catheter ablation - Europe PMC

1 downloads 0 Views 1MB Size Report
Technique of pulmonary vein isolation by ... Keywords: atrial fibrillation, pulmonary veins, catheter ... monaryvein stenosis, while the formationofcoagulum.
REVIEW ARTICLE

Technique

of

pulmonary vein isolation

by

catheter ablation

F.H.M. Wittkampf, R. Derksen, E.F.D. Wever, T.A. Simmers, L.V.A. Boersma, E.P.A. Vonken, B.K Velthuis, N. Sreeram, B.J. Rensing, M.J. Cramer

In selected patients with atrial fibrillation, the fibrillation episodes may be initiated by single or short bursts of ectopy often originating from one or more pulmonary veins (PVs). Therefore, electrical isolation of these veins by catheter ablation is currently being explored as a treatment modality for patients with paroxysmal and even more permanent types of atrial fibrillation. At present, two different techniques are used: 1) selective ablation of electrical connections between left atrium and myocardial sleeves inside the PVs; and 2) contiguous encircling lesions around and outside the PV ostia. WVith both techniques, moderate to high success rates have been reported with a limited follow-up duration. Both types of procedure are very complex and require a highly skilful team. With the variable anatomy of the PVs, non-invasively acquired angiographic images may serve as a roadmap for catheter manipulation. Modern threedimensional catheter navigation techniques can be applied to facilitate accurate catheter positioning with limited fluoroscopic exposure. Experimental and clinical research is needed to define patient selection criteria. (Neth Heart J 2002;10:241-4.)

Keywords: atrial fibrillation, pulmonary veins, catheter ablation F.H.M. Wlttkampf. R. Defksen. E.F.D. Wever. T.A. Simmers. LV.A. Boersma. BJ. Rensing. M.J. Cramer. Department of Cardiology, Heart Lung Centre Utrecht. E.P.A. Vonken. B.K. Veithuls. Department of Radiology, University Medical Centre Utrecht. N. Sreeram. Department of Cardiology, Wilhelmina Children's Hospital, Utrecht. Address for correspondence: F.H.M. Wittkampf. E-mail: [email protected].

Netherlands Heart Journal, Volumc 10, Number 5, May 2002

Electrical isolation ofpulmonaryveins (PVs) from the left atrial myocardium by catheter ablation is currently being explored as a treatment modality for patients with paroxysmal and persistent atrial fibrillation."-5 The basis for this approach is the presumably arrhythmogenic property ofsleeves of atrial myocardium, often extending 1 to 2 cm into the PVs.6'7 These arrhythmogenic properties have been demonstrated by recordings of: 1) rapidly firing ectopic foci located inside the PV, often initiating atrial fibrillation, and 2) relatively long conduction delays between left atrial and PV potentials (figure 1 ).1,8 9 The myocardial sleeves may thus act as the site of origin of triggers for atrial fibrillation, but may also serve as the substrate of micro-reentry. The therapeutic effect of complete electrical PV isolation may therefore result in elimination of all ectopy from these veins, isolation ofthe reentrant circuit, or both. Isolation of the PV ostia may not be successful in patients with chronic atrial fibrillation in the setting of structural heart disease, due to fibrosis, remodelling, and the vulnerability of the atria. These atria may require a more aggressive surgical approach or, in the foreseeable future, a catheter maze procedure.'0"' Therefore, patients with idiopathic paroxysmal atrial fibrillation, frequent, uniform atrial ectopy originating from PVs, and inducibility by multiple extra stimuli or burst pacing only, seem to be the most likely candidates for PV isolation.'2 Patient selection is, however, still a matter of debate. Clinical studies in combination with meticulous analysis of the effect of catheter ablation in different patient categories are necessary and are currently being performed to define these criteria. Positive reports about the, at least short term, success of this procedure in patients with paroxysmal and even chronic atrial fibrillation have led to the application of this technique in various experienced catheter ablation centres.'-5 In the present paper we describe the current technologies applied to perform the electrical isolation procedure in the catheterisation laboratory. Ablation technique Catheter ablation in narrow ostia may lead to pulmonary vein stenosis, while the formation of coagulum 241

