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Aim: To describe the causes and computed tomography (CT) and angiographic appearances of transpleural systemic artery-to-pulmonary artery shunts in patients without chronic inflammatory lung disease and determine their best management., Materials and Methods: All patients referred to a tertiary referral unit between January 2009 and January 2020 in whom a diagnosis of a systemic-to-pulmonary artery communication without underlying chronic inflammatory lung disease was subsequently made have been included in this report. Medical records and imaging findings were reviewed retrospectively., Results: Ten patients (male: female ratio = 7:3; median age 42 years [range 22-70 years]) with systemic artery-to-pulmonary artery shunts without chronic inflammatory lung disease were identified. Five were misdiagnosed as having a pulmonary arteriovenous malformation and had been referred for embolisation. In six patients, there was either a history of accidental or iatrogenic thoracic trauma or of inflammatory disease involving the pleura, and in two patients, in whom a previous medical history could not be obtained, there were CT features suggesting previous pleural inflammatory disease. Two shunts were thought to be congenital. All individuals were asymptomatic other than one with localised thoracic discomfort that dated from the time of surgery. All patients were managed conservatively and have remained well with a median follow-up of 4.5 years (range 1-11.3 years)., Conclusions: Localised transpleural systemic artery-to-pulmonary artery shunts in the absence of chronic inflammatory lung disease are usually related to previous thoracic trauma/intervention or abdominal or pulmonary sepsis involving a pleural or diaphragmatic surface. Congenital shunts are rare. The present study and much of the literature supports conservative management., (Copyright © 2021 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.)

Objective: To examine the MRI safety of metallic coils and Amplatzer vascular plugs. Currently, concern regarding MR safety of devices used to treat pulmonary arteriovenous malformations (PAVMs) causes delays in performing emergency MRI in patients presenting with acute neurological symptoms., Methods: A retrospective audit was performed on all patients who underwent PAVM embolization at Hammersmith Hospital, London UK between 1984 and 2017. Outcomes of all MRI studies performed at our institution were recorded. In addition, known outcomes of all known MRI studies performed on patients treated with the earliest steel coils (1984-1995) were recorded., Results: At our institution, 20 patients underwent 1.5 T MRI after the insertion of 100 steel coils (15.5 - 28.6, median 22 years later), 140 coils designated MR-conditional (0.42 - 12.7, median 9.3 years later), and 54 MRI-conditional Amplatzer vascular plugs (0.17 - 8.0, median 0.75 years later) , many in combination. The majority of scans were for cerebral indications, but other body regions scanned included spinal, thoracic, and pelvic regions. No adverse events were reported. Similarly, there were no adverse events in any MR scan known to have been performed in other institutions in seven further patients treated with the earliest steel coils (1984-1995). Again, the majority of scans were for cerebral indications., Conclusion: The findings demonstrate MR safety at 1.5 T of all PAVM embolization devices inserted in a main UK centre since inception in 1984., Advances in Knowledge: MRI of patients who have had PAVMs treated by embolization can be implemented without contacting specialist pulmonary arteriovenous malformation treatment centres for approval.

Pulmonary arteriovenous malformations (PAVMs) are abnormal communications between the pulmonary arteries and veins, which result in a right-to-left (R-L) shunt with resultant hypoxemia, the severity of which will depend upon the size and number of lesions. Most PAVMs occur in individuals with hereditary haemorrhagic telangiectasia (HHT) and are a cause of serious morbidity and mortality largely related to cerebrovascular complications secondary to paradoxical embolization. The importance of their recognition and treatment by embolization, even in the absence of symptoms, is well known. Their appearances on chest radiographs are often, but not always, characteristic and the CT appearances are diagnostic; however, there are a number of both vascular and non-vascular diseases that can cause confusion. This review serves to highlight these PAVM "mimics"., (Copyright © 2014 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.)

