Atrial fibrillation is an asynchronous excitation and subsequent contraction of individual atrial sites, resulting from abnormal, disorganized electrical activity of the atrial myocardium, accompanied by a violation of the rhythm of ventricular contraction.
Depending on the duration and type of the course of rhythm disturbance, atrial fibrillation is divided into several forms: paroxysmal (accompanied by complete independent leveling of symptoms within 48 hours), persistent (it is impossible to restore normal rhythmicity of cardiac activity without drug correction) and constant (can not be treated with medication ).
This pathological state occupies a leading position among all possible forms of cardiac rhythm disturbance in morbidity indicators, which progressively increase with the age of patients. The risk group for the incidence of this or that form of atrial fibrillation is the elderly with a history of the disease, burdened with chronic cardiovascular pathology.
Causes of Atrial Fibrillation
The main factors provoking the development of atrial fibrillation of varying severity include: hypertension , ischemic myocardial damage, acquired valvular defects of rheumatic and non-rheumatic nature, as well as thyroid disease with concomitant hyperthyroidism .
Despite the significant progress of therapeutic approaches to the treatment of rheumatism, still the greatest number of recorded episodes of atrial fibrillation have a rheumatic origin. In a situation where the patient has a combination of acquired mitral malformation of rheumatic nature and hypertensive disease, the risk of cardiac rhythm disturbance in the type of atrial fibrillation increases several fold.
Chronic ischemic damage to the myocardium of the heart is accompanied by atrial fibrillation only in case of development of signs of heart failure, and in the case of acute ischemic attack with myocardial infarction , permanent atrial fibrillation is observed in 30% of cases.
In fact, any pathology of the heart accompanied by a marked dilatation of the left atrial cavity can be considered a background disease that provokes the development of signs of atrial fibrillation. For this reason, aortic heart defects are rarely a background disease for atrial fibrillation.
A separate category of patients are those with congenital defect of the interatrial septum and Ebstein's anomaly. On the basis of this fact, these patients need dynamic observation and echocardiographic monitoring throughout life.
When performing surgery on the structures of the heart and coronary arteries, it must be borne in mind that these manipulations often provoke paroxysm of atrial fibrillation. The appearance of signs of rhythm disturbance in this situation arises both in the postoperative period, and immediately during the operative manual. The pathogenesis of fibrillation is based on increased activity of the sympathetic-adrenal system, acute myocardial hypoxia and pericardial damage.
Extracardiac causes of atrial fibrillation include chronic alcoholism and thyroid diseases with hyperthyroid syndrome. In the first situation, the onset of fibrillation is provoked by acute intoxication or alcoholic cardiomyopathy, since ethyl alcohol has an inhibitory effect on atrial conductivity. In hyperthyroidism, atrial fibrillation occurs as a result of potentiating the effects of catecholamines on the process of atrial excitability. Manifest hyperthyroidism, as a provoker of atrial fibrillation, is observed in old age and only 25% is accompanied by severe arrhythmia.
The electrophysiological mechanism of the development of atrial fibrillation consists in the formation of several riientri waves in atria, which are characterized by an unstable character, as a result of which they are able to divide into daughter waves. Thus, the combination of an increase in the size of the atria with a short RI wave is the main condition for the development of atrial fibrillation.
Due to the fact that atrial fibrillation in most cases is accompanied by hypercoagulable changes in blood plasma and activation of platelet cells, this pathology is a provocateur of the formation of intracardiac thrombi, which can subsequently provoke thromboembolic complications.
Symptoms of Atrial Fibrillation
Preliminary diagnosis of "atrial fibrillation" an experienced cardiologist can establish by primary contact with the patient, based on the history and objective examination of the patient. But it should be borne in mind that in some situations atrial fibrillation is not accompanied by severe clinical symptoms and its detection occurs at the time of an electrocardiographic examination of a person. However, the severity of clinical manifestations in atrial fibrillation is not at all dependent on the rate of increase in heart rate and dysfunction of ventricular contraction caused by the underlying disease.
The debut disease is the appearance in the patient of a feeling of rapid heartbeat, dyspnea, dizziness , weakness and their appearance is possible in any other pathologies that are not accompanied by a violation of the rhythm of cardiac activity. To the category of rare manifestations of atrial fibrillation is a short-term disorder of consciousness and typical attacks of stenocardic pain syndrome.
