Motor Vehicle Accidents in Patients With an Implantable Cardioverter-Defibrillator

Transcription

1 180 JACC Vl. 26, N. 1 July 1995:180-4 Mtr Vehicle in Patients With an Implantable Cardiverter-Defibrillatr ANNE B. CURTIS, MD, FACC, JAMIE B. CONTI, MD, FACC, KELLY J. TUCKER, MD, PAUL S. KUBILIS, MS, ROBERTA E. REILLY, BA, DAVID A. WOODARD, MD Gainesville, Flrida Objectives. This study was designed t examine driving safety in patients at risk fr sudden death after implantatin f a cardiverter-defibrillatr. Backgrund. Cardiverter-defibrillatrs are frequently implanted in patients at high risk fr sudden death. Despite cncern abut the safety f driving in these patients, little is knwn abut their actual mtr vehicle accident rates. Methds. Surveys were sent t all 742 physicians in the United States invlved in cardiverter-defibrillatr implantatin and fllw-up. Physicians were questined abut numbers f patients fllwed up, numbers f fatal and nnfatal accidents, physician recmmendatins t patients abut driving and knwledge f state driving laws. Results. Surveys were returned by 452 physicians (61%). A ttal f 30 mtr vehicle accidents related t shcks frm implantable defibrillatrs were reprted by 25 physicians ver a 12-year perid frm 1980 t Of these, nine were fatal accidents invlving eight patients with a defibrillatr and ne passenger in a car driven by a patient. N bystanders were fatally injured. There were 21 nnfatal accidents invlving 15 patients, 3 passengers and 3 bystanders. The estimated fatality rate fr patients with a defibrillatr, 7.5/100,000 patient-years, is significantly lwer than that fr the general ppulatin (18.4/100,000 patient-years, p < 0.05). The estimated injury rate, 17.6/100,000 patient-years, is als significantly lwer than that fr the general public (2,224/100,000 patient-years, p < 0.05). Only 10.5% (30 f 286) f all defibrillatr discharges during driving resulted in accidents. Regarding physician recmmendatins, mst physicians (58.1%) ask their patients t wait a mean (-+SD) f mnths after implantatin r a shck befre driving again. Cnclusins. The mtr vehicle accident rate caused by discharge frm an implantable cardiverter-defibrillatr is lw. Althugh restricting driving fr a shrt perid f time after implantatin may he apprpriate, excessive restrictins r a ttal ban n driving appears t be unwarranted. (J Am Cil Cardil 1995;26:180-4) Driving recmmendatins fr patients with an implantable cardiverter-defibrillatr (ICD) vary widely amng cardilgists, with n natinal cnsensus at the present time. Despite the emtinally charged discussins that this tpic may generate, there are limited data n the risk f driving in patients with ICDs. There have been tw surveys f physician practices regarding patients with ICDs (1,2), but these did nt include data n specific utcmes in ICD patients wh drive. It is well knwn that many patients with ICDs drive against physician advice. In a survey f ICD recipients fllwed up at the University f Suth Carlina, 70% f patients resumed driving, mst by 8 mnths after implantatin (3). Tw f the patients reprted discharge f their ICDs while driving, but n accident r injury was reprted. An analysis f driving hazard, defined as ccurrence f ventricular tachycardia r fibrillatin, syncpe r defibrillatr discharge, in patients with ICDs frm ne university hspital fund that it was maximal in the first Frm the Department f Medicine, University f Flrida, Gainesville, Flrida. Manuscript received Octber ; revised manuscript received February 6, 1995, accepted February 27, Address fr crrespndence: Dr. Anne B. Curtis, Bx , University f Flrida, Gainesville, Flrida mnths after ICD implantatin and diminished substantially after that (4). This led t the recmmendatin t restrict driving in the first 7 mnths after ICD implantatin. Hwever, natinal data n actual accident rates and fatalities in patients with ICDs culd be helpful in frmulating plicy. We therefre cnducted a survey f all physicians invlved in ICD implantatin and fllw-up in the United States t determine their recmmendatins t patients regarding driving and t cllect infrmatin n mtr vehicle accidents and fatalities in patients with ICDs. The results f the survey frm the basis f this reprt. Methds All physicians invlved in ICD implantatin and fllw-up were identified frm a cmputer list prvided by Cardiac Pacemakers, Inc. Infrmatin requested in the survey included the length f time that the physician had been perfrming defibrillatr implantatins, the apprximate ttal number f patients fllwed up, recmmendatins made t patients regarding driving, what factrs physicians cnsidered in making thse recmmendatins (i.e., type f device, type and stability f presenting arrhythmia), knwledge f state laws abut driving in patients with arrhythmias and accidents and fatalities and injuries reprted by patients and their families. T main by the American Cllege f Cardilgy /95/$ (95)00133-O

