Effects of ultrasound and ultrasound contrast agent on vascular tissue

Contrast-enhanced echocardiographic diagnosis of benign and malignant cardiac tumors and its correlation with pathology

Background

This study aimed to explore the diagnostic value of contrast-enhanced echocardiography (CEE) in benign and malignant cardiac tumors and detect the correlation of CEE parameters and immunohistochemistry (IHC) markers.

Methods

The data of 44 patients with cardiac tumors confirmed by pathology were reviewed. Lesions were examined before surgery using transthoracic echocardiography (TTE) and CEE with time-intensity curve analysis. The expression of CD31, VEGF and Ki67 was measured by IHC staining. Microvessel density (MVD) was quantified via IHC for CD31. The clinical variables, TTE, CEE and IHC parameters were compared between benign and malignant cardiac tumors. Receiver operating characteristic curve were used to analyze the value of factors in predicting malignant cardiac tumors. The correlation between CEE and IHC parameters was analyzed.

Results

Among 44 cardiac tumors, 34 were benign and 10 were malignant. There were significant differences in the TTE parameters (pericardial effusion, tumor boundary, diameter, basal width), CEE parameters (tumor peak intensity (TPI), peak intensity ratio of tumor to myocardium (TPI/MPI), area under time-intensity curve (AUTIC)) and IHC parameters (Ki67, MVD, CD31, VEGF) between the benign and malignant tumor groups (all P < 0.05). Receiver operating characteristic curve analysis showed that the CEE and IHC parameters had diagnostic value in malignant cardiac tumors. There was a correlation between TPI/MPI and Ki67 (r = 0.62), AUTIC and Ki67 (r = 0.50), and AUTIC and CD31 (r = 0.56).

Conclusion

TTE and CEE parameters were different between benign and malignant cardiac tumors. CEE is helpful to differentiate the properties of cardiac tumors. There is a correlation between CEE parameters and IHC markers. AUTIC and TPI/MPI can reflect the proliferation and invasion of tumors.

Functional Activity and Endothelial-Lining Integrity of Ex Vivo Arteries Exposed to Ultrasound-Mediated Microbubble Destruction

Ultrasound-mediated microbubble destruction (UMMD) is a promising strategy to improve local drug delivery in specific tissues. However, acoustic cavitation can lead to harmful bioeffects in endothelial cells. We investigated the side effects of UMMD treatment on vascular function (contraction and relaxation) and endothelium integrity of ex vivo Wistar rat arteries. We used an isolated organ system to evaluate vascular responses and confocal microscopy to quantify the integrity and viability of endothelial cells. The arteries were exposed for 1-3 min to ultrasound at a 100 Hz pulse-repetition frequency, 0.5 MPa acoustic pressure, 50% duty cycle and 1%-5% v/v microbubbles. The vascular contractile response was not affected. The acetylcholine-dependent maximal relaxation response was reduced from 78% (control) to 60% after 3 min of ultrasound exposure. In arteries treated simultaneously with 1 min of ultrasound exposure and 1%, 2%, 3% or 5% microbubble concentration, vascular relaxation was reduced by 19%, 58%, 80% or 93%, respectively, compared with the control arteries. Fluorescent labeling revealed that apoptotic death, detachment of endothelial cells and reduced nitric oxide synthase phosphorylation are involved in relaxation impairment. We demonstrated that UMMD can be a safe technology if the correct ultrasound and microbubble parameters are applied. Furthermore, we found that tissue-function evaluation combined with cellular analysis can be useful to study ultrasound-microbubble-tissue interactions in the optimization of targeted endothelial drug delivery.

Endothelial Cells, First Target of Drug Delivery Using Microbubble-Assisted Ultrasound

Microbubble-assisted ultrasound has emerged as a promising method for local drug delivery. Microbubbles are intravenously injected and locally activated by ultrasound, thus increasing the permeability of vascular endothelium for facilitating extravasation and drug uptake into the treated tissue. Thereby, endothelial cells are the first target of the effects of ultrasound-driven microbubbles. In this review, the in vitro and in vivo bioeffects of this method on endothelial cells are described and discussed, including aspects on the permeabilization of biologic barriers (endothelial cell plasma membranes and endothelial barriers), the restoration of their integrity, the molecular and cellular mechanisms involved in both these processes, and the resulting intracellular and intercellular consequences. Finally, the influence of the acoustic settings, microbubble parameters, treatment schedules and flow parameters on these bioeffects are also reviewed.

