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Bradycardia: Difference between revisions
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Bradycardias are defined as symptomatic heart rhythm disorders resulting in a inappropriately low heart rhythm during during physiologic conditions. Generally this results in a cut-off value of <60 beats per minute, however variation of heart rate exists. For instance, during sleep and in athletes the heart rate can be as low as 40 beats per minute. | Bradycardias are defined as symptomatic heart rhythm disorders resulting in a inappropriately low heart rhythm during during physiologic conditions. Generally this results in a cut-off value of <60 beats per minute, however variation of heart rate exists. For instance, during sleep and in athletes the heart rate can be as low as 40 beats per minute. | ||
Bradycardia can be caused by a variety of intrinsic and extrinsic causes. | Bradycardia can be caused by a variety of intrinsic and extrinsic causes. The most common intrinsic cause is ageing, but ischaemic heart disease, infiltrative diseases or surgery can result in conduction disorders. Medication that modifies the excitability of the heart is the most frequent extrinsic cause, however electrolyte and metabolic disorders may influence the heart rate directly or indirect. To understand the pathophysiologic basis of most conduction disorders or disorders of impulse formation it is important to have knowledge about the physiology of cardiac conduction and mechanisms of arrhythmia as detailed in the general cardiac arrhythmia section [Link]. | ||
The heart being a mechanical pump, complaints from bradycardia result from an insufficient capacity of the pump to supply the rest of the body with blood. Complaints of palpitation, syncope or heart failure may result from conduction disorders, however often vague symptoms for instance like dizzines, faintness or fatigue may be caused by bradycardia. | |||
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If the two fascicles of the left bundle branch there is a left bundle branch block, this bifascicular block is uncommon in healthy patients and further cardiologic investigations need to be performed to screen for underlying disease. | If the two fascicles of the left bundle branch there is a left bundle branch block, this bifascicular block is uncommon in healthy patients and further cardiologic investigations need to be performed to screen for underlying disease. | ||
Treatment | |||
Fortunately the human heart has a couple of backup mechanisms that can sustain a heart rate in case of severe bradycardia. These escape mechanisms can occur in every part of the heart (i.e. atrium, AV, node, ventricle). In general, the rate of the escape mechanism is faster when the escape rhythm is located higher in the conduction system. | |||