An accelerated heart rate is called tachycardia. This can be of two types: ventricular (it involves only the ventricles) or supraventricular (both atria and ventricles are involved).
In some cases, atrioventricular node can send electrical impulses faster than the sinus node, causing tachycardia.
Whatever the cause, tachycardias are classified according to location. Thus, ventricular tachycardia occurs in the ventricles (the lower heart chambers) and supraventricular tachycardias originate in the upper chambers, the atria or in the median-atrioventricular node or His-Purkinje system.
Tachycardia may present the following symptoms: palpitations, increased heart rate, dizziness, weakness and fainting.
Ventricular tachycardia- accelerated rhythm in the ventricles, can be life threatening. The most serious heart rhythm disturbance is ventricular fibrillation, when the lower chambers trembles instead of pumping blood. If the patient does not receive emergency medical care, there is a risk of cardiac arrest or sudden death.
Treated in time, ventricular tachycardia and ventricular fibrillation can be converted to a normal rhythm by electrical shock. Tachycardia can be controlled with medication or by identifying and destroying ectopic foci. An effective method of correcting rhythm disorders is the use of an electronic device called an implantable defibrillator.
Mechanism of Ventricular Tachycardia
Normal heartbeat is controlled by electrical signals that start in the sinoatrial node. Sinoatrial node is located in the top of the right atrium. The heart is divided into four chambers: two atria on top and two ventricles at the bottom. Normally, the electrical impulse from the sinoatrial node spreads to the atria, and the electrical impulse reaches the atrioventricular node where beam through His and the Purkinje network is transmitted to the ventricles.
Ventricular tachycardia is a heart rhythm disorder (arrhythmia), in which the ventricles contract abnormally fast. These rapid heartbeats are stimulated by electrical signals that reach to the ventricles of specialized heart cells (clutter impulse formation) signals that originate in the ventricles (ectopic foci) or can be caused by electrical signals that do not follow the normal driving electric system pulse (electrical impulse reentries).
In case of ventricular tachycardia, the electrical signals reach the ventricles further from the level of ventricles or abnormal electrical signals are due to a faulty electrical impulse conduction system of the heart.
Types of Ventricular Tachycardia
Ventricular tachycardias are classified according to their duration (supported or unsupported), and if they have a cause (such as coronary artery disease) or not. Short episodes, unsupported ventricular tachycardia generally produce no symptoms and require no treatment. However, a long episode, supported by the ventricular tachycardia in the presence of underlying heart disease, is a medical emergency. In time, ventricular tachycardia can lead to heart failure or may degenerate into ventricular fibrillation, which can lead to cardiac arrest.
Specific types of ventricular tachycardia are:
Unsustained ventricular tachycardia: an episode of ventricular tachycardia that lasts less than 30 seconds, but at least three heart beats.
Sustained ventricular tachycardia: an episode of ventricular tachycardia that lasts more than 30 seconds.
Monomorphic ventricular tachycardia: fast paced, but regular.
Polymorphic ventricular tachycardia: fast, erratic.
Ventricular tachycardia stable: heart pumps enough oxygenated blood to satisfy the body’s needs.
Unstable ventricular tachycardia: the patient shows signs due to decreased amount of oxygenated blood that reaches the organs.
Torsades de pointes: is a form of ventricular tachycardia that is extremely fast and dangerous that often occurs as a result of drugs or in patients with congenital long QT syndrome.
Accelerated idioventricular rhythm (slow ventricular tachycardia) is a form of ventricular tachycardia slower and less dangerous.
Causes of ventricular tachycardia
Ventricular tachycardia may develop, sometimes without being able to identify a specific cause. This type of ventricular tachycardia is known as idiopathic ventricular tachycardia and tends to be less dangerous than the rest of ventricular tachycardia. Other causes of ventricular tachycardia include:
Myocardial infarction (death of the heart muscle by sudden blockage of the coronary artery) that are interested in one or both ventricles.
Congenital heart malformations (heart defects that are present at birth) such as tetralogy of Fallot or long QT syndrome.
Myocarditis (inflammation of heart muscle).