2 JACC Vl. 26, N, I CURTIS ET AL. 18] July 1995:180 4 AUTO ACCIDENTS AND DEFIBRILLATORS Mtr Vehicle 30 Figure 1. Mtr vehicle accidents invlving implantable cardiverter-defibrillatr recipients. There were a ttal f 30 fatal and nnfatal injuries reprted. Nnfatal / \ / 21 \ patients passengers bystanders tain cnfidentiality, the surveys were cded by number. If mre than ne survey was returned frm ne institutin r practice, the survey f the mst senir member f the grup as defined by lnger duratin f time frm first implantatin and greater number f patients fllwed up was retained, and the ther(s) set aside. Reprts f accidents and injuries were checked by ne f us fr duplicatin by examining the state f rigin f the reprt. If mre than ne accident was reprted frm any ne state, the surveys were examined further fr the descriptin f the accident and whether tw reprts came frm the same institutin, with duplicates set aside. There was ne duplicate reprt each f a fatality and an injury. The frequency f fatal and nnfatal injuries was cmpared with similar data frm the U.S. Bureau f the Census. Sme f the physicians left blanks fr sme f the questins, s that nt all f the percentages presented here add up t 100%. Statistical analysis. Data fr cntinuus variables are summarized and reprted as mean value +_ SD. Percentages and rates estimated frm the survey respnses are reprted with 95% cnfidence intervals (CI) when apprpriate. The chisquare statistic r Fisher exact test was used t cmpare respnse percentages between independent grups f respndents. Methds based n the Pissn distributin were used t cmpare fatality, injury and accident rates amng ICD recipients with thse amng knwn ppulatin rates (5). Results Physician experience. A ttal f 742 surveys were mailed ut, f which 452 (61%) were returned. Fifty surveys prvided duplicate infrmatin fr certain centers and were nt analyzed further, s that a ttal f 402 surveys were analyzed fr this reprt. The physicians in the survey, wh represented 48 states and the District f Clumbia, had been implanting ICDs fr a mean f 5.8 _+ 2.6 years (range 1 t 12). The mean number f 1CD recipients fllwed up by each physician was estimated by the physicians themselves t be 141 _+ 144 (range I t 1,000), r >54,000 fr all respndents f the survey. At the time the survey was sent ut (1992), ~-32,000 patients were knwn t have received ICDs in the United States (persnal cmmunicatin with U.S. ICD manufacturers). Thus, because 61% f the surveys were returned, the physicians had clearly verestimated the actual number f patients with an ICD and fllw-up data. amng ICD recipients. Despite the large number f ICDs implanted natinwide, very few accidents have been reprted amng ICD recipients. Fully 93.3% (374 f 401, 95% CI 90.8% t 95.7%) f the physicians were unaware f any accidents amng their patients. Twenty-five physicians reprted 30 accidents; f the 25, 3 physicians reprted 2 accidents each, and 1 reprted 3 accidents. Nt surprisingly, the mst experienced implanters were mre likely t be aware f accidents invlving patients with devices. Fr physicians with up t 50 1CD implantatins, nly 1.4% (2 f 140, 95% CI 0.0% t 3.4%) were aware f accidents, whereas 9.4% f physicians with 51 t 1,000 implants (23 f 244, 95% CI 5.8% t 13.1%) had knwledge f accidents amng patients with devices (p = 0.002). There were eight patient fatalities, all related t lss f cnsciusness with the device firing while the patient was driving. There was ne fatality f a passenger in a vehicle driven by a patient with an ICD, but n bystanders were fatally injured (Fig. 1). T determine a driving-related fatality rate fr ICD recipients, certain assumptins were necessary because f the verestimatin f the numbers f ICD recipients by the respnding physicians. At the time f the survey, -32,000 patients had received ICDs in the United States. Using 1- t 7-year survival rates fr ICD recipients (all-cause mrtality; persnal cmmunicatin, Cardiac Pacemakers, Inc., AICD Database; als ref. 6), and extraplating 8- t ll-year survival rates by assuming a yearly survival rate f 95% after 7 years, the ttal number f patient-years represented by the 32,000 ICD recipients thrugh 1992 is -195,900. If 61% f all ICD recipients are assumed t be represented by the 61% f physicians wh respnded t the survey, then 119,500 patientyears are represented by the survey results. Nine drivingrelated fatalities amng ICD recipients reprted in the survey wuld thus yield a ttal fatality rate f 7.5/100,000 patientyears (95% CI 4.1/100,000 t 17.1/100,000). This rate is statistically lwer than the 1989 general ppulatin driving-related

