Late Gadolinium Enhancement Signal Research Articles

Conditions for late gadolinium enhancement MRI in myocardial infarction model rats that better reflect microscopic tissue staining

Late gadolinium enhancement (LGE) is a widely used magnetic resonance imaging method for assessing cardiac disease. However, the relationship between different LGE signal thresholds and microscopic tissue staining images is unclear. In this study, we performed cardiovascular MRI on myocardial infarction (MI) model rats and evaluated the relationship between LGE with different signal thresholding methods and tissue staining images. We prepared 16 rats that underwent MRI 14–18 days following a surgery to create an MI model. We captured cine and LGE images of the cardiac short-axis and longitudinal two- and four-chamber views. The mean ± 2SD, ± 3SD, and ± 5SD of the pixel values in the non-infarcted area were defined as the LGE area. We compared areas of Sirius red staining, determined by the color tone, with their respective LGE areas at end-diastole and end-systole. We observed that the LGE area calculated as the mean ± 2SD of the non-infarcted area at end-diastole demonstrated a significant positive correlation with the area of Sirius red staining (Pearson’s correlation coefficient in both: 0.81 [p < 0.01]). Therefore, the LGE area calculated as the mean ± 2SD of the non-infarcted area at end-diastole best reflected the MI area in tissue staining.

PO-05-192 LOCAL HETEROGENEITY OF LATE GADOLINIUM ENHANCEMENT PREDICTS VENTRICULAR ARRHYTHMIA IN HYPERTROPHIC CARDIOMYOPATHY

Hypertrophic cardiomyopathy (HCM) is the most common cause of sudden cardiac death in young people. Despite recent advances in risk stratification using cardiac magnetic resonance (CMR) imaging, risk prediction remains suboptimal. Improved risk stratification is therefore warranted. Whether local heterogeneity of Late Gadolinium Enhancement (LGE) signal is associated with ventricular arrhythmia remains unknown. To determine whether local heterogeneity of LGE signal on CMR predicts ventricular arrhythmia and appropriate shocks after implantable cardioverter defibrillator (ICD) implantation in patients with HCM. Local heterogeneity was quantified by LGE-CMR signal dispersion score and compared with cardiovascular outcomes in 179 HCM patients who underwent ICD implantation. The primary outcome was appropriate ICD shocks. During a median follow-up time of 7.3 years the event rate was 0.015 per person year. History of ventricular arrhythmia (HR 9.413, p<0.001) and sudden cardiac death (HR 13.82, p<0.001) were associated with receiving an appropriate ICD shock in both univariable and multivariable analyses. History of syncope, family history of sudden cardiac death, non-sustained ventricular tachycardia, left ventricular wall thickness and presence of LGE were not associated with the primary outcome. When compared to patients without ICD shock, patients who received ICD shocks had higher burden of LGE gray zone (16.8±7.5% vs 25.8±3.5% p<0.001) and scar (10.5±6.7% vs 18.7±4.3% p<0.001) on CMR. Importantly, patients with ICD shocks had a higher dispersion score (1.20 vs 0.97, respectively), signifying higher degree of LGE signal heterogeneity (p=0.047). Dispersion score, a marker of local LGE signal heterogeneity of scar and gray zone was associated with a higher burden of ICD shocks in HCM patients who received ICDs. Mechanistically, local LGE signal heterogeneity could represent complex scar. These results may contribute to improved risk stratification for ventricular arrhythmia in HCM patients.

The relationship between the quantitative extent of late gadolinium enhancement and burden of nonsustained ventricular tachycardia in hypertrophic cardiomyopathy: A delayed contrast-enhanced magnetic resonance study.

To examine the relationship between late gadolinium enhancement (LGE) extent and nonsustained ventricular tachycardia (NSVT) characteristics in patients with hypertrophic cardiomyopathy (HCM). NSVT has been shown to be independently associated with sudden cardiac death (SCD) in HCM. Previous studies have found LGE on cardiac magnetic resonance (CMR) to be independently associated with NSVT. Seventy-three patients who had 14-day Holter monitoring for either risk stratification for SCD (n = 62) or evaluation of atrial fibrillation (n = 11) on a CMR study were included. Areas of LGE in left ventricle (LV) were visually identified and analyzed quantitatively for both high (≥6 SD above the mean signal intensity of normal myocardium) and intermediate (≥4 but <6 SD) LGE signal intensity. Patients with more extensive LGE had longer (P = 0.0028) and more frequent (P = 0.02) episodes of NSVT. In univariate analyses, frequency of NSVT was associated with LGE extent (rs = 0.43, P = 0.001), LV ejection fraction (rs = -0.38, P < 0.001), LV mass (rs = 0.32, P = 0.005), LV maximal wall thickness (rs = 0.28, P = 0.016), and left atrium diameter (rs = 0.29, P = 0.001); maximal length of NSVT was associated with LGE extent (rs = 0.52, P < 0.001), LV ejection fraction (rs = -0.44, P < 0.001), LV mass (rs = 0.37, P = 0.001), and left atrium diameter (rs = 0.3, P < 0.001). In multivariable analyses, LGE extent remained the sole variable independently associated with frequency (P = 0.001) and maximal length of episodes of NSVT (P = 0.001). No significant association was found between the rate of NSVT and LGE extent. LGE extent is independently associated with a greater burden and longer episodes of NSVT in HCM. These findings support the association between myocardial fibrosis as represented by LGE and ventricular tachyarrhythmias in HCM.

