster-than-normal heartbeat, an individual has tachycardia.
Tachycardia is generally caused by a disruption in the normal electrical impulses that control our heart's pumping action - the rate at which our heart pumps. The following situations, conditions, and illnesses are possible causes:
- a reaction to certain medications
- congenital abnormalities of the heart
- consuming too much alcohol
- consumption of cocaine and some other recreational drugs
- electrolyte imbalance
- heart disease which has resulted in poor blood supply and damage to heart tissues, including coronary artery disease, heart valve disease, heart failure, heart muscle disease, tumors, or infections
- an overactive thyroid gland
- certain lung diseases
Sometimes, the medical team may not be able to identify the exact cause of the tachycardia.
Treatment options vary, depending on the cause of the condition, the age and general health of the person with tachycardia, and other factors.
The aim of treatment is to address the cause of the tachycardia. When clinically applicable, the doctor may try to slow the rate, prevent subsequent episodes of tachycardia, and reduce risk complications.
In some cases, all that is required is to treat the cause. In other cases, no underlying cause is found, and the doctor may have to try out different therapies.
Ways to slow down a fast heartbeat
The vagal nerve helps regulate our heartbeat. Maneuvers that affect this nerve include coughing, heaving (as if you were having a bowel movement), and placing an ice pack on the person's face.
Antiarrhythmic drugs can be administered orally or by injection. They restore a normal heartbeat. This is done in a hospital.
Available drugs restore normal heart rhythm, control the heart rate, or both. Sometimes an individual will need to take more than one antiarrhythmic drug.
Paddles or patches are used to deliver an electric shock to the heart. This affects the electrical impulses in the heart and restores normal rhythm. This is carried out in a hospital.
There are certain measures that can prevent a heartbeat becoming too fast or escalating into a health problem.
Radiofrequency catheter ablation
Catheters enter the heart via blood vessels. Electrodes at the ends of the catheter are heated to ablate, or damage. the small sections of the heart responsible for the abnormal heartbeat.
When taken regularly, anti-arrhythmic medications can prevent tachycardia.
A doctor may prescribe other medications to be taken in combination with antiarrhythmics, for example, channel blockers, such as diltiazem (Cardizem) and verapamil (Calan), or beta-blockers, such as propranolol (Inderal) and esmolol (Brevibloc).
Implantable cardioverter defibrillator (ICD)
A device that continuously monitors the heartbeat is surgically implanted into the chest. The ICD detects any heartbeat abnormality and delivers electric shocks to restore normal heart rhythm.
Sometimes, surgery is needed to remove a section of tissue. The surgeon may create a pattern of scar tissue. Scar tissue is a bad conductor of electricity. This procedure is generally only used when other therapies have not been effective, or if the person has another heart disorder.
Novel oral anticoagulants (NOACs), or blood-thinners
NOACs makes it harder for the blood to clot and is given to individuals with a high or moderate risk of developing stroke or heart attack.
Although these medications increase the risk of bleeding, a doctor will prescribe them for a person whose risk of stroke or heart attack is greater than their risk of bleeding.
The following signs and symptoms of tachycardia are possible:
- a fast pulse
- chest pain
- low blood pressure
- shortness of breath
- sudden weakness
It is not unusual for some cases with tachycardia to cause no symptoms at all. In such cases, the condition is typically discovered when the individual has a physical examination.
The risk of complications depends on several factors, including:
- heart rate
- whether or not other heart conditions are present
The most common complications include:
- Blood clots: These significantly increase the risk of heart attack or stroke.
- Heart failure: If the condition is not controlled, the heart is likely to get weaker. This may lead to heart failure. Heart failure is when the heart does not pump blood around the body efficiently or properly. The left side, right side, or even both sides of the body can be affected.
- Fainting spells: A person with a rapid heartbeat may lose consciousness.
- Sudden death: This generally only linked to ventricular tachycardia or ventricular fibrillation.
The most common types of tachycardia include:
Sometimes, electrical activity can arise from the left atrium rather than the sinus node. This causes the chambers to contract at an excessively high and irregular rate. This is atrial fibrillation.
