Cryoablation for Ventricular Arrhythmias Arising From the Papillary Muscles of the Left Ventricle Guided by Intracardiac Echocardiography and Image Integration

JACC: CLINICAL ELECTROPHYSIOLOGY

VOL. 1, NO. 6, 2015

ª 2015 BY THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION

ISSN 2405-500X/$36.00

PUBLISHED BY ELSEVIER INC.

http://dx.doi.org/10.1016/j.jacep.2015.07.012

NEW RESEARCH PAPERS

Cryoablation for Ventricular Arrhythmias Arising From the Papillary Muscles of the Left Ventricle Guided by Intracardiac Echocardiography and Image Integration Santiago Rivera, MD,* Maria de la Paz Ricapito, MD,* Juan Espinoza, MD,* Diego Belardi, MD,* Gaston Albina, MD,* Alberto Giniger, MD,* Jean-François Roux, MD,y Felix Ayala-Paredes, MD, PHD,y Fernando Scazzuso, MD*

ABSTRACT OBJECTIVES This case series reports outcomes and complications of catheter cryoablation at the papillary muscles (PM) of the left ventricle (LV). BACKGROUND Catheter radiofrequency ablation is an effective treatment for ventricular arrhythmias (VAs) arising from the PM of the LV. The use of cryoablation at PMs has not been described. METHODS Ten patients (70% men; median age: 38 years [range: 34 to 45 years]) with drug-refractory premature ventricular contractions or ventricular tachycardia underwent catheter cryoablation. VAs were localized using 3-dimensional (3D) mapping, multidetector computed tomography, and intracardiac echocardiography, with arrhythmia foci being mapped at either the anterolateral PM or posteromedial papillary muscle (PMPM) of the LV. Focal ablation, up to 240 s with freeze–thaw–freeze cycles was performed using an 8-mm cryoablation catheter via a transmitral approach. RESULTS Termination of ventricular arrhythmia was observed in all 10 patients during ablation. Median follow-up was 6 months after ablation. The PMPM had higher prevalence of clinical arrhythmias (100% PMPM VAs vs. 10% anterolateral PM VAs). The PM base was the most frequent site of origin of the arrhythmias (60% of patients). Pace-mapping showed $11/12 match in all treated PM at the site of effective lesion. All VAs arising from the base of the PM showed Purkinje potentials. There were no post-procedure complications. VA recurred in 1 patient. CONCLUSIONS Cryoablation for arrhythmias arising from the PMs of the LV can be performed, and is a safe and effective alternative energy source for ablation. (J Am Coll Cardiol EP 2015;1:509–16) © 2015 by the American College of Cardiology Foundation.

T tricular

he papillary muscles (PMs) from the left

has been associated with poor catheter stability and

ventricle (LV) are complex anatomic struc-

manipulation compared with other VAs (2). Catheter

tures and potential sites of origin for ven-

ablation by RF energy has successfully eliminated

arrhythmias

(VAs)

in

patients

without

cardiac arrhythmias showing irreversible tissue injury

cardiomyopathies (1). Catheter ablation has been

at temperatures of $50 C (3). Nevertheless, tissue

described as an effective treatment for these arrhyth-

disruption during RF ablation and steam pops are po-

mias. Radiofrequency (RF) delivery at these regions

tential causes of myocardial damage and a major

From the *Cardiovascular Institute of Buenos Aires (ICBA), Ciudad Autonoma de Buenos Aires, Buenos Aires, Argentina; and the yCentre Hospitalaire Universitaire de Sherbrooke (CHUS), Sherbrooke, Quebec, Canada. The authors have reported that they have no relationships relevant to the contents of this paper to disclose. Manuscript received May 13, 2015; revised manuscript received July 27, 2015, accepted July 31, 2015.

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Cryoablation for Ventricular Arrhythmias

ABBREVIATIONS

concern

Acute

advanced toward the right atrium (home view) and

AND ACRONYMS

mitral valve dysfunction due to PM injury is

RVOT sequentially. The ICE 2-dimensional catheter

a major concern while delivering RF energy

was positioned toward the RVOT and rotated in a

at PMs, although it has not yet been reported.

clockwise fashion to visualize the different LV

3D = 3-dimensional ECG = electrocardiogram

during

procedures

(4–7).

