Time is critical for the thousands of patients that suffer from an ST-elevation myocardial infarction (STEMI) each year. Current American College of Cardiology/American Heart Association (ACC/AHA) guidelines recommend that a hospital’s door-to-balloon (D2B) times for STEMI patients be 90 minutes or less, starting from the moment patients enter the emergency department (ED) to the second a percutaneous coronary intervention (PCI) is performed. Hospitals with catherization laboratories are using a range of methods, varying from the use of advanced technologies to the implementation of certain protocols, to meet this target and shave off their D2B times.
Starting at the Scene
1. Transmitting ECGs from the field to the hospital
Remote defibrillator/monitors carried by emergency medical services (EMS) can transmit electrocardiogram (ECG) waveforms from the field to receiving stations at hospitals for immediate reading and interpretation. Cardiologists can then make a diagnosis and start activating the cath lab before the STEMI patient arrives, reducing prep time. Vendors that offer remote defibrillator/monitors for measuring prehospital ECG (PH-ECG) include Physio-Control, Zoll and Philips. The Zoll E Series of monitor defibrillators offers easy configurable options and documentation capabilities, and is designed to withstand the hectic environment of EMS. Also available is the HeartStart MRx monitor/defibrillator from Philips, which uses the company’s DXL 12-lead ECG algorithm to provide diagnostic measurements and STEMI clinical decision support tools, among other features. The HeartStart MRx was introduced for EMS in March 2012.
2. Training EMS staff to read and interpret PH-ECGs
Training EMS staff to read and interpret PH-ECGs on the scene also allows for faster diagnosis of STEMI and subsequent activation of the cath lab. Once a patient is confirmed with STEMI, EMS staff can notify the ED, who then activates the cath lab and team while the patient is on the way. Some hospitals also train EMS staff to read 12-lead ECGs and make the call directly to the cath lab themselves. By activating the labs early, hospitals are ensuring patients can be treated immediately upon arrival.
Some critics note that despite reducing measured D2B times, implementation of PH-ECG can possibly prolong actual scene times and, thus, overall ischemic times for patients. A study published online earlier this year in March in the Journal of the American College of Cardiology (JACC) measured the impact of PH-ECG on scene-to-hospital times for patients with chest pains suspected of cardiac origin. The study’s authors compared scene times and transport times of STEMI and non-STEMI patients before and after implementation of PH-ECG, using data over a five-year period from the city of San Diego’s emergency medical system. The study found that following PH-ECG implementation in 2005, median scene and transport times experienced minimal increases, with the difference being a matter of seconds. However, when compared to non-STEMI chest pain patients, STEMI patients had shorter scene, transport and overall scene-to-hospital times. The authors concluded that obtaining a PH-ECG for patients with chest pain minimally prolongs scene and transport times, but potentially reduces total ischemic times for patients eventually identified with STEMI.
At Kapiolani Medical Center in Hawaii, John Kao, M.D., FACC, medical director of cardiovascular services, and member of the DAIC Editorial Board, says use of PH-ECG has kept D2B times relatively low. “EMS here are trained to perform and interpret 12-lead ECG in the field and can transmit the ECG to centers with receiving units. We don’t have a unit to receive ECG transmissions, but what we have done is gone one step further and are having EMS basically activate the cath lab as soon as they diagnose a STEMI,” Kao says.
Minimizing Time at the Hospital
Once patients arrive at the hospital, whether by walking in or with EMS personnel, there are several examples of protocols that can minimize the time it takes for a patient to be treated for STEMI.
3. Cross-training staff to prepare the cath lab
Cross-training staff can help ensure that cath labs are available and ready even outside typical operating hours, or when cardiologists and regular staff are away at meetings or from the hospital. Hospitals can cross-train cardiac care unit (CCU) and ER nurses and physicians to prep the patient and the cath lab once the call is made. This reduces any unnecessary waiting time for patients in the ER and allows cardiologists to begin working on revascularization as soon as possible, without waiting for cath lab activation and preparation.
4. Direct transfer to catherization
Using protocols such as PH-ECG for STEMI diagnosis and early cath lab activation, patients can sometimes be transferred directly from the care of EMS staff to the cath lab, avoiding time — and potential delays — in the ER altogether. DAIC Editorial Board Member Mladen I. Vidovich, M.D., FACC, FSCAI, chief of cardiology at the Jesse Brown VA Medical Center in Chicago, reports that empowering EMS in the field to make the activation call has shaved roughly 20 minutes off the medical center’s average D2B time. With paramedics trained to read ECGs, patients are able to go straight from the ambulance to the cath lab.
5. Immediate access to patient ECGs
Regardless of where they are, cardiologists can also quickly pull up a patient’s ECG on mobile devices such as smart phones or tablets while on the move. This allows for faster review and diagnosis of the patient, as doctors may be in a meeting, in another area of the hospital or at home when a STEMI patient is en route. ECG waveforms stored in a hospital’s electronic health record (EHR) can be retrieved on mobile devices with integrated applications, such as AirStrip Cardiology’s platform integrated with GE’s Muse cardiology information system. AirStrip announced in June 2012 the expansion of its platform to include real-time mobile access to patient information, including ECGs, in EHR systems for clinicians. In addition, AirStrip has a partnership with defibrillator/monitor vendor Physio-Control that enables dynamic waveforms (rather than static images) to be accessed on mobile devices.
Hospitals looking to hit target D2B times can accomplish their goals with a combination of advanced information technologies and protocols, from the field to the cath lab.