ACS patients, NSTEMI and STEMI, with a culprit lesion in the LAD will be treated according to standard treatment, PCI followed by stent placement, with or without PICSO therapy. In NSTEMI patients, PICSO therapy will be given during PCI and stenting for a minimum of 30 minutes or the duration of the PCI and stent procedure. In STEMI patients PICSO therapy will be given after successful primary percutaneous coronary intervention of a left anterior descending coronary artery culprit lesion. PICSO therapy is initiated prior to stent deployment and continued during stenting. The functional efficacy measures, related to the PICSO duration and coronary sinus pressures, will be stored on the PICSO Impulse console and analysed offline. The clinical efficacy measures, cardiac enzyme release during 24 hour following PCI, cardiac function, infarct size and level of microvascular obstruction will be assessed by cMRI. Patients will be followed for a maximum of 4 months after the primary PCI procedure