Objectives:

To understand whether the implementation of warfarin dose management using NextDose (nextdose.org) at The First Affiliated Hospital of Soochow University (Suzhou, China) improves the quality of anticoagulation therapy.

Endpoint Primary

1. Percentage of time within the acceptable INR range estimated using linear interpolation during the 28 days after initiation of warfarin.

Secondary 2.1 Percentage of Time Measures 2.2 Time to Stable Dose 2.3 Safety Outcomes 2.4 Acceptability of NextDose Recommendations Exploratory 3.1 Percentage of Time Measures 3.2 Time to Stable Dose 3.3 Safety Outcomes 3.4 Acceptability of NextDose Recommendations 3.5 Model Evaluation 3.6 INR Variability

Population:

240 participants of any sex between the age of 18 and 80 years. Patients requiring treatment with warfarin following cardiac surgery.

Objectives:

To understand whether the implementation of warfarin dose management using NextDose (nextdose.org) at The First Affiliated Hospital of Soochow University (Suzhou, China) improves the quality of anticoagulation therapy.

Endpoint Primary

1. Percentage of time within the acceptable INR range estimated using linear interpolation during the 28 days after initiation of warfarin.

   Secondary 2.1 Percentage of Time Measures

   1. Percentage of time within the acceptable INR Range estimated using linear interpolation during the 90 days after initiation of warfarin.
   2. Percentage of time spent above and below the acceptable INR range at day 28, and 90 after initiation of warfarin estimated by linear interpolation.

   2.2 Time to Stable Dose a. Number of days to achievement of stable dose (defined as 3 consecutive INR measurements within acceptable range for the same mean daily dose).

   2.3 Safety Outcomes a. Number of participants who experience at least one of the following safety events: major bleeding within 30 days, INR of 4 or greater within 30 days, death within 30 days, and symptomatic or asymptomatic VTE confirmed by objective testing within 60 days of surgery.

   2.4 Acceptability of NextDose Recommendations

   1. Percentage of prescribed doses within 0.625 mg of the NextDose proposed dose.
   2. Mean difference between the prescribed dose and the NextDose proposed dose. Exploratory 3.1 Percentage of Time Measures

   a. The percentage of time spent within, above and below the acceptable INR range estimated by numerical integration with the Bayesian parameter estimates of the PKPD model at day 28 and at day 90 after initiation of warfarin.

   3.2 Time to Stable Dose a) Days to first INR measurement within the acceptable range. b) Days to second consecutive INR measurement within the acceptable range. c) Number of dose adjustments to achievement of stable dose (3 consecutive INR measurements within acceptable range for the same mean daily dose).

   d) Total number of dose adjustments at day 90. e) Total number of INR measurements at day 90. 3.3 Safety Outcomes

   a) Incidence of minor and major bleeding events. b) Incidence of thromboembolic events. c) 30 day all-cause mortality. d) 90 day all-cause mortality. e) 90 day cardiovascular mortality. f) Number of warfarin doses withheld due to high INR (as determined by the treating clinician).

   3.4 Acceptability of NextDose Recommendations a) Percentage of prescribed doses within 20% of the NextDose proposed dose. 3.5 Model Evaluation

   a) Predictive performance of the model for patients with steady-state warfarin doses below 2 or above 7 mg/day.

   3.6 INR Variability

   a) INR variability as described by Lind et al. (the standard deviation of transformed INR values).

   Population:

240 participants of any sex between the age of 18 and 80 years. Patients requiring treatment with warfarin following cardiac surgery.

Inclusion Criteria:

• Scheduled to undergo cardiac surgery with planned warfarin anticoagulation for at least three months.
• Age ≥ 18 and < 80 years.
• Written informed consent has been obtained.

Exclusion Criteria:

• Allergy to warfarin tablet or excipients.

• Enrollment or planned enrollment in other research that would conflict with full participation in the study or confound the observation or interpretation of the study findings.

• Patients who in the opinion of the recruiting clinician are:

  • unwilling or unable to comply with the protocol requirements and/or,
  • considered unreliable concerning the requirements for follow-up during the study and/or, compliance with drug administration.

• Patient with life expectancy less than the expected duration of the trial due to concomitant disease.

• Contraindication to warfarin therapy. The following are examples but not an exhaustive list:

  • Pregnancy.
  • Cerebral infarction or cerebral haemorrhage (from patients' medical record) within the 3 months prior to heart valve replacement
  • Severe heart failure (New York Heart Function Class IV)
  • Severe renal failure (CLcr (Cockcroft-Gault) ≤20mL / min)
  • Severe liver failure (Child-Pugh≥10)
  • Abnormal liver function (elevated transaminase more than three times the upper limit of the local hospital clinical laboratory).

All patients who are screened for enrolment will be allocated an enrolment number. The recruiting clinician will record into a logbook the details of all patients screened for enrolment, including the reason for exclusion from trial entry.

A randomization sequence using block randomization with random block sizes of 4, 6 and 8 (to maintain equal sample size in each arm) will be created by researchers using PASS. Assignments will be enclosed in sequentially numbered, opaque, sealed envelopes.

Participants who provide written informed consent and are enrolled will be allocated to study arm by the study pharmacists. The pharmacist will be responsible for opening envelopes sequentially, writing the participant enrollment number on the envelope prior to opening, and recording the envelope number and study arm allocation in the CRF. On conclusion of the data collection phase, the (actual) study allocation status of the participants will be compared to the randomization sequence.