Impact of Contrast Echocardiography on Evaluation of Ventricular Function and Clinical Management in a Large Prospective Cohort

Contrast Echocardiography in Heart Failure: Update 2023

PURPOSE OF REVIEW

The application of ultrasound-enhancing agents (contrast agents) has improved the accuracy and reproducibility of echocardiography. The review focuses on the currently approved and evolving indications for contrast echocardiography in patients with heart failure, specifically examining clinical studies conducted after the publication of the guidelines in 2017 and 2018.

RECENT FINDINGS

The current ASE/EACVI recommendations for contrast echocardiography are based on its accuracy and reproducibility in comparison to non-enhanced echocardiography or other imaging modalities like cardiac MRI. However, tissue characterization remains limited with contrast echocardiography. During the last few years, several studies have demonstrated the clinical impact of using contrast agents on the management of patients with heart failure. There is growing evidence on the benefit of using contrast echocardiography in critically ill patients where echocardiography without contrast agents is often suboptimal and other imaging methods are less feasible. There is no risk of worsening renal function after the administration of ultrasound-enhancing agents, and these agents can be administered even in patients with end-stage renal disease. Contrast echocardiography has become a valuable tool for first-line imaging of patients with heart failure across the spectrum of patients with chronic heart failure to critically ill patients.

Global longitudinal strain in long-term risk prediction after acute coronary syndrome: an investigation of added prognostic value to ejection fraction

AIMS

This study aimed to investigate the additional value of global longitudinal strain (GLS) on top of left ventricular ejection fraction (LVEF) in long-term risk prediction of combined death and heart failure (HF) re-hospitalization after acute coronary syndrome (ACS).

METHOD AND RESULTS

This retrospective study included patients admitted with ACS between 2008 and 2014 from the three participating university hospitals. LVEF and GLS were assessed at a core lab from images acquired during the index hospital stay. Their prognostic value was studied with the Cox proportional hazards model (median follow-up 6.2 years). A nested model comparison was performed with C-statistics. A total of 941 patients qualified for multivariable analysis after multiple imputation of missing baseline covariables. The combined outcome was reached in 17.7% of the cases. Both GLS and LVEF were independent predictors of the combined outcome, hazard ratio (HR) 1.068 (95% CI 1.017-1.121) and HR 0.980 (95% CI 0.962-0.998), respectively. The C-statistic increased from 0.742 (95% CI 0.702-0.783) to 0.749 (95% CI 0.709-0.789) (P = 0.693) when GLS entered the model with clinical data and LVEF.

CONCLUSION

GLS emerged as an independent long-term risk predictor of all-cause death and HF re-hospitalization. However, there was no significant incremental predictive value of GLS when LVEF was already known.

Incidence of Severe Adverse Drug Reactions to Ultrasound Enhancement Agents in a Contemporary Echocardiography Practice

OBJECTIVES

Prior data indicate a very rare risk of serious adverse drug reaction (ADR) to ultrasound enhancement agents (UEAs). We sought to evaluate the frequency of ADR to UEA administration in contemporary practice.

METHODS

We retrospectively reviewed 4 US health systems to characterize the frequency and severity of ADR to UEA. Adverse drug reactions were considered severe when cardiopulmonary involvement was present and critical when there was loss of consciousness, loss of pulse, or ST-segment elevation. Rates of isolated back pain and headache were derived from the Mayo Clinic Rochester stress echocardiography database where systematic prospective reporting of ADR was performed.

RESULTS

Among 26,539 Definity and 11,579 Lumason administrations in the Mayo Clinic Rochester stress echocardiography database, isolated back pain or headache was more frequent with Definity (0.49% vs 0.04%, P < .0001) but less common with Definity infusion versus bolus (0.08% vs 0.53%, P = .007). Among all sites there were 201,834 Definity and 84,943 Lumason administrations. Severe and critical ADR were more frequent with Lumason than with Definity (0.0848% vs 0.0114% and 0.0330% vs 0.0010%, respectively; P < .001 for each). Among the 3 health systems with >2,000 Lumason administrations, the frequency of severe ADR with Lumason ranged from 0.0755% to 0.1093% and the frequency of critical ADR ranged from 0.0293% to 0.0525%. Severe ADR rates with Definity were stable over time but increased in more recent years with Lumason (P = .02). Patients with an ADR to Lumason since the beginning of 2021 were more likely to have received a COVID-19 vaccination compared with matched controls (88% vs 75%; P = .05) and more likely to have received Moderna than Pfizer-Biotech (71% vs 26%, P < .001).

CONCLUSION

Severe and critical ADR, while rare, were more frequent with Lumason, and the frequency has increased in more recent years. Additional work is needed to better understand factors, including associations with recently developed mRNA vaccines, which may be contributing to the increased rates of ADR to UEA since 2021.

Multi-Ethnic Study of Atherosclerosis Early Heart Failure Study: Rationale, Design, and Baseline Characteristics

BACKGROUND

Current prevalence estimates of heart failure (HF) are primarily based on self-report or HF hospitalizations. There is an unmet need to define the prevalence and pathogenesis of early symptomatic HF, which may be undiagnosed and precedes HF hospitalization.

METHODS

The MESA (Multi-Ethnic Study of Atherosclerosis) Early HF study was conducted during MESA exam 6 to determine the prevalence of early HF and investigate the transition from risk factors to early HF in a diverse population-based cohort of older adults. Between 2016 and 2018, 3285 MESA participants from 6 field centers underwent comprehensive speckle-tracking echocardiography with passive leg raise maneuver, Kansas City Cardiomyopathy Questionnaire, 6-minute walk test, arterial stiffness assessment, and proteomics (including NT-proBNP [N-terminal pro-B-type natriuretic peptide]).

RESULTS

Median age was 73 (25th-75th percentile 67-81) years, 53.2% were female, 25.6% were Black, 12.8% were Chinese, and 40.0% were White. The prevalence of HF risk factors was high: hypertension, 61.9%; former or current smoking, 53.7%; obesity 34.8%; diabetes; 24.7%; and chronic kidney disease; 22%. Overt cardiovascular disease, which ranged from 2.1% (HF) to 13.6% (atrial fibrillation), was less common. Of the 3285 participants, 96% underwent proteomics, 94% Kansas City Cardiomyopathy Questionnaire, 93% speckle-tracking echocardiography with passive leg raise, 82% arterial stiffness exam, and 77% 6-minute walk test. Feasibility of resting speckle-tracking echocardiography (87%-99% across cardiac chambers) and passive leg raise Doppler/speckle-tracking echocardiography (>84%) measurements was high. A total of 120 unique echocardiographic indices were measured.

CONCLUSIONS

The MESA Early HF study is a key resource for cardiovascular researchers who are interested in improving the epidemiological and phenotypic characterization of early HF.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT00005487.

Efficacy and safety of use of ultrasound enhancing agent in patients hospitalized with COVID-19

PURPOSE

The efficacy and safety of ultrasound enhancing agent (UEA) was unknown in the COVID-19 hospitalized patients. We set out to establish the utility of UEA and its safety profile.

METHODS

A retrospective observational study of prospectively assessed hospitalized patients referred for transthoracic echocardiography (TTE) for suspected cardiac pathology due to COVID-19. The indications and subsequent ability to answer the indications for all TTE were reviewed, as well as impact on diagnosis and management. UEA safety was considered through 48 h mortality.

