Technology & Innovations
For a 2014 update about imaging, see my AF Report: Non-Invasive Electrocardiographic Imaging—ECGI—CardioInsight.
Most of the imaging technologies described here are in use today and represent huge advances in patient treatment.
Ordinary ablations use Fluoroscopy, a type of X-ray to see inside and ablate the heart. But it is two dimensional. Intercardiac Echocardiography (Ultrasound) (ICE) is also 2-D but provides excellent anatomic detail and assistance in navigating and positioning the catheter.
Electroanatomic Mapping (EAM) offers a 3-D view both outside and inside the heart in almost real time. New technologies combine both of these technologies. CartoSound (Biosense Webster, Cincinnati, OH) uses a proprietary 3D EAM system and incorporates the information obtained from an intracardiac ultrasound probe to visualize and map the heart. (3-D intracardiac ultrasound probes are being developed which would provide real-time 3-D imaging and navigating.)
From a patient’s perspective, should you try to find a larger facility that has CartoSound rather than one that only uses 2-D fluoroscopy?
Doctors using CartoSound would seem to have better imaging tools to do ablations. But doctors using fluoroscopy also get good results.
Computed Tomography (CT) can also be used to obtain detailed images of the left atrium. Rotational Angiography uses standard fluoroscopic equipment to obtain 3-D CT-like images while rotating around the patient. (Posted: February 19, 2011)
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Last updated: Sunday, February 15, 2015
2015 International AF Symposium
by Steve S. Ryan, PhD
This overview should give you a sense of the topics floating through the three days in Orlando and the over sixty presentations by fifty A-Fib experts and researchers. (Most recent brief reports listed first)
(Please be advised that the Symposium organizers go to great lengths not to identify or unfairly publicize one device over another. When writing these reports I often have to do a good deal of research to correctly identify and describe particular devices that are demonstrated, as a service to readers. But this in no way implies or suggests that one device is superior to another.)
Dr. Gerhard Hindricks of the University of Leipzig in Germany gave a dynamic presentation of a catheter ablation of a 46-year-old female with paroxysmal A-Fib using the Rhythmia 3-dimensional multipolar mapping system by Boston Scientific. Along with his colleagues Drs. Andreas Bollmann and Jedrzej Kosiuk, they used the Rhythmia special basket catheter to generate a 3-D map of electrogram voltages and activation times. To me it seemed amazingly fast. The eight-splined bidirectional catheter produced 1,000 data points per minute. In what seemed like only a few passes, they produced a 3-D color reconstruction of the patient’s left atrium.
The actual ablation was routine. They terminated the A-Fib into sinus rhythm without having to use Electrocardioversion. But they found that the PV isolation was incomplete. Using the same Rhythmia 3-D mapping catheter, they were easily and quickly able to locate the gap in the Left Superior PV and ablate it.
Dr. Vivek Reddy from Mount Sinai School of Medicine in New York City gave a very well referenced and persuasive presentation on the Watchman device which closes off the Left Atrial Appendage to prevent clots and strokes. The theory behind the Watchman device is that most A-Fib clots originate in the Left Atrial Appendage (LAA). The Watchman closes off the LAA where 90-95% of A-Fib strokes come from. It’s a very low risk procedure that takes as little as 20 minutes to install. Afterward, you would usually not need to be on blood thinners. (For more, see my article, The Watchman Device: The Alternative to Blood Thinners).
Dr. Reddy certainly persuaded me that the FDA should approve the Watchman device. Dr. Reddy, earlier in Washington, had made the same persuasive arguments before the FDA.
Dr. Andrew Farb from the FDA took the bull by the horns and gave his perspective on the various LAA Closure (Occlusion) Devices. But as one would expect, he didn’t indicate how the FDA would rule on the Watchman device, since deliberations were still ongoing.
After his presentation, I asked him several pointed questions about this, but he was, of course, careful not to comment about current FDA deliberations. My guess? If body language, momentum, mood of the presentations, and more importantly recent research indicate anything, the Watchman device probably will not be approved by the FDA.
There was a palpable sense of sadness at the end of these presentations. The attendees realized that the game may be over for the Watchman device. I hope I am wrong, since the Watchman device would be an important tool to help A-Fib patients. Once the FDA rules and the current clinical trials of the Watchman device end, you will probably have to go to Canada or overseas to get a Watchman device installed.
