1Universitäts-Herzzentrum Freiburg / Bad Krozingen Klinik für Kardiologie und Angiologie Bad Krozingen, Deutschland; 2Inselspital - Universitätsspital Bern Universitätsklinik für Kardiologie Bern, Schweiz; 3Klinikum Würzburg Mitte gGmbH Kardiologie & Internistische Intensivmedizin Würzburg, Deutschland
Background:
Immature platelets (IP) or also called reticulated platelets are newly developed platelets that have just been released from the bone marrow into the bloodstream. They have a larger volume, increased RNA content and are more reactive than normal platelets. Studies have shown that higher levels of IPs are associated with major adverse cardiovascular events in patients with acute myocardial infarction as well as stroke. Additionally, patients with atrial fibrillation (AF) have increased levels of IP in comparison to sinus rhythm (SR). Aim of this analysis is to find out, if increased levels of IP in patients with AF are associated with increased risk of thromboembolic events.
Methods:
PRISCA-AF is a prospective, monocentric study for the evaluation of immature blood cells for clinical risk stratification in patients with AF. The study includes patients who were hospitalized in our heart center because of AF, either because of acute onset or for therapy in know paroxysmal or persistent AF. Therefore, patient could be in AF or SR at time of admission. Blood samples were taken immediately at hospitalization and IPs were measured automatically with a cytometer (Sysmex XN-1000). After 1 year follow up was performed with a written or phone call questionnaire.
Results:
In this study, 1636 patients were included. Follow up was fully completed in 1374 patients (84 %) of which 487 were female (35.4%) and median age was 70 years [61-77 years]. Levels of IP were significant higher (p = 0.011) in patients with AF (9.5 x 10³/µl [6.8-13.3]) than in SR (9.0 x 10³/µl [6.4-12.3]). At the time of study inclusion, 1242 (90.4%) of the patients were on oral anticoagulation, 1338 (97.4%) at the one-year follow-up.
At the time of follow-up 23 thrombembolic events (1.7%) occurred, including 12 (0.9%) strokes. Logistic regression analyses showed no significant association of IP fraction and thrombembolic (p = 0.135; KI 0.972-1.232; OR 1.094) and no associations was seen between the absolute IP number (p = 0.211; KI 0.982-1.085; OR 1.032) with thrombembolic events.
Conclusion:
Our analysis confirms that IP are higher in patients with AF than in SR. But neither higher levels of absolute IP nor the IP fraction are associated with thromboembolic events. Reason could be the very low number of overall thromboembolic events (1.7%) at one year follow-up and the very high rate of oral anticoagulation (97.4%).