Background: Patients with pulmonary arteriovenous malformations (PAVMs) are unusual because hypoxemia results from right-to-left shunting and not airway or alveolar disease. Their surprisingly well-preserved exercise capacity is not generally appreciated., Methods: To examine why exercise tolerance is preserved, cardiopulmonary exercise tests were performed while breathing room air in 21 patients with radiologically proven PAVMs, including five restudied 3 to 12 months after embolization when their PAVMs had regressed. Where physiologic matching was demonstrable, comparisons were made with 12 healthy control subjects., Results: The majority of patients achieved their predicted work rate despite a resting arterial oxygen saturation (SaO₂) of 80% to 96%. Peak work rate and oxygen consumption (VO₂) were no lower in patients with more hypoxemia. Despite higher SaO₂ following embolization (median, 96% and 90%; P = .009), patients achieved similar work rates and similar peak VO₂. Strikingly, treated patients reset to virtually identical peak oxygen pulses (ie, VO₂ per heart beat) and in many cases to the same point on the peak oxygen pulse/work rate plot. The 21 patients had increased minute ventilation (VE) for given increases in CO₂ production (VE/VCO₂ slope), but perceived dyspnea was no greater than in the 12 control subjects or in the same patients before compared to after embolization comparison. Overall, work rate and peak VO₂ were associated not with oxygenation parameters but with VE/VCO₂ slope, BMI, and anaerobic threshold., Conclusions: Patients with hypoxemia and PAVMs can maintain normal oxygen delivery/VO₂ during peak exercise. Following improvement of SaO₂ by embolization, patients appeared to reset compensatory mechanisms and, as a result, achieved similar peak VO₂ per heart beat and peak work rates.

Background: Pulmonary first pass filtration of particles marginally exceeding ∼7 µm (the size of a red blood cell) is used routinely in diagnostics, and allows cellular aggregates forming or entering the circulation in the preceding cardiac cycle to lodge safely in pulmonary capillaries/arterioles. Pulmonary arteriovenous malformations compromise capillary bed filtration, and are commonly associated with ischaemic stroke. Cohorts with CT-scan evident malformations associated with the highest contrast echocardiographic shunt grades are known to be at higher stroke risk. Our goal was to identify within this broad grouping, which patients were at higher risk of stroke., Methodology: 497 consecutive patients with CT-proven pulmonary arteriovenous malformations due to hereditary haemorrhagic telangiectasia were studied. Relationships with radiologically-confirmed clinical ischaemic stroke were examined using logistic regression, receiver operating characteristic analyses, and platelet studies., Principal Findings: Sixty-one individuals (12.3%) had acute, non-iatrogenic ischaemic clinical strokes at a median age of 52 (IQR 41-63) years. In crude and age-adjusted logistic regression, stroke risk was associated not with venous thromboemboli or conventional neurovascular risk factors, but with low serum iron (adjusted odds ratio 0.96 [95% confidence intervals 0.92, 1.00]), and more weakly with low oxygen saturations reflecting a larger right-to-left shunt (adjusted OR 0.96 [0.92, 1.01]). For the same pulmonary arteriovenous malformations, the stroke risk would approximately double with serum iron 6 µmol/L compared to mid-normal range (7-27 µmol/L). Platelet studies confirmed overlooked data that iron deficiency is associated with exuberant platelet aggregation to serotonin (5HT), correcting following iron treatment. By MANOVA, adjusting for participant and 5HT, iron or ferritin explained 14% of the variance in log-transformed aggregation-rate (p = 0.039/p = 0.021)., Significance: These data suggest that patients with compromised pulmonary capillary filtration due to pulmonary arteriovenous malformations are at increased risk of ischaemic stroke if they are iron deficient, and that mechanisms are likely to include enhanced aggregation of circulating platelets.

