Ventricular fibrillation (VF) from Latin. fibrillatio ventriculorum is a life-threatening disorder of the heart rhythm. It is characterized by the occurrence of disordered, uncoordinated excitations in the cells of the heart muscle - cardiomyocytes. What are the causes and symptoms of ventricular fibrillation? How is the treatment going?
VF( VF ) in Latinfibrillatio ventriculorumis a life-threatening arrhythmia characterized by disorderly, uncoordinated beats in the heart muscle cells, the cardiomyocytes. This results in a very high frequency of heart contractions, which unfortunately are not effective.
The main function of the heart is thus disturbed - pumping blood to the blood vessels and its circulation in our body. VF may occur, for example, secondary to myocardial infarction or be associated with an electric shock. Untreated VF leads to death.
How to recognize ventricular fibrillation?
The primary diagnostic tool for both VF and other arrhythmias is electrocardiography (EKG). In this study, ventricular fibrillation is characterized by a flicker wave between 300 and 800 / min. This wave is an irregularly shaped sine wave with variable amplitude.
Normal heart beat - physiology
In order to find out about the causes of ventricular fibrillation, we need to know a little more about how our heart works. The contractions of the heart are caused by the contraction of individual cells of the striated muscle, which in turn are stimulated by the heart's conductive stimulus system.
This system plays a major role in stimulating the heart to work. It consists of specialized cells of the heart that have the ability to spontaneously generate electrical impulses and also to distribute them further, resulting in the contraction of the heart muscle cells.
The superior center (primary) in this case is the sinoatrial node, which produces approximately 72 such pulses per minute on average. This number corresponds to the number of heart contractions in a statistical adult human, which can be observed, for example, in the form of a pulse measured on the radial or femoral artery.
inferior center (secondary),which also has the ability to generate potentials is the atrioventricular node. It generates pulses of a lower frequency - about 50 beats per minute. Purkinje fibers are other structures with this ability.
The last center that can stimulate the heart to contract, in the case of failure of the superior centers, are cardiomyocytes, i.e. the cells of the heart muscle. In this case, the heart rate will be the lowest and may be around 30 beats per minute.
To sum up, during the physiological work of the heart, electrical impulses run from the place of origin, along specific fibers of the stimulating system, to the cells of the heart muscle.
The location of the sinoatrial node in the wall of the right atrium causes the atria to contract first, forcing blood into the ventricles. In the next stage, the ventricles contract and the blood pumped into the vessels moves throughout the body. If this physiology is disturbed at any stage of the generation or conduction of impulses, we can recognize cardiac arrhythmia.
Ventricular fibrillation - pathophysiology. How does VF arise?
Sinus rhythm is the rhythm that corresponds to a normal heart beat. The emerging potentials travel along the pathways of the stimulatory-conducting system from the site of origin, i.e. from the sinoatrial node, through the cells in the atria, the atrioventricular node, Purkinje fibers, to the heart muscle cells, which build the heart chambers and cause their contraction . Then the potentials are muted and the cells are ready to receive the next stimulation.
During VF, the conduction and circulation of the impulse in the heart is disrupted. The spreading excitation hits the cells that have just been activated and are able to receive the next impulse and pass it on.
There is a so-called re-entry phenomenon - the phenomenon of a reversing wave. The impulses circulate along the stimulated tissues in the form of waves with a very high frequency, thus making it impossible to coordinate the contraction of the heart. The heart begins to contract very quickly, but in a chaotic manner. Due to the short period of diastole, the blood does not enter the ventricles in sufficient quantity and therefore only a small amount is pumped into the aorta. When there is zero cardiac output, it is called cardiac arrest. As a result, blood cannot be distributed throughout the body - hypoxia occurs, and as a result, necrosis of hypoxic tissues.
Ventricular fibrillation, causes
As one of the main causes leading toventricular fibrillation, it is necessary to consider a very common chronic disease (which is now characterized by epidemics), i.e. ischemic heart disease. If left untreated, it can lead to a heart attack. Closed coronary vessels do not supply the oxygen cells necessary for life, cardiomyocytes die, and thus the entire structure of the heart is damaged - both muscular and related to the stimulus-conducting system. This pathology significantly increases the possibility of arrhythmias, including ventricular fibrillation.
