Effect of ischemic postconditioning on microvascular obstruction in reperfused myocardial infarction. Results of a randomized multicenter study in patients and data of an experimental model

Purpose: Ischemic Postconditioning (PCON) appears as a potentially beneficial tool to complement primary angioplasty in ST-segment elevation myocardial infarction (STEMI). We evaluated the impact of PCON on Microvascular Obstruction (MVO) both in patients and in a highly controlled swine model. Methods: In a multicenter study, 101 patients with a first STEMI were randomized to undergo primary angioplasty followed by PCON or primary angioplasty alone (non-PCON). MVO (lack of contrast uptake in the core of the hyperenhanced infarcted area) was quantified in late enhancement cardiac magnetic resonance imaging. In an anterior STEMI swine model based on a 90-min angioplasty balloon coronary occlusion and 3-day reperfusion, MVO was defined as a lack of thioflavin-S staining in the core of the infarcted area (with triphenyltetrazolium-chloride staining). The extent of MVO (% of left ventricular mass) was quantified in a core laboratory. Results: In the clinical study, patients treated with (n=49) and without PCON (n=52) were well matched in terms of baseline characteristics and time to revascularization. MVO (> 1 segment in the 17 segments model) occurred in 12 (24%) PCON and in 18 (35%) non-PCON patients, p=0.3. PCON did not significantly reduce MVO (1.4±2.9% vs. 1.9±3.6% of LV mass, p=0.3). IS was similar in PCON and non-PCON patients (18±13 vs. 21±14% of LV mass, p=0.2). No significant differences were observed between PCON and non-PCON patients in LV volumes, ejection fraction or the extent of hemorrhage. In the swine model, MVO occurred in 4/6 (67%) PCON and in 4/6 (67%) non-PCON pigs, p=1. The extent of MVO (7.8±5.5% vs. 5.6±5.4% of LV mass, p=0.5) and IS (22±14 vs. 24±10% of LV mass, p=0.8) were not reduced in PCON compared with non-PCON pigs. Conclusions: Ischemic postconditioning does not reduce microvascular obstruction in STEMI.