Study Highlights Reasons for Delays in STEMI Transfer System

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Patients with ST-segment elevation myocardial infarction (STEMI) who are transferred for primary percutaneous coronary intervention (PCI) can experience treatment delays for many reasons, most linked to the referral site. According to findings published online September 19, 2011, ahead of print in Circulation, the effect of such delays also varies widely, with only some having an impact on in-hospital mortality.

Timothy D. Henry, MD, and colleagues at the Minneapolis Heart Institute (Minneapolis, MN), prospectively documented the experiences of 2,034 STEMI patients transferred for PCI at their center from March 2003 to December 2009. Thirty-one hospitals belonged to the transfer system, of which 11 were located within a distance of 60 miles (n = 1,195) and 20 were located between distances of 60 and 210 miles (n = 839).

Some Delays Preventable, Some Not

In all, 30.4% of patients were treated within 90 minutes of their initial presentation at the referral hospital and 65.7% within 120 minutes. Patients who experienced delays beyond 120 minutes were more likely to be older, have diabetes, and present with cardiac shock. Current smokers, on the other hand, were more likely to be treated promptly.

Most delays occurred at referral hospitals (64.0%), while some happened during transfer (12.6%) or at the PCI center itself (15.7%). Referral hospital delays had various causes:

• Awaiting transportation (26.4% of all delayed patients)
• Emergency department delays (14.3%)
• Nondiagnostic ECG (9.1%)
• Diagnostic dilemma (8.7%)
• Cardiac arrest/shock (5.5%)

At the referral hospital, median delays were longest after diagnostic dilemmas (95.5 minutes) and nondiagnostic ECGs (81 minutes). Awaiting transport had the least effect, contributing a median delay of 59 minutes. In-hospital mortality was highest among patients delayed by cardiac arrest/shock (30.6%). Notably, while nondiagnostic ECGs were associated with lengthy delays, no in-hospital deaths could be attributed to this type of lag.

During transport, the most common reason for delays among patients transferred within 60 miles was weather, while distance itself could be blamed for the delays experienced by patients transferred from between distances of 60 and 210 miles. But mortality rates were similar regardless of whether patients did or did not experience transport delays.

Once patients reached the PCI center, only 317 (15.7%) had door-to-balloon times greater than 30 minutes. Among these, both catheterization team delays (7.1%) and need for complex procedures (5.8%) were most likely to lengthen the time to treatment; each added median delays of 38 minutes. Diagnostic dilemmas resulted in the longest lags at a median of 92.5 minutes. Mortality was highest among patients with cardiogenic shock/cardiac arrest (44.2%). Most of those who died from this condition developed it before arrival at the referral hospital or within 30 minutes after (68.4%), while comparatively few had the complication arise during transport to the PCI hospital (15.8%).

Transfer Networks Still Need Improvement

In a telephone interview with TCTMD, Dr. Henry said that recent efforts to reduce door-to-balloon time have produced excellent results in PCI hospitals. But “we’ve still got a long way to go” for STEMI patients who are transferred, he added.

Dr. Henry stressed, however, that the 90-minute cutoff stipulated for primary PCI by American College of Cardiology/American Heart Association guidelines should not discourage intervention in patients who exceed that time frame. The European Society of Cardiology guidelines, for example, have extended the door-to-balloon time to 120 minutes for transferred patients, and Dr. Henry said he hopes the United States will follow suit.

According to Dr. Henry, the current findings support such an expansion “by pointing out the specific delays and the relationship between delays and outcomes.” For example, in patients who had cardiac shock or cardiac arrest, the study found “it was the severity of their illness that caused the delay, not the delay causing their illness,” he noted, adding that more flexibility would encourage the use of PCI over fibrinolytic therapy.

Avoiding the Numbers Game

Sorin J. Brener, MD, of Weill Cornell Medical College (New York, NY), agreed that it is important to remember what is really at stake—total ischemic time—rather than specific numbers. “We meet frequently at national and international meetings and discuss this. The emphasis on this time interval, be it 90 or 120 minutes, is too much,” he said in an interview with TCTMD, noting that it all comes down to individual patient needs. “Being rigid is not that helpful. What this analysis does is help us see what works well and what doesn’t work well.”

Dr. Brener added that awaiting transport is a key area for improvement, not because it can worsen outcomes but rather because it is “something that’s totally avoidable.” In New York and elsewhere, he pointed out, ambulances often simply bypass referral hospitals and take patients directly to PCI centers.

Other improvements can take place in the emergency department. To avoid delays associated with diagnostic dilemmas, Dr. Brener said, the results show “we need better doctors who can [identify the diagnosis] with more certainty and not embark on a lot of tests for [things that should be] relatively straightforward.” At the same time, physicians in this situation need to be more sensitive in recognizing acute MI, he advised. “Elderly patients who present with somewhat unusual complaints should have an ECG as part of their initial evaluation, just to be sure they are not one of those who present atypically or cannot articulate their symptoms well.”

PCI centers may want to direct patients straight to the cath lab, avoiding a stop at the emergency department, Dr. Brener added.

Dr. Henry emphasized preparedness at a regional level. “Each cardiology group, each hospital should be working to set up their own system,” he said. “If you’re at a non-PCI hospital, what you want to do is establish a relationship with a 1 or more PCI centers, so that when someone comes in with a STEMI you have it all worked out ahead of time what you’re going to do” in terms of protocols and transfer methods.

In developing a STEMI system, the focus should be on non-PCI centers, Dr. Henry noted. “You want to be able to keep track of your data, know where your delays are, and then work hard at improving them,” he said.

 

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Source:
Miedema MD, Newell MC, Duval S, et al. Causes of delay and associated mortality in patients transferred with ST-segment elevation myocardial infarction. Circulation. 2011;Epub ahead of print.

 

 

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