RESULTS

From a total of 364 patients (mean age 64.8yrs, 64% males) hospitalized with COVID-19 with TTE requested, an indication could be identified in 363, and 61 required administration of UEA. Standard TTE was able to answer the original indication in 275 (75.8%) patients. This was increased to 322 (88.7%) patients, a relative increase of 17.1%, with the use of UEA (p < 0.001). There was subsequent change in diagnosis in 22 out of 61 (36%) patients receiving UEA and change in management in 13 out of 61 (21.3%). There was no significant increase in 48 h (p = 0.14) mortality with UEA use. The patient population of TTE with UEA versus TTE without UEA differed in having a higher incidence of left ventricular systolic dysfunction, right ventricular dilatation, and self-defined white ethnicity.

CONCLUSION

The use of UEA in COVID-19 hospitalized patients, including those who were critically ill, provided incremental information when compared to TTE without UEA resulting in both changes in diagnosis and management plan and appears to be safe.

Validation of administrative claims to identify ultrasound enhancing agent use

BACKGROUND

Ultrasound enhancing agents (UEAs) are an invaluable adjunct to stress and transthoracic echocardiography (STE) to improve left ventricular visualization. Despite multiple single center studies evaluating UEA use, investigation into the rates, sources of variation, and outcomes of UEA use on a national level in the United States (US) has been limited by lack of validation of UEA codes for claims analyses.

METHODS

We conducted a retrospective cross-sectional study, 2019-2022, using linked multicenter electronic medical record (EMR) data from > 30 health systems linked to all-payor claims data representing > 90% of the US population. Individuals receiving STE in both EMR and claims data on the same day during the study window were included. UEA receipt as identified by presence of a Current Procedural Terminology (CPT) or National Drug Code (NDC) for UEA use within 1-day of the index STE event. We evaluated the performance of claims to identify UEA use, using EMR data as the gold standard, stratified by inpatient and outpatient status.

RESULTS

Amongst 54,525 individuals receiving STE in both EMR and claims data, 12,853 (23.6%) had a UEA claim in EMR, 10,461 (19.2%) had a UEA claim in claims, and 9140 (16.8%) had a UEA claim in both within the 1-day window. The sensitivity, specificity, accuracy, positive, and negative predictive values for UEA claims were 71.1%, 96.8%, 90.8%, 87.4%. and 91.6% respectively. However, amongst inpatients, the sensitivity of UEA claims was substantially lower (6.8%) compared to outpatients (79.7%).

CONCLUSIONS

While the overall accuracy of claims to identify UEA use was high, there was substantial under-capture of UEA use by claims amongst inpatients. These results call into question published rates of UEA use amongst inpatients in studies using administrative claims, and highlight ongoing need to improve inpatient coding for UEA use.

High-definition blood flow imaging improves quantification of left ventricular volumes and ejection fraction

AIMS

The accuracy and reproducibility of echocardiography to quantify left ventricular ejection fraction (LVEF) is limited due to image quality. High-definition blood flow imaging is a new technique which improves cavity delineation without the need for medication or intravenous access. We sought to examine the impact of high-definition blood flow imaging on accuracy and reproducibility of LV systolic function assessment.

METHODS AND RESULTS

Prospective observational study of consecutive patients undergoing 2D and 3D transthoracic echocardiography (TTE), high-definition blood flow imaging, and cardiac magnetic resonance (CMR) within 1 h of each other. Left ventricular systolic function characterized by left ventricular end-systolic volumes and left ventricular end-diastolic volumes and LVEF were measured. Seventy-six patients were included. Correlation of 2D TTE with CMR was modest (r = 0.68) with a worse correlation in patients with three or more segments not visualized (r = 0.58). High-definition blood flow imaging was feasible in all patients, and the correlation of LVEF with CMR was excellent (r = 0.88). The differences between 2D, high-definition blood flow, and 3D TTE compared to CMR were 5 ± 9%, 2 ± 5%, and 1 ± 3%, respectively. The proportion of patients where the grade of LV function was correctly classified improved from 72.3% using 2D TTE to 92.8% using high-definition blood flow imaging. 3D TTE also had excellent correlation with CMR (r = 0.97) however was only feasible in 72.4% of patients.

CONCLUSION

High-definition blood flow imaging is highly feasible and significantly improves the diagnostic accuracy and grading of LV function compared to 2D echocardiography.

Assessment of left ventricular ejection fraction in artificial intelligence based on left ventricular opacification

Background

Left ventricular opacification (LVO) improves the accuracy of left ventricular ejection fraction (LVEF) by enhancing the visualization of the endocardium. Manual delineation of the endocardium by sonographers has observer variability. Artificial intelligence (AI) has the potential to improve the reproducibility of LVO to assess LVEF.

Objectives

The aim was to develop an AI model and evaluate the feasibility and reproducibility of LVO in the assessment of LVEF.

Methods

This retrospective study included 1305 echocardiography of 797 patients who had LVO at the Department of Ultrasound Medicine, Union Hospital, Huazhong University of Science and Technology from 2013 to 2021. The AI model was developed by 5-fold cross validation. The validation datasets included 50 patients prospectively collected in our center and 42 patients retrospectively collected in the external institution. To evaluate the differences between LV function determined by AI and sonographers, the median absolute error (MAE), spearman correlation coefficient, and intraclass correlation coefficient (ICC) were calculated.

Results

In LVO, the MAE of LVEF between AI and manual measurements was 2.6% in the development cohort, 2.5% in the internal validation cohort, and 2.7% in the external validation cohort. Compared with two-dimensional echocardiography (2DE), the left ventricular (LV) volumes and LVEF of LVO measured by AI correlated significantly with manual measurements. AI model provided excellent reliability for the LV parameters of LVO (ICC > 0.95).

Conclusions

AI-assisted LVO enables more accurate identification of the LV endocardium and reduces observer variability, providing a more reliable way for assessing LV function.

Current and Future Role of Ultrasonography in the Cardiac Intensive Care Unit

The contemporary practice of ultrasonography in the cardiac intensive care unit integrates the principles of echocardiography with whole-body imaging to create a more expansive paradigm of critical care ultrasonography (CCUS). This article will review the use of CCUS for diagnostic assessment, monitoring, therapeutic guidance, and prognosis.

Multimodal Cardiac Imaging in the Assessment of Patients Who Have Suffered a Cardioembolic Stroke: A Review

Cardioembolic strokes account for 20-25% of all ischaemic strokes, with their incidence increasing with age. Cardiac imaging plays a crucial role in identifying cardioembolic causes of stroke, with early and accurate identification affecting treatment, preventing recurrence, and reducing stroke incidence. Echocardiography serves as the mainstay of cardiac evaluation. Transthoracic echocardiography (TTE) is the first line in the basic evaluation of structural heart disorders, valvular disease, vegetations, and intraventricular thrombus. It can be used to measure chamber size and systolic/diastolic function. Trans-oesophageal echocardiography (TOE) yields better results in identifying potential cardioembolic sources of stroke and should be strongly considered, especially if TTE does not yield adequate results. Cardiac computed tomography and cardiac magnetic resonance imaging provide better soft tissue characterisation, high-grade anatomical information, spatial and temporal visualisation, and image reconstruction in multiple planes, especially with contrast. These techniques are useful in cases of inconclusive echocardiograms and can be used to detect and characterise valvular lesions, thrombi, fibrosis, cardiomyopathies, and aortic plaques. Nuclear imaging is not routinely used, but it can be used to assess left-ventricular perfusion, function, and dimensions and may be useful in cases of infective endocarditis. Its use should be considered on a case-by-case basis. The accuracy of each imaging modality depends on the likely source of cardioembolism, and the choice of imaging approach should be tailored to individual patients.

