Milne, D.A.

Obel, I.W.P.

Scott Millar, R.N.

English

AJOL - African Journals Online

434 _'-- _8. Read AE. The liver and drugs. In: Wriglu R, Millward-Saddler GH,Alberri KJM..M., Keraan S, eds. Liver and BIliary Disease. Vo!. 2.London: Bailliere Tindall WB Saunders, 1985: 1003-1031.9. McConnell ]B, Powell-Jackson PR, Davis M, Williams R Use ofliver function tests as predictors of rifampicin metabolism in cirrho-sis. QJMed 1981; 50: 77-82.10. Capelle P, Dhumeaux D, Mora M, er aJ. EffectS of rifampicin onliver function in man. GlII 1972; 13: 366-371.I!. Leysen DC, Haemers A, Pattyn SR. Mycobactcria and the newquinolones. Amimicrob Agencs Chemolher 1989; 33: 1-5.12. McDermot W. Pyrazinamide, isoniazid in tuberculosis. AmericanReview of Tuberculosis 1954; 69: 319-350.13. Gronhagen-Riska C. Predispo ing factors in hepatitis induced byisoniazid-rifampicin treatment of tuberculosis. Am Rev Respir Dis1968; 118: 461-466.14. Robson Se. Drug-induced allergic hepatotoxicity. CU" Allergy1991; 4: 12-16.15. Brummer DL. Isoniazid and liver disease. Ann Intern Med 1971; 75:643-647.16. Lees A\V, Asgher B, Hasheim MA, Sinha BN. Jaundice afterrifampicin. Br J Dis Chesl 1970; 64: 85-89.17. Black M, Mitchell JR, Zimmerman HJ, ec aJ. Isoniazid-associatedhepatitis in 114 patients. Gastroenlerology 1975; 69: 289-302.18. Mitchell JR, Thorgeirsson UP, Black M, ec aJ. Increased incidenceof isoniazid hepatitis in rapid acetylators. Possible relation tohydrazine metabolites. Clin Phannacol Ther 1975; 180: 70-79.OCCASIONAL REVIEW19. Zimmerman HJ. Drug-induced chronic hepatic disease. Med ClinNonh Am 1979; 63: 567.20. Scheuer PJ, La! S, Sommerfield JA, Sherlock S. Rifampicin hepa-titis. Lancer 1974; 1: 421-425.21. Cohen CD, Sayed AR, Kirsch RE. Hepatic complications of anti-tuberculosis therapy revisited. S Aft Med J 1983; 63: 960-963.22. Macloed H..M., Hay D, Stewart SM. The use of pyrazinamide plusisoniazid in the treatment of pulmonary tuberculosis. Tubercle 1959;40: 14.23. Conn HO, Binder HJ, Orr HD. Ethionamide-induced hepatitis: are,~ew \\~th a report of an additional case. Am Rev Respir Vis 1964;90: 542-552.24. Parrish AG, Robson SC, Trey C, Kirsch RE. Retrospective surveyof drug-induced liver disease at GrOOte Schuur Hospital, CapeTown - 1983 - 1987. S Aft MedJ 1989; 77: 199-202.25. Davidson CS, Levy CM, Chamberlayne EC, eds. Guidelines forDecemim of Heparoroxiciry due ro Dntgs and Chemicals (1'.TIH publica-tion _TO. 79-313). Washington, DC: DHEW, 1979.26. Benatar SR. Tuberculosis in the 1980s, ,vith particular reference toSouth Africa. S Aft Med J 1982; 62: 359-364.27. Stanford}L, Grange JM, Pozniak A. Is Africa lost? Lancer 1991;338: 557-558.28. Smith FE, Palmer DL. Alcoholism, infection and altered hostdefences: a review of clinical and experimental observations. J ChronDis 1976; 29: 35.'Map and zap' - electrode catheter techniques fortreattnent of supraventricular tachycardiasR. N. SCOTT MILLAR, D. A. MILNE, I. w. P. OBELC ardiac electrophysiologists around the worldhave become increasingly interested in the use ofelectrode catheters to ablate critical areasinvolved in the genesis and transmission of supra-ventricular tacbycardias (svrs). 1bis interest has beenstimulated by the demonstration that accessory atrio-ventricular (AV) connections in patients with Wolff-Parkinson-White (WPW) syndrome can be selectivelydamaged by radiofrequency energy (RP) delivered viacatheters insened percutaneously without general anaes-thesia. The technique and results of its use were themain topics of interest at the 9th World Symposium onCardiac Pacing and Electrophysiology held inWashington, DC, in June 1991. Effective cure of WPWsyndrome entailing freedom from tachycardias withoutdrug treatment has been reponed in more than 90% ofpatients undergoing this procedure. I Not surprisingly,this has generated a great deal of excitement as previ-ously these patients required either lifelong treatmentwith potentially toxic anti-arrhythmic drugs or open-hean surgery to ablate the accessory AV pathwaysresponsible for the tachycardias.2 The SVTs which areamenable to treatment with RF current include atrialfibrillation and flutter with uncontrollable ventricularresponse (AV node ablation), ths: WPW syndrome(accessory pathway ablation) and the extremely com-mon form of SVT, AV nodal re-entrant tachycardia (AVnode modification).Cardiac Clinic, Deparunent of Medicine, Groote SchuurHospital and University of Cape TownR. N. SCOTT MIllAR, F.C.P. (SA)D. A. MILNE, F.C.P. (SA)Milpark Hospital, Auckland Park, Johannesburg1. W. P. OBEL, F.C.P. (SA)Accepted 8 Jun 1992.Practical techniques for the