Jürgen Duchenne

Recent advances in echocardiography: strain and strain rate imaging

Deformation imaging by echocardiography is a well-established research tool which has been gaining interest from clinical cardiologists since the introduction of speckle tracking. Post-processing of echo images to analyze deformation has become readily available at the fingertips of the user. New parameters such as global longitudinal strain have been shown to provide added diagnostic value, and ongoing efforts of the imaging societies and industry aimed at harmonizing methods will improve the technique further. This review focuses on recent advances in the field of echocardiographic strain and strain rate imaging, and provides an overview on its current and potential future clinical applications.

Comparison of Feasibility, Accuracy, and Reproducibility of Layer-Specific Global Longitudinal Strain Measurements Among Five Different Vendors: A Report from the EACVI-ASE Strain Standardization Task Force

Background: Despite standardization efforts, vendors still use information from different myocardial layers to calculate global longitudinal strain (GLS). Little is known about potential advantages or disadvantages of using these different layers in clinical practice. The authors therefore investigated the reproducibility and accuracy of GLS measurements from different myocardial layers. Methods: Sixty‐three subjects were prospectively enrolled, in whom the intervendor bias and test‐retest variability of endocardial GLS (E‐GLS) and midwall GLS (M‐GLS) were calculated, using software packages from five vendors that allow layer‐specific GLS calculation (GE, Hitachi, Siemens, Toshiba, and TomTec). The impact of tracking quality and the interdependence of strain values from different layers were assessed by comparing test‐retest errors between layers. Results: For both E‐GLS and M‐GLS, significant bias was found among vendors. Relative test‐retest variability of E‐GLS values differed significantly among vendors, whereas M‐GLS showed no significant difference (range, 5.4%–9.5% [P = .032] and 7.0%–11.2% [P = .200], respectively). Within‐vendor test‐retest variability was similar between E‐GLS and M‐GLS for all but one vendor. Absolute test‐retest errors were highly correlated between E‐GLS and M‐GLS for all vendors. Conclusions: E‐GLS and M‐GLS measurements showed no relevant differences in robustness among vendors, although intervendor bias was higher for M‐GLS compared with E‐GLS. These data provide no technical argument in favor of a certain myocardial layer for global left ventricular functional assessment. Currently, the choice of which layer to use should therefore be based on the available clinical evidence in the literature.

Assessment of mechanical dyssynchrony can improve the prognostic value of guideline-based patient selection for cardiac resynchronization therapy

Aim To determine if incorporation of assessment of mechanical dyssynchrony could improve the prognostic value of patient selection based on current guidelines. Methods and results Echocardiography was performed in 1060 patients before and 12 ± 6 months after cardiac resynchronization therapy (CRT) implantation. Mechanical dyssynchrony, defined as the presence of apical rocking or septal flash was visually assessed at the baseline examination. Response was defined as ≥15% reduction in left ventricular end-systolic volume at follow-up. Patients were followed for a median of 59 months (interquartile range 37-86 months) for the occurrence of death of any cause. Applying the latest European guidelines retrospectively, 63.4% of the patients had been implanted with a Class I recommendation, 18.2% with Class IIa, 9.4% with Class IIb, and in 9% no clear therapy recommendation was present. Response rates were 65% in Class I, 50% in IIa, 38% in IIb patients, and 40% in patients without a clear guideline-based recommendation. Assessment of mechanical dyssynchrony improved response rates to 77% in Class I, 75% in IIa, 62% in IIb, and 69% in patients without a guideline-based recommendation. Non-significant difference in survival among guideline recommendation classes was found (Log-rank P = 0.2). Presence of mechanical dyssynchrony predicted long-term outcome better than guideline Classes I, IIa, IIb (Log-rank P < 0.0001, 0.006, 0.004, respectively) and in patients with no guideline recommendation (P = 0.02). Comparable results were observed using the latest American Guidelines. Conclusion Our data suggest that current guideline criteria for CRT candidate selection could be improved by incorporating assessment of mechanical asynchrony.

