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Directcurrentelectricshockshavebeenusedto tvmni-nateatrialarrhythmias(cardioversion)inhumanssincethe 1960s.Thelikelihoodof successfulcardioversionandmaintenanceof sinusrhythmisincreasedif theleftatriumisnotmarkedlyenlargedandfibrotic,if thereisnomarkedleftatrialhypmtension(e.g.,mi~l stmosis),and if thearrhythmiaisnotlong-standing.Tominimizethe risk of ihrombaembolicphenoniena,therap@icanticoagulationshouldbe establishedfor at least3weeksbeforeandfor4 weeksaftercardioversion;cw-madinis usuallyusedfor thispurpose.A marerecentapproachusesiransesophagealechacardiagraphytodemonstratetheabsenceof thrambiin theleftatriumandleftatrialappendage.Ifnothrombiareevident,48hoursofheparinanticaagulaiionmaybeadequatepriorto cardioversion.Anticoagulationis stillrequiredafterCardkwersian.Quinidineanddigitalis,singlyor incom-bination,are frequentlyusedto achieveand maintainsinusrhythmin associationwithcardioversion.ForthePracedureitself,traditionalhand-held-@Me&ctrodesorself-adhesiveelectrodepadsmaybeused;theapex-

anteriorandanterior+sterior positionsareequallyef-fe@ve. &l coupkmtsandfirmpressureshouldahvays

beusedwithhand-heldpaddlestoreducetransthomcicimpedanceand maximizecurrentflow.. Electrodesshouldbewidelysepamtedtoavoidshuntingofcurrentalong the chestwall belweenelectrodes.Generally,electrodesshouldbe large in size;small“pediatric”electrodesshouldonlybeusedininfants<1 yearofage(c1O kg).ShacksshouldalwaysbesynchronizedtotheRwavetoavoidihevulnembleperiodandtheinadver-tent”inductionofventricularfib”llation.Initialshocksfora~”alfibrillationshouldbeginat 100J;atrialfluitergen-erallyrequiresa smallershock(initialshocksat 50 J).Effectiveanesthesia,notmerelysedation,isrequiredtoachieveamnesiaand avoidpain.Excitingnewdevel-opmentsin defibrillationand cardioversionhave oc-curred.Itisnowunderstoodthatexcessiveenergyandcurrentmayinducecardiacdamage,andrecentstudiessuggestsuchdamagemaybemediatedin partby freeradicals.Newshackwaveforms,suchas biphasicandmuhiphasicwavefwmsfrom multipleencirclingelec-trodes,maybe superiortothestandarddampedsinu-so-kialwaveform.

(AmJCardiol1996;78(suppl8A):22-26)

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From the Departmentof InternalMedicine, University of Iowa Haspi-tals and Clinics, Iowa City, Iowa.

Address for reprints: Richard E. Kerber, MD, Departmentof inter-nal Medicine, University of Iowa Hospital, 200 Hawkins Drive, lowaCity, lowa 52242.

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