From Theory to Practice: Implementation of Pre-Hospital Electrocardiogram Transmission in ST-Elevation Myocardial Infarction — A Multicenter Experience

ABSTRACT: Background. Percutaneous coronary intervention for ST-elevation myocardial infarction (STEMI) reduces morbidity and mortality if performed rapidly. We examined whether timely intervention in myocardial perfusion times achieved at NorthEast Medical Center (NEMC) using pre-hospital (PH) electrocardiography (ECG) could be maintained during a 3-year follow-up period, and whether a similar system could be implemented at 6 other larger hospitals in a prospective, multicenter study. Methods. We calculated median door-to-reperfusion times for emergency medical services (EMS) and self-transport patients. PH wireless ECG transmission was attempted by trained EMS personnel with transmission to an on-call cardiologist’s hand-held device. A standardized “STEMI code system” was implemented to further improve door-to-reperfusion times. Results. At NEMC, door-to-reperfusion times were similar in both the pilot study and follow-up periods, with a median time of 63 minutes. However, successful PH-ECG transmission was less frequent during the follow-up period (20% vs. 56%; p Conclusion. Initial reduction of reperfusion time at NEMC using PH-ECG transmission to the cardiologist was maintained over time, however, there was a decrease in the PH-ECG transmission rate. PH-ECG transmission was difficult to achieve in larger-sized communities. Successful PH-ECG transmission to an on-call cardiologist, together with an effective STEMI code system, can markedly reduce door-to-reperfusion times. J INVASIVE CARDIOL 2010;22:520–525 Key words: PCI, STEMI, pre-hospital ECG, reperfusion ———————————————————— In patients with ST-elevation myocardial infarction (STEMI), time-to-treatment is a critical element in reducing morbidity and mortality.^1,2 Wireless transmission of pre-hospital electrocardiograms (PH-ECG) is a method designed to address the need for rapid triage and treatment of STEMI patients.³ Use of the pre-hospital ECG has been shown to reduce the time from hospital arrival to treatment.^4–9 However, several years of experience was required for the pre-hospital ECG to be recommended as a method for reducing time to treatment.¹⁰ The new American College of Cardiology/American Heart Association guidelines now recommend that each community develop a STEMI system of care that involves a process for pre-hospital diagnosis identification and treatment activation (Class I indication).¹¹ The TIME (Timely Intervention in Myocardial Emergency) research initiative has investigated the potential benefits of pre-hospital 12-lead ECG wireless transmission to an on-call cardiologist.⁴ The TIME-North East (TIME-NE) pilot study in the NorthEast Medical Center (NEMC) in Concord, North Carolina, investigated whether wireless transmission of pre-hospital ECGs suggesting STEMI ECGs transmitted to the hand-held computer (Smartphone or Personal Digital Assistant) of the on-call cardiologist reduces door-to-reperfusion times.⁴ This study demonstrated that pre-hospital wireless ECG transmission to the on-call cardiologist significantly reduced the time from emergency department (ED) arrival to reperfusion by a median of 50 minutes, thus achieving the recommended American College of Cardiology/ American Heart Association goal for patients with STEMI.⁴ The prospective Timely Intervention in Myocardial Emergency-Multicenter study (TIME-MC) was performed to determine if the reduced door-to-reperfusion time demonstrated in the TIME-NE study could be: 1) maintained in the NEMC community during the 3-year post-study period; and 2) attained in larger communities with more complex medical care systems.