(Happily I was wrong on this prediction. Update: The U.S. Food and Drug Administration (FDA) approved Boston Scientific’s WATCHMAN™ LAA closure technology for use in the U.S. on March 13, 2015. It has been available internationally since 2009. The FDA approval of the WATCHMAN device is based on the clinical program which consists of numerous studies, with more than 2,400 patients and nearly 6,000 patient-years of follow-up. The Watchman device will be available first at U.S. centers where it has been used in clinical studies.)
Watchman May Win FDA Approval
In my earlier brief reports on the Orlando AF Symposium, based on the recent research and the FDA presentation, I said the Watchman device probably won’t be approved in the US. I’m happy to say that I am most likely wrong.
At the LAA Symposium 2015 in Marina del Rey, CA, it was suggested that the Watchman device may be approved by the middle of this year. One presenter described how the FDA chairman talked with several people who were going to Canada to have the Watchman device installed. He seemed embarrassed that the Watchman was available everywhere in the world but not in the US and said that it has to be approved.
Other doctors I talked with at the LAA Symposium were of the same opinion. Presenters described how clinical trials for other LAA closure devices were on hold so that they could get approved in comparison to the Watchman (Non-Inferiority Trials). Dr. Dhanunjaya Lakkireddy of the University of Kansas Medical Center said that we are at a “tipping point” for the (A-Fib) industry.
As everyone, including the FDA, is well aware, A-Fib innovations usually start in Europe where they are more easily approved. Then only later do they move to the US for FDA approval, since the FDA generally requires more data than European regulators.
Drs. Jun Dong and Andrew Farb from the FDA described the FDA’s ‘Easy Feasibility Study’ (EFS) program where medical device innovations could be evaluated in the US without having to go to Europe first. He encouraged researchers and attendees to take advantage of the new EFS program. This is major news and may make the development of A-Fib innovations much easier to accomplish in the US.
For further information, contact: Andrew Farb, Email: Andrew.email@example.com. 301-796-6317
Dr. Luigi Di Biase from the Albert Einstein College of Medicine in the Bronx, NY and Dr. Daniel Singer from Massachusetts General Hospital in Boston each described potentially great developments in reversal agents for apixaban (Eliquis) and rivaroxaban (Xarelto).
Dr. Di Biase described studies where leaving people on uninterrupted rivaroxaban and apixaban before, during and after an ablation dramatically reduced the amount of silent thromboembolic lesions and were as safe as warfarin with regards to stroke and TIAs. (This didn’t work with dabigatran [Pradaxa].) But if patients develop bleeding or effusion during the ablation, they are in trouble because there is no direct reversal agent as there is for warfarin. He has used Factor IV as an indirect reversal agent. Dr. Singer also described how Factor IV was used as a reversal agent for apixaban.
But there are new reversal agents for apixaban and rivaroxaban which promise to completely reverse the effects of these two drugs in less than four minutes. The FDA is speeding up studies on these reversal agents. But one never knows when or if the FDA will approve them.
Dr. John Day of the Intermountain Heart Institute in Murray, UT (and recently elected president of the Heart Rhythm Society) may be the first A-Fib leader to publicly question whether women should be given one point on the stroke risk CHA2DS2-VASc scale just because of their gender. Many doctors have said this in a circumspect way. Dr. Eric Prystowsky in a presentation at last year’s AHS meeting thought that most doctors would agree with Dr. Day, “as long as there wasn’t a camera focused on them.” He gave the example of a 45-year-old woman in good health and a 45-year-old man with hypertension who according to current guidelines should both be given one point on the stroke risk CHA2DS2-VASc score.
As readers of A-Fib.com, you know that’s been my opinion ever since the original European guidelines came out. Women in their child-bearing years are much less at risk of stroke because of the blood-thinning effect of losing blood each month. And even after menopause women have less risk of stroke. But eventually they do have more strokes. But not because of an innate inferiority, but because women live longer than men. Stroke is age related. An observational Danish registry study documents this.
For more, see The Denmark Study: Women in A-Fib Not at Greater Risk of Stroke Contrary to CHA2DS2-VASc Guidelines!) (Be advised that the original European guidelines were written by doctors with major conflicts of interest.) These guidelines may be a not so very subtle form of gender bias.
