Higher Order Singular Value Decomposition Filter for Contrast Echocardiography.

Assessing the coronary circulation with contrast-enhanced echocardiography has high clinical relevance. However, it is not being routinely performed in clinical practice because the current clinical tools generally cannot provide adequate image quality. The contrast agent's visibility in the myocardium is generally poor, impaired by motion and nonlinear propagation artifacts. The established multipulse contrast schemes (MPCSs) and the more experimental singular value decomposition (SVD) filter also fall short to solve these issues. Here, we propose a scheme to process amplitude modulation/amplitude-modulated pulse inversion (AM/AMPI) echoes with higher order SVD (HOSVD) instead of conventionally summing the complementary pulses. The echoes from the complementary pulses form a separate dimension in the HOSVD algorithm. Then, removing the ranks in that dimension with dominant coherent signals coming from tissue scattering would provide the contrast detection. We performed both in vitro and in vivo experiments to assess the performance of our proposed method in comparison with the current standard methods. A flow phantom study shows that HOSVD on AM pulsing exceeds the contrast-to-background ratio (CBR) of conventional AM and an SVD filter by 10 and 14 dB, respectively. In vivo porcine heart results also demonstrate that, compared to AM, HOSVD improves CBR in open-chest acquisition (up to 19 dB) and contrast ratio (CR) in closed-chest acquisition (3 dB).

Potential role of left atrial strain in estimation of left atrial pressure in patients with chronic heart failure.

AIMS: In a large proportion of heart failure with reduced ejection fraction (HFrEF) patients, echocardiographic estimation of left atrial pressure (LAP) is not possible when the ratio of the peak early left ventricular filling velocity over the late filling velocity (E/A ratio) is not available, which may occur due to several potential causes. Left atrial reservoir strain (LASr) is correlated with LV filling pressures and may serve as an alternative parameter in these patients. The aim of this study was to determine whether LASr can be used to estimate LAP in HFrEF patients in whom E/A ratio is not available. METHODS AND RESULTS: Echocardiograms of chronic HFrEF patients were analysed and LASr was assessed with speckle tracking echocardiography. LAP was estimated using the current ASE/EACVI algorithm. Patients were divided into those in whom LAP could be estimated using this algorithm (LAPe) and into those in whom this was not possible because E/A ratio was not available (LAPne). We assessed the prognostic value of LASr on the primary endpoint (PEP), which comprised the composite of hospitalization for the management of acute or worsened HF, left ventricular assist device implantation, cardiac transplantation, and cardiovascular death, whichever occurred first in time. We studied 153 patients with a mean age of 58 years of whom 76% men and 82% who were in NYHA class I-II. A total of 86 were in the LAPe group and 67 in the LAPne group. LASr was significantly lower in the LAPne group as compared with the LAPe group (15.8% vs. 23.8%, P < 0.001). PEP-free survival at a median follow-up of 2.5 years was 78% in LAPe versus 51% in LAPne patients. An increase in LASr was significantly associated with a reduced risk of the PEP in LAPne patients (adjusted hazard ratio: 0.91 per %, 95% confidence interval 0.84-0.98). An abnormal LASr (<18%) was associated with a five-fold increase in reaching the PEP. CONCLUSIONS: In HFrEF patients in whom echocardiographic estimation of LAP is not possible due to due to unavailability of E/A ratio, assessing LASr potentially carries added clinical and prognostic value.

Left ventricular high frame rate echo-particle image velocimetry: clinical application and comparison with conventional imaging.