Diagnosis of cardiovascular disease in patients with chronic kidney disease

Patients with chronic kidney disease (CKD) are at high risk of cardiovascular disease (CVD) and cardiovascular death. Identifying and monitoring cardiovascular complications and hypertension is important for managing patients with CKD or kidney failure and transplant recipients. Biomarkers of myocardial ischaemia, such as troponins and electrocardiography (ECG), have limited utility for diagnosing cardiac ischaemia in patients with advanced CKD. Dobutamine stress echocardiography, myocardial perfusion scintigraphy and dipyridamole stress testing can be used to detect coronary disease in these patients. Left ventricular hypertrophy and left ventricular dysfunction can be detected and monitored using various techniques with differing complexity and cost, including ECG, echocardiography, nuclear magnetic resonance, CT and myocardial scintigraphy. Atrial fibrillation and other major arrhythmias are common in all stages of CKD, and ambulatory heart rhythm monitoring enables precise time profiling of these disorders. Screening for cerebrovascular disease is only indicated in asymptomatic patients with autosomal dominant polycystic kidney disease. Standardized blood pressure is recommended for hypertension diagnosis and treatment monitoring and can be complemented by ambulatory blood pressure monitoring. Judicious use of these diagnostic techniques may assist clinicians in detecting the whole range of cardiovascular alterations in patients with CKD and enable timely treatment of CVD in this high-risk population.

Automated Detection of Apical Foreshortening in Echocardiography Using Statistical Shape Modelling

OBJECTIVE

Automated detection of foreshortening, a common challenge in routine 2-D echocardiography, has the potential to improve quality of acquisitions and reduce the variability of left ventricular measurements. Acquiring and labelling the required training data is challenging due to the time-intensive and highly subjective nature of foreshortened apical views. We aimed to develop an automatic pipeline for the detection of foreshortening. To this end, we propose a method to generate synthetic apical-four-chamber (A4C) views with matching ground truth foreshortening labels.

METHODS

A statistical shape model of the four chambers of the heart was used to synthesise idealised A4C views with varying degrees of foreshortening. Contours of the left ventricular endocardium were segmented in the images, and a partial least squares (PLS) model was trained to learn the morphological traits of foreshortening. The predictive capability of the learned synthetic features was evaluated on an independent set of manually labelled and automatically curated real echocardiographic A4C images.

RESULTS

Acceptable classification accuracy for identification of foreshortened views in the testing set was achieved using logistic regression based on 11 PLS shape modes, with a sensitivity, specificity and area under the receiver operating characteristic curve of 0.84, 0.82 and 0.84, respectively. Both synthetic and real cohorts showed interpretable traits of foreshortening within the first two PLS shape modes, reflected as a shortening in the long-axis length and apical rounding.

CONCLUSION

A contour shape model trained only on synthesized A4C views allowed accurate prediction of foreshortening in real echocardiographic images.

Safety of Lumason® (SonoVue®) in special populations and critically ill patients

Evidence for the safe use of Lumason® (SonoVue®), an ultrasound enhancing agent (UEA), in special patient populations is critical to enable healthcare professionals to make informed decisions concerning its use in such patients. Herein, we provide insight on the safety and tolerability of Lumason® in special patient populations. Findings are presented from clinical pharmacology studies conducted in patients with compromised cardiopulmonary conditions, from a retrospective study performed in critically ill patients, and from post-marketing surveillance data from over 20 years of market use of Lumason® (SonoVue®). No detrimental effects of Lumason® on cardiac electrophysiology were observed in patients with coronary artery disease (CAD), and no significant effects on pulmonary hemodynamics were noted in patients with pulmonary hypertension or congestive heart failure. Similarly, no effects on several assessments of pulmonary function (e.g., FVC) were observed in patients with chronic obstructive pulmonary disease (COPD), and no clinically meaningful changes in O2 saturation or other safety parameters were observed after administration of Lumason® to patients with diffuse interstitial pulmonary fibrosis (DIPF). The retrospective study of critically ill patients revealed no significant difference for in-hospital mortality between patients administered Lumason® for echocardiography versus those who had undergone echocardiography without contrast agent. Post-marketing surveillance revealed very low reporting rates (RR) for non-serious and serious adverse events and that serious hypersensitivity reactions were rare. These findings confirm that Lumason® is a safe and well tolerated UEA for use in special populations and critically ill patients.

Ultrasound Enhancing Agents with Transthoracic Echocardiography for Maximal Wall Thickness in Hypertrophic Cardiomyopathy

Objectives

To determine whether ultrasound enhancing agent (UEA) changes maximal wall thickness (WT) in hypertrophic cardiomyopathy (HCM), and if it improves correlation with magnetic resonance imaging (MRI).

Patients and Methods

A total of 107 patients with HCM were prospectively enrolled at a single tertiary referral center between July 10, 2014, and August 31, 2017, and underwent transthoracic echocardiography (TTE) with and without UEA and MRI. Maximal WT measurements were compared, and variability among the 3 modalities was evaluated using a simple linear regression analysis and paired t tests and Bland-Altman plots. Interobserver variability for each technique was assessed.

Results

Most (63%) of cardiac imagers found UEA helpful in determining maximal WT by TTE, with 49% reporting change in WT. Of 52 patients where UEA changed WT measurement, 32 (62%) reported an increase and 20 (38%) reported a decrease in WT. The UEA did not alter the median discrepancy in WT between MRI and TTE. However, where UEA increased reported WT, the difference between MRI and TTE improved in 79% of cases (P=.001) from 2.0-0.5mm. In those with scar on MRI, UEA improved agreement of WT between TTE and MRI compared with that of TTE without UEA (79% vs 39%; P=.011). Interclass correlation coefficient for WT for TTE without UEA, with UEA, and MRI was 0.84; (95% CI, 0.61-0.92), 0.88; (95%CI, 0.82-0.92), and 0.97; (95%CI, 0.96-0.98), respectively.

Conclusion

Although use of UEA did not eliminate differences in WT discrepancy between modalities, the addition of UEA to TTE aided in WT determination and improved correlation with MRI in those with greater WT and in all patients with myocardial scars.

[Contrast-enhanced ultrasound: history, application and perspectives]

The article discusses the stages of formation and development of ultrasound diagnostics, including those with contrast enhancement. The main types of contrast agents and their mechanism of action are presented. Examples of the use of contrast-enhanced ultrasound in various fields of medicine are given. The prospects of the method and its place in clinical practice are discussed.

Overcoming biological barriers to improve treatment of a Staphylococcus aureus wound infection

Chronic wounds frequently become infected with bacterial biofilms which respond poorly to antibiotic therapy. Aminoglycoside antibiotics are ineffective at treating deep-seated wound infections due to poor drug penetration, poor drug uptake into persister cells, and widespread antibiotic resistance. In this study, we combat the two major barriers to successful aminoglycoside treatment against a biofilm-infected wound: limited antibiotic uptake and limited biofilm penetration. To combat the limited antibiotic uptake, we employ palmitoleic acid, a host-produced monounsaturated fatty acid that perturbs the membrane of gram-positive pathogens and induces gentamicin uptake. This novel drug combination overcomes gentamicin tolerance and resistance in multiple gram-positive wound pathogens. To combat biofilm penetration, we examined the ability of sonobactericide, a non-invasive ultrasound-mediated-drug delivery technology to improve antibiotic efficacy using an in vivo biofilm model. This dual approach dramatically improved antibiotic efficacy against a methicillin-resistant Staphylococcus aureus (MRSA) wound infection in diabetic mice.

