Cardiac arrhythmias are irregularities in the normal activity of the heart. A further distinction can be made as to whether the heart beats too fast (tachycardia) or too slow (bradycardia). Heart activity can also be irregular. Some cardiac arrhythmias are of no further concern, while others can have life-threatening consequences. Therefore, cardiac arrhythmias should always be clarified by a physician.
A heartbeat occurs when the heart muscle contracts under the influence of an electrical signal (excitation). The electrical signals required for this are formed and transmitted by special cardiac muscle cells of the conduction system. The electrical voltage is generated by the different distribution of charged particles (electrolytes) inside and outside a cardiac muscle cell. A complex flow of electrolytes in and out (action potential) allows the signal to be transmitted through the conduction system.
The signal or rhythm normally originates in the sinus node, which is located in the right atrium of the human heart. There, specific pacemaker cells, which have their own clock, generate 60 to 80 electrical impulses per minute and transmit this to the conduction system. The rhythm is transmitted from the sinoatrial node via the node connecting the atria and ventricles, the AV node. From there, the impulse is transmitted to the His bundle further into the two ventricular legs (tawara legs) and up to the apex of the heart. From the apex of the heart, the tawara legs branch into many thin fibers (Purkinje fibers) that terminate in the myocardium.
Under the influence of the electrical signals, the muscles of the heart contract and pump blood into the systemic circulation. Then the heart muscle cells relax again until the next impulse is sent out by the sinus node. The basic frequency of the sinus node is about 60-80 beats per minute. However, this can increase significantly during exercise or stress. The subsequent sections of the conduction system also have a rhythm of their own, but it is slower than that of the sinus node, which is why they only take over when the sinus node fails.
The electrical rhythm of the conduction system triggers muscle contraction and thus the heartbeat. However, electrical excitation and muscle contraction are strictly speaking two different processes. In rare cases, electrical rhythm and muscle contraction can also occur decoupled from each other (pulseless electrical activity).
If the sinus node cannot generate the electrical rhythm appropriately, if the rhythm is not transmitted or if other impulses occur in the heart, we speak of cardiac arrhythmias. Both "dangerous" and "less dangerous" types exist.
Cardiac arrhythmias can be classified according to their place of origin, as well as according to the heart rate. Some factors, such as physical exertion, excitement, illness or medication can also cause a change in the normal heartbeat, but without this being judged as pathological.
Tachycardia is when the heart beats too fast. The pulse is over 100 beats/minute at rest.
Atrial fibrillation | Point of origin: atrium Non-ordered impulses pass from the atrium to the ventricle, following each other very quickly. |
Supraventricular tachycardia | Place of origin: sinus node, AV node, myocardial cells of the atrium Additional impulses are generated in the atrium. As a result, the heart beats faster. This so-called racing of the heart can occur suddenly and last for several minutes to hours. As a rule, supraventricular tachycardia is not considered life-threatening, but it should in any case be clarified by a doctor and also checked regularly. |
Wolf-Parkinson-White (WPW) Syndrome | Place of origin: atrium There is an additional conduction between the atrium and the ventricle, which is present from birth. This conduction leads to attacks of palpitations in affected individuals. |
Ventricular fibrillation | Point of origin: ventricle In this type of cardiac arrhythmia, the mechanical pumping function of the heart comes to a standstill. The ventricular rate is greatly increased (>320/minute). This heart movement is very uncoordinated - the blood can no longer be pumped sufficiently through the body. When this condition occurs, it is also referred to as "functional cardiac arrest." |
Ventricular tachycardia | Place of origin: ventricle This cardiac arrhythmia is considered dangerous. It occurs when extra impulses are generated in the heart chambers, causing the heart to beat faster and increasingly inefficiently. Ventricular tachycardia can lead to life-threatening ventricular fibrillation. |
Bradycardia is the condition when the heart beats more slowly than usual. The pulse is less than 60 beats/minute. Specialists often assess bradycardia as medically relevant only from less than 50 beats/minute, because well-trained people (athletes) can also have a slow resting pulse without this being pathological.
Sinus node dysfunction (sick sinus syndrome) | Place of origin: sinus node The natural pacemaker function of the sinus node is no longer present. As a result, a slowed heartbeat occurs. |
Heart block | Place of origin: transition area between atria and ventricles The transmission of the excitation impulse does not occur or is delayed. A distinction is made between sinus atrial (SA) block, in which conduction between the sinus node and the atrium is disturbed, and atrio-valvular (AV) block, in which conduction between the atrium and the ventricle does not occur properly. In addition, there are also different types of thigh block. |
Extrasystoles (extra beats) | Point of origin: transitional area between atria and ventricles Extrasystoles are additionally occurring heartbeats that are not subject to the regular basic rhythm. These additional heartbeats can occur both before and after the basic rhythm. There can be single beats, but also several, or clustered beats. Sometimes, individual beats also drop out. |
Cardiac arrhythmias occur when the conduction system of the heart is disturbed or blocked. In most cases, underlying heart diseases are the cause. The arrhythmias can be triggered, for example, when heart muscle cells are not supplied with sufficient oxygen or are scarred (for example, by a heart attack).
