Feasibility and accuracy of left ventricular volumes and ejection fraction determination by fundamental, tissue harmonic, and intravenous contrast imaging in difficult-to-image patients

Challenges in Echocardiography for the Diagnosis and Prognosis of Non-Ischemic Hypertensive Heart Disease

It has been well established that arterial hypertension is considered as a predominant risk factor for the development of cardiovascular diseases. Despite the link between arterial hypertension and cardiovascular diseases, arterial hypertension may directly affect cardiac function, leading to heart failure, mostly with preserved ejection fraction (HFpEF). There are echocardiographic findings indicating hypertensive heart disease (HHD), defined as altered cardiac morphology (left ventricular concentric hypertrophy, left atrium dilatation) and function (systolic or diastolic dysfunction) in patients with persistent arterial hypertension irrespective of the cardiac pathologies to which it contributes, such as coronary artery disease and kidney function impairment. In addition to the classical echocardiographic parameters, novel indices, like speckle tracking of the left ventricle and left atrium, 3D volume evaluation, and myocardial work in echocardiography, may provide more accurate and reproducible diagnostic and prognostic data in patients with arterial hypertension. However, their use is still underappreciated. Early detection of and prompt therapy for HHD will greatly improve the prognosis. Hence, in the present review, we shed light on the role of echocardiography in the contemporary diagnostic and prognostic approaches to HHD.

A new perspective on an old method: gated SPECT imaging for left ventricular contractile function assessment

The ejection fraction (LVEF) is a commonly used marker of left ventricular function. However, because it is strongly influenced by loading conditions, it can be inaccurate in representing cardiac contractility. We therefore evaluated a gated SPECT based tool to simultaneously assess preload, afterload, and contractility. Using gated SPECT-determined ventricular volumes and arterial tension measurements, we calculated ventricular and arterial elastance (Ev and Ea), as well as end-diastolic volumes, which are surrogates for contractility, afterload, and preload, respectively. We applied this protocol to 1462 consecutive patients and assessed the ventricular function in patients with and without myocardial infarction. The median LVEF was 68% (IQR 62-74%). Patients with infarction exhibited decreased contractility (ventricular elastance of 3 mmHg/ml vs. 6 mmHg/ml), compensated by an increase of preload (end-diastolic volume of 100 ml vs. 78 ml) and a decrease in afterload (arterial elastance of 1.8 mmHg/ml vs. 2.2 ml/mmHg). These interactions yielded a preserved ejection fraction in both groups. Gated SPECT-measured volumes were consistent with values reported in the literature. In addition, the combination of nuclear imaging and arterial tension measurement accounted for not only the ejection fraction but also the loading context, providing a more accurate representation of cardiac contractility.

LVEF by Multigated Acquisition Scan Compared to Other Imaging Modalities in Cardio-Oncology: a Systematic Review

Purpose of Review

The prevalence of cancer therapy-related cardiac dysfunction (CTRCD) is increasing due to improved cancer survival. Serial monitoring of cardiac function is essential to detect CTRCD, guiding timely intervention strategies. Multigated radionuclide angiography (MUGA) has been the main screening tool using left ventricular ejection fraction (LVEF) to monitor cardiac dysfunction. However, transthoracic echocardiography (TTE) and cardiac magnetic resonance imaging (CMR) may be more suitable for serial assessment. We aimed to assess the concordance between different non-radiating imaging modalities with MUGA to determine whether they can be used interchangeably.

Recent Findings

In order to identify relevant studies, a PubMed search was performed. We included cross-sectional studies comparing MUGA LVEF to that of 2D TTE, 3D TTE, and CMR. From 470 articles, 22 were selected, comprising 1017 patients in total. Among others, this included three 3D TTE, seven 2D harmonic TTE + contrast (2DHC), and seven CMR comparisons. The correlations and Bland-Altman limits of agreement varied for CMR but were stronger for 3D TTE and 2DHC.

Summary

Our findings suggest that MUGA and CMR should not be used interchangeably whereas 3D TTE and 2DHC are appropriate alternatives following an initial MUGA scan. We propose a multimodality diagnostic imaging strategy for LVEF monitoring in patients undergoing cancer treatment.

Cardiotoxicity Associated with Chemotherapy Used in Gastrointestinal Tumours

Cardiotoxicity is a well-recognised side effect of cancer-related therapies with a great impact on outcomes and quality of life in the cancer survivor population. The pathogenesis of chemotherapy-induced cardiotoxicity in patients with gastrointestinal cancers involves various molecular mechanisms, and the combined use of various chemotherapies augments the risk of each drug used alone. In terms of cardiotoxicity diagnosis, novel biomarkers, such as troponins, brain natriuretic peptide (BNP), myeloperoxidases and miRNAs have been recently assessed. Echocardiography is a noninvasive imaging method of choice for the primary assessment of chemotherapy-treated patients to generally evaluate the cardiovascular impact of these drugs. Novel echocardiography techniques, like three-dimensional and stress echocardiography, will improve diagnosis efficacy. Cardiac magnetic resonance (CMR) can evaluate cardiac morphology, function and wall structure. Corroborated data have shown the importance of CMR in the early evaluation of patients with gastrointestinal cancers, treated with anticancer drugs, but further studies are required to improve risk stratification in these patients. In this article, we review some important aspects concerning the cardiotoxicity of antineoplastic drugs used in gastrointestinal cancers. We also discuss the mechanism of cardiotoxicity, the role of biomarkers and the imaging methods used in its detection.