Feasibility of Left Ventricle Ejection Fraction Calculation Using Electrocardiographically Gated SPECT Acquisition of 99m Tc-HDP Bone Scintigraphy in Cardiac Amyloidosis

ABSTRACT

We performed bone scintigraphy in 6 patients with suspected cardiac amyloidosis. To evaluate feasibility of left ventricle function analysis, we additionally performed electrocardiographically gated SPECT acquisition. The cardiac-gated SPECT data confirmed adequate tracer uptake for automatic myocardial contour determination. LVEF estimations ranged between 24% and 54%. Comparison with LVEF estimations from prior echocardiography generally showed only small differences. In one patient, the LVEF measurements from both methods seemed discordant, probably reflecting actual LVEF worsening, which was confirmed at follow-up echocardiography. Therefore, our results may suggest that cardiac-gated SPECT acquisition at bone scintigraphy can provide meaningful estimates of LVEF.

Novel Utilization of Ultrasound Enhancing Agents in Complex Congenital Heart Disease Following Superior Cavopulmonary Connection

BACKGROUND

Children with single-ventricle congenital heart disease typically undergo a superior cavopulmonary connection (SCPC) as the second stage in their surgical palliation. Postoperatively, stenoses of the SCPC and branch pulmonary arteries can occur. If there are clinical concerns and echocardiography is insufficient for diagnosis, patients undergo invasive evaluation with exposure to radiation and anesthesia. The use of ultrasound enhancing agents (UEAs) to improve echocardiographic diagnostic capabilities has not previously been described in this population.

METHODS

A single-center, retrospective case review was conducted of children who underwent echocardiography with UEA, following SCPC, from March 1, 2020, to April 15, 2022, at the Children's Hospital of Philadelphia. Twenty-two patients with hypoxemia or concern for obstruction following SCPC underwent UEA echocardiography. Extracted clinical data included patient demographics, echocardiographic images, angiography, surgical and transcatheter interventions, as well as available follow-up data.

RESULTS

Six of the 22 UEA echocardiograms demonstrated stenosis or occlusion of either the SCPC or a pulmonary artery. All six patients underwent cardiac catheterization and five required intervention. Angioplasty was performed in each case with one requiring subsequent surgical revision. Sixteen of 22 UEA echocardiograms demonstrated no evidence of stenosis. Ten of these 16 patients improved, while six experienced persistent hypoxemia prompting referral for cardiac catheterization. Angiography confirmed the UEA echocardiographic findings (absence of stenosis) in four of these six patients. There were no adverse reactions related to UEA administration.

CONCLUSIONS

Echocardiography with UEAs is a valuable and safe adjunctive imaging modality following SCPC, particularly when two-dimensional and color imaging is limited. This novel application of UEAs in complex patients with congenital heart disease provides an "angiogram-like" image, better delineating vessel walls and improving assessment of postoperative obstruction. As experience with UEAs increases in the congenital heart disease population, there may be opportunities to decrease invasive and costly procedures, while expediting the care of patients in need of intervention.

Case report: Diagnosis of apical hypertrophic cardiomyopathy that escaped clinical and echocardiographic investigations for twenty years: Reasons and clinical implications

Background

Apical hypertrophic cardiomyopathy (ApHCM) is a rare form of hypertrophic cardiomyopathy which predominantly affects the apex of the left ventricle. The diagnosis can be challenging due to several factors, ranging from no typical clinical and electrocardiogram (EKG) findings to potential difficulties in executing and interpreting the echocardiographic examination.

Case presentation

We report the case of an 84-year-old woman who came to our echo-lab to undergo a routine echocardiogram. She had a history of permanent atrial fibrillation, paced rhythm and previous episodes of heart failure (HF), allegedly explained by a diagnosis of hypertensive heart disease that had been confirmed many times over the previous 20 years. The clinical examination and the EKG were unremarkable. The echocardiographic images were poor quality. But a senior cardiologist, expert in imaging and echocardiography, noted the lack of delineation of the endocardial border of the left ventricular (LV) apex region. Contrast echocardiography was performed and severe apical hypertrophy discovered.

Conclusion

ApHCM can be a challenging diagnosis. Contrast echocardiography must always be applied in cases of poor delineation of the LV apical endocardial border at baseline echocardiography. Timely detection and appropriate lifestyle intervention might slow the development of LV hypertrophy, and possibly minimize and delay heart failure (HF) related symptoms and arrhythmias. The prognosis remains relatively benign during long term follow-up.

Established and emerging roles for ultrasound enhancing agents (contrast echocardiography)

The ability to opacify the left ventricle and delineate the endocardium after intravenous injection of microbubble ultrasound enhancing agents is of established value to quantify volumes and function in suboptimal unenhanced images, particularly in stress echocardiograms. However, applications other than quantitation of left ventricle structure and function exist for contrast enhanced left ventricular opacification. Contrast agents enable recording of Doppler velocity signals in patients with poor ultrasound transmission, providing estimates of aortic stenosis gradient and pulmonary artery pressures. Contrast echo is of value in detecting apical hypertrophic cardiomyopathy and accompanying apical aneurysms. Most importantly, ultrasound enhancing agents can identify apical and left atrial masses when they cannot be visualized in unenhanced images, and can distinguish thrombi from tumors by visualizing the vascularity inherent in tumors. Contrast agents distinguish trabecular from compacted myocardium in noncompaction syndrome, and hypertrabeculation with other abnormal conditions. A major potential application of ultrasound enhancing agents is myocardial opacification, which can assist in identifying nonviable myocardium. Also, the delayed reappearance of myocardial perfusion after microbubble destruction identifies impaired contrary flow and can diagnose coronary stenosis. Innovative applications of ultrasound contrast agents currently under investigation, include visualizing the vaso vasorum to identify plaques and assess their vulnerability, and theranostic agents to deliver drugs and biologists and to assist in sonothrombolysis. It is anticipated that the role of ultrasound contrast agents will continue to increase in the future.

Cardiac CT for intra-cardiac thrombus detection in embolic stroke of undetermined source (ESUS)

INTRODUCTION

Embolic stroke of undetermined source (ESUS) is a common medical challenge regarding secondary prevention strategy. Cardiac imaging is the cornerstone of embolic stroke workup, in an effort to diagnose high risk cardio-embolic sources. Cardiac computed tomography angiography (CCTA) is an emerging imaging modality with high diagnostic performance for intra-cardiac thrombus detection. The yield of CCTA implementation in addition to standard care in ESUS workup is unknown. Thus, the aim of this study was to assess the utility of CCTA in detecting intra-cardiac thrombi in the routine ESUS workup.

PATIENTS AND METHODS

This is a retrospective observational analysis of ESUS cases managed in vascular neurology unit between 2019 and 2021. Within this ESUS registry, consecutive patients undergoing CCTA were included and carefully analyzed.

