Simultaneous alterations of QRS configuration and tachycardia cycle length during radiofrequency ablation of idiopathic left ventricular tachycardia

Journal of Electrocardiology Vol. 33 No. 1 2000

Simultaneous Alterations of QRS Configuration and Tachycardia Cycle Length During Radiofrequency Ablation of Idiopathic Left Ventricular Tachycardia

H a n L e e , M D , K u a n - C h e n g C h a n g , M D , Y u - C h i n Lin, M D , Hsiang-Tai Chou, MD, PhD, and Jui-Sung Hung, MD, FACC

Abstract: Idiopathic left ventricular tachycardia is characterized by a QRS

morphology of right bundle branch block pattern and left axis deviation. Alterations in the QRS configuration and tachycardia cycle length, as well as shifting of the earliest activation site occurred after eliminating the original tachycardia by radi0frequency current in an I8-year-old man with idiopathic left ventricular tachycardia. Activation mapping and entrainment mapping during tachycardia identified 2 putative tachycardia exits, 15 mm apart. Elimination of both tachycardias was accomplished after applying radiofrequency current to each exit separately. We proposed that the first radiofrequency application might have altered the exit site and the zone of slow conduction adjacent to the exit site, such that the vefitricular tachycardia had a different QRS morphology and became slower in this patient. Key words: QRS configuration, cycle length, idiopathic left ventricular tachycardia.

(4), the exact nature of the reentry circuit remains unclear. Recent studies (5-7) have shown variations of the QRS complex but without a significant change in the tachycardia cycle length during radiofrequency (RF) ablation of ILVT. This suggests that presence of multiple exits in the reentry circuit is possible in LLVT. In this article, the simultaneous changes of the QRS morphology and the tachycardia rate, as well as shifting of the earliest activation site, were observed after eliminating the original ILVT by the first RF application. The second tachycardia was also abolished by RF ablation.

Idiopathic left ventricular tachycardia (ILVT) is a distinct entity characterized by a QRS morphology of right bundle branch block pattern and left-axis deviation. The tachycardia, which usually occurs in young patients without structural heart disease, is responsive to verapamil but not to adenosine and can be induced and terminated by programmed stimulation (1-3). Although reentry involving the left posterior fascicle and the specialized conduction tissues is believed to be the underlying mechanism

From the Divisimi of Cardiology, Department of Medicine, China Medical College Hospital, Taichgng, Taiwan,

Reprint requests: Kuan-ChengChang, MD, Divisionof Car~tiology, Department of Medicine, China MedicalCollegeHospital, 2 Yuh-Der Road, Taichung,Taiwan.

Case Report An 18-year-old man had a 4-year history of episodic palpitations (on average 4 times per year),

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associated with dizziness, chest tightness, nausea, and diaphoresis. Each episode lasted from several hours to a whole day, if not treated. Complete electrocardiogram (ECG) during an attack documented a wide QRS complex tachycardia with right bundle branch block pattern and superior axis. The tachycardia cycle lengths ranged from 340 to 400 msec. The tachycardia could be terminated by verapamil 5 mg administered intravenously, but not by adenosine 12 rag. Because of frequent recurrence of the tachycardia, despite oral verapamil therapy, RF catheter ablation had been performed 2 years earlier at another institution. However, the tachycardia recurred 3 months after the ablation therapy. During the last prolonged episode, the tachycardia failed to respond to verapamil 20 mg given in divided doses, and the patient was admitted for ablation therapy. There was no evidence of structural heart disease by physical examination, chest roentgenography, echocardiography, and coronary angiography in this patient. After obtaining informed written consent, electrophysiologic study was performed in the postabsorptive state after discontinuation of all antiarrhythmic agents for at least 5 half-lives. Three 6-French quadripolar electrode catheters were inserted into the right femoral vein and positioned in the high right atrium, His-bundle region and right

Fig. 1. Twelve-lead ECG of an induced clinical ventricular tachycardia (left panel) and the second ventricular tachycardia (right panel). Marked variations in QRS configuration with a different tachycardia rate is noted between the tachycardias. VTI, clinical ventricular tachycardia; VT2, the second ventricular tachycardia.

