Sonicated Dextrose Albumin Research Articles

Phosphomimetic endothelial nitric oxide synthase-loaded microbubbles-mediated cardiac shock wave transfection therapy for angiogenesis in the ischemic myocardium

Abstract Background Cardiac shock wave therapy is a potential and effective remedy to promote revascularization in the ischemic myocardium of patients with refractory coronary heart disease (CHD). Although gene therapy holds great promise as a treatment for coronary heart disease, current clinical application is hampered by the development of safe and efficient systems for local gene delivery to a specific tissue or organ. Purpose In this study, we developed an experimental pulsed- focused electrohydraulic shock wave therapy system and investigated its effectiveness on myocardial angiogenesis in the hypercholesterolemic rabbit accompanied by phosphomimetic endothelial nitric oxide synthase-loaded microbubbles administration, wherein a high resolution diagnostic ultrasound is adjuncted with the therapy system, with a goal of increased safety. Methods Briefly, New Zealand white rabbits underwent 2% cholesterol rich diet injury for sixteen weeks. Histopathology results showed the formation of foam cells-rich soft atherosclerotic plaques with severe stenosis in all of the rabbits' coronary arteries. Then treatment group underwent extracorporeal electrohydraulic pulsed-focused shock waves (25kV, 0.5Hz, 150 pulses) accompanied by phosphomimetic endothelial nitric oxide synthase-loaded PESDA (Perfluorocarbon Exposed Sonicated Dextrose Albumin) microbubbles (100 ml/kg, 2.5x105 bubbles/ml) administration. Results Results from ultrasonography and histopathology showed a significant increase in the mean value for myocardial neovessels density in the treatment group compared with the control group (p<0.05). Conclusion Enhanced angiogenesis and sonoporation effect of electrohydraulic shock wave therapy, induced by inertial collapsed microbubbles, accompanied by phosphomimetic endothelial nitric oxide synthase-mediated shock wave transfection therapy, can cause to enhance the nitric oxide synthesis and VEGF, interleukin8 (IL8), stromal cell- derived factor 1 (SDF1) and matrix metalloproteinase 9 (MMP9) secretion in the hypercholesterolemic rabbits' coronary arteries, resulting in the differentiation and recruitment of endothelial progenitor cells (EPCs), promotion of revascularization in the ischemic myocardium and improvement of the cardiac function. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): Mehrad Research Lab

Early stage atherosclerosis regression using combined sonotherapy and mitoxantrone-mediated sonoporation therapy

Abstract Background In atherosclerosis, local inflammation and associated macrophage activity can lead to foam cell-rich plaque formation, which results to plaque rupture and thrombosis, making inflammation an important therapeutic target in cardiovascular disease. The early stage of atherosclerosis is characterized by the accumulation of low-density lipoprotein (LDL) droplets, leading to the creation of foam cells. Foam cells are generated by uncontrolled uptake of modified LDL, especially oxidized LDL (oxLDL). Purpose In this study, we developed an experimental focused ultrasound-based combined sonotherapy and sonoporation therapy system, and investigated its effectiveness on macrophage-derived foam cells reduction, wherein a high resolution diagnostic ultrasound is adjuncted with combination therapy system, with a goal of increased safety. Methods Briefly, New Zealand white rabbits underwent primary balloon dilatation injury at the right common carotid artery followed by a 1.5% cholesterol-rich diet injury for three weeks. Histopathology results showed the early stage atherosclerosis formation in all of the rabbits' arteries. Then common carotid arteries of the treatment group at the lesion region, treated using extracorporeal low-level pulsed-focused ultrasound (P=11 W, F=1.1 MHz, DF=50%) sonotherapy accompanied by mitoxantrone-loaded PESDA (Perfluorocarbon-Exposed Sonicated Dextrose Albumin) microbubbles (100 ml/kg, 2–5x105 bubbles/ml)-mediated sonoporation therapy. Foam cells density were evaluated in the treatment group compared with the other groups using B-mode ultrasonography and histopathology. Results Results from B-mode ultrasonography and histopathology showed a significant reduction in the mean value for immune cells and foam cells density within the early stage atherosclerotic lesion in the treatment group compared with the other groups (p<0.05). Conclusion Enhanced sonoporation effect of ultrasound, induced by collapsed PESDA microbubbles accompanied by anti-inflammatory effect of sonotherapy and antineoplastic and cytotoxic effect of mitoxantrone can cause to reduce the immune cells and foam cells density within the lesion. These finding provide the basis for developing low-level pulsed-focused ultrasound-based combined sonotherapy and sonoporation therapy for a successful clinical application in the treatment of the early stage atherosclerosis. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): Mehrad Research Lab

