Contrast echocardiography: review and future directions

Perspectives on high resolution microvascular imaging with contrast ultrasound

Recent developments in contrast enhanced ultrasound have demonstrated a potential to visualize small blood vessels in vivo, unlike anything possible with traditional grayscale ultrasound. This Perspective article introduces microvascular imaging strategies and their underlying technology.

Update on cardiotoxicity of anti-cancer treatments

BACKGROUND AND AIMS

Anti-cancer treatments markedly improved the prognosis of patients, but unfortunately might be hampered by cardiotoxicity. Both symptomatic and asymptomatic clinical forms of heart failure have been reported, which may be reversible or irreversible. The aim of this review is to provide an overview of the antineoplastic agents associated with cardiac toxicity and of the available diagnostic techniques.

METHODS AND METHODS

This narrative review is based on material from MEDLINE and PUBMED up to November 2015. We looked at the terms antineoplastic drugs and cardiac toxicity in combination with echocardiography, troponins, cardiac magnetic resonance, and positron emission tomography.

RESULTS

Anthracyclines, monoclonal antibodies, fluoropyrimidines, taxanes, alkylating agents, vinka alkaloids were reported to induce different clinical manifestations of cardioxicity. Chest radiotherapy is also associated with various forms of cardiac damage, which are indistinguishable from those found in patients with heart disease of other aetiologies and that may even appear several years after administration. Among diagnostic techniques, echocardiography is a noninvasive, cost-effective, and widely available imaging tool. Nuclear imaging and cardiac magnetic resonance may be used but are not so widely available and are more difficult to perform. Finally, some biomarkers, such as troponins, may be used to evaluate cardiac damage, but establishing the optimal timing of troponin assessment remains unclear and defining the cut-off point for positivity is still an important goal.

CONCLUSIONS

Cardiotoxicity of anti-cancer treatments is associated with development of heart failure. Novel diagnostic tools might be relevant to early recognize irreversible forms cardiac diseases.

Cancer and cardiovascular disease: the use of novel echocardiography measures to predict subsequent cardiotoxicity in breast cancer treated with anthracyclines and trastuzumab

As the population of breast cancer survivors grows, it has become evident that chemotherapy has significant cardiotoxic side effects. Echocardiography is a noninvasive, cost-effective, and widely available imaging tool that is well positioned to serve as a primary modality for monitoring chemotherapy-induced cardiotoxicity. Although left ventricular ejection fraction is a standard measurement by which to monitor chemotherapy-induced cardiotoxicity, its predictive value in identifying subsequent cardiotoxicity is limited. More sophisticated echocardiography modalities may offer improved sensitivity and specificity for detecting chemotherapy-induced cardiotoxicity. These include tissue Doppler imaging measures, newer techniques based upon two- and three-dimensional strain and torsion analysis, and three-dimensional measures of cardiac size. While these modalities are not all currently part of clinical practice, a body of data supporting their use is steadily building. More research remains to be performed, and noninvasively detecting cancer therapy-induced cardiac dysfunction at the earliest stages is of increasing interest.

Cardiac complications of chemotherapy: role of imaging

OPINION STATEMENT

New advances in cancer diagnosis and treatment have increased survival rates in patients with cancer. In parallel with this increase in the number of cancer survivors is an increasing prevalence of cardiac complications from cancer treatment. Chemotherapy-induced cardiac dysfunction is a major contributor to adverse morbidity and mortality rates in cancer patients. Evidence suggests that both clinical symptoms and the traditional left ventricular ejection fraction (LVEF) may lack sensitivity as measures of cardiotoxicity. The early identification of subclinical LV dysfunction is becoming increasingly important, as this may allow cancer patients and their physicians to make informed decisions about therapeutic options. The features of echocardiography make it a useful tool in the diagnosis and monitoring of cardiotoxicity. This review will examine the role of cardiac imaging in detecting cardiotoxicity, focusing primarily on the conventional and more recent echocardiographic approaches for assessing subclinical cardiotoxicity.

Assessing the Cardiac Toxicity of Chemotherapeutic Agents: Role of Echocardiography

Advancements in cancer treatment have resulted in sufficient survival length for patients to experience treatment-related cardiac complications. In particular, chemotherapy-induced cardiac dysfunction significantly impacts morbidity and mortality rates in cancer patients. The presence of cardiotoxicity from chemotherapy has been traditionally assessed using clinical symptoms and decreases in left ventricular ejection fraction (LVEF). However, in this indication, LVEF lacks accuracy as a measure of subclinical cardiotoxicity and its prognostic value is controversial. There is an emphasis to identify subclinical and left ventricular dysfunction early, in order to allow cancer patients and their physicians to make informed decisions about therapeutic options. Echocardiography is a readily available noninvasive tool to measure cardiac function and plays a major role in the diagnosis of cardiotoxicity. This review focuses on the role of echocardiography in detecting cardiotoxicity, and will discuss conventional and more recent echocardiographic approaches for assessing subclinical cardiotoxicity.

