Cardiac magnetic resonance using late gadolinium enhancement and atrial T1 mapping predicts poor outcome in patients with atrial fibrillation after catheter ablation therapy

Tissue characterization of acute lesions during cardiac magnetic resonance-guided ablation of cavo-tricuspid isthmus-dependent atrial flutter: a feasibility study

AIMS

To characterize acute lesions during cardiac magnetic resonance (CMR)-guided radiofrequency (RF) ablation of cavo-tricuspid isthmus (CTI)-dependent atrial flutter by combining T2-weighted imaging (T2WI), T1 mapping, first-pass perfusion, and late gadolinium enhancement (LGE) imaging. CMR-guided catheter ablation offers a unique opportunity to investigate acute ablation lesions. Until present, studies only used T2WI and LGE CMR to assess acute lesions.

METHODS AND RESULTS

Fifteen patients with CTI-dependent atrial flutter scheduled for CMR-guided RF ablation were prospectively enrolled. Directly after achieving bidirectional block of the CTI line, CMR imaging was performed using: T2WI (n = 15), T1 mapping (n = 10), first-pass perfusion (n = 12), and LGE (n = 12) imaging. In case of acute reconnection, additional RF ablation was performed. In all patients, T2WI demonstrated oedema in the ablation region. Right atrial T1 mapping was feasible and could be analysed with a high inter-observer agreement (r = 0.931, ICC 0.921). The increase in T1 values post-ablation was significantly lower in regions showing acute reconnection compared with regions without reconnection [37 ± 90 ms vs. 115 ± 69 ms (P = 0.014), and 3.9 ± 9.0% vs. 11.1 ± 6.8% (P = 0.022)]. Perfusion defects were present in 12/12 patients. The LGE images demonstrated hyper-enhancement with a central area of hypo-enhancement in 12/12 patients.

CONCLUSION

Tissue characterization of acute lesions during CMR-guided CTI-dependent atrial flutter ablation demonstrates oedema, perfusion defects, and necrosis with a core of microvascular damage. Right atrial T1 mapping is feasible, and may identify regions of acute reconnection that require additional RF ablation.

Recurrence After Atrial Fibrillation Ablation and Investigational Biomarkers of Cardiac Remodeling

BACKGROUND

Recurrence after atrial fibrillation (AF) ablation remains common. We evaluated the association between recurrence and levels of biomarkers of cardiac remodeling, and their ability to improve recurrence prediction when added to a clinical prediction model.

METHODS AND RESULTS

Blood samples collected before de novo catheter ablation were analyzed. Levels of bone morphogenetic protein-10, angiopoietin-2, fibroblast growth factor-23, insulin-like growth factor-binding protein-7, myosin-binding protein C3, growth differentiation factor-15, interleukin-6, N-terminal pro-brain natriuretic peptide, and high-sensitivity troponin T were measured. Recurrence was defined as ≥30 seconds of an atrial arrhythmia 3 to 12 months postablation. Multivariable logistic regression was performed using biomarker levels along with clinical covariates: APPLE score (Age >65 years, Persistent AF, imPaired eGFR [<60 ml/min/1.73m2], LA diameter ≥43 mm, EF <50%; which includes age, left atrial diameter, left ventricular ejection fraction, persistent atrial fibrillation, and estimated glomerular filtration rate), preablation rhythm, sex, height, body mass index, presence of an implanted continuous monitor, year of ablation, and additional linear ablation. A total of 1873 participants were included. A multivariable logistic regression showed an association between recurrence and levels of angiopoietin-2 (odds ratio, 1.08 [95% CI, 1.02-1.15], P=0.007) and interleukin-6 (odds ratio, 1.02 [95% CI, 1.003-1.03]; P=0.02). The area under the receiver operating characteristic curve of a model that only contained clinical predictors was 0.711. The addition of any of the 9 studied biomarkers to the predictive model did not result in a statistically significant improvement in the area under the receiver operating characteristic curve.

