Bradycardia ( Greek βραδυκαρδία bradycardia , German , Langsamherzigkeit ' ) is a slow heartbeat and referred to in the medicine in adult humans, a heart rate below 60 beats per minute. The opposite of bradycardia is called tachycardia : in adults, a pulse rate of over 100 beats per minute at rest.
When heart healthy people, the frequency of heart beats is determined by the conduction system control of the heart. The frequency of the heartbeats, to be determined by feeling the pulse , depends u. a. on the level of physical exertion. Usually the heart rate does not fall below 40 beats per minute, exceptions are well-trained endurance athletes, for whom a lower frequency at rest can be considered normal, provided that the heart rate increases adequately during exercise. Then there is controlled bradycardia (sinus bradycardia). In addition, the heart rate is usually lower when lying down than when sitting down.
The article sports heart describes the normal adaptation of the heart to endurance training . Since a sports heart is associated with bradycardia, left-sided hypertrophy (increase in heart muscle mass) and an increase in heart volume, a sports heart can mask a pathological change in the heart, so that a diagnosis of heart disease may not be possible. On the other hand, it is considered impossible that exercise can damage a healthy heart.
Pathological causes of bradycardia can only be identified by a resting ECG . These include the irritation disorder sinus bradycardia (slowing of the nomotopic, starting from the sinus node, stimulation to a frequency of less than 60 beats per minute) and conduction disorders :
- Disease of the sinus node without a sufficient increase in heart rate during exercise ( chronotropic incompetence ) and low resting frequency (sinus bradycardia in sick sinus syndrome = syndrome of the sick sinus node),
- Blocking of the excitation conduction via the atria ( SA block ),
- Disease of the AV node with second to third degree blockage ( AV block ),
- slow atrial fibrillation ( bradyarrhythmia absoluta ).
In addition to a heart disease such as coronary heart disease , drugs ( beta blockers , clonidine , verapamil , diltiazem , digitalis ) can often be the cause. Increased intracranial pressure also often causes bradycardia.
The severity of symptoms can vary greatly, from freedom from symptoms in the case of mild bradycardia to reduced performance to fainting spells ( syncope ), deterioration ( decompensation ) of an existing heart failure or cardiac arrest with death.
The safest method for diagnosing bradycardia is the ECG. Phases of slow heartbeat can be recorded in the long-term ECG . If there are fewer pulse beats to be felt than to be counted in the ECG, one speaks of a pulse deficit . In the context of pulse oximetric monitoring, the pulse rate is always output, but this method is prone to errors, since only the pulse is counted, not the electrical heart action. Even with ultrasound , by Doppler heart rate are determined. Last but not least, you can listen to the heart ( auscultation ).
If drugs are out of the question as the cause of permanent or recurrent , pathological bradycardia, implantation of a pacemaker is necessary. A temporary variant can also be used to bridge the gap with little effort. Medicinal measures such as the administration of parasympatholytics (e.g. atropine ) or sympathomimetics (e.g. adrenaline ) can only be used to bridge the gap in emergency situations. Chest compressions may be required.
A pacemaker is usually not indicated for slow heartbeats that occur purely at night during sleep, even with extremely low heart rate values.
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