It is characterized by an altered and very fast heart rate.
In adults, the heart normally beats 60-100 times per minute. A heart rate greater than 100 beats per minute is called tachycardia. Tachycardia can occur in both children and adults.
In newborns and infants, tachycardia is defined when the heart rate is greater than 150 beats per minute.
There are numerous causes of tachycardia and the condition is very common. Although some forms are harmless, others are potentially lethal.
Tachycardia can be caused by exertion, strenuous exercise, emotions, hyperthyroidism (overactive thyroid gland), some diseases, injuries, heart disorders, or exposure to certain drugs or chemicals.
Basic function of the heart
The heart has four chambers: two upper chambers (atria) and two lower chambers (ventricles).
The atria and ventricles have muscular walls.
A heartbeat occurs when this muscle suddenly contracts (squeezes) so that the chambers get smaller and the blood inside is expelled.
Control of the heartbeat begins with a small group of cells in the right atrium, called the sinoatrial node (which is the heart’s natural pacemaker).
The sinoatrial node generates electrical signals that control the speed (heart rate) and pattern (rhythm) of the heartbeat.
These impulses cause the atria to contract and pump blood into the ventricles.
The sinoatrial node also sends electrical impulses to another collection of cells, the atrioventricular node.
The atrioventricular node conducts impulses down an electrical pathway to the ventricles, which contract and pump blood from the heart to the lungs and the rest of the body.
The atrioventricular node determines the rate of contraction of the ventricles. The pulse felt in the wrist is due to the contraction of the ventricles.
Any type of abnormal heart rate or rhythm is called an arrhythmia.
Tachycardia is a type of arrhythmia in which the electrical signals that control the heart travel through the heart faster than normal, causing the heart to beat too fast.
Types and symptoms of tachycardia
Sinus tachycardia is a rhythm that is formed by the electrical impulse originating from the atrioventricular node in the normal way. However, the rate is faster than normal.
The normal heart rate range is 50-100 beats per minute in adults.
The rate in sinus tachycardia is 150 beats per minute.
It is also not unusual for the PR and QT intervals to decrease in length with higher rates.
This is a common rhythm that in response to any of a variety of stimuli is completely normal.
There are situations in which the appearance of a sinus tachycardia is completely normal:
- In response to a daily exercise (appears even when you are normally climbing a flight of stairs).
- Anxiety or some other emotional disorder.
- When you have a fever.
- During pregnancy.
- By ingesting too much caffeine or alcohol.
- When you smoke.
There are also situations in which the accelerated heart rate arises in response to abnormal physiological conditions such as:
- Variations in blood pressure.
- In cases of heart failure.
- When the individual suffers from heart disease.
- When there is a myocardial attack.
The normal maximum heart rate of a patient decreases with age.
At age 16, peak rates under exertion of 220 beats per minute would not be unusual.
However, by age 50, the same peak rate of people under exertion can drop to 160 beats per minute.
People with sinus tachycardia often have rapid rates of heart palpitations, dizziness, confusion, or a variety of symptoms related to the condition.
Generally, no type of treatment is recommended when the patient has sinus tachycardia.
But, if sinus tachycardia arises when the patient is sitting or without doing any activity, it is necessary to indicate some medications.
Sinus tachycardia is rarely a primary cardiac arrhythmia and is almost always caused by one of the above conditions.
Sinus tachycardia syndrome has been described and is a form of autonomic dysfunction.
Sinus node modification or ablation procedures can be performed, however, they present a risk of causing significant sinus node dysfunction, requiring implantation of a pacemaker.
Ventricular tachycardia specifically refers to tachycardia that starts in the ventricles of the heart.
In the case of ventricular tachycardia, a regular electrical signal is sent from the ventricles but with a very fast frequency.
If the heart rate remains at a high rate for more than 30 seconds, then ventricular tachycardia is a life-threatening condition.
In these cases, cardiac arrest can occur.
A person with ventricular tachycardia may require an electric shock or medications to change the arrhythmia to normal sinus rhythm.
Ventricular tachycardia can cause the following symptoms:
- Pressure or pain in the chest.
- Fainting, also known as syncope or near syncope.
- Lightheadedness or dizziness
- Palpitations, which may skip, flap, or beat in the chest.
- Short of breath.
It is important to note that children may not know how to describe what they feel during a period of ventricular tachycardia.
They may have trouble keeping up with other children or find that they are having discomfort and want to sit up and rest.
Sometimes a child may not experience any symptoms at all.
If the heart rate during an episode of ventricular tachycardia is extremely fast or continues for several seconds, you may experience some or all of these symptoms.
- Palpitations or a feeling that your heart is beating very fast.
- A slight pain in the chest.
- Some trouble breathing.
- Dizziness or vertigo
Supraventricular tachycardia begins in the area of the heart above the ventricles.
When the heart beats normally, its muscle walls contract (tighten) to push blood out and around the body.
Then they relax, so that the heart can fill with blood again.
