Sinus Tachycardia

Generality

Sinus tachycardia is an "arrhythmia characterized by" an increase in the frequency and speed of the sinus rhythm, ie the beat imposed on the heart by the sinoatrial node. Sinus tachycardia is the most common form of tachycardia and is often NOT an alarming episode. In fact, similar arrhythmic manifestations can be the normal consequence of physical exercises or a strong emotion, physiological events at the end of which the heart rhythm returns to normal. Therefore, no specific treatments are required. Sinus tachycardia episodes are common in the case of fever, but disappear when the body temperature returns to normal. The case of sinus tachycardias due to stable and serious pathologies, such as heart disease or anemia, is quite different.

Arrhythmias, what are they?

Before proceeding with the description of sinus tachycardia, it is appropriate to briefly review what cardiac arrhythmias are.
Cardiac arrhythmias are alterations in the normal heartbeat rhythm, also called sinus rhythm as it originates from the sinoatrial node. The sinoatrial node emits the impulses for the contraction of the heart and is considered the dominant pathway center, as it is responsible for the normal heartbeat.

The heart rate is expressed in beats per minute and is considered normal if it stabilizes within a range of values ​​between 60 and 100 beats per minute. There are three possible alterations and it is sufficient for one to occur only for an "arrhythmia to arise. They are:

1. Changes in the frequency and regularity of the sinus rhythm. The heart rate may become faster (over 100 beats per minute → tachycardia) or slower (less than 60 beats per minute → bradycardia).
2. The variation of the seat of the dominant marker center, that is the point of origin of the primary impulse that determines the cardiac muscle contraction. The footpath centers are more than one in the heart, but the sinoatrial node is the main one and the others should serve only for the propagation of the contraction impulses generated by it.
3. Impulse propagation (or conduction) disturbances.

The pathophysiological mechanisms * underlying these three alterations make it possible to distinguish arrhythmias into two large groups:

1. Arrhythmias mainly due to a modification of automaticity. Arrhythmias with:
   • Changes in the frequency and regularity of the sinus rhythm.
   • Variation of the seat of the dominant marker center.
2. Arrhythmias mainly due to a modification of the conduction (or propagation) of the impulse. Arrhythmias with:
   • Impulse propagation disorders.

Automaticity, together with rhythmicity, are two unique properties of some muscle cells that make up the myocardium (the heart muscle).

1. Automaticity: it is the ability to form impulses of muscle contraction spontaneously and involuntarily, that is, without an input coming from the brain.
2. Rhythmicity: is the ability to neatly transmit contraction impulses.

* pathophysiology is the study of the changed functions, due to a pathological condition, of a tissue, of an organ or, in general, of an organism

The physiopathological classification is not the only one. We can also consider the site of origin of the disorder and distinguish arrhythmias into:

1. Sinus arrhythmias. The disturbance concerns the impulse coming from the sinoatrial node. Generally, the frequency changes are gradual.This is the case, for example, of sinus tachycardia.
2. Ectopic arrhythmias. The disorder concerns a pathway other than the sinoatrial node; this is the case, for example, of paroxysmal tachycardia. Typically, they arise abruptly.
   The affected areas divide ectopic arrhythmias into:
   • Supraventricular. The disorder affects the atrial area.
   • Atrioventricular, or nodal. The affected area concerns the atrioventricular node.
   • Ventricular. The disorder is located in the ventricular area.

What is sinus tachycardia

Sinus tachycardia (from the Greek ταχύς, speed, and καρδία, heart) is an "arrhythmia characterized by an increase in the frequency and speed of the normal heart rhythm (alteration # 1). The term sinus indicates the sinus node as the site d "origin of the arrhythmic disorder.

Upon the occurrence of a sinus tachycardia, the heart rate can reach up to 180 beats per minute, thus exceeding the maximum threshold value, relative to normal, of 100 bpm. The onset and termination of the tachycardia event are gradual.

Sinus tachycardia is the most common form of arrhythmia and is usually not an alarming episode. In fact, it is commonly observed in infancy, adolescence and in response to transient situations involving a greater demand for oxygen by the tissues, such as exercise, emotions, pregnancy and even fever. the higher oxygen demands, a higher cardiac output (blood flow) is required. To raise the cardiac output, the body increases the heart rate, generating tachycardia.
So, a brief outline of what happens during a sinus tachycardia is:

1. Greater oxygen demand →
2. Increased heart rate (tachycardia) →
3. Increased cardiac output →
4. Greater amount of oxygenated blood to the tissues

Causes of sinus tachycardia

The causes, or factors, of sinus tachycardia are diverse. They are distinguished by the severity and transience of conditions that require more oxygen.
Non-serious transient circumstances, capable of causing sinus tachycardia, are divided into physiological stimuli and pathophysiological stimuli.

