Table 1

Operationalisation of exposure variable and study outcomes

VariableSourceTime of collectionOperationalisation
TelemedicineHF registry, telemedicine-generated dataT0, T1*, T2Whether a patient receives telemedicine. Five categories: (1) no telemonitoring†; (2) telemonitoring by telephone; (3) telemonitoring, non-invasive based on traditional parameters (eg, blood pressure, ECG); (4) telemonitoring using ICD based on HF parameters; and (5) telemonitoring, invasive using sensors in the bloodstream or heart.
Primary outcome
Number of days spent alive without unplanned hospitalisations within 1 year of follow-upHF registryT1*, T2Number of days directly related to unplanned cardiac hospital admission due to HF. Number of admission days will be summed up over a period between follow-up moments and subtracted from 365 days.
Secondary outcomes
CostsDerived from HF registry, external data source, EHR, interviewsT0, T1*, T2Costs estimated from patient, disease and treatment characteristics. Information taken into account includes medication use, whether the patient underwent cardiac interventions (eg, pacemaker implantation, percutaneous coronary intervention), use of telemedicine, hospital admission days, visits to the outpatient clinic, visits to the emergency room, admission days at an intensive care unit and visits to the GP related to HF.
All-cause mortalityHF registry, external data sourceT1*, T2Mortality status, determined after verification at the Personal Records Database (in Dutch: Basisregistratie Personen). Mortality is independent of HF (all-cause).
Functional statusHF registryT0, T1*, T2NYHA classification: a functional classification of patients based on severity of symptoms and physical activity, with specific attention to fatigue, palpitation and dyspnoea. Scores are linked to one of four NYHA classes: class I: no limitation; class II: slight limitation; class III: marked limitation; and class IV: unable to carry on any physical activity without discomfort.1
Health statusHF registryT0, T1*, T2SF-36 or SF-12 questionnaire (subset of SF-36)54: a validated patient-reported survey of patient health. Both questionnaires consist of eight sections with scores: vitality, physical functioning, bodily pain, general health perceptions, physical role functioning, emotional role functioning, social role functioning and mental health. Each score is transformed into a scale of 0–100 on the assumption that each question carries equal weight. The lower the score, the more disability.
Health-related quality of lifeHF registryT0, T1*, T2SF-36 or SF-12 questionnaire. QALY will be calculated based on the SF-6D, a model in which a single, preference-based score can be directly calculated for the SF-36 and SF-12.55 Scores range from 0.0 (worst health state) to 1.0 (best health state).
Healthcare utilisationExternal data source, EHRT1, T2Healthcare utilisation based on (1) the number of outpatient visits, plus (2) the number of visits to the general practice related to HF.
  • *The HF registry collects data standard at baseline (T0), after 6 months (T1) and after 12 months (T2). The RELEASE-HF study conforms to the timeframes of the HF registry. Therefore, data will be collected at 6 months, although the outcome measurements are after 12 months.

  • †The HF registry defines telemedicine as telemonitoring.

  • EHR, electronic health record; GP, general practitioner; HF, heart failure; ICD, implantable cardioverter defibrillator; NYHA, New York Heart Association; QALY, quality-adjusted life year; RELEASE-HF, REsponsible roLl-out of E-heAlth through Systematic Evaluation – Heart Failure; SF-12, 12-item short form health survey; SF-36, 36-item short form health survey; SF-6D, six-dimensional health state short form.