615

LETTERS TO THE EDITOR

To the Editor:Mittal and Lerman1 recently raised serious doubts about

the clinical utility and diagnostic value of the head-up tilttesting (HUT) protocol, especially when nitroglycerin (TNT)challenge is used.

TNT-HUT is a specific test provided some basic rules areobserved. An Expert Consensus Document of the Ameri-can College of Cardiology2 and the more recent Guidelineson Syncope of the European Society of Cardiology3 pro-vided specific recommendations on the methodology of thetest and the interpretation of the results. HUT is consideredpositive (being the test interrupted) only when syncope oc-curs. Presyncope, minor symptoms, and pure vasodepressiveresponses after TNT (“exaggerated responses”) should notbe considered positive responses. When such criteria arefollowed, TNT-HUT maintains a positivity rate >50% andspecificity >90%.4 Since 2000, the standardized TNT-HUTprotocol is known as The Italian Protocol.5 The protocolused by Mittal et al.6 differs from The Italian Protocol in thatit lacks a drug-free phase and induction of syncope is notrequired for positivity; therefore, the relative limitations ofMittal’s protocol cannot be extended to The Italian protocol.

We agree with the authors that there are several limita-tions relative to the clinical role of HUT. Several studies onfollow-up failed to show any correlation between the type orseverity of the HUT response and the syncope recurrences.The weak correlation between the patterns of the HUT in-duced and the spontaneous syncope reduces the role of HUTin defining the optimal treatment in individual patients. Fi-nally, the poor reproducibility of the positive responses alsoweakens the usefulness of HUT for assessing any treatment.Based on that, the clinical role of HUT must be reconsidered,but this does not mean that the test is lacking any clinicalutility and therefore is “on the road to obsolescence.” In fact,HUT still maintains a relevant utility for diagnostic as well asprognostic purposes. As a diagnostic tool, HUT can be usefulif it is performed properly on patients with recurrent unex-plained syncope, especially in the elderly. In this age group,vasovagal syncope often presents with atypical clinical mani-festations (absence of prodromes and/or typical precipitatingfactors) that make diagnosis based on the clinical history un-certain. Moreover, by itself, HUT may have a “therapeutic”effect in preventing recurrences. The uncertainty about theetiology of disturbance may lead to a degree of anxiety thatcan facilitate recurrence. A significant decrease of syncopalrecurrences has been observed after a positive HUT.7 Finally,identification of clinical prodromes during HUT can help pa-tients to recognize the incipient syncope, thus decreasing itsseverity and possibly preventing it with measures such ascounterpressure maneuvers.

Therefore, we believe think the tilt test is not obsolete andmaintains some utility provided it is used with a standardizedprotocol with appropriate indications.

ATTILIO DEL ROSSO, M.D.Department of CardiologyOspedale San Pietro Igneo

Fucecchio, ItalyE-mail: elettrofisiologia@usl11.tos.it

ANGELO BARTOLETTI, M.D.Department of Cardiology

Ospedale Nuovo San Giovanni di DioFlorence, Italy

MICHELE BRIGNOLE, M.D.Department of Cardiology

Ospedali RiunitiLavagna, Italy

References

1. Mittal S, Lerman BB: Tilt testing: On the road to obsolescence? J Car-diovasc Electrophysiol 2003;14:925-926.

2. Benditt DG, Ferguson DW, Grubb BP, et al: ACC expert consensusdocument. Tilt table testing for assessing syncope. J Am Coll Cardiol1996;28:263-275.

3. Brignole M, Alboni P, Benditt D, et al: Guidelines on management(diagnosis and treatment) of syncope. Eur Heart J 2001;2:1256-1306.

4. Del Rosso A, Ungar A, Bartoli P, et al: Usefulness and safety of short-ened head-up tilt testing potentiated with sublingual glyceryl trinitratein older patients with recurrent unexplained syncope. J Am Geriatr Soc2002;50:1324-1328.

5. Bartoletti A, Alboni P, Ammirati F, et al: “The Italian Protocol”: A sim-plified head-up tilt testing potentiated with oral nitroglycerin to assesspatients with unexplained syncope. Europace 2000;2:339-342.

6. Mittal S, Stein KM, Markowitz SM, et al: In search of an optimal tilttest protocol. Circulation 1999;106:II-85.

7. Sheldon R, Rose S, Flanagan P, et al: Risk factors for syncope recur-rence after a positive tilt-table test in patients with syncope. Circulation1996;93:973-981.

doi: 10.1046/j.1540-8167.2004.03697.x

Reply to the Editor:In a recent editorial, we raised several issues regard-

ing the clinical utility of tilt table testing.1 Drs. Del Rossoet al. have expressed some concerns about our pessimism.We appreciate their comments.

