Contrast echocardiography is superior to tissue harmonics for assessment of left ventricular function in mechanically ventilated patients

Myocardial Viability Testing in the Management of Ischemic Heart Failure

Although major advances have occurred lately in medical therapy, ischemic heart failure remains an important cause of death and disability. Viable myocardium represents a cause of reversible ischemic left ventricular dysfunction. Coronary revascularization may improve left ventricular function and prognosis in patients with viable myocardium. Although patients with impaired left ventricular function and multi-vessel coronary artery disease benefit the most from revascularization, they are at high risk of complications related to revascularization procedure. An important element in selecting the patients for myocardial revascularization is the presence of the viable myocardium. Multiple imaging modalities can assess myocardial viability and predict functional improvement after revascularization, with dobutamine stress echocardiography, nuclear imaging tests and magnetic resonance imaging being the most frequently used. However, the role of myocardial viability testing in the management of patients with ischemic heart failure is still controversial due to the failure of randomized controlled trials of revascularization to reveal clear benefits of viability testing. This review summarizes the current knowledge regarding the concept of viable myocardium, depicts the role and tools for viability testing, discusses the research involving this topic and the controversies related to the utility of myocardial viability testing and provides a patient-centered approach for clinical practice.

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. 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.

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.

Safety With Echocardiographic Contrast Agents

In October 2007, the Food and Drug Administration mandated significant revisions to product labeling for the commercially available echocardiographic contrast agents (ECA) Definity and Optison after spontaneous healthcare provider reports of 4 patient deaths and ≈190 severe cardiopulmonary reactions occurring in close temporal relationship to ECA administration. Since then, multiple large ECA safety studies have been published and have included outpatients, hospitalized patients (including the critically ill), patients undergoing stress echocardiography, and patients with pulmonary hypertension. In addition, the Food and Drug Administration has convened 2 Advisory Committee meetings and the product labels for Optison and Definity have been substantially revised with a softening of safety restrictions. In this review, we will address the safety of ECA use in patients with serious cardiopulmonary conditions, patients with intracardiac shunts, and special patient populations including pulmonary hypertension, pediatrics, and pregnancy. In addition, we will discuss the confounding role of pseudocomplication in attribution of adverse events during diagnostic testing, the current status of the ECA Black Box Warning, and recommended safety precautions during ECA administration.

Quantification of perflutren microsphere contrast destruction during transit through an ex vivo extracorporeal membrane oxygenation circuit

BACKGROUND

Echocardiography is a key investigation in the management of patients on extracorporeal membrane oxygenation (ECMO). However, echocardiographic images are often non-diagnostic in this patient population. Contrast-enhanced echocardiography may overcome many of these limitations but contrast microspheres are hydrodynamically labile structures prone to destruction from shear forces and turbulent flow, which may exist within an ECMO circuit. This study sought to evaluate microsphere destruction (utilising signal intensity as a marker of contrast concentration) during transit through an ECMO circuit.

METHODS

Activated Definity® contrast was diluted to 50 ml with normal saline and infused into a crystalloid primed ex vivo ECMO with a Quadrox oxygenator at 150 ml/h. Imaging was performed on pre- and post-pump head/oxygenator sections of the circuit using a Philips iE33 scanner and S5-1 transducer. Five-millimetre regions of interest were placed in the centre of the ultrasound field. Average signal intensity (decibels) was calculated at speeds of 1000, 2000, 3000 and 4000 rpm and then repeated with an infusion rate of 300 ml/h. The oxygenator was then spliced out of the circuit and the measures repeated.

RESULTS

There was a significant reduction in contrast concentration during passage through the ECMO circuit at all speeds (with higher pump head speeds resulting in greater microsphere destruction). In a circuit with an oxygenator, relative decrease in signal intensity was 21.4 versus 5.2 % without an oxygenator. There was significant destruction of contrast microspheres during passage through the ECMO circuit at all pump head speeds. An oxygenator contributed to microsphere destruction at a significantly greater level than the pump head alone. There was no significant difference in mean signal intensity reduction in the circuit between an infusion of 150 or 300 ml/h (3.5 ± 3.2 versus 3.6 ± 2.5 dB, respectively, p = 0.79).

