Christian T. RuffStroke Prevention in Atrial Fibrillation

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Stroke Prevention in Atrial FibrillationChristian T. Ruff, MD, MPH

Atrial fibrillation (also called AF orA Fib) is the most common ab-normal heart rhythm or arrhythmia.The hearts job is to pump blood to therest of the body. During each heart-beat, the 2 upper chambers of the heart(atria) contract, followed by the 2lower chambers (ventricles). The hearthas its own electric circuit that coordi-nates activity among the differentchambers of the heart so that they allpump efficiently together at the sametime. The normal heartbeat begins in aspecialized area of the heart called thesinoatrial node, which is located in thetop right chamber. The electric signalthen travels to the lower chambers ofthe heart, which pump the blood to thelungs and the body. Because this signalis sent at regular intervals, we nor-mally have a regular heartbeat. In AF,instead of a single regular signal, thereare multiple electric signals. Althoughnot all of these extra signals are able toactivate the electric system of theheart, some of them do. This usuallyleads to an irregular and fast heartbeat.

What CausesAtrial Fibrillation?

Several factors and medical conditionsmake it more likely to develop AF. AF

is more common in older people and inthose individuals with conditions thatcan damage the hearts electric system.Damage can be caused by any of thefollowing:

High blood pressure Heart attacks Abnormal heart valves Heart defects you are born with

(congenital) Overactive thyroid or other meta-

bolic imbalance Stimulants: medications, caffeine,

tobacco, or alcohol Previous heart or lung surgery Lung disease Stress caused by pneumonia, sur-

gery, or other illnesses Sleep apnea Obesity

What Are the Symptoms ofAtrial Fibrillation?

Some patients do not experience anysymptoms (the Table) when they are inAF, but many patients feel like theirheart is pounding or have chest dis-comfort. Sometimes people feel dizzyand lightheaded or get short of breathand tire more easily. Most symptomsof AF are related to how fast the heart

is beating and often improve when theheart rate is slowed.

How Is AtrialFibrillation Diagnosed?

AF is diagnosed on the basis of amedical history, a physical examina-tion, and the results from tests andprocedures (Figure 1): The most common test is an electro-

cardiogram (ECG or EKG), which isa recording of the electric activity ofthe heart. This is a simple procedurein which electrodes are placed onthe skin at specific locations on thebody (chest, arms, and legs) thatallow an electric tracing of thehearts activity to be recorded. On anormal ECG, the electric activity ofthe heart appears as regular peaksand valleys. On an ECG of a person

Table. Symptoms of Atrial Fibrillation

Palpitations (feeling that your heart is skipping abeat or fluttering)

Shortness of breath

Fatigue

Chest pain

Dizziness

The information contained in this Circulation Cardiology Patient Page is not a substitute for medical advice, and the American Heart Associationrecommends consultation with your doctor or healthcare professional.

From the TIMI Study Group, Brigham and Womens Hospital, Harvard Medical School, Boston, MA.Correspondence to Christian T. Ruff, MD, MPH, TIMI Study Group, 350 Longwood Ave, 1st Floor Offices, Boston, MA 02115. E-mail

cruff@partners.org(Circulation. 2012;125:e588-e590.) 2012 American Heart Association, Inc.Circulation is available at http://circ.ahajournals.org DOI: 10.1161/CIRCULATIONAHA.111.067843

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with AF, the peaks and valleys arenot regular and usually are closertogether because the heart rate is toofast. Occasionally, other types of

portable ECG devices are used(called Holter or event monitors)that allow doctors to monitor yourheartbeat for longer periods of time.

Blood tests are performed to checkthe level of the thyroid hormone inyour body and the balance of yourbodys electrolytes such as potas-sium and magnesium, which are im-portant in maintaining a normalheart rhythm.

An echocardiography, or echo, is acommon test that uses sound wavesto create a picture of your heart thatallows doctors to see how effec-tively the heart is pumping and tomake sure there are no structuralabnormalities of the heart.

ComplicationsIn AF, the upper chambers of the heartdo not pump all of the blood into thelower chambers. When this happens, ablood clot can form. If the clot breaksoff, it can leave the heart and block anartery in the brain, causing a stroke(Figure 2). People with AF are at amuch higher risk of stroke. The riskcan vary, depending on the age of thepatient and the presence of other med-ical conditions such as hypertension,diabetes mellitus, heart failure, andwhether the patient has already suf-fered a prior stroke. Most patients withAF, except those who are very youngand have no other medical problems,require treatment to prevent strokes.

Possible TreatmentsPreventing blood clots from formingis the most important part of thetreatment of AF. Doctors prescribeblood-thinning medications to reducethe risk of stroke. Several options areavailable:

The most effective medications arecalled anticoagulants and includewarfarin, dabigatran, and rivaroxa-ban. Patients taking any of thesemedications require close supervi-sion by their doctor and may requireblood tests to check how well themedications are working and tomake sure that they are not bleeding.For patients with a lower risk ofstroke or those at a high risk ofbleeding, aspirin can be used insteadto prevent strokes, although it is notas effective as an anticoagulant. It is

Figure 1. Diagnosis of atrial fibrillation. Illustration by Medmovie (http://www.medmovie.com/).

Figure 2. Atrial fibrillation and the risk of stroke. Source: National Heart, Lung, and BloodInstitute, National Institutes of Health, US Department of Health and Human Services(http://www.nhlbi.nih.gov/health/health-topics/topics/af/signs.html).

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important to talk to your doctorabout which blood thinner is rightfor you.

Other treatment goals are to slowthe heart rate to improve the heartsability to pump effectively and poten-tially to return you to a normal heartrhythm.

If the heart rate is allowed to be toofast for a long period of time, it cancause heart failure, which makespatients feel really tired and short ofbreath. -blockers and calciumchannel blockers are types of medi-cations that can slow the heart rate.

Sometimes your doctor may try toget you back into a normal heartrhythm. This is called cardioversion.It can be accomplished by severalmethods. Electric cardioversion is aprocedure in which an electriccharge is given to the heart throughthe chest while a patient is sedated.Special drugs called antiarrhythmicsmay also be given to restore a nor-mal rhythm. Other procedures in-volving surgery or use of a catheter

are available for individuals withsevere symptoms. A catheter abla-tion is performed by inserting a wirethrough a vein until it reaches theheart. Radio-wave energy is sentthrough the wire to destroy abnor-mal heart tissue that causes AF. Asurgical operation called a Mazeprocedure may also be done inwhich precise surgical incisions aremade to prevent the abnormal im-pulses from affecting the heart.

Although slowing the heart rate andrestoring a normal rhythm can makepatients feel better, patients usuallystill are a high risk of stroke and mostneed a blood thinner for the rest oftheir lives.

PreventionFollowing a healthy lifestyle and tak-ing steps to lower the risk of heartdisease may help prevent AF. Thesesteps include the following:

Being physically active Not smoking Maintaining a healthy weight

Limiting alcohol excess Treating high blood pressure, high

cholesterol, and diabetes mellitus ifyou have these conditions

PrognosisIf patients with AF see their doctorsregularly, take their medications asprescribed, and live a healthy lifestyle,they can live normal and active lives.

Further InformationFor additional information, please con-sult one of the following resources:

American Heart Association (www.americanheart.org)

National Heart, Lung, and BloodInstitute (www.nhlbi.nih.gov/health/health-topics/topics/af/)

To learn about clinical trials, seewww.clinicaltrials.gov.

DisclosuresDr Ruff has received research grants fromAstraZeneca and Merck and consultingfees from Alere, Beckman Coulter, andDaiichi Sankyo.

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