Visualization of acute edema in the left atrial myocardium after radiofrequency ablation: Application of a novel high-resolution 3-dimensional magnetic resonance imaging sequence

Ablation-induced left atrial (LA) edema may result in procedural failure due to reversible pulmonary vein isolation. Conventional T2-weighted magnetic resonance edema imaging is limited by low spatial resolution. The purpose of this pilot study was to optimize and validate a 3-dimensional (3D) sampling perfection with application-optimized contrasts using different flip-angle evolution (SPACE) sequence for quantification of T2 signal in the LA, and to apply it in recently ablated patients, comparing myocardial edema on T2-SPACE to tissue damage on late gadolinium enhancement (LGE) imaging. Phantom studies were performed to identify 3D-SPACE parameters for optimal contrast between normal and edematous myocardium. Fourteen AF patients were imaged with both 3D-SPACE and dark-blood turbo-spin echo (DB-TSE) to compare image quality and signal intensity between the 2 techniques. Eight patients underwent pre- and postablation 3D-SPACE and 3D-LGE imaging. Ablation points were co-registered with corresponding myocardial sectors, and ablation-induced changes in T2 and LGE signal intensities were measured. Signal-to-noise ratio and contrast-to-noise ratio were higher on SPACE vs DB-TSE (65.5 ± 33.9 vs 35.7 ± 17.9; P=.01; and 59.4 ± 33.0 vs 32.9 ± 17.7; P = .04, respectively). T2-signal correlated well on 3D-SPACE and DB-TSE, such that each unit increase in TSE intensity correlated with a 0.69-unit increase in SPACE intensity (95% confidence interval 0.56-0.82; P <.001). T2 and LGE signal intensities were acutely increased at ablation sites. The extent of postablation edema was higher compared to LGE, although the spatial distribution of hyperenhancement around pulmonary veins seemed similar in both modalities. T2-SPACE can be used to map the extent of acute postablation edema in the thin LA myocardium, with improved resolution and lower artifact compared to traditional DB-TSE.

USE OF CARDIAC MAGNETIC RESONANCE TO IDENTIFY MITRAL VALVE FIBROTIC CHANGES AFTER MYOCARDIAL INFARCTION: VALIDATION IN A LARGE ANIMAL MODEL

Mitral valve (MV) fibrosis and thickening have been described after myocardial infarction (MI), potentially contributing to ischemic mitral regurgitation. There is currently no imaging tool available to explore those changes. MV late gadolinium enhancement (LGE) has been observed retrospectively in post-MI patients with cardiac magnetic resonance (CMR), potentially reflecting MV fibrotic changes. However, MV LGE has never been validated with histopathology. Baseline CMR was performed in 16 sheep. Mid-systolic MV LGE was assessed by CMR (200 milliseconds after QRS to avoid rapid leaflet motion during the acquisition). Metoprolol was given as needed when heart rate was over 100 beats per minute. Inferior MI was induced by surgical coronary ligation in 13 sheep; the survivors (n=9) had repeated CMR 3 months after MI, followed by sacrifice. Three normal animals were used as controls. MV LGE signal was correlated with MV thickness (microscopy) and collagen content (Masson Trichrome). Post-MI sheep had mild decrease in left ventricle ejection fraction (51±4 vs 61±9% at baseline, p=0.02). Among post-MI animals, 3/9 (33%) developed significant (greater than mild) mitral regurgitation. MV LGE was present in 2/16 (13%) sheep at baseline vs 6/9 (66%) after MI (p=0.02). MV LGE was present in all (3/3) post-MI sheep with mitral regurgitation at follow-up, vs 3/6 (50%) of post-MI sheep without regurgitation. By microscopy, post-MI sheep had thicker MV leaflets (p < 0.01), with more collagen positive areas (normalized for leaflet length) vs controls (364±91 vs 195±49 μm2/μm, p=0.01). MV showing LGE were significantly thicker (1057±240 μm vs 656 ±197 μm for those without LGE, p=0.003). In this animal model, MI was associated with thicker mitral valves with increased collagen. Presence of MV LGE was associated with increased MV thickness and all animals with post-MI mitral regurgitation had positive LGE. Development of non-invasive tools to identify MV fibrotic changes can enable the exploration of MV fibrosis in clinical studies.

