Novel Utilization of Ultrasound Enhancing Agents in Complex Congenital Heart Disease Following Superior Cavopulmonary Connection

BACKGROUND

Children with single-ventricle congenital heart disease typically undergo a superior cavopulmonary connection (SCPC) as the second stage in their surgical palliation. Postoperatively, stenoses of the SCPC and branch pulmonary arteries can occur. If there are clinical concerns and echocardiography is insufficient for diagnosis, patients undergo invasive evaluation with exposure to radiation and anesthesia. The use of ultrasound enhancing agents (UEAs) to improve echocardiographic diagnostic capabilities has not previously been described in this population.

METHODS

A single-center, retrospective case review was conducted of children who underwent echocardiography with UEA, following SCPC, from March 1, 2020, to April 15, 2022, at the Children's Hospital of Philadelphia. Twenty-two patients with hypoxemia or concern for obstruction following SCPC underwent UEA echocardiography. Extracted clinical data included patient demographics, echocardiographic images, angiography, surgical and transcatheter interventions, as well as available follow-up data.

RESULTS

Six of the 22 UEA echocardiograms demonstrated stenosis or occlusion of either the SCPC or a pulmonary artery. All six patients underwent cardiac catheterization and five required intervention. Angioplasty was performed in each case with one requiring subsequent surgical revision. Sixteen of 22 UEA echocardiograms demonstrated no evidence of stenosis. Ten of these 16 patients improved, while six experienced persistent hypoxemia prompting referral for cardiac catheterization. Angiography confirmed the UEA echocardiographic findings (absence of stenosis) in four of these six patients. There were no adverse reactions related to UEA administration.

CONCLUSIONS

Echocardiography with UEAs is a valuable and safe adjunctive imaging modality following SCPC, particularly when two-dimensional and color imaging is limited. This novel application of UEAs in complex patients with congenital heart disease provides an "angiogram-like" image, better delineating vessel walls and improving assessment of postoperative obstruction. As experience with UEAs increases in the congenital heart disease population, there may be opportunities to decrease invasive and costly procedures, while expediting the care of patients in need of intervention.

Contrast-enhanced ultrasound in pediatric echocardiography

The safety and benefits of cardiac contrast-enhanced ultrasound (CEUS) have been demonstrated in children and adolescents for a variety of clinical indications, including congenital heart disease. Cardiac CEUS is performed with US and the intravenous administration of ultrasound contrast agents (UCAs). It improves transthoracic echocardiography, which can be challenging in children and adults with acoustic window limitations (e.g., from obesity) and alterations in chest wall and cardiac geometry (e.g., from prior surgical procedures). Cardiac CEUS is also used to evaluate ischemia in the follow-up of congenital and acquired heart disease. In 2019, the United States Food and Drug Administration (FDA) approved a UCA for pediatric echocardiography. This article focuses on the clinical applications of UCAs in pediatric and adult echocardiography, outlining its diagnostic value, safety and potential for future applications.

Feasibility of Real-Time Myocardial Contrast Echocardiography to Detect Cardiac Allograft Vasculopathy in Pediatric Heart Transplant Recipients

BACKGROUND

Cardiac allograft vasculopathy (CAV) is an important adverse prognostic factor for pediatric heart transplant (HT) recipients. Invasive coronary angiography (ICA) is the gold standard for CAV detection but lacks sensitivity for early microvascular changes and cumulative radiation exposure is of concern. Real-time myocardial contrast echocardiography (RTMCE) using ultrasound enhancing (contrast) agents performed during dobutamine stress echocardiography (DSE) can assess myocardial function, perfusion, and microvascular integrity. The objective of this study was to determine the safety and feasibility of RTMCE during DSE to detect CAV in a pediatric HT population.

METHODS

HT patients 10-21 years of age were recruited to undergo DSE with RTMCE to determine technical feasibility, test tolerability and adverse event rate, and detection of perfusion defects compared with ICA-detected CAV. Thirty-six patients from two centers were enrolled, with a mean age 13.5 ± 4.3 years; 21 (58%) were male. Wall motion and myocardial perfusion were qualitatively assessed and compared with ICA findings of CAV. Myocardial blood flow (MBF) at rest and peak stress was quantified, and myocardial blood flow reserve (MBFR) was defined as the ratio of peak to rest MBF.

