We aimed to describe the logistics of a prehospital triage system for patients with acute chest pain in the region of Amsterdam, The Netherlands. Ambulance electrocardiograms (ECGs) were evaluated immediately in 1 of the percutaneous coronary intervention (PCI)-capable centers. Patients accepted for primary PCI (PPCI) were directly transferred to the catheterization laboratory. Two thousand three hundred fifty ECGs of 2,192 patients were transmitted to the region’s intervention centers. Median duration of chest complaints before ambulance dispatch was 67 minutes; ambulance crews recorded the first ECG within 7 minutes after arrival. Actual transmission of the ECG took an additional (median) 10 minutes. Seven hundred eleven patients (32.4%) were transported to the catheter laboratory and were treated with PPCI. Time between first prehospital ECG and start of PPCI procedure was 66 minutes. The PPCI procedure started 36 minutes after ambulance arrival at the hospital. In conclusion, the results of this study compare favorably to other reported performances of prehospital triage systems of PPCI for ST-segment elevated myocardial infarction and demonstrate that the European Society of Cardiology and American Heart Association guidelines for treatment of patients with ST-segment elevated myocardial infarction can be met.
Several reports have described region-specific solutions for the development of care systems for patients with ST-segment elevated myocardial infarction (STEMI). Systems may differ based on local organization of ambulance care, number of hospitals, travel distances, and size of the area to be serviced. In the Amsterdam region, which has 3 percutaneous coronary intervention (PCI) centers and 7 non-PCI centers, prehospital triage was effectively organized in collaboration with the ambulance services. Direct transportation of patients with STEMI to the catheter laboratory of a PCI center was expected to shorten the time between first medical contact and primary PCI (PPCI). As a consequence, this may lead to short intervals between “first medical contact” and time of reperfusion, resulting in a better clinical outcome. In 2003, cardiologists of all 10 hospitals in the region of Amsterdam decided to develop a prehospital triage system for patients with chest pain in close collaboration with regional ambulance services. After several months of preparation, protocol development, and training of ambulance staff, the system was implemented in February 2004. The present report describes the logistics of this prehospital triage system for patients with chest pain and suspicion of acute MI.
Methods
The Amsterdam region consists of an area with 1.3 million inhabitants with 3 (high-volume) PCI-capable hospitals and 7 noninterventional hospitals. Catchment areas for the 10 hospitals are generally defined by postal codes. Each of the 7 noninterventional hospitals is affiliated with 1 PCI-capable center for (preferential) referral for elective and primary PCI. Each PCI-capable center provides services 24 hours/day, 7 days/week for primary PCI to their own and to their affiliated catchment area. The total volume of PPCI among the 3 PCI centers, including patients from outside the Amsterdam region, consists of approximately 1,500 to 2,000 procedures annually.
The Amsterdam region has 2 ambulance services operating with a total of 68 ambulances. Each ambulance is staffed by 1 paramedic (specialized nurse) and an ambulance driver and is equipped with uniform defibrillators, capable of acquiring and transmitting 12-lead electrocardiograms (ECGs). Ambulances are dispatched by a central dispatch center. When ambulance personnel has the suspicion of an acute MI in a patient with chest pain at rest within the previous 12 hours, a 12-lead ECG is recorded and transmitted to the PCI-capable center that services that particular area. The ECG is first reviewed by a (dedicated) cardiac care unit nurse and/or cardiology resident and supervisor. If the ECG is considered unequivocally not diagnostic of acute MI, the ambulance is instructed to transfer the patient to a local hospital. Otherwise, when an infarction is suspected, the ECG is submitted to the interventional cardiologist on call. The interventional cardiologist takes the decision to accept the patient for primary PCI or not, if necessary, after having direct telephone contact with ambulance personnel or the general physician. In general, patients are accepted for primary PCI if the ECG shows ≥0.1-mV ST-segment elevation in 2 contiguous leads but patients with other electrocardiographic abnormalities suggestive of acute myocardial ischemia that may benefit from immediate angiography are accepted at the discretion of the interventional cardiologist on call. Patients accepted for PPCI are directly transferred to the catheterization laboratory of the PCI center, thus bypassing the regional hospital and the emergency department of the PCI center; after a successful PPCI, patients are transferred to a local non-PCI hospital.
This was an observational cohort study of prospectively collected data from 2,129 consecutive patients with chest pain suspicious of MI in which the prehospital ECG was transmitted to 1 of the 3 PCI-capable centers from February 1, 2004 to February 1, 2006.
