Contact Force–Guided Pulmonary Vein Isolation

JACC: CLINICAL ELECTROPHYSIOLOGY

VOL. 2, NO. 6, 2016

ª 2016 BY THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION

ISSN 2405-500X/$36.00

PUBLISHED BY ELSEVIER

http://dx.doi.org/10.1016/j.jacep.2016.09.008

EDITORIAL COMMENT

Contact Force–Guided Pulmonary Vein Isolation The Quest for Perfection Continues* Saurabh Kumar, BSC(MED)/MBBS, PHD,a Hugh Calkins, MD,b Gregory F. Michaud, MDa

T

he past few years have seen a burgeoning up-

feedback, catheter stability on fluoroscopy or map-

take in the use of contact force (CF)–sensing

ping

technology in catheter ablation of atrial

impedance (baseline or after ablation), had only

fibrillation (AF). On the basis of a number of pre-

modest predictive value for actual tissue contact

clinical studies, it is well accepted that CF is a key

(5,6). Even the most experienced operators quickly

determinant of lesion size, volume, and depth (1,2).

realized that recognition of both high and low tissue

There are a number of key drivers for the rapid accep-

contact in the absence of CF monitoring was impre-

tance of CF-sensing technology. The first is the

cise (4,6). A number of subsequent retrospective,

suboptimal procedural success rate, even for parox-

case control, and prospective studies demonstrated

systems,

electrogram

characteristics,

and

ysmal AF (w80% freedom from atrial arrhythmias

that CF sensing reduced procedural and fluoroscopy

at $3 years of follow-up after multiple procedures)

time, improved impedance falls, reduced radiofre-

despite a well-defined mechanism attributed to the

quency (RF) ablation time required to isolate PVs,

pulmonary veins (PVs) (3). Ablation failure is thought

and decreased the likelihood of residual gaps after

to be due to nontransmural lesions and gaps in the

completion of the anatomical circumferential abla-

ablation line; it is hoped that CF sensing might over-

tion ring and of acute and chronic PV reconnection

come the limitation of lesion nontransmurality by

when

avoiding low force applications (4). It was also hoped

(7,8). However, it also emerged that simply using

that monitoring CF would lower the risk of complica-

the CF-sensing catheter or obtaining a higher abso-

tions, particularly the risk of cardiac tamponade, by

lute CF did not necessarily translate to improved clin-

preventing excessive CF leading to atrial perforation

ical outcomes such as AF recurrence, suggesting the

and/or steam pop formation (4). Another driver for

presence of other confounding factors mediating the

the rapid acceptance of CF sensing is the realization

relationship

that surrogate markers for contact, such as tactile

Furthermore, there remains significant interest in

compared

with

between

non–CF-sensing

CF

and

catheters

outcomes

(9–11).

elucidating the optimal CF required to achieve maximal efficacy and minimal complications. *Editorials published in JACC: Clinical Electrophysiology reflect the views

SEE PAGE 691

of the authors and do not necessarily represent the views of JACC: Clinical Electrophysiology or the American College of Cardiology. From the

a

Cardiovascular Division, Brigham & Women’s Hospital,

The recent contribution of Reddy et al. (12), in this

Department of Medicine, Harvard Medical School, Boston, Massachu-

issue of JACC: Clinical Electrophysiology examines 2

setts; and the bDivision of Cardiology, Johns Hopkins University School of

critical

Medicine, Baltimore, Maryland. Dr. Kumar is a recipient of the Neil

and interlesion distance, and their relationship to

Hamilton Fairley Overseas Research scholarship, which is cofunded by the National Health and Medical Research Council and the National Heart

confounders,

namely

catheter

stability

AF recurrence at 12-month follow-up in a sub-

Foundation of Australia; and is the recipient of the Bushell Travelling

analysis

Fellowship funded by the Royal Australasian College of Physicians. Dr.

SMARTTOUCH Catheter for the Treatment of Symp-

Calkins is a consultant for Medtronic. Dr. Michaud has received consul-

tomatic Paroxysmal Atrial Fibrillation) multicenter

ting fees/honoraria from Boston Scientific, Medtronic, and St. Jude Medical; and research funding from Boston Scientific and Biosense Webster.

from

the

SMART-AF

(THERMOCOOL

study (9). Patients with drug-refractory paroxysmal AF underwent PV isolation with confirmation of entrance

Kumar et al.

