Discussion
This study mainly investigated the association between SII level and
adverse outcomes in patients with AF, and tried to evaluate the
prognostic value of SII as a new inflammatory factor in AF. The major
finding was that high SII level was strongly associated with adverse
outcomes and was an independent predictor for death from all causes and
death from cardiovascular diseases in
patients with AF. Our study is the
first study to report the association and prognostic value of SII in
patients with AF. This finding adds to current knowledge regarding the
predictive relationship between SII and adverse outcomes in AF patients.
Previous studies13,14,17,27 have established that
inflammation plays a key role in development and progression of AF.
Inflammatory factors, such as PLR15,
IL-617, IL-1018 and
CRP19, were proven to be risk factors in AF and were
potential predictors of prognosis in patients developed AF. As for SII,
which combined neutrophil, lymphocyte and platelet count, serving as a
detectable biomarker for systemic inflammatory activity and reflecting
the inflammatory state28. Previously, SII emerged as a
reliable and powerful predictor in various malignant diseases, including
hepatocellular carcinoma21, gastric
cancer22 and renal cell cancer29.
Evidence is accumulating that SII level, apart from their well-known
predictive value in cancer, were close related with in-hospital
mortality in infective endocarditis30 and the
incidence of major cardiovascular events in coronary artery
disease23,31,32. Until now, the association between
SII level and AF is still unknown. Therefore, we utilized a novel
predictor, SII, which was demonstrated to be significantly related to
adverse outcomes in AF patients.
SII was measured based on the counts of three types of circulating
immune cells: platelets, lymphocytes, and neutrophils. Our study showed
that AF patients with high SII level had increased risk for mortality.
Neutrophils, which constitute the largest proportion of leukocyte, are
of great importance for initiating and modulating immune
processes33,34. Lymphocytes are also an important
component of white blood cells, mediate adaptive immunity and function
in innate immunity. Both neutrophils and lymphocytes can mediate
adaptive and innate immunity. Platelets could be considered as aspecific
first line inflammatory biomarkers which bind to leukocytes, influencing
the function of inflammatory elements of these
cells35. In several clinical studies, mediators of the
inflammatory response were supported to be associated with remodeling of
AF36,37. Inflammation can initiate AF, which
subsequently generates an inflammatory response that further enhances
atrial electrical and structural remodeling and perpetuates the
arrhythmia.
Our study had several strengths. The sample size was relatively large to
identify the significant association between SII and adverse outcomes in
patients with AF. Moreover, we adjusted the potential confounders which
might influence the prognostic value of SII in patients with AF.
However, some limitations on this study also should be mentioned. First,
because of the retrospective study design, results of our study need to
be verified by multicenter, prospective studies. In addition, we only
collected the baseline data of SII, rather than collecting data at
multiple times.