Diseases of the heart valves – mitral valve prolapse (most commonly cause ventricular extra-systoles but can occur and episodes of ventricular tachycardia).
Arrhythmogenic right ventricular dysplasia is defined by replacing progressive fibroadipose with the right ventricular myocardium, meets frequently at young people; arrhythmias and sudden death are common.
Heart surgery, can rare lead to ventricular tachycardia.
Hypokalemia (low amount of potassium in the blood), hypomagnesemia (low magnesium in the blood), hyperkalemia (high amounts of potassium in blood), acidosis, alkaline acid balance disorders. Hypokalemia and hypomagnesemia may occur in patients taking diuretics.
Hypoxia (low amount of oxygen in the blood) and hypercapnia (increased carbon dioxide in the blood). Hypoxia may occur in pulmonary diseases such as emphysema or chronic obstructive pulmonary disease (COPD).
Medications such as digoxin, aminophylline, tricyclic antidepressants, amitriptyline, pseudoephedrine, ephedrine and fluoxetine. Herbal remedies (especially those that contain ma huang or ephedrine) and weight loss pills are often triggers of the ventricular tachycardia.
Excess in alcohol, tobacco and coffee;
Stimulant drugs such as cocaine, ecstasy and amphetamines.
Hyperthyroidism is endocrine diseases that is due to excessive secretion of thyroid hormone and which predispose to the occurrence of arrhythmias.
Advances in genetic research have led to the discovery of a gene that is involved in the regulation of cardiac electrical activity. Finding ways to use the gene therapy to correct the defects of the heart’s electrical system will significantly reduce the risk of ventricular tachycardia to progress to more serious heart problems.
Symptoms of ventricular tachycardia
Patients with ventricular tachycardia may have no symptoms (asymptomatic) and ventricular tachycardia to be discovered incidentally at a routine clinical examination or electrocardiogram.
Symptoms of ventricular tachycardia are:
Palpitations- patients with ventricular tachycardia say that they have palpitations- the person feels changes in heart rate or feels like the heart skipped a beat. Palpitations can create discomfort and anxiety (fear) in some people.
Dyspnea (difficulty breathing is) or tachypnea (rapid breathing, shallow).
Chest pain with chest pain characteristics (chest pain or discomfort that occurs when there is not sufficient quantity of blood in the heart).
Dizziness or syncope (fainting).
Symptoms of ventricular tachycardia are due to the diminishing ability of the heart to pump blood to other organs (especially to the brain and heart). Ventricular tachycardia causes decreased cardiac output and decreased blood pressure.
The first step in the diagnosis of ventricular tachycardia are obtaining the patient’s medical history and conducting a physical examination:
Pulse is fast (more than 100 beats / min), more or less regularly;
Blood pressure is normal or low
Are signs of pulmonary edema (alveolar invasion by blood plasma to cross the capillary wall) or cardiogenic shock (severe renal syndrome caused by a heart pump) especially when the frequency of ventricular tachycardia is high, appears in a previous heart sick with low ejection fraction.
They are useful in diagnosing the cause of ventricular tachycardia:
The level of potassium, magnesium and calcium in blood;
the amount of drugs (digoxin, Aminophylline) and blood drug;
myocardial enzymes (phospho-creatine kinase, troponin) may be performed to establish the diagnosis of acute myocardial infarction;
The dosage of blood gases (to be objective acidosis or hypoxemia);
B-type natriuretic peptide is useful for diagnosing heart failure (complication of ventricular tachycardia).
ECG is often considered the best diagnostic tool when ventricular tachycardia or any other type of arrhythmia is suspected.
If the ECG is normal, but the doctor suspects a cardiac arrhythmia, the patient can wear a portable ECG device that monitors the heart rhythm for 24 hours. This device monitors the heart rate for 24 hours, which allows physicians to diagnose arrhythmias unsupported occurring outside the medical office.
Chest radiography may reveal the presence of cardiomegaly (the presence of a much enlarged heart size), pulmonary edema (invasion of alveoli by blood plasma to cross the capillary wall), etc.
