Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “EMBOLISM”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,045 records · Page 58Linked to original sources
PubMedDate not supplied

CT angiography of pulmonary embolism: diagnostic criteria and causes of misdiagnosis.

Computed tomographic (CT) pulmonary angiography is becoming the standard of care at many institutions for the evaluation of patients with suspected pulmonary embolism. This pathologic condition, whether acute or chronic, causes both partial and complete intraluminal filling defects, which should have a sharp interface with intravascular contrast material. In acute pulmonary embolism that manifests as complete arterial occlusion, the affected artery may be enlarged. Partial filling defects due to acute pulmonary embolism are often centrally located, but when eccentrically located they form acute angles with the vessel wall. Chronic pulmonary embolism can manifest as complete occlusive disease in vessels that are smaller than adjacent patent vessels. Other CT pulmonary angiographic findings in chronic pulmonary embolism include evidence of recanalization, webs or flaps, and partial filling defects that form obtuse angles with the vessel wall. Factors that cause misdiagnosis of pulmonary embolism may be patient related, technical, anatomic, or pathologic. The radiologist needs to determine the quality of a CT pulmonary angiographic study and whether pulmonary embolism is present. If the quality of the study is poor, the radiologist should identify which pulmonary arteries have been rendered indeterminate and whether additional imaging is necessary.

Adult↗
PubMed1990

Pulmonary vascular pressure-flow characteristics in canine pulmonary embolism.

We tested the hypothesis that, in canine embolic pulmonary hypertension, upstream transmission of increased left atrial pressure (LAP) is inversely related to the level of the pressure intercept (PI) obtained by extrapolation from the linear pulmonary vascular pressure-flow (P-Q) plot. P-Q coordinates were obtained by varying Q through systemic fistulas. Seven group 1 dogs were embolized with autologous blood clot to produce marked pulmonary hypertension and mean pulmonary arterial pressure (PAP), and PI increased from 15 to 41 mmHg (P less than 0.001) and from 8.8 to 31 mmHg (P less than 0.001), respectively. Before and after embolization we assessed effects of increased LAP, produced by inflation of a left atrial balloon, on PAP at constant Q. Embolization depressed the mean slope of this relationship from 0.78 to 0.16 (P less than 0.001). Subsequently, six group 2 dogs were embolized to produce moderate pulmonary hypertension with a mean PI of 22 mmHg. This value was significantly less than PI in group 1 (P less than 0.01). After embolization, the slope of the PAP-LAP relationship was greater in group 2 than group 1: 0.47 vs. 0.16 (P less than 0.01). We conclude that the upstream transmission of left atrial pressure is inversely related to PI and that marked embolic pulmonary hypertension produces an effective vascular waterfall.

Animals↗
PubMed1998

Disrupted mobile aortic plaques are a major risk factor for systemic embolism in the elderly.

Protruding aortic plaques--especially those with mobile properties--on transesophageal echocardiography (TEE) are a potential source of stroke and systemic embolism in the elderly. Whether the various morphologies of atheromas with mobile components represent potential differences in the risk for embolic events has not been thoroughly elucidated. The goal of the present study was to determine the association between embolic events and the various types of mobile lesions in the thoracic aorta. Our population consisted of 569 consecutive patients (age 18-83 years) referred for TEE over 27 months; 108 (19%) of them were referred to evaluate recent embolism (cerebral in 97 and peripheral or both in 11; group I) and the remaining 461 were admitted for reasons unrelated to embolism (group II). In group I, 35 patients (32%) exhibited protruding plaques; those were fixed in 10 (9%) and with a mobile component in 25 (23%). In group II, plaques were found in only 13 patients (3%); fixed in 9 (2%) and mobile in 4 (1 %). Twenty-four patients with mobile lesions in group I were > 50 years old, and 21 of them (88%) were > 60 years old. While the presence of fixed plaques was associated with a moderate increase in the risk for systemic embolism (adjusted odds ratio 4.1; 95% confidence interval 1.3-56.4), mobile lesions were linked to a striking augmentation of this risk (odds ratio 30.1; 95% confidence interval 7.8-132.6). The majority of mobile lesions (76%) in group I represented disrupted atheromas with characteristic ulcerations or echolucency within the plaque suggestive of intraatheroma hemorrhage, whereas these TEE features were not observed in 89% of the mobile lesions in group II (p = 0.0003). We conclude that among the various types of mobile aortic lesions, the disrupted protruding plaques are a major risk factor for stroke and embolic events in the elderly.

