Delayed Enhancement Magnetic Resonance Imaging Research Articles

ISCHEMIC OR NON-ISCHEMIC MYOCARDIAL SCAR QUANTIFICATION PREDICTS FUTURE ARRHYTHMIC EVENTS IN CANDIDATES FOR PRIMARY PREVENTION ICD

Background: Patients with ischemic cardiomyopathy (ICM) and non-ischemic cardiomyopathy (NICM) are at risk of sudden cardiac arrest (SCA). Delayed enhancement (DE) MRI may identify sub-populations at higher risk of arrhythmic events. This study evaluates the role of DE MRI scar quantification for the prediction of future events in both ICM and NICM populations. Methods: 125 consecutive patients referred for cardiac MRI to determine ICD eligibility (ICM = 61 pts, NICM =64 pts) were enrolled. DE MRI was done in a standard fashion and signal threshold analysis blindly performed. Total scar was defined as any signal ≥2SD above normal reference myocardium, while the difference between 3 and 5SD thresholds being defined as “borderzone”. All patients were prospectively followed for the primary combined endpoint of appropriate ICD therapy or SCA. A composite secondary endpoint of major adverse events (SCA, appropriate ICD therapy and all-cause mortality) was also evaluated. Results: The mean age and EF was 61.4±11.2 yo and 26.5±7.5% (range 8.9 to 40%), respectively. A total of 76 pts received an ICD. During a median follow-up of 412±191days, 16 patients (13%) had a primary endpoint (15 ICD therapies and 1 aborted SCA). An additional 6 patients had death from any cause contributing to the secondary endpoint. The mean total scar mass was significantly higher in pts with a primary outcome (65.1±27.8 g vs. 31.3±18.7 g, p<0.001) or secondary outcome (54.5±29.6 g vs. 31.6±19.1 g, p<0.001). Similarly, the borderzone mass was higher in pts with a primary event (25.3±10.8g vs. 18.3±9.8g, p=0.009) or secondary event (23.7±10.5 g vs. 18.2±9.9g p=0.02). ROC analysis revealed that total scar mass had the greatest AUC values of 0.85 (0.73~0.96, p<0.001) and 0.74 (0.63~0.86, P<0.001) for primary and secondary events, respectively. Only total scar mass remained predictive of the primary or secondary outcome in multivariate analysis. In subgroup analysis of both ICM and NICM patients, total scar mass remained the sole predictor of adverse events. Conclusion: Total scar mass predicts arrhythmic events in patients being considered for primary prevention ICD irrespective of ischemic or nonischemic etiology.

MRI of Coronary Wall Remodeling in a Swine Model of Coronary Injury Using an Elastin-Binding Contrast Agent

The extracellular matrix (ECM) plays an important role in the pathogenesis of atherosclerosis and in-stent restenosis. Elastin is an essential component of the ECM. ECM degradation can lead to plaque destabilization, whereas enhanced synthesis typically leads to vessel wall remodeling resulting in arterial stenosis or in-stent restenosis after stent implantation. The objective of this study was to demonstrate the feasibility of MRI of vascular remodeling using a novel elastin-binding contrast agent (BMS-753951). Coronary injury was induced in 6 pigs by endothelial denudation and stent placement. At day 28, delayed-enhancement MRI coronary vessel wall imaging was performed before and after injection of gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA). Two days later, DE-MRI was repeated after administration of BMS-753951. Contrast-to-noise-ratio and areas of enhancement were determined. Delayed-enhancement MRI with BMS-753951 caused strong enhancement of the aortic, pulmonary artery, and injured coronary artery walls, whereas Gd-DTPA did not. Delayed-enhancement MRI of the stented coronary artery with BMS-753951 yielded a 3-fold higher contrast-to-noise-ratio when compared with the balloon-injured and control coronary artery (21±6 versus 7±3 versus 6±4; P<0.001). The area of enhancement correlated well with the area of remodeling obtained from histological data (R(2)=0.86, P<0.05). We demonstrate the noninvasive detection and quantification of vascular remodeling in an animal model of coronary vessel wall injury using an elastin-specific MR contrast agent. This novel approach may be useful for the assessment of coronary vessel wall remodeling in patients with suspected coronary artery disease. Further studies in atherosclerotic animal models and degenerative ECM disease are now warranted.