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.

Echocardiographic assessment of myocardial function and mechanics during veno-venous extracorporeal membrane oxygenation

BACKGROUND

Transthoracic echocardiography (TTE) plays a fundamental role in the management of patients supported with extra-corporeal membrane oxygenation (ECMO). In light of fluctuating clinical states, serial monitoring of cardiac function is required. Formal quantification of ventricular parameters and myocardial mechanics offer benefit over qualitative assessment. The aim of this research was to compare unenhanced (UE) versus contrast-enhanced (CE) quantification of myocardial function and mechanics during ECMO in a validated ovine model.

METHODS

Twenty-four sheep were commenced on peripheral veno-venous ECMO. Acute smoke-induced lung injury was induced in 21 sheep (3 controls). CE-TTE with Definity using Cadence Pulse Sequencing was performed. Two readers performed image analysis with TomTec Arena. End diastolic area (EDA, cm2), end systolic area (ESA, cm2), fractional area change (FAC, %), endocardial global circumferential strain (EGCS, %), myocardial global circumferential strain (MGCS, %), endocardial rotation (ER, degrees) and global radial strain (GRD, %) were evaluated for UE-TTE and CE-TTE.

RESULTS

Full data sets are available in 22 sheep (92%). Mean CE EDA and ESA were significantly larger than in unenhanced images. Mean FAC was almost identical between the two techniques. There was no significant difference between UE and CE EGCS, MGCS and ER. There was significant difference in GRS between imaging techniques. Unenhanced inter-observer variability was from 0.48-0.70 but significantly improved to 0.71-0.89 for contrast imaging in all echocardiographic parameters.

CONCLUSION

Semi-automated methods of myocardial function and mechanics using CE-TTE during ECMO was feasible and similar to UE-TTE for all parameters except ventricular areas and global radial strain. Addition of contrast significantly decreased inter-observer variability of all measurements.

Clinical practice of contrast echocardiography: recommendation by the European Association of Cardiovascular Imaging (EACVI) 2017

Contrast echocardiography is widely used in cardiology. It is applied to improve image quality, reader confidence and reproducibility both for assessing left ventricular (LV) structure and function at rest and for assessing global and regional function in stress echocardiography. The use of contrast in echocardiography has now extended beyond cardiac structure and function assessment to evaluation of perfusion both of the myocardium and of the intracardiac structures. Safety of contrast agents have now been addressed in large patient population and these studies clearly established its excellent safety profile. This document, based on clinical trials, randomized and multicentre studies and published clinical experience, has established clear recommendations for the use of contrast in various clinical conditions with evidence-based protocols.

Magnetic Resonance Imaging in Myocardial Fibrosis Related to Ischemic Events

Given the higher amount of detail it offers, the use of magnetic resonance (MR) in the field of cardiology has increased, thus leading to a decrease in the use of invasive and irradiating methods for diagnosing various cardiovascular disorders. The only precautions for MR imaging are metallic implants and advanced-stage chronic kidney disease. For the acquisition of clear and dynamic myocardial images, methods such as spin echo imaging for anatomical description, steady-state free precession imaging for the assessment of ventricular cavity size and function, flow velocity encoding for blood flow measurements, radiofrequency tagging for dynamics, and even spectroscopy for metabolism evaluation are used. Cardiac magnetic resonance (CMR) is considered the gold standard imaging method for the anatomical characterization of the heart and obtaining information related to myocardial dynamics. In case of ischemic events, CMR is used for a detailed description of the necrotic area and the complications, and for tracking the ventricular remodeling. By administrating a contrast agent (gadolinium), the difference between sub-endothelial and transmural infarctions can be distinguished, highlighting even microvascular lesions responsible for the extension of the necrosis. The assessment of the dynamics of ventricular remodeling and viability through late gadolinium enhancement (LGE) technology highlights the area of fibrosis and the occurrence of late complications.

Comparison between Radionuclide Ventriculography and Echocardiography for Quantification of Left Ventricular Systolic Function in Rats Exposed to Doxorubicin

Background

Radionuclide ventriculography (RV) is a validated method to evaluate the left ventricular systolic function (LVSF) in small rodents. However, no prior study has compared the results of RV with those obtained by other imaging methods in this context.

Objectives

To compare the results of LVSF obtained by RV and echocardiography (ECHO) in an experimental model of cardiotoxicity due to doxorubicin (DXR) in rats.

Methods

Adult male Wistar rats serving as controls (n = 7) or receiving DXR (n = 22) in accumulated doses of 8, 12, and 16 mg/kg were evaluated with ECHO performed with a Sonos 5500 Philips equipment (12-MHz transducer) and RV obtained with an Orbiter-Siemens gamma camera using a pinhole collimator with a 4-mm aperture. Histopathological quantification of myocardial fibrosis was performed after euthanasia.