RESULTS

During the study period 1066 Ischemic stroke (IS) cases were treated and evaluated. 266/1066 (25%) met ESUS criteria and 129/266 (48%) underwent CCTA. Intra-cardiac thrombus was detected by CCTA in 22/129 (17%; 95% CI, 11.5%-23.5%) patients: left ventricular thrombus (LVT) in 13 (10.1%) patients, left atrial appendage (LAA) thrombus in 8 (6.2%) patients, and left atrial (LA) thrombus in 1 (0.8%) patient. Only 5/22 (23%) of these thrombi were suspected, but could not be confirmed, in trans-thoracic echocardiogram (TTE). Among CCTA-undergoing patients, 27/129 (21%; 95% CI, 14%-28%) were found to have an indication (including pulmonary embolism) for commencing anticoagulation (AC) treatment, rather than anti-platelets. In favor of CCTA implementation, 22/266 (8.2%; 95% CI, 4.9%-11.5%) patients within the entire ESUS cohort were diagnosed with intra-cardiac thrombus, otherwise missed.

CONCLUSION

CCTA improves the detection of intra-cardiac thrombi in addition to standard care in ESUS patients. The implementation of CCTA in routine ESUS workup can change secondary prevention strategy in a considerable proportion of patients.

Impact of ultrasound enhancing agents on clinical management

PURPOSE OF REVIEW

Ultrasound enhancing agents (UEAs), microbubbles which are composed of lipid or albumin shells containing high molecular weight gases with nonlinear acoustic properties in the ultrasound field, are important components of the diagnostic armamentarium in echocardiography. This review highlights the substantial value of UEAs in delineating endocardial border definition and influencing downstream decision-making in cardiovascular ultrasound.

RECENT FINDINGS

In this article, we review recent updates to the clinical applications of UEAs, special circumstances regarding use, the impact of use on downstream testing and cost-effectiveness, and recommended approaches for optimizing workflow in the echocardiography laboratory with UEAs.

SUMMARY

In multiple studies, UEAs have been identified as a useful tool in echocardiography, improving study accuracy and reader confidence, while reducing downstream testing and procedures and resulting in significant changes in clinical management. Despite their proven efficacy and cost-effectiveness, recent studies have suggested utilization remains low, in part due to perceived concerns and workflow issues that impair uptake. With an increasingly broader list of indications for echocardiography, UEAs will continue to play an important role in the diagnosis and management of patients with cardiovascular and noncardiovascular diseases.

CEUS cardiac exam protocols International Contrast Ultrasound Society (ICUS) recommendations

The present CEUS Cardiac Exam Protocols represent the first effort to promulgate a standard set of protocols for optimal administration of ultrasound enhancing agents (UEAs) in echocardiography, based on more than two decades of experience in the use of UEAs for cardiac imaging. The protocols reflect current clinical CEUS practice in many modern echocardiography laboratories throughout the world. Specific attention is given to preparation and dosing of three UEAs that have been approved by the United States Food and Drug Administration (FDA) and additional regulatory bodies in Europe, the Americas and Asia–Pacific. Consistent with professional society guidelines (J Am Soc Echocardiogr 31:241–274, 2018; J Am Soc Echocardiogr 27:797–810, 2014; Eur Heart J Cardiovasc Imaging 18:1205, 2017), these protocols cover unapproved “off-label” uses of UEAs—including stress echocardiography and myocardial perfusion imaging—in addition to approved uses. Accordingly, these protocols may differ from information provided in product labels, which are generally based on studies performed prior to product approval and may not always reflect state of the art clinical practice or guidelines.

Advanced Echocardiography Techniques: The Future Stethoscope of Systemic Diseases

Cardiovascular disease (CVD) has been showing patterns of extensive rise in prevalence in the contemporary era, affecting the quality of life of millions of people and leading the causes of death worldwide. It has been a provocative challenge for modern medicine to diagnose CVD in its crib, owing to its etiological factors being attributed to a large array of systemic diseases, as well as its non-binary hideous nature that gradually leads to functional disability. Novel echocardiography techniques have enabled the cardiac ultrasound to provide a comprehensive analysis of the heart in an objective, feasible, time- and cost-effective manner. Speckle tracking echocardiography, contrast echocardiography, and 3D echocardiography have shown the highest potential for widespread use. The uses of novel modalities have been elaborately demonstrated in this study as a proof of concept that echocardiography has a place in routine general practice with supportive evidence being as recent as its role in the concurrent COVID-19 pandemic. Despite such evidence, many uses remain off-label and unexploited in practice. Generalization of echocardiography at the point of care can become a much-needed turning point in the clinical approach to case management. To actualize such aspirations, we recommend further prospective and interventional studies to examine the effect of implementing advanced techniques at the point of care on the decision-making process and evaluate their effectiveness in prevention of cardiovascular morbidities and mortalities.

Multimodality Imaging in Ischemic Chronic Cardiomyopathy

Ischemic chronic cardiomyopathy (ICC) is still one of the most common cardiac diseases leading to the development of myocardial ischemia, infarction, or heart failure. The application of several imaging modalities can provide information regarding coronary anatomy, coronary artery disease, myocardial ischemia and tissue characterization. In particular, coronary computed tomography angiography (CCTA) can provide information regarding coronary plaque stenosis, its composition, and the possible evaluation of myocardial ischemia using fractional flow reserve CT or CT perfusion. Cardiac magnetic resonance (CMR) can be used to evaluate cardiac function as well as the presence of ischemia. In addition, CMR can be used to characterize the myocardial tissue of hibernated or infarcted myocardium. Echocardiography is the most widely used technique to achieve information regarding function and myocardial wall motion abnormalities during myocardial ischemia. Nuclear medicine can be used to evaluate perfusion in both qualitative and quantitative assessment. In this review we aim to provide an overview regarding the different noninvasive imaging techniques for the evaluation of ICC, providing information ranging from the anatomical assessment of coronary artery arteries to the assessment of ischemic myocardium and myocardial infarction. In particular this review is going to show the different noninvasive approaches based on the specific clinical history of patients with ICC.

Contrast Ultrasound, Sonothrombolysis and Sonoperfusion in Cardiovascular Disease: Shifting to Theragnostic Clinical Trials

Contrast ultrasound has a variety of applications in cardiovascular medicine, both in diagnosing cardiovascular disease as well as providing prognostic information. Visualization of intravascular contrast microbubbles is based on acoustic cavitation, the characteristic oscillation that results in changes in the reflected ultrasound waves. At high power, this acoustic response generates sufficient shear that is capable of enhancing endothelium-dependent perfusion in atherothrombotic cardiovascular disease (sonoperfusion). The oscillation and collapse of microbubbles in response to ultrasound also induces microstreaming and jetting that can fragment thrombus (sonothrombolysis). Several preclinical studies have focused on identifying optimal diagnostic ultrasound settings and treatment regimens. Clinical trials have been performed in acute myocardial infarction, stroke, and peripheral arterial disease often with improved outcome. In the coming years, results of ongoing clinical trials along with innovation and improvements in sonothrombolysis and sonoperfusion will determine whether this theragnostic technique will become a valuable addition to reperfusion therapy.

