Elimination of Fluoroscopy Use in a PediatricElectrophysiology Laboratory UtilizingThree-Dimensional MappingGRACE SMITH, M.D. and JOHN M. CLARK, M.D.From the Heart Center, Division of Pediatric Cardiology, Akron Children’s Hospital, Akron, Ohio

Objectives: The aim of this study was to quantify fluoroscopy use in catheter ablation procedures usinga three-dimensional mapping system as the primary source of catheter guidance.

Background: Three-dimensional mapping allows continuous visualization of the location of mappingand ablation catheter electrodes. It has been shown to decrease fluoroscopy times. However, the extent towhich it can decrease fluoroscopy time has not been completely defined.

Methods: Thirty patients (mean age 12.9 years; range 4–27 years) with reentrant supraventricular tachy-cardia underwent catheter ablation using standard protocols. Mapping was performed using the EnSitesystem (St. Jude Medical, St Paul, MN, USA) in the NavX mode (NavX). Eighteen patients had AVNRT, 12had AVRT. Fluoroscopy times were compared to an age-matched and rhythm-matched control population.

Results: Procedural success was achieved in 30 of 30 patients (100%). Mean procedure time was3.27 hours (range 1.83–5.8 hours). Mean fluoroscopy time was 1.05 minutes (range 0–14.8 minutes).Twenty-four of 30 (80%) received no fluoroscopy. Mean fluoroscopy time for the control group was 21.37minutes (range 5.13–77.13 minutes). Thus fluoroscopy time was 95% less in the study group compared tocontrol (1.05 ± 2.96 vs 21.37 ± 18.35 minutes, P < 0.001).

Conclusions: NavX was used to effectively guide catheters during ablation procedures resulting in asignificant decrease in fluoroscopy use. In 80% of the procedures, no fluoroscopy was used. Furtheradvances in the technology may permit additional decreases in x-ray exposure for the 20% of patientswho required it. (PACE 2007; 30:510–518)

ablation, pediatrics, mapping, electrophysiology, clinical

IntroductionRadiation exposure related to diagnostic or

therapeutic medical procedures carries knownassociated risks.1–3 These include dermatitis,cataracts, birth defects, and malignancies. Theserisks accrue to the patient as well as to the staffperforming the procedure and are dose-dependentand cumulative over time. An expert consensusdocument on “Radiation Safety in the Practice ofCardiology,”4 published by the American Collegeof Cardiology, recommends that all catheterizationlaboratory staff adopt the principle of ALARA (ra-diation doses “as low as reasonably achievable”).Multiple authors have published methods to min-imize x-ray exposure during catheterizations.5–8

This is of particular relevance to the pediatric pop-ulation due to the longer life expectancy of the pa-tient. Many young patients with congenital defectswill require multiple procedures for diagnostic or

There are no grants, contracts, or other forms of financial sup-port relative to this manuscript.

There are no conflicts of interest.

Address for reprints: John Clark, M.D., Akron Children’s Hospi-tal, One Perkins Square, Akron, OH 44308. Fax: 330-543-8208;e-mail: jclark@chmca.org

Received October 5, 2006; revised November 12, 2006; acceptedDecember 30, 2006.

therapeutic purposes. This can result in significantlifelong cumulative radiation exposure. Therefore,any steps taken to minimize the radiation dose willbenefit both the patient and the staff.

Three-dimensional electrophysiologic map-ping systems have been in use since the late1990s. One of the benefits of this technology is todecrease x-ray exposure by giving the electrophys-iologist a nonfluoroscopic tool to visualize the lo-cation of the catheter electrodes. The effectivenessof these systems for this purpose has been welldocumented.9–11 In our laboratory, we have beenusing the Ensite system (St. Jude Medical, St Paul,MN, USA) for catheter guidance since early 2003.For all uncomplicated supraventricular tachycar-dias (SVTs) it is used in the NavX mode (NavX). Af-ter more than 2 years experience with NavX, it hasbecome our primary imaging modality for catheterablation, with fluoroscopy functioning as an ad-junct. This report presents successful reduction orelimination of fluoroscopy use in a large group ofpatients with reentrant SVT.

MethodsPatient Selection

The ablation registry at Akron Children’s Hos-pital was searched for all patients who had un-dergone catheter ablation for reentrant SVT during

C©2007, The Authors. Journal compilation C©2007, Blackwell Publishing, Inc.