An atrial fibrillation episode may last from a few hours to several days. Sometimes, the episode does not go away without treatment. Most people with atrial fibrillation have some heart abnormality related to the condition.
The atria beat rapidly, but regularly. This is caused by a circuit problem within the right atrium. The contractions of the atria are weak because of the rapid heartbeat.
An atrial flutter episode may last a few hours or some days. Sometimes it may not go away until treated. Atrial flutter is sometimes a complication of surgery, but it can also be caused by various forms of heart disease. People with atrial flutter commonly also experience atrial fibrillation.
Supraventricular tachycardias (SVTs)
This refers to any accelerated heart rhythm originating above the ventricular tissue. The abnormal circuitry in the heart is usually present at birth and creates a loop of overlapping signals. An SVT episode may last from a few seconds to several hours.
Abnormal electrical signals in the ventricles result in a rapid heart rate. The speed of the heartbeat does not allow the ventricles to fill and contract properly, resulting in poor blood supply to the body. This type of tachycardia is frequently a life-threatening condition and is treated as a medical emergency.
The ventricles quiver in an ineffective way, resulting in poor blood supply to the body. If normal heart rhythm is not restored rapidly, blood circulation will cease, causing death. People with an underlying heart condition or those who have been struck by lightning causing serious trauma may experience ventricular fibrillation.
Tachycardia risk is increased if an individiual has a condition which either damages heart tissue or puts a strain on the heart.
The following factors are linked to a higher risk of tachycardia:
- Age: People over the age of 60 years have a significantly higher risk of experiencing tachycardia, compared with younger individuals
- Genetics: People who have close relatives with tachycardia or other heart rhythm disorders have a higher risk of developing the condition themselves
Other potential risk factors include:
A doctor can usually diagnose tachycardia by asking some questions regarding symptoms, carrying out a physical exam, and ordering some tests. These may include:
Electrodes are attached to the skin to measure electrical impulses given off by the heart.
This test will also show any previous heart disease that may have contributed to the tachycardia.
An echocardiogram is a type of ultrasound investigation. By bouncing sounds of the structures in the body and registering the echoes, a moving image of the heart can be produced. This can help look for structural or congenital abnormalities that might be playing a role in tachycardia.
These help determine whether thyroid problems or other substances may be factors contributing to tachycardia.
The person with tachycardia wears a portable device that records all their heartbeats. It is worn under the clothing and records information about the electrical activity of the heart while the person goes about their normal activities for 1 or 2 days.
This device is similar to a Holter monitor, but it does not record all the heartbeats. There are two types:
- One type uses a phone to transmit signals from the recorder while the person is experiencing symptoms.
- The other type is worn all the time for a long time. These can sometimes be worn for as long as a month.
This event recorder is good for diagnosing rhythm disturbances that happen at random moments.
Electrophysiological testing (EP studies)
This is an invasive, relatively painless, non-surgical test and can help determine the type of arrhythmia, its origin, and potential response to treatment.
The test is carried out in an EP lab by an electrophysiologist and makes it possible to reproduce troubling arrhythmias in a controlled setting.
If an individual experiences fainting spells, dizziness, or lightheadedness, and neither the ECG nor the Holter revealed any arrhythmias, a tilt-table test might be performed.
This monitors blood pressure, heart rhythm, and heart rate while they are moved from a lying to an upright position.
When reflexes work correctly, they cause the heart rate and blood pressure to change when moved to an upright position. This is to make sure the brain gets an adequate supply of blood.
If the reflexes are inadequate, this could explain the fainting spells and associated symptoms.
The X-ray images help the doctor check the state of the individual's heart and lungs. Other conditions that explain the tachycardia might also be detected.
The complications of tachycardia include:
- fainting and dizziness
- tiredness and fatigue
- shortness of breath
It can also lead to:
- blood clots and a higher risk of heart attack or stroke
- heart failure, when the heart can no longer pump the blood effectively
In some cases, it might result in sudden death.