IMAGING TECHNOLOGIES
    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.)
 
     CartoSound (Biosense Webster, Cincinnati, Ohio).
Left, ICE image with a contour drawn around the atrial border and pulmonary vein.
Right, EAM integrated onto a live ICE image.   
  

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.

 

 

A 3-D reconstruction of a left atrium obtained by rotational angiography.
LAO indicates left anterior oblique.
RAO right anterior oblique
CRAN cranial
CAUD caudal

   

Rotational Angiography is currently not in wide use.

BALLOON CATHETERS
    CRYOBALLOON CATHETER
    In this author's opinion, one of the most exciting, important new technologies for A-Fib patients is the recently FDA approved CryoBalloon Catheter. The balloon system can be used to fit into a Pulmonary Vein opening, then ablate it with a minimum number of lesions. This could be a vast improvement over current RF catheters which use pinpoint lesions to perform large-area ablations in a point-by-point fashion and which require a great deal of operator skill and manual dexterity. CryoBalloon ablations might become easier and faster to do than RF.
    Using the energy source Cryo to make ablations may also be a major improvement for A-Fib patients. Cryo uses very cold temperatures to freeze tissue to create lesions without the vaporization, charring, and tissue damage of RF. It preserves heart tissue integrity rather than burning it. When cold temperatures are applied, Cryo catheters stick to the heart tissue they touch, much like a tongue on cold metal. Since the heart is beating and in constant motion during an ablation, this is a significant advantage. And Cryo produces no crust formations. RF burns can cause a crust to form over the ablated area (called a "thrombus"). This crust can fall off and lodge in a blood vessel, perhaps causing a blood clot and stroke. (That’s one of the reasons blood thinners like heparin are used during RF ablations, to prevent these blood clots.) In the clinical trials, the CryoBalloon catheter was safer for patients. There were no strokes, no pulmonary vein stenosis, no esophageal injury, and no coronary artery injury as sometimes occurs with RF ablation. http://www.theheart.org/article/877315.do There is also little danger of perforation and tamponade with the CryoBalloon catheter.
    (Added 3/7/11: Results from the North American Arctic Front STOP-AF trial did show a PV stenosis rate of 3.1% which did not show up in the European trials. This may have come from the use of a smaller 23 mm balloon which possibly penetrates too far into the Pulmonary Vein opening.)²⁴² To see a video demonstration of the CryoBalloon Catheter, go to http://www.cryocath.de/en/4.products/af.presentation.asp 
    But preliminary anecdotal comments from doctors indicate that Cryo ablations may have more reconnection/reconduction problems than RF (perhaps because Cryo doesn't damage heart tissue as much as RF). And the two sizes of Cryo balloons don't always fit neatly into pulmonary vein openings.
    The Cryo (freezing) can affect the Phrenic Nerve and cause breathing problems, but these usually resolve over time.²³⁹ (Added 3/7/11: The North American Arctic Front STOP-AF trial showed a Phrenic Nerve Palsy (paralysis, weakening) of 11.2 %. Some of these cases did not resolve within 12 months (18 %). This Phrenic Nerve damage may have come from the use of the smaller 23 mm balloon which gets closer to the Phrenic Nerve. Dr. Kuck has had good results using only the larger 28 mm balloon.⁾²⁴² Doctors doing CryoBalloon ablations now pace the Phrenic Nerve during the ablation. If they notice that the Phrenic Nerve is affected by the Cryo (freezing), they immediately stop the ablation. The Phrenic Nerve "defrosts" and returns to normal. This technique reportedly eliminates cases of Phrenic Nerve Palsy. 
    In some centers the CryoBalloon catheter has to be withdrawn and RF non-balloon catheters inserted to "touch up" areas the balloon catheter missed, which often requires considerable time and more fluoroscopy exposure. This also increases the cost of an A-Fib ablation, so that hospitals and insurance companies may actively discourage the use of additional catheters.
    However, with more experience doctors may overcome these problems.
    (The CryoBalloon catheter may be a "Gateway Technology" allowing many more doctors to enter the field. The number of A-Fib doctors today can take care of less than 1% of the A-Fib population annually.²³⁶ An increase in the number of doctors able to perform successful A-Fib ablations would be a major help in our current A-Fib epidemic.
    But in these first days of CryoBalloon ablation, patients should be cautious and seek out high volume, experienced centers.)

