2022 Volume 86 Issue 4 Pages 591-599
Acute cardiovascular disease, such as acute myocardial infarction and aortic disease, can lead to a serious life-threatening state within minutes to hours, so early accurate diagnosis, and appropriate treatment without delay are essential. To provide high-quality and timely treatment, 24-h availability of medical staff and cardiologists, as well as a cardiac catheterization laboratory are needed. In Japan, the number of patients with acute cardiovascular disease is increasing with the aging population and westernization of lifestyle; however, workstyle reforms for physicians, including a policy to limit overtime work, have been legislated. Under these conditions, it is necessary to centralize hospitals that treat cardiovascular emergency diseases as high-volume centers and build a patient triage system for allocating patients before hospital arrival. The prehospital 12-lead electrocardiogram (ECG) plays a central role in prehospital diagnosis and triage, and its importance will increase in future. We discuss the current and future state of the cardiovascular emergency medical care system utilizing prehospital 12-lead ECG in urban areas of Japan.
Acute cardiovascular diseases, such as acute myocardial infarction (AMI) and aortic disease, are the leading causes of death in Europe and the USA. In Japan, acute cardiovascular disease is the second cause of death after malignancy, but the number of patients is increasing with aging of society and westernization of lifestyles. Characteristically, acute cardiovascular disease often develops and progresses rapidly and can become life-threatening within minutes to hours. Therefore, early accurate diagnosis and appropriate medical treatment without delay are essential, requiring medical staff, such as trained nurses, medical engineers, radiology technicians and cardiologists, as well as a cardiac catheterization laboratory be available 24-h a day.
In 2021, the revised Medical Care Act, which includes “workstyle reforms” for physicians, was enacted in Japan. This amendment includes a policy to limit the overtime of physicians from 2024, which will have various effects on the management of medical institutions and local administration. It will be necessary to build collaborative networks by taking into consideration the broader region, rather than on a hospital-by-hospital basis, as soon as possible.
To achieve this, functional differentiation and specialization of hospitals will be necessary. Hospitals that treat cardiovascular emergency diseases will be centralized as high-volume centers, and other hospitals will be required to expand their function of treating emergency patients with lower severity and urgency, as well as patients in the post-acute phase from high-volume centers. Furthermore, a patient triage system for allocating patients before hospital arrival is needed. The prehospital 12-lead electrocardiogram (ECG) plays a central role in prehospital diagnosis and triage,1 and its importance will increase in future. However, the implementation rate of prehospital 12-lead ECG is still not high in Japan.
We discuss the current and future states of the cardiovascular emergency medical care system utilizing prehospital 12-lead ECG in urban areas of Japan.
Although there are advantages and disadvantages of cardiovascular emergency care centralization (Table 1), there is robust evidence of its effectiveness in improving patient prognosis. Reports from The Organization for Economic Cooperation and Development (OECD) show that hospitals with a high-volume of AMI cases have lower 30-day AMI mortality rates.2 In addition, categorizing by hospital performance according to the 30-day AMI mortality rate shows that high performing hospitals show an improvement in longer-term prognosis compared with low performing hospitals.3 This means that receiving treatment at high performing hospitals in the acute phase of AMI leads to not only an improvement of in-hospital prognosis, but also long-term benefits. Several reports from the USA, France, South Korea, and Japan have shown the relationship between hospital volume and clinical outcomes in AMI patients.4–8 We reported, using JROAD-DPC data, that AMI patients treated at high percutaneous coronary intervention (PCI) volume hospitals had a lower in-hospital mortality rate than those treated at low PCI volume hospitals, regardless of the regional population density.4 Furthermore, importantly, a multivariate analysis revealed that the size of the hospital (i.e., large), not the transport distance, was related to improved prognosis. The hospital volume-outcome relationship is generally reported not only for AMI, but also cardiogenic shock, acute aortic dissection, ruptured aortic aneurysm, and other diseases that require prompt treatment.9 In the hospital volume-outcome relationship for AMI, a shortened time to reperfusion is thought to be the key. Clinical outcomes of ST-segment elevation myocardial infarction (STEMI) patients depends on time to reperfusion of the infarct-related artery after symptom onset.10 We studied 369 STEMI patients within 12 h after symptom onset who were admitted to 12 emergency