Prognostic significance of infarct core pathology in ST-elevation myocardial infarction survivors revealed by non-contrast T1 mapping cardiac magnetic resonance

Background: Myocardial longitudinal relaxation time (T1, ms) is a fundamental magnetic property of tissue that is related to water content and mobility. The pathophysiological and prognostic importance of native myocardial T1 values in acute ST-elevation myocardial infarction (STEMI) patients is unknown. We aimed to assess the clinical significance of infarct core native T1. Methods: We performed a prospective single center cohort study in reperfused STEMI patients who underwent CMR 2 days and 6 months post-MI. Native T1 CMR (MOLLI investigational prototype sequence: 3 (3) 3 (3) 5) was measured in myocardial regions-of-interest. The infarct territory and microvascular obstruction (MVO) were depicted with late gadolinium enhancement CMR. Adverse remodeling was defined as an increase in LV end-diastolic volume (LVEDV) ≥ 20% at 6 months. All-cause death or heart failure hospitalization was a pre-specified outcome that was assessed during follow-up. Results: 300 STEMI patients (mean±SD age 59±12 years, 74% male, 114 with anterior STEMI) gave informed consent and had CMR (14 July 2011 - 22 November 2012). Of these, 288 STEMI patients had evaluable T1 maps. Infarct size was 18 ±14% of LV mass. One hundred and forty five (50%) of 288 patients had late MVO, whereas 160 (56%) patients had infarct core pathology revealed by native T1. Native T1 within the infarct core (996.9±57.3; p<0.01) was higher than in the remote zone (961±25 ms; p<0.01) but lower than in the area-at-risk (1097 ±52 ms). In multivariable linear regression, native T1 in the infarct core was negatively associated with age, initial systolic blood pressure, TIMI coronary flow grade at initial angiography, Killip class at presentation and neutrophil count (all p<0.05), independent of LVEF, LVEDV or infarct size. At 6 months, LVEDV increased by 5 (25) ml (n=262 patients with evaluable data). Adverse remodeling occurred in 30 (12%) patients and 23 (76.7%) of these patients MVO at baseline. T1 in the infarct core was a multivariable predictor of adverse remodeling (-0.01 (-0.02, -0.00); p=0.048). 288 (100%) patients were followed-up for a median of 845 days. Thirty (10.4%) patients died or experienced a heart failure event and 13 (4.5%) of these patients experienced the event post-discharge. Infarct core native T1 predicted all-cause death or heart failure post-discharge (hazard ratio 0.969, 95% CI 0.953, 0.985; p<0.001) including after adjustment for LVEF (p<0.001) and LVEDV at baseline (p<0.001), and was comparable with MVO

Myocardial hemorrhage after acute reperfused ST-segment-elevation myocardial infarction:Relation to microvascular obstruction and prognostic significance

