When emergency medical technicians (EMTs) wirelessly transmit eletrocardiograms (ECG) directly to a cardiologist's hand-held device, heart attack patients can potentially receive direct clot removal in half the usual time, according to cardiologists at Duke University Medical Center and NorthEast Medical Center, Concord, N.C.
Cutting this "door-to-reperfusion" time is critical, the cardiologists said, because the sooner a patient suffering from a heart attack receives an artery-opening procedure, the more likely heart muscle can be saved, and that the patient will potentially derive a survival benefit.
While the American College of Cardiology (ACC) and the American Heart Association recommend that patients have their arteries opened directly within 90 minutes of arriving at the hospital -- the NorthEast Medical Center team was able to cut that time to 50 minutes. The national average "door-to-reperfusion" is about 100 minutes, the researchers said.
The results of the pilot project were presented March 13, 2006, by Duke Clinical Research Institute cardiology fellow George Adams, M.D., during the 55th annual scientific sessions of the ACC in Atlanta.
The team achieved this significant time savings by directly linking EMTs with cardiologists and bypassing the hospital's emergency department for the small proportion of those patients with chest pain whose ECG is distinctly diagnostic. In the current study, specially trained EMTs transmitted ECG tracings electronically from the scene or in the ambulance to an on-call cardiologist's personal digital assistant (PDA). The cardiologist -- on spotting the definitive signs of a heart attack -- could mobilize the catheterization laboratory while the patient was en route to the hospital.
While the time savings achieved in the current pilot project are significant, the researchers point out that the results will need to replicated in more diverse settings. In the current project, NorthEast is staffed by a small number of interventional cardiologists at one hospital with one ambulance service. Duke researchers are currently organizing a 12-site study across the U.S. in larger and smaller cities with different sized hospitals and ambulance services.
"We found that the pre-hospital wireless transmission of an ECG directly to a cardiologist's hand-device significantly reduced the time from emergency room door to reperfusion," Adams said. "When the cardiologist can directly see an ECG, it clarifies the decision to mobilize all the personnel necessary for the cath lab to be ready to go when the patient arrives."
The researchers were studying a specific kind of heart attack known as an ST-segment elevation myocardial infarction (STEMI). When a cardiologist spots a major elevation of the tracing in the ST portion of an ECG study, there is little question that patient is having a heart attack, Adams said.
In the final two years of the four-year pilot project, the team enrolled patients with a suspected STEMI who were taken to NorthEast Medical Center. During the intervention phase of trial, the team enrolled 101 self-transported patients, and 24 ambulance patients where the wireless ECG transmission was successful, and 19 patients for whom the wireless transmission was unsuccessful.
"The median 'door-to-reperfusion' time for those with a successful transmission was 50 minutes, significantly faster than the 96 minutes for those who transported themselves and the 78 minutes for those whose transmission failed," Adams said.
Key to the success of the project, the researchers said, is the training of the EMTs. Currently, almost all ambulance services are equipped to perform an ECG at the scene or in the ambulance. However, for any such project to be successful, the researchers said, an EMT needs to be able to spot tell-tale abnormalities, since only about five percent of patients experiencing chest pains need an immediate catheterization.
"Wireless ECG transmission gets at the 'heart' of the problem, which is communication." said Duke cardiologist Galen Wagner, M.D., senior member of the research team. "We have ability to transport patients and we are good at clearing clots from arteries -- the challenge is to remove the barriers in between."
Also importantly, said the researchers, the findings add further evidence that patients or families should always call for an ambulance instead of driving themselves to a hospital if a heart attack is suspected. While it may seem intuitive that a patient could get themselves to a hospital sooner, they will typically have to go through the emergency room triage system before actually going to the catheterization lab, if appropriate, noted the researchers.
Interestingly, as the project became known to Cabarrus County residents over the four-year period, the researchers noticed a decline in the number of potential heart attack patients transporting themselves to the hospital.
While the upcoming trial will test wireless transmission capabilities in a number of different settings, it will also study the effects of shortening the "door-to-reperfusion" time on mortality and heart muscle salvage. It is estimated that more than 500,000 Americans will come to a hospital with an STEMI.
The pilot project was supported by the William T. Morris Foundation, N.Y., the Duke Endowment, Charlotte, N.C., and Welch Allyn, Skaneateles Falls, N.Y., which provided some of the equipment. The investigators have no financial interest in Welch Allyn.
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