Intracardiac Echocardiography2

8/3/2019 Intracardiac Echocardiography2

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Intracardiac Echocardiography guided Pulmonary Vein

Isolation in Patients with Paroxysmal Atrial Fibrillation:

Impact on Outcome and Complications

Sherif H. Zaky MD, Mostafa Alrefaee MD, Salah Atta MD, Hesham Hegazy MD,

Jehan Abd Alhalim,MD, Laila Al-Hoty, NSc, Mahmood S Nsc.

From Babtain Cardiac Center, Dammam , Saudi Arabia

Background: Pulmonary (PV) antrum ablation is considered the proper modality for

electrical isolation of PV (PVI) and treatment of drug refractory paroxysmal atrial

fibrillation (PAF). Conventional PVI using fluoroscopy alone can not guarantee neither

the exact antral site of ablation nor the limit for radiofrequency power titration . The

objective of this study was to assess the role of intracardiac echocardiography (ICE) forvisualization & proper ablation of the PV antrum and its effect on both short-term success

and incidence of complications in patients undergoing PVI for treatment of PAF.

Patients and Methods: Thirty one patients (21 males, mean age 41.3+5.1 ys.) underwent

PVI for treatment of PAF. Each patient underwent antral isolation of all PVs using an 8-

mm tip or irrigated tip ablation catheters. PVI was performed using electrophysiologic

circular mapping (CM) alone (group1, 14 patients), CM and ICE (group 2, 17 patients)

with titration of radiofrequency energy based on visualization of microbubble by ICE in

case of group 2 or impedance rise in case of groop1. Pulsed wave Doppler was done

before and after ablation of PVs in group 2 patients to assess for PV stenosis.

Results: There was a significant difference between both groups in terms of mean

fluoroscopy time (85 + 32 in group 1 vs.61 + 44 min. in group 2, p< 0.05) and meannumber of RF lesions per vein for complete isolation (15.5 + 2 vs. 8.5 + 2, P< 0.05)

respectively. After a mean follow-up time of 12.5 + 2.3 months, 35% (5/14) of patients in

groups 1, and 17.5% (3/17) experienced recurrence of AF, respectively (P< 0.05).

Moreover, no one in group 2 patients experienced severe (>70%) PV stenosis

postoperatively. Whereas, severe PV stenosis with dyspnea was documented in 3 out of

14 (3.5%) patients in group 1. No embolic events occurred in either groups.

Conclusion: Use of ICE improves the outcome of PVI, reduces both fluoroscopy time

and number of lesions per pulmonary vein. Power adjustment guided by direct

visualization of microbubble formation reduces the lesions sufficient for complete PVI

and thus risk of PV stenosis and improves short term cure.

Key words : atrial fibrillation ablation pulmonary vein isolation - intracardiac echo

(ICE).

Introduction

Radiofrequency (RF) catheter ablation has become first-line therapy for patients with

drug-refractory atrial fibrillation (AF).(1,2) An early ablation strategy consisted of focal

ablation of triggers inside the pulmonary veins (PVs) (3). To prevent complications of PV


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stenosis, this method was modified to electrical isolation of the PV by segmental isolation

at the ostium.(4,5) Strategies evolved to include wide area encircling of the PV antrum

using sophisticated three-dimensional mapping systems that could reconstruct atrial

anatomy for guiding ablation and limiting fluoroscopy time.(6,7)

Phased-array intracardiac echocardiography has been shown to be helpful in definingright and left atrial structures most importantly the exact antrum of pulmonary veins. (8).

In interventional electrophysiology procedures, effective ablation of cardiac tissue is

dependent on the extent of contact between the ablation catheter tip and the endocardial

surface.(9).

We hypothesized that intracardiac echocardiography (ICE) would improve the success

rates and minimize complications associated with PV isolation procedures by allowing

real-time monitoring of both PV ostium and radiofrequency (RF) energy delivery. The

purpose of this study was to compare the efficacy and safety of PV isolation using

circular mapping alone versus circular mapping with intracardiac echo (ICE) guidance in

patients with paroxysmal AF and to assess the utility of ICE-detected microbubbles as aguide to RF titration.

Methods

Patients

Between December 2006 and june 2008, 31 consecutive patients were referred to our

laboratory for ablation of AF. All patients signed a written informed consent .

