Media Releases

Researchers plot locations where AEDs could save more lives

May 2, 2013

TORONTO, ON – Prompt use of an auto­mat­ed exter­nal defib­ril­la­tor, or AED, can great­ly increase the sur­vival rates of peo­ple who suf­fer a car­diac arrest. And MIE Pro­fes­sor Tim Chan, work­ing with Dr. Lau­rie Mor­ri­son at St. Michael’s Hos­pi­tal, has devel­oped a for­mu­la to deter­mine where best to place these cost­ly but life-sav­ing devices.

In a paper pub­lished in Cir­cu­la­tion, Chan and Mor­ri­son note that pub­licly reg­is­tered AEDs in Toron­to are not in the best loca­tions to help vic­tims of car­diac arrest. In fact, less than one in four of all car­diac arrests had an AED close by (with­in 100 metres is the required dis­tance). The aver­age dis­tance to the near­est AED was clos­er to 300 meters.

Cur­rent guide­lines sug­gest areas asso­ci­at­ed with the high­est risk of car­diac arrest should be tar­get­ed for AED deploy­ment, after they have been placed in obvi­ous high-traf­fic areas such as trans­porta­tion hubs or major sports venues. But it’s not clear how to iden­ti­fy these “car­diac hot spots.”

Chan and Mor­ri­son looked at the loca­tions of all 1,310 pub­lic car­diac arrests in Toron­to between Decem­ber 2005 and July 2010 and the loca­tions of all 1,699 AEDS reg­is­tered with Toron­to Emer­gency Med­ical Ser­vices.

They found that 304 car­diac arrests occurred with­in 100 metres of at least one AED (23 per cent).One hun­dred metres was cho­sen as the yard­stick because it’s the approx­i­mate dis­tance a bystander could trans­port an AED in a 1.5‑minute walk—the max­i­mum rec­om­mend­ed by the Amer­i­can Heart Asso­ci­a­tion.

There were almost three times as many pub­lic car­diac arrests in down­town Toron­to as the rest of the city – 3.5 per square kilo­me­ter per year vs. 0.4 – said Chan. Almost half of all down­town car­diac arrests were near an exist­ing AED com­pared to only 17 per cent those out­side of down­town.

Chan then looked at the 1,006 car­diac arrests that did not take place near an AED. He said that be plac­ing AEDs in the top 30 car­diac arrest “hot spots,” they could have cov­ered an addi­tion­al 112 his­tor­i­cal arrests, or 32 per cent. The aver­age dis­tance between a car­diac arrest and an AED would fall to 262 metres from 281 metres.

“Reduc­ing the dis­tance a bystander needs to trav­el by 20 metres or up to 40 metres in a roundtrip has the poten­tial to save close to half a minute in response time,” said Mor­ri­son, an emer­gency med­i­cine spe­cial­ist who heads Res­cu, the largest research team of its kind in Cana­da ded­i­cat­ed to improv­ing out-of-hos­pi­tal resus­ci­ta­tion.

“If you have a car­diac arrest, every sec­ond counts. Out-of-hos­pi­tal car­diac arrest kills an esti­mat­ed 300,000 peo­ple in North Amer­i­ca annu­al­ly,” she said. “Only five per cent of peo­ple who suf­fer out-of-hos­pi­tal car­diac arrest sur­vive to be dis­charged from hos­pi­tal. The prob­a­bil­i­ty of sur­vival decreas­es up to 10 per cent with each minute of delay between col­lapse and treat­ment.”

Chan said his math­e­mat­i­cal mod­el is more accu­rate than a pop­u­la­tion-based mod­el, in which AEDs are placed in areas of dens­est day­time pop­u­la­tion.

“Our opti­miza­tion mod­el should be viewed as a deci­sion-sup­port tool to help pri­or­i­tize place­ment of AEDs, make effi­cient use of pub­lic, donor or pri­vate funds direct­ed toward pub­lic access defib­ril­la­tor pro­grams, and poten­tial­ly max­i­mize sur­vival on the basis of geo­graph­ic pat­terns of car­diac arrest,” said Chan. “Because AEDs are expen­sive and can­not be placed every­where, our mod­el allows a deci­sion-mak­er to quan­ti­fy the trade-off between the num­ber of AEDS deployed and cov­er­age.”

While it was not part of the research paper, Chan used his math­e­mat­i­cal mod­el to indi­cate the top 10 car­diac hot spots in Toron­to not cur­rent­ly cov­ered by AEDs:

  1. Jarvis and Ger­rard
  2. Queen and Bay
  3. Jarvis and Dun­das
  4. Brim­ley and Progress
  5. Eglin­ton and War­den
  6. Welling­ton and Stra­chan
  7. Dun­das and Spad­i­na
  8. Queen and Shel­bourne
  9. Dan­forth and Pape
  10. Jarvis and Ade­laide

About St. Michael’s Hos­pi­tal

St. Michael’s Hos­pi­tal pro­vides com­pas­sion­ate care to all who enter its doors. The hos­pi­tal also pro­vides out­stand­ing med­ical edu­ca­tion to future health care pro­fes­sion­als in more than 23 aca­d­e­m­ic dis­ci­plines. Crit­i­cal care and trau­ma, heart dis­ease, neu­ro­surgery, dia­betes, can­cer care, and care of the home­less are among the Hospital’s rec­og­nized areas of exper­tise. Through the Keenan Research Cen­tre and the Li Ka Shing Inter­na­tion­al Health­care Edu­ca­tion Cen­ter, which make up the Li Ka Shing Knowl­edge Insti­tute, research and edu­ca­tion at St. Michael’s Hos­pi­tal are rec­og­nized and make an impact around the world. Found­ed in 1892, the hos­pi­tal is ful­ly affil­i­at­ed with the Uni­ver­si­ty of Toron­to.

About Uni­ver­si­ty of Toron­to Engi­neer­ing

Found­ed in 1873, U of T Engi­neer­ing has approx­i­mate­ly 5,200 under­grad­u­ate stu­dents, 1,950 grad­u­ate stu­dents and 240 fac­ul­ty mem­bers. U of T Engi­neer­ing is at the fore of inno­va­tion in engi­neer­ing edu­ca­tion and research and ranks first in Cana­da and among the top Engi­neer­ing schools world­wide.


For more infor­ma­tion, con­tact:

Ter­ry Laven­der
Com­mu­ni­ca­tions & Media Rela­tions Strate­gist
Fac­ul­ty of Applied Sci­ence & Engi­neer­ing, Uni­ver­si­ty of Toron­to
Tel: 416–978-4498