BACKGROUND: Echo-Particle Image Velocimetry (echoPIV) tracks speckle patterns from ultrasound contrast agent(UCA), being less angle-sensitive than colour Doppler. High frame rate (HFR) echoPIV enables tracking of high velocity flow in the left ventricle (LV). We aimed to demonstrate the potential clinical use of HFR echoPIV and investigate the feasibility and accuracy in patients. METHODS: Nineteen patients admitted for heart failure were included. HFR contrast images were acquired from an apical long axis view (ALAX), using a fully-programmable ultrasound system. A clinical UCA was continuously infused with a dedicated pump. Additionally, echocardiographic images were obtained using a clinical system, including LV contrast-enhanced images and pulsed-wave (PW) Doppler of the LV inflow and outflow in ALAX. 11 patients underwent CMR and 4 cardiac CT as clinically indicated. These CMR and CT images were used as reference. In 10 patients with good echoPIV tracking and reference imaging, the intracavitary flow was compared between echoPIV, conventional and UCA echocardiography. RESULTS: EchoPIV tracking quality was good in 12/19 (63%), moderate in 2/19 (10%) and poor in 5/19 (26%) subjects. EchoPIV could determine inflow velocity in 17/19 (89%), and outflow in 14/19 (74%) patients. The correlation of echoPIV and PW Doppler was good for the inflow (R2 = 0.77 to PW peak; R2 = 0.80 PW mean velocity) and moderate for the outflow (R2 = 0.54 to PW peak; R2 = 0.44 to PW mean velocity), with a tendency for echoPIV to underestimate PW velocities. In selected patients, echoPIV was able in a single acquisition to demonstrate flow patterns which required multiple interrogations with classical echocardiography. Those flow patterns could also be linked to anatomical abnormalities as seen in CMR or CT. CONCLUSION: HFR echoPIV tracks multidirectional and complex flow patterns which are unapparent with conventional echocardiography, while having comparable feasibility. EchoPIV tends to underestimate flow velocities as compared to PW Doppler. It has the potential to provide in one acquisition all the functional information obtained by conventional imaging, overcoming the angle dependency of Doppler and low frame rate of classical contrast imaging.

Relation Between Early Diastolic Mid-Ventricular Flow and Elastic Forces Indicating Aneurysm Formation in Hypertrophic Cardiomyopathy.

BACKGROUND: The early diastolic paradoxical midventricular flow is suggestive of apical aneurysm (AA) formation in hypertrophic cardiomyopathy (HCM). We aimed to determine whether early diastolic paradoxical midventricular flow may be a useful screening tool in patients, following the time progression of HCM to the aneurysmal stage. METHODS: One hundred twenty-one HCM patients with dominant hypertrophy in the mid and apical segments, based on echocardiography and/or cardiovascular magnetic resonance, were selected from our HCM database, which comprises 1,332 patients. They were further stratified according to the presence of AA. All imaging studies in a period of 16 years (2005-2021) were considered for time progression. Midventricular Doppler (pulsed-wave, continuous-wave, color, and color M mode) were analyzed. RESULTS: Thirty-five patients (29% of the study group and 2.6% of all HCM patients) had AA. Early diastolic paradoxical midventricular flow had a sensitivity of 92% and specificity of 98.6% for the detection of AA in the study group. In 108 patients, follow-up echocardiography was performed (median, 5 [3-9] studies). Sixteen patients (15%) with 10 [7-12] years of follow-up displayed progressive time changes in left ventricle (LV) apical morphology and/or mid-LV flow. Ten patients (9%) progressed to an AA, during 7 [4-11] years of follow-up. Patients progressing to AA were younger (P = .009), with more severe LV hypertrophy (P = .01) and more often a significant mid-LV systolic gradient (≥30 mm Hg, P < .001). A wall thickness over 20 mm had 70% sensitivity and 69% specificity in detecting evolution toward AA. With significant systolic gradient, sensitivity was 80% and specificity was 62%. Furthermore, patients with AA had a higher incidence of ventricular tachycardia (log-rank P = .03). CONCLUSIONS: Early diastolic paradoxical midventricular flow reliably detects AA presence and should prompt extra imaging studies. In HCM with mid and apical dominant involvement there is a progressive trend toward aneurysm formation, especially in patients with wall thickness over 20 mm and significant mid-LV systolic gradient (≥30 mm Hg), which can be monitored through serial Doppler studies.

