Contrast-enhanced magnetic resonance imaging identifies focal regions of intramyocardial fibrosis in patients with severe aortic valve disease: Correlation with quantitative histopathology

Ventricular arrhythmias in patients with bicuspid aortic valves

INTRODUCTION

Bicuspid aortic valves (BAV) are the most common congenital heart defects and the extent of ventricular arrhythmias (VA) in patients with BAV is unclear. The objective of this study is to describe VAs and late gadolinium enhancement cardiac magnetic resonance imaging (LGE-CMR) in patients with BAV.

METHODS

A total of 19 patients with BAV (18 males, age: 58 ± 13 years) were referred for VA ablation procedures. Ten patients had BAVs at the time of ablation, nine patients had prior aortic valve replacement for a BAV. All but one patient had LGE-CMR and all patients underwent programmed ventricular stimulation at the time of the ablation.

RESULTS

Frequent PVCs were the targeted VAs in 17/19 patients and VT in 2/19 patients. Monomorphic ventricular tachycardia (VT) was inducible in 6 patients. A total of 15 VTs were inducible (2.5 ± 1.0 VTs per patient with a mean cycle length of 322 ± 83 msec). LGE was present in 13 patients. Patients with inducible VT had larger borderzone and core scar compared to non-inducible patients (7.8 ± 2.1 cm3 vs. 2.5 ± 3.1 cm3 and 5.1 ± 2.6 cm3 vs. 1.9 ± 3.0 cm3, p-value < .05 for both). PVCs and VTs were mapped to the periaortic valve area in 12 patients and 4 patients, respectively. The PVC burden was reduced from 27 ± 13 to 3 ± 6 (p < .001) and the ejection fraction improved from 49 ± 13% to 55 ± 9% (p = .005).

CONCLUSIONS

VAs in patients with BAV often originate from the perivalvular area and patients often have LGE and inducible VT. LGE may be due to ventricular remodeling secondary to the presence of BAV and harbors the arrhythmogenic substrate for VT.

Diagnostic value of LGE and T1 mapping in multiple myeloma patients'heart

BACKGROUND

Unidentified heart failure occurs in patients with multiple myeloma when their heart was involved. CMR with late gadolinium enhancement (LGE) and T1 mapping can identify myocardial amyloid infiltrations.

PURPOSE

To explore the role of CMR with late gadolinium enhancement (LGE) and T1 mapping for detection of multiple myeloma patients'heart.

MATERIAL AND METHODS

A total of 16 MM patients with above underwent CMR (3.0-T) with T1 mapping (pre-contrast and post-contrast) and LGE imaging. In addition, 26 patients with non-obstructive hypertrophic cardiomyopathy and 26 healthy volunteers were compared to age- and sex-matched healthy controls without a history of cardiac disease, diabetes mellitus, or normal in CMR. All statistical analyses were performed using the statistical software GraphPad Prism. The measurement data were represented by median (X) and single sample T test was adopted. Enumeration data were represented by examples and Chi-tested was adopted. All tests were two-sided, and P values < 0.05 were considered statistically significant.

RESULTS

In MM group, LVEF was lower than healthy controls and higher than that of non-obstructive hypertrophic cardiomyopathy group, but without statistically significant difference (%: 49.1 ± 17.5 vs. 55.6 ± 10.3, 40.4 ± 15.6, all P > 0.05). Pre-contrast T1 values of MM group were obviously higher than those of healthy controls and non-obstructive hypertrophic cardiomyopathy group (ms:1462.0 ± 71.3vs. 1269.3 ± 42.3, 1324.0 ± 45.1, all P < 0.05). 16 cases (100%) in MM group all had LGE.

CONCLUSION

LGE joint T1 mapping wider clinical use techniques and follow-up the patients'disease severity.

Soluble ST2 levels are related to replacement myocardial fibrosis in severe aortic stenosis

INTRODUCTION AND OBJECTIVES

Patients with aortic stenosis (AS) exhibit left ventricular (LV) remodeling and replacement myocardial fibrosis (RMF). Whether sST2 is associated with RMF measured by cardiac magnetic resonance and with sex remains unknown.

METHODS

We recruited 79 consecutive patients (73.0 [68.0-78.0] years; 61% men) with severe isolated AS underdoing valve replacement. RMF was identified and quantified by late gadolinium enhancement (LGE). Serum sST2 levels were determined.

RESULTS

RMF was associated with higher circulating sST2 levels, LV hypertrophy and dilation, and lower LV ejection fraction. All patients with LV dysfunction had RMF. Circulating levels of sST2 ≥ 28.8 ng/mL were associated with RMF and greater LV hypertrophy. LGE mass was correlated with LV remodeling and sST2. Of note, sST2 levels were also associated with the RMF pattern, being higher in midwall than in subendocardial fibrosis. Multivariate analyses showed that only LV ejection fraction and sST2 levels were associated with RMF. Moreover, men had higher levels of sST2 and RMF. RMF was associated with higher LV dilation and hypertrophy only in men and was correlated with LGE mass.

CONCLUSIONS

SST2 was an independent factor for RMF in patients with severe isolated AS. The presence of RMF was predicted by sST2 ≥ 28.2 ng/mL, and was associated with greater LV hypertrophy. sST2 expression and clinical associations may be sex-specific.

Is myocardial fibrosis appropriately assessed by calibrated and 2D strain derived integrated backscatter?