This is the first case series describing the

ICE = intracardiac echocardiography

IQR = interquartile range LV = left ventricle MDCT = multidetector computed tomography

structures.

use of cryoenergy for the treatment of ven-

By ICE direct visualization, we attributed 3 seg-

tricular tachycardia (VT) and premature ven-

ments to each PM to specify the origin and catheter

tricular contractions (PVCs) localized at the

position of the VAs: the apex, which corresponded

PMs of the LV, with the aid of intracardiac

with the most distal third of the PM, at the point of

echocardiography (ICE) and image integration.

insertion of the chords; the body, representing the intermediate third of the PM; and the proximal third

PMPM = posteromedial

METHODS

papillary muscle

of the PM, in contact with the LV wall, was considered the PMs base (Figure 1). Continuous ICE monitoring

PM = papillary muscle PP = Purkinje potentials PVC = premature ventricular complex

PVC = premature ventricular

The study population was drawn from 71

was performed for possible complications. Special

consecutive patients (49% male; median age,

attention was paid to PM injury and mitral valve

42 years [range: 28 to 54 years]) with symp-

dysfunction. Catheter position, contact, and stability

tomatic idiopathic sustained VT (n ¼ 9),

were also assessed through this method.

contraction

nonsustained VT (n ¼ 18), or PVC (n ¼ 44)

Multidetector computed tomography (MDCT) was

RF = radiofrequency

referred for catheter ablation to the Buenos

performed with a 64-detector Phillips Brilliance

Aires Cardiovascular Institute (Buenos Aires,

(Phillips Medical Systems, Best, the Netherlands) <15

Argentina) between January 2014 and April

days before catheter ablation. No ionic contrast

outflow tract

2015. The sites of origin of VAs included the

material was used (Optiray 350 mg/ml) and scanning

VAs = ventricular arrhythmias

right ventricular (RV) outflow tract (RVOT) in

was performed with a collimated slice thickness of

45 patients (63%), aortic root in 3 (4%), aor-

0.9 mm. Prospective electrocardiographic gating at

tomitral continuity in 5 (7%), mitral annulus

75% of the R-R interval was performed to eliminate

in 1 (1.5%), fascicles of the left bundle branch in 2

cardiac motion artifacts and reduce radiation dose.

(3%), anterolateral PM in 1 (1.5%), posteromedial

Integration of the cardiac MDCT image into the

papillary muscle (PMPM) in 10 (14%), and other sites

mapping system was performed.

RV = right ventricular RVOT = right ventricular

VT = ventricular tachycardia

in 3 (4%). This case series retrospectively included 10 patients with symptomatic and drug-refractory VAs originated at the PMs of the LV. Each patient gave written informed consent, and all antiarrhythmic drugs were discontinued for $5 half-lives before the study.

SEGMENTATION. Raw MDCT data were loaded into

the 3D electroanatomic system equipped with an image integration module (EnSite Velocity 3.0.1.1, St. Jude Medical Inc.). The segmentation process has been described elsewhere (8). The accuracy of this technique has been validated in previous studies

SEE PAGE 517

(9,10). The 3D structures of the LV were segmented. The 3D reconstructed LV and PM images were then

All patients underwent electrophysiological study

registered.

and catheter ablation. Catheter ablation was per-

REGISTRATION. Previously

formed under conscious sedation. For mapping and

(MDCT images) were aligned with the NavX system.

pacing, standard multi-electrode catheters were

Fiducial point pairs were created by an operator

placed in the coronary sinus, His bundle region, and

identifying and selecting locations on the NavX sys-

RV apex through the right femoral vein. An 8-mm

tem, and matching these on the MDCT model to the

acquired

3D

model

cryoablation catheter was advanced into the LV

same anatomic area. Matching of the fiducial points

through a transeptal and transmitral approach.

created on the NavX system was confirmed by ICE.

