More than one million
Americans will suffer an acute myocardial infarction (AMI) this year. Within the first 60
minutes of chest pain, 250,000 will die. Before
reaching any medical attention, a total of 375,000, (one-third) will die.
While thrombolytic therapy saves more than 20,000 lives per year compared with placebo, and while primary percutaneous coronary intervention (PCI) saves an additional 20,000 lives per year over thrombolytic therapy (representing a more than 50% relative reduction in AMI mortality compared with placebo), this number of lives can be saved by a 12% relative reduction in mortality in the pre-hospital phase of AMI. Thus, strategies having even a small relative benefit result in a large reduction in mortality, because of the staggering number of individuals at risk.
As
shown, time-to-treatment is an important
predictor of mortality in AMI. The benefit of
thrombolytic therapy drops off rapidly as a function of increasing time between symptom
onset and application of therapy, particularly early in the course of AMI. Together, the data in Figures 1 and 2 strongly
suggest that efforts aimed at reducing the delay between AMI onset and therapy can reduce
mortality significantly. This is the impetus
behind the National Heart Attack Alert Program (NHAAP).
Concept Overview
The underlying, basic concept of PIERS is to bring critical parts of the Emergency Department to the patient in a simple, rapid, reliable, inexpensive, non-threatening way that lowers the barrier to entry into the medical treatment system. This effort must be integrated seamlessly with the current EMS and 911 system, and not become an additional cause of delay between symptom onset and treatment.
In the absence of ongoing acute ischemia or available provocative tests, coronary artery disease is detectable only by history. Both the past medical history, particularly cardiac risk factors, and the current history of a syndrome involving chest discomfort are key elements that provide clinical clues to an ACS. In the presence of ongoing symptoms, the ECG is a simple, inexpensive, objective test that can often detect cardiac ischemia. The emergency department procedures for the initial evaluation of the ACS patient include past and current history, and a comparison of a past with a current ECG.
Two distinct, but related groups of patients at risk for
developing ACS including acute myocardial infarction are recognized: 1) high-risk patients -- those with known
coronary, peripheral or cerebrovascular atherosclerosis, and 2) the general population.
As an initial step, PIERS is directed at patients at
high-risk for developing an ACS. Patients are identified as high-risk by their physician,
who prescribes PIERS. PIERS provides these
patients with a near credit-card device (Patient’s Personal Module, PPM) capable of
transmitting stored demographic information, past medical history information (including
medications and cardiac risk factors), baseline ECG and current ECG from any telephone to
a System Server which is available immediately at all times.
The System Server has multiple functions. It interprets the current ECG and compares it with the baseline ECG. In the case where an AMI or ACS is clearly evident, EMS is dispatched automatically without human intervention. In cases where AMI or ACS is not clearly evident on the current ECG, the System Server routes the received patient information and ECGs to a Cardiac Teleconsultant and establishes voice contact between the Teleconsultant and the patient. The Cardiac Teleconsultant is trained to review the patient’s incoming data, question the patient regarding his symptoms (guided by an interrogation algorithm), and use the System Server’s ECG interpretation to develop a disposition for the patient. Dispositions may range from dispatch of EMS to an appointment with the treating physician. In cases of clear AMI or ACS in which the System Server automatically dispatches EMS without human intervention, the System Server still routes all information to a Cardiac Teleconsultant and establishes voice contact between the patient and Teleconsultant.
For the general population, the PPM or a PPM-like device can be made available at selected public places, such as pharmacies, sports arenas, office buildings, shopping malls, or airports, where, with the help of trained personnel, the ECG may be acquired and transmitted. Then a voice link can be established with the PIERS Telecon-sultant through the System Server.
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