Myocardial fibrosis is not associated with reduced quality of life in patients with dilated or hypertrophic cardiomyopathy

Background and objectives Patients with Dilated Cardiomyopathy (DCM) and Hypertrophic Cardiomyopathy (HCM) frequently demonstrate non-ischemic pattern myocardial fibrosis (MF) on delayed enhancement magnetic resonance imaging (DE-MRI). The clinical significance of this finding with respect to impact on Quality of Life (QOL) is poorly understood. In this study we identify the prevalence of MF in patients with HCM and DCM and assess its relationship with standardized measures of QOL. Methods One-hundred and seven consecutive patients with either DCM (n=50) or HCM (n=57) referred for MRI evaluation were identified. DCM was defined as a LVEF 3SD above reference myocardium) using validated commercial software. Results

Impact of right ventricular dysfunction assessed by cardiac magnetic resonance imaging on prediction of short term and long term prognoses after acute inferior myocardial infarction

Method We analyzed 20 consecutive patients (14 male; age 64 ± 12 years) with first acute inferior MI due to proximal right coronary lesion. All patients were assessed with cardiac MRI after primary percutaneous coronary intervention and followed up for a median (25, 75 percentiles) of 6 (5, 6) months. We assessed the association of RV function with length of cardiac care unit (CCU) treatment as an index of short-term prognosis by using multiple regression analysis, and used Kaplan-Meier analysis to demonstrate the association of RV dysfunction with occurrence of heart failure (HF) after discharge as an index of long-term prognosis. Results RV involvement was diagnosed with delayed enhancement MRI in 11 patients (55%). Patients with RV involvement had lower RV ejection fraction (EF) (32.4 ± 8.6 % vs 43.2 ± 7.7 %; p = 0.009) and longer duration of CCU treatment (5.3 ± 2.3 days vs 3.5 ± 1.9 days; p = 0.038) than those without RV involvement, although there were no significant differences regarding clinical, angiographic and the other MRI characteristics such as left ventricular parameters. By multiple regression analysis, RVEF was an independent predictor of length of CCU treatment (standardized partial regression coefficient -0.799, partial regression coefficient -0.127; 95% confidence interval -0.222 to -0.031; p = 0.017). KaplanMeier analysis demonstrated that RVEF <30% was associated with increased occurrence of HF in chronic phase (p = 0.003).

3D visualization of myocardial substrate using Delayed Enhancement MRI for pre-planning and guidance of ablation procedures of ventricular tachycardia

Background In patients with prior myocardial infarction, intra-scar surviving fibers may create conducting channels (CC) which are the substrate of most sustained monomorphic ventricular tachycardias (VT). These channels can be identified by endocardial voltage mapping. Recent studies show high correlation between information from endocardial voltage mapping and delayed-enhanced MRI (DE-MRI) images.

An automatic segmentation for improved visualization of atrial ablation lesions using magnetic resonance imaging

Background Delayed-enhancement (DE) MRI is an effective technique for imaging left atrial (LA) ablation lesions following radio-frequency ablation for atrial fibrillation (AF). Existing techniques for segmentation/visualization of lesions require manual interaction of an expert user making them prone to high observer variability. Oakes et al.[1] applied thresholding on the intensity histogram of the manually-outlined atrial wall. Peters et al.[2] used maximum intensity projections (MIPs) to generate volume lesion visualizations for expert-user interpretation. Knowles et al.[3] employed MIP followed by userinteractive thresholding for lesion surface visualization.

The utility of delayed-enhancement and t2-weighted cardiovascular mri for predicting clinical outcomes in patients at high risk for cardiac sarcoidosis

The utility of delayed-enhancement (DE) has been extensively studied in patients with sarcoidosis who are asymptomatic or at low risk for cardiac involvement. However, there is lack of data regarding the utility of DE in patients with sarcoidosis who present with high grade cardiovascular symptoms. Also, the utility of T2-weighted imaging has not been evaluated in these patients.