Sono- shock wave combination angiogenic therapy for cardiac function improvement in the hypercholesterolemic hamsters with myocardial ischemia

Background and Aims : Cardiac shockwave therapy is a novel, noninvasive approach that has been shown to ameliorate the myocardial ischemia and improve cardiac function. Cardiac shockwave therapy is a potential and effective remedy to promote revascularization in the ischemic myocardium of patients with refractory coronary heart disease. The technique is both safe and non-invasive.; however, the underlying molecular mechanism remains unclear. In this study, we developed an sono- shock wave combination therapy system and investigated its effectiveness on myocardial angiogenesis in the hamsters accompanied by PESDA (Perfluorocarbon- Exposed Sonicated Dextrose Albumin) microbubbles administration.

B- mode ultrasound- guided balloon angioplasty of occluded artery accompanied by combined focused ultrasound sonodynamic therapy and catheter- based 192Ir- mediated brachytherapy

Abstract Background and aims Three mechanisms are responsible for the development of restenosis: elastic recoil, intimal hyperplasia and late vascular constriction, all grouped under the catch phrase “negative remodeling”. Neointimal hyperplasia is usually defined in an artery as thickening of the intimal layer after an injury such as balloon angioplasty methods. The aim of this study was to evaluate the effect of combined ultrasound sonodynamic therapy and catheter- based 192Ir-mediated β-brachytherapy on restenosis reduction after balloon angioplasty. Methods Briefly, golden Syrian hamsters were submitted to common carotid artery advanced atherosclerotic occlusion by primary perivascular Co2 laser-mediated far-infrared injury followed by a 2% cholesterol-rich diet for six weeks. Histopathology results showed the formation of a thick-cap fibroatheromatic plaque, resulted to occlusion in all of the hamsters' arteries. Then treatment group (n=10) underwent B-mode ultrasound-guided balloon angioplasty followed by combined pulsed low level focused ultrasound (F=750 KHz, I=1.5 W/cm2, PD=120 ms)-mediated sonosensitizer protoporphyrin-IX-loaded PESDA (Perfluorocarbon Exposed Sonicated Dextrose Albumin) microbubbles (100ml/kg, 2–5×105 bubbles/ml) sonodynamic therapy and catheter- based β-brachytherapy (125I−, 18 Gy). Results Results from ultrasonography and histopathology showed a significant reduction in the mean value for macrophages and smooth muscle hyperplasia cells density after balloon angioplasty in the treated group compared with the other groups (p<0.05). Conclusions Enhanced anti-inflammatory effect of sonodynamic therapy, induced by collapsed microbubbles accompanied by apoptotic effect of β-brachytherapy, can cause to reduce the inflammation and smooth muscle hyperplasia cells in the intimal layer. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): Mehrad Research Lab

Sonothrombolysis of embolic carotid artery, using pesda microbubbles- mediated B-mode ultrasound- guided extracorporeal pulsed low- level focused confocal dual frequency ultrasound accompanied by streptokinase administration

Background and Aims: Therapeutic ultrasound was found to selectively lyse thrombi with a wide margin of safety. Ultrasound effects sonothrombolysis by selective disruption of the fibrin matrix of the thrombus. In this study, we developed an experimental sonothrombolysis system, and investigated its effectiveness on carotid artery recanalization, accompanied by intravenous streptokinase and PESDA (perfluorocarbon exposed sonicated dextrose albumin) microbubbles administration, wherein diagnostic ultrasound imaging system is combined with the therapy system, with a goal of increased safety.

