Definition
If there is no circulation of blood in the vessels of the affected person due to a missing (or non-productive) heart action, this is called a (cardiac) arrest.
Introduction
In emergency medicine, cardiac arrest represents an acutely life-threatening condition. The partially congruent use of the term “clinical death” is misleading in that a cardiac arrest can be reversed if countermeasures are taken in time. While emergency cardiac massage and respiration (cardiopulmonary resuscitation) can at best resuscitate the patient and possibly even escape without permanent damage, this procedure is not always successful.
If the heart, and thus the circulation of the affected person, does not get going again, the definitive irreversible death is the inevitable consequence of a cardiac arrest without artificial maintenance of the blood circulation in the course of appropriate apparatus medicine. If this occurred unexpectedly and suddenly, it was a so-called sudden cardiac death.
- Cardiac arrest – causes & immediate measures
- First aid
Causes
The vast majority of observed cardiac arrests are associated with coronary heart disease (CHD) or severe cardiac arrhythmias. An enlarged heart (dilated or hypertrophic cardiomyopathy) can also be the cause of cardiac arrest. Other diseases leading to severe cardiac arrhythmias are rarer, as are other congenital and genetic as well as acquired errors in the anatomical or electrophysiological structure of the heart.
Likewise, deviations of the concentrations of potassium (hyper- or hypokalemia), calcium (hypercalcaemia), magnesium (hypomagnesemia) or H+ ions (acidosis) in the blood from their optimum can trigger cardiac arrest. In extreme cases, a strong allergic reaction (anaphylactic shock) as well as an overactivation of the so-called sympathetic nervous system, for example due to severe stress, can lead to cardiac arrest. Also rare, but also possible, is the opposite cause, an overstimulation of the so-called parasympathetic regulation of the cardiac activity, for example by a foreign body stuck in the esophagus, which then, by exerting pressure on the parasympathetic nerve cord (nervus vagus) leading to the heart, slows down the heart rhythm (bradycardia) to such an extent that the heart action can finally come to an absolute standstill.
This so-called vagal reflex can also be triggered by sudden cold, such as jumping into ice water, or sudden very strong pain or violence on the upper abdominal nerve plexus (solar plexus). Other mechanical-reflective causes of cardiac arrest include carotissinus syndrome. In this syndrome, the cells measuring the blood pressure in the large cervical arteries (carotides) falsely report too high blood pressure due to pressure (from the outside or inside, for example due to a tumor) or faulty regulation.
In this way they inhibit the heart’s action. On the other hand, strong pressure exerted on the heart itself – for example in an accident – is a possible cause. In rare cases, poisoning or medication (overdoses) (such as with diazepam or antiarrhythmic drugs), as well as drug use (cocaine) are also causes of cardiac arrest.
Other possible causes are a general lack of pumpable blood (hypovolaemia) and mechanical obstruction of the heart’s action, for example by fluid in the pericardium (pericardial tamponade). Furthermore, severe lung problems (e.g. pneumothorax or pulmonary embolism) or damage to the brain (e.g. in the course of a stroke) can also lead to cardiac arrest, as can hyperthermia or an electrical accident. In general, cardiac arrest can be classified into one of the following categories, depending on the cause
- In so-called asystole, the heart is neither electrically nor mechanically active, while electromechanical decoupling is characterized by the failure to transmit electrical signals to the heart muscles of the ventricles and/or atria, which otherwise contract towards them.
- The total functional failure of the heart in pulseless ventricular tachycardia is based on such a high rate of repetitive contraction that the pumping pauses (diastoles) are too short to allow blood to flow into the heart during this time.
- Finally, ventricular fibrillation is caused by the fact that erroneously “circling” excitation in the ventricle leads to a continuous, uncontrolled contraction of the heart, which also prevents pumping.