AIMS

Increased collagen content of the myocardium modifies tissue reflectivity and integrated backscatter (IBS) indexes are suggested as markers of myocardial fibrosis (MF). We sought to assess the correlation between calibrated (c) IBS and bidimensional (2D) strain derived IBS with left ventricular (LV) MF in patients with severe aortic stenosis (AS).

METHODS AND RESULTS

We made a prospective observational cohort study including 157 patients with severe AS referred for surgical aortic valve replacement (AVR), with complete preoperative transthoracic echocardiography, cardiac magnetic resonance (CMR) and endomyocardial biopsy (EMB) obtained from the anterior basal septum at the time of surgery. Two groups of 30 patients were specifically evaluated, with and without late gadolinium enhancement (LGE) at CMR. IBS was obtained at QRS peak from both parasternal long axis (PLAX) and apical-three-chamber (AP3C) views and measured in decibels (dB). Whole-cardiac cycle IBS at basal anterior septum was obtained from 2D longitudinal strain. Correlation analysis of reflectivity indexes was performed with global and segmental (anterior basal septum) values of native T1 and extracellular volume (ECV), and EMB collagen volume fraction (CVF) (Masson´s Trichrome). IBS values were compared in both group of patients (LGE + vs. LGE -). 60 patients (74 [36-74] years, 45% male) with high gradient (mean gradient: 63 ± 20mmHg), normal flow (45 ± 10mL/m2) AS and preserved left ventricular ejection fraction (60 ± 9%) were included. Basal septum cIBS was - 17.45 (-31.2-10.95) and - 9.17 ± 9.45dB from PLAX and A3C views, respectively. No significant correlations were found between IBS and both non-invasive CMR tissue characterization and CVF: median MF of 9.7(2.1-79.9)%. Acoustic indexes were not significantly different according to the presence of pre-operative LGE.

CONCLUSION

In this group of patients with classical severe AS, IBS reflectivity indexes are of no added value to discriminate the presence of MF.

Left Ventricular Remodeling in Degenerative Aortic Valve Stenosis

Aortic stenosis was once considered a pure isolated valve obstacle challenging left ventricle driving force of contraction and flow generation. Left ventricular (LV) adaptation was merely interpreted as a uniform hypertrophic response to increased afterload. However, in these last 2 decades cardiac imaging research and some histopathology correlation studies brought insight towards the complex interaction between the vasculature, the valve and the myocardium. Verily, LV remodeling in this setting is a complex multidetermined process that goes further beyond myocardial hypertrophy. Ultrastructural changes involving both diffuse and replacement fibrosis of the myocardium take part and might explain the transition of clinical phenotypes with distinct prognosis, from compensated hypertrophy to LV maladaptive dysfunction and heart failure. Presently, the combined appropriate use of echocardiography and cardiac magnetic resonance may better assess the global LV afterload, hypertrophy and geometric remodeling, global and regional LV function, beyond ejection fraction, and structural changes that include the fibrotic burden of the myocardium. As a whole these may not only better stratify individual risk of disease progression but also identify patients benefiting from earlier valve intervention. In this paper, we review the maladaptive response of the LV to chronic pressure overload, describing the different signaling pathways and mechanisms that underly both hypertrophy and remodeling. Histomorphology changes in this setting are described and we try to make sense of the use of new imaging tools for LV characterization.

Targeting cardiac fibrosis in heart failure with preserved ejection fraction: mirage or miracle?

Cardiac fibrosis is central to the pathology of heart failure, particularly heart failure with preserved ejection fraction (HFpEF). Irrespective of the underlying profibrotic condition (e.g. ageing, diabetes, hypertension), maladaptive cardiac fibrosis is defined by the transformation of resident fibroblasts to matrix-secreting myofibroblasts. Numerous profibrotic factors have been identified at the molecular level (e.g. TGFβ, IL11, AngII), which activate gene expression programs for myofibroblast activation. A number of existing HF therapies indirectly target fibrotic pathways; however, despite multiple clinical trials in HFpEF, a specific clinically effective antifibrotic therapy remains elusive. Therapeutic inhibition of TGFβ, the master-regulator of fibrosis, has unfortunately proven toxic and ineffective in clinical trials to date, and new approaches are needed. In this review, we discuss the pathophysiology and clinical implications of interstitial fibrosis in HFpEF. We provide an overview of trials targeting fibrosis in HFpEF to date and discuss the promise of potential new therapeutic approaches and targets in the context of underlying molecular mechanisms.

Aortic valvular imaging with cardiovascular magnetic resonance: seeking for comprehensiveness

Cardiovascular magnetic resonance (CMR) has an emerging role in aortic valve disease evaluation, becoming an all-in-one technique. CMR evaluation of the anatomy and flow through the aortic valve has a higher reproducibility than echocardiography. Its unique ability of in vivo myocardial tissue characterization, significantly improves the risk stratification and management of patients. In addition, CMR is equivalent to cardiac CT angiography for trans-aortic valvular implantation and surgical aortic valve replacement planning; on the other hand, its role in the evaluation of ventricular function improving and post-treatment complications is undisputed. This review encompasses the existing literature regarding the role of CMR in aortic valve disease, exploring all the aspects of the disease, from diagnosis to prognosis.