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the period from December 2005 through May 2006.During that period, 30 patients underwent the pro-cedure. The patient charts were reviewed for clin-ical data including age, height, weight, tachycar-dia mechanism, procedure duration, fluoroscopytime, type of ablation performed (radiofrequencyor cryoablation), total number of lesions, total le-sion time, success, and complications. Althoughthe majority of patients were in a pediatric agerange, age was not a criterion for entry into thisreview. The only criterion for inclusion was thepresence of reentrant SVT. All patients had anechocardiogram to document normal cardiac andvascular anatomy prior to procedure. Written in-formed consent was obtained for each procedure.Antiarrhythmic medications were discontinuedfor at least 5 half-lives prior to procedure. Fora control group, the same hospital registry wassearched for patients undergoing the procedurejust prior to our first use of NavX in 2003. Patientswere matched for age and tachycardia mechanism.To get a matched control group required includingpatients from the database between 2001 and 2003.During this time period we were not yet perform-ing cryoablation.

Procedure

All procedures were performed under gen-eral anesthesia. A transesophageal pacing catheterwas placed and positioned to give the largest ob-tainable atrial signal. This catheter was used asthe stable reference catheter for the NavX sys-tem. Additional mapping catheters and the ab-lation catheter were then placed from a femoralvenous approach. Electrophysiology study wasperformed using standard protocols. If the tachy-cardia mechanism could not be defined at base-line the patient received Isuprel prior to ablation.In all cases the patient was restudied both at restand on Isuprel postablation. For patients with left-sided pathways requiring transseptal puncture, IVheparin was given at a dose of 100 units/kg up toa maximum of 10,000 units. Additional heparinboluses were given to maintain activated clottingtimes greater than 250 seconds.

Three-Dimensional Geometry

For placement of the venous catheters, theNavX system was focused at the femoral vein. Thecatheter could be seen as it exited the femoralsheath and entered the vein. The catheter wasguided up the IVC. Entrance into a renal or hepaticvein could be directly visualized and, under NavXguidance, it could be withdrawn and redirectedup the IVC. Intracardiac location of the catheterwas confirmed by the presence of atrial electro-grams. The point at which the atrial electrogramswere first seen was marked on NavX as the IVC-

right atrial junction. The catheter was then ad-vanced through the right atrium and into the SVC.The point at which atrial electrograms disappearedwas marked on NavX as the SVC-right atrial junc-tion. With these two reference points located, aright atrial geometry was created. The multipolecatheter was maneuvered around the right atriumrecording various points. Creation of an adequate,3D image of the right atrium could be completedin several minutes. Next, the tricuspid valve wasmarked on the geometry. The tricuspid annuluswas located by electrograms having equal atrialand ventricular signals. The catheter was then po-sitioned to record a His electrogram. Once the Hiselectrogram was identified, the catheter was shad-owed on NavX to give a continuous marker of theHis bundle. Finally, the catheter was positionedin the coronary sinus and a shadow of coronary si-nus location was marked. The resulting 3D imageis shown in Figs. 1 and 2. The image can be viewedfrom any angle and at any magnification. With thecavoatrial junctions, tricuspid valve, His bundle,and coronary sinus all marked, all catheters couldbe freely maneuvered and visualized within theright atrium. From this point on, the electrophysi-ology (EP) study and ablation were performed us-ing standard protocols and procedures.

At this institution, cryoablation is the pre-ferred energy source for all reentrant SVTs. In thecurrent study, all but two patients had cryoabla-tion as the energy source of first choice. The major-ity of patients had cryoablation performed using a4-mm tip Freezor catheter (Cryocath Inc., Kirk-land, Quebec, Canada). In these patients, a cry-omap was defined as a preset temperature of −30◦Cto −50◦C for 1 minute or less. A cryoablation wasdefined as a preset temperature of −60◦C to −80◦Cfor any length of time. In the remaining patientsundergoing cryoablation, a 6-mm tip catheter wasused. In these patients, a cryomap was defined asa lesion lasting less than or equal to 1 minute.A cryoablation was defined as any lesion lastinggreater than 1 minute. In these patients, achievedcatheter tip temperatures were −70◦C to −80◦C.If a cryomap site became a cryoablation, this sitewas considered a cryoablation and not counted asa cryomap. For the control group, radiofrequencyenergy was used in all patients. This occurred be-cause we began using NavX in 2003, shortly be-fore we began using cryoablation. Therefore, allpatients in whom NavX was not used could nothave received cryoablation.