The following diseases are common causes of cardiac arrhythmias:
| Cause of the cardiac arrhythmia | Trigger |
| Myocardial (affecting the heart muscles) | Coronary artery disease (CAD), heart attack |
| Hemodynamic (concerning the disturbance mechanics) | Volume loading of the heart(heart failure), valvular defects, pressure loading of the heart(high blood pressure) |
| Extracardiac (cause outside the heart) | Psychovegetative factors, Roemheld syndrome, electrolyte disturbances, hyperthyroidism, hypoxia, medications (e.g., cardiac glycosides, antidepressants), alcohol, caffeine, drugs, toxins, hyperreactive carotid sinus. |
Since the various cardiac arrhythmias are very different, a wide range of symptoms can also occur. Often, cardiac arrhythmias also go unnoticed.
Possible symptoms are:
The diagnosis of a cardiac arrhythmia is primarily made with the aid of an electrocardiogram (ECG). Here, the currents and charges flowing in the heart are recorded via electrodes on the skin. With the help of an ECG, the heart rhythm can be determined and structural abnormalities in the heart can also be detected (e.g. heart attack). Often a short measurement of these heart currents (a few seconds) is sufficient. Sometimes it is useful to record a longer period of the heart rate (from 24 to 72 hours) in the case of cardiac arrhythmias that occur only occasionally (long-term ECG). Some cardiac arrhythmias occur only under stress. In this case, an exercise ECG can be arranged, in which the recording is made during exertion on a bicycle ergometer.
In general, the following types of ECG can be distinguished:
In some cases, it may be necessary to perform further examinations to clarify cardiac arrhythmias. The following examinations, for example, serve to determine the type and origin of cardiac arrhythmias more precisely. In addition, the effectiveness of medications can also be checked.
Once a precise diagnosis has been made, cardiac arrhythmias can be treated either with medication or also by means of so-called electrotherapy. Sometimes, however, cardiac arrhythmias are chronic and cannot be completely cured.
The drugs used to treat arrhythmias are also called antiarrhythmics. These can generally be divided into four different classes:
| Class | Drugs | Indications |
|---|---|---|
| I. Sodium channel blockers | z. E.g., ajmaline, propafenone, flecainide, lidocaine, quinidine | z. B. Acute ventricular arrhythmias, atrial fibrillation. |
| II. beta receptor blockers | z. e.g. propranolol, metoprolol, bisoprolol, nebivolol | z. e.g. tachycardia, after myocardial infarction |
| III. potassium channel blockers | z. e.g. amiodarone, sotalol | z. B. Ventricular arrhythmias, atrial fibrillation |
| IV. Calcium antagonists | z. e.g. nifedipine, diltiazem, verapamil | z. B. Supraventricular tachyarrhythmias |
| Unclassified antiarrhythmics | Adenosine, magnesium, dronedarone, vernakalant | - |
Electrotherapy of cardiac arrhythmias can be generally divided into three treatment methods:
If there is another heart disease in addition to an arrhythmia (e.g., CHD, valvular heart disease, high blood pressure, myocarditis, cardiac insufficiency), this is usually treated first. Often, underlying heart disease is causative for arrhythmia.
In addition, any other risk factors for arrhythmias should also be treated. These include, for example, hyperthyroidism, obesity or diabetes mellitus.
The prognosis depends on the type of arrhythmia as well as other underlying diseases. Some arrhythmias, such as isolated supraventricular extrasystoles, do not require any treatment, whereas ventricular fibrillation is an acute life-threatening condition that often ends in death.
A healthy lifestyle with a balanced diet, regular exercise, weight management, moderate alcohol consumption and abstinence from smoking can protect against the occurrence of cardiac arrhythmias. Furthermore, existing diseases and diseases that trigger cardiac arrhythmias should be prevented or, at best, treated. In the case of regular symptoms such as palpitations or heart palpitations, a doctor should be consulted in order to clarify the cause.
Dr. med. univ. Moritz Wieser
Thomas Hofko
Browse our extensive database of medications from A-Z, including effects, side effects, and dosage.
All active ingredients with their effects, applications, and side effects, as well as the medications they are contained in.
Symptoms, causes, and treatments for common diseases and injuries.
The presented content does not replace the original package insert of the medication, especially regarding the dosage and effects of individual products. We cannot assume liability for the accuracy of the data, as the data has been partially converted automatically. Always consult a doctor for diagnoses and other health-related questions.
© medikamio