The role of CT in detecting AF substrate

https://doi.org/10.1016/j.tcm.2020.10.004Get rights and content

Abstract

Despite technological advancements and evolving ablation strategies, atrial fibrillation catheter ablation outcome remains suboptimal for a cohort of patients. Imaging-based biomarkers have the potential to play a pivotal role in the overall assessment and prognostic stratification of AF patients, allowing for tailored treatments and individualized care. Alongside consolidated evaluation parameters, novel imaging biomarkers that can detect and stage the remodelling process and correlate it to electrophysiological phenomena are emerging. This review aims to provide a better understanding of the different types of atrial substrate, and how Computed Tomography can be used as a pre-ablation risk stratification tool by assessing the various novel imaging biomarkers, providing a valuable insight into the mechanisms that sustain AF and potentially allowing for a patient-specific ablation strategy.

Introduction

Atrial fibrillation (AF) is the most common sustained arrhythmia, and a rise in the worldwide incidence and prevalence of AF is expected, with significant effects on associated morbidity and mortality [1]. Catheter ablation is considered more effective than antiarrhythmic drug therapy in maintaining sinus rhythm [2]. Despite technological advancements and evolving ablation strategies, the success rates remain suboptimal for a cohort of patients. Pulmonary vein isolation (PVI) is well-established and widely used as a first-line approach [3]. This has demonstrated good short- and long-term results for paroxysmal AF (PAF) [4,5]. Procedural success proves more difficult to attain in patients with non-paroxysmal AF (non-PAF) after PVI alone, as evidenced by the majority of data [6,7]. Beside this, no supplementary ablation target has been proven to be clearly superior to PVI in reducing AF recurrence in this group [8]. This may be explained by the fact that AF results from a complex interaction between triggers and substrate. Triggers are primarily responsible for AF initiation, whilst substrate perpetuates the remodelling processes, leading to AF maintenance and progression. It is generally believed that triggers weigh more on paroxysmal AF while substrate remodelling plays a key role in non-paroxysmal forms. Consequently, PVI may not be sufficient to prevent recurrences in non-PAF, and the lower success rates in this group may be explained by the difficulty to identify the key non-PV sources that sustain AF.

This review aims to provide a better understanding of the different types of atrial substrate and how Computed Tomography (CT) can be used as a pre-ablation risk stratification tool by assessing the various novel imaging biomarkers, providing a valuable insight about the mechanism that sustain AF and potentially allowing for a patient-specific tailored ablation strategy.

Section snippets

AF triggers and substrate

Triggers are usually represented by rapidly firing atrial foci. Ectopic beats are due to triggered activity, automaticity and re-entry. Pulmonary vein (PV) cardiomyocytes exhibit specific action potential properties that are modulated by atrial stretch and autonomic tone, and an architectural disarrangement at the entrance of the PVs predisposes to arrhythmogenesis [9]. Haissaguerre demonstrated that PVs are an important source of ectopic beats, initiating frequent paroxysms of AF, laying the

Computed tomography and AF substrate

CT is widely used in the anatomical assessment of the heart prior to AF ablation [40]. Its high resolution allows for accurate measurements of indices including LA volume, well recognised as an important prognostic factor [41]. Compared to TTE, CT provides a more accurate evaluation of atrial volume and correlates well with MRI measurements [42]. In addition, the evaluation of the LA sphericity index provides adjunctive information to further estimate the degree of atrial remodelling [43].