3 182 CURTIS ET AL. JACC Vl. 26, N. l AUTO ACCIDENTS AND DEFIBRILLATORS July 1995:180 4 c 300 U) 400 *P= t J= 0, m f~,d u~ >,.c a. N~ [] Advised Against Driving Did Nt Advise Against Driving # Patients with shcks while driving Figure 2. Number f patients whse implantable cardiverterdefibrillatr fired while driving, as reprted by each physician. fatality rate f 18.4/100,000 patient-years (p < 0.05) (6). If the results f the survey are assumed t represent all 195,900 ICD-recipient patient-years, the driving-related fatality rate fr this grup wuld be even lwer, 4.6/100,000 patient-years (95% CI 2.1/100,000 t 8.7/100,000), and wuld als differ significantly frm the 1989 general ppulatin rate (p < 0.05). Fifteen nnfatal injuries ccurred amng patients with ICDs; in additin, three passengers and three bystanders were injured (Fig. 1). With 21 injuries amng 19,520 patients with an ICD, the driving-related injury rate is 17.6/100,000 patientyears (95% CI 10.9/100,000 t 26.9/100,000). If the 21 reprted injuries represented the ttal number fr all 195,900 implant recipient patient-years, the injury rate wuld be 10.7/100,000 patient-years (95% CI 6.6/100,000 t 16.4/100,000). In either case, these rates are clearly lwer than the 1990 natinal rate f 2,224/100,000 patient-years (p < 0.05) (7). Hwever, the prprtin f all injuries that were fatal is much higher amng ICD recipients than amng the general public. The percentage fr ICD recipients is 30% (9 f 30, 95% CI 13.6% t 46.4%), whereas that based n natinal statistics is 0.83% (18.4 f 2,224) (p < ). Althugh the fatality and injury rates were lw amng ICD recipients, a much larger percentage f physicians reprted that patients had their devices fire while they were driving withut any accident r injury. Fully 30.9% f the physicians wh respnded (124 f 401, 95% CI 26.4% t 35.4%) reprted having patients whse devices had fired while they were driving. Eighty-fur f these physicians (67.7%, 95% CI 59.5% t 76.0%) reprted ne r tw instances f ICD shck delivery during driving; the rest reprted frm 3 t 15 instances (Fig. 2). Because 30 fatal and nnfatal injuries were reprted, nly 10.5% f ICD discharges (30 f 286 ttal reprted firings, 95% CI 6.9% t 14.0%) resulted in accidents. Driving recmmendatins. Driving is permitted by 79% f the physicians respnding t the survey; nly 20.8% (83 f 400, 95% CI 16.8% t 24.7%) issue a blanket prhibitin f driving t their patients. Hwever, the majrity f physicians recmmend that their patients wait a variable length f time befre resuming driving. Mst physicians (58.1%, r 233 f 401, 95% CI 53.3% t 62.9%) ask their patients t refrain frm driving J~ E z 100 Aware f Unaware f Figure 3. Effect f physician awareness f mtr vehicle accidents amng implantable cardiverter-defibrillatr recipients n driving recmmendatins. until a specified length f time has passed withut a shck (mean 7.3 _+ 3.4 mnths). The mst cmmn shck-free interval mentined was 6 mnths, which was the recmmendatin f 66.1% f the physicians wh specified a waiting perid (154 f 233, 95% CI 60.0% t 72.2%). Awareness f ICD-related accidents influenced the plicies recmmended by physicians t their patients. Of the physicians wh were aware f ICD-related driving accidents invlving their patients, 44% (11 f 25, 95% CI 24.5% t 63.5%) advised their patients t refrain frm driving, whereas nly 19.4% f physicians (72 f 372, 95% CI 15.3% t 23.4%) wh were unaware f accidents invlving their patients advised against driving (p = 0.003) (Fig. 3). Physician awareness f driving laws. Physician awareness f the driving laws in their wn states was rather pr. Only 31.2% (125 f 401, 95% CI 26.6% t 35.7%) knew the legal requirements in their wn states; the rest reprted being unaware f relevant laws. Physician experience with ICDs did nt crrelate with knwledge f laws abut driving (Table 1). Of the 125 physicians wh did knw their state's laws, 26 (20.8%, 95% CI 13.7% t 27.9%) admitted t advising their patients cntrary t thse laws. Influence f type f device and primary event n driving recmmendatins. The nature f the patient's primary event influenced many physicians' willingness t recmmend that their patients drive. Whether the patient's primary event was ventricular tachycardia r ventricular fibrillatin was imprtant in decisin making fr 59.8% f the physicians (237 f 396, Table I. Physician Implantatin Experience Versus Knwledge f State Law Regarding Driving Restrictins Aware f State Driving Law (%) N. f Implantatins Perfrmed < (I >200 Yes N

