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Atrial fibrillation as condition

What is atrial fibrillation?

The heart is a pumping organ which runs on electrical current. It has four chambers; two upper chambers called atria and two lower chambers called ventricle. Normally the current is generated in a place called the sinus node which is located in the right upper chamber. The electricity stimulates the upper chambers in an organized fashion and subsequently spreads to the lower chambers after a brief pause at the junction between the chambers (called the AV node).The organized and harmonious spread of the electrical current is absent in atrial fibrillation.  The electrical current on the other hand is chaotic. It is believed that it occurs as a consequence to very rapid impulses arising from the pulmonary veins (draining blood from the lungs into the upper left chamber ).

What are the symptoms a patient with atrial fibrillation feel?

Majority of patients feel fluttering inside the chest; some others feel very tired and exhausted while doing ordinary activities and they experience palpitations (rapid beating of the heart) during exertion.  Approximately 20% of patients do not feel any symptoms and the first presentation may be a stroke.

What are the treatment options available for atrial fibrillation?

The two main options of treatment are [1] Restoring the normal rhythm (sinus rhythm) [2] Controlling the rate at which the heart beats.

How can normal rhythm be restored?

This can be done either by giving drugs or by passing electric current through the heart (DC cardioversion). Direct current cardioversion is done at the hospital using a defibrillator. Patients are put to sleep so that they do not experience pain / chest discomfort during the procedure.  

Are there any precautions to be taken before the rhythm is restored?

Yes. The duration the patient has been in atrial fibrillation is an important determinant for the treatment plan. If patient can distinctly remember the time when he/ she developed atrial fibrillation , the physician can use this as the index time and base the treatment accordingly. However, if patients are unsure, they have to wait for anti-coagulation to take effect before the rhythm is restored. This normally takes at least 4 weeks. Patients who report to the hospital within 48 hours of the onset of atrial fibrillation would be treated with DC cardioversion (as described above) without a waiting period for oral anticoagulation to take effect.

Why is it important to take anti-coagulation?

During atrial fibrillation there is no effective contraction of the upper chambers of the heart. This results in stagnation of blood and consequent clot formation. The clot can be dislodged into the  blood stream. This is called embolism.  Embolism can occur to any vital organ in the body such as the brain (resulting in stroke), heart muscle (resulting in “heart attack”) , kidney (resulting in acute damage).Therefore by taking oral anticoagulant (OAC) this can be almost completely negated, provided the blood “thinning” levels are in the desired range (INR 2 – 3)

How is the dose of oral anti-coagulation adjusted?

The blood “thinning” levels are adjusted by peforming a test called PROTHROMBIN TIME. The result of this test is expressed as INR (International normalized range). The desired range  of INR is between 2 and 3. Lower values of INR will predispose to emoblization and values higher than 4 to excessive bleeding.  Those taking the newer oral anticoagulants such as Rivoraxaban or Apixiban would not require adjustment of the INR. You could have a discussion on the choice of anticoagulation with your doctor. 

Do all patients require anti-coagulation before conversion to normal rhythm?

No. If the patient has approached the hospital within 48 hours of the onset of atrial fibrillation, he/she has very low risk for embolization. 

Do all patients require anti-coagulation on long term basis?

No. The use of oral anticoagulation (OAC) is based on a scoring system which identifies patients at high risk for embolization. Only these patients would be recommended OAC. Others who are scheduled for atrial fibrillation ablation will also be asked to take OAC. 

What is the invasive treatment option for atrial fibrillation?

As discussed earlier, the pulmonary veins (veins draining blood from the lungs) are responsible for atrial fibrillation in those who have paroxysms (bouts) of this abnormal rhythm. These veins can be electrically isolated so that the rapid impulses do not reach the upper chambers.  It should be understood that AF ablation is not a curative procedure. It has 70% success and 30% chance for recurrence after the operation. Therefore one-third of patients will have to undergo a second procedure to restore normal sinus rhythm. 

Are the treatment options different for those who have persistent form of atrial fibrillation?