ventricular apex, respectively. A 6-French decapolar electrode catheter (Daig Corp., Minnetonka, MN) was placed in the coronary sinus via the right internal jugular vein. This catheter was positioned with its proximal poles at the orifice of the coronary sinus. ECG leads I, aVF, and V1, as well as intracardiac electrograms were simultaneously displayed and recorded on a multichannel oscilloscopic recorder (Prucka Engineering, Inc, Houston, TX). A clinical tachycardia with a QRS morphology of right bundle branch block pattern and extreme left axis deviation (180 °) (Fig. t) was induced by rapid ventricular pacing at cycle lengths ranging from 380 to 340 msec without isoproterenol provocation. Ventriculoatrial dissociation and negative H-V intervals established the diagnosis of ventricular tachycardia and excluded supraventricutar tachycardia with aberrant conduction or accessory pathway mediated tachycardia. An attempt to entrain the tachycardia by pacing from the right ventricular outflow tract and the right ventricular apex was not successful. A 7-French deflectable quadripolar electrode catheter with a 4-mm tip and 2-5-2-mm interelectrode spacing (Cordis-Webster, Baldwin Park, CA) was inserted through the right femoral artery and positioned in the left ventricle for pacing, mapping and ablation. At a mid-septal location, a Purkinje potential preceding the onset of QRS corn-

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Fig. 2. Entrainment mapping during ventricular tachycardia. Upper panel: Pacing from the site with the earliest activation of Purkinje potential produced QRS complexes very similar to the spontaneous VT1 and the postpacing interval (PPI) measured from the proximal ablation electrode was only 20 msec longer than the tachycardia cycle length. Lower panel: Pacing from the site with the earliest ventricular activation produced QRS complexes almost identical to the spontaneous VT2 and the PPI measured from the proximal ablation electrode was equal to the tachycardia cycle length. HRA, high right atrium; CS 1-5, bipolar recordings of the coronary sinus electrode from distal to proximal; HBE, His bundle electrogram; RVa, right ventricular apex; ABL d, distal ablation electrode; ABL p, proximal ablation electrode; d, distal; m, middle; p, proximal.

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estimated PPI at the distal ablation electrode recording would be equal to the tachycardia cycle length, because the activation of the spike potential was 20 msec earlier in the distal than in the proximal electrogram. A single temperature-guided RF pulse delivered at the distal ablation electrode site resuited in immediate termination of the tachycardia within one second, but a second tachycardia with a different QRS morphology and a longer tachycardia cycle length (480 msec) was generated during the same RF pulse (Fig. 3). Continuous mapping revealed that at a more inferior-apical site of the ventricular septum, at least 15 m m away from the first ablation site, the earliest activation of the second tachycardia was identified (Fig. 4). A small Purkinje potential preceding the onset of QRS complex by 25 msec during tachycardia was recorded at the distal bipolar electrogram of the ablation catheter. Pacing this site produced QRS complexes almost identical to the spontaneous ventricular tachycardia and the PPI measured from the proximal bipolar electrogram of the ablation catheter was equal to the tachycardia cycle length (Fig. 2). This indicated that the estimated PPI at the distal ablation electrode recording would be only 10 msec longer than the tachycardia cycle length, because the activation of the spike potential was 10 msec earlier in the proximal than in the distal electrogram. Ablation of the second ventricular tachycardia was attempted at the distal ablation electrode site because of its earliest ventricular activation with a better obtainable pacemap match and transient termination of the tachycardia caused by applying pressure to this site via the catheter. A 13 W RF energy application at this site resulted in an electrode-tissue interface temperature of 60°C and elimination of the tachycardia in 5 seconds (Fig. 3). Postablation programmed stimulation, with or without isoproterenol infusion, failed to induce any tachycardia. A repeat electrophysiologic study performed after a 4-month palpitation-free interval confirmed successful elimination of the ILVT.

Discussion plex by 36 msec was recorded at the distal bipolar electrogram of the ablation catheter. Pacing this site during tachycardia produced QRS complexes very similar to the spontaneous ventricular tachycardia and the postpacing interval (PPI) measured from the proximal bipolar electrogram of the ablation catheter was only 20 msec longer than the tachycardia cycle length (Fig. 2). This indicated that the

The following clinical and electrophysiologic characteristics in this patient are consistent with typical ILVT: ( 1 ) Occurrence in young patient without structural heart disease, (2) Typical ECG pattern of right bundle branch block and superior axis, (3) Response to verapamil but not to adenosine, (4) Induction and termination by programmed ventricular stimulation, and (5) Successful RF ablation

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Fig. 3. Activation mapping and ventricular tachycardia ablation. Upper panel: The earliest activation of Purkinje potential (arrow) preceding the onset of ORS complex by 36 msec was identified. Radiofrequency (RF) current applied at this site resulted in immediate termination of the VT1. Tile VT2 with a longer cycle length (480 msec) occurred after a sinus beat (*) during tile same RF pulse application. It was nonsustained initially and became sustained later. Lower panel: The earliest ventricular activation of the VT2 was inscribed in the distal ablation electrode with a small Purkinje potential (arrow) preceding tile onset of QRS complex by 25 msec, whereas tile earliest activation of Purkinje potential (-35 msec) was recorded at the proximal ablation electrode. Ablation from the distal recording site terminated the VT2 within 5 seconds. Arrowhead, tile spike potential at ABL p; w, watt. Other abbreviations as in Fig. 2.