hospitals (1 tertiary emergency center and 11 community hospitals) in an urban setting in Japan.11 The tertiary emergency center had shorter median door-to-balloon time than the community hospitals (63 vs. 104 min, P<0.001). Of note, presentation out-of-hours at the community hospitals significantly prolonged the door-to-balloon time by 27 min, as compared with presentation during regular hours, whereas the time of presentation did not influence the door-to-balloon time in the tertiary emergency center. However, the low mortality rates at high-volume centers cannot be explained by shortened time to reperfusion alone, and other factors must substantially contribute. Those factors include PCI operator’s skills, highly advanced medical care systems, such as mechanical circulatory support devices (e.g., Impella and veno-arterial extracorporeal membrane oxygenation (ECMO)), and the knowledge and skills of the medical staffs. It is important for operators and medical staffs to continuously experience treatment of AMI patients to maintain the technical capabilities of PCI and the ability to respond to sudden changes in the patient’s condition. According to results of a population-based study from the PCI reporting system of New York, hospital case volumes of <400 PCIs/year and operator case volumes of <75 PCIs/year were associated with poor prognoses.12 Therefore, the guidelines of the American College of Cardiology (ACC)/American Heart Association (AHA), the European Society of Cardiology (ESC), and the Japanese Circulation Society (JCS) all recommend that primary PCI should be performed by operators with a large number of annual cases at high-volume centers.13–15 It is not recommended that low-volume operators perform PCI at low volume centers (Class III recommendation).13
| Advantages |
| (1) Improved prognoses of patients with cardiovascular diseases requiring prompt response, such as acute myocardial infarction, cardiogenic shock, acute aortic dissection, and ruptured aortic aneurysm at high-volume centers |
| • Shortened time to treatment by improved emergency response system |
| • Advanced medical care provision systems, such as mechanical circulatory support devices |
| • Abundant experience and knowledge of physicians and medical staff |
| • Collaboration with other departments, such as cardiac surgery |
| (2) Improved working environment for cardiologists |
| • Shift work with sufficient number of physicians at partnership-enhanced hospitals (high-volume centers) |
| • Reduced burden of emergency response at other partnered hospitals |
| Disadvantages |
| (1) Possibility of worsening business conditions at partnered hospitals |
| (2) Comprehensive cardiovascular care can no longer be provided at one hospital |
| • Reduced patient convenience |
| • Education of cardiologists |
One of the important advantages of high-volume centers is cooperation with cardiac surgeons. Serious mechanical complications that occur early after the onset of AMI include interventricular septal perforation, left ventricular free wall rupture, and rupture of the mitral valve papillary muscle. These mechanical complications are rare (≈1% of AMI), but when they do occur, hemodynamics deteriorate immediately. The natural prognosis is extremely poor, and early surgery is recommended.15,16 It is high risk to transfer such a patient at this stage. Additionally surgical treatment may be needed for some PCI complications, including coronary artery perforation/rupture by coronary balloon angioplasty or wire, blood vessel damage at the access site, and occlusion. Coronary artery bypass grafting (CABG) may be required as reperfusion therapy. In the treatment of STEMI patients, the most important thing is prompt coronary reperfusion. In STEMI patients, coronary reperfusion can be achieved by primary PCI faster than emergency CABG; hence, CABG is selected as reperfusion therapy in a limited number of patients. In some AMI patients, a hybrid of PCI and CABG or CABG alone is desirable as the method of reperfusion therapy. CABG is required for 5–10% of non-ST-segment elevation acute coronary syndrome (ACS) cases.17 Even for STEMI, the guidelines recommend discussing emergency CABG with the heart team for patients in whom PCI is unsuccessful or technically difficult, with persistent myocardial ischemia, or who have unstable hemodynamics refractory to medical treatment (cardiogenic shock, heart failure, lethal arrhythmia thought to be due to myocardial ischemia).15,18 In a study of 4,601 hospitals and 587,779 AMI patients in the USA, the number of institutional AMI patients, the number of beds, and the ability to surgically operate were independently associated with favorable prognoses.19 The risk of surgery in the acute phase of AMI is high and its indications need to be carefully discussed by the heart team. However, it is important to consider several reperfusion strategies and decide the best one for each patient at a facility where such surgical treatments are available. It has also been reported that prognosis is poor in hospitals with a treatment strategy that is biased towards PCI for revascularization in heart failure due to multivessel ischemic heart disease.20