Methods

Patient inclusion. All patients with a diagnosis of acute STEMI defined as 1 mm ST segment elevation in two spatially contiguous leads were included. There were two major subgroups: emergency medical services (EMS) and self-transport patients. Self-transport patients, who did not have PH-ECG transmission, served as a comparison group. Study period and clinical definitions. The TIME-MC study was conducted from June 2003 to June 2008 at NEMC (Figure 1) and from May 2005 to September 2008 at the six larger medical centers (Figure 2). Two groups were studied. Group 1 included patients at NEMC and Group 2 included patients at the other six medical sites. The study was divided into three periods:

1. Pre-study period (Group 1 and Group 2). No PH-ECG transmission system was available. 2. Study period (Group 1 and Group 2). PH-ECG transmission to a cardiologist’s hand-held device was attempted through pre-assigned EMS ambulances equipped with a wireless ECG transmission device in addition to a STEMI code system. In Group 1, this referred to the pilot study at NEMC from June 2003 to May 2005. 3. Post-study period (Group 1). PH-ECG transmission and a STEMI code system implemented after the pilot study period.

Interventional measures for system implementation. A pre-defined STEMI Code System was established and implemented in each study hospital. Its goal was to foster a team approach and effective coordination between pre-hospital care providers, ED physicians and cardiologists. It was also designed to remove any communication barriers that would delay patient management and future intervention. This was crucial to increase awareness, educate medical staff and decrease transfer time for STEMI patients. If the pre-hospital care provider was unable to transmit an ECG wirelessly to the on-call cardiologist, he/she interpreted the ECG and relayed this interpretation to the ED physician by radio. Both the ED physicians and cardiologists were instructed to foster a supportive relationship with pre-hospital care providers and to encourage them to make their best ECG interpretation. A system that identified the specific on-call interventional cardiologist was established to eliminate unnecessary delays associated with locating the responsible interventional cardiologist, and these physicians were instructed to ask brief questions of EMS and ED colleagues. Each false activation of the catheterization laboratory was carefully evaluated to minimize recurrences. In each study community, there were EMS, ED and Cardiology “Champions” whose duties were to identify any challenge that may arise during this process and address it expeditiously. There were also frequent meetings with study coordinators to review door-to-reperfusion time progress and provide recommendations for future improvements. For self-transport patients, the hospital check-in ED nursing staff identified those presenting with chest pain, rapidly acquired ECGs, secured the patient in a monitored room, and reported immediately to the ED physician. The same educational initiatives were also implemented for self-transport patients. Primary and secondary outcomes. The primary outcome was door-to-reperfusion time; calculated as the time from hospital arrival to balloon inflation or needle insertion. The secondary outcome was successful pre-hospital wireless ECG transmission. Device. The Welch Allyn Smartlink Wireless 12-Lead ECG transmission system incorporates 4 elements: 1) a pre-hospital 12-Lead monitor/defibrillator; 2) trained EMS personnel familiar with the device and its function; 3) a hospital ECG transmission receiving station; and 4) an on-call cardiologist with a cellular telephone or Personal Digital Assistant capable of receiving ECG transmissions. The 12-Lead monitor/defibrillator was capable of obtaining a 12-Lead ECG, digitizing it into a portable document format and transmitting the 12-Lead ECG waveform over a cellular network in less than 10 seconds. The ECG receiving station was a standard desktop computer on which the Welch Allyn Smartlink Wireless transmission software was installed. The