Wireless Technology Speeds STEMI Patients to Hospital, Improves Outcomes

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A fully automated wireless network that allows emergency medical personnel to transmit electrocardiograms (ECGs) to cardiologists substantially shortens door-to-balloon (D2B) times and improves markers of myocardial damage for patients with suspected ST-segment elevation myocardial infarction (STEMI), according to a single-center study published in the February 2011 issue of JACC: Cardiovascular Interventions.

Results from the study were previously presented at the American Heart Association Scientific Sessions 2010 in Chicago, IL.

Researchers led by Marc Klapholz, MD, of the University of Medicine and Dentistry of New Jersey/New Jersey Medical School (Newark, NJ), evaluated the STAT-MI (ST-Segment Analysis Using Wireless Technology in Acute Myocardial Infarction) network’s feasibility at an inner city safety-net hospital located in Newark over a 33-month period ending in 2009. The system employs Bluetooth-enabled Lifepak 12 defibrillators (Medtronic, Minneapolis, MN) to automatically transmit 12-lead ECG results to phones worn by EMS personnel. The phones then forward the ECG to e-mail addresses of on-call cardiologists for evaluation. The ECG can be magnified and manipulated on the smartphone screen allowing for detailed ST-segment and other waveform analyses.

Patients Triaged Before Hospital Arrival

In all, 330 ECGs were transmitted by EMS to on-call cardiologists, who diagnosed the majority of patients (n = 238; 72%) as having conditions other than STEMI such as prior bundle branch block, left ventricular hypertrophy, and early repolarization. These subjects were triaged to the emergency department. The remaining 96 patients (28%) had ECGs consistent with STEMI and were triaged directly from the field to the cath lab for primary PCI.

Among the group with intended PCI, 78% underwent the procedure in the culprit lesion (22% had noncritical coronary stenosis or were referred for CABG). The primary PCI patients were compared with a group of 50 controls who arrived at the hospital either as walk-ins or via ambulances not equipped with the STAT-MI network. Most baseline characteristics were similar between the network patients and controls, with the exception of higher self-reported cocaine use in the control group (22% vs. 6%; P = 0.005).

Median D2B, the primary endpoint, was lower in the STAT-MI patients than in controls at 63 min (range, 42-87 min) vs. 119 min (96-178 min), respectively (P < 0.00004). This improvement was consistently observed in both peak and off hours. There was an interaction, however, between the time of presentation and patient cohort; STAT-MI patients presenting from 7 a.m. to 5 p.m. had the shortest D2B, while control patients presenting at other times had the longest D2B.

Secondary outcomes such as peak troponin and creatine phosphokinase-MB (CPK-MB), LVEF, and length of stay all were improved by the automated network. There also was a reduction in mortality, although the trend did not reach statistical significance (table 1).

Table 1. Secondary Outcomes: Median (Range)

 

Control Group
(n = 43)

STAT-MI Group
(n = 72)

P Value

Peak Troponin, ng/mL

87.6 (38.4-227)

39.5 (11-120.5)

0.005

Peak CPK-MB, ng/mL

290.3 (102.4-484)

126.1 (37.2-280.5)

0.001

LVEF

35% (25-52%)

50% (35-55%)

0.004

Length of Stay, days

5.5 (3.5-10.5)

3 (2-4)

< 0.001

Mortality

6.0%

1.1%

0.125


“Time delays in patient evaluations and ECG acquisition and transmissions in busy [emergency departments] delays the timely management of STEMI patients,” the investigators write. “Our study took advantage of wireless technology by completely automating the process of ECG acquisition and transmission from the field to handheld smartphones worn by cardiologists and eliminated many intermediary personnel-induced time delays in treating acute myocardial infarction patients.”

One downside to the network was its 24% rate of false-positive activation, with the most common ECG abnormalities being left bundle-branch block, previous MI, and early repolarization, they note. On the other hand, no STEMI cases were missed.

Another issue, the authors say, is that the control and STAT-MI groups may not be comparable, because walk-ins are generally more stable than patients who arrive by ambulance.

That being said, “[c]ontinued efforts to eliminate unnecessary intermediate steps in the treatment of patients who present with STEMI are crucial in the design of STEMI pathways,” Dr. Klapholz and colleagues conclude, adding that the STAT-MI network effectively brings the interventional cardiologist to the patient’s ‘door.’ “The improved outcomes that we have observed reinforce development of pathways that concentrate on eliminating unnecessary intermediate steps.”

Despite Weaknesses, Study Inspires

During a telephone interview with TCTMD, Ajay J. Kirtane, MD, SM, of Columbia University Medical Center (New York, NY), expressed enthusiasm about the actual technology, but was less impressed by the study design.

In particular, Dr. Kirtane pointed out that the control group was a “mixed bag.” He questioned not only the comparison with walk-ins but also wondered whether ambulances equipped with the network differed from those without it. A better approach, he suggested, might be one in which half of the city’s ambulances used STAT-MI and the other half did not. Patients treated in these 2 types of ambulances then could be directly compared.

Even with those concerns, “[t]here’s really very little downside to doing it, aside from the false positive activation,” Dr. Kirtane said, noting that the frequency observed in the study was not unreasonable. “As a cardiologist, I can say that I’d rather see the ECG myself than hear it through an EMS or ER person’s voice. So in some respects, it’s actually better that the person coming in to do the procedure is actually seeing the ECG themselves.” As long as the quality of the field ECGs is sufficient, this is a reliable approach, he added.

“If you can reduce door-to-balloon times by this degree, that is a dramatic benefit in terms of helping people with STEMI,” Dr. Kirtane commented. Mobilizing the cath lab team ahead of time saves as much as 45 minutes, he reported.

Dr. Kirtane said the main challenge to implementing the approach is integrating disparate hospital services. “EMS is run by the ER, and the cath lab is the cath lab, so you need to have 3 teams working together at a systems level. That from a logistical standpoint can sometimes be difficult, but clearly that doesn’t excuse it,” he stressed. “This is something where, with this type of impact on door-to-balloon time, those conversations need to be had.”

The greatest benefit to be gained may be in the “sickest of the sick,” such as patients in shock or those with left main occlusion, Dr. Kirtane noted. “If you don’t get to them early, they’re going to die anyway. Those patients are the ones whose lives could be saved by technology such as this.”

 


Source:
Sanchez-Ross M, Oghlakian G, Maher J, et al. The STAT-MI (ST-Segment Analysis Using Wireless Technology in Acute Myocardial Infarction) trial improves outcomes. J Am Coll Cardiol Intv. 2011;4:222-227.

 

 

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Disclosures
  • Drs. Klapholz and Kirtane report no relevant conflicts of interest.

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