Living in A-Fib is more dangerous than having an ablation, according to Dr. Josef Kautzner from Prague, the Czech Republic. Studies have documented that the adverse effects of living in A-Fib, having to take A-Fib drugs and anticoagulants for life are both pragmatically and statistically worse than having an ablation. Dr. Kautzner discussed how A-Fib can cause or is associated with silent brain lesions and dementia. Any time you go into a hospital is a risk. And no one would say that a catheter ablation is a walk in the park. But an ablation is a low risk procedure, though not risk free. The risk is similar to having your tubes tied. The possible adverse effects of an ablation procedure (like bleeding at the groin) are generally temporary, unlike the lasting, permanent damage you can do to your heart, body and brain by living in A-Fib for years.
The most hotly discussed topic at this year’s symposium was rotors. The opinions expressed about rotors were at times very heated, more than I had ever seen at an AF Symposium. Dr. Shih-Ann Chen of Taipei, Taiwan disagreed with Dr. Sanjiv Narayan of Stanford, CA about the basic concepts of rotors and how they should be defined. Dr. Ravi Mandapati of UCLA and Loma Linda University disagreed with Dr. Narayan which was all the more striking in that he had worked with Dr. Narayan when he was at UCLA. Dr. Pierre Jais of Bordeaux, France said that the FIRM mapping system misses 40% of the atrium area.
Drs. Haissaguerre and Jais from Bordeaux and Dr. Sebastien Knecht of Brussels, Belgium gave presentations on how they were using the CardioInsight body surface mapping vest to perform ablations of “drivers” at many different centers, while Dr. Karl-Heinz Kuck from Hamburg, Germany using a different body surface mapping system said that he couldn’t ablate rotors. Dr. Narayan says the FIRM system finds a maximum of 2-3 rotors in the atria, while other systems find as many as seven. The FIRM system says rotors are usually relatively stable and can last as long as 30 seconds while others say they rotate in one fixed spot for only one or two rotations, that they tend to migrate within a certain area.
The presenters obviously didn’t share a consensus of basic concepts of what rotors are, how they work, their importance in A-Fib, how they should be correctly identified, used, and ablated. (It seems to me the Bordeaux group has the best understanding and pragmatic use of rotors. They refer to “rotors” and focal sources as “drivers.”) But the CardioInsight system Bordeaux uses isn’t currently available or isn’t being tested in the US.
Obesity was one of the most often discussed topics. There is a growing consensus among EPs that it isn’t enough to just give obese patients a catheter ablation while not dealing with their obesity. If the obesity isn’t dealt with, their A-Fib is very likely to re-occur. A-Fib will develop in other spots that haven’t been ablated. The condition (obesity) that triggered or caused the A-Fib will trigger or cause it again, if it isn’t taken care of.
Dr. Prashanthan Sanders of Adelaide, Australia described the great results he is getting in his clinic which includes a weight loss program and counseling. He convinces his overweight patients to buy into the program, lose weight, and keep it off. The program works so well that just by losing weight patients become A-Fib free. This program is a holistic approach to health and also is developed to work for diabetes, sleep apnea, hypertension, binge drinking and smoking.
Dr. Sanders foresees a world where some patients become A-Fib free simply by changing their life style, where they don’t have to have a catheter ablation to become A-Fib free.
Many other doctors commented that A-Fib treatment at many centers today includes or should include much more than A-Fib ablation and drugs. A-Fib centers should have nutritionists, exercise therapists, sleep apnea specialists, etc. as part of their A-Fib program.
Dr. John Day of the Intermountain Heart Institute in the Challenging Cases Discussion described his experience with the dreaded Atrial Esophageal Fistula. Though very rare, this is one of the few possible complications of a catheter ablation that can kill you. An ablation, if not done with caution, can irritate and damage the esophagus which often lies right next to the heart. Over 2-3 weeks stomach acid can eat through this damaged area to produce a hole or fistula from the esophagus into the heart.
As soon as Dr. Day saw this patient, he knew it was a fistula and immediately called surgeons and a GI doctor. All the surgeons were doing operations and didn’t want to do the surgery in the EP lab. Dr. Day described how he and his colleagues ran down the hospital hallway to the operating room while giving the patient a transfusion and at the same time pumping out the blood escaping from his heart.
The GI doctor got there first and put in a stent in the esophagus to plug the hole. There was lots of discussion as to whether this was the best approach, but it worked. The patient survived but had to spend a month in the hospital.