Yes. The mechanism of atrial fibrillation in this group of people is not as clear as those who suffer paroxysmal form of this arrhythmia. It is more complex and hence the treatment procedure is also more time consuming. Linear ablation is done within the upper chambers to break the chaotic circuits in addition to isolating the pulmonary veins.

Who should undergo invasive atrial fibrillation ablation?

Patients who experience more than 2 episodes of atrial fibrillation in 6 months while on the anti-arrhythmic drugs (Amiodarone/ Sotalol) appears to benefit the most relief as compared to those with fewer episodes.   Patients who are already suffering from persistent atrial fibrillation would have higher recurrence even after ablation as compared to the paroxysmal group.

What are the preparations involved for the invasive treatment strategy?

  1. All patients should have atleast three weeks of oral anti-coagulation. The level of anti-coagulation has to be monitored using Prothrombin time (INR) and it has to be maintained in the therapeutic range [INR 2 to 3] for atleast 3 weeks. 
  2. Oral anticoagulation may be stopped for 36hrs prior to date of procedure 
  3. Patient will undergo imaging study of the upper chambers at least 24 hours prior to the ablation [CT imaging of the LA] as per the protocol. 
  4. Trans-esophageal echocardiogram will be done to exclude any clots lingering within the chambers.
  5. On the day of the procedure, patients will be given all their routine medications (except OAC and Enoxaparin) and taken up after fasting for 6 hours. Rest of the procedure is similar to the ablation technique that is described in the section on “Radiofrequency ablation”.  Patients can opt for general anaesthesia to reduce the discomfort during the procedure.

What are the complications of AF ablation?

This is a fairly safe procedure with 96% not experiencing any complication. Obviously, all efforts will be taken to ensure that none of the complications occur.  However, just as any other invasive procedure it has its share of problems; the commonest being bruising at the site of venous puncture(groin). Rarely patients may develop a stroke or an embolic event. The heart may perforate while crossing the septum between the upper chambers to reach the pulmonary vein. This can be managed most often without an open heart surgery. Very seldom patients may be taken to the operation theater for closure of the defect under direct vision. Very rarely the normal conduction system can be damaged and patient may require a permanent pacemaker. The veins which are electrically isolated may become small in caliber. This can lead to shortness of breath and patient may require stenting to keep it open.  There have been reports of injury to the nerve supplying the diaphragm. Often this is temporary and recovers with time. Permanent damage can result in shortness of breath while exerting. The food pipe (esophagus) lies behind the upper chamber. There is a rare possibility that this may perforate and air can leak into the heart chamber. This can be fatal and occurs as a late complication of the procedure. It is therefore recommended that endoscopy is avoided in all patients after AF ablation (for a period of 6 months).  As a precautionary method all patients are given treatment for reducing acid production in the stomach (Pantoprazole) for a period of atleast 6 weeks.

What happens after AF ablation?

  1. It is not uncommon for patients to feel chest discomfort for a week after ablation. If the pain is unbearable please contact the treating cardiologist.
  2. You will receive the same dose of oral anticoagulation (OAC) on the night after the procedure if it is Warfarin or Coumadin. Those taking the newer oral anticoagulation will be given the usual dose the morning after the procedure.  Enoxaparin is given subcutaneously  6 hours after sheath removal (from the groin). This will be discontinued the next day morning once the OAC has been restarted. 
  3. The antiarrhythmic drug will be continued (Amiodarone/ Sotalol) along with other medications that you were receiving prior to ablation.
  4. Echocardiogram will be done the day after the procedure. ECG and Chest Xray will be done periodically.

What should I do if develop atrial fibrillation after ablation?

It is not unusual if you develop atrial fibrillation after ablation.  In the first three months after ablation, you should see a cardiologist within 24 hours of onset of atrial fibrillation for DC cardioversion.  This will be done as per the guidelines. After the first three months, if there is recurrence of Atrial fibrillation, it means that you have developed a relapse and would require to undergo AF ablation again.