Cost effectiveness analysis of minimally invasive internal thoracic artery bypass versus percutaneous revascularisation for isolated lesions of the left anterior descending artery

Abstract

Objective: To compare the cost effectiveness of percutaneous transluminal coronary artery stenting with minimally invasive internal thoracic artery bypass for isolated lesions of the left anterior descending artery.

Design: Cost effectiveness analysis.

Data sources: Embase, Medline, Cochrane, Google Scholar, and Health Technology Assessment databases (1966-2005), and reference sources for utility values and economical variables.

Methods: Decision analytical modelling and Markov simulation were used to model medium and long term costs, quality of life, and cost effectiveness after either intervention using data from referenced sources. Probabilistic sensitivity and alternative analyses were used to investigate the effect of uncertainty about the value of model variables and model structure.

Results: Stenting was the dominant strategy in the first two years, being both more effective and less costly than bypass surgery. In the third year bypass surgery still remained more expensive but became marginally more effective. As the incremental cost effectiveness was 1,108,130.40 pounds sterling (1 682,146.00 euros; $2,179,194) per quality adjusted life year (QALY), the additional effectiveness could not be said to justify the additional cost at this stage. By five years, however, the incremental cost effectiveness ratio of 28,042.95 pounds sterling per QALY began to compare favourably with other interventions. At 10 years the additional effectiveness of 0.132 QALYs (range -0.166 to 0.430) probably justified the additional cost of 829.02 pounds sterling (range 205.56 pounds sterling to 1452.48 pounds sterling), with an incremental cost effectiveness of 6274.02 pounds sterling per QALY. Sensitivity and alternative analysis showed the results were sensitive to the time horizon and stent type.

Conclusions: Minimally invasive left internal thoracic artery bypass may be a more cost effective medium and long term alternative to percutaneous transluminal coronary artery stenting.

Fig 1 Decision analytical model comparing outcome after percutaneous transluminal coronary artery stenting (PTCS) with minimally invasive direct internal thoracic coronary artery bypass (MIDCAB). Patients start Markov simulation depending on primary treatment. Branches immediately after Markov nodes show possible states that patients can enter. Model structure is the same after both interventions, but transition state probabilities, cost, and utility pay-offs associated with each intervention differ

Fig 2 Distribution of incremental costs and incremental effectiveness of minimally invasive internal thoracic artery bypass compared with transluminal stenting

Fig 3 Scatter plot of incremental cost effectiveness ratio. Incremental cost effectiveness ratio for base case is plotted at £6274.02 per QALY and 95% confidence intervals (Fieller's method) are plotted at £8505.13 per QALY and £5007.67 per QALY. 71.1% of the points lie under the cost effectiveness thresholds, arbitrarily plotted at £20 000 per QALY

Fig 4 Cost effectiveness acceptability curves for different time horizons, showing certainty with which minimally invasive internal thoracic artery bypass is the most cost effective intervention as amount healthcare providers are prepared to pay for one QALY varies

Fig 5 Effect of time horizon on incremental cost effectiveness ratio for minimally invasive internal thoracic artery bypass compared with transluminal stenting