Paper copies of ECGs and the recording and arrival time at the PCI-capable center were retrieved from medical archives of the 3 centers. Ambulance dispatch time, arrival, and departure time at a patient’s site and arrival time at the PCI-capable center were retrieved from records of the ambulance dispatch center. For patients who underwent PPCI, time of onset of symptoms and time of start of PCI procedure were retrieved from the patient’s medical records at the intervention center.
We calculated the duration of the following intervals: from onset of symptoms to first ECG, from ambulance dispatch to ambulance arrival at a patient’s site, from ambulance arrival to recording of the first ECG, from recording of the first ECG to transmission of the ECG, from ambulance arrival at the patient site to departure for the PCI-capable center, and from departure from a patient’s site to arrival at the intervention center. For patients who underwent PPCI, we calculated the following intervals: from ambulance arrival at the PCI-capable center to puncture of the femoral or radial artery, from first ECG to puncture, from arrival at the hospital to arterial puncture, and from arrival at the hospital to first balloon inflation (door-to-balloon time). Although the latter interval is considered a reference in many studies, patient characteristics (i.e., emergency stabilization measures) might bias its dimensions instead of describing the logistics of the triage system; we therefore focused on the former intervals as performance measurements in this study.
Intervals are expressed as cumulative frequencies or medians. To describe differences in intervals between groups of patients, we constructed Kaplan-Meier curves; differences in events over time were compared with log-rank test.
Results
During the 2-year inclusion period, 2,350 ECGs were transmitted from ambulances in the Amsterdam region. The transmissions concerned 2,192 patients; 159 ECGs (6.8%) were transmitted to >1 intervention center. The region dimensions in area, population, and ambulance cover and baseline patient data are presented in Table 1 .
| Region | |
| Total surface (square miles) | 391 |
| Total population | 1,374,727 |
| Women | 698,555 (50.8%) |
| Ambulances (total) | 68 |
| Dispatches/year | 100,800 |
| All patients (n = 2,129) | |
| Women | 662 (30.2%) |
| Age (years) | 62.7 (15.1%) |
| Age >75 years | 530 (24.2%) |
| Duration of chest pain at first electrocardiogram | 67 (38–131) |
| Patients with primary percutaneous coronary intervention (n = 711) | |
| Women | 177 (24.9%) |
| Age (years) | 62.7 (13.1%) |
| Age >75 years | 143 (20.1%) |
| Duration of chest pain at first electrocardiogram | 63 (38–112) |
Table 2 lists median durations between various time points from the prehospital phase to time of coronary intervention for all patients and those treated with PPCI. The median interval between the first prehospital ECG and start of the PPCI procedure was 66 minutes. Start of the revascularization procedure occurred 36 minutes (median) after ambulance arrival in the hospital. This interval includes offloading the patient from the ambulance, transport from the ambulance garage to the catheter laboratory, delays (if any) while awaiting the intervention team to arrive outside office hours, and workup for the procedure itself. Of the total population, 1,345 patients (61.3%) did not require PPCI and were medically stabilized. Seven hundred eleven patients (32.4%) were treated with PPCI directly after arrival at the hospital. Thirty-nine patients (1.8%) underwent emergency angiography directly after arrival but were not treated by PPCI for various reasons; 77 patients (3.5%) underwent PCI in a semiurgent setting within the first day of admittance. Of 20 patients (0.09%) the final treatment procedure in the hospital could not be determined.
| Interval | Patients | Median | Interquartile Range |
|---|---|---|---|
| All patients | |||
| Dispatch to arrival ambulance | 2,127 | 8 | 6–10 |
| Arrival ambulance to first electrocardiogram | 2,127 | 7 | 3–10 |
| First electrocardiogram to transmission electrocardiogram | 2,192 | 10 | 7–14 |
| Patients treated with primary percutaneous coronary intervention | |||
| Dispatch ambulance to first electrocardiogram | 708 | 14 | 10–18 |
| First electrocardiogram to transmission | 711 | 10 | 7–14 |
| First electrocardiogram to start transport | 707 | 18 | 13–23 |
| First electrocardiogram to hospital arrival | 707 | 30 | 24–36 |
| First electrocardiogram to arterial access | 579 | 66 | 55–80 |
| First electrocardiogram to balloon | 221 | 82 | 70–98 |
| Hospital arrival to arterial access | 575 | 36 | 24–50 |
| Hospital arrival to balloon | 219 | 52 | 38–68 |
| Ambulance arrival to balloon | 219 | 90 | 76–105 |
| Patients with known time of symptom onset | |||
| Symptom onset to arterial access | 442 | 134 | 105–190 |
| Symptom onset to balloon (ischemic time) | 216 | 150 | 115–219 |
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