PubMed · 11793488
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Carlo Di Mario. 2002. Closure devices: case closed?. https://doi.org/10.1002/ccd.10077
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Economic endpoints have been increasingly included in long-term clinical trials, but they pose several methodologic challenges, including how best to collect, describe, analyse and interpret medical cost data. Cost of care can be measured by converting billed charges, performing detailed micro-costing studies, or by measuring use of key resources and assigning cost weights to each resource. The latter method is most commonly used, with cost weights based either on empirical regression models or administratively determined reimbursement rates. In long-term studies, monetary units should be adjusted to reflect cost inflation and discounting. The temporal pattern of accumulating costs can be described using a modification of the Kaplan-Meier curve. Regression analyses to evaluate factors associated with cost are best performed on the log of costs due to their typically skewed distribution.Cost-effectiveness analysis attempts to measure the value of a new therapy by calculating the difference in cost between the new therapy and the standard therapy, divided by the difference in benefit between the new therapy and the standard therapy. The cost-effectiveness ratio based on the results of a randomized trial may change substantially with longer follow-up intervals, particularly for therapies that are initially expensive but eventually improve survival. A model that projects long-term patterns of cost and survival expected beyond the end of completed follow-up can provide an important perspective in the setting of limited trial duration.
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BACKGROUND: Restenosis remains the major limitation of coronary catheter-based intervention. In small vessels, the amount of neointimal tissue is disproportionately greater than the vessel caliber, resulting in higher restenosis rates. In the Randomized Study With the Sirolimus-Eluting Bx Velocity Balloon-Expandable Stent (RAVEL) trial, approximately 40% of the vessels were small (<2.5 mm). The present study evaluates the relationship between angiographic outcome and vessel diameter for sirolimus-eluting stents. METHODS AND RESULTS: Patients were randomized to receive either an 18-mm bare metal Bx VELOCITY (BS group, n=118), or a sirolimus-eluting Bx VELOCITY stent (SES group, n=120). Subgroups were stratified into tertiles according to their reference diameter (RD; stratum I, RD <2.36 mm; stratum II, RD 2.36 mm to 2.84 mm; stratum III, RD >2.84 mm). At 6-month follow-up, the restenosis rate in the SES group was 0% in all strata (versus 35%, 26%, and 20%, respectively, in the BS group). In-stent late loss was 0.01+/-0.25 versus 0.80+/-0.43 mm in stratum I, 0.01+/-0.38 versus 0.88+/-0.57 mm in stratum II, and -0.06+/-0.35 versus 0.74+/-0.57 mm in stratum III (SES versus BS). In SES, the minimal lumen diameter (MLD) remained unchanged (Delta -0.72 to 0.72 mm) in 97% of the lesions and increased (=late gain, DeltaMLD <-0.72 mm) in 3% of the lesions. Multivariate predictors for late loss were treatment allocation (P<0.001) and postprocedural MLD (P= 0.008). CONCLUSIONS: Sirolimus-eluting stents prevent neointimal proliferation and late lumen loss irrespective of the vessel diameter. The classic inverse relationship between vessel diameter and restenosis rate was seen in the bare stent group but not in the sirolimus-eluting stent group.