This cautionary and very dramatic tale certainly got the attention of all the attendees. No matter how rare a fistula is, every EP and A-Fib center must have an established protocol in place to deal with it. I remember Dr. Hugh Calkins in a previous Symposium advising, “There are only two kinds of EPs—those who have not had an Atrial Esophageal Fistula and those who have!” (Dr. Calkins’ patient with fistula also survived.)
Dr. Peter Kowey of Lankenau Hospital in Winnewood, PA described a case that illustrates the kind of dilemma both doctors and patients often have to face. A 92-year-old woman with paroxysmal A-Fib who had been treated for many years with warfarin had some bruising and nuisance bleeding, but never anything major.
Dr. Kowey thought that ethically he should tell her about the different new anticoagulants which may be superior to warfarin, then see if she wanted to change. She went with apixaban (Eliquis), then six months later had a stroke even though she was taking apixaban properly and conscientiously. Happily, she made an almost full recovery. She returned to warfarin which had worked for her in the past and which she was comfortable using.
One of the reasons Dr. Kowey discussed the new anticoagulants with his 92-year-old patient was because warfarin is considered more apt to cause bleeding in older patients. The newer anticoagulants in clinical trials caused less bleeding. But we don’t have much data from the clinical trials on people over 90 years old.
Can we say that apixaban didn’t work or was ineffective? No. Anticoagulants reduce but do not totally eliminate the risk of an A-Fib stroke. Just because she had a stroke doesn’t mean apixaban didn’t work.
Dr. Jeremy Ruskin pointed out that there has never been and probably never will be a head-to-head comparison of the three new anticoagulants. But in my opinion apixaban (Eliquis) appears to have tested better and is safer than the others
For more, see my 2013 BAFS articles, The New Anticoagulants (NOACs) and Warfarin vs. Pradaxa and the Other New Anticoagulants.
In the satellite case live presentations, Drs. Rodney Horton and Amin Al-Ahmad from the Texas Cardiac Arrhythmia Institute in Austin, TX surprised us by doing an ablation without wearing the standard lead aprons to prevent fluoroscopy exposure. Even more surprising was one of the lab assistants who was pregnant. She could work on the ablation because no fluoroscopy was used. The doctors did the whole ablation using ICE (Intracardiac Echo) and 3D mapping. They showed for example how ICE can be used to thread the catheter up into the heart and into the left atrium. Dr. Horton said that not having to wear those heavy lead aprons would probably add 5-10 years to his ablation career.
(They didn’t wear surgical masks during the ablation which was surprising to me. I will write them for an explanation.)
The live satellite case from Beijing, China was technically flawless and probably a first of its kind. But it wasn’t much of a learning experience for the attendees. The Chinese EPs only used one catheter and had to frequently pull out the mapping catheter and replace it with the ablation catheter, etc. When the expert panel asked them questions, the Chinese EPs either didn’t understand or simply didn’t answer them. They seemed very uncomfortable. It seemed like a throwback to ablation techniques of 20 years ago.
Drs. Claudio Tondo, Gaetano Fassini, Massimo Moltrasio, and Antonio Dello Russo from Milan, Italy showed how they do a catheter ablation for A-Fib and install the Watchman device in the same procedure, when it’s needed. They do the ablation procedure first. Then when the patient is in sinus rhythm, they install the Watchman device. (This can’t be done in the US, because the Watchman device hasn’t received FDA approval. In later discussions including representatives of the FDA, there was an all too real possibility that the Watchman will never receive FDA approval.)
Drs. Kevin Heist and Moussa Mansour from Massachusetts General in Boston showed in a live case how they used a Contact Force Sensing catheter combined with Jet Ventilation. (There are two Contact Force Sensing catheters approved by the FDA—the ThermoCool Smart Touch device by Biosense Webster (approved Feb. 24, 2014) and the TactiCath Quartz Contact Force Ablation Catheter by St. Jude Medical (approved Oct. 27, 2014). This live case used the TactiCath catheter but didn’t imply or suggest it is superior to the ThermoCool catheter. For a description of each, see my 2014 AF Symposium report The New Era of Catheter Ablation Technology: Force Sensing Catheters.