CONCLUSIONS

Higher angiopoietin-2 and interleukin-6 levels were associated with recurrence after atrial fibrillation ablation in multivariable modeling. However, the addition of biomarkers to a clinical prediction model did not significantly improve recurrence prediction.

Atrial Ablation Lesion Evaluation by Cardiac Magnetic Resonance: Review of Imaging Strategies and Histological Correlations

Cardiac magnetic resonance (CMR) imaging is a valuable noninvasive tool for evaluating tissue response following catheter ablation of atrial tissue. This review provides an overview of the contemporary CMR strategies to visualize atrial ablation lesions in both the acute and chronic postablation stages, focusing on their strengths and limitations. Moreover, the accuracy of CMR imaging in comparison to atrial lesion histology is discussed. T2-weighted CMR imaging is sensitive to edema and tends to overestimate lesion size in the acute stage after ablation. Noncontrast agent-enhanced T1-weighted CMR imaging has the potential to provide more accurate assessment of lesions in the acute stage but may not be as effective in the chronic stage. Late gadolinium enhancement imaging can be used to detect chronic atrial scarring, which may inform repeat ablation strategies. Moreover, novel imaging strategies are being developed, but their efficacy in characterizing atrial lesions is yet to be determined. Overall, CMR imaging has the potential to provide virtual histology that aids in evaluating the efficacy and safety of catheter ablation and monitoring of postprocedural myocardial changes. However, technical factors, scanning during arrhythmia, and transmurality assessment pose challenges. Therefore, further research is needed to develop CMR strategies to visualize the ablation lesion maturation process more effectively.

Association of Plasma Myeloperoxidase with Inflammation and Diabetic status in HFpEF

Background

Inflammation and oxidative stress are thought to play an important role in the pathophysiology of heart failure with preserved ejection fraction (HFpEF) through the development of endothelial dysfunction. Myeloperoxidase (MPO) functions as a link between oxidative stress and inflammation and is an interesting therapeutic target. The objective of this observational cohort study was to compare MPO levels between HFpEF and old controls, to define clinical characteristics associated with high levels of MPO and to assess the relation between MPO levels and vascular function.

Methods

Patients with HFpEF (N = 55) and controls > 60 years (N = 18) were prospectively included. All subjects underwent complete echocardiography and blood sampling. MPO levels were dosed by ELISA assay. Effective arterial elastance (Ea) and peripheral arterial tonometry (EndoPAT reactive hyperemia index RHI and augmentation index AIx) were used to assess vascular function. Characteristics between groups defined by the median of MPO were compared using independent samples t-test or chi square test.

Results

Patients with HFpEF (80 ± 8.7 years, 65% female) had higher levels of MPO compared to controls (75 ± 5.0 years, 72% female) (34.7 ng/mL [22.7; 44.0] vs 22.6 [18.2; 32.0], p = 0.026). MPO levels were correlated with markers of inflammation; C-reactive protein (Pearson's R = 0.46, p = 0.001) and neutrophile to lymphocyte ratio (R = 0.36, p = 0.031) and with signs of left ventricular (LV) remodelling and elevated filling pressures, namely NT-proBNP levels (R = 0.32, p = 0.019), decreased LV ejection fraction (LVEF, R = -0.36, p = 0.008) and E/e' ratio (R = 0.35, p = 0.011). HFpEF patients with levels of MPO above the median were more often men (48% vs 21%, p = 0.037) and suffered more often from diabetes (48% vs 18%, p = 0.017). Intriguingly, they had lower indices of vascular stiffness (augmentation index 11.1 [0.1; 30.7] vs 19.9 [10.5; 33.4], p = 0.018 and arterial elastance Ea 2.06 ± 0.676 vs 2.43 ± 0.721, p = 0.065) and there was no difference in endothelial function (1.82 [1.34; 2.30] vs 1.66 [1.32; 1.95], p = 0.55).

