Cardiac arrhythmias: atrial fibrillation
Atrial fibrillation is the most common type of arrhythmia, as it affects 2% of the population; the likelihood of developing this condition increases with age
The heart functions by emitting electrical impulses generated in the right atrium that stimulate its contraction.
In atrial fibrillation, the electrical activity of the atria is completely disorganised and does not correspond to effective mechanical activity
The atrioventricular node receives numerous impulses from the atrium and transmits a limited number of them to the ventricles.
This variability in atrioventricular conduction causes the ventricles to contract irregularly.
The irregular and rapid contraction of the cardiac chambers causes a reduction in the volume of blood ejected at each systole, thus resulting in an altered blood supply to all organs, sometimes leading to symptoms and signs of heart failure.
Generally, the first episodes of atrial fibrillation begin and end spontaneously after a few hours: this is called paroxysmal atrial fibrillation.
If left untreated, these episodes increase in frequency and duration
If an onset episode does not spontaneously regress, external intervention is required to terminate it (persistent atrial fibrillation: lasting more than 7 days; atrial fibrillation that ends with cardioversion).
External intervention consists of electrical or pharmacological cardioversion, aimed at terminating atrial fibrillation and restoring normal heart rhythm.
When attempts to terminate the arrhythmia are no longer considered appropriate, due to the long duration of the arrhythmia or the patient’s condition and comorbidities, we speak of permanent atrial fibrillation.
ATRIAL FIBRILLATION, WHO DOES IT AFFECT?
Conditions that predispose to atrial fibrillation include arterial hypertension; coronary artery disease; heart valve disease, especially mitral valve disease; congenital heart disease; congestive heart failure; pericarditis and hyperthyroidism.
When atrial fibrillation occurs in healthy young people without any type of heart disease, it is referred to as isolated atrial fibrillation.
The most frequent symptom will be palpitations; fatigue, breathing difficulties and chest pain or tightness may also occur.
Some patients suffering from atrial fibrillation will not notice it as it is often asymptomatic; this should not, therefore, lead to a tendency to neglect it as its lack of symptoms will make it more difficult to combat.
COMPLICATIONS AND RISKS
If the heart rate is high and the arrhythmia persists for prolonged periods of time, the contraction force of the heart may progressively decrease, the ventricles will dilate and you may experience heart failure and heart failure.
In atria subject to cardiac fibrillation, blood will tend to stagnate instead of being expelled by normal contraction.
This will create favourable conditions for the formation of clots that can enter the circulation as emboli.
The most dangerous emboli will be those released from the left atrium as they can reach the cerebral circulation causing major damage, including stroke.
The diagnosis of atrial fibrillation will be made thanks to an electrocardiogram
The problem is represented by the difficulty of detecting the arrhythmia when it is present, due to its short duration or to the total lack of reference symptoms.
Even in follow-up, the main obstacle is the difficulty of detecting episodes of atrial fibrillation with certainty.
For this, prolonged electrocardiographic recording systems (of 1 or more days) or small electrocardiographic monitors implanted subcutaneously are used.
In addition to identifying atrial fibrillation with the electrocardiogram, a complete diagnostic work-up is necessary to demonstrate or rule out cardiac or endocrine pathologies that cause or facilitate atrial fibrillation and require treatment.
Treatments for atrial fibrillation will be:
- Cardioversion, applied in cases of paroxysmal and persistent atrial fibrillation, will be achieved by pharmacological treatment, which is effective especially in short-lived forms, or by administering an electric shock to the heart in a state of deep sedation.
- In clinical practice, drugs precede electrical treatment, which will be carried out if the former prove ineffective.
- Ablation; atrial fibrillation will begin when the others receive a burst of premature electrical stimulation.
The arrhythmia is maintained because the electrical stimulus finds long and irregular paths through dilated atria or in which degenerative processes are underway that will increase the fibrous component in the wall.
Ablation consists of the application of small ‘lesions’ on the inner surface of the heart, thanks to which barriers are formed to the circulation of the electrical stimulus.
These ‘lesions’ are placed at strategic points, so as to block the bursts of extrasystoles that initiate the arrhythmia and/or prevent the free circulation of the stimulus at the atrial level.
The probability of resolving the problem is greater in paroxysmal forms, amounting to around 80%, slightly less in persistent forms.
The procedure is performed through catheters) introduced into the heart via the venous system, all under local anaesthesia and sedation.
Depending on the characteristics of the patient and the arrhythmia, ablative treatment can be performed by means of cryoablation or radiofrequency.
A pacemaker will be implanted when the heart rate is too unstable, combined with ablation of the atrioventricular node to prevent the heart from exceeding the rate determined by the artificial stimulator.
Anticoagulant treatment will be resorted to for all those patients who present a moderate or high risk; the therapy will have to be maintained even if it proves to be apparently effective since there is always the risk of asymptomatic episodes.
If treatments aimed at maintaining normal heart rhythm should prove ineffective, frequency control will be recommended; this will be achieved by pharmacological treatment aimed at optimising the mean heart rate during atrial fibrillation, which is considered permanent.
The aim will be to achieve, and maintain, a heart rate between 60 and 90 beats per minute.
The first visit, following the course of treatment and admission, will take place approximately 50 days after discharge, and a Holter will be performed, which will allow monitoring for 24 hours.
A very effective monitoring system used to monitor the results of the ablative process is the subcutaneous implantation of a ‘mini holter’ of the pulse, loop recorder.
This device continuously detects the heartbeat and stores any changes in rhythm.
The arithmologist will then extrapolate the stored data, analysing the heartbeat and optimising therapy.