Smartlink Wireless transmission software enabled automatic or manual transmission forwarding. The manual forward option allowed the ED nurse to forward a 12-Lead ECG obtained by EMS to the on-call cardiologist’s Smartphone or Personal Digital Assistant. Standard portable document format-viewer software allowed the cardiologist to view all 12 ECG leads simultaneously or to enlarge a specific lead for individual analysis. Each medical center was equipped with a Welch Allyn Smartlink Wireless 12-Lead ECG transmission device that was placed in a designated EMS ambulance. Each site had multiple devices for transmissions to one EMS provider. Procedures. A pre-hospital 12-lead ECG was acquired for all EMS-transport patients experiencing acute chest pain. Attending EMS personnel with previous training in ECG analysis interpreted the ECG. If the ECG displayed threshold ST-segment elevation, the ECG transmission sequence was initiated. A “transmit” button on the Welch Allyn PIC-50 monitor/defibrillator was pushed, and this began the 10- to 20-second process of file digitization and compression. The compressed ECG data were then sent via serial cable from the mobile monitor/defibrillator to an associated Windows Cellular Enabled Personal Digital Assistant equipped with Welch Allyn eSync software. The user initiated eSync software, then wirelessly transmitted the portable document ECG file via the service provider’s cellular voice/data network to the Smartlink Wireless receiving station. EMS personnel typically notified the ED nurse via telephone or radio of the incoming ECG. Upon receipt of the transmitted ECG file, the receiving station sounded an alarm and displayed the 12-Lead ECG for advanced medical interpretation. Once the ECG arrived at the hospital receiving station and advanced interpretation indicated a need for intervention, the ECG was automatically forwarded from the receiving station to an e-mail account accessible to the on-call cardiologist on a Smartphone or Personal Digital Assistant. The cardiologist typically also received telephone notification. If transmission failure occurred, the cardiologist or ED physician provided patient management instruction to the EMS personnel over the telephone. If ECG transmission was otherwise successful, the cardiologist interpreted the ECG and communicated any subsequent patient-management decision to EMS personnel. Management decisions regarding reperfusion included transport of the patient directly to the catheterization laboratory for PCI (only in Group 1), effectively bypassing the ED, or transport of the patient to the ED to be evaluated by the on-call cardiologist. If primary PCI was not immediately ordered, the patient was re-evaluated in the ED to determine if any contraindication for reperfusion therapy existed. If EMS personnel were instructed to bring the patient directly to the catheterization laboratory, the cardiologist activated both the catheterization laboratory call-team and the study nurse. He or she also advised the acute-care unit to be available for patient registration and to initiate catheterization preparation. The patient and EMS personnel were met in the catheterization laboratory by the on-call team and cardiac catheterization was performed. Data collection. Data were collected by the study coordinators at each site. The ECG times on the case report form were taken directly from the ECG receiving station, which was manually synchronized with the 911-center atomic clock. This standardized timing mechanism was used throughout the study on all ECG transmission and receiving devices. In addition to door-to-reperfusion time, age, sex, infarct-related artery, and mode-of-transport were collected. Statistical analysis. Patient characteristics for the three periods were compared with the chi-square statistic for categorical variables and one-way analysis of variance for age. The Wilcoxon rank-sum statistic was used to compare time-to-reperfusion in the pre-study and study periods as well as in the Group 1 post-study period. Comparisons were performed separately for EMS and self-transport groups.