First-in-Man Analysis of the Relationship Between Electrical Rotors From Noninvasive Panoramic Mapping and Atrial Fibrosis From Magnetic Resonance Imaging in Patients With Persistent Atrial Fibrillation.

Late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) imaging can be used to evaluate characteristics of atrial fibrosis. The novel noninvasive epicardial and endocardial electrophysiology system (NEEES) allows for the identification of sources with rotor activity. This study describes a new technique to examine the relationship between rotors and LGE signal intensity in patients with persistent atrial fibrillation (PERS) scheduled for ablation. Ten consecutive patients underwent pulmonary vein isolation for persistent atrial fibrillation. LGE CMR of both atria was performed, and NEEES-based analysis was conducted to identify rotors. For each mapping point, the intracardiac locations were transferred onto an individual CMR-derived 3-dimensional shell. This allowed the LGE signal intensity to be projected onto the anatomy from the NEEES analysis. NEEES analysis identified a total number of 410 electric rotors, 47.8% were located in the left atrium and 52.2% in the right atrium. Magnetic resonance imaging analysis was performed from 10 right atria and 10 left atria data sets, including 86 axial LGE CMR planes per atrium. The mean LGE burden for left atrium and right atrium was 23.9±1.6% and 15.9±1.8%, respectively. Statistical analysis demonstrated a lack of regional association between the extent of LGE signal intensity and the presence of rotors. This is the first study demonstrating that the presence of rotors based on NEEES analysis is not directly associated with the extent and anatomic location of LGE signal intensity from CMR. Further studies evaluating the relationship between rotors and fibrosis in patients with persistent atrial fibrillation are mandatory and may inform strategies to improve ablation outcome.

T1-refBlochi: high resolution 3D post-contrast T1 myocardial mapping based on a single 3D late gadolinium enhancement volume, Bloch equations, and a reference T1

BackgroundHigh resolution 3D T1 mapping is important for assessment of diffuse myocardial fibrosis in left atrium or other thin-walled structures. In this work, we investigated a fast single-TI 3D high resolution T1 mapping method that directly transforms a 3D late gadolinium enhancement (LGE) volume to a 3D T1 map.MethodsThe proposed method, T1-refBlochi, is based on Bloch equation modeling of the LGE signal, a single-point calibration, and assumptions that proton density and T2* are relatively uniform in the heart. Several sources of error of this method were analyzed mathematically and with simulations. Imaging was performed in phantoms, eight swine and five patients, comparing T1-refBlochi to a standard spin-echo T1 mapping, 3D multi-TI T1 mapping, and 2D ShMOLLI, respectively.ResultsThe method has a good accuracy and adequate precision, even considering various sources of error. In phantoms, over a range of protocols, heart-rates and T1 s, the bias ±1SD was -3 ms ± 9 ms. The porcine studies showed excellent agreement between T1-refBlochi and the multi-TI method (bias ±1SD = −6 ± 22 ms). The proton density and T2* weightings yielded ratios for scar/blood of 0.94 ± 0.01 and for myocardium/blood of 1.03 ± 0.02 in the eight swine, confirming that sufficient uniformity of proton density and T2* weightings exists among heterogeneous tissues of the heart. In the patients, the mean T1 bias ±1SD in myocardium and blood between T1-refBlochi and ShMOLLI was -9 ms ± 21 ms.ConclusionT1-refBlochi provides a fast single-TI high resolution 3D T1 map of the heart with good accuracy and adequate precision.

T(Rho) and magnetization transfer and INvErsion recovery (TRAMINER)-prepared imaging: A novel contrast-enhanced flow-independent dark-blood technique for the evaluation of myocardial late gadolinium enhancement in patients with myocardial infarction.