Increasing evidence supports the use of embolisation to treat pulmonary arteriovenous malformations (AVMs). Most pulmonary AVM patients have hereditary haemorrhagic telangiectasia (HHT), a condition that may be associated with pulmonary hypertension. The current authors tested whether pulmonary AVM embolisation increases pulmonary artery pressure (P(pa)) in patients without baseline severe pulmonary hypertension. P(pa) was measured at the time of pulmonary AVM embolisation in 143 individuals, 131 (92%) of whom had underlying HHT. Angiography/embolisation was not performed in four individuals with severe pulmonary hypertension, whose systemic arterial oxygen saturation exceeded levels usually associated with dyspnoea in pulmonary AVM patients. In 143 patients undergoing pulmonary AVM embolisation, P(pa) was significantly correlated with age, with the most significant increase occurring in the upper quartile (aged >58 yrs). In 43 patients with repeated measurements, there was no significant increase in P(pa) as a result of embolisation. In half, embolisation led to a fall in P(pa). The maximum rise in mean P(pa) was 8 mmHg: balloon test occlusion was performed in one of these individuals, and did not predict the subsequent rise in P(pa) following definitive embolisation of the pulmonary AVMs. In the present series of patients, which excluded those with severe pulmonary hypertension, pulmonary artery pressure was not increased significantly by pulmonary arteriovenous malformation embolisation.

Background: Brain abscesses and ischaemic strokes complicate pulmonary arteriovenous malformations (PAVMs). At risk individuals are poorly recognised. Stroke/abscess risk factors have not been defined., Methods: A cohort study of 323 consecutive individuals with PAVMs (n = 219) and/or the commonly associated condition hereditary haemorrhagic telangiectasia (HHT, n = 305) was performed. Most of the 201 individuals with PAVMs and HHT had no respiratory symptoms, and were unaware they had HHT. Anderson-Gill models assessed constant and time dependent potential predictive variables for stroke/abscess, and rate reduction by PAVM embolisation., Results: 57 individuals with PAVMs and HHT experienced brain abscess or ischaemic stroke, usually prior to the diagnosis of underlying PAVMs/HHT. The primary determinants of stroke and abscess risks were unrelated to severity of PAVMs. Males had higher brain abscess rates (hazard ratio 3.61 (95% CI 1.58, 8.25), p = 0.0024); interventional histories and bacteriological isolates suggested dental sources. Once adjusted for gender, there was a marginal association between brain abscess and low oxygen saturation. For ischaemic stroke, there was no association with any marker of PAVM severity, or with conventional neurovascular risk factors. Surprisingly, low mean pulmonary artery pressure was strongly associated with ischaemic stroke (hazard ratio 0.89 (95% CI 0.83, 0.95) per mm Hg increase; p = 6.2x10(-5)). PAVM embolisation significantly reduced ischaemic stroke rate (p = 0.028); no strokes/abscesses occurred following obliteration of all angiographically visible PAVMs. The mean PAVM diagnosis-treatment interval was longer, however, when neurological risks were unrecognised., Conclusions: Ischaemic strokes and brain abscesses occur commonly in undiagnosed HHT patients with PAVMs. Risk reduction could be improved.

Objective: This study assessed the effect and safety of percutaneous transcatheter coil embolization of pulmonary arteriovenous malformations., Materials and Methods: In 58 (88%) of 66 patients, all malformations with feeding vessels greater than or equal to 3 mm in diameter were embolized with steel coils. Arterial oxygen saturation at rest and exercise, intrapulmonary right-to-left anatomic shunt fraction ((99m)Tc-macroaggregate injection), maximum exercise capacity (incremental work rate test), and pulmonary function were measured before and after embolization. Complications were analyzed., Results: Three categories of patients were identified. Patients in group 1 (27%) had complete occlusion of all angiographically visible pulmonary arteriovenous malformations; patients in group 2 (61%) had complete occlusion of all malformations with feeding vessels greater than or equal to 3 mm in diameter, but with smaller lesions persisting; and patients in group 3 (12%) had incomplete embolization, with feeding vessels greater than or equal to 3 mm in diameter remaining. The mean right-to-left shunt after embolization was least in group 1 (7%), intermediate in group 2 (10%), and greatest in group 3 (19%). Arterial oxygen saturation and right-to-left shunt fraction returned to normal levels (>96% and <3.5%, respectively) in 33% of patients. A significant improvement occurred after embolization in carbon monoxide diffusing capacity per unit of alveolar volume and in exercise capacity in 16 and 10 patients, respectively. In 93 procedures, 12 complications (13%) occurred., Conclusion: Coil embolization of pulmonary arteriovenous malformations is effective in reducing right-to-left anatomic shunt fraction and in improving arterial oxygenation. Coil embolization of pulmonary arteriovenous malformations is well tolerated and has a low complication rate.