Results

The control animals showed comparable results in the LVSF analysis obtained with ECHO and RV (83.5 ± 5% and 82.8 ± 2.8%, respectively, p > 0.05). The animals that received DXR presented lower LVSF values when compared with controls (p < 0.05); however, the LVSF values obtained by RV (60.6 ± 12.5%) were lower than those obtained by ECHO (71.8 ± 10.1%, p = 0.0004) in this group. An analysis of the correlation between the LVSF and myocardial fibrosis showed a moderate correlation when the LVSF was assessed by ECHO (r = -0.69, p = 0.0002) and a stronger correlation when it was assessed by RV (r = -0.79, p < 0.0001). On multiple regression analysis, only RV correlated independently with myocardial fibrosis.

Conclusion

RV is an alternative method to assess the left ventricular function in small rodents in vivo. When compared with ECHO, RV showed a better correlation with the degree of myocardial injury in a model of DXR-induced cardiotoxicity.

Diagnostic Strategies for Early Recognition of Cancer Therapeutics-Related Cardiac Dysfunction

Cardiovascular toxicity in the form of cardiac dysfunction continues to be an obstacle for patients with cancer. Survival and quality of life of cancer survivors are frequently affected by increased incidence of cardiovascular disease. The involvement of the cardiovascular system by primary or secondary malignancies, as well as its dysfunction secondary to the administration of antineoplastics, has led to the development of a new discipline called Cardio-Oncology, an exciting cardiology subspecialty with more questions than answers and as a result an enormous opportunity for research in the field. Multidisciplinary efforts have been focused on the prevention, diagnosis, and treatment of cancer therapeutics-related cardiovascular dysfunction (CTRCD). This review article will focus on the early diagnosis of left ventricular dysfunction associated with chemotherapy. Currently, the identification of cardiac toxicity associated with cancer treatment is the cornerstone for critical decisions regarding anticancer therapy and cardioprotective strategies. Its early detection, especially in subclinical phases, allows immediate intervention to prevent further impairment of the myocardium and other cardiovascular structures. The most significant published studies were selected for this revision, providing an updated document for the health professionals involved in the care of patients with cancer. We examined the current evidence and recommendations for biochemical and noninvasive diagnostic techniques, including their specific role for identification of CTRCD. Traditional and advanced imaging modalities, used alone or in combination with cardiovascular biomarkers, are essential for the recognition of cardiotoxicity during cancer therapy. Evolving basic and clinical research are focused on the development of more sensitive and specific diagnostic tools and for the recognition of cardiac toxicity.

Safety of Perflutren Ultrasound Contrast Agents: A Disproportionality Analysis of the US FAERS Database

INTRODUCTION

Perflutren microbubble/microsphere ultrasound contrast agents have a black-box warning based on case reports of serious cardiopulmonary events. There have been several subsequent observational safety studies. Large spontaneous reporting databases may help detect/refine signals of rare adverse events that elude other data sources/study designs.

OBJECTIVE

The objective of this study was to supplement existing knowledge of the reported safety of perflutren using statistical analysis of spontaneous reports.

METHODS

We analyzed information from the US Food and Drug Administration Adverse Event Reporting System using a disproportionality analysis. Analysis of overall reporting for perflutren was supplemented by subset (age, indication) analysis. A signal of disproportionate reporting (SDR) was defined as EB05 >2.

RESULTS

Overall, 18/380 Preferred Terms and 1/83 Standardized Medical Queries had SDRs. Most were small (EB05 = 2-4). Back pain and flank pain were the largest SDRs followed by events compatible with signs/symptoms of hypersensitivity. The general pattern of SDRs in the subset analysis was consistent with the overall analysis. Almost all events with SDRs were literally or conceptually labeled. Except for chest pain (higher in the age <65 years subgroup) and back pain (higher in the age ≥65 years subgroup), there were no statistically significant differences between age subsets. Except for the Preferred Terms Pruritus and Urticaria and the narrow Standardized Medical Queries Ventricular tachyarrhythmia, Angioedema, Oropharyngeal allergic conditions, and Hypersensitivity (higher in the stress test subgroup), there were no statistically significant reporting differences between indication subsets. There were no SDRs associated with the major cardiovascular events of death, myocardial infarction/ischemia, angina, arrhythmias, or convulsions in any analysis.

CONCLUSIONS

Our combined signal detection/evaluation analysis did not identify SDRs of novel adverse events or major cardiovascular events associated with perflutren ultrasound contrast agents. The negative results for major cardiovascular events extend previous signal evaluation exercises supporting the relative cardiovascular safety of these agents.

Clinical application and laboratory protocols for performing contrast echocardiography

Technically difficult echocardiographic studies with suboptimal images remain a significant challenge in clinical practice despite advances in imaging technologies over the past decades. Use of microbubble ultrasound contrast for left ventricular opacification and enhancement of endocardial border detection during rest or stress echocardiography has become an essential component of the operation of the modern echocardiography laboratory. Contrast echocardiography has been demonstrated to improve diagnostic accuracy and confidence across a range of indications including quantitative assessment of left ventricular systolic function, wall motion analysis, and left ventricular structural abnormalities. Enhancement of Doppler signals and myocardial contrast echocardiography for perfusion remain off-label uses. Implementation of a contrast protocol is feasible for most laboratories and both physicians and sonographers will require training in contrast specific imaging techniques for optimal use. Previous concerns regarding the safety of contrast agents have since been addressed by more recent data supporting its excellent safety profile and overall cost-effectiveness.