RESULTS

Five (14%) patients had CAV by ICA, two with obstructive disease and three with mild CAV. Real-time myocardial contrast echocardiography was feasible in 32 (89%) patients. Three patients had wall motion defects, including one with a mixed defect and two with fixed defects. A perfusion abnormality was present in five patients, two of whom had obstructive CAV and one with mild CAV. Sensitivity and specificity of RTMCE for CAV detection were 60% and 94%, respectively, and diagnostic accuracy was 89%. MBFR assessment was feasible in 20 (63%) patients. The mean MBFR was 3.4 ± 0.7. Patients with CAV had lower MBFR than those without (2.0 ± 0.2 vs 3.7 ± 0.8; P < .01). There were no serious adverse events related to RTMCE.

CONCLUSIONS

Dobutamine stress RTMCE appears to be safe and feasible for the assessment of CAV in pediatric HT recipients. Further assessment is warranted to determine whether this noninvasive technique could provide a reliable alternative to ICA.

Myocardial stress perfusion magnetic resonance in children with hypertrophic cardiomyopathy

BACKGROUND

Microvascular dysfunction in hypertrophic cardiomyopathy has been associated with poor clinical outcome. Several studies have demonstrated a reduced perfusion reserve proportional to the magnitude of the hypertrophy. We investigated the utility of stress perfusion cardiac MRI to detect microvascular dysfunction in children with hypertrophic cardiomyopathy.

METHODS

From January 2016 to January 2017, 13 patients, with a mean age of 15.3 years, with hypertrophic cardiomyopathy underwent regadenoson stress perfusion cardiac MRI (1.5-T Siemens Aera). A single-shot, T1-weighted saturation recovery gradient echo was used for first-pass perfusion in a multiple-slices group, including three short-axis slices and one four-chamber slice. Coronary vasodilatory stress was achieved using bolus injection of regadenoson (lexiscan 0.4 mg/5 ml) and dynamic perfusion during rest and stress performed by administering 0.05 mmol/kg of gadolinium contrast agent (gadoteridol) injected at a rate of 3.5 ml/s, followed by assessment of viability using two-dimensional phase-sensitive inversion recovery of the entire myocardium.

RESULTS

All patients completed protocols with no interruptions. In all, seven patients developed perfusion defects after the administration of regadenoson. Asymmetric septal hypertrophy was the most common pattern of hypertrophic cardiomyopathy (n=4) in those with abnormal perfusion. A total of four patients with perfusion defects had a maximum wall thickness <30 mm. The finding of perfusion defects in areas without late gadolinium enhancement in some of our patients indicates that gadolinium enhancement by itself could underestimate the true extension of microvascular disease. Out of seven patients, five patients with positive stress cardiac MRI have undergone implantable cardioverter defibrillator placement based on current guidelines.

CONCLUSIONS

Regadenoson stress cardiac MRI is feasible and clinically valuable in paediatric patients. It is particularly effective in unmasking abnormal myocardial perfusion in the presence of microvascular dysfunction in children with hypertrophic cardiomyopathy.

Off-Label Use of Ultrasound Contrast Agents for Intravenous Applications in Children: Analysis of the Existing Literature

OBJECTIVES

The purpose of this study was to collect and analyze the published data related to intravenous (IV) use of ultrasound (US) contrast agents in children.

METHODS

We searched the literature to collect all of the published studies reporting the IV administration of a second-generation US contrast agent in children.

