Ventricular fibrillation is a very serious disorder of the heart’s normal rhythm (which often puts vital issues).
The disease is characterized by uncoordinated contraction of ventricular myocardial fibers. In ventricular fibrillation myocardium does not move uniformly, rather shaking. If this rhythm disorder (arrhythmia) lasts more than a few minutes, the patient may die because blood circulation becomes unable to provide the oxygen needs of the body. Experts describe this disorder as a chaotic and asynchronous heart. Ventricular fibrillation is a medical emergency!
Ventricular fibrillation is a relatively common disease in the European population (especially in the Nordic countries) and annual incidence of mortality it is 6 to 10,000 cases of cardiac death. Epidemiological studies have shown that men are more commonly affected than women, although after a certain age (70 years) percentages are balanced. There are two peaks of incidence of ventricular fibrillation: in the first 6 months of life and between 55-75 years.
Causes of Ventricular Fibrillation
The heart is the organ that pumps blood in the body permanently, with an average frequency of 75 beats / minute, at a steady pace. If this rate is severely affected (by a ventricular arrhythmia) heart no longer fulfills the role of the pump and vital organ perfusion is compromised. If ventricular fibrillation does not stop in time, syncope will appear and the patient dies.
Ventricular fibrillation occurs most frequently in the context of heart disease (most often ischemic heart disease, but also in cardiomyopathies, myocarditis), drug overdose or serious disturbances of acid-base balance. However, the exact etiology of ventricular fibrillation remains incompletely known – post-mortem studies (performed on autopsied bodies) have revealed the presence of an acute myocardial infarction as a potential trigger pathology in
many cases. Specialists believe there are a number of pathophysiological and electrophysiological changes that ultimately lead to onset of ventricular fibrillation. If it is not treated, the patient’s evolution is particularly severe, with a mortality of approximately 100%. Causes of appearance are classified in non-cardiac and heart causes.
1. Structural heart disease may be the type of myocardial ischemia or myocardial infarction caused by atherosclerotic disease (atherosclerosis is most commonly incriminated in triggering phenomena of obstruction and ischemic coronary vessels), cardiomyopathy (dilated, hypertrophic), aortic stenosis, aortic dissection, cardiac tamponade , myocarditis, congenital heart disease. Incriminating non-structural heart disease: traumatic accident (electric shock), preexcitation syndromes, intracardiac conduction blocks.
2. Non-cardiac causes include
– Pulmonary: bronchospasm, aspiration of foreign bodies, sleep apnea, primary pulmonary hypertension, pulmonary embolism, tension penumotorax;
– Metabolic: acidosis, acid-base balance disorders;
– Toxic causes: toxic substances, sepsis;
– Neurological: seizures, stroke (ischemic or haemorrhagic).
There are situations when ventricular fibrillation occurs on a background apparently healthy, but often patients had risk factors for cardiac events: smoke, are hypertensive or diabetic. Idiopathic ventricular fibrillation (without an identifiable cause) occurs in 1% of cases of sudden death, in 14% of patients under 40 years and 3% of patients undergoing ventricular fibrillation in the absence of myocardial infarction.
Symptoms of Ventricular Fibrillation
Patients with ventricular fibrillation lose consciousness because vital organs are not perfused. The attack comes suddenly, without any premonitory signs and symptoms.
An hour before the patient faints, symptoms that may indicate a possible heart condition:
– Chest pain (angina pain);
– Dyspnea (shortness of breath);
– Fatigue – intense;
– Tachycardia (especially in serious cases).
If the patient is not revived as quickly as possible (within 5 minutes), appears irreversible brain damage that will leave permanent sequelae (if it is, however, saved).
Due to the seriousness of the situation, the patient is investigated as quickly as once a diagnosis of certainty, to initiate treatment.
Clinical physical examination:
– Pulse – very weak;
– Reduced breath sounds;
– The absence of responses to stimuli.
Electrocardiographic recording is very important because it shows changes through which the heart muscle
occurs during ventricular fibrillation. Also, on the ECG can be observed other disorders or conditions that may increase the patient’s risk.
Other investigations performed in patients with ventricular fibrillation (after their condition is stabilized or after being brought to the emergency room) are:
– Chest X-ray: may show pulmonary edema, cardiomegaly, injuries, aspiration pneumonia;
– Laboratory determinations of serum levels of electrolytes, including calcium and magnesium, cardiac enzymes;
– CBC (to determine if there is anemia);
– Dosage of blood gases (for proper objective to acidosis or hypoxemia);
– Toxicological investigations (whether clinical context requires).
