Understanding Atrial Fibrillation

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• The heart is a muscle that works like a pump
  
  
• The two upper chambers (atriums) receive and collect blood
  
  
• The two lower chambers (ventricles) pump the blood to the rest of the body, delivering oxygen and nutrients
  

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• Heart's natural pacemaker, the S-A Node, produces electrical impulses that set the proper rhythm Electrical impulses cause the atrium to contract and pump blood into the ventricles

• Impulses travel to the ventricles through a special pathway causing them to contract and pump blood to the body

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• Several sites in the atrial send "extra" electrical waves, interfering with the S-A
  node's pacemaking role
  
  
• Atria quiver, or fibrillate, causing the heart to beat too fast
  
  
• Ventricles have less time to fill with blood - the heart pumps less efficiently
  
  
• Not all blood is pumped - some pools and can form into blood clots (especially in the left atrial appendage)

Most Common AF Risk Factors / Possible Causes

• Heart diseases such as: leaky valves, coronary artery disease, inflammation near the heart, previous heart attack or congestive heart failure
• High blood pressure
• Diabetes
• Thyroid, lung or nerve conditions
• Excessive stimulants such as caffeine
• High levels of alcohol use

Symptoms of AF

• Dizziness, lightheadedness, shortness of breath and fatigue
• Some patients have palpitations or an uncomfortable sensation in their chest, while others have no sense at all that their heart is fibrillating

How AF is Diagnosed

• EKG/ECG - records the heart's electrical impulses (heart beats) on graph paper
  
• Holter Monitor - device worn by patients for 1 - 2 days that provides continuous ECG readings
  
• Event Monitor - device worn by patients for up to 30 days that records episodes of AF
  
• Echocardiogram - uses ultrasound to evaluate heart size, pumping strength and how well valves function
• Stress Test - assesses effects of stress on the heart brought on by exertion

Three Classifications of AF (from 2007 Heart Rhythm Society Consensus Statement)

• Paroxysmal - Recurrent AF episodes lasting < 7 days that stop on their own without medical treatment
• Persistent - AF episodes lasting > 7 days or that stop only after medical treatment
• Longstanding Persistent - Continuous AF lasting longer than 1 year

AF Treatment Options

Three Goals of Treatment

• Reduce the patient's stroke risk
• Manage or control their AF - render asymptomatic
• Restore a normal heart rhythm
  

• Electrical shock delivered to heart so it beats regularly again
• Often performed in early stages of AF
• Does not cure AF; results usually temporary
• For most patients, followed up with a medication regimen (blood thinner and rhythm or rate-control drug)

Rx - Rhythm & Rate Control Drugs

• Don't cure, but try to control or minimize symptoms of irregular heartbeat
• Rhythm control drugs try to put heart back into normal sinus rhythm but only work for < ½ of patients and can have serious side effects over time ¹⁵
• Rate control drugs are used to slow the heart down enough that symptoms aren't as severe (heart not returned to a normal sinus rhythm)

Rx - Anticoagulants or Blood Thinners

• For stroke prevention, most patients with AF are prescribed an anticoagulant like Coumadin^® (warfarin) to prevent the formation of blood clots caused by the pooling of blood in the quivering atria
• Aspirin is much less effective and only used in patients at low risk of stroke
• In studies, warfarin reduced the risk of stroke by 68% compared to no treatment at all ¹⁶
• Warfarin requires careful monitoring every 4-6 weeks to ensure correct blood levels because effectiveness is limited to a vary narrow range ¹⁷ - below the range doesn't prevent clots from forming & above range can cause internal bleeding ¹⁸
• Consistent use is absolutely critical -- activity limitations need to be accepted & dietary restrictions must be followed
• Patients need to make all doctors aware of all other drugs and dietary supplements being taken as there are many that can either increase or decrease warfarin's effectiveness

• Small catheters (or tubes) are threaded through a vein in the groin and up to the heart
• Electrodes at the end of the catheter are used to detect the faulty electrical sites causing AF
• An energy source (such as radio-frequency) is used to ablate, or scar, these sites with a series of small, concentric energy bursts to block errant electrical signals from getting through
• Single-procedure success rate is ~ 60%⁺ for patients w/intermittent (paroxysmal) AF and < 30% for patients with persistent AF ¹⁹
• Repeat procedures are often necessary
• On average, requires a 1-2 night hospital stay

