• Mau T Nguyen, Celine Gallagher, Bradley M Pitman, Mehrdad Emami, Kadhim Kadhim, Jeroen M Hendriks, Melissa E Middeldorp, Kurt C Roberts-Thomson, Rajiv Mahajan, Dennis H Lau, Prashanthan Sanders, and Christopher X Wong.
• Centre for Heart Rhythm (CHRD), South Australian Health and Medical Research Institute (SAHMRI), University of Adelaide and the Royal Adelaide Hospital, Adelaide, SA, Australia.
• Heart Lung Circ. 2020 Aug 1; 29 (8): 1122-1128.

BackgroundStudies have shown that suboptimal anticoagulation quality, as measured by time in therapeutic range (TTR), affects a significant percentage of patients with atrial fibrillation (AF). However, TTR has not been previously characterised in Indigenous Australians who experience a greater burden of AF and stroke.MethodIndigenous and non-Indigenous Australians with AF on warfarin anticoagulation therapy were identified from a large tertiary referral centre between 1999 and 2012. Time in therapeutic range was calculated as a proportion of daily international normalised ratio (INR) values between 2 and 3 for non-valvular AF and 2.5 to 3.5 for valvular AF. INR values between tests were imputed using the Rosendaal technique. Linear regression models were employed to characterise predictors of TTR.ResultsFive hundred and twelve (512) patients with AF on warfarin were included (88 Indigenous and 424 non-Indigenous). Despite younger age (51±13 vs 71±12 years, p<0.001), Indigenous Australians had greater valvular heart disease, diabetes, and alcohol excess compared to non-Indigenous Australians (p<0.05 for all). Time in therapeutic range was significantly lower in Indigenous compared to non-Indigenous Australians (40±29 vs 50±31%, p=0.006). Univariate predictors of poorer TTR included Indigenous ethnicity, younger age, diuretic use, and comorbidities, such as valvular heart disease, heart failure and chronic obstructive pulmonary disease (p<0.05 for all). Valvular heart disease remained a significant predictor of poorer TTR in multivariate analyses (p=0.004).ConclusionIndigenous Australians experience particularly poor warfarin anticoagulation quality. Our data also suggest that many non-Indigenous Australians spend suboptimal time in therapeutic range. These findings reinforce the importance of monitoring warfarin anticoagulation quality to minimise stroke risk.Copyright © 2019 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ). All rights reserved.

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