Assessment of Aortic Stenosis by Cardiac Magnetic Resonance Imaging: Quantification of Flow, Characterization of Myocardial Injury, Transcatheter Aortic Valve Replacement Planning, and More

Cardiac MR (CMR) imaging contributes uniquely to the comprehensive assessment and management of aortic stenosis (AS), beyond the information provided by transthoracic echocardiography. The severity of AS and subsequent ventricular remodeling response can be assessed using cine images and phase-contrast mapping. CMR imaging also identifies myocardial tissue characteristics, which are valuable markers of left ventricular decompensation and adverse outcomes in AS. CMR imaging may be used as an alternative modality for transcatheter aortic valve replacement (TAVR) planning and post-TAVR management. This article explores the clinical utility of CMR imaging evaluation.

Role of Cardiac Computed Tomography in the Diagnosis of Left Ventricular Myocardial Diseases

Multimodality imaging is indicated for the evaluation of left ventricular (LV) myocardial diseases. Cardiac magnetic resonance (CMR) allows morphological and functional assessment of the LV along with soft tissue characterization. Technological advances in cardiac computed tomography (CT) have led to the development of techniques for diagnostic acquisition in LV myocardial disease. Cardiac CT facilitates the characterization of LV myocardial disease based on anatomy, function, and enhancement pattern. LV regional and global functional parameters are evaluated using multi-phasic cine CT images. CT myocardial perfusion facilitates the identification of hemodynamically significant coronary artery stenosis. Cardiac CT with delayed enhancement is used to detect myocardial scarring or fibrosis in myocardial infarction and non-ischemic cardiomyopathy, and for the measurement of extracellular volume fraction in non-ischemic cardiomyopathy. In this review, we review imaging techniques and key imaging features of cardiac CT used for the evaluation of myocardial diseases, along with CMR findings.

CMR quantitation of change in mitral regurgitation following transcatheter aortic valve replacement (TAVR): impact on left ventricular reverse remodeling and outcome

Current echocardiographic data reporting the impact of concomitant mitral regurgitation (MR) on outcome in patients who undergo transcatheter aortic valve replacement (TAVR) are conflicting. Using cardiovascular magnetic resonance (CMR) imaging, this study aimed to assess the impact of MR severity on cardiac reverse remodeling and patient outcome. 85 patients undergoing TAVR with CMR pre- and 6 m post-TAVR were evaluated. The CMR protocol included cines for left (LV) and right ventricular (RV) volumes, flow assessment, and myocardial scar assessment by late gadolinium enhancement (LGE). Patients were dichotomised according to CMR severity of MR fraction at baseline (‘non-significant’ vs ‘significant’) and followed up for a median duration of 3 years. Forty-two (49%) patients had ‘significant MR’ at baseline; they had similar LV and RV size and function compared to the ‘non-significant MR’ group but had greater LV mass at baseline. In those with significant MR at baseline, 77% (n = 32) had a reduction in MR post-TAVR, moving them into the ‘non-significant’ category at 6-months, with an overall reduction in MR fraction from 34 to 17% (p < 0.001). Improvement in MR was not associated with more favourable cardiac reverse remodeling when compared with the ‘non-improvers’. Significant MR at baseline was not associated with increased mortality at follow-up. Significant MR is common in patients undergoing TAVR and improves in the majority post-procedure. Improvement in MR was not associated with more favourable LV reverse remodeling and baseline MR severity was not associated with mortality.

Multimodality imaging for the quantitative assessment of mitral regurgitation

The natural history of mitral regurgitation (MR) results in significant morbidity and mortality. Innovations in non-invasive imaging have provided new insights into the pathophysiology and quantification of MR, in addition to early detection of left ventricular (LV) dysfunction and prognostic assessment in asymptomatic patients. Transthoracic (TTE) and transesophageal (TOE) echocardiography are the mainstay for diagnosis, assessment and serial surveillance. However, the advance from 2D to 3D imaging leads to improved assessment and characterization of mitral valve (MV) disease. Cardiovascular magnetic resonance (CMR) is increasingly used for MR quantitation and can provide an alternative imaging method if echocardiography is suboptimal or inconclusive. Other techniques such as exercise echocardiography, tissue Doppler imaging and speckle-tracking echocardiography can further offer complementary information on prognosis. This review summarises the current evidence for state-of-the-art cardiovascular imaging for the investigation of MR. Whilst advanced echocardiographic techniques are superior in the evaluation of complex MV anatomy, CMR appears the most accurate technique for the quantification of MR severity. Integration of multimodality imaging for the assessment of MR utilises the advantages of each imaging technique and offers the most comprehensive assessment of MR.

Cardiovascular magnetic resonance in the evaluation of heart valve disease

BACKGROUND

Over the last 25 years, cardiovascular magnetic resonance imaging (CMR) has emerged as an alternative to echocardiography for assessment of valvular heart disease (VHD). Although echo remains the first-line imaging modality for the assessment of patients with VHD, CMR can now provide a comprehensive assessment in many instances. Using a combination of techniques, CMR provides information on valve anatomy and enables quantitative analysis of the severity of the valve lesion.

MAIN TEXT

In this review, the fundamentals of CMR in assessment of VHD are described, together with its strengths and weaknesses. We detail the utility of CMR for studying all aspects of VHD, including valve anatomy, flow quantification as well as ventricular volumes and function. The optimisation of CMR for evaluating the commonest valve lesions (aortic stenosis, aortic regurgitation, mitral regurgitation, mitral stenosis) as well as in right-sided VHD and prosthetic valves is summarised. The focus of this review is to enable the reader to optimise the use of CMR in his or her own evaluation of heart valve lesions in clinical practice.

