Atrial fibrillation is the most common signifier of cardiac arrhythmia ; it involves the two upper Chamberss of the bosom known as the atria. During atrial fibrillation the normal pulsations generated by the sinoatrial node are overcome by the electrical pulsations that are generated in the atria and pneumonic venas, which leads to irregular urges being conducted to the ventricles, and hence irregular pulses are generated.
Figure: An ECG Waveform. AF is identified by rapid and oscillating moving ridges that vary in amplitude, form and clocking alternatively of regular P-waves. Electrocardiograms are hence used normally to name AF in patients.
Arterial Fibrillation can show asymptomatically intending that it can show in a patient but show no symptoms, it is considered to be non life endangering in many instances although it can ensue in bosom palpitations, fainting, thorax hurting and in chronic instances congestive bosom failure. The hazard of stroke is besides increased due to the fact that blood may pool and organize coagulums in ill undertaking atria. Patients with AF are normally given blood-thinning medicine such as Coumadin to halt coagulums organizing. Atrial fibrillation can happen in the absence of structural bosom disease, known as lone AF, although this lone occurs in approx. 15 % of instances. Commonly AF is associated with high blood pressure, diabetes, fleshiness, coronary arteria disease, pneumonic disease, valvular bosom disease and coronary bosom failure.
Basic Pathophysiology of Atrial Fibrillation
Atrial fibrillation normally begins with increased premature atrial contractions ( ectopic beats ) come oning to brief tallies of atrial fibrillation normally that are normally self-terminating, over clip these episodes can increase in continuance and sometimes go relentless. During this patterned advance structural alterations in the atria occur every bit good as biochemical alterations in the atrial myocytes. Pathophysiological version of the atria to fibrillation has been loosely termed reconstructing. More specifically, the alterations chiefly impacting the irritability and electrical activity of the atrial myocytes have been termed electrophysiological remodeling.
The primary alteration in the construction of the atria is fibrosis, which is normally considered to be due to the atrial dilation, although in some instances familial influences and redness can besides be a cause. In 1990 Sanfilippo stated that atrial dilation was non a effect of AF although more late in 2005 Osranek stated that atrial dilation was non a effect of AF.
Dilation is due to about any structural abnormalcy of the bosom, such as high blood pressure, valvular bosom disease and congestive bosom failure ; this structural abnormalcy causes a rise in intra-cardiac force per unit areas. Showing the strong relationship between atrial fibrillation and structural bosom disease. Once dilation does happen it begins sequences of events that lead to the activation of the rein aldosterone angiotonin system and a subsequent addition in matrix metaloproteinases and disintegrin, taking to reconstructing of the atria and fibrosis. Fibrosis is non limited to muscle mass of the atria, it can happen in fistula node and atroventricular node besides, associating to sinus node disfunction ( ill fistula syndrome ) .
During normal electrical conductivity of the bosom the SA node generates a pulsation that propagates to and stimulates the musculus of the bosom ( myocardium ) , when stimulated the myocardium contracts. The order of stimulation is what causes right contraction of the bosom, leting the bosom to map right. During atrial fibrillation the urge produced by the SA node is overcome by rapid electrical discharges produced in the atria and next parts of the pneumonic venas. When AF progresses from paroxysmal to persistent the beginnings of these conflictions addition and localise in the atria.
Principles of Catheterization and Ablation
The cardinal purpose of catheter extirpation is to extinguish ectopic beats that arise most frequently in the pneumonic venas and less frequently in the superior vein cova and coronary fistula. This is accomplished through catheter interpolation into blood venas in order to make the bosom, isolation of unnatural bosom tissue and extirpation of this unnatural bosom tissue through the usage of radiofrequency, cryoblation or high strength focused ultrasound.
Rate Control and Rhythm Control
Despite ablative techniques and antiarrhythmic drugs available, direction of common beat perturbation remains a job. Rate control is the preferable intervention for lasting atrial fibrillation and for some patients with relentless atrial fibrillation, if they are either over 65 old ages of age or have coronary bosom disease. Rate control is normally done through the usage of pharmaceutical drugs ( normally beta blockers or rate confining Ca channel blockers ) in order to decelerate ventricular bosom rate and halt the atria from fibrillating. Rhythm control is most normally used for the intervention of paroxysmal atrial fibrillation and in some instances of relentless atrial fibrillation if the patient is either less than 65 old ages of age, has lone atrial fibrillation or congestive bosom failure. Rhythm control is normally achieved through the usage of either a cardioversion ( electrically or pharmacological ) or the usage of pharmaceutical drugs ( normally beta blockers ) in order to keep sinus beat. This intervention is needed for a longer clip in order to halt reoccurrence of atrial fibrillation. [ hypertext transfer protocol: //www.cks.nhs.uk/atrial_fibrillation/management/detailed_answers/first_or_new_presentation_of_af/rate_or_rhythm_control # -391784 ) . Atrial fibrillation is treated most normally pharmaceutically although if the drugs can non command the AF or if the patient is holding a bad reaction to the medicine, catheter extirpation therapy allows for greater control of bosom rate and beat than drug therapy although it does show more hazard to the patient.