As a result of an increase in the synthesis of natriuretic hormone and an increase in the tone of the sympathetic-adrenal system, most patients note the appearance of a pathognomonic symptom, such as polyuria.
Most patients with atrial fibrillation report an acute sudden debut of clinical manifestations against a background of complete well-being and only rarely connect these changes with excessive consumption of alcohol, coffee, stressful effects and excessive physical activity.
Clinical objective examination of the patient is accompanied by the detection of irregular heartbeats and a significant fluctuation in the figures of blood pressure. The pulse in atrial fibrillation is mostly rapid, and only with the weakness of the sinoatrial node there is a bradycardia . The auscultatory sign of atrial fibrillation is the appearance of a clapping first tone of uneven sonority.
At the basis of the separation of atrial fibrillation into clinical forms is the principle of the duration of its course and the time of disappearance of not only clinical, but also electrocardiographic signs. Cardiologists in the world practice use a single classification, according to which several forms of atrial fibrillation are distinguished. This division is important for determining the tactics of treating a patient and choosing an appropriate method of therapy.
The most favorable form of atrial fibrillation for the life of the patient is "paroxysmal", in which the available clinical manifestations independently level out no later than 7 days. This variant of fibrillation is characterized by inconsistent clinical symptoms that can appear and self-stop several times throughout the day.
In a situation where clinical and electrocardiographic parameters of atrial fibrillation persist for more than 7 days, cardiologists establish a diagnosis of a "persistent" form of atrial fibrillation, and resort to a medical method of correction of cardiac arrhythmias.
The most severe form of fibrillation is "persistent", the symptoms of which persist even when medication is used. In addition, atrial fibrillation is divided into 3 options, depending on the concomitant increase in frequency or reduction in the frequency of cardiac contractions.
Paroxysmal atrial fibrillation
Paroxysmal atrial fibrillation is one of the most common types of cardiac arrhythmias, and its occurrence depends on the disruption of the normal functioning of the sinus node, followed by a chaotic reduction in cardiomyocytes in the fasted mode. These changes affect all structures of the circulatory system and lead to cardiohemodynamic disorders of varying severity. The most favorable variant of paroxysmal atrial fibrillation is normosystolic, in which there is no significant change in the frequency of cardiac contraction.
In a situation where paroxysm of atrial fibrillation is characterized by several episodes, it is a question of such a concept as "recurrence". At a young age, it is often impossible to reliably determine the time of an attack of fibrillation with any etiological factor, so in this situation, the conclusion is "idiopathic paroxysmal atrial fibrillation." In elderly people, in most cases it is possible to recognize the provoking factor of paroxysmal development (ischemic myocardial damage, increased intracavitary pressure in the left atrium, the pathology of the valvular apparatus of the heart, various forms of cardiomyopathy ).
Most experts in cardiology state that the severity of clinical manifestations in the paroxysm of atrial fibrillation has a clear dependence on changes in the frequency of cardiac contractions, and in a situation where this index does not change, the patient does not feel any changes in his state of health at all. If, however, the patient exhibits a significant increase in heart rate during paroxysm of atrial fibrillation, a classic clinical symptom complex develops, consisting of a sudden appearance of a palpitations, a feeling of heart failure, difficulty breathing, and increasing dyspnea, which is pathognomically amplified in the supine position, marked sweating and internal anxiety.
The reverse situation, when the paroxysm of atrial fibrillation arises against the background of a significant decrease in the heart rate, the patient exhibits all the signs of hypoxia (loss of consciousness, lack of pulse and respiratory activity). This condition for the patient is critical and requires immediate implementation of a full range of resuscitation measures. With this variant of the course of paroxysmal atrial fibrillation, the risk of life-threatening conditions of the patient significantly increases ( cardiogenic shock , acute respiratory failure, cardiac arrest). The long-term effects of even short-term paroxysm of atrial fibrillation include activation of thrombogenesis processes, which subsequently become sources for embolic complications.
Determining the optimal tactics for treating a patient with a paroxysmal form of atrial fibrillation depends primarily on the duration of the onset of the attack. So, if the duration of the attack at the time of its establishment does not exceed the limit of 48 hours, the main goal of treatment is complete restoration of the sinus rhythm. In a situation where the duration of the attack of atrial fibrillation exceeds two days, the patient is recommended to perform transesophageal echocardioscopy, which allows to detect even minimal thrombotic layers and to establish the possibility of immediate restoration of the sinus rhythm.
