Posted By admin on April 26, 2009

Prehospital triage of STEMI patients reduces door-to-balloon times
April 22, 2009 | Sue Hughes
Los Angeles, CA - More evidence that a coordinated regional approach to the treatment of STEMI patients, with prehospital triage and cath-lab activation, leads to a consistent reduction in door-to-balloon times, has come from a new study [1].

The paper, published in the April 2009 issue of the Journal of the American College of Cardiology: Cardiovascular Interventions, was authored by a team led by Dr Ivan Rokos (University of California, Los Angeles Olive View Medical Center).

Rokos told heartwire that this paper was the result of a collaborative effort among 10 regions that have adopted a system of prehospital triage of STEMI patients in which paramedics perform ECGs in the ambulance and then take the patient to the nearest primary PCI-capable hospital, having already activated the cath lab.

He noted that while both the AHA and the ACC have initiatives promoting such systems, their actual implementation in practice is still somewhat pioneering. “We are hoping that our data will encourage more regions to go down this route,” he said. “A key rule of cardiology is ‘time is muscle,’ and we have clearly shown that regions implementing a prehospital triage system for STEMI patients consistently reduce time to PCI, which should translate into better outcomes.”

The current paper reports a pooled analysis of 10 independent, prospective, observational registries involving 72 hospitals. Data were collected on all consecutive patients with a prehospital ECG diagnosis of STEMI. In total, paramedics transported 2712 such patients directly to a PCI hospital. A primary PCI was performed in 2053 patients (76%), and 86% of these had a door-to-balloon time of less than 90 minutes, well above the ACC benchmark of 75%.

In addition, door-to-balloon times were less than 60 minutes in 50% of patients, less than 45 minutes in 25% of patients, and less than 30 minutes in 8% of patients, which the authors say demonstrates that this system possesses “substantial capacity to consistently deliver very rapid primary PCI.” They suggest that such fast time to reperfusion should translate into lives being saved, noting that a recent registry analysis has shown additional in-hospital mortality reductions as door-to-balloon times are reduced from 90 to 30 minutes.

EMS-to-balloon times: A new standard

The authors also report another measure—emergency medical services (EMS)-to-balloon time (E2B)—which was below 90 minutes in 68% of patients in which this was tracked. “Our data provides the first evidence that the rate of E2B <90 minutes may represent an appropriate metric for assessing the performance of coordinated regional STEMI care systems,” they write.

In this study, time zero for EMS-to-balloon times was defined as the time of the prehospital ECG, whereas the authors point out that the most recent STEMI guidelines use time of EMS arrival on the scene. “In reality, the true patient-centered time zero for STEMI systems is the time of the 911 call, and hence this time point represents the ideal starting point of EMS-to-balloon times that should be tracked in future analyses,” they add.

Rokos explained that for the purposes of this paper, he and his colleagues invited those regions they knew had adopted such systems to share their data. In addition to the 10 regions included, there are some other regions that are using similar systems but did not take up the offer to share their data at this point, he said.

He noted that the most common method for interpreting ECGs in the ambulance was use of a computer algorithm. “These computers read the ECG and tell you whether the patient is having a STEMI or not. This is not quite as good as having a cardiologist read the ECG and can lead to some false positives, but it seems to be the most practical method at present,” he added. While transmission of the ECG to a cardiologist for interpretation would be the ideal, this has proven challenging to implement because the different proprietary ECG systems are not always compatible with the receiving equipment used at a particular hospital. “It seems incredible that we can email a photograph around the world, but we haven’t yet found an easy way of transmitting an ECG to a nearby hospital,” Rokos commented to heartwire.

Rokos noted that the data included in this paper did not include interhospital transfer programs. “This is the other half of the equation and a very challenging part. When patients present to a non-PCI hospital and need transferring to a PCI center, this is a very complicated procedure, with a whole chain of bureaucratic events that have to happen, which slows things down considerably. Even if a patient presents to the emergency department of a PCI hospital, because these departments are so busy, it can be difficult to get an ECG done fast, but if a STEMI patient comes in by ambulance, these delays are often avoided because paramedics with suspected STEMI patients can be given a fast lane to the cath lab.”

Rokos told heartwire that the director of the regional emergency services was the ideal person to coordinate setting up a regional STEMI system such as those described in this paper. “Primary PCI-capable hospitals must recognize that the emergency services are responsible for the delivery of approximately one-half of all STEMI patients, and thus they are in a unique and powerful position to foster collaboration among competing hospitals and drive quality in a region,” he said.

Better data collection needed

In an accompanying editorial [2], Dr Christopher Granger (Duke Clinical Research Institute, Durham, NC) describes the paper by Rokos et al as “an important demonstration project.”

“It can no longer be argued that it is impossible to establish an integrated EMS and hospital system to provide faster primary PCI,” he comments.

But he notes that the system can be improved further by recording additional data necessary for assessing performance, such as times of first medical contact, first ECG, and catheterization-laboratory activation; false activations; bypass of non-PCI centers; and clinical complications during transport. “It is an embarrassment that we have a health system in the US whereby critical medical information from the prehospital phase of care is often not available to hospital providers. As more critical aspects of care for STEMI, stroke, and cardiac arrest are moved into the prehospital setting, this has become a major deficiency that needs to be fixed,” Granger writes.

Pointing out that in this study 24% of patients for whom the cath lab was activated did not have primary PCI, he suggests that standard definitions of “false activation” and acceptable rates of false activation are important topics for further study, but they cannot be understood until there is better data collection and tracking.

Granger concludes: “The most important lesson of this study is that reperfusion with primary PCI can be provided more rapidly if EMS is placed in its rightful position as the front line for integrated STEMI care. Expansion of what these 10 networks have done on a national scale—refined and coupled with better EMS support, data collection, and feedback—will improve care and save lives.”

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