CONCLUSIONS

CMR can be used for the comprehensive evaluation of VHD. This exciting, non-invasive imaging modality is likely to have increasing utility in the clinical evaluation of patients with VHD.

Chronic Heart Disease after Treatment of Oral Acute Chagas Disease

We describe the recurrence of cardiac abnormalities in a patient treated during the acute phase of Chagas disease after outpatient follow-up of 5 years.

Prevalence, predictors, and prognostic implications of residual impairment of functional capacity after transcatheter aortic valve implantation

Background

Patients with degenerative aortic stenosis (AS) referred for transcatheter aortic valve implantation (TAVI) typically have advanced cardiac and vascular adverse remodeling and multiple comorbidities and, therefore, might not recover a normal functional capacity after valve replacement. We sought to investigate the prevalence, the predictors, and the prognostic impact of residual impairment of functional capacity after TAVI.

Methods and results

Out of 790 patients undergoing TAVI with impaired functional capacity (NYHA II–IV) at baseline, NYHA functional class improved in 592 (86.5%) and remained unchanged/worsened in 92 (13.5%) at follow-up [median (IQR): 419 (208–807) days] after TAVI. Normal functional capacity (NYHA I) was recovered in 65.5% (n = 448) of patients, while the rest had variable degrees of residual impairment. On multivariable regression analysis, atrial fibrillation [odds ratio-OR, 2.08 (1.21–3.58), p = 0.008], low-flow–low-gradient AS [OR, 1.97 (1.09–3.57), p = 0.026], chronic obstructive pulmonary disease [OR, 1.92 (1.19–3.12), p = 0.008], and lower hemoglobin at baseline [OR, 1.11 (1.01–1.21) for each g% decrement, p = 0.036] were independently associated with residual impairment of functional capacity. All-cause and cardiac mortality were significantly higher in those with residual impairment of functional capacity than in those in NYHA I class [hazard ratio-HR: 2.37 (95% CI: 1.51–3.72), p < 0.001 and 2.16 (95% CI: 1.08–4.35), p = 0.030, respectively]. Even mild residual functional impairment (NYHA II) was associated with a higher all-cause [HR: 2.02 (95% CI: 1.10–3.72), p = 0.023] and cardiac [HR: 2.08 (95% CI: 1.42–3.07), p < 0.001] mortality.

Conclusion

Residual impairment of functional capacity is common after TAVI and is independently associated with increased mortality. Predictors of residual impairment of functional status are predominantly patient-rather than procedure-related.

Electronic supplementary material

The online version of this article (doi:10.1007/s00392-017-1119-9) contains supplementary material, which is available to authorized users.

Differences in Aortic Valve and Left Ventricular Parameters Related to the Severity of Myocardial Fibrosis in Patients with Severe Aortic Valve Stenosis

OBJECTIVE

This study investigated the morphological and functional characteristics of the aortic valve and the left ventricular (LV) systolic functional parameters and myocardial mass related to the severity of myocardial fibrosis (MF) in patients with severe aortic valve stenosis (AS).

MATERIALS AND METHODS

We retrospectively enrolled 81 patients (48 men; mean age: 59±12 years) with severe AS who underwent transthoracic echocardiography (TTE), cardiac computed tomography (CCT), and cardiovascular magnetic resonance (CMR) within 1 month and subsequent aortic valve surgery. Degree of MF was determined on delayed contrast-enhanced CMR with visual sub-segmental analysis-based quantification and was classified into three groups (no, mild, and severe) for identifying the differences in LV function and characteristics of the aortic valve. One-way ANOVA, Chi-square test or Fisher's exact test were used to compare variables of the three groups. Univariate multinomial logistic regression analysis was performed to determine the association between the severity of MF and variables on imaging modalities.

RESULTS

Of 81 patients, 34 (42%) had MF (mild, n = 18; severe, n = 16). Aortic valve calcium volume score on CCT, aortic valve area, LV mass index, LV end-diastolic volume index on CMR, presence of mild aortic regurgitation (AR), transaortic mean pressure gradient, and peak velocity on TTE were significantly different among the three groups and were associated with severity of MF on a univariate multinomial logistic regression analysis. Aortic valve calcium grade was different (p = 0.008) among the three groups but not associated with severity of MF (p = 0.375).

CONCLUSIONS

A multi-imaging approach shows that severe AS with MF is significantly associated with more severe calcific AS, higher LV end-diastolic volume, higher LV mass, and higher prevalence of mild AR.

The role of cardiovascular magnetic resonance in the assessment of severe aortic stenosis and in post-procedural evaluation following transcatheter aortic valve implantation and surgical aortic valve replacement

Degenerative aortic stenosis (AS) is the most common valvular disease in the western world with a prevalence expected to double within the next 50 years. International guidelines advocate the use of cardiovascular magnetic resonance (CMR) as an investigative tool, both to guide diagnosis and to direct optimal treatment. CMR is the reference standard for quantifying both left and right ventricular volumes and mass, which is essential to assess the impact of AS upon global cardiac function. Given the ability to image any structure in any plane, CMR offers many other diagnostic strengths including full visualisation of valvular morphology, direct planimetry of orifice area, the quantification of stenotic jets and in particular, accurate quantification of valvular regurgitation. In addition, CMR permits reliable and accurate measurements of the aortic root and arch which can be fundamental to appropriate patient management. There is a growing evidence base to indicate tissue characterisation using CMR provides prognostic information, both in asymptomatic AS patients and those undergoing intervention. Furthermore, a number of current clinical trials will likely raise the importance of CMR in routine patient management. This article will focus on the incremental value of CMR in the assessment of severe AS and the insights it offers following valve replacement.

