2014 Korean guidelines for appropriate utilization of cardiovascular magnetic resonance imaging: a joint report of the Korean Society of Cardiology and the Korean Society of Radiology

Aortic Valve Area and Strain Measurements by Cardiac MRI and Transthoracic Echocardiography in Severe Aortic Stenosis with Normal Left Ventricular Function

Background

Transthoracic echocardiography (TTE) is the recommended imaging technique for the evaluation of patients with aortic stenosis (AS). However, in cases with inconclusive findings, cardiac magnetic resonance (CMR) planimetry is used to grade AS severity. This study aimed to compare the results derived from TTE and CMR in patients with severe AS with normal left ventricular (LV) function.

Methods

In a prospective study, 20 patients with severe AS were recruited and data derived from TTE and CMR modalities were compared with the archived records of 28 age- and sex-matched healthy controls. The data included aortic valve area (AVA), MRI-derived biventricular global strains, and TTE-derived global longitudinal strain (GLS). SPSS software was used to analyze the data with independent samples t test, intraclass correlation coefficient (ICC), and Pearson correlation. P<0.05 was considered statistically significant.

Results

An excellent agreement was found in AVA values derived from CMR and TTE with an average ICC of 0.932 (95% CI=0.829-0.973). There was a significant difference in LV-GLS, LV global radial strain (GRS), right ventricular (RV) GRS, and RV global circumferential strain between the groups. A good correlation was found between CMR- and TTE-derived GLS with an average ICC of 0.721 (95% C=0.255-0.896). The mean aortic valve pressure gradient in TTE had a significant inverse linear correlation with LV-GRS in CMR (r=-0.537). All P values were <0.05.

Conclusion

There was a good agreement between AVA and strain values derived from cardiac MRI and TTE. The myocardial strain was impaired in patients with severe AS and normal LV function and correlated with disease severity.

The Use of Feature Tracking Technique for the Quantification of Ventricular Strain Pattern in Patients with Ebstein's Anomaly: A Case-Control Study

Background

Ebstein's anomaly (EA) is a congenital heart disorder characterized by abnormal function of the tricuspid valve. There are several ways to study tissue composition using magnetic resonance imaging (MRI). One of the most accurate methods is strain calculation using the feature tracking (FT) technique. Due to the novelty of the FT technique in cardiac magnetic resonance (CMR) imaging, there is a lack of comprehensive guidelines to conduct FT-MRI and to present a quantitative report. The current study is aimed to evaluate the FT technique in EA patients and to compare the obtained numerical values with those of healthy individuals.

Methods

A total of 33 individuals were enrolled in a study conducted in 2018-2019 at Shahid Rajaei Hospital, Tehran, Iran. Radial, longitudinal, and circumferential strain patterns of the left and right ventricles were determined in both the patients and the controls using the FT technique. Data were analyzed using SPSS software, version 22.0.

Results

The results showed a significantly lower left ventricular (LV) radial strain in EA patients compared to the control group (P=0.002). In addition, the right ventricular (RV) global longitudinal strain (GLS) in EA patients was significantly lower than in the controls (P=0.001). Other parameters (LV global longitudinal strain, RV radial strain, LV circumferential strain, and RV circumferential strain) did not differ significantly between the two groups.

Conclusion

Determination of strain patterns using cardiac MRI is a promising method for the diagnosis of EA. Markers such as LV longitudinal strain and RV-GLS are the most suitable parameters for the early diagnosis of heart dysfunction.

The prognostic role of CMR using global planimetric criteria in patients with excessive left ventricular trabeculation

OBJECTIVES

Although cardiovascular magnetic resonance (CMR) is widely used in the assessment of left ventricular non-compaction (LVNC), there are no universally accepted diagnostic criteria and limited data regarding their prognostic value. We assessed the long-term prognostic role of the planimetric global Grothoff's criteria and of the CMR findings in predicting adverse cardiovascular events (CE).

METHODS

We prospectively enrolled 78 patients (46.7 ± 18.7 years, 33.3% females) with documented positive Jenni's echocardiographic criteria for LVNC. Cine images were used to quantify function parameters and to assess for the presence of all four quantitative Grothoff's criteria (global Grothoff's criteria). Late gadolinium enhancement (LGE) images were acquired to detect the presence of replacement myocardial fibrosis.