To evaluate a new dark-blood late gadolinium enhancement (LGE) technique called "T(Rho) And Magnetization transfer and INvErsion Recovery" (TRAMINER) for the ability to detect myocardial LGE versus standard "bright-blood" inversion recovery (SIR) imaging. This Institutional Review Board (IRB)-approved, Health Insurance Portability and Accountability Act (HIPAA)-compliant prospective study included 40 patients (62 ± 14 years [mean ± standard deviation (SD)], 29 males) with suspected myocardial infarction (MI) referred for the assessment of myocardial viability. The patients underwent a 1.5T cardiac magnetic resonance imaging (MRI) including postcontrast SIR and TRAMINER acquisitions. Normalized images were evaluated by two readers. Subjective (3-point Likert scale) and objective image qualities were compared using Mann-Whitney U-test and paired t-test, respectively. Interobserver agreement, LGE detection rate, and level of certainty were compared using Cohen's kappa, Wilcoxon-test, and Mann-Whitney U-test, respectively. Results are reported as mean ± SD or mean [95% confidence interval]. Overall, image quality was rated similar between TRAMINER and SIR; however, TRAMINER performed better on a visual assessment of the ability to differentiate LGE from blood (Likert scale: 3.0 [3.0-3.0] vs. 2.0 [1.7-2.2], P < 0.0001). TRAMINER provided significantly higher signal intensity range (69.8 ± 10.2 vs. 9.6 ± 7.6, P < 0.0001) and a 4-fold higher signal intensity ratio (4.2 ± 1.9 vs. 1.1 ± 0.1, P < 0.0001) between LGE and blood signals. TRAMINER detected more patients (19/40 vs. 17/40) and segments (91/649 vs. 79/649) with LGE with higher level of certainty (2.9 [2.8-3.0] vs. 2.7 [2.5-2.8], P = 0.0185). Interobserver agreement was good to excellent for LGE detection. TRAMINER provides better contrast between LGE and blood and consequently may have increased ability to discriminate thin subendocardial and papillary muscle enhancement from the blood signal, which can have an indistinct appearance using SIR. 2 J. MAGN. RESON. IMAGING 2017;45:1429-1437.

16-26: Electrical Remodeling Does not Reproducibly Mirror Structural Change on Atrial MRI

Purpose of the Study: Left atrial (LA) late gadolinium enhancement (LGE) CMR has been proposed to guide ablation therapy and predict procedure outcome. AF electrical and structural remodeling are known to occur to varying extents in patients with AF. The extent to which pre-procedural LGE CMR reflects LA electrophysiological remodeling is unknown. Methods Used: Intracardiac contact mapping during programmed stimulation was used to characterize conduction delay, activation dispersion, electrogram morphology and AF vulnerability in 8 patients undergoing first-time pulmonary vein isolation. Pre-procedural LGE CMR imaging was performed and quantified by LGE signal intensity (SI; image intensity ratio, IIR), % LGE area and LA sphericity indices. Summary of Results: Although electrogram voltage was significantly reduced at areas of high SI (IIR > 0.97 - 0.9mV vs 1.3mV P = 0.049), IIR showed no relationship with electrogram duration (17.7ms vs 18.3ms, P = 0.673), conduction delay (322ms vs 316ms, P = 0.3939) or conduction block (262ms vs. 262ms, P = 0.8667). There was no relationship between % LGE area or sphericity and any of the LA remodeling parameters (all P > 0.05). LA extrastimulus conduction curves showed significant variation between patients with similar LGE CMR findings (Figure).

A randomized prospective mechanistic cardiac magnetic resonance study correlating catheter stability, late gadolinium enhancement and 3 year clinical outcomes in robotically assisted vs. standard catheter ablation.

AimsTo prospectively compare cardiac magnetic resonance late gadolinium enhancement (LGE) findings created by standard vs. robotically assisted catheter ablation lesions and correlate these with clinical outcomes.Methods and resultsForty paroxysmal atrial fibrillation patients (mean age 54 ± 13.8 years) undergoing first left atrial ablation were randomized to either robotic-assisted navigation (Hansen Sensei® X) or standard navigation. Pre-procedural, acute (24 h post-procedure) and late (beyond 3 months) scans were performed with LGE and T2W imaging sequences and percentage circumferential enhancement around the pulmonary vein (PV) antra were quantified. Baseline pre-procedural enhancements were similar in both groups. On acute imaging, mean % encirclements by LGE and T2W signal were 72% and 80% in the robotic group vs. 60% (P = 0.002) and 76%(P = 0.45) for standard ablation. On late imaging, the T2W signal resolved to baseline in both groups. Late gadolinium enhancement remained the predominant signal with 56% encirclement in the robotic group vs. 45% in the standard group (P = 0.04). At 6 months follow-up, arrhythmia-free patients had an almost similar mean LGE encirclement (robotic 64%, standard 60%, P = 0.45) but in recurrences, LGE was higher in the robotic group (43% vs. 30%, P = 0.001). At mean 3 years follow-up, 1.3 procedures were performed in the robotic group compared with 1.9 (P < 0.001) in the standard to achieve a success rate of 80% vs. 75%.ConclusionRobotically assisted ablation results in greater LGE around the PV antrum. Effective lesions created through improved catheter stability and contact force during initial treatment may have a role in reducing subsequent re-do procedures.

