JACC Vol . 2 3 . No. 2February 1994 :525-32

PFVIEW ARTICLES

PerspectivesLoul's F .

n Invasive CLecture

RICHARD GORLIN, MD, FACC

New York, New York

The list growing and complex field of invasive cardiologyoffers a host of opportunities and challenges for the clinician .Scientific and technical advances ranging front molecular biologyto microtechnology are changing how physicians make decisionsconcerning treatment of coronary artery disease, myocardial

Interventional cardiology refers to intravascular, catheter-mediated procedures that can open, widen or close a vascu-lar pathway or can stimulate, suppress or ablate electricalactivity of the heart or provide circulatory assistance . The1993 annual meeting of the American College of Cardiologyheld no less than 20 expert panels and 30 meeting sessionsand published nearly 300 abstracts solely on subjects con-cerned with eardiologic intervention. The field is so enor-mous and is changing so fast that any "fact" presented heremay already be out of date, and any judgments must beregarded as tentative .

These interventions fall into two main categories : themechanical and the electrical . Among the earliest pervascu-lar mechanical procedures was atrioseptostomy, developedby William Rashkind (1) to create an artificial atrial septaldefect in the neonate . This led to other procedures : valvu-loplasty, percutaneous transluminal coronary angioplasty(PTCA) and atherectomy, shunt closures and circulatoryassistance, all through catheter techniques .

The era of electrical intervention began with the work ofFurman and Robinson (2), who introduced catheters forelectrical pacing of the heart . This led to the installation,through the venous system, of permanent, indwelling pace-makers. All of these procedures led ultimately to the devel-opment of focal ablation for the treatment of cardiac arrhyth-mias .

valvUloplastyThe use of catheter-mounted balloons to dilate stenotic

valves has achieved widespread application over the past

From The Mount Sinai Medical Center, New York, New York . Dr . Gorlinis the Dr. George Baehr Professor of Clinical Medicine and Senior VicePresident, The Mount Sinai Medical Center,

Manuscript received June 14, 1993 ; revised manuscript received Septem-ber 22, 1993, accepted September 27, 1993 .

Address for carmapM&M : Dr. Richard Gorlin, The Mount Sinai MedicalCenter, Box 1018, Gustave L. Levy Place, New York, New York 10029 .

01994 by the American College of Cardiology

14th160

525

infarction, unstable angina and electrophysiotogic dysfunction .The economic impact and ethical implications presented by thesedevelopments contribute to the difficulty of achieving optimaltherapeutic solutions for individual patients .

(,f Am Coll Cardiol 1994 ;23,-525-32)

decade . In mitral stenosis the balloons are advanced acrossthe atrial septum into the stenotic orifice and inflated,iadudng a satisfactory commissurotomy, with valve areasoften doubling . Results are excellent in centers with ade-quate experience when patients are carefully selected byprecise clinical and echocardiographic criteria (3,4) . Vil!vu-loplasty has almost completely replaced surgery for isolatedpulmonary stenosis . Aortic stenosis can be treated withvalvuloplasty, mainly for palliation, particularly in the eld-erly (5) and in those with advanced noncardiac disease, forwhom surgery is too hazardous (6) . Preference should begiven to surgical therapy when possible, owing to the gen-erally unsatisfactory or evanescent results of aortic vaivulo-plasty .

Vascular and Cardiac Occl densCatheter-borne closure devices, such as umbrellas, first

developed by King and Mills (7) and Rashkind (8), have nowbeen produced in sizes large enough to repair patent ductusarteriosus and atrial and ventricular septal defects . Althoughthese devices cannot be used in every case, in some circum-stances they may obviate surgery .

AngioplastyAlthough balloon angioplasty currently dominates the

field, the term is used here for any technical means ofwidening the coronary artery . The dilation technique origi-nated with Dotter and Judkins (9), who passed a guidethrough the superficial femoral artery and something akin toa bougie along the guide and through the stenosis (Fig . 1) .The introduction of the balloon catheter followed, andangioplasty was soon refined for the peripheral circulation .The late Andreas Grfintzig (10) had the courage to try it incoronary artery stenosis . This opened a new era of interven-tional cardiology (Fig . 2) .

