CONTRAST-EHANCED MRI IN TIME-STRUCTURE ANALYSIS OF MYOCARDIAL DAMAGE IN ACUTE INFARCTION AND EARLY PREHOSPITAL THROMBOLYTIC THERAPY

Abstract

Purpose:to evaluate the dependence of absolute and relative thickness of damaged myocardium in the acute myocardial infarction (AMI) area from the time interval between oncet of pain and start of intravenous thrombolysis (so-called “pain–needle time”), in AMI patients treated with prehospital intravenous thrombolysis and also later on with subsequent percutaneous coronary angiplasty (PCA) and stenting, using contrast-enhanced MRI of the heart Materials and methods. The study comprised data of CE-MRI studies in 25 patients with theyr first acute myocardial infarction, in whom the pre-hospital thrombolytic therapy (TLT) was carried out in the course of 35–300 min after onset of chest pain, with coronarography and percutaneous coronary angioplasty and stenting after admission to the institute of cardiology. In six patients the TLT was not success ful and in these the restoration of coronary blood flow was obtained only at PCA. In all patients in terms 18–34 hours after TLT the CE-MRI of the heart was carried out using gadobutrol or gadoversetamid, as 0.1 mM per kg of BW, in T1-weighted mode with fat suppression and as inversion-recovery with inversion time adjusted to get the normal myocardium “nulled”. We calculated the segmental extension of damage, the thickness of infarcted irreversibly damaged myocardium and of non-damaged myocardium in the same locations, the index of transmurality, as ratio of thickness of damaged myocardium to the overall wall thickness. We analyzed the dependence of these indices of damage from the time interval between pain oncet and beginning of intravenous thrombolytic therapy (or PCA – when TLT was unsuccessful).Results.The dependence of thickness of non-damaged myocardium from the “pain-needle” time was as exponential as Y = 2.08 + 17.11 · exp(−t/42.4), r = 0.843, p < 0.002. Index of transmurality did depend on the time interval “pain – needle” as Boltzmann function, pretty closely to reverse exponential one: No-reflow zone with absent blood flow in the infarcted area was present only in cases with the “pain–needle” time interval over 70 min. Later on the full or partial restoration of contractility in infarcted segments was observed only if the IT was below 0.55–0.6.Conclusion.CE-MRI delivers adequate quantitative estimates of anatomic transmural extent of myocardial infarction from early acute period of the AMI. The depth of myocardial damage is a function of “pain–needle” time and approaches the half of wall thickness for as short as 55–65 min, determining by this the future prognosis of the mechanical restitution of contractility in the infarcted region. It is suggested the CE-MRI of the heart must be carried out in every patient in whom due to AMI the thrombolytic therapy and/or percutaneous coronary angioplasty has been done, for unbiased myocardium-focused control of efficiency of restoration of coronary arterial patency.