A primer on the methods and applications for contrast echocardiography in clinical imaging

Advanced Echocardiography Techniques: The Future Stethoscope of Systemic Diseases

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

Point-of-care echocardiography for the evaluation of right-to-left cardiopulmonary shunts: a narrative review

Right-to-left pulmonary and cardiac shunts (RLS) are important causes of refractory hypoxia in the critically-ill perioperative patient. Using a point-of-care ultrasound (POCUS) agitated saline bubble study for an early diagnosis allows patients with clinically significant RLSs to receive expedited therapy. This narrative review discusses the principles of agitated saline ultrasonography as well as the role of POCUS in detecting the most common RLS types seen in the intensive care unit, including patent foramen ovale, atrial septal defects, and pulmonary arterio-venous malformations. An illustrated discussion of the procedure, as well as shunt-enhancing maneuvers (Valsalva or lung recruitment maneuver with subsequent rapid release) is provided. With the wide dissemination of bedside ultrasound within the perioperative and critical care arena, POCUS practitioners should be knowledgeable of the potential pitfalls leading to both false-positive and false-negative studies. False-positive studies may be due to congenital abnormalities, mischaracterization of intrapulmonary shunts as intracardiac shunts (and vice versa), or evidence of the Valsalva effect. False negatives are typically due to respiratory-phasic variation, performing an inadequate shunt-enhancing maneuver, inadequate injection of agitated saline, or pathophysiologic states of elevated left atrial pressure. Finally, alternative POCUS methods for determining presence of an RLS in patients with poor echocardiographic windows are discussed, with a focus on pulsed-wave Doppler interrogation of arterial signals.

High-Frequency Multipulse, Plane-Wave Acoustic Contrast Imaging

Multipulse (MP) ultrasound contrast agent (UCA) imaging is a method to increase the contrast-to-background (CBR) ratio in regions of blood flow. Plane-wave imaging allows high frame rates, and with high-frequency ultrasound, fine-spatial and temporal resolution. MP and plane-wave imaging have not been applied to high-frequency ultrasound. Here, an 18-MHz linear array was employed to implement the MP methods of pulse inversion (PI) and amplitude modulation (AM) using high-speed, multiangle, compound plane-wave imaging. A flow of the UCA DEFINITY^© at a dilution ratio of 2000:1 circulating through a 2-mm-diameter flow channel in a tissue-mimicking phantom was used to characterize CBR and compared with cases of standard, multiangle compound plane-wave imaging. The relative improvement of PI and AM versus standard plane-wave imaging ranged from 5 to 10 dB. The CBR was observed to be stable over a 60-min time duration for a 2000:1 dilution ratio and a 2000:1 dilution ratio provided an optimal CBR.

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This literature review in devoted to the potential of application of contrast-enhanced echocardiography (CEE) for assessment of structure and function of left cardiac chambers. It contains based on current recommendations discussion of main indications for CEE and analysis of its possibilities in evaluation of perfusion of the left ventricular myocardium, detection of myocardial ischemia, and assessment of myocardial viability. Data on CEE safety and possible side effects associated with the use of ultrasound contrasts are also presented.

Added value of contrast echocardiography in characterization of nonischemic cardiomyopathy

Nonischemic cardiomyopathy (NICM) is a group of noncoronary heterogonous myocardial diseases. The heterogonous nature of NICM has impeded its diagnosis. In the present case series, we demonstrate the added value of using contrast echocardiography in the characterization of NICM. Two patients of advanced age were admitted for possible acute coronary syndrome, which was subsequently excluded by coronary angiography. Conventional and contrast echocardiography revealed characteristic structural and dynamic features of the left ventricle that were compatible with two distinct NICM diseases: stress-induced cardiomyopathy and noncompaction of the ventricular myocardium. Contrast echocardiography characterizes the cardiac structure and allows for real-time assessment of myocardial motion and perfusion. It may help to distinguish diseases with different etiologies.

Physiological Consequences of Coronary Arteriolar Dysfunction and Its Influence on Cardiovascular Disease

To date, the major focus of diagnostic modalities and interventions to treat coronary artery disease has been the large epicardial vessels. Despite substantial data showing that microcirculatory dysfunction is a strong predictor of future adverse cardiovascular events, very little research has gone into developing techniques for in vivo diagnosis and therapeutic interventions to improve microcirculatory function. In this review, we will discuss the pathophysiology of coronary arteriolar dysfunction, define its prognostic implications, evaluate the diagnostic modalities available, and provide speculation on current and potential therapeutic opportunities.

Contrast echocardiography in daily clinical practice

Ultrasound contrast agents have unique acoustic properties that enable them to enhance the cardiac blood flow and thus are used broadly in modern echocardiography laboratories for salvage of nondiagnostic studies, improving accuracy and reducing variability even in the presence of adequate image quality. Contrast echocardiography is also used as an adjunctive technique when unenhanced echocardiography falls short in the differentiation of cardiac structural abnormalities such as cardiac masses. Ultrasound contrast agents are pure intravascular tracers. Development of innovative ultrasound imaging techniques has led to myocardial perfusion imaging with contrast echocardiography. Although currently an off-label indication, it has been shown that perfusion imaging with contrast echocardiography adds incremental value to stress echocardiography in the detection of coronary artery disease. Moreover, it can be used for assessment of myocardial viability. In this paper we briefly discuss the basics of contrast echocardiography and its use in daily clinical practice.

Perioperative Takotsubo Cardiomyopathy: A Systematic Review of Published Cases

Takotsubo cardiomyopathy (TCM) is a condition that is characterized as a transient ventricular dysfunction in the absence of obstructive coronary artery disease (CAD) and is usually triggered by an acute medical illness or intense physical or emotional stress. Multiple cases of perioperative TCM (pTCM) have been reported from around the world, but a qualitative analysis of these cases has not yet been done. For this systematic review, we searched PubMed for case reports and case series of pTCM published from 1966 to April 2015 with the objective being to evaluate whether differences in demographics, clinical features and outcomes exist between pTCM and nonperioperative (npTCM), as well as to attempt to identify any predictors of the severe form of pTCM, which requires mechanical circulatory support (MCS) devices or leads to death. A total of 93 articles describing 102 cases were retrieved and reviewed. The findings were compared with the analysis of the International Takotsubo Registry by Templin et al and a systematic review of mainly non-perioperative TCM (npTCM) by Gianni et al. Although we were unable to identify definitive risk factors for pTCM, our review suggests that pTCM appears to occur in younger patients and with a lower likelihood of ST segment elevations and T-wave abnormalities than in npTCM. No demographic or clinical factors were identified that were predictive of more severe outcomes. As TCM in general can be a life-threatening event, it would therefore be prudent to consider pTCM within a differential diagnosis in any patient who decompensates in the perioperative period.

Bedside myocardial perfusion assessment with contrast echocardiography

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency medicine 2016. Other selected articles can be found online at http://www.biomedcentral.com/collections/annualupdate2016. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901.