Association of Left Atrial Fibrosis Detected by Delayed-Enhancement Magnetic Resonance Imaging and the Risk of Stroke in Patients With Atrial Fibrillation

This study tried to determine the association between left atrial (LA) fibrosis, detected using delayed-enhanced magnetic resonance imaging (DE-MRI), and the CHADS(2) score (point system based on individual clinical risk factors including congestive heart failure, hypertension, age, diabetes, and prior stroke) variables, specifically stroke. In patients with atrial fibrillation (AF), conventional markers for the risk of stroke base their higher predictive effect on clinical features, particularly previous stroke history, and not individual LA pathophysiological properties. We aimed to determine the association between LA fibrosis, detected using DE-MRI, and the CHADS(2) score variables, specifically stroke. Patients with AF who presented to the AF clinic and received a DE-MRI of the LA were evaluated. Their risk factor profiles, including a CHADS(2) score, were catalogued. The degree of LA fibrosis was determined as a percentage of the LA area. Any history of previous strokes, warfarin use, or cerebrovascular disease was recorded. A total of 387 patients, having a mean age of 65 ± 12 years, 36.8% female, were included in this study. A history of previous stroke was present in 36 (9.3%) patients. Those patients with previous strokes had a significantly higher percentage of LA fibrosis (24.4 ± 12.4% vs. 16.2 ± 9.9%, p < 0.01). A larger amount of LA fibrosis was also seen in those patients with a higher CHADS(2) score (≥ 2: 18.7 ± 11.4 vs. <2: 14.7 ± 9.2, p < 0.01). A logistic regression analysis of all variables except strokes (CHAD score) demonstrated that LA fibrosis independently predicted cerebrovascular events (p = 0.002) and significantly increased the predictive performance of the score (area under the curve = 0.77). Our preliminary, multicenter results suggest DE-MRI-based detection of LA fibrosis is independently associated with prior history of strokes. We propose that the amount of DE-MRI-determined LA fibrosis could represent a marker for stroke and a possible therapeutic target with potential applicability for clinical treatment for patients with AF.

Improved Detection of Subendocardial Hyperenhancement in Myocardial Infarction Using Dark Blood–Pool Delayed Enhancement MRI

Delayed enhancement MRI using fast segmented k-space inversion recovery (IR) gradient-echo imaging is a well established "bright-blood" technique for identifying myocardial infarction and is used as the reference standard sequence in this study. The purpose of this study was to validate a recently developed dark blood-pool delayed enhancement technique in a porcine animal model, evaluate its performance in human patients, and quantify its performance compared with the reference standard in both. In an animal study, the reference standard and dark blood-pool delayed enhancement were assessed in three pigs with induced myocardial infarction. In a human study, 26 patients, 31-81 years old (19 men and seven women), with a known history of myocardial infarction were imaged using the reference standard and dark blood-pool delayed enhancement. Contrast-to-noise ratio (CNR), signal intensity ratio, signal-to-noise ratio (SNR), and qualitative scores of hyperenhancement were recorded. Measurements were compared using paired samples t test and Wilcoxon's signed rank test. In the animal study, the mean CNR of infarct to blood pool was 11 times higher for dark blood-pool delayed enhancement than for the reference standard. The mean SNR was 4.4 times higher for the reference standard. In the human study, the mean CNR and signal intensity ratio of hyperenhancing myocardium to the blood pool were 1.9 (p = 0.04) and 5.5 (p < 0.01) times higher, respectively, for dark blood-pool delayed enhancement compared with reference standard. The mean CNR and signal intensity ratio of hyperenhancing myocardium to normal myocardium and SNR were 2.8 (p < 0.01), 1.3 (p = 0.07), and 2.8 (p < 0.01) higher, respectively, for the reference standard. Qualitative analysis identified seven extra segments with grade 1 scars using dark blood-pool delayed enhancement (p < 0.01). Dark blood-pool delayed enhancement is complementary to the reference standard. It can detect more subendocardial foci of hyperenhancement, thus potentially identifying more infarcts and changing patient management.

