Flow cytometry for comprehensive assessment of platelet functional activity in response to ADP stimulation.

OBJECTIVES: Flow cytometry with adenosine diphosphate (ADP) allows to characterize molecular changes of platelet function caused by this physiologically important activation, but the methodology has not been thoroughly investigated, standardized and characterized yet. We analyzed the influence of several major variables and chose optimal conditions for platelet function assessment. METHODS: For activation, 2.5 µM CaCl2 , 5 µM ADP and antibodies were added to diluted blood and incubated for 15 min. We analyzed kinetics of antibody binding and effects of their addition sequence, agonist concentration, blood dilution, exogenous calcium addition and platelet fixation. RESULTS: We tested our protocol on 11 healthy children, 22 healthy adult volunteers, 9 patients after a month on dual antiplatelet therapy after percutaneous coronary intervention (PCI), 7 adult patients and 14 children with immune thrombocytopenia (ITP). We found that our protocol is highly sensitive to ADP stimulation with low percentage of aggregates formation. The assay is also sensitive to platelet function inhibition in post-PCI patients. Finally, platelet preactivation with ITP plasma was stronger and caused increase in activation response to ADP stimulation compared to preactivation with low dose of ADP. CONCLUSIONS: Our assay is sensitive to antiplatelet therapy and platelet preactivation in ITP patients under physiological conditions with minimal percentage of aggregates formation.

International Prospective Registry of Acute Coronary Syndromes in Patients With COVID-19.

BACKGROUND: Published data suggest worse outcomes in acute coronary syndrome (ACS) patients and concurrent coronavirus disease 2019 (COVID-19) infection. Mechanisms remain unclear. OBJECTIVES: The purpose of this study was to report the demographics, angiographic findings, and in-hospital outcomes of COVID-19 ACS patients and compare these with pre-COVID-19 cohorts. METHODS: From March 1, 2020 to July 31, 2020, data from 55 international centers were entered into a prospective, COVID-ACS Registry. Patients were COVID-19 positive (or had a high index of clinical suspicion) and underwent invasive coronary angiography for suspected ACS. Outcomes were in-hospital major cardiovascular events (all-cause mortality, re-myocardial infarction, heart failure, stroke, unplanned revascularization, or stent thrombosis). Results were compared with national pre-COVID-19 databases (MINAP [Myocardial Ischaemia National Audit Project] 2019 and BCIS [British Cardiovascular Intervention Society] 2018 to 2019). RESULTS: In 144 ST-segment elevation myocardial infarction (STEMI) and 121 non-ST-segment elevation acute coronary syndrome (NSTE-ACS) patients, symptom-to-admission times were significantly prolonged (COVID-STEMI vs. BCIS: median 339.0 min vs. 173.0 min; p < 0.001; COVID NSTE-ACS vs. MINAP: 417.0 min vs. 295.0 min; p = 0.012). Mortality in COVID-ACS patients was significantly higher than BCIS/MINAP control subjects in both subgroups (COVID-STEMI: 22.9% vs. 5.7%; p < 0.001; COVID NSTE-ACS: 6.6% vs. 1.2%; p < 0.001), which remained following multivariate propensity analysis adjusting for comorbidities (STEMI subgroup odds ratio: 3.33 [95% confidence interval: 2.04 to 5.42]). Cardiogenic shock occurred in 20.1% of COVID-STEMI patients versus 8.7% of BCIS patients (p < 0.001). CONCLUSIONS: In this multicenter international registry, COVID-19-positive ACS patients presented later and had increased in-hospital mortality compared with a pre-COVID-19 ACS population. Excessive rates of and mortality from cardiogenic shock were major contributors to the worse outcomes in COVID-19 positive STEMI patients.

Discordance between the Clinical Presentation and Morphology of Myocardial Infarction in a Patient with Acute Post-Hemorrhagic Anemia.

While atherosclerotic plaque disruption remains the hallmark of type 1 myocardial infarction (T1MI), multiple other mechanisms provoking myocardial supply/demand mismatch (eg, anemia and tachyarrhythmias) are recognized as the potential causes of type 2 myocardial infarction (T2MI). In clinical practice, angiography is underutilized in patients with MI that have typical T2MI triggers, although the presence of these triggers and various forms of atherosclerotic coronary artery disease is not mutually exclusive. We describe a 70-year-old man that developed MI during hospitalization for gastrointestinal bleeding. He was treated conservatively without angiography due to posthemorrhagic anemia, which is a recognized T2MI trigger, and subsequently developed refractory cardiogenic shock. Autopsy revealed atherothrombosis, which is characteristic of T1MI.