Efficacy and safety of sonothombolysis versus non-sonothombolysis in patients with acute ischemic stroke: A meta-analysis of randomized controlled trials

Recent studies have shown that inconsistent results of safety and efficacy between sonothombolysis vs. non-sonothombolysis in acute ischemic stroke (AIS). We implemented a meta-analysis to explore the value of sonothrombolysis in AIS treatment. The MEDLINE, EMBASE, and Cochrane Library databases were searched for randomized controlled trials (RCTs) which had evaluated sonothrombolysis or ultrasound thrombolysis in AIS. One hundred five studies were retrieved and analyzed, among them, 7 RCTs were included in the current meta-analysis. In comparison with the non-sonothombolysis, sonothrombolysis significantly improved complete recanalization (RR 2.16, 95% CI 1.51 to 3.08, P < 0.001), complete or partial recanalization (RR 1.90, 95% CI 1.26 to 2.88, P = 0.002), there is also a tendency to improvement of ≥ 4 points in NIHSS score (RR 1.43, 95% CI 0.99 to 2.07, P = 0.057). However, sonothrombolysis and non-sonothrombolysis had insignificant differences in neurological recovery and adverse events. In subgroup analysis, we found that “With t-PA”, “NIHSS > 15”, “Treatment time ≤ 150min”, and “Age ≤ 65 years” are potential favorable factors for efficacy outcomes of sonothombolysis. Sonothrombolysis can significantly increase the rate of recanalization in patients with AIS compared with non-sonothrombolysis, but there is no significant effect on improving neurological functional recovery and avoiding complications.

Unexpected High Incidence of Coronary Vasoconstriction in the Reduction of Microvascular Injury Using Sonolysis (ROMIUS) Trial

High-mechanical-index ultrasound and intravenous microbubbles might prove beneficial in treating microvascular obstruction caused by microthrombi after primary percutaneous coronary intervention for ST-segment elevation myocardial infarction (STEMI). Experiments in animals have revealed that longer-pulse-duration ultrasound is associated with an improvement in microvascular recovery. This trial tested long-pulse-duration, high-mechanical-index ultrasound in STEMI patients. Non-randomly assigned, non-blinded patients were included in this phase 2 trial. The primary endpoint was any side effect possibly related to the ultrasound treatment. The study was aborted after six patients were included; three patients experienced coronary vasoconstriction of the culprit artery, unresponsive to nitroglycerin. Therefore, coronary artery diameter was measured in five pigs. Coronary artery diameters distal to the injury site decreased after application of ultrasound, after balloon injury plus thrombus injection (from 1.89 ± 0.24 mm before to 1.78 ± 0.17 after ultrasound, p = 0.05). Long-pulse-duration ultrasound might cause coronary vasoconstriction distal to the culprit vessel location.

Contrast Ultrasound Imaging Does Not Affect Heat Shock Protein 70 Expression in Cholesterol-Fed Rabbit Aorta

OBJECTIVES

Diagnostic ultrasound imaging is enhanced by the use of circulating microbubble contrast agents (UCAs), but the interactions between ultrasound, UCAs, and vascular tissue are not fully understood. We hypothesized that ultrasound with a UCA would stress the vascular tissue and increase levels of heat shock protein 70 (Hsp70), a cellular stress protein.

METHODS

Male New Zealand White rabbits (n = 32) were fed a standard chow diet (n = 4) or a 1% cholesterol, 10% fat, and 0.11% magnesium diet (n = 28). At 21 days, 24 rabbits on the cholesterol diet were either exposed to ultrasound (3.2-MHz f/3 transducer; 2.1 MPa; mechanical index, 1.17; 10 Hz pulse repetition frequency; 1.6 microseconds pulse duration; 2 minutes exposure duration at 4 sites along the aorta) with the UCA Definity (1× concentration, 1 mL/min; Lantheus Medical Imaging, North Billerica, MA) or sham exposed with a saline vehicle injection (n = 12 per group). Four rabbits on the cholesterol diet and 4 on the chow diet served as cage controls and were not exposed to ultrasound or restrained for blood sample collection. Animals were euthanized 24 hours after exposure, and aortas were quickly isolated and frozen in liquid nitrogen. Aorta lysates from the area of ultrasound exposure were analyzed for Hsp70 level by Western blot. Blood plasma was analyzed for cholesterol, Hsp70, and von Willebrand factor, a marker of endothelial function.

