We studied the electrophysiological characteristics of systolic (SP) and diastolic (DP) potentials recorded during sinus rhythm (SR) in the left interventricular septum of a 27 year-old woman presenting with verapamil-sensitive idiopathic left ventricular tachycardia (VT). During SR, and during VT, SP was activated from ventricular base-to-apex, and DP from apex-to-base. SP and DP were both detected at the site of successful ablation during SR, whereas during VT, DP was detected away from the earliest activation site. Thus, SP apparently reflected a critical component of the reentrant circuit, while DP reflected the activation of a bystander pathway

Iijima, Takafumi

Irie, Tadanobu

Kaneko, Yoshiaki

Kato, Toshimitsu

Kobayashi, Hiroaki

Kurabayashi, Masahiko

Nakajima, Tadashi

Ota, Masaki

Tamura, Mio

English

Via Medica Journals

CASE REPORTCardiology Journal2012, Vol. 19, No. 4, pp. 418–42310.5603/CJ.2012.0075Copyright © 2012 Via MedicaISSN 1897–5593418 www.cardiologyjournal.orgAddress for correspondence: Yoshiaki Kaneko, MD, PhD, Department of Medicine and Biological Science, Gunma UniversityGraduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma, Japan, 371-8511, tel: +81 27 220 8145,fax: +81 27 220 8158, e-mail: kanekoy@gunma-u.ac.jpReceived: 13.01.2011 Accepted: 25.02.2011Characteristics of systolic and diastolic potentialsrecorded in the left interventricular septum inverapamil-sensitive left ventricular tachycardiaYoshiaki Kaneko, Tadashi Nakajima, Tadanobu Irie, Masaki Ota, Toshimitsu Kato,Takafumi Iijima, Mio Tamura, Hiroaki Kobayashi, Masahiko KurabayashiDepartment of Medicine and Biological Science,Gunma University Graduate School of Medicine, Maebashi, Gunma, JapanAbstractWe studied the electrophysiological characteristics of systolic (SP) and diastolic (DP) potentialsrecorded during sinus rhythm (SR) in the left interventricular septum of a 27 year-old womanpresenting with verapamil-sensitive idiopathic left ventricular tachycardia (VT). During SR,and during VT, SP was activated from ventricular base-to-apex, and DP from apex-to-base.SP and DP were both detected at the site of successful ablation during SR, whereas during VT,DP was detected away from the earliest activation site.  Thus, SP apparently reflected a criticalcomponent of the reentrant circuit, while DP reflected the activation of a bystander pathway.(Cardiol J 2012; 19, 4: 418–423)Key words: Purkinje fiber, bystander pathway, essential pathway, catheterablation, idiopathic ventricular tachycardiaIntroductionVerapamil-sensitive idiopathic left ventriculartachycardia (VT) is uniquely characterized by rightbundle-branch block QRS morphology, superior axisdeviation and responsiveness to verapamil [1–3]. Itoften originates from the left interventricular sep-tum (LIVS), where several investigators have detect-ed pre-systolic potentials during ongoing tachycar-dia, which may reflect a critical segment of the re-entrant circuit supporting the arrhythmia [4–10].We recently reported the presence of systolic(SP) and diastolic (DP) potentials during sinusrhythm (SR) on the LIVS in structurally normalhearts and in the absence of ventricular arrhythmias[11]. The characteristics of SP and DP, includingtheir a) basal or midseptal location, b) morphologyand activation sequence, and c) slow conductionproperties, are strikingly similar to those of the pre-systolic potentials detected in patients with vera-pamil-sensitive VT, though the role they play in thearrhythmic mechanism remains to be clarified.The aim of this study was to define the characte-ristics and electrophysiological properties of SP and DPin a patient presenting with verapamil-sensitive VT.Case reportA 27 year-old woman without apparent struc-tural heart disease was admitted to our hospital forcatheter ablation of a paroxysmal tachycardia withright bundle branch QRS morphology and left axisdeviation, terminated by intravenous administrationof verapamil, 2.5 mg, i.v.Transthoracic two-dimensional echocardio-graphy revealed the absence of left ventricular falsetendons. The patient, who had granted her writteninformed consent, underwent electrophysiological419Yoshiaki Kaneko et al., Systolic and diastolic potentials in left idiopathic