Molecular and clinical aspects of targeting the VEGF pathway in tumors

Tumor angiogenesis is a complex process resulting from many signals from the tumor microenvironment. From preclinical animal models to clinical trials and practice, targeting tumors with antiangiogenic therapy remains an exciting area of study. Although many scientific advances have been achieved, leading to the development and clinical use of antiangiogenic drugs such as bevacizumab, sorafenib, and sunitinib, these therapies fall short of their anticipated benefits and leave many questions unanswered. Continued research into the complex signaling cascades that promote tumor angiogenesis may yield new targets or improve upon current therapies. In addition, the development of reliable tools to track tumor responses to antiangiogenic therapy will enable a better understanding of current therapeutic efficacy and may elucidate mechanisms to predict patient response to therapy.

Immunological evaluation of the new stable ultrasound contrast agent LK565: a phase one clinical trial

Background

Ultrasound contrast agents (UCAs) allow the enhancement of vascular definition, thereby providing more diagnostic information. LK565 is a new second-generation UCA based on synthetic polymers of aspartic acid which is eliminated from the blood stream via phagocytosis. LK565 forms very stable air-filled microspheres and is capable of repeated passage through the pulmonary capillary bed after peripheral intravenous injection. This characteristic allows examination of the cardiac function or extracardiac vessel abnormalities up to 15 minutes.

Methods

A phase one clinical study was conducted on 15 healthy volunteers to identify the development of an undesirable immune response. Phagocytosis capacity, TNF-α secretion, and MHC class II upregulation of monocytes was monitored, as well as microsphere specific antibody development (IgM, IgG). Furthermore, the kinetics of the activation surface markers CD69, CD25, CD71, and CD11b on leukocytes were analyzed.

Results

Due to LK565-metabolism the administration of the UCA led to saturation of phagocytes which was reversible after 24 hrs. Compared to positive controls neither significant TNF-α elevation, neither MHC class II and activation surface markers upregulation, nor specific antibody development was detectable.

Conclusion

The administration of LK565 provides a comfortable duration of signal enhancement, esp. in echocardiography, without causing a major activation cascade or triggering an adaptive immune response. To minimize the risk of undesirable adverse events such as anaphylactoid reactions, immunological studies should be included in clinical trials for new UCAs. The use of LK565 as another new ultrasound contrast agent should be encouraged as a safe means to provide additional diagnostic information.

Development of a novel method for synthesis of a polymeric ultrasound contrast agent

Medical ultrasound is a highly valuable diagnostic tool, especially when compared with other imaging modalities. It is a noninvasive, real-time, portable, extremely safe method compared with X-ray and inexpensive relative to magnetic resonance imaging. However, ultrasound is limited in its ability to distinguish between diseased and normal tissue. This limitation has led to the development of contrast agents. We have produced novel poly (lactic-co-glycolic) acid air-filled microcapsules that work well as ultrasound contrast agents, giving up to 24 and 25 dB enhancement when insonated in the medical imaging range at 5 and 7.5 MHz, respectively. The capsules were fabricated by modifying a double emulsion method to encapsulate camphor in the oil phase and ammonium carbonate in the aqueous phase, and later sublime the encapsulated material, leaving voids capable of being filled with a gas in their place. The role of the surfactant, poly vinyl alcohol, solution temperature, was studied and found to play an important role in the morphology of the capsules, altering their acoustic response.

Usefulness of intravenous myocardial contrast echoardiography in the early left ventricular remodeling in acute myocardial infarction

The aim of this study was to assess the role of intravenous myocardial contrast echocardiography (IMCE) in the prediction of left ventricular (LV) remodeling in patients with acute myocardial infarction (AMI). Sixty-three patients with AMI, who were successfully treated with acute coronary angioplasty, underwent IMCE and low-dose dobutamine echocardiography during hospital admission. IMCE was graded semiquantitatively on a score of 0 (no visible contrast effect), 0.5 (patchy myocardial contrast enhancement), and 1 (homogenous contrast effect). Patients were considered to have microvascular impairment if <50% of segments within the infarct-related area had score of 1. A mean perfusion score index was calculated for each patient. Patients with a good perfusion at IMCE (IMCE+) showed a lower creatine kinase peak (p = 0.001) and lower creatine kinase-MB (p = 0.01), and a better baseline regional contractile function compared with patients who had negative results at IMCE (IMCE-) (p <0.0001) and a higher amount of myocardial viability at low-dose dobutamine echocardiography (p = 0.03). At follow-up, a higher improvement in regional systolic function (p = 0.0006) was observed in IMCE+ patients, whereas IMCE- patients showed an evident increase in LV end-diastolic volume from baseline to 6-month follow-up (p <0.0001), implying LV remodeling, which has been associated with a higher incidence of adverse cardiac events (p = 0.005). By stepwise multiple regression analysis, microvascular impairment at IMCE was a significant independent predictor of LV remodeling (p <0.0001). Thus, IMCE seems to be an important diagnostic tool, able to predict LV remodeling in patients with AMI.

Use of Inoue balloon dilatation method for treatment of Cor triatriatum stenosis in a child

An 8-year-old girl was referred for evaluation of a heart murmur and progressive dyspnea with exertion. Transthoracic echocardiogram revealed Cor triatriatum with severe stenosis at its orifice. The resting transmembrane CW Doppler velocity was 2.3 m/sec. Cardiac catheterization and hemodynamic assessment were performed and demonstrated a marked increase in pulmonary capillary wedge and pulmonary artery pressures. The stenosis was successfully dilated with an Inoue balloon using a transseptal technique. This is the first description of dilation of a Cor triatriatum using the Inoue technique. Only one previous case report of balloon dilatation for Cor triatriatum sinister has appeared in the English literature using a different technique (double balloon method).

Advances in ultrasound

Ultrasound (US) has undergone dramatic changes since its inception three decades ago; the original cumbersome B-mode gantry system has evolved into a high resolution real-time imaging system. This review describes both recent advances in ultrasound and contrast media and likely future developments. Technological advances in electronics and computing have revolutionized ultrasound practice with ever expanding applications. Developments in transducer materials and array designs have resulted in greater bandwidths with improvements in spatial and contrast resolution. Developments in digital signal processing have produced innovations in beam forming, image display and archiving. Technological advances have resulted in novel imaging modes which exploit the non-linear behaviour of tissue and microbubble contrast agents. Microbubble contrast agents have dramatically extended the clinical and research applications of ultrasound. Not only can Doppler studies be enhanced but also novel non-linear modes allow vessels down to the level of the microcirculation to be imaged. Functional and quantitative studies allow interrogation of a wide spectrum of tissue beds. The advent of tissue-specific agents promises to improve the sensitivity and specificity of ultrasound in the detection and characterization of focal liver lesions to rival that of computed tomography (CT) and magnetic resonance imaging (MRI). Ultrasound has recently moved into therapeutic applications with high intensity focused ultrasound (HIFU) and microbubble assisted delivery of drugs and genes showing great promise.

Is the technically limited echocardiographic study an endangered species? endocardial border definition with native tissue harmonic imaging and Optison contrast: a review of 200 cases

OBJECTIVE

Our goal was to determine whether contrast adds diagnostic value to both fundamental and native tissue harmonic imaging (NTHI) for endocardial border definition.

METHODS

Two hundred consecutive patients who underwent stress echocardiography imaging were studied in either fundamental (n = 52) or NTHI mode (n = 148) with an Acuson Sequoia echocardiographic system. Contrast agent (Optison) was administered (0.5 to 1 mL) for enhancement of endocardial borders. Two- and 4-chamber views were analyzed before and after administration of contrast at peak stress for grading of 5 endocardial border segments. Scores from 0 to 5 were assigned to each study for all the images both before and after contrast (0 = 0 segments completely visualized; 5 = 5 segments completely visualized).

RESULTS

The use of Optison contrast significantly enhanced border definition when imaging was performed in either fundamental or NTHI mode. Addition of contrast resulted in better endocardial border definition in fundamental mode (4.1 + or - 1.0 versus 2.3 + or - 1.3, P <.001). However, in NTHI mode, the presence of contrast resulted in enhanced definition of endocardial border compared with its absence (4.8 + or - 0.5 versus 3.3 + or - 1.1, P <.001). The combination of NTHI and contrast resulted in more visualization of endocardium when compared with the combination of fundamental imaging and contrast (4.8 + or - 0.5 versus 4.1 + or - 1.0, P <.001). In addition, interobserver agreement for border detection increased from 83% in fundamental mode without contrast to 95% with the use of NTHI with Optison (P <.001).

CONCLUSION

As defined in 200 cases, the combination of NTHI with Optison contrast results in nearly complete and consistent endocardial border definition.

Developments in cardiac ultrasound

This article gives an overview of recent developments in cardiac ultrasound for the general hospital physician. It discusses contrast echocardiography, harmonic imaging, three-dimensional echocardiography, Doppler tissue imaging and perfusion imaging and give an outlook on future perspectives.

Clinical impact of second harmonic imaging and left heart contrast in echocardiographic stress testing

Second harmonic imaging and left heart contrast agents are recent echocardiographic advancements that enhance the assessment of wall motion. Because little information exists concerning their clinical impact on echocardiographic stress testing in daily practice, this was determined for 9-month periods before (1997) and after (1998) their introduction. Harmonic imaging was used in all patients after its introduction. A second generation intravenous left heart contrast agent (Optison) was used at the discretion of the sonographer and physician team. Both exercise and dobutamine stress tests were included. At the time of study interpretation, diagnostic confidence was assigned as high, medium, or low. For all patients who underwent coronary angiography < or = 6 months after stress testing, the diagnostic accuracy was determined (true positive plus true negative/total studies). There were 574 studies before and 746 studies after implementation. Optison was used in 28% of the harmonic imaging studies. Study cancellations due to uninterpretable images fell from 6.4% to 1.2% (p <0.001) despite a more obese population completing testing (body mass index: 29 +/- 7 to 31 +/- 8 kg/m2, p = 0.02), whereas high diagnostic confidence increased from 55% to 64% (p <0.001). For the 7% of patients who underwent cardiac catheterization, the diagnostic accuracy remained unchanged (74 vs 73%) although a prior negative stress test was less common (40% to 20% p = 0.04). Thus, these new technologies had a favorable clinical impact.

Bubble contrast echocardiography in detecting pulmonary arteriovenous shunting in children with univentricular heart after cavopulmonary anastomosis

OBJECTIVES

We sought to compare bubble contrast echocardiography and pulmonary angiography in detecting pulmonary arteriovenous malformation (PAVM) in children with cavopulmonary anastomosis (CPA), and to examine anatomic and physiologic variables associated with the development of PAVM.

BACKGROUND

Development of PAVM in patients with CPA may cause profound cyanosis. Pulmonary arteriovenous malformation has been traditionally diagnosed by pulmonary angiography with reported incidence of 20% to 25% in patients with CPA.

METHODS

Fourteen patients (age 1.1 to 12.6 years) with any forms of CPA and normal pulmonary venous drainage formed the study population. All patients underwent cardiac catheterization and pulmonary angiography. Bubble contrast echocardiographic studies were performed with injection of 10 ml of agitated saline solution into branch pulmonary arteries. Transthoracic echocardiograms using an apical view were performed to assess the appearance of bubble contrast in the systemic ventricles. We compared the results of pulmonary angiograms and contrast echocardiograms, and findings of contrast echocardiograms between lungs with hepatic venous blood flow and lungs without hepatic venous blood.

RESULTS

Ten of the 14 patients (71%) had positive contrast echocardiographic studies, compared with three (21%) detected by pulmonary angiograms (p = 0.01). No difference was found in pulmonary artery pressure, transpulmonary gradient or presence of heterotaxy syndrome between patients with positive contrast echocardiographic studies and patients with negative studies. However, patients with positive contrast echocardiograms tended to have lower oxygen saturation (81%) and higher hemoglobin (16.4 g/dl) compared with patients with negative studies (88% and 14.7 g/dl, p = 0.10 and p = 0.18 respectively). Patients with Glenn shunt or unidirectional Fontan had higher incidence of PAVM (10/11) compared with patients with classic or lateral tunnel Fontan (0/3, p = 0.01). All 12 lungs with no perfusion of hepatic venous blood had positive contrast echocardiographic studies. Lungs with no hepatic venous blood flow were more likely to develop PAVM compared with lungs with hepatic venous blood flow (12/12 and 3/16 respectively, p < 0.01).

CONCLUSIONS

Bubble contrast echocardiography is more sensitive in detecting PAVM compared with pulmonary angiography. The prevalence of PAVM in patients with CPA may be much higher than what had been reported previously. Lungs with no hepatic venous blood flow are more likely to develop PAVM than lungs with hepatic venous blood flow.

Balloon valvuloplasty for mitral stenosis

Balloon mitral valvuloplasty (BMV) for mitral stenosis is a procedure that has evolved significantly since its introduction by Inoue et al. in 1984. This article reviews currently used techniques, advantages, and limitations as well as outcomes in comparison with surgical procedures. Included is a review of imaging techniques that facilitate BMV, such as transesophageal echocardiography and the recently developed tri-dimensional transthoracic echocardiography and intracardiac echocardiography. In a separate section, the application of BMV in specific clinical situations, such as in patients with multivalvular disease, during pregnancy, in children, in the presence of thrombi, and in patients with bioprostheses, is discussed.