Open Heart Surgical Ablation (Cox-Maze Procedure)

• In 1987 Dr. James Cox developed the "cut-and-sew" Maze Procedure - an open heart surgery with a heart-lung bypass
• Created multiple atrial cuts with a scalpel and then sutured to create scar-tissue "lesions" which acted as electrical blocks and disrupted the flow of errant electrical impulses causing AF
• Lesions created a "maze" that guided electrical impulses along their proper pathway
• > 90% success at eliminating AF for patients with intermittent (paroxysmal) and persistent AF ²⁰
• Considered the "gold standard" for AF treatment, but not widely used due to complexity of surgery

Open Heart Surgical Ablation (Concomitant Procedure)

• Development of alternative energy sources used to create ablations (scarring) that replace the "cut-and-sew" lesions of the Cox-Maze - made procedure less complex and more widely available
• Still a major, open heart procedure, so almost exclusively done concomitantly (at the same time as another open heart surgery - such as a valve or bypass procedure)
• Using a clamp-like instrument with a controlled energy source, the surgeon can make linear ablation lines (or scars) that will block the main sources of the errant electrical impulses from getting through
• A pen-like instrument is used to identify and then ablate other areas where errant electrical impulses are getting through
• A small pouch on the heart (the left atrial appendage) is usually removed as this is believed to be the primary site where stroke-causing blood clots form during AF ²¹
• Successful elimination of AF in > 90% of patients with intermittent (paroxysmal) AF ²² and up to 56%⁺ with persistent AF ²³

Minimally Invasive Surgical (MIS) Ablation Sole therapy in which small incisions are made on the side of the chest - a tiny camera & video-guided instruments allow surgeon to reach the heart without opening the chest - performed on a beating heart (eliminating risks associated with heart-lung bypass) Like concomitant procedure, uses clamp & pen-like instruments with a controlled energy source to ablate (scar) the areas where the errant electrical impulses causing AF are getting through Left atrial appendage also usually removed to reduce stroke risk Minimally-invasive approach results in a shorter hospital stay & a quicker return to normal activity Similar success rates to concomitant procedure: 80%-90% in patients with intermittent (paroxysmal) AF 24 56% + with persistent AF 25

REFERENCES (cont)

15 Chandramouli, et al. Atrial fibrillation: Drug therapies for ventricular rate control and restoration of sinus rhythm. Geriactrics 1998;53(6):46-60.

16 Hirsh J, et al. Oral Anticoagulants: Mechanism of Action, Clinical Effectiveness, and Optimal Therapeutic Range. Chest 1995;108:231-246.

17 Ansel J, et al. Comparing self-management of oral anticoagulant therapy with clinical management: a randomized trial. Ann Intern Med. 2005 Han 4;142(1):1-10.

18 Horton JD, et al. Clinical Pharmacology. Warfarin therapy: evolving strategies in anticoagulation. American Family Physician: Vol. 59/No. 3

19 Caulkins H, et al. HRS/EHRA/ECAS Expert Consensus Statement on Catheter and Surgical Ablation. Heart Rhythm 2007;4(6):9.

20 Cox JL, et al. Current status of the Maze procedure for the treatment of atrial fibrillation. Seminars in Thoracic & Cardiovascular Surgery. 2000;12:15-19.

21 Sievert H, et al. Percutaneous left atrial appendage transcatheter occlusion to prevent stroke in high-risk patients with atrial fibrillation: early clinical experience. Circulation 2002;105(16):1887-1889.

22 Gaynor, Sydney L., et al. A prospective, single-center clinical trial of a modified Cox maze procedure with bipolar radiofrequency ablation. J Thorac Cardiovasc Surg 2004;128:535-42.

23 Estes NA & Damiano RJ. Curing atrial fibrillation: Two decades of progress. J Interv Card Electrophysiol (2007)20:127-131.

24 McClelland JH, et al. Preliminary Results of a Limited Thoracotomy: New Approach to Treat Atrial Fibrillation. J Cardiovasc Electrophysiol 2007;18:1289-1295.

25 Edgerton JR, Jackman WM, and Mack MJ. Minimally invasive pulmonary vein isolation and partial atonomic denervation for surgical treatment of atrial fibrillation. J Interv Card Electrophysiol DOI 10.1007/s10840-007-0177-y.