Original Research: Cardiovascular Disease |

Factors Affecting Quality of Anticoagulation Control Among Patients With Atrial Fibrillation on WarfarinAnticoagulation Control in Atrial Fibrillation: The SAMe-TT2R2 Score

Stavros Apostolakis, MD, PhD; Renee M. Sullivan, MD; Brian Olshansky, MD; Gregory Y. H. Lip, MD
Author and Funding Information

From the University of Birmingham Centre for Cardiovascular Sciences (Drs Apostolakis and Lip), City Hospital, Birmingham, England; and the Division of Cardiovascular Medicine (Drs Sullivan and Olshansky), University of Iowa Hospitals and Clinics, Iowa City, IA.

Correspondence to: Gregory Y. H. Lip, MD, University of Birmingham Centre for Cardiovascular Sciences, City Hospital, Dudley Rd, Birmingham, B18 7QH, England; e-mail: g.y.h.lip@bham.ac.uk

For editorial comment see page 1437

Funding/Support: The authors have reported to CHEST that no funding was received for this study.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.

Chest. 2013;144(5):1555-1563. doi:10.1378/chest.13-0054
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Background:  When oral anticoagulation with adjusted-dose vitamin K antagonist (VKA) is used, the quality of anticoagulation control (as reflected by the time in therapeutic range [TTR] of the international normalized ratio [INR]) is an important determinant of thromboembolism and bleeding. Our objective was to derive a validated scheme using patient-related clinical parameters to assess the likelihood of poor INR control among patients with atrial fibrillation (AF) on VKA therapy.

Methods:  The Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) trial population was randomly divided into derivation and internal validation cohorts using a 1:1 ratio. We used linear regression analysis to detect the clinical factors associated with TTR and binary logistic regression to evaluate the predictive performance of a model incorporating these factors for different cutoff values of TTR. The derived model was validated externally in a cohort of patients receiving anticoagulant therapy who were recruited prospectively.

Results:  In the linear regression model, nine variables emerged as independent predictors of TTR: female sex (P < .0001), age < 50 years (P < .0001), age 50 to 60 years (P = .02), ethnic minority status (P < .0001), smoking (P = .03), more than two comorbidities (P < .0001), and being treated with a β-blocker (P = .02), verapamil (P = .02), or, inversely, with amiodarone (P = .05). We incorporated these factors into a simple clinical prediction scheme with the acronym SAMe-TT2R (sex female, age < 60 years, medical history [more than two comorbidities], treatment [interacting drugs, eg, amiodarone for rhythm control], tobacco use [doubled], race [doubled]). The score demonstrated good discrimination performance in both the internal and external validation cohorts (c-index, 0.72; 95% CI, 0.64-0.795; and c-index, 0.7; 95% CI, 0.57-0.82, respectively).

Conclusions:  Common clinical and demographic factors can influence the quality of oral anticoagulation. We incorporated these factors into a simple score (SAMe-TT2R2) that can predict poor INR control and aid decision-making by identifying those patients with AF who would do well on VKA (SAMe-TT2R2 score = 0-1), or conversely, those who require additional interventions to achieve acceptable anticoagulation control (SAMe-TT2R2 score ≥ 2).

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