Procedural Success

Procedural success was defined accordingto tachycardia mechanism. In patients with atri-oventricular (AV) nodal reentrant tachycardia(AVNRT), success was defined as no inducible

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Figure 1. Three-dimensional geometry as it appears during ablation. Anteroposterior (left) andlateral view (right). CS = catheter shadowing location of coronary sinus. His = catheter shadowingthe location of the His bundle, with the distal tip marking the area of His bundle recording. IVC= inferior vena cava; RAA = right atrial appendage; TV = tricuspid valve. The blue catheter is adecapolar mapping catheter, which at the time of this image is located within the coronary sinus.The red and green catheter is the ablation catheter. Red spheres mark the location of cryolesionsin this patient with AVNRT.

Figure 2. Three-dimensional geometry as it appears during ablation. Right anterior oblique (left)and left anterior oblique view (right). CS = catheter shadowing location of coronary sinus. His= catheter shadowing the location of the His bundle, with the distal tip marking the area of Hisbundle recording. IVC = inferior vena cava; RAA = right atrial appendage; TV = tricuspid valve.The blue catheter is a decapolar mapping catheter, which at the time of this image is locatedwithin the coronary sinus. The red and green catheter is the ablation catheter. Red spheres markthe location of cryolesions in this patient with AVNRT.

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SVT either at rest or on Isuprel for greater than30 minutes postablation. Isolated echo beats wereacceptable, but not more than single echo beats.For accessory pathway-mediated tachycardia, suc-cess was defined as no inducible SVT, either at restor on Isuprel, for at least 30 minutes beyond thelast lesion. In addition, we documented transientAV block with adenosine. In patients with con-cealed pathways, transient block was documentedin a retrograde fashion. In patients with manifestpreexcitation, transient AV block was documentedboth antegrade and retrograde. If a patient had ret-rograde conduction postablation, then pacing pro-tocols were performed to document that the loca-tion of retrograde conduction was within the atrialseptum and that it had decrimental retrogradeproperties consistent with conduction through theAV node. Procedure time was defined as the timeinterval from initial femoral venous sheath place-ment until femoral venous sheath removal.

Statistical Analysis

Values are shown as mean ± standard devia-tion unless otherwise specified. Comparisons weremade with an independent samples T test or aMann-Whitney two sample test, as appropriate. AP value of less than or equal to 0.05 was consideredstatistically significant.

ResultsPatients

Thirty patients (16 females, 14 males) areincluded in this retrospective review (Table I).Mean age was 12.9 ± 4.9 years; height 157 ± 23cm; and weight 54 ± 21 kg. Although the agerange was 4–27 years, only one patient was over18 years. Eighteen patients had AVNRT and 12patients had atrioventricular reentrant tachycar-dia (AVRT). Among patients with AVRT, acces-sory pathway locations were as follows: two rightanteroseptal, three right posteroseptal, one rightlateral, three left posteroseptal, two left postero-lateral, and one left anterolateral. Nine of theaccessory pathways showed manifest preexcita-tion and three were concealed. All patients hadstructurally normal hearts and one patient withwolffparkinson-white (WPW) had a dilated car-diomyopathy. One of the patients had under-gone two previous catheter ablation attempts. Inthe control group there were 19 females and 11males. Mean age was 12.3 ± 4.8 years; height154 ± 19 cm; and weight 51 ± 18 kg. Eighteenpatients had AVNRT and 12 had AVRT.

Success

Procedural success was achieved in 30 out of30 of the study patients. For the 18 patients with

AVNRT, slow pathway conduction was completelyeliminated in 16 patients and modified in the re-maining 2 patients. Sixteen patients had no echobeats and no evidence of dual AV nodal physiol-ogy postablation. Of the 28 patients undergoingcryoablation, 27 (96%) had successful eliminationof their tachycardia mechanism with cryoablationalone. As previously stated, one patient with aright free-wall manifest accessory pathway failedcryoablation and had radiofrequency ablationperformed during the same setting. For those un-dergoing cryoablation, there was a mean numberof cryomaps of 8.3 with a range of 0–30. The meannumber of cryoablation lesions was 5.9 with arange of 2–13. The total cryoablation time averaged21 minutes with a range of 8–52 minutes. Two pa-tients with left-sided accessory pathways had ra-diofrequency ablation as the sole energy source. Inboth of these patients it was felt that, due to the pa-tient’s size and pathway location, the larger stiffercryocath would be difficult to maneuver to the tar-get site, and therefore, radiofrequency (RF) waschosen as the primary tool. For those three patientsreceiving radiofrequency ablation, the mean num-ber of RF lesions was 24 with a range of 6–35. Thetotal RF time was 11 minutes, with a range of 5.5–16 minutes.

