Tachycardia: causes, symptoms, therapies

The heart beats wildly. If we have just done a run, there are no problems, it is an absolutely natural fact, but if, on the other hand, there is no external justification it is appropriate to contact the doctor. In general, in fact, any arrhythmia, that is an alteration of the heart rhythm, deserves attention, whether it is bradycardia (a drop in heart rate below the minimum values considered normal), or tachycardia (the increase in frequency above the values considered maximum, usually over 100 beats per minute). Here we focus our attention precisely on the second.

Heart rate: a matter of electrical impulses

Before going into the merits of tachycardia, it is good to make a brief and simplified review of the mechanisms underlying the heart rate.

The mechanical action of the heart, that is, the one that allows blood to be pumped, is made possible by an electrical activity capable of causing the contraction and release of the heart muscle in regular succession. This phenomenon is possible thanks to the presence of a group of specialized cells, capable of generating an electrical impulse.

The contractions start from a particular electrical stimulus that arises at a precise point, the sinus node (or sinoatrial node), which is located in the upper part of the right atrium and works as a sort of natural pacemaker. Since the beat is imposed on the heart by the sinus node, the heart rhythm is called sinus.

From the sinus node the impulse always travels in an orderly manner and reaches the atrioventricular node (which is located between the mitral valve and the tricuspid, at the base of the right atrium) from which it is sent first to the bundle of His (which is located between the ventricles) and subsequently to all the muscle fibers of the ventricles.

Tachycardia: what is it

Tachycardia is a symptom that indicates a heart rhythm disorder in which there is an increase (over 100 beats / minute) in the frequency of heartbeats. It usually appears suddenly and at rest.

Under stress, in fact, it is normal that the heart rate can increase.

At rest, the heart rate varies according to age:

There is no single form of tachycardia. The most common (but usually also less worrying) is sinus tachycardia, that is, an increase, generally gradual, of the rhythm that concerns the impulse that originates in the sinoatrial node. Paroxysmal tachycardia is different, which not only appears abruptly and suddenly, but derives from a change in the propagation of the myocardial contraction impulse, which instead of originating from the sinoatrial node, propagates from the atrioventricular node.

Depending on the part of the heart involved, we can distinguish between ventricular tachycardia or atrial (or supraventricular) tachycardia. In the latter case, however, the ventricles autonomously establish a correct rhythm, which is not the case in the case of ventricular tachycardia, which is therefore generally more serious.

Atrial fibrillation, ventricular fibrillation and atrial flutter are finally conditions of cardiac arrhythmia in which the heart beats over 100 beats per minute.

Atrial fibrillation consists of an increase in heart rate beyond 400 beats per minute, in a totally uncoordinated way, which does not allow to produce an effective mechanical activity.

In ventricular fibrillation, the increase in heart rate is linked to rapid and irregular contractions of the ventricles and can result in so-called sudden cardiac death: the heart beats irregularly and so quickly that it can no longer pump blood into the body, and then stops.

Finally, in atrial flutter, there is an increase in atrial heart rate to 300/400 beats per minute, in a coordinated manner. The ventricular frequency, on the other hand, does not undergo alterations. In practice, for example, every three impulses that originate from the sinus node, only one manages to be transmitted to the ventricles and from the 300 atrial beats we have a heart rate of 100 beats per minute.

How widespread is it

Recent estimates suggest that tachycardia itself is relatively widespread, but some forms (atrial fibrillation) are prevalent with increasing age.

Main causes of tachycardia

Tachycardia may be due to physiological events (e.g. pregnancy) or excessive consumption of coffee (or other caffeinated beverages), alcohol or drugs. Even stress, anxiety, sudden emotion (the heart rate is in fact under the control of the nervous system) and above all physical activity cause an increase in beats (during the effort) completely physiological.

More often, however, it is the indicator of more or less serious pathological conditions, such as:

• hyperthyroidism
• anaemia
• arterial hypotension
• diabetes
• cardiovascular diseases
• heart disease and cardiomyopathies of various kinds.

There are tachycardias linked to arrhythmias on a genetic basis, some of which are also hereditary, which are usually among rare diseases and which can determine, if not diagnosed, ventricular fibrillation and consequent sudden cardiac death. Examples include:

• Brugada syndrome (genetic disorder characterized by a dysfunction of proteins that regulate cardiac electrical activity in particular in the right side of the heart)
• long QT syndrome or short QT syndrome (genetic heart diseases characterized by an alteration of the electrical proteins that regulate the electrical activity of the heart and cause respectively a prolongation or shortening of the electrical recovery period of cardiac cells)
• catecholamine polymorphic ventricular tachycardia (genetic arrhythmogenic disease in which abnormalities of the heart’s electrical system are caused by impaired calcium control within heart cells).

In most cases, resting heart rhythm disturbances are caused by a previous heart disease and occur as a complication. Among the conditions that can favor its onset, heart attack is found first, especially in the period immediately following the acute attack. A tachycardia can be for example the first symptom of heart failure.

Sometimes the heart beats fast, but it’s not the heart’s fault. Do you want to know the other causes? Read this article.

Symptoms and diagnosis

Tachycardia is felt as a feeling of discomfort and sometimes you can feel the increased rhythm by resting your head on the pillow.

Typical symptoms that may be associated with tachycardia are also:

• palpitations (the sensation of feeling a rapid heartbeat)
• feeling of weight and chest pain
• dizziness
• feeling lightheaded
• syncope (i.e. fainting).

However, there are cases in which no particular symptoms are felt and tachycardia can be identified by chance during a medical examination.

The increase in resting heartbeats can be up to 300-400 beats per minute. In these cases, tachycardia (atrial fibrillation), if not promptly treated, can put the life of the affected person at risk.

The diagnosis of tachycardia is made by electrocardiogram. If the episodes are repeated several times a day, it may be useful to perform the continuous electrocardiogram for 24 hours (Holter).

It is a minimally invasive examination and very important for the diagnosis and treatment of the most difficult tachycardias to treat.

Thanks to neonatal examinations and also sports medicine, hardly a person reaches 40 years without ever having had an electrocardiogram. This examination, if performed by a competent operator, also allows to detect any small anomalies of the spy trace of hereditary genetic arrhythmias. In this case, an echocardiogram and possibly genetic tests are necessary to confirm the diagnosis.

Complications

When the heart rhythm is too fast and uncontrolled it is possible that blood circulation slows down and it is also likely that small thrombi are repeatedly pushed from the heart towards vessels even very far away.

For example, if during a heart attack an acute tachycardia such as atrial fibrillation occurs, small thrombi can push up to the cerebral vessels and cause a stroke.

Moreover, as we have already had the opportunity to reiterate, especially if the tachycardia is ventricular, it can determine the so-called sudden cardiac death.

Treatment

Some forms of tachycardia do not require any treatment, while in other cases it is necessary to intervene with pharmacological or surgical therapy.

Drugs to combat tachycardia are called antiarrhythmics (and include various types of medicines, including beta blockers).

In addition to antiarrhythmics, it is also necessary that the person affected by heart rhythm disorders take coagulant drugs in order to prevent the formation of thrombi.

Of course, all these treatments must be prescribed by the doctor and must be kept under strict control so that their effectiveness can be verified.

The correct heart rhythm can also be restored through the so-called external electrical cardioversion: it is an intervention that is done in the hospital, under sedation, and involves sending electrical shocks to the heart, through a specific defibrillator, to reset cardiac electrical activity. Similar, but not overlapping is the most commonly known defibrillation, which is used in cases of emergency; The defibrillator, in fact, sends in this case stronger electrical discharges, which are used to restart the heart that has momentarily stopped.

In some cases (for example in situations of atrial fibrillation) catheter ablation can be used: in practice, through a catheter introduced into the heart through a blood vessel, using radiofrequency, the heart tissue responsible for rhythm problems is eliminated.

Even if there is a diagnosis of arrhythmogenic disease on a hereditary genetic basis and therefore you are at risk of sudden cardiac death, it is possible to implement different medical and surgical prevention strategies to remove this danger, based on the individual risk of the patient: generally we resort to the use of drugs such as beta blockers or antiarrhythmics and only in the most complex cases to an implantable automatic defibrillator.

When to consult your doctor

Many times, especially in young people, tachycardia can be a momentary disorder that resolves spontaneously. But when the symptom is repeated for a few days in a row and for several days, always at rest, it is good to hear the opinion of the family doctor.

Older people who already suffer from cardiovascular disorders should be constantly under medical supervision.