RESULTS

Petersen's CMR criterion for LVNC (NC/C ratio > 2.3 in at least one myocardial segment) was fulfilled in the whole population. Twenty-six patients fulfilled the global Grothoff's criteria (four out of four). The mean duration of the follow-up was 44.2 ± 27.4 months and 28 CE were registered: 10 ventricular tachycardias, 12 episodes of heart failure (HF), four strokes, and two cardiac deaths. In the multivariate analysis, the independent predictive factors for CE were positive global Grothoff's criteria (hazard ratio, HR = 3.33, 95% CI = 1.52-7.29; p = 0.003) and myocardial fibrosis (HR = 2.41, 95% CI = 1.08-5.36; p = 0.032).

CONCLUSIONS

Positive global Grothoff's criteria and myocardial fibrosis were powerful predictors of CE in patients with a diagnosis of LVNC by CMR Petersen's criterion. Thus, we strongly suggest a step approach confirming the diagnosis of LVNC by using the global planimetric Grothoff's criteria, which showed a prognostic impact.

KEY POINTS

• Positive global Grothoff's criteria and replacement myocardial fibrosis were powerful predictors of cardiovascular events in patients with a diagnosis of LVNC by CMR Petersen's criterion. • Positive global Grothoff's criteria were associated with a higher frequency of ventricular arrhythmias in patients with a diagnosis of LVNC by CMR Petersen's criterion.

Characterization of Left Ventricular Non-Compaction Cardiomyopathy

Left ventricle non-compaction cardiomyopathy (LVNC) has gained great interest in recent years, being one of the most controversial cardiomyopathies. There are several open debates, not only about its genetic heterogeneity, or about the possibility to be an acquired cardiomyopathy, but also about its possible overdiagnosis based on imaging techniques. In order to better understand this entity, we identified 38 LVNC patients diagnosed by cardiac MRI (CMRI) or anatomopathological study that could underwent NGS-sequencing and clinical study. Anatomopathological exam was performed in eight available LVNC hearts. The genetic yield was 34.2%. Patients with negative genetic testing had better left ventricular ejection fraction (LVEF) or it showed a tendency to improve in follow-up, and a possible trigger factor for LVNC was identified in 1/3 of them. Nonetheless, cerebrovascular accidents occurred in similar proportions in both groups. We conclude that in LVNC there seem to be different ways to achieve the same final phenotype. Genetic testing has a good genetic yield and provides valuable information. LVNC without an underlying genetic cause may have a better prognosis in terms of LVEF evolution. However, anticoagulation to prevent cerebrovascular accident (CVA) should be carefully evaluated in all patients. Larger series with pathologic examination are needed to help better understand this entity.

Guideline for Cardiovascular Magnetic Resonance Imaging from the Korean Society of Cardiovascular Imaging-Part 1: Standardized Protocol

Cardiac magnetic resonance (CMR) imaging is widely used in many areas of cardiovascular disease assessment. This is a practical, standard CMR protocol for beginners that is designed to be easy to follow and implement. This protocol guideline is based on previously reported CMR guidelines and includes sequence terminology used by vendors, essential MR physics, imaging planes, field strength considerations, MRI-conditional devices, drugs for stress tests, various CMR modules, and disease/symptom-based protocols based on a survey of cardiologists and various appropriate-use criteria. It will be of considerable help in planning and implementing tests. In addressing CMR usage and creating this protocol guideline, we particularly tried to include useful tips to overcome various practical issues and improve CMR imaging. We hope that this document will continue to standardize and simplify a patient-based approach to clinical CMR and contribute to the promotion of public health.

The planimetric Grothoff's criteria by cardiac magnetic resonance can improve the specificity of left ventricular non-compaction diagnosis in thalassemia intermedia

