Total Occlusion Study of Canada - TOSCA-2 – Presented at AHA 2006


The goal of the trial was to evaluate late left ventricular (LV) function and patency associated with percutaneous coronary intervention (PCI) compared with medical therapy among stable, high-risk patients with persistent total occlusion of the infarct-related artery post-myocardial infarction (MI).

Study Design

Study Design:

Patients Enrolled: 381
Mean Follow Up: One year
Mean Patient Age: Mean age, 58 years
Female: 17

Patient Populations:

Enrollment in the OAT trial; OAT trial enrollment criteria included angiography on day 3-28 post-MI with evidence of total occlusion of the infarct-related artery with poor or absent antegrade flow coronary (TIMI flow grade 0 or 1); and met a criterion for increased risk, defined as EF <50%, proximal occlusion of a major epicardial vessel with a large risk region, or both.


New York Heart Association class III or IV heart failure, shock, serum creatinine concentration >2.5 mg/dl, angiographically significant left main or three-vessel coronary artery disease, angina at rest, or severe ischemia on stress testing

Primary Endpoints:

1) Change in LVEF, and 2) infarct-related artery patency

Secondary Endpoints:

Change in LVEDVI, LVESVI, and regional wall motion score

Drug/Procedures Used:

The study was a subgroup of patients in the larger OAT trial. Patients with persistent total occlusion of the infarct-related artery 3-28 days post-MI were randomized to PCI with stenting (n = 195) or medical therapy (n = 186). Follow-up angiography was performed 1 year post-MI. A core laboratory evaluated the qualifying and follow-up angiograms.

Principal Findings:

One-year angiographic follow-up was available in 87% (n = 332) of the 381 patients enrolled in the angiographic substudy. Median time from index MI to randomization was 10 days. Concomitant medical therapy with recommended agents was high in both groups, 1-year use of aspirin in 94% of patients, beta-blockers in ~90%, and lipid-lowering agents in 90%. Thienopyridine was used at discharge in 93% of the PCI cohort and 31% of the medical therapy cohort.

Change in LV ejection fraction (LVEF) at 1 year, a primary endpoint, did not differ between the PCI and medical therapy group (4.2% increase with PCI vs. 3.5% increase with medical therapy, p = 0.47). Patency at 1 year, the co-primary endpoint, was higher in the PCI group compared with the medical therapy group (83% vs. 25%, p < 0.001). Percent diameter stenosis at 1 year averaged 52.5% in the PCI group and 90.2% in the medical therapy group (p < 0.001). Binary restenosis was present in 46% of the PCI group. LV end-systolic volume index (LVESVI) decreased by a median 0.5 ml/m2 in the PCI group and increased by 1.0 ml/m2 in the medical therapy cohort (p = 0.10). LV end-diastolic volume index (LVEDVI) increased by a median 3.2 ml/m2 in the PCI group compared with 5.3 ml/m2 in the medical therapy cohort (p = 0.07).


Among stable, high-risk patients with persistent total occlusion of the infarct-related artery post-MI, performance of PCI 3-28 days post-MI was associated with no difference in LV function, but higher rates of patency at 1 year compared with medical therapy. However, this angiographic difference did not translate into a clinical difference in the overall OAT trial, which showed no difference in the composite of death, reinfarction, or severe heart failure through a mean follow-up of 3 years with PCI compared with medical therapy.

The trial was designed based on the assumption that increased patency with PCI, even if delayed, would improve LV function and remodeling. However, the high patency rate at 1 year with PCI compared with medical therapy did not translate into any improvements in LVEF. LVEF was actually improved from baseline to 1 year in both treatment groups.

Unlike the present trial, early reperfusion therapy in ST elevation MI has been associated with reductions in clinical events, leading to the development of the so-called early open-artery hypothesis. Conversely, data from the OAT and corresponding TOSCA-2 studies do not support a "late" open-artery hypothesis for patients with stable but persistent total occlusion.


Dzavik V, Buller CE, Lamas GA, et al. Randomized trial of percutaneous coronary intervention for subacute infarct-related coronary artery occlusion to achieve long-term patency and improve ventricular function: the Total Occlusion Study of Canada (TOSCA)-2 trial. Circulation 2006;114:2449-57.

Presented by Dr. Vladimir Dzavik at the American Heart Association Annual Scientific Sessions, Chicago, IL, November 2006.

Clinical Topics: Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Acute Heart Failure

Keywords: Myocardial Infarction, Follow-Up Studies, Ventricular Function, Left, Heart Failure, Constriction, Pathologic, Stents, Percutaneous Coronary Intervention, Thienopyridines

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