Epidemiology and etiology of blood stream infections in a Belgian burn wound center.

BACKGROUND: Infections are a major cause of morbidity in burn patients. We aimed to investigate the epidemiology and antibiotic susceptibility of blood stream infections in order to gain a better understanding of their role and burden in our Burn Wound Center. METHODS: This retrospective epidemiological investigation analyzed data derived from medical files of patients admitted to our Burn Wound Center having had at least one positive blood culture between 1 January and 31 December 2018. We focused on the prevalence of causative agents in blood stream infections in function of the time after injury and on their drug sensitivity. RESULTS: Among the 363 patients admitted to our Burn Wound Center during the study period, 29 had at least one episode of blood stream infection. Gram-negative organisms accounted for 56,36% of the pathogens in blood stream infections, Gram-positives for 38,17%, and yeasts for 5,45%. Pseudomonas aeruginosa was the most common bacterium (20%), followed by Staphylococcus epidermidis (16.36%), Escherichia coli and Klebsiella pneumoniae (9,09% each). A third of the Gram-negative isolates were multidrug resistant. Gram-positive cocci were isolated from blood cultures at a median of 9 days after the injury, earlier than Gram-negative rods (median 15 days). The main sources of blood stream infections were the burn wounds, followed by infected catheters. CONCLUSIONS: Multidrug resistant bacteria must be considered when selecting empirical antibiotic therapy in septic burn patients. In our center, we need to update our antibiotic guidelines, to review the hospital infection control measures and to introduce routine typing technology.

Right ventricular functional assessment by 2D multi-plane echocardiography prior to left ventricular assist device implantation.

OBJECTIVES: Right ventricular (RV) failure post left ventricular assist device (LVAD) implantation is associated with increased morbidity and mortality. A novel RV multi-plane imaging method using two-dimensional echocardiography and electronic plane rotation (MPE) was used to quantify RV function prior to LVAD implantation and to identify potential added value in this patient population. METHODS: In twenty-five end-stage heart failure patients (age 58.9 ± 6.8 years, 76% male), systolic function of four different RV walls (lateral, anterior, inferior and inferior coronal) were evaluated from one focussed apical view using MPE. RESULTS: Feasibility of tricuspid annular plane systolic excursion (TAPSE) and tricuspid annular peak systolic velocity (RV-S') measurements were high (84-100%), with lower TAPSE values measured in the inferior (14.2 ± 4.6 mm) and inferior coronal (12.3 ± 5.0 mm) walls compared to the lateral (16.3 ± 4.5 mm) and anterior walls (16.0 ± 4.5 mm). RV wall longitudinal strain (RV-LS) measurement was most feasible in the lateral wall (80%; mean: -12.1 ± 4.2%). TAPSE and RV-LS values were significantly reduced in patients compared to matched healthy individuals (p = <0.001). Seven (28%) patients who developed moderate to severe RV failure (RVF) early post-implant (≤30 days) had lower pre-implant values across all multi-plane parameters compared to those without significant post-implant RVF, notably four-wall averaged TAPSE (11.1 ± 3.4 mm vs 15.9 ± 4.0 mm; p = 0.02). CONCLUSION: 2D MPE was highly feasible for RV wall quantification pre-LVAD surgery, detecting differences in regional wall function. This novel method comprehensively quantifies RV wall function and could complement current pre-LVAD screening protocols.

Prognostic value of temporal patterns of global longitudinal strain in patients with chronic heart failure.