Background—The success of coronary reperfusion therapy in ST-segment–elevation myocardial infarction (MI) is commonly limited by failure to restore microvascular perfusion. Methods and Results—We performed a prospective cohort study in patients with reperfused ST-segment–elevation MI who underwent cardiac magnetic resonance 2 days (n=286) and 6 months (n=228) post MI. A serial imaging time-course study was also performed (n=30 participants; 4 cardiac magnetic resonance scans): 4 to 12 hours, 2 days, 10 days, and 7 months post reperfusion. Myocardial hemorrhage was taken to represent a hypointense infarct core with a T2* value of <20 ms. Microvascular obstruction was assessed with late gadolinium enhancement. Adverse remodeling was defined as an increase in left ventricular end-diastolic volume ≥20% at 6 months. Cardiovascular death or heart failure events post discharge were assessed during follow-up. Two hundred forty-five patients had evaluable T2* data (mean±age, 58 [11] years; 76% men). Myocardial hemorrhage 2 days post MI was associated with clinical characteristics indicative of MI severity and inflammation. Myocardial hemorrhage was a multivariable associate of adverse remodeling (odds ratio [95% confidence interval]: 2.64 [1.07–6.49]; P=0.035). Ten (4%) patients had a cardiovascular cause of death or experienced a heart failure event post discharge, and myocardial hemorrhage, but not microvascular obstruction, was associated with this composite adverse outcome (hazard ratio, 5.89; 95% confidence interval, 1.25–27.74; P=0.025), including after adjustment for baseline left ventricular end-diastolic volume. In the serial imaging time-course study, myocardial hemorrhage occurred in 7 (23%), 13 (43%), 11 (33%), and 4 (13%) patients 4 to 12 hours, 2 days, 10 days, and 7 months post reperfusion. The amount of hemorrhage (median [interquartile range], 7.0 [4.9–7.5]; % left ventricular mass) peaked on day 2 (P<0.001), whereas microvascular obstruction decreased with time post reperfusion. Conclusions—Myocardial hemorrhage and microvascular obstruction follow distinct time courses post ST-segment–elevation MI. Myocardial hemorrhage was more closely associated with adverse outcomes than microvascular obstruction

Remote Zone Extracellular Volume and Left Ventricular Remodeling in Survivors of ST-Elevation Myocardial Infarction

The natural history and pathophysiological significance of tissue remodeling in the myocardial remote zone after acute ST-elevation myocardial infarction (STEMI) is incompletely understood. Extracellular volume (ECV) in myocardial regions of interest can now be measured with cardiac magnetic resonance imaging. Patients who sustained an acute STEMI were enrolled in a cohort study (BHF MR-MI [British Heart Foundation Magnetic Resonance Imaging in Acute ST-Segment Elevation Myocardial Infarction study]). Cardiac magnetic resonance was performed at 1.5 Tesla at 2 days and 6 months post STEMI. T1 modified Look-Locker inversion recovery mapping was performed before and 15 minutes after contrast (0.15 mmol/kg gadoterate meglumine) in 140 patients at 2 days post STEMI (mean age: 59 years, 76% male) and in 131 patients at 6 months post STEMI. Remote zone ECV was lower than infarct zone ECV (25.6±2.8% versus 51.4±8.9%; P<0.001). In multivariable regression, left ventricular ejection fraction was inversely associated with remote zone ECV (P<0.001), and diabetes mellitus was positively associated with remote zone ECV (P=0.010). No ST-segment resolution (P=0.034) and extent of ischemic area at risk (P<0.001) were multivariable associates of the change in remote zone ECV at 6 months (ΔECV). ΔECV was a multivariable associate of the change in left ventricular end-diastolic volume at 6 months (regression coefficient [95% confidence interval]: 1.43 (0.10–2.76); P=0.036). ΔECV is implicated in the pathophysiology of left ventricular remodeling post STEMI, but because the effect size is small, ΔECV has limited use as a clinical biomarker of remodeling

Defining myocardial tissue abnormalities in end-stage renal failure with cardiac magnetic resonance imaging using native T1 mapping

Noninvasive quantification of myocardial fibrosis in end-stage renal disease is challenging. Gadolinium contrast agents previously used for cardiac magnetic resonance imaging (MRI) are contraindicated because of an association with nephrogenic systemic fibrosis. In other populations, increased myocardial native T1 times on cardiac MRI have been shown to be a surrogate marker of myocardial fibrosis. We applied this method to 33 incident hemodialysis patients and 28 age- and sex-matched healthy volunteers who underwent MRI at 3.0T. Native T1 relaxation times and feature tracking–derived global longitudinal strain as potential markers of fibrosis were compared and associated with cardiac biomarkers. Left ventricular mass indices were higher in the hemodialysis than the control group. Global, Septal and midseptal T1 times were all significantly higher in the hemodialysis group (global T1 hemodialysis 1171 ± 27 ms vs. 1154 ± 32 ms; septal T1 hemodialysis 1184 ± 29 ms vs. 1163 ± 30 ms; and midseptal T1 hemodialysis 1184 ± 34 ms vs. 1161 ± 29 ms). In the hemodialysis group, T1 times correlated with left ventricular mass indices. Septal T1 times correlated with troponin and electrocardiogram-corrected QT interval. The peak global longitudinal strain was significantly reduced in the hemodialysis group (hemodialysis -17.7±5.3% vs. -21.8±6.2%). For hemodialysis patients, the peak global longitudinal strain significantly correlated with left ventricular mass indices (R = 0.426), and a trend was seen for correlation with galectin-3, a biomarker of cardiac fibrosis. Thus, cardiac tissue properties of hemodialysis patients consistent with myocardial fibrosis can be determined noninvasively and associated with multiple structural and functional abnormalities