As a first-aid preparation for the first time paroxysm of atrial fibrillation, it is recommended to use Cordarone in a dose of 5 mg / kg of a patient's weight diluted in a 5% glucose solution in a volume of 250 ml intravenously, as this drug has a beneficial effect on the normalization of cardiac contractions in the shortest possible time in combination with minimal adverse reactions. At the pre-hospital stage, the most optimal drug for arresting an attack of paroxysmal atrial fibrillation is Propanorm in a daily dose of 600 mg orally.
Diagnosis of Atrial Fibrillation
The main diagnostic measures that allow in almost 100% of cases to establish a reliable diagnosis of "atrial fibrillation" are echocardioscopy and electrocardiography. However, in order to determine the tactics of management and the expedient treatment regimen for a patient with this form of arrhythmia, it is necessary to find the cause of its occurrence, for which the patient is recommended to undergo a full screening monitoring (coronary angiography, stress drug tests, laboratory diagnosis of thyroid status, and others).
Atrial fibrillation on the ECG-film has characteristic pathognomonic features, which allow correctly to establish not only the fact of presence of fibrillation, but also to determine its clinical form. The main ECG criteria for atrial fibrillation include: the appearance of random fibrillation waves with a frequency of up to 600 per minute of varying amplitude and duration, with no P-wave in all leads, recording various RR intervals indicative of abnormal ventricular contraction, an electrical alternative consisting in the appearance oscillations in the amplitude of the QRS complex and the complete absence of changes in its shape.
When conducting an ECG study, it is possible to detect the indirect signs of focal myocardial infringements of the ischemic nature that allow us to establish the cause of the development of atrial fibrillation.
Qualitatively carried out echocardiography should contain data on the contractility of myocardium of the left ventricle, the state of the valvular apparatus of the heart, the presence of thrombotic intraluminal layers.
Treatment of atrial fibrillation
At present, the world association of cardiologists has developed and is applying a single algorithm of therapeutic measures aimed at arresting atrial fibrillation. All the methods of therapy of atrial fibrillation are used either to reduce clinical symptoms or to prevent possible complications that threaten the life of the patient.
Not in all situations it is advisable to achieve full recovery of normal sinus rhythm, but it is enough only to ensure the optimal rate of heart rate. Restoring the sinus rhythm, you can achieve complete elimination of arrhythmia and hemodynamic disturbances caused by it, and significantly improve the patient's life.
When optimizing the heart rate and preserving the signs of fibrillation, the risk of thromboembolic disorders increases significantly, so this category of patients needs a long course of anticoagulant therapy. The optimal heart rate in the category of patients with a constant variant of atrial fibrillation is 90 beats per minute, and the average daily heart rate recorded during Holter monitoring should not exceed 80 beats per minute.
In a situation where the patient completely lacks clinical manifestations of fibrillation and hemodynamic disorders, one should resort to expectant management for 72 hours, since in almost 50% of patients spontaneous leveling of signs of cardiac arrhythmias is observed. If the patient is observed preservation of signs of atrial fibrillation, the restoration of a constant sinus rhythm contributes to the appointment of antiarrhythmic therapy and electrical cardioversion. In addition, patients who have persistent atrial fibrillation need an optimal reduction in the heart rate before using antiarrhythmic drugs (digoxin 0.25 mg intravenously every 2 hours until the maximum possible dose of 1.5 mg, Amiodarone orally in the daily dose of 800 mg, propranolol intravenously at the calculated dose of 0.15 mg / kg of weight of the patient, Verapamil intravenously at a dose of 0.15 mg / kg of weight of the patient). Thus, the full stable recovery of sinus rhythm should be started only after achieving an adequate reduction in heart rate.
The chances of a complete recovery of a stable sinus rhythm in a patient who has constant atrial fibrillation in combination with a severe form of mitral stenosis are minimal. At the same time, a large percentage of patients in the acute period of fibrillation can achieve complete recovery of sinus rhythm by a method of drug or electropulse cardioversion.
For patients who do not have significant structural damage to the myocardium and valvular heart apparatus, the drugs of choice for drug-induced cardioversion are Quinidine (daily loading dose 300 mg) and Propafenone (intravenously sprayed at a dose of 1 mg / kg of patient weight), and if there is no positive result these drugs should be replaced with Amiodarone (a daily loading dose of 800 mg) or Procainamide (intravenously-drip in a dose of 5 mg / 1 kg of the patient's weight).