RESULTS

We analyzed 9 case series and 5 case reports, as well as 5 individual cases, of pediatric contrast-enhanced US use reported in a study group that also included adults. We found that 502 children underwent contrast-enhanced US examinations (mean age, 9.7 years; range, 1 day-18 years). Most patients (89%) were injected with the sulfur hexafluoride contrast agent SonoVue (Bracco SpA, Milan, Italy). The mean dose used was 1.5 mL (range, 0.1-9.6 mL). Only 10 patients (2%) had adverse reactions related to the contrast agent administration: 1 life-threatening anaphylactic shock and 9 mild transitory adverse effects. We additionally found 38 papers in which the study groups included at least 1 child; thus, we obtained a total of 540 reported cases of off-label use of IV US contrast agents in children. The most frequent target organ was the liver, and most indications were related to space-occupying lesion characterization and abdominal evaluations after blunt trauma. Some studies also evaluated the diagnostic performance of contrast-enhanced US in different clinical scenarios and found very good accuracy. Concordance between contrast-enhanced US imaging and the respective reference-standard imaging methods ranged between 83% and 100% in different studies.

CONCLUSIONS

Our results support the idea that the IV use of US contrast agents in children is safe, feasible, diagnostically robust, and effective.

Contrast echocardiography: latest developments and clinical utility

Ultrasound enhancing agents (UEAs) are being utilized for a growing number of applications with real-time very low mechanical index (MI) techniques in clinical cardiology today. This article will review recent developments on the safety of UEAs and their effectiveness in myocardial perfusion imaging, three-dimensional quantification of left ventricular function, and vascular imaging. UEAs are now being utilized in all age groups, with new indications that add incremental value to the currently approved by the Food and Drug Administration. These include the incremental value in cardiac imaging, where the off-label analysis of myocardial perfusion observed with UEAs adds to the enhanced endocardial border delineation. In carotid artery imaging, UEAs improve the detection of plaque but also can examine plaque neovascularization. Vascular surgeons now utilize UEAs in the evaluation of endovascular repair to detect endoleaks without the need of ionizing radiation. Newer applications are emerging in the detection of left atrial appendage thrombi and quantification of myocardial blood flow and volume in transplant patients.

An observational study of the occurrence of serious adverse reactions among patients who receive optison in routine medical practice

BACKGROUND

Reports of ultrasound contrast agent safety have been derived mainly from retrospective databases rather than from studies specifically designed to assess safety. The purpose of this study was to prospectively determine the safety of Optison (GE Healthcare, Princeton, NJ) in routine medical practice.

METHODS

Patients referred for routine rest or stress two-dimensional echocardiography who had indications for contrast were enrolled. Vital signs were obtained at baseline and at intervals up to 1 hour after dosing of Optison. Patients were followed for the development of any serious adverse event (SAE), defined as an event that causes death, is life threatening, requires or prolongs hospitalization, or causes another important event, for 24 hours after Optison administration.

RESULTS

A total of 1,039 patients were enrolled, and 76% had 24-hour follow-up. The median age was 60 years (range, 20-97 years), and 62% were men. The mean body mass index was 33 ± 9 kg/m(2). Patient comorbidities included hypertension (73%), hyperlipidemia (64%), smoking (52%), and diabetes (37%). There were significant increases in systolic blood pressure, heart rate, and respiratory rate between the baseline, 5- to 15-min, 30-min, and 60-min time points after the administration of Optison in patients undergoing stress studies but none in those undergoing rest studies. There was a total of six SAEs during the study, which were felt to be related not to Optison but rather to the stress test itself or to the patient's underlying pathology. Although two events were classified as SAEs because of hospitalization, the hospitalizations were appropriate for pathology that would have been missed without Optison use.

CONCLUSIONS

In this large, prospective safety study of Optison during routine resting and stress echocardiography, no SAEs related to Optison developed. Optison helped define abnormalities that required appropriate hospitalization for further management.

Prevention of arteriovenous shunt occlusion using microbubble and ultrasound mediated thromboprophylaxis

Background

Palliative shunts in congenital heart disease patients are vulnerable to thrombotic occlusion. High mechanical index (MI) impulses from a modified diagnostic ultrasound (US) transducer during a systemic microbubble (MB) infusion have been used to dissolve intravascular thrombi without anticoagulation, and we sought to determine whether this technique could be used prophylactically to reduce thrombus burden and prevent occlusion of surgically placed extracardiac shunts.