Reproducibility of echocardiographic techniques for sequential assessment of left ventricular ejection fraction and volumes: application to patients undergoing cancer chemotherapy

OBJECTIVES

The aim of this study was to identify the best echocardiographic method for sequential quantification of left ventricular (LV) ejection fraction (EF) and volumes in patients undergoing cancer chemotherapy.

BACKGROUND

Decisions regarding cancer therapy are based on temporal changes of EF. However the method for EF measurement with the lowest temporal variability is unknown.

METHODS

We selected patients in whom stable function in the face of chemotherapy for breast cancer was defined by stability of global longitudinal strain (GLS) at up to 5 time points (baseline, 3, 6, 9, and 12 months). In this way, changes in EF were considered to reflect temporal variability of measurements rather than cardiotoxicity. A comprehensive echocardiogram consisting of 2-dimensional (2D) and 3-dimensional (3D) acquisitions with and without contrast administration was performed at each time point. Stable LV function was defined as normal GLS (≤-16.0%) at each examination. The EF and volumes were measured with 2D-biplane Simpson's method, 2D-triplane, and 3-dimensional echocardiography (3DE) by 2 investigators blinded to any clinical data. Inter-, intra-, and test-retest variability were assessed in a subgroup. Variability was assessed by analysis of variance and compared with Levene's or t test.

RESULTS

Among 56 patients (all female, 54 ± 13 years of age), noncontrast 3D EF, end-diastolic volume, and end-systolic volume had significantly lower temporal variability than all other methods. Contrast only decreased the temporal variability of LV end-diastolic volume measurements by the 2D biplane method. Our data suggest that a temporal variability in EF of 0.06 might occur with noncontrast 3DE due to physiological differences and measurement variability, whereas this might be >0.10 with 2D methods. Overall, 3DE also had the best intra- and inter-observer as well as test-retest variability.

CONCLUSIONS

Noncontrast 3DE was the most reproducible technique for LVEF and LV volume measurements over 1 year of follow-up.

Novel techniques for assessment of left ventricular systolic function

The evaluation of left ventricular systolic function is one of the most common reasons for referral for a non-invasive cardiac imaging study. In addition to its diagnostic and prognostic value, an assessment of ejection fraction can also be used to guide medical and device therapy. Thus, obtaining an accurate and reproducible assessment of LVEF is essential for patient management. This review will focus on novel multi-modality techniques used for the quantification of left ventricular systolic function. Emerging echocardiography techniques such as three-dimensional echocardiography and strain imaging and their incremental role over traditional 2D imaging will be discussed. In addition, new developments expanding nuclear imaging techniques' evaluation of left ventricular systolic function will be reviewed. Finally, an overview of advances in imaging techniques such as cardiac magnetic resonance and cardiac computed tomography, which now allow for an accurate and highly reproducible assessment of LVEF, will be presented.

Cardiac toxicity screening by echocardiography in healthy volunteers: a study of the effects of diurnal variation and use of a core laboratory on the reproducibility of left ventricular function measurement

BACKGROUND

In investigational medicinal products testing centers (IMP), reliable methods for monitoring early signs of cardiotoxicity of a potential new drug in healthy volunteers are essential. This study examines what levels of left ventricular ejection fraction (LVEF) variance can be achieved with two-dimensional echocardiography (2DE) in a core laboratory versus a site laboratory. Diurnal variability of LVEF and diastolic parameters were also reviewed.

METHODS AND RESULTS

64 healthy males, (age range 18-40 years), with optimal echo windows were recruited. Two-dimensional and tissue Doppler (TDI) echocardiography was performed by one dedicated sonographer using an Acuson Sequoia C256 machine. Heart rate and blood pressure were recorded simultaneously. Echocardiograms were performed at set time points (0, 1, 4, and 20 hours) on all subjects. The images were analyzed independently by one on-site, unblinded, sonographer reader (site lab) and one experienced off-site blinded physician over reader (core lab). The core lab showed significantly less variance in LVEF measurements than the site lab (5.5% vs. 19.9%). There was no significant diurnal variation in mean blood pressure, LVEF or E:A ratio measurements over 20 hours.

CONCLUSIONS

The core lab had better reproducibility and significantly less variance in LVEF measurements by 2DE than the site lab. There was no diurnal variation in LV function measurement.

Comparison of contrast enhanced three dimensional echocardiography with MIBI gated SPECT for the evaluation of left ventricular function

Background

In clinical practice and in clinical trials, echocardiography and scintigraphy are used the most for the evaluation of global left ejection fraction (LVEF) and left ventricular (LV) volumes. Actually, poor quality imaging and geometrical assumptions are the main limitations of LVEF measured by echocardiography. Contrast agents and 3D echocardiography are new methods that may alleviate these potential limitations.

Methods

Therefore we sought to examine the accuracy of contrast 3D echocardiography for the evaluation of LV volumes and LVEF relative to MIBI gated SPECT as an independent reference. In 43 patients addressed for chest pain, contrast 3D echocardiography (RT3DE) and MIBI gated SPECT were prospectively performed on the same day. The accuracy and the variability of LV volumes and LVEF measurements were evaluated.

