Mean Platelet Volume and Cardiac Surgery-Associated Atrial Fibrillation.

Postoperative atrial fibrillation (AF) is the most common complication after cardiac surgery. Although reported incidences vary widely, postoperative AF occurs in as many as 30% to 50% of patients.1Mathew JP Fontes ML Tudor IC et al.A multicenter risk index for atrial fibrillation after cardiac surgery..JAMA. 2004; 291: 1720-1729Crossref PubMed Scopus (910) Google Scholar Mean platelet volume (MPV)—a marker of platelet activation and peri-surgical inflammation— recently was reported to be associated with postoperative AF in a small-scale study involving patients undergoing isolated coronary artery bypass grafting surgery.2Erdem K Ayhan S Ozturk S et al.Usefulness of the mean platelet volume for predicting new onset atrial fibrillation after isolated coronary artery bypass grafting.Platelets. 2014; 25: 23-26Crossref PubMed Scopus (23) Google Scholar Higher MPV values reflect increased platelet activity, a key inflammatory response that has been associated with numerous adverse outcomes in critical illness settings, as well as after cardiac surgery.3Crowther MA Cook DJ Meade MO et al.Thrombocytopenia in medical-surgical critically ill patients: Prevalence, incidence, and risk factors.J Crit Care. 2005; 20: 348-353Crossref PubMed Scopus (159) Google Scholar,4Kertai MD Zhou S Karhausen JA et al.Platelet counts, acute kidney injury, and mortality after coronary artery bypass grafting surgery.Anesthesiology. 2016; 124: 339-352Crossref PubMed Scopus (67) Google Scholar Extensive cross-talk between activated platelets and other cell types has been described in the early phase of the inflammatory response reaction.5Stokes KY Granger DN Platelets: A critical link between inflammation and microvascular dysfunction.J Physiol. 2012; 590: 1023-1034Crossref PubMed Scopus (148) Google Scholar Of note, we recently demonstrated an independent association between the magnitude of postoperative MPV changes and the development of postoperative acute kidney injury and its severity.6Ramakrishnan A Zheng C Fontes ML et al.Mean platelet volume and cardiac-surgery associated acute kidney injury: A retrospective study [e-pub ahead of print].Can J Anaesth. 2020; https://doi.org/10.1007/s12630-020-01811-4Crossref Scopus (3) Google Scholar We tested our primary hypothesis that postoperative changes in MPV after cardiac surgery are associated independently with postoperative AF. We conducted a single-center, retrospective observational study at a tertiary academic center on 4,071 patients older than 18 years who underwent cardiac surgery between December 12, 2011, and June 5, 2018. A standard set of perioperative data were abstracted and collected from the institutional Society of Thoracic Surgeons Adult Cardiac Surgery Database, the Perioperative Data Warehouse (developed and maintained by the institutional Department of Anesthesiology and Perioperative Informatics Research Division), and the patients’ electronic medical records. Demographics, clinical characteristics, preoperative and postoperative medication use, cardiopulmonary bypass duration, intraoperative and postoperative blood product administration, platelet counts, and MPV were considered risk factors for postoperative AF. Platelet counts and MPV were measured by the institutional clinical pathology laboratory preoperatively and for the first 10 days postoperatively or until discharge, whichever came first. The baseline MPV values were defined as the value available closest to the date of surgery. The average postoperative MPV values were mean values of the daily measurements before the occurrence of postoperative AF within 10 days after surgery for patients with postoperative AF, or mean values of the daily measurements during the first two days (ie, the median follow-up time or time to postoperative