Methods and Results

Heparin‐bonded ePTFE tubular vascular shunts of 4 mm×2.5 cm (Propaten; W.L Gore) were surgically placed in 18 pigs: a right‐sided side‐to‐side arteriovenous (AV, carotid‐jugular) shunt, and a left‐sided arterio‐arterial (AA, carotid‐carotid) interposition shunt in each animal. After shunt implantation, animals were randomly assigned to one of 3 groups. Transcutaneous, weekly 30‐minute treatments (total of 4 treatments) of either guided high MI US+MB (Group 1; n=6) using a 3% MRX‐801 MB infusion, or US alone (Group 2; n=6) were given separately to each shunt. The third group of 6 pigs received no treatments. The shunts were explanted after 4 weeks and analyzed by histopathology to quantify luminal thrombus area (mm²) for the length of each shunt. No pigs received antiplatelet agents or anticoagulants during the treatment period. The median overall thrombus burden in the 3 groups for AV shunts was 5.10 mm² compared with 4.05 mm² in AA (P=0.199). Group 1 pigs had significantly less thrombus burden in the AV shunts (median 2.5 mm²) compared with Group 2 (median 5.6 mm²) and Group 3 (median 7.5 mm²) pigs (P=0.006). No difference in thrombus burden was seen between groups for AA shunts.

Conclusion

Transcutaneous US with intravenous MB is capable of preventing thrombus accumulation in arteriovenous shunts without the need for antiplatelet agents, and may be a method of preventing progressive occlusion of palliative shunts.

The year 2012 in the European Heart Journal-Cardiovascular Imaging: Part I

The new multi-modality cardiovascular imaging journal, European Heart Journal - Cardiovascular Imaging, was started in 2012. During its first year, the new Journal has published an impressive collection of cardiovascular studies utilizing all cardiovascular imaging modalities. We will summarize the most important studies from its first year in two articles. The present 'Part I' of the review will focus on studies in myocardial function, myocardial ischaemia, and emerging techniques in cardiovascular imaging.

Microbubble mediated thrombus dissolution with diagnostic ultrasound for the treatment of chronic venous thrombi

Background

Central venous catheter (CVC) thrombi result in significant morbidity in children, and currently available treatments are associated with significant risk. We sought to investigate the therapeutic efficacy of microbubble (MB) enhanced sonothrombolysis for aged CVC associated thrombi in vivo.

Methods and Results

A model of chronic indwelling CVC in the low superior vena cava with thrombus in situ was established after feasibility and safety testing in 7 pigs; and subsequently applied for repeated, sonothrombolytic treatments in 9 pigs (total 24 treatments). Baseline intracardiac echocardiography (ICE, 10.5F, Siemens), fluoroscopy and saline flushing confirmed the absence of any pre-existing CVC thrombus. A thrombus was then allowed to form and age over 24 hours. The created thrombus was localized and measured by ICE, and transthoracic image guided high mechanical index (MI) two-dimensional US treatments (1.1–1.7 MI; iE33, Philips) applied intermittently whenever intravenously infused MBs (3% MRX-801; NuVox) were visualized near the thrombus (n = 10; Group A). Control pigs (n = 10; Group B) received US without MB. All treatments were randomized. Post-treatment thrombus area by ICE planimetry was compared with pre-treatment measurements. Thrombus area measurements before and after treatment were 0.22 and 0.10 cm² respectively in Group A; compared to 0.24 and 0.21 cm² in Group B (p  = 0.0003). Effectiveness of longer duration US and MB thrombolytic treatments were studied (n = 4), which suggested that near complete thrombus dissolution is possible. No pulmonary emboli, alterations in oxygen saturation, or hemodynamics occurred with either treatment.

Conclusions

Guided high MI diagnostic US+systemic MB facilitates reduction of aged CVC associated thrombi in vivo. MB enhanced sonothrombolytic therapy may be a non-invasive safe alternative to thrombolytic agents in treating thrombotic CVC occlusions.