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Vladimir Dzavík, MD

Photo courtesy of the American Heart Association

Vladimir Dzavík, MD, presented the results of the Total Occlusion Study of Canada (TOSCA)-2, which was a mechanistic sub-study of the Occluded Artery Trial (OAT) funded by the National Institutes of Health. Observational studies have suggested beneficial effects of opening a persistently occluded infarct related artery so called “open artery hypothesis”, and the TOSCA-2 study set out to determine the effects of stent-based interventions 3 to 28 days post-myocardial infarction. The co-primary endpoints were the change in the heart's pumping ability as measured by left ventricular ejection fraction (LVEF) and the number of arteries which were still open after one year (patency). Secondary endpoints included the changes in left ventricular end-systolic volume index (LVESVI) and left ventricular end-diastolic volume index (LVEDVI).

In this sub-study, 381 patients were enrolled between May 2000 and July 2005 in eight countries, 195 to percutaneous coronary intervention plus optimal medical therapy (PCI), and 186 to optimal medical therapy alone (MED). The participants were similar in baseline characteristics except for a history of diabetes which was more frequent in MED (25 % vs. 16% in PCI). The arterial occlusion at baseline was 99% in PCI and 100% in MED. The majority of patients in both groups (>80%) took beta-blockers, ace inhibitors, and statins during the trial.

After one year, patency was significantly greater in the PCI group (83% vs. 25%, respectively; p<0.0001). More surprising was the finding that the LVEF significantly improved in both groups, with no statistically significant difference between the two treatment arms (p=0.47). “Assignment to PCI was not predictive of improvement in LVEF” said Dr. Dzavík. There was, however, a trend favoring PCI in the secondary measures of volume (LVESVI percent change p=0.07, LVEDVI percent change p=0.09), especially when LAD was the infarct-related artery. The investigators have therefore concluded that PCI establishes and sustains coronary artery patency but does not result in improved LVEF. One explanation is that although the epicardial artery is opened during PCI, the downstream microvasculature remains obstructed. It is also possible that the follow-up period was not long enough to illustrate a benefit of PCI, so the investigators plan to continue following the patients for a longer period of time. The results of the TOSCA-2 study were published online on November 14, 2006 in Circulation (www.circulationaha.org; DOI 10.1161 CIRCULATIONAHA.106.669432).