An electrophysiology study is a procedure in which a thin tube (catheter) is inserted through a vein or artery (for example in the groin) and guided to the heart, where they can perform specific measurements of the electrical activity of the heart. During electrophysiological study, the doctor may or may not reproduce ventricular tachycardia. If the tachycardia may be reproduced, patient has a particularly high risk of going into cardiac arrest in the future.
Electrophysiological studies are also an important part of the treatment of ventricular tachycardia. They are usually performed before surgery or radiofrequency ablation. These studies can locate the exact source of the arrhythmia, allowing physicians to act specifically on the affected area.
Treatment of ventricular tachycardia episode
Treatment of ventricular tachycardia crisis is an emergency treatment given the opportunity of degeneration into ventricular fibrillation, followed by sudden death.
Antiarrhythmic drugs may be more effective in the treatment of ventricular tachycardia.
Lidocaine injected intravenously at a dose of 1 mg / kg, is most commonly used in ventricular tachycardia crisis. Lidocaine blocks the discharge of potential channels of sodium in the cell membrane. Amiodarone may be used alone or in combinations, especially when ventricular tachycardia is fast and there is a dysfunction of the left ventricle. Amiodarone should not be used by injection than in a specialized hospital environment and under continuous surveillance (ECG, BP). Other antiarrhythmic drugs given by injection in a case of ventricular tachycardia are procainamide and sotalol.
Defibrillators are devices that restore sinus rhythm (normal rhythm of the heart) by applying an electric shock to the chest. Defibrillation involves the application using two paddles that fits the patient’s chest; electric shock intensity is between 300-360 J that “resets” the heartbeat. This method should be used immediately in case of ventricular fibrillation.
Endocavitary stimulation is an effective method to reduce arrhythmias. It is necessary when ventricular tachycardia is tolerated well enough so that the patient has time to be transferred to a specialized clinic. Pacemaker consists of an electrical pulse generator connected to one or two wire electrodes placed on the cardiac venous cavities. When the generator remains outside the patient’s body, it creates a temporary pacemaker. The probe can then be left in place for several days to minimize any recurrence of ventricular tachycardia.
Prevention of ventricular tachycardia
Unlike curative treatment, preventive treatment is more difficult.
The medicine most commonly used is Amiodarone because of its efficiency and because of its good tolerance in cases of severe left ventricular dysfunction. Amiodarone is particularly advantageous for treatment of lasting ventricular tachycardia recurring.
Class 1C antiarrhythmics (flecainide, propafenone) are equally effective, but more difficult to handle because of proarrhythmic effect (favoring the emergence of other arrhythmias) and negative inotropic (decreased heart muscle contraction). Beta-blockers are often used in small doses in combination with Amiodarone, especially in patients with coronary artery disease.
It requires a long-term treatment, most commonly, the implantation of a cardioverter-defibrillator (ICD). This device monitors the patient’s heart rhythm and, if necessary, administers an electric shock to correct abnormal heart rhythms (arrhythmias).
It is to eliminate abnormal heart tissue using radiofrequency waves. Probes used for electrophysiological study can radiate radio frequency to destroy heart tissue that sends electrical signal inappropriately (creating small scars at heart tissue to block electrical waves responsible for the occurrence of arrhythmia). This action restores normal heart rhythm.
Current studies have shown that omega-3 fatty acids in tuna, herring, sardines and mackerel, have reduced the risk of ventricular tachycardia and sudden cardiac death. In a study conducted on a small group of patients who had at least one episode of ventricular tachycardia, administration of omega-3 fatty acids stabilize the electrical activity and decreased risk of ventricular tachycardia during electrophysiological testing.
The most common form of supraventricular tachycardia is atrial fibrillation. Supraventricular tachycardia consists of accelerated heartbeat originating from the atria (the heart has four rooms: two atria and two ventricles), this can be deduced from its name condition (supraventricular means above the ventricles, that is the atria, tachy means fast and cardia means heart).
