Early risk stratification in suspected Non-ST-elevation Acute Coronary Syndrome

Chest pain suspected for Acute Coronary Syndrome (ACS) is one of the most common reasons for calling Emergency Medical Services (EMS). Within the EMS setting, only an electrocardiogram is made to differentiate between suspected ST-elevation ACS or suspected Non-ST-elevation ACS (NSTE-ACS). If ST-elevation ACS is suspected, patients are immediately transferred to a hospital with percutaneous coronary intervention (PCI) facilities for direct coronary angiography, reducing time to revascularization and hospital discharge. In contrast, for patients suspected of NSTE-ACS, no further prehospital risk stratification is performed. These patients are transferred to the nearest hospital, with or without PCI facilities, for further diagnostic work-up in the emergency department. The majority of these patients do not have life-threatening pathology and can be discharged the same day after an often time consuming diagnostic process. Those ultimately diagnosed with true NSTE-ACS may be admitted to a hospital with or without PCI facilities, depending on proximity. However, patients admitted to a hospital without PCI facilities experience longer delays to revascularization and hospital discharge, undergo more invasive coronary diagnostics, and will have higher healthcare costs. During my doctoral research, we studied the available diagnostic tools in the prehospital setting for further risk stratification in suspected NSTE-ACS, identified those with the best diagnostic performance, and assessed the clinical and logistical impact on patients of implementing such tools. We conducted a systematic review and meta-analysis to catalog and compare all available diagnostic tools within the prehospital setting. Our findings indicate that on-site point-of-care troponin testing and HEART-derived clinical risk scores (such as the preHEART and modified HEART score) provided the best diagnostic performance for risk stratification tools in suspected NSTE-ACS. A retrospective analysis of hospital claim data from 9641 patients assessed differences in outcomes and process parameters for NSTE-ACS patients initially transferred by the EMS to a hospital with PCI facilities versus those transferred to a hospital without PCI facilities. We found that patients initially transferred to a hospital with PCI facilities had a shorter hospital stays, reduced time to revascularization, underwent fewer invasive diagnostics, and had lower healthcare costs. In a retrospective study performed within the emergency department in patients suspected of non-ST-elevation ACS, we compared various clinical risk scores, including high-sensitivity troponin. Our results showed that the preHEART, HEART and T-MACS score had the best diagnostic performance. Between 2021 and 2022, we conducted the TRIAGE-ACS study, a prospective, multicentre, two-cohort study evaluating the impact of prehospital risk stratification in EMS. Using the preHEART score, a clinical risk score including point-of-care troponin, we stratified patients suspected of NSTE-ACS in low- or high risk categories. High risk patients were directly transferred to the emergency department of a hospital with PCI facilities for further diagnostic work-up, while low risk patients were transferred to a hospital without PCI facilities. A total of 1069 patients suspected of NSTE-ACS were included in this study. We concluded that prehospital risk stratification and a direct transfer to a PCI centre, based on the preHEART score, reduces time from first medical contact to final invasive diagnostics and revascularisation, reduces duration of hospital admission and decreases healthcare costs in patients with NSTE-ACS in need for coronary angiography or revascularisation. As a substudy of the TRIAGE-ACS study, we conducted a comparative analysis within the EMS setting to evaluate the diagnostic performance of the three most studied clinical risk scores, including a point-of-care troponin, We found that the preHEART and HEART scores outperformed the T-MACS and point-of-care troponin alone in overall diagnostic accuracy. To enhance prehospital risk stratification, we developed an artificial intelligence model to diagnose NSTE-ACS within the prehospital ECG and implemented this model into a clinical risk score. Our results demonstrated that artificial intelligence improved the diagnostic performance of both ECG interpretation and clinical risk scores. To determine whether low risk patients identified by use of a clinical risk score in the EMS setting could be safely managed at home or referred to a general practitioner, we conducted a global individual patient data meta-analysis. This analysis included 6 studies and individual data from 5239 patients. We found that, prehospital risk stratification in patients suspected of NSTE-ACS, based on HEART-derived clinical risk scores, demonstrated high negative predictive value and sensitivity for identifying low-risk patients and is unaffected by the time interval between symptom onset and risk stratification. Consequently, HEART-derived clinical risk scores are both safe and effective tools for optimizing prehospital diagnostic pathways in patients with suspected NSTE-ACS. Finally, we conducted a prospective, observational pilot study to assess coronary physiology in patients diagnosed with myocardial infarction with non-obstructive coronary arteries (MINOCA). We found, that in MINOCA patients undergoing immediate coronary angiography, continuous thermodilution assessment and microvascular resistance reserve (MRR) measurements were feasible and safe in the acute setting. Notably, evidence of functional CMD could be observed in one-third of the MINOCA patients.