control of SVTs bymeans of catheter ablation were first described in1982Y High-energy DC shocks from a defibrillatorwere transmitted via an electrode adjacent to the Hisbundle. The aim was to induce complete hean blockto allow control of the ventricular rate in patients withatrial flutter or fibrillation, otherwise uncontrollable bydrugs. Successful induction of complete hean blockrequired the implantation of a permanent pacemaker.General anaesthesia was required because of the painand muscle spasm induced by the DC shock. The highenergies (200 - 300 J) resulted in arcing at the cathetertip and vaporisation of blood that produced transientpressures up to 20 atmospheres.' The resulting baro-trauma may have been responsible for ventricular dys-function and the production of arrhythmogenic foci.Late sudden death has occurred in a small number ofpatients.6 In addition, AV conduction recurred hours tomonths later in a sizeable number of patients, presum-ably because the AV node or proximal bundle of Hishad been stunned rather than destroyed.Alternative energy sources were therefore developed.Modification of the output of the defibrillator allowedthe use of much lower energies (20 - 50 J), avoiding thebarotrauma while preserving the high-voltage heatingeffect of the shock.' 1bis method is still in use, whereashigh-energy DC shock has largely been abandoned. In1987, the use of RP energy from standard surgicalcautery machines was reponed. 8,- It was shown thatsmall, discrete lesions could be produced, providing thecatheter was in contact with the endocardium and suc-cessful ablation of the AV node could be achieved. 'oBecause RF energy does not affect nerves or muscles,general anaesthesia is not necessary. The homogeneouslesions produced seem less likely to result in newarrhythmias. The safety of the technique was somewhatoffset by a lower efficacy, probably because of the build--_---------,-----'---------------'- 435up of resistance due to charring of blood at the electrodetip and because the smaller lesions required more pre-cise positioning of the electrode. These problems havebeen addressed by the development of speciallydesigned electrodes, which can be steered and have alarger surface area. These have improved the successrates." Rerum of conduction and late arrhythmias anddepression of cardiac mechanical performance havebeen virtually eliminated.High-energy DC shocks were tried in patients withWPW syndrome, initially with limited success and signi-ficant complications, particularly in those with left-sidedaccessory pathways. However, more recently Warin eral. 12 reported impressive results in a large series ofpatients. They ablated left-sided pathways by placingthe catheter in the left atrium or the left ventricle adja-cent to the mitral annulus. Nevertheless, it was theadvent of RF ablation that led to the current widespreaduse of catheter ablation to treat patients with WPW syn-drome. Pathways in all locations around the AV ring cannow be dealt with successfully. Left-sided pathways areapproached by passing the catheter across the aorticvalve into the left ventricle and curving it behind theposterior leaflet of the mitral valve; the tip is placedagainst the mitral annulus. Accurate location of theaccessory pathway by electrophysiological mapping ofthe AV ring is essential and requires a fully equippedelectrophysiology laboratory and an experienced electro-physiologist. Procedure times of 4 - 6 hours are usualand may be considerably longer, but a high success ratecan be anticipated. A successful result means that thepatient is effectively cured without the need for surgeryor anti-arrhythmic drugs. This is both cost-effective andgratifying in a condition which results in significant -morbidity and occasionally causes sudden death. 13Complication rates appear to be low 1 and recurrencesuncommon.Where does this leave surgical treatment of WPWsyndrome? Despite the high success rates reported, ·it isacknowledged that not all patients can be successfullytreated by catheter ablation. The treatment of thosewith multiple accessory pathways and associated defectssuch as Ebstein's anomaly of the tricuspid valve is morelikely to fail. So far, RF catheter ablation of accessorypathways has been attempted in 14 patients with WPWsyndrome in South Africa and was successful in 8; 2were successfully operated on after catheter ablationfailed, 1 of whom had Ebstein's anomaly with twoaccessory pathways. There is undoubtedly a learningcurve with reported initial success rates around 50%"and improved results are anticipated with greater experi-ence. This, together