Biomedical subjects

Feng Xie

Publications and source records attributed to Feng Xie.

At least 37 records · Page 2Linked to original sources

PubMed2005

Effectiveness of lipid microbubbles and ultrasound in declotting thrombosis.

The objectives of this study were to determine the effectiveness of lipid-encapsulated microbubbles and ultrasound (US) in recanalizing arteriovenous graft thrombi and the effect that tissue attenuation has on the success rate. A total of 55 thrombotic occlusions were created in four canines. The thrombosed grafts were randomly treated with two different 1-MHz US intensities, low (0.4 to 0.6 W/cm(2)) and high (10 W/cm(2)). Intragraft microbubbles were compared with intragraft saline and with the same dose of microbubbles given IV. IV microbubbles were also given both in the presence and absence of a tissue-mimicking phantom. High-intensity US (10 W/cm(2)) with intragraft microbubbles produced significantly higher patency and flow scores than did US with saline (p < 0.01). US with IV microbubbles had higher success rates in recanalizing thrombosed grafts than did US alone at all intensities. Attenuation reduced the rate at which successful recanalization occurred at both low and high intensities. US and microbubbles are capable of recanalizing acute arteriovenous graft thromboses. Higher intensities may be needed in the presence of tissue attenuation.

Acute Disease↗

PubMed2005

Diagnostic accuracy and prognostic value of dobutamine stress myocardial contrast echocardiography in patients with suspected acute coronary syndromes.

BACKGROUND: Both early stress testing and cardiac troponin I (cTnI) measurements are useful in assessing the prognosis of patients with acute coronary syndrome (ACS). We sought to determine the accuracy and prognostic value of wall motion analysis (WMA) and myocardial perfusion analysis (MPA) with real-time myocardial contrast echocardiography (RTMCE) during dobutamine stress in this patient population. METHODS: We performed dobutamine stress RTMCE to assess perfusion in 158 consecutive patients (mean age: 61 +/- 13 years) with chest pain and possible ACS. Of these, 119 had normal cTnI, while 39 had isolated elevations of cTnI (range: 0.5-9.0 ng/ml). Quantitative angiography was performed within 1 month of RTMCE in 61 patients. Patients were followed for 16 months (range: 6-46 months). Cardiac events included death, nonfatal myocardial infarction, recurrent unstable angina, or need for urgent revascularization. RESULTS: The sensitivity, specificity, and accuracy of MPA for detecting a >50% coronary stenosis were 92%, 77%, and 88%, respectively, while they were 62%, 85%, and 67% for WMA. Three-year event-free survival was 87% in patients with negative WMA and MPA, 49% in those with positive WMA and MPA, and 51% in patients with negative WMA but positive MPA. Age-adjusted multivariate analysis demonstrated that the only independent predictors of cardiac events were a positive MPA (hazard ratio = 3.23; 95% CI = 1.23-8.49) and male sex (hazard ratio = 3.29; 95% CI = 1.21-8.97). CONCLUSIONS: In patients suspected of having an ACS, RTMCE improved the accuracy of dobutamine stress echocardiography for detecting coronary artery disease, and was an independent predictor of outcome.

Angina, Unstable↗

PubMed2005

Phylogenetic relationships of the tribe Paini (Amphibia, Anura, Ranidae) based on partial sequences of mitochondrial 12s and 16s rRNA genes.

Partial sequences of mitochondrial 12S and 16S rRNA genes from 19 Asian frog species of the tribe Paini (Ranidae, Dicroglossinae) allowed a first molecular study of the phylogenetic relationships of this tribe. This analysis confirmed that this tribe is a monophyletic group, but suggested relationships did not agree with previous generic classification of this clade based on morphology. Two major clades were recognized within the Paini. For one of them, the generic name Quasipaa is available. Phylogenetic relationships within the other group are not yet fully clarified and need further study.

Animals↗

PubMed2005

Noninvasive diagnosis of coronary artery disease in patients with diabetes by dobutamine stress real-time myocardial contrast perfusion imaging.