In the control group, acute success wasachieved in 29 out of 30 patients.

Fluoroscopy Time

Mean fluoroscopy time for the control groupwas 21.4 ± 18.3 minutes. Mean fluoroscopy timefor the study group was 1.05 ± 2.9 minutes (Ta-ble II). Thus, the group in which NavX was usedreceived 95% less fluoroscopy than the controlgroup (21.4 vs 1.05, P < 0.001). Only 6 of theNavX patients received any fluoroscopy; the re-maining 24 patients (80%) received none. Fluo-roscopy times for the 6 patients who received itranged from 1.2 to 14.8 minutes, with a mean of5.3 ± 4.9 minutes. When compared to the con-trol group, this also was significantly less (21.4vs 5.3, P = 0.001). None of the 18 patients withAVNRT required fluoroscopy. Six of the 12 patientswith AVRT did require fluoroscopy. Of these, 5 hadleft-sided accessory pathways which necessitatedthe use of fluoroscopy to perform a transseptalpuncture. Only one patient required fluoroscopywho did not also require a transseptal punc-ture. This patient had a right free-wall accessorypathway.

Procedure Time

Mean procedure time was 3.27 hours with arange of 1.83–5.73 hours. Mean procedure timefor the control group was 3.17 hours with a rangeof 1.63–5.13 hours. Thus, there was no significant

PACE, Vol. 30 April 2007 513

SMITH AND CLARKTa

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Table II.

Results of Study Group versus Control

NavX Group, Control Group,Mean, (SD) Mean (SD) P Value

N 30 30 NSAge (years) 12.9 (4.9) 12.3 (3.8) NSWeight (kg) 54.1 (21.4) 52 (18.4) NSProcedure time (hours) 3.27 (1.18) 3.17 (1.13) NSFluoroscopy time (minutes) 1.05 (2.96) 21.37 (18.35) <0.001Acute success 30/30 29/30 NSRecurrence 4/30 3/29 NS

difference in procedure times between the twogroups (P = 0.754).

Complications

Some form of transient AV block was seenduring 10 applications of cryotherapy. Nine pa-tients had transient second- or third-degree AVblock and one patient had transient right bun-dle branch block (RBBB). Both patients with an-teroseptal accessory pathways had transient com-plete AV block. Seven patients with AVNRT hadtransient AV Block. The patient with RBBB hadAVNRT as his tachycardia mechanism. In all pa-tients the AV block resolved quickly after discon-tinuation of the freeze. There was no long-term AVblock and no other complications.

Recurrence

During follow-up of 3 months (range 1–6months), 4 of 30 patients (13%) had a recurrence.Two of these patients had AVNRT, and 2 patientshad AVRT. In the control group, 3 of 29 patients(10.3%) had a recurrence. In both groups, freedomfrom tachycardia was 87% at 2 months postproce-dure (26 out of 30 patients). In the control groupthere were no further recurrences at 1-year follow-up.

DiscussionIn the national pediatric ablation registry the

average fluoroscopy time for ablation of SVT is 40minutes.12 Fluoroscopy times any greater than av-erage are associated with a small but measurableincrease in the incidence of malignancy.13 Thisrisk is lifelong and therefore greater in youngerpatients. The ALARA principle was published toremind all physicians and staff that radiation ex-posure should be kept to a minimum. Methods toachieve this goal include using lower image framerates, lower resolution imaging, and stepping onthe fluoroscopy pedal only as long as necessary.

In the present study NavX was used as thesole imaging modality in the majority of patients.It must be noted, however, that this was aftermore than 2 years experience using and learningthe system in conjunction with fluoroscopy. NavXpresents data in a manner similar but not identicalto fluoroscopy. There is a learning curve necessaryfor the user to become accustomed to this new wayof viewing catheters, as well as for the more tech-nical adjustments necessary with the equipment.As our own confidence with the system increased,a deliberate approach developed to maximize ourutilization of NavX and minimize fluoroscopy. Thepresent study is a result of that deliberate bias.In 80% of the procedures NavX eliminated fluo-roscopy use. In the remaining patients it decreasedfluoroscopy use by 75%. This degree of radiationdose reduction has the potential to significantlydecrease long-term risks to both patient and staff.

