Analytical approach:
A decision analytic Markov model was used to assess costs and outcomes associated with the two interventions under study. The model was developed in discussion with two clinical advisors. The time horizon of the study was the lifetime of the patient. The authors reported that the perspective adopted in the economic analysis was that of the UK National Health Service (NHS) and personal social services (PSS).
Effectiveness data:
Clinical and effectiveness data were derived from previously published studies. The main measure of effectiveness was all-cause mortality and hospitalisations for cardiovascular causes. These estimates were derived from a comprehensive systematic review and indirect meta-analysis. Relevant studies were identified from a search of 18 electronic databases. The review was supplemented by a recent systematic review (see Other Publications of Related Interest). The analysis was undertaken using Bayesian meta-regression methods. These methods allowed the full evidence base of trials in both the post-myocardial infarction heart failure population and the general heart failure population to be utilised.
Monetary benefit and utility valuations:
Utility estimates for people with heart failure were obtained from a study in which patients enrolled in a clinical trial were followed-up using the EQ-5D. To reflect the decreasing utility of patients as they aged, the authors used UK age- and sex-adjusted norms adjusted downward by approximately 5% to reflect the existence of heart failure.
Measure of benefit:
The measure of benefit was quality-adjusted life-years (QALYs). As benefits could be generated over the lifetime of the patient, future benefits were discounted using an annual rate of 3.5%.
Cost data:
The direct costs included in the study were for medications and costs of treating cardiovascular events (such as acute myocardial infarction, heart failure, stroke and ventricular arrhythmia). Costs of medications were obtained from the British National Formulary. Costs of treating most cardiovascular events were obtained from the National Schedule of Reference Costs for NHS trusts. Costs for heart failure were obtained from a British Heart Foundation report. The price year was 2007/08. Costs could be incurred over the lifetime of the patient so future costs were discounted using an annual rate of 3.5%. All costs were reported in UK pounds sterling (£).
Analysis of uncertainty:
The model was run probabilistically by using Monte Carlo simulation. Uncertainty in the parameters was characterised by probability distributions. Results were presented using a cost-effectiveness acceptability curve. A value of information analysis was performed to quantify the cost associated with the decision uncertainty.