Letter to the Editor Effect of sinus rhythm restoration on platelet function in patients with lone atrial fibrillation Marcin Makowski a, ⁎, Ireneusz Smorąg c , Andrzej Bissinger a , Tomasz Grycewicz a , Konrad Masiarek a , Joanna Makowska b ,Włodzimierz Grabowicz a , Andrzej Lubiński a , Zbigniew Baj c a Department of Interventional Cardiology, Medical University of Lodz, Poland b Department of Immunology, Rheumatology and Allergy, Medical University of Lodz, Poland c Department of Pathophysiology and Immunology, Medical University of Lodz, Poland article info Article history: Received 15 September 2013 Accepted 21 December 2013 Available online 7 January 2014 Keywords: Atrial fibrillation Platelet activation Thrombosis Atrial fibrillation (AF) is associated with increased risk of thrombo- embolic complications. The aim of the study was to assess if arrhythmia, independent of other risk factors leads to increased platelet activation. The study involved 34 (mean age 50 +/- 9.03, range 21–59) male patients with lone persistent atrial fibrillation. The exclusion criteria were: age N 60, coronary artery disease, left ventricular dysfunction (ejection fraction EF b 40%), congenital and acquired heart defects, artificial heart valve, diabetes, thyroid disease, inflammatory diseases, cancer, renal disease, and active smoking. The exclusion criteria precluded more than 95.4% of patients with AF hospitalized in our Department within the last 6 years. The AF patients underwent cardioversion to restore sinus rhythm and remained subsequently under observation for 1 month. Echocardi- ography, ECG and blood collection was performed before cardioversion (T0) and 4 weeks after successful cardioversion (T1). During the study period, patients were contacted and examined weekly along with 24-hour ECG monitoring. In all patients sinus rhythm was maintained at the end of the study period, however in 12 patients recurrence of AF was observed, confirmed by 24-hour ECG monitoring (atrial fibrillation recurrence group — AFR). In 10 patients the episodes of arrhythmia were asymp- tomatic, while only 2 patients complained of arrhythmia symptoms. In 22 patients no recurrence of AF in 24-hour ECG monitoring was observed (sinus rhythm group — SR). Parameters of resting platelets collected from peripheral blood activation was measured using flow cytometry. Platelet activation was assessed by expression of p-selectin (CD62) on platelets (CD61 positive cells). The platelet aggregate number was presented as a percentage of CD61+ blood elements bigger than platelets. The platelet derived microparticles (PDMPs) were assessed based on FSC histogram profile as CD61+ particles smaller than platelets. The leukocyte–platelet aggregates were detected based on coexpression of CD11b and CD62 antigens. Data are shown as mean and standard error of the mean (SEM). Statistical analysis to compare data in the same group was analysed by Willcoxon test, and Mann Whitney was used to compare different groups. Statistical significance was defined as p b 0.05. Also, for primary outcomes, post-hoc power analysis was done. Post-hoc power estima- tion was based on the observed variance and the pre-determined relevant difference (Tables 1 and 2). Four weeks (T1) after successful electrical cardioversion in all patients, sinus rhythm has been maintained. However in 12 patients 24-hour ECG monitoring performed every week during the study period also revealed short (up to 2 min long) episodes of asymptomatic AF recurrence (AFR group). The AF episodes terminated spontaneously without any additional treatment. Twenty two patients were free of arrhythmia and AF was not observed in repeated 24-hour ECG monitor- ing (SR group). In all patients (n = 34) the restoration of left atrium mechanical function was observed. In both the SR and AFR groups, a similar improvement of echocardiographic parameters was observed. Atrial fibrillation is the most common sustained cardiac arrhythmia and usually occurs in patients with concomitant diseases like International Journal of Cardiology 172 (2014) e22–e23 ⁎ Corresponding author at: USK nr 2. im WAM, Poland. E-mail addresses: drmarmak@gmail.com, drmarmak@poczta.onet.pl (M. Makowski). Table 1 The result of flow cytometric assessment of platelets in the whole group of patients with AF (n = 34). T0 T1 P CD62 (MFI) 5.64 +/- 0.17 4.31 +/- 0.26 b0.0001 CD41 (MFI) 343.40 +/- 16.94 322.50 +/- 14.58 0.29 Platelet-leukocyte aggregates (%) 11.85 +/- 0.59 6.09 +/- 0.47 b0.0001 Platelet aggregates (%) 4.89 +/- 0.15 3.39 +/- 0.17 b0.0001 PDMPs (%) 1.58 +/- 0.11 1.15 +/- 0.13 0.002 0167-5273/$ – see front matter © 2014 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijcard.2013.12.093 Contents lists available at ScienceDirect International Journal of Cardiology journal homepage: www.elsevier.com/locate/ijcard