Comparison of direct-current and radiofrequency ablation of free wall accessory atrioventricular pathways in the Wolff-Parkinson-White syndrome

Comparison of Direct-Current and Radiofrequency Ablation of Free Wall Accessory Atrioventricular Pathways in the Wolff -Parkinson-White Syndrome Shih-Ann Chen, MD, Wing-Ping Tsang, MD, Chih-Ping Hsia, MD, Der-Chih Wang, MD, Chern-En Chiang, MD, Hon-I Yeh, MD, Jaw-Wen Chen, MD, Chuen-Wang Chiou, MD, Chih-Tai Ting, MD, Chi-Woon Kong, MD, Shih-Pu Wang, MD, Benjamin N. Chiang, MD, and Mau-Song Chang, MD

To evaluate and compare the safety and efficacy of catheter-mediated direct-current (DC) or radiofrequency (RF) ablation in patients with free wall accessory atrioventricular pathways, 95 patients with free wall accessory atrioventricular pathwaymediated tachyarrhythmias underwent catheter ablation. Immediately after ablation, 27 of 30 accessory pathways (SO%) were ablated successfully with DC, but 2 of the 27 had early return of conduction and received a second ablation session; 3 of 8 (38%) and 57 of 62 (92%) accessory pathways were ablated successfully with RF through a small-tip (2 mm) and a large-tip (4 mm) electrode catheter, respectively. Complications in DC ablation included transient hypotension (2 patients) and pulmonary air-trapping (2 patients) and in RF ablation, cardiac tamponade (1 patient) and suspicious aortic dissection (1 patient); myocardial injury and proarrhythmic effects were more severe in DC ablation. Procedure and radiation exposure time were significantly longer in RF ablation (DC, 3.6 f 0.2 hours, 34 f 4 minutes; RF 4.2 f 0.5 hours, 50 f 10 minutes). This study confirms that RF ablation is associated with little morbidity and few complications, and RF ablation with a large-tip electrode catheter is an effective and relatively safe nonsurgical method for treatment of free wall accessory atrioventricular pathway-mediated tachyarrhythmias. (Am J Cardiol 1992;70:321-326)

From the Division of Cardiology, Department of Medicine, National Yang-Ming Medical College, Taipei and Taipei Veterans General Haspital-Taipei, Taipei, Taiwan, Republic of China. This study was sup ported in part by the grants from National Science Council (NSC) and Academia Sinica, Taipei, Republic of China. Manuscript received Feb ruary 3,1992; revised manuscript received April 13,1992, and accepted April 19. Address for reprints: Shih-Ann Chen, MD, Division of Cardiology, Department of Medicine, Veterans General Hospital-Taipei, 201 Set 2. Shih-Pai Road, Taipei, Taiwan, Republic of China.

F

ree wall accessory atrioventricular pathways serve as electrical links between the atrium and ventricle and are found coursing over the mitral or tricuspid annulus.’ Successful interruption of these pathways without damage to the normal conduction results in cure of Wolff-Parkinson-White syndrome.*-l4 Highenergy shocks are associated with infrequent but serious complications.5-9 Animal studies have suggested that radiofrequency (RF) energy could safely produce lesions that would be successful in ablating accessory pathways.15 The purpose of this study was to evaluate and compare the safety and efficacy of catheter ablation of free wall accessory atrioventricular pathways with direct-current (DC) and RF current in 95 unselected, consecutive patients. METHODS Patient characteristics: The study population

consisted of 95 consecutive patients with symptomatic tachyarrhythmias associated with accessory atrioventricular pathways. Patients were not excluded for any technical reason, including the presence of multiple pathways, or previous unsuccessful catheter ablation. They were refractory or intolerable to 3 f 1 antiarrhythmic drugs. Their ages ranged from 20 to 78 years (mean 50 f 10). Ten patients had associated cardiovascular disorders, including dilated cardiomyopathy (5 patients), pulmonary disease (2 patients), severe hypertension (2 patients) and Ebstein’s anomaly (1 patient). Mapping and ablation: Five to 6 multipolar electrode catheters were inserted percutaneously into the right internal jugular, and into the right and left femoral veins, and used for programmed atria1 and ventricular stimulation and for localization of the accessory pathway. Accessory pathways were presumed to be localized at the sites of recording accessory pathway activation potentials, near the sites of earliest ventricular activation during anterograde accessory pathway conduction (sinus rhythm or atria1 pacing), or the sites of earliest atria1 activation during retrograde accessory pathway conduction (atrioventricular reentrant tachycar&a or ventricular pacing). To localize left-sided accessory pathways, one 6Fr hexapolar electrode catheter with 2 mm interelectrode space or 1 to 2 othogonal electrode catheters were used in the coronary sinus. To localize right-sided accessory pathways, a catheter with a CATHETER