The sophisticated catheters with guide wires, balloons

0735-1097/94/$7 .00

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and pressure delivery and infusion devices have been joinedby the laser beams, shavers, burrs and drills that can beadvanced against an atheroma to ablate it and even remove thedebris. Mason Sones, the father of selective coronary angiog-raphy, used to speculWkoe that if we were not so chary aboutabrading the coronary arteries with the catheter for fear ofproducing intimal damage, we could put a Roto-Rooter into

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Figure 1 . A, Spring guide has passed through an occlu-sion I cm in length. 8, Immediate result of full dilation .Imt, Patency continues at 8 weeks. Reproduced fromDotter and iudkins 9 with permission of the AmericanHeart Association .

them and obliterate these obstructions. Now, 30 years later,just such devices enable us to do so with reasonable impunity .

Algorithm for angioplasty . The treatment algorithm forcoronary artery disease moves along an arbitrary time line,beginning with the assessment of clinical needs, moving onto angiographic assessment and finally to the selection andimplementation of an appropriate intervention .

Figure 2 . Coronary angiography showed8511/o stenosis of the left anterior descendingcoronary artery a . A thallium-201 scanshowed a severe anteroseptal defect afterstress testing . Vessel during and immediatelyafter dilation b and c . An angiogram taKen 4weeks after coronary angioplasty showed asmooth, patent vessel d . The thallium-201exercise myocardial perfusion scintigramwas normal 6 months after coronary angio-plasty . Reprinted f.- ,m Griintzig et al . 10 bypermission of the New England Journal ofMedicine, 301 ;61-8, 1979.

JACC Vol. 23, No . 2February 1994:525-32

In the clinical assessment one must consider whether thepatient s symptoms justify intervention, whether there isevidence of inducible myocardial ischemia, whether thereare fixed or reversible perfusion deficits on imaging, thestatus of left ventricular function and, finally, patient age .gender and associated diseases . The latter three attributesinfluence both risk and efficacy. This part of the assessmentshould be made by a clinical cardiologist, not by the personwho will perform the procedure .

Assessment for coronary angioplasty includes two com-ponents: the anatomic characteristics of the vessel andlesion and certain character traits of the angioplaster . Thenumber of affected arteries and lesions, their location, cali-ber and tortuosity and whether and where there may benearby branches all need to be evaluated . To these variablesmug be added the operator s judgment and experience aswell as a personal, subjective component : The angioplasteris vulnerable to certain conflicts that could affect the deci-sion to attempt angioplasty on a given lesion . The physicianis paid for these procedures and may be referring patients tohimself or herself. Finally, personal risk tolerance, althoughbased partly on experience, will influence the physician sjudgment. How much risk is the practitioner willing toaccept, and at what price, to carry out what may be a difficultprocedure? Dispassionate insight into one s own compe-tence, confidence in one s ability and awareness of one slimitations are essential in an angioplaster .

The next issue in assessment for angioplasty is the lesionitself. Is it soft or hard calcified ? Is it concentric or eccen-tric? Is it longstanding or of recent origin? These features,in addition to those already considered, will influence thechoice of a device . There are situations in which an atherec-tomy device may be preferable to a balloon 11 . The operatormust have experience, know the attributes of the equipmentand be properly trained in its use .

The same caveats apply to stents . Experience in placingthem and understanding how and when to use them areobviously critical for anyone performing angioplasty .

Results of angioplasty justify its increasingly widespreaduse. In New York State for the first half of 1991, 31 hospitalsreported results of procedures in 5,827 patients 12 . Thisbroad sample ensures that the data represent the norm,rather than only the best or most experienced operators orspecific referral patterns . The results show rates of 0 .6% formortality, 1 .1% for myocardial infarction, 1 .7% for emer-gency bypass surgery, 3 .2% for overall complications, and88% for angiographic success . One reason for the goodresults is the point in time on a decades-long learning curve .Before 1991 most interventions were performed on only onevessel, whereas only 2 years later multiple vessels wereroutinely approached with an attendant increase in risk . In1991 fully 85% of the experience was with single-vesselangioplasty, with a low mortality rate of 0 .56%. Approxi-mately 13%, or 700 patients, underwent two-vessel angio-plasty, with a mortality rate of <I% . Only with three-vesselor left main coronary artery angioplasty did the mortality

GO!UJN

527INVASIVE CARDIOLOGY

figures begin to exceed the results from surgery 1 .9% and3.7%, respectively .