Results

Age and sex of the patients were similar across study periods (Table 1). Infarct location varied across the study periods, although most infarcts occurred in the inferior region. EMS utilization was greater in Group 2 compared to Group 1. Overall, there were 146 patients included in the Group 1 post-study period; 6 had missing door-to-reperfusion times (Figure 1). Of the 69 patients who were transported by EMS, 14 had successful PH-ECG transmission, with a median door-to-reperfusion time of only 39 minutes (Table 2). This result was similar to the 50-minute door-to-reperfusion time achieved in the pilot study. There were fewer successful PH-ECG transmissions (20%) compared to the TIME-NE pilot study results, where 24 (56%) patients had successful PH-ECG transmission (p

Discussion

The rate of successful pre-hospital transmission decreased over time in Group 1 from 56% during the pre-study period, to 20% post-study period. The utilization of PH-ECG in Group 1 decreased significantly because there were few unsuccessful transmissions reported. In Group 1 (NEMC), EMS-transported patients had a median door-to-reperfusion time of 63 minutes in both pre-study and post-study periods. On the other hand, self-transported patients had a significant decrease in door-to-reperfusion time in the post-study period. In Group 2 (6 medical sites), PH-ECG transmission was rare; however, there were lower door-to-reperfusion times during the study period in both EMS and self-transport patients. There were few successful PH-ECG transmissions in Groups 1 and 2, suggesting that implementation of STEMI protocols was probably an important factor in decreasing door-to-reperfusion time. Several unmeasured factors could have accounted for the decline in door-to-reperfusion time in the self transport group. For those with successful PH-ECG transmission, door-to-reperfusion time was superior to that for STEMI care alone, represented by the self-transport group. Therefore, we believe that improvement in STEMI care protocols is the most likely reason for the decline in door-to-reperfusion time in the self-transport group, with a further reduction in the EMS transport group door-to-reperfusion time when successful PH-ECG transmission occurred. The TIME-MC study was performed not only to reproduce the TIME-NE study experience, but also to evaluate whether it is possible to implement a PH-ECG transmission system in more complex medical systems located in larger communities. The ACC/AHA guidelines recommend PH-ECG transmission (Class I indication), but few hospitals in the Untited States are in compliance. We found that implementation of PH-ECG transmission was challenging and difficult to achieve in larger communities with multiple EMS providers. Implementation of a STEMI code system across all medical centers was essential, as PH-ECG transmission was not always successful.⁴ The core measures implemented in our STEMI code system were designated to increase medical staff awareness regarding patient management and to foster efficient working relations among the various providers, with the goal of improving survival and reducing door-to-reperfusion time. There were many factors that may have resulted in lower PH-ECG transmission rates. There were many factors that prevented transmission of PH-ECG. For instance, among the 6 medical centers was a hospital that serves a large, densely populated metropolitan area. This site was allocated the largest number of PIC-50s,³ yet did not record a single transmission. This was largely due to the fact that there were so many EMS systems (65) and competing hospitals with primary PCI capability (7 within 30 minutes). With the large number of systems and ambulances and the limited number of transmission devices available for research purposes, it was not possible to “saturate” the numerous systems with transmission devices. Rather, the devices were strategically placed with EMS systems that were historically more likely to transport STEMI patients to specific hospitals. Yet, during the 1-year study period, no ECGs were transmitted. Conversely, at NEMC (Group 1), Cabarrus County EMS was the only system transporting patients, and all its vehicles were equipped with the Welch Allyn devices. In addition, NEMC (Group 1) was located in a smaller city in terms of both geographic area and population, and was also the primary medical provider for nearby rural areas. Another challenge encountered in Group 2 hospitals was that ambulances were carrying redundant monitor/defibrillator systems. They were equipped with both their primary-use device and the PIC-50. The purpose of carrying two devices was that the high turnover rate of EMS personnel resulted in some not being properly trained in the use of the research device. Untrained personnel would use the primary device, while properly-trained personnel would use the PIC-50. The inevitable result of having redundant systems on the ambulance was that personnel used the device that they were most comfortable using. Many who had been using the primary device for several years often chose to use it rather than the PIC-50, even though ECG transmission to the cardiologist was not possible with the primary device. Implementation of PH-ECG transmission in a community hospital that serves a medium-sized city and surrounding area with a single EMS is possible. However, it is challenging, but not impossible, in larger and more complex community hospitals. For a successful ECG transmission system, five elements are required: 1) a pre-hospital 12-Lead monitor/defibrillator; 2) well-trained EMS personnel; 3) a hospital ECG transmission receiving station; 4) an on-call cardiologist with a wirelessly capable ECG-receiving device; and 5) a team model among pre-hospital care providers, ED physicians and cardiologists. If one of these is missing, the system will fail. Well-trained EMS personnel who are capable of using the device are needed for successful transmission. As the system evolves, the pre-hospital care provider will become more autonomous in identifying STEMIs, resulting in adaptation of the protocol for bypassing the ED, as seen at NEMC.