We differentiated the left ventricle non-compaction (LVNC) from hypertrabeculated myocardium due to a negative remodeling in thalassemia intermedia (TI) patients applying linear and planimetric criteria and comparing the cardiovascular magnetic resonance (CMR) findings. CMR images were analyzed in 181 TI patients enrolled in the Myocardial Iron Overload in Thalassemia Network and 27 patients with proved LVNC diagnosis. The CMR diagnostic criteria applied in TI patients were: a modified linear CMR Petersen's criterion based on a more restrictive ratio of diastolic NC/C > 2.5 at segmental level and the combination of planimetric Grothoff's criteria (percentage of trabeculated LV myocardial mass LV-MM ≥ 25% of global LV mass and total LV-MMI NC ≥ 15 g/m²). Seventeen TI patients showed at least one positive NC/C segment. Compared to LVNC patients, these patients showed a lower frequency of segments with non-compaction areas (2.41 ± 1.33 vs 5.48 ± 2.26; P < 0.0001), significantly lower LV-MM NC percentage (10.99 ± 4.09 vs 28.20 ± 4.27%; P < 0.0001), LV-MMI (7.58 ± 4.86 vs 19.88 ± 5.02 g/m²; P < 0.0001) and extension of macroscopic fibrosis (0.44 ± 0.18 vs 4.65 ± 2.89; P = 0.004), and significantly higher LV ejection fraction (61.29 ± 5.17 vs 48.50 ± 17.55%; P = 0.016) and cardiac index (4.80 ± 1.49 vs 3.46 ± 1.11 l/min/m²; P = 0.002). No TI patient fulfilled the Grothoff's criteria. All TI patients with an NC/C ratio > 2.5 showed morphological and functional CMR parameters significantly different from the patients with a proved diagnosis of LVNC. Differentiation of LVNC from hypertrabeculated LV in β-TI patients due to a negative heart remodeling depends on the selected CMR criterion. We suggest using planimetric Grothoff's criteria to improve the specificity of LVNC diagnosis.

Grading of aortic stenosis severity: a head-to-head comparison between cardiac magnetic resonance imaging and echocardiography

AIM

To prospectively evaluate the accuracy of cardiac magnetic resonance (cMR) imaging for the assessment of aortic valve effective orifice area (EOA) by continuity equation and anatomical aortic valve area (AVA) by direct planimetry, as compared with transthoracic (TTE) and transesophageal (TEE) two-dimensional (2D) echocardiography, respectively.

METHODS AND RESULTS

A total of 31 patients (21 men, 10 women, mean age 69 ± 10 years) with moderate-to-severe aortic stenosis (AS) diagnosed by TTE and scheduled for elective aortic valve replacement, underwent both cMR and TEE. AVA by cMR was obtained from balanced steady-state free-precession cine-images. EOA was computed from phase-contrast MR flow analysis. AVA at cMR (0.93 ± 0.42 cm²) was highly correlated with TEE-derived planimetry (0.92 ± 0.32 cm²) (concordance correlation coefficient, CCC = 0.85). By excluding 11 patients with extensively thickened and heavily calcified cusps, the CCC increased to 0.93. EOA at cMR (0.86 ± 0.30 cm²) showed a strong correlation with TTE-derived EOA (0.78 ± 0.25 cm²) (CCC = 0.82).

CONCLUSIONS

cMR imaging is an accurate alternative for the grading of AS severity. Its use may be recommended especially in patients with poor transthoracic acoustic windows and/or in case of discordance between 2D echocardiographic parameters.

2017 Multimodality Appropriate Use Criteria for Noninvasive Cardiac Imaging: Expert Consensus of the Asian Society of Cardiovascular Imaging

In 2010, the Asian Society of Cardiovascular Imaging (ASCI) provided recommendations for cardiac CT and MRI, and this document reflects an update of the 2010 ASCI appropriate use criteria (AUC). In 2016, the ASCI formed a new working group for revision of AUC for noninvasive cardiac imaging. A major change that we made in this document is the rating of various noninvasive tests (exercise electrocardiogram, echocardiography, positron emission tomography, single-photon emission computed tomography, radionuclide imaging, cardiac magnetic resonance, and cardiac computed tomography/angiography), compared side by side for their applications in various clinical scenarios. Ninety-five clinical scenarios were developed from eight selected pre-existing guidelines and classified into four sections as follows: 1) detection of coronary artery disease, symptomatic or asymptomatic; 2) cardiac evaluation in various clinical scenarios; 3) use of imaging modality according to prior testing; and 4) evaluation of cardiac structure and function. The clinical scenarios were scored by a separate rating committee on a scale of 1–9 to designate appropriate use, uncertain use, or inappropriate use according to a modified Delphi method. Overall, the AUC ratings for CT were higher than those of previous guidelines. These new AUC provide guidance for clinicians choosing among available testing modalities for various cardiac diseases and are also unique, given that most previous AUC for noninvasive imaging include only one imaging technique. As cardiac imaging is multimodal in nature, we believe that these AUC will be more useful for clinical decision making.