Coronary angioplasty in acute nmyocardial infarction andunstable angina . Recent reports suggest that primary angio-plasty in acute myocardial infarction may be more effectivethan thrombolytic therapy 13-16 . In acute myocardialinfarction, angioplasty is most successful when performed 1early 1 to 2 h from the onset of pain in the course of a largeanterior infarction, 2 in cardiogenic shock where little else iseffective, 3 when there is unresolved ischemia, and 4 whenthrombolytic therapy is contraindicated . But there are dis-advantages as well. It is costly . Availability is limited bothnationally and locally . Centers performing angioplasty in theacute stage of infarction must have a catheterization labora-tory and nursing and surgical teams on 24-h standby . Thereare 900 angioplasty centers nationwide, and the prospect ofequipping them to serve the 3,000 catheterization laborato-ries and 10,000 coronary care units staggers the imagination .Recent work indicates that because of the generally shortertime to intervention, intravenous thrombolysis might bepreferred to coronary angioplasty in acute myocardial infarc-tion 17 .

The single greatest disadvantage of angioplasty in acutemyocardial infarction is its unpredictability . When success-ful, the results are good, but if procedural failure or abruptvessel closure occurs, the mortality rate becomes unaccept-able 18 .

Finally, primary angioplasty for unstable angina is still anopen question . Thrombolytic therapy does not appear to ethe answer, and we are not yet certain where primaryangioplasty fits, except in patients with unremitting myocar-dial ischemia .

Restenosis . Depending on definition and criteria clinical,angiographic or pharmacologic , resteposis occurs in 30% to55% of all interventions, irrespective of the technique ordevice used, and it poses the key limitation to angioplasty/atherectomy 19,20 . Restenosis is a reparative processinitiated by the abrupt disruption of the arterial wall, involv-ing injury and denudation of endothelium and tearing orcutting of intima, often with extension to the medial layer ofsmooth muscle . The response is multifaceted, involvingplatelets and white cells attaching to binding molecules in theintimal and medial layers . There is deposition of fibrin,preceded by activation of thrombin . Release of growthfactors from a variety of cells leads to extensive constitutiveand induced gene expression for cell growth and migration .As a consequence, with time, in addition to local platelet-fibrin-thrombin interaction and adhesion, there is intimalthickening from proliferation of smooth muscle cells andconversion of some to fibroblasts . Thus, in 2 to 4 months, afibromuscular scar evolves that intrudes on the arterial!omen but to a highly variable extent .

Restenosis seems particularly aggressive at certain vas-cular anatomic sites with deep-injury angioplasty lesions andwhen the patient has been a smoker or has diabetes orelevated low density lipoprotein LDL or lipoprotein a .

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Certain tissue markers found in atherectomy specimenscan predict which patients will have early and exuberantrestenosis 21 , but whatever the physiologic process, thesize of the residual lumen determines whether there will besignificant ischemia . Danchin et al . 22 , from a study oflumen diameters versus measures of ischemia, state that ingeneral a final lumen diameter of -2 mm will forestall thelikelihood of myocardial ischemia . Angina or its equivalentwill prompt reexamination of the angioplasty result . Thequestion is not only whether restenosis has occurred, butwhat clinical meaning it has for the patient .

Approaches to restenosis. Mechanical approaches to theproblem of restenosis include excess dilation 23 and stent-ing 24,25 , whereas pharmacologic and molecular ap-proaches seek to inhibit platelet attachment, tissue growthand cell migration .

Mechanical methods . With mechanical dilation, as withany other, both the immediate and anticipated tong-termresults affect the choice of intervention . The goal is toachieve a lumen diameter adequate to avoid ischemia . Forexample, in keeping with the observation of Danchin et al .,in a vessel with a stenotic lumen < 1 mm, one will try toexpand it beyond the diameter of the normal vessel wallsegment so that when elastic recoil occurs and tissue over-growth sets in, a lumen diameter of 2 mm might remain .There is conflicting evidence that such dilation or debulking,although permitting a larger short , term postprocedure cross-sectional area, may result in deeper injury and provoke amore vigorous proliferative response with similar restenosis11 .Pharmacologic methods . Many pharmacologic agents .

ranging from antineoplastic agents 26 to agents for reducingLDL cholesterol 27 , have been used in an attempt to inhibitrestenosis . For the most part these have been found wanting .There is some slight evidence that LDL apheresis 28 or theadministration of fish oil 2931 may attenuate the fre-quency of restenosis Table 1 .