Medically Accurate Four-Dimensional Digital Organ Models for Education: A Workflow and Visualisation Pipeline for Modelling the Heart

Background: Digital models are an increasingly important teaching and learning tool in medical education. Many earlier 3D (three-dimensional) models have been constructed by merging data from different subjects into one generic approximation. These approaches result in averaged representations that are limited in accuracy and ability to reproduce individual variation. Alternatively, techniques used to illustrate medically accurate single patient data have been typically challenging for the novice viewers to appreciate. We present a rationale and one possible workflow for producing anatomically and physiologically accurate digital models of organs. As an example from our recent work, we describe a visualisation pipeline for a spatially calibrated 4D (3D +time) model of the heart. Methods: A 55 year old male, with a kidney function impairment, underwent a free breathing cardiac magnetic resonance (MR) at 3.0 Tesla. A developmental 3D radial sampling acquisition protocol, with intravenous ferumoxytol (Rienso®, Tradeka Pharma) contrast, was used for data acquisition. The data was reconstructed offline, using a three stage workflow defined by Deng et al; including a respiratory signal extraction, sorting data into 16 phases of cardiac cycle and image reconstruction on a per-phase basis. The volumetric dataset was then used to evaluate two study aims. Firstly, the feasibility of producing a 4D model with a commonly available medical visualisation software packages was explored. Secondly, a simplified visualisation pipeline was defined for producing 4D visualisations of organs for medical education. Results: The use of radial acquisition scheme (sampling a signal along spikes around the k-space centre, instead of parallel rows as in a traditional plane based MR) allowed accelerated image acquisition, higher spatial resolution and introducing time as a new parameter (i.e. 4D). We found that OsiriX provided the best compatibility with file format requirements of common digital education software packages. As an open source application, its adaptability was essential for novel 4D models. A visualisation pipeline was optimised for OsiriX Lite (Pixmeo SARL, version 8.5.1) and can be used to illustrate medically accurate digital 4D models of organ systems. Our spatially calibrated model of the heart is optimised for illustrating intrinsic cardiac contraction. It provides a good contrast between the blood pool and other tissues, while further optimisation is needed for definition of the epicardial contours and small vessels. Conclusions: Introducing time as the fourth parameter to the medically accurate digital models of organs is useful for educational applications. These models allow users to appreciate real anatomy and physiology of internal organs in vivo, while reducing boundaries of traditional teaching settings and encouraging the use of effective educational strategies. In our specific example, visualising the intrinsic cardiac contraction has been challenging with the earlier image processing approaches. For a novice viewer, the myocardial contraction may have gotten masked by the bulk respiratory movement in the chest cavity, due to the pulsatile blood flow in the vasculature and because of ‘through plane’ motion in the traditional acquisitions (plane based +time). While the proposed workflow and visualisation pipeline produce a novel educational 4D model of the heart, the same approach can be easily expanded also to other organ systems

Quasistationaere Messungen des Stoppverhaltens von Motorgueterschiffsverbaenden Schlussbericht

Available from TIB Hannover: RN2805(1319) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman