High-tech EMT unit triages, treats chest pain patients

Emergency medical technicians may soon be able to triage chest pain patients in the field, allowing early intervention in those with myocardial intervention in those with myocardial infarctions and avoiding unnecessary hospitalizations in those with chest pain due to other causes.

The chair of the department of emergency medicine at Virginia Commonwealth University in Richmond hopes to launch a telemedicine project that would allow paramedics to initiate fibrinolytic therapy and transport high-risk patients, as well as monitor low-risk patients at home until they consul with their doctors. At a conference sponsored by the National Heart, Lung, and Blood Institute, it was reported the approach to "a high-tech house call" EMS vehicles would be equipped with audio-visual equipment directly linked by satellite to Richmond’s emergency departments. The link would allow face-to-face doctor-patient interaction and would transmit the results of multiple tests, including blood enzyme and ECG findings, performed by the paramedics.

If the data confirm that an MI is in progress, paramedics could initiate fibrinolytic therapy under direct order of the telemedicine physician and transport the patient. If there is no obvious MU and all of the other cardiac tests are negative, the team could equip the patient with a wearable automatic defibrillation (AED) unit is linked to a global positioning satellite (GPS) unit. The AED will deliver a shock within 20 seconds of detecting an unstable heart rhythm, and transmit the GPS coordinates to a dispatch unit. The approach is a lot safer than existing care, in which some patients leave the emergency room without a diagnosis and later experience a cardiac event. The wearable AED would increase "the degree of safety of these patients." The 80-lead electrocardiogram is one of the developments that adds a degree of safety to in-the-field triage. The device generates a three-dimensional color-coded image of heart function and detects most of the acute ST elevation MIs that are missed by a standard 12-lead ECG, said at the conference, also sponsored by the Centers for Disease Control and Prevention and the American Heart Association.

In a study conducted by associates, the PRIME-ECG body map system, which was recently approved by the Food and Drug Administration, was 100 percent sensitive for detecting MIs defined by elevated creatinine kinase MB, and 93 percent sensitive for detecting MIs as defined by elevated troponin levels. Specificity was comparable for the 12- lead and the 80-lead systems. Among 647 adults with chest pain assessed by 12- and 80-lead ECG systems, the 80-lead system identified 28 MIs missed by the 12-lead system: Four septal, 21 posterior, and three inferior MIs. The incidence of extensive right ventricular involvement diagnosable only with the 80-lead system was 22 percent. At least 20,000-40,000 hard-to-diagnose MIs (one percent-five percent of all heart attacks) are missed in the emergency department each year; about 20 percent of them are fatal. The 80-lead system picks up these hard-to-see MIs in the lateral and posterior walls better than a 12-lead system.

They are looking at the same ECG signals, but we have 80 of them instead of just 12, and we have them distributed over the entire chest, including the right side and the back. Computer technology has progressed now to the point where it can process data from 80 leads simultaneously. That wasn’t possible five years ago. The PRIME body map ECG system marketed in the United States, generates color-coded images as either a flat body map showing "unfolded" views of the front and back of the torso. Conventional analog tracings are also available for either 80-lead or 12-lead readings. The image display positive ST segment deviations in red, negative ST segment deviation in blue, and neutral values in green. Easily recognizable patterns are associated with each kind of heart attack. For instance, a lateral wall MI shows up as a bright red area under the left arm. A posterior wall MI shows up over the back and a right ventricular MI shows up under the right arm and over the right chest.