Objective: Metallic coils have been used for vascular embolization for many years but controlled-release coils have only recently become commercially available. Most of these devices are microcoils that were manufactured primarily for the packing of intracerebral aneurysms; therefore, they lack radial force and are not ideal agents for the occlusion of high-flow lesions such as pulmonary arteriovenous malformations (PAVMs). The objective of this study was to review our experience with a new detachable coil based on the conventional Gianturco-Wallace coil., Subjects and Methods: The new detachable coil was initially used for the treatment of varicocele in 20 patients. Subsequently, the coil was used in 48 patients during 90 procedures for the treatment of PAVMs., Results: A total of 548 coils were used. Complete occlusion of the testicular vein was achieved in all patients with varicocele. Successful occlusion of the PAVM being treated was achieved in all patients, and no instances of recanalization were documented in any of the patients who returned for follow-up angiography. Forty-one coils had to be removed completely from the catheter before detachment because of inappropriate size or position. Eight coils failed to detach easily, and six of these had to be removed. Most of these device failures were associated with kinking of the screw thread mechanism between the coil and the delivery wire., Conclusion: The Jackson detachable coil allows safer, more accurate, and more distal embolization of PAVMs than is possible with nondetachable coils. Complications associated with its use have been few.

Pulmonary arteriovenous malformations (PAVMs) are uncommon lesions, but are the cause of considerable morbidity and occasional mortality. They most commonly occur in association with hereditary haemorrhagic telangectasia and screening of families with this condition is therefore important. Embolization of PAVMs by coils is a well tolerated effective procedure with a low complication rate in skilled hands. Treatment results in both symptomatic and physiological improvement, and evidence for a reduction in stroke and cerebral abscess is accumulating. Radiological techniques now represent the primary treatment of choice, with surgical resection rarely required.

Objective: The purpose of this study was to determine the effects of percutaneous transcatheter coil embolization of pulmonary arteriovenous malformations on arterial oxygen saturation, pulmonary gas exchange, anatomic right-to-left shunt, and lung function and to assess the complications of the procedure., Subjects and Methods: Fifty-three patients were included in the study: 42 (79%) had associated hereditary hemorrhagic telangiectasia. Nineteen (36%) had neurologic problems compatible with paradoxical embolization. During 102 separate embolization procedures, all malformations with feeding vessels > or = 3 mm in diameter were embolized with steel coils. Arterial oxygen saturation at rest and on exercise and the intrapulmonary right-to-left shunt fraction (99mTc-macroaggregate injection), forced expiratory volume in 1 sec, vital capacity, diffusing capacity for carbon monoxide, and transfer coefficient were measured before and after embolization. Complications of the procedure were recorded and investigated., Results: Before treatment, all patients had hypoxemia in the supine posture (SaO2, 89 +/- 1% [standard error of the mean]), which fell a further 6% (absolute) on standing. Mean values for transfer coefficient and diffusing capacity for carbon monoxide were reduced, at 85 +/- 3% and 78 +/- 3% (predicted value), respectively. After embolization, the mean values for supine and erect SaO2 rose to 94 +/- 1% and 93 +/- 1%. Transfer coefficient increased by a mean of 5.4% of predicted value. The mean shunt fraction fell from 23 +/- 2% preembolization to 9 +/- 1% postembolization. In 102 procedures, there were 18 complications, 12 mild, two moderate, and four potentially serious (systemic coil embolization in two patients, cerebrovascular accident [transient], and myocardial puncture), but there were no lasting sequelae., Conclusion: Our results show that coil embolization is an effective and well-tolerated method for treatment of pulmonary arteriovenous malformations. Improvements in pulmonary gas exchange and lung function and a decrease in right-to-left shunting occurred after treatment. The procedure was well tolerated and had a low complication rate.