VTwww.cardiologyjournal.orgstudy and catheter ablation procedure after dis-cintinuation of all antiarrhythmic drugs for > 5 half--lives. Multi-electrode catheters were placed trans-venously in the high right atrium (HRA), His-bun-dle region and at the right ventricular apex (RVA)or the right ventricular outflow tract (RVOT). Bi-polar intracardiac electrograms were filtered be-tween 30 and 400 Hz and stored with the 12-leadsurface electrocardiogram on electronic medium(EPLab/EP Amp™, Quinton Electrophysiology Co.,Seattle, WA, USA) for further analysis. A 20-pole,7 F, A-20™ steerable electrode catheter (BiosenseWebster, Inc., Diamond Bar, CA, USA) with 1-mminterelectrode spacing and 3-mm distance betweenadjacent electrode pairs was introduced retrograde-ly into the left venricle. The LIVS surface was me-ticulously mapped during sinus rhythm in searchof potentials following the ventricular electrogram.We identified two types of low-frequency late po-tentials along a narrow base-to-apex line at the baseor mid segment of the left posterior fascicle. Thefirst (SP) was recorded during systole, in a ventri-cular base-to-apex direction; the second (DP) wasrecorded during diastole, in an apex-to-base direc-tion (Fig. 1A). The position of the mapping catheterrecording these potentials, viewed in the right andleft anterior oblique fluoroscopic projections, isshown in Figure 1C.Single extrastimuli, and trains of stimuli, weredelivered from the HRA, RVA and RVOT duringFigure 1. Systolic and diastolic potentials recorded during sinus rhythm (A) and high right atrial extrastimulation (B),and right (RAO) and left (LAO) anterior oblique fluoroscopic views (C) showing the position of the mapping catheter(MAP); A. Activation of the left bundle branch potentials in a basal-to-apical sequence, preceding activation of theventricular myocardium from apex to base suggests that the Purkinje-muscle junction was located near the fusionpoint of the two potentials. Solid and dashed arrows indicate the direction of systolic (SP) and diastolic (DP)potentials activation, respectively; AH = 78 ms; HV = 45 ms; QRS onset to SP = 98–143 ms; SP amplitude = 0.20––0.86 mV; QRS onset to DP = 370–498 ms; SP amplitude = 0.37–0.86 mV; B: At an S1–S2 coupling interval of 340 msand S1–S1 basic cycle length of 600 ms, the V2–DP interval is shorter than the V1–DP interval, suggesting incremen-tal conduction properties of the tissue between the site of ventricular pacing and DP. SP is no longer visible after S2,as the effective refractory period of the tissue between the site of ventricular pacing and SP has been reached;C. Recordings of SP and DP (A17–18 to A5–6) are from the basal septum just below the aortic valve to the mid septum;I, II, V1 = surface ECG leads; HRA — high right atrium; HBE — His-bundle electrogram; A19–20 to A1–2 — leftventricular mapping sites from base to apexA B C420Cardiology Journal 2012, Vol. 19, No. 4www.cardiologyjournal.orgstable recordings of SP and DP in SR. Atrial andventricular pacing reproduced the same SP and DPmorphology and activation sequence observed du-ring SR (Figs. 1B, 2). Atrial or ventricular extrasti-mulation, or increasingly faster atrial or ventricularoverdrive pacing, were associated with a graduallylonger delay between ventricular activation and SP,consistent with decremental conduction propertiesof the tissue between ventricular capture and SPactivation (Fig. 2A). Furthermore, the disappear-ance of SP after atrial or ventricular extrastimuli atcritically short coupling intervals suggested that theeffective refractory period of the tissue between theventricular myocardium and the recording site ofSP had been reached (Fig. 1B). In contrast to SP,atrial or ventricular pacing was associated with in-cremental conduction properties of DP (Fig. 1B).Single extrastimuli or burst stimulation from theRVA or RVOT reproducibly induced verapamil-sen-sitive VT with a 105-ms QRS duration and A-V dis-sociation (Fig. 2), terminated by ventricular burststimulation. During VT (Fig. 2B) and entrainmentpacing from the HRA, the activation sequence of SPand DP was similar to that observed during SR. Thesite of earliest ventricular activation was in the midseptum, away from the recording of DP (Fig. 2B).Entrainment pacing from the RVOT confirmeda reentrant mechanism of VT, capturing the ven-tricular myocardium, followed by SP, which was ac-tivated in a base-to-apex sequence, similar to thatobserved during VT. VT was induced while both SPand DP were being recorded during SR (Fig. 3A)from an ablation catheter located in the inferior midseptum (Fig. 3C). Entrainment from that site sug-A BFigure 2. Systolic (SP) and diastolic (DP) potentials recorded during ventricular tachycardia induced by extrastimula-tion at the right ventricular apex (A) and right ventricular outflow tract (B). Solid and dashed arrows show thedirection of activation of SP and DP, respectively; A. At an S1–S2 coupling interval of 280 ms and S1–S1 basic cyclelength of 500 ms, S2–SP is distinctly longer than S1–SP, particularly at the apical end of SP (A9–10), indicating thepresence of decremental conduction between ventricular myocardium and SP activation; B. Induction of ventriculartachycardia by ventricular extrastimulation at an S1–S2 interval of 220 ms and S1–S1 basic cycle length of 500 ms(not shown). The activation sequence of SP and DP during ongoing ventricular tachycardia is similar to that shownduring sinus rhythm in Figure 1A. Note that the earliest ventricular activation is at A1–2, in the mid septum, awayfrom the recording of DP. Other abbreviations are as in Figure 1.421Yoshiaki Kaneko et al., Systolic and diastolic potentials in left idiopathic VTwww.cardiologyjournal.orgFigure 3. Intracardiac electrograms at the site of successful ablation during sinus rhythm (SR) (A) and entrainmentpacing (B). Catheter positions during pace-mapping of ventricular tachycardia (VT) with the ablation catheter (ABL) atthe site of successful ablation, in the right anterior oblique (RAO) (C) and antero-posterior (AP) (D) fluoroscopicviews; A. A spiky Purkinje potentials preceded the ventricular electrograms at the site of successful ablation during SR.Note that SP (solid arrows) and DP (dashed arrows) were both recorded at that site; B. Entrainment pacing at a cyclelength of 290 ms shows constant fusion. At the site of successful ablation (ABL1–2) during VT, a Purkinje potentialpreceded the onset of the QRS complex by –13 ms (solid arrows) and low-amplitude, low-frequency SP or DP(dashed arrows) were recorded. The 300-ms post-pacing interval is equal to the tachycardia cycle length. Thesefindings suggest that the entrainment site (ABL1–2) is located near the exit of a critical segment of the reentrantcircuit, which entrainment pacing captured simultaneously with the surrounding ventricular myocardium, thusexhibiting constant fusion; C, D. The ablation catheter (ABL) at the site of successful ablation was in the inferior midseptum. ABL1–2 and 3–4 — distal and proximal ablation catheter recordings. Other abbreviations are as in Figure 1.gested that the pacing site was located on a criticalsegment of the reentry circuit (Fig. 3B). VT termi-nated approximately two seconds after a single de-livery of radiofrequency at that site, and was nolonger inducible thereafter. These combined obser-vations confirmed the diagnosis of left ventricularverapamil-sensitive VT.DiscussionThe main observations made in the analysis ofthis case of verapamil-sensitive VT were: 1) SP andDP were detected during SR along a basal-to-apicalline on the LIVS surface; 2) both SP and DP were alsorecorded during VT; 3) during SR, SP and DP wereboth recorded at the site of successful ablation, where-as during VT, DP was recorded away from the site ofearliest ventricular activation.The characteristics of SP and DP, includinga) their anatomical location, b) morphology and acti-vation sequence, c) the decremental conductionproperties and effective refractory period of SP, andd) the incremental conduction properties of DP,were similar to those found in subjects with struc-422Cardiology Journal 2012, Vol. 19, No. 4www.cardiologyjournal.orgFigure 4. Hypothetical representation of activation of systolic (SP) and diastolic (DP) potentials, His-Purkinje systemand interventricular septum, during sinus rhythm (A) and ventricular tachycardia (B). See text for detailed explanation.turally normal hearts and no ventricular arrhyth-mias, as described in our previous