Infarct tissue heterogeneity assessed with contrast-enhanced MRI predicts spontaneous ventricular arrhythmia in patients with ischemic cardiomyopathy and implantable cardioverter-defibrillator

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

Imaging for sudden cardiac death risk stratification: Current perspective and future directions

Sudden cardiac death (SCD) accounts for one fifth of global deaths, and occurs when a trigger (e.g. myocardial ischemia, premature ventricular contraction) interacts with an arrhythmic substrate (e.g. myocardial scar, dilated cardiomyopathy). Multimodality imaging (echocardiographic, cardiac magnetic resonance and nuclear techniques) can potentially visualize many predisposing substrates and triggers. Implantable cardioverter-defibrillator (ICD) is the most effective approach to primary prevention of SCD, and current guidelines regarding ICD implantation are based on a left ventricular ejection fraction (LVEF) ≤35%. This practice is limited by a low sensitivity and specificity, and has limited value when applied to different etiologies. In this review, the role of multimodality imaging in SCD risk-stratification and the limitations of an LVEF-based approach, are discussed. Additional randomized, prospective data are eagerly awaited to inform on the role of imaging in SCD risk-stratification, and ongoing/ planned trials are subsequently discussed.

Myocardial viability of the peri-infarct region measured by T1 mapping post manganese-enhanced MRI correlates with LV dysfunction

BACKGROUND

Manganese-enhanced MRI (MEMRI) detects viable cardiomyocytes based on the intracellular manganese uptake via L-type calcium-channels. This study aimed to quantify myocardial viability based on manganese uptake by viable myocardium in the infarct core (IC), peri-infarct region (PIR) and remote myocardium (RM) using T1 mapping before and after MEMRI and assess their association with cardiac function and arrhythmogenesis.

METHODS

Fifteen female swine had a 60-minute balloon ischemia-reperfusion injury in the LAD. MRI (Signa 3T, GE Healthcare) and electrophysiological study (EPS) were performed 4 weeks later. MEMRI and delayed gadolinium-enhanced MRI (DEMRI) were acquired on LV short axis. The DEMRI positive total infarct area was subdivided into the regions of MEMRI-negative non-viable IC and MEMRI-positive viable PIR. T1 mapping was performed to evaluate native T1, post-MEMRI T1, and delta R1 (R1_post-R1_pre, where R1 equals 1/T1) of each territory. Their correlation with LV function and EPS data was assessed.

RESULTS

PIR was characterized by intermediate native T1 (1530.5 ± 75.2 ms) compared to IC (1634.7 ± 88.4 ms, p = 0.001) and RM (1406.4 ± 37.9 ms, p < 0.0001). Lower post-MEMRI T1 of PIR (1136.3 ± 99.6 ms) than IC (1262.6 ± 126.8 ms, p = 0.005) and higher delta R1 (0.23 ± 0.08 s^-1) of PIR than IC (0.18 ± 0.09 s^-1, p = 0.04) indicated higher myocardial manganese uptake of PIR compared to IC. Post-MEMRI T1 (r = -0.57, p = 0.02) and delta R1 (r = 0.51, p = 0.04) of PIR correlated significantly with LVEF.

CONCLUSIONS

PIR is characterized by higher manganese uptake compared to the infarct core. In the subacute phase post-IR, PIR viability measured by post-MEMRI T1 correlates with cardiac function.

Relationship of non-invasive quantification of myocardial blood flow to arrhythmic events in patients with implantable cardiac defibrillators

BACKGROUND

Ischemia contributes to arrhythmogenesis though its role is incompletely understood. Abnormal myocardial perfusion measured by PET imaging may predict ventricular arrhythmias (VAs) in a high-risk population.

METHODS

Patients with implantable cardiac defibrillators who had undergone rubidium-82 cardiac PET imaging were identified. Patients were stratified by median MBF and MFR values for analysis. The Cox proportional hazards model was used to assess the impact of myocardial perfusion on survival free of VT independent of critical covariates.

RESULTS

A total of 159 patients (124 (78%) males, median age 65.9 years, IQR [56.76-72.63]) were followed for 1.43 years IQR [0.83-2.21]. VA occurred in 29 patients (23.7%). After adjustment for ejection fraction, age, and sex, impaired stress MBF was associated with an increased risk of VA (adjusted HR per ml/min/g 1.52, 95% CI (1.01-2.31), P = 0.04). Summed rest and stress scores were not predictive of VA. Among patients with severe LV dysfunction, stress MBF remained an independent predictor of VA (adjusted HR per 1 ml/min/g HR 1.69, 95% CI (1.03-11.36), P = 0.03), while residual EF, summed rest, and summed stress scores were not (P > 0.05).

CONCLUSIONS

Impaired stress myocardial blood flow was associated with less survival free of ventricular arrhythmias.

Multimodality imaging in ischaemic heart failure

In heart failure, extensive evaluation with modern non-invasive imaging modalities is needed to assess causes, pathophysiology, and haemodynamics, to determine prognosis and consider therapeutic options. This systematic evaluation includes a stepwise assessment of left ventricular size and function, the presence and severity of coronary artery disease, mitral regurgitation, pulmonary hypertension, right ventricular dilation and dysfunction, and tricuspid regurgitation. Based on this imaging-derived information, the need for specific therapies besides optimised medical therapy can be determined. The need for revascularisation, implantation of an implantable cardiac defibrillator, and mitral or tricuspid valve repair or replacement, can be (partially) guided by non-invasive imaging. Importantly, randomised controlled trials on the use of non-inasive imaging to guide therapy are scarce in this field and most non-pharmacological therapies are based on expert-consensus, but whenever trials are available, they will be addressed in this paper.

Dynamical anchoring of distant arrhythmia sources by fibrotic regions via restructuring of the activation pattern

Rotors are functional reentry sources identified in clinically relevant cardiac arrhythmias, such as ventricular and atrial fibrillation. Ablation targeting rotor sites has resulted in arrhythmia termination. Recent clinical, experimental and modelling studies demonstrate that rotors are often anchored around fibrotic scars or regions with increased fibrosis. However, the mechanisms leading to abundance of rotors at these locations are not clear. The current study explores the hypothesis whether fibrotic scars just serve as anchoring sites for the rotors or whether there are other active processes which drive the rotors to these fibrotic regions. Rotors were induced at different distances from fibrotic scars of various sizes and degree of fibrosis. Simulations were performed in a 2D model of human ventricular tissue and in a patient-specific model of the left ventricle of a patient with remote myocardial infarction. In both the 2D and the patient-specific model we found that without fibrotic scars, the rotors were stable at the site of their initiation. However, in the presence of a scar, rotors were eventually dynamically anchored from large distances by the fibrotic scar via a process of dynamical reorganization of the excitation pattern. This process coalesces with a change from polymorphic to monomorphic ventricular tachycardia.