Adolescent↗
PubMed2005

Percutaneous embolization for cervicofacial neoplasms and hemorrhages.

OBJECTIVE: To retrospectively assess the effectiveness of percutaneous embolization for curative, preoperative or palliative management of hypervascular neoplasms, vascular malformations and bleedings of the head and neck area. METHODS: A retrospective 8-year analysis of outcomes in 85 patients undergoing preoperative embolization for tumors or vascular lesions of the head and neck or embolization for refractory tumor bleeding and epistaxis at our hospitals was performed by reviewing case records. Outcome of the preoperatively embolized patients was defined as successful if intraoperative bleeding was <500 ml and/or postinterventional angiogram showed complete occlusion of all tumor-feeding or bleeding vessels. RESULTS: Complete preoperative tumor embolization was achieved in 83.5% of the patients. Partial embolization was possible in 10.5%. All tumor bleedings refractory to conservative therapy and bleedings from epistaxis showed a successful outcome. CONCLUSIONS: In vascular lesions and tumors of the head and neck, preoperative percutaneous embolization improved the surgical outcome, reduced intraoperative blood loss significantly and facilitated tumor resectability. Cervicofacial bleeding resulting from a tumor, vascular malformation or epistaxis can be managed effectively by endovascular techniques.

Adult↗
PubMed1997

Plasma levels of atrial natriuretic peptide and endothelin-1 in experimental fat embolism.

In order to understand the role of vasoactive peptides in fat embolism, arterial plasma atrial natriuretic peptide (ANP) and endothelin-1 concentrations were investigated in an experimental study. Nine anesthetized and mechanically ventilated pigs received an intracaval infusion of allogeneic bone marrow suspension at a dose of 100 mg/kg (fat embolism group); 9 control pigs received saline. The observation period was 5 h. In the fat embolism group, cardiac index and heart rate decreased within 30 min, whereas mean arterial pressure remained stationary. Pulmonary capillary wedge pressure rose transiently and central venous pressure rose slightly in time, while mean pulmonary arterial pressure, pulmonary vascular resistance and pulmonary shunt increased immediately and persistently after the bone marrow suspension infusion. Simultaneously, arterial oxygen tension and arterial hemoglobin oxygen saturation decreased markedly. Arterial plasma ANP and endothelin-1 concentrations remained stable in the fat embolism animals, whereas in the controls ANP and endothelin-1 levels decreased at 3 and 5 h. Arterial epinephrine concentrations were stable in animals receiving bone marrow suspension, while in the controls arterial epinephrine concentrations decreased towards the end of the experiment. Arterial norepinephrine concentrations remained unchanged in both groups. To conclude, impaired pulmonary function and consequent systemic hypoxemia distinguish the present fat embolism model. Unchanged arterial ANP and endothelin-1 concentrations in the fat embolism group suggest that these circulating vasoactive hormones have a minor impact on the pathogenesis of the current experimental fat embolism.

Animals↗
PubMed2002

Transcatheter closure of interatrial communications for secondary prevention of paradoxical embolism: single-center experience.