In Yokohama city, prehospital 12-lead ECG recording by the emergency medical service (EMS) was introduced in 2004, and all 79 EMS units are now equipped. However, the implementation rate of prehospital 12-lead ECG is still <60% even in STEMI patients,21 and the overall rate of utilizing prehospital 12-lead ECG for all cardiovascular diseases is suspected to be even lower. In our previous survey of emergency paramedics, the following trend was elucidated: (1) if the patient had a family physician, that was the first contact for treatment, and (2) if a transportation destination hospital is found immediately, prehospital 12-lead ECG tended to not be performed (Figure 1).22 There are several possible reasons why prehospital 12-lead ECG recording by the EMS is not sufficiently widespread in urban areas (Table 2). First, it increases the workload of the paramedics and prolongs the transportation time. Next, in urban areas of Japan, family physicians and emergency care hospitals are densely located, and thus usually it is not difficult to find a hospital to which the patient can be transported. The emergency paramedics may recognize the shorter transporting time without performing prehospital 12-lead ECG as preferable to the longer time required to perform the additional prehospital 12-lead ECG. In essence, it is important to notify ECG information to the hospital in advance and to transport the patient to a hospital that can promptly provide appropriate treatment. This provides greater benefit than a slightly prolonged transport time. In addition, because the utilization of prehospital 12-lead ECG differs greatly depending on hospitals to which patients are transported,21 there is likely to be a difference between hospitals that can effectively use this information and those that cannot. Due to these factors, prehospital 12-lead ECG is often not performed at present. To establish a high-quality cardiovascular emergency care system, prehospital care and triage utilizing prehospital 12-lead ECG must become indispensable (Table 2).
Survey results of 388 paramedics in Yokohama city regarding use of a prehospital 12-lead ECG. ACS, acute coronary syndrome; ECG, electrocardiogram.
| Possible factors affecting implementation of prehospital ECG in urban areas |
| • Requires time and effort |
| • Relatively easy hospital selection due to large numbers of family physician hospitals and emergency hospitals |
| • Shorter transport time |
| • Hospitals may not be able to use the prehospital ECG effectively |
| Factors contributing to the increasing importance of prehospital ECG |
| Current and future predictions in urban areas |
| Current status of medical care for acute myocardial infarction |
| • Presence of many PCI-capable hospitals nearby |
| • Several primary PCIs are performed in medium-sized hospitals |
| Aging population |
| • Incidence of AMI will increase, but large increases in heart failure and chronic diseases are also expected |
| • Decreased workforce |
| Workstyle reform |
| • Limitation of working hours to improve the working environment of physicians |
| Future reform of cardiovascular medical care |
| Hospital functional differentiation |
| • Hospitals that accept highly acute diseases become high-volume centers |
| • Establishment of hospitals that accept patients in the post-acute, convalescent, and chronic phases |
| Development of a patient triage system using prehospital diagnosis |
AMI, acute myocardial infarction; ECG, electrocardiogram; PCI, percutaneous coronary intervention.
Cardiovascular diseases, such as chronic coronary syndrome and heart failure, are expected to increase significantly with the increasing elderly population. In particular, it is estimated that the number of elderly patients with heart failure will increase significantly. Therefore, the demand for medical care in the post-acute, convalescent, and chronic phases will be greater than the increase in the demand for the advanced acute phase medical care. Therefore, medical resources can be effectively used by appropriately transporting patients who are severely ill and requiring advanced medical care to a high-volume center, and transporting less severely ill patients to other designated emergency hospitals. The prehospital 12-lead ECG as well as the taking of medical history and physical examination by paramedics will play a major role in prehospital diagnosis and triage in the cardiovascular field. Prehospital 12-lead ECG shortened the time to reperfusion in STEMI patients treated with primary PCI and reduced the mortality rate by 32%, according to a meta-analysis of more than 200,000 people.1 To date, prehospital 12-lead ECG systems have been implemented in several countries, and performing the prehospital 12-lead ECG and notifying the emergency care service in advance are Class I recommendations from the ACC/AHA and ESC guidelines.23,24 The JCS guideline also notes the importance of the prehospital 12-lead ECG.15 Table 3 summarizes the characteristics of prehospital 12-lead ECGs. An appropriate triage of critically ill patients to high-volume centers likely contributes most to reducing mortality rates.
