This study revealed that TAVI was strongly associated with a DPC, the nadir platelet count was reached on approximately postoperative day 3, and a large DPC was associated with BEV use and low BMI. Our findings regarding the nadir platelet count agree with previous reports that the nadir platelet count is reached on day 2–3 and begins to recover on day 5 [4, 6–9].
It remains unclear whether post-TAVI thrombocytopenia differs according to the use of BEVs or SEVs [13]. Three studies and a sub-group analysis from a recent systematic review revealed that BEVs were associated with a higher risk of post-TAVI thrombocytopenia [7, 8, 11, 13]. Our study also revealed similar results, although the underlying mechanisms remain unclear. The TAVI procedure may be associated with mechanical platelet destruction, increased coagulation, and inflammation-related platelet consumption [13], while other reports have suggested that thrombocytopenia is associated with BEV use because of endothelial damage and shear stress factors [7, 20–23]. Thus, it is possible that differences in prosthesis design and/or implantation technique generate variable degrees of endothelial damage and shear stress, which might underly the relationship between BEV use and thrombocytopenia [8, 21]. For example, BEV use might generate greater shear stress because of the balloon that is used during deployment. Hernandez-Enriquez et al. evaluated patients who received SEVs or BEVs and reported that the average DPC was 32.5 ± 13.9% [8], which is noticeably lower than the average DPC in our study (51 ± 13%). We suspect this difference is related to the greater proportion of BEV use in our study (84% vs. 57% of cases) [8]. Furthermore, Jilaihawi et al. [6] evaluated thrombocytopenia after only BEV implantation and reported that the average DPC was 61 ± 15%, which agrees with our result.
Use of contrast agents may also influence the DPC [5, 10], which may be related to the agent’s chemical properties, immune-allergic reactions, or genetic predisposition [7, 8, 10, 23]. For example, Mitrosz et al. reported that the DPC after TAVI using a BEV (Edwards Sapien XT) was associated with the contrast agent volume [5]. However, we did not observe any significant inter-group differences in the contrast agent volume, although we used smaller amounts (86.7 ± 26.0 mL) than those used by Mitrosz et al. (229.0 ± 74.3 mL) [5]. Our ability to use less contrast agent is likely related to the use of the transoesophageal echocardiography to confirm appropriate valve positioning.
A large DPC was associated with low BMI, which is also associated with mortality and thrombocytopenia risk after other high-risk percutaneous cardiac procedures [25, 26]. Moreover, patients with low BMI have increased risks of thrombocytopenia and acute myocardial infarction-related mortality, regardless of revascularisation status [26, 27]. Four reports have evaluated whether post-TAVI thrombocytopenia was associated with BMI [7, 8, 15, 16], although only Flaherty et al. reported a significant association [15]. Therefore, the relationship between post-TAVI thrombocytopenia and low BMI remains controversial, as previous reports have mainly evaluated European and American patients, who tend to have higher BMI than Japanese patients [7, 8, 15, 16]. For example, the mean BMI in our study (22 kg/m2) was lower than the mean BMI in the aforementioned studies: 28.7 ± 4.7 kg/m2 [7], 26.0 ± 5.2 kg/m2 [8], 29 kg/m2 [15], and 26.9 kg/m2 [16]. To the best of our knowledge, this is the first report to examine whether low BMI was associated with post-TAVI DPC among Japanese patients, who are more likely to have lower BMI and may be more prone to developing more severe thrombocytopenia. The relationship between thrombocytopenia and low BMI remains unclear, although large amounts of fluids are infused during the perioperative period in TAVI patients, and patients with a low BMI may be more susceptible to haemodilution, leading to a large DPC. Furthermore, we did not detect any instances of infection, sepsis, or disseminated intravascular coagulation leading to thrombocytopenia. Moreover, the mean intraoperative blood loss was 84.6 ± 115 mL, which suggests that thrombocytopenia was not likely related to platelet loss.
In conclusion, the present study revealed that low BMI and BEV use were associated with a larger DPC after TAVI in Japanese patients with severe aortic valve stenosis. Platelet count monitoring count after TAVI, especially when using BEV devices, is essential for Japanese patients, who are more likely to have a lower BMI.