Review of: Le May MR, Davies RF, Dionne R, et al: “Comparison of early mortality of paramedic-diagnosed ST-segment elevation myocardial infarction with immediate transport to a designated primary percutaneous coronary intervention center to that of similar patients transported to the nearest hospital.” The American Journal of Cardiology. 98(10):1329-33, 2006
This study conducted in Ottawa, Canada, examined the impact of paramedics identifying ST-segment elevation myocardial infarction (STEMI) patients and the transport of these patients to the nearest primary percutaneous coronary intervention (PCI) center. The authors compared outcomes of similar patients who during the two years previous to the study were transported to the nearest hospital and received thrombolytics (control group).
Paramedics were educated to recognize STEMI on 12-lead ECGs and alert the only PCI center in the city of the patient s impending arrival. They treated 108 consecutive STEMI patients. PCI was performed on 93.5% of the study group and only 8.9% of the control group. Median door-to-balloon time was 63 minutes. In-hospital mortality was 1.9% in the “paramedic-referred PCI” group and 8.9% in the control group.
While at first blush when reading the abstract and the title, one would assume that this is a paper that resoundingly supports the adoption of prehospital 12-lead acquisition and preferred routing of patients to PCI centers. However, let s look more closely at it.
First of all, the control group is composed of patients who over a two-year period (before the study began) taken to the nearest facility for treatment of suspected STEMI. It is unknown whether they received prehospital 12-leads. They were all taken to a facility that performed few PCI at that time. It is unknown what happened to the patients that were transported to the study facility during this time and whether or not they were identified by 12-lead.
Then the study facility started doing 12-leads and all STEMIs were taken to it. It is unknown what happened to patients who continued to be taken to non PCI facilities.
Clearly, there were better outcomes as far as mortality is considered between the historical controls who got thrombolytics and those that got PCI. However, further analysis of the PCI group shows that half the patients had statistically significant delays in getting to the cath lab when they arrived “after hours.” Mean door-to-balloon time was 39 minutes during the day and 81 minutes at night. There is no further discussion of the difference in mortality between these two groups. Even so, the patients who had delayed PCI had a door-to-balloon time 45 minutes shorter than the historical controls.
While other studies have proven the feasibility of prehospital identification of STEMI, this study is more an evaluation of the effect of instituting PCI in a system and comparing it to their previous experience with thrombolytics. A true test of PCI vs. thrombolytics would be to have the patients randomly assigned to one hospital or another. However, recent studies indicate that primary PCI is superior to thombolytics.
While I congratulate the authors on their results, it is important to recognize that the benefit to the patient came primarily with the advancement of PCI but could not have been successful had it not been for the ability of the paramedics to identify quality candidates.