BACKGROUND: Patients with a patent foramen ovale (PFO) after cerebral, coronary, or systemic embolic events of presumed paradoxical origin are at risk for recurrent thromboembolism. We report our single-center experience of interventional closure of interatrial communications for secondary prevention of presumed paradoxical embolism. Methods and Results- Since 1997, percutaneous closure of interatrial communications was performed at our institution in 66 patients (mean age 47.8+/-12.7 years; 31 males) with a PFO or an atrial septal defect and at least 1 documented presumed paradoxical thromboembolic event. Fifty-eight patients had cerebral embolism, 10 had coronary embolism, and 3 had peripheral embolism. Several patients experienced multilocal arterial embolism. Fifty-four patients had a PFO, 33 of them with an atrial septal aneurysm, and 12 had an atrial septal defect. The implantation procedure was successful and without complication in all patients. After 3 months, only 2 patients showed a residual shunt, which disappeared in both cases after 12 months. In 112.2 patient-years of follow-up (range, 5 weeks to 3.5 years), we have not seen any recurrent thromboembolic event. CONCLUSIONS: Interventional closure of interatrial communications is a safe and effective therapeutic option for the secondary prevention of presumed paradoxical embolism. To further evaluate this strategy, randomized trials comparing interventional closure with anticoagulation have been initiated by us and others.

Adolescent↗
PubMed2002

S-nitrosoglutathione reduces asymptomatic embolization after carotid angioplasty.

BACKGROUND: The major complication of carotid angioplasty is embolic stroke, which may occur after balloon inflation and deflation or in the early postintervention period. Platelet adhesion and aggregation to the angioplasty site with subsequent embolization seems to plays a major role in early postangioplasty embolization and stroke. During this period, asymptomatic embolic signals can be detected in patients by transcranial Doppler ultrasound despite aspirin and heparin treatment. S-nitrosoglutathione (GSNO) is a nitric oxide donor that appears to have relative platelet specificity. We evaluated its effectiveness in reducing embolization after carotid angioplasty. METHODS AND RESULTS: Sixteen patients undergoing carotid angioplasty and stenting for symptomatic > or =70% internal carotid artery stenosis were randomized in a double-blind manner to GSNO or placebo given after surgery for 90 minutes. All patients were pretreated with aspirin and given heparin for 24 hours after the procedure. Transcranial Doppler recordings were made from the ipsilateral middle cerebral artery for 1 hour before treatment and at 0 to 3, 6, and 24 hours after treatment. GSNO resulted in a rapid reduction in the frequency of embolic signals of 95% at 0 to 3 hours and 100% at 6 hours (P=0.007 and P=0.01 versus placebo, respectively). In the placebo group, 2 patients experienced ipsilateral stroke after the angioplasty. No cerebrovascular events occurred in the GSNO group. CONCLUSIONS: S-nitrosoglutathione was highly effective in rapidly reducing the frequency of embolic signals after endovascular treatment for symptomatic high-grade carotid stenosis.

Angioplasty↗
PubMed2004

Thrombolysis compared with heparin for the initial treatment of pulmonary embolism: a meta-analysis of the randomized controlled trials.

BACKGROUND: Randomized trials and meta-analyses have reached conflicting conclusions about the role of thrombolytic therapy for the treatment of acute pulmonary embolism. METHODS AND RESULTS: We performed a meta-analysis of all randomized trials comparing thrombolytic therapy with heparin in patients with acute pulmonary embolism. Eleven trials, involving 748 patients, were included. Compared with heparin, thrombolytic therapy was associated with a nonsignificant reduction in recurrent pulmonary embolism or death (6.7% versus 9.6%; OR 0.67, 95% CI 0.40 to 1.12, P for heterogeneity=0.48), a nonsignificant increase in major bleeding (9.1% versus 6.1%; OR 1.42, 95% CI 0.81 to 2.46), and a significant increase in nonmajor bleeding (22.7% versus 10.0%; OR 2.63, 95% CI 1.53 to 4.54; number needed to harm=8). Thrombolytic therapy compared with heparin was associated with a significant reduction in recurrent pulmonary embolism or death in trials that also enrolled patients with major (hemodynamically unstable) pulmonary embolism (9.4% versus 19.0%; OR 0.45, 95% CI 0.22 to 0.92; number needed to treat=10) but not in trials that excluded these patients (5.3% versus 4.8%; OR 1.07, 95% CI 0.50 to 2.30), with significant heterogeneity between these 2 groups of trials (P=0.10). CONCLUSIONS: Currently available data provide no evidence for a benefit of thrombolytic therapy compared with heparin for the initial treatment of unselected patients with acute pulmonary embolism. A benefit is suggested in those at highest risk of recurrence or death. The number of patients enrolled in randomized trials to date is modest, and further evaluation of the efficacy and safety of thrombolytic therapy for the treatment of high-risk patients with acute pulmonary embolism appears warranted.

Acute Disease↗
PubMed1983

Echocardiographic tissue characterization and range-gated Doppler ultrasound for the diagnosis of pulmonary embolism.

We evaluated reflection and absorption indexes of ultrasound as well as Doppler estimates of intrapulmonary blood flow for diagnosing pulmonary embolism. The pulmonary reflection coefficient (PRC), coefficient of tissue attenuation (alpha R) and range-gated blood Doppler signals were studied in 25 patients with pulmonary embolism, 19 with pneumonia, nine with atelectasis, 20 with congestive heart failure, 20 with chronic obstructive lung disease and 10 normal subjects. The PRC was significantly diminished in pulmonary embolism, pneumonia and atelectasis, but was not altered by underlying chronic obstructive lung disease or congestive heart failure. The alpha R in pulmonary embolism was 1.03 +/- 0.04 db/MHz cm, significantly lower than that for pneumonia, 1.48 +/- 0.03 db/MHz cm (p less than 0.001), but not significantly different from that for atelectasis, 0.95 +/- 0.05 db/MHz cm. Doppler signals indicating blood flow in the affected area of lung were present in only two of 25 patients with pulmonary embolism, compared with seven of nine with atelectasis and 17 of 19 with pneumonia. The combined use of PRC, alpha R and blood Doppler signals correctly diagnosed pulmonary embolism in 23 of 25 patients. Thus, ultrasound offers a reliable noninvasive method for diagnosis of pulmonary embolism.

Echocardiography↗
PubMed1988

Ventricular interaction during experimental acute pulmonary embolism.

Although stroke volume may decrease markedly after acute pulmonary embolism, left ventricular end-diastolic pressure (LVEDP) usually changes very little, which suggests that compliance or contractility or both are reduced. To test the hypothesis that the altered LV function during pulmonary embolism is primarily due to reduced preload mediated by increased pericardial constraint, hemodynamics and chamber dimensions (measured by sonomicrometry) were assessed in seven anesthetized dogs during control volume loading, after pulmonary embolism (with autologous blood clot), and after repeated pulmonary embolism in the volume-loaded state. The correlation between LVEDP and an index of LVED volume (LVED area index) throughout a wide range of LVEDP before and after embolism was poor (mean r = 0.42; range, 0-0.82). However, the correlation between transmural LVEDP (LVEDP-directly measured pericardial pressure) and LVED area index (mean r = 0.78; range, 0.61-0.94) was significantly higher (p = 0.03). Similarly, an index of stroke work (LV area stroke work) correlated less well (p less than 0.01) with LVEDP (mean r = 0.43; range, 0.07-0.77) than with transmural LVEDP (mean r = 0.82; range, 0.68-0.92). LV area stroke work also correlated well with the LV area index (mean r = 0.84; range, 0.70-0.95). These data indicate that neither compliance nor contractility is substantially altered during acute pulmonary embolism. The altered LV performance is due to reduced LV preload as reflected by a decrease in transmural LVEDP. This study also demonstrates that LVEDP is a poor index of LV preload during pulmonary embolism, whereas transmural LVEDP accurately reflects LVED dimensions.

Acute Disease↗
PubMedDate not supplied

Early recurrent embolism associated with nonvalvular atrial fibrillation: a retrospective study.

Nonvalvular atrial fibrillation (NVAF) can be a source of cardiogenic brain embolism. We retrospectively reviewed the clinical features of 56 patients with acute brain infarction and NVAF. Based on clinical criteria, 35 infarcts (63%) were classified as probably embolic, 13 infarcts (23%) as probably nonembolic and 8 infarcts (14%) as of indeterminate pathogenesis. Among the 35 patients with presumed embolic infarcts, 12 patients were immediately anticoagulated without hemorrhagic complications. Of 23 patients who did not receive immediate anticoagulation, three (13%) experienced recurrent embolism (one each to brain, kidney and leg) within 10 days of initial embolism. There were no early recurrent emboli in patients receiving immediate anticoagulation or patients in the nonembolic or indeterminate category. Five additional patients experienced probable brain or systemic emboli within the 11 days prior to the marker stroke event. Including these patients, 20% (8 of 40) of all NVAF patients who were not immediately anticoagulated experienced recurrent embolism within 11 days of the initial embolus. Early recurrent emboli are common in NVAF patients who experience embolic stroke.

Adult↗
PubMed1993

Acute ischemic stroke from fibrocartilaginous embolism to the middle cerebral artery.

BACKGROUND AND PURPOSE: Fibrocartilaginous embolism from the nucleus pulposus has been reported as a rare cause of spinal cord ischemia. We were unable to find previous reports of embolism from this source to cerebral arteries. CASE DESCRIPTION: A previously healthy 17-year-old girl fell during a basketball game. Left hemiparesis and unresponsiveness developed followed by signs of right uncal herniation and death over a 3-day period. There was no evidence of neck, head, or spine trauma, and cardiac evaluation was normal. Neuropathological examination showed extensive ischemic infarction of the right middle cerebral artery territory, brain edema, and herniation. Complete embolic occlusion of the right middle cerebral artery by fibrocartilaginous material, consistent with nucleus pulposus, was documented. Small, terminal coronary artery branches also showed embolism by the same material and limited areas of myocardial infarction. CONCLUSIONS: Acute cerebral embolism after minor trauma in a young patient may be rarely due to fibrocartilaginous embolism from the nucleus pulposus. The pathogenesis of this problem remains poorly understood, but systemic embolism appeared to have occurred in this case.

Adolescent↗
PubMed1995

Asymptomatic cerebral embolic signals in patients with carotid stenosis. Correlation with appearance of plaque ulceration on angiography.

BACKGROUND AND PURPOSE: Asymptomatic cerebral emboli may be detected in patients with carotid stenosis by transcranial Doppler ultrasonography of the middle cerebral artery (MCA). The aim of this study was to determine the angiographic correlates of such embolic signals. METHODS: Doppler signals from 48 MCAs in 26 patients with carotid stenosis that was either symptomatic (n = 20) or asymptomatic (n = 6) were recorded for 40 minutes. The grade of carotid stenosis and the ulcerated or nonulcerated appearance of the plaque were assessed using the criteria of the North American Symptomatic Carotid Endarterectomy Trial. RESULTS: Embolic signals were detected in 8 MCAs from 7 patients; 4 (50%) of these MCAs were clinically symptomatic compared with 16 (40%) without embolic signal. Although there was a trend toward more severe stenosis in the cases with embolic signals, this was not significant (mean +/- SD, 67 +/- 29% versus 55 +/- 36%). In contrast, an image of ulceration was found on ipsilateral carotid angiography in 5 cases (63%) with embolic signals and in only 9 cases (23%) without embolic signals (odds ratio, 5.74; 95% confidence interval, 1.15 to 28.79, by multivariate regression analysis). CONCLUSIONS: This study demonstrates that the occurrence of embolic signals in patients with carotid stenosis is associated with the appearance of plaque ulceration on angiography.

Carotid Arteries↗
PubMed1997

Use of a decibel threshold in detecting Doppler embolic signals.

BACKGROUND AND PURPOSE: To improve reproducibility and reliability in the identification of embolic signals detected with the use of Doppler ultrasound, many studies have used an intensity threshold. However, variable thresholds between 3 and 12 dB have been used, and often the method of measurement of intensity is not stated. Potentially different methods of measurement could result in different intensity measurements for the same embolic signal. We determined the effect of these differences using commercial transcranial Doppler systems. METHODS: We analyzed 81 embolic signals recorded from the middle cerebral arteries of patients with carotid artery disease using three different methods of measuring intensity that had been previously used in research studies. In method 1 individual time frames of the frequency spectra were analyzed, in method 2 a color-coded intensity scale was used, and in method 3 automated software was used. RESULTS: There was a highly significant correlation between measurements made by the different techniques (method 1 versus method 2: r = .68, P < .0001; method 1 versus method 3: r = .66, P < .0001; method 2 versus method 3: r = .70, P < .0001). However, the absolute values of intensity for the same embolic signals varied markedly for the different methods. For example, a 4-dB threshold according to method 1 was equivalent to an approximately 7-dB threshold measured by method 2. These differences had major effects on the proportion of embolic signals detected with the use of the same decibel threshold but with intensity measured in the different ways. For example, using a threshold of 7 dB would result in only 4.9% of signals being missed by method 2 but 42.2% and 51.4% being missed by methods 1 and 3, respectively. CONCLUSIONS: Our results demonstrate that the intensities of the same embolic signals, recorded with the same parameters, are markedly different when analyzed in the different ways used in previous studies. This has important implications when a decibel threshold is used and emphasizes that criteria developed by one investigator on one machine cannot be used by another investigator without initial reevaluation. This could account for some of the differences in frequencies of embolic signals reported in previous clinical studies.

Differential Threshold↗
PubMed1997

Intercenter agreement in reading Doppler embolic signals. A multicenter international study.

BACKGROUND AND PURPOSE: Different frequencies of asymptomatic Doppler embolic signals have been reported in studies. There has been concern that different criteria for identification may account for some of this variation. A previous reproducibility study between two centers found good agreement, but no studies among large numbers of centers have been performed. We performed an international reproducibility study among nine centers, each of which had published recent studies of embolic signal detection in peer-reviewed journals. METHODS: Each center performed blinded analysis of a taped audio Doppler signal composed of transcranial Doppler middle cerebral artery recordings from 6 patients with symptomatic carotid artery stenosis. The exact time of any embolic signal was recorded. Six centers also measured the intensity increase of any embolic signals detected. Interobserver agreement was determined by a method based on the proportion of specific agreement. RESULTS: Seven centers reported between 39 and 55 signals, but one center reported 142 embolic signals. The probability of agreement between observers was .678, which rose to .791 when the data from the highest reporting center were excluded. Introducing a decibel threshold resulted in a significant increase in the probability of agreement; a decibel threshold of > 7 dB resulted in a probability of agreement of .902. Intensity measurements made by different centers were usually highly correlated, but this was not always the case, and 3 of the 15 correlations were not significant. The absolute values of the intensities measured varied between centers by as much as 40%. CONCLUSIONS: Although most centers report similar numbers of embolic signals, some use less specific criteria and report more events. The use of a decibel threshold improves reproducibility. However, intensity thresholds developed by one center cannot be directly transferred without validation to another center; differing methods of measurement are being used, and this results in different intensity values for the same embolic signals, even when the same equipment is used.

Carotid Stenosis↗
PubMed2002

In situ beta radiation to prevent recanalization after coil embolization of cerebral aneurysms.

BACKGROUND AND PURPOSE: Endovascular treatment of cerebral aneurysms, a minimally invasive alternative to surgery, is too often followed by recanalization and recurrences. The purpose of this work was to assess if in situ beta radiation can inhibit recanalization after coil embolization. METHODS: Radioactive platinum coils (32P-coils) were produced by ion implantation of 32P. A single-coil arterial occlusion model was used to compare angiographic and pathological results at 1 to 12 weeks after nonradioactive and 32P-coil embolization of maxillary, cervical, and vertebral arteries in 26 dogs. Coils of varying activities were used and results compared to define the minimal activity required to inhibit recanalization. Similar experiments were performed in 16 porcine maxillary and lingual and 8 rabbit axillary arteries. Results of 32P-coil embolization of bifurcation aneurysms were then compared with embolization with nonradioactive coils in 12 dogs at 3 months. RESULTS: Nonradioactive coil embolization of canine arteries led to occlusion at 1 week, followed by recanalization at 2 weeks, which persisted at 3 months in all cases. 32P-coils, ion-implanted with activities above 0.13 microCi/cm, led to persistent occlusion at 3 months in 80% of arteries. 32P-coils ion-implanted with the same activity inhibited recanalization in porcine and rabbit arteries. Bifurcation aneurysms treated with 32P-coils had better angiographic results at 3 months (P=0.006) than aneurysms treated with nonradioactive coils. Arteries occluded were filled with fibrous tissue at 3 months. Aneurysms embolized with 32P-coils showed more complete neointimal coverage of the neck, without recanalization, as compared with aneurysms treated with nonradioactive coils. CONCLUSION: In situ low-dose beta radiation inhibits recanalization after coil embolization and may improve long-term results of endovascular treatment of aneurysms.