Arrhythmia induction was attempted by programmed

Fiduciary points from the base, body, and apex of the

electrical stimulation from the RV apex, RVOT, and

PMs were obtained and matched to the MDCT images

coronary sinus, with 1, 2, and 3 extrastimuli intro-

during shell construction (11). Figure 2 shows the final

duced after an 8-beat drive train, if necessary, with

3D anatomy obtained from the 3D reconstructed

the addition of an isoproterenol infusion. Intravenous

MDCT images after fusing them with the fiduciary

heparin was administered to maintain an activated

points obtained by ICE imaging.

clotting time of $300 s.

MAPPING

AND

CRYOABLATION. Activation

and

IMAGING. A 2-dimensional ICE prove (ViewFlex,

pacemapping was performed in all cases to identify

St. Jude Medical Inc., St. Paul, Minnesota) was

the site of the VA origin. The VAs electrograms to QRS

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Cryoablation for Ventricular Arrhythmias

F I G U R E 1 Assessing Catheter Position and Complications by Intracardiac Echocardiography

Cryocatheter placed at the apex (A), body (B), and base (C) of the posteromedial papillary muscle (PMPM). Cryocatheter placed at the apex (D), body (E), and base (F) of the anterolateral papillary muscle (ALPM). The ablation catheter is accessing the left ventricle through transmitral approach, towards the PMPM (G). Color Doppler of mitral valve flow showing no mitral regurgitation during cryoenergy delivery at the PMs (H).

interval was measured systematically (Figure 3).

terminated, and the catheter was repositioned. The

Electroanatomic 3D LV anatomic shells and activation

endpoint of the catheter ablation was the elimination

maps (EnSite Velocity, St. Jude Medical Inc.) of the LV

and noninducibility of VAs during isoproterenol

were obtained in all cases. No voltage maps were

infusion (2 to 10 m g/min) and burst pacing from the

performed. Pace mapping was performed at a pacing

RV to a cycle length as short as 300 ms. Procedural

cycle of 600 milliseconds and stimulus amplitude of

success was defined as abolition of inducible or

1 mA greater than the late diastolic threshold. We

spontaneous ventricular arrhythmia.

used 2 different pacemapping criteria: 1) paced QRS match of $11/12 leads; and 2) a pace mapping score determined from the R/S ratio and fine notch of the QRS in the 12-lead electrocardiogram (ECG) as previously reported (perfect pace mapping ¼ 24 points) (12). Notching was defined as a high frequency component of either the upstroke or the downstroke of the QRS at any lead. Cryoenergy was delivered at myocardial sites exhibiting the earliest bipolar activity or local unipolar QS pattern or at a Purkinje network with an

ECG ANALYSIS. Twelve-lead ECGs during the VAs

and pace mapping were recorded digitally at a sweep speed of 100 to 200 mm/s in all patients for offline analysis. The QRS duration and axis, notching, and R/S transition in precordial leads were measured with electronic calipers (EP-WorkMate 4.2 System, St. Jude Medical Inc.) by 2 experienced investigators blinded to the site of the origin. If there were discrepancies between those results, they were adjudicated by a third investigator.

early activity preceding the QRS onset for $25 ms

FOLLOW-UP. All patients were monitored continu-

during the VA (Figure 4) at pace mapping areas

ously for 24 h after the ablation procedure. Electro-

exhibiting QRS match of $11/12 or a pace mapping

cardiography and echocardiography were performed

score of $20. If pacemapping showed a QRS match

before discharge in all patients. Follow-up information

of $11/12 and a score of #20 due to discrepancies in

was obtained from direct evaluation in our arrhythmia

fine notch matching, cryoenergy was delivered any-

clinic. Patients underwent 24-h Holter monitoring and

way. Focal ablation was performed with an 8-mm

baseline electrocardiography before and 1, 3, and 6

cryoablation catheter (Freezor MAX 3, Medtronic,

months after the procedure. Arrhythmia burden was

Inc., Minneapolis, Minnesota). When a reduction in

assessed before and after catheter ablation. All pa-

the incidence of VT or PVCs was observed cryoenergy

tients who reported symptoms underwent Holter

was delivered for up to 240 s with 2 freeze–thaw–

monitoring to document the cause of symptoms.

freeze cycles; otherwise, cryoenergy delivery was

Successful long-term catheter ablation was defined

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F I G U R E 2 Integrating CT Into Mapping Systems

the interquartile range (IQR). Categorical variables were presented as numbers and percentages.