    LASER BALLOON CATHETER
    The variable size balloon of the Laser catheter (CardioFocus, Inc., Marlborough, MA) can be positioned in a vein opening to encircle the vein. Two overlapping laser energy ablations can usually completely isolate the vein without any gaps. The catheter features direct visualization (endoscopic). The doctor sees directly through the catheter the area he/she is ablating. Though the Laser Balloon Catheter is probably years away from FDA approval, it may have more potential than the CryoBalloon catheter. The variable size of the Laser Balloon makes it easier to manipulate and might enable it to fit better into the different sizes of pulmonary vein openings. Laser energy might produce more lasting lesions than Cryo. And direct visualization would certainly be a help to doctors doing an ablation and would reduce the amount of radiation patients and medical staff are exposed to.


This is an example of what the doctor sees. "LSPV" is the Left Superior Pulmonary Vein, "LIPV" is the Left Inferior Pulmonary Vein.
http://www.cardiofocus.com/pdf/Schmidt_CircEP_Laser.pdf

    MULTIELECTRODE RF ABLATION CATHETERS
    These circular and mesh array shaped catheters are also probably years away from FDA approval. Like balloon catheters they can fit into a pulmonary vein opening and isolate the opening in two or more passes. These catheters also offer ablation at specific poles to produce pin-point ablation of A-Fib spots in the heart. Currently none of the versions offer internal or external irrigation. (Most RF catheter ablation today uses open irrigation to cool the catheter tip, which allows more energy to be delivered without the limitation of overheating the catheter tip.) 

FORCE-SENSING TECHNOLOGIES
    It's been discovered that the force applied to heart tissue during RF ablation affects the size and safety of the lesions. Too little force results in lesions that are smaller in volume and depth and may not be effective. Too much force can result in pressure- and overheating-related complications such as steam pops, coagulum formation, or charring at the electrode. In worst cases they can lead to perforation and/or stroke. (That's why A-Fib patients are advised to seek out A-Fib doctors with experience who perform enough ablations a year to maintain and develop the "touch," manual dexterity, and skill necessary to produce good ablations. Unlike other arrhythmias, A-Fib ablation requires greater technical skill, more time, and more lesions.) New force-sensing technologies help doctors apply appropriate force. Sensors on the catheter give instantaneous feedback on the force applied at the catheter tip and even the angle of the catheter. 

The Contact Force Sensor Catheter (TactiCath, Endosense, SA) uses three optical fibers to measure "microdeformation"---how much the catheter tip bends when pressed against heart tissue. The force applied changes the wavelength of light in the optical fibers. The force applied during an ablation shows up on a imaging/mapping system as either yellow, green or red. Doctors can see when they make an ablation how much force they applied to a particular spot.

REMOTE CONTROL ABLATION---HANSON, STEREOTAXIS
    REMOTE ROBOTIC NAVIGATION
    In manual ablation the doctor controls the catheter tip by a combination of plunger movements, rotation, and advancing and retracting from about three feet away from the heart.    
    In the Hanson Robotic system, the doctor uses a motion controller with a flexible guide catheter directly responsive to an operator's touch that replicates an operator's natural hand movements. The Hanson system is portable and attaches to a procedure table.

    REMOTE MAGNETIC NAVIGATION    
    The Stereotaxis mouse and click system uses two large magnets that are incorporated into the EP laboratory. It requires a dedicated EP lab and space commitment. After making an ablation, there is about a 5-7 second delay before the operator can move on to another spot. 

     The doctor interface screen displays fluoroscopy, intracardiac electrograms, and the EAM system. The magnetic vector can be manipulated from the mapping system or fluoroscopy screen.
 





   
   
    The Stereotaxis system has reported an excellent safety record. The lower contact forces may reduce pressure-related complications, such as steam pops and perforations. The Hanson system also is equipped with a limited force-sensing technology.
    "Automated schemes work reasonably well in the smooth surface of the left atrium but are less reliable in more trabeculated surfaces."²³⁴ Anecdotally the author has heard that doctors with access to the Stereotaxis system often work manually instead, because it is faster and less exasperating than the 5-7 second delay.
    The Hanson robotic system still requires extensive manual skill, while the Stereotaxis system is automated. Even with skilled, experienced operators it is still possible with a robotic system to have misplaced ablation burns or accidents such as perforations. Whereas the magnetic system using a mouse to make the ablations may be safer, and also more capable of being used by new operators.
    Should a patient seek out centers with these remote technologies? Probably not. In this author's opinion, these remote systems will not survive if they can not incorporate the advances in catheter development described above.