Conclusions

HFpEF patients have higher levels of MPO than controls, reflecting leukocyte activation and oxidative stress. Among patients, high levels of MPO are associated with male sex, diabetic status, subtle left ventricular dysfunction and pronounced diastolic dysfunction. The association between oxidative stress and vascular stiffness, on the other hand could not be demonstrated.

Clinical Trial Registration

Clinical trial NCT03197350.

Prediction of Recurrence of Atrial Fibrillation Post-ablation Based on Atrial Fibrosis Seen on Late Gadolinium Enhancement MRI: A Metaanalysis

OBJECTIVES

This meta-analysis aims to investigate the recurrence of atrial fibrillation (AF) post-ablation based on the various stages of fibrosis seen in the late gadolinium enhancement magnetic resonance imaging (LGE-MRI).

METHODS

Electronic databases were searched using specific terms and identified nine studies that met the inclusion criteria. A total of 1,787 patients underwent LGE-MRI to assess atrial fibrosis before catheter ablation for AF. We performed three analyses: first, we compared stage IV versus stage I (reference group). The second set examined the combined stages III and IV versus stages I and II (reference group). The third set compared stage IV versus combined stages I, II, and III. The metanalysis relied on a random-effects model to pool the odds ratios (OR) and 95% confidence intervals (CI) using the DerSimonian and Laird method. The data was analyzed using StatsDirect software in England.

RESULTS

The study showed a higher rate of AF recurrence after ablation in stage IV atrial fibrosis than in stage I (OR, 9.54; 95% CI, 3.81 to 28.89; P<00001). Also, in patients with combined stages III & IV of atrial fibrosis, AF recurrence was significantly higher after ablation than in stages I & II groups (OR, 2.37; 95% CI, 1.61 to 3.50; P<00001). Similarly, compared to combined stages I, II, and III, patients with stage IV have higher odds of recurrence post-ablation (OR, 4.24; 95% CI, 2.39- 7.52, P < 0.001).

CONCLUSION

This metanalysis demonstrates the strong association between left atrial fibrosis in LGE-MRI and AF post-ablation recurrence. The finding of this study will further assist clinicians in predicting the recurrence rate of AF based on the amount of fibrosis and tailor therapeutic decisions for further management.

Right atrial function and fibrosis in relation to successful atrial fibrillation ablation

AIMS

Bi-atrial remodelling in patients with atrial fibrillation (AF) is rarely assessed and data on the presence of right atrial (RA) fibrosis, the relationship between RA and left atrial (LA) fibrosis, and possible association of RA remodelling with AF recurrence after ablation in patients with AF is limited.

METHODS AND RESULTS

A total of 110 patients with AF undergoing initial pulmonary vein isolation (PVI) were included in the present study. All patients were in sinus rhythm during cardiac magnetic resonance (CMR) imaging performed prior to ablation. LA and RA volumes and function (volumetric and feature tracking strain) were derived from cine CMR images. The extent of LA and RA fibrosis was assessed from 3D late gadolinium enhancement images. AF recurrence was followed up for 12 months after PVI using either 12-lead electrocardiograms or Holter monitoring. Arrhythmia recurrence was observed in 39 patients (36%) after the 90-day blanking period, occurring at a median of 181 (interquartile range: 122-286) days. RA remodelling parameters were not significantly different between patients with and without AF recurrence after ablation, whereas LA remodelling parameters were different (volume, emptying fraction, and strain indices). LA fibrosis had a strong correlation with RA fibrosis (r = 0.88, P < 0.001). Both LA and RA fibrosis were not different between patients with and without AF recurrence.

CONCLUSIONS

This study shows that RA remodelling parameters were not predictive of AF recurrence after AF ablation. Bi-atrial fibrotic remodelling is present in patients with AF and moreover, the amount of LA fibrosis had a strong correlation with the amount of RA fibrosis.