Results

Due to good endocardial delineation, LV volumes and LVEF measurements by contrast RT3DE were feasible in 99% of the patients. The mean LV end-diastolic volume (LVEDV) of the group by scintigraphy was 143 ± 65 mL and was underestimated by triplane contrast RT3DE (128 ± 60 mL; p < 0.001) and less by full-volume contrast RT3DE (132 ± 62 mL; p < 0.001). Limits of agreement with scintigraphy were similar for triplane andfull-volume, modalities with the best results for full-volume. Results were similar for calculation of LV end-systolic volume (LVESV). The mean LVEF was 44 ± 16% with scintigraphy and was not significantly different with both triplane contrast RT3DE (45 ± 15%) and full-volume contrast RT3DE (45 ± 15%). There was an excellent correlation between two different observers for LVEDV, LVESV and LVEF measurements and inter observer agreement was also good for both contrast RT3DE techniques.

Conclusion

Contrast RT3DE allows an accurate assessment of LVEF compared to the LVEF measured by SPECT, and shows low variability between observers. Although RT3DE triplane provides accurate evaluation of left ventricular function, RT3DE full-volume is superior to triplane modality in patients with suspected coronary artery disease.

American Society of Echocardiography Consensus Statement on the Clinical Applications of Ultrasonic Contrast Agents in Echocardiography

ACCREDITATION STATEMENT: The American Society of Echocardiography (ASE) is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. The ASE designates this educational activity for a maximum of 1 AMA PRA Category 1 Credit.trade mark Physicians should only claim credit commensurate with the extent of their participation in the activity. The American Registry of Diagnostic Medical Sonographers and Cardiovascular Credentialing International recognize the ASE's certificates and have agreed to honor the credit hours toward their registry requirements for sonographers. The ASE is committed to resolving all conflict-of-interest issues, and its mandate is to retain only those speakers with financial interests that can be reconciled with the goals and educational integrity of the educational program. Disclosure of faculty and commercial support sponsor relationships, if any, have been indicated.

TARGET AUDIENCE

This activity is designed for all cardiovascular physicians, cardiac sonographers, and nurses with a primary interest and knowledge base in the field of echocardiography; in addition, residents, researchers, clinicians, sonographers, and other medical professionals having a specific interest in contrast echocardiography may be included.

OBJECTIVES

Upon completing this activity, participants will be able to: 1. Demonstrate an increased knowledge of the applications for contrast echocardiography and their impact on cardiac diagnosis. 2. Differentiate the available ultrasound contrast agents and ultrasound equipment imaging features to optimize their use. 3. Recognize the indications, benefits, and safety of ultrasound contrast agents, acknowledging the recent labeling changes by the US Food and Drug Administration (FDA) regarding contrast agent use and safety information. 4. Identify specific patient populations that represent potential candidates for the use of contrast agents, to enable cost-effective clinical diagnosis. 5. Incorporate effective teamwork strategies for the implementation of contrast agents in the echocardiography laboratory and establish guidelines for contrast use. 6. Use contrast enhancement for endocardial border delineation and left ventricular opacification in rest and stress echocardiography and unique patient care environments in which echocardiographic image acquisition is frequently challenging, including intensive care units (ICUs) and emergency departments. 7. Effectively use contrast echocardiography for the diagnosis of intracardiac and extracardiac abnormalities, including the identification of complications of acute myocardial infarction. 8. Assess the common pitfalls in contrast imaging and use stepwise, guideline-based contrast equipment setup and contrast agent administration techniques to optimize image acquisition.

Contrast echocardiography: evidence for clinical use

The failure of echocardiography to give diagnostically useful information in a significant proportion of patients has led to the development of specific contrast agents to enhance imaging. Suitable contrast media must have the ability to modify ultrasound characteristics, be capable of crossing the pulmonary capillary bed, show stability over the duration of a procedure, offer low blood solubility with low toxicity and be rapidly eliminated. The current generation of ultrasound contrast agents comprises microbubbles of a high molecular-weight gas encapsulated in a shell of phospholipid or protein. A review of the clinical evidence shows that these agents are clinically effective in enhancing echocardiographic imaging. They enable the rescue of failed procedures, often sparing patients from invasive tests, but appear not to add to the burden of side effects. Indeed, the benefits of using contrast agents in stress echocardiography have been recommended in recently published American Society of Echocardiography guidelines. Myocardial contrast echocardiography has now developed to the stage where assessment of myocardial perfusion for the detection of coronary artery disease is possible with the same diagnostic accuracy as radionuclide imaging. However, in comparison with the latter technique, it is less expensive, is more portable, and avoids the use of ionizing radiation. It is precisely the ability of myocardial contrast echocardiography to simultaneously assess function and perfusion at the bedside that has given it a unique role in clinical practice. This review provides an overview of the clinical evidence supporting the efficacy of contrast echocardiography in the assessment of myocardial structure, function, and perfusion.

Three-dimensional echocardiographic analysis of left ventricular function during hemodialysis

BACKGROUND

The effects of hemodialysis (HD) on left ventricular (LV) function have been studied by various echocardiographic techniques (M-mode, 2D echocardiography). These studies are hampered by a low accuracy of measurements because of geometric assumptions regarding LV shape. Three-dimensional echocardiography (3DE) overcomes this limitation.

METHODS

We tested the feasibility of 3DE assessment of LV function during HD. Conventional biplane Simpson rule (BSR) and single plane area length method (SPM) for LV function analysis were used as a reference.