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deflectable curve and closely spaced (2 mm interelectrode space) conventional electrodes was used to map the tricuspid annulus. The presumed site of accessory pathway was marked on the imaging intensifier monitor for electrophysiologic and radiographic reference of the catheter ablation for the accessory pathway. Catheter ablation was performed after the initial electrophysiologic study and careful mapping. Each patient gave informed consent for the ablation and the postablation evaluation after the possible benefits and risks had been fully explained. A 7Fr arterial cannula was inserted into the left femoral artery to continuously monitor arterial blood pressure. Coronary arteriography revealed that the dominant artery was not on the site of the accessory pathway in every patient. Direct-current ablation: The first 29 patients re ceived DC ablation. As described previously,9-11 the distal 2 electrodes (connected common) of a 6Fr quadripolar catheter with 5 mm interelectrode space (USCI, or Mansfield) was used to deliver DC from the cathodal output of a life pack defibrillator, and the anode was a large skin electrode (81 cm*, R-6, NIKOMED) positioned opposite the catheter used for ablation. In patients with left parietal accessory pathways, the elec trode catheter used for ablation was inserted into the left atrium by the atria1 transseptal technique, then advanced to the ablation site, with the distal electrode against the mitral annulus. Intravenous heparin in a bolus dose of 5,000 U and an infusion of 1,000 U/hour were administered. In patients with right parietal accessory pathways, the distal electrode of a deflectable, quadripolar catheter used for ablation was positioned on the presumed site of accessory pathway, with the electrode against the tricuspid ammlus. The bipolar recording from the distal pair (electrodes 1,2) had a larger V and smaller A wave, and from the middle pair (elec trodes 2,3) had a larger a and smaller u wave or A/V amplitude ratio near 1. After a short-acting anesthetic agent (0.5 to 1 mg/kg methohexital sodium) was administered intravenously, 1 synchronous DC shock was delivered. Energy ranged from 200 to 250 J/shock in the initial 10 patients; then it was reduced to 100 to 150 J/shock in the remaining 19 patients. If the first shock was successful in interrupting the accessory pathway, isoproterenol (3 to 4 pg/min) was administered to ascertain the conduction of the accessory pathway 30 minutes later. If the accessory pathway elective for ablation was present after the first shock or reappeared after isoproterenol administration, then the mapping procedures were repeated, and additional shocks were delivered. If the accessory pathway was not present after isoproterenol administration, 1 additional DC shock was delivered to the same ablation site with the same or lower energy to minimize the possibility of resumption of conduction through the accessory pathway. The total procedure and radiation exposure time were calculated. Radiohquency ablation group: A catheter with a small-tip electrode (2 mm) in the first 8 patients or a large-tip electrode (7Fr; length 4 mm; surface area 27 mm*, deflectable [Mansfield-Webster Catheters, Boston Scientific, Watertown, Massachusetts]) in the re322