Antiarrhythmic drugs were discontinued at least 5 half-lives before the ablation

procedure. Immediately before the procedure, transesophageal echocardiography was

performed in all study patients to rule out any left atrial masses. Paroxysmal AF was

defined as self-terminating episodes lasting < 7 days. We excluded Persistent AF whichwas considered when AF episodes lasted longer than 7 days and when pharmacological

or DC cardioversion was needed to restore sinus rhythm and permanent AF defined as

episodes failing cardioversion (1)

Anaethesia workup : All patients were fasting before procedure, transcutaneous

cardioversion/defiberllation pads placed prior to induction. All patients were monitored

by12 leads ECG , invasive, arterial blood pressure and pulse oximeter monitoring .Allpatients but 8 (4 in each group) receivedpropofol/fentanyl induction of general

anesthesia with laryngeal mask airway and spontaneous breathing of 60% oxygen in air

supplemented with sevoflurane inhalation to deepen the anesthesia. In 8 patients

laryngeal mask airway was not tolerated and required endotracheal intubation, muscle

relaxation using atracurium and were mechanically ventilated , all patients were safely

extubated and stayed under full monitored observation in the recovery area for at least

one hour before shifting to the cardiac wards.

Circular MappingGuided PV Isolation

In all patients of both groups a decapolar coronary sinus catheter was inserted via rightfemoral sheath. The left atrium was instrumented using an 8 F sheath (Swartz SR0,


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St.Jude) via Rt.femoral vein via a trans-septal puncture if no patent foramen oval was

found. Pulmonary vein ostia were localized by performing PV angiogram. All pulmonary

veins were canulated with the sheath or an inner 6 F NIH catheter where PV angiography

during adenosine-induced (range, 12 to 24 mg) asystole was performed. The PV

angiogram was obtained in both 45-degree left anterior oblique and 30-degree right

anterior oblique views (LAO). Twenty to 25 mL of manually injected contrast was usedfor each angiogram. A guide wire (0.035) was then advanced to the left atrium through

the trans-septal sheath then sheath withdrawn to Rt.atrium. An ablation catheter was

passed through a third sheath in Rt.femoral vein. The ablation catheter was advanced to

the left atrium through same transeptal puncture guided by the wire and fluoroscopy in

LAO view. The sheath was advanced to the left atrium again and wire replaced by a

deflectable 3uperior3 circumferential catheter (LASSO) with deflectable ring diameterranging from 15 to 25 mm.

The Lasso catheter was positioned at the pulmonary vein ostia under fluoroscopy

guidance only in group 1 patients. Electrical mapping of PV and left atrial potentials was

used to apply proximal lesions guided by PV potentials proximally recorded by Lassocatheter in the antrum of PV as defined by angiogram (At junction with appendage edge

in case of left PVs, or lateral border of ineratrial septum in case of right PVs.).

Intracardiac Echocardiogram and Circular

MappingGuided PV Isolation

In group 2 patients (17 patients), a 9 F, deflectable, 64 element phased-array ultrasound

imaging ICEcatheter ( (ViewFlex, EP-med systems, New Jersy) was introduced

through a 10-Fr sheath via the left femoral vein additional to the previously described

three catheters.

The ICE catheter with bidrodirectional tip deflectability was introducedand,

fluoroscopically positioned in the right atrium. The ICE catheter was connected to an

ultrasound platform (Viewmate system). The electrophysiologist performing the mapping

and ablation procedure optimized the ICE images. The trans-septal puncture was

performed under ICE guidance to visualize the intra-atrial septum in group 2 patients. All

PV ostia were defined after transseptal puncture .

Pulsed-wave 3uperio flow velocities of all PVs were recorded before and after ablation

to assess PV narrowing, and ablation at the PV ostium was aborted when the PV diastolic

flow velocity exceeded 1.5 m/sec..

In group 2 patients, RF energy was delivered using the same ablation catheters applyingthe ablation protocol described above for group 1 patients.

Microbubbles Monitoring With Intracardiac Echocardiogram

In group 2, ICE was used not only to ensure circular mapping catheter positioning

(Figure 1) and appropriate site of energy delivery but also to guide energy titration by

monitoring microbubble formation. Two types of bubble patterns were seen with ICE: (1)

scattered microbubble (type 1), reflecting early tissue overheating (Figure 2); and (2)

brisk shower of dense microbubbles (type 2), reflecting impending impedance rise

(Figure 3).


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Protocol of RF ablation.

Ablation catheters used were either 8 mm Tip , (Blazer, EP Technologies) or Irrigated

tip 4 mm thermocool catheter, (Bisense Webster ). A 35C target temperature was

chosen for RF energy delivery through the cooled-tip catheter. A 50C was set as target

in case of 8 mm tip catheters and in both a Stockert RF generator (Biosense Webster) wasused. Although we applied the same energy delivery protocol for group 1 and 2 patients,

power was titrated upward (5-watt increments), watching for formation of type 1 bubbles

only in the latter group while watching for impedance rise only in group 1. When the type

1 microbubble pattern was seen, energy was titrated down by 5-watt decrements until

microbubble generation subsided. Energy delivery was terminated when type 2 bubbles

were seen.