report [11]. Webelieve that these potentials are not specificallyfound in patients with verapamil-sensitive VT.We hypothesized that the substrates responsi-ble for SP and DP are separate thin bundles, connect-ed to the Purkinje network in a single direction [11].Figure 4 is a schematic representation of the impulsepropagation during SR and during VT. During SR, SPis activated from base-to-apex and DP from apex-to--base. Both bundles are penetrated by wavefrontspropagating through the interventricular septal myo-cardium. SP and DP were both recorded at the site ofsuccessful ablation during SR, whereas during VT, DPwas recorded away from that site (Fig. 2B).This observation suggests that SP was a criti-cal component of the reentrant circuit, whereas DPwas a bystander pathway passively activated out-side the main reentry circuit. During VT, the SP--associated bundle was penetrated in a base-to-apexdirection, activating the whole heart throughPurkinje fibers connected to the SP-associated bun-dle and His-Purkinje system. The interval betweenventricular activation and DP was shorter during VTthan during SR, probably because of incrementalconduction properties of the DP.Pre-systolic potentials preceding the Purkinje orbundle branch potentials have been described in pa-tients with verapamil-sensitive idiopathic left VT,which may reflect a critical segment of the reen-trant circuit on the basis of high success rates ofcatheter ablation or from observations made fromentrainment studies [4–10]. The basal or mid sep-tal recording sites, morphology and activation se-quence of the potentials, and slow conduction pro-perties described, are characteristics strikingly si-milar to those associated with our SP or DP.Although the SP or DP are frequently found not onlyin patients with verapamil-sensitive VT but also innormal subjects as described earlier, further stud-ies are needed to determine whether the SP or DPduring SR may be indicative of successful ablationsite of verapamil-sensitive VT.Conflict of interest: none declaredConclusionsIn a patient with verapamil-sensitive VT, SPand DP were detected on the LIVS surface duringSR and during VT. This seemed to represent a cri-tical component of the reentrant circuit, and a by-stander pathway, respectively.References1. Belhassen B, Rotmensch HH, Laniado S. Response of recurrentsustained ventricular tachycardia to verapamil. 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J Am Coll Cardiol, 2000; 36: 811–823.6. Aiba T, Suyama K, Matsuo K et al. Mid-diastolic potential isrelated to the reentrant circuit in a patient with verapamil-sensi-tive idiopathic left ventricular tachycardia. J Cardiovasc Electro-physiol, 1998; 9: 1004–1007.7. Tsuchiya T, Okumura K, Honda T et al. Significance of latediastolic potential preceding Purkinje potential in verapamil-sen-sitive idiopathic left ventricular tachycardia. Circulation, 1999;99: 2408–2413.8. Tsuchiya T, Okumura K, Honda T, Iwasa A, Ashikaga K. Effectsof verapamil and lidocaine on two components of the re-entrycircuit of verapamil-sensitive idiopathic left ventricular tachy-cardia. J Am Coll Cardiol, 2001; 37: 1415–1421.9. Aiba T, Suyama K, Aihara N et al. The role of Purkinje and pre-Purkinje potentials in the reentrant circuit of verapamil-sensi-tive idiopathic LV tachycardia. Pacing Clin Electrophysiol, 2001;24: 333–344.10. Maruyama M, Tadera T, Miyamoto S, Ino T. Demonstration ofthe reentrant circuit of verapamil-sensitive idiopathic leftventricular tachycardia: Direct evidence for macroreentry asthe underlying mechanism. J Cardiovasc Electrophysiol, 2001;12: 968–972.11. Kaneko Y, Taniguchi Y, Nakajima T et al. Myocardial bundleswith slow conduction properties are present on the left inter-ventricular septal surface of normal human hearts. J CardiovascElectrophysiol, 2004; 15: 1010–1018.

Characteristics of systolic and diastolic potentials recorded in the left interventricular septum in verapamil-sensitive left ventricular tachycardia

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Characteristics of systolic and diastolic potentials recorded in the left interventricular septum in verapamil-sensitive left ventricular tachycardia

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