Background: Current treatment of patients with pulmonary arteriovenous malformations requires serial embolisations by means of steel coils or balloons. Measurement of right to left shunt is the most specific index of response to treatment. A new method of measuring shunt has been developed that is less invasive than traditional methods., Methods: Right to left pulmonary shunt (expressed as percentage of cardiac output) was measured at rest in 19 patients with pulmonary arteriovenous malformations and six normal subjects by using intravenously injected albumin microspheres labelled with technetium-99m. The technique was compared with a simultaneous shunt measurement in subjects breathing 100% oxygen while they rested. The microsphere technique was adapted to measure the right to left shunt during exercise in 12 patients and five normal subjects with a new method of quantification., Results: The mean (SD) shunt at rest as measured by the microsphere method was 23.2% (15.6%) in the patients and 2.7% (1.2%) in the normal subjects. When these values were compared with those of the 100% oxygen method the difference in mean values was 1% and the limits of agreement between the two methods -32% to +45%. The microsphere method is less invasive (arterial blood gas sampling is not required), quicker, and more comfortable for patients than the 100% oxygen method. In five of the normal subjects the mean (SD) 99mTc microsphere shunt increased from 2.9% (1.3%) at rest to 5.1% (2.9%) during exercise. In the 12 patients studied during exercise the shunt increased from 33.7% (12.7%) at rest to 41.7% (13.3%) during exercise in eight but decreased from 22.6% (2.4%) at rest to 17.6% (2.2%) during exercise in four. Arterial desaturation during exercise correlated with change in the size of the right to left shunt during exercise (r = +0.80)., Conclusions: The microsphere method allows measurement of right to left shunt at rest and during exercise. Serial measurements at rest provide a simple, safe assessment of the physiological response to embolisation in patients with pulmonary arteriovenous malformations.

The effects of percutaneous transcatheter embolization on pulmonary function and exercise capacity were assessed in 15 patients with pulmonary arteriovenous malformations (PAVM). Vital capacity (VC), FEV1, DLCO, SaO2, exercise performance, and right-to-left shunt (100% oxygen method) were measured before and 2 to 6 months after treatment. Surgical correction had been attempted in 9 patients prior to referral, and 11 had associated hereditary hemorrhagic telangiectasia (HHT). Lung function tests before intervention showed normal VC and FEV1/VC ratios, reduced DLCO (mean 71% predicted, range 36 to 123%), a resting supine SaO2 of 86% (range 67 to 95%) and mean shunt fraction of 33% (range 15 to 47%). Despite further marked falls in SaO2 on exertion, exercise capacity was well preserved. Following steel coil embolization of all PAVM with a feed vessel internal diameter greater than 3 mm (one to four sessions per patient), mean shunt fraction improved from 33 to 19% and resting SaO2 from 86 to 92% with no change in VC. A consistent improvement in diffusing capacity was seen only in patients with coexisting HHT. Exercise capacity increased in the majority (unchanged in 6), and SaO2 during maximal exercise improved in all except one patient. There were no long-term complications following embolization. These findings indicate that embolization of all macroscopic PAVM, undertaken primarily to reduce the risk of paradoxical embolization, is safe and results in substantial improvements in resting and exercise SaO2 without evidence of loss of normal lung. The right-to-left shunts remaining following embolization may reflect the presence of numerous microscopic PAVM in these patients.

Sixteen patients with pulmonary arteriovenous malformations (PAVM) have been treated by percutaneous transvenous coil embolization. In the ten patients who have had all their angiographically demonstrable PAVM's embolised there has been a reduction of right to left shunting from a mean of 28.1% to 13% and an improvement in mean arterial oxygen saturation from 87.4% to 92.4%. Eight of these ten patients now have oxygen saturations of more than 90%. All patients have shown symptomatic improvement. There have been three complications relating to the embolizations, none of which has been serious. Coil embolization of PAVM's is an effective, safe and well tolerated procedure. Embolization should be performed in all cases of PAVM's to prevent paradoxical embolization.