AF) for patients without AF. Subsequently, changes in postoperative MPV values were calculated as the difference between baseline values and average postoperative values. New-onset postoperative AF was determined based on documentation of postoperative electrocardiogram or rhythm strip or at least two of the following forms of documentation in the electronic health records of the patients: progress notes, nursing notes, discharge summary, or change in medication. A logistic regression model was used to determine associations among changes in postoperative MPV, changes in postoperative platelet counts, and postoperative AF as a binary variable after adjusting for the prespecified clinical risk factors. The median (25th-75th) postoperative MPV change was 0.23 fL (0.04-0.40) for patients with postoperative AF and 0.20 fL (0.07-0.37) for patients without postoperative AF (p = 0.032), and the median platelets count change was –69 × 109/L (–108 to –39) for patients with postoperative AF, and –66 × 109/L (–102 to –35) for patients without postoperative AF (p = 0.044). Demographic, clinical, and perioperative characteristics of the patients with postoperative AF and without postoperative AF are presented in Table 1.Table 1Demographic and Clinical Characteristics of the Study Population, n = 4071PredictorsPatients Without Atrial Fibrillation (n = 2703)Patients With Atrial Fibrillation (n = 1368)p ValueDemographicsAge62 (54-70)68 (61-75)<0.001*Data analyzed with Wilcoxon rank sum test.Sex0.21*Data analyzed with Wilcoxon rank sum test. Female780 (29)369 (27) Male1923 (71)999 (73)Race0.024†Data analyzed with Pearson test with p < 0.05 as significant. White2323 (91)1208 (93) African American196 (8)69 (5) Other38 (1)18 (1)Body mass index, kg/m229.1 (25.4-33.6)29.2 (25.4-33.6)0.83*Data analyzed with Wilcoxon rank sum test.Medical historyChronic lung disease564 (21)337 (25)0.006†Data analyzed with Pearson test with p < 0.05 as significant.Hypertension2086 (77)1096 (80)0.032†Data analyzed with Pearson test with p < 0.05 as significant.Prior heart failure386 (14)202 (15)0.68†Data analyzed with Pearson test with p < 0.05 as significant.Peripheral vascular disease260 (10)152 (11)0.13†Data analyzed with Pearson test with p < 0.05 as significant.Diabetes mellitus1188 (44)586 (43)0.50†Data analyzed with Pearson test with p < 0.05 as significant.Obstructive sleep apnea333 (12)203 (15)0.023†Data analyzed with Pearson test with p < 0.05 as significant.Cardiovascular disease448 (17)261 (19)0.048†Data analyzed with Pearson test with p < 0.05 as significant.Smoker<0.001†Data analyzed with Pearson test with p < 0.05 as significant. Never1582 (59)889 (65) Former395 (15)238 (17) Current725 (27)241 (18)Previous myocardial infarction1053 (39)504 (37)0.20†Data analyzed with Pearson test with p < 0.05 as significant.Preoperative medication Acetylsalicylic acid2001 (74)993 (73)0.32†Data analyzed with Pearson test with p < 0.05 as significant. Adenosine diphosphate inhibitors, 5 d before surgery675 (25)334 (24)0.70†Data analyzed with Pearson test with p < 0.05 as significant. Amiodarone87 (6)48 (7)0.61†Data analyzed with Pearson test with p < 0.05 as significant. Angiotensin-converting enzyme inhibitors1127 (42)559 (41)0.64†Data analyzed with Pearson test with p < 0.05 as significant. Anticoagulants929 (34)435 (32)0.10†Data analyzed with Pearson test with p < 0.05 as significant. Antiplatelets, 5 d before surgery69 (3)28 (2)0.29†Data analyzed with Pearson test with p < 0.05 as significant. Beta-blockers1964 (73)997 (73)0.87†Data analyzed with Pearson test with p < 0.05 as significant. Coumadin10 (0)5 (0)0.12†Data analyzed with Pearson test with p < 0.05 as significant. Glycoprotein IIb/IIIa inhibitor12 (0)0 (0)0.72†Data analyzed with Pearson test with p < 0.05 as significant. Lipid lowering medications1817 (67)901 (66)0.40†Data analyzed with Pearson