This process is repeated for each heart beat.
In supraventricular tachycardia, the heart muscle contracts so fast that it cannot relax between contractions.
This reduces the amount of blood that is pumped around the body, which can lead to dizziness and shortness of breath.
Supraventricular tachycardia is a heart condition that features episodes of abnormally fast heart rate.
Episodes can last for seconds, minutes, hours, or (in rare cases) days.
They can occur regularly, several times a day, or very infrequently, once or twice a year.
The heart rate can be as high as 250 beats per minute, but is generally between 140 and 180 (compared to a normal heartbeat which should be 60 to 100 beats per minute at rest).
Usually heart palpitations (noticeable heartbeats) and a rapid pulse are felt.
Supraventricular tachycardia is caused by abnormal electrical impulses that start suddenly in the upper chambers of the heart (the atria).
The presence of these impulses can modify the natural rhythm of the heart.
It is often a short circuit in the heart’s electrical system that causes these spontaneous impulses.
The short circuit causes an electrical signal to travel continuously around a circle.
Each time the signal completes the circuit, the impulse spreads to the rest of the heart, forcing it to beat rapidly.
The presence of supraventricular tachycardias in general is not very risky.
They are not due to a “heart attack” and in children with healthy hearts, they do not cause sudden death.
However, if they occur very often or over long periods of time (hours or days), then they can cause difficulties with the pumping action of the heart and pose a lot of risk if not treated in time.
There are many additional subtypes of supraventricular tachycardia:
- Atrioventricular node reentry tachycardia: is a shunt near the atrioventricular node. Special cells near the atrioventricular node allow the impulse to travel at different speeds. A circuit is created when the impulse leaves the fast cells and returns through the slow cells.
- Atrial flutter : the impulse travels around the atria in a circular pattern causing the heart to beat faster than normal.
- Atrioventricular Reciprocal Tachycardia: The impulse starts normally but travels back to the atria through an additional pathway between the atrium and the ventricle. This type of tachycardia is most often associated with Wolff-Parkinson-White syndrome.
- Atrial tachycardia: The impulse begins in a small area of abnormal tissue within the atria and causes the heart to beat faster than normal.
- Junctional tachycardia: The abnormal impulse starts from the atrioventricular node between the atria and the ventricles. This type is more common after heart surgery.
There are certain symptoms that are commonly experienced in these types and they are:
- Dizziness or lightheadedness
- Syncope (fainting)
- Sharp chest pain, also called angina pectoris.
- Excessive palpitations.
Diagnosis of tachycardias
There are several different types of procedures that can be used to diagnose tachycardias:
An EKG is a measure of the electrical activity of the heart .
When electrodes are placed on specific places on the body such as the chest, arms, and legs, a graphical representation, or trace, of the electrical activity of the heart is obtained through the EKG equipment.
An electrocardiogram indicates the presence of arrhythmias, if there is damage to the heart caused by ischemia or lack of oxygen in the heart muscle, the occurrence of a myocardial infarction (or heart attack), a problem with the heart valves or some other type of affections in the heart.
Currently there are several types of tests performed with the help of electrocardiograms such as:
The resting electrocardiogram: In this procedure, small sticky patches called electrodes are attached to the chest, arms, or legs. The electrodes are in turn connected to the electrocardiogram equipment.
The electrocardiogram machine records the electrical activity of the heart for about a minute. The patient is lying down during this EKG.
Stress test: During the test, the patient exercises by walking on a treadmill or pedaling a stationary bike while the EKG is recorded. This test assesses changes in the EKG during activities, such as exercise, that cause stress.
Electrophysiological studies: These are a test in which a small, thin tube called a catheter is inserted into a large blood vessel in the leg or arm and from there to the heart.
This gives the physician the ability to find the site of origin of the arrhythmia within the heart tissue, thus determining how to treat it. Sometimes an attempt to treat the arrhythmia can be made by ablating at the time of the study.
In the electrophysiological study, the electrodes are passed through the blood vessels to the heart to record the electrical signals. This analysis creates a detailed map of the electrical circuits and detects anomalies.
Additionally, this procedure can be used to induce arrhythmias, allowing the physician to evaluate the effectiveness of medications for treatment.
Holter monitor: is a continuous recording of an electrocardiogram made over a period of 24 hours or more. The electrodes are attached to the patient’s chest and then connected to a small portable EKG recording equipment via cables.
The patient goes about their daily activities during this procedure.
Holter monitoring can be performed when an arrhythmia is suspected but not seen on a resting EKG, as arrhythmias can be transient in nature and not seen during the shorter recording times of the resting EKG.
Event Monitor – This is similar to a Holter monitor, but the EKG is recorded only when the patient begins to feel symptoms. These event monitors can be used longer than Holter monitors. The monitor can be removed to allow showering or bathing.
Mobile heart monitoring – This is similar to Holter and event monitor. The electrocardiogram is constantly monitored to allow the detection of arrhythmias, which are recorded and sent to your doctor regardless of whether or not symptoms are present.