In essence, Drs. Del Rosso et al. take issue with our po-sition because they believe that a nitroglycerin-based tilt testprotocol, as represented by The Italian Protocol, is an effec-tive diagnostic test for assessing neurally mediated syncope.2

However, we have considerable reservations with the utilityof a test that in our laboratory has a specificity of 50%.3 If thechances of a false-positive outcome are similar to the odds ofa coin flip, little benefit can be gained by performing the test.

A pertinent question is whether our methodology differssignificantly from that used in The Italian Protocol and there-fore accounts for differences in specificity. We do not believethis is the case. We too considered a test positive only ifsyncope developed. Although, in contrast to The Italian Pro-tocol, our control subjects did not first undergo a drug-freetilt phase, we believe that if this factor affected outcome, itwas to underestimate the false-positive rate, not increase it.

We agree that a test able to diagnose neurally mediatedsyncope in the elderly has important clinical relevance. How-ever, drug-free, isoproterenol, and adenosine tilt tests all showreduced “sensitivity” in elderly patients,4-6 and although ithas been suggested that nitroglycerin-based tilt testing isnot prone to the same limitation,7 others have shown poor

616 Journal of Cardiovascular Electrophysiology Vol. 15, No. 5, May 2004

specificity of nitroglycerin tilt testing in an elderly patientpopulation.8 Therefore, in our opinion, it is unclear if thereis a tilt test protocol that can reliably diagnose neurally me-diated syncope in the elderly.

Finally, it was not our intent to suggest that tilt table testingis presently obsolete. In fact, we suggested that tilt table test-ing has “modest clinical value.” However, in our judgment,without the advent of newer provocative agents that havehigher positive yields and specificity than those presentlyavailable, the future of tilt table testing for evaluating patientswith suspected neurally mediated syncope is suspect.

SUNEET MITTAL, M.D.BRUCE B. LERMAN, M.D.

Department of MedicineDivision of Cardiology

Cornell University Medical CenterNew York, New York, USA

E-mail: sum2010@med.cornell.edu

References

1. Mittal S, Lerman BB: Tilt testing: On the road to obsolescence? J Car-diovasc Electrophysiol 2003;14:925-926.

2. Bartoletti A, Alboni P, Ammirati F, Brignole M, Del Rosso A, FogliaManzillo G, Menozzi C, Raviele A, Sutton R: “The Italian Protocol”:A simplified head-up tilt testing potentiated with oral nitroglycerin toassess patients with unexplained syncope. Europace 2000;2:339-342.

3. Mittal S, Stein KM, Markowitz SM, Slotwiner DJ, Iwai S, Das MK,Cohen JD, Hao SC, Lerman BB: In search of an optimal tilt test protocol.Circulation 2002;19:II-85.

4. Lipsitz LA, Marks ER, Koestner J, Jonsson PV, Wei JV: Reduced sus-ceptibility to syncope during postural tilt in old age. Arch Intern Med1989;149:2709-2712.

5. Sheldon R: Effects of aging on responses to isoproterenol tilt-table test-ing in patients with syncope. Am J Cardiol 1994;74:460-463.

6. Mittal S, Stein KM, Markowitz SM, Iwai S, Guttigoli A, Lerman BB:A single-stage adenosine tilt test in patients with unexplained syncope.J Cardiovasc Electrophysiol 2004;(In press).

7. Mussi C, Tolve I, Foroni M, Valli A, Ascari S, Salvioli G: Specificityand total positive rate of head-up tilt testing potentiated with sublingualnitroglycerin in older patients with unexplained syncope. Aging ClinExp Res 2001;13:105-111.

8. Kumar NP, Youde JH, Ruse CE, Fotherby MD, Masud T: Responses tothe prolonged head-up tilt followed by sublingual nitrate provocation inasymptomatic older adults. Age Ageing 2000;29:419-424.

doi: 10.1046/j.1540-8167.2004.04018.x

ECG Algorithm for Idiopathic VentricularOutflow Tract Tachycardia

To the Editor:In a recent publication, Ito et al.1 reported an ECG algo-

rithm for identifying the optimal ablation site for idiopathicventricular outflow tract tachycardia. They reviewed 80 pa-tients with outflow tract ventricular tachycardia (VT).

We have published an article reviewing idiopathicmonomorphic VT originating from the left aortic cusp intwo children.2 The ECGs from these children demonstratedleft bundle branch block morphology, no r wave in lead V1,and inferior QRS axis. R/S wave transition was between leadsV2–V3 in one case and V4–V5 in the other. The initial impres-sion was right ventricular outflow tract (RVOT) tachycardia.However, tachycardia foci could not be located in the RVOT

region. VT foci were identified with left ventricular outflowtract (LVOT) mapping in both cases at the left aortic cusp area,approximately 1cm below the left coronary artery. Coronaryangiograms were performed before and after successful RFablations in both cases. When the ECG algorithm proposedby Ito et al. 1 is followed, both of these cases seem to haveVT with RVOT origin. In one of our patients, the RVOT areademonstrated early local electrograms (<20 ms comparedto the QRS complex). Therefore, if LVOT and the coronarycusp areas were not mapped, we would not have been able tolocate the correct focus. Coronary angiography guided care-ful ablation strategy in the aortic cusp region can eliminatethe VT focus safely and successfully, as was demonstrated inthese children.