Rotors are waves of cardiac excitation like a tornado causing cardiac arrhythmia. Recent research shows that they are found in ventricular and atrial fibrillation. Burning (via ablation) the site of a rotor can result in the termination of the arrhythmia. Recent studies showed that rotors are often anchored to regions surrounding scar tissue, where part of the tissue still survived called fibrotic tissue. However, it is unclear why these rotors anchor to these locations. Therefore, in this work, we investigated why rotors are so abundant in fibrotic tissue with the help of computer simulations. We performed simulations in a 2D model of human ventricular tissue and in a patient-specific model of a patient with an infarction. We found that even when rotors are initially at large distances from the fibrotic region, they are attracted by this region, to finally end up at the fibrotic tissue. We called this process dynamical anchoring and explained how the process works.

Detailed Analysis of the Relation Between Bipolar Electrode Spacing and Far- and Near-Field Electrograms

OBJECTIVES

This study sought to evaluate the relation between bipolar electrode spacing and far- and near-field electrograms.

BACKGROUND

The detailed effects of bipolar spacing on electrograms (EGMs) is not well described.

METHODS

With a HD-Grid catheter, EGMs from different bipole pairs could be created in each acquisition. This study analyzed the effect of bipolar spacing on EGMs in 7 infarcted sheep. A segment was defined as a 2-mm center-to-center bipole. In total, 4,768 segments (2,020 healthy, 1,542 scar, and 1,206 in border areas, as defined by magnetic resonance imaging [MRI]) were covered with an electrode pair of spacing of 2 mm (Bi-2), 4 mm (Bi-4), and 8 mm (Bi-8).

RESULTS

A total of 3,591 segments in Bi-2 were free from local abnormal ventricular activities (LAVAs); 1,630 segments were within the MRI-defined scar and/or border area. Among them, 172 (10.6%) segments in Bi-4 and 219 (13.4%) segments in Bi-8 showed LAVAs. In contrast, LAVAs were identified in 1,177 segments in Bi-2; 1,118 segments were within the MRI-defined scar and/or border area. Among them, LAVAs were missed in 161 (14.4%) segments in Bi-4 and in 409 (36.6%) segments in Bi-8. In segments with LAVAs, median far-field voltage increased from 0.09 mV (25th to 75th percentile: 0.06 to 0.14 mV) in Bi-2, to 0.16 mV (25th to 75th percentile: 0.10 to 0.24 mV) in Bi-4, and to 0.28 mV (25th to 75th percentile: 0.20 to 0.42 mV) in Bi-8 (p < 0.0001). Median near-field voltage increased from 0.14 mV (25th to 75th percentile: 0.08 to 0.25 mV) in Bi-2, to 0.21 mV (25th to 75th percentile: 0.12 to 0.35 mV) in Bi-4, and to 0.32 mV (25th to 75th percentile: 0.17 to 0.48 mV) in Bi-8 (p < 0.0001). The median near-/far-field voltage ratio decreased from 1.67 in Bi-2, to 1.43 in Bi-4, and 1.23 in Bi-8 (p < 0.0001).

CONCLUSIONS

Closer spacing better discriminates surviving tissue from dead scar area. Although far-field voltage systematically increases with spacing, near-field voltages were more variable, depending on local surviving muscular bundles. Near-field EGMs are more easily observed with smaller spacing, largely due to the reduction of the far-field effect.

Detailed comparison between the wall thickness and voltages in chronic myocardial infarction

BACKGROUND

The relationship between the local electrograms (EGMs) and wall thickness (WT) heterogeneity within infarct scars has not been thoroughly described. The relationship between WT and voltages and substrates for ventricular tachycardia (VT) was examined.

METHODS

In 12 consecutive patients with myocardial infarction and VT, WT, defined by a multidetector computed tomography, and voltage were compared. In multicomponent EGMs, amplitudes of both far- and near-field components were manually measured, and the performance of the three-dimensional-mapping system automatic voltage measurement was assessed.

RESULTS

Of 15 748 points acquired, 2677 points within 5 mm of the endocardial surface were analyzed. In total, 909 (34.0%) multicomponent EGMs were identified; 785 (86.4%) and 883 (97.1%) were distributed in the WT less than 4 and 5 mm, respectively. Far-field EGM voltages increased linearly from 0.14 mV (0.08-0.28 mV) in the WT: 0 to 1 mm to 0.70 mV (0.43-2.62 mV) in the WT: 4 to 5 mm (ρ = 0.430; P < 0.001), and a significant difference was demonstrated between any two WT-groups (P ≤ 0.001). In contrast, near-field EGM voltages varied from 0.27 mV (0.11-0.44 mV) in the WT: 0 to 1 mm to 0.29 mV (0.17-0.53 mV) in the WT: 4 to 5 mm with a poorer correlation (ρ = 0.062, P = 0.04). The proportion of points where the system automatically measured the voltage on near-field EGMs increased from less than 10% in areas of WT: 4 to 5 mm to 50% in areas less than 2 mm. Of 21 VTs observed, seven hemodynamically stable VTs were mapped and terminated in WT: 1 to 4 mm area.

CONCLUSIONS

Although far-field voltages gradually increase with the WT, near-field does not. The three-dimensional-mapping system preferentially annotates the near-field components in thinner areas (center of the scar) and the far-field component in thicker areas when building a voltage map. Critical sites of VT are distributed in WT: 1 to 4 mm areas.

Geometry-Dependent Arrhythmias in Electrically Excitable Tissues

Little is known about how individual cells sense the macroscopic geometry of their tissue environment. Here, we explore whether long-range electrical signaling can convey information on tissue geometry to individual cells. First, we studied an engineered electrically excitable cell line. Cells grown in patterned islands of different shapes showed remarkably diverse firing patterns under otherwise identical conditions, including regular spiking, period-doubling alternans, and arrhythmic firing. A Hodgkin-Huxley numerical model quantitatively reproduced these effects, showing how the macroscopic geometry affected the single-cell electrophysiology via the influence of gap junction-mediated electrical coupling. Qualitatively similar geometry-dependent dynamics were observed in human induced pluripotent stem cell (iPSC)-derived cardiomyocytes. The cardiac results urge caution in translating observations of arrhythmia in vitro to predictions in vivo, where the tissue geometry is very different. We study how to extrapolate electrophysiological measurements between tissues with different geometries and different gap junction couplings.

Three-dimensional holographic visualization of high-resolution myocardial scar on HoloLens

Visualization of the complex 3D architecture of myocardial scar could improve guidance of radio-frequency ablation in the treatment of ventricular tachycardia (VT). In this study, we sought to develop a framework for 3D holographic visualization of myocardial scar, imaged using late gadolinium enhancement (LGE), on the augmented reality HoloLens. 3D holographic LGE model was built using the high-resolution 3D LGE image. Smooth endo/epicardial surface meshes were generated using Poisson surface reconstruction. For voxel-wise 3D scar model, every scarred voxel was rendered into a cube which carries the actual resolution of the LGE sequence. For surface scar model, scar information was projected on the endocardial surface mesh. Rendered layers were blended with different transparency and color, and visualized on HoloLens. A pilot animal study was performed where 3D holographic visualization of the scar was performed in 5 swines who underwent controlled infarction and electroanatomic mapping to identify VT substrate. 3D holographic visualization enabled assessment of the complex 3D scar architecture with touchless interaction in a sterile environment. Endoscopic view allowed visualization of scar from the ventricular chambers. Upon completion of the animal study, operator and mapping specialist independently completed the perceived usefulness questionnaire in the six-item usefulness scale. Operator and mapping specialist found it useful (usefulness rating: operator, 5.8; mapping specialist, 5.5; 1–7 scale) to have scar information during the intervention. HoloLens 3D LGE provides a true 3D perception of the complex scar architecture with immersive experience to visualize scar in an interactive and interpretable 3D approach, which may facilitate MR-guided VT ablation.

Sudden Death Risk-Stratification in 2018-2019: The Old and the New

Sudden Cardiac Death (SCD) is a major public health issue, accounting for half of all cardiovascular deaths world-wide. The implantable cardioverter-defibrillator (ICD) has been solidified as the cornerstone therapy in primary prevention of SCD in ischaemic and non-ischaemic cardiomyopathy. However, what has become increasingly clear is that the left ventricular ejection fraction (LVEF) is an inadequate tool to select patients for a prophylactic ICD, despite its widespread use for this purpose. Use of LVEF alone has poor specificity for arrhythmic versus non-arrhythmic death. In addition, the vast majority of sudden deaths occur in patients with more preserved cardiac function. Alternate predictors of sudden death include electrophysiology study, non-invasive markers of electrical instability, myocardial fibrosis, genetic and bio-markers. The challenge for the future is finding a risk stratification test, or combination of tests, that adequately select patients at high risk of SCD with low competing risk of non-sudden death.

TpTe and TpTe/QT: novel markers to predict sudden cardiac death in ESRD?

INTRODUCTION

Reliable markers to predict sudden cardiac death (SCD) in patients with end stage renal disease (ESRD) remain elusive, but electrocardiogram (ECG) parameters may help stratify patients. Given their roles as markers for myocardial dispersion especially in high risk populations such as those with Brugada syndrome, we hypothesized that the Tpeak to Tend (TpTe) interval and TpTe/QT are independent risk factors for SCD in ESRD.

METHODS

Retrospective chart review was conducted on a cohort of patients with ESRD starting hemodialysis. Patients were US veterans who utilized the Veterans Affairs medical centers for health care. Average age of all participants was 66 years and the majority were males, consistent with a US veteran population. ECGs that were performed within 18 months of dialysis initiation were manually evaluated for TpTe and TpTe/QT. The primary outcomes were SCD and all-cause mortality, and these were assessed up to 5 years following dialysis initiation.

RESULTS

After exclusion criteria, 205 patients were identified, of whom 94 had a prolonged TpTe, and 61 had a prolonged TpTe/QT interval (not mutually exclusive). Overall mortality was 70.2% at 5 years and SCD was 15.2%. No significant difference was observed in the primary outcomes when examining TpTe (SCD: prolonged 16.0% vs. normal 14.4%, p=0.73; all-cause mortality: prolonged 55.3% vs. normal 47.7%, p=0.43). Likewise, no significant difference was found for TpTe/QT (SCD: prolonged 15.4% vs. normal 15.0%, p=0.51; all-cause mortality: prolonged 80.7% vs. normal 66.7%, p=0.39).

CONCLUSIONS

In ESRD patients on hemodialysis, prolonged TpTe or TpTe/QT was not associated with a significant increase in SCD or all-cause mortality.

Isotropic Reconstruction of MR Images Using 3D Patch-Based Self-Similarity Learning

Isotropic three-dimensional (3D) acquisition is a challenging task in magnetic resonance imaging (MRI). Particularly in cardiac MRI, due to hardware and time limitations, current 3D acquisitions are limited by low-resolution, especially in the through-plane direction, leading to poor image quality in that dimension. To overcome this problem, super-resolution (SR) techniques have been proposed to reconstruct a single isotropic 3D volume from multiple anisotropic acquisitions. Previously, local regularization techniques such as total variation have been applied to limit noise amplification while preserving sharp edges and small features in the images. In this paper, inspired by the recent progress in patch-based reconstruction, we propose a novel isotropic 3D reconstruction scheme that integrates non-local and self-similarity information from 3D patch neighborhoods. By grouping 3D patches with similar structures, we enforce the natural sparsity of MR images, which can be expressed by a low-rank structure, leading to robust image reconstruction with high signal-to-noise ratio efficiency. An Augmented Lagrangian formulation of the problem is proposed to efficiently decompose the optimization into a low-rank volume denoising and a SR reconstruction. Experimental results in simulations, brain imaging and clinical cardiac MRI, demonstrate that the proposed joint SR and self-similarity learning framework outperforms current state-of-the-art methods. The proposed reconstruction of isotropic 3D volumes may be particularly useful for cardiac applications, such as myocardial infarction scar assessment by late gadolinium enhancement MRI.

Impact of Coronary Artery Chronic Total Occlusion on Arrhythmic and Mortality Outcomes: A Systematic Review and Meta-Analysis

OBJECTIVES

This study aimed to examine the relationship between chronic coronary artery total occlusion (CTO) status and the occurrence of ventricular tachycardia (VT)/ventricular fibrillation (VF) or appropriate implantable cardioverter-defibrillator (ICD) therapy.

BACKGROUND

CTO is a significant problem in patients with ischemic heart disease. However, the extent to which it predisposes affected individuals to VT/VF and whether these arrhythmic events could be prevented by revascularization are unclear. Therefore, a systematic review and meta-analysis were conducted to examine the relationship between CTO status and the occurrence of VT/VF or appropriate ICD therapy.

METHODS

PubMed and Embase databases were searched until November 16, 2017, identifying 137 studies.

RESULTS

Seventeen studies involving 54,594 subjects (mean age, 61 ± 21 years of age, 81% male) with a mean follow-up of 43 ± 31 months were included. The presence of CTO was associated with higher risk of VT/VF or appropriate ICD therapy (adjusted hazard ratio [aHR]: 1.99; 95% confidence interval (CI): 1.53 to 2.59; p < 0.0001, I² = 3%) but not in cardiac mortality (aHR: 2.59; 95% CI: 0.64 to 10.59; p = 0.18, I² = 86%) or in all-cause mortality (aHR: 1.70; 95% CI: 0.84 to 3.46; p = 0.14; I² = 64%). Compared to patients with non-infarct-related CTOs, those with infarct-related CTOs have a higher risk of VT/VF or appropriate ICD therapy (aHR: 2.47; 95% CI: 1.76 to 3.46; p < 0.0001; I² = 14%), cardiac mortality (aHR: 2.73; 95% CI: 1.02 to 7.30; p < 0.05; I² = 79%) and higher all-cause mortality (aHR: 1.69; 95% CI: 1.19 to 2.40; p < 0.01; I² = 40%). Nonrevascularization of CTOs tended to be associated with an increased risk of all-cause mortality compared to successful revascularization (unadjusted HR: 1.52; 95% CI: 0.96 to 2.43; p = 0.08; I² = 76).

CONCLUSIONS

CTOs, especially infarct-related, are associated with high risk of VT/VF or appropriate ICD therapy and mortality. ICD implantation could be beneficial. However, it is not clear that revascularization has an impact on the outcome of patients with CTOs.

Empirical Mode Decomposition and Monogenic Signal-Based Approach for Quantification of Myocardial Infarction From MR Images

Quantification of myocardial infarction on late Gadolinium enhancement cardiovascular magnetic resonance (LGE-CMR) images into heterogeneous infarct periphery (or gray zone) and infarct core plays an important role in cardiac diagnosis, especially in identifying patients at high risk of cardiovascular mortality. However, quantification task is challenging due to noise corrupted in cardiac MR images, the contrast variation, and limited resolution of images. In this study, we propose a novel approach for automatic myocardial infarction quantification, termed DEMPOT, which consists of three key parts: Decomposition of image into intrinsic modes, monogenic phase performing on combined dominant modes, and multilevel Otsu thresholding on the phase. In particular, inspired by the Hilbert-Huang transform, we perform the multidimensional ensemble empirical mode decomposition and 2-D generalization of the Hilbert transform known as the Riesz transform on the MR image to obtain the monogenic phase that is robust to noise and contrast variation. Then, a two-stage algorithm using multilevel Otsu thresholding is accomplished on the monogenic phase to automatically quantify the myocardium into healthy, gray zone, and infarct core regions. Experiments on LGE-CMR images with myocardial infarction from 82 patients show the superior performance of the proposed approach in terms of reproducibility, robustness, and effectiveness.

Sudden Cardiac Death Risk Prediction: The Role of Cardiac Magnetic Resonance Imaging

Sudden cardiac death (SCD) accounts for more than 4 million global deaths per year. While it is most commonly caused by coronary artery disease, a final common pathway of ventricular arrhythmias is shared by different etiologies. The most effective primary and secondary prevention strategy is an implantable cardioverter-defibrillator (ICD). The decision to implant an ICD for primary prevention is largely based on a left ventricular ejection fraction ≤ 35%, but this criterion in isolation is neither sensitive nor specific. Novel imaging parameters hold promise to improve ICD candidate selection. Cardiac magnetic resonance (CMR) imaging is a powerful and versatile technique, with the ability to comprehensively assess cardiac structure and function. A range of variables based on CMR techniques (late gadolinium enhancement, T₁ mapping, T₂* relaxometry, deformation imaging) have been associated with ventricular arrhythmias and SCD risk. The role of CMR in the estimation of ventricular arrhythmias and SCD risk in coronary artery disease, nonischemic cardiomyopathies, cardiac transplant, iron-overload cardiomyopathy and valvular heart disease is reviewed in this article. Prospective, randomized trials and standardization of CMR techniques are required before its routine use can be recommended for guiding SCD prevention strategies.

Sudden death risk markers for patients with left ventricular ejection fractions greater than 40

The major burden of sudden cardiac death (SCD) in patients with heart disease occurs in those with a left ventricular ejection fraction > 40%. Although the annual risk of SCD may be lower in these patients compared to those with lower LVEF, their lifetime cumulative risk of SCD may be greater due to a better overall prognosis. It is plausible that those with LVEF > 40% who are at highest risk of life-threatening arrhythmia will benefit from implantable cardioverter defibrillators. Features that identify patients with a LVEF > 40% at high risk of SCD are urgently needed. We review existing studies examining SCD markers in this sub-group and discuss gaps in the current evidence base.

Cardiac magnetic resonance imaging in heart failure: where the alphabet begins!

Cardiac Magnetic Resonance Imaging has become a cornerstone in the evaluation of heart failure. It provides a comprehensive evaluation by answering all the pertinent clinical questions across the full pathological spectrum of heart failure. Nowadays, CMR is considered the gold standard in evaluation of ventricular volumes, wall motion and systolic function. Through its unique ability of tissue characterization, it provides incremental diagnostic and prognostic information and thus has emerged as a comprehensive imaging modality in heart failure. This review outlines the role of main conventional CMR sequences in the evaluation of heart failure and their impact in the management and prognosis.

Complexity of scar and ventricular arrhythmias in dilated cardiomyopathy of any etiology: Long-term data from the SCARFEAR (Cardiovascular Magnetic Resonance Predictors of Appropriate Implantable Cardioverter-Defibrillator Therapy Delivery) Registry

BACKGROUND

Late gadolinium enhancement (LGE) assessed with cardiovascular magnetic resonance (CMR) correlates with ventricular arrhythmias and survival in patients with structural heart disease. Whether some LGE characteristics may specifically improve prediction of arrhythmic outcomes is unknown.

HYPOTHESIS

We sought to evaluate scar characteristics assessed with CMR to predict implantable cardioverter-defibrillator (ICD) interventions in dilated cardiomyopathy of different etiology.

METHODS

96 consecutive patients evaluated with CMR received an ICD. Biventricular volumes, ejection fraction, and myocardial LGE were evaluated. LGE was defined as "complex" (Cx-LGE) in presence of ≥1 of the following: ischemic pattern, involving ≥2 different coronary territories; epicardial pattern; global endocardial pattern; and presence of ≥2 different patterns. The primary endpoint was occurrence of any appropriate ICD intervention. A composite secondary endpoint of cardiovascular death, cardiac transplantation, or ventricular assist device implantation was also considered.

RESULTS

During a median follow-up of 75 months, 30 and 25 patients reached the primary and secondary endpoints, respectively. Cx-LGE was correlated with a worse primary endpoint survival (log-rank P < 0.001). Cx-LGE and right ventricular end-diastolic volume were independently associated with the primary endpoint (HR: 3.22, 95% CI: 1.56-6.65, P = 0.002; and HR: 1.06, 95% CI: 1.00-1.12, P = 0.045, respectively), but not with the secondary endpoint.

CONCLUSIONS

Cx-LGE identified at CMR imaging seems promising as an independent and specific prognostic factor of ventricular arrhythmias requiring ICD therapy in dilated cardiomyopathy of different etiologies.

High spatial resolution free-breathing 3D late gadolinium enhancement cardiac magnetic resonance imaging in ischaemic and non-ischaemic cardiomyopathy: quantitative assessment of scar mass and image quality

PURPOSE

To compare breath-hold (BH) with navigated free-breathing (FB) 3D late gadolinium enhancement cardiac MRI (LGE-CMR) MATERIALS AND METHODS: Fifty-one patients were retrospectively included (34 ischaemic cardiomyopathy, 14 non-ischaemic cardiomyopathy, three discarded). BH and FB 3D phase sensitive inversion recovery sequences were performed at 3T. FB datasets were reformatted into normal resolution (FB-NR, 1.46x1.46x10mm) and high resolution (FB-HR, isotropic 0.91-mm voxels). Scar mass, scar edge sharpness (SES), SNR and CNR were compared using paired-samples t-test, Pearson correlation and Bland-Altman analysis.

RESULTS

Scar mass was similar in BH and FB-NR (mean ± SD: 15.5±18.0 g vs. 15.5±16.9 g, p=0.997), with good correlation (r=0.953), and no bias (mean difference ± SD: 0.00±5.47 g). FB-NR significantly overestimated scar mass compared with FB-HR (15.5±16.9 g vs 14.4±15.6 g; p=0.007). FB-NR and FB-HR correlated well (r=0.988), but Bland-Altman demonstrated systematic bias (1.15±2.84 g). SES was similar in BH and FB-NR (p=0.947), but significantly higher in FB-HR than FB-NR (p<0.01). SNR and CNR were lower in BH than FB-NR (p<0.01), and lower in FB-HR than FB-NR (p<0.01).

CONCLUSION

Navigated free-breathing 3D LGE-CMR allows reliable scar mass quantification comparable to breath-hold. During free-breathing, spatial resolution can be increased resulting in improved sharpness and reduced scar mass.

KEY POINTS

• Navigated free-breathing 3D late gadolinium enhancement is reliable for myocardial scar quantification. • High-resolution 3D late gadolinium enhancement increases scar sharpness • Ischaemic and non-ischaemic cardiomyopathy patients can be imaged using free-breathing LGE CMR.

Sudden Cardiac Death in Ischemic Heart Disease: Pathophysiology and Risk Stratification

Sudden cardiac death (SCD) accounts for approximately 360,000 deaths annually in the United States. Ischemic heart disease is the major cause of death in the general adult population. SCD can be due to arrhythmic or nonarrhythmic cardiac causes. Arrhythmic SCD may be caused by ventricular tachyarrhythmia or pulseless electrical activity/asystole. This article reviews the most recent pathophysiology and risk stratification strategies for SCD, emphasizing electrophysiologic surrogates of conduction disorder, dispersion of repolarization, and autonomic imbalance. Factors that modify arrhythmic death are addressed.

Ventricular Arrhythmias and Sudden Cardiac Death

Ventricular arrhythmias remain a significant cause of sudden cardiac death (SCD), and knowledge of their cause and high-risk features is important. SCD occurs when the interaction between vulnerable substrates and acute triggers results in sustained ventricular tachycardia progressing to ventricular fibrillation. Here, the authors aim to review the role of ventricular arrhythmias in SCD, first by approaching the substrates that support ventricular arrhythmias, and then by exploring features of these substrates and the acute triggers that may lead to SCD.

Cardiac Imaging in Patients With Ventricular Tachycardia

Ventricular tachycardia (VT) is a major cause of sudden cardiac death. The majority of malignant VTs occur in patients with structural heart disease. Multimodality imaging techniques play an integral role in determining the underlying etiology and prognostic significance of VT. In recent years, advances in imaging technology have enabled characterization of the structural arrhythmogenic substrate in patients with VT with increasing precision. In parallel with these advances, the role of cardiac imaging has expanded from a largely diagnostic tool to an adjunctive tool to guide interventional approaches for treatment of VT. Invasive and noninvasive imaging techniques, often used in combination, have made it possible to integrate structural and electrophysiological information during VT ablation procedures. An important area of current development is the use of noninvasive imaging techniques based on body surface electrocardiographic mapping to elucidate the mechanisms of VT. In the future, these techniques may provide a priori information on mechanisms of VT in patients undergoing interventional procedures. This review provides an overview of the role of cardiac imaging in patients with VT.

Role of Cardiac Imaging in Evaluating Risk for Sudden Cardiac Death

Sudden cardiac death (SCD) is a major cause of death from cardiovascular disease. Our ability to predict patients at the highest risk of developing lethal ventricular arrhythmias remains limited. Despite recent studies evaluating risk stratification tools, there is no optimal strategy. Cardiac imaging provides the opportunity to assess left ventricular ejection fraction, strain, fibrosis, and sympathetic innervation, all of which are pathophysiologically related to SCD risk. These modalities may play a role in the identification of vulnerable anatomic substrates that provide the pathophysiologic basis for SCD. Further studies are required to identify optimal imaging platform for risk assessment.