The Effects of Fibrotic Cell Type and Its Density on Atrial Fibrillation Dynamics: An In Silico Study

Remodeling in atrial fibrillation (AF) underlines the electrical and structural changes in the atria, where fibrosis is a hallmark of arrhythmogenic structural alterations. Fibrosis is an important feature of the AF substrate and can lead to abnormal conduction and, consequently, mechanical dysfunction. The fibrotic process comprises the presence of fibrotic cells, including fibroblasts, myofibroblasts and fibrocytes, which play an important role during fibrillatory dynamics. This work assesses the effect of the diffuse fibrosis density and the intermingled presence of the three types of fibrotic cells on the dynamics of persistent AF. For this purpose, the three fibrotic cells were electrically coupled to cardiomyocytes in a 3D realistic model of human atria. Low (6.25%) and high (25%) fibrosis densities were implemented in the left atrium according to a diffuse fibrosis representation. We analyze the action potential duration, conduction velocity and fibrillatory conduction patterns. Additionally, frequency analysis was performed in 50 virtual electrograms. The tested fibrosis configurations generated a significant conduction velocity reduction, where the larger effect was observed at high fibrosis density (up to 82% reduction in the fibrocytes configuration). Increasing the fibrosis density intensifies the vulnerability to multiple re-entries, zigzag propagation, and chaotic activity in the fibrillatory conduction. The most complex propagation patterns were observed at high fibrosis densities and the fibrocytes are the cells with the largest proarrhythmic effect. Left-to-right dominant frequency gradients can be observed for all fibrosis configurations, where the fibrocytes configuration at high density generates the most significant gradients (up to 4.5 Hz). These results suggest the important role of different fibrotic cell types and their density in diffuse fibrosis on the chaotic propagation patterns during persistent AF.

Relaxin and the Cardiovascular System: from Basic Science to Clinical Practice

The peptide hormone relaxin was originally linked to reproductive physiology, where it is believed to mediate systemic and renal hemodynamic adjustments to pregnancy. Recently, its broad range of effects in the cardiovascular system has been the focus of intensive research regarding its implications under pathological conditions and potential therapeutic potential. An understanding of the multitude of cardioprotective actions prompted the study of serelaxin, recombinant human relaxin-2, for the treatment of acute heart failure. Despite early promising results from phase II studies, recently revealed RELAX-AHF-2 outcomes were rather disappointing and the treatment for acute heart failure remains an unmet medical need. This article reviews the physiologic actions of relaxin on the cardiovascular system and its relevance in the pathophysiology of cardiovascular disease. We summarize the most updated clinical data and discuss future directions of serelaxin for the treatment of acute heart failure. This should encourage additional work to determine how can relaxin's beneficial effects be exploited for the treatment of cardiovascular disease.

Novel Approaches in Cardiac Imaging for Non-invasive Assessment of Left Heart Myocardial Fibrosis

In the past, the identification of myocardial fibrosis was only possible through invasive histologic assessment. Although endomyocardial biopsy remains the gold standard, recent advances in cardiac imaging techniques have enabled non-invasive tissue characterization of the myocardium, which has also provided valuable insights into specific disease processes. The diagnostic accuracy, incremental yield and prognostic value of speckle tracking echocardiography, late gadolinium enhancement and parametric mapping modules by cardiac magnetic resonance and cardiac computed tomography have been validated against tissue samples and tested in broad patient populations, overall providing relevant clinical information to the cardiologist. This review describes the patterns of left ventricular and left atrial fibrosis, and their characterization by advanced echocardiography, cardiac magnetic resonance and cardiac computed tomography, allowing for clinical applications in sudden cardiac death and management of atrial fibrillation.