Repeat left atrial catheter ablation: cardiac magnetic resonance prediction of endocardial voltage and gaps in ablation lesion sets.

Studies have reported an inverse relationship between late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) signal intensity and left atrial (LA) endocardial voltage after LA ablation. However, there is controversy regarding the reproducibility of atrial LGE CMR and its ability to identify gaps in ablation lesions. Using systematic and objective techniques, this study examines the correlation between atrial CMR and endocardial voltage. Twenty patients who had previous ablation for atrial fibrillation and represented with paroxysmal atrial fibrillation or atrial tachycardia underwent preablation LGE CMR. During the ablation procedure, high-density point-by-point Carto voltage maps were acquired. Three-dimensional CMR reconstructions were registered with the Carto anatomies to allow comparison of voltage and LGE signal intensity. Signal intensities around the left and right pulmonary vein antra and along the LA roof and mitral lines on the CMR-segmented LA shells were extracted to examine differences between electrically isolated and reconnected lesions. There were a total of 6767 data points across the 20 patients. Only 119 (1.8%) of the points were ≤ 0.05 mV. There was only a weak inverse correlation between either unipolar (r = -0.18) or bipolar (r = -0.17) voltage and LGE CMR signal intensities with low voltage occurring across a large range of signal intensities. Signal intensities were not statistically different for electrically isolated and reconnected lesions. This study demonstrates that there is only a weak point-by-point relationship between LGE CMR and endocardial voltage in patients undergoing repeat LA ablation. Using an objective method of assessing gaps in ablation lesions, LGE CMR is unable to reliably predict sites of electrical conduction.

The Concordance Rates between LV Hypertrophy and RV Hypertrophy in Patients with Hypertrophic Cardiomyopathy as Diagnosed by Cardiovascular MRI with Fibrosis Imaging

Introduction: CMR has become the leading modality to define the clinical impact of hypertrophic cardiomyopathy (HCM). Late gadolinium enhancement (LGE) accurately identifies regions of myocardial fibrosis. It is well known that myocardial fibrosis can occur in patients with HCM and is independently linked to a poorer prognosis than those without fibrosis by CMR. Hypothesis: We hypothesize that there is significant RV involvement in HCM when incorporates a CMR analysis for RV hypertrophy and fibrosis. Methods: A retrospective review of all patients referred for HCM was performed. SSFP/LGE techniques were used to diagnose patients with HCM, using gadolinium administration (0.15 mmol/kg). Post-injection (10 minutes) LGE images were obtained using manual T1-weighted, IR-preparations. Regions of myocardium with LGE signals were visually designated as fibrotic. LV/RV mass indices (LVMI/RVMI) and ejection fractions were calculated. Results: Via 72 patients referred for HCM, 47(65%) were CMR confirmed. The mean LVMI was 108 ± 44 g/m2 while the mean RVMI was 30 ± 21 g/m2. As well, 34/47 (72%) had evidence of LV fibrosis while 24/47 (51%) had evidence for RV fibrosis. Of the RVH positive patients, 26/34 (76%) patients were LV LGE positive and 18/34 (52%) were RV LGE positive. Conclusion: The high frequency of RVH and RV fibrosis in the setting of HCM is surprising in that this phenomenon is rarely described. However, there is no reason to expect the phenotypic expression should be limited to the LV. Interestingly, as for the LV, the presence or absence of RV fibrosis has little predictive power towards the systolic function.