|1t y-

Technique of pulmonary vein isolation by catheter ablation

V

La

-

.-1

r

I

_U

~

Ln 4A

~

Iu

~

~

-

I

..-u_

aminrr_

Ln67

----w uv_ _

Figure 1. Electro(cardio)grams in a patient with idiopathic paroxysmal atrialfibrillation. During atrial stimulation via a catheter in the cornarysinus (CS), widely split bipolarelectrograms are recorded from the decapolar Lasso (Las) catheter situated apprximately I cm inside the leftsuperiorpulmonaryvein ostium. The pulmonary vein potentials recorded with bipolar Lasso electrograms 1,2 to 6,7 consist of two discrete potentiak after the stimulusartefact, Thefirstpotential coincideswithatrial ativation atthePVoricie, whik the potential 80 ms latersuggests the presence ofan arrhyMtmogenic substrate with an extremely long conduction delay within the PVskeve ofexcitable myocardial tissue.

and protein aggregation during radiofrequency application are potentially harmftil, especially in the left atrium.3"3 Incomplete isolation obscures follow-up analysis and this complex procedure may require long fluoroscopic exposure times. The quality ofthe ablation procedure is therefore of utmost importance and it should only be performed by highly experienced operators. At present,

PV isolation is performed using two distinctly different techniques. Haissaguerre et al. demonstrated the presence of a limited number of connections between the left atrium and myocardial sleeves inside the PV as a result of which complete isolation of the PV could be achieved by a limited number of accurately placed lesions in the PV orifice.' After obtaining left atrial access by transseptal puncture(s) or open foramen ovale, angiography of the proximal PVs is performed to mark the ostia on fluoroscopic images. Then, two catheters are inserted into the left atrium: a decapolar circumferential catheter (Lasso, Biosense Webster, Inc, Diamond Bar, CA) for perimetric mapping of the PV ostia and a standard ablation catheter for RF energy delivery. After careful positioning ofthe Lasso catheter a few mm inside the PV ostium, the site of earliest breakthrough of atrial activation into the PV is determined from the Lasso electrograms. This analysis may require left atrial stimulation via a catheter in the distal coronary sinus to separate PV potentials from the left atrial signal. 242

Figure 2. Three-dimensional image (posterocranial view) of the left atrium andprximal parts ofthepulmonary veinsobtained with magnetic resonance angiography (MRA). After ARA imaging, special image processing software is applied to remove structures that are irrelevant for the ablation procedure such as the aorta, pulmonary arteries, ventricles and fine arterial and venous pulmonary branches. The software ako allowsfor measurement of the pulmonary vein ostium diameter in multiple directions for selecting the optimal Lasso diameter.

During ablation, the tip electrode of the ablation catheter has to be positioned very close and proximal to the earliest Lasso electrode and RF energy is applied to isolate this site. Thereafter, another breakthrough may be found and ablated until complete isolation is achieved. Radiofrequency power is limited to approximately 30 Watt and an ablation tip temperature of 50°C to avoid unnecessary deep lesions, thrombus formation and PV stenosis. The alternative method, described by Pappone et al., aims at complete encircling of the PV ostia with a continuous line of ablation lesions.2"4 The lesions are intentionally positioned outside and around the ostia to reduce the chance of PV stenosis. The relatively long contiguous encircling lines of lesions not only isolate the PVs, but possibly also a relatively large section of the posterior left atrium that may contain ectopy foci or a substrate for reentry. This technique requires a large number of lesions and relatively high RF energy settings and most importantly an extremely skilful operator to achieve a contiguous encircling line of lesions around the PV ostia. So far, most centres prefer the method as described by Haissaguerre for performing such PV isolation, as does our centre.

Netherlands Heart Journal, Volume 10, Number 5, May 2002

Technique of pulmonary vein isolation by catheter ablation

Anatomical imaging With the variable anatomy of the PVs, non-invasive magnetic resonance angiography (MRA) or a computerised tomography (CT) scan of the left atrium may serve as a roadmap for catheter mapping. MRA may take more time and be more expensive than a CT scan, but the patient is not subjected to a relatively high dose ofradiation and the images are very detailed (figure 2). The MRA images enable measurement of PV ostium diameters in more than one dimension and selection of the optimal Lasso diameter while it identifies the presence of small proximal PV branches that may complicate the ablation/isolation procedure and are easily missed with standard contrast angiography.