An Updated Review of the Efficacy and Safety of Direct Oral Anticoagulants in Treatment of Left Ventricular Thrombus

Left ventricular (LV) thrombus is a potentially serious complication affecting males and females with ischemic and nonischemic cardiomyopathy-specifically, after acute myocardial infarctions of the anterior left ventricular wall and long-standing tachyarrhythmias, respectively. LV thrombi pose significant risks for systemic embolization and devastating stroke events, while also demanding a treatment carrying inherent risks of its own. It is therefore imperative to have accurate detection of these ventricular thrombi and an appropriate understanding of the risks and benefits regarding management. Anticoagulation using warfarin has long been established as the gold-standard level of care in the current guidelines of the American College of Cardiology but the advent of direct oral anticoagulants (DOACs) prompts a re-examination of the literature. The particular question we seek to answer lies in the efficacy of these drugs and the safety and outcomes when used to treat LV thrombi. Recent case reports, meta-analyses, and most recently, the breakthrough of 2 novel randomized controlled trials have shown DOACs to be a promising treatment for LV thrombus. Contrarily, some retrospective cohort reviews suggest less-than-promising outcomes. This meta-analysis hopes to provide a current, curated review of up-to-date safety and efficacy in the documented tales of DOACs and LV thrombi that has been published since early 2020-by selecting these curated case studies, and analyzing the most recent randomized controlled trials, we hope to engage the reader with clearer illustrations of the key components of both the advocacy and warning of this pharmaceutical intervention.

Echocardiography in the time of Covid-19: Ultrasound enhancing agents save time and augment diagnostic information

BACKGROUND

There are currently no clear guidelines regarding the use of ultrasound enhancing agents (UEAs) with transthoracic echocardiography (TTE) for patients hospitalized with Covid-19. We investigated whether the performance of TTE with UEAs provides more diagnostic information and allows for shorter acquisition time compared to unenhanced TTE imaging in this patient population.

METHODS

We analyzed the TTEs of 107 hospitalized Covid-19 patients between April and June 2020 who were administered UEAs (Definity®, Lantheus). The time to acquire images with and without UEAs was calculated. A level III echocardiographer determined if new, clinically significant findings were visualized with the addition of UEAs.

RESULTS

There was a mean of 11.84±3.59 UEA cineloops/study vs 20.74±8.10 non-UEA cineloops/study (p < 0.0001). Mean time to acquire UEA cineloop images was 72.28±28.18 s/study compared to 188.07±86.04 s/study for non-UEA cineloop images (p < 0.0001). Forty-eight patients (45%) had at least one new finding on UEA imaging, with a total of 62 new findings seen. New information gained with UEAs was more likely to be found in patients with acute respiratory distress syndrome (21 vs 9, p < 0.001) and in those on mechanical ventilation (21 vs 15, p = 0.046).

CONCLUSIONS

TTE with UEAs required less time and fewer cineloop images compared to non-UEA imaging in patients hospitalized with Covid-19. Additionally, Covid-19 patients with severe respiratory disease benefited most with regard to new diagnostic information. Health care personnel should consider early use of UEAs in select hospitalized Covid-19 patients in order to reduce exposure and optimize diagnostic yield.

Impact of Multimodality Imaging on the Diagnosis of Left Ventricular Apical Thrombus in Patients after Anterior Myocardial Infarction

BACKGROUND

The presence of the left ventricle (LV) apical thrombus is one of the most critical complications of anterior myocardial infarction (MI). Due to the high risk of systemic embolization, the determination of LV apical thrombus (LVAT) is essential. We aimed to compare the two-dimensional echocardiography (2DE), contrast-2DE and real-time three-dimensional echocardiography (RT-3DE) in the diagnosis of LVAT and determine which imaging modality is superior.

METHODS

The study was designed as a prospective cohort study, and 161 patients were included. Patients with low ejection fraction (<40%) and LV apical wall motion abnormality (severe hypokinetic, akinetic or dyskinetic) were included. 2DE, contrast-2DE, RT-3DE, and magnetic resonance imaging (MRI) were performed on all patients within one month after anterior MI.

RESULTS

Transthoracic 2DE detected thrombi in 29 patients, contrast-2DE detected thrombi in 33 patients, RT-3DE detected thrombi in 32 patients, and MRI detected thrombi in 28 patients. While MRI is accepted as the gold standard for non-invasive imaging, the specificity of detecting thrombus with 2DE is 90%, and the sensitivity is 57%, contrast-2DE had 82% sensitivity and 92% specificity for the detection of LVAT. The specificity for detecting thrombus with RT-3DE is 93%, and the sensitivity is 85%. Accuracy was 84%, 90% and 92% with 2DE, contrast-2DE and RT-3DE, respectively.

CONCLUSIONS

We found that RT-3DE was more sensitive and more specific than 2DE and contrast-2DE in the diagnosis of LVAT. The diagnostic accuracy of RT-3DE was higher than 2DE and contrast-2DE for LVAT.

Left Ventricular Apical Aneurysms in Hypertrophic Cardiomyopathy: Equivalent Detection by Magnetic Resonance Imaging and Contrast Echocardiography

BACKGROUND

Left ventricular (LV) apical aneurysm is a unique morphological entity and novel adverse risk marker existing within the broad phenotypic spectrum of hypertrophic cardiomyopathy (HCM). Its true prevalence in the HCM population is likely underestimated because of inherent limitations of conventional noncontrast echocardiography. The authors hypothesized that contrast echocardiography is a reliable imaging technique compared with cardiovascular magnetic resonance (CMR) for the detection of apical aneurysms. The aim of this study was to assess the effectiveness of contrast echocardiography in the detection of LV apical aneurysms in patients with HCM in comparison with the gold standard, CMR.

METHODS

One hundred twelve patients with HCM identified from an institutional clinical database, who underwent echocardiographic and CMR examinations within 12 months and had LV apical aneurysms identified on either or both imaging modalities, were retrospectively analyzed. Discordant cases were reviewed by an expert panel, and a consensus was reached regarding the presence or absence of an apical aneurysm. The reason for any discrepancy was recorded.

RESULTS

The mean age of the patients was 59 ± 13 years, and 73% were men. Sixty-four (57%) underwent contrast echocardiography. The median interval between echocardiography and CMR was 118 days (interquartile range, 61-237 days). Thirty-nine patients (35%) had discordance between echocardiographic and CMR findings, of whom 20 had aneurysms reported on echocardiography but not CMR and 19 vice versa. Upon reanalysis by the expert panel, aneurysms were initially missed on CMR in 16 patients (80%), largely because of interpretation error secondary to small aneurysms, with a mean aneurysm size of 0.82 ± 0.38 cm in these cases. Before secondary review by the expert panel, contrast echocardiography had sensitivity of 97% compared with 85% for CMR (P = .0198) and 64% for noncontrast echocardiography (P = .0001). After secondary review, contrast echocardiography had sensitivity of 98% compared with 67% for noncontrast echocardiography (P = .0001) and 97% for CMR (P = 1.00).

CONCLUSIONS

Contrast echocardiography has high sensitivity for detecting LV apical aneurysms and should be used routinely in the evaluation and risk stratification of patients with HCM.

Echocardiography, lung ultrasound, and cardiac magnetic resonance findings in COVID-19: A systematic review

BACKGROUND

The manifestations of COVID-19 as outlined by imaging modalities such as echocardiography, lung ultrasound (LUS), and cardiac magnetic resonance (CMR) imaging are not fully described.

METHODS

We conducted a systematic review of the current literature and included studies that described cardiovascular manifestations of COVID-19 using echocardiography, CMR, and pulmonary manifestations using LUS. We queried PubMed, EMBASE, and Web of Science for relevant articles. Original studies and case series were included.

RESULTS

This review describes the most common abnormalities encountered on echocardiography, LUS, and CMR in patients infected with COVID-19.