Quantitative diffusion-weighted magnetic resonance imaging in the assessment of myocardial fibrosis in hypertrophic cardiomyopathy compared with T1 mapping

To identify myocardial fibrosis in hypertrophic cardiomyopathy (HCM) subjects using quantitative cardiac diffusion-weighted imaging (DWI) and to compare its performance with native T1 mapping and extracellular volume (ECV). Thirty-eight HCM subjects (mean age, 53 ± 9 years) and 14 normal controls (mean age, 51 ± 8 years) underwent cardiac magnetic resonance imaging (CMRI) on a 3.0T magnetic resonance (MR) machine with DWI, T1 mapping and late gadolinium enhancement (LGE) imaging as the reference standard. The mean apparent diffusion coefficient (ADC), native T1 value and ECV were determined for each subject. Overall, the HCM subjects exhibited an increased native T1 value (1241.04 ± 78.50 ms), ECV (0.31 ± 0.03) and ADC (2.36 ± 0.34 s/mm(2)) compared with the normal controls (1114.60 ± 37.99 ms, 0.24 ± 0.04, and 1.62 ± 0.38 s/mm(2), respectively) (p < 0.05). DWI differentiated healthy and fibrotic myocardia with an area under the curve (AUC) of 0.93, while the AUCs of the native T1 values (0.93), (p > 0.05) and ECV (0.94), (p > 0.05) exhibited an equal differentiation ability. Both HCM LGE+ and HCM LGE- subjects had an increased native T1 value, ECV and ADC compared to the normal controls (p < 0.05). HCM LGE+ subjects exhibited an increased ECV (0.31 ± 0.04) and ADC (2.43 ± 0.36 s/mm(2)) compared to HCM LGE- subjects (p < 0.05). HCM LGE+ and HCM LGE- subjects had similar native T1 values (1250 ± 76.36 ms vs. 1213.98 ± 92.30 ms, respectively) (p > 0.05). ADC values were linearly associated with increased ECV (R(2) = 0.36) and native T1 values (R(2) = 0.40) among all subjects. DWI is a feasible alternative to native T1 mapping and ECV for the identification of myocardial fibrosis in patients with HCM. DWI and ECV can quantitatively characterize the extent of fibrosis in HCM LGE+ and HCM LGE- patients.

Histological Validation of measurement of diffuse interstitial myocardial fibrosis by myocardial extravascular volume fraction from Modified Look-Locker imaging (MOLLI) T1 mapping at 3 T

BACKGROUND

Gadolinium (Gd) Extracellular volume fraction (ECV) by Cardiovascular Magnetic Resonance (CMR) has been proposed as a non-invasive method for assessment of diffuse myocardial fibrosis. Yet only few studies used 3 T CMR to measure ECV, and the accuracy of ECV measurements at 3 T has not been established. Therefore the aims of the present study were to validate measurement of ECV by MOLLI T1 mapping by 3 T CMR against fibrosis measured by histopathology. We also evaluated the recently proposed hypothesis that native-T1 mapping without contrast injection would be sufficient to detect fibrosis.

METHODS

31 patients (age = 58 ± 17 years, 77% men) with either severe aortic stenosis (n = 12) severe aortic regurgitation (n = 9) or severe mitral regurgitation (n = 10), all free of coronary artery disease, underwent 3 T-CMR with late gadolinium enhancement (LGE) and pre- and post-contrast MOLLI T1 mapping and ECV computation, prior to valve surgery. LV biopsies were performed at the time of surgery, a median 13 [1-30] days later, and stained with picrosirius red. Pre-, and post-contrast T1 values, ECV, and amount of LGE were compared against magnitude of fibrosis by histopathology by Pearson correlation coefficients.

RESULTS

The average amount of interstitial fibrosis by picrosirius red staining in biopsy samples was 6.1 ± 4.3%. ECV computed from pre-post contrast MOLLI T1 time changes was 28.9 ± 5.5%, and correlated (r = 0.78, p < 0.001) strongly with the magnitude of histological fibrosis. By opposition, neither amount of LGE (r = 0.17, p = 0.36) nor native pre-contrast myocardial T1 time (r = -0.18, p = 0.32) correlated with fibrosis by histopathology.

CONCLUSIONS

ECV determined by 3 T CMR T1 MOLLI images closely correlates with histologically determined diffuse interstitial fibrosis, providing a non-invasive estimation for quantification of interstitial fibrosis in patients with valve diseases. By opposition, neither non-contrast T1 times nor the amount of LGE were indicative of the magnitude of diffuse interstitial fibrosis measured by histopathology.

Cardiac imaging in patients with chronic kidney disease

Patients with chronic kidney disease (CKD) carry a high cardiovascular risk. In this patient group, cardiac structure and function are frequently abnormal and 74% of patients with CKD stage 5 have left ventricular hypertrophy (LVH) at the initiation of renal replacement therapy. Cardiac changes, such as LVH and impaired left ventricular systolic function, have been associated with an unfavourable prognosis. Despite the prevalence of underlying cardiac abnormalities, symptoms may not manifest in many patients. Fortunately, a range of available and emerging cardiac imaging tools may assist with diagnosing and stratifying the risk and severity of heart disease in patients with CKD. Moreover, many of these techniques provide a better understanding of the pathophysiology of cardiac abnormalities in patients with renal disease. Knowledge of the currently available cardiac imaging modalities might help nephrologists to choose the most appropriate investigative tool based on individual patient circumstances. This Review describes established and emerging cardiac imaging modalities in this context, and compares their use in CKD patients with their use in the general population.

Prognostic significance of LGE by CMR in aortic stenosis patients undergoing valve replacement

BACKGROUND

Prior studies have shown that late gadolinium enhancement (LGE) by cardiac magnetic resonance (CMR) can detect focal fibrosis in aortic stenosis (AS), suggesting that it might predict higher mortality risk.

OBJECTIVES

This study was conducted to evaluate whether LGE-CMR can predict post-operative survival in patients with severe AS undergoing aortic valve replacement (AVR).

METHODS

We prospectively evaluated survival (all-cause and cardiovascular disease related) according to LGE-CMR status in 154 consecutive AS patients (96 men; mean age: 74 ± 6 years) without a history of myocardial infarction undergoing surgical AVR and in 40 AS patients undergoing transcatheter aortic valve replacement (TAVR).

RESULTS

LGE was present in 29% of patients undergoing surgical AVR and in 50% undergoing TAVR. During a median follow-up of 2.9 years, 21 patients undergoing surgical AVR and 20 undergoing TAVR died. In surgical AVR, the presence of LGE predicted higher post-operative mortality (odds ratio: 10.9; 95% confidence interval [CI]: 1.2 to 100.0; p = 0.02) and worse all-cause survival (73% vs. 88%; p = 0.02 by log-rank test) and cardiovascular disease related survival (85% vs. 95%; p = 0.03 by log-rank test) on 5-year Kaplan-Meier estimates of survival after surgical AVR. Multivariate Cox analysis identified the presence of LGE (hazard ratio: 2.8; 95% CI: 1.3 to 6.9; p = 0.025) and New York Heart Association functional class III/IV (hazard ratio: 3.2; 95% CI: 1.1 to 8.1; p < 0.01) as the sole independent predictors of all-cause mortality after surgical AVR. The presence of LGE also predicted higher all-cause mortality (p = 0.05) and cardiovascular disease related mortality (p = 0.03) in the subgroup of patients without angiographic coronary artery disease (n = 110) and higher cardiovascular disease related mortality in 25 patients undergoing transfemoral TAVR.

CONCLUSIONS

The presence of LGE indicating focal fibrosis or unrecognized infarct by CMR is an independent predictor of mortality in patients with AS undergoing AVR and could provide additional information in the pre-operative evaluation of risk in these patients.

Ex-vivo Assessment of Coronary Artery Atherosclerosis by Magnetic Resonance Imaging: Correlation with Histopathology

Introduction: In recent years, high-resolution magnetic resonance imaging (MRI) has emerged as a very promising technique for studying atherosclerotic disease in humans. Aim: In the present study we sought to determine whether MRI allowed for the morphological characterization of the coronary vessel wall and atherosclerotic plaques using histopathological assessment as the reference standard. Methods: The study population consisted of 13 patients who died of acute myocardial infarction and underwent autopsy. The proximal portions of the coronary arteries were excised and were evaluated both by MRI and by histopathology. For each arterial segment, the following parameters were calculated through manual planimetry: 1. total vessel area (TVA); 2. luminal area (LA) and 3. plaque area (PA). Results: A total of 207 coronary artery cross-sections were found to be suitable for analysis by both MRI and histopathology and were included in the final analyses. Both methods demonstrated moderate to good agreement for the quantification of TVA (mean difference = 2.4±2.4 mm², 95‰ limits of agreement from -2.4 to +7.2 mm²; CCC = 0.69, 95‰ CI from 0.63 to 0.75), LA (mean difference = 0.0±1.7 mm², 95‰ limits of agreement from -3.3 to + 3.3 mm²; CCC = 0.84, 95‰ CI from 0.80 to 0.88) and PA (mean difference = 2.4±2.4 mm², 95‰ limits of agreement from -2.3 to + 7.1 mm²; CCC = 0.64, 95‰ CI from 0.58 to 0.71). Conclusion: In this ex vivo experimental model we demonstrated good agreement between coronary artery morphometrical measurements obtained by high-resolution MRI and by histopathology.

When to consider cardiovascular magnetic resonance in patients undergoing transcatheter aortic valve replacement?

PURPOSE OF REVIEW

To discuss the relevant techniques as well as the recent evidence that enhance the understanding of the reader on the applications of cardiovascular magnetic resonance (CMR) in transcatheter aortic valve replacement (TAVR). With different cardiac imaging modalities available as well as the advent of TAVR, it is important to define when CMR can be helpful in the periprocedural evaluation.

RECENT FINDINGS

The topics of interest covered in this review are CMR evaluation of aortic stenosis/regurgitation, TAVR sizing, vascular measurements for access planning, postimplantation paravalvular regurgitation (PVR), and the potential role of delayed enhancement assessment in patients undergoing TAVR.