4 JACC Vl. 26, N. 1 CURTIS ET AL. 183 July 1995:180-4 AUTO ACCIDENTS AND DEFIBRILLATORS 95% CI 55.0% t 64.7%), but it made n difference fr 40.2% (159 f 396, 95% CI 35.3% t 45.0%). Lw and high vlume implanters were similarly influenced by the patient's primary arrhythmia. If a patient's primary rhythm disturbance was stable ventricular tachycardia, nly three physicians (0.7%, r 3 f 402, 95% CI 0.0% t 1.6%) thught that driving shuld be prscribed. In cntrast, 64.2% f physicians (258 f 402, 95% CI 59.5% t 68.9%) wuld nt allw patients t drive with unstable ventricular tachycardia r ventricular fibrillatin. Twenty-five percent f physicians (99 f 402, 95% CI 20.4% t 28.8%) wuld nt allw driving fr any f these rhythm disturbances. The mst cnservative physicians were the least likely t be influenced by the type f arrhythmia in advising their patients. Only 20.7% f thse wh advised against driving cmpletely (17 f 82, 95% CI 12.0% t 29.5%) thught that the presenting arrhythmia made any difference, whereas 75.3% f thse wh advised a 6-mnth wait (116 f 154, 95% CI 68.5% t 82.1%) cnsidered the presenting arrhythmia t be imprtant (p = ). Only a small number f physicians (19.4%, r 78 f 402, 95% CI 15.5% t 23.3%) thught that the newer generatins f ICDs with memry and antitachycardia pacing wuld influence their plicies regarding driving. These were mst likely t be the lw vlume implanters (26.2%, r 37 f 141, 95% CI 19.0% t 33.5%); the high vlume implanters were less likely t state that newer devices wuld alter their plicies (11.3%, r 39 f 344, 95% CI 8.0% t 14.7%, p = 0.001), pssibly because they may already have had access t these devices in clinical trials. Discussin Physicians are respnsible fr advising their patients regarding their activities after discharge frm the hspital. Driving is a key cmpnent f these instructins. T develp a ratinal plicy fr driving fr ICD recipients, data regarding actual event rates are imprtant. In ur survey f 742 physicians invlved in ICD implantatin and fllw-up in the United States, nly 30 accidents were reprted ver a cumulative experience f 12 years. Of these, nly nine were fatal, all f which were patient fatalities except fr ne passenger. In additin, 21 nnfatal injuries ccurred. Our survey results prbably represent the majrity f ICD recipients in the United States and prbably mst f the accidents. Physicians with experience t reprt wuld have been mst likely t return the survey. The cnclusin t be reached when these data are cmpared with data frm the U.S. Census is that ICD recipients are much less likely than the general public t be invlved in accidents resulting in serius injury, and the fatality rate fr patients is lwer than the natinal rate. Of curse, there is n way t knw frm the results f the survey just hw ften and what distances ICD recipients drive, althugh we knw frm anther study that mst patients d resume driving (3). Larsen et al. (4) analyzed the driving hazard amng 501 patients at ne university medical center and fund that the 1-year event rate (ccurrence f ventricular tachycardia r fibrillatin, syncpe r defibrillatr discharge) was 17%. Hwever, the majrity f patients were treated with antiarrhythmic drugs, and nly 8% received an ICD. Thse investigatrs fund that event rates were highest in the first mnth after discharge, declined t an intermediate level fr mnths 2 t 7 and then, at the eighth mnth, drpped t 0% t 1.2%/mnth. Therefre, they recmmended a 7-mnth perid f abstinence frm driving. In the interest f keeping ur survey simple t maximize the number f returns, we did nt cllect infrmatin as t time after implantatin when the accidents ccurred, s we cannt make any cnclusins as t hw many f the accidents wuld have ccurred within this 7-mnth windw. It shuld be nted that the calculatins f Larsen et al. (4) may actually underestimate the number f shcks