28Does a greater contact force create more scar? A quantification of the relationship between late gadolinium enhancement on cardiac MR imaging and catheter contact on af ablation

Introduction: Catheter-myocardium contact force (CF) is an important determinant of radiofrequency (RF) lesion generation. Novel RF-catheters enable real-time monitoring of CF, but evidence that CF is the primary determinant of lesion quality is lacking in humans. We used late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) to assess the relationship between applied contact force and chronic scar formation. Method: Twelve patients underwent pulmonary vein isolation using a CF-sensing catheter (SmartTouch Thermocool, Biosense-Webster, CA, USA). Ablation position was recorded using the CARTO-3 electroanatomical mapping system. LGE CMR was performed at a median of 7.2 (range 3-11) months post- ablation using an Achieva 3.0T MRI scanner (Philips, Amsterdam, The Netherlands) with a 3D ECG triggered, free-breathing inversion recovery turbo field echo scan sequence. The LGE-CMR images were segmented using Seg3D by an experienced observer. Signal intensities (SI) were projected onto the segmented shell, using a maximum intensity projection and fused to the CARTO-3 shell using an Iterative Closest Point (ICP) algorithm. The two shells (Contact Force and LGE signal) were then compared using custom built software. The shells were thresholded to blind the observer to local variations in LGE SI and CF before paired paths along the ablation lines were manually drawn on the surface of each shell. Results: For 1710 ablation points across 12 patients, there is a small but significant relationship between applied CF and chronic scar formation as indicated by CMR LGE SI (p<0.0001, R2=0.02) and between grouped CF and mean LGE SI (one- ANOVA, p=0.02). For every ablation line, regions are identifiable in which there is a relationship between CF and SI (see figure). Conversely, other regions of the same ablation lines do not show a close correlation between applied CF and resulting scar formation. Conclusions: Post-ablation scar, as assessed by MRI LGE signal intensity, is qualitatively related to CF, and quantitative analysis shows a weak but significant correlation. However, the majority of variation in scar formation is not explained purely by contact force, and may be related to other ablation parameters such as local cardiac anatomy, regional cooling effects and catheter stability. ![Graphic][1] [1]: /embed/inline-graphic-1.gif

Myocardial T2 signal enhancement in hypertrophic cardiomyopathy: prevalence, clinical profile and pathologic correlation

Background Abnormal myocardial T2 signal has been described in a minority of patients with hypertrophic cardiomyopathy (HCM). This phenomenon has been associated with arrhythmic outcomes and, given its more restrictive prevalence versus late gadolinium enhancement (LGE), offers a potentially useful biomarker for risk stratification. To date, postulated mechanisms include active tissue disease or unique collagen species, however, no histopathologic correlation has been reported. In this study, we examine the prevalence of T2 signal abnormalities among patients with HCM and examine for associations with other imaging-based markers of HCM phenotypic expression. Incrementally, we provide comprehensive histopathologic correlation of a patient undergoing cardiac transplantation receiving detailed in-vivo and ex-vivo (explanted heart) imaging. Methods Consecutive patients with HCM underwent a standardized imaging protocol using a 3-Tesla MR system. This was inclusive of T2-weighted imaging using a short-Tau inversion-recovery (STIR) fast spin echo sequence in serial short axis imaging planes both with and without body surface coils. Cine and LGE imaging was performed in identical slice orientations. Blinded analysis of left ventricular (LV) wall thickness, LV volumes, T2 signal enhancement and LGE signal abnormalities were performed using commercial software. In a patient planned for transplantation, a detailed in-vivo and ex-vivo imaging protocol was performed, the latter performing high-resolution isotropic T2-weighted imaging. Tissue was sampled from regions with and without abnormal T2 signal and exposed to comprehensive histologic examination. Results

Quantitative Magnetic Resonance Imaging Analysis of the Relationship Between Contact Force and Left Atrial Scar Formation After Catheter Ablation of Atrial Fibrillation

Catheter contact force (CF) is an important determinant of radiofrequency (RF) lesion quality during pulmonary vein isolation (PVI). Late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) allows good visualization of ablation lesions. This study describes a new technique to examine the relationship between CF during RF delivery and LGE signal intensity (SI) following PVI. Six patients underwent PVI for paroxysmal AF using a CF-sensing catheter and following preprocedural MRI. During ablation, CF-time integral (FTI) and position was documented for each RF application. All patients underwent repeat LGE MRI 3 months later. The LGE SIs were projected onto a MRI-derived 3-dimensional left atrial (LA) shell and a CF map was generated on the same shell. The entire LA surface was divided into 5 mm(2) segments. Force and LGE maps were fused and compared for each 5 mm(2) zone. An effective lesion was defined when MRI-defined scar occupied >90% of a 5 mm(2) analysis zone. Acute PVI was achieved in 100%. Two hundred sixty-eight RF lesions were tagged on the LA shells and given a lesion-specific FTI. Increasing FTI correlated with increased LGE SI, which was greater when the FTI was > 1,200 gs. Below an FTI of 1,200 gs, an increment in the FTI resulted in only a small increment in scar, whereas above 1,200 gs an increment in the FTI resulted in a large change of scar. There is a correlation between FTI and LGE SI in MRI following AF ablation. Real-time FTI maps are feasible and may prevent inadequate lesion formation.

