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Perfusion Studies (perfusion + studies)
Selected AbstractsEffect of Chronic Sustained-Release Dipyridamole on Myocardial Blood Flow and Left Ventricular Function in Patients With Ischemic CardiomyopathyCONGESTIVE HEART FAILURE, Issue 3 2007Mateen Akhtar MD Dipyridamole increases adenosine levels and augments coronary collateralization in patients with coronary ischemia. This pilot study tested whether a 6-month course of sustained-release dipyridamole/aspirin improves coronary flow reserve and left ventricular systolic function in patients with ischemic cardiomyopathy. Six outpatients with coronary artery disease and left ventricular ejection fraction (LVEF) <40% were treated with sustained-release dipyridamole 200 mg/aspirin 25 mg twice daily for 6 months. Myocardial function and perfusion, including coronary sinus flow at rest and during intravenous dipyridamole-induced hyperemia, were measured using velocity-encoded cine magnetic resonance stress perfusion studies at baseline, 3 months, and 6 months. There was no change in heart failure or angina class at 6 months. LVEF increased by 39%±64% (31.0%±13.3% at baseline vs 38.3%±10.7% at 6 months; P=.01), hyperemic coronary sinus flow increased more than 2-fold (219.6±121.3 mL/min vs 509.4±349.3 mL/min; P=.01), and stress-induced relative myocardial perfusion increased by 35%±13% (9.4%±3.4% vs 13.9%±8.5%; P=.004). Sustained-release dipyridamole improved hyperemic myocardial blood flow and left ventricular systolic function in patients with ischemic cardiomyopathy. [source] Design of an Ultrasound Contrast Agent for Myocardial PerfusionECHOCARDIOGRAPHY, Issue 2000Michel Schneider Ph.D. Myocardial contrast echography (MCE) has been a major research objective in cardiovascular ultrasound for almost two decades. The design of a contrast agent fulfilling the needs of MCE requires taking into consideration a number of points: a basic decision has to be made whether a deposit agent or a free-flowing agent would be more appropriate and whether an agent active at low/medium mechanical index (MI) is preferable to an agent active only at high MI; only a small percentage of the cardiac output enters the coronary microcirculation, which means that highly sensitive bubble detection methods, such as harmonic imaging or pulse inversion, are needed; the low velocity of blood in the microcirculation that leads to extensive bubble destruction during imaging means that intermittent imaging and/or an agent active at low MI is (are) required; the duration of the contrast effect must be sufficient to allow a complete examination and is affected by the rate of contrast administration; the performance of the contrast agent should not be equipment-dependent. The ultimate goal in MCE is to be able to quantify blood flow in the various segments to determine if adequate oxygenation is achieved. Ultrasound-mediated bubble destruction followed by the measurement of bubble replenishment kinetics opens new perspectives for quantification. SonoVue is a free-flowing ultrasound contrast agent made of sulphur hexafluoride microbubbles stabilized by a highly elastic phospholipid monolayer. SonoVue is able to produce myocardial opacification at a wide range of acoustic pressures and in particular at Mis as low as 0.1. Its performance is not equipment-dependent. Good results for myocardial opacification have been observed in all animal species tested (dogs, minipigs, rabbits), using continuous as well as intermittent imaging. Trials are in progress to demonstrate the clinical utility of SonoVue for rest and stress perfusion studies, in particular for the diagnosis of CAD, the detection of myocardial infarction, the assessment of the success of interventions and myocardial viability, and the detection of hibernating myocardium. [source] Evaluation of effects of rofecoxib on platelet function in an in vitro model of thrombosis with circulating human bloodEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 4 2004M. R. Hernandez Abstract Background, Cyclooxygenase (COX)-2-selective non-steroidal anti-inflammatory drugs have been used for anti-inflammatory therapy. However, it has also been described that they may increase risk of cardiovascular events. Objectives, To study the effects of COX2 inhibitor rofecoxib on platelet function using in vitro tests. Results were compared with those obtained in a parallel experiment with acetyl salicylic acid (ASA). Methods, Studies of platelet aggregation, using different agonists, were performed by a turbidimetric method. Adhesive and cohesive function of platelets were analyzed by perfusion techniques, treated blood was exposed to thrombogenic surfaces and platelet interaction was morphometrically evaluated. Results, Twenty-five µM of rofecoxib induced a prolonged lag time and a reduction in the percentage of aggregation when arachidonic acid, ADP or collagen were used as agonists. In perfusion studies with parallel chamber rofecoxib 50 µM and ASA 500 µM reduced overall platelet interaction with the collagen surface (17·4 ± 3·7, P < 0·05; vs. 32·1 ± 2·6%P < 0·05 and 17·9 ± 2·4, vs. 31·9 ± 3·24, P < 0·05, respectively). In studies performed on annular chambers, 25 µM of rofecoxib reduced platelet interaction; values of the thrombus and covered surface were 17·4 ± 4·5%; P < 0·05 and 21·1 ± 4·1%; P < 0·05, respectively, vs. 30·4 ± 7·5% and 33·5 ± 6·5 in the control. ASA did also impair thrombus formation but differences did not reach the levels of statistical significance. Moreover, rofecoxib but not ASA reduced significantly thrombus height and thrombus area (7·4 ± 0·5 µM; P < 0·005 and 96·0 ± 21·2 µM2; P < 0·05 vs. control 11·2 ± 0·9 µM and 220·0 ± 47·7µM2, respectively). Conclusion, We conclude that under our experimental conditions, rofecoxib diminished platelet aggregation induced by different agonists and inhibited platelet-mediated thrombogenesis in an in vitro model of thrombosis. [source] Susceptibility Contrast and Arterial Spin Labeled Perfusion MRI in Cerebrovascular DiseaseJOURNAL OF NEUROIMAGING, Issue 1 2003Ronald L. Wolf MD ABSTRACT Purpose. To directly compare dynamic susceptibility contrast (DSC) and continuous arterial spin labeled (CASL) magnetic resonance (MR) perfusion techniques in patients with known cerebrovascular disease, with the goals of identifying possible pitfalls in interpretation and determining potential for a complementary role in this setting. Methods. DSC and CASL MR perfusion studies were performed and compared in 11 patients with acute and/or chronic cerebrovascular disease. Using an automated segmentation technique, Pearson correlation coefficients were generated for CASL perfusion measurements compared to DSC perfusion maps (time-to-peak [TTP], relative cerebral blood volume [rCBV], cerebral blood flow [rCBF], and mean transit time [MTT]) by hemisphere and vascular territory. Results. TTP maps obtained using DSC perfusion MR correlated best both subjectively and objectively with CASL perfusion MRmeasurements when all patients studied were considered. If patients with a major transit delay were excluded, DSC rCBF correlated best with CASL CBF measurements. Conclusion. There may be a complementary role for CASL and DSC perfusion MR methods in cerebrovascular disease, especially in the setting of a marked transit delay. [source] von Willebrand factor stimulates thrombin-induced exposure of procoagulant phospholipids on the surface of fibrin-adherent plateletsJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 3 2003J. J. Briedé Summary., Studies from our laboratory have demonstrated that von Willebrand factor (VWF) stimulates thrombin generation in platelet-rich plasma. The precise role of VWF and fibrin in this reaction, however, remained to be clarified. In the present study we utilized thrombin-free planar fibrin layers and washed platelets to examine the relationship between platelet,fibrin interaction and exposure of coagulation-stimulating phosphatidylserine (PS) under conditions of low and high shear stress. Our study confirms that platelet adhesion to fibrin at a shear rate of 1000 s,1 requires fibrin-bound VWF. The cytosolic calcium concentration ([Ca2+]i) of stationary platelets was not elevated and PS exposing platelets were virtually absent (2 ± 2%). However, thrombin activation resulted in a marked increase in the number of PS exposing platelets (up to 85 ± 14%) along with a transient elevation in [Ca2+]i from 0.05 µmol L,1 up to 1.1 ± 0.2 µmol L,1. Platelet adhesion to fibrin at a shear rate of 50 s,1 is mediated by thrombin but not by fibrin-bound VWF. The [Ca2+]i of these thrombin-activated platelets was elevated (0.2 ± 0.1 µmol L,1), but only a minority of the platelets (11 ± 8%) exposed PS. The essential role of VWF in this thrombin-induced procoagulant response became apparent from low shear rate perfusion studies over fibrin that was incubated with VWF and botrocetin. After treatment with thrombin, the majority of the adherent platelets (57 ± 23%) exposed PS and had peak values of [Ca2+]i of about 0.6 µmol L,1. Taken together, these results demonstrate that thrombin-induced exposure of PS and high calcium response on fibrin-adherent platelets depends on shear- or botrocetin-induced VWF,platelet interaction. [source] Lung perfusion studies after transcatheter closure of persistent ductus arteriosus with the Amplatzer duct occluder,CATHETERIZATION AND CARDIOVASCULAR INTERVENTIONS, Issue 3 2010Tugcin Bora Polat MD Abstract Background: Reduced left lung perfusion has been described after transcatheter closure of the patent ductus arteriosus (PDA) with several prostheses. Although the Amplatzer ductal occluder (ADO) device is currently the most widely used occluder for closure of large-sized PDAs, the potential consequences of flow distribution to the lungs of this device have not been completely clarified. We evaluated lung perfusion following occlusion of PDA with the ADO device. Methods: Forty-seven patients underwent successful transcatheter PDA occlusion using the ADO device were included in this study. Lung perfusion scans were performed 6 months after the procedure. Results: Decreased perfusion to the left lung (defined as < 40% of total lung flow) was observed in 17 patients (36%), 5 of whom were low-weight symptomatic infants. Ductal ampulla length was significantly shorter and minimal ductal diameter to ampulla diameter ratio was significantly higher in patients with decreased left lung perfusion and correlated well with left lung perfusion values (r = 0.516 and r = ,0.501, respectively). A cut-off value of ,5.8 mm for the ductal ampulla length and ,1.9 for ampulla diameter to ampulla length ratio showed high sensitivity and specificity for reduced lung perfusion. Conclusions: The incidence of abnormal left lung perfusion is high 6 months after transcatheter closure of PDA with the ADO, more likely in the low weight symptomatic infants and in patients with a short duct or a relatively shallow duct having abrupt narrowing of a large ampulla. © 2010 Wiley-Liss, Inc. [source] Characteristics of patients with abnormal stress technetium Tc 99m sestamibi SPECT studies without significant coronary artery diameter stenosesCLINICAL CARDIOLOGY, Issue 11 2003Peter Ammann M.D. Abstract Background: Single-photon emission computed tomography (SPECT) sestamibi (MIBI) is an excellent tool for detection of coronary artery disease (CAD), preoperative risk assessment, and follow-up management after coronary revas-cularization. While the sensitivity of MIBI SPECT for detecting CAD has been reported to exceed 90%, the specificity ranges between 53,100%. Hypothesis: The study was undertaken to assess characteristics of patients with abnormal stress technetium Tc 99m sestamibi SPECT (MIBI) studies without significant coronary artery diameter stenoses (< 50%). Methods: Between January 1999 and November 2000, 270 consecutive patients were referred for coronary angiography due to reversible MIBI uptake defects during exercise. In 41 patients (15%; 39% women, mean age 59 ± 9 years), reversible MIBI uptake defects were assessed although coronary angiography showed no significant CAD. These patients were compared with age- and gender-matched patients with perfusion abnormalities (39% women, mean age 60 ± 9 years), due to significant CAD (coronary artery stenosis > 50%). Results: There were no significant differences between the two groups regarding body mass index, left bundle-branch block (LBBB), or method of stress test (dipyridamole in patients with LBBB or physical inactivity [n= 11] and exercise in all the others [n= 30]). Left ventricular hypertrophy (44 vs. 23%, p = 0.05) and left anterior fascicularblock (LAFB) (17 vs. 0%, p = 0.005) were more common in patients with perfusion abnormalities with no significant CAD, whereas ST-segment depression during exercise (17 vs. 37% p = 0.05) and angina during exercise (15 vs. 29%, p = 0.02) were significantly less common than in patients with abnormal MIBI perfusion studies and angiographically significant CAD. Sestamibi uptake defects during exercise were significantly smaller in patients without significant CAD than in matched controls with significant CAD (p < 0.0004). Conclusion: Of 270 consecutive patients, 41 (15%) referred to coronary angiography due to reversible MIBI uptake defects showed coronary artery stenoses <50%. Twenty-six (10%) of these presented angiographically normal coronary arteries. The significantly higher proportion of left ventricular hypertrophy and LAFB in patients with reversible MIBI uptake defects without significant CAD suggest microvascular disease, angiographically underestimated CAD, and conduction abnormalities as underlying mechanisms. [source] | ||||||||||