Ultrasound Imaging in an Animal Model of Vascular Inflammation Following Balloon Injury

Cardiovascular disease is a major cause of morbidity and mortality in the world and better prevention and treatment strategies are needed. Studies from this laboratory have shown that perfluorocarbon exposed sonicated dextrose albumin (PESDA) microbubbles bind to inflamed vasculature through interactions with scavenger receptors (SR). This current study details the use of PESDA as a tool for accessing and quantifying the extent of vascular inflammation. Angioplastied rat aortas were evaluated with low mechanical index microbubble imaging techniques contrast pulse sequencing (CPS); Siemens Acuson Sequoia 15L8, 7–15 MHz ultrasound probe with a mechanical index of 0.09 to detect microbubble binding. Real-time polymerase chain reaction (RT-PCR) analysis of angioplastied aortas demonstrated a significantly (p < 0.01) increased expression of both SRs and Interleukin 6 (IL-6). Vessel wall enhancement was quantified using densitometry of CPS ultrasound images and correlated with the upregulated expression of scavenger receptors, Toll-like receptors and IL-6. This study demonstrates that PESDA, in conjunction with CPS ultrasound, is an effective imaging technique to better detect early vascular inflammation and potential cardiovascular disease.

A method for the making and utility of gadolinium-labeled albumin microbubbles

Objective Perfluorocarbon-exposed sonicated dextrose albumin microbubbles (PESDA) binds scavenger receptors and can be noninvasively imaged. To enhance imaging, gadolinium (Gd)-labeled PESDA was developed and tested in a model of vascular inflammation by magnetic resonance imaging (MRI). Methods and Results Purified human serum albumin (HSA) (5%) was labeled with Gd via the covalent binding of diethylenetriaminepentacetic acid. Abdominal aortic tissues in Sprague–Dawley rats ( n=5 per group) were analyzed by 7-T MRI and scanning electron microscopy to evaluate PESDA binding. Labeling-purified 5% human albumin resulted in an average of 16.1 Gd atoms per albumin molecule as determined by atomic absorption. Forty-eight hours after balloon angioplasty, aortic tissue was enhanced with Gd-PESDA as compared to control tissue. 7-T MRI of explanted tissues was sensitive to the detection of retained PESDA. Enhancement of aortic tissue in vivo was present albeit to a lesser extent than explanted tissue from the same animals. Conclusions HSA was successfully labeled, and an albumin-based microbubble with Gd was synthesized. This contrast agent, Gd-PESDA, may serve as an additional agent for the MRI evaluation of innate inflammation and used to noninvasively image early vascular pathophysiologic processes. Condensed Abstract In this study, Gd-PESDA microbubbles and were synthesized and shown to detect the binding of these microbubbles using MRI in injured aortic tissue. The method for synthesizing Gd-PESDA is detailed, and the proposed utility of this new contrast agent is discussed.

Albumin-based Microbubbles Bind Up-regulated Scavenger Receptors following Vascular Injury

We have shown previously that perfluorocarbon-exposed sonicated dextrose albumin (PESDA) microbubbles bind to injured vascular tissue and can be detected with ultrasound imaging techniques. Prior studies have shown that scavenger receptors (SRs) are regulators of innate and adaptive immune responses and are involved in the progression of vascular disease such as atherosclerosis. In this study, we sought to determine the molecular mechanism of PESDA binding to balloon-injured vasculature. RT-PCR analysis of angioplastied aortas demonstrated a significantly (p ≤ 0.01) increased expression of SRs. Binding to SRs was confirmed using SR-expressing CHO cells, and this binding was blocked by competitive inhibition with the SR-binding ligands oxidized LDL and malondialdehyde-acetaldehyde-modified LDL. Confocal imaging confirmed the co-localization of PESDA microbubbles to CD36, SRB-1, and Toll-like receptor 4, but not to monocytes/macrophages. This study demonstrates that PESDA binds to SRs and that this binding is in major part dependent upon the oxidized nature of PESDA microbubble shell proteins. The extent of SR mRNA expression was increased with injury and associated with microbubble retention as defined by scanning electron microscopy and immunohistochemistry. These findings clarify the mechanisms of how albumin-based microbubbles bind to injured and inflamed vasculature and further support the potential of this imaging technique to detect early vascular innate inflammatory pathophysiologic processes.