Limits and future outlook

The knowledge of the pathogenic mechanisms that sustain AF has matured significantly and a new type of AF categorization (rather than simply based on its chronicity) is required. Imaging biomarkers have the potential to play a pivotal role in the assessment and prognostic stratification of AF patients (Table 1), allowing for tailored treatments and individualized care. Moreover, these novel biomarkers may help to clarify specific pathogenic pathways which can be potential targets for drugs (

Conclusion

CT is a well-established and increasingly used imaging modality in patients undergoing AF ablation. Alongside consolidated evaluation parameters, novel imaging biomarkers that can detect and stage the remodelling process and correlate it to electrophysiological phenomena are emerging. Standard CT imaging biomarkers such as LAWT and EAT could help to identify both anatomical and electrical AF substrate. With improving imaging technology, CE-MDCT and (FDG)-CT/PET may emerge as alternatives for

References (94)

  • S.S. Chugh et al.

    Worldwide epidemiology of atrial fibrillation: a global burden of disease 2010 study

    Circulation

    (2014)
  • D.L. Packer et al.

    Effect of Catheter ablation vs antiarrhythmic drug therapy on mortality, stroke, bleeding, and cardiac arrest among patients with atrial fibrillation: the CABANA randomized clinical trial

    JAMA - J Am Med Assoc

    (2019)
  • P. Kirchhof et al.

    2016 ESC Guidelines for the management of atrial fibrillation developed in collaboration with EACTS

    Eur Heart J

    (2016)
  • Z. Kis et al.

    The short and long-term efficacy of pulmonary vein isolation as a sole treatment strategy for paroxysmal atrial fibrillation: a systematic review and meta-analysis

    Curr Cardiol Rev

    (2017)
  • J.A. Clarnette et al.

    Outcomes of persistent and long-standing persistent atrial fibrillation ablation: a systematic review and meta-analysis

    Europace

    (2018)
  • A.C. Perino et al.

    Secular trends in success rate of catheter ablation for atrial fibrillation: the SMASH-AF cohort

    Am Heart J

    (2019)
  • A. Verma et al.

    Approaches to catheter ablation for persistent atrial fibrillation

    N Engl J Med

    (2015)
  • G. Cheniti et al.

    Atrial fibrillation mechanisms and implications for catheter ablation

    Front Physiol

    (2018)
  • M. Haïssaguerre et al.

    Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins

    N Engl J Med

    (1998)
  • A.D. Margulescu et al.

    Persistent atrial fibrillation vs paroxysmal atrial fibrillation: differences in management

    Expert Rev Cardiovasc Ther

    (2017)
  • R. Pathak et al.

    Structural and functional remodeling of the left atrium: clinical and therapeutic implications for atrial fibrillation

    J Atr Fibrillation

    (2013)
  • J.M.B. Anumonwo et al.

    Fatty infiltration of the myocardium and arrhythmogenesis: potential cellular and molecular mechanisms

    Front Physiol

    (2018)
  • C.X. Wong et al.

    Epicardial fat and atrial fibrillation: current evidence, potential mechanisms, clinical implications, and future directions

    Eur Heart J

    (2017)
  • R. Singhal et al.

    Intrinsic cardiac autonomic ganglionated plexi within epicardial fats modulate the atrial substrate remodeling: experiences with atrial fibrillation patients receiving catheter ablation

    Acta Cardiol Sin

    (2016)
  • M. Zhou et al.

    Epicardial adipose tissue and atrial fibrillation: possible mechanisms, potential therapies, and future directions

    PACE - Pacing Clin Electrophysiol

    (2020)
  • M. Osranek et al.

    Left atrial volume predicts cardiovascular events in patients originally diagnosed with lone atrial fibrillation: three-decade follow-up

    Eur Heart J

    (2005)
  • A. Njoku et al.

    Left atrial volume predicts atrial fibrillation recurrence after radiofrequency ablation: a meta-analysis

    Europace

    (2018)
  • E. Donal et al.

    EACVI/EHRA Expert Consensus Document on the role of multi-modality imaging for the evaluation of patients with atrial fibrillation

    Eur Heart J Cardiovasc Imaging

    (2016)
  • J. Zhuang et al.

    Association between left atrial size and atrial fibrillation recurrence after single circumferential pulmonary vein isolation: a systematic review and meta-analysis of observational studies

    Europace

    (2012)
  • M.G. Rabbat et al.

