Rationale and design of the MGuard for acute ST elevation reperfusion MASTER trial.

BACKGROUND: Primary percutaneous coronary intervention (PCI) improves survival compared with thrombolytic therapy in ST-segment elevation myocardial infarction (STEMI), with much of the benefit attributable to greater rates of normal epicardial and myocardial perfusion resulting in enhanced myocardial salvage. However, reduced tissue reperfusion after primary PCI may occur from distal thromboemboli with capillary plugging. The MGuard stent consists of a balloon-expandable metallic scaffold with mesh sleeve fibers of polyethylene terephthalate attached to its outer surface to trap friable debris/thrombi and reduce distal embolization. The MGuard for Acute ST Elevation Reperfusion (MASTER) trial has been designed to evaluate the MGuard stent in patients with STEMI.

STUDY DESIGN: The MASTER trial is a prospective, multicenter, randomized study designed to compare the incidence of complete (=70%) ST-segment resolution with PCI using bare metal or drug-eluting stents (the control arm) versus PCI with the MGuard stent, measured 60 to 90 min after the last angiogram (primary endpoint). Secondary endpoints include the rates of TIMI flow and myocardial blush, and clinical outcomes through 1-year follow-up. The study has enrolled 432 patients with STEMI undergoing primary or rescue angioplasty within 12 hr of symptom onset and includes substudies with cardiac magnetic resonance imaging and quantitative coronary angiography to evaluate infarct size, microvascular obstruction, and angiographic restenosis.

CONCLUSIONS: Distal embolization is common during primary PCI and results in reduced myocardial perfusion and lack of reduction of infarct size. The MASTER trial is a prospective, randomized trial designed to assess the potential of the novel MGuard stent with protective mesh net to reduce embolization and enhance myocardial reperfusion compared with routine PCI in the setting of STEMI.