What is Atrial Fibrillation?
Atrial Fibrillation(AF) is a cardiovascular disorder that is caused by irregular heartbeat of atria chambers. It is the most common form of arrhythmia, as 50% of the arrhythmia patients are diagnosed with atrial fibrillation. Our heart beats by responding to a regular pattern of electric signals, which allows blood supply all over the body system. Atrial Fibrillation involves having disorganized electrical signals, skipping beats and rapid beating of atrial chambers.
Atrial Fibrillation (AF) is a common disease that occurs in our society nowadays, with its prevalence of 50% worldwide. More than 37,574 million people in the world are diagnosed with AF and 1 in 4 people over 40s are diagnosed with AF. Because the occurrence of AF is so high, the AF related market is expected to reach $14.68 million by 2026. The prevalence of AF increasing rapidly every year rather than decreasing and its incidence is expected to double in the next 20 years.
The biggest risk of AF is a stroke. Patients that are diagnosed with AF are 5 times more likely to suffer from stroke. With an irregular heartbeat of atria chambers, it develops blood clots and if these blood clots travel to the cerebrovascular, it causes a stroke. Around 20% of ischaemic strokes are caused by blood clots originating in the heart (cardioembolic); of these, AF is the most common cause. AF needs to be diagnosed as soon as possible, as it is associated with various life-threatening risks such as stroke, heart failure, blood clot formation, heart attack and dementia.
Diagnosis of AF Detection
If Atrial Fibrillation is not properly diagnosed or treated, it could cause a severe stroke. However, detecting Atrial Fibrillation is very important but not easy because of the following reasons.
First, most of the time there are not symptoms in AF patients. Even though it is a serious AF which might cause irrevocable results, it is sometimes asymptomatic.
Second, episodes occur irregularly throughout the time, therefore the chance of capturing episodes during finite monitoring period remains low. Statistically, 50% of AF patients are not diagnosed.
Third, patients have limited access to monitoring systems, as they are only available in hospitals. Therefore, the most important thing to detect AF is continuous monitoring of cardiac signals.
There are many individual differences on the symptoms of AF. Some people respond very sensitively, but other people have very severe AF but often do not notice any symptoms. Thus, it is difficult to treat only with symptoms. However, People with Atrial Fibrillation normally have some common symptoms as below:
– Shortness of breath
– Chest pain
AF is classified based on its duration and its reversibility into sinus rhythm. AF classifications differ in their frequency of reoccurrence. The longer the AF remains untreated in patients, the more likely that the patient will suffer from risks that are associated with Atrial Fibrillation. The only way to prevent AF from progressing into a more severe condition is to continuously monitor the cardiac signals and detect AF for early treatment.
1) Paroxysmal AF (PAF)
– terminates spontaneously or with intervention within 7 days of onset
2) Persistent AF (PeAF)
– is continuously sustained beyond 7 days, including episodes terminated by cardioversion (drugs or electrical cardioversion) after≥7days
– Long standing persistent AF (LSPeAF)
– Continuous AF of>12months’ duration when decided to adopt a rhythm control strategy
3) Permanent AF
– is accepted by the patient and physician, and no further attempts to restore/maintain sinus rhythm will be undertaken
The causes of Atrial Fibrillation are diverse, and the mechanism of its occurrence is still not sufficiently known. In the past, rheumatic valve disease was the most common cause of heart disease, and it is associated with other valve disease, coronary artery disease, hypertensive heart disease, cardiomyopathy, and other diseases associated with hyperthyroidism or chronic lung disease. It can also be caused by causes such as heart surgery.
In addition, Atrial Fibrillation can occur in people who do not have structural abnormalities or underlying diseases of the heart. Also, it is known that the incidence increases mainly due to aging. The lists below are the potential causes of Atrial Fibrillation.
– Cardiovascular Disease
– Pulmonary Embolus
– Hypokalemia, Hypomagnesaemia
– Acute Infections
/ 10 years
Valvular disease of the heart
Left ventricular dysfunction
Diagnosis of Atrial Fibrillation
ECG screening is a conventional technique that is used for atrial fibrillation diagnosis. It measures electrical signals in the heart and distinguished irregular heartbeat by comparing the ECG graph of atrial fibrillation with normal sinus rhythm.
ECG signals are intermittently measured through attaching number of electrodes on different locations of the body. ECG monitoring devices have developed over time by reshaping various features of them.
It started from 12 lead ECG machine, to 3 lead ECG machine, wired monitoring devices, patches and now into wearable devices.
Throughout the 100 years of development, ECG devices have reshaped in various ways to satisfy the unmet demand of “continuous monitoring”. Although it has taken more than 100 years for ECG devices to develop their capability, there is still no perfect medical device that can accurately measure cardiac signals continuously to detect atrial fibrillation.
Treatment of Atrial FIbrillation
Treatment goals for atrial fibrillation are to improve symptoms, restore or preserve heart function, and prevent thromboembolism such as stroke, which in turn reduces mortality from atrial fibrillation. To this end, there are the following therapeutic approaches.
1) Transition to Sinus rhythm
A significant number of paroxysmal atrial fibrillation may automatically switch to a normal rhythm, but if it persists for more than 48 hours or the exact duration is not known, it is normal to have 2-3 weeks of anticoagulant therapy to prevent thromboembolism. Then electric shock or antiarrhythmic drugs can be used to try to transition to a normal rhythm.
At this time, TEE(transesophageal echocardiography) is performed immediately without waiting for 2-3 weeks, and if there is no blood clot in the atrium, it is often attempted to switch to a normal rhythm immediately. It is a principle to maintain anticoagulant therapy for 2 to 3 weeks even after it si converted to a normal rhythm.
2) Rate control
In the case of atrial fibrillation that has become chronic after the paroxysmal stage, it is decided whether to switch to the normal rhythm or to control only the pulse rate in consideration of the chronicized period, the patient’s age, and the size of the left atrium. Drugs used to control pulse rate include beta blockers, calcium antagonists, and digoxin.
If the normal rhythm is not maintained and the risk of thromboembolism is high, aspirin or a more potent warfarin should be used to prevent thromboembolism. Warfarin treatment is required for atrial fibrillation if you have already experienced a stroke in the past. The use of warfarin is recommended as a high-risk group for embolism.
4) Catheter Ablation
In the case of atrial fibrillation patients who are not effective in drug treatment and are relatively young and do not have structural heart disease, recently, an electrode catheter ablation is used to electrically separate the pulmonary veins from the atrium to restore and maintain a normal rhythm. Currently, a success rate of 60 to 80% is reported, and a higher success rate can be expected in the future as the electrophysiological knowledge and experience accumulate and the development of equipment. Atrial flutter can be cured relatively easily with catheter ablation.
It is performed in cases of cryo-node disorder or very slow pulse (bradycardia) accompanying atrial fibrillation.