The incidence of stroke in patients with early echocardiography after acute myocardial infarction

Left ventricular (LV) thrombus formation after ST-elevation myocardial infarction (STEMI) increases the risk of stroke. In our center, most echocardiograms are performed within 2 days post-STEMI. However, LV thrombi often become visible later. We assessed the 1-year incidence of stroke in patients without LV thrombus on echocardiography performed early (1-2 days) vs. later (day ≥ 3) post-STEMI. This retrospective observational study included 416 patients with acute STEMI. Patients with atrial fibrillation were excluded. All patients underwent echocardiography during admission. Patients with stroke within 12 months post-STEMI were identified from the hospital charts and administrative databases. Most echocardiograms (75%) were performed ≤ 2 days post-STEMI. LV thrombus was identified in 12 patients. One (8.3%) patient with LV thrombus and 10 (2.5%) patients without LV thrombus suffered stroke within 12 months post-STEMI. Most patients with stroke had apical akinesis. Most strokes occurred during the index admission or within 67 days of STEMI. There was no significant difference in the incidence of stroke between the patients with early vs. later echocardiography post-STEMI. The incidence of stroke after STEMI is low and similar between patients with echocardiography performed early vs. later post-STEMI which supports our current clinical practice. Importantly, most strokes occur in patients without LV thrombus on early echocardiography. High reported mortality rate associated with stroke following STEMI justifies the need for further validation in prospective studies to identify patients who may benefit from repeat imaging to detect later LV thrombus formation, and how this will impact patient outcomes and healthcare costs.

Impact of Contrast Echocardiography on Outcomes in Critically Ill Patients

Limited data suggests ultrasound enhancing agent (UEA) use is associated with changes in clinical management and lower mortality in intensive care unit (ICU) patients. We conducted a retrospective observational study to determine if contrast echocardiography (vs non-contrast echocardiography) is associated with differences in length of stay (LOS) and subsequent resource utilization in the ICU setting. The Premier Healthcare Database (Charlotte, NC) was analyzed to identify patients receiving Definity vs. no use of contrast during the initial rest transthoracic echocardiogram (TTE) in an ICU setting. The primary outcomes of interest were subsequent TTE and transesophageal echocardiography (TEE) during the index hospitalization, and ICU LOS. Propensity scoring was used to statistically model treatment selection to minimize selection bias. A total of 1,538,864 patients from 773 hospitals were identified as undergoing resting TTE in the ICU with use of DEFINITY in 51,141 (3.3%) patients and no contrast agent use in 1,487,723 (96.7%) patients. After adjusting for patient, clinical, and hospital characteristics, patients in the Definity cohort were less likely to undergo a subsequent TTE or TEE as compared to those in the no contrast cohort (odds ratio = 0.704 for TTE, odds ratio = 0.841 for TEE; p < 0.0001 for both). Adjusted mean ICU LOS for the Definity cohort was shorter than that of the no contrast cohort (4.59 vs 4.15 days, p < 0.0001). In conclusion, Definity-enhanced echocardiography in the ICU setting (in comparison with non-contrast TTE) is associated with lower rates of subsequent TTE and TEE during the index hospitalization, and shorter ICU LOS.

Validity of echocardiography for detection of left ventricular thrombus with surgical validation in patients awaiting durable left ventricular assist device

OBJECTIVE

Unrecognized left ventricular thrombi (LVT) can have devastating clinical implications and precludes patients with end-stage heart failure from undergoing left ventricular assist device (LVAD) implantation without cardiopulmonary bypass assistance. We assessed the reliability of an echocardiogram to diagnose LVT in patients with end-stage heart disease who underwent LVAD implantation.

METHODS

A single-center retrospective study evaluated 232 consecutive adult patients requiring implantation of durable LVADs between 2005 and 2019. The validity of preoperative transthoracic echocardiogram (TTE) and intraoperative transesophageal echocardiogram (TEE) for diagnosing LVT was compared to direct inspection at the time of LVAD implantation.

RESULTS

There were 232 patients that underwent LVAD implantation, with 226 patients (97%) receiving a preoperative TTE. Of those 226 patients, 32 patients (14%) received ultrasound enhancing agents (UEA). Intraoperative TEE images were available in 195 patients (84%). The sensitivity of TTE without UEA was 22% and specificity was 90% for detecting LVT, compared to 50% and 86%, respectively, for TTE with UEA. For intraoperative TEE, the sensitivity and specificity were 46% and 96%, respectively. The false omission rate ranged from 4% to 8% for all modalities of echocardiography.

CONCLUSION

Among patients undergoing LVAD implantation, preoperative TTE and intraoperative TEE had poor sensitivity for LVT detection. Up to 8% of echocardiograms were incorrectly concluded to be negative for LVT on surgical validation. The low sensitivity and positive predictive value for diagnosing LVT suggest that echocardiography has limited reliability in this cohort of patients who are at high risk of LVT formation and its subsequent complications.

Contrast-Enhanced Echocardiography Application in Patients Supported by Extracorporeal Membrane Oxygenation (ECMO): A Narrative Review

Extracorporeal membrane oxygenation (ECMO) is a lifesaving intervention increasingly used to support patients with severe respiratory and cardiac dysfunction. Echocardiography is an important tool, aiding implantation and monitoring during ECMO therapy, but often its use is limited by poor acoustic windows. This limitation may be overcome by the use of echocardiography contrast agents to improve diagnostic yield and reduce the need for other imaging modalities that may require patient transfer, involve ionizing radiation and, occasionally, nephrotoxic radio-opaque contrast medium. In this article the authors review the literature addressing the use of contrast-enhanced echocardiography (CEE) in ECMO-supported patients. The authors discuss the role of CEE in guiding implantation of ECMO, cardiac assessment and diagnosis of complications during ECMO therapy, as well as the safety of ultrasound-enhancing agents in this cohort of patients.

Bibliometric Analysis of Global Research Trends on Ultrasound Microbubble: A Quickly Developing Field

Background: Microbubbles are widely used as highly effective contrast agents to improve the diagnostic capability of ultrasound imaging. Mounting evidence suggests that ultrasound coupled with microbubbles has promising therapeutic applications in cancer, cardiovascular, and neurological disorders by acting as gene or drug carriers. The aim of this study was to identify the scientific output and activity related to ultrasound microbubble through bibliometric approaches. Methods: The literature related to ultrasound microbubble published between 1998 and 2019 was identified and selected from the Science Citation Index Expanded of Web of Science Core Collection on February 21, 2021. The Scopus database was also searched to validate the results and provided as supplementary material. Quantitative variables including number of publications and citations, H-index, and journal citation reports were analyzed by using Microsoft Excel 2019 and GraphPad Prism 8.0 software. VOS viewer and CiteSpace V were used to perform coauthorship, citation, co-citation, and co-occurrence analysis for countries/regions, institutions, authors, and keywords. Results: A total of 6088 publications from the WoSCC were included. The United States has made the largest contribution in this field, with the majority of publications (2090, 34.3%), citations (90,741, 46.6%), the highest H-index (138), and close collaborations with China and Canada. The most contributive institution was the University of Toronto. Professors De Jong N and Dayton P A have made great achievements in this field. However, the research cooperation between institutions and authors was relatively weak. All the studies could be divided into four clusters: "ultrasound diagnosis study," "microbubbles' characteristics study," "gene therapy study," and "drug delivery study." The average appearing years (AAY) of keywords in the cluster "drug delivery study" was more recent than other clusters. For promising hot spots, "doxorubicin" showed a relatively latest AAY of 2015.49, followed by "nanoparticles" and "breast cancer." Conclusion: There has been an increasing amount of scientific output on ultrasound microbubble according to the global trends, and the United States is staying ahead in this field. Collaboration between research teams still needs to be strengthened. The focus gradually shifts from "ultrasound diagnosis study" to "drug delivery study." It is recommended to pay attention to the latest hot spots, such as "doxorubicin," "nanoparticles," and "breast cancer."