Impact of CT-based Attenuation Correction on the Registration Between Dual-gated Cardiac PET and High-Resolution CT

A high-resolution CT (HRCT) used as anatomical prior information during PET reconstruction can enhance the quality of a corresponding low-resolution PET image, provided that it is accurately registered to the PET dataset of interest. In this work, the impact of different PET/CT attenuation correction (AC) protocols on the registration between a dual-gated cardiac 18F-FDG PET image and an HRCT image is investigated. The aim is to explore the impact of AC on PET-to-HRCT registration, and to identify the AC strategy that yields the best alignment between the left-ventricles in the PET and the HRCT images for subsequent partial volume correction. Simulations were performed using XCAT phantoms. Shallow breathing and a regular beating pattern were simulated and both noise-free and noisy data were evaluated. Respiratory motion during the acquisition of the CT used for attenuation correction strongly affected the dual-gated PET reconstructions, resulting in artefacts and quantification errors in the PET image and poor PET-to-HRCT registration accuracy. The blurring introduced by the beating heart, on the other hand, proved to have a negligible effect on PET-CT registration. Dual-gated PET images reconstructed without attenuation correction could be well registered to the HRCT if a good initial alignment between the starting images was provided. A commercially available strategy to deal with an AC CT that is acquired in the wrong respiratory phase was also evaluated, and yielded not only enhanced quantitative accuracy but also accurate PET-to-HRCT registration. The effect of a high level of noise, as present in a dual-gated cardiac PET study, was also investigated. Registrations proved to be sensitive to noise, but noise is not a major limiting factor for PET-to-HRCT registration. A selection of the investigated attenuation correction procedures was also evaluated using cardiac PET/CT data measured in sheep. The PET-to-HRCT registration performance confirmed the XCAT-based predictions.

Timing of myocardial shortening determines left ventricular regional myocardial work and regional remodelling in hearts with conduction delays

Aims The interaction between asynchronous regional myocardial activation and left ventricular (LV) wall remodelling has not been well established. We investigated the relationship between time of onset of longitudinal shortening (Tonset), regional myocardial work, and segmental LV wall thickness (SWT) in patients treated with cardiac resynchronization therapy (CRT). Methods and results We analysed 26 patients with sinus rhythm, non-ischaemic cardiomyopathy (63 ± 9 years, 69% male, QRS duration 174 ± 18 ms) and positive response to CRT (15% reduction in end-systolic volume). Longitudinal strain was obtained by 2D speckle-tracking echocardiography before and after [14.5 (7-29) months] CRT. Tonset and SWT were measured in 18 segments per LV. Segmental myocardial work was calculated from non-invasive segmental stress-strain loop area. Before CRT, Tonset was the shortest in septal and anteroseptal and the longest in lateral and posterior walls (P < 0.001) and not different after CRT (P = 0.733). Before CRT, septal and anteroseptal walls were significantly thinner than lateral and posterior. After CRT, reverse remodelling increased thickness in septal and anteroseptal and thinned lateral and posterior segments (P < 0.001). Before CRT, non-uniformity in work distribution with reduced work in septal and anteroseptal and increased work in lateral and posterior walls (P < 0.001) was observed. After CRT, distribution of myocardial work was uniform (P = 0.215). Conclusion Dys-synchronous myocardial shortening is related to thinning of early and thickening of late activated segments in heart failure with conduction delay. Correction of dys-synchrony leads to regression of inhomogeneity towards more evenly distributed wall thickness. Regional differences in myocardial work load that are homogenized by successful CRT are considered as the underlying pathophysiological mechanism.

Right ventricular remodelling after transcatheter pulmonary valve implantation

To define the optimal timing for percutaneous pulmonary valve implantation (PPVI) in patients with severe pulmonary regurgitation (PR) after Fallots Tetralogy (ToF) correction.