Physiological stimuli

1. Exercise.
2. Emotion.
3. Pregnancy.
4. Anxiety.

Pathophysiological stimuli

1. Fever.
2. Hyperthyroidism.
3. Pheochromocytoma.

A sinus tachycardia can also be attributed to NON transient pathological conditions, much more serious than a simple fever, such as:

1. Anemia.
2. Arterial hypotension.
3. Shock.
4. Pulmonary embolism.
5. Myocardial ischemia.
6. Heart failure.

They are pathological circumstances that are different from each other, but at the basis of which there are two common symptoms:

1. Decreased tissue oxygenation.
2. Decreased cardiac output.

To compensate for these decreases, the heart responds by increasing the heart rate, resulting in episodes of tachycardia. The mechanism is reminiscent of that induced by physiological (physical exercise) and pathophysiological (fever) stimuli, but there is a substantial difference: the transience of the patient's conditions. In the case of fever, in fact, tachycardia disappears spontaneously when exhausted. the fever itself. Therefore, no antiarrhythmic treatment is required. The same applies to "emotion and physical exercise: at the end of these, the heartbeat resumes normal sinus rhythm. A" myocardial ischemia, on the other hand, is a much more serious and stable pathological circumstance, so much so that the complications it causes they require pharmacological and surgical interventions of a certain importance. Only after successful therapy is the problem of sinus tachycardia resolved.

Finally, episodes of sinus tachycardia can also arise at rest, in the absence of a higher oxygen demand. The responsible agents are:

1. Medicines (for example atropine and catecholamines).
2. Alcohol.
3. Nicotine.
4. Caffeine.

Symptoms

The typical symptoms, which characterize sinus tachycardia, depend on their association or not with the other pathologies described in the previous chapter. In other words, the symptomatology is all the more critical and articulated in its manifestations, the more worrying and advanced the pathological states of an individual suffering from tachycardia. A list of the main symptoms, from the least severe (but always present) to the most severe, is as follows:

1. Heartbeat (or palpitation). It is the natural consequence of the increased heart rate. It is observed in all subjects affected by sinus tachycardia, both healthy and cardiopathic.
2. Anxiety. It is related to heartbeat.
3. Dyspnea (or shortness of breath). It is difficult breathing. The onset mechanism is a demonstration of the link between the respiratory system and the circulatory system. In fact, the greater demand for oxygen by the tissues, both in transitory conditions and in severe and stable ones, forces the individual to increase the number of acts respirators to elevate cardiac output However, especially in severe pathological circumstances, this response does not compensate for oxygen demand, resulting in the sensation of shortness of breath and shortness of breath.
4. Pain in the chest, below the breastbone. It is associated with heart disease.

Diagnosis

An accurate diagnosis requires a cardiological visit. Traditional tests, valid for the evaluation of any arrhythmic / tachycardic episode, are:

1. Pulse measurement.
2. Electrocardiogram (ECG).
3. Dynamic electrocardiogram according to Holter.

Pulse measurement. The physician can draw basic information from the evaluation of:

1. Arterial pulse. Inform about the frequency and regularity of the heart rhythm.
2. Jugular venous pulse. Its rating reflects atrial activity. It is generally useful for understanding the type of tachycardia present.

Electrocardiogram (ECG). It is the instrumental examination indicated to evaluate the course of the electrical activity of the heart. On the basis of the resulting traces, the doctor can estimate the extent and severity of the sinus tachycardia.

Dynamic electrocardiogram according to Holter. It is a normal ECG, with the advantageous difference that the monitoring lasts for 24-48 hours, without preventing the patient from carrying out normal activities of daily life. It is useful when tachycardia episodes are sporadic and unpredictable.

Therapy

The therapeutic approach is based on the causes that determine sinus tachycardia. In fact, if it is due to particular cardiac disorders or other pathologies, the therapy to be adopted is both pharmacological and surgical. The most suitable antitachycardia drugs are:

1. Antiarrhythmics. They serve to normalize the heart rhythm. For instance:
   1. Quinidine
   2. Procainamide
   3. Disopyramide
2. Beta blockers. They are used to slow down the heart rate. For instance:
   1. Metoprolol
   2. Timolol
3. Calcium channel blockers. They are used to slow down the heart rate. For instance:
   1. Diltiazem
   2. Verapamil

The route of administration is both oral and parenteral.
The surgical intervention depends on the particular heart disease linked to the tachycardic episode.
It should be noted that, in these circumstances, tachycardia is a symptom of heart disease; therefore, surgery aims to cure, first of all, heart disease and, as a consequence, also the associated arrhythmic disorder. In fact, if only the antitachycardia drug treatment were implemented, this would not be sufficient to solve the problem.
If, on the other hand, sinus tachycardia occurs in healthy subjects, without heart problems, and manifests itself as a sporadic episode after a run, or a strong emotion, no particular therapeutic measures are required. This arrhythmia, in fact, ends on its own and its gradual onset, not abrupt, arouses less concern than a paroxysmal tachycardia, for example, with sudden and sudden onset. Sometimes, if the cause of sinus tachycardia depends on an "excessive intake of caffeine, a correction of the doses taken may be sufficient to resolve the disorder."