Unrecognized myocardial scars detected by delayed–enhanced MRI are associated with increased levels of NT-proBNP

Patients with unrecognized myocardial infarction (UMI) scars detected by delayed-enhanced magnetic resonance imaging (DE-MRI) have a decreased left ventricular ejection fraction and an increased left ventricular mass. N-terminal pro-brain natriuretic peptide (NT-proBNP) is a marker of heart failure, and troponin I (TnI) is a marker of myocardial injury. The primary aim of this study was to investigate whether NT-proBNP plasma levels (in addition to ejection fraction) differed in patients with UMI scars compared with normal participants. The second aim was to compare whether the TnI levels differed in those two groups. Data from the Prospective Investigation of Vasculature in Uppsala Seniors study were used. The participants who had undergone cardiac MRI were included in this study (n=248). Patients were divided into three groups depending on the existence of a myocardial infarction (MI) scar in DE-MRI and their earlier history of MI. In all the patients, a peripheral blood sample was collected and the plasma levels of NT-proBNP and TnI were determined. Patients with UMI had higher plasma levels of NT-proBNP (median 140.2 ng/l; 25th-75th percentiles: 79-225.5) than no-MI participants (median 94.9 ng/l; 25th-75th percentiles: 59.2-144.2; P=0.01) and lower levels than patients with recognized MI (median 310.4 ng/l; 25th-75th percentiles: 122.6-446.5; P=0.02). Plasma TnI values did not differ among the three groups. Patients with UMI scars detected by DE-MRI have increased plasma levels of NT-proBNP that is known to correlate with an increased risk of future cardiovascular adverse events.

Early Experience with Delayed-Enhancement Magnetic Resonance Imaging for Atrial Fibrillation Ablation

Early Experience with Delayed-Enhancement Magnetic Resonance Imaging for Atrial Fibrillation Ablation

Intracoronary versus intravenous bolus abciximab application in patients with ST-elevation myocardial infarction undergoing primary percutaneous coronary intervention: 6-month effects on infarct size and left ventricular function

Administration of abciximab during primary percutaneous coronary intervention (PCI) reduces major adverse cardiac events (MACE) in patients with ST-elevation myocardial infarction (STEMI). Intracoronary (IC) abciximab bolus application during PCI results in high local drug concentration, improved perfusion, reduction of infarct size, and less microvascular obstruction early after infarction. Aim of this study was to investigate whether the early benefits of an IC abciximab administration in STEMI patients undergoing PCI are sustained at 6 months. We performed 6-month follow-up of 154 STEMI patients undergoing PCI, who were randomised to either IC (n = 77) or intravenous (IV) (n = 77) bolus abciximab administration with subsequent 12-h intravenous infusion. The primary endpoint was infarct size at 6-month follow-up as assessed by delayed enhancement magnetic resonance imaging. Clinical end points were MACEs within 6 months after infarction. The median infarct size after 6 months was significantly reduced in the IC abciximab group (16.7 vs. 24.1%, p = 0.002). A significant recovery of LV function was only observed in the IC abciximab group (p < 0.001), and IC abciximab group patients had significantly less adverse remodelling as compared to standard IV abciximab treatment (p = 0.03). These beneficial effects also translated into a strong trend towards a reduced MACE rate in the IC abciximab group at 6-month follow-up (10 vs. 21%, p = 0.07). Intracoronary abciximab application in STEMI patients undergoing PCI is superior to standard IV treatment with respect to infarct size, recovery of LV function and reverse remodelling 6 months after infarction.

Left Ventricular Basal Myocardial Scarring Detected by Delayed Enhancement Magnetic Resonance Imaging Predicts Outcomes After Surgical Therapies for Patients With Ischemic Mitral Regurgitation and Left Ventricular Dysfunction

Treatment of heart failure by surgical procedures such as mitral annuloplasty and left ventricular (LV) restoration is increasingly applied to patients with ischemic mitral regurgitation (IMR) and LV dysfunction. The clinical efficacy of delayed enhancement magnetic resonance imaging (DE-MRI) was studied to predict LV functional recovery and adverse outcomes after these therapies. In 26 patients with IMR and a LV ejection fraction < 40%, DE-MRI was performed before the operation and the percentage of regional myocardial scarring was quantified at the basal, mid, and apical LV. Calculated percentage of fibrosis was 12 ± 12% at the base, 24 ± 15% at the mid, and 35 ± 31% at the apical LV. The degree of basal fibrosis was a significant predictor of less improvement of LV ejection fraction and postoperative restrictive diastolic filling. A linear correlation was noted between basal fibrosis and postoperative ejection fraction (P = 0.001, R = -0.61), the early to late mitral valve flow ratio (P = 0.0005, R = 0.66), and deceleration time (P = 0.01, R = -0.51). Logistic regression analysis demonstrated that the percentage of basal fibrosis was the independent predictor of postoperative adverse clinical outcomes (odds ratio, 1.26; P = 0.04). In patients undergoing surgical heart failure therapy for IMR, the extent of basal fibrosis characterized by DE-MRI might be a useful predictor of postoperative LV systolic and diastolic functional recovery and postoperative adverse outcomes.