    Left atrial volume assessment in atrial fibrillation using multimodality imaging: a comparison of echocardiography, invasive three-dimensional CARTO and cardiac magnetic resonance imaging

    Int J Cardiovasc Imaging

    (2015)
  • M. Cameli et al.

    Left atrial strain: a useful index in atrial fibrillation

    Int J Cardiol

    (2016)
  • S.S. Kuppahally et al.

    Left atrial strain and strain rate in patients with paroxysmal and persistent atrial fibrillation: relationship to left atrial structural remodeling detected by delayed-enhancement MRI

    Circ Cardiovasc Imaging

    (2010)
  • E. Pilichowska-Paszkiet et al.

    Noninvasive assessment of left atrial fibrosis. Correlation between echocardiography, biomarkers, and electroanatomical mapping

    Echocardiography

    (2018)
  • G. Bajraktari et al.

    Left atrial structure and function predictors of recurrent fibrillation after catheter ablation: a systematic review and meta-analysis

    Clin Physiol Funct Imaging

    (2020)
  • F.J. Olsen et al.

    Multimodality cardiac imaging for the assessment of left atrial function and the association with atrial arrhythmias

    Circ Cardiovasc Imaging

    (2016)
  • T. Kojima et al.

    Left atrial global and regional function in patients with paroxysmal atrial fibrillation has already been impaired before enlargement of left atrium: velocity vector imaging echocardiography study

    Eur Heart J Cardiovasc Imaging

    (2012)
  • D.W. den Uijl et al.

    Impact of left atrial volume, sphericity, and fibrosis on the outcome of catheter ablation for atrial fibrillation

    J Cardiovasc Electrophysiol

    (2018)
  • S. Nakamori et al.

    Incremental value of left atrial geometric remodeling in predicting late atrial fibrillation recurrence after pulmonary vein isolation: a cardiovascular magnetic resonance study

    J Am Heart Assoc

    (2018)
  • P. Gal et al.

    Magnetic resonance imaging of atrial fibrosis: redefining atrial fibrillation to a syndrome

    Eur Heart J

    (2017)
  • N. Akoum et al.

    Atrial fibrosis helps select the appropriate patient and strategy in catheter ablation of atrial fibrillation: a DE-MRI guided approach

    J Cardiovasc Electrophysiol

    (2011)
  • N.F. Marrouche et al.

    Association of atrial tissue fibrosis identified by delayed enhancement MRI and atrial fibrillation catheter ablation: the DECAAF study

    JAMA - J Am Med Assoc

    (2014)
  • K. Higuchi et al.

    Cardiac MRI assessment of atrial fibrosis in atrial fibrillation: implications for diagnosis and therapy

    Heart

    (2014)
  • M. Sramko et al.

    Clinical value of assessment of left atrial late gadolinium enhancement in patients undergoing ablation of atrial fibrillation

    Int J Cardiol

    (2015)
  • R.J. Hunter et al.

    Diagnostic accuracy of cardiac magnetic resonance imaging in the detection and characterization of left atrial catheter ablation lesions: a multicenter experience

    J Cardiovasc Electrophysiol

    (2013)
  • G. Pontecorboli et al.

    Use of delayed-enhancement magnetic resonance imaging for fibrosis detection in the atria: a review

    Europace

    (2017)
  • H. Calkins et al.

    2017 HRS/EHRA/ECAS/APHRS/SOLAECE expert consensus statement on catheter and surgical ablation of atrial fibrillation

    Europace

    (2018)
  • A.S. Helms et al.

    Relation of left atrial volume from three-dimensional computed tomography to atrial fibrillation recurrence following ablation

    Am J Cardiol

    (2009)

    • Declaration of Competing Interest: None.

    1

    Equally contributing authors.

    View full text
    © 2020 Elsevier Inc. All rights reserved.