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What is Atrial Fibrillation?

 

Your heart is separated into four chambers, a left and right atria and a left and right ventricle. Blood is efficiently pumped through the body as a result of synchronized contraction where the atria will first contract to push blood down into the ventricles and then the ventricles will pump to push blood up and out into either the body or lungs .

 

What allows for this synchrony is ‘electrical coupling’ so that when one heart cell within a chamber fires, it can tell its neighbor to also fire. Your brain isn’t in direct control of this firing, and despite your best attempts, you aren’t consciously making your heart beat nor can you make your heart beat faster or slower.

 

There are groups of specialized cells at specific points within the heart called ‘pacemaker’ cells which do this job for you. This group of specialized cells will fire at regular intervals on their own causing a cascade of firing or depolarization in adjacent heart muscle cells in a very orderly manner. This is very similar to a row of dominos that we might have set up as children where one domino falling causes the ones next to it to also fall. One pacemaker cell firing causes the ones downstream to also fire. It’s all very coordinated and very efficient.

 

Problems arise when points within the heart or even the tubes coming off the heart ‘rebel’ and decide to stop listening to the pacemaker cells and fire on their own. Atrial fibrillation is a result of progressive scarring, or fibrosis, of the atria believed to arise from either the chamber getting too large (called dilatation), genetics, or inflammation. It is hypothesized that scarring is a major factor in the development of these ‘rebellious’ heart cells. Without the control of its pacemaker, the rebel cells of the atria contract whenever they please at a VERY fast rate (150-300 beats a minute).

 

In this situation, there are essentially two bosses in the heart, the pacemaker cells and these rebellious cells. Both are trying to get everyone downstream to listen to them, some do and others don’t. It’s all very chaotic and messy. This loss of beautiful synchrony leads to ineffective pumping of the atria which then results in inefficient filling of the ventricles and finally poor blood distribution to the lungs and body.

 

Your doctor may give your atrial fibrillation a classification. This is meant to help communicate your condition to other doctors as well as help to drive treatment decisions. The classifications can be based on ECG pattern, epicardial or endocavitary recordings, mapping of atrial electrical activity or clinical features.

 

 

Atrial Fibrillation Category Defining Characteristics
First detected only one diagnosed episode
Paroxysmal recurrent episodes that stop on their own in less than 7 days
Persistent recurrent episodes that last more than 7 days
Permanent an ongoing long-term episode
Lone absence of clinical or ECG findings of other cardiovascular disease(including hypertension), related pulmonary disease, or cardiac abnormalities such as enlargement of the left atrium, and age under 60 years
Nonvalvular no rheumatic heart disease, prosthetic heart valve or mitral valve repair
Secondary where a pre-existing cardiac condition like a heart attack, heart surgery, pulmonary embolism or pneumonia is the cause of the AF

 

 

Symptoms of Atrial Fibrillation

AFib may be noticeable to some people while others are not aware of the the fibrillating. Symptoms range from mild to difficulty in breathing, shortness of breath, and palpitations. Additional symptoms include fatigue, weakness, dizziness, confusion,  lightheadedness, and chest pain and /or discomfort.

 

How is it diagnosed?

History and physical exam

To discover signs, symptoms, and risk factors

Electrocardiogram (ECG)

To look at electrical activity of the heart and see the atrial fibrillation

Echocardiogram

To look inside of the heart and see how it is working

Additional testing – exercise testing, Holter monitoring, thyroid testing, complete blood count (CBC), serum creatinine, analysis for proteinuria, test for diabetes mellitus

To look for the atrial fibrillation, causes, risk factors, and baseline

 

**Risk factors:

 

Heart

*Hypertensive heart disease (high blood pressure)

*Coronary heart disease

Heart failure

Heart valve disease (stenosis, regurgitation, prolapse)

Recent heart surgery (coronary artery bypass graft or CABG, cardiac valve surgery)

Rheumatic heart disease

Heart attack

Hypertrophic cardiomyopathy

Congenital heart disease (atrial septal defects, Ebstein’s anomaly, patent ductus arteriosus, etc.)