Animals↗
PubMed1990

Granulocyte depletion attenuates sustained pulmonary hypertension and increased pulmonary vasoreactivity caused by continuous air embolization in sheep.

Chronic pulmonary hypertension can develop in diseases associated with acute or repeated inflammation in the lungs, e.g., adult respiratory distress syndrome, chronic bronchitis. Inflammation has also been associated with some animal models of chronic pulmonary hypertension. We have previously shown that 12 days of continuous air embolization into sheep results in the functional and structural changes of chronic pulmonary hypertension. To determine whether granulocytes contribute to these changes, five sheep were granulocyte-depleted with hydroxyurea immediately before and during air embolization (AIR-PMN) and were compared with sheep receiving air embolization (AIR only). Air embolization was discontinued briefly every 4 days for monitoring of pulmonary vascular pressures and assessment of pulmonary vasoreactivity to a bolus injection of PGH2-A. After 12 days of air embolization, the lungs were removed for structural studies. AIR-PMN sheep did not develop the sustained increase in pulmonary artery pressure seen in the AIR sheep (Day 12, AIR-PMN = 20 +/- 3 cm H2O; AIR = 29 +/- 2; mean +/- SE). Similarly, the increased pulmonary pressor response to PGH2-A seen in AIR sheep was not found in the AIR-PMN group. Structural studies of the barium-injected lungs of AIR-PMN sheep revealed a twofold increase in medial thickness of normally muscular arteries and a significant increase in the percent of muscular intraacinar arteries (similar to findings in lungs from AIR sheep). The number of barium-filled arteries was increased in AIR-PMN sheep when compared with that in AIR sheep, but the number was still less than in the control sheep. We conclude that granulocytes may contribute to the functional changes of chronic pulmonary hypertension after continuous air embolization in sheep, but they do not play a role in structural changes involving pulmonary arterial smooth muscle cells and their precursors. The present data also suggest that the reduction in peripheral arterial filling is the structural alteration that contributes most to the sustained rise in pulmonary artery pressure. The data further suggest that pulmonary hypertension after air embolization may have a vasoconstrictive component that is granulocyte-dependent.

Animals↗
PubMed1992

Treatment of pulmonary arteriovenous malformations by therapeutic embolization. Rest and exercise physiology in eight patients.

Pulmonary arteriovenous malformations (AVM) lead to chronic hypoxemia and systemic emboli. These lesions can now be treated by catheter embolization. In order to examine physiologic abnormalities during exercise in AVM patients, and to evaluate functional improvement after therapeutic embolization, eight patients underwent detailed physiologic studies at rest and during exercise before and after therapeutic embolization. Before treatment, six patients noted dyspnea on exertion and three had symptoms suggesting paradoxical embolism. Resting studies showed hypoxemia, abnormally increased shunt fractions, chronic alveolar hyperventilation, mild decreases in diffusing capacity, and abnormal wasted ventilation (VD). During exercise, oxygenation changed little from the resting values but VD increased markedly. Functional impairment was observed in most patients, and was correlated with shunt fraction. Obliteration of the AVM was accomplished by therapeutic embolization with placement of coils or balloons in the feeder vessels. This treatment resulted in immediate relief of dyspnea and improvement in resting PaO2 and shunt fraction. Exercise studies after embolization showed improvement in exercise capacity and gas exchange. However, chronic alveolar hyperventilation and reduced diffusing capacity remained unchanged. In summary, therapeutic embolization effectively reduces the degree of shunting, with improvement in respiratory symptoms, exercise capacity, and gas exchange at rest and during exercise. The abnormally decreased diffusing capacity and increased VD suggest the presence of a diffuse pulmonary vascular abnormality, of which further study is warranted.

Adult↗