OBJECTIVE: The aim of this study was to assess the accuracy of real-time myocardial contrast perfusion imaging (MCPI) during dobutamine stress in the diagnosis and localization of coronary artery disease (CAD) in patients with diabetes. Myocardial contrast echocardiography is a new technique that allows evaluation of myocardial perfusion. Its utility in diabetic patients has not been defined. RESEARCH DESIGN AND METHODS: Dobutamine-atropine stress test was performed in conjunction with MCPI using Optison or Definity at rest and at peak stress in 128 patients with diabetes and suspected CAD who underwent coronary angiography within 1 month. CAD was defined as > or =50% stenosis in one or more coronary artery. MCPI was considered diagnostic of CAD in the presence of reversible perfusion abnormalities. The normalcy rate of MCPI was additionally determined in 18 asymptomatic nondiabetic patients with low probability. RESULTS: CAD was detected in 101 (79%) patients by angiography. Reversible perfusion abnormalities were detected in 90 patients with and 13 patients without CAD. The overall sensitivity of MCPI was 89% (95% CI 83-95), specificity 52% (33-71), and accuracy 81% (75-88). Reversible abnormalities were detected in two or more vascular distributions in 44 of 56 patients with multivessel CAD and in 8 of 63 patients without (sensitivity 68%, specificity 87%, positive predictive value 84%, and accuracy 79%). Regional sensitivity was 75% (65-85) for left anterior descending CAD, 71% (60-83) for left circumflex, and 67% (55-78) for right CAD. MCPI was normal in 16 of the 18 patients with low clinical probability of CAD (normalcy rate 89%). CONCLUSIONS: MCPI is a useful noninvasive technique for the diagnosis and localization of CAD in diabetic patients. The extent of perfusion abnormalities can identify patients with multivessel CAD with a moderate sensitivity and high specificity.

Adrenergic beta-Agonists↗

PubMed2005

Incidence of cardiac arrhythmias with therapeutic versus diagnostic ultrasound and intravenous microbubbles.

OBJECTIVE: The purpose of this study was to determine the type of arrhythmias induced with therapeutic versus diagnostic transthoracic low-frequency ultrasound (TLFUS) transducers in the presence of intravenous microbubbles. METHODS: Intravenous perfluorocarbon-exposed sonicated dextrose albumin (PESDA) microbubbles were infused or given as a bolus injection while TLFUS was applied in the standard parasternal and apical views with either a 1-MHz therapeutic ultrasound transducer or high-mechanical-index diagnostic ultrasound (1.7 MHz). RESULTS: Significantly more ectopy was produced by the therapeutic transducer, especially at higher-intensity settings in the continuous wave mode after bolus injections of PESDA (P < .001 compared with lower intensities and lower continuous infusion rates). Six patients (15%) had either clinical supraventricular tachycardia or nonsustained ventricular tachycardia after intravenous PESDA with therapeutic TLFUS. In comparison, diagnostic high-mechanical-index ultrasound produced only isolated ventricular ectopy and no sustained ventricular arrhythmias. CONCLUSIONS: Intravenously injected microbubbles and low-frequency therapeutic transducers operating at longer duty cycles and wide beam widths have the capability of eliciting clinically important arrhythmias in patients at high risk for such events.

Adult↗

PubMed2005

[Study on using a new biodegradable conduit to repairing rat's peripheral nerve defect].

OBJECTIVE: Nerve conduit, a new way to repair peripheral nerve, has good prospect. Now, the main obstacle of the conduit's clinical using is the absence of material with both ideal physical property and good biocompatibility. In this study, the PLA is added to chitosan to form a novel material used to make a new nerve conduit. And the rat modal is used to get the data of the nerve conduit made of new material to repair the defect of peripheral nerve in vivo. METHODS: Chitosan-PLA Composite Biodegradable material was used to produce a nerve conduit with depth of 200 um, diameter of 1.5 mm. This new conduit was used to repair the sciatic nerve's defect of 5 mm long. The other two groups as control groups repairs the same defects using silicon conduit or nerve's autograft respectively. 12 weeks after operation, normal assessments were performed including movement of hindlimb, hindlimb's retraction after being pricked by needle and ulcer in claw's palm. Special assessment was performed including histology, ECG, image analysis and weighing of triceps muscle of calf. The data of three groups was statistically analyzed by group t test. RESULTS: As the normal observation showing: after 12 weeks, the regenerating nerve succeeded to path through the gap and dominated the muscle. Special assessment including ECG, image analysis and weighing of triceps muscle of calf showed that the group using Chitosan-PLA Composite conduit had the nervous regeneration better than silicon conduit group both in the nerve's quality and in axon's quantity. And the nervous regeneration of Chitosan-PLA Composite conduit group was as good as that of nervous autograft's group. CONCLUSIONS: Chitosan-PLA Composite Biodegradable conduit could repair the defect of peripheral nerves successfully. It is an ideal material for nerve conduit.

Absorbable Implants↗

PubMed2004

Comparative accuracy of real-time myocardial contrast perfusion imaging and wall motion analysis during dobutamine stress echocardiography for the diagnosis of coronary artery disease.

OBJECTIVE: This study sought to compare the accuracy of myocardial contrast echocardiography (MCE) and wall motion analysis (WMA) during submaximal and peak dobutamine stress echocardiography (DSE) for the diagnosis of coronary artery disease (CAD). BACKGROUND: The relative merits of MCE and WMA for the detection of CAD during DSE have not been studied in a large number of patients. METHODS: We studied 170 patients who underwent dobutamine (up to 50 microg/kg/min)-atropine stress testing and coronary angiography. The WMA and MCE (using repeated boluses of Optison [Mallinckrodt, St. Louis, Missouri] or Definity [Bristol-Myers Squibb, New York, New York]) were performed at rest, at intermediate stress (65% to 75% of maximal heart rate), and at peak stress. The diagnosis of CAD (>/=50% stenosis in >/=1 coronary artery) was based on reversible wall motion and perfusion abnormalities. RESULTS: Coronary artery disease was detected in 127 (75%) patients. Sensitivity of MCE was higher than that of WMA at maximal stress (91% vs. 70%; p = 0.001) and at intermediate stress (84% vs. 20%; p = 0.0001). Specificity was lower for MCE compared with WMA (51% vs. 74%; p = 0.01). Overall accuracy was higher for MCE than for WMA (81% vs. 71%; p = 0.01). Sensitivity for detection of CAD based on abnormalities in >/=2 vascular regions was higher for MCE than for WMA (67% vs. 28%; p < 0.01). CONCLUSIONS: The majority of inducible perfusion abnormalities occur at an intermediate phase of the stress test, without wall motion abnormalities. Myocardial contrast echocardiography provides better sensitivity than WMA, particularly in patients with submaximal stress and in identifying patients with multivessel CAD.

Aged↗

PubMed2004

The use of microbubbles to target drug delivery.

Ultrasound-mediated microbubbles destruction has been proposed as an innovative method for noninvasive delivering of drugs and genes to different tissues. Microbubbles are used to carry a drug or gene until a specific area of interest is reached, and then ultrasound is used to burst the microbubbles, causing site-specific delivery of the bioactive materials. Furthermore, the ability of albumin-coated microbubbles to adhere to vascular regions with glycocalix damage or endothelial dysfunction is another possible mechanism to deliver drugs even in the absence of ultrasound. This review focuses on the characteristics of microbubbles that give them therapeutic properties and some important aspects of ultrasound parameters that are known to influence microbubble-mediated drug delivery. In addition, current studies involving this novel therapeutical application of microbubbles will be discussed.

Drug Delivery Systems↗

PubMed2004

Detection of retained microbubbles in carotid arteries with real-time low mechanical index imaging in the setting of endothelial dysfunction.