Diagnostic Performance of Coronary CT Angiography, Stress Dual-Energy CT Perfusion, and Stress Perfusion Single-Photon Emission Computed Tomography for Coronary Artery Disease: Comparison with Combined Invasive Coronary Angiography and Stress Perfusion Cardiac MRI

Objective

To investigate the diagnostic performance of coronary computed tomography angiography (CCTA), stress dual-energy computed tomography perfusion (DE-CTP), stress perfusion single-photon emission computed tomography (SPECT), and the combinations of CCTA with myocardial perfusion imaging (CCTA + DE-CTP and CCTA + SPECT) for identifying coronary artery stenosis that causes myocardial hypoperfusion. Combined invasive coronary angiography (ICA) and stress perfusion cardiac magnetic resonance (SP-CMR) imaging are used as the reference standard.

Materials and Methods

We retrospectively reviewed the records of 25 patients with suspected coronary artery disease, who underwent CCTA, DE-CTP, SPECT, SP-CMR, and ICA. The reference standard was defined as ≥ 50% stenosis by ICA, with a corresponding myocardial hypoperfusion on SP-CMR.

Results

For per-vascular territory analysis, the sensitivities of CCTA, DE-CTP, SPECT, CCTA + DE-CTP, and CCTA + SPECT were 96, 96, 68, 93, and 68%, respectively, and specificities were 72, 75, 89, 85, and 94%, respectively. The areas under the receiver operating characteristic curve (AUCs) were 0.84 ± 0.05, 0.85 ± 0.05, 0.79 ± 0.06, 0.89 ± 0.04, and 0.81 ± 0.06, respectively. For per-patient analysis, the sensitivities of CCTA, DE-CTP, SPECT, CCTA + DE-CTP, and CCTA + SPECT were 100, 100, 89, 100, and 83%, respectively; the specificities were 14, 43, 57, 43, and 57%, respectively; and the AUCs were 0.57 ± 0.13, 0.71 ± 0.11, 0.73 ± 0.11, 0.71 ± 0.11, and 0.70 ± 0.11, respectively.

Conclusion

The combination of CCTA and DE-CTP enhances specificity without a loss of sensitivity for detecting hemodynamically significant coronary artery stenosis, as defined by combined ICA and SP-CMR.

Myocardial T1 and T2 Mapping: Techniques and Clinical Applications

Cardiac magnetic resonance (CMR) imaging is widely used in various medical fields related to cardiovascular diseases. Rapid technological innovations in magnetic resonance imaging in recent times have resulted in the development of new techniques for CMR imaging. T1 and T2 image mapping sequences enable the direct quantification of T1, T2, and extracellular volume fraction (ECV) values of the myocardium, leading to the progressive integration of these sequences into routine CMR settings. Currently, T1, T2, and ECV values are being recognized as not only robust biomarkers for diagnosis of cardiomyopathies, but also predictive factors for treatment monitoring and prognosis. In this study, we have reviewed various T1 and T2 mapping sequence techniques and their clinical applications.

The evaluation of non-ischemic dilated cardiomyopathy with T1 mapping and ECV methods using 3T cardiac MRI

PURPOSE

The aim of this study was to examine the correlation between ventricular function and the extracellular volume fraction (ECV) in patients with non-ischemic dilated cardiomyopathy (NIDCM) using 3.0 T magnetic resonance imaging (MRI). We also hypothesized that native T1 and ECV values would be increased in patients with NIDCM, independent of the left ventricular ejection fraction (LVEF). The findings of our study could lead to further studies of the follow-up protocols.

MATERIALS AND METHODS

In total, 53 consecutive dilated cardiomyopathy patients who had undergone cardiac MRI were functionally evaluated and underwent tissue characterization.

RESULTS

The mean native T1 value was 1235 ± 10 ms, and the mean ECV value was 35.4 ± 2.7% in the myocardia. The LVEF values ranged from 29 to 44%. No significant correlations were observed between functional analysis measurements and native T1 or ECV values.

CONCLUSIONS

Our results showed that myocardial fibrosis is unrelated to cardiac functional findings in NIDCM patients. Therefore, we propose that these patients should be evaluated using MRI and tissue characterization techniques, in addition to cardiac functional analysis.

Hemodynamic Measurement Using Four-Dimensional Phase-Contrast MRI: Quantification of Hemodynamic Parameters and Clinical Applications

Recent improvements have been made to the use of time-resolved, three-dimensional phase-contrast (PC) magnetic resonance imaging (MRI), which is also named four-dimensional (4D) PC-MRI or 4D flow MRI, in the investigation of spatial and temporal variations in hemodynamic features in cardiovascular blood flow. The present article reviews the principle and analytical procedures of 4D PC-MRI. Various fluid dynamic biomarkers for possible clinical usage are also described, including wall shear stress, turbulent kinetic energy, and relative pressure. Lastly, this article provides an overview of the clinical applications of 4D PC-MRI in various cardiovascular regions.