Definition of Successful PV Isolation

PV isolation was considered acutely successful after abolition of all ostial PV potentials

recorded on the circular mapping catheter during sinus rhythm or coronary sinus and

right atrial pacing

Fig. 1 Circular mapping catheter (Lasso) positioned at the ostium of the left superiorpulmonary vein (LSPV(

Fig.2 Type 2 ( Localized) microbubbles during ablation at the ostium of the right 4superior PV(RSPV). The Lasso catheter (arrows) is placed at the ostium of the vein


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Fig.3 Shower of dense microbubbles (type 2 bubbles) extending to the left atrial cavity observedduring radiofrequency delivery at the ostium of the right superior pulmonary vein (RSPV).

Fig.4Transeptal puncture under ICE guidance.( arrow at needle tip puncturing the inter

atrial septum) LA: left atrium, RA right atrium.


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During the procedure, systemic anticoagulation was achieved with

intravenous heparin for all patients. After a loading dose of100 U/kg, a

standard heparin infusion of10 U/kg/hour was initiated. Activated clotting

times (ACT) was checked at 10- to 15-minute intervals until therapeutic

anticoagulation is achieved and then at 30 minute intervals during the case.

The lower level of anticoagulation should be maintained at an ACT of at

least 250350 seconds throughout the procedure.

Statistical Analysis

Continuous variables are expressed as meanSD. Continuous variables were compared

by Students ttest. Differences among groups of continuous variables were determined

by ANOVA. Categorical variables were compared by X2 analysis or with Fishers exacttest.

Follow-Up

Patients were discharged home the day after ablation. All patients were discharged on

oral anticoagulation with warfarin (keeping INR at range 2.5-3.0) and one antiarrhythmic

drug (either propaphenone or Amiodarone) for three months.Patients were also

monitored with Holter recording before discharge and at 3- and 6-month follow-up.

Follow-up was scheduled at 1, 3, 6, and 12 months after ablation. After 3 months,

anticoagulation andantiarrhythmic drug was stopped unless patients experiencedrecurrence of AF. For analysis, recurrence of AF was defined as AF occurring 8 or more

weeks after the procedure.

Table 1 Patients' Demographics

Group 2

With ICE((

Group 1

)Without ICE(

10/711/4No. patients (male/female(

40.7+1.943.1+2.3Age (ys(.

3.1+1.22.6+1.8Duration of AF, y

3/172/14SHD


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4.3+0.5

54+7

4.2+0.6

53+11

LA size, cm

Ejection fraction,,%

SHD : structural heart disease LA : left atrium

Results :

Thirty one consecutive patients were referred to our laboratory for

ablation of symptomatic paroxysmal AF (21 males, mean age 41.3+5.1

ys.).Structural heart disease was present in 5 patiens (16%). The demographics of

the study population are given in Table 1. There was no significant difference

between both groups as regards age, gender, duration of AF, LA size, use of

AAD, or presence of Structural heart disease

Pulmonary vein isolation :

A total of 112 PVs in 31 patients were mapped and successfully isolated. A common PV

ostium was found in 6 cases ( 3 pts on the right PVs (10.5%) and in 10.5% of the left PVs(3 of 31). A mean of 10.5 + 2 RF lesions (range 6 21 lesions) per PV were delivered to

achieve complete isolation. In group 1 pts a mean of 15.5 + 2 lesions per vein were

given.

Table 2 depicts the acute results in both groups. It was evident that there was a significant

difference in terms of fluoroscopy time (85 + 32min. in group 1 Vs. 61 + 44 min. in

group2, p


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Recurrence : As in Table 2 which demonstrates follow-up results, after a mean follow up

period of 12.6 + 0.5 months , 8 out of the 31 studied patients ( 26%) experienced

recurrence . The recurrence rate was higher in group 1 patients , 5 out of 14 ( 35%) in

comparison to 3 out of 17 in ICE guided ablation group 2 (17.5%) ( P < 0.05).

Complications included : one case with tamponade (group 1), 4 had significant PV-

stenosis (> 70%) detected by angiography at end of procedure (3 in group1). PV stenosistended to be higher in group 1 than group 2 although not statistically significant.

A B

Fig. 5 Pulmonary vein angiography ( RSPV) before ( A) and at end of procedure(B(

TABLE 2. Pulmonary Vein Isolation and Follow-Up Results

P.

