The role of contrast enhancement in echocardiographic assessment of left ventricular function

High-definition blood flow imaging in the assessment of left ventricular function: Initial experience and comparison with contrast echocardiography

OBJECTIVES

The study aimed to assess the accuracy and reproducibility of the high-definition blood flow imaging (HD-Flow) in evaluation of left ventricular (LV) function by comparison with contrast echocardiography (Contrast).

BACKGROUND

Contrast improves endocardial border visualization and assists in precise assessment of LV function. HD-Flow, a novel ultrasound technique that enhances blood flow discrimination in LV, could possibly be used for improving endocardial border definition without contrast.

METHODS

Eighty patients with technically limited transthoracic echocardiograms had HD-Flow, and contrast performed sequentially. LV endocardial visualization, image acquisition time, wall motion, volumes, ejection fraction (EF), stroke volume (SV), and stroke volume index (SVI) were compared. Inter- and intra-observer agreements were examined in a randomly selected subgroup.

RESULTS

Both HD-Flow and contrast significantly improved the percentage of the well-defined endocardial border segments (71% at baseline vs 94.1% by HD-Flow vs 94.9% by contrast, X²  = 401, P < 0.001). The acquisition time for HD-Flow was significantly less when compared to contrast (2.13 ± 1.18 minutes vs 10.96 ± 3.51 minutes, P < 0.001). LV end-diastolic volume (EDV), end-systolic volume (ESV), EF, SV, and SVI measured by the two methods correlated well (EDVr = 0.97, ESVr = 0.96, EFr = 0.90, SVr = 0.77, SVIr = 0.74, all P < 0.001). In comparison, HD-Flow was neither significantly different in detecting LV wall motion abnormality nor in EF, SV, and SVI measurements, but slightly underestimated LV volumes.

CONCLUSIONS

HD-Flow imaging is feasible and user-friendly in enhancing LV endocardial definition. This technique is useful in both qualitative and quantitative assessment of LV function.

Impact of Contrast Echocardiography on Assessment of Ventricular Function and Clinical Diagnosis in Routine Clinical Echocardiography: Korean Multicenter Study

Background

Fundamental echocardiography has some drawbacks in patients with difficult-to-image echocardiograms. The aim of this study is to evaluate impact of contrast echocardiography (CE) on ventricular function assessment and clinical diagnosis in routine clinical echocardiography.

Methods

Two hundred sixty patients were prospectively enrolled over 3 years in 12 medical centers in Korea. General image quality, the number of distinguishable segments, ability to assess regional wall motion, left ventricular (LV) apex and right ventricle (RV) visualization, LV ejection fraction, changes in diagnostic or treatment plan were documented after echocardiography with and without ultrasound contrast agent.

Results

Poor or uninterpretable general image was 31% before contrast use, and decreased to 2% (p<0.05) after contrast use. The average number of visualized LV segments was 9.53 before contrast use, and increased to 14.46 (p<0.001) after contrast use. The percentage of poor or not seen LV regional wall motion was decreased from 28.4% to 3.5% (p<0.001). The percentage of poor or not seen LV apex and RV was decreased from 49.4% to 2.4% (p<0.001), from 30.5% to 10.5% (p<0.001), respectively. Changes in diagnostic procedure and treatment plan after CE were 30% and 29.6%, respectively.

Conclusion

Compared to fundamental echocardiography, CE impacted LV function assessment and clinical decision making in Korean patients who undergo routine echocardiography.

Assessing left ventricular systolic function in shock: evaluation of echocardiographic parameters in intensive care

Introduction

Assessing left ventricular (LV) systolic function in a rapid and reliable way can be challenging in the critically ill patient. The purpose of this study was to evaluate the feasibility and reliability of, as well as the association between, commonly used LV systolic parameters, by using serial transthoracic echocardiography (TTE).

Methods

Fifty patients with shock and mechanical ventilation were included. TTE examinations were performed daily for a total of 7 days. Methods used to assess LV systolic function were visually estimated, "eyeball" ejection fraction (EBEF), the Simpson single-plane method, mean atrioventricular plane displacement (AVPDm), septal tissue velocity imaging (TDIs), and velocity time integral in the left ventricular outflow tract (VTI).