RESULTS

12 HD patients were studied and in 10 (83%) a total of 80 3D datasets were acquired. In 3 patients, one dataset (4%) was of insufficient quality and excluded from analysis. Correlation between SPM, BSR and 3DE for calculation of end-diastolic (EDV, r = 0.89 and r = 0.92, respectively), end-systolic volume (ESV, r = 0.92 and r = 0.93, respectively) and for ejection fraction (EF, r = 0.90 and r = 0.88, respectively) was moderate. Limits-of-agreement results for EDV and ESV were poor with confidence intervals larger than 30 ml. Both 2DE methods underestimated end-diastolic and end-systolic volume, while overestimating ejection fraction.

CONCLUSION

3DE is feasible for image acquisition during HD, which opens the possibility for accurate and reproducible measurement of LV function during HD. This may improve the assessment of the acute effect of HD on LV performance, and guide therapeutic strategies aimed at preventing intradialytic hypotension.

Echocardiography in Heart Failure

Echocardiography is well qualified to meet the growing need for noninvasive imaging in the expanding heart failure (HF) population. The recently-released American College of Cardiology/American Heart Association guidelines for the diagnosis and management of HF labeled echocardiography "the single most useful diagnostic test in the evaluation of patients with HF...," because of its ability to accurately and noninvasively provide measures of ventricular function and assess causes of structural heart disease. It can also detect and define the hemodynamic and morphologic changes in HF over time and might be equivalent to invasive measures in guiding therapy. In this article we will discuss: 1) the clinical uses of echocardiography in HF and their prognostic value; 2) the use of echocardiography to guide treatment in HF patients; and 3) promising future techniques for echocardiographic-based imaging in HF. In addition, we will highlight some of the limitations of echocardiography.

Contrast echocardiography in Canada: Canadian Cardiovascular Society/Canadian Society of Echocardiography position paper

As an adjunct to transthoracic, transesophageal and stress echocardiography, contrast echocardiography (CE) improves the diagnostic accuracy of technically suboptimal studies when used in conjunction with harmonic imaging. Intravenous ultrasound contrast agents are indicated for left ventricular (LV) opacification and improvement of LV endocardial border delineation in patients with suboptimal acoustic windows. Demonstrated benefits of CE include improvement in the accuracy of LV measurements, regional wall motion assessment, evaluation of noncompaction cardiomyopathy, thrombus detection, Doppler signal enhancement and conjunctive use with stress echocardiography. Studies have shown the value of CE in the assessment and quantification of myocardial perfusion, and recent clinical trials have suggested a role for contrast perfusion imaging in the stratification of patients with suspected coronary artery disease. While it adds some time and cost to the echocardiographic study, CE frequently obviates the need for additional specialized, expensive and less accessible cardiac investigations, and allows for prompt and optimal subsequent patient management. Despite its proven advantages, CE is presently underused in Canada, and this situation will, unfortunately, not improve until several barriers to its use are overcome. Resolving these important hurdles is vital to the future of CE and to its eventual implementation into clinical practice of promising contrast-based diagnostic and therapeutic applications, including the assessment of perfusion by myocardial CE.

The assessment of left ventricular hypertrophy in hypertension

The presence of left ventricular hypertrophy (LVH) in hypertension, as detected by the electrocardiogram or echocardiography, is associated with an increased risk of mortality and morbidity several times above and beyond the risk of hypertension alone. The LIFE (Losartan Intervention For Endpoint reduction in hypertension) study confirmed that pharmacological agents, which reduce LVH, confer further reduction in morbidity and mortality. This makes the identification of patients with LVH all the more important. In this article we describe the various methods available to diagnose the presence of LVH in patients with hypertension, and consider their strengths and their place in clinical practice and in research.

Improved assessment of left ventricular volumes and ejection fraction by contrast enhanced harmonic color Doppler echocardiography

AIMS

Test the accuracy of contrast enhanced harmonic color Doppler technique (CHCD) to determine left ventricular volumes and ejection fraction (LVEF) compared to equilibrium radionuclide ventriculography (MUGA).

METHODS AND RESULTS

A total of 35 patients were enrolled (male 74.3%) with the mean age of 64.5 +/- 10 years and 6.8 +/- 4.9 days between echo and MUGA scans. The correlation of LVEF by CHCD with MUGA was better (R2 = 0.89) than that of harmonic 2D (H2D) and of contrast enhanced harmonic 2D (CH2D) (R2 = 0.74, R2 = 0.82, respectively). The RMS residual of CHCD (0.056) was smaller than that of H2D and CH2D (0.079, 0.067, respectively). The LVED and LVES volumes by H2D, CH2D and CHCD correlate well with MUGA but there was a significant over estimation of LVED and LVES volumes by H2D and CH2D as compared to MUGA. Also, the RMS residuals were the lowest for the CHCD method. The CHCD had the highest mean inter-observer agreement (90.9%) for LVEF compared with H2D and CH2D (78.9% and 88.1%, respectively).

CONCLUSIONS

CHCD has been feasible in all patients in the present study and it has shown a good concordance with ejection fraction and volumes provided by MUGA.