SUMMARY

CMR is a complementary modality in the assessment of TAVR candidates. The ability of CMR to assess the hemodynamic significance of aortic stenosis and other valvulopathies, as well as to assess accurately the left ventricular ejection fraction and vascular anatomy, makes this technique well rounded. The roles of delayed enhancement for myocardial scar in the evaluation of TAVR candidates and PVR assessment in the postimplant patient are promising, but still yet to be fully defined.

Increased frequency of fragmented QRS in patients with severe aortic valve stenosis

OBJECTIVE

To investigate the presence of myocardial fibrosis determined by fragmented QRS in patients with severe aortic valve stenosis.

SUBJECTS AND METHODS

Eighty-seven consecutive patients with severe aortic valve stenosis and 83 age- and gender-matched control subjects were enrolled into this study. Severe aortic valve stenosis was defined as an aortic valve area <1 cm(2), a Vmax >4 m/s, or a mean gradient ≥40 mm Hg. Fragmented QRS was assessed using a 12-lead electrocardiogram.

RESULTS

Fragmented QRS was detected in 40 (46%) patients in the aortic valve stenosis group and in 15 (18%) control subjects (p < 0.001). In multivariate binary logistic regression analysis, the presence of aortic valve stenosis was the only independent factor associated with fragmented QRS (OR = 3.69; 95% CI 1.81-7.55, p < 0.001).

CONCLUSION

A higher frequency of fragmented QRS was detected in patients with severe aortic valve stenosis compared to controls.

Assessment of valve haemodynamics, reverse ventricular remodelling and myocardial fibrosis following transcatheter aortic valve implantation compared to surgical aortic valve replacement: a cardiovascular magnetic resonance study

Objective

To compare the effects of transcatheter aortic valve implantation (TAVI) and surgical aortic valve replacement (SAVR) on aortic valve haemodynamics, ventricular reverse remodelling and myocardial fibrosis (MF) by cardiovascular magnetic resonance (CMR) imaging.

Design

A 1.5 T CMR scan was performed preoperatively and 6 months postoperatively.

Setting

University hospitals of Leeds and Leicester, UK.

Patients

50 (25 TAVI, 25 SAVR; age 77±8 years) high-risk severe symptomatic aortic stenosis (AS) patients.

Main outcome measures

Valve haemodynamics, ventricular volumes, ejection fraction (EF), mass and MF.

Results

Patients were matched for gender and AS severity but not for age (80±6 vs 73±7 years, p=0.001) or EuroSCORE (22±14 vs 7±3, p<0.001). Aortic valve mean pressure gradient decreased to a greater degree post-TAVI compared to SAVR (21±8 mm Hg vs 35±13 mm Hg, p=0.017). Aortic regurgitation reduced by 8% in both groups, only reaching statistical significance for TAVI (p=0.003). TAVI and SAVR improved (p<0.05) left ventricular (LV) end-systolic volumes (46±18 ml/m² vs 41±17 ml/m²; 44±22 ml/m² vs32±6 ml/m²) and mass (83±20 g/m² vs 65±15 g/m²; 74±11 g/m² vs 59±8 g/m²). SAVR reduced end-diastolic volumes (92±19 ml/m² vs 74±12 ml/m², p<0.001) and TAVI increased EF (52±12% vs 56±10%, p=0.01). MF reduced post-TAVI (10.9±6% vs 8.5±5%, p=0.03) but not post-SAVR (4.2±2% vs 4.1±2%, p=0.98). Myocardial scar (p≤0.01) and baseline ventricular volumes (p<0.001) were the major predictors of reverse remodelling.

Conclusions

TAVI was comparable to SAVR at LV reverse remodelling and superior at reducing the valvular pressure gradient and MF. Future work should assess the prognostic importance of reverse remodelling and fibrosis post-TAVI to aid patient selection.

Evaluation of the aortic and mitral valves with cardiac computed tomography and cardiac magnetic resonance imaging

Cardiac computed tomography (CT) produces high-quality anatomical images of the cardiac valves and associated structures. Cardiac magnetic resonance imaging (MRI) provides images of valve morphology, and allows quantitative evaluation of valvular dysfunction and determination of the impact of valvular lesions on cardiovascular structures. Recent studies have demonstrated that cardiac CT and MRI are important adjuncts to echocardiography for the evaluation of aortic and mitral valvular heart diseases (VHDs). Radiologists should be aware of the technical aspects of cardiac CT and MRI that allow comprehensive assessment of aortic and mitral VHDs, as well as the typical imaging features of common and important aortic and mitral VHDs on cardiac CT and MRI.

T1 Mapping in cardiomyopathy at cardiac MR: comparison with endomyocardial biopsy

PURPOSE

To determine the utility of cardiac magnetic resonance (MR) T1 mapping for quantification of diffuse myocardial fibrosis compared with the standard of endomyocardial biopsy.

MATERIALS AND METHODS

This HIPAA-compliant study was approved by the institutional review board. Cardiomyopathy patients were retrospectively identified who had undergone endomyocardial biopsy and cardiac MR at one institution during a 5-year period. Forty-seven patients (53% male; mean age, 46.8 years) had undergone diagnostic cardiac MR and endomyocardial biopsy. Thirteen healthy volunteers (54% male; mean age, 38.1 years) underwent cardiac MR as a reference. Myocardial T1 mapping was performed 10.7 minutes ± 2.7 (standard deviation) after bolus injection of 0.2 mmol/kg gadolinium chelate by using an inversion-recovery Look-Locker sequence on a 1.5-T MR imager. Late gadolinium enhancement was assessed by using gradient-echo inversion-recovery sequences. Cardiac MR results were the consensus of two radiologists who were blinded to histopathologic findings. Endomyocardial biopsy fibrosis was quantitatively measured by using automated image analysis software with digital images of specimens stained with Masson trichrome. Histopathologic findings were reported by two pathologists blinded to cardiac MR findings. Statistical analyses included Mann-Whitney U test, analysis of variance, and linear regression.