Patients with atrial fibrillation on the background of congestive heart failure are advisable to carry out cardioversion Amiodarone, since this drug not only reduces the heart rate, but also has a minimal inotropic effect. In treating patients with persistent atrial fibrillation, propaphenone should be preferred.
Electrical cardioversion in atrial fibrillation can be carried out in an urgent and planned manner. Indication for the urgent use of electropulse therapy is the fact of paroxysm of atrial fibrillation combined with acute coronary syndrome , hypertensive crisis, acute cardiovascular insufficiency. By the method of electrical cardioversion, several positive results can simultaneously be achieved: to improve the indices of cardiohemodynamics, to reduce the manifestations of heart failure. However, do not forget about the possible complications of this technique, consisting in the appearance of signs of embolism, ventricular tachycardia , arterial hypotension and acute left ventricular failure.
Absolute indications for the use of electrical cardioversion in the planned order are the following criteria: complete lack of effectiveness from the use of medications, individual intolerance or the presence of contraindications to the use of any component of antiarrhythmic therapy, persistent progression of signs of heart failure, the availability of data on successful episodes of cardioversion in a patient's anamnesis .
Like any medical manipulation, the method of electrical cardioversion has a number of contraindications to the use (chronic intoxication with drugs of the group of cardiac glycosides, persistent hypokalemia , infectious group of diseases in the period of exacerbation, decompensated cardiovascular failure ). Before applying the procedure for electrical cardioversion, it is necessary to prepare the patient for complete elimination of diuretics and cardiac glycosides for at least 5 days, correcting existing electrolyte disorders, using antiarrhythmic drugs in saturating doses, performing anticoagulant therapy and premedication just before the procedure.
In the era of the progression of technologies in the field of cardiac surgery, conditions are created for effective surgical removal of atrial fibrillation, consisting in creating additional obstacles for riientri waves in the myocardium of the atria and preventing fibrillation. This technique allows you to effectively restore and maintain a sinus rhythm, not only with a paroxysmal, but also a permanent variant of atrial fibrillation. The disadvantage of surgical treatment is the need for carrying out electrocardiostimulation in a remote rehabilitation postoperative period. At present, surgical treatment of atrial fibrillation in an isolated form is extremely rare and in most cases is combined with surgical correction of valvular heart defects .
Prevention of atrial fibrillation
After the patient has seen all the signs of normal sinus rhythm restoration, supportive antiarrhythmic therapy should be prescribed, mostly to prevent the next paroxysm of fibrillation. To this end, the preparations of the Propaghenon group are excellent, allowing in 50% of cases to maintain a sinus rhythm within one year. Absolute contraindications to the use of this drug are the post-infarction period and left ventricular dysfunction. However, recent randomized trials of the use of antiarrhythmic drugs and their positive effect on the prevention of recurrence of the disease prove the greatest efficacy of Amiodarone, which is devoid of most adverse reactions and can be used for a long period of time in a maintenance dosage.
Medication prophylaxis in atrial fibrillation is used only in the case of an increased risk of relapse that worsens the patient's condition. After the first episode of idiopathic paroxysmal atrial fibrillation, there are no indications for the prescription of drug antiarrhythmics as a prophylactic measure and it is sufficient to observe the regime of limiting provoking factors. In the case where the cause of fibrillation is any chronic pathology, the prevention of its recurrence will consist in the use of etiotropic therapy.
The main method of non-drug prophylaxis with proven positive efficacy is catheter-based linear ablation of the atrioventricular node, whose mechanism of action is to create additional barriers that prevent the propagation of excitation waves. According to statistical data, this technique allows 40% of patients to do without the use of medication prophylaxis of recurrence of fibrillation.
Preventative measures for atrial fibrillation should be aimed not only at preventing recurrence of the disease, but also at reducing the risk of complications, among which the leading position is occupied by thromboembolization of cerebral vessels. As the main preventive regimen of treatment in this situation, adequate anticoagulant therapy acts, which must be used for patients with mitral defects, hypertension, the presence of myocardial infarction and episodes of ischemic attack of the brain in the anamnesis. The drug of choice for the prevention of thromboembolic complications is Acetylsalicylic acid at an average daily dose of 365 mg orally.