Catheter ablation without the use of fluo-roscopy was first reported by Drago et al. in 2002.14

In that study the authors used CARTO (CordisWebster, Marlton, NJ, USA) as their navigation tooland radiofrequency as their energy source. Theylimited their patient selection to right-sided free-wall accessory pathways. More recently, Grubbet al. have reported the use of NavX to minimizeor eliminate fluoroscopy in adult patients.15 NavXhas several advantages for a nonfluoroscopic ap-proach. First, the system visualizes all cathetersthat are used during the procedure, not just the ab-lation catheter. Second, any EP or ablation cathetercan be used and therefore either cryoablation orradiofrequency can be chosen for the procedure.Cryoablation offers a safer approach to tachycardiasubstrates on the atrial septum in children.16–18 Be-cause of this, NavX allows for ablation in these ar-eas without the use of fluoroscopy. Since catheterscan be positioned in the His bundle and coro-nary sinus and visualized continuously on NavX,Koch’s triangle is easily defined and precise loca-tion of lesion delivery can be tightly controlled. It

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is our practice that all tachycardia substrates nearthe AV node be approached first with cryoablation.This is particularly important in procedures donewithout fluoroscopy since it confers a greater de-gree of protection against permanent heart block.

It is of particular interest that none of the pa-tients with AVNRT in this study required fluo-roscopy. In fact, of the 25 patients whose tachy-cardias were ablated from the right atrium, 24(96%) received no fluoroscopy. One patient witha right atrial free-wall manifest accessory path-way required fluoroscopy. In this patient, initialattempts at cryoablation of the pathway failed andradiofrequency was then attempted. However, ini-tial attempts at radiofrequency ablation also failed.We therefore switched to shaped sheaths to assistwith catheter tip positioning against the pathway.Since the shaped sheaths cannot be seen on NavX,this necessitated the use of fluoroscopy. Sheathswith electrode tips would be very useful in thesesituations.

The most common reason for fluoroscopy usein this group of patients was the need to performa transseptal puncture. This was the case in 5 ofthe 6 patients requiring fluoroscopy. An area ofparticular research interest is to evaluate meth-ods of transseptal puncture that do not requirex-ray exposure. Intracardiac echocardiography isa well-known adjunct to perform a transseptalpuncture,19 and this may be the best approach foreliminating fluoroscopy entirely. Transesophogealechocardiography is easier to position without flu-oroscopy and gives a greater range of views of theheart. It may, therefore, also be a reasonable al-ternative. Verma and Borganelli reported the useof NavX to visualize a Brockenbrough needle dur-ing transseptal puncture.20 The addition of elec-trode tips to the sheath and dilator would greatlyenhance the ease with which a transseptal punc-ture could be performed. Detailed mapping of theatrial septum may delineate the fossa ovalis, andechocardiography can confirm successful place-ment. If a reliable method for transseptal puncturecan be developed then fluoroscopy during catheterablation may become an uncommon to rare occur-rence.

In addition to decreased radiation exposure,NavX guidance for catheter ablation offers severalother potential benefits. The first is cath lab staffcomfort. In our laboratory the staff no longer wearslead aprons during the procedure. In the few pa-tients requiring transseptal puncture, a lead apronis donned for the short period during which thetransseptal puncture is being performed. There-after the lead can be removed for the remainderof the case. Another potential benefit of NavX isportability. Because all of the equipment involvedis relatively small and portable, it is now quite fea-

sible to do an ablation in the ICU rather than trans-porting a sick patient to the cath lab. A bedside ab-lation procedure could be easily performed withNavX, utilizing portable fluoroscopy if necessary.Finally, NavX guidance offers the possibility of do-ing ablations at times that would otherwise havebeen precluded. Specifically, an ablation could beperformed on a female during pregnancy withoutsignificant risk of x-ray exposure to the fetus.