Normally, the rhythm and heart rate are carefully controlled by a power management system. In supraventricular tachycardia, accelerated heartbeats are triggered by disorders of initiation or transmission of electrical impulses that cause the heart contractions. Usually, the heart rate during supraventricular tachycardia episodes are located between 150 and 200 beats per minute, occasionally more than 300 per minute. After a period of time, the heart returns to the normal heart rate (from 60 to 100 beats per minute), spontaneously or by following the treatment. Other names synonymous with supraventricular tachycardia are: “paroxysmal supraventricular tachycardia” or “paroxysmal atrial tachycardia.”
In some cases increased heart rate is normal (for example: during exercise, fever, stress). This rapid heart rate, called sinus tachycardia, constitutes a normal response to physical or mental stress factors and is not considered pathological (abnormal).
Pathological forms of supraventricular tachycardia are:
Atrial fibrillation (the most common);
Supraventricular tachycardia with atrioventricular input, including The
A common cause of supraventricular tachycardia is given by the existence of some abnormal electrical circuits on the heart, as it does in atrioventricular reentrant tachycardia and atrial tachycardia by entering and this happens frequently in individuals that have no other heart problems. Nobody knows the exact cause of this phenomenon. Some experts believe those reentrant tachycardias intra-atrial (especially in the case of Wolf-Parkinson-White syndrome) are inherited.
Overdose of some medications such as digoxin (Lanoxin or Lanoxicaps) or the theophylline bronchodilators (Brankodyl, Elixophilin, Sio-Bid, Sio-Philin or Teotard);
Other disease conditions such as chronic obstructive pulmonary disease, heart failure, pneumonia, or metabolic disorders.
Some risk factors related to lifestyle increases the chances of triggering an episode of supraventricular tachycardia, as is the case of consumption of excessive amounts of coffee, cigarettes or alcohol or using drugs, such as cocaine or methamphetamine (stimulants of the nervous system central). Moreover decongestant medications (used to treat colds) may contain substances that can induce tachycardia, as is the case oxymetazoline (for example Afrin) or pseudoephedrine (Sudafed, Actifed, etc.). Doctors recommend caution regarding the use of pharmaceutical products that can be purchased from pharmacies without a prescription, as many of them have in their content caffeine, ephedrine plant “ma hung” and other stimulants of the heart.
A special form of supraventricular tachycardia, multifocal atrial tachycardia (MAT) can be triggered by preexisting conditions such as chronic obstructive pulmonary disease, pneumonia, heart failure (impaired function of the heart) and pulmonary embolism (one or more of the pulmonary arteries clog and thus, the territory served by them will not be well vascularized and it will be necrosis, losing his position).
Because it has been hypothesized that Wolf-Parkinson-White syndrome may be inherited genetically, doctors recommend those who have close relatives suffering from this disease to consult a specialist to determine if there is an opportunity to further develop this rhythm disorder.
The symptomatology in reentry tachycardia in the atrioventricular node, including Wolff-Parkinson-White syndrome, begins in the teenage years and young adult. WPW syndrome can trigger episodes of life-threatening heart rhythms such as ventricular fibrillation, although this phenomenon happens very rarely. It is therefore advisable for the patient to inform medical personnel on his situation, in the event of a crisis.
Reentry tachycardia in atrial node usually starts somewhere in the period between adolescence and middle age. If a patient develops an episode of supraventricular tachycardia, is expected to repeat this phenomenon. These arrhythmias are resolved spontaneously by simple vagal maneuvers, but also may require daily medication, if they persist. Medication is represented by beta-blockers, calcium channel blockers or digoxin. It may also be necessary to administer antiarrhythmic drugs or radiofrequency ablation performance.
If tachycardia occurs in a patient with known coronary artery disease (blood vessels that supply the heart) the heart may not receive enough blood compared to needs while elevated heart beat with increased frequency. In this case the heart is deprived of oxygen it is possible for a heart attack (myocardial infarction).
Because deciding the type of treatment depends on the type of tachycardia applied to the patient is very important to establish an accurate diagnosis. Sometimes the diagnosis of supraventricular tachycardia can be established only through a routine medical examination, in conjunction with the establishment of personal history and family history of the patient (what disease the patient had and his close relatives) and by developing some simple investigations.