RESULTS PATIENT CHARACTERISTICS. Ten patients under-

went PM VAs catheter ablation. The median age was 38 years (IQR: 34 to 45 years) and 70% were males. The median left ejection fraction was 55% (IQR: 55% to 58%). None of the patients presented underlying cardiomyopathy. Only 1 patient had mitral valve prolapse of the posterior leaflet with moderated regurgitation. This was the only patient exhibiting VAs at both the anterolateral and PMPM. Only 3 patients were treated with antiarrhythmic drugs before catheter ablation (Table 1). All patients were drug free after cryoablation. The population baseline characteristics are summarized in Table 1. PROCEDURAL OUTCOMES. Termination of the arrhy-

thmia was observed in all patients without further inducibility (100% procedural success rate). There were no intraoperative complications. Catheter stability was achieved in all patients. The PMPM had higher prevalence of clinical arrhythmias (100% PMPM VAs vs. 10% anterolateral PM VAs). Only 1 patient had PVCs originating at the anterolateral PM. That same patient also presented with a NSVT arising from the PMPM. The PM base was the most frequent site of origin of VAs (n ¼ 6). Pace mapping showed a $11/12 match in all treated PMs at the site of effective (A) Fusion of the MDCT and the electroanatomic mapping system allowing catheter navigation on the 3D reconstructed CT of the left atrium, left ventricle (LV), and aortic

lesion.

Purkinje

potentials

(PP)

were

observed in 6 patients. All patients who presented the

root. (B) The left atrium was removed from the screen and the LV size was magnified in

site of effective lesion at the base of the PM also

order to recognize and navigate over the ALPM (light blue) and PMPM (yellow). Both

showed PP. In those patients where PP were not

anterior and posterior leaflets of the mitral valve, along with the chordae can be observed

observed (n ¼ 4), the effective lesion site was located

in the 3D reconstructed anatomy. CT ¼ computed tomography; MDCT ¼ multidetector

at the body or apex. Total fluoroscopy time was

computed tomography; 3D ¼ 3-dimensional; other abbreviations as in Figure 1.

14 min (IQR: 9 to 17 min) and total procedure time was 124 min (IQR: 100 to 142 min). LONG-TERM OUTCOMES. Patients were seen in routine

as a significant reduction or absence of the clinical arrhythmia at 1, 3, and 6 months of follow-up. Significant reduction of the clinical arrhythmia was defined as Holter burden reduction of the clinical VA by $50% when compared with Holter recordings prior catheter ablation. No antiarrhythmic drugs were continued after catheter ablation unless VA recurred. All patients underwent echocardiography with color Doppler at discharge and 30 days after the ablation to evaluate the mitral valve, specifically the degree of mitral regurgitation.

follow-up at 1, 3, 6, and 12 months after catheter ablation (median follow-up, 6 months; IQR: 4 to 10 months). Follow-up Holter monitors were placed once for 24 h at 1, 3, and 6 months after cryoablation. All patients reported immediate improvement in symptoms at the first month of follow-up and no evidence of postprocedure complications assessed by cardiac ultrasound. Only 1 patient had recurrent symptomatic VT during the first week after the procedure and required a second catheter ablation with RF energy. One patient had PVC-induced cardiomyopathy (left ejection fraction of 45%) with 40% Holter

STATISTICAL ANALYSIS. Variables with nonnormal

burden despite flecainide treatment. After PM cryoa-

distributions were expressed as median values with

blation, Holter burden was reduced 50%, the patient

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Cryoablation for Ventricular Arrhythmias