None of the patients in this study had signif-icant congenital heart disease. Performing an ab-lation without fluoroscopy in a patient with com-plex heart disease would be a more difficult taskto undertake. However, it would still be expectedthat NavX could decrease fluoroscopy times inthose patients due to the ability to see the cathetersin real-time 3D. Papagiannis et al. recently re-ported both a decrease in fluoroscopy time anda decrease in overall procedure time when NavXwas used during catheter ablation in children.21

In the present study there was no significant dif-ference in procedure time between the study groupand controls. The most likely reason for this isthat the study group received primarily cryoab-lation, while in the control group radiofrequencywas used. A single radiofrequency lesion takes1 minute, while a cryo lesion takes 4 minutes,thus adding time to the procedure. Additionally,in those cases in which NavX is used without flu-oroscopy, more time is usually spent to generatean ideal geometry before proceeding to ablation.

There was a 13% recurrence rate by 2 monthsfollow-up in the study group. Thus, at 2 monthspostprocedure, 87% were tachycardia free. This isnot significantly different from the Prospective As-sessment after Pediatric Cardiac Ablation database(PAPCA).22 In that group there was a 4% acute fail-ure rate and 7% recurrence rate at 2 months. Thus,in the PAPCA group 89% were tachycardia freeat 2 months postprocedure. Possible causes of re-currence include method of ablation (cryoablationvs radiofrequency) and accuracy of lesion locationusing NavX versus fluoroscopy. Long-term recur-rence rates remain to be seen.

Potential areas of concern with a nonfluoro-scopic approach include risk of perforation, riskof catheter knot, risk of heart block, and risk ofgeometry frame shift. The risk of perforation ispresent with any cardiac catheterization. However,it would not be anticipated that perforation wouldbe more likely using NavX guidance versus flu-oroscopy since, with NavX, there is continuousreal-time biplane catheter imaging, compared tointermittent single-plane visualization using flu-oroscopy. With cryoablation the risk of perma-nent AV block should be quite remote as long ascare is taken to look for His signals on the ab-lation catheter prior to lesion delivery and AV

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conduction is monitored closely during cryoabla-tion. Transient AV block is a commonly reportedfinding16–18; however, permanent heart block israre. As previously stated, cryoablation is our first-line approach to all tachycardia substrates on theatrial septum. Catheter entanglement or catheterknot is a potential problem with NavX. Since NavXcan only visualize the electrodes of the catheterand not the catheter shaft there is the potentialfor two catheters to become entangled. However,this would most likely be felt as a change in resis-tance to catheter manipulation, at which point thecatheters could be visualized under fluoroscopyand, if there is entanglement, appropriate ma-neuvers to disentangle them could be performed.The final concern about NavX is geometry refer-ence shift. This happens if the reference cathetermoves inadvertently. In our study, we chose anesophageal catheter as the reference catheter. Thiseliminates the chance of dislodgement by contactwith transvenous catheters. There remains a smallchance of catheter movement related to peristalticmovement of the esophagus. However, we have notwitnessed this in practice during our procedures.This is more likely to be an issue in a consciouspatient as compared to an anesthetized patient.Other locations that have been used include theright ventricular apex and the coronary sinus. Al-though these catheter positions tend to be quitestable, they can be dislodged during manipula-tion of the ablation catheter. We, therefore, preferan esophageal catheter. Ultimately, a surface elec-trode may be the best solution for this problem.

The surface electrode can be marked in locationso that even if the lead is dislodged it can be repo-sitioned in the exact location.

Study Limitations

This study has a relatively small number ofsubjects reported. Because of this, complicationswhich are uncommon or rare cannot be fully eval-uated. A much larger sample size will be neces-sary to evaluate whether or not this approach willhave any impact on the uncommon or rare compli-cations. Also, follow-up times are short and long-term success remains to be determined. This studyis not a randomized comparison of NavX to flu-oroscopy. The authors acknowledge a deliberatebias toward the use of NavX and away from theuse of fluoroscopy. Finally, any conclusions maderegarding the differences between the NavX groupand controls must be made with the awareness thatthe two groups also differed in their method of ab-lation.

ConclusionNavX guidance can safely and effectively be

used as the primary catheter visualization toolduring catheter ablation. It decreases fluoroscopyuse in all cases and in most right-sided tachycar-dia mechanisms it eliminates the need for fluo-roscopy altogether. This will decrease the radia-tion risks to both the patient and the staff. Furtherresearch and technological advances are neededbefore it will replace fluoroscopy for left-sidedtachycardias.

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