Effect of Ischemic Postconditioning on Microvascular Obstruction in Reperfused Myocardial Infarction. Results of a Randomized Study in Patients

INTRODUCTION

In ST-segment elevation myocardial infarction (STEMI) timely coronary reperfusion is the primary therapeutic goal to improve patients' outcome and to reduce left ventricular (LV) infarct size (IS). Unfortunately, despite successful reperfusion of the epicardial blood flow an impairment of microvascular perfusion persists in a significant number of patients, a phenomenon referred to as microvascular obstruction (MVO). This is a multifactorial process caused, among other factors, by microembolization, vasospasm and cells plugging. Cell reperfusion injury related to inflammation as well as to mitochondrial damage provoked by a rapid normalization of the acidotic myocardial environment do play a key role in the pathophysiology of MVO. In recent years MVO has been demonstrated to be a powerful and independent predictor of adverse outcome and larger IS. Cardiovascular magnetic resonance imaging (CMR) has become the state of the art technique for an early non-invasive comprehensive assessment of the structural consequences of STEMI, this including MVO.

Availability of inexpensive and easy-to-implement therapies that could solidly reduce MVO and subsequently optimize the beneficial effects of prompt primary percutaneous intervention would be of utmost importance. In recent years ischemic postconditioning (PCON) has appeared as a promising option. It permits a progressive, rather than brisk, restoration of blood flow to the jeopardized myocardium by means of consecutive cycles of inflation and deflation of the angioplasty balloon used to open the acute coronary occlusion. Previous experimental evidence and preliminary clinical data suggest that this simple strategy exerts, in comparison with the traditional rapid reperfusion using single balloon inflations, a number of protective myocardial effects.

During the last two years the effect of PCON on CMR-derived infarct size in STEMI patients has been evaluated but the results have been controversial. In routine practice, the time window to achieve any additional reduction in IS beyond that derived from timely coronary reperfusion is extremely tight. To the contrary, MVO owing to its pathophysiology and more progressive time course, seems a more suitable and realistic objective to explore the impact of this complementary therapy. Nevertheless the effect of PCON on MVO in STEMI is unknown so far.

In the present study we aim to analyse the effect of PCON on CMR-derived MVO in a randomized series of patients with a first STEMI treated with primary angioplasty.