Comparison of Myocardial Contrast Echocardiography Versus Rest Sestamibi Myocardial Perfusion Imaging in the Early Diagnosis of Acute Coronary Syndrome

It remains unclear whether myocardial contrast echocardiography (MCE) is as accurate as myocardial perfusion imaging with technetium-99m sestamibi (MPI) for the diagnosis of acute coronary syndrome (ACS). We sought to directly compare the diagnostic accuracy of MCE with resting MPI in a head-to-head fashion. We prospectively enrolled 98 consecutive patients (mean age; 59+/-9 years, 68 males) who presented to the emergency department with chest pain suggestive of acute myocardial ischemia. Early MCE was performed by using continuous infusion of perfluorocarbon-exposed sonicated dextrose albumin (PESDA) during intermittent power Doppler harmonic imaging. Myocardial perfusion defects observed in at least one coronary territory were considered positive. Sestamibi was injected immediately after MCE and MPI was obtained within 6 hours of tracer injection. ACS was confirmed in 67 patients. There were 32 patients with acute myocardial infarction (AMI) and 35 patients with unstable angina requiring urgent revascularization. The sensitivities of MCE and MPI for the diagnosis of ACS were 72% and 61%, respectively, which were significantly higher than those of ST segment change (24%, p<0.001 vs. MCE and vs. MPI) and troponin I (27%, p<0.001 vs. MCE and vs. MPI), with similar specificities of 90% to 100%. On a receiveroperating characteristics curve demonstrating diagnostic accuracy for ACS, the area under the curve of MCE was significantly larger than that of MPI (0.86 vs. 0.77, respectively; p=0.019). MCE and MPI overcome the low sensitivity of routine triage tests for detecting ACS, and MCE is more accurate than MPI for the diagnosis of ACS in the emergency department.

Myocardial Injury Induced by Ultrasound-Targeted Microbubble Destruction: Evidence for the Contribution of Myocardial Ischemia

Ultrasound-targeted microbubble destruction (UTMD) can cause left ventricular (LV) dysfunction and tissue alterations in rats when high ultrasound (US) energy and long duration of imaging are used. However, the mechanism underlying these alterations remains unclear. The aim of the present work was to investigate the possible role of ischemia in the pathogenesis of the UTMD-induced LV damages in rats. To address this issue, rat hearts were exposed in situ to perfluorocarbon-enhanced sonicated dextrose albumin (PESDA) and US at peak negative pressures of 0.6, 1.2 or 1.8 MPa for 1, 3, 9, 15 or 30 min. Blood pressure and electrocardiogram were continuously recorded during insonation. LV function was assessed before and immediately after US exposure, as well as at 24 h and 7 d. At each time point, groups of rats were euthanized and their hearts were harvested for morphologic analysis. Rats exposed to either PESDA alone or US alone showed no functional or morphologic abnormalities. By contrast, rats exposed to both PESDA and US exhibited transient LV dysfunction, transient ST-segment elevation, premature ventricular contractions, microvascular ruptures, contraction band necrosis and morphologic tissue damage. These bio-effects were spontaneously and completely reversible by one week, except in the groups exposed to the highest peak negative pressure for the longest duration, in which mild dysfunction persisted and interstitial fibrosis developed. In conclusion, simultaneous exposure of rat hearts to PESDA and US in vivo results in significant bio-effects that are similar to myocardial ischemia, including transient regional LV dysfunction, transient ST-segment elevation and myocyte contraction band necrosis. (E-mail: vanoverschelde@card.ucl.ac.be)

Giant Right Coronary Artery Aneurysm Associated With Bilateral Coronary Artery to Pulmonary Artery Fistula

A 75-year-old woman presented with progressive chest discomfort. She had not experienced any chest trauma or thoracic surgery. Her chest x-ray film showed cardiomegaly with a bulging contour at right hilar area suspicious of anterior mediastinal mass (Fig 1). Echocardiography revealed a huge, round-shaped, cyst-like mass with partial right atrial collapse due to the compression of the mass with normal global left ventricular systolic function. Contrast echocardiography showed filling of dye within the mass after perfluorocarbon exposed sonicated dextrose albumin infusion.

Release of cardiac bio-markers during high mechanical index contrast-enhanced echocardiography in humans

Recent experimental data have shown that the combined exposure of rodent hearts to high acoustic pressure and ultrasound contrast agents can induce vascular injury and cell damage. The aim of the present work was to test whether similar effects can be observed in humans. Twenty patients underwent simultaneous arterial and coronary sinus blood sampling during contrast-enhanced echocardiography using Perfluorocarbon-enhanced Sonicated Dextrose Albumin. Control subjects were compared to groups of patients exposed to either high mechanical index (MI = 1.5) triggered second harmonic (1.3-2.6 MHz) imaging or low mechanical index (MI = 0.2) real-time power modulation imaging for 15 min. No significant changes arterio-venous differences in lactate, total creatine kinase (CK) and myoglobin occurred over time in the three groups. Similarly, the arterio-venous difference in CK-MB and troponin I remained stable over time in control and low-MI patients. By contrast, these two parameters progressively increased over time in the high-MI group (P < 0.05 vs. baseline and vs. controls). Our data suggest that high-MI contrast-enhanced echocardiography can cause subclinical release of cardiac bio-markers in humans, while low-MI real-time imaging appears to be safer.

Detection of coronary artery disease using real-time myocardial contrast echocardiography: a comparison with dual-isotope resting thallium-201/stress technectium-99m sestamibi single-photon emission computed tomography

Real-time myocardial contrast echocardiography (MCE) has the potential to evaluate myocardial perfusion and wall motion (WM) simultaneously. The purposes of this study were to correlate the diagnostic value of MCE with radionuclide single-photon emission computed tomography (SPECT), and to assess the sensitivity and specificity of real-time MCE in detecting coronary artery disease (CAD). Seventy patients with clinically suspected CAD underwent MCE and SPECT at baseline and after dipyridamole infusion. Segmental perfusion with MCE using low mechanical index after 0.3-0.4-ml bolus injections of perfluorocarbon exposed sonicated dextrose albumin solution was performed. All patients had a dual-isotope (rest thallium-201, stress sestamibi) study performed both at baseline and after dipyridamole infusion, and 40 patients had subsequent quantitative coronary angiography. Abnormalities were noted in 27 patients (38.6%) by MCE, in 29 patients (41.4%) by WM analysis, and in 30 patients (42.9%) by SPECT imaging. When MCE and WM analysis were combined, the agreement with SPECT imaging improved from 75.7% (Kappa = 0.50) to 82.0% (Kappa = 0.62). In 40 patients (120 territories) who underwent coronary angiography, good perfusion concordance was achieved for the left anterior descending and left circumflex arteries, and was fair for the right coronary arteries. Compared with quantitative angiography, there was no difference in sensitivity, specificity, and accuracy in detecting significant CAD among the three modalities. The combination of MCE and WM had a better sensitivity (84%), specificity (93.3%), and accuracy (87.5%) than the MCE and WM analysis alone. However, the difference did not reach statistical significance. Real-time MCE has a good agreement with SPECT imaging for detecting CAD. The combination of MCE and WM appears to have higher sensitivity, specificity, and accuracy in detecting CAD than either technique alone.

Bioeffects of albumin-encapsulated microbubbles and real-time myocardial contrast echocardiography in an experimental canine model

Myocardial contrast echocardiography has been used for assessing myocardial perfusion. Some concerns regarding its safety still remain, mainly regarding the induction of microvascular alterations. We sought to determine the bioeffects of microbubbles and real-time myocardial contrast echocardiography (RTMCE) in a closed-chest canine model. Eighteen mongrel dogs were randomly assigned to two groups. Nine were submitted to continuous intravenous infusion of perfluorocarbon-exposed sonicated dextrose albumin (PESDA) plus continuous imaging using power pulse inversion RTMCE for 180 min, associated with manually deflagrated high-mechanical index impulses. The control group consisted of 3 dogs submitted to continuous imaging using RTMCE without PESDA, 3 dogs received PESDA alone, and 3 dogs were sham-operated. Hemodynamics and cardiac rhythm were monitored continuously. Histological analysis was performed on cardiac and pulmonary tissues. No hemodynamic changes or cardiac arrhythmias were observed in any group. Normal left ventricular ejection fraction and myocardial perfusion were maintained throughout the protocol. Frequency of mild and focal microhemorrhage areas in myocardial and pulmonary tissue was similar in PESDA plus RTMCE and control groups. The percentages of positive microscopical fields in the myocardium were 0.4 and 0.7% (P = NS) in the PESDA plus RTMCE and control groups, respectively, and in the lungs they were 2.1 and 1.1%, respectively (P = NS). In this canine model, myocardial perfusion imaging obtained with PESDA and RTMCE was safe, with no alteration in cardiac rhythm or left ventricular function. Mild and focal myocardial and pulmonary microhemorrhages were observed in both groups, and may be attributed to surgical tissue manipulation.

Value of adenosine infusion for infarct size determination using real-time myocardial contrast echocardiography

BackgroundMyocardial contrast echocardiography has been used for determination of infarct size (IS) in experimental models. However, with intermittent harmonic imaging, IS seems to be underestimated immediately after reperfusion due to areas with preserved, yet dysfunctional, microvasculature. The use of exogenous vasodilators showed to be useful to unmask these infarcted areas with depressed coronary flow reserve. This study was undertaken to assess the value of adenosine for IS determination in an open-chest canine model of coronary occlusion and reperfusion, using real-time myocardial contrast echocardiography (RTMCE).MethodsNine dogs underwent 180 minutes of coronary occlusion followed by reperfusion. PESDA (Perfluorocarbon-Exposed Sonicated Dextrose Albumin) was used as contrast agent. IS was determined by RTMCE before and during adenosine infusion at a rate of 140 mcg·Kg-1·min-1. Post-mortem necrotic area was determined by triphenyl-tetrazolium chloride (TTC) staining.ResultsIS determined by RTMCE was 1.98 ± 1.30 cm2 and increased to 2.58 ± 1.53 cm2 during adenosine infusion (p = 0.004), with good correlation between measurements (r = 0.91; p < 0.01). The necrotic area determined by TTC was 2.29 ± 1.36 cm2 and showed no significant difference with IS determined by RTMCE before or during hyperemia. A slight better correlation between RTMCE and TTC measurements was observed during adenosine (r = 0.99; p < 0.001) then before it (r = 0.92; p = 0.0013).ConclusionRTMCE can accurately determine IS in immediate period after acute myocardial infarction. Adenosine infusion results in a slight better detection of actual size of myocardial damage.

Effect of Different Conditioning on Perfluorocarbon Exposed Sonicated Dextrose Albumin Manufacture

Effect of Different Conditioning on Perfluorocarbon Exposed Sonicated Dextrose Albumin Manufacture

Targeted vascular delivery of antisense molecules using intravenous microbubbles

Perfluorocarbon-exposed sonicated dextrose albumin (PESDA) microbubbles bind the antisense to the c-myc protooncogene (anti-c-myc) which prevents neointimal hyperplasia following vascular endothelial injury. The microbubbles also adhere to sites of damaged vascular endothelium and thus may be a method of systemically targeting delivery of anti-c-myc. Laser scanning microscopy was performed on the aorta of 10 mice (five which were complement depleted) that received intravenous FITC-PESDA following aortic endothelial injury. C-myc expression was quantified following selective intracoronary injury in nine pigs that received intravenous (IV) anti-c-myc bound to PESDA. Finally, neointimal formation was measured following intracoronary stent deployment in 30 pigs that received either IV anti-c-myc alone or the same dose bound to PESDA. Fluorescent microscopy confirmed selective PESDA microbubble adherence to aortic endothelium in all mice with aortic injury. This binding was nearly abolished when serum complement was depleted prior to injury. C-myc expression at the site of coronary endothelial injury was significantly lower in pigs treated with systemic anti-c-myc bound to PESDA. There was a 33% reduction in % stenosis and a 28% reduction in intimal area at 45 days post-stent deployment in pigs that received IV antisense plus PESDA. The stent margins also had reduced neointimal formation. Systemic administration of anti-c-myc bound to PESDA microbubbles may be a good method for preventing coronary neointimal formation within and around implanted stents.