The role of echocardiography in the embolic stroke of undetermined source

: Echocardiography plays an important role both in the diagnosis and the treatment/prevention of embolic stroke of undetermined source and should be performed as soon as possible for preventing ischemic stroke recurrencies, which occur more frequently during the first week after the first ischemic event. Early identification of the cause of a transient ischemic attack or stroke is indeed a primary goal for the neurologist in the Stroke Unit and requires specific diagnostic strategies. Echocardiography, together with other diagnostic tools such as carotid and transcranial ultrasounds, provides this information promptly. In particular, echocardiography might be able to detect the main sources of the embolic stroke, such as atrial fibrillation, ventricular akinesia, aortic atheroma plaques and/or cardiac shunts. The present review discusses the importance and the practical role of echocardiography as a crucial diagnostic tool for detecting the main source of emboli in the setting of the acute stroke.

Optimizing contrast-enhanced echocardiography by employing a sonographer driven protocol

Background

The use of enhancing agents in echocardiography has been shown to facilitate improved study quality. Despite the known benefits, its use remains limited by institutional policies.

Methods

We aimed to retrospectively evaluate if allowing sonographers to place a peripheral intravenous catheter and administer enhancing agent led to a decrease in time to complete outpatient transthoracic echocardiograms in comparison to using nursing personnel. Three separate protocols were employed. The ‘nurse driven protocol’ utilized nurses to place a peripheral intravenous catheter and inject enhancing agent. In a ‘mixed protocol,’ a nurse placed a peripheral intravenous catheter and the sonographer gave the enhancing agent. The ‘sonographer driven protocol’ involved the sonographer placing the peripheral intravenous catheter and delivering enhancing agent.

Results

A total of 232 echocardiograms were included for analysis. Patient characteristics across the three protocols were not statistically significant. The ‘mixed protocol’ had an average study time that was significantly less than the ‘nurse driven protocol’ (49.4 min ± 11.4 vs 54.6 min ± 12.9; p = 0.024). The ‘sonographer driven protocol’ also showed a significant reduction in study time (50.3 min ± 12.6) when compared to the ‘nurse driven protocol’ (p = 0.017). The additional task for the sonographer to place the peripheral intravenous catheter did not significantly increase the time to complete the study.

Conclusion

Allowing sonographers to administer enhancing agent reduced individual echocardiogram study times by approximately 5 min, supporting that a ‘sonographer driven protocol’ is more efficient with potential downstream economic benefits.

High frequency ultrasound nonlinear scattering from porphyrin nanobubbles

Emerging contrast imaging studies have highlighted the potential of nanobubbles for both intravascular and extravascular applications. Reports to date on nanobubbles have generally utilized low frequencies (<12 MHz), high concentrations (>10⁹ mL^-1), and B-mode or contrast-mode on preclinical and clinical systems. However, none of these studies directly examined nanobubble acoustic signatures systematically to implement nonlinear imaging schemes in a methodical manner based on nanobubble behaviour. Here, nanobubble nonlinear behaviour is investigated at high frequencies (12.5, 25, 30 MHz) and low concentration (10⁶ mL^-1) in a channel phantom, with different pulse types in single- and multi-pulse sequences to examine behaviour under conditions relevant to high frequency imaging. Porphyrin nanobubbles are demonstrated to initiate nonlinear scattering at high frequencies in a pressure-threshold dependent manner, as previously observed at low frequencies. This threshold behaviour was then utilized to demonstrate enhanced nanobubble imaging with pulse inversion, amplitude modulation, and a combination of the two, progressing towards the improved sensitivity and expanded utility of these ultrasound contrast agents.

Comparative Assessments of Left and Right Ventricular Function by Two-Dimensional, Contrast Enhanced and Three-Dimensional Echocardiography with Gated Heart Pool Scans in Patients Following Myocardial Infarction

Multiple noninvasive imaging modalities are available to measure biventricular function, although limited studies have assessed agreement between modalities in assessing left and right ventricular ejection fraction (LVEF & RVEF) in the same cohort of patients. In this study we prospectively compared the agreement of 2-dimensional echocardiography (2DE), contrast enhanced 2DE, 3-dimensional echocardiography (3DE), and gated heart pool scan (GHPS) measures of LVEF and RVEF in patients with acute ST-elevation myocardial infarction. We recruited 95 consecutive ST-elevation myocardial infarction patients (mean age 61.4 ± 12.0, male: 79.5%) admitted to a major tertiary hospital between July 2016 and May 2018. Despite minimal inter- and intra-observer variability (coefficient of variance < 5% in both categories), substantial discrepancies exist between modalities with Pearson's correlation coefficients ranging from 0.64 to 0.91 for LVEF measurements, and 0.27 to 0.86 for RVEF measurements. Bland-Altman plots demonstrated no systematic bias between modalities. GHPS and 3DE offered the closest agreement for both LVEF and RVEF, demonstrating the greatest correlation coefficient (r = 0.91 and 0.86 respectively), lowest mean absolute differences (4% and 3% respectively), and narrowest Bland-Altman limits of agreement (19% and 18% respectively). Greater than 10% of 2DE and contrast enhanced 2DE scans discordantly showed LVEF values >40% for patients whose LVEF was measured as ≤ 40% by 3DE or GHPS. In conclusion, substantial variation exists between modalities when assessing LVEF and RVEF, although we demonstrate that 3DE and GHPS have the closest agreement. This variability should be considered in clinical management of patients, and modalities should not be used interchangeably in sequential patient follow-up.

Assessing the Robustness of Frequency-Domain Ultrasound Beamforming Using Deep Neural Networks

We study training deep neural network (DNN) frequency-domain beamformers using simulated and phantom anechoic cysts and compare to training with simulated point target responses. Using simulation, physical phantom, and in vivo scans, we find that training DNN beamformers using anechoic cysts provided comparable or improved image quality compared with training DNN beamformers using simulated point targets. The proposed method could also be adapted to generate training data from in vivo scans. Finally, we evaluated the robustness of DNN beamforming to common sources of image degradation, including gross sound speed errors, phase aberration, and reverberation. We found that DNN beamformers maintained their ability to improve image quality even in the presence of the studied sources of image degradation. Overall, the results show the potential of using DNN beamforming to improve ultrasound image quality.

Contrast echocardiography: current status and future directions

Contrast echocardiography is a family of ultrasound-based procedures, whereby acoustic enhancing agents, usually microbubbles, are administered by intravenous route and detected in order to improve diagnostic performance. This review describes: (1) the agents that have been designed for diagnostic imaging, (2) current clinical applications where either left ventricular opacification or microvascular perfusion imaging with myocardial contrast echocardiography have been demonstrated to provide incremental information to non-contrast echocardiography and (3) future diagnostic and therapeutic applications of contrast ultrasound that rely on unique compositional design of ultrasound-enhancing agents.