Contrast Echocardiography Improves the Diagnostic Yield of Transthoracic Studies Performed in the Intensive Care Setting by Novice Sonographers

BACKGROUND

Bedside portable echocardiography in the intensive care department (ICU) is technically difficult, but crucial for directing patient care. Prior studies have shown contrast echocardiography (CE) in the ICU clarifies left ventricular wall motion when performed by experienced sonographers (ESO). However, in most hospitals, ESO are unavailable around the clock, and less experienced cardiovascular fellows or trainees may be asked to perform these examinations.

METHODS

Transthoracic echocardiograms were retrospectively evaluated by level III trained echocardiographers for 213 patients in the ICU. Most were performed to assess left ventricular function (65% or 139 of 213) and were scanned by cardiology fellows (70% or 149 of 213) with less than 3 months echocardiography experience. Contrast agent was used in 29% (62 of 213) of all patients.

RESULTS

The conversion of suboptimal or diagnostically inadequate apical 4- and 2-chamber views to diagnostically adequate with contrast was statistically significant when performed by both cardiology fellows and ESO (Fischer exact test, P < .0002).

CONCLUSIONS

CE is effective in improving the diagnostic yield of transthoracic echocardiographic ICU studies performed by both novice sonographers and ESO. Using cardiology fellows to perform CE in this setting can be appropriate, particularly in after-hour situations, when ESO are not always available and the clinical question is left ventricular function. Results also suggest cardiology fellows can easily learn CE.

Assessment of systolic left ventricular function: a multi-centre comparison of cineventriculography, cardiac magnetic resonance imaging, unenhanced and contrast-enhanced echocardiography

AIMS

To assess the agreement of left ventricular ejection fraction (LVEF) determinations from unenhanced echocardiography, contrast-enhanced echocardiography, magnetic resonance imaging (MRI), and cineventriculography as well as the inter-observer agreement for each method.

METHODS AND RESULTS

In 120 patients, with evenly distributed EF-groups (> 55, 35-55, < 35%), cineventriculography, unenhanced echocardiography with second harmonic imaging, and contrast echocardiography at low mechanical index with iv administration of SonoVue were performed. In addition, cardiac MRI at 1.5 T using a steady-state free precession sequence was performed in a subset of 55 patients. On-site, and two blinded off-site assessments were performed for unenhanced and contrast echocardiography, cineventriculography, and MRI according to pre-defined standards. Intra-class correlation coefficients (ICCs) were determined to assess inter-observer reliability between all three readers (i.e. one on-site and two off-site). EF was 56.2 +/- 18.3% by cineventriculography, 54.1 +/- 12.9% by MRI, 50.9 +/- 15.3% by unenhanced echocardiography, and 54.6 +/- 16.8% by contrast echocardiography. Correlation on EF between cineventriculography and echocardiography increased from 0.72 with unenhanced echocardiography to 0.83 with contrast echocardiography (P < 0.05). Similarly, correlation on EF between MRI and echocardiography increased from 0.60 with unenhanced echocardiography to 0.77 with contrast echocardiography (P < 0.05). The inter-observer reliability ICC was 0.91 (95% CI 0.88-0.94) in contrast echocardiography, followed by cardiac MRI (0.86; 95% CI 0.80-0.92), cineventriculography (0.80; 95% CI 0.74-0.85), and unenhanced echocardiography (0.79; 95% CI 0.74-0.85).

CONCLUSIONS

Unenhanced echocardiography resulted in slight underestimation of EF and only moderate correlation compared with cineventriculography and MRI. Contrast echocardiography resulted in more accurate EF and significantly improved correlation with cineventriculography and MRI. Contrast echocardiography significantly improved inter-observer agreement on EF compared with unenhanced echocardiography. Inter-observer reliability on EF using contrast echocardiography reaches a level comparable to MRI and is better than those obtained by cineventriculography.

Effect of tissue harmonic imaging and contrast upon between observer and test-retest reproducibility of left ventricular ejection fraction measurement in patients with heart failure

AIMS

To investigate the effects of tissue harmonic imaging (THI) and contrast chamber opacification (LVO) upon measurement variability and reproducibility of echocardiographic left ventricular (LV) volume and ejection fraction (EF) measurements in patients with heart failure (HF).

BACKGROUND

Echocardiography is often used in HF patients to determine LV volumes and EF. However, current echo methods are variable and may not be applicable for repeat testing in individual patients. THI and LVO have both been shown to improve endocardial visualisation, but it remains to be determined whether this results in better measurement reproducibility.

METHODS

Thirty-one HF patients and 30 control subjects underwent echocardiography on two separate days. LV volumes were measured under four different imaging conditions: fundamental, THI, LVO and LVO with ECG-triggered Power Doppler. Chamber opacification, pulmonary transit time (PTT), endocardial enhancement, reproducibility and bias were assessed.

RESULTS

Chamber opacification was inferior and the PTT longer in the HF patients. PTT was related to LV volumes, EF, jugular venous pressure and mitral filling pattern. THI improved endocardial visualisation, and although LVO improved endocardial visualisation in the controls, it offered no benefit over THI in the HF patients. LV volumes and EF were different for each method and THI was the least variable method for repeat measurements.

CONCLUSIONS

THI improved endocardial visualisation and was the least variable of the techniques. LVO offered no further advantage in patients with HF and thus cannot be routinely advocated and since LV volumes and EF were different for each, these methods are neither comparable nor interchangeable for follow-up assessments.