3D catheter localisation Until recently, fluoroscopy was the only technique that allowed real-time visualisation of electrode catheters. In this type of procedure, however, fluoroscopic exposure times may be extremely high due to the transseptal puncture, angiographic visualisation of the PVs, and catheter manoeuvring. A few years ago, the Carto system (Biosense Webster, Inc, Diamond Bar, CA) was introduced as a non-fluoroscopic catheter navigation tool. Using an externally applied magnetic field, the position of a magnetic sensor inside the distal section of the mapping/ablation catheter can be localised in 3D space and the position of that catheter is displayed on a computer screen. This method has

been successfully applied by Pappone et al. to create a 3D map of the left atrium, mark the positions of the PVs, the ablation catheter, and all ablation sites.2"4 With the more widely accepted technique of Haissaguerre, both the Lasso and the ablation catheter have to be visualised. The Carto system cannot localise the Lasso because the size ofthe magnetic sensors does not allow incorporation in that catheter. With biplane fluoroscopy, it may also be very difficult and time consuming to determine the exact position of the ablation catheter tip electrode relative to one of the Lasso catheter electrodes, especially to those at 3 and 9 o'clock of the Lasso loop (figures 3 and 4). Fluoroscopy is also inadequate in detecting minor, but critically important shifts in the position of the Lasso catheter in the course ofthe procedure. The positions ofmultiple RF lesions cannot be marked either. Recently, the LocaLisa system (Medtronic Inc, Minneapolis, US) has become commercially available."I This system applies a transthoracic electrical field via six standard skin electrodes and uses the conventional catheter electrodes as position sensors. Besides inputs for the mapping/ablation catheter, the system provides eight extra input channels. This allows 3D localisation of both the mapping/ablation catheter as well as a major section of the Lasso loop (figure 5). The standard Lasso electrodes are very small, approximately 0.5 mm in diameter and length, and consequently have a relatively high tissue-electrode interface impedance.

Figures 3 and 4. Biplane fluoroscopic images showing the positions offour atrial catheters. Quadripolar catheters in the right atrial appendage and distal coronary sinus, the decapolarLasso catheter in the left superiorpulmonary vein ostium and the quadripolar ablation catheter still in the left atrium. The orientation of the Lasso loop makes itvery difficult to determine the exact location of the different Lasso electrodes; especially the position of those located at 3 and 9 o'clock in the Lasso loop is confusing.

Netherlands Heart Journal, Volume 10, Number 5, May 2002

243

Technique of pulmonary vein isolation by catheter ablation

accuracy and safety, and shorten the duration of this complex and challenging catheter ablation procedure. Experimental and clinical research is needed to clarify the aetiology of paroxysmal atrial fibrillation, the role of the PV, and most importantly to define optimal patient selection cnteria. E Acknowledgement We very much appreciated the invaluable advice of Dr Peter Loh, Munster, Germany, about these catheter ablation procedures. ---_Fige _. Image of ._

Loea_isa _reen

showing

...... Lazo

-o

-w

References 1

..

2

F res5.Imageofthe - Lsua sceen shin chedLassol the.. cahee shft

.....

Intay

thi reaivl

hig

withs total.

3

4

Haissaguerre M, Shah DC, Jais P, Hocini M, Yamane T, Deisenhofer I, et al. Electrophysiological breakthroughs from left atrium to the pulmonary veins. Circulation 2000;102:2463-5. Pappone C, Rosanio S, Oreto G, Tocchi M, Gugliotta F, Vicedomini G, et al. Circumferential radiofrequency ablation of pulmonary vein ostia. A new anatomical approach for curing atrial fibrillation. Circulation 2000;102:2619-28. Moak JP, Moore HJ, Lee SW, Giglia TM, Sable CA, Furbush NC, et al. Case report: pulmonary vein stenosis following RF ablation of paroxysmal atrial fibrillation: successful treatment with balloon dilation. JInterp Card Ekctropkysiol 2000;4:621-31. Gerstenfeld EP, Guerra P, Sparks PB, Hattori K, Lesh MD. Clinical outcome after radiofrequency catheter ablation of focal atrial

fibrillation. J Cardiovasc Ekltrophysiol 2001;12:900-8.