amng ICD recipients because antiarrhythmic drug treatment, if effective, wuld be expected t decrease the number f episdes f ventricular tachycardia and fibrillatin verall. Lng-term experience with the ICD has shwn that 54% t 66% f patients receive shcks ver fllw-up perids ranging frm 9 mnths t several years (6,8,9). The majrity f these shcks are fr dcumented r suspected ventricular tachycardia r fibrillatin, and the remainder are inapprpriate and delivered fr prblems such as sinus tachycardia, atrial fibrillatin, nnsusrained ventricular tachycardia and device malfunctins. If 60% f ICD recipients have received shcks, then an abslute minimum f 19,000 shcks have ccurred amng all patients in the United States. Mst patients spend cmparatively little time driving, and nt surprisingly, the majrity f shcks d nt ccur during driving. Thus, <1% f shcks ccurred during driving, and f these, nly 10.5% resulted in accidents. Develpment f driving plicy. In develping a driving plicy fr ICD recipients, it is imprtant t keep in mind that accidents related t heart disease d nt ccur slely in patients with ICDs. In ne study (10) f 1,348 patients wh died f crnary artery disease, 71 (5%) died while driving. Cllisins related t sudden death f the driver in the pre-icd era were estimated t be <6/10,000 mtr vehicle accidents (11). If we ignre the risk in patients with a recent mycardial infarctin r in thse with cngestive cardimypathy, and we prscribe driving nly in patients with implantable devices, we culd make ICDs unacceptable thera W t many patients. At the present time, mst physicians d permit ICD recipients t drive at a mean f 7.3 _+ 3.4 mnths after implantatin. These results are cmparable t thse f DiCarl et al. (2), wh surveyed 58 physicians in three states regarding their practices and fund that 82% f the physicians recmmended a perid f abstinence f 6 _+ 3 mnths. Althugh it was a general cnsensus amng the physicians in ur survey that the hemdynamic stability f the presenting arrhythmia is imprtant in decisin making abut driving, ne ther study f device patients des nt supprt this apprach. In that study (12), regardless f whether a patient's shcks had previusly been assciated with syncpe, there was a 15% incidence f syncpe with any newly ccurring shcks. In ur survey, physicians were mre likely t recmmend

5 184 CURTIS ET AL. JACC Vl. 26, N. 1 AUTO ACCIDENTS AND DEFIBRILLATORS July 1995:180-4 abstinence frm driving if they were aware f accidents amng ICD recipients. In making recmmendatins t their patients, physicians are mst likely cncerned nt nly with patient safety, but with their wn ptential liability if accidents ccur after they have permitted driving. Hwever, it is imprtant t remember that as we all wrestle with the prblem f a ratinal plicy fr these patients, many patients simply d nt listen t the recmmendatins f their physicians. As mentined earlier, 70% f patients in ne study (3) resumed driving by 8 mnths after implantatin, even thugh all f them had been advised t abstain frm driving permanently. In view f the data regarding the very lw accident rate in patients with ICDs, and the finding that event rates are highest in the first few mnths, a reasnable plicy wuld be t recmmend that patients nt drive fr at least 1 mnth and perhaps as lng as 6 mnths after implantatin. In additin, as we frmulate a plicy fr patients with ICDs, the prblem f inapprpriate discharges must be addressed as well. It has been estimated that 27% t 41% f defibrillatr discharges arc spurius (13). If inapprpriate shcks frm a defibrillatr arc determined t have a crrectable cause, such as supraventricular tachycardia r device malfunctin, then crrectin f the prblem shuld allw a patient t resume driving immediately if he r she wuld therwise be able t drive. Finally, if the cnsensus is frmed amng physicians invlved in ICD implantatin and fllw-up that a perid f abstinence frm driving is necessary, the recmmendatins are unlikely t be fllwed by patients unless tee state Department f Mtr Vehicles is ntified. Study limitatins. The results and cnclusins presented in this reprt must be cnsidered within the cntext f certain limitatins. The data cllectin was retrspective and relied n physician recall. It is unlikely, nr did we expect, that physicians went thrugh their recrds befre respnding t us. This may explain the verestimatin by respnding physicians f the ttal number f implant recipients. It is impssible t knw just hw many patients are