RESULTS

Median myocardial fibrosis was 8.5% (interquartile range, 5.7-14.4). T1 times were greater in control subjects than in patients without and in patients with evident late gadolinium enhancement (466 msec ± 14, 406 msec ± 59, and 303 msec ± 53, respectively; P < .001). T1 time and histologic fibrosis were inversely correlated (r = -0.57; 95% confidence interval: -0.74, -0.34; P < .0001). The area under the curve for myocardial T1 time to detect fibrosis of greater than 5% was 0.84 at a cutoff of 383 msec.

CONCLUSION

Cardiac MR with T1 mapping can provide noninvasive evidence of diffuse myocardial fibrosis in patients referred for evaluation of cardiomyopathy.

Assessment of myocardial fibrosis with cardiovascular magnetic resonance

Diffuse interstitial or replacement myocardial fibrosis is a common feature of a broad variety of cardiomyopathies. Myocardial fibrosis leads to impaired cardiac diastolic and systolic function and is related to adverse cardiovascular events. Cardiovascular magnetic resonance (CMR) may uniquely characterize the extent of replacement fibrosis and may have prognostic value in various cardiomyopathies. Myocardial longitudinal relaxation time mapping is an emerging technique that could improve CMR's diagnostic accuracy, especially for interstitial diffuse myocardial fibrosis. As such, CMR could be integrated in the monitoring and therapeutic management of a large number of patients. This review summarizes the advantages and limitations of CMR for the assessment of myocardial fibrosis.

Prognostic significance of myocardial fibrosis quantification by histopathology and magnetic resonance imaging in patients with severe aortic valve disease

OBJECTIVES

We sought to determine whether the quantitative assessment of myocardial fibrosis (MF), either by histopathology or by contrast-enhanced magnetic resonance imaging (ce-MRI), could help predict long-term survival after aortic valve replacement.

BACKGROUND

Severe aortic valve disease is characterized by progressive accumulation of interstitial MF.

METHODS

Fifty-four patients scheduled to undergo aortic valve replacement were examined by ce-MRI. Delayed-enhanced images were used for the quantitative assessment of MF. In addition, interstitial MF was quantified by histological analysis of myocardial samples obtained during open-heart surgery and stained with picrosirius red. The ce-MRI study was repeated 27+/-22 months after surgery to assess left ventricular functional improvement, and all patients were followed for 52+/-17 months to evaluate long-term survival.

RESULTS

There was a good correlation between the amount of MF measured by histopathology and by ce-MRI (r=0.69, p<0.001). In addition, the amount of MF demonstrated a significant inverse correlation with the degree of left ventricular functional improvement after surgery (r=-0.42, p=0.04 for histopathology; r=-0.47, p=0.02 for ce-MRI). Kaplan-Meier analyses revealed that higher degrees of MF accumulation were associated with worse long-term survival (chi-square=6.32, p=0.01 for histopathology; chi-square=5.85, p=0.02 for ce-MRI). On multivariate Cox regression analyses, patient age and the amount of MF were found to be independent predictors of all-cause mortality.

CONCLUSIONS

The amount of MF, either by histopathology or by ce-MRI, is associated with the degree of left ventricular functional improvement and all-cause mortality late after aortic valve replacement in patients with severe aortic valve disease.

Cardiac assessment in chronic kidney disease

Patients with chronic kidney disease are well recognized to develop a wide range of cardiac structural and functional abnormalities. These changes may be progressive and relate directly to a grossly aggravated risk of cardiovascular events and reduced survival. Although conventional methods of cardiac assessment have been shown to be useful, they are limited by insufficient sensitivity and specificity, to fully appreciate the overall degree of myocardial distress that is common in these patients. This article aims to review the use of established and emerging cardiac imaging tools and, in particular, their application in patients with chronic kidney disease.

Calculations of cardiovascular shunts and regurgitation using magnetic resonance ventricular volume and aortic and pulmonary flow measurements

BACKGROUND

Cardiovascular magnetic resonance measurements of the volumes of the right and left ventricle and of the flows in the ascending aorta and main pulmonary artery contribute to the assessment of patients with valvular regurgitation or intracardiac or extracardiac shunts. Ventricular volumes are measured by planimetry and summation of end-diastolic and end-systolic areas measured in a stack of ventricular short-axis cines. The volumes of blood flowing through planes transecting the great arteries are measured using phase contrast velocity mapping. The two approaches are essentially different and can be used either for mutual validation, or separately or in combination to quantify regurgitation and/or shunting. In the presence of shunts, the relations between the stroke volumes and arterial flows of each side of the heart vary depending on the level of shunting (for example, atrial, ventricular or ductal).

CONCLUSION

This article aims to explain and illustrate the technical and theoretical basis for calculations using volumetric and flow measurements, providing formulae and diagrams to facilitate the interpretation of results.