Venous thromboembolic disease (deep vein thrombosis or DVT, pulmonary embolism or PE)

Endocarditis

 

Other Risks

Long-term binge drinking of alcohol

Hyperthyroidism

Chronic obstructive pulmonary disease (COPD)

Obesity (BMI > 30 kg/m2)

Diabetes

Chronic kidney disease

Family history (1st degree relative with Afib)

Genetics (if present, usually > 1 gene involved)

Male sex

Older age

Low birth weight

Inflammation and infection

 

* Most common in developed countries

** This list does not include every possible risk factor; please refer to your doctor for more information about your risk factors

 

Drug Treatment for New Onset Atrial Fibrillation:

  1. In patients who are asymptomatic or mildly symptomatic elderly patients with cardiovascular or hypertensive issues, the first goal is to establish rate control. For rate control, the first line of therapy is typically Beta Blockers and Calcium Channel Blockers.

→ Metoprolol (Beta Blocker) and Diltiazem (Calcium Channel Blocker) are commonly used

If the patient is unresponsive to the first line of therapy, Amiodarone is next suggested.

  1. Anticoagulation is another important aspect to medical therapy for atrial fibrillation, due to the risk of forming clots, which may lead to a stroke. The patient is typically started on both Heparin and Warfarin. The patient is subsequently monitored for a therapeutic level of anticoagulation using International Normalized Ratio (INR), which is between 2 and 3.    Other anticoagulation therapy that may be used in substitution of warfarin include the following: Dabigatran, Rivaraxaban, and Apaxiban.  Although more costly, these medications don’t require monitoring of INR levels.

 

Surgical vs. Nonsurgical  Treatment

 

  1. Electrical cardioversion
  • Electrical cardioversion is a procedure where the patient receives a shock outside the chest via paddles or patches; It is used to reset the heart’s normal rhythm. The procedure is similar to defibrillation but uses lower levels of electricity
  • Before doing electrical cardioversion, provider will have the patient undergo Transesophageal echocardiography (TEE)
    • This involves using a small ultrasound device that doctors will place down your mouth and looks in and around the heart
  1. Radiofrequency ablation (RFA)
  • Ablation is used when long term medical therapy or electrical cardioversion is not effective or contraindicated in the patient
  • Before ablation is performed, electrical mapping is used to identify where the origin of the atrial fibrillation is located. the map tells which areas are creating problematic electrical signal
  • A catheter or thin flexible tube is inserted into patients blood vessels and guided to the heart. the physician carefully destroys malfunctioning tissue via extra electrical currents in the pulmonary veins
  1. AV node ablation and pacemaker placement
  • If the trigger for AF occurs in the AV node, then the AV is ablated and pacemaker is implanted
  • A pacemaker is a small device implanted with chest with wires that placed in various parts of the heart; used to regulate heart beat
  • Implanted under the skin, near the collarbone
  • Sends steady, contracting rhythm in the heart
  • Pacemaker sense when heart is too fast or too slow
  1. Open Heart Maze Procedure
  • Maze procedure is where the heart surgeon creates small cuts in the upper part of your heart; the cuts are then stitched together and scar tissue forms; the scar tissue interferes with the transmission of electrical impulses that cause AFib.

 

 

Informational Video on Atrial Fibrillation:  http://www.youtube.com/watch?v=HyQjpQf_eME

 

 

References:

 

Cheng, A., & Kumar, K. (2014, October 21). Overview of atrial fibrillation. UpToDate. Retrieved from http://www.uptodate.com/contents/overview-of-atrial-fibrillation

Rosenthal, L. (2014, August 25). Atrial Fibrillation – Practice Essentials  Medscape Emedicine. Retrieved from http://emedicine.medscape.com/article/151066-overview on October 22, 2014.

 

Ganz, L. (2014, September 11). Epidemiology of and risk factors for atrial fibrillation. UpToDate. Retrieved from http://www.uptodate.com/contents/epidemiology-of-and-risk-factors-for-atrial-fibrillation


(2014, September 14). Understand your risk for arrhythmia. American Heart Association. Retrieved from http://www.heart.org/HEARTORG/Conditions/Arrhythmia/UnderstandYourRiskforArrhythmia/Understand-Your-Risk-for-Arrhythmia_UCM_002024_Article.jsp

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