with a relatively low complicationrate, augurs well for the future.The other common cause of paroxysmal SVT is re-entry within the AV node. While this usually respondswell to agents which delay AV nodal conduction ([3-blockers, veraparnil, digitalis), it occasionally becomes amajor clinical problem and fails to respond even to themore toxic anti-arrhythmic agents such as disopyramide,propafenone or amiodarone. It is now possible tomodify the upper pan of the AV node by RF energy viaa catheter so that the retrograde pathway is selectivelydamaged." Thi prevents further episodes of tachycardiawhile leaving AV conduction intact. However, there is arisk of about 10% that antegrade transmission will alsobe damaged, resulting in AV block and the need for apermanent pacemaker. It is to be hoped that refine-ments in technique will reduce this risk so that the pro-cedure can be offered to more patients.\Xlhile these 'high-tech' solutions may seem inappro-priate in the economic and social climate of present-daySouth Africa, it should be remembered that the peopleaffected by these conditions are usually young and eco-nomically active. A procedure which offers freedomfrom daily medication and the fear of breakthroughtachycardias has much to recommend it.We would like to thank Drs T. Mabin, E. Uoyd and J.Tyrrell for information about their patients.REFERENCESI. Jackman WM, Wang X, Friday KJ, ef al. Catheter ablation of acces-sory atrioventricular pathways (\Volff-Parkinson-\'\Ihite syndrome)by radiofrequency current. N Engl J Med 1991; 324: 1605-1611.2. Gallagher 11, Sealy WC, Cox JL, ef al. Results of surgery for pre-excitation caused by accessory pathways in 267 consecutive cases.In: Josephson ME, Wellens H11, eds. Tachycardias: Mechanisms,Diagnosis and Treafmem, Philadelphia: Lea & Febiger, 1984: 259-269.3. Scheinman l\1M. Morady F, Hess DS, Gonzales R. Catheter-induced ablation of the atrioventricular junction to control refractorysupraventricular arrhythmias. JAMA 1982; 248: 851- 55.4. Gallagher 11, Svenson RH, Kasell ]H, er al. Catheter technique forclosed-chest ablation of the atrioventricular conduction system. NEnglJ Med 1982; 306: 194-200.5. Bardy GH, Coltorti F, Ivey TD, er al. Some factors affecting bubbleformation with catheter-mediated defibrillator pulses. CirCIIlalion1986; 73: 525-538.6. Scheinman M.~, Evans-Bell T. Catheter ablation of the atrioven-rricular junction: a repon of the percutaneous mapping and ablationregistry. Circulation 1984; 70: 1024-1029.7. Cunningharn D, Rowland E, Rickards AF. A new low-energy powersource for catheter ablation. PACE 1986; 9: 1384-1390.8. Huang SK, Bharati S, Graham AR, er al. Closed-chesr catheterdesiccation of the atrioventricular junction using radiofrequencyenergy - a new method of catherer ablation. JAm Coll Cardiol1987; 9: 349-358.9. Aubert AE, Gewillig M, Joossens J, ef al. A new method of catheterablation of the atrioventricular junction using high frequency energy.In: Belhassen B, Feldman S, Copperman Y, eds. Cardiac Pacing andElecrrophysiology: Proceedings of rhe 8rh World Symposium on CardiacPacing and Eleclrophysiology. Tel Aviv: R+ L CreativeCommunications, 19 7: 3 9-396.10. Huang SK, Bharati S, Lev M, Marcus FI. Electrophy iologic andhistologic observations of chronic atrioventricular block induced byclosed-chest catheter desiccation "ith radiofrequency energy. PACE1987; 10: 805-816. .11. Langberg 11, Chin M, Scharnp DJ, Lee MA, er al. Ablation of theatrioventricular junction with radiofreqeuncy energy using a newelectrode catheter. Am]CardioI1991; 67: 142-147.12. Warin J-F, Haissaguerre M, D'Ivernois C, Le Metayer P,Momserrat P. Catheter ablation of accessary pathways: rechniqueand results in 248 patients. PACE 1990; 13: 1609-1614.13. GaIlaghef 11, Pritchen ELC, Sealy WC, Kasell J, Wallace AE. Thepre-exciration syndmmes. Prog CardilYUasc Dis 1978; 20: 2 5-327.14. Leather RA, Leitch lW, Klein GJ, Guiraudon GM, Yee R, KimYH. Radiofrequency catheter ablauon of accessory pathways: alearning experience. Am J Cardio11991; 68: 1651-1655.15. Haissaguerre M, Warin J-F, Lematayer P, Saoudi N, Guillem JP,Blanchor P. Closed-chest ablation of retrograde conduction inpatients with atrioventricular nodal reentrant tachycardia. N Engl JMed 1989; 320: 426-433.

'Map and zap' - electrode catheter techniques for treatment of supraventricular tachycardias

https://www.ajol.info/index.php/samj/article/download/157955/147553

'Map and zap' - electrode catheter techniques for treatment of supraventricular tachycardias

Abstract

Similar works

Full text

Available Versions

AJOL - African Journals Online