Molecular approaches . A promising and dramatic ap-proach to diminishing restenosis may be through molecularbiology, Efforts can be targeted at platelets, monocytes,endothelium or vascular smooth muscle . For example, con-centrating on vascular smooth muscle the aim is to inhibitsmooth muscle cell growth either by inhibiting growth fac-tors or receptors in the vascular smooth muscle to whichgrowth factors attach or by altering the transmembranesignals that permit growth factors to influence the cell .Another approach is to inhibit those genes that producevascular smooth muscle growth and migration .

Nabel 32 has transferred genetic material directly intothe arterial wall of the Yucatan minipig. Other groups 33have demonstrated the feasibility of introducing geneticmaterial directly into the vessel wall using catheters .

Another exciting approach is the so-called gene knockoutusing antisense molecules . Simons et al . 34 used an an-tisense oligonucleotide to inhibit the expression of the proto-oncogene c-mvb in rat arteries . This resulted in inhibition of

Table 1 . Agents Purported to Impede Restenosis AfterPercutaneous Transluminal Coronary Angioplasty

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*Possibly effective . LDL = low density lipoprotein .

smooth muscle cell prolif®ration and the resulting intimalhyperplasia after balloon injury .

Marmur et at . 35 have used in situ hybridization todemonstrate expression of tissue factor within vascularsmooth muscle of the media within hours of vessel wallinjury. Taubman M.T., personal communication March1993 has used an antisense oligonucleotide to block theexpression of tissue factor in smooth muscle cell culture .This is a prototype for similar work in vivo . These promisingapproaches, along with others, may ultimately allow us toinhibit the excessive proliferative response to vPasel wallinjury and thus control restenosis .

Economic considerations . Initial angioplasty is much lessexpensive than bypass surgery Fig. 3 . Although the costsfor the use of a catheterization laboratory or an operatingroom are similar, the ensuing hospital stay accounts for thehigher cost in patients undergoing a bypass operation 36 .The problem with angioplasty is that reintervention addsenormously to the cost because restenosis occurs in up to50% of cases 36,37 . Perhaps the unpredictability of angio-plasty costs could be managed by introducing a 30% to 40%premium to the initial cost to cover reintervention in thatportion of patients who develop significant restenosis . Thispremium could be applied in such a way that future reinter-ventions would be at no cost to the patient or to the insurer,a measure that would motivate both the angioplaster and thenospital to provide the highest quality procedures possible .

The cost of medical therapy versus angioplasty or surgeryfor angina pectoris would at first appear to be decisivelyadvantageous, ranging from $1,000 to $3, /year. But diffi-culties cloud the issue as time progresses beyond the firstyear of any therapy. Patients receiving medical therapyusually advance symptomatically or do not tolerate therapyand require coronary angioplasty or revascularization . Sim-ilarly, late restenosis after angioplasty and diminished graftpatency in patients who have had bypass surgery further

AgentStudy

first author Reference

ColchicineAntineoplastic RTiclopidine, aspirin/

dipyridamoleCoumadin/aspirinProstacyclin

O KeefeMuller et al. 26White

ThorntonKnudson

J Am Coll Cardiol 1991 ;17:181AJ Am Coll Cardiol 1991 ;17 :1268Circulation 1987 ;76 :IV-213

Circulation 1984 ;69 :721Circulation 1986 ;74 :11-282

NifedipineDiltiazem

WhiteworthCorcos

J Am Coll Cardiol 1986 ;8 :1271Am Heart J 1985 ;109:926

LDL-apheresis*Fish oil*

DaidaDehrner

J Am Coll Cardiol 1993 ;21 :34AN Engi J Med 1988 ;319 :733

Milner Am J Cardic! 1989 ;64 :249Reis Lancet 1989 ;77 :177

Lovastatin* Sahni Am Heart J 1991 ;121 :1600

JACC Vol. 23, No. 2February 1994 : 52 5-32

25

Figure 3 . Proportional contribution of various costs to the total1-year cost of bypass surgery CABG , coronary angioplastyPTCA and medical treatment for angina pectoris . Costs are givenin thousands of Dutch guilders Dfl . in 1987 1 DO had an averagevalue of 0 .49 U.S . dollar. Open bar = reinterventions ; hatched bar= operating room ; crosshatched bar = hospital stay ; solid bar =medication . Reprinted, with permission, from van den Brand et al .36 . © 1990 European Society of Cardiology .

complicate the long-term course of bypass surgery . Alongthe way, native artery disease progresses as well . Whenjudging costs it is critical to weigh the time line whencomparing the options .

