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ED overcrowding causing many heart attack patients to have dangerous waits for clot-busting drugs


Almost 60% of heart attack patients are treated in overcrowded emergency departments (EDs) in Ontario, and as a result, over a third of them wait more than an hour to get life-saving “clot-busting” drugs, a new study from the Institute for Clinical Evaluative Sciences (ICES) shows.

Researchers examined the association between ED overcrowding and delays in the time from when a suspected heart attack patient arrives at the ED until they receive these clot-busting medications, known as the “door-to-needle time” (DNT), for patients from 25 Ontario community and teaching hospitals between 1998 and 2000.

The study grouped EDs located close together and sharing a common ambulance diversion system into “networks” consisting of 2 to 5 hospitals each. ED network overcrowding was calculated as the percentage of EDs that were diverting ambulances, categorized as none (0%), moderate (less than 60%), and high (60% or more).


  • The overall median DNT was 43 minutes for the 3,452 patients in the study. The recommended DNT of 30 minutes or less was achieved in 29.2% of patients, with a further 35.9% receiving the drugs between 30 to 60 minutes, and 34.9% suffering a major delay of more than 60 minutes.
  • Heart attack patients treated in an ED network with high network crowding were 40% more likely to experience a major delay of more than an hour in getting the clot-busting drugs.
  • The median DNT was 3.0 minutes longer for patients treated in moderate network crowding and 5.8 minutes longer for patients treated in high network crowding. Heart attack treatment delays increased when more EDs within a network were overcrowded.

“Every minute counts when a patient is experiencing a heart attack because the longer they wait for clot-busting medications, known at thrombolytics, to be administered, the higher the mortality,” said lead author and ICES scientist Dr. Michael Schull.

“However, as the results from our study demonstrate, patients are not only affected by ED overcrowding at the hospital where they’re receiving treatment, but also by how crowded neighbouring EDs are as well. Efforts to reduce life-threatening delays caused by ED overcrowding must be coordinated across hospital networks, as opposed to efforts only in individual hospitals.

“Solutions to ED overcrowding should focus on initiatives such as improving primary and ambulatory care services for elderly patients with chronic illnesses, exacerbations of which frequently lead to hospitalization and ED overcrowding, or increasing capacity and efficiency across neighbouring hospitals for patients admitted from EDs,” said Dr. Schull.

The study, “Emergency department crowding and thrombolysis delays in acute myocardial infarction”, is in the December 2004 issue of the Annals of Emergency Medicine.

Author affiliations: ICES (Drs. Schull and Morrison, and Ms. Vermeulen); Clinical Epidemiology Unit, Sunnybrook and Women’s College Health Sciences Centre (Dr. Schull); Department of Emergency Services, Sunnybrook and Women’s College Health Sciences Centre (Drs. Schull and Morrison); Department of Medicine, University of Toronto (Drs. Schull and Morrison); Faculty of Medicine, University of Western Ontario (Mr. Slaughter); Division of Cardiology, University Health Network, University of Toronto (Dr. Daly)

ICES is an independent, non-profit organization that uses population-based health information to produce knowledge on a broad range of healthcare issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting healthcare needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad, and is widely used by government, hospitals, planners, and practitioners to make decisions about care delivery and to develop policy.


  • Julie Argles
  • Media Relations Officer, ICES
  • (416) 480-4780 or cell (416) 432-8143


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