F I G U R E 3 Image Integration and Intracardiac Recordings

(A) Visualization of the cryocatheter at the apex of the PMPM by ICE. At the bottom, 12-lead ECG during VT and intracardiac recordings. The VEGM-QRS interval is 28 ms at the effective ablation site. No Purkinje potentials were recorded at this location. (B) Same patient. Visualization of the cryocatheter at the apex of the PMPM by image integration with cardiac multidetector computed tomography. At the bottom, pace mapping at the effective ablation site at the apex of the PMPM. ECG ¼ electrocardiogram; ICE ¼ intracardiac echocardiography; VEGM-QRS ¼ interval between the earliest activation (VEGM) during the clinical arrhythmia and the QRS; VT ¼ ventricular tachycardia; other abbreviations as in Figure 1.

remained asymptomatic, and left ejection fraction

the 1-, 3-, and 6-month follow-ups (Table 2). No pa-

improved to 54% without the use of antiarrhythmic

tient required antiarrhythmic drugs after ablation.

drugs. The remaining patients had no evidence of

ECG ANALYSIS. The mean QRS duration was 146 ms

recurrent arrhythmias during Holter monitoring at

(IQR: 138 to 150 ms). VAs with an RSr pattern were

F I G U R E 4 Interruption of Sustained VT During Cryoenergy Delivery

(A) Electroanatomic 3D shell of the LV, ALPM, and PMPM. The cryocatheter is placed at the earliest V-QRS interval at the body of the PMPM, during sustained monomorphic VT. (B) Initiation of cryoenergy delivery and interruption of the ventricular tachycardia. Cryoenergy delivery generates an artifact over the cryocatheter on the NavX system, accounting for the “melt down” effect. This movement of the catheter during energy delivery is only apparent and due to ice formation at the distal electrode. The catheter remains stable during cryoenergy delivery. (C) Twelve lead ECG and high speed intracardiac recording (200 mm/s) showing a VEGM-QRS interval of 25 ms at the effective lesion site. Abbreviations as in Figure 1 to 3.

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site of origin of the VAs was at the base of the PMs.

T A B L E 1 Baseline Patient Demographics and Follow-Up

Discrepancies between pace mapping match of $11/12

Patient # Age, yrs Sex LVEF CMP AADs

VA

1

34

M

57

-

-

VT

1

12

-

-

Both exhibited perfect paced QRS match with the

2

49

M

55

-

-

VT

1

10

Yes

-

clinical VA but poor pace mapping score. This was

3

27

F

60

-

-

PVC

1

3

-

-

4

38

M

55

-

-

VT

1

7

-

-

Flec

PVC

5

37

M

45

TM

6

38

M

55

-

7

44

M

58

-

-

8

45

F

55

-

-

9

21

M

60

-

10

57

F

55

-

VAM Follow-Up (months) REC AADs CA

and pace mapping score were observed in 2 patients.

attributed to the presence of notching during pacemapping as compared with the clinical VA, account-

1

6

-

-

2

6

-

-

NSVT

1

6

-

-

can be identified at the effective ablation site. Good

NSVT

1

7

-

-

et al. (13) reported the presence of PP in all treated PM

-

VT

1

12

-

-

VAs, whereas Doppalapudi et al. (14) did not identify

Sot

NSVT

1

4

-

-

PP at the effective ablation site. No information about

Diltz NSVT

AADs ¼ antiarrhythmic drugs used before catheter ablation; AADs CA ¼ antiarrhythmic drugs used after catheter ablation; CMP ¼ cardiomyopathy; Diltz ¼ diltiazem; Flec ¼ flecainide; Isch ¼ ischemic; LVEF ¼ left ejection fraction; NSVT ¼ nonsustained ventricular tachycardia; PVC ¼ premature ventricular contraction; Rec ¼ recurrence of the clinical arrhythmia after catheter ablation; Sot ¼ sotalol; TM ¼ tachycardiomyopathy; VA ¼ clinical presentation of the ventricular arrhythmia; VAM ¼ number of morphologies of the clinical arrhythmia; VT ¼ ventricular tachycardia.

ing for a lower score. It is controversial weather PPs

the specific site of VA origin at the PM (apex, body, or base) was provided in these studies. In our study, PP were seen in 60% of VAs, and only in those with VAs originating at the base of the PM. This finding may suggest that the Purkinje network may not extend further from the base of the PM, hence the absence of

more frequent at the base of PM (57.1%, n ¼ 4), whereas an rSR pattern was more frequent at the body (66.7%; n ¼ 2). There was no correlation between early or late precordial RS transition and the site of effective lesion at the base, body or apex of the PM. Electrocardiographic and procedural characteristics are summed up in Table 3.

PP at the body or apex. It has been reported that ablation at sites with excellent pace mapping is usually unsuccessful (15), suggesting that the site of VA origin may be located away from the breakout site, which can be recognized as the site with the best pace map. In our case series, cryoablation at sites with excellent pace mapping was always successful. It has also been reported that almost one-half of these

DISCUSSION

patients present multiple VT morphologies (15),

MAIN FINDINGS. This study demonstrates that cry-

sites. The patients included in this study presented

which may be due to the presence of multiple exit

oablation has a favorable success rate and low

only single VAs morphology.

recurrence rate for ablation of ventricular arrhyth-

RF ENERGY. Because of ventricular thickness, higher

mias arising from the LV PMs. Catheter stability was

power settings are often required for LV catheter

achieved in all cases due to cryocatheter adherence to

ablation when using RF energy (16). Catheter irriga-

the myocardium, which is a potential advantage over

tion is often used to cool the ablation electrode such

the use of RF ablation. Mitral valve regurgitation or

that more power can be delivered without being

PM injury or rupture was not observed. The PMPM

limited by the formation of thrombus at the catheter–

was the most arrhythmogenic and the most frequent

tissue interface (17). Excessive intramyocardial heating can produce steam formation and abrupt volume expansion, which may be audible as steam pops (18).

T A B L E 2 Holter Burden of Clinical Arrhythmias During Follow-Up

Pops are capable of causing deep tissue tears, and

HB-PCA

HB-1 Mo

HB-3 Mo

HB-6 Mo

patients with ventricular perforations are more likely

1

VT

0% VT

0% VT

0% VT

to require surgical repair (19). A potential complica-

2

VT

0% VT

0% VT

0% VT

tion during RF ablation is mitral valve dysfunction by

3

10% PVC

2% PVC

1% PVC

-

injury or rupture of the PMs, especially when using

4

VT

0% VT

0% VT

0% VT

5

40% PVC

19% PVC

9% PVC

12% PVC

6

32% NSVT

4% PVC

1% PVC

2% PVC

7

NSVT

0% NSVT

0% NSVT

0% NSVT

8

2% NSVT

0% NSVT

0% NSVT

0% NSVT

9

VT

0% VT

0% VT

% VT

10

20% NSVT

0.6% PVC

0% NSVT

-

Patient #

HB-1 Mo ¼ Holter burden of the clinical arrhythmia at 1 month after cryoablation; HB-3 Mo ¼ at 3 months; HB-6 Mo ¼ at 6 months; HB PCA ¼ Holter burden of the clinical arrhythmia previous to cryoablation; other abbreviations as in Table 1.

irrigated tip ablation catheters, although this has not yet been reported. CRYOENERGY. Cryoablation has been reported as a

safe alternative for catheter ablation in idiopathic VT arising from the RVOT, aortic cusps, and epicardium (20,21). Cryothermal safety profile is attributed to the mechanism of tissue destruction (22). Histology of chronic lesions shows well-demarcated lesions with minimal tissue disruption and preserved underlying

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T A B L E 3 Electrocardiographic and Procedural Characteristics

Patient #

QRSP

Axis

Notch

RS

QRSD (ms)

PM

Induction

PP

VEGM-QRS (ms)

EL

PMS

NCL

FT (min)

PT (min)

1

rSR

S

-

V4

142

P

Is

-

30

Body

24

4

15

142

2

RSR

S

-

V3

148

P

PS

Yes

34

Base

24

4

17

135

3

rSR

S

Yes

V5

126

P

Is

Yes

32

Base

22

3

12

124

4

RSr

S

-

V4

156

P

Sp

Yes

33

Base

19

4

15

142

5

RSr

S

Yes

V3

160

P

Sp

-

31

Body

25

4

14

123

6

RSr

S

Yes

V5

146

P

Is

Yes

30

Base

24

3

18

168

6

RSr

I

Yes

V5

135

A

Is

-

35

Apex

22

2

18

168

7

rSR

S

-

V5

142

P

Is, PS

-

25

Body

18

4

10

90

8

RSr

S

-

V4

138

P

Is

-

31

Apex

23

2

9

100

9

RSr

S

Yes

V6

150

P

Is, PS

Yes

45

Base

23

3

9

95

10

rSR

S

Yes

V5

148

P

Is

Yes

37

Base

24

4

7

115

A ¼ anterolateral; Axis ¼ QRS electrical axis; EL ¼ location of the effective lesion site; FT ¼ fluoroscopy time; I ¼ inferior; Induction ¼ induction of the clinical arrhythmia; Is ¼ isoproterenol; NCL ¼ number of cryolesions; P ¼ posteromedial; PM ¼ papillary muscle; PMS ¼ pace mapping score; PP ¼ presence of Purkinje potentials; PS ¼ programmed stimulation; PT ¼ procedural time; QRSD ¼ duration of the QRS interval in milliseconds; QRSP ¼ QRS morphology; RS ¼ precordial transition from R to S; S ¼ superior; Sp ¼ spontaneous; VEGM-QRS ¼ interval between the earliest activation (VEGM) during the clinical arrhythmia and the QRS, at the effective lesion site.

architecture. Catheter stabilization during ablation

Recently, Latchamsetty et al. (31) showed that PVCs

at the PMs is a major consideration. Stabilization

originating in the PMs were associated with low RF

is achieved due to catheter-tissue adherence after

ablation success rates (60%), high recurrence rate,

reaching temperatures of 80 C.

long procedure times, and the delivery of large

IMAGING TECHNIQUES. Cardiac multi-imaging inte-

gration constitutes an important tool for PM ablation, providing an accurate anatomy, and aiding catheter manipulation during the ablation procedure. ICE

amounts of RF energy. Our case series shows the safety and feasibility of catheter cryoablation in arrhythmias from the LV PMs, providing catheter adherence and preservation of ultrastructural integrity.

represents a key element in our study guiding the

STUDY LIMITATIONS. The small number of patients

fusion process between cardiac MDCT images and

in our report does not allow for any outcome to be

electroanatomic mapping systems, allowing for real-

statistically representative. This is due in part to the

time visualization. This permits navigation on a 3D

fact that patients with PM arrhythmias represent a

model of the LV with precise detail on the PMs,

small subset of subjects referred for ablation, making

chordae, and mitral valve leaflets. Catheter position,

them less suitable for larger studies. Voltage mapping

stability, lesion formation, and continuous moni-

has not been performed in any of the patients.

toring for complications are achieved through these

This is not a comparative study so no comparison

methods. Fascicular VT represents the most common

can be performed with RF catheter ablation, which

form of idiopathic left ventricular arrhythmia. The

is the most used technique in this subset of patients.

12-lead ECG for arrhythmia arising at the LV PM is similar to that of fascicular VTs (23), so as the fluo-

CONCLUSIONS

roscopic ablation catheter position (24). The differventricular

This case series demonstrated that catheter cryoa-

arrhythmia by ECG analysis only is almost impossible.

blation for ventricular arrhythmias originating at the

The advent of ICE has allowed us to recognize and

PMs of the LV is technically feasible, safe and effec-

differentiate PM VT (25). The arrhythmogenic mech-

tive. Catheter stability was always achieved with

anism; this arrhythmia has been described as focal.

cryoablation.

Some authors even wonder if PM VT could be a variant

ACKNOWLEDGMENTS The authors acknowledge the

of fascicular VT, although the last one depends on

Cardiovascular Institute of Buenos Aires (ICBA) and

reentry maintained by an excitable gap between a

Alberto Alves de Lima, MD PhD, and Diego Conde,

slow pathway (P1) and the left bundle branch (P2) (26).

MD.

ential

diagnosis

for

both

forms

of

Monomorphic ventricular PVCs originating from the PMs have been found to initiate ventricular fibrillation

REPRINT REQUESTS AND CORRESPONDENCE TO:

or polymorphic VT. Catheter ablation of PVC-triggered

Dr. Santiago Rivera, Cardiovascular Institute of

ventricular fibrillation polymorphic VT is highly suc-

Buenos Aires, Ciudad Autonoma de Buenos Aires,

cessful (27,28). Ventricular arrhythmias from the RV

6302 Avenue Libertador, Buenos Aires C1428DCO,

PMs have been described in only 2 studies (29,30).

Argentina. E-mail: [email protected].

515

516

Rivera et al.

JACC: CLINICAL ELECTROPHYSIOLOGY VOL. 1, NO. 6, 2015 DECEMBER 2015:509–16

Cryoablation for Ventricular Arrhythmias

PERSPECTIVES COMPETENCY IN MEDICAL KNOWLEDGE: Catheter

TRANSLATIONAL OUTLOOK: Although this is a small

cryoablation can be used to eliminate ventricular ar-

case series with a relatively short follow-up, longer term

rhythmias originating at the PMs of the LV with high

studies may provide further data regarding long-term

success rates and without complications. Imaging tech-

benefits of cryoablation.

niques are diagnostic and therapeutic corner stones in these patients.

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frequency catheter ablation as a cure for idiopathic tachycardia of both left and right ventricular origin. J Am Coll Cardiol 1994;23:1333–41.

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left main coronary artery: a case series. Heart Rhythm 2014;11:34–8. 22. Lemola K, Dubuc M, Khairy P. Transcatheter cryoablation part II: clinical utility. Pacing Clin Electrophysiol 2008;31:235–44. 23. Nogami A, Naito S, Tada H, et al. Verapamilsensitive left anterior fascicular ventricular tachycardia: Results of radiofrequency ablation in six patients. J Cardiovasc Electrophysiol 1998;9: 1269–78. 24. Kawamura M, Hsu JC, Vedantham V, et al. Clinical and electrocardiographic characteristics of idiopathic ventricular arrhythmias with right bundle branch block and superior axis: Comparison of apical crux area and posterior septal left ventricle. Heart Rhythm 2015;12:1137–44. 25. Bunch TJ, Weiss JP, Crandall BG, et al. Image integration using intracardiac ultrasound and 3D reconstruction for scar mapping and ablation of ventricular tachycardia. J Cardiovasc Electrophysiol 2010;21:678–84. 26. Madhavan M, Asirvatham SJ. The fourth dimension: endocavitary ventricular tachycardia. Circ Arrhythm Electrophysiol 2010;3:302–4. 27. Van Herendael H, Zado ES, Haqqani H, et al. Catheter ablation of ventricular fibrillation: importance of left ventricular outflow tract and papillary muscle triggers. Heart Rhythm 2014;11:566–73. 28. Santoro F, Di Biase L, Hranitzky P, et al. Ventricular fibrillation triggered by PVCs from papillary muscles: clinical features and ablation. J Cardiovasc Electrophysiol 2014;25:1158–64. 29. Santoro F, Di Biase L, Hranitzky P, et al. Ventricular tachycardia originating from the septal papillary muscle of the right ventricle: electrocardiographic and electrophysiological characteristics. J Cardiovasc Electrophysiol 2015;26:145–50. 30. Crawford T, Mueller G, Good E, et al. Ventricular arrhythmias originating from the papillary muscles in the right ventricle. Heart Rhythm 2010; 7:725–30. 31. Latchamsetty R, Yokokawa M, Morady F, et al. Multicenter outcomes for catheter ablation of idiopathic premature ventricular complexes. J Am Coll Cardiol EP 2015;1:116–23.

21. McDonnell K, Rhee E, Srivathsan K, Su W.

KEY WORDS cardiac multidetector tomography, catheter ablation, cryoablation,

Novel utility of cryoablation for ventricular arrhythmias arising from the left aortic cusp near the

intracardiac echocardiography, ventricular arrhythmia