Group 2

)With ICE(

No.= 17

Group 1

)Without ICE(

No.= 14

NS63

)17/15/17/14(

49

)14/11/14/10(

No. isolated PVs,(LSPV/LIPV/RSPV/RIPV)

NS1.9+0.41.8+0.5AAD

NS198+72261 + 54Procedure time, min

>0.0561+4485+32Fluoroscopy time, min

>0.058.5+215.5 + 2Mean No. RF lesions/PV

NS10+513+4Follow-up, months

RSPV


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>0.053/17)17.5%(5/14)35%(Recurrence of AF

NS2/17)11.5%(4/14)28%(Complications

ICE indicates intracardiac echo; PV, pulmonary veins; RSPV, right superior pulmonary vein; RIPV, right inferiorpulmonary vein; LSPV, left superior pulmonary vein; LIPV, left inferior pulmonary vein; LA, left atrium; and AAD,

antiarrhythmic drug

Fig.6 Termination of an AF paroxysm during RF ablation of right superior pulmonary

vein(RSPV.(

A

B


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C

Fig. 7 Left superior pulmonary vein (lspv) isolation. A) before isolation under coronary

sinus pacing B) start of conduction block between atrial and PV potentials C) after

complete isolation note disappearance of PV potentials.

Discussion

Our study despite limited number of patients, proves that ICE-guided pulmonary vein

isolation is more effective than angiography-guided circular mapping. In addition,

monitoring of energy delivery using ICE additionally improved long-term success and

was associated with decreased risk of complications.

Circular mappingguided PV isolation for treatment of AF has been reported to beeffective and feasible.(10,11).The superiority of ICE-guided PV isolation compared with

angiography-guided isolation using circular mapping could be explained by 2 factors.

First, it appeared that angiography-based placement of the circular mapping catheter is

less accurate than ICE-assisted positioning. True ostial PV isolation requires abolition of

all PV potentials that extend to the PV antrum proximal to the tube-like portion of the

vein. Electrical mapping of the sleeves using the circular catheter and direct visualization

of the PV ostium (Figure 1) were enhanced by ICE.

Second, the poor contact between the ablation catheter tip and the endocardial surface

reduces heat transfer to the tissue and allows convective heat loss into the circulating

blood.(12,13). Diminished heat delivery to the PV ostial tissue may result in increased

power output, inefficient lesion formation, and increased risk of coagulum formation.Kalman et al (14) reported that less than 50% of fluoroscopically guided RF lesions were

delivered with good perpendicular contact.

Ensuring stability and proper ablation catheter tip tissue contact using ICE might have

played an important role in the cure of AF and in the development of severe PV stenosis

in our study patients.

Mangrum et al(15) reported their experience using radial cross-sectional intracardiac

echocardiography to guide anatomically based ostial PV isolation and reported a

recurrence rate of 36% after 13+7 months of follow-up in patients with paroxysmal AF.In our study population, all PVs were isolated, whereas Mangrum et al isolated only PVs

triggering APCs and AF during the procedur, this might explain our higher success rate

in group 2 patients (17.5 %recurrence) in a comparable period of follow up.


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Monitoring of Energy Delivery : Radiofrequency energy is conventionally delivered

using temperature, power, and impedance monitoring. Energy delivery is typically

terminated after approaching programmedablation time or after a sudden increase in

impedance that suggests excessive tissue heating. Increase in impedance has been

associated with increased risk of coagulum formation (12) and could be a sign of

improper lesion formation,which could create the milieu for PV stenosis. In anexperimental model, Kalman et al (14) reported that showers of microbubbles and

occasionally of coagulum preceded rises in impedance. These findings occurred with

higher frequency when the electrode-tissue contact was suboptimal. In the present study,

we noticed microbubbles in 75% of lesions in group 2 patients coinciding with less pulses

needed for complete isolation of pulmonary veins, hence presumably better and effective

lesions.

Using microbubble generation to guide energy delivery may optimize lesion formation

ensuring effective energy delivery and avoiding tissues overheating. In addition,

conventional RF energy delivery using a cooled-tip catheter is generally

limited to a target temperature of 35C. By using the ICE-guided microbubble monitoring

strategy, we increased the power based on objective findings. Of interest, prevention of adense shower of microbubbles with ICE imaging also seemed to diminish the risk of

embolic events in our patient population.

Study Limitations The limited number of patients and lack of random assignment to

treatment groups could have affected our findings. However, given the similarity among

the treatment groups in baseline characteristics, we feel this is unlikely. We had acquired

an increased experience that may have resulted in improved technical expertise at

performing circular mapping and ablation. On the other hand, the first 14 patients

undergoing circular mappingguided isolation alone were among the learning curve and

could have affected the outcomes reported.

Conclusions

This study has compared ICE-guided PV isolation to circular mappingguided PV

isolation in patients with AF. ICE-guided PV isolation seems to be was more effective

than conventional circular mappingguided PV isolation in patients with AF with better

initial outcome and less rate of recurrence.In addition to improved short term success

rates, monitoring of microbubble formation using ICE during radiofrequency energy

delivery decreased rate of complications namely thromboembolism and PV stenosis.

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Intracardiac Echocardiography2