Emergency cardiac monitoring strategy tested in ambulances
A new UCSF-designed strategy for hastening treatment for heart attack victims is being tested in a mountainous California county where drive times to hospitals are often long. Since August, all ambulances in Santa Cruz County have been equipped with sophisticated cardiac monitors that can send vital data directly by cell phone to the emergency department of the receiving hospital.
"Every minute that heart cells are deprived of blood flow, they are dying," says Barbara Drew, RN, PhD, the study's principal investigator and a professor of physiological nursing in the University of California, San Francisco School of Nursing. "Once heart cells are dead, they don't regenerate. So the initial treatment goal is to get the blockage in the obstructed artery open as quickly as possible before any more heart cells die."
The new "tele-electrocardiography" system consists of an easily-attachable 12-lead cardiac monitor that takes readings every 30 seconds and can detect ischemia, the diminished flow of blood through an artery that signals heart damage. It's hooked to a cell phone that transmits the information directly to the emergency department of the receiving hospital. Based on her years of experience in cardiac intensive care units, Drew came up with the idea to develop such an easily-attachable monitor with ischemia detection capabilities and to use it in ambulances in conjunction with a cell phone.
"Usually when patients arrive at a hospital, they are evaluated by a triage nurse," Drew says. "If their condition warrants it, they are attached to a cardiac monitor for further evaluation. But all that takes time. What we wanted to do was to move the clinical decision-making to a point before the patient even gets to the hospital."
The standard heart monitoring procedure used by medics responding to calls from people experiencing heart attack symptoms involves attaching a cardiac monitor with a single recording lead to the patient's chest. The monitor provides only a basic electrocardiogram (ECG) that measures the patient's heart rate and rhythm. It can't detect ischemia. Some ambulances in the United States are equipped with 12-lead cardiac monitors. Although these can detect ischemia, they require attachment of ten separate electrodes to the patient's chest and they make only a single 10-second recording, which may miss rapidly changing abnormalities common in heart attacks.
The "tele-electrocardiography" system Drew is using in her study consists of several components:
A 12-lead cardiac monitor that requires only a five-electrode attachment to the patient's chest.
Software that analyzes the ECG every 30 seconds for signs of ischemia and heart damage.
A cell phone hook-up from the monitor to the emergency department of the receiving hospital.
Once patients are attached to the monitor, ambulance medics push a button to send the first reading to an emergency department computer. An audible alert accompanies the transmission. If the software detects changes in subsequent ECGs, it automatically transmits them, as well.
Drew chose Santa Cruz County as a testing ground for the new system because the county is large and mountainous and has only two hospitals, both located near the coast. For many residents, hospital transit times are long. "If hospital teams had advance notice of the patient's condition," Drew says, "it would give them time to get ready for immediate treatment."
As of August, ambulance medics in Santa Cruz County have been attaching all patients who may be suffering from heart attacks to the equipment. A computer program then randomly assigns each patient to the study group or the control group. Only the ECGs of patients randomized into the study group show up on the computers in the emergency departments. For all patients, medics have access only to the standard information provided by a one-lead ECG, and they are not informed of the patients' group assignment. Drew expects that it will take five years to enroll and determine outcomes of 2,468 patients, the number required to determine with statistical significance whether the system will improve survival and long-term health of heart attack victims.
For Alec Popovich, one of the first heart attack victims enrolled in the study, the system has already provided meaningful results. On Sunday morning, August 10, Popovich, 50, felt a tightness in his arm. Having suffered two previous heart attacks, he suspected the third was now on its way. Popovich, who lives in the Santa Cruz mountains, hopped into his truck for the half-hour drive to the hospital. But after four miles he pulled over, got out of the truck and collapsed to the ground. He had just enough energy left to dial 911 on his cell phone to report his condition and approximate location to the operator.
When medics finally found Popovich, they hooked him to the new 12-lead cardiac monitor even before he entered the ambulance. Using the cell-phone hookup, a medic transmitted Popovich's ECG to the emergency department of Dominican Hospital in Santa Cruz. Because computer software then randomized Popovich into the study group, the emergency room doctor received the ECG and immediately alerted James Glancy, MD, a cardiologist who was in the hospital making his rounds. Glancy is medical director of Cardiovascular Services at Dominican, as well as an assistant clinical professor in UCSF's School of Nursing and a co-investigator in the tele-electrocardiography study.
Glancy read the ECG and determined that Popovich was suffering from the kind of heart attack that requires either stent placement or balloon angioplasty to open a coronary artery, procedures that are performed in Dominican's cardiac catheterization lab. With this advance notice, Glancy was able to prepare for the ambulance's arrival.
Popovich was in the hospital only 48 minutes before a catheter was used to clear his blocked artery, 43 minutes ahead of the hospital's average treatment time of 93 minutes. The American College of Cardiology and American Heart Association have set a target time of 90 minutes, plus or minus 30 minutes, for performance of this procedure from the time of a patient's arrival. The average time for California hospitals that participated in the 2002-2003 National Registry for Myocardial Infarction is 109 minutes.
"This was a very exciting outcome, because we've worked hard for years to put this study together and this was the first time that it became apparent to all of the investigators that what we were doing might make a difference," Drew says.
However, Drew says, despite this initial positive outcome, it will take five years and the enrollment of hundreds of patients to determine whether Popovich' s case is the exception or the rule. "It would be irresponsible to spend the money necessary to equip thousands of ambulances with the system unless it can be shown that, overall, outcomes such as better long-term health and survival are improved," Drew says.
Popovich spent 22 hours in Dominican Hospital and was then transferred to Kaiser Hospital in Los Gatos, where he spent less than half a day before being discharged. He returned to work on October 13.
Additional investigators in the study are Kathleen Dracup, RN, FNP, DNSc, FAAN, dean and professor, UCSF School of Nursing; Steven Paul, PhD, principal statistician, Office of Research, UCSF School of Nursing; Mitchell Krucoff, MD, Duke Clinical Research Institute, Durham, NC; Kent Benedict, MD, medical director, Emergency Medical Services Santa Cruz County; Elise Dempsey, RN, MS, manager of cardiovascular services, Dominican Hospital.
The study was funded by the National Institute of Nursing Research, National Institutes of Health.