Feasibility of real time integration of high-resolution scar images with invasive electrograms in electro-anatomical mapping system in patients undergoing ventricular tachycardia ablation

Background Ventricular tachycardia (VT) ablation is generally guided by invasive mapping of the left ventricle (LV) using electro-anatomical voltage mapping (EAM) to identify the VT substrate [1]. Late gadolinium enhancement (LGE) MRI allows excellent visualization of the scar. Heterogeneous area in LGE images has been shown to correlate with the VT substrate in animal models of VT. Retrospective studies in patients have also correlated the LGE signal enhancement to low voltage in EAM maps. However, current clinical EAM platform such as the Carto3 (Biosense Webster) does not allow integration of LGE images for facilitating the VT ablation. In this study, we described a workflow to integrate scar geometry extracted from highresolution 3D LGE images with EAM.

Comparison of the amount of affected myocardium quantified by late gadolinium enhancement and the degree of myocardial necrosis measured by cardiac troponin T in patients with myocarditis

Background The diagnosis of myocarditis is challenging due to its often subclinical or unspecific course. Yet, myocardial focal late gadolinium enhancement (LGE) patterns, which represent focal myocardial necrosis and imply negative clinical outcomes, can be assessed by cardiovascular magnetic resonance (CMR). Serologically, not only focal but also diffuse myocardial cell necrosis can be highly accurately detected by the cardiac-specific release of cardiac troponin T (cTnT) which has shown to have also prognostic value in these patients. However, data regarding the relationship between the focal necrosis size visualized by LGE-CMR and the serum marker of myocardial cell damage measured by cTnT are scarce. Therefore, we sought to investigate the relationship between focal LGE-CMR patterns, applying different standard deviations (std) of the LGE signal intensity, and serum levels of cTnT. Methods We retrospectively included 44 myocarditis patients (39 male, 5 female). CMR images were acquired on a 1.5 T whole-body MRI (Achieva, Philips Healthcare) and LGE imaging was performed (Gadolinium-DTPA (Magnevist, Bayer Schering Pharma), 0.2 mmol/kg body weight) using an inversion-recovery SSFP sequence. Short-axis LGE images were analyzed with a dedicated scar software (cmr42, Circle Cardiovascular Imaging) which allowed the measurement of the myocardial mass affected by focal LGE applying different std of contrast enhancement (2, 3, 4, 5, 6, 8, 10 std). Values for cTnT or high-sensitive cardiac troponin T (hscTnT) where applicable were retrieved from the patients’ records. Correlation analysis was performed using Pearson’s r or Spearman’s rho where applicable (p-value<0.05 was regarded significant).

The predictive value of DE-CMR in patients with severe chronic aortic regurgitation and extremely dilated left ventricular chamber

To determine whether preoperative contrast delay-enhanced cardiovascular magnetic resonance imaging (DE-CMR) could help predict long-term survival of patients with severe chronic aortic regurgitation and extremely dilated left ventricular chamber after aortic valve replacement. Totally 37 patients enrolled between February 2008 and November 2010 with severe chronic aortic regurgitation and extremely dilated left ventricular chamber, who met the echo criteria, that was left ventricular end diastolic dimension > 70 mm or left ventricular end systolic dimension > 55 mm, and were scheduled to the surgery. The 2-dimensional echocardiographic examinations and CMR with late gadolinium-enhancement (LGE) were performed routinely preoperatively. According to the results of CMR, the patients were divided into 2 groups: the LGE positive(+) group and LGE negative(-) group. The association of LGE with event free survival, postoperative cardiac function and postoperative hospital stay time was investigated. Fifteen patients had significant LGE signals in CMR films, while the other twenty-two were silent. All of them received the operative procedures, including aortic valve replacement in 28 cases, Bentall procedure in 3 cases, aortic valve replacement and ascending aorta replacement in 6 cases, and concomitant mitral valve repair in 11 cases. Over a follow-up of 33.6 months, 1-year, 2-year and 3-year event free survival rates in LGE(-) group were 94.7%, 88.4%, and 72.6%, respectively, compared to 80.0%, 48.9%, and 32.6%, respectively in LGE(+) group (χ(2) = 7.244, P = 0.007). The postoperative hospital stay time of LGE(-) group was (9 ± 2) days, which of LGE(+) group was (10 ± 3) days (t = 1.175, P = 0.248). LGE positive signal in CMR films is a potential predictor of persistent cardiac failure after aortic valve replacement for patients with severe chronic aortic regurgitation and extremely dilated left ventricular chamber. It has intimate relationship with malignant arrhythmia and sudden death, which makes it a valuable technique in preoperative evaluation and risk stratification.