Ventricular fibrillation is a medical emergency and must be treated as quickly and correctly as possible.
If VF occurs on the street, ideally, those who accompany him have to announce emergency services and until medical professionals arrive, give the patient first aid: – The patient is placed in safe position – ensure high airway patency, ensure artificial respiration by mouth-to-mouth technique or mouth or nose; – External chest compression is performed (cardiac massage – compressing the sternum 4-5 cm, with a frequency of 100 compressions / minute).
Caregivers should work against the clock. In an emergency such this are made investigations of the highest importance, the patient’s condition will be completely re-evaluated when it is stabilized.
Specialists will continue (or undertake) maneuvers of cardiopulmonary resuscitation and first aid, and will transport the patient to hospital.
Treatment consists in electrical converting of ventricular fibrillation rhythm by applying external electric shocks using a defibrillator. Treatment is continued to the emergency room of the hospital.
Electric shock is meant to induce electrical activity in the heart which will then stimulate the heart to resume function and uniform muscle contraction. Effective defibrillation (allowing the heart to re-enter in function) depends on two important factors:
– The time elapsed between the onset of ventricular fibrillation and defibrillation;
– Metabolic state of the myocardium and functional reserve of the heart;
The success rate of defibrillation decreases by 5-10% with every minute since the onset of ventricular fibrillation and its effectiveness can be predicted by the appearance of ECG tracing.
Treatment guidelines are very clear on the steps to be taken to stabilize the patient. Its condition is evaluated every 2 minutes, defibrillation with CPR timing is very important. If the situation requires, medications will be administered to improve cardiac status of the patient and to correct any complications that were installed as a result of ischemia.
During resuscitation are corrected the states that can complicate treatment and patient evolution: hypovolemia, hypoxia, acidosis, hyper / hypokalemia, hypoglycemia, hypothermia, thrombosis (coronary, pulmonary).
The goal of treatment is to end the episode of ventricular fibrillation, restore the electrical rhythm of the heart and correct cardiac output. Treatment success decreases as the duration of ischemia increases. Defibrillation is supported by drug treatment, which may include vasopressors, antiarrhythmics, electrolytes.
Vasopressors (vasopressin, epinephrine) is administered to increase perfusion pressure through the vessels of the heart (and thus improves cardiac irrigation). Antiarrhythmic agents are especially administered if defibrillation and vasopressor therapy does not improve the patient’s condition or are administered after conversion to prevent relapses.
Other drugs that may be used (depending on the clinical context, associated diseases and evolution of treatment): magnesium sulfate, propranolol (or other beta blockers), sodium bicarbonate (to treat hyperkalemia which can be at the origin of ventricular fibrillation or induced acidosis by prolonged cardiac arrest).
Patients who survived a ventricular fibrillation and are at the risk of another episode of this type may be advised to wear an implantable defibrillator to lower the risk.
If the patient remains in coma after conversion it seems best to be kept several hours in hypothermic condition (body temperature to be several degrees lower than normal). Such therapies appear to reduce mortality and improve prognosis.
The prognosis of surviving patients remains reserved and highly dependent on the time between onset of fibrillation and treatment initiation (while organism has been deprived of oxygen). Rapid defibrillation is what makes the difference between permanent sequelae or sequelae that can be recovered.
Permanent sequelae after resuscitation directly depend on the degree of damage to the central nervous system during ventricular fibrillation. If nothing is done after 4 minutes, prognosis is unfavorable. If resuscitation is delayed more than 8 minutes, the survival rate is very low (just theoretical).
Survival rate (ranging between 2-25%) depends on many factors:
– Area of the patient: rural, urban,
– Access to emergency medical services,
– Previous medical condition of the patient,
The most common complication of ventricular fibrillation is death.
For survivors, possible complications include:
– Neurological Disorders (similar to those of stroke);
– Myocardial injury;
– Post-defibrillation arrhythmias;
– Aspiration pneumonia;
– Injuries occurred during resuscitation (if they were very energetic)
– Skin lesions (due to the use of defibrillator).
Measures to prevent ventricular fibrillation are varied and include:
– Use of an implantable defibrillator;
– Managing a chronic treatment to control any diseases that may represent a risk factor for the occurrence of ventricular fibrillation;
– Participation in training of first aid and CPR (a helpful tip for relatives of patients who have ventricular fibrillation or cardiac problems as a risk of it);
– If the patient has acute myocardial infarction, administration of beta-blockers (such as metoprolol) is beneficial and protects against fibrillation, reducing cardiac events and mortality.