Association of the degree of thrombocytopenia with cause of death in patients with atrial fibrillation: the Fushimi AF Registry
Authors: Ishigami K , Ikeda S , Doi K , Hamatani Y , Ide Y , Fujino A , An Y , Ishii M , Iguchi M , Ogawa H , Masunaga N , Wada H , Hasegawa K , Abe M , Akao M 
Published: October 2021

Abstract

Background
Thrombocytopenia is sometimes found in routine blood tests and is associated with an increased risk of mortality in general population. We have previously reported that atrial fibrillation (AF) patients with thrombocytopenia have a higher mortality than those without thrombocytopenia. However, association of the degree of thrombocytopenia with cause of death in AF patients is unknown.

Purpose
We aimed to investigate the association of baseline platelet count with cause of death including cardiac death, intracranial death, malignancy, infection, extracranial bleeding death, renal failure death, respiratory failure death and undetermined death.

Methods
The Fushimi AF Registry was designed to enroll all of the AF patients in Fushimi-ku, Kyoto. Fushimi-ku is densely populated with a total population of 283,000 and is assumed to represent a typical urban community in Japan. We started to enroll patients from March 2011, and follow-up data with baseline platelet counts less than 150,000/μL were available in 853 patients by the end of September 2020. We divided them into 3 groups according to baseline platelet level: Mild thrombocytopenia (100,000–149,999/μL, n=703), Moderate thrombocytopenia (50,000–99,999/μL, n=120), and Severe thrombocytopenia (&lt;50,000/μL, n=30).

Results
In the entire cohort, the mean age was 76 years, 34% were women, the mean body weight and body mass index was 59.3 kg and 22.9 kg/m2, and the median platelet count were 121,000/μL (interquartile range 109,000 to 141,000/μL). Compared to Mild thrombocytopenia, patients with Moderate or Severe thrombocytopenia were more likely to have chronic kidney disease (42.2% vs 54.2% vs 73.3%, p=0.0003), have higher HAS-BLED score (1.90 vs 2.14 vs 2.00, p=0.047) and lower hemoglobin (12.8g/dL vs 11.7g/dL vs 11.2g/dL, p&lt;0.0001) and were less often prescribed anti platelet drugs. Age, sex, body weight, systolic blood pressure, previous stroke, previous major bleeding, hypertension, diabetes mellitus, CHADS2 score and CHA2DS2-VASc score were comparable between three groups. During the median follow-up period, the incidence rate (per 100 person-years) of all-cause death was 6.82 vs 15.27 vs 9.64. (p&lt;0.001) On univariate analysis, the incidence of all-cause death was higher in Moderate group than Mild group. (HR: 2.15; 95% CI 1.61–2.87, p&lt;0.0001), but there was no significant difference between Mild and Severe groups. (HR: 1.44; 95% CI 0.78–2.64, p=0.243). The incidence of cardiac death was comparable between three groups. (Mild vs Moderate: HR 0.65; 95% CI 0.15–2.75, p=0.56, Mild vs Severe: HR 1.11; 95% CI 0.15–8.23, p=0.92) Regarding other causes of death such as intracranial bleeding, extracranial bleeding, malignancy, infection, renal failure, respiratory failure and undetermined cause, there was no significant difference.

Conclusion
Mortality was higher according to the degree of thrombocytopenia in AF patients, but the cause of death was not different among three groups.

Funding Acknowledgement
Type of funding sources: None.