CABG Found a Cut Above Stents Over Time

LONDON, March 23 -- Minimally invasive coronary artery bypass grafts (CABG) are at least as effective as stenting, and maybe cheaper over the long haul.

Those conclusions come from three studies in the March 24 issue of BMJ, looking at the comparative efficacy, safety, and cost of minimally invasive internal thoracic artery bypass compared with percutaneous revascularization for isolated lesions of the left anterior descending artery.

For example, in a meta-analysis of randomized studies comparing CABG with percutaneuous coronary intervention with stenting, surgeon Thanos Athanasiou, M.D., of Imperial College London and colleagues, found that patients who received stents had higher rates of angina recurrence, adverse cardiovascular and cerebrovascular events, and repeat revascularization.

The studies fuel the already burning debate surrounding the relative benefits versus costs and risks of stents, both the bare-metal and drug eluting variety, compared with CABG, noted heart surgeon David P Taggart M.D., of the University of Oxford, in an editorial.

"Disquiet about the lack of improved clinical outcome with drug eluting stents, despite their increased costs, has recently been superseded by concerns about the increased risk of late thrombosis and its high associated mortality." Dr. Taggart wrote. "These clinical concerns are compounded by cost implications. Drug eluting stents cost more than bare metal stents, and new recommendations that patients remain on clopidogrel [Plavix] for at least a year and possibly indefinitely will add greatly to costs."

In the first study, Dr. Athanasiou and colleagues conducted a meta-analysis comparing outcomes between minimally invasive left internal thoracic artery bypass and percutaneous coronary artery stenting as primary interventions for isolated lesions of the left anterior descending artery.

They looked at both randomized and non-randomized studies, and found a total of 12 reporting results from eight groups, involving at total of 1,952 patients. The trials included a retrospective study, one prospective non-randomized study, and six prospective randomized studies.

In the randomized trials, patients who underwent percutaneuous coronary intervention with stenting had a higher rate of angina recurrence (odds ratio 2.62, 95% confidence interval 1.32 to 5.21), a higher incidence of major adverse coronary and cerebral events (odds ratio 2.86, 95% CI, 1.62 to 5.08), and a greater need for repeat revascularization (odds ratio 4.63, 95% CI,2.52 to 8.51) compared with patients who underwent bypass surgery.

There were no significant differences in rates of myocardial infarction, stroke, or mortality at latest follow-up between interventions.

"The findings from our meta-analysis," the authors wrote "suggest that minimally invasive direct coronary artery bypass produces a more definitive revascularization in the mid-term for isolated lesions of the left anterior descending [artery] than does percutaneous transluminal coronary artery stenting, with a reduced rate of recurrence of angina, incidence of the composite outcome of major adverse coronary and cerebral events, and need for repeat revascularization. One explanation may be that stenting has a greater potential to occlude septal branches and diagonals, affecting interventricular septal blood supply."

Two other studies in the same issue of the BMJ issue looked at the cost-effectiveness of the two procedures. The first study, also by Dr. Athanasiou and colleagues, used decision analysis tools to model medium and long term costs, quality of life, and cost effectiveness after either intervention, using data from the sources used in their meta-analysis. The cost-benefit analysis pertained only to bare metal stents versus percutaneous coronary intervention, since drug-eluting stents don't have enough of a track record, the authors noted.

Their base case analysis assumed a cohort of 61-year-old men (the average age of patients in the meta-analysis studies). They extended the analysis out to 10 years, with one-year Markov cycles, and discounted costs and effects 3.5% per year.

They found that after two years, stenting was associated with better clinical results and was less costly. But by the third year, stenting had lost its clinical edge, although not its cost advantage over percutaneous coronary intervention.

At three years, the incremental cost of stenting over percutaneous coronary intervention was ,179,94 per quality-adjusted life year (QALY), which was not enough to justify a marginal clinical benefit for bypass.

But by the fifth year of the analysis, the incremental cost effectiveness ratio was ,964 per QALY, which, according to the authors, compares favorably 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 ,585.69, range .90 to .86, with an incremental cost effectiveness of ,297.08 per QALY, the authors wrote.

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

In the third study, Harry Hemingway, M.Sc., of the University of York, and colleagues at University College London, and at Brunel University, also in London, tried to assess "whether revascularization that is considered to be clinically appropriate is also cost effective."

They conducted a prospective observational study comparing cost effectiveness of CABG, percutaneous coronary intervention, and medical management within groups of patients deemed to be appropriate candidates for revascularization.

Their main outcome measure was cost per QALY gained over six year follow-up, calculated with a National Health Service cost perspective and discounted at 3.5%/year.

They found that "among patients judged clinically appropriate for coronary revascularization, coronary artery-bypass grafting seemed cost effective, but percutaneous coronary intervention did not. Cost effectiveness analysis based on observational data suggests that the clinical benefit of percutaneous coronary intervention may not be sufficient to justify its cost."

In his editorial, Dr. Taggart maintained that drug-eluting stents will not be able to match the effectiveness of surgery in patients with multivessel disease.

"Firstly, because bypass grafts are placed to the midcoronary vessels, surgery protects whole zones of vulnerable proximal myocardium against the 'culprit' lesion (of any complexity) and against new lesions in diffusely diseased endothelium," he wrote. "In contrast, stents deal only with 'suitable' culprit lesions and offer no protection against new disease. Secondly, the failure of stenting to achieve complete revascularization in most patients with multi-vessel disease reduces survival proportional to the degree of incomplete revascularization."

He concluded that Hemingway and colleagues "highlight the tension between the adverse economic implications of the phenomenal growth in stent procedures and the absence of an appropriate evidence base to support such a policy."

"More importantly," he added, "this strategy has denied many patients with multivessel disease the prospect of a better long term outcome in terms of survival and freedom from reintervention offered by surgery. This highlights the dangers of individual practitioners rather than multidisciplinary teams making recommendations for stenting in patients with multivessel disease."

None of the other authors declared competing interests.