On physical examination is useful to perform a carotid massage (gently massage the neck where the carotid artery’s route and this procedure should have the effect of decreasing heart rate).
Investigations useful for monitoring heart rate and determining the type of tachycardia that the patient has are:
Electrocardiogram (ECG) which records the electrical activity of the heart, if it succeeds the route ECG recording while the patient suffers an episode of tachycardia it can get extremely useful information;
Holter monitoring is a continuous method of recording the electrical activity of the heart, usually more than 24 hours, and this procedure is useful for patients whose symptoms are inconstant; There are many types of ambulatory monitoring;
Electrophysiological study by introducing flexible wires (that at the end had some recording electrodes) through the veins (most commonly in the thigh) and pushing them gradually to the level of the heart, it can directly record the electrical activity of the heart; This method can identify and locate the exact pathways of abnormal driving electrical impulses; more can be achieved by catheter ablation (respectively circuit interfere with radiofrequency waves) and can interrupt these pathological circuits
Therapeutic Diagnosis: through the administration of certain drugs during the episode of tachycardia and by tracking their effects can cause sometimes the type of tachycardia.
After diagnosing the condition, it is useful to find the cause that determined the appearance. There are specific investigations for certain types of tachycardia like:
Determination of thyroid hormones (these hormones have an influence on heart rate);
Determining the amount of blood electrolytes (for example potassium and calcium influences heart rate and rhythm);
Chest radiography and pulmonary function testing can detect lung diseases;
Chest radiography and pulmonary function testing can detect lung diseases.
Treating supraventricular tachycardia requires in case of:
Patient experiences dizziness, chest pain, syncope that are caused by rapid heart rate;
Rapid heart rate episodes are frequent or subside spontaneously (without treatment fail).
Treatment of episodes of tachycardia recently installed (acute)
For this kind of disorder, we can initially try vagal maneuvers application (carotid massage, breath with the glottis closed, facial immersion in cold water, eyeballs compression and coughing). These maneuvers available to stimulate the vagus nerve play an important role in lowering the heart rate. These procedures should be performed on the advice and instructions given by the doctor.
If vagal maneuvers performed did not work, you can try the administration of medication acting in a short term, administered orally. They can help the patient to take the medication at home if tachycardia returns, without having to go to the emergency service at every occasion.
If heart rate is not thinning, the patient should report to the emergency room where the patient is being administered Adenosine or Verapamil, fast acting medications is. If this measure does not work, then you can use that electrical cardioversion by controlled administration of electric shocks can restore the normal heart rate.
Long-term treatment of recurrent tachycardia
In this form of tachycardia is recommended administration of medications at need, or every day, regardless of the presence of the crisis. Medicines commonly used are beta-blockers, calcium channel blockers step, digoxin and other antiarrhythmic drugs. In individuals with frequent recurrences, these medicines can reduce the number of seizures. However, such medication is often to a side effect.
Increasingly more frequently to treat these patients is used radiofrequency ablation that relies on blocking abnormal electrical circuit to the heart, and in this way to solve the problem and the patient will not be forced to take medication. However the maneuver is not without risks, including the development of infection, bleeding and damage to the heart. The patient will have to make a decision based on careful evaluation of the two possibilities: either the administration of medicines for life or risking an invasive procedure. Another constraint of the procedure is that it is not done only in a few medical centers that own required medical equipment (for exameple Bucharest, Timişoara, Iaşi, Tărgu Mureş).
Treatment of reentrant tachycardia in the atrioventricular node
In this case you can opt for either medication taken daily or in time of crisis, either for radiofrequency ablation. If the patient has infrequent episodes of tachycardia that lasts a few hours and not accompanied by significant symptoms, you can choose to only take medicines crisis. These are represented by antiarrhythmic medicines such as propafenone, calcium channel blockers such as verapamil or beta-blockers, such as propranolol.
The doctor also may recommend daily calcium blockers, beta-blockers and / or digoxin if seizures are common. If these medicines are not effective in stopping recurrent seizures of tachycardia, the patients can opt for taking antiarrhythmic medication. In patients treated daily with drugs to which the crises are frequent and accompanied by significant symptoms can opt for catheter ablation.