Background: We investigated whether repeatedly measured global longitudinal strain (GLS) has incremental prognostic value over repeatedly measured left ventricular ejection fraction (LVEF) and N-terminal pro B-type natriuretic peptide (NT-proBNP), and a single "baseline" GLS value, in chronic heart failure (HF) patients. Methods: In this prospective observational study, echocardiography was performed in 173 clinically stable chronic HF patients every six months during follow up. During a median follow-up of 2.7 years, a median of 3 (25th-75th percentile:2-4) echocardiograms were obtained per patient. The endpoint was a composite of HF hospitalization, left ventricular assist device, heart transplantation, cardiovascular death. We compared hazard ratios (HRs) for the endpoint from Cox models (used to analyze the first available GLS measurements) with HRs from joint models (which links repeated measurements to the time-to-event data). Results: Mean age was 58 ± 11 years, 76% were men, 81% were in New York Heart Association functional class I/II, and all had LVEF < 50% (mean ± SD: 27 ± 9%). The endpoint was reached by 53 patients. GLS was persistently decreased over time in patients with the endpoint. However, temporal GLS trajectories did not further diverge in patients with versus without the endpoint and remained stable during follow-up. Both single measurements and temporal trajectories of GLS were significantly associated with the endpoint [HR per SD change (95%CI): 2.15(1.34-3.46), 3.54 (2.01-6.20)]. In a multivariable model, repeatedly measured GLS maintained its prognostic value while repeatedly measured LVEF did not [HR per SD change (95%CI): GLS:4.38 (1.49-14.70), LVEF:1.14 (0.41-3.23)]. The association disappeared when correcting for repeatedly measured NT-proBNP. Conclusion: Temporal evolution of GLS was associated with adverse events, independent of LVEF but not independent of NT-proBNP. Since GLS showed decreased but stable values in patients with adverse prognosis, single measurements of GLS provide sufficient information for determining prognosis in clinical practice compared to repeated measurements, and temporal GLS patterns do not add prognostic information to NT-proBNP.

Echocardiography from a transhepatic approach in left ventricular assist device patients with difficult transthoracic imaging.

BACKGROUND: Left ventricular assist devices (LVADs) are increasingly used in the treatment of end-stage heart failure. One important limitation in the follow-up of these patients is the very difficult echocardiographic image, because of the interposition of implanted materials. CASE SUMMARY: We present here a case series of LVAD patients with severely limited transthoracic echocardiographic windows in whom the echocardiographic analysis of the left and right ventricular function could be obtained from a very unusual approach, using a right intercostal transhepatic window, allowing visualization of the heart chambers and quantification of function even in these very challenging cases. In one case, the result was confirmed by computed tomography. In the second case, computed tomography images were unreliable because of strong artefacts from the LVAD system and implantable cardioverter-defibrillator leads, but the transhepatic approach still provided sufficient image quality in order to allow the imaging follow-up of the patient. In the third case, the transhepatic window was the only approach that provided echocardiographic images, and due to the good visualization of the heart cavities, this imaging technique was considered sufficient for follow-up studies in this stable subject with LVAD as destination therapy. DISCUSSION: The transhepatic window may represent a good alternative in selected LVAD patients with very difficult acoustic access in traditional transthoracic views. Modified or alternate echocardiographic windows may reduce the need for invasive procedures (transoesophageal echocardiography) or imaging methods using radiations.

A Cluster of Plasmodium ovale Infections in Belgian Military Personnel after Deployment in Kindu, Democratic Republic of Congo: A Retrospective Study.

Plasmodium ovale malaria is often neglected due to its less severe course compared to Plasmodium falciparum. In 2011-2012, Belgian Armed Forces identified a cluster of P. ovale cases among military personnel after deployment in the Democratic Republic of Congo (DRC). In this retrospective, monocentric, observational study, clinical and biological features of soldiers diagnosed with P. ovale after deployment in DRC were reviewed. Species diagnosis was based on polymerase chain reaction (PCR) and/or thick blood smear. Medical records of 149 soldiers screened at the Queen Astrid Military Hospital after deployment were reviewed. Eight cases (seven P. ovale infections and one P. ovale-falciparum coinfection) were identified. All had positive thick smears, and seven were confirmed by PCR. Chemoprophylaxis was mefloquine in all subjects. Median time of disease onset was 101 days after return from the endemic region. Median delay between return and diagnosis was 103 days. All P. ovale bouts were uncomplicated. None had relapses after primaquine treatment. This military cohort highlights a hotspot of P. ovale in Eastern DRC. Non-specific symptoms, the less severe presentation, the lack of sensitive parasitological tools in the field and long delays between infection and symptoms probably lead to underestimation of P. ovale cases.