Efficacy of Myocardial Contrast Echocardiography in the Diagnosis and Risk Stratification of Acute Coronary Syndrome

We examined the hypothesis that myocardial contrast echocardiography (MCE) is superior to conventional electrocardiographic, echocardiographic, and troponin I criteria for the diagnosis of acute coronary syndrome. We prospectively enrolled 114 consecutive patients (60+/-10 years of age, 73 men) who presented to the emergency room with chest pain on exertion and at rest. Exclusion criteria included an age<40 years, presence of Q wave or ST-segment elevation, and a poor echocardiographic window. Echocardiography and MCE were performed to assess regional wall motion abnormalities (RWMAs) and myocardial perfusion defects by using continuous infusion of perfluorocarbon-exposed sonicated dextrose albumin. Acute coronary syndrome was confirmed in 87 patients. There were no deaths; 46 patients had acute myocardial infarction, and 41 patients required urgent revascularization. On multiple logistic regression analysis, myocardial perfusion defect (odd ratio 87, p<0.001) was the only independent variable for diagnosing acute coronary syndrome. Myocardial perfusion defect (odd ratio 21, p=0.001) and troponin I levels (odd ratio 3, p=0.009) were independent predictors for acute myocardial infarction. The sensitivity of myocardial perfusion defect for diagnosing acute coronary syndrome was 77%, which is significantly higher than the sensitivities of ST change, troponin I increase, and RWMA (28%, 34%, and 49%, respectively), with similar specificities of 85% to 96%. In conclusion, MCE is more sensitive than the currently used electrocardiographic and troponin I criteria, and evaluation of myocardial perfusion defect by MCE complements RWMA analysis by conventional echocardiography for accurate diagnosis of acute coronary syndrome.

Myocardial delivery of colloid nanoparticles using ultrasound-targeted microbubble destruction

Ultrasound (US)-targeted microbubble destruction (UTMD) is a promising method for delivering genetic material to the heart. The aim of this study was: (i) to test whether colloid nanoparticles can be delivered to the rat myocardium using UTMD; and (ii) to determine whether tissue damage and contractile dysfunction occurs in hearts exposed to UTMD in vivo. Hearts from anaesthetized rats were exposed to perfluorocarbon-enhanced sonicated dextrose albumin (PESDA) (at two different microbubble concentrations) and US at peak pressures of 0.6, 1.2, or 1.8 MPa for 1, 3, or 9 min. During US, pairs of 30 and 100 nm fluorescent nanospheres were infused intravenously. Left ventricular function was assessed before and immediately after US, as well as at 24 h and 7 days. At the end of the experiments, the number of ruptured microvessels and the amount of nanospheres deposited were quantified. Rats exposed to PESDA alone or US alone showed no functional abnormalities, no capillary ruptures, and no nanosphere delivery. In contrast, rats exposed to both PESDA and US exhibited microvascular ruptures and nanosphere deposits. They also showed transient contractile dysfunction and premature ventricular contractions. All these changes were time-, US peak pressure-, and PESDA concentration-dependent. UTMD allows colloid nanoparticles to be delivered to the rat myocardium through microvessel rupture sites. The efficacy of delivery depends on the peak pressure applied, the duration of US exposure, and contrast concentration. UTMD also causes time- and peak pressure-dependent contractile dysfunction, and tissue alterations that are spontaneously reversible over time.

Targeting vascular endothelium with avidin microbubbles

Targeting microbubbles (MBs) to specific vascular beds enables contrast ultrasound to be used for molecular imaging. There are several methods for attaching targeting moieties to the surface of MBs. In the present study, we demonstrate that avidin (Av) can be incorporated into the shell of perfluorocarbon-exposed sonicated dextrose albumin (PESDA) MBs (Av-PESDA-MBs) and serve as an anchor that links Av-PESDA-MBs to biotinylated monoclonal antibodies (mAbs). This novel linking strategy was used to conjugate Av-PESDA-MBs to mAbs specific for endoglin (CD105) or a control IgG. MBs targeted to CD105 specifically bound to endothelial cells, but not to fibroblasts, in vitro but Av-PESDA-MBs conjugated with the control IgG did not specifically target either cell type. We conclude that Av-PESDA-MBs represent a novel and attractive tool to conjugate MBs with biotinylated mAbs for the purposes of vascular targeting and molecular imaging. (E-mail: rolf.brekken@utsouthwestern.edu)