What is an arrhythmia and why do they occur?

Dr. Mont is a prestigious Cardiologist specialized in Arrhythmias. His more than 30 years in the profession guarantee an extensive career in various fields of clinical electrophysiology and cardiac stimulation.

Definition of arrhythmia

Any abnormality in the rhythm of the heart is called an arrhythmia. Arrhythmias are divided into two main groups:

  • Bradycardias: arrhythmias caused by slowing of the heart’s electrical activity.
  • Tachycardias: These are arrhythmias that appear due to an increase in the heart’s frequency.

Arrhythmias, risk factors

Arrhythmias occur for many reasons. To discuss in more detail the possible diseases that produce arrhythmias, it is easier to consider the two main groups:

  • Bradycardias. Bradycardia is defined as frequencies lower than 40-50 beats per min. However, there is a wide variation, and occasionally, particularly in athletes at rest, marked bradycardias may occur that do not involve any disease.
  • Bradycardias often occur in the elderly, due to an aging of the electrical tissue of the heart. This leads to a decrease in the number of beats per minute and may result in fatigue or even syncope (sudden loss of consciousness, often with a traumatic fall).
  • Treatment of bradycardias involves the use of pacemakers. The pacemaker generates an electrical impulse that replaces the heart’s too slow rhythm with an appropriate rhythm.
  • There are bradycardias of congenital origin that appear in childhood. They are also susceptible to treatment with pacemakers.
  • Tachycardias or tachyarrhythmias. These are arrhythmias due to excessive electrical activity. They can be isolated, such as extrasystoles (premature beats) or continuous, causing tachycardias (i.e., a rapid heart rhythm). There are many causes of tachycardias, often benign. It is therefore important to consider the major groups of tachycardias because of their diverse etiology and their specific treatment.
  • Ventricular extrasystoles. This is the most frequent arrhythmia. It consists of premature beats that provoke an irregular pulse. In general, it is a benign disorder that only requires specific treatment to control the symptoms, or in special cases, when they generate a worsening of heart function.
  • Atrial fibrillation. This is the most common sustained tachycardia. It causes a totally irregular activity, which is detected with an irregular pulse. It is frequent in elderly patients, beyond 70 years of age, especially associated with arterial hypertension, diabetes, hyperthyroidism and any cardiac disease. Occasionally appears in younger patients, often associated with endurance sports activity (cycling, running, swimming, etc).
  • Supraventricular tachycardia. These are tachycardias that often appear in patients without heart disease. Occasional episodes of acceleration of the heart, which sometimes stop, sometimes require medical intervention. Many supraventricular tachycardias are due to minimal congenital electrical disorders (present from birth) and are treatable by catheter ablation.
  • Ventricular tachycardias: These are infrequent tachycardias due to a rapid heart rhythm originating in the ventricle. They frequently occur in patients with a history of heart disease such as myocardial infarction. They are infrequent and require careful evaluation to determine the need for automatic defibrillator implantation in case they are considered life-threatening. In other cases, they are benign tachycardias, without cardiac disease, which can be managed by medication.
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The dangers of arrhythmias

  • Most arrhythmias are not immediately serious, but they should be carefully evaluated to distinguish those that require specific treatment. Some arrhythmias only produce palpitations, which cause discomfort but are not serious, but require treatment because of the discomfort they cause. Other arrhythmias, such as atrial fibrillation, may increase the risk of embolism, so the embolic risk should be assessed individually. Finally, in extreme cases, arrhythmias such as complete block, or ventricular tachycardia, can cause loss of consciousness and even sudden death. An assessment of the patient will allow us to establish the potential severity of the case.

Diagnosis of arrhythmias

  • The simplest way to detect an arrhythmia is by taking the pulse. An irregular or too rapid pulse (greater than 100 per minute at rest) allows us to suspect tachycardia. A slow pulse, less than 40 beats per minute, allows us to suspect bradycardia.
  • The most useful tool in the detection of arrhythmia is the electrocardiogram. An electrocardiogram performed during the arrhythmia episode allows us to see which arrhythmia the patient is suffering from. The limitation is that if the arrhythmia does not occur while the patient is connected to the electrocardiogram, it is not detected.
  • Holter recording allows the patient to remain connected to the electrocardiogram for a more or less prolonged period of time, from 24 hours to prolonged recordings by means of T-shirts that monitor the rhythm for a longer period of time.
  • Another way of detecting arrhythmias is the electrophysiological study. The introduction of a catheter-electrode into the heart through the femoral veins makes it possible to detect and stimulate the heart, provoking arrhythmias and being able to diagnose them, when the arrhythmias have not been detected by the electrocardiogram or Holter recording. In addition, during the same electrophysiological study, tachycardia ablation (destruction of the tissue that generates the arrhythmia, by means of radiofrequency energy) can be performed. In this way, an electrophysiological study can be diagnostic as well as therapeutic.
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How to treat arrhythmias?

  • Arrhythmias can be treated by means of antiarrhythmic medications, implantable devices such as pacemakers or defibrillators, or ablation through catheters.
  • Pacemakers are used in the treatment of bradycardias, and are implantable devices under the skin, which generate an electrical stimulus that replaces the damaged activity of the heart.
  • Implantable defibrillators are devices that can also be implanted under the skin, which detect the presence of ventricular tachycardias and administer an electric shock to return the heart to its normal rhythm.
  • Catheter ablation involves the application of an energy, usually radiofrequency (heat destruction) or cryotherapy (freezing) through the catheter to a damaged area of the heart to destroy the abnormal area and prevent it from causing tachycardias.