- © 2007 Canadian Medical Association or its licensors
In their article on delays to reperfusion therapy in the province of Quebec, Thao Huynh and associates concluded that for most patients the time to primary percutaneous coronary intervention exceeded current recommendations.1 This conclusion might be misleading because of some limitations of the study.
The authors did not exclude from their analysis patients for whom there was an explainable delay in the diagnosis of ST-segment elevation myocardial infarction. Some patients with suspected aortic dissection or pulmonary embolism may have undergone additional investigation prior to receiving reperfusion therapy. Also, it is not clear whether the authors excluded patients whose initial electrocardiogram was not diagnostic. A sizable number of patients with acute coronary syndromes may develop clear ST-segment elevation only after a follow-up electrocardiogram is done while they are under observation in the emergency department. Patients with a delayed diagnosis or a contraindication to thrombolytic therapy, or who need cardiopulmonary resuscitation, intubation or defibrillation, may be more likely to receive primary percutaneous coronary intervention. These patients are expected to have longer delays to reperfusion therapy. In particular, it appears that patients transferred from distant hospitals for primary percutaneous coronary intervention because of contraindications to thrombolytic therapy were included in the analysis.
Also, the authors do not clarify whether they included patients referred for rescue percutaneous coronary intervention. The data for these patients would obviously have increased the calculated delays to reperfusion therapy for transferred patients.
Door-to-balloon time is not always the best indicator of treatment delays. In our institution, we use door-to-open-artery time to measure treatment delays. As many as 29% of patients with ST-segment elevation will have thrombolysis in myocardial infarction (TIMI) scores of 2 or 3 for flow in the culprit vessel when the first coronary angiogram is done.2 In these patients, the operator may choose to take time to perform a ventriculogram and additional coronary views, administer additional medications or use a thrombus extraction catheter before performing coronary angioplasty. In these patients, door-to-open-artery time provides a better indication of delays to reperfusion therapy.
Footnotes
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Competing interests: Dr. Dery holds a research grant from Eli Lilly.