^8,12 Another measure that could work in complex academic medical centers would be transmission of the PH-ECG to an on-call cardiology fellow rather than to a cardiology attending. Fellows are usually more aware of hospital bed status and are more likely to be present in the hospital.^6,7 Additional measures that can improve time-to-reperfusion include establishment of clinical pathways that bypass the coronary care unit/cardiac ward admission to achieve rapid reperfusion resulting in smaller infarct size and improved survival in STEMI patients.¹² Properly designed regional communication networks can foster coordination between EMS and hospitals and facilitate interhospital transfer. Equipping areas with regional communication networks can result in timely access to quality STEMI care, as Rokos et al have shown.¹³Study limitations. First, we did not assess other factors that could have improved reperfusion times during the study period (2003–2008). Second, more EMS vehicles should have been equipped with Welch Allyn PIC-50 monitor/defibrillator devices. In more complex and larger communities served by numerous ambulances and different EMS, providing one vehicle with one PIC-50 device was inadequate. Unfortunately, there were insufficient resources to provide more vehicles equipped with PIC-50 devices. Third, not all EMS personnel were adequately trained to use the device. For these reasons, the likelihood of PH-ECG transmission was greatly reduced. We did not evaluate outcomes such as mortality or morbidity after PCI, which is also important to determine cost effectiveness. We classified both failed and unattempted PH-ECG transmissions under the same category of “unsuccessful transmission” as there were many reported failed transmissions. Because there were few PH-ECG transmissions among Group 2, we did not perform a direct comparison between Groups 1 and 2. In addition NEMC (Group 1) had only 1 emergency medical system, whereas the others had multiple systems and hospitals. NEMC serves a predominantly rural area, whereas the other centers serve urban areas. Associated with its rural location, NEMC had a higher proportion of self-transport patients. Therefore, because of these and other differences, it would be difficult to make a direct comparison using multivariate statistical methods. Our study is significant, as we have shown that the implementation of PH-ECG transmission and STEMI care protocols to improve door-to-reperfusion time is quite challenging and will require combined efforts and consensus on the county, state, and national levels, so that all small and large hospitals providing care for both rural and urban communities can follow guidelines and recommendations. In larger communities, it is particularly important that there be coordination between multiple medical centers with PCI capabilities. We found that even in a medium-sized community hospital such as NorthEast Medical Center, the rate of PH-ECG transmission was lower compared to the study period 3 years earlier. Although national guidelines recommend the use of the PH-ECG in STEMI patients, there is limited information about its current use and effectiveness.¹⁴ The national use of the pre-hospital ECG to diagnose and facilitate treatment of STEMI remains low.¹⁵ Wireless transmission of the PH-ECG is associated with a significantly shorter time to reperfusion. Implementation of a wireless PH-ECG transmission in a medium-sized community with one EMS provider was successful during the TIME-NE study. However, in the 3-year follow-up period PH-ECG transmission rates were lower following its initial implementation. Using effective STEMI code systems and PH-ECG transmission resulted in lower door-to- reperfusion times that not only met the American College of Cardiology/American Heart Association 90-minute goal, but exceeded it. When used in hospitals serving larger communities, PH-ECG transmission was more difficult to achieve. More funds are needed to insure successful PH-ECG transmission. Once these transmission systems are implemented, surveillance and monitoring or quality improvement efforts should be instituted. Moreover, a parallel and ubiquitous supply of wirelessly capable ECG transmission devices with well-trained EMS personnel is required to foster such a change. Participating hospitals. The 6 participating institutions in Group 2 were: Bethesda North Hospital in Cincinnati, Ohio; University of Pittsburgh Medical Center-Presbyterian in Pittsburgh, Pennsylvania; Duke University Medical Center and Durham Regional Hospital in Durham, North Carolina; South Miami Hospital in South Miami, Florida; Shands at Alachua General Hospital in Gainesville, Florida; and Salinas Valley Memorial Hospital in Salinas, California.

References

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———————————————————— From Duke Clinical Research Institute, Durham, North Carolina; University of Texas Medical Branch, Galveston, Texas; University of Washington, Seattle, Washington; NorthEast Medical Center, Concord, North Carolina. Disclosures: Dr. Wagner discloses that funds were received from MRL and Welch-Allyn for study development. Manuscript submitted May 6, 2010, provisional acceptance given June 15, 2010, final version accepted August 9, 2010. Address for correspondence: Galen S. Wagner, MD, Duke Clinical Research Institute, Cardiology Division-Internal Medicine, 2400 Pratt Street, Room 0306 Terrace Level, Durham, NC 27705. E-mail: galen.wagner@duke.edu