JACC: CLINICAL ELECTROPHYSIOLOGY VOL. 2, NO. 6, 2016 NOVEMBER 2016:700–2

block using the SMART-TOUCH CF-sensing catheter and the CARTO-3 mapping system (Biosense Webster,

Contact Force–Guided Pulmonary Vein Isolation

F I G U R E 1 Factors Confounding the Relationship Among CF, Lesion Size, and

Ablation Outcomes

Diamond Bar, California). Of the 162 patients in the SMART-AF study, 40 patients in whom complete CF and ablation stability data from the VISITAG module (Biosense Webster) were available were the subjects of the present analysis. Of note, the VISTAG module was retrospectively analyzed for lesions that met post hoc specified, including stability of 2 mm giving consideration to cardiac and respiratory movement, application of RF energy for a minimum of 10 s at each ablation site, and a minimum CF of 5 g. The average CF during the procedure was classified into tertiles (<6.5 g, 6.5 to 10.3 g, and >10.3 g). The main finding was the presence of a U-shaped relationship between average CF and 12-month success: a CF range of 6.5 to 10.3 g was associated with a 3-fold increase in procedural success compared with <6.5 g, whereas CF ranges of <6.5 g and >10.3 g yielded a lower and similar procedural success. Moreover, procedural success increased when stable CF was applied $73% of the time within the investigator’s pre-selected CF range. Last, patients with lesions that did not meet pre-defined VISITAG criteria with an interlesion distance >10.6 mm had 3-fold worse procedural success compared with patients who did not (12).

A myriad of factors potentially explain the variable relationship among CF, lesion size, and outcomes in the published data. Superscript numbers are reference numbers. CF ¼ contact force; FTI ¼ force-time integral; PV ¼ pulmonary vein.

The results of these well-conducted analyses strengthen emerging data that the contact quality, not just the absolute quantity of CF is likely a significant

applications when strict criteria for catheter stability

contributor to procedural success. Indeed, Shah et al.

were applied. Higher CF did, however, increase the

(1) elegantly demonstrated 6 years ago that constant

extent of tissue edema as assessed by cardiac magnetic

compared with variable and intermittent contact

resonance, suggesting potential for future gap forma-

(where there is loss of CF in diastole) resulted in greater

tion as the lesion edge recovers from tissue edema (14).

lesion size (1). A lower average CF made it more likely

Continuity index (number of catheter movements

that contact was intermittent, with 51% of lesions

between subsequent RF applications) (15), catheter

exhibiting diastolic loss of CF (0 g) if the average

stability in addition to contact (16), effects of cardiac

CF was <4 g compared with 3% if average CF was

and respiratory motion (17), anatomic location of CF

>20 g (13). The importance of low CF lesions was

delivery (6,18), anatomical wall thickness (18), and

highlighted by Neuzil et al. (8), who showed that

lesion density and interlesion distance (19) have all

chronic PV reconnection had a stronger association

emerged as important factors potentially influencing

with minimum CF and force-time integral within a PV

ablation efficacy with the use of CF-sensing catheters

segment rather than the average CF or force-time in-

(Figure 1). Moreover, there are other intraprocedural

tegral in that segment, suggesting that the durability of

markers of lesion completeness, such as loss of pace

PVI is contingent upon the worse lesion delivered in

capture (20) and electrogram-based assessment of

any PV segment. Further work showed that procedural

lesion transmurality (21), and novel cardiac magnetic

success was markedly enhanced when the RF lesions

resonance applications that provide additional infor-

were delivered in the operator pre-defined CF working

mation beyond CF that may also play an important role

range $80% of the time (9) or when $90% lesions were

in improving procedural efficacy.

delivered with an average CF of $10 g (10). More

Although limitations of the present study include

recently in a porcine model, Williams et al. (14) showed

analysis of only one-fourth of the original SMART-AF

that chronic RF lesion size was not significantly

study population, its retrospective nature, and the

different between low CF (<10 g) and high CF (>20 g)

small sample size, it lays the foundation for further

701

702

Kumar et al.