MR imaging assessment of cardiac function

Magnetic resonance (MR) imaging is an accurate and reproducible technique for assessment of ventricular function. Although echocardiography is the mainstay for evaluation of cardiac function, dobutamine stress MR imaging has been shown to be as safe as echocardiography for patients with coronary artery disease and more accurate in patients with suboptimal echocardiographic image quality. This article reviews MR imaging techniques, methods of pharmacologic stress, and clinical applications for assessment of cardiac function, primarily left ventricular function.

Contrast Echocardiography: Clinical Utility for the Evaluation of Left Ventricular Systolic Function

Despite continued improvements in imaging technology, transthoracic echocardiography does not reliably provide images adequate for interpretation in all patients. In these patients, the administration of ultrasound contrast agents can markedly enhance the diagnostic utility of the test. Contrast echocardiography relies on the ultrasound detection of contrast agents composed of encapsulated microbubbles that are generally smaller than red blood cells. Intravenous administration of microbubble contrast agents results in left ventricular opacification and facilitates delineation of the endocardial border. This procedure has been shown to consistently increase the number of myocardial segments that can be interpreted, to improve accuracy of assessing regional and global left ventricular function, to decrease interinterpreter variability, to increase interpreter confidence, and to be a cost-effective strategy. Accordingly, patient selection for contrast echocardiography should be based not only on adequacy of the baseline images, but also on the clinical question being asked.

Evaluation of outcome and cost-effectiveness using an FDG PET-guided approach to management of patients with coronary disease and severe left ventricular dysfunction (PARR-2): rationale, design, and methods

Patients with severe ventricular dysfunction and coronary disease have high morbidity and mortality. They may benefit from revascularization but have significant perioperative morbidity and mortality. Positron emission tomography (PET) imaging with F-18-fluorodeoxyglucose (FDG) can detect viable myocardium that may recover from revascularization in such patients. It is unclear whether use of FDG PET in this population improves outcome or is cost-effective. The principal aim of this study is to determine whether FDG PET-guided therapy improves clinical outcome compared to standard care. Secondary objectives are to determine whether FDG PET-guided therapy improves left ventricular (LV) function, improves quality of life, and provides a cost benefit versus standard care. Included in this multicenter randomized controlled trial are patients with coronary artery disease and severe LV dysfunction who are referred for revascularization, heart failure, or cardiac transplantation or in whom FDG PET is potentially useful. Consenting subjects will be randomized to therapy directed by FDG PET or standard care. The primary outcome is the composite cardiovascular endpoint of cardiac death, myocardial infarction, transplantation, or rehospitalization for unstable angina or heart failure. Secondary outcomes include health-related quality of life, costs, mortality, cardiovascular events, and LV function. Assuming two-sided alpha=0.05, power=80%, a sample size of 206 patients per group is required to detect a 15% absolute difference in the primary outcome between PET-directed therapy compared to standard care. Analyses will be conducted on an intention-to-treat basis. To our knowledge, this is the first large trial to evaluate whether FDG PET-directed therapy is effective and provides a cost benefit in patients with severe LV dysfunction. If so, thousands of such patients can be risk-stratified to select who is likely to benefit from revascularization.

Comparison of Echocardiography Using Tissue Harmonics and Contrast Harmonics with Radionuclide Angiography for the Assessment of Left Ventricular Function

Background

Left ventricular ejection fraction (LVEF) is a significant predictor of morbidity and mortality; however, the optimal noninvasive modality for the quantitative determination of LVEF is not apparent.

Hypothesis

We verified the hypothesis that the various echocardiographic methods of assessing LVEF using the Method of Discs with contrast (Optison human albumin microspheres; Amersham Health, Princeton, NJ) and visual assessment of LVEF using tissue harmonics and contrast harmonics compare favorably with radionuclide angiography (RNA).

Methods

In a prospective analysis, 24 consecutive patients scheduled to undergo RNA had an echocardiogram using tissue harmonics and contrast harmonics on the same day. LVEF was assessed by RNA by an experienced, blinded reader using manual determination of the region of interest. LVEF was calculated using the Method of Discs (Simpson's Rule) by a blinded sonographer. LVEF was visually estimated by two blinded readers using echocardiography with tissue harmonics and contrast harmonics on separate occasions.

Results

By linear regression analysis, LVEF determination by echocardiography with contrast using the Method of Discs correlated well with RNA (r = .835, p < .0005). Using Bland-Altman analysis, the second echocardiogram reader had excellent agreement with RNA, whereas the first reader had a mean difference of 5.25% (CI 1.3–9.2; p = .012) with visual assessment using tissue harmonics and a mean difference of 4.67% (CI 0.4–8.8; p = .031) with visual assessment using contrast harmonics compared with RNA. Thus, a small difference in agreement between RNA and echocardiographic visual estimation was noted that appeared to be primarily reader dependent.

Conclusions

LVEF determination with echocardiography with contrast using the Method of Discs correlated well with RNA and provided agreement across a range of cardiac functions. Visual echocardiographic assessment of LVEF with both tissue harmonics and contrast harmonics correlated well with RNA, but contrast harmonics did not appear to offer an advantage over tissue harmonics alone.