CONCLUSIONS

Flow of contrast through an ECMO circuit results in significant destruction of microspheres. Circuits with an oxygenator result in significantly greater levels of contrast destruction than by the pump head alone. Clinicians should be cognisant of the relationship between ECMO circuit configurations, pump head speed and contrast destruction when performing a contrast-enhanced echocardiogram in patients supported with ECMO.

CRITICAL CARE ECHO ROUNDS: Extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation (ECMO) is an advanced form of organ support indicated in selected cases of severe cardiovascular and respiratory failure. Echocardiography is an invaluable diagnostic and monitoring tool in all aspects of ECMO support. The unique nature of ECMO, and its distinct effects upon cardio-respiratory physiology, requires the echocardiographer to have a sound understanding of the technology and its interaction with the patient. In this article, we introduce the key concepts underpinning commonly used modes of ECMO and discuss the role of echocardiography.

Feasibility of perflutren microsphere contrast transthoracic echocardiography in the visualization of ventricular endocardium during venovenous extracorporeal membrane oxygenation in a validated ovine model

BACKGROUND

Transthoracic echocardiography (TTE) during extra corporeal membrane oxygenation (ECMO) is important but can be technically challenging. Contrast-specific TTE can improve imaging in suboptimal studies. These contrast microspheres are hydrodynamically labile structures. This study assessed the feasibility of contrast echocardiography (CE) during venovenous (VV) ECMO in a validated ovine model.

METHOD

Twenty-four sheep were commenced on VV ECMO. Parasternal long-axis (Plax) and short-axis (Psax) views were obtained pre- and postcontrast while on VV ECMO. Endocardial definition scores (EDS) per segment were graded: 1 = good, 2 = suboptimal 3 = not seen. Endocardial border definition score index (EBDSI) was calculated for each view. Endocardial length (EL) in the Plax view for the left ventricle (LV) and right ventricle (RV) was measured.

RESULTS

Summation EDS data for the LV and RV for unenhanced TTE (UE) versus CE TTE imaging: EDS 1 = 289 versus 346, EDS 2 = 38 versus 10, EDS 3 = 33 versus 4, respectively. Wilcoxon matched-pairs rank-sign tests showed a significant ranking difference (improvement) pre- and postcontrast for the LV (P < 0.0001), RV (P < 0.0001) and combined ventricular data (P < 0.0001). EBDSI for CE TTE was significantly lower than UE TTE for the LV (1.05 ± 0.17 vs. 1.22 ± 0.38, P = 0.0004) and RV (1.06 ± 0.22 vs. 1.42 ± 0.47, P = 0.0.0006) respectively. Visualized EL was significantly longer in CE versus UE for both the LV (58.6 ± 11.0 mm vs. 47.4 ± 11.7 mm, P < 0.0001) and the RV (52.3 ± 8.6 mm vs. 36.0 ± 13.1 mm, P < 0.0001), respectively.

CONCLUSIONS

Despite exposure to destructive hydrodynamic forces, CE is a feasible technique in an ovine ECMO model. CE results in significantly improved EDS and increased EL.

Use of contrast echocardiography in intensive care and at the emergency room

Bedside echocardiography in emergency room (ER) or in intensive care unit (ICU) is an important tool for managing critically ill patients, to obtain a timely accurate diagnosis and to immediately stratify the risk to the patient’s life. It may also render invasive monitoring unnecessary. In these patients, contrast echocardiography may improve quality of imaging and also may provide additional information, especially regarding myocardial perfusion in those with suspected coronary artery disease. This article focuses on the principle of contrast echocardiography and the clinical information that can be obtained according to the most frequent presentations in ER and ICU.

A retrospective comparison of mortality in critically ill hospitalized patients undergoing echocardiography with and without an ultrasound contrast agent

OBJECTIVES

To compare acute mortality in critically ill hospitalized patients undergoing echocardiography with and without an ultrasound contrast agent (UCA).

BACKGROUND

Because of serious cardiopulmonary reactions reported immediately after administration of perflutren-containing UCAs, the FDA required a black box safety warning for this class of agents, including perflutren protein-type A microspheres injectable suspension.