Electromechanical wave imaging and electromechanical wave velocity estimation in a large animal model of myocardial infarction

Echocardiography is often used in the clinic for detection and characterization of myocardial infarction. Electromechanical wave imaging (EWI) is a non-invasive ultrasound-based imaging technique based on time-domain incremental motion and strain estimation that can evaluate changes in contractility in the heart. In this study, electromechanical activation is assessed in infarcted heart to determine whether EWI is capable of detecting and monitoring infarct formation. Additionally, methods for estimating electromechanical wave (EW) velocity are presented, and changes in the EW propagation velocity after infarct formation are studied. Five (n  =  5) adult mongrels were used in this study. Successful infarct formation was achieved in three animals by ligation of the left anterior descending (LAD) coronary artery. Dogs were survived for a few days after LAD ligation and monitored daily with EWI. At the end of the survival period, dogs were sacrificed and TTC (tetrazolium chloride) staining confirmed the formation and location of the infarct. In all three dogs, as soon as day 1 EWI was capable of detecting late-activated and non-activated regions, which grew over the next few days. On final day images, the extent of these regions corresponded to the location of infarct as confirmed by staining. EW velocities in border zones of infarct were significantly lower post-infarct formation when compared to baseline, whereas velocities in healthy tissues were not. These results indicate that EWI and EW velocity might help with the detection of infarcts and their border zones, which may be useful for characterizing arrhythmogenic substrate.

Role of cardiovascular magnetic resonance in the management of patients with stable coronary artery disease

Cardiovascular magnetic resonance (CMR) assesses cardiac function, ischaemia, viability and tissue characterisation, all within a single scan. Many studies regarding the role of CMR in stable coronary artery disease (CAD) have been published over the last decade providing important technical advances, large-scale clinical validation and prognostic data. As a result, CMR has emerged as a highly accurate technique for diagnosis and risk stratification in stable CAD and has been incorporated into national and international guidelines. Furthermore, clinical pathways utilising CMR have been shown to be the most cost-effective in several healthcare systems. In this review, we summarise the key roles and guideline recommendations for CMR in stable CAD supported by contemporary clinical evidence.

Cardiac magnetic resonance imaging: Which information is useful for the arrhythmologist?

Cardiac magnetic resonance (CMR) is a non-invasive, non-ionizing, diagnostic technique that uses magnetic fields, radio waves and field gradients to generate images with high spatial and temporal resolution. After administration of contrast media (e.g., gadolinium chelate), it is also possible to acquire late images, which make possible the identification and quantification of myocardial areas with scar/fibrosis (late gadolinium enhancement, LGE). CMR is currently a useful instrument in clinical cardiovascular practice for the assessment of several pathological conditions, including ischemic and non-ischemic cardiomyopathies and congenital heart disease. In recent years, its field of application has also extended to arrhythmology, both in diagnostic and prognostic evaluation of arrhythmic risk and in therapeutic decision-making. In this review, we discuss the possible useful applications of CMR for the arrhythmologist. It is possible to identify three main fields of application of CMR in this context: (1) arrhythmic and sudden cardiac death risk stratification in different heart diseases; (2) decision-making in cardiac resynchronization therapy device implantation, presence and extent of myocardial fibrosis for left ventricular lead placement and cardiac venous anatomy; and (3) substrate identification for guiding ablation of complex arrhythmias (atrial fibrillation and ventricular tachycardias).

Accelerated multicontrast volumetric imaging with isotropic resolution for improved peri-infarct characterization using parallel imaging, low-rank and spatially varying edge-preserving sparse modeling

PURPOSE

To achieve consistent effectiveness in reconstruction of fine image features for cases of varying contrast-to-noise ratio (CNR) to facilitate translating accelerated multicontrast volumetric imaging with isotropic resolution toward clinical utility in peri-infarct characterization.

THEORY AND METHODS

A low-rank and spatially varying edge-preserving constrained compressed sensing parallel imaging reconstruction method (CP-LASER) is developed to effectively preserve contrast of small-scale structures for highly accelerated multicontrast volumetric imaging in CNR-limited scenarios. CP-LASER synergistically integrates parallel imaging, low-rank and spatially varying edge-preserving sparse modeling to achieve high signal-to-noise-ratio efficiency by leveraging prior knowledge about signal properties including coil sensitivity weighting, spatiotemporally correlated signal relaxation, and spatially varying sparsity.

RESULTS

In the preclinical study using highly accelerated multicontrast volumetric imaging with an isotropic 1.5-mm resolution, CP-LASER demonstrated robust multicontrast reconstruction of peri-infarct characteristics with excellent correspondence with histopathology. CP-LASER provides better delineation of the peri-infarct border zone with improved sharpness than alternative methods in a clinical demonstration on 1.5T with an isotropic 2.2-mm resolution achieved in a single breath-hold.

CONCLUSION

Accelerated multicontrast volumetric imaging with isotropic resolution using CP-LASER has demonstrated the potential to improve peri-infarct characterization in a clinical setting. Magn Reson Med 79:3018-3031, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

High-risk patients with mild-moderate left ventricular dysfunction after a previous myocardial infarction. A long-term prognostic data by cardiac magnetic resonance

BACKGROUND

Few studies have explored prognosis in patients with previous myocardial infarction (MI) with mild-moderate (MM) left ventricular (LV) dysfunction (D). The aim of our study was to investigate whether combining LV parameters obtained by cardiac magnetic resonance (CMR) improves risk stratification of patients with previous MI and MM-LV-D.

METHODS

In 418 consecutive patients (63.3±11.3years old, female 12.9%) with previous MI, we quantified LVEF, volumes and wall motion score index (WMSI) and measured the infarct extent by late gadolinium enhancement (LGE). According to LVEF, patients were considered with normal LVEF (>55%), MM-LV-D (LVEF>30 and ≤55%) and severe (S) LV-D (LVEF ≤30).

RESULTS

During follow-up (median, 39.7months) cardiac events (cardiac death or appropriate intra-cardiac defibrillator shocks) occurred in 17/99 of patients with S-LV-D, in 15/201 with MM-LV-D, and in only 1/118 of those with normal LV-EF. After adjustment for age, an extent of LGE >11.3%, a dilated LV (male >112ml/m²; female >92ml/m²) and a WMSI>1.59 were associated with adverse cardiac events in patients with MM-LV-D. In patients with MM-LV-D, when each of these 3 factors was observed, the prognosis was worse respect to those with 1-2 factors and no factor (p=0.035 and p=0.004, respectively). Prognosis was similar (p=0.61) between MM-LV-D patients with all 3 factors and those with S-LV-dysfunction.

CONCLUSIONS

A multiparametric CMR approach, which includes LGE, dilated LV and WMSI, permits to identify post MI patients with MM-LV-D with a risk of cardiac events similar to those with S-LV-D. Further multicenter studies are needed to confirm our data.

Current Clinical Applications and Next Steps for Cardiac Innervation Imaging

PURPOSE OF REVIEW

Autonomic innervation is crucial for regulating cardiac function. Sympathetic innervation imaging with ¹²³I-mIBG and analogous PET tracers assesses disease in ways that differ from customary methods. This review describes practical use in various clinical scenarios, discusses recent guidelines, presents new data confirming risk stratification power, describes an ongoing prospective study, and looks forward to wider use in patient management.

RECENT FINDINGS

ASNC ¹²³I-mIBG guidelines are available, expanding on European guidelines. ADMIRE-HF patient follow-up increased to 2 years in ADMIRE HFX, demonstrating independent mortality risk reclassification. ADMIRE-HF findings were substantiated in a Japanese consortium study and in the PAREPET ¹¹C-HED PET study. Exciting potential uses of adrenergic imaging are management of LVADs and VT ablation. CZT cameras provide advantages, but derived parameters differ from Anger camera values. Independent risk stratification utility of adrenergic imaging with ¹²³I-mIBG and PET tracers is continuously being confirmed. An ongoing prospective randomized study promises to establish patient management utility. There is potential for wider use and improved images with newer cameras and PET.

Ventricular Tachycardia in Ischemic Heart Disease

Ventricular arrhythmias are a significant cause of morbidity and mortality in patients with ischemic structural heart disease. Endocardial and epicardial mapping strategies include scar characterization channel identification, and recording and ablation of late potentials and local abnormal ventricular activities. Catheter ablation along with new technology and techniques of bipolar ablation, needle catheter, and autonomic modulation may increase efficacy in difficult to ablate ventricular arrhythmias. Catheter ablation of ventricular arrhythmias seem to confer mortality and morbidity benefits in patients with ischemic heart disease.

Cardiovascular Magnetic Resonance to Predict Appropriate Implantable Cardioverter Defibrillator Therapy in Ischemic and Nonischemic Cardiomyopathy Patients Using Late Gadolinium Enhancement Border Zone: Comparison of Four Analysis Methods

BACKGROUND

Late gadolinium enhancement (LGE) border zone on cardiac magnetic resonance imaging has been proposed as an independent predictor of ventricular arrhythmias. The purpose was to determine whether size and heterogeneity of LGE predict appropriate implantable cardioverter defibrillator (ICD) therapy in ischemic cardiomyopathy (ICM) and nonischemic cardiomyopathy (NICM) patients and to evaluate 4 LGE border-zone algorithms.

METHODS AND RESULTS

ICM and NICM patients who underwent LGE cardiac magnetic resonance imaging prior to ICD implantation were retrospectively included. Two semiautomatic algorithms, expectation maximization, weighted intensity, a priori information and a weighted border zone algorithm, were compared with a modified full-width half-maximum and a 2-3SD threshold-based algorithm (2-3SD). Hazard ratios were calculated per 1% increase in LGE. A total of 74 ICM and 34 NICM were followed for 63 months (1-140) and 52 months (0-133), respectively. ICM patients had 27 appropriate ICD events, and NICM patients had 7 ICD events. In ICM patients with primary prophylactic ICD, LGE border zone predicted ICD therapy in univariable and multivariable analysis measured by the expectation maximization, weighted intensity, a priori information, weighted border zone, and modified full-width half-maximum algorithms (hazard ratios 1.23, 1.22, and 1.05, respectively; P<0.05; negative predictive value 92%). For NICM, total LGE by all 4 methods was the strongest predictor (hazard ratios, 1.03-1.04; P<0.05), though the number of events was small.

CONCLUSIONS

Appropriate ICD therapy can be predicted in ICM patients with primary prevention ICD by quantifying the LGE border zone. In NICM patients, total LGE but not LGE border zone had predictive value for ICD therapy. However, the algorithms used affects the predictive value of these measures.

Sudden Cardiac Death Substrate Imaged by Magnetic Resonance Imaging: From Investigational Tool to Clinical Applications

Sudden cardiac death (SCD) is a devastating event afflicting 350 000 Americans annually despite the availability of life-saving preventive therapy, the implantable cardioverter defibrillator. SCD prevention strategies are hampered by over-reliance on global left ventricular ejection fraction <35% as the most important criterion to determine implantable cardioverter defibrillator candidacy. Annually in the United States alone, this results in ≈130 000 implantable cardioverter defibrillator placements at a cost of >$3 billion but only a 5% incidence per year of appropriate firings. This approach further fails to identify individuals who experience the majority, as many as 80%, of SCD events, which occur in the setting of more preserved left ventricular ejection fraction. Better risk stratification is needed to improve care and should be guided by direct pathophysiologic markers of arrhythmic substrate, such as specific left ventricular structural abnormalities. There is an increasing body of literature to support the prognostic value of cardiac magnetic resonance imaging with late gadolinium enhancement in phenotyping the left ventricular to identify those at highest risk for SCD. Cardiac magnetic resonance has unparalleled tissue characterization ability and provides exquisite detail about myocardial structure and composition, abnormalities of which form the direct, pathophysiologic substrate for SCD. Here, we review the evolution and the current state of cardiac magnetic resonance for imaging the arrhythmic substrate, both as a research tool and for clinical applications.

Effects of electrophysiological heterogeneity on vulnerability to re-entry in human ventricular tissue: A simulation study

In this study, we constructed a two-dimensional ventricular tissue sheet with cellular electrophysiology modified from the Ten Tusscher 2006 Model. Heterogeneity was created by dividing the tissue into endocardium, midmyocardium and epicardium, further enhanced by a central ischemic zone. Subsequently, we investigated how electrophysiological heterogeneity affects re-entry initiation and maintenance in this tissue. Furthermore, we analyzed the vulnerable window (VW) under several conditions and concluded that heterogeneity across various myocardia expands the VW further than the monolayer myocardium model does.

Cardiac Fibrosis and Arrhythmogenesis

Myocardial injury, mechanical stress, neurohormonal activation, inflammation, and/or aging all lead to cardiac remodeling, which is responsible for cardiac dysfunction and arrhythmogenesis. Of the key histological components of cardiac remodeling, fibrosis either in the form of interstitial, patchy, or dense scars, constitutes a key histological substrate of arrhythmias. Here we discuss current research findings focusing on the role of fibrosis, in arrhythmogenesis. Numerous studies have convincingly shown that patchy or interstitial fibrosis interferes with myocardial electrophysiology by slowing down action potential propagation, initiating reentry, promoting after-depolarizations, and increasing ectopic automaticity. Meanwhile, there has been increasing appreciation of direct involvement of myofibroblasts, the activated form of fibroblasts, in arrhythmogenesis. Myofibroblasts undergo phenotypic changes with expression of gap-junctions and ion channels thereby forming direct electrical coupling with cardiomyocytes, which potentially results in profound disturbances of electrophysiology. There is strong evidence that systemic and regional inflammatory processes contribute to fibrogenesis (i.e., structural remodeling) and dysfunction of ion channels and Ca2+ homeostasis (i.e., electrical remodeling). Recognizing the pivotal role of fibrosis in the arrhythmogenesis has promoted clinical research on characterizing fibrosis by means of cardiac imaging or fibrosis biomarkers for clinical stratification of patients at higher risk of lethal arrhythmia, as well as preclinical research on the development of antifibrotic therapies. At the end of this review, we discuss remaining key questions in this area and propose new research approaches. © 2017 American Physiological Society. Compr Physiol 7:1009-1049, 2017.

Relation of Myocardial Contrast-Enhanced T1 Mapping by Cardiac Magnetic Resonance to Left Ventricular Reverse Remodeling After Cardiac Resynchronization Therapy in Patients With Nonischemic Cardiomyopathy

Myocardial scar is known to be associated with limited left ventricular (LV) reverse remodeling after cardiac resynchronization therapy (CRT). However, the impact of diffuse myocardial interstitial fibrosis, as assessed with myocardial T₁ mapping cardiac magnetic resonance (CMR), has not been studied in patients with CRT. Therefore, we aimed at evaluating the association between diffuse myocardial interstitial fibrosis, in nonischemic cardiomyopathy patients, and LV reverse remodeling after CRT. A total of 40 patients (61 ± 11 years) with nonischemic cardiomyopathy who underwent CMR before CRT implantation were included. Myocardial T₁ mapping was performed using an inversion-recovery Look-Locker sequence after gadolinium injection. Myocardial contrast-enhanced T₁ time values were assessed from segments without delayed contrast enhancement and normalized for heart rate. At 6-month follow-up, LV reverse remodeling was assessed by the reduction in LV end-systolic volume. Before CRT implantation, mean myocardial contrast-enhanced T₁ time was 351 ± 46 ms. At 6-month follow-up, LV end-systolic volume decreased by 24 ± 21%. Myocardial contrast-enhanced T₁ time showed a significant correlation with LV reverse remodeling (r = 0.5, p = 0.001) together with hemoglobin level, renal function, LV dyssynchrony, and presence of delayed contrast enhancement. Multivariate regression analysis identified myocardial contrast-enhanced T₁ time (β -0.160, p = 0.022), LV dyssynchrony (β -0.267, p = 0.002), and renal function (β -0.334, p = 0.021) as independent associates of LV reverse remodeling. In conclusion, in nonischemic cardiomyopathy, diffuse interstitial myocardial fibrosis quantified with T₁ mapping CMR is independently associated with LV reverse remodeling after CRT and might, therefore, be used to optimize patient selection.

The Role of Cardiovascular Magnetic Resonance in Cardiac Resynchronization Therapy

Randomized, controlled trials have shown that cardiac resynchronization therapy (CRT) is beneficial in patients with heart failure, impaired left ventricular (LV) systolic function, and a wide QRS complex. Other studies have shown that targeting the LV pacing site can also improve patient outcomes. Cardiovascular magnetic resonance (CMR) is a radiation-free imaging modality that provides unparalleled spatial resolution. In addition, emerging data suggest that targeted LV lead deployment over viable myocardium improves the outcome of patients undergoing CRT. This review explores the role of CMR in the preoperative workup of patients undergoing CRT.

Clinical performance of high-resolution late gadolinium enhancement imaging with compressed sensing

PURPOSE

To evaluate diagnostic image quality of 3D late gadolinium enhancement (LGE) with high isotropic spatial resolution (∼1.4 mm³ ) images reconstructed from randomly undersampled k-space using LOw-dimensional-structure Self-learning and Thresholding (LOST).

MATERIALS AND METHODS

We prospectively enrolled 270 patients (181 men; 55 ± 14 years) referred for myocardial viability assessment. 3D LGE with isotropic spatial resolution of 1.4 ± 0.1 mm³ was acquired at 1.5T using a LOST acceleration rate of 3 to 5. In a subset of 121 patients, 3D LGE or phase-sensitive LGE were acquired with parallel imaging with an acceleration rate of 2 for comparison. Two readers evaluated image quality using a scale of 1 (poor) to 4 (excellent) and assessed for scar presence. The McNemar test statistic was used to compare the proportion of detected scar between the two sequences. We assessed the association between image quality and characteristics (age, gender, torso dimension, weight, heart rate), using generalized linear models.

RESULTS

Overall, LGE detection proportions for 3D LGE with LOST were similar between readers 1 and 2 (16.30% vs. 18.15%). For image quality, readers gave 85.9% and 80.0%, respectively, for images categorized as good or excellent. Overall proportion of scar presence was not statistically different from conventional 3D LGE (28% vs. 33% [P = 0.17] for reader 1 and 26% vs. 31% [P = 0.37] for reader 2). Increasing subject heart rate was associated with lower image quality (estimated slope = -0.009 (P = 0.001)).

CONCLUSION

High-resolution 3D LGE with LOST yields good to excellent image quality in >80% of patients and identifies patients with LV scar at the same rate as conventional 3D LGE.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017;46:1829-1838.

Assessment of stable coronary artery disease by cardiovascular magnetic resonance imaging: Current and emerging techniques

Coronary artery disease (CAD) is a leading cause of death and disability worldwide. Cardiovascular magnetic resonance (CMR) is established in clinical practice guidelines with a growing evidence base supporting its use to aid the diagnosis and management of patients with suspected or established CAD. CMR is a multi-parametric imaging modality that yields high spatial resolution images that can be acquired in any plane for the assessment of global and regional cardiac function, myocardial perfusion and viability, tissue characterisation and coronary artery anatomy, all within a single study protocol and without exposure to ionising radiation. Advances in technology and acquisition techniques continue to progress the utility of CMR across a wide spectrum of cardiovascular disease, and the publication of large scale clinical trials continues to strengthen the role of CMR in daily cardiology practice. This article aims to review current practice and explore the future directions of multi-parametric CMR imaging in the investigation of stable CAD.