Three-dimensional echocardiography for left ventricular quantification: fundamental validation and clinical applications

One of the earliest applications of clinical echocardiography is evaluation of left ventricular (LV) function and size. Accurate, reproducible and quantitative evaluation of LV function and size is vital for diagnosis, treatment and prediction of prognosis of heart disease. Early three-dimensional (3D) echocardiographic techniques showed better reproducibility than two-dimensional (2D) echocardiography and narrower limits of agreement for assessment of LV function and size in comparison to reference methods, mostly cardiac magnetic resonance (CMR) imaging, but acquisition methods were cumbersome and a lack of user-friendly analysis software initially precluded widespread use. Through the advent of matrix transducers enabling real-time three-dimensional echocardiography (3DE) and improvements in analysis software featuring semi-automated volumetric analysis, 3D echocardiography evolved into a simple and fast imaging modality for everyday clinical use. 3DE provides the possibility to evaluate the entire LV in three spatial dimensions during the complete cardiac cycle, offering a more accurate and complete quantitative evaluation the LV. Improved efficiency in acquisition and analysis may provide clinicians with important diagnostic information within minutes. The current article reviews the methodology and application of 3DE for quantitative evaluation of the LV, provides the scientific evidence for its current clinical use, and discusses its current limitations and potential future directions

The role of cardiac magnetic resonance in identifying appropriate candidates for cardiac resynchronization therapy - a systematic review of the literature

Despite the strict indications for cardiac resynchronization therapy (CRT) implantation, a significant proportion of patients will fail to adequately respond to the treatment. This systematic review aims to present the existing evidence about the role of cardiac magnetic resonance (CMR) in identifying patients who are likely to respond better to the CRT. A systematic search in the MedLine database and Cochrane Library from their inception to August 2021 was performed, without any limitations, by two independent investigators. We considered eligible observational studies or randomized clinical trials (RCTs) that enrolled patients > 18 years old with heart failure (HF) of ischaemic or non-ischaemic aetiology and provided data about the association of baseline CMR variables with clinical or echocardiographic response to CRT for at least 3 months. This systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA Statement). Following our search strategy, 47 studies were finally included in our review. CMR appears to have an additive role in identifying the subgroup of patients who will respond better to CRT. Specifically, the presence and the extent of myocardial scar were associated with increased non-response rates, while those with no scar respond better. Furthermore, existing data show that scar location can be associated with CRT response rates. CMR-derived markers of mechanical desynchrony can also be used as predictors of CRT response. CMR data can be used to optimize the position of the left ventricular lead during the CRT implantation procedure. Specifically, positioning the left ventricular lead in a branch of the coronary sinus that feeds an area with transmural scar was associated with poorer response to CRT. CMR can be used as a non-invasive optimization tool to identify patients who are more likely to achieve better clinical and echocardiographic response following CRT implantation. [Abstract copyright: © 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.

Functional Assessment for Congenital Heart Disease

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Cardiac resynchronization therapy guided by cardiovascular magnetic resonance

Cardiac resynchronization therapy (CRT) is an established treatment for patients with symptomatic heart failure, severely impaired left ventricular (LV) systolic dysfunction and a wide (> 120 ms) complex. As with any other treatment, the response to CRT is variable. The degree of pre-implant mechanical dyssynchrony, scar burden and scar localization to the vicinity of the LV pacing stimulus are known to influence response and outcome. In addition to its recognized role in the assessment of LV structure and function as well as myocardial scar, cardiovascular magnetic resonance (CMR) can be used to quantify global and regional LV dyssynchrony. This review focuses on the role of CMR in the assessment of patients undergoing CRT, with emphasis on risk stratification and LV lead deployment

Comparison of Left Ventricular Strains and Torsion Derived from Feature Tracking and DENSE CMR

Background: Cardiovascular magnetic resonance (CMR) feature tracking is increasingly used to quantify cardiac mechanics from cine CMR imaging, although validation against reference standard techniques has been limited. Furthermore, studies have suggested that commonly-derived metrics, such as peak global strain (reported in 63% of feature tracking studies), can be quantified using contours from just two frames – end-diastole (ED) and end-systole (ES) – without requiring tracking software. We hypothesized that mechanics derived from feature tracking would not agree with those derived from a reference standard (displacement-encoding with stimulated echoes (DENSE) imaging), and that peak strain from feature tracking would agree with that derived using simple processing of only ED and ES contours. Methods: We retrospectively identified 88 participants with 186 pairs of DENSE and balanced steady state free precession (bSSFP) image slices acquired at the same locations across two institutions. Left ventricular (LV) strains, torsion, and dyssynchrony were quantified from both feature tracking (TomTec Imaging Systems, Circle Cardiovascular Imaging) and DENSE. Contour-based strains from bSSFP images were derived from ED and ES contours. Agreement was assessed with Bland-Altman analyses and coefficients of variation (CoV). All biases are reported in absolute percentage. Results: Comparison results were similar for both vendor packages (TomTec and Circle), and thus only TomTec Imaging System data are reported in the abstract for simplicity. Compared to DENSE, mid-ventricular circumferential strain (Ecc) from feature tracking had acceptable agreement (bias: − 0.4%, p = 0.36, CoV: 11%). However, feature tracking significantly overestimated the magnitude of Ecc at the base (bias: − 4.0% absolute, p \u3c 0.001, CoV: 18%) and apex (bias: − 2.4% absolute, p = 0.01, CoV: 15%), underestimated torsion (bias: − 1.4 deg/cm, p \u3c 0.001, CoV: 41%), and overestimated dyssynchrony (bias: 26 ms, p \u3c 0.001, CoV: 76%). Longitudinal strain (Ell) had borderline-acceptable agreement (bias: − 0.2%, p = 0.77, CoV: 19%). Contour-based strains had excellent agreement with feature tracking (biases: − 1.3–0.2%, CoVs: 3–7%). Conclusion: Compared to DENSE as a reference standard, feature tracking was inaccurate for quantification of apical and basal LV circumferential strains, longitudinal strain, torsion, and dyssynchrony. Feature tracking was only accurate for quantification of mid LV circumferential strain. Moreover, feature tracking is unnecessary for quantification of whole-slice strains (e.g. base, apex), since simplified processing of only ED and ES contours yields very similar results to those derived from feature tracking. Current feature tracking technology therefore has limited utility for quantification of cardiac mechanics

