Implanted cardiac arrhythmia devices can detect atrial tachyarrhythmias (atrial high-rate episodes [AHREs]) that are considered to correlate with atrial fibrillation and risk of stroke. In the IMPACT trial, oral anticoagulation was initiated when AHREs were detected by implanted cardioverter-defibrillators and withdrawn when they abated, according to a protocol accounting both for AHRE duration as detected by remote device monitoring and stroke risk assessment. In this analysis, we ascertained determinants of time in therapeutic range (TTR) among protocol-determined vitamin K antagonist–treated patients during the trial. We enrolled 2,718 patients with at least 1 additional stroke risk factor (CHADS 2 score ≥1) at 104 arrhythmia centers. The sex, age <60, medical history, treatments interacting with VKA, tobacco use (2 points) and race (2 points for non-Caucasian) (SAMe-TT 2 R 2 ) score is a simple clinical-derived score designed to aid decision-making on whether a patient is likely to achieve good anticoagulation control on vitamin K antagonist (e.g., warfarin), which was calculated and related to TTR achieved using the Rosendaal method. We analyzed 229 patients (mean age 66.7 years; mean CHADS 2 score 2.85 [SD 1.1]) with mean TTR of 0.536 (SD 0.23) overall. Univariate analysis identified 5 variables associated with differences in mean TTR. Mean TTR was lower in those who were women (p = 0.031), of black race (p = 0.005) and in New York Heart Association class IV (p = 0.014), whereas hemoglobin >13.5 g/dl (p = 0.010) and New York Heart Association class I (p = 0.037) were associated with higher mean TTR. There was a significant difference in mean TTR value between US and non-US sites (Canada and Germany) (mean TTR for US: 0.513 vs non-US: 0.686; p <0.0001). Mean TTR was significantly lower (Δ = 0.1382, 95% CI 0.0382 to 0.2382) for patients with SAMe-TT 2 R 2 scores of 4 (p = 0.007) and higher (Δ = 0.0612, 95% CI 0.0005 to 0.1219) for patients with SAMe-TT 2 R 2 scores of 1 (p = 0.048). Linear regression confirmed a significant association between lower SAMe-TT 2 R 2 score and improved anticoagulation control (p = 0.0021) with a 1-unit decrease in SAMe-TT 2 R 2 score associated with an increase in TTR of 0.0404 (95% CI 0.0149 to 0.0659). In conclusion, clinical, geographical, and demographic factors were associated with the quality of anticoagulation control as reflected by TTR. Although overall TTR in this population was poor, lower SAMe-TT 2 R 2 scores were associated with better TTR.
Implanted cardiac arrhythmia devices can detect atrial tachyarrhythmias (atrial high-rate episodes) that are considered to correlate with atrial fibrillation and risk of stroke. In The IMPACT of BIOTRONIK Home Monitoring Guided Anticoagulation on Stroke Risk in Patients with ICD and CRT-D Devices trial, 2,718 patients with implanted cardioverter-defibrillators (ICD) or resynchronization devices (CRT-D) were randomized to a strategy of starting and stopping anticoagulation based on remote rhythm monitoring versus usual office-based follow-up with anticoagulation determined by standard clinical criteria. The trial was stopped after 2 years median follow-up due to futility assessment for the primary end point, whereby a strategy of early initiation and interruption of anticoagulation based on remotely detected atrial tachyarrhythmias (AT) did not reduce the combined risk of thromboembolism and major bleeding.
Various clinical factors have been associated with the quality of anticoagulation control among vitamin K antagonist (VKA) users. Quality of anticoagulation control is commonly expressed as the average time in therapeutic range (TTR) between international normalized ratio (INR) 2.0 to 3.0, that is closely related to efficacy and safety (being maximal at TTR >65% to 70%). Several clinical factors that influence TTR have been incorporated into a clinical score, the SAMe-TT 2 R 2 (sex, age <60, medical history, treatments interacting with VKA, tobacco use (2 points) and race [2 points for non-Caucasian]) score, to aid clinical decision-making in identifying patients likely to do well on a VKA (SAMe-TT 2 R 2 score 0 to 1) or those less likely to sustain VKA therapy successfully despite acceptable TTR (SAMe-TT 2 R 2 score ≥2). Such patients could be flagged for more frequent surveillance and supplemental education about VKA control, or treated with a non-VKA oral anticoagulant.
Here, we report a prespecified TTR analysis to ascertain determinants of TTR among protocol-defined VKA-treated patients during the trial. The SAMe-TT 2 R 2 score and observed TTR were analyzed to determine if SAMe-TT 2 R 2 was associated with the quality of anticoagulation control in this group.
Methods
In the IMPACT trial, 2,718 patients with at least 1 additional stroke risk factor (CHADS 2 score ≥1) were enrolled at 104 arrhythmia centers. For patients in both the treatment and control groups, all OAC starts, stops, and restarts were recorded along with all INR values and dose changes.
For subjects in the intervention group, the only difference in anticoagulation was when to start and stop. Medications used, dosage, and frequency of INR testing was all done as per “usual” standard of care.
TTR was determined using the Rosendaal method for patients with at least 3 INR values. The SAMe-TT 2 R 2 score is determined by: Sex (female) = 1 point; Age <60 years = 1 point; Medical history of more than 2 specific co-morbidities = 1 point; Treatment with interacting drugs = 1 point; Tobacco use (current) = 2 points; and Race (non-Caucasian) = 2 points. For this analysis, current tobacco use was unknown and not included in score calculations.
For analysis of TTR in relation to thromboembolism and major bleeding, TTR leading up to the first thromboembolic or major bleeding event was compared with TTR for subjects without the event. Hemorrhagic stroke was grouped with major bleeding events. We assessed the relation of the SAMe-TT 2 R 2 score to the observed TTR.
The mean, SD, and 95% CI was calculated for continuous variables, and frequencies and percentages were calculated for categorical variables. Continuous variables were analyzed using 1-way analysis of variance or independent sample Student t test. Relations between variables were analyzed by simple linear regression. Stated p values are for independent sample Student t test unless otherwise indicated, with significance accepted at the 95% confidence level (p <0.05). Analyses were performed using InStat, version 3.10 (GraphPad Software, Inc., La Jolla, California).
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