Echocardiographic left atrial reverse remodeling after catheter ablation of atrial fibrillation is predicted by preablation delayed enhancement of left atrium by magnetic resonance imaging

Atrial fibrosis is a hallmark of atrial structural remodeling (SRM) and leads to structural and functional impairment of left atrial (LA) and persistence of atrial fibrillation (AF). This study was conducted to assess LA reverse remodeling after catheter ablation of AF in mild and moderate-severe LA SRM. Catheter ablation was performed in 68 patients (age 62 ± 14 years, 68% males) with paroxysmal (n = 26) and persistent (n = 42) AF. The patients were divided into group 1 with mild LA SRM (<10%, n = 31) and group 2 with moderate-severe LA SRM (>10%, n = 37) by delayed enhancement magnetic resonance imaging (DEMRI). Two-dimensional echocardiography, LA strain, and strain rate during left ventricular systole by velocity vector imaging were performed pre and at 6 ± 3 months postablation. The long-term outcome was monitored for 12 months. Patients in group 1 were younger (57 ± 15 vs 66 ± 13 years, P = .009) with a male predominance (80% vs 57%, P < .05) as compared to group 2. Postablation, group 1 had significant increase in average LA strain (Δ↑: 14% vs 4%, P < .05) and strain rate (Δ↑: 0.5 vs 0.1 cm/s, P < .05) as compared to group 2. There was a trend toward more patients with persistent AF in group 2 (68% vs 55%, P = .2), but it was not statistically significant. Group 2 had more AF recurrences (41% vs 16%, P = .02) at 12 months after ablation. Mild preablation LA SRM by DEMRI predicts favorable LA structural and functional reverse remodeling and long-term success after catheter ablation of AF, irrespective of the paroxysmal or persistent nature of AF.

Impact of early abciximab administration on infarct size in patients with ST-elevation myocardial infarction

BackgroundEarly abciximab administration in patients requiring transportation to undergo primary percutaneous coronary intervention (PPCI) has been reported to improve clinical outcome. We aimed to verify whether early administration leads to reduced infarct size (IS), assessed by delayed-enhancement magnetic resonance imaging (DE-MRI). MethodsWe randomized 110 patients with acute myocardial infarction with symptom-to-diagnosis time <6h to either early (55 patients) or late (55 patients) abciximab administration. DE-MRI was performed at 4days and 6months. The primary end point was IS at 6months. Secondary end points were the rate of ST-segment elevation resolution ≥50% (STR) at 60min after PPCI, the extent of microvascular obstruction at 4days, and the change in IS and transmurality at 6months vs. 4days. ResultsDE-MRI was performed in 103 patients after 4days, and in 87 at 6months. The mean IS at 6months was 13.8±9.0% in the early vs. 13.0±9.9% in the Late group (P>0.2). Similarly, microvascular obstruction and the change in IS were not significantly different. The Early group showed a significantly higher STR (94.5% vs. 80.0%, P=0.04) and a larger reduction in infarct transmurality (−9.2±7.0% vs. −5.9±6.4%; P=0.03), while a larger reduction in IS was observed only in patients with ECG-to-Cath Lab time >60min. ConclusionsEarly abciximab administration did not lead to a smaller IS at 6-month DE-MRI, and was associated with a significant reduction in IS and transmurality only in patients with longer transportation time, warranting further investigation in this patient subset.

Effect of postconditioning on infarct size in patients with ST elevation myocardial infarction

BackgroundSmall studies suggest that postconditioning reperfusion interrupted by brief repetitive cycles of reocclusions, may protect the myocardium in the clinical setting.ObjectiveTo test the hypothesis that postconditioning limits infarct size in...