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maining 58 patients was used for ablation. For right free wall accessory pathways, the tip electrode was positioned against the atria1 aspect of the tricuspid annulus (all from the femoral vein approach, Figure 1). For concealed left free wall accessory pathways, the tip electrode was positioned against the mitral annulus, beneath (from retrograde ventricular approach) or above (through a patent foramen ovale, transseptal approach or retrograde ventricular approach) the leaflet; for manifest left free wall accessory pathways, the tip electrode was positioned beneath the valve leaflet and high against the mitral annulus (from the retrograde ventricular approach). For the first 8 patients, RF current (continuous-wave, 750 KHz) was generated by a conventional electrosurgical unit (Valleylab) modified with a transformer to increase voltage, and for the other patients by a more powerful unit (Radionic3C). Both units were coupled to a device that provided real-time monitoring of root-mean-square voltage, current and impedance. RF current was delivered at 45 to 70 V between the tip electrode and a standard adhesive electrosurgical dispersive pad (3 M, Medical and Surgical Division) applied to the chest wall. Energy was usually applied during sinus rhythm in patients with preexcitation, and during ventricular pacing or atrioventricular reentrant tachycardia in patients with concealed accessory pathways. When accessory pathway conduction was lost within 10 to 15 seconds, the application of energy was maintained for 60 to 120 seconds (longer application time in right-sided pathways), but was terminated immediately in the event of an increase in impedance (resulting from formation of coagulum on the electrode) or displacement of the catheter electrode. Immediate electrophysiologic study (under isoproterenol) was performed at 30 minutes after successful ablation. If the accessory pathway elective for ablation was present, then the mapping and ablation procedures were repeated. As in DC ablation, heparin was administered to all patients requiring a catheter in the left side of the heart. The total procedure and radiation exposure time were calculated. Postablation monitoring and evakation: All patients were monitored in the coronary care unit for 24 hours, then underwent continuous electrocardiographic monitoring for 3 additional days. Serial creatine kinase and creatine kinase-MB fraction (every 6 hours) were measured for 3 days. Complete 1Zlead electrocardiograms were obtained immediately, every 6 hours on the first day, then once daily for 6 days after ablation. A Doppler and transesophageal echocardiogram (immediately and 2 to 3 days later), a technetium pyrophosphate scintigram, a pulmonary ventilation-perfusion scintigram (2 to 4 days later) and a nuclear ventriculogram (1 week later) were recorded. A follow-up electrophysiologic study was performed 1 to 2 weeks and 3 to 5 months later. Coronary angiography was performed in the late follow-up electrophysiologic study. Furthermore, to assess the possible arrhythmogenic effects of catheter ablation, atria1 and ventricular programmed stimulation from 2 right ventricular sites with 2 extrastimuli were performed during control and isoproterenol

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infusion (3 to 4 pg/min). Twenty-four-hour Halter recordings and ventricular late potentials were obtained on the first and seventh day, and on the first and third month after ablation. Long term efficacy was assessed clinically based on the resting surface electrocardiogram, 24-hour Holter monitoring and clinical symptom%

A

llllll/\l~lllli

Statistical analysis: All values are expressed as means f SE. Differences among the electrophysiologic data obtained before and after the ablation procedures were compared with Student’s 1 test. Comparisons between different groups were obtained with Fisher exact test (Ztail). A probability <0.05 was considered statistically significant.

B

HBE,-

cs+----RV

Y”

PfGURE1.Abla6onofahghflaferal~ pathway. Pane/ A, ablafion catheter was posifioned on the laferal aspecf of friampidomnhcs(TA).Tbebip&uresodngsfrom~ 1,3 (TAl) hadventricularacfivation 36 ms earlier than fhe surface ~~deltawave,anda~~ pathway potential (AP). Infracadograms were lvxodedfromtbelfghf atrium (RA), HIarea @BE), coronary &us orl#ce, proximal and mid& reghm (CSg, CS3 and CS3). Panel B, radiofrequmcyumvnfwasappkdtofhelargelargclp elWrodeoftbeTAcatbeterat0.6OA,62V,aml~ power372W.Arory~ay~cea~1.6secondsfferthe~of~appCcationofradiofrequenc ycmrenfandwasrefktedbythe krr%henngoffhePRinfervafandnomdhhn m of the GRS complex (arrow). C, radiiraphs (leff ante&r oblique (LAO) and lateral (UT) projectbns sbewing the posi6on of the large-fip elechde (arrow) used for ablation.

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TABLE

I Locations

and Characteristics

of Accessory

Pathways

Conduction(n) Left-Sided

DC RF

APW

Right-Sided

APW

ERP(ms)

P

PL

Lat.

AL

P

Lat.

A

Ant. + Ret

7 11

6 6

4 23

0 4

3 7

3 8

7 11

16 39

Ant. Only

Ret. Only

0 3

14 28

RR-AF Ant. 265k 26Ok

b-m)

Ret. 5 7

255t 2502

7 5

257k8 252 r 8

A = anterior; Ant. = anterograde; AL = anterolateral; AP = accessory pathways; DC = direct-current; ERP = effective EfrXtOiY period; Lat. = lateral; P = posterior; PL = posterolateral; Ret. = retrograde; RF = radiofrequency; RR-AF = shortest RR intern during atrial fibrillation.

cessful RF ablation underwent predischarge electrophysiologic studies. Six patients (5 with concealed leftsided and 1 with concealed right-sided accessory pathpathways are summarized in Table I. Accessory path- ways) had return of retrograde conduction with proway potentials were recorded in 20 patients. A mean of longed ventriculoatrial conduction time (effective retro2.7 f 0.1 applications of DC eliminated 27 accessory grade refractory period from ‘250 f 4 to 405 f 8 ms), pathways successfully (single ablation session), and and tachycardia was not inducible. failed in 3 accessory pathways (1 left posterolateral, 1 Late results: DIRECT-CURRENT ABLATION GROUP: Durright lateral, and 1 right posterior location). The 2 pa- ing a mean follow-up of 24 f 2 months (range 18 to tients with a left posterolateral and right lateral path- 31), all patients with a successful outcome had experienced no recurrence of arrhythmia and were free of way had successful RF ablation 1 year later. Cumulative energy delivered per session was 410 f 22 J, proce- antiarrhythmic medication. One patient with cardiomydure time lasted a mean of 3.6 f 0.2 hours (range 2 to opathy still had paroxysmal attacks of atria1 fibrillation 6) and patients’ mean radiation exposure time per ses- with atrioventricular nodal conduction, and the ventricsion was 34 f 4 minutes (range 15 to 48). Twenty-six ular rate could be controlled with digitalis. One patient patients underwent early follow-up. Two patients had with a right posterior accessory pathway had reappearinducible tachycardia and underwent a single repeated ance of a delta wave 2 weeks after ablation. Follow-up session with successful results. In the RF ablation study showed the pathway was modified with prolongagroup, success was achieved in 56 patients (63 patients tion of anterograde and retrograde refractory periods with a single pathway, 2 patients with 2 pathways, and from 300 to 500 ms and from 230 to 520 ms, respective 1 patient with 3 pathways). The locations and charac- ly. Tachycardia was not inducible. A late electrophysioteristics of accessory pathways were summarized in Ta- logic study (mean 4 f 1 months, 18 patients), including ble I. Accessory pathway potentials could be recorded in the 2 patients who had undergone a second ablation ses30 patients. These electrophysiologic parameters were sion, did not show reappearance of accessory pathway not significantly different from the DC ablation group. conduction even during administration of intravenous Successful ablation of accessory pathways (single abla- isoproterenol (3 to 4 pg/min). The remaining 11 pation session) required a median of 9 applications of RF tients did not have reappearance of preexcitation or any current (range 1 to 64 and a median of 6 and 13 for left symptom related to tachycardia attack. During a mean and right-sided free wall pathways, respectively) at a follow-up of 11 f 1 months (4 to 17 months in the RF power of 35.7 f 1.1 W delivered for a duration of 66.6 ablation group), 2 patients with a successful outcome f 3.7 seconds. Accessory pathway conduction was in- had experienced recurrence of arrhythmia. One patient terrupted at 3.8 f 0.3 seconds after initiation of energy (left lateral manifest accessory pathway) had return of (range 1 to 15 seconds). In the first 8 patients, accessory retrograde conduction with tachycardia attack at 40 days after ablation and he took procainamide to control pathways were ablated with a small tip electrode cathe ter and elimination of accessory pathways was achieved tachycardia. One patient (left lateral concealed accessoin 3 (38%) but was unsuccessful in 5 patients. Four of ry pathway) had a tachycardia attack at 66 days after the 5 patients (all had left-sided free wall pathways) ablation, which subsided with the Valsalva maneuver. A with unsuccessful RF ablation had a successful DC ab- late electrophysiologic study (4 f 1 months) in 36 palation in the same ablation session, and the other patient tients did not show reappearance of accessory pathway had a successful outcome of surgical ablation. In the conduction, and tachycardia was noninducible even durremaining 58 patients, elimination of accessory path- ing administration of intravenous isoproterenol (3 to 4 ways was achieved in 53 patients (91%) with a large-tip pg/min). None of the remaining 30 patients had reapelectrode catheter. Three of the 5 patients (2 with left- pearance of preexcitation or recurrent tachycardia. Complications of catheter ablation: DIRECT-CURRENT sided and 1 with right-sided free wall pathways) with unsuccessful RF ablation had a successful DC ablation ABLATION GROUP: A small suspicious lesion of air-trapin the same session. Cumulative energy delivered per ping in the right lower lobe was seen in 2 patients with session was 10,800 f 3,400 J, procedure time lasted for DC ablation of right-sided pathways. However, they a mean of 4.2 f 0.5 hours (range 2 to 9), and patients’ were asymptomatic and the follow-up examinations (2 mean radiation exposure time per session was 50 f 10 weeks later) were normal. Atria1 arrhythmias were not studminutes (range 18 to 136). The 56 patients with SUD inducible in the early and late electrophysiologic RESULTS

Immediate and early results: tmEc-r-cummT ABLATION GROUP: Locations and characteristics of accessory

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ies. Nonsustaincd monomorphic ventricular tachycardia (maximum 6 beats) were inducible in 2 patients in the early study, and were noninducible in the late follow-up study (Table II). In the RF ablation group, one patient with a manifest left lateral accessory pathway had a successful ablation of anterograde conduction on the ventricular insertion, and the abolition of retrograde conduction could be achieved only above the mitral leaflet with the retrograde technique. This patient complained of severe chest pain during delivery of the RF energy (40 W, 40 seconds) on the atria1 side. Hypotension with cardiac tamponade occurred about 2 hours after ablation. Intrapericardial blood was drained after urgent pericardiocentesis, and the patient did not require surgery. One 70-year-old patient had severe hypertension associated with tortuosity of the aorta. He complained of progressively sharp back pain immediate ly after successful ablation. The urgent computer tomogram with contrast enhancement revealed suspicious aortic diisection. Fortunately, the follow-up computer tomogram and digital subtraction angiography of the aorta did not show a definite lesion and the patient’s course was uneventful. Holter examination on the first and seventh day showed the numbers of atria1 and ventricular beats were leas in the RF ablation group. Data obtained from ventricular late potentials were normal (Table III). Atria1 and ventricular arrhythmias were not inducible in the early and late electrophysiologic studies. Patients who had atria1 fibrillation with rapid ventricular preexication before ablation did not have inducible atria1 fibrillation in follow-up studies.

TABLE II Results of Follow-Up After Ablation

Examination

and Complications

Direct-Current Transient hypotension Cardiac tamponade Aortic dissection Tc-99 scintigram Peak CK-MB (IU/liter) Pathologic Q wave lschemic ST-T change Coronary angiography Coronary sinus Nuclear EF(RV/LV %) Before After Echocardiogram New valvular regurgitation Thrombus Wall motion impairment V-P scintigram Proarrhythmias

Radiofrequency

2 0 0 Normal 32 2 2 0 0 Normal(18/18) Normal(l8/18)

0 1 l(suspicious) Normal 12 * 2 0 0 Normal(36/36) Normal(36136)

48-c 3152 -t 3 47 + 3152 f 2

46 2 4152 zk 2 47 k 5153 f 4

0

0

0 0 Air-trapping(2) More

0 0 Normal Less

All values are mean ? SEM. EF = ejection fraction; LV = left ventricle: RV = right ventricle; V-P = pulmonary ventilation-perfusion scintigram.

Tc = iechnetlum,

ed accessory pathways. l7 Eight pathways could not bc ablated successfully by ventricular insertion; ablation was achieved from the atria1 insertion with the tip elcctrode resting on the mitral annulus or above the mitral leaflet. Unlike DC energy delivery, rupture of the coronary sinus, sustained arrhythmias, pressure changes or perforations have not been reported after RF was u~cd.~~-~~ DISCUSSION Although DC energy was delivered to the atria1 endoDC energy was delivered to the atria1 insertion of cardium, there were still more early proarrhythmic efaccessory pathways in all patients to decrease and avoid fects than there were in the RF ablation group. In the early or late ventricular proarrhythmias. The trans- pathologic studies, RF lesions were small and homogeseptal approach was learned from our expcrienccs with neous, which probably explain their low potential to transseptal balloon mitral valvuloplasty.16 RF energy produce cardiac dysrhythmias.18 Because RF energy afwas delivered to the atria1 insertion of right-sided acces- fects cardiac tissue by resistive heating without arcing, a sory pathways owing to the findings that the weak link chronic effect is usually maintained. However, DC along the atrium accessory pathway ventricle is the atri- shocks affect cardiac tissue by barotrauma and may al insertion in the right-sided accessory pathways.13 achieve accessory pathway conduction block even when Furthermore, mapping and ablation of the right-sided the shock is delivered to an anatomically imprecise accessory pathways were all from the femoral vein ap- region. Recurrence of accessory pathway conduction proach and not from the jugular vein approach.‘“-l4 RF within 24 hours of a “successful” DC shock is frequentenergy was first delivered to the ventricular insertion of ly reported.6 The recurrence rate is lower in the RF the left-sided accessory pathways according to the find- than in the DC ablation group. Other studies13-l5 have ings that the weak link along the atrium-accessory path- reported similar results. This suggests that the tissue efway-ventricle axis is the ventricular insertion in left-sid- fects of RF energy may be reversible less frequently TABLE

Ill

Proarrhythmias

After Direct-Current

APBs(/D)

Pre-A 1D

1w 1M 3M

DC

RF

40 f 5

45 24

160*10*

85 f 6* 75 f 5 55 k 4

or Radiofrequency

VPBs(/D) DC

352

RF

3

7025

190?11*

50% 5 52k4 47 i 6

120r8* 4524 40 f 5

Ablation

VCs(/D)

48 rt 5 120

lr 8*

60 f 5 55 r 8 582 4

DC

Short RF

0.5 2 0.2

0.5 r 0.2

5.5 f

3.4

l.O*

3.0 k 0.5* 0.8 +- 0.2 0

of Free Wall Accessory

f 0.8*

1.1 f 0.3 0.2 2 0.1 0.7 f 0.2

DC

0

Run VT RF

Pathways LAS(ms)

RMS($J) DC

RF

DC

RF

0.1 * 0.1 1.5 f 0.8*

5922

58k4

2522

2823

1.7 2 l.O*

48 + 4

52 2 2

25 t 3

30 f 2

0 0 0

0.2 It 0.1 O.l-tO.1 0

4722 4823 52~3

56-t3 56kl 54k3

28k4 31k2 28k2

2923 2822 2922

*p <0.05. Values are mean + SEM. APB = atrial premature beats; ID = number per day; DC = direct-current; LAS = low-amplitude signal; Pm-A = before ablation; RF = radiofrequency; RMS = root-mean-square; VCs = ventricular couplets; VPBs = ventricular premature beats; VT = ventriculartachycardia; ID, lW, IM, 3M = 1 day, 1 week, 1 month, 3 months after ablation.

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than the effects of DC shocks. More precise mapping and longer RF delivery time (up to 60 to 120 seconds) may decrease the recurrence rate. Although myocardial infarction was not found, several studies reported acute coronary spasm or infarction in patients with DC ablation.5-8 Furthermore, our study showed DC ablation produced more extensive myocardial injury than RF ablation. Ventricular function did not deteriorate in both groups, but animal studies showed acute ventricular dysfunction after DC ablation.lg Pulmonary air-trapping suggests transient spasm of small bronchi due to barotrauma. Cardiac tamponade occurred in 1 patient, and this suggests that ablation from the atria1 side should be undertaken with caution, and lower RF power should be considered for patients with pathways that cannot be ablated from beneath the mitral annulus. Suspicious aortic dissection was possibly related to manipulation of the catheter used for ablation. This suggests that the atrial transseptal approach to left-sided accessory pathways may be more appropriate in some patients with marked tortuosity of the aorta, avoiding manipulation of the catheter in the aorta. The late complications after RF ablation are unknown, and careful long-term observation of patients is required. A significantly higher SU~GW rate was found when ablation was attempted with the largetip rather than the small-tip electrode catheter. Similar results have been reported.g~20 There have also been attempts to lower energy requirements, improve efficiency and shorten procedure and radiation exposure times with either active fixation or suction electrodes. The total procedure and radiation exposure time are longer in the RF group, and the success rate was the same in both groups. Although the patients selected were sequential and unselected, prior experiences in DC and not in RF may have biased the results. Nevertheless, this study could confirm that catheter delivery of RF current with a large-tip electrode is highly effective (92%) in ablating free wall accessory pathways, with no mortality and little morbidity. REFERENCES

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