JACC: CLINICAL ELECTROPHYSIOLOGY VOL. 2, NO. 6, 2016 NOVEMBER 2016:700–2

Contact Force–Guided Pulmonary Vein Isolation

prospective, randomized studies that should examine

that further studies are needed to elucidate optimal

the role of catheter stability in addition to CF in

CF accommodating aforementioned factors, such as

enhancing procedural efficacy. It is possible that the

catheter stability. Until then, the quest for achieving

optimal CF ranges derived may have differed with

optimal procedural success in AF ablation remains

different stability criteria. Nevertheless, an emerging

very much alive.

paradigm is that facilitating homogenous contact is likely a key determinant of procedural success. The

REPRINT REQUESTS AND CORRESPONDENCE: Dr.

discrepancy between the finding of an optimal force

Saurabh Kumar, Cardiovascular Division, Brigham &

range of 6.5 to 10.3 g in the present study (12),

Women’s Hospital, 75 Francis Street, Boston, Massa-

compared with >20 g in prior studies (8,13), means

chusetts 02445. E-mail: [email protected].

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9. Natale A, Reddy VY, Monir G, et al. Paroxysmal AF catheter ablation with a contact force sensing catheter: results of the prospective, multicenter SMART-AF trial. J Am Coll Cardiol 2014;64: 647–56. 10. Reddy VY, Dukkipati SR, Neuzil P, et al. Randomized, controlled trial of the safety and effectiveness of a contact force-sensing irrigated catheter for ablation of paroxysmal atrial fibrillation: results of the TactiCath Contact Force Ablation Catheter Study for Atrial Fibrillation (TOCCASTAR) Study. Circulation 2015;132:907–15. 11. Ullah W, McLean A, Tayebjee MH, et al. Randomized trial comparing pulmonary vein isolation using the SmartTouch catheter with or without real-time contact force data. Heart Rhythm 2016; 13:1761–7. 12. Reddy VY, Pollak S, Lindsay BD, et al. Relationship between catheter stability and 12-month success after pulmonary vein isolation: a subanalysis of the SMART-AF trial. J Am Coll Cardiol EP 2016;2:691–9. 13. Reddy VY, Shah D, Kautzner J, et al. The relationship between contact force and clinical outcome during radiofrequency catheter ablation of atrial fibrillation in the TOCCATA study. Heart Rhythm 2012;9:1789–95.

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16. Okumura Y, Watanabe I, Iso K, et al. Clinical utility of automated ablation lesion tagging based on catheter stability information (VisiTag Module of the CARTO 3 System) with contact force-time integral during pulmonary vein isolation for atrial fibrillation. J Interv Card Electrophysiol 2016;47: 245–52. 17. Kumar S, Morton JB, Halloran K, et al. Effect of respiration on catheter-tissue contact force during ablation of atrial arrhythmias. Heart Rhythm 2012; 9:1041–7.e1. 18. Chikata A, Kato T, Sakagami S, et al. Optimal force-time integral for pulmonary vein isolation according to anatomical wall thickness under the ablation line. J Am Heart Assoc 2016;5: e003155. 19. Park CI, Lehrmann H, Keyl C, et al. Mechanisms of pulmonary vein reconnection after radiofrequency ablation of atrial fibrillation: the deterministic role of contact force and interlesion distance. J Cardiovasc Electrophysiol 2014;25:701–8. 20. Steven D, Sultan A, Reddy V, et al. Benefit of pulmonary vein isolation guided by loss of pace capture on the ablation line: results from a prospective 2-center randomized trial. J Am Coll Cardiol 2013;62:44–50. 21. Bortone A, Brault-Noble G, Appetiti A, Marijon E. Elimination of the negative component of the unipolar atrial electrogram as an in vivo marker of transmural lesion creation: acute study in canines. Circ Arrhythm Electrophysiol 2015;8: 905–11.

KEY WORDS catheter stability parameters, contact force, paroxysmal atrial fibrillation, pulmonary vein isolation, radiofrequency catheter ablation