represented by the 61% f physicians wh respnded, and s ur estimates must be taken as just that. Althugh underestimatin f the number f accidents, injuries r fatalities recalled by physicians may als have ccurred, we think that this is much less likely due t the extrardinary nature f these events. We were able t eliminate sme degree f verestimatin f bth ttal implant recipients and driving-related events by crss-referencing respndents by implantatin center and cnsidering nly the survey respnses f the mst senir respndent at a given center as representing the implant recipients at that center. We further crss-referenced accident reprts n an individual basis and excluded apparent duplicates. Hwever, the pssibility remains that sme patients may have been cunted mre than nce. Anther limitatin f ur study cncerns the validity f the estimate f ttal number f patient-years f ICD experience, which was based n all-cause mrtality rates prvided by Cardiac Pacemakers, Inc. Such validity ultimately depends n the cmpleteness f mrtality reprting t the cmpany during the 7-year perid utilized in ur calculatin. Early in this perid, reprting was passive, and underreprting f ICD patient mrtality may have ccurred. Underreprting f mrtality wuld result in an verestimatin f ttal ICD-recipient patient-years. Active reprting mechanisms were eventually put int place during this perid that wuld have increased the chances f capturing mrtality events in ICD recipients. A final ptential limitatin f ur survey is that we sent surveys nly t physicians wh had ever implanted defibrillatrs frm ne cmpany. At the time the surveys were sent ut, these defibrillatrs were the nly nes apprved by the Fd and Drug Administratin. Althugh sme centers were implanting investigatinal devices, it is nt likely that a center wuld have been implanting investigatinal devices but never a cmmercially released device. Thus, we are cnfident that the survey was distributed t the vast majrity f physicians wh were perfrming implantatin at the time. Cnclusins. The mtr vehicle accident rate caused by discharge frm an ICD is lw. Althugh restricting driving fr a shrt perid f time after implantatin may be apprpriate, excessive restrictins r a ttal ban n driving may be unwarranted. Wc are indebted t Debrah L. Gdwin fr secretarial assistance. References 1. Strickberger SA, Cantilln CO, Friedman PL. When shuld patients with lethal ventricular arrhythmia resume driving'? An analysis f state regulatins and physician practices. Ann Intern Med 1991;115: DiCarl LA, Winstn SA, Hnway S, Reed P. Driving restrictins advised by midwestern cardilgists implanting cardiverter defibrillatrs: present practices, criteria utilized, and cmpatibility with existing state laws. PACE 1992;15: Finch NJ, Leman RB, Kratz JM, Gillette PC. Driving safety amng patients with autmatic implantable cardiverter defibrillatrs. JAMA 1993;270: Larsen GC, Stupcy MR, Walance CG, et al. Recurrent cardiac events in survivrs f ventricular fibrillatin r tachycardia: implicatins fr driving restrictins. JAMA 1994;271: Breslw NE, Day NE. Statistical Methds in Cancer Research: Vlume IL The Design and Analysis f Chrt Studies. IARC Science Publicatin N. 82. Lyn: Internatinal Agency fr Research n Cancer, 1987: Winkle RA, Mead RH, Ruder MA, et al. Lng-term utcme with the autmatic implantable cardiverter-defibrillatr. J Am Cil Cardil 1989;13: U.S. Bureau f the Census. Statistical Abstract f the United States: l l3th ed. Washingtn (DC): U.S. Gvernment Printing Office, 1993: Kelly PA, Cannm DS, Garan H, et al. The autmatic implantable cardiverter-defibrillatr: efficacy, cmplicatins and survival in patients with malignant ventricular arrhythmias. J Am Cll Cardil 1988;11: EchI DS, Armstrng K, Schmidt P, Oyer PE, Stinsn EB, Winkle RA. Clinical experience, cmplicatins and survival in 70 patients with the autmatic implantable cardiverter/defibrillatr. Circulatin 1985;71: Myerburg RJ, Davis JH. The medical eclgy f public safety. I: sudden death due t crnary heart disease. Am Heart J 1964;68: I I. Baker SP, Spitz WU. An evaluatin f the hazard created by natural death at the wheel. N Engl J Med 1970;283: Ku WH, Calkins H, Lewis RR, et al. Incidence f lss f cnsciusness during autmatic implantable cardiverter-defibrillatr shcks. Ann Intern Med 199l;115: Gabry MD, Brdman R, Jhnstn D, et al Autmatic implantable cardivertcrdefibrillatr: patient survival, batte R, lngevity and shck delivery, analysis. J Am Cil Cardil 1987;9: