Magnetic resonance estimates of the extent and heterogeneity of scar tissue in ICD patients with ischemic cardiomyopathy predict ventricular arrhythmia

Deep learning for automatic volumetric segmentation of left ventricular myocardium and ischaemic scar from multi-slice late gadolinium enhancement cardiovascular magnetic resonance

AIMS

This study details application of deep learning for automatic volumetric segmentation of left ventricular (LV) myocardium and scar and automated quantification of myocardial ischaemic scar burden from late gadolinium enhancement cardiovascular magnetic resonance (LGE-CMR).

METHODS AND RESULTS

We included 501 images and manual segmentations of short-axis LGE-CMR from over 20 multinational sites, from which 377 studies were used for training and 124 studies from unique participants for internal validation. A third test set of 52 images was used for external evaluation. Three models, U-Net, Cascaded U-Net, and U-Net++, were trained with a novel adaptive weighted categorical cross-entropy loss function. Model performance was evaluated using concordance correlation coefficients (CCCs) for LV mass and per cent myocardial scar burden. Cascaded U-Net was found to be the best model for the quantification of LV mass and scar percentage. The model exhibited a mean difference of -5 ± 23 g for LV mass, -0.4 ± 11.2 g for scar mass, and -0.8 ± 7% for per cent scar. CCC were 0.87, 0.77, and 0.78 for LV mass, scar mass, and per cent scar burden, respectively, in the internal validation set and 0.75, 0.71, and 0.69, respectively, in the external test set. For segmental scar mass, CCC was 0.74 for apical scar, 0.91 for mid-ventricular scar, and 0.73 for basal scar, demonstrating moderate to strong agreement.

CONCLUSION

We successfully trained a convolutional neural network for volumetric segmentation and analysis of LV scar burden from LGE-CMR images in a large, multinational cohort of participants with ischaemic scar.

Sudden cardiac death in ischaemic heart disease: coronary thrombosis or myocardial fibrosis?

The mechanisms underlying sudden cardiac death (SCD) in patients with ischaemic heart disease (IHD) caused by coronary atherosclerosis are not yet clarified. For decades, acute coronary causes have been sought as the main triggers of SCD in these patients. In fact, angiographic and pathological studies in cardiac arrest survivors and SCD victims, respectively, consistently show that acute plaque events occur in ∼50% of SCD of patients with IHD. Among the acute events, plaque rupture and erosion triggering acute coronary thrombosis remain the main substrates; however, a significant percentage of plaque haemorrhage (20%) is identified by pathological studies. Its role in acute coronary thrombosis is unknown and deserves future intravascular imaging developments. In the remaining 50% of SCD, the atherosclerotic coronary disease shows the characteristics of structural stability. More recent studies have focused attention not only on the coronary tree and on the search for acute complications of atherosclerotic plaques but also on myocardial tissue, identifying replacement and patchy fibrosis as the most frequent findings in the post-mortem hearts of these patients, a feature followed by cardiac hypertrophy, as assessed by the heart weight, usually associated with fibrosis. The possibility of characterizing myocardial fibrosis in vivo, besides confirming the pathological data, now offers new risk stratification perspectives to prevent SCD in IHD, alongside the consolidated secondary prevention criteria based on left ventricular dysfunction.

Advanced imaging for risk stratification for ventricular arrhythmias and sudden cardiac death

Sudden cardiac death (SCD) is a leading cause of mortality, comprising approximately half of all deaths from cardiovascular disease. In the US, the majority of SCD (85%) occurs in patients with ischemic cardiomyopathy (ICM) and a subset in patients with non-ischemic cardiomyopathy (NICM), who tend to be younger and whose risk of mortality is less clearly delineated than in ischemic cardiomyopathies. The conventional means of SCD risk stratification has been the determination of the ejection fraction (EF), typically via echocardiography, which is currently a means of determining candidacy for primary prevention in the form of implantable cardiac defibrillators (ICDs). Advanced cardiac imaging methods such as cardiac magnetic resonance imaging (CMR), single-photon emission computerized tomography (SPECT) and positron emission tomography (PET), and computed tomography (CT) have emerged as promising and non-invasive means of risk stratification for sudden death through their characterization of the underlying myocardial substrate that predisposes to SCD. Late gadolinium enhancement (LGE) on CMR detects myocardial scar, which can inform ICD decision-making. Overall scar burden, region-specific scar burden, and scar heterogeneity have all been studied in risk stratification. PET and SPECT are nuclear methods that determine myocardial viability and innervation, as well as inflammation. CT can be used for assessment of myocardial fat and its association with reentrant circuits. Emerging methodologies include the development of "virtual hearts" using complex electrophysiologic modeling derived from CMR to attempt to predict arrhythmic susceptibility. Recent developments have paired novel machine learning (ML) algorithms with established imaging techniques to improve predictive performance. The use of advanced imaging to augment risk stratification for sudden death is increasingly well-established and may soon have an expanded role in clinical decision-making. ML could help shift this paradigm further by advancing variable discovery and data analysis.

Greyzone myocardial fibrosis and ventricular arrhythmias in patients with a left ventricular ejection fraction >35

AIMS

To determine whether myocardial fibrosis and greyzone fibrosis (GZF) on cardiovascular magnetic resonance (CMR) is associated with ventricular arrhythmias in patients with coronary artery disease (CAD) and a left ventricular ejection fraction (LVEF) >35%.

METHODS AND RESULTS

In this retrospective study of CAD patients, GZF mass using the 3SD method (GZF3SD) and total fibrosis mass using the 2SD method (TF2SD) on CMR were assessed in relation to the primary, combined endpoint of sudden cardiac death, ventricular tachycardia, ventricular fibrillation, or resuscitated cardiac arrest. Among 701 patients [age: 65.8 ± 12.3 years (mean ± SD)], 28 (3.99%) patients met the primary endpoint over 5.91 years (median; interquartile range 4.42-7.64). In competing risks analysis, a GZF3SD mass ≥5.0 g was strongly associated with the primary endpoint [subdistribution hazard ratio (sHR): 17.4 (95% confidence interval, CI 6.64-45.5); area under receiver operator characteristic curve (AUC): 0.85, P < 0.001]. A weaker association was observed for TF2SD mass ≥23 g [sHR 10.4 (95% CI 4.22-25.8); AUC: 0.80, P < 0.001]. The range of sHRs for GZF3SD mass (1-527) was wider than for TF2SD mass (1-37.6).

CONCLUSIONS

In CAD patients with an LVEF >35%, GZF3SD mass was strongly associated with the arrhythmic endpoint. These findings hold promise for its use in identifying patients with CAD and an LVEF >35% at risk of arrhythmic events.

Multimodality imaging of myocardial viability: an expert consensus document from the European Association of Cardiovascular Imaging (EACVI)

In clinical decision making, myocardial viability is defined as myocardium in acute or chronic coronary artery disease and other conditions with contractile dysfunction but maintained metabolic and electrical function, having the potential to improve dysfunction upon revascularization or other therapy. Several pathophysiological conditions may coexist to explain this phenomenon. Cardiac imaging may allow identification of myocardial viability through different principles, with the purpose of prediction of therapeutic response and selection for treatment. This expert consensus document reviews current insight into the underlying pathophysiology and available methods for assessing viability. In particular the document reviews contemporary viability imaging techniques, including stress echocardiography, single photon emission computed tomography, positron emission tomography, cardiovascular magnetic resonance, and computed tomography and provides clinical recommendations for how to standardize these methods in terms of acquisition and interpretation. Finally, it presents clinical scenarios where viability assessment is clinically useful.

Ventricular arrhythmia risk is associated with myocardial scar but not with response to cardiac resynchronization therapy

AIMS

Sudden cardiac death (SCD) risk estimation in patients referred for cardiac resynchronization therapy (CRT) remains a challenge. By CRT-mediated improvement of left ventricular ejection fraction (LVEF), many patients loose indication for primary prevention implantable cardioverter-defibrillator (ICD). Increasing evidence shows the importance of myocardial scar for risk prediction. The aim of this study was to investigate the prognostic impact of myocardial scar depending on the echocardiographic response in patients undergoing CRT.

METHODS AND RESULTS

Patients with indication for CRT were prospectively enrolled. Decision about ICD or pacemaker implantation was based on clinical criteria. All patients underwent delayed-enhancement cardiac magnetic resonance imaging. Median follow-up duration was 45 (24-75) months. Primary outcome was a composite of sustained ventricular arrhythmia, appropriate ICD therapy, or SCD. A total of 218 patients with LVEF 25.5 ± 6.6% were analysed [158 (73%) male, 64.9 ± 10.7 years]. Myocardial scar was observed in 73 patients with ischaemic cardiomyopathy (ICM) (95% of ICM patients); in 62 with non-ischaemic cardiomyopathy (45% of these patients); and in all but 1 of 36 (17%) patients who reached the primary outcome. Myocardial scar was the only significant predictor of primary outcome [odds ratio 27.7 (3.8-202.7)], independent of echocardiographic CRT response. A total of 55 (25%) patients died from any cause or received heart transplant. For overall survival, only a combination of the absence of myocardial scar with CRT response was associated with favourable outcome.

CONCLUSION

Malignant arrhythmic events and SCD depend on the presence of myocardial scar but not on CRT response. All-cause mortality improved only with the combined absence of myocardial scar and CRT response.

Left ventricular mechanical dispersion in ischaemic cardiomyopathy: association with myocardial scar burden and prognostic implications

AIMS

Left ventricular (LV) mechanical dispersion (MD) may result from heterogeneous electrical conduction and is associated with adverse events. The present study investigated (i) the association between LV MD and the extent of LV scar as assessed with contrast-enhanced cardiac magnetic resonance (CMR) and (ii) the prognostic implications of LV MD in patients after ST-segment elevation myocardial infarction.

METHODS AND RESULTS

LV MD was calculated by echocardiography and myocardial scar was analysed on CMR data retrospectively. Infarct core and border zone were defined as ≥50% and 35-50% of maximal signal intensity, respectively. Patients were followed for the occurrence of the combined endpoint (all-cause mortality and appropriate implantable cardioverter-defibrillator therapy). In total, 96 patients (87% male, 57 ± 10 years) were included. Median LV MD was 53.5 ms [interquartile range (IQR) 43.4-62.8]. On CMR, total scar burden was 11.4% (IQR 3.8-17.1%), infarct core tissue 6.2% (IQR 2.0-12.7%), and border zone was 3.5% (IQR 1.5-5.7%). Correlations were observed between LV MD and infarct core (r = 0.517, P < 0.001), total scar burden (r = 0.497, P < 0.001), and border zone (r = 0.298, P = 0.003). In total, 14 patients (15%) reached the combined endpoint. Patients with LV MD >53.5 ms showed higher event rates as compared to their counterparts. Finally, LV MD showed the highest area under the curve for the prediction of the combined endpoint.

CONCLUSION

LV MD is correlated with LV scar burden. In addition, patients with prolonged LV MD showed higher event rates. Finally, LV MD provided the highest predictive value for the combined endpoint when compared with other parameters.

Myocardial Fibrosis as a Predictor of Sudden Death in Patients With Coronary Artery Disease

BACKGROUND

The "gray zone" of myocardial fibrosis (GZF) on cardiovascular magnetic resonance may be a substrate for ventricular arrhythmias (VAs).

OBJECTIVES

The purpose of this study was to determine whether GZF predicts sudden cardiac death (SCD) and VAs (ventricular fibrillation or sustained ventricular tachycardia) in patients with coronary artery disease (CAD) and a wide range of left ventricular ejection fractions (LVEFs).

METHODS

In this retrospective study of CAD patients, the presence of myocardial fibrosis on visual assessment (MF_VA) and GZF mass in patients with MF_VA were assessed in relation to SCD and the composite, arrhythmic endpoint of SCD or VAs.

RESULTS

Among 979 patients (mean age [± SD]: 65.8 ± 12.3 years), 29 (2.96%) experienced SCD and 80 (8.17%) met the arrhythmic endpoint over median 5.82 years (interquartile range: 4.1 to 7.3 years). In the whole cohort, MF_VA was strongly associated with SCD (hazard ratio: 10.1; 95% confidence interval [CI]: 1.42 to 1,278.9) and the arrhythmic endpoint (hazard ratio: 28.0; 95% CI: 4.07 to 3,525.4). In competing risks analyses, associations between LVEF <35% and SCD (subdistribution hazard ratio [sHR]: 2.99; 95% CI: 1.42 to 6.31) and the arrhythmic endpoint (sHR: 4.71; 95% CI: 2.97 to 7.47) were weaker. In competing risk analyses of the MF_VA subcohort (n = 832), GZF using the 3SD method (GZF_3SD) >5.0 g was strongly associated with SCD (sHR: 10.8; 95% CI: 3.74 to 30.9) and the arrhythmic endpoint (sHR: 7.40; 95% CI: 4.29 to 12.8). Associations between LVEF <35% and SCD (sHR: 2.62; 95% CI: 1.24 to 5.52) and the arrhythmic endpoint (sHR: 4.14; 95% CI: 2.61 to 6.57) were weaker.

CONCLUSIONS

In CAD patients, MF_VA plus quantified GZF_3SD mass was more strongly associated with SCD and VAs than LVEF. In selecting patients for implantable cardioverter-defibrillators, assessment of MF_VA followed by quantification of GZF_3SD mass may be preferable to LVEF.

Primary Prevention Implantable Cardioverter-Defibrillator Therapy in Heart Failure with Recovered Ejection Fraction

Given recent advances in both pharmacologic and nonpharmacologic strategies for improving outcomes related to chronic systolic heart failure, heart failure with recovered ejection fraction (HFrecEF) is now recognized as a distinct clinical entity with increasing prevalence. In many patients who once had an indication for active implantable cardioverter-defibrillator (ICD) therapy, questions remain regarding the usefulness of this primary prevention strategy to protect against syncope and cardiac arrest after they have achieved myocardial recovery. Early, small studies provide convincing evidence for continued guideline-directed medical therapy (GDMT) in segments of the HFrecEF population to promote persistent left ventricular myocardial recovery. Retrospective data suggest that the risk of sudden cardiac death is lower, but still present, in HFrecEF as compared with HF with reduced ejection fraction, with reports of up to 5 appropriate ICD therapies delivered per 100 patient-years. The usefulness of continued ICD therapy is weighed against the unfavorable effects of this strategy, which include a cumulative risk of infection, inappropriate discharge, and patient-level anxiety. Historically, many surrogate measures for risk stratification have been explored, but few have demonstrated efficacy and widespread availability. We found that the available data to inform decisions surrounding the continued use of active ICD therapies in this population are incomplete, and more advanced tools such as genetic testing, evaluation of high-risk structural cardiomyopathies (such as noncompaction), and cardiac magnetic resonance imaging have emerged as vital in risk stratification. Clinicians and patients should engage in shared decision-making to evaluate the appropriateness of active ICD therapy for any given individual. In this article, we explore the definition of HFrecEF, data underlying continuation of guideline-directed medical therapy in patients who have achieved left ventricular ejection fraction recovery, the benefits and risks of active ICD therapy, and surrogate measures that may have a role in risk stratification.

Multi-contrast volumetric imaging with isotropic resolution for assessing infarct heterogeneity: Initial clinical experience

BACKGROUND

To evaluate accelerated multi-contrast volumetric imaging with isotropic resolution reconstructed using low-rank and spatially varying edge-preserving constrained compressed sensing parallel imaging reconstruction (CP-LASER), for assessing infarct heterogeneity on post-infarction patients as a precursor to studies of utility for predicting ventricular arrhythmias.

METHODS

Eleven patients with prior myocardial infarction were included in the study. All subjects underwent cardiovascular magnetic resonance (CMR) scans including conventional two-dimensional late gadolinium enhancement (2D LGE) and three-dimensional multi-contrast late enhancement (3D MCLE) post-contrast. The extent of the infarct core and peri-infarct gray zone of a limited mid-ventricular slab were derived respectively by analyzing MCLE images with an isotropic resolution of 2.2 mm and an anisotropic resolution of 2.2×2.2×8.8 mm 3 , and LGE images with a resolution of 1.37×2.7×8 mm 3 ; the respective measures across all subjects were statistically compared.

RESULTS

Using 3D MCLE, the infarct core size measured with isotropic resolution was similar to that measured with anisotropic resolution, while the peri-infarct gray zone size measured with isotropic resolution was smaller than that measured with anisotropic resolution ( p<0.001 , Cohen's dz=1.33 ). Isotropic 3D MCLE yielded a significantly smaller measure of the peri-infarct gray zone size than conventional 2D LGE ( p=0.0016 , Cohen's dz=1.20 ). Overall, we have successfully shown the utility of isotropic 3D MCLE in a pilot patient study. Our results suggest that smaller voxels lead to more accurate differentiation between isotropic 3D MCLE-derived gray zone and core infarct because of diminished partial volume effect.

CONCLUSION

The CP-LASER accelerated 3D MCLE with isotropic resolution can be used in patients and yields excellent delineation of infarct and peri-infarct gray zone characteristics.

Predicting ventricular tachyarrhythmia in patients with systolic heart failure based on texture features of the gray zone from contrast-enhanced magnetic resonance imaging

BACKGROUND

Previous research showed that gray zone detected by late gadolinium enhancement cardiovascular magnetic resonance (LGE-CMR) imaging could help identify high-risk patients. In this study, we investigated whether LGE-CMR gray zone heterogeneity measured by image texture features could predict cardiovascular events in patients with heart failure (HF).

METHOD

This is a retrospective cohort study. Patients with systolic HF undergoing CMR imaging were enrolled. Cine and LGE images were analyzed to derive left ventricular (LV) function and scar characteristics. Entropy and uniformity of gray zones were derived by texture analysis.

RESULTS

A total of 82 systolic HF patients were enrolled. After a median 1021 (25%-75% quartiles, 205-2066) days of follow-up, the entropy (0.60 ± 0.260 vs. 0.87 ± 0.28, p = 0.013) was significantly increased while the uniformity (0.68 ± 0.14 vs. 0.53±0.15, p = 0.016) was significantly decreased in patients with ventricular tachycardia or ventricular fibrillation (VT/VF). The percentage of core scar (21.9 ± 10.6 vs. 30.6 ± 10.4, p = 0.029) was higher in cardiac mortality group than survival group while the uniformity (0.55 ± 0.17 vs. 0.67 ± 0.14, p = 0.018) was lower in cardiac mortality group than survival group. A multivariate Cox regression model showed that higher percentage of gray zone area (HR = 8.805, 1.620-47.84, p = 0.045), higher entropy (>0.85) (HR = 1.391, 1.092-1.772, p = 0.024) and lower uniformity (≦0.54) (HR = 0.535, 0.340-0.842, p = 0.022) were associated with VT/VF attacks. Also, higher percentage of gray zone area (HR = 5.716, 1.379-23.68, p = 0.017), core scar zone (HR = 1.939, 1.056-3.561, p = 0.025), entropy (>0.85) (HR = 1.434, 1.076-1.911, p = 0.008) and lower uniformity (≦0.54) (HR = 0.513, 0.296-0.888, p = 0.009) were associated with cardiac mortality during follow-up.

CONCLUSIONS

Gray zone heterogeneity by texture analysis method could provide additional prognostic value to traditional LGE-CMR substrate analysis method.

Arrhythmic risk stratification by cardiac magnetic resonance tissue characterization: disclosing the arrhythmic substrate within the heart muscle

Sudden cardiac death (SCD) is a pivotal health problem worldwide. The identification of subjects at increased risk of SCD is crucial for the accurate selection of candidates for implantable cardioverter defibrillator (ICD) therapy. Current strategies for arrhythmic stratification largely rely on left ventricular (LV) ejection fraction (EF), mostly measured by echocardiography, and New York Heart Association functional status for heart failure with reduced EF. For specific diseases, such as hypertrophic and arrhythmogenic cardiomyopathy, some risk scores have been proposed; however, these scores take into account some parameters that are a partial reflection of the global arrhythmic risk and show a suboptimal accuracy. Thanks to a more comprehensive evaluation, cardiac magnetic resonance (CMR) provides insights into the heart muscle (the so-called tissue characterization) identifying cardiac fibrosis as an arrhythmic substrate. Combining sequences before and after administration of contrast media and mapping techniques, CMR is able to characterize the myocardial tissue composition, shedding light on both intracellular and extracellular alterations. Over time, late gadolinium enhancement (LGE) emerged as solid prognostic marker, strongly associated with major arrhythmic events regardless of LVEF, adding incremental value over current strategy in ischemic heart disease and non-ischemic cardiomyopathies. The evidence on a potential prognostic role of mapping imaging is promising. However, mapping techniques require further investigation and standardization. Disclosing the arrhythmic substrate within the myocardium, CMR should be considered as part of a multiparametric approach to personalized arrhythmic stratification.

Peri-Infarct Quantification by Cardiac Magnetic Resonance to Predict Outcomes in Ischemic Cardiomyopathy

Background:

In ischemic cardiomyopathy, cardiac magnetic resonance assessment of the peri-infarct zone, a potential substrate for arrhythmogenesis, may serve as a novel prognosticator and guide the optimal use of implantable cardioverter-defibrillators. We undertook a systematic review and meta-analysis assessing the prognostic value of the peri-infarct zone on late gadolinium enhancement cardiac magnetic resonance in ischemic cardiomyopathy.

Methods:

We searched MEDLINE (Medical Literature Analysis and Retrieval System Online), EMBASE (Medical Literature Analysis and Retrieval System Online), and CENTRAL (Medical Literature Analysis and Retrieval System Online) from inception to January 2019 for prognostic studies relating peri-infarct size with clinical outcomes in ischemic cardiomyopathy. Two authors independently performed study selection and data extraction. Pooled effect estimates were calculated with random effects models, risk of bias and strength of evidence were assessed by the Quality in Prognostic Studies tool and Grading of Recommendations Assessment, Development, and Education, respectively.

Results:

Twenty studies were eligible, representing 14 cohort studies (n=1518) with mean follow-up of 3.6 years and 6 cross-sectional studies (n=189). The extent of the peri-infarct zone was significantly predictive of all-cause mortality (3 studies; n=539; hazard ratio, 1.34/10 g [95% CI, 1.13–1.59]; I 2 =0%; high-quality evidence), appropriate implantable cardioverter-defibrillator therapy (5 studies; n=361; hazard ratio, 1.31/10 g [95% CI, 1.17–1.47]; I 2 =0%; high-quality evidence), and inducibility of ventricular tachycardia on electrophysiological study (5 studies; n=167; OR, 2.63/g [95% CI, 1.39–4.96]; I 2 =14%; low-quality evidence). After adjusting for age and left ventricular ejection fraction, the peri-infarct zone, as a percentage of total infarct size, remained an independent predictor of all-cause mortality (2 studies; n=445; hazard ratio, 1.29/10% [95% CI, 1.15–1.44]; I 2 =0%; high-quality evidence).

Conclusions:

There is limited but consistent evidence that quantification of the peri-infarct zone predicts long-term mortality and appropriate implantable cardioverter-defibrillator therapy in ischemic cardiomyopathy. Future studies should confirm whether late gadolinium enhancement-cardiac magnetic resonance assessment may improve implantable cardioverter-defibrillator treatment decisions.

Clinical Trial Registration:

URL: https://www.crd.york.ac.uk/prospero/ . Unique identifier: CRD42017077337.

Red cell distribution width predicts death and appropriate therapy in patients with implantable cardioverter defibrillator: A simple measurement with prognostic value in a variety of diseases, may help in better selection of patients who will benefit the most from this device

BACKGROUND

Red cell distribution width (RDW) is a measure of the size variation of erythrocytes. Its prognostic value has been described in a variety of cardiac and noncardiac diseases. Implantable cardioverter defibrillator (ICD) is useful in preventing sudden cardiac death in high-risk patients, but many of these patients continue to survive without needing ICD therapy. We sought to examine whether RDW, with its prognostic values, can benefit in risk stratification of patients with ICD by predicting death and ICD therapy, and thus help in the selection of patients who will benefit the most from ICD, and minimizing its implantation in others at low risk of death and arrhythmias.

METHODS

In a retrospective study, we enrolled patients with ICD implanted for both primary and secondary prevention of sudden cardiac death. Baseline RDW values, demographics, and clinical characteristics, as well as the occurrence of death or first appropriate ICD therapy in postimplantation follow-up were collected. We examined whether RDW can predict higher-risk ICD-implanted patients prone to death and first appropriate ICD therapy (the combined outcome).

RESULTS

Final population included 432 patients. Compared to others, patients in the upper RDW tertile were older and had more comorbidities and outcomes. In multivariate analysis including RDW, age, gender, and ejection fraction, RDW was the only predictor of the combined outcome.

CONCLUSION

RDW may be useful in risk stratification of patients selected for ICD implantation. But larger prospective randomized trials are needed.

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.

Recent advances in the management of ventricular tachyarrhythmias

Ventricular arrhythmias are an important cause of cardiovascular morbidity and mortality, particularly in those with structural heart disease, inherited cardiomyopathies, and channelopathies. The goals of ventricular arrhythmia management include symptom relief, improving quality of life, reducing implantable cardioverter defibrillator shocks, preventing deterioration of left ventricular function, reducing risk of arrhythmic death, and potentially improving overall survival. Guideline-directed medical therapy and implantable cardioverter defibrillator implantation remain the mainstay of therapy to prevent sudden cardiac death in patients with ventricular arrhythmias in the setting of structural heart disease. Recent advances in imaging modalities and commercial availability of genetic testing panels have enhanced our mechanistic understanding of the disease processes and, along with significant progress in catheter-based ablative therapies, have enabled a tailored and more effective management of drug-refractory ventricular arrhythmias. Several gaps in our knowledge remain and require further research. In this article, we review the recent advances in the diagnosis and management of ventricular arrhythmias.