Treatment of atrial reentrant tachycardia
And in this type of tachycardia they can choose either daily treatment with medication or treatment only when the crisis appears, it depends on the frequency of this occurrence. Medications such as digoxin, beta-blockers and calcium channel blockers (verapamil and diltiazem) are often effective in stopping episodes of this kind of tachycardia.
However, there is a type of tachycardia with atrioventricular nodal reentrant, called Wolf-Parkinson-White syndrome in whom this type of treatment can induce the occurrence of extremely rapid heart rate, which may occur with the feeling of “heavy head “, fainting (syncope) and even death. Treatment of Wolff-Parkinson-White syndrome can be achieved with antiarrhythmic medication such as Propafenone, which decreases conduction velocity of electrical impulses in the accessory pathway. Radiofrequency ablation is frequently recommended for patients with this syndrome, especially in those with severe symptoms or who develop atrial fibrillation or atrial flutter (very common is due to contraction of the atria). Ablation can cup about 95% of Wolf-Parkinson-White syndrome. There is a low risk (5%) that this disease will relapse (reoccur), even with a successful ablation. But almost always a second ablation will be able to permanently occupy the arrhythmia.
In the treatment of symptomatic supraventricular tachycardia can use medications.
For severe symptoms (chest pain, shortness of breath, feelings presyncope, fainting) can be administered fast-acting antiarrhythmic drugs by a health care specialists equipped with the equipment necessary to monitor heart rate. This category of drugs includes:
Calcium channel blockers (particularly verapamil and diltiazem);
Beta-blockers (especially Propanolol, metoprolol and esmolol).
Long-term medication may also be useful for countering the occurrence and treatment of recurrent episodes of tachycardia. In this category are:
Calcium channel blockers;
Other antiarrhythmic drugs.
Open heart surgery for this type of condition is made rarely and only where other forms of treatment (medication or catheter ablation) didn’t show any result, are contraindicated or inaccessible. If surgery is done for another concomitant condition, surgical ablation of the electrical circuit in the same time can be achieved.
Electrical cardioversion (external electric shock administration) may be necessary in patients with supraventricular tachycardia that does not respond to vagal maneuvers or fast-acting antiarrhythmic medication and the symptoms are severe. Electric conversion is used only in emergencies. If the patient is conscious, will be administered pain medication and anesthesia (for patient causes drowsiness) during the maneuver.
Electrophysiological study (measuring currents in the heart through direct measurements through electrodes inserted into the cardiac cavities) can identify the accessory pathway causing the arrhythmia in question and can perform radiofrequency ablation (destruction of those pathways).
These episodes of tachycardia can be prevented by avoiding toxins that stimulate the heart rate, such as coffee, nicotine and certain medications (nasal decongestants), drugs (methamphetamine and cocaine), excessive alcohol, lack of sleep or excessive consumption of food from a single table. If the heart rate is increased continuously, can be administered long-term medications (beta-blockers) to prevent their occurrence.
The lifestyle of those with tachycardia
It is indicated to monitor the heart rate at home and addressing measures to decrease heart rate when tachycardia occurs. One can try writing a “diary” in which to record the symptomatology and the heart rate during each tachycardia.
The patient will be instructed how to check their pulse during episodes and record the values in the “diary “. The patient must realize that during episodes of symptomatic tachycardia is difficult to measure pulse rate and counted accurately. By writing the “diary” mentioned above, the patient can identify the factors that cause tachycardia.
It is useful to avoid caffeine, nicotine and drugs (such as ecstasy, cocaine or methamphetamine). For highly sensitive individuals even decaffeinated coffee and tea can cause episodes of supraventricular tachycardia. Avoid also nasal decongestants such as oxymetazoline (for example Afrin) pseudoephedrine (for example: Sudafed, Actifed, etc.) and the products used as supplements for weight loss (many contain caffeine, ephedrine, ephedra, ma huang plant or other stimulants). Patients will be instructed how to perform at home vagal maneuvers (coughing, exhale with the glottis closed, facial immersion in cold water, etc.) in order to reduce heart rates.