Lesion quantification and detection in myocardial 18F-FDG PET using edge-preserving priors and anatomical information from CT and MRI: a simulation study

BackgroundThe limited spatial resolution of the clinical PET scanners results in image blurring and does not allow for accurate quantification of very thin or small structures (known as partial volume effect). In cardiac imaging, clinically relevant questions, e.g. to accurately define the extent or the residual metabolic activity of scarred myocardial tissue, could benefit from partial volume correction (PVC) techniques.The use of high-resolution anatomical information for improved reconstruction of the PET datasets has been successfully applied in other anatomical regions. However, several concerns linked to the use of any kind of anatomical information for PVC on cardiac datasets arise. The moving nature of the heart, coupled with the possibly non-simultaneous acquisition of the anatomical and the activity datasets, is likely to introduce discrepancies between the PET and the anatomical image, that in turn might mislead lesion quantification and detection. Non-anatomical (edge-preserving) priors could represent a viable alternative for PVC in this case.In this work, we investigate and compare the regularizing effect of different anatomical and non-anatomical priors applied during maximum-a-posteriori (MAP) reconstruction of cardiac PET datasets. The focus of this paper is on accurate quantification and lesion detection in myocardial 18F-FDG PET.MethodsSimulated datasets, obtained with the XCAT software, are reconstructed with different algorithms and are quantitatively analysed.ResultsThe results of this simulation study show a superiority of the anatomical prior when an ideal, perfectly matching anatomy is used. The anatomical information must clearly differentiate between normal and scarred myocardial tissue for the PVC to be successful. In case of mismatched or missing anatomical information, the quality of the anatomy-based MAP reconstructions decreases, affecting both overall image quality and lesion quantification. The edge-preserving priors produce reconstructions with good noise properties and recovery of activity, with the advantage of not relying on an external, additional scan for anatomy.ConclusionsThe performance of edge-preserving priors is acceptable but inferior to those of a well-applied anatomical prior that differentiates between lesion and normal tissue, in the detection and quantification of a lesion in the reconstructed images. When considering bull’s eye plots, all of the tested MAP algorithms produced comparable results.

Partial volume correction of doubly-gated cardiac datasets using anatomical and edge-preserving priors

Positron emission tomography (PET) images suffer from partial volume (PV) effects due to the poor spatial resolution of the PET system. In cardiac imaging, additional blurring is caused by the breathing motion and the beating of the heart. Dual gating of the cardiac datasets is one possible approach to remove the motion blur [1], but it dramatically reduces the statistics of the dataset and leads to extremely noisy reconstructions (still to be corrected for PV).

Validation of anatomy-enhanced cardiac FDG-PET imaging: An ex vivo sheep study

PET images suffer from partial volume effects (PVE) due to the poor spatial resolution of the PET system. Anatomy-enhanced PET reconstruction allows to restore such loss of resolution in PET images and attempt to reveal more accurately the actual tracer distribution [1] [4].

Papillary muscles contribute significantly more to left ventricular work in dilated hearts

Aims Left ventricular (LV) dilatation results in increased sphericity and affects position and orientation of papillary muscles (PMs), which may influence their performed work. The aim of this study was to assess the contribution of PM to LV function and its changes with dilatation. Methods and results Fifteen sheep were investigated. Ten animals were subjected to 8 weeks of rapid (180 bpm) pacing, inducing LV dilatation. Five animals served as controls. High-resolution gated computed tomography was performed to assess LV volumes, left ventricular ejection fraction (LVEF), global longitudinal strain (GLS), sphericity index, and PM angle, width and fractional shortening. 18F-fluorodeoxyglucose positron emission tomography (PET) was used to measure glucose metabolism as surrogate of regional myocardial work. Spatial resolution of PET images was maximized by electrocardiogram- and respiratory-gating. 18F-fluorodeoxyglucose uptake was measured in PM and compared with remaining left ventricular myocardium (MYO) to obtain a PM/MYO ratio. Animals with dilated heart had a more spherical left ventricle, with reduced LVEF (P < 0.0001) and GLS (P < 0.0001). In dilated hearts, PET analysis revealed a higher contribution of both PM to LV myocardial work (P < 0.0001); and PM angle towards LV wall correlated with PM work, together with PM width and the LV sphericity index. Sphericity index and posterior PM angle were strongest determinants of posterior PM/MYO ratio (R2 = 0.754; P < 0.0001), while anterior PM/MYO was mostly determined by sphericity index and the PM width (R2 = 0.805; P < 0.0001). Conclusion In dilated hearts, PM contribute relatively more to LV myocardial work. We hypothesize that this is caused by the more cross-sectional orientation of the subvalvular apparatus, which leads to a higher stress on the PM compared with the spherical LV walls. The reduced cross-sectional area of the PM may further explain their increased stress.