It is worth adding that the vast majority of patients who experienced ventricular fibrillation had previously struggled with heart disease (previous infarction; severe valvular disease). A history of a heart attack or a ventricular fibrillation attack significantly increases the risk of a repeat episode of this arrhythmia.
Other factors that should be mentioned would be:
- all kinds of cardiomyopathies, including those secondary to other heart disorders
- congenital heart defects causing its abnormal structure (also in terms of the stimulus-conducting system)
- Brugada syndrome - a rare, genetically determined disease associated with the abnormal structure of ion channels, the first symptoms of which may appear in adulthood and lead to death
- long QT syndrome- briefly explaining this enigmatic name, the QT interval is a fragment of the ECG recording, allowing the assessment of depolarization and repolarization of the ventricular muscles. When its value is too high (the interval time measured in milliseconds is too much), we can expect the patient's predisposition to develop serious cardiac arrhythmias
- metabolic disorders
- hormonal disorders
- electrolyte disturbances, especially potassium (hypokalaemia) and magnesium (hypomagnesaemia)
- effects of some drugs (including amiodarone, some antibiotics such as clarithromycin, erythromycin, trimethoprim, antidepressants: amitriptyline, escitalopram or antipsychotics such as haloperidol, quetiapine). Their ability to induce ventricular fibrillation in overdose is associated with effects on cardiac potassium channels and prolongation of the QT interval
- drugs like cocaine or methamphetamine
We can also distinguish idiopathic ventricular tachycardia, i.e. tachycardia, the mechanism of its origin we are unable to explain.
Ventricular fibrillation may be the result of another pre-existing arrhythmia, the so-called ventricular flutter. It is a condition where the heart rate is in the range of 200-300 / min. The reason for this is because of impulsesin the heart chambers instead of the sinoatrial node.
Ventricular fibrillation - symptoms
Symptoms of ventricular fibrillation include :
- sudden fainting, which may also occur in situations not preceded by physical exertion
- dizziness
- feeling of pounding heart
Symptoms, especially at the beginning, can be very uncharacteristic, and ventricular fibrillation itself may, on rare occasions, resolve itself. That is why it is so important not to ignore the disturbing symptoms and see a doctor as soon as possible in order to start diagnosing possible possible causes of malaise.
At a later stage, the symptoms of VF are symptoms of sudden cardiac arrest. In this case, the person loses consciousness - he does not respond to voice or touch, shaking, does not breathe or his breathing is abnormal (agonizing), and we cannot feel the pulse on large arteries.
Ventricular fibrillation - how do we treat?
The basic treatment for VF in the first stage of premedical care is the same as for the treatment of other causes of SCA (sudden cardiac arrest). The standard is to undertake immediate cardiopulmonary resuscitation, i.e. a set of activities that are skillfully performed, significantly increasing the chances of survival. For this reason, it is so important to disseminate in the society the ability to follow the basic principles of first aid. More and more often, various types of institutions organize first aid training, and schools enrich their program with such activities so that even the youngest citizens are able to help in a life-threatening situation.
When undertaking resuscitation, please follow the International Guidelines established by the European Resuscitation Council (ERC). The latest guidelines are from 2015. When done correctly, these actions enable the maintenance of ventilation and heart rate while waiting for the arrival of qualified medical personnel.
This allows key organs such as the brain, heart and kidneys to be supplied with oxygen continuously. Upon arrival, the Medical Rescue Team decides on further treatment - defibrillation and administration of drugs (adrenaline, amiodarone). During defibrillation, a strong electric discharge occurs, which causes all cells of the heart muscle to be stimulated simultaneously. In this way, the stimuli again begin to move correctly along their designated paths. This is the only method that can restore your heart rate to normal. The fasterdefibrillation will be performed, the greater the chances of survival become.
The chances of survival during cardiac arrest are also significantly increasing thanks to the appearance of AEDs (Automatic External Defibrillators) in public spaces. These devices are able to easily understand them through verbal and visual commands to guide anyone through the safe defibrillation procedure.
These devices can now be found both at stations and in shopping malls, cinemas, theaters, in places where the probability of cardiac arrest is higher due to the large number of people. The cameras are intended for use by any person who is witness to such an event.
At a later stage of treatment, in addition to pharmacotherapy, it is possible to implant a cardioverter - defibrillator, and above all, treatment of the underlying disease is started.