guided by Purkinje potential at left ventricular septum. The u n i q u e feature in the present case is the e m e r g e n c e of second ventricular tachycardia with a different QRS m o r p h o l o g y and a slow tachycardia rate during RF ablation of the original tachycardia. A significant, simultaneous alteration in tachycardia rate has not been observed in previous studies (5,6) addressing variations of QRS complex during ILVT. Washizuka et al. (5) showed that alternation of the QRS configuration can occur spontaneously during ILVT and n e w ventricular tachycardias with different QRS morphologies can be induced after eliminating the original tachycardia by RF current. Chen et al. (6) reported up to 5 types of m o r p h o logically different tachycardia but with similar tachycardia cycle length (variation ~ 35 msec) during RF ablation of ILVT. In their articles, the cycle lengths of the different tachycardias were essentially similar and the putative exit sites served as the targets for RF ablation were within a limited area of the left ventricle (0 to 10 mm). They postulated that the variations in ECG m o r p h o l o g y might be due to activation of alternative pathways

within a single r e e n t r a n t circuit leading to different exits caused by heating effects of RF ablation. In o u r case, the putative exit site of the original tachycardia was located at a mid-septal area. RF ablation at this site resulted in immediate termination of the tachycardia (430 msec), but a second ventricular tachycardia with a different QRS configuration and a significant longer tachycardia cycle length (480 msec) e m e r g e d during the same RF pulse application. The exit site of the second tachycardia was recorded at an inferior-apical septal area of the left ventricle. From the fluoroscopic images in the right anterior oblique projection, this site was estimated to be 15 m m away from the first exit site. We postulated that the first RF pulse application might have modified the path of the r e e n t r a n t circuit and changed both the tachycardia cycle length and exit. This might be the reason w h y the second ventricular tachycardia was manifested only after the RF ablation of the original tachycardia. However, possibility of the existence of 2 separate r e e n t r a n t circuits resulting in different exit pathways c a n n o t be completely excluded in this case. During RF ablation, the first ventricular tachycardia

Alteration in Idiopathic VT during RF Ablation

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Fig. 4. Fluoroscopic location of the successful ablation sites (arrows). The distance between the two putative exit sites used as the targets for ablation was estimated to be 15 mm from the fluoroscopic images in the right anterior oblique projection. The first exit was located at a mid-septal area of the left ventricle, and the second was at a more distal septal location. The left panels were taken from 30 ° right anterior oblique projection (RAO) and the right panels from 60 ° left anterior oblique projection (LAO). HIS, His bundle; asterisk, inadvertently displaced HRA catheter. Other abbreviations as in Fig. 2.

i m m e d i a t e l y t e r m i n a t e d after 1 tachycardia beat followed by a sinus beat, t h e n the second ventricular tachycardia started for 4 beats followed w i t h the first ventricular tachycardia beat. Because the changes in the tachycardia m o r p h o l o g y a n d the cycle length w e r e preceded by a sinus beat, this finding m i g h t favor a different circuit rather t h a n 2 exits. M o r e o v e r , it m a y also be possible that the previous ablation p r o c e d u r e h a v e modified the tachycardia circuit resulting in m o r e t h a n o n e area of slow conduction. Use of high resolution ventricular m a p p i n g s y s t e m m a y be necessary to clarify the exact m e c h a n i s m of changing QRS m o r p h o l o g y a n d tachycardia cycle length in ILVT during RF ablation.

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References 1. Zipes DP, Foster PR, Troup PJ, et al: Atrial induction ventricular tachycardia: Reentry versus triggered automaticity. Am J Cardiol 44:1, 1979 2. Lin FC, Finley CD, Rahimotoola SH, et al: Idiopathic

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paroxysmal ventricular tachycardia with a QRS pattern of right bundle branch block and left axis deviation: A unique clinical entity with specific properties. Am J Cardiol 52:95, 1983 Ohe T, Shimomura K, Aihara N, et al: Idiopathic sustained left ventricular tachycardia: Clinical and electrophysiologic characteristics. Circulation 77:560, 1988 Okumura K, Henthorn RW, Epstein AE, et al: Further observations on transient entrainment: importance of pacing site and properties of the components of the reentry circuit. Circulation 72:1293, 1987 Washizuka T, Aizawa Y, Chinushi M, et al: Alternation of QRS morphology and effect of radiofrequency ablation in idiopathic ventricular tachycardia. PACE 18(Pt. I):18, 1995 Chert YJ, Chert SA, Tai CT, et al: Radiofrequency ablation of idiopathic left ventricular tachycardia with changing ECG morphology. PACE 21:1668, 1998 Zivin A, Goyal R, Daoud E, et al: Idiopathic left ventricular tachycardia with left and right bundle branch block configurations. J Cardiovasc Electrophysiol 8:441, 1997