To the Editor, Myocardial infarction is the leading cause of morbidity and mortality in our setting. Percutaneous coronary intervention has improved the prognosis of patients with ST-segment elevation myocardial infarction (STEMI).1 However, there is a subgroup of patients who suffer from suboptimal myocardial reperfusion with appearance of myocardial fibrosis, ventricular dysfunction, and development of heart failure.2 Recently, several pharmaceutical and procedural strategies have been developed to improve these results.3 The PiCSO system (Pressure-controlled intermittent coronary sinus occlusion) developed by Miracor Medical SA, Belgium consists of a balloon catheter to occlude the coronary sinus periodically: 1) During the occlusion stage (5 to 15 s), venous flow is redistributed from well perfused areas towards ischemic regions through the formation of collateral circulation. Also, through an increased venous systolic pressure, the plasma skimming phenomenon allows better perfusion of venules with oxygen-and-metabolite-rich plasma. 2) During the release stage (3 to 4 s) the dramatic drop of venous pressure creates a gradient that ends up clearing all thrombotic debris, toxic metabolites, and myocardial edema. 3) These pressure variations can induce mechanotransduction by activating vascular cells and releasing growth factors, vasodilator substances, and microRNA into microcirculation (figure 1). Figure 1. Representation of the mechanism of action of the PiCSO system in the...