Optimization of Microbubble Concentration and Acoustic Pressure for Left Ventricular High-Frame-Rate EchoPIV in Patients.

High-frame-rate (HFR) echo-particle image velocimetry (echoPIV) is a promising tool for measuring intracardiac blood flow dynamics. In this study, we investigate the optimal ultrasound contrast agent (UCA: SonoVue) infusion rate and acoustic output to use for HFR echoPIV (PRF = 4900 Hz) in the left ventricle (LV) of patients. Three infusion rates (0.3, 0.6, and 1.2 ml/min) and five acoustic output amplitudes (by varying transmit voltage: 5, 10, 15, 20, and 30 V-corresponding to mechanical indices of 0.01, 0.02, 0.03, 0.04, and 0.06 at 60-mm depth) were tested in 20 patients admitted for symptoms of heart failure. We assess the accuracy of HFR echoPIV against pulsed-wave Doppler acquisitions obtained for mitral inflow and aortic outflow. In terms of image quality, the 1.2-ml/min infusion rate provided the highest contrast-to-background ratio (CBR) (3-dB improvement over 0.3 ml/min). The highest acoustic output tested resulted in the lowest CBR. Increased acoustic output also resulted in increased microbubble disruption. For the echoPIV results, the 1.2-ml/min infusion rate provided the best vector quality and accuracy; mid-range acoustic outputs (corresponding to 15-20-V transmit voltages) provided the best agreement with the pulsed-wave Doppler. Overall, the highest infusion rate (1.2 ml/min) and mid-range acoustic output amplitudes provided the best image quality and echoPIV results.

Determinants of changes in pulmonary artery pressure in patients with severe aortic stenosis treated by transcatheter aortic valve implantation.

BACKGROUND: Elevated pulmonary artery pressure (PAP) in patients with severe aortic stenosis (AS) is a strong predictor of adverse prognosis. This study sought to assess the relation between PAP and clinical and echocardiographic parameters in elderly patients with severe AS, as well as to identify the determinants of the change in PAP after transcatheter aortic valve implantation (TAVI). METHODS: The study included 170 subjects (age 81 ± 7 years, 45% men) with symptomatic severe AS who were treated by TAVI. They underwent a clinical evaluation and a transthoracic echocardiography before the TAVI procedure and 6 months after. RESULTS: In a multivariable analysis, the independent predictors for baseline PAP were the body mass index (BMI) (ß = 0.21, p = .006), COPD GOLD class (ß = 0.20; p = .009), the E/e' ratio (ß = 0.20; p = .02) and the degree of aortic regurgitation (ß = 0.20; p = .01). After TAVI, there was significantly less (51% vs. 29%, p<.0001) pulmonary hypertension, defined as a tricuspid regurgitation velocity ≥2.8 m/s. The baseline variables related to an improvement in PAP were the tricuspid regurgitation velocity (p = .0001) and the E/e' (p = .005). From the parameters potentially modified with TAVI, the only independent predictor of PAP variation was the change in the E/e' ratio (ß = 0.23; p = .01). CONCLUSIONS: Independent predictors for baseline PAP in elderly patients with symptomatic AS were the BMI, GOLD class, the aortic regurgitation and the E/e' ratio. The baseline predictors for a change in PAP 6 months after TAVI were the baseline PAP and E/e', with only the change in the E/e' ratio being correlated to the change in PAP.

Evaluation of patients with a HeartMate 3 left ventricular assist device using echocardiographic particle image velocimetry.