METHODS

This study used the largest hospital service-level database in the U.S. All adult patients undergoing in-patient echocardiography between January 2003 and October 2005 were identified (n = 2,588,722, of which 22,499 received perflutren protein-type A microspheres injectable suspension). Of the 22,499 contrast echocardiography patients, 2,900 had diagnoses meeting criteria for critical illness (heart failure, acute myocardial infarction, arrhythmia, respiratory failure, pulmonary embolism, emphysema, and pulmonary hypertension). To control for the differences between the contrast and noncontrast patients, we used propensity score matching. Variables used in the construction of the propensity score included comorbidities, demographic factors, hospital-specific factors, level of care, and mechanical ventilation status. Patients receiving contrast echocardiography were matched to 4 control patients who received noncontrast echocardiography. Conditional logistic regression was used to estimate mortality effects.

RESULTS

There were 167 deaths in the study among critically ill patients, 38 of 2,900 from the contrast group and 129 of 11,600 from the control group. The contrast agent was not associated with an increase in same-day mortality (odds ratio: 1.18; 95% confidence interval: 0.82 to 1.71; p = 0.37). Before matching, contrast patients showed greater morbidity than noncontrast patients (Deyo-Charlson comorbidity score 2.45 vs. 2.25, p < 0.0001). After propensity score matching, these differences were significantly reduced, showing that both groups were well balanced.

CONCLUSIONS

There is no increase in mortality in critically ill patients undergoing echocardiography with the UCA compared with case-matched control patients.

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.

Acute mortality in hospitalized patients undergoing echocardiography with and without an ultrasound contrast agent (multicenter registry results in 4,300,966 consecutive patients)

We sought to define acute mortality in a large multicenter cohort of hospitalized patients undergoing clinically indicated echocardiography with and without use of an ultrasound contrast agent. Although the United States Food and Drug Administration recently relaxed the issued warnings for perflutren-containing ultrasound contrast agents on May 13, 2008, concerns still exist regarding the safety of these compounds, particularly in critically ill patients. A retrospective analysis was performed using the Premier Perspective Database. Patients undergoing echocardiography during hospitalization were separated into those performed without contrast enhancement and those performed with perflutren lipid microsphere (PLM) injectable suspension contrast agent (Definity, Lantheus Medical Imaging, North Billerica, Massachusetts). Vital status within 1 day of the echocardiogram was available for all patients using hospital billing data. Between January 1, 2002 and October 31, 2007, 4,300,966 patients underwent transthoracic echocardiography at rest during hospitalization (unenhanced studies n = 4,242,712 and contrast-enhanced studies n = 58,254). Multivariate logistic regression analysis was used to compare 24-hour mortality, controlling for case mix and clinical covariates; 1-day mortality rates were 1.08% (n = 45,789 deaths) for patients undergoing noncontrast studies and 1.06% (n = 616 deaths) for patients undergoing contrast-enhanced examinations (p = 0.613). Multivariate logistic regression analysis revealed that, in patients undergoing an echocardiogram, patients receiving PLM injectable suspension contrast agent were 24% less likely to die within 1-day than patients not receiving a contrast agent (adjusted odds ratio = 0.76, 95% confidence interval 0.70 to 0.82). In conclusion, acute crude mortality was not increased in patients receiving PLM injectable suspension contrast agent. Multivariate logistic regression analysis revealed that, compared with patients not receiving a contrast agent, administration of PLM injectable suspension contrast agent during echocardiography was associated with a 24% decreased risk of mortality.

The safety of deFinity and Optison for ultrasound image enhancement: a retrospective analysis of 78,383 administered contrast doses

BACKGROUND

The purpose of this retrospective analysis was to define the incidence of severe adverse events after exposure to ultrasound contrast agents.