Performance standards for angioplasty. When consider-ing standards for angioplasty, there are three categories toconsider : 1 operator proficiency, experience and case vol-ume adequate to maintain skills ; 2 clinical and anatomicguidelines; and 3 ethical principles. When weighing theclinical anatomic guidelines there must be constant eco-nomic as well as medical revision . When will medicaltherapy alone suffice to alleviate angina or myocardial isch-emia if improving survival is not the overriding issue? Whencan an intervention be delayed without undue risk? Are theongoing clinical trials of value?

Comparison Mth medical or surgical therapy. The diffi-culty of comparing angioplasty with medical or surgicaltherapy lies in substratification for the major variables : theinfinite range of vessel pathoanatomy, operator variabilityand, finally, selection of a device . Weintraub 38 has re-pocted registry data from trials comparing bypass surgeryand angioplasty . Mortality, myocardial infarction and 5-yearsurvival were comparable, but more revascularization pro-cedures were required after 5 years in those who underwentangioplasty . Other studies reflect this as well . The random-ized trial, RITA 37 , reports that bypass surgery and angio-plasty are comparable with respect to mortality and myocar-uial infarction . An overwhelming number of patients in theangioplasty arm, however, required reintervention for re-

Table 2 . AN Success of Percutaneous Trarrslurninal CoronaryAngioplasty in the Randomised Intervention Treatment ol AnginaRITA Trial 510 patients *

*R UA Trial Participants 37 .

stenosis and recurren ,,-e of myocardial ischemia, eventhou-gh the initial success rate was high Table 2, Fig . 4 .Preliminary results of the GAB] trial 39 reflect the sametrends. Whatever the advantages of coronary angioplastymay be, restenosis remains a serious obstacle .

Except for the small ACME trial 40 of isolated diseaseof the left anterior descending coronary artery, the clinicaltrials do not address how patients receiving optimal medicaltreatment with a combination of heta-adrenergic blockingagents, nitrates and aspirin calcium channel blockingagents fare compared with those undergoing coronary an-gioplasty or bypass surgery . Moreover, results of clinicaltrials may be confounded by the introduction of new tech-niques during their course as well as by the current ttndencyto perform multivessel angioplasty . They can, however,provide overall guidelines to selection of therapy .

Physiologic and anatomic assessment . We need to performmore physiologic evaluations before carrying out angio-plasty. Although the angioplaster naturally tends to ap-proach a lesion as an anatomic obstruction to be disposed ofby technical prowess, the patiLaCS outcome might be betterif we more routinely used intravascular ultrasound imagingfor a better quantitative as well as descriptive anatomy of thelesion. This should bt coupled with physiologic evaluation ofthe significance of any anatomic lesion 41,42 . Lesions thatappear angiographically significant may produce only atrivial decrease in pressure or Doppler flow velocity, andresponse to vasodilators may exhibit virtually normal reac-tive hyperemia. Such lesions may require no intervention .Coupling a good physiologic evaluation with our anatomicstudies may improve our long-term success rate with angio-plasty and help reduce costs through avoidance of unwar-ranted procedures .

Ethical guidelines . There is an inherent conflict of interestfor both practitioners and hospitals in the performance ofthese interventionaI procedures . They are remunerative,Thus, we must be scrupulously conscientious in ensuringthat we are not performing them to fill our hospital beds andto support our practices . Self-referral is an obvi ,. u , : ethicalmistake .

Finally, returning to the matter of risk taking, it is crucialthat angioplasters be aware of their own threshold of risktolerance and be objective about their own experience andcompetence so that decisions can be made only in the best

GORLIN

529INVASIVE CARDIOLOGY

Dilations Attemptedno.

Initial Success%

I vessel 261 902 vessels 11 58 S43 vessels 47 77

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GORLININVASIVE CARDIOLOGY

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interest of the patient. This may mean deferring the proce-dure or refeiring the patient to another interventional phy-sician .

We must also avoid being driven by the wonders oftechnology. There are no fewer than 18 devices for perform-ing atherectomy alone, as well as catheter devices for otherprocedures . It is easy to be seduced by the lure of what wecan do when we ought to be considering what we should doin the interest of our patients. Unlimited, sweeping use ofthese interventions clearly should await our ability to controlthe biologic response to injury .

Financial ethics must also govern the use of these proce-dures. Even with a good initial outcome, increased costsresulting from reinterventions and from use of these proce-dures in acute myocardial infarction need to be addressed bythe cardiologic profession before the health care system doesit for us.