Determinants of Postinfarction Ventricular Tachycardia

Structural factors contributing to the development of postinfarction ventricular tachycardia (VT) are unclear. The purpose of this study was to analyze infarct architecture and electrogram characteristics in patients with and without inducible VT and to identify correlates of postinfarction VT. Twenty-four postinfarction patients (median age, 64 [53, 70] years) were referred for radiofrequency catheter ablation of VT (n = 12) or frequent symptomatic premature ventricular contractions (PVCs) (n = 12). Delayed-enhanced (DE) MRI was obtained before ablation. Electroanatomical mapping was performed and scar area and electrogram characteristics of the scar tissue compared in patients with and without inducible VT. The median ejection fraction in patients with and without inducible VT was 27% (22%, 43%) and 43% (40%, 47%), respectively (P = 0.085). Subendocardial infarct area determined by DE-MRI was larger in patients with inducible VT (43 [38, 62] cm(2)) than in those with noninducible VT (8 [4, 11] cm(2); P = 0.002), and unipolar and bipolar voltages on electroanatomical maps were significantly lower in patients with inducible VT (both P<0.05). An infarct volume of >14% identified 11 of 12 patients with inducible VT (area under the curve, 0.94; P = 0.007). On electroanatomical mapping, distinct sites with isolated potentials (IPs) were more prevalent in patients with inducible VT than in those without (13.2% versus 1.1% of points within scar; P < 0.001). The number of inducible VTs correlated with the number of distinct sites with IPs (R = 0.87; P<0.0001). Scar tissue in postinfarction patients with inducible VT shows quantitative and qualitative differences from scars in patients without inducible VT. Scar size and IPs are correlated with VT inducibility.

E0145 Study of MRI in tracking magnetically labelled mesenchymal stem cells

ObjectiveTo investigate the potential ability of MRI in tracking magnetically labelled mesenchymal stem cells (MR-MSCs) in a swine myocardial infarction (MI) model.MethodsAdult Chinese mini pigs (n=6) were subjected to open-chest...

Atrial Fibrosis Helps Select the Appropriate Patient and Strategy in Catheter Ablation of Atrial Fibrillation: A DE-MRI Guided Approach

MRI for AF Patient Selection and Ablation Approach. Left atrial (LA) fibrosis and ablation related scarring are major predictors of success in rhythm control of atrial fibrillation (AF). We used delayed enhancement MRI (DE-MRI) to stratify AF patients based on pre-ablation fibrosis and also to evaluate ablation-induced scarring in order to identify predictors of a successful ablation. One hundred and forty-four patients were staged by percent of fibrosis quantified with DE-MRI, relative to the LA wall volume: minimal or Utah stage 1; <5%, mild or Utah stage 2; 5-20%, moderate or Utah stage 3; 20-35%, and extensive or Utah stage 4; >35%. All patients underwent pulmonary vein (PV) isolation and posterior wall and septal debulking. Overall, LA scarring was quantified and PV antra were evaluated for circumferential scarring 3 months post ablation. LA scarring post ablation was comparable across the 4 stages. Most patients had either no (36.8%) or 1 PV (32.6%) antrum circumferentially scarred. Forty-two patients (29%) had recurrent AF over 283 ± 167 days. No recurrences were noted in Utah stage 1. Recurrence was 28% in Utah stage 2, 35% in Utah stage 3, and 56% in Utah stage 4. Recurrence was predicted by circumferential PV scarring in Utah stage 2 and by overall LA wall scarring in Utah stage 3. No recurrence predictors were identified in Utah stage 4. Circumferential PV antral scarring predicts ablation success in mild LA fibrosis, while posterior wall and septal scarring is needed for moderate fibrosis. This may help select the proper candidate and strategy in catheter ablation of AF.

Use of Imaging Techniques to Guide Catheter Ablation Procedures

Paralleling the growth in ablation of complex arrhythmias such as atrial fibrillation and ventricular tachycardia, advanced imaging technologies are becoming more commonplace in the care of the electrophysiology patients. Although intracardiac ultrasound remains the most commonly used imaging technique, advances in real-time MRI may change this in the future. We discuss the current use of intracardiac ultrasound, CT, including rotational angiography, MRI, with an emphasis on delayed-enhancement MRI, and positron emission tomography-CT in advanced ablation procedures. Image integration is emphasized and new technologies such as direct endoscopic visualization are discussed.