METHODS

Data between January 1, 2001, and September 30, 2007, were collected using invited responses to an on-line web-based questionnaire from 1 general and 12 cardiac ultrasound laboratories. During a period of 4.5 +/- 2.4 years, a total of 66,164 doses of Definity (Lantheus Medical Imaging, North Billerica, MA) and 12,219 doses of Optison (GE Healthcare, Buckinghamshire, UK) were administered, reflecting contrast use in 5% of transthoracic and 28% of stress echocardiographic procedures. More than 10,000 doses were given to critically ill patients in intensive care unit settings or to patients with acute chest pain of suspected cardiac origin. The median age of patients who received an ultrasound contrast agent was 60 years, 49% were male, and the mean body mass index was 32 +/- 1.4 g/m(-2).

RESULTS

Severe reactions that were considered "probably" related to an ultrasound contrast agent developed in 8 patients (0.01%), all of whom were outpatients, and 4 (0.006%) of these were consistent with anaphylactoid reactions. There were no deaths reported. All patients recovered with treatment. No serious events were seen in inpatients.

CONCLUSION

This multicenter, retrospective analysis includes the largest number of doses of ultrasound contrast agents ever published and a large number of patients evaluated in a wide variety of settings, including the critically ill. It shows that these agents have a good safety profile in both cardiac and abdominal ultrasound applications. The incidence of severe adverse reactions to ultrasound contrast agents is no greater, and may be lower, than that reported for contrast agents commonly used in other cardiac imaging tests.

Head to head comparison of transesophageal and transthoracic contrast-enhanced echocardiography during dobutamine administration for the detection of coronary artery disease

Dobutamine stress echocardiography (DSE) has been shown to be a very useful non-invasive technique for the detection of coronary artery disease. However, inadequate transthoracic images preclude the use of DSE in a significant proportion of patients. Transesophageal (TEE) or transthoracic contrast echocardiography (CE) can however overcome this limitation. The comparison between the two techniques has never been investigated during a stress test. Therefore, we designed a prospective study to compare DSE-CE and DSE-TEE for the detection of coronary artery disease in patients with poor echo image quality. We studied 42 patients scheduled for quantitative coronary angiography. Prospective DSE-CE and DSE-TEE with maximum one day interval were performed in a random order. Significant coronary artery disease was detected in 30 patients, nine with single vessel disease and 21 with multivessel disease. Sensitivity of DSE was higher with CE than with TEE (90% vs 87%, p=NS). There was no significant difference with respect to specificity in both groups (100% vs 92%, p=NS). The diagnostic accuracy was similar in both groups (93% vs 88%, NS). The kappa value for identical interpretation of a stress echocardiography study was nearly identical with both modalities 0.75 to 0.78. In poorly echogenic patients, DSE-CE is a valuable alternative for the detection of myocardial ischemia in comparison with DSE-TEE. Because DSE-CE is more comfortable than TEE, it should be used in patients with suboptimal transthoracic echocardiograms for the evaluation of coronary artery disease during DSE.

Recent advances in ultrasound technology

Technical improvements have made profound changes in diagnostic ultrasound imaging. Some of these changes, such as encoded pulses and receive focusing, occur in the background and are essentially nonadjustable. Others, including harmonics and compounding, are real-time options and are adjustable by the imager. New technologies that offer great promise for improved characterization of lesions include contrast ultrasound and elastography. This article will attempt to update the small animal imager on the clinical applications of these newer technologies.

Quantitative left ventricular systolic function: From chamber to myocardium

One of the most common indications for obtaining a Doppler echocardiographic study is to ascertain left ventricular (LV) systolic function. There are many ways in which LV function can be determined, but an important assumption that is often overlooked is that every measure that we commonly use is only a surrogate marker of LV function due to the fact that it is impossible to characterize the complex geometric and volumetric function of the ventricle (or myocyte) in a single number. Stated in another way, there is no one perfect measure of LV function. The ejection fraction has emerged as the preeminent method to express LV performance, but although ejection fraction is universally accepted, there are a number of other techniques that can assess LV function and, when taken together, provide a more comprehensive picture both of global and regional LV function. Each of these measures (including ejection fraction) has variable dependence on loading conditions, heart rate, and geometric position that limits its accuracy. Understanding the limitations of each measure will allow the physician to more intelligently understand the true status of the myocardium.

Echocardiographic measurement of ventricular function

PURPOSE OF REVIEW

We review new findings concerning ventricular function in patients in intensive care units with shock or unexplained respiratory distress syndrome analyzed using echocardiography.

RECENT FINDINGS

Bedside echocardiography is not only an imaging technique but should be considered as a hemodynamic method. Left-ventricular systolic function can be assessed in daily clinical practice by measuring shortening fraction, fraction area change and ejection fraction. But these indices are dependent on load conditions. Index of myocardial performance can be also used. Rate of left-ventricular pressure increase may be measured from mitral regurgitation. Other indices such a maximal elastance and preload-adjusted maximal power were developed to evaluate myocardial systolic function but are not still used in clinical practice in patients in intensive care. Cardiac output measurement can be calculated easily from aortic annulus diameter and the velocity time integral of aortic blood flow. To complete the assessment of ventricular function, left-ventricular diastolic function and pressure as well as right ventricular size, septal movement and right pressures should be analyzed.

SUMMARY

Using echocardiography the intensivist can examine both the mechanism and the cause of shock or pulmonary edema. It is time to increase the use of this technique in intensive care units.

Clinical utility of contrast-enhanced echocardiography

Over the past three decades, echocardiography has become a major diagnostic tool in the arsenal of clinical cardiology for real-time imaging of cardiac dynamics. More and more, cardiologists' decisions are based on images created from ultrasound wave reflections. From the time ultrasound imaging technology provided the first insight into a human heart, our diagnostic capabilities have increased exponentially as a result of our growing knowledge and developing technologies. One of the most intriguing developments that brought about a decade-long combination of expectations and disappointments was the introduction of echocardiographic contrast agents. Despite repeated waves of controversy regarding the readiness of this technology for clinical use, it has overcome multiple hurdles and currently provides useful clinical information that helps cardiologists to diagnose heart disease accurately. Since the initial reports on the use of ultrasound contrast media such as agitated saline or renografin, the major advances in the field of contrast echocardiography have included (1) the development of stable perfluorocarbon-filled microbubbles, frequently referred to as second-generation contrast agents; and (2) the development of contrast-targeted nonlinear imaging modes, such as harmonic imaging, pulse inversion, and power modulation, which allow consistent real-time visualization of these agents. These contrast agents in conjunction with the new imaging technology constitute powerful tools that improve our ability to evaluate left ventricular function and myocardial perfusion, and allow differential diagnosis of thrombi and intravascular masses. In this manuscript, we briefly review some of the literature that has provided the scientific basis for the use of echocardiographic contrast agents in the context of these important variables.

Safety and efficacy of intravenous contrast imaging in pediatric echocardiography

This study was performed to determine the safety and efficacy of intravenous contrast echocardiography in children attending a tertiary cardiac center. This was a prospective study to evaluate the use of Optison contrast agent in children with severely limited transthoracic echocardiographic windows. Twenty children (median age, 15 years; range, 9-18) underwent fundamental imaging (FI), harmonic imaging (HI), and HI with intravenous contrast (Optison FS-069). Endocardial border delineation was determined based on a visual qualitative scoring system (0, none: 4, excellent). Endocardial border definition was significantly improved in all patients using contrast echocardiography (FI vs Optison, p < 0.001 for each). Improved border definition was most dramatic in the apical and left ventricular (LV) free wall regions. Left ventricular ejection fraction (LVEF) was measurable in 20 patients (100%) using contrast compared to 11 (55%) with FI or HI (p < 0.05). The echocardiographic diagnosis was correctly delineated in 1 patient with a severely dyskinetic LV segment only with use of intravenous contrast and HI. No patients suffered adverse hemodynamic effects, changes in taste, or flushing episodes. Three patients experienced transient headaches. Intravenous contrast echocardiography offers an additional tool in evaluating children with very poor transthoracic echocardiographic windows. Such a strategy increases diagnostic accuracy and allows accurate LVEF determination. Adverse hemodynamic effects related to intravenous contrast are exceedingly rare.