Interregional electro-mechanical heterogeneity in the rabbit myocardium

BACKGROUND

Increased electrical heterogeneity has been causatively linked to arrhythmic disorders, yet the knowledge about physiological heterogeneity remains incomplete. This study investigates regional electro-mechanical heterogeneities in rabbits, one of the key animal models for arrhythmic disorders.

METHODS AND FINDINGS

7 wild-type rabbits were examined by phase-contrast magnetic resonance imaging in vivo to assess cardiac wall movement velocities. Using a novel data-processing algorithm regional contraction-like profiles were calculated. Contraction started earlier and was longer in left ventricular (LV) apex than base. Patch clamp recordings showed longer action potentials (AP) in LV apex compared to the base of LV, septum, and right ventricle. Western blots of cardiac ion channels and calcium handling proteins showed lower expression of Cav1.2, KvLQT1, Kv1.4, NCX and Phospholamban in LV apex vs. base. A single-cell in silico model integrating the quantitative regional differences in ion channels reproduced a longer contraction and longer AP in apex vs. base.

CONCLUSIONS

Apico-basal electro-mechanical heterogeneity is physiologically present in the healthy rabbit heart. An apico-basal electro-mechanical gradient exists with longer APD and contraction duration in the apex and associated regionally heterogeneous expression of five key proteins. This pattern of apical mechanical dominance probably serves to increase pumping efficiency.

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.

Life-Threatening Ventricular Arrhythmias: Current Role of Imaging in Diagnosis and Risk Assessment

Sudden cardiac arrest continues to be a major cause of death from cardiovascular disease but our ability to predict patients at the highest risk of developing lethal ventricular arrhythmias remains limited. Left ventricular ejection fraction is inversely related to the risk of sudden death but has a low sensitivity and specificity for the population at risk. Nevertheless, it continues to be the main variable considered in identifying patients most likely to benefit from implantable defibrillators to prevent sudden death. Imaging myocardial sympathetic innervation with PET and SPECT as well as imaging characteristics of myocardial infarcts using gadolinium-enhanced cardiac magnetic resonance are emerging as imaging modalities that may further refine patient selection beyond ejection fraction. This review will primarily focus on employing advanced imaging approaches to identify patients with left ventricular dysfunction that are most likely to develop lethal arrhythmias and benefit from inserting a primary prevention implantable cardiac defibrillator. While not yet tested in prospective studies, we will review risk prediction models incorporating quantitative imaging and biomarkers that have been developed that appear promising to identify those at highest risk of sudden death.

Improving the appropriateness of sudden arrhythmic death primary prevention by implantable cardioverter-defibrillator therapy in patients with low left ventricular ejection fraction. Point of view

It is generally accepted that the current guidelines for the primary prevention of sudden arrhythmic death, which are based on ejection fraction, do not allow the optimal selection of patients with low left ventricular ejection fraction of ischemic and nonischemic etiology for implantation of a cardioverter-defibrillator. Ejection fraction alone is limited in both sensitivity and specificity. An analysis of the risk of sudden arrhythmic death with a combination of multiple tests (ejection fraction associated with one or more arrhythmic risk markers) could partially compensate for these limitations. We propose a polyparametric approach for defining the risk of sudden arrhythmic death using ejection fraction in combination with other clinical and arrhythmic risk markers (i.e. late gadolinium enhancement cardiac magnetic resonance, T-wave alternans, programmed ventricular stimulation, autonomic tone, and genetic testing) that have been validated in nonrandomized trials. In this article, we examine these approaches to identify three subsets of patients who cannot be comprehensively assessed by the current guidelines: patients with ejection fraction of 35% or less and a relatively low risk of sudden arrhythmic death despite the ejection fraction value; patients with ejection fraction of 35% or less and high competitive risk of death due to evolution of heart failure or noncardiac causes; and patients with ejection fraction between 35 and 45% with relatively high risk of sudden arrhythmic death despite the ejection fraction value.