OBJECTIVES: We sought to determine if intravenously injected microbubbles would be retained by the carotid arteries (CAs) in the setting of endothelial dysfunction (ED) using a linear transducer equipped with a low mechanical index pulse sequence scheme (PSS). BACKGROUND: Microbubbles normally pass freely through large and small vessels but are retained in regions with ED. New high-frequency low mechanical index PSS can potentially be utilized to image these retained microbubbles. METHODS: Intravenous albumin- and lipid-encapsulated microbubbles were administered in seven pigs while imaging the CAs before and after a 20% intralipid infusion to induce hypertriglyceridemia. The degree of microbubble retention was quantified by measuring endothelial acoustic intensity (AI) after clearance of free-flowing microbubbles. Microbubble adherence was also evaluated after selective balloon injury of the CAs. The CA diameter responses to acetylcholine were quantified. RESULTS: After induction of hypertriglyceridemia, adherence of albumin-encapsulated microbubbles was visually evident in all CAs, and endothelial AI increased significantly (p < 0.001 compared with baseline). The CA responses to acetylcholine went from vasodilation at baseline to vasoconstriction during hypertriglyceridemia. Endothelial AI also increased in the balloon-stretched vessels (p < 0.01 compared with uninjured vessels) after albumin-encapsulated microbubble injection, with a ring of microbubbles selectively adhering to the injured segment. This retention was not observed with lipid-encapsulated microbubbles. Scanning electron microscopy confirmed that albumin-coated microbubbles adhered to endothelial cells. CONCLUSIONS: Retention of intravenously injected albumin microbubbles occurs in the setting of both global and regional ED in large vessels and can be noninvasively imaged with high-frequency low mechanical index PSS.

Acoustics↗

PubMed2004

Intracranial clot lysis with intravenous microbubbles and transcranial ultrasound in swine.

BACKGROUND AND PURPOSE: Destruction of microbubbles by transcutaneous low-frequency ultrasound (LFUS) has been used to lyse adjacent clot and recanalize acutely thrombosed vessels. LFUS with intraarterial microbubbles has been shown to lyse cerebral clot rapidly in pigs without thrombolytic drugs. We hypothesized that intravenous platelet-targeted microbubbles with LFUS may be a rapid noninvasive technique to recanalize thrombosed intracerebral vessels. METHODS: After angiography, 0.5 cc of autogenous thrombus was injected into 1 ascending pharyngeal artery of a pig, occluding it and the rete mirabile. These vessels connect the carotid to the internal carotid and are the main cerebral blood supply. Saline control or intravenous decafluorobutane-sonicated dextrose albumin microbubbles tagged with a subtherapeutic quantity of glycoprotein 2b/3a receptor inhibitor eptifibatide (75 U/kg plus 12 cc of microbubbles administered over 21 minutes), or eptifibatide control, was given with transcutaneous temporal LFUS (1 MHz at 2.0 W/cm2) for 24 minutes. Angiography followed with scoring of declotting and flow. The same protocol was repeated on the contralateral side with the other test fluid so each animal received a saline control and either tagged microbubble or eptifibatide alone. RESULTS: Fifteen pigs completed the protocol with a mean clot age of 4.6 hours. Using tagged microbubbles, 6 of 8 achieved success compared with 0 of 7 receiving eptifibatide alone (P=0.007) and 1 of 15 receiving saline alone (P=0.02). CONCLUSIONS: Intravenous platelet-targeted microbubbles combined with transcranial LFUS can rapidly open acute intracranial thrombotic occlusions. Further development for ischemic stroke therapy is justified.

Animals↗

PubMed2004

Drug and gene delivery and enhancement of thrombolysis using ultrasound and microbubbles.

This article reviews some important characteristics of microbubbles that give them therapeutic properties. It discusses the use of microbubbles and ultrasound for targeted delivery of adenovirus and nonviral vectors to myocytes and endothelial cells and for the dissolution of thrombus or potentiation of fibrinolytic agents for acutely thrombosed vessels. Potential applications, such as induction of angiogenesis, inhibition of neointimal hyperplasia, and in the setting of acute myocardial infarction and ischemic stroke,are discussed briefly.

Cardiovascular Agents↗

PubMed2004

Molecular phylogeny of the genus Paramesotriton (Caudata: Salamandridae).

To elucidate the phylogeny of the genus Paramesotriton (Caudata: Salamandridae), we investigated three mitochondrial DNA gene fragments (1207 bp in total) of cytochrome b, ND2, and ND4 for its six recognized species. The phylogenetic relationships within Paramesotriton were reconstructed by maximum parsimony (MP) and maximum likelihood (ML) methods. Phylogenetic trees (MP and ML trees) that were constructed from the combined data set of the three gene fragments indicated that all six species of Paramesotriton formed a monophyletic group, with P. caudopunctatus as basal to the other five species. This result suggests that P. fuzhongensis is a valid species in Paramesotriton.

Animals↗

PubMed2003

Microbubble responses to a similar mechanical index with different real-time perfusion imaging techniques.

The purpose of this study was to determine differences in contrast enhancement and microbubble destruction rates with current commercially available low-mechanical index (MI) real-time perfusion imaging modalities. A tissue-mimicking phantom was developed that had vessels at 3 cm (near field) and 9 cm (far field) from a real-time transducer. Perfluorocarbon-exposed sonicated dextrose albumin microbubbles (PESDA) were injected proximal to a mixing chamber, and then passed through these vessels while the region was insonified with either pulses of alternating polarity with pulse inversion Doppler (PID) or pulses of alternating amplitude by power modulation (PM) at MIs of 0.1, 0.2 and 0.3. Effluent microbubble concentration, contrast intensity and the slope of digital contrast intensity vs. time were measured. Our results demonstrated that microbubble destruction already occurs with PID at an MI of 0.1. Contrast intensity seen with PID was less than with PM. Therefore, differences in contrast enhancement and microbubble destruction rates occur at a similar MI setting when using different real-time pulse sequence schemes.

Acoustics↗

PubMed2003

Right ventricular outflow versus apical pacing in pacemaker patients with congestive heart failure and atrial fibrillation.

INTRODUCTION: Prior studies suggest that right ventricular apical (RVA) pacing has deleterious effects. Whether the right ventricular outflow tract (RVOT) is a more optimal site for permanent pacing in patients with congestive heart failure (CHF) has not been established. METHODS AND RESULTS: We conducted a randomized, cross-over trial to determine whether quality of life (QOL) is better after 3 months of RVOT than RVA pacing in 103 pacemaker recipients with CHF, left ventricular (LV) systolic dysfunction (LV ejection fraction < or = 40%), and chronic atrial fibrillation (AF). An additional aim was to compare dual-site (RVOT + RVA, 31-ms delay) with single-site RVA and RVOT pacing. QRS duration was shorter during RVOT (167 +/- 45 ms) and dual-site (149 +/- 19 ms) than RVA pacing (180 +/- 58 ms, P < 0.0001). At 6 months, the RVOT group had higher (P = 0.01) role-emotional QOL subscale scores than the RVA group. At 9 months, there were no significant differences in QOL scores between RVOT and RVA groups. Comparing RVOT to RVA pacing within the same patient, mental health subscale scores were better (P = 0.03) during RVOT pacing. After 9 months of follow-up, LVEF was higher (P = 0.04) in those assigned to RVA rather than RVOT pacing between months 6 and 9. After 3 months of dual-site RV pacing, physical functioning was worse (P = 0.04) than during RVA pacing, mental health was worse (P = 0.02) than during RVOT pacing, and New York Heart Association (NYHA) functional class was slightly better (P = 0.03) than during RVOT pacing. There were no other significant differences between RVA, RVOT and dual-site RV pacing in QOL scores, NYHA class, distance walked in 6 minutes, LV ejection fraction, or mitral regurgitation. CONCLUSION: In patients with CHF, LV dysfunction, and chronic AF, RVOT and dual-site RV pacing shorten QRS duration but after 3 months do not consistently improve QOL or other clinical outcomes compared with RVA pacing.

Aged↗

PubMed2003

A method of detecting and quantifying severity of myocardial perfusion defects with intravenous ultrasound contrast and breath holding during stress echocardiography.