Contrast Echocardiography Can Save Nondiagnostic Exams in Mechanically Ventilated Patients

Patients in an intensive care unit (ICU) under mechanical ventilation (MV) are very difficult to image by transthoracic echocardiography, diminishing the beneficial information that could be obtained by this noninvasive approach. The objective of this study is to assess whether the addition of a contrast agent to fundamental imaging (FI) can improve or change the initial diagnosis in cardiac postoperative patients under mechanical ventilation by enhancing endocardial border delineation and Doppler flow signal. Thirty mechanically ventilated post-cardiac surgery patients (20 men, mean age 61 +/- 13 years) were evaluated with FI before and after intravenous injection of contrast. Left ventricular endocardial border delineation score index (EBDSI), estimated left ventricular ejection fraction (LVEF), and color and spectral Doppler were analyzed. The use of contrast resulted in a significant increase in the number of well-delineated segments, with a salvage rate of 77% of nondiagnostic studies. EBDSI was 1.62 +/- 0.61, before contrast, increasing to 2.05 +/- 0.53 after it (P < 0.001). There was a change in the LVEF estimation in 5 exams, and a new wall motion abnormality was detected in other 4 exams, after the use of contrast. Moreover, a significant change was observed in the quantification of mitral regurgitation in 5 patients, in the aortic transvalvular peak gradient in 1 patient, and measurement of tricuspid regurgitation peak flow velocity in 8 patients. It is concluded that in cardiac postoperative patients under mechanical ventilation, intravenous injection of a contrast agent using FI resulted in a high salvage rate of studies and changed the initial diagnosis in a significant number of patients.

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.

Salvage of nondiagnostic transthoracic echocardiograms on patients in intensive care units with intravenous ultrasound contrast

Transthoracic echocardiography (TTE) is often technically difficult on patients in intensive care units. Contrast echocardiography can improve left ventricular wall visualization and the assessment of regional and global left ventricular wall motion. Our study undertook to determine what proportion of nondiagnostic TTE studies on patients in intensive care units could be salvaged (i.e., converted to diagnostic studies) with contrast. Ninety-two patients with nondiagnostic TTEs had a repeat study after contrast. Using predefined criteria, 51% of studies were salvaged with contrast. Female gender emerged as the only factor associated with less likelihood of salvaging a study.

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.

Pharmacological prevention of reperfusion injury in acute myocardial infarction. A potential role for adenosine as a therapeutic agent

The concept of reperfusion injury, although first recognized from animal studies, is now recognized as a clinical phenomenon that may result in microvascular damage, no-reflow phenomenon, myocardial stunning, myocardial hibernation and ischemic preconditioning. The final consequence of this event is left ventricular (LV) systolic dysfunction leading to increased morbidity and mortality. The typical clinical case of reperfusion injury occurs in acute myocardial infarction (MI) with ST segment elevation in which an occlusion of a major epicardial coronary artery is followed by recanalization of the artery. This may occur either spontaneously or by means of thrombolysis and/or by primary percutaneous coronary intervention (PCI) with efficient platelet inhibition by aspirin (acetylsalicylic acid), clopidogrel and glycoprotein IIb/IIIa inhibitors. Although the pathophysiology of reperfusion injury is complex, the major role that neutrophils play in this process is well known. Neutrophils generate free radicals, degranulation products, arachidonic acid metabolites and platelet-activating factors that interact with endothelial cells, inducing endothelial injury and neutralization of nitrous oxide vasodilator capacity. Adenosine, through its multi-targeted pharmacological actions, is able to inhibit some of the above-mentioned detrimental effects. The net protective of adenosine in in vivo models of reperfusion injury is the reduction of the infarct size, the improvement of the regional myocardial blood flow and of the regional function of the ischemic area. Additionally, adenosine preserves the post-ischemic coronary flow reserve, coronary blood flow and the post-ischemic regional contractility. In small-scale studies in patients with acute MI, treatment with adenosine has been associated with smaller infarcts, less no-reflow phenomenon and improved LV function. During elective PCI adenosine reduced ST segment shifts, lactate production and ischemic symptoms. During the last years, three relatively large placebo-controlled clinical trials have been conducted: Acute Myocardial Infarction Study of Adenosine Trial (AMISTAD) I and II and Attenuation by Adenosine of Cardiac Complications (ATTACC). In the AMISTAD trials, the final infarct size was reduced and the LV systolic function was improved by adenosine treatment, mainly in patients with anterior MI localization. However, morbidity and mortality were not affected. In the ATTACC study, the LV systolic function was not affected by adenosine, however, trends towards improved survival were observed in patients with anterior MI localization. The possibility of obtaining a Thrombolysis in Myocardial Infarction (TIMI) grade 3 flow in the infarct-related artery in up to 95% of patients with acute MI (increasing the occurrence of reperfusion injury) has turned back the interest towards the protection of myocardial cells from the impending ischemic and reperfusion injury in which adenosine alone or together with other cardio-protective agents may exert important clinical effects.