This combination of Force Sensing Catheter with Jet Ventilation for RF ablation probably represents the most advanced RF ablation strategy available today. Jet Ventilation doesn’t stop the heart from beating as in bypass surgery. But to this observer it seemed to put the heart in a type of slow motion with a lot less movement than when the heart is beating in normal sinus rhythm. You could really see a difference when they turned the Jet Ventilation off and on. Slowing down the heart like this helps the ablation doctor make lesions in hard-to-access areas and makes it easier to hold the catheter steady and apply the right contact pressure.
Drs. Michel Haissaguerre and Pierre Jais from Bordeaux/LYRIC gave presentations on the ECGI system. The day before their ablation, the patient lies down on his/her back and a technician places a vest-like device with 256 electrodes over his/her chest and stomach. These electrodes combine with rapid CT (Computed Tomography) scans to produce a very detailed 3D color map of the heart. (For a detailed description and discussion of the ECGI system, see 2013 BAFS: Non-Invasive Electrocardiographic Imaging [ECG]) The system automatically detects rotors and foci and computes them into a “Cumulative Map” or movie. These driver regions are ranked, based on statistical prevalence.
Then, Dr. Sebastien Knecht from CHU Brugmann, Brussels, Belgium, described the AFACART trial design and preliminary results using the CardioInsight ECGI system. Many centers in Europe including four in Germany are now using the CardioInsight. Requiring very little training, technicians and EPs using the CardioInsight system are getting similar great results like the Bordeaux group. Though these studies just started, it looks like the CardioInsight ECGI mapping and ablation system is poised to revolutionize the way EPs map and perform ablations.
Dr. Jose Jalife of the University of Michigan in Ann Arbor, MI, continued his exciting research on fibrosis and A-Fib. In previous Symposiums Dr. Jalife demonstrated how A-Fib produces fibrosis. When he paced sheep into A-Fib, their hearts became fibrotic within a very short time. The markers of fibrosis (collagen and scarring) increased progressively as the sheep went from paroxysmal to persistent A-Fib. (See A-Fib Produces Fibrosis—Experimental and Real-World Data.)
Fibrosis is tissue that has fiber-like characteristics which develop in place of the normal smooth walls of the heart. Fibrotic tissue is scarred, immobile, basically dead tissue with reduced or no blood flow and no transport function. It results in a loss of atrial muscle mass. Over time it makes the heart stiff, less flexible and weak, overworks the heart, reduces pumping efficiency and leads to other heart problems. Fibrosis, up to now, was considered permanent and irreversible. But Dr. Jalife gave his sheep a Gal-3 inhibitor GM-CT-01 that actually prevented and reduced fibrosis! (For his previous presentations, see 2014 BAFS: The Holy Grail: Preventing A-Fib by a GAL-3 Inhibitor.)
In his continuing studies of sheep, Dr. Jalife found that fibrosis predicts recurrence, and that fibrosis can not be reversed if it is well established, even with GAL-3 Inhibitors.
Last updated: Wednesday, January 18, 2017
Diagnostic Tests for Atrial Fibrillation
Doctors have several technologies and diagnostic tests to aid them in evaluating your A-Fib. Your doctor will likely make use of several from this list.
Blood tests check the level of thyroid hormone, the balance of your body’s electrolytes (i.e., potassium, magnesium, calcium, sodium, etc.), look for signs of infection, measure blood oxygen levels and hormone levels, and other possible indicators of an underlying cause of Atrial Fibrillation.Blood tests can also reveal whether a patient has anemia or problems with kidney function, which could complicate Atrial Fibrillation.
An Electrocardiogram (ECG or EKG) is a simple, painless test that uses up to twelve sensors attached to your body to create a graphical representation of the electrical activity of your heart. The standard ECG records for only a few seconds. It can only detect an A-Fib episode if it happens during the test. For a longer period of time, a portable ECG monitor is used.
VIDEO 1: Watch a real-time EKG display of a heart in Atrial Fibrillation. (:30) (Hint: Turn down the music track.) Look for the rapid, but irregular tracing. Uploaded on Apr 19, 2009. By HeartStart Skills Frasco.
NOTE: For an in depth explanation of the ECG/EKG waveform signal and how to “read” an ECG tracing, see my report Understanding the EKG Signal.
Those with occasional A-Fib (Paroxysmal) may not experience an A-Fib episode during your ECG. So, doctors have other means of capturing your A-Fib data.