Atrial fibrosis and substrate based characterization in atrial fibrillation: Time to move forwards

Atrial fibrillation (AF) is the most commonly encountered cardiac arrhythmia in clinical practice. However, current therapeutic interventions for atrial fibrillation have limited clinical efficacy as a consequence of major knowledge gaps in the mechanisms sustaining atrial fibrillation. From a mechanistic perspective, there is increasing evidence that atrial fibrosis plays a central role in the maintenance and perpetuation of atrial fibrillation. Electrophysiologically, atrial fibrosis results in alterations in conduction velocity, cellular refractoriness, and produces conduction block promoting meandering, unstable wavelets and micro-reentrant circuits. Clinically, atrial fibrosis has also linked to poor clinical outcomes including AF-related thromboembolic complications and arrhythmia recurrences post catheter ablation. In this article, we review the pathophysiology behind the formation of fibrosis as AF progresses, the role of fibrosis in arrhythmogenesis, surrogate markers for detection of fibrosis using cardiac magnetic resonance imaging, echocardiography and electroanatomic mapping, along with their respective limitations. We then proceed to review the current evidence behind therapeutic interventions targeting atrial fibrosis, including drugs and substrate-based catheter ablation therapies followed by the potential future use of electro phenotyping for AF characterization to overcome the limitations of contemporary substrate-based methodologies.

Efficacy of LGE-MRI-guided fibrosis ablation versus conventional catheter ablation of atrial fibrillation: The DECAAF II trial: Study design

INTRODUCTION

Success rates of catheter ablation in persistent atrial fibrillation (AF) remain suboptimal. A better and more targeted ablation strategy is urgently needed to optimize outcomes of AF treatment. We sought to assess the safety and efficacy of targeting atrial fibrosis during ablation of persistent AF patients in improving procedural outcomes.

METHODS

The DECAAF II trial (ClinicalTrials. gov identifier number NCT02529319) is a prospective, randomized, multicenter trial of patients with persistent AF. Patients with persistent AF undergoing a first-time ablation procedure were randomized in a 1:1 fashion to receive conventional pulmonary vein isolation (PVI) ablation (Group 1) or PVI + fibrosis-guided ablation (Group 2). Left atrial fibrosis and ablation induced scarring were defined by late gadolinium enhancement magnetic resonance imaging at baseline and at 3-12 months postablation, respectively. The primary endpoint is the recurrence of atrial arrhythmia postablation, including atrial fibrillation, atrial flutter, or atrial tachycardia after the 90-day postablation blanking period. Patients were followed for a period of 12-18 months with a smartphone ECG Device (ECG Check Device, Cardiac Designs Inc.). With an anticipated enrollment of 900 patients, this study has an 80% power to detect a 26% reduction in the hazard ratio of the primary endpoint.

RESULTS AND CONCLUSION

The DECAAF II trial is the first prospective, randomized, multicenter trial of patients with persistent AF using imaging defined atrial fibrosis as a treatment target. The trial will help define an optimal approach to catheter ablation of persistent AF, further our understanding of influencers of ablation lesion formation, and refine selection criteria for ablation based on atrial myopathy burden.

The impact of tissue-tracking strain on the left atrial dysfunction in the patients with left ventricular dysfunction

Background

The extracellular volume (ECV) calculated by T1 mapping, and tissue-tracking strain using cardiac magnetic resonance (CMR) are useful for assessing the left ventricular (LV) function. However, those parameters are controversial for assessing left atrial (LA) function. This study aimed to investigate the usefulness of CMR to evaluate the LA function using those parameters. Furthermore, those LA function parameters were compared in each LV function.

Methods

A total of 65 consecutive patients who underwent contrast CMR were prospectively enrolled (age 55.7 ± 14. 6 years, males 67.7%). Among the 65 patients, there were 15 without hypertension, diabetes, or atrial fibrillation (Healthy group). The remaining 50 patients were divided into two groups according to a left ventricular ejection fraction (LVEF) of 50%. We assessed the correlations between the LV- and LA-CMR parameters among the three groups (LVEF < 50%; n = 20, LVEF ≥ 50%; n = 30, and Healthy; n = 15).