Association of cardiovascular disease risk factors with left ventricular mass, biventricular function, and the presence of silent myocardial infarction on cardiac MRI in an asymptomatic population

The purposes of this study were to evaluate the relationship between risk factors for cardiovascular disease (CVD) and cardiac mass and function on cardiac magnetic resonance imaging (MRI), and to investigate possible risk factors for silent myocardial infarction (SMI) in an asymptomatic Asian population. We included 647 asymptomatic subjects (485 males, mean age 54.8 ± 6.7 years; 162 females, mean age 55.2 ± 7.6 years) who underwent 1.5-T cardiac MRI during a health checkup. The association between biventricular functional parameters as evaluated on MRI and CVD risk factors was examined using multivariable regression and analysis of variance. The left ventricular mass-to-volume ratios were positively related to body mass index (β = 0.153, p < 0.001), systolic (β = 0.165, p = 0.001) and diastolic (β = 0.147, p = 0.002) blood pressure, triglyceride levels (β = 0.197, p = 0.006), and C-reactive protein levels (β = 0.130, p < 0.001), and were negatively related to estimated glomerular filtration rates (β = -0.076, p = 0.025). No significant relationship was present between ventricular parameters and the presence of SMI after adjusting for confounders. The prevalence (6.9 %, 7/101) of SMI in diabetics was significantly greater than that in non-diabetics patients (0.9 %, 5/546; confidence interval 1.739-12.848; p < 0.001). Traditional CVD risk factors are associated with ventricular mass, geometry and function in asymptomatic subjects. Silent MI may not independently influence ventricular mass and function and diabetes mellitus may contribute to the development of SMI.

Quantification of left ventricular trabeculae using cardiovascular magnetic resonance for the diagnosis of left ventricular non-compaction: evaluation of trabecular volume and refined semi-quantitative criteria

BACKGROUND

Left ventricular non-compaction (LVNC) is an unclassified cardiomyopathy and there is no consensus on the diagnosis of LVNC. The aims of this study were to establish quantitative methods to diagnose LVNC using cardiovascular magnetic resonance (CMR) and to suggest refined semi-quantitative methods to diagnose LVNC.

METHODS

This retrospective study included 145 subjects with mild to severe trabeculation of the left ventricle myocardium [24 patients with isolated LVNC, 33 patients with non-isolated LVNC, 30 patients with dilated cardiomyopathy (DCM) with non-compaction (DCMNC), 27 patients with DCM, and 31 healthy control subjects with mild trabeculation]. The left ventricular (LV) ejection fraction, global LV myocardial volume, trabeculated LV myocardial volume, and number of segments with late gadolinium enhancement were measured. In addition, the most prominent non-compacted (NC), compacted (C), normal mid-septum, normal mid-lateral wall, and apical trabeculation thicknesses on the end-diastolic frames of the long-axis slices were measured.

RESULTS

In the patients with isolated LVNC, the percentage of trabeculated LV volume (TV%, ​42.6 ± 13.8 %) ​relative to total LV myocardial volume was 1.4 times higher than in those with DCM (30.3 ± 14.3 %, p < 0.001), and 1.7 times higher than in the controls (24.8 ± 7.1 %, p < 0.001). However, there was no significant difference in TV% between the isolated LVNC and DCMNC groups (47.1 ± 17.3 % in the DCMNC group; p = 0.210). The receiver operating characteristic curve analysis using Jenni's method for CMR classification as the standard diagnostic criteria revealed that a value of TV% above 34.6 % was predictive of NC with a specificity of 89.7 % (CI: 74.2 - 98.0 %) and a sensitivity of 66.1 % (CI: 52.6 - 77.9 %). A value of NC/septum over 1.27 was considered predictive for NC with a specificity of 82.8 % (CI: 64.2 - 94.2 %) and a sensitivity of 57.6 % (CI: 44.1 - 70.4 %). In addition, a value of apex/C above 3.15 was considered predictive of NC with a specificity of 93.1 % (CI: 77.2 - 99.2 %) and a sensitivity of 69.5 % (CI: 56.1 - 80.8 %).

CONCLUSIONS

A trabeculated LV myocardial volume above 35 % of the total LV myocardial volume is diagnostic for LVNC with high specificity. Also, the apex/C and NC/septum ratios could be useful as supplementary diagnostic criteria.