THE WATCHMAN DEVICE
    An important recent innovation for patients is the Watchman Device. The theory behind the Watchman Device is most A-Fib clots originate in the Left Atrial Appendage (LAA). The Watchman Device closes off the LAA where 90-95% of A-fib strokes come from. It's a relatively low risk procedure compared to open heart surgery. It takes only a short time to install. Then you would usually not need to be on blood thinners.
    Here's how it works:
Once a patient's Left Atrial Appendage is measured, a wide-sheathed catheter with a spline is used to insert the Watchman device which has a self-expanding Nitinol (a special metal) open-ended circular frame. The atrial surface of this frame is covered with a thin, permeable 160 μm (micron) pore filter made of polyester material (Polyethylene Terephthalate known as Dacron or PET). This filter allows blood to pass through while stopping clots. Little hooks or anchors called fixation barbs at the middle of the device make sure it is attached firmly to the LAA wall. The Watchman device comes in multiple sizes from 21mm to 33mm to accommodate the different sizes of LAAs.
     Before the catheter is removed (which fixes the Watchman device in place), contrast agents are used to make sure the Watchman device is stable and entirely closes off the LAA opening. Over time heart tissue grows over the polyester (PET) material so that it completely closes off the LAA with smooth heart tissue similar to other heart surfaces. In this Occlusion slide, heart tissue has completely covered the Watchman device after only nine months.
    Some doctors are inserting the Watchman device in as little as 20 minutes. There is no surgery or ablation involved.
    Patients on Coumadin continue to take it for six weeks after the Watchman device is inserted. They are then examined using a TEE (Transesophageal Echocardiogram) to make sure there is complete closure of the LAA. At that time they are taken off of Coumadin.

You can see a video of how the Watchman device is deployed at http://www.atritech.net/animation.html

    Coumadin reduces but does not totally eliminate the risk of stroke. Even with the proper INR levels of Coumadin, a small number of people with A-Fib have had strokes. The Watchman device also reduces but does not totally eliminate the risk of stroke. Like Coumadin, the Watchman is not an absolute guarantee one will never have a stroke. It basically reduces the risk of stroke similar to that of a person with a normal heart.
    Those of us who hate having to take Coumadin or blood thinners will be able to go in for a  procedure that takes as little as 20 minutes, and replace Coumadin and blood thinners with the Watchman. This is incredibly good news for many of us. 
    Even while we are waiting for or trying to decide on having a Pulmonary Vein Ablation, we can have the Watchman inserted and reduce our risk of stroke similar to that of a person with a normal heart.
    The Watchman device may become part of most catheter ablation procedures. If the catheter ablation procedure were unsuccessful or in case of silent A-Fib attacks after ablation, patients would still be protected from an A-Fib stroke by the closing off of the Left Atrial Appendage. The Watchman Device may become standard therapy not just for people with A-Fib, but also for anyone at risk of a stroke.
    (Added 4/12/2011: However, removing or closing off the Left Atrial Appendage (LAA) may affect how well the heart pumps and is of special concern to athletes and to those with heart pumping problems. In canine studies the LAA provided 17.2% of the whole left atrial volume of blood pumped.²⁵⁷ It's possible that removing or closing off the LAA may lead to heart pumping problems and exercise intolerance.)
    Though still in clinical trials, the Watchman Device is available for most people. For a list of US doctors installing the Watchman Device, go to Doctors Installing the Watchman Device.

LARIAT ii SUTURE DELIVERY DEVICE
    A noose device to close off the Left Atrial Appendage is inserted from outside the heart (Lariat II, SentreHeart, Inc., Palo Alto, CA) (unlike for example the Watchman device which is inserted into the LAA from inside the heart).  It is used in cases where the patient can not tolerate anticoagulants like Coumadin. (The Watchman device requires a patient be on anticoagulants for a couple of months.)
    From the inside of the heart a balloon is placed inside the Left Atrial Appendage to expand it and make it accessible to the noose device which is inserted from the outside of the heart. The positioning balloon is withdrawn before the Lariat noose is closed around the base of the Left Atrial Appendage. The noose completely closes off the Left Atrial Appendage which dies and is no longer electrically active. The Lariat II snare device has been approved by the FDA.  
    The Lariat device was invented by Dr. William E. "Billy" Cohn, Director of Minimally Invasive Surgical Technology at the Texas Heart Institute at St. Luke's Episcopal Hospital. 

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