Death

__

1

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215

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Figure 4 . Cumulative risk of later coronary angioplastyPTCA , bypass surgery CABG , myocardial infarctionMI or death in patients randomized to coronary angio-plasty top and bypass surgery bottom in the RandomisedIntervention Treatment for Angina RITA trial 37 . Re-printed with permission from RITA Trial Participants . Cor-onary angioplasty versus coronary artery bypass surgery :the Randomised Intervention Treatment of Angina RITATrial . Lancet 1993 ; .341 :573-80 . 0 by The Lancet Ltd 1993 .

Ablative Therapy for ArrhythmiasDrug therapy for arrhythmias is often inadequate and

ineffective and may be poorly tolerated. Furthermore, somedrugs are associated with high toxicity, and others haveproarrhythmic effects .

The past 10 to 15 years have seen the emergence oftargued tissue ablation to control arrhythmias through theelimination of either normal or accessory conduction tracts .Ablation has also sought to eliminate foci of cctopic impulseformation . Distal intracoronary injections of necrosingagents and the application of various forms of electricalcurrent proved too inexact and too traumatic for cardiactissue. The use of radiofrequency energy finally evolvedthrough the work of Gallagher et al . 43 and Scheinman etal . 44 . This energy impulse creates a well demarcated,shallow lesion and has become the technique of choice forcreating a focal lesion at the desired site . This can best be

JACC Vol. 23, No . 2February 1994 :525-32

seen in selective ablation of the atrioventricular AV nodeand certain bypass tracts 43,44 .

Antiarrhythmic drug therapy should be avoided whenpossible, particularly in young patients who could be receiv-ing these agents for life and in patients who are or whointend to become pregnant . Catheter ablation provides anopportunity to treat qualifying arrhythmias not only in suchpatients but also in those whose condition remains refractoryto drugs. Patients with a rapid ventricular response to atrialflutter or fibrillation, for which there is no pharmacologicremedy, can be treated by AV junction ablation and place-ment of a pacemaker 44,45 . Various bypass tracts leadingto AV node reentry, Wolfs Parkinson-White syndrome and,finally, certain ventricular tachycardias can now be treated46-52 .

Experience with 97 patients at The Mount Sinai MedicalCenter has yielded a 78% to 10119 success rate in a widevariety of conditions, with no mortality and only one unin-tended AV block . Reports from other major centers 45-51show that these arrhythmias respond well, with a success orcure rate between 859% and 99% . Complications are rare .Techniques for avoiding such complications as perforationand thromboses are improving daily .

Economics of ablative therapy. One year of medical ther-apy for AV node reentrant tachycardia may cost >$7,600,resulting from an average of 7.5 visits to the emergencyroom, 06 office visits, a few hospitalizations and daily use ofmultiple medications 53 . Ablative surgery is eight timesmore expensive, whereas radiofrequency ablation by cathe-ter is only about twice as expensive as medical therapy . Thecost of medical therapy is recovered in 2 years .

Ablation seems to be safe, effective and cost-effective .Therefore, it should be the primary therapy for certainsupraventricular and ventricular tachycardias .

The future . The future will see continued selective local-ization and ablation of foci of automaticity or reentry .Catheter approaches to the atrial arrhythmias to effect themaze or corridor procedure and to relieve atrial fibrillation orflutter should be explored . Ventricular arrhythmias otherthan those originating in the outflow tract of the rightventricle are becoming amenable to catheter approaches .Multiple foci can now be identified and treated . An approachis needed to the slow conducting tracts that often lie atvarying depths within the ventricular myocardium not easilyaccessible by current ablative techniques .

SummaryThe field of interventional cardiology represents the ful-

fillment of the cardiologist s perceived manifest destiny toachieve therapeutic goals through an intravascular pathwaywith diminished application of major surgery and evenpharmaceutical agents. We are limited only by the imagina-tion of the physician and the inventiveness of the microtech-nologist. In adapting to a constrained health care environ-

GORLININVASIVE CARDIOLOGY

531

meat the creativity that brought us to interve0onalcardiology can guide us to cost-effectiveness as well .

Drs. John Ambrose, J . Anthony Gomes . Davendra Mehta, Mark Taubman,Sabino Forre and Steven Winters contributed invaluable advice and criticismof the manuscript . Karen Sadock provided editorial review and preparation .

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