A Holter Monitor is a small, portable recorder that’s clipped to a belt, kept in a pocket, or hung around your neck and worn during your normal daily activities. The leads from the Holter Monitor attach to your body like the sensors of an ECG. The Holter Monitor records your heart’s electrical activity for a full 24–48 hour period in hopes of capturing data during an A-Fib attack.
An Event Monitor is similar to a Holter Monitor, but records data only when activated by the patient. Pressing a button saves several minutes of data preceding and several minutes afterward. Some event monitors start automatically when they sense abnormal heart rhythms. You might wear an event monitor for one to two months.
VIDEO 2: The “Band-aid” Cardiac Monitor. Instead of a bulky holter monitor, the Zio® Patch cardiac monitor looks similar to a 2-by-5-inch adhesive bandage and sticks to a patient’s chest. Steven Higgins, MD, talks about this single-use ambulatory cardiac monitor; the device can continuously monitor your heart rhythm for up to 14 days without the need for removal during exercise, sleeping or bathing. From a May 2012 TV news story. (1:52 min.)
An Implantable Monitor is a type of event monitor without wires that’s inserted under the skin through a small incision. It’s used for patients with infrequent, unexplained fainting or passing-out when other tests have not found the cause. The implantable monitor is used for up to a year or more.
NOTE: For an in depth look at ECG monitors (including DIY/consumer heart rate monitors), see my report A Primer: Ambulatory Heart Rhythm Monitors.
Exercise Stress Test
During a stress test, you walk (or jog) on a treadmill while an ECG records your heart’s activity. This is often combined with an echocardiogram before and after the stress test to view and measure heart functions.
When the cause of dizziness, fainting or light-headedness isn’t detected by ECG or the Holter/event monitor, a tilt-table test may be performed. The table tilts the patient upright at a 70–80 degree angle for 30–45 minutes. As you are moved from a horizontal to an upright position, your blood pressure, heart rate and heart rhythm are monitored.
VIDEO 3: Tilt table test: Patient introduction to the tilt table test. Description of the test as we see a technician take a patient through a tilt table test. (1:15) Video posted on the New York Cardiovascular Associates website.
An electrophysiology study is a special catheterization test to examine the electrical activity inside your heart. It’s used to determine if and why the rhythm is abnormal. An electrophysiologist (EP) inserts several electrode catheters through the veins in your groin. Real-time images or moving X-rays (fluoroscopy) help guide the catheters into the heart. Once in place, the EP uses the catheters (and perhaps arrhythmia drugs) to artificially stimulate your arrhythmia. By recording data from strategic locations within the heart, most kinds of cardiac arrhythmias can be fully documented.
Echocardiography (Cardiac Ultrasound)
An Echocardiograph uses ultrasound waves to create a moving picture of your heart. As special sound waves are bounced off the structures of your heart, a computer converts them into pictures. These images show the size and shape of your heart and how well your heart chambers and valves are working. Your cardiologist can locate areas of poor blood flow and previous damage, and areas that are fibrillating or not contracting properly as well as identify and measure deformations of heart chambers and thickening of heart walls.
Transesophageal Echocardiography (TEE)
In this test, a tube with an ultrasound device is passed down through your esophagus. A clear image is captured of the heart muscle and other parts of the heart. As ultrasound waves are directed into the heart, the reflected sound waves are converted into pictures. The TEE is often administered just before an ablation to look for blood clots in your atria. If blood clots are found, anticoagulants are prescribed to dissolve them.
Computerized Tomography (CT) or Magnetic Resonance Imaging (MRI)
‘Cardiac CT’ uses an X-ray machine and a computer for detailed images of the heart and to make three-dimensional (3D) pictures of your heart and chest. The electrophysiologist uses them to perform catheter ablations inside the heart. A ‘cardiac MRI’ uses radio waves, magnets and a computer to create snapshots and video of your beating heart and can measure the amount of fibrosis (which can be a factor in A-Fib).
X-ray images help your doctor see the condition of your lungs and heart such as fluid buildup in the lungs, an enlarged heart, and other complications of A-Fib.
There are several tests your doctor may use to evaluate your A-Fib. A basic understanding of these tests helps you ask informed questions and discuss test results.
• Sleep Apnea: Home Testing Now Available New
• A Primer: Ambulatory Heart Rhythm Monitors
• Consumer (DIY) Heart Rate Monitors – Updated
• Understanding the EKG Signal
• The CHADS2 Stroke-Risk Grading System
Last updated: Friday, February 6, 2015