Results

The LA-longitudinal strain for an LVEF < 50% was lower than that for the others (LVEF < 50%; 13.6 ± 7.9%, LVEF ≥ 50%; 24. 5 ± 13.5%, Healthy; 24.5 ± 9.8%, p = 0.003). However, the LA-ECV did not significantly differ among the three groups (LVEF < 50%; 50.3 ± 3.6%, LVEF ≥ 50%; 53.1 ± 4.9%, Healthy; 53.2 ± 6.5%, p = 0.12). A multiple regression model after adjusting for the patient background revealed that a worse LA-longitudinal strain was correlated with a low LVEF and large LA-volume, but the LA-ECV was not associated with those.

Conclusions

The LA-strain in LV dysfunction patients was significantly lower. However, the LA-ECV did not significantly differ from that in those without LV dysfunction. Tissue-tracking strain is more useful for evaluating the LA dysfunction than T1 mapping.

Do most patients with obesity or type 2 diabetes, and atrial fibrillation, also have undiagnosed heart failure? A critical conceptual framework for understanding mechanisms and improving diagnosis and treatment

Obesity and diabetes can lead to heart failure with preserved ejection fraction (HFpEF), potentially because they both cause expansion and inflammation of epicardial adipose tissue and thus lead to microvascular dysfunction and fibrosis of the underlying left ventricle. The same process also causes an atrial myopathy, which is clinically evident as atrial fibrillation (AF); thus, AF may be the first manifestation of HFpEF. Many patients with apparently isolated AF have latent HFpEF or subsequently develop HFpEF. Most patients with obesity or diabetes who have AF and exercise intolerance have increased left atrial pressures at rest or during exercise, even in the absence of diagnosed HFpEF. Among patients with AF, those who also have latent HFpEF have increased risk for systemic thromboembolism and death. The identification of HFpEF in patients with obesity or diabetes alters the risk-to-benefit relationship of commonly prescribed treatments. Bariatric surgery and statins can ameliorate AF and reduce the risk for HFpEF. Conversely, antihyperglycaemic drugs that promote adipogenesis or cause sodium retention (insulin and thiazolidinediones) may increase the risk for heart failure in patients with an underlying ventricular myopathy. Patients with obesity and diabetes who undergo catheter ablation for AF are at increased risk for AF recurrence and for post-ablation increases in pulmonary venous pressures and worsening heart failure, especially if HFpEF coexists. Therefore, AF may be the earliest indicator of HFpEF in patients with obesity or type 2 diabetes, and recognition of HFpEF alters the management of these patients.

Heightened risk of intensive rate control in patients with atrial fibrillation who are obese or have type 2 diabetes: A critical review and re-evaluation

Atrial fibrillation (AF) is common in patients with obesity and diabetes; the arrhythmia (if long-standing) is typically managed by rate control and anticoagulation. However, the coexistence of these two metabolic disorders complicates therapeutic options for rate control. The likely pathogenesis of AF in these patients is an expansion of epicardial adipose tissue whose inflammation is transmitted to the left atrium causing electromechanical remodeling. However, this same process is also transmitted to the left ventricle (LV), impairing its distensibility and its ability to tolerate volume, leading to heart failure with preserved ejection fraction. Unfortunately, the latter diagnosis (although commonly present in patients with AF and a coexistent metabolic disorder) is often ignored. To achieve rate control, physicians prescribe intensive treatment with atrioventricular (AV) nodal-blocking drugs, often at doses that are titrated to blunt exercise as well as resting heart rate responses. However, strict rate control (target rate, <80/min) is associated with somewhat worse outcomes than lenient rate control (target rate, <110/min). Furthermore, any rate slowing that facilitates diastolic filling may aggravate filling pressures that are already disproportionately increased because the LV is stiff and overfilled as a result of cardiac inflammation. Rate slowing in AF with beta blockers may not achieve the benefit expected from the blockade of adrenergically mediated cardiotoxicity, and some AV nodal-blocking drugs (digoxin and dronedarone) can increase the risk of death in patients with AF. Finally, cardiac fibrosis in obesity and diabetes may affect the conduction system, which can predispose to serious bradyarrhythmias if patients are prescribed AV nodal-blocking drugs.