| Factors that reduce mortality |
| Triage to a high-volume center for critically ill patients |
| Shortening the time to treatment (revascularization) |
| Factors that shorten the time to treatment (revascularization) |
| Transfer of STEMI patients to PCI-capable hospital, not to PCI-incapable hospital |
| Early activation of cardiac catheterization laboratory and early call to a catheterization team |
| • Decrease in total system delay |
| • Decrease in the door-to-balloon time |
| Improvement of ACS diagnosis by detecting ECG changes at the early stage of onset |
ACS, acute coronary syndrome; ECG, electrocardiogram; PCI, percutaneous coronary intervention; STEMI, ST-segment elevation myocardial infarction.
The other important advantage of the prehospital 12-lead ECG is the reduced time to reperfusion in STEMI patients. Figure 2 shows the previous reports on the effects of prehospital 12-lead ECGs on time to treatment.21,22,25–40 Utilizing the prehospital 12-lead ECGs shortens the time to treatment because STEMI patients are directly transferred to a primary PCI-capable hospital, enabling rapid reperfusion, and thus avoids delays caused by transportation to a primary PCI-incapable hospital. It has been reported that the time to reperfusion will be delayed by approximately 60–80 min if a primary PCI-incapable hospital is chosen.31–33,41–43 Not only the selection of destination, but an early diagnosis also shortens the subsequent time to reperfusion and thus enables prompt treatment. The prehospital 12-lead-ECG produces the greatest reduction in time to diagnosis of STEMI and it has been reported that prehospital 12-lead ECG with advance emergency department notification reduces the first medical contact-to-reperfusion time, door-to-balloon time, and door-to-needle time, compared with no prehospital 12-lead ECG, in STEMI patients.27,35,44–52 The effect of the prehospital 12-lead ECG on shortening the door-to-device time at PCI centers is suggested to be approximately 13–30 min, according to reports from other countries; previous studies from Japan have reported 4–18 min.21,27,34–40,48 These differences are likely due to differences in the time required to activate the cardiac catheterization laboratory. It is possible that prehospital 12-lead ECG recording in the ambulance by paramedics may lead to prolongation of transport time. According to reports from Japan and other countries, that delay is approximately 1–5 min (Figure 2).21,25–29 Based on the report of the Yokohama Heart Disease Study Group, we compared the transport time (from first contact with the EMS to arrival at hospital) of 2,763 patients suspected of ACS, with and without prehospital 12-lead ECG recording: 26±10 min for 1,231 prehospital 12-lead ECG cases and 24±10 min for 1,532 no prehospital 12-lead ECG cases. The average transport time was delayed by 2 min due to prehospital 12-lead ECG recording.30
Effect of prehospital ECG on the components of treatment delay in STEMI. ECG, electrocardiogram; PCI, percutaneous coronary intervention; STEMI, ST-segment elevation myocardial infarction.
As stated, if the destination is decided upon immediately, the prehospital 12-lead ECG tends to be omitted, and the patient is often transported to the family physician regardless of whether PCI could be performed or not. The most important thing in field triage of critically ill patients, such as STEMI patients, is to provide appropriate treatment quickly rather than to transfer patients to hospitals quickly. However, often patients are transfered to the nearest hospital or their family hospital which can not provide appropriate treatment. Therefore, even patients who have a family physician should be transported to a high-volume center if they have STEMI. We herein present a patient in which EMS paramedics properly selected a hospital based on the prehospital 12-lead ECG. The patient was a man in his 40 s with a history of two episodes of spontaneous pneumothorax without an arteriosclerosis risk factor. He called an ambulance for sudden right-sided chest pain. The prehospital 12-lead ECG (Figure 3A) performed by the paramedics showed ST-segment elevation in leads I, aVL, and V1–5, and the patient was transported to Yokohama City University Medical Center. It took 35 min from the onset of symptoms to calling the EMS, and the first medical contact-to-door time was 26 min. Although it was a very rapid transfer, the 12-lead ECG on hospital arrival already showed a decreased R wave in leads V1–3, indicating that the infarction had progressed rapidly. After primary PCI for the proximal left anterior descending coronary artery (LAD) occlusion, the R wave recovered in height on the ECG. At discharge, cardiac function was maintained well for having experienced a non-Q wave AMI (Figure 3B). It is likely that stunned myocardium was able to recover without necrosis because of prompt treatment. Given the past history of this patient, he might have been transferred to the hospital where he was previously treated for pneumothorax because recurrence would have been suspected more than AMI. The patient’s chief complaint was right-sided chest pain; nevertheless the paramedics performed a prehospital 12-lead ECG, and he was transferred to a hospital capable of primary PCI. If treatment was delayed by having to be transferred from a PCI-incapable hospital, the myocardial infarction due to the proximal LAD occlusion would have become quite large and worsened the prognosis.