PURPOSE: Poor left ventricular (LV) function may affect the physiological intraventricular blood flow and physiological vortex formation. The aim of this study was to investigate the pattern of intraventricular blood flow dynamics in patients with LV assist devices (LVADs) using echocardiographic particle image velocimetry. MATERIALS AND METHODS: This prospective study included 17 patients (mean age 57 ± 11 years, 82% male) who had received an LVAD (HeartMate 3, Abbott Laboratories, Chicago, Illinois, USA) because of end-stage heart failure and poor LV function. Eleven (64%) patients had ischemic cardiomyopathy, and six patients (36%) had nonischemic cardiomyopathy. All patients underwent echocardiography, including intravenous administration of an ultrasound-enhancing agent (SonoVue, Bracco, Milan, Italy). Echocardiographic particle image velocimetry was used to quantify LV blood flow dynamics, including vortex formation (Hyperflow software, Tomtec imaging systems Gmbh, Unterschleissheim, Germany). RESULTS: Contrast-enhanced ultrasound was well tolerated in all patients and was performed without adverse reactions or side effects. The LVAD function parameters did not change during or after the ultrasound examination. The LVAD flow was on average 4.3 ± 0.3 L/min, and the speed was 5247 ± 109 rotations/min. The quantification of LV intraventricular flow demonstrated substantial impairment of vortex parameters. The energy dissipation, vorticity, and kinetic energy fluctuation indices were severely impaired. CONCLUSIONS: Echo particle velocimetry is safe and feasible for the quantitative assessment of intraventricular flow in patients with an LVAD. The intraventricular LV flow and vortex parameters are severely impaired in these patients.

A direct comparison of natural and acoustic-radiation-force-induced cardiac mechanical waves.

Natural and active shear wave elastography (SWE) are potential ultrasound-based techniques to non-invasively assess myocardial stiffness, which could improve current diagnosis of heart failure. This study aims to bridge the knowledge gap between both techniques and discuss their respective impacts on cardiac stiffness evaluation. We recorded the mechanical waves occurring after aortic and mitral valve closure (AVC, MVC) and those induced by acoustic radiation force throughout the cardiac cycle in four pigs after sternotomy. Natural SWE showed a higher feasibility than active SWE, which is an advantage for clinical application. Median propagation speeds of 2.5-4.0 m/s and 1.6-4.0 m/s were obtained after AVC and MVC, whereas ARF-based median speeds of 0.9-1.2 m/s and 2.1-3.8 m/s were reported for diastole and systole, respectively. The different wave characteristics in both methods, such as the frequency content, complicate the direct comparison of waves. Nevertheless, a good match was found in propagation speeds between natural and active SWE at the moment of valve closure, and the natural waves showed higher propagation speeds than in diastole. Furthermore, the results demonstrated that the natural waves occur in between diastole and systole identified with active SWE, and thus represent a myocardial stiffness in between relaxation and contraction.

Local myocardial stiffness variations identified by high frame rate shear wave echocardiography.

BACKGROUND: Shear waves are generated by the closure of the heart valves. Significant differences in shear wave velocity have been found recently between normal myocardium and disease models of diffusely increased muscle stiffness. In this study we correlate in vivo myocardial shear wave imaging (SWI) with presence of scarred tissue, as model for local increase of stiffness. Stiffness variation is hypothesized to appear as velocity variation. METHODS: Ten healthy volunteers (group 1), 10 hypertrophic cardiomyopathy (HCM) patients without any cardiac intervention (group 2), and 10 HCM patients with prior septal reduction therapy (group 3) underwent high frame rate tissue Doppler echocardiography. The SW in the interventricular septum after aortic valve closure was mapped along two M-mode lines, in the inner and outer layer. RESULTS: We compared SWI to 3D echocardiography and strain imaging. In groups 1 and 2, no change in velocity was detected. In group 3, 8/10 patients showed a variation in SW velocity. All three patients having transmural scar showed a simultaneous velocity variation in both layers. Out of six patients with endocardial scar, five showed variations in the inner layer. CONCLUSION: Local variations in stiffness, with myocardial remodeling post septal reduction therapy as model, can be detected by a local variation in the propagation velocity of naturally occurring shear waves.