Left ventricular mechanics in repaired tetralogy of Fallot with and without pulmonary valve replacement: analysis by three-dimensional speckle tracking echocardiography

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Left ventricular dyssynchrony in patients with left bundle branch block and patients after myocardial infarction: integration of mechanics and viability by cardiac magnetic resonance

Aims To quantify left ventricular (LV) dyssynchrony in patients with left bundle branch block (LBBB) and in patients after myocardial infarction (MI) applying an accelerated three-dimensional (3D) tagging cardiac magnetic resonance (CMR) technique, and to combine dyssynchrony information with viability data obtained by late gadolinium enhancement (LGE) CMR. Methods and results Thirty-two patients (59 ± 11 years) after first MI (PatsMI), 10 patients (63 ± 10 years) with LBBB (ejection fraction < 40%; PatsLBBB<40), 13 patients (63 ± 11) with LBBB (ejection fraction ≥ 40%; PatsLBBB≥40), and 15 healthy controls (53 ± 10 years) underwent 3D tagging CMR and LGE imaging at 1.5 T. As a measure of mechanical LV dyssynchrony, the standard deviation of Tmax over the LV, the circumferential uniformity ratio estimate (CURE) index, and a segmental-based circumferential systolic dyssynchrony index (SDI) were calculated. All three parameters detected significantly increased circumferential dyssynchrony in patients compared with controls. The CURE and SDI showed a good correlation (r = 0.93, P < 0.0001) and detected most severe dyssynchrony in PatsLBBB<40 (P < 0.001 vs. controls, P < 0.005 vs. PatsMI). Systolic dyssynchrony index additionally allowed integration of localized viability information to yield SDIviable which was highest in PatsLBBB<40. Conclusion Dyssynchrony patterns in the LV can be quantified globally and regionally by 3D tagging CMR. Combination of viability and dyssynchrony information allows for a comprehensive dyssynchrony quantification in patients with LBBB or post-MI. Future studies are required to test the value of the method to predict responsiveness to resynchronizatio

VALIDATION, OPTIMIZATION, AND IMAGE PROCESSING OF SPIRAL CINE DENSE MAGNETIC RESONANCE IMAGING FOR THE QUANTIFICATION OF LEFT AND RIGHT VENTRICULAR MECHANICS

Recent evidence suggests that cardiac mechanics (e.g. cardiac strains) are better measures of heart function compared to common clinical metrics like ejection fraction. However, commonly-used parameters of cardiac mechanics remain limited to just a few measurements averaged over the whole left ventricle. We hypothesized that recent advances in cardiac magnetic resonance imaging (MRI) could be extended to provide measures of cardiac mechanics throughout the left and right ventricles (LV and RV, respectively). Displacement Encoding with Stimulated Echoes (DENSE) is a cardiac MRI technique that has been validated for measuring LV mechanics at a magnetic field strength of 1.5 T but not at higher field strengths such as 3.0 T. However, it is desirable to perform DENSE at 3.0 T, which would yield a better signal to noise ratio for imaging the thin RV wall. Results in Chapter 2 support the hypothesis that DENSE has similar accuracy at 1.5 and 3.0 T. Compared to standard, clinical cardiac MRI, DENSE requires more expertise to perform and is not as widely used. If accurate mechanics could be measured from standard MRI, the need for DENSE would be reduced. However, results from Chapter 3 support the hypothesis that measured cardiac mechanics from standard MRI do not agree with, and thus cannot be used in place of, measurements from DENSE. Imaging the thin RV wall with its complex contraction pattern requires both three-dimensional (3D) measures of myocardial motion and higher resolution imaging. Results from Chapter 4 support the hypothesis that a lower displacement-encoding frequency can be used to allow for easier processing of 3D DENSE images. Results from Chapter 5 support the hypothesis that images with higher resolution (decreased blurring) can be achieved by using more spiral interleaves during the DENSE image acquisition. Finally, processing DENSE images to yield measures of cardiac mechanics in the LV is relatively simple due to the LV’s mostly cylindrical geometry. Results from Chapter 6 support the hypothesis that a local coordinate system can be adapted to the geometry of the RV to quantify mechanics in an equivalent manner as the LV. In summary, cardiac mechanics can now be quantified throughout the left and right ventricles using DENSE cardiac MRI