Similar cases have been reported in adults in whom themorphology during VT appeared to be consistent with anRVOT origin; however, extensive mapping demonstrated afocus in the left aortic cusp. A recent study reviewed VToriginating from the aortic cusp region.3 In that review, itwas proposed that, based on ECG criteria, it may be possibleto differentiate between VT of RVOT origin from that ofaortic cusp origin. It is of note that the ECG criteria proposedin that article could not be verified in pediatric patients.2

Ito et al.1 had 11 patients with VT of left sinus of Valsalvaorigin. All of their patients were adults. The different ECGpatterns in children could have been related to the age andsize of the patients. Therefore, before proposing reliable ECGalgorithms for determining the focus of idiopathic VT, morepatients including children need to be studied. Also, in anypatient with an ECG pattern suggestive of VT of RVOT origin,the possibility of aortic cusp origin should be considered.

VOLKAN TUZCU, M.D.Cincinnati Children’s Hospital Medical Center

University of CincinnatiCincinnati, OH, USA

E-mail: volkan.tuzcu@cchmc.org

References

1. Ito S, Naito S, Kurosaki K, Ueda M, Hoshizaki H, Miyamori I, TaniguchiK, Nogami A: Development and validation of an ECG algorithm foridentifying the optimal ablation site for idiopathic ventricular outflowtract tachycardia. J Cardiovasc Electrophysiol 2003;14:1280-1286.

2. Gonzalez y Gonzalez MB, Will JC, Tuzcu V, Schranz D, Blaufox AD,Saul JP, Paul T: Idiopathic monomorphic ventricular tachycardia origi-nating from the left aortic sinus cusp in children: Endocardial mappingand radiofrequency catheter ablation. Z Kardiol 2003;92:155-163.

3. Quyang F, Fotuhi P, Ho SY, Hebe J, Volkmer M, Goya M, Burns M, AntzM, Ernst S, Cappatto R, Kuck KH: Repetitive monomorphic ventriculartachycardia originating from the aortic sinus cusp. J Am Coll Cardiol2002;39:500-508.

doi: 10.1046/j.1540-8167.2004.03700.x

Reply to the Editor:We thank Dr. Tuzcu for his comment. We agree that there

are several cases that do not match our developed ECG al-gorithm.1 As pointed out by Dr. Tuzcu, the age and size ofthe patients may affect the ECG pattern of the outflow tracttachycardia in pediatric patients. However, we cannot deter-mine this because we do not the ECG data for the children.Nevertheless, we continue to believe that our ECG algorithm

Letters to the Editor 617

can be used to identify the optimal ablation site, with highsensitivity and specificity, when it applies to adult patientswith idiopathic ventricular outflow tract tachycardia.

HIROSHI TADA, M.D.Division of Cardiology

Gunma Prefectural Cardiovascular CenterMaebashi, Gunma, Japan

E-mail: tada.h@cvc.pref.gunma.jp

Reference

1. Ito S, Tada H, Naito S, Kurosaki K, Ueda M, Hoshizaki H, MiyamoriI, Oshima S, Taniguchi K, Nogami A: Development and validationof an ECG algorithm for identifying the optimal ablation site for idio-pathic ventricular outflow tract tachycardia. J Cardiovasc Electrophysiol2003;14:1280-1286.

doi: 10.1046/j.1540-8167.2004.04013.x

Double Potentials as a Criterion forCavotricuspid Isthmus Block?

To the Editor:In the September 2003 issue of the Journal, Tada et al.1

presented data on the influence of isoproterenol and/or amio-darone on the double potential interval along the ablation lineacross the cavotricuspid isthmus. They revealed that amio-darone results in rate-dependent prolongation of this inter-val, whereas isoproterenol has opposite effect, despite thepresence of complete isthmus block, and this effect is ac-centuated by amiodarone. The authors conclude that doublepotential criteria of the block should not be used when abla-tion is performed in the presence of amiodarone. Althoughthese data are interesting, it appears that the main principleof analysis of double potentials along the ablation line, asinitially suggested by Shah et al.,2,3 is not appreciated. In re-ality, it should be based on timing of the second componentthat must be the latest in the right atrium, regardless of theabsolute values of the double potential interval. However, the