Disease-treatment interactions in the management of patients with obesity and diabetes who have atrial fibrillation: the potential mediating influence of epicardial adipose tissue

Both obesity and type 2 diabetes are important risk factors for atrial fibrillation (AF), possibly because they both cause an expansion of epicardial adipose tissue, which is the source of proinflammatory adipocytokines that can lead to microvascular dysfunction and fibrosis of the underlying myocardium. If the derangement of epicardial fat adjoins the left atrium, the result is an atrial myopathy, which is clinically manifest as AF. In patients with AF, there is a close relationship between epicardial fat volume and the severity of electrophysiological abnormalities in the adjacent myocardial tissues, and epicardial fat mass predicts AF in the general population. The expansion of epicardial adipose tissue in obesity and type 2 diabetes may also affect the left ventricle, impairing its distensibility and leading to heart failure with a preserved ejection fraction (HFpEF). Patients with obesity or type 2 diabetes with AF often have HFpEF, but the diagnosis may be missed, if dyspnea is attributed to increased body mass or to the arrhythmia. The expected response to the treatment for obesity, diabetes or AF may be influenced by their effects on epicardial inflammation and the underlying atrial and ventricular myopathy. Bariatric surgery and metformin reduce epicardial fat mass and ameliorate AF, whereas insulin promotes adipogenesis and cardiac fibrosis, and its use is accompanied by an increased risk of AF. Rate control strategies for AF may impair exercise tolerance, because they allow for greater time for ventricular filling in patients who cannot tolerate volume loading because of cardiac fibrosis and HFpEF. At the same time, both obesity and diabetes decrease the expected success rate of rhythm control strategies for AF (e.g., electrical cardioversion or catheter ablation), because increased epicardial adipose tissue volumes and cardiac fibrosis are important determinants of AF recurrence following these procedures.

A Compelling Case for Less Aggressive Arrhythmia Management in Patients With Chronic Heart Failure and Long-Standing Atrial Fibrillation

BACKGROUND AND METHODS

Atrial fibrillation (AF) is common in chronic heart failure, and some have advocated intensive rate and/or rhythm control strategies for these patients. However, the loss of atrial systole and irregularity of the ventricular response has not been shown to contribute to the progression of heart failure, and the presence or rate of long-standing AF in patients with chronic heart failure does not have prognostic significance.

RESULTS

In randomized clinical trials, pharmacological rhythm control has not been shown to be superior to rate-control in influencing long-term outcomes, but the use of membrane-active antiarrhythmic drugs can increase the risk of both pump failure and arrhythmic deaths in patients with heart failure. Additionally, intensive efforts to slow the ventricular rate in AF can potentially cause clinically inapparent bradyarrhythmias, which can trigger rate-dependent lethal rhythm disturbances or hemodynamic abnormalities. In patients with AF, a more stringent approach to rate control (target rate <80/min) is not superior to a more lenient strategy (target rate <110/min) on the risk of major events. Little is known about the effects of catheter ablation of long-standing AF in established heart failure, particularly in patients with a preserved or a meaningfully reduced ejection fraction, but ablation can add to the fibrotic burden of the left atrium and impair its capacitance functions.

CONCLUSIONS

For all of these reasons, the management of heart failure and long-standing AF should be primarily directed to slowing of the progression of their underlying cardiomyopathic process rather than the treatment of the arrhythmia. In addition, patients should receive long-term oral anticoagulation with non-vitamin K-antagonist oral anticoagulants to reduce the risk of thromboembolic events. The utility of intensive rate and rhythm control interventions for long-standing AF in patients with established heart failure requires further study.