test with p < 0.05 as significant.Intraoperative characteristics and medicationsTiming of surgery0.39†Data analyzed with Pearson test with p < 0.05 as significant. Elective1624 (60)841 (61) Emergent1079 (40)527 (39)Type of surgery<0.001†Data analyzed with Pearson test with p < 0.05 as significant. Isolated CABG1832 (68)785 (57) Valve only497 (18)315 (23) CABG and valve194 (7)159 (12) Other180 (7)109 (8)Operative approach0.09†Data analyzed with Pearson test with p < 0.05 as significant. Full conventional sternotomy2461 (91)1224 (90) Other235 (9)141 (10)Duration of cardiopulmonary bypass total, min59 (0-107)84 (0-132)<0.001*Data analyzed with Wilcoxon rank sum test.Cross-clamp duration, min73 (54-98)82(61-110)<0.001*Data analyzed with Wilcoxon rank sum test.Intra-aortic balloon pump use137 (5)74 (5)0.64†Data analyzed with Pearson test with p < 0.05 as significant.Epsilon aminocaproic acid use1371 (51)788 (58)<0.001†Data analyzed with Pearson test with p < 0.05 as significant.Tranexamic acid use17 (1)18 (1)0.025†Data analyzed with Pearson test with p < 0.05 as significant.Intraoperative blood product administration964 (36)616 (45)<0.001†Data analyzed with Pearson test with p < 0.05 as significant.Preoperative hemodynamic and laboratory tests Preoperative ejection fraction, %55 (47-60)55 (47-60)0.68*Data analyzed with Wilcoxon rank sum test. Mean platelet volume, fL10.30 (9.75-10.90)10.27 (9.75-10.90)0.56*Data analyzed with Wilcoxon rank sum test. Platelet count, 109/L220 (178-266)212 (176-254)0.008*Data analyzed with Wilcoxon rank sum test. Creatinine, mg/dL1.00 (0.84-1.24)1.07 (0.89-1.33)<0.001*Data analyzed with Wilcoxon rank sum test.Postoperative laboratory tests Average mean platelet volume, fL10.51 (9.97-11.10)10.56 (10.02-11.12)0.44*Data analyzed with Wilcoxon rank sum test. Average mean platelet volume change0.20 (0.07-0.37)0.23 (0.04-0.40)0.032*Data analyzed with Wilcoxon rank sum test. Average platelet count, 109/L149 (115-184)138 (105-174)<0.001*Data analyzed with Wilcoxon rank sum test. Average platelet count change–66 (–102 to –35)–69 (–108 to –39)0.044*Data analyzed with Wilcoxon rank sum test.Postoperative blood products administration535 (20)355 (26)<0.001†Data analyzed with Pearson test with p < 0.05 as significant.NOTE. All data are represented either as median (25th-75th) or number (%).Abbreviations: CABG, coronary artery bypass graft. Data analyzed with Wilcoxon rank sum test.† Data analyzed with Pearson test with p < 0.05 as significant. Open table in a new tab NOTE. All data are represented either as median (25th-75th) or number (%). Abbreviations: CABG, coronary artery bypass graft. The incidence of postoperative AF was 33.6% (n = 1368). The multivariate analysis showed that there was no significant association between MPV and postoperative AF (Fig 1). In the multivariate analysis, older age, male sex, higher body mass index, obstructive sleep apnea, and longer cardiopulmonary bypass duration were associated with elevated odds for postoperative AF. In a separate sensitivity analysis when we adjusted for postoperative blood product administration, the association among preoperative (baseline) average MPV and platelet counts, postoperative changes in MPV and platelet counts, and postoperative AF remained unchanged (Fig 2). Thus, this study of cardiac surgery patients at high risk for postoperative AF found no evidence that a postoperative increase in MPV was associated with a higher risk for postoperative AF.Fig 2The estimated odds ratio of having postoperative atrial fibrillation adjusted clinical risk factors and postoperative blood product administration. The diamond shape and the horizontal segment represent the odds ratio and 95% CI, respectively. All effects were estimated from the multivariate logistic model.View Large Image Figure ViewerDownload Hi-res image Download (PPT) None.