STEMI Interventions: Commentary
This month’s review of the recently published work from Ottawa, Canada, entitled ‘A Citywide Protocol for Primary PCI in ST-segment Elevation Myocardial Elevation’(NEJM, 2008; 358:231–240, see article abstract on next page), provides an opportunity to reflect upon numerous critical aspects that are related to the effective triage and management of patients with STEMI.
The Ottawa study is the latest in the series of notable works that the NEJM has published in the last several months on the critical subject of primary PCI and regarding the dramatic global changes that are occurring in the these patients.
To begin with, I want to congratulate the researchers at the University of Ottawa Heart Institute for their pioneering work. It is unambiguous how significantly this work will impact on the design of global STEMI care in large metropolitan areas. This reviewer is already involved in designing similar initiatives in several Asian cities for the effective triage and treatment of STEMI patients and the relevance of the Ottawa experience is transparent. This notable work supplements the work of several large projects from Europe and from the United States. Most notably, relevant comparisons to the Ottawa study can be made with the tremendous work that has been done at the Mayo Clinic and at the Abbott Northwestern Heart Center in Minneapolis.
The Ottawa protocol is unique in several aspects:
1) It is the largest published work in STEMI interventions involving systematic primary PCI for 800,000 people living in the Ottawa metropolitan area where no patient was treated with fibrinolysis alone. Notably, this care required a redesign of the traditional care of these patients, the development of new protocols for ambulance transport, changes in physician-referral patterns, and changes in emergency department (ED) protocols. This strategy is markedly different that the pharmaco-invasive, “hub and spoke” models that are practiced at the Mayo Clinic and at the Abbott Northwestern Minneapolis, and at numerous other superb U.S. programs. It is also very different than the thrust for the very early, prehospital pure fibrinolysis or facilitated fibrinolysis strategies that are advocated by a few premier European sites. Although the role of thrombolytic therapy in the era of primary PCI continues to evolve, the Ottawa study makes a further dent in the utility of this approach.
2) The work has made further inroads into the establishment of the Advanced Care Paramedics that were trained in cardiac life support and who routinely performed and interpreted 12-lead EKG at the scene, and independently performed the triage and transfer of STEMI patients to the designated center for primary PCI.
3) It has quantified with a large cohort of patients the benefits of a strategy in which paramedics independently referred patients to a designated primary PCI center and bypassed the obligatory logistical delays of presentation of the STEMI patient at an ED. Recognizing the door-to-balloon (D2B) times as the best correlate for STEMI mortality, the Ottawa protocol demonstrated a D2B time <90 minutes in 79.7% of patients that were transferred from the field and a D2B time <90 minutes in 11.9% of those transferred from the ED (p < 0.001) — these results are indisputable testimony to the overwhelming benefits of a strategy of direct transfer to the primary PCI institution!
The publication of the Ottawa protocol for primary PCI also provides an opportunity to reflect upon the status of STEMI care in the United States and benefit from some of the observations from this study. In the United States, the median time to the closest PCI hospital is 11.4 minutes, and the median distance is 8.0 miles, with nearly 80% of the adult population living within 60 minutes of activation of the EMS to arrival at the PCI center. This compares with 10 minutes of traveling distance in Ottawa and 55-65% of patients that live within 30 minutes of a PCI center in Ontario. Clearly, the United States has longer transfer distances, yet there are large opportunities to improve the transfer process and decrease the time to treatment. Although data from the National Registry of Myocardial Infarction is a few years old (it is widely expected that these results have considerably improved since), it revealed that the median D2B time in 4,278 patients undergoing interhospital transfer for primary PCI was 180 minutes, with only 4% of patients having a D2B time <90 minutes and 15% <120 minutes!
Three other related subjects deserve mention beyond the clear benefits of a direct transfer strategy for STEMI interventions:
a) Education of the patient is paramount for STEMI care and the message is unambiguous — urgency in seeking care reduces time to treatment, and calling 911 as opposed to self-transport, is critical;
b) Legislation may be required to override the financial and political constraints that prevent patients from reaching a primary PCI center directly and bypassing the community hospital that has numerous benefits in acquiring this patient;
c) A national STEMI policy akin to the national trauma system is needed.