Background
Mutations in the clonal hematopoiesis of indeterminate potential (CHIP)-driver genes DNMT3A and TET2 have been previously shown to be associated with short-term prognosis in patients undergoing TAVI for degenerative aortic valve stenosis. We aimed to extend these findings on long-term outcome in a large cohort and to gain potential mechanistic insight by determining the site of mutations.

Methods
A total of 453 consecutive patients undergoing TAVI were prospectively followed. Primary endpoint was all-cause mortality. As DNMT3A is related with DNA-methylation, never-smokers were analized separately to exclude interfering effects. Next-generation sequencing was used to identify DNMT3A- and/or TET2-CHIP-driver mutations. Sites of mutation were classified as involving proline-tryptophan-proline-tryptophan (PWWP), zinc-finger (ADD), or methyl-transferase (MTase) domains for DNMT3A; and dioxygenase (DD) or Cys-rich (CD) domains for TET2.

Results
DNMT3A-/TET2-CHIP-driver mutations were present in 32,4% of patients (DNMT3A n=92, TET2 n=71), and were more frequent in women (52.4% vs 38.9%, p = 0.007) and older participants (83.3 vs. 82.2 years, p = 0.011), while clinical characteristics or derived parameters did not differ.

CHIP-driver mutations were associated with a significantly higher mortality up to 2 years after TAVI in both univariate (p = 0.023) and multivariate analyses including sex and age (HR 1.657, 95% IC 1.014-2.706, p = 0.044). The difference was even more pronounced (p = 0.007) in patients who never smoked, a  factor known to interfere with DNA methylation.

Compared to TET2 mutation carriers, patients with DNMT3A mutations had significantly less frequently concomitant coronary and peripheral artery disease. Within the DNMT3A gene, CHIP-driver mutations were most frequently observed in the MTase domain (78%), while mutations in the DD domain were most frequently observed in patients carrying a TET2 mutation (81%).

Conclusion
DNMT3A- and TET2 CHIP-driver mutations are associated with long-term mortality in patients with aortic stenosis even after a successful TAVI. The association is also present in never-smokers, in whom no biasing effect from smoking on DNA methylation is to be expected. Mutations in DNMT3A and TET2 genes mostly affect MTase and DD domains, respectively.