Figure 1. Setup of signals for a simplified electrophysiologic approach during low right atrial (LRA) pacing with the second multipolar diagnostic catheterplaced within the coronary sinus (CS 2.1 to 10.9) and ablation catheter on the cavotricuspid isthmus line (ABL d). The complex on the left side of the figuredocuments the situation before creation of complete block; the right side of the figure shows complete isthmus block. The first pair of arrows marks narrowlyspaced double potentials on the line before block; the second pair of arrows identifies widely separated double potentials after achievement of block. Notethat the timing of the second component is later than the local electrogram from CS 9,10. This pattern should be expressed at any point along the ablationline.

prerequisite for such analysis is point-by-point deploymentof the linear lesion and not dragging of the catheter during ra-diofrequency energy application. Only this allows meaning-ful analysis in all cases. Accordingly, Anselme et al.,4 whoused a stepwise withdrawal technique during energy delivery,found clear-cut double potentials suggesting block in only54% patients, while 39% presented with ambiguous doublepotentials.

Based on the pioneering work of the Bordeaux group,2,3

we use a modified, electrophysiologically guided approach toablation of cavotricuspid isthmus that allows immediate as-sessment of the block.5 In principle, two electrophysiologiccatheters are used to delineate both sides of the cavotricuspidisthmus width, i.e., a quadripolar catheter placed in the lowright atrium adjacent to the isthmus and a quadripolar or mul-tipolar catheter located in the coronary sinus. The interval be-tween local electrograms from the right atrium and proximalcoronary sinus ostium provides guidance for catheter abla-tion. Low right atrial pacing is used when flutter terminatesand/or when the procedure is performed from the beginningin sinus rhythm. Keeping the signal from the ablation catheterin between the above signals ensures a lesion perpendicularto the advancing wavefront and minimizes the need for fluo-roscopy. Radiofrequency applications are delivered point bypoint, starting at the tricuspid annulus. After each applica-tion, the catheter is moved slightly toward the inferior venacava until previously created double signals merge together,and this is the point for another application. Achievement ofblock is easy to follow (Fig. 1). Similar criteria apply whenassessing the effect during coronary sinus ostial pacing. Incase of any doubt, so-called differential pacing is easily appli-cable.6 In addition, this technique enables detailed analysisof the morphology of double potentials.7,8

Besides assessment of the block, this approach allows sig-nificant reduction of both procedural and fluoroscopy time.Analysis of 86 consecutive cases of flutter ablation performedwith an 8-mm tip over a 12-month period revealed meanprocedural time of 106.6 ± 53.5 minutes and total fluoro-scopic time of 3.8 ± 2.8 minutes. The acute success rate was95.3% (in 3 of 4 failures, only transient block was achieved).Therefore, we believe that double potential analysis along the

618 Journal of Cardiovascular Electrophysiology Vol. 15, No. 5, May 2004

ablation line is a preferable method for determining completebidirectional cavotricuspid isthmus block.

JOSEF KAUTZNER, M.D., PH.D.ROBERT CIHAK, M.D., PH.D.

PETR PEICHL, M.D.Department of Cardiology

Institute for Clinical and Experimental MedicinePrague, Czech Republic

References

1. Tada H, ´Ozaydin M, Ghugh A, et al: Effects of isoproterenol and amio-darone on the double potential interval after ablation of the cavotricuspidisthmus. J Cardiovasc Electrophysiol 2003;14:935-939.

2. Shah DC, Haissaguerre M, Jais P, et al: Simplified electrophysiolog-ically directed catheter ablation of recurrent common atrial flutter.Circulation 1997;96:2505-2508.

3. Shah DC, Takahashi A, Jais P, et al: Local electrogram-based criteria ofcavotricuspid isthmus block. J Cardiovasc Electrophysiol 1999;10:662-669.

4. Anselme F, Savoure A, Cribier A, Saoudi N: Catheter ablation of typi-cal atrial flutter: a randomized comparison of 2 methods for determin-ing complete bi-directional isthmus block. Circulation 2001;103:1434-1439.

5. Kautzner J: Electrophysiologically directed catheter ablation of atrialflutter. (Abstract) Europace 2001;2(Suppl B):B71.

6. Shah DC, Haissaguerre M, Takahashi A, et al: Differential pacing fordistinguishing block from persistent conduction through an ablationline. Circulation 2000;102:1517-1522.

7. Tada H, Oral H, Sticherling C, et al: Double potentials along the ablationline as a guide to radiofrequency ablation of typical atrial flutter. J AmColl Cardiol 2001;38:750-755.

8. Tada H, Oral H, Sticherling C, et al: Electrogram polarity and cavotricus-pid isthmus block during ablation of typical atrial flutter. J CardiovascElectrophysiol 2001;12:393-399.

doi: 10.1046/j.1540-8167.2004.04008.x