Case presentation of usefulness of the prehospital ECG in prehospital diagnosis and triage. (A) Paramedics performed prehospital 12-lead ECG, which ensured the patient was transferred to high-volume hospital. (B) ECG on the hospital arrival showed a decrease in the R wave, which recovered its height after revascularization. ECG, electrocardiogram.
In triage using the 12-lead ECG recorded by paramedics, there are generally 3 ways to interpret it: (1) paramedics notify the computer diagnosis of the ECG to doctors at hospitals, (2) paramedics interpret the ECG and notify the findings, and (3) paramedics transmit the ECG recording and a physician makes the diagnosis. Although the accuracy of computer diagnosis of the ECG has improved, misdiagnosis is likely. Interpretation of the 12-lead ECG in the acute phase of ACS is not always easy, and paramedics must be trained to perform ECG interpretation. For this reason, Yokohama city have been conducting 12-lead ECG recording training for paramedics. Even if the findings notified by the ambulance crew are inadequate, it is very advantageous for ACS diagnosis if the 12-lead ECG recording is available as soon as the ambulance doors open upon arrival at the hospital. In some observational studies, trained paramedics were able to identify typical STEMI on the prehospital ECG in prehospital situations.31,42,53–58 In a report from Japan, a diagnosis of ACS based on the physical findings by paramedics and the prehospital 12-lead ECG had high diagnostic accuracy with a sensitivity of 94.8%, specificity of 91.3%, positive prediction value of 78.6%, and a negative prediction value of 98.1%.59 Furthermore, artificial intelligence has been recently investigated for analyzing prehospital 12-lead ECGs.60,61 In Europe and the USA, STEMI diagnosis and triage using the prehospital 12-lead ECG are common, but is not yet widespread in Japan. Since 2010, the paramedics in Yokohama city have been instructed by the Yokohama City Medical Control Council to record a 12-lead ECG in an ambulance for hospital selection (triage) if ACS is suspected. Currently, paramedics read ECGs and communicate the findings to a physician at the destination hospital, or transmit it by e-mail.
Prehospital diagnosis and triage using the prehospital 12-lead ECG, and centralization of advanced emergency medical care for cardiovascular disease are required as the future system. Recently, important results were reported from the K-ACTIVE registry, a multi-institute registry of AMI in Kanagawa Prefecture.21 A total of 5,648 individuals, who developed AMI between 2015 and 2019, were included. Of them, 2,035 STEMI patients were analyzed, excluding non-ST-elevation MI, walk-in patients, transportation from other hospitals, out-of-hospital cardiopulmonary arrest, and patients with in-hospital MI. If a prehospital 12-lead ECG was performed and the first contact was a cardiologist at the time of hospital arrival, the in-hospital mortality rate was about one-third even after multivariate adjustment. In addition, when a prehospital ECG was performed and the first contact was with a cardiologist, the door-to-device time was significantly shorter. Patients admitted to high-volume centers were more frequently contacted first by a cardiologist than patients at other centers.
The functional prognosis of cardiovascular disease can be improved by early diagnosis and appropriate treatment by specialists without delay. With an aging population, the number of patients with cardiovascular diseases will increase, and the working age population will continue to decrease. It is also necessary to improve the working environment for physicians to correspond with the legislated reforms of physicians’ workload. In order to effectively improve both the use of medical resources and the prognosis of patients, cardiovascular emergency medical care must be centralized and prioritized. For this change, prehospital triage utilizing the prehospital 12-lead ECG will become more important in Japan.
The authors declare that there are no conflicts of interest. K.K. and M.K. are members of the Editorial Team of Circulation Journal.
None.