Although breath holding is commonly used to improve and maintain image quality during stress echocardiography, its effects on the qualitative and quantitative analysis of myocardial contrast enhancement (MCE) following intravenously injected microbubbles is unknown. The purpose of this study was to determine how breath holding affects MCE following either an intravenous bolus or continuous infusion of perfluorocarbon containing microbubbles. In 48 patients, intravenous Optison was given at peak dobutamine stress to assess myocardial perfusion. The degree of myocardial opacification was assessed immediately following a breath hold in inspiration (BH(ini)), at the end of a breath hold (BH(term)), and following expiration and a subsequent second breath hold (BH(reinsp)). Pulmonary venous time velocity integrals were recorded during these different phases as well. Eleven patients had quantitative coronary angiography. Mean duration of the breath hold was 7 +/- 1 seconds. Pulmonary venous return fell by 29% +/- 18% at BH(term) (P < 0.001). There was complete disappearance of MCE at BH(term) in 27 of 35 bolus injection patients at peak stress, and no return of MCE following flash destruction during breath holding in 11 of 13 patients receiving continuous infusions. BH(reinsp) resulted in a boluslike return of contrast, with a transient, bright MCE in 44 of 48 patients, and a time intensity plot that resembled a gamma variate function. Perfusion defects were visualized in 25 patients during BH(ini) and 28 patients during BH(reinsp). Coronary artery territory agreement between perfusion assessed during BH(ini) and BH(reinsp) and quantitative coronary angiography was 76% and 81%, respectively.

Albumins↗

PubMed2003

Differences in definity and optison microbubble destruction rates at a similar mechanical index with different real-time perfusion systems.

The purpose of this study was to determine microbubble responses to different pulse sequence schemes that exist on low mechanical index (MI) real-time perfusion imaging systems using either intravenous albumin-coated (Optison) or lipid-encapsulated (Definity) microbubbles. A tissue-mimicking phantom was created that permitted insonation of microbubbles at 3 cm (near field) and 9 cm (far field) from the diagnostic transducer face. Differences in effluent microbubble concentration were measured after they passed through vessels being insonified with pulse sequence schemes that transmitted alternating polarity (pulse inversion Doppler), alternating amplitude (power modulation), or both (contrast pulse sequencing) at a similar MI, frame rate, and transmit frequency. Normalized contrast signal intensity within a recirculating chamber was also measured in the near and far field. Pulse inversion Doppler produced less initial normalized contrast signal intensity and greater destruction rates than amplitude varying pulse sequence schemes like power modulation or contrast pulse sequencing at both the 0.1- and 0.2-MI settings. These differences indicate that the same MI setting on different real-time perfusion imaging techniques will produce different microbubble responses.

Albumins↗

PubMed2002

Clinical experience in the detection of coronary artery disease with myocardial contrast echocardiography.

Myocardial contrast enhancement following intravenous infusions or injections of perfluorocarbon-containing microbubbles has now been observed consistently in humans. Currently, the major challenge facing us is interpreting accurately what we see. The myocardial contrast patterns we observe have, thus far, been shown to detect myocardial perfusion abnormalities during dipyridamole, adenosine, and dobutamine stress echocardiography. They also have been shown to detect zones of no reflow following coronary revascularization in patients with acute myocardial infarction. These preliminary data will require validation in larger multicenter clinical studies.

Animals↗

PubMed2002

Chronological age-grading of house flies by using near-infrared spectroscopy.

The sensitivity and accuracy of near-infrared spectroscopy (NIRS) was compared with that of the pteridine fluorescence technique for estimating the chronological age of house flies, Musca domestica (L.). Although results with both techniques were significantly correlated with fly age, confidence limits on predicted ages generally were smaller with NIRS. Young flies could be readily differentiated from old flies by using NIRS. Age predictions using the pteridine method are dependent upon size, sex, and temperature at which adult flies are exposed. In contrast, those factors do not need to be determined for age-grading using NIRS. Classification accuracy using the NIRS method was similar for whole flies, fresh heads, dried heads, and ethanol-preserved heads. The NIRS method was also suitable for predicting age of stable flies, Stomoxys calcitrans (L.), and face flies, Musca autumnalis De Geer. NIRS has several advantages over the measurement of pteridine levels for age-grading field-collected flies, including speed and portability of instrumentation, and not needing to determine sex, size, and temperatures to which adult flies were exposed.

Animals↗