Recordings can also be initiated by the patient when symptoms are felt. Monitors can be used for 30 days.
Echocardiogram: A transducer sends ultrasound waves through the chest to create a visual image of moving structures in the heart.
The treatment to be administered will be adopted according to the severity of the symptoms experienced.
As well as the presence of other conditions such as diabetes, kidney failure or heart failure that can disrupt the normal course of treatment.
The doctor usually suggests lifestyle modification such as withdrawal of caffeine, alcohol, or any other substance that is possibly causing the condition.
In cases where stress is suspected to be the cause of the tachycardia, measures to reduce the stress level are generally recommended, with therapies such as meditation, stress management therapies, exercise programs or psychotherapy.
If the doctor chooses to use medications, the decision of which medication to use will be determined by the severity of the symptoms, other conditions that may be present, and other medications the patient is already taking.
Medicines can slow or regulate your heart rate.
Certain medications may require a brief hospital stay while the body adjusts.
Examples of these medications include:
- Calcium channel blockers, these are a group of drugs that lower blood pressure by relaxing the cells of the heart muscle.
- Beta-blockers to treat heart conditions and digoxin which is a drug that slows down the heart rate.
Other medications can be used to convert tachycardia, normal rhythm, such as amiodarone, propafenone, and flecainide.
Blood thinners are types of drugs that manipulate the blood clotting process (called plasma clotting).
They inhibit the formation of thrombi, which means that they prevent blood clots from forming.
Clotting can cause a stroke or heart attack.
Blood thinners, such as warfarin , can be used to prevent blood clots from forming in the arteries.
Radiofrequency catheter ablation
In catheter ablation, catheters are inserted through blood vessels in the heart to heat or freeze tissue and destroy (remove) abnormal electrical conduction pathways.
Providing relief for patients who may not respond well to medication, prefer not to take medication, or cannot take medication.
Ablation is commonly used to treat Wolff-Parkinson-White syndrome, atrial fibrillation, and atrial flutter.
The procedure involves threading a small metal-tipped catheter through a vein or artery in the leg and into the heart.
In those cases where fluoroscopy or X-rays are used, the catheter is guided through the blood vessel until it reaches the heart.
Extra catheters, inserted through the vein in the leg and neck, contain electrical sensors to find the area causing the arrhythmia. This procedure is called mapping.
The metal-tipped catheter is maneuvered to each site in the heart that causes the irregular heartbeat.
Radio frequency waves or current are sent through the tip of the catheter, cauterizing or burning cells to destroy additional electrical pathways that cause abnormal heart rhythms.
Cryoablation, sometimes called cryopreservation, is similar to radiofrequency catheter ablation in that it is a procedure that interrupts the abnormal electrical pathway in the heart.
However, instead of burning cells, cryoablation destroys cells by freezing them.
Cryoablation has been very effective in treating children with arrhythmias.
Like radiofrequency catheter ablation, cryoablation involves threading a small metal-tipped catheter through a vein or artery in the leg and into the heart.
The catheter is guided through the blood vessel to the heart using fluoroscopy or x-ray techniques.
Extra catheters, inserted through the vein in the leg and neck, contain electrical sensors to help “map” or find the area causing the arrhythmia.
The metal-tipped catheter is maneuvered into the areas of the heart that are causing the irregular heartbeat.
Cryoablation then freezes extra cells or electrical pathways that cause abnormal heart rhythms.
Implantable cardioverter defibrillator
An implantable cardioverter defibrillator is not a cure for heart rhythm problems, but it can stop a very fast heartbeat and bring the heartbeat back to normal.
An implantable cardioverter defibrillator is a small device, similar to a pacemaker, that is implanted under the skin, often in the shoulder area just below the collarbone.
The implantable cardioverter defibrillator can detect what the patient’s heart rate is.
When the heart rate exceeds a speed programmed into the device, it delivers an electric shock to the heart to correct the rhythm to a slower, normal heart rate.
This procedure is used in order to stop certain arrhythmias, such as atrial fibrillation, supraventricular tachycardia or atrial flutter.
The patient is connected to an EKG monitor, which in turn is connected to a defibrillator.
During an EKG, an electric shock is delivered at the precise point to turn the abnormal heart rhythm into a normal one.
Emergency asynchronous defibrillation
Defibrillation is similar to cardioversion, except that the procedure delivers higher energy shocks more quickly in an attempt to convert life-threatening arrhythmias such as ventricular tachycardia and pulseless ventricular fibrillation.
In the case of arrhythmias, surgical treatment is usually carried out only when the possible options have already failed.
Surgical ablation is a major surgical procedure that requires general anesthesia.
The chest opens, exposing the heart.
After the arrhythmia site is located, the tissue is destroyed or removed to nullify the source of the arrhythmia.
This surgery interrupts the abnormal electrical pathways in the heart.