In Hypertrophic Cardiomyopathy Reduction of Relative Resting Myocardial Blood Flow Is Related to Late Enhancement, T2-Signal and LV Wall Thickness

ObjectivesTo quantify resting myocardial blood flow (MBF) in the left ventricular (LV) wall of HCM patients and to determine the relationship to important parameters of disease: LV wall thickness, late gadolinium enhancement (LGE), T2-signal abnormalities (dark and bright signal), LV outflow tract obstruction and age.Materials and MethodsSeventy patients with proven HCM underwent cardiac MRI. Absolute and relative resting MBF were calculated from cardiac perfusion MRI by using the Fermi function model. The relationship between relative MBF and LV wall thickness, T2-signal abnormalities (T2 dark and T2 bright signal), LGE, age and LV outflow gradient as determined by echocardiography was determined using simple and multiple linear regression analysis. Categories of reduced and elevated perfusion in relation to non- or mildly affected reference segments were defined, and T2-signal characteristics and extent as well as pattern of LGE were examined. Statistical testing included linear and logistic regression analysis, unpaired t-test, odds ratios, and Fisher’s exact test.Results804 segments in 70 patients were included in the analysis. In a simple linear regression model LV wall thickness (p<0.001), extent of LGE (p<0.001), presence of edema, defined as focal T2 bright signal (p<0.001), T2 dark signal (p<0.001) and age (p = 0.032) correlated inversely with relative resting MBF. The LV outflow gradient did not show any effect on resting perfusion (p = 0.901). Multiple linear regression analysis revealed that LGE (p<0.001), edema (p = 0.026) and T2 dark signal (p = 0.019) were independent predictors of relative resting MBF. Segments with reduced resting perfusion demonstrated different LGE patterns compared to segments with elevated resting perfusion.ConclusionIn HCM resting MBF is significantly reduced depending on LV wall thickness, extent of LGE, focal T2 signal abnormalities and age. Furthermore, different patterns of perfusion in HCM patients have been defined, which may represent different stages of disease.

Understanding why edema in salvaged myocardium is difficult to detect by late gadolinium enhancement

T2-weighted cardiac magnetic resonance (CMR) can visualize myocardial edema in salvaged myocardium which appears non-infarcted by late gadolinium enhancement (LGE) CMR. However, the mechanisms governing why LGE does not visualize edema in noninfarcted myocardium remain unclear. The objective of the study was to evaluate the extracellular volume fraction (ECV) of edematous salvaged myocardium using quantitative T1-mapping techniques in order to better understand why this tissue may be difficult to detect by LGE imaging. Methods Dogs (n=10) underwent coronary occlusion and reperfusion, followed by 1.5T CMR. Salvaged myocardium was defined as having bright signal intensity on T2-prepared steady-state free precession (T2-prep) images and the absence of infarction by LGE, and signal intensities were quantified SD units brighter than remote myocardium. Myocardial extracellular volume fraction (ECV) was measured by T1 quantification before and after GdDTPA contrast administration and calibration by blood hematocrit. Results LGE signal intensity of salvaged and infarcted myocardium were 1.7±0.4 and 8.1±1.5 SD from remote, respectively. T2-prep signal intensity of salvaged and infarcted myocardium were 2.8±0.2 and 4.9±1.0 SD from remote, respectively. Compared to remote myocardium, T1 of salvaged myocardium was 14% higher before contrast (1050±114ms vs 919±66ms, p<0.001) and 10% lower 30 minutes after contrast (461±57ms vs 512±67ms, p<0.001). The ECV of salvaged myocardium was 34 +/-7% which was significantly different than ECV of normal myocardium 24+/-3% (p=0.04). Conclusions Salvaged myocardium has a post-contrast T1 which is approximately 50 ms less than remote myocardium and has an LGE image intensity less than 2 SD from remote, making it difficult to appreciate in LGE images. However, contrast concentration, and thus extracellular space, is determined by the change in 1/T1 (R1) which occurs from pre- to post-contrast. The combined and directionally opposed differences in pre- and post-contrast T1 explain why the extracellular volume fraction of salvaged myocardium is increased compared to remote. LGE image intensity does not incorporate information on pre-contrast T1, thus giving the impression of no change in the size of the extracellular space of salvaged myocardium despite the presence of extracellular edema.