VERIFIED CONTENTConsultation: dr hab. n. med. Marcin Grabowski, specialist in internal medicine, cardiologist, 1st Department and Clinic of Cardiology, Medical University of Warsaw

Bradycardia, i.e. a slow heart rate, does not always require therapeutic intervention. The Czech runner Zatopek felt great, even though his resting heart only beat 30 times a minute. However, for most of us, such a slow heart rate impairs our daily life, unless a pacemaker is implanted.

Bradycardiaisheart rateless than 50 beats per minute, but it is an arbitrary limit. For physiological reasons, the heart rate can be much lower, for example in young people practicing sports (especially endurance sports). They have a strong, trained heart muscle, which throws out more blood during contraction than in others, so it is able to ensure optimal blood supply to the body at a slower, 30-40 beats per minute, pulse.

However, bradycardia can also be pathological, but not always treated. It depends on the patient's age, well-being and comorbidities. If a person functions well with a pulse that is too slow according to the standards, he is usually only watched. We have more and more evidence that the slower the heart beats, the potentially longer life will be.

The heart also slows down at night, when the demand for its work decreases. This is a natural and desirable phenomenon, the absence of which is pathology. In he althy people, the heart rhythm during sleep, even below the imaginary bradycardia limit, has no consequences.

Bradycardia - symptoms

Symptoms of bradycardia may be mild at first and gradually worsen, or they may occur suddenly and be dramatic, including interruptions in the heartbeat. The most common symptoms are:

  • dizziness,
  • spots in front of eyes,
  • slow running,
  • weakness,
  • lack of vigor,
  • decreased physical performance.

However, fainting and short-term blackouts related to the brain's oxygen deficit may also occur. Their consequence is falls, often leading to head injuries and bone fractures.

All these symptoms are nonspecific, ie they can be attributed to many diseases, therefore their causes other than bradycardia should be considered. However, it is a specific symptomthe so-called chronotropic incompetence, i.e. failure to accelerate the heart rate in situations in which it should occur (stress, exercise).

Bradycardia - causes

The cause does not always lie in the stimulus-conducting system. The causes of bradycardia may include :

  • other diseases of the heart muscle,
  • hypertension, neurological disorders,
  • medications taken,
  • electrolyte disturbances (excessive potassium concentration),
  • hypothyroidism.

These are secondary causes and are usually eliminable. The primary ones are in the stimulus-conducting system itself. The most common of these is fibrosis of the sinoatrial node or the conduction pathways due to aging.

The reason for the slow rhythm (sometimes also irregular) is also damage to this system as a result of infection (e.g. myocarditis or Lyme disease), scars on the conduction paths as a result of a heart attack.

Bradycardia can also be a consequence of another arrhythmia - paroxysmal atrial fibrillation, common in people in their sixties, which causes a weakening of the conductive stimulus system.

Therefore, in elderly people there are alternating acceleration and deceleration of the heart rhythm, called tachycardia-bradycardia syndrome.

Bradycardia and the sinus node and heart blocks

Sinus node disease and heart blocks are the two main types of disorders that cause bradycardia. The first is related to the failure of the natural pacemaker - the sinoatrial node.

It generates too few impulses in relation to the organism's needs or stops sending them for a while. Then its function is taken over by substitute stimulus centers - heart cells specialized in generating electrical impulses. But the rhythm they generate is too slow.

It happens that the natural pacemaker works fine, but the stimulations it sends are inhibited or blocked in the conduction pathways: in the atrioventricular node, the bundle of His or its branches. This condition is called a heart block or atrioventricular (AV) block. There are three levels of it:

  • 1st degree all atrial impulses go to the ventricles, but too slowly,
  • in II - some of them do not reach them,
  • in III they do not reach at all and the chambers start a substitute rhythm, slower than the sinus rhythm.

Bradycardia - treatment

People with a he althy heart can tolerate bradycardia well. However, if the condition of this organ and the circulatory system in general (e.g. cerebral arteries) leaves much to be desired, the low heart rate, interruptions in itswork not only handicap life, but also pose a risk to it if it is not treated.

It consists in the implantation of a pacemaker (pharmacotherapy is used only temporarily). This compact device consists of a battery-powered pulse generator and electrodes. The generator is implanted under the skin in the subclavian region, usually on the left side, and the lead or electrodes are vein inserted into the right atrium and / or right ventricle, depending on where the arrhythmias arise. They are most often placed in both cavities of the heart, because it provides a natural sequence of atrial and ventricular contractions.

Pacemaker implantation is an invasive procedure with the risk of complications, so it is only performed when necessary.

The electrodes conduct pulses from the generator to the cavities of the heart and, as a feedback, information about its natural stimulations. The device is "intelligent". It constantly monitors the action of the heart muscle and sends electrical pulses only when needed.

It may have one more remarkable property - adjust the frequency of stimulation to the needs of the body, thus increasing the heart rate during exercise and slowing down when resting.

Implantation of a pacemaker connects the patient with a cardiologist for life. It is necessary to check-up every 6-12 months, replace the battery every 4-7 years (depending on how often the device is turned on), sometimes also the electrodes, or reprogram the device (the doctor does not have to remove it from under the skin). These certain inconveniences are compensated by the comfort of life and its extension for many years.

  • Tachycardia means fast heartbeat
  • Cardiac arrhythmias: causes and symptoms
  • Cardiac arrhythmia - symptoms, effects, diagnosis, treatment

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