Multiparametric cardiovascular magnetic resonance imaging in acute myocarditis: a comparison of different measurement approaches

BACKGROUND

Myocardial T1 and T2 mapping are reliable diagnostic markers for the detection and follow up of acute myocarditis. The aim of this study was to compare the diagnostic performance of current mapping measurement approaches to differentiate between myocarditis patients and healthy individuals.

METHODS

Fifty patients with clinically defined acute myocarditis and 30 healthy controls underwent cardiovascular magnetic resonance (CMR). Myocardial T1 relaxation times, T2 relaxation times, left ventricular (LV) function, T2 ratio, early gadolinium enhancement ratio, and presence of late gadolinium enhancement (LGE) were analysed. Native T1 and T2 relaxation times, as well as extracellular volume fraction (ECV) were measured for the entire LV myocardium (global), within the midventricular short axis slice (mSAX), within the midventricular septal wall (ConSept), and within the remote myocardium (remote). Receiver operating characteristics analysis was performed to compare diagnostic performance.

RESULTS

All measurement approaches revealed significantly higher native T1 and T2 relaxation times as well as ECV values in patients compared to healthy controls (p < 0.05 for all parameters). The global measurement approach showed highest diagnostic performance regarding all mapping parameters (AUCs, native T1: 0.903, T2: 0.847, ECV: 0.731). Direct comparison of the different measurement approaches revealed significant differences in diagnostic performance between the global and the remote approach regarding T1 relaxation times and ECV (p = 0.001 and p = 0.002 respectively). Further, the global measurement approach revealed significantly higher T1 relaxation times compared to the ConSept approach (AUCs: 0.903 vs. 0.783; p = 0.003) and nearly significant differences compared to the mSAX approach (AUC: 0.850; p = 0.051). T2 relaxation times showed no significant differences between all measurement approaches (p > 0.050 for all parameters).

CONCLUSIONS

Native T1 and T2 mapping allow for accurate detection of acute myocarditis irrespective of the measurement approach used. Even measurements performed exclusively within remote myocardium allow for reliable detection of acute myocarditis, demonstrating diffuse involvement of disease despite a mostly regional or patchy distribution pattern of visible pathologies. The global measurement approach provides the overall best diagnostic performance in acute myocarditis for both T1 and T2 mapping.

Quantitative cardiac MRI

Cardiac MRI has become an indispensable imaging modality in the investigation of patients with suspected heart disease. It has emerged as the gold standard test for cardiac function, volumes, and mass and allows noninvasive tissue characterization and the assessment of myocardial perfusion. Quantitative MRI already has a key role in the development and incorporation of machine learning in clinical imaging, potentially offering major improvements in both workflow efficiency and diagnostic accuracy. As the clinical applications of a wide range of quantitative cardiac MRI techniques are being explored and validated, we are expanding our capabilities for earlier detection, monitoring, and risk stratification of disease, potentially guiding personalized management decisions in various cardiac disease models. In this article we review established and emerging quantitative techniques, their clinical applications, highlight novel advances, and appraise their clinical diagnostic potential. Level of Evidence: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2020;51:693-711.

Relaxin and fibrosis: Emerging targets, challenges, and future directions

The peptide hormone relaxin is well-known for its anti-fibrotic actions in several organs, particularly from numerous studies conducted in animals. Acting through its cognate G protein-coupled receptor, relaxin family peptide receptor 1 (RXFP1), serelaxin (recombinant human relaxin) has been shown to consistently inhibit the excessive extracellular matrix production (fibrosis) that results from the aberrant wound-healing response to tissue injury and/or chronic inflammation, and at multiple levels. Furthermore, it can reduce established scarring by promoting the degradation of aberrant extracellular matrix components. Following on from the review that describes the mechanisms and signaling pathways associated with the extracellular matrix remodeling effects of serelaxin (Ng et al., 2019), this review focuses on newly identified tissue targets of serelaxin therapy in fibrosis, and the limitations associated with (se)relaxin research.