Is there a role for intravenous transpulmonary contrast imaging in pediatric stress echocardiography?

OBJECTIVE

Intravenous transpulmonary contrast echocardiography plays a significant role in the enhancement of endocardial border delineation during stress echocardiography in the adult population. The current study was conducted to evaluate the feasibility of intravenous transpulmonary contrast in pediatric patients and to compare the quality of endocardial visualization by harmonic 2-dimensional (2D) imaging alone with harmonic 2D echocardiography with contrast imaging.

METHODS

Twenty-two children, age 9.3 +/- 3.9 underwent dobutamine (19 patients) or exercise (3 patients) stress echocardiography. None had intracardiac shunting. Each patient underwent both harmonic 2D imaging alone and harmonic 2D imaging with contrast administration at peak stress. Oxygen saturation, heart rate, and blood pressure were monitored. Endocardial delineation was evaluated by qualitative grading of 22 endomyocardial regional segments in each patient. Contrast images were graded by an echocardiographer who was blinded to the scores previously assigned to harmonic 2D echocardiography images.

RESULTS

There were no changes in saturation, heart rate, or blood pressure during or after contrast administration. Use of contrast significantly improved endocardial visualization in 11 of 22 segments (P <.05), particularly lateral, apical, and anterior left ventricular wall segments.

CONCLUSION

Intravenous intrapulmonary administration is feasible and has no obvious adverse effects in a small pediatric patient group. Contrast echocardiography improves endocardial border delineation over harmonic imaging in pediatric stress echocardiography.

Echocardiographic and magnetic resonance methods for diagnosing hibernating myocardium

Hibernating myocardium refers to regions of impaired left ventricular function at rest due to coronary artery disease that is reversible with revascularization. The accurate identification and assessment of myocardial viability is a critical aspect of the management of the patient with coronary artery disease and left ventricular dysfunction. Several non-invasive methods exist to assist the clinician in distinguishing those patients with significant regions of hibernating myocardium from those who have non-viable scar. This is important not only to identify those patients who would most benefit from percutaneous intervention or surgery, but also to spare the latter group from the morbidity and mortality associated with a revascularization procedure that would provide little benefit. While nuclear medicine imaging is the most widely used means for evaluating myocardial viability, alternative modalities have emerged and have gained increasing acceptance in recent years. This article will review the echocardiographic and magnetic resonance imaging (MRI) methods that are currently available or under investigation to assess myocardial viability. These techniques include rest and stress echocardiography, myocardial contrast echocardiography, stress MRI, contrast-enhanced MRI and magnetic resonance spectroscopy (MRS).

Recent advances in myocardial contrast echocardiography

Myocardial contrast echocardiography (MCE) has undergone many advances in the past several years through remarkable developments in contrast agent and ultrasound equipment technology. Microbubble ultrasound contrast agents can now safely transit the pulmonary circulation to provide opacification of the left ventricular cavity, improved endocardial border definition, and detection of myocardial perfusion. The role of contrast echocardiography in enhancing technically difficult images is now well established in clinical practice, and has proven especially useful in the stress and intensive care unit settings. Major progress has been made in the application of MCE for myocardial perfusion assessment in acute and chronic ischemic heart disease syndromes, and comprises the focus of this review. Advances in novel applications of contrast echocardiography, including targeted delivery of genetic and pharmaceutical materials, have also occurred, but remain in a preclinical phase. In summary, the combination of recent innovations in ultrasound equipment, and microbubble acoustics, allows for exciting exploration of the expanding role of contrast echocardiography in clinical practice.