RESULTS

Plasma total cholesterol levels increased to an average of 705 mg/dL. Ultrasound did not affect plasma von Willebrand factor, plasma Hsp70, or aorta Hsp70. Restraint increased Hsp70 (P < .001, analysis of variance).

CONCLUSIONS

Restraint, but not ultrasound with the UCA or cholesterol feeding, significantly increased Hsp70.

Contrast Ultrasound Imaging of the Aorta Does Not Affect Progression of Atherosclerosis or Cardiovascular Biomarkers in ApoE-/- Mice

OBJECTIVES

Ultrasound contrast agents (UCAs) enhance cardiovascular ultrasound imaging. Adverse biological effects have occurred after administration of UCAs, and more research is needed for a comprehensive understanding of the risks involved. We used the ApoE(-/-) mouse model of atherosclerosis to characterize the effects of ultrasound and UCAs on atherosclerosis and plasma biomarkers.

METHODS

Male ApoE(-/-) mice (8 weeks old; n = 24) were intravenously infused with a UCA (2 × 10(10) Definity microbubbles per hour; Lantheus Medical Imaging, North Billerica, MA) and exposed to 2.8-MHz center frequency ultrasound (10 Hz pulse repetition frequency, 1.4 microseconds pulse duration, 2 minutes exposure duration, and 2 sites) at 1 of 3 derated peak rarefactional pressure amplitudes (0, 1.9, or 3.8 MPa), and then consumed either a chow or Western diet for 4 weeks (n = 4 per group). Blood plasma samples were collected before ultrasound exposure and at 2 and 4 weeks after exposure and assayed for total cholesterol and von Willebrand Factor (vWF). A pathologist measured atheroma thickness in formalin-fixed, hematoxylin-eosin-stained transverse aorta sections and scored them for severity of atherosclerosis.

RESULTS

Plasma total cholesterol initially averaged 286 mg/dL in the Western diet group and increased to 861 mg/dL after 4 weeks on the diet (P < .0001). Total cholesterol did not increase significantly in the chow diet group. Plasma vWF increased after 2 weeks on the Western diet (P < .0001). Atheroma thickness was greater in animals consuming the Western diet than in chow-fed animals (P < .05). Ultrasound had no significant effect on plasma total cholesterol, plasma vWF, or atheroma thickness.

CONCLUSIONS

Contrast ultrasound did not increase the severity of atherosclerosis or alter cardiovascular biomarkers in the ApoE(-/-) mouse model.

Ultrasound-mediated drug delivery for cardiovascular disease

INTRODUCTION

Ultrasound (US) has been developed as both a valuable diagnostic tool and a potent promoter of beneficial tissue bioeffects for the treatment of cardiovascular disease. These effects can be mediated by mechanical oscillations of circulating microbubbles, or US contrast agents, which may also encapsulate and shield a therapeutic agent in the bloodstream. Oscillating microbubbles can create stresses directly on nearby tissue or induce fluid effects that effect drug penetration into vascular tissue, lyse thrombi or direct drugs to optimal locations for delivery.

AREAS COVERED

The present review summarizes investigations that have provided evidence for US-mediated drug delivery as a potent method to deliver therapeutics to diseased tissue for cardiovascular treatment. In particular, the focus will be on investigations of specific aspects relating to US-mediated drug delivery, such as delivery vehicles, drug transport routes, biochemical mechanisms and molecular targeting strategies.

EXPERT OPINION

These investigations have spurred continued research into alternative therapeutic applications, such as bioactive gas delivery and new US technologies. Successful implementation of US-mediated drug delivery has the potential to change the way many drugs are administered systemically, resulting in more effective and economical therapeutics, and less-invasive treatments.