L theocabledationcatheer.o ifistoerce elperdesalucte dtlprinof T npstonwt he LocaLisa whenaraltmennfloocopimiplayrof system thes boticthestesandathu acuatepst nnfthetetiphi ofolewe conductesion l usual de toverythin hressane.thnceablesio abltincatheter reatv y tioron modfitescatinothete eLectrods. eothL caused ssoand 1-2 cmaeor of isouarye bimedan whnacomp1are iption then, wimthehe LocaLisa system haveduccessfullys wue andoveythers hrdwisarce. Sianc whentpo the bt arhtefacsond thue eecstro,grams corresponding w catheter on of thee hasso shft.tiptouchts. thisrelatively insted sigtotal usesdation this reital-time thisree-dimensigtonal syshtem shfor rnitallyim, cthessyter the lLaoisa agcLisa beletsonlvya

la mbifabthe Lasso catterand theomai ne Tspe on th oe hes AccaLsuacy ofteoaLs cnathe Loaisar imoicage. system po simu belectrodves ltaneouly.

with and ablation catheters oneo the Lasso

5 6 7

8

9 10

11

12

successively.

13

Conclusion

Electrophysiological studies in patients with paroxysmal atrial fibrilation have demonstrated the arrhythmogenic properties of sleeves of myocardial tissue inside

PV ostia. In selected patients, moderate to high success rates have been achieved by electrical isolation of these

veins by catheter ablation. Modern imaging and catheter navigation techniques may improve the

244

14

15

Oral H, Knight BP, Tada H, Ozaydin M, Chugh A, Hassan S, et al. Pulmonary vein isolation for paroxysmal and persistent atrial fibrillation. Circulation 2002;105:1077. Saito T, Waki K, Becker AE. Left atrial myocardial extension onto pulmonary veins in humans: anatomical observations relevant for atrial arrhythmias. J Cardiovasc Electrophysiol 2000;11:888-94. Ho SY, Cabrera JA, Tran VH, Farre J, Anderson RH, S'anchezQuitana D. Architecture ofthe pulmonaryveins: relevance to radiofrequency ablation. Heart2001;86:265-70. Haissaguerre M, Jais P, Shah DC, Takahashi A, Hocini M, Quinou G, et al. Spontaneous initiation of atrial fibrillation byectopic beats originating in the pulmonary veins. NEnglJMed 1998;339:65966. Hocini M, Shah DC, Jais P, Haissaguerre M, Peng JT, Yamane T, et al. Concealed left pulmonaryvein potentials unmasked by left atrial stimulation. Pacing Clin Ekctrophysiol 2000;23:1832-5. Cox JL, Schuessler RB, D'Agostino HJ Jr, Stone CM, Chang BC, Cain ME, et al. The surgical treatment of atrial fibrillation. III. Development of a definitive surgical procedure. J Thorac Cardiovasc Surg 1992;104:1491-4. Ernst S, Ouyang F, Schneider B, Kuck KH. Prevention of atrial fibrillation by complete compartmentalization of the left atrium using a catheter technique.JCardiovascEkctrophysiol2000;11(6): 686-90. Ramanna H, Hauer RNW, Wittkampf FHM, Bakker JMT de, Wever EFD, Elvan A, et al. Identification of the substrate of atrial vulnerability in patients with idiopathic atrial fibrillation. Circulation 2000;101:995-1001. Demolin JM, Eick OJ, Munch K, Koullick E, Nakagawa H, Wittkampf FHM. Soft thrombus formation in radiofrequency catheter ablation? Pacing Clin Ekctrophysiol 2002 (in press). Pappone C, Oreto G, Rosanio S, Vicedomini G, Tocchi M, Gugliotta F, et al. Atrial electroanatomic remodeling after circumferential radiofrequency pulmonary vein ablation. Circulation 2001;104:2539-44. WittkampfFHM, Wever EFD, Derksen R, Wide AAM, Ramanna H, Hauer RNW, et al. LocaLisa: New technique for real-time 3D localization of regular intracardiac electrodes. Circulation 1999; 99:1312-7.

Netherlands Heart Journal, Volume 10, Number 5, May 2002