Radiofrequency Catheter Ablation
Electrically insulating arhythmogenic thoracic venas is the most of import facet of this process. The application of radiofrequency energy to an endocardial surface is used to do cellular electrical devastation with the loss of cellular electrical belongingss, basically the devastation of unnatural electrical activity [ 39,40 ] . This technique can be enhanced through the usage of larger extirpation electrodes, [ 41-46 ] leting the creative activity of deeper lesions. During the process a doctor will map the country to turn up unnatural electrical activity, this is facilitated through the usage of electroanatomic function system ( fig 2 ) leting for better pilotage when the catheter is inserted into the arteria. Reported success of radiofrequency extirpation is dependent on the badness of the status and ranges from 65 % to 85 % and patients showing with complications is 5 % . [ cryostat ]
Figure: Electroanatomic map of segmental pneumonic vena isolation created utilizing the Biosense CARTO function system.
The most used format of cryoblation is the cryoballoon attack. This involves a deflectable a deflectable over-the-wire catheter with an inner and outer balloon inserted, leting for anatomical discrepancy this balloon is available in two sizes ( 23mm and 28mm ) . The guidewire is positioned in the distal portion of the pneumonic vena, the chapfallen balloon is so progressed to the pneumonic vena ostium. Using the cardinal balloon marker the balloon place is so estimated before rising prices, one time the coveted place is found the balloon is inflated ; pressurized N20 is so delivered to the tip of the catheter via an ultrafine injection tube down a cardinal lms in the interior balloon, working like an enlargement chamber. Sudden enlargement of the liquid gas causes vaporization and soaking up of heat from tissue and low temperatures are so achieved ( Approx -80dc ) . An occlusion angiogram is so performed in the cardinal lms of the catheter to guarantee good balloon pneumonic vena contact. Cryoblation is so started for at least five proceedingss under the status that optimal pneumonic venous occlusion is achieved. The most of import issue when utilizing this technique is to set up optimal contact between the pneumonic vena antrum and the balloon.
High Intensity Focused Ultrasound ( HIFU )
High strength ultrasound is used in transdermal extirpation of atrial fibrillation through the usage of a dirigible balloon catheter. The high strength focused ultrasound balloon is positioned at the ostium of the pneumonic venas and forms a sonicating ring to ablate pneumonic venas antrum when high strength focused ultrasound is delivered. An arrhythmia-free rate of 59 % -75 % was achieved by HIFU balloon in several surveies look intoing its effectivity in atrial fibrillation ablation.15-17
Commercially Available Devices and Systems
Medtronic GENius Multichannel RF Generator
Figure: The GENius multi-channel radiofrequency extirpation generator manufactured by Medtronic
This generator is used for the creative activity of endocardial lesions during cardiac extirpation processs for the intervention of supraventricular arrhythmias. The generator delivers temperature-controlled radiofrequency energy, using five radiofrequency energy manner choices: bipolar merely, unipolar merely, and combination energy mode choices of 4:1, 2:1, and 1:1. This system must be used with a catheter that is individual usage and sold individually to the device. The generator automatically recognizes the affiliated Cardiac Ablation Catheter and loads preset default temperature, clip, and energy manner puting parametric quantities. Ablation parametric quantities such as extirpation continuance, energy manner, mark temperature and channels can besides be manually selected.
Medtronic Cardiac CryoAblation Device
Figure: The Cardiac cryoblation device system with accesories manufactured by Medtronic
The CryoConsole contains both electrical and mechanical constituents every bit good as sole package for commanding and entering a cryotherapy process. This system requires catheters that are purchased individually such as Medtronics Artic forepart cryoablation catheter ( Fig. 3 ) . This system shops and controls the bringing of the liquid refrigerant through the coaxal umbilical to the catheter, recovers the refrigerating vapour from the catheter under changeless vacuity, and disposes of the refrigerant through the infirmary scavenging system. Multiple characteristics are built into both the CryoConsole system and catheters to guarantee safety.
Epicor™ Cardiac Ablation System Price
The Epicor™ LP Cardiac Ablation System delivers High Intensity Focused Ultrasound utilizing algorithms designed to exactly present energy up to 10mm. Unlike the other interventions high strength focused ultrasound has the ability to make lesions from the interior out, lodging energy at the endocardium foremost and so constructing the lesion back up to the surface. The ability to concentrate HIFU cardiac extirpation energy helps cut down the hazard of tissue break, coaling and indirect harm every bit good as overcome procedural restrictions that have historically been associated with other extirpation engineerings.
In footings of extirpation the umbrella nomenclature of Atrial Fibrillation does non take into history the complex nature of the disease. If a patient presents with paroxysmal atrial fibrillation they may merely necessitate a individual catheter to be used, nevertheless if this status becomes more continuous/chronic the patient may necessitate multiple catheters and 3D navigational package. The three techniques described in this study look to be similar in footings of their success rate, radiofrequency and cryoablation have a success rate of approx. 65-85 % while High strength focused ultrasound has a success rate of approx. 59-75 % , this possibly indicates that high strength focused ultrasound may non be as effectual in handling atrial fibrillation as radiofrequency and cryoablation although it is deserving observing that these figures are taken from different research surveies at different times and affect different patients that could be showing greater or lesser a badness of atrial fibrillation.