Advanced Flow Cytometry Using the SYTO-13 Dye for the Assessment of Platelet Reactivity and Maturity in Whole Blood.

Newly produced immature platelets are larger, contain higher amounts of residual RNA, and are more reactive than mature platelets. Flow cytometry using the SYTO-13 dye is a method for the subdivision of immature platelets from mature platelets based on the labelling of intracellular platelet RNA, enabling the simultaneous investigation of the reactivity of each platelet population. This method provides detailed information on several aspects of platelet physiology using a combination of platelet surface markers and agonists. Currently, no standardized protocol exists across laboratories. Here, we describe a flow cytometry protocol in detail to investigate platelet reactivity and its relation to platelet maturity. We analyzed 20 healthy individuals with the protocol and compared the platelet subpopulation with the highest SYTO-13 labelling (in the first quintile, "SYTO-high") corresponding to the most immature platelets (highest RNA content) with the platelet subpopulation with the lowest SYTO-13 labelling (in the fifth quintile, "SYTO-low") corresponding to the mature platelets with the lowest RNA content. SYTO-high platelets had overall significantly increased platelet reactivity compared with that of SYTO-low platelets. The presented method may be a valuable research tool for the analysis of platelet reactivity and its relation to platelet maturity.

Flow Cytometric Assessment of Changes in Platelet Reactivity after Acute Coronary Syndrome: A Systematic Review.

Increased platelet activity is an important predictor for recurrent cardiovascular events in patients with acute coronary syndromes (ACS). Flow cytometry is an advanced method for evaluation of platelet activity. We aimed to summarize the current literature on dynamic changes in platelet activity analyzed by flow cytometry in patients with ACS. Employing the guidelines of Preferred Report Items for Systematic Reviews and Meta-Analyses (PRISMA), we searched PubMed and Embase on October 26, 2021, and identified studies measuring platelet activity with flow cytometry in ACS patients in the acute phase (baseline) and at follow-up in a more stable phase. In the 12 included studies, fibrinogen receptor, α-granule secretion, platelet reactivity index, monocyte-platelet aggregates, neutrophil-platelet aggregates, and reticulated platelets were measured. The fibrinogen receptor and α-granule secretion were either unchanged or lower during follow-up measurements than in the acute phase. Platelet reactivity index showed inconsistent results. Values of monocyte-platelet aggregates and neutrophil-platelet aggregates were lower at follow-up than at baseline (p-values <0.05). Reticulated platelets were either unchanged (p-value >0.64) or lower at 1 to 2 months follow-up (p-value 0.04), and also lower at 5 months to 1-year follow-up (p-value >0.005) compared with baseline. Overall, flow cytometric analyses of platelet function in ACS patients showed that platelet activity was lower at follow-up than at baseline. However, in some patients, platelet activity remained unchanged from baseline to follow-up, possibly indicating a sustained high platelet activity that may increase the risk of recurrent cardiovascular events.

Quantitative flow ratio for immediate assessment of nonculprit lesions in patients with ST-segment elevation myocardial infarction-An iSTEMI substudy.

OBJECTIVES: We evaluated the diagnostic performance of quantitative flow ratio (QFR) assessment of nonculprit lesions (NCLs) based on acute setting angiograms obtained in patients with ST-segment elevation myocardial infarction (STEMI) with QFR, fractional flow reserve (FFR), and instantaneous wave-free ratio (iFR) in the staged setting as reference. BACKGROUND: QFR is an angiography-based approach for the functional evaluation of coronary artery lesions. METHODS: This was a post-hoc analysis of the iSTEMI study. NCLs were assessed with iFR in the acute setting and with iFR and FFR at staged (median 13 days) follow-up. Acute and staged QFR values were computed in a core laboratory based on the coronary angiography recordings. Diagnostic cut-off values were ≤0.80 for QFR and FFR, and ≤0.89 for iFR. RESULTS: Staged iFR and FFR data were available for 146 NCLs in 112 patients in the iSTEMI study. Among these, QFR analysis was feasible in 103 (71%) lesions assessed in the acute setting with a mean QFR value of 0.82 (IQR: 0.73-0.91). Staged QFR, FFR, and iFR were 0.80 (IQR: 0.70-0.90), 0.81 (IQR: 0.71-0.88), and 0.91 (IQR: 0.87-0.96), respectively. Classification agreement of acute and staged QFR was 93% (95%Cl: 87-99). The classification agreement of acute QFR was 84% (95%CI: 76-90) using staged FFR as reference and 74% (95%CI: 65-83) using staged iFR as reference. CONCLUSIONS: Acute QFR showed a very good diagnostic performance with staged QFR as reference, a good diagnostic performance with staged FFR as reference, and a moderate diagnostic performance with staged iFR as reference.

How to set up an effective national primary angioplasty network: lessons learned from five European countries.

AIMS: Percutaneous coronary interventions (PCI) are used to treat acute and chronic forms of coronary artery disease. While in chronic forms the main goal of PCI is to improve the quality of life, in acute coronary syndromes (ACS) timely PCI is a life-saving procedure - especially in the setting of ST-elevation myocardial infarction (STEMI). The aim of this study was to describe the experience of countries with successful nationwide implementation of PCI in STEMI, and to provide general recommendations for other countries. METHODS AND RESULTS: The European Association of Percutaneous Cardiovascular Interventions (EAPCI) recenty launched the Stent For Life Initiative (SFLI). The initial phase of this pan-European project was focused on the positive experience of five countries to provide the best practice examples. The Netherlands, the Czech Republic, Sweden, Denmark and Austria were visited and the logistics of ACS treatment was studied. Public campaigns improved patient access to acute PCI. Regional networks involving emergency medical services (EMS), non-PCI hospitals and PCI centres are useful in providing access to acute PCI for most patients. Direct transfer from the first medical contact site to the cathlab is essential to minimise the time delays. Cathlab staff work is organised to provide acute PCI services 24 hours a day / seven days a week (24/7). Even in those regions where thrombolysis is still used due to long transfer distances to PCI, patients should still be transferred to a PCI centre (after thrombolysis). The highest risk non-ST elevation acute myocardial infarction patients should undergo emergency coronary angiography within two hours of hospital admission, i.e. similar to STEMI patients. CONCLUSIONS: Three realistic goals for other countries were defined based on these experiences: 1) primary PCI should be used for >70% of all STEMI patients, 2) primary PCI rates should reach >600 per million inhabitants per year and 3) existing PCI centres should treat all their STEMI patients by primary PCI, i.e. should offer a 24/7 service.