Results

EBEF, AVPDm, TDIs, VTI, and the Simpson were obtained in 100%, 100%, 99%, 95% and 93%, respectively, of all possible examinations. The correlations between the Simpson and EBEF showed r values for all 7 days ranging from 0.79 to 0.95 (P < 0.01). the Simpson correlations with the other LV parameters showed substantial variation over time, with the poorest results seen for TDIs and AVPDm. The repeatability was best for VTI (interobserver coefficient of variation (CV) 4.8%, and intraobserver CV, 3.1%), and AVPDm (5.3% and 4.4%, respectively), and worst for the Simpson method (8.2% and 10.6%, respectively).

Conclusions

EBEF and AVPDm provided the best, and Simpson, the worst feasibility when assessing LV systolic function in a population of mechanically ventilated, hemodynamically unstable patients. Additionally, the Simpson showed the poorest repeatability. We suggest that EBEF can be used instead of single-plane Simpson when assessing LV ejection fraction in this category of patients. TDIs and AVPDm, as markers of longitudinal function of the LV, are not interchangeable with LV ejection fraction.

The role of non-invasive imaging in patient selection

Cardiac resynchronization therapy (CRT) is an established therapy for patients with advanced heart failure, depressed left ventricular (LV) function and wide QRS complex. A substantial amount of patients do not respond to CRT. Recent studies suggest that assessment of mechanical dyssynchrony may allow identification of potential CRT responders. In addition, presence of scar tissue and venous anatomy may play a role in the selection of candidates. This article summarizes the role of non-invasive cardiac imaging modalities addressing these issues in the selection of CRT candidates.

[Echocardiography in the Intensive Care Unit]

The echocardiography can provide important and relevant information and the critically ill patient presents a challenge for the echocardiographer: from limitations in image acquisition to interpretation in the context of rapid physiological and intervention changes. The most frequent reason for requesting an echocardiogram in the ICU is probably to assess left ventricular function. In any case, information of direct relevance for clinical management can in relationship to abnormalities of structure and function can be obtained and used to estimate pulmonary arterial and venous pressures. It can help to investigate the consequences of myocardial ischemia, valvular dysfunction and pericardial disease and detect changes characteristic of specific conditions (e.g. sepsis, pulmonary thromboembolism), although this must be interpreted in the context of each individual patient. The echocardiography also can be used to monitor the therapeutic interventions. The applications of echocardiography in the critical care setting are reviewed, with special emphasis on the assessment of cardiac physiology.

Use of ultrasound guidance and contrast enhancement: a study of continuous infraclavicular brachial plexus approach

PURPOSE

We describe our experience of combining the use of ultrasound (US) guidance with contrast enhancement and peripheral nerve stimulation for the insertion of infraclavicular brachial plexus catheters.

METHODS

Thirty patients scheduled to have upper limb surgery under regional block were studied. Under US guidance and peripheral nerve stimulation assistance, continuous peripheral nerve block needle and stimulating catheter were placed in the infraclavicular area. Needle and catheter tip location was confirmed with agitated 5% dextrose and seen under colour Doppler with US before injecting local anaesthetic (LA). Patients were evaluated in terms of onset times and efficacy of block. Post-operatively, on block recession a catheter was stimulated and visualization of spread of LA during injection through the catheter was done. Secondary block (subsequent to re-injection of LA) was assessed. Patients were followed-up for a week.

RESULTS

Mean time to onset of block was 19.7 (+/- 4.9) min. There were no incomplete blocks and all components of the plexus were blocked completely. Post-operatively, in 95.7% of patients, the spread of hand-agitated LA via the catheter could be seen by color Doppler with ultrasonography. All patients had excellent post-operative analgesia and high degree of satisfaction. There were no complications.

CONCLUSION

Contrast enhancement with US guidance during infraclavicular brachial plexus block enables direct visualization of needle and catheter tip location. Our early experience suggests that this leads to successful initial and subsequent post-operative block. Further controlled studies are needed to compare this technique with more prevalent and conventional techniques of catheter insertion.

Imaging studies in patients with heart failure: current and evolving technologies

Technological advances continue to expand the clinical role of echocardiography in the intensive care unit, particularly in patients with heart failure. It has many advantages over tomographic techniques such as echo cardiac magnetic resonance imaging and cardiac computed tomography, can provide rapid bedside cardiac assessment, and facilitate emergent decision-making for critically ill patients. Image quality problems in the intensive care setting have largely been overcome by the use of harmonic imaging, contrast opacification, and when indicated, transesophageal echocardiography. Newer techniques promise to advance the scope and prognostic power of echocardiography, and to expand the portability and availability of this tool.

The value of contrast dobutamine stress echocardiography on detecting coronary artery disease in overweight and obese patients

BACKGROUND

Dobutamine stress echocardiography (DSE) is an established method of detecting myocardial ischemia. Its diagnostic accuracy solely depends on wall motion assessment. Clear visibility of the left ventricular endocardium is essential for reliable assessment of a wall motion abnormality. However, incremental benefits of contrast DSE for the detection of coronary artery disease (CAD) have not been demonstrated in overweight or obese patients.

OBJECTIVES

The purpose of the present study was to test the incremental benefits of contrast DSE in detecting CAD in overweight or obese patients.

METHODS

Sixty-two overweight or obese patients (body mass index 26 kg/m(2) to 33 kg/m(2)) underwent DSE with or without contrast and coronary angiography. Contrast-enhanced images were achieved at rest and during peak DSE after administration of SonoVue (Bracco Diagnostics Inc, Italy) or Optison (Mallinckrodt, USA). The endocardial border resolution for each myocardial segment was graded as 0, 1 or 2. A total of 992 segments from 62 subjects were analyzed. The results of DSE with or without contrast were compared with the findings on angiography.

RESULTS

The differences in the score grading between the two groups with or without contrast, at rest and during peak DSE were statistically significant (P<0.001). The sensitivity, specificity and accuracy of contrast DSE in detecting CAD, compared with the studies without contrast, were improved (82% versus 70%, 78% versus 67% and 81% versus 69%, respectively).

CONCLUSIONS

SonoVue and Optison can enhance left ventricular endocardial border delineation in overweight or obese patients, optimizing the evaluation of wall motion both at rest and during peak stress. This increases the diagnostic value of DSE in detecting CAD.

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.

Bedside echocardiography in the assessment of the critically ill

Advances in ultrasound technology continue to enhance its diagnostic applications in daily medical practice. Bedside echocardiographic examination has become useful to properly trained cardiologists, anesthesiologists, intensivists, surgeons, and emergency room physicians. Cardiac ultrasound can permit rapid, accurate, and noninvasive diagnosis of a broad range of acute cardiovascular pathologies. Although transesophageal echocardiography was once the principal diagnostic approach using ultrasound to evaluate intensive care unit patients, advances in ultrasound imaging, including harmonic imaging, digital acquisition, and contrast for endocardial enhancement, has improved the diagnostic yield of transthoracic echocardiography. Ultrasound devices continue to become more portable, and hand-carried devices are now readily available for bedside applications. This article discusses the application of bedside echocardiography in the intensive care unit. The emphasis is on echocardiography and cardiovascular diagnostics, specifically on goal-directed bedside cardiac ultrasonography.

Bedside Ultrasonography in the ICU

This is the second of a two-part review on the application of bedside ultrasonography in the ICU. In this part, the following procedures will be covered: (1) echocardiography and cardiovascular diagnostics (second part); (2) the use of bedside ultrasound to facilitate central-line placement and to aid in the care of patients with pleural effusions and intra-abdominal fluid collections; (3) the role of hand-carried ultrasound in the ICU; and (4) the performance of bedside ultrasound by the intensivist. The safety and utility of bedside ultrasonography performed by adequately trained intensivists has now been well demonstrated. This technology, as a powerful adjunct to the physical examination, will become an indispensable tool in the management of critically ill patients.

Assessment of left ventricular function with contrast echocardiography

Echocardiography continues to be the primary noninvasive imaging modality for the assessment of cardiac structure and function because of significant advances in ultrasound imaging technology over the last two decades, yet quantification of the LV function has remained an elusive goal. The introduction of contrast agents has represented a major advance in clinicians' ability to visualize the endocardium and to assess LV function accurately, particularly in patients who have poor acoustic windows. Ongoing and future refinements in imaging technology used with contrast enhancement have placed automated quantification of LV function on the brink of widespread clinical use.