Reperfusion Rates of Pulmonary Arteriovenous Malformations after Coil Embolization: Evaluation with Time-Resolved MR Angiography or Pulmonary Angiography

An Alternative Endovascular Technique for Treatment of Pulmonary Arteriovenous Malformation: Microballoon-occluded Transcatheter Embolization Using n-butyl-2-cyanoacrylate

PURPOSE

To investigate the safety and efficacy of microballoon-occluded transcatheter embolization using n-butyl-2-cyanoacrylate (NBCA) in patients with a single pulmonary arteriovenous malformation (PAVM).

METHODS

From November 2017 to November 2020, this retrospective study included 38 previously untreated patients with a single PAVM who underwent microballoon-occluded transcatheter embolization using NBCA. All 38 patients had follow-up that included simple chest radiography and contrast-enhanced chest computed tomography (CT).

RESULTS

A microballoon was successfully placed in a feeding artery of the PAVM to control the delivery of the NBCA cast in all 38 patients, with complete embolization of sacs and the feeding artery achieved in all cases. The mean diameters of the feeding artery, sac, and draining vein were 3.9 ± 0.9 mm, 7.5 ± 2.6 mm, and 4.6 ± 1.3 mm, respectively. A fixed 1:2 NBCA/Lipiodol ratio was used, and the mean amount of embolic mixture per patient was 1.4 mL (range 0.6-2.2 mL). There were no complications related to microballoon adhesion and non-target embolization of the systemic circulation. Follow-up CT in all 38 patients with a mean delay of 34.5 ± 8.8 months (range 20.7-56.5 months) showed no continued perfusion of the PAVM.

CONCLUSION

In our hands, microballoon-occluded n-butyl-2-cyanoacrylate embolization seemed to be safe and appeared to be clinically effective in patients with simple and complex types of single PAVM. Therefore, the present technique has the potential to become a standard treatment for a single PAVM.

ACR Appropriateness Criteria® Pulmonary Arteriovenous Malformation (PAVM): 2023 Update

Pulmonary arteriovenous malformations (PAVMs) occur in 30% to 50% of patients with hereditary hemorrhagic telangiectasia. Clinical presentations vary from asymptomatic disease to complications resulting from the right to left shunting of blood through the PAVM such as paradoxical stroke, brain abscesses, hypoxemia, and cardiac failure. Radiology plays an important role both in the diagnosis and treatment of PAVM. Based on different clinical scenarios, the appropriate imaging study has been reviewed and is presented in this document. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

ELECT: prospective, randomized trial comparing microvascular plug versus platinum-fibered microcoils for embolization of aneurysm sac side branches before endovascular aortic aneurysm repair

BACKGROUND

Preemptive selective embolization of aneurysm sac side branches (ASSBs) has been proposed to prevent type II endoleak after endovascular aortic aneurysm repair (EVAR). This study aimed to explore if an embolization strategy using microvascular plugs (MVP) reduces intervention time and radiation dose compared to platinum-fibered microcoils. Furthermore, the effectiveness of the devices in occluding the treated artery was assessed.

METHODS

Sixty patients scheduled for EVAR underwent percutaneous preemptive embolization of ASSBs using MVPs or coils after a 1:1 randomization. Follow-up imaging was performed during aortic stentgraft implantation.

RESULTS

Overall, 170 ASSBs were successfully occluded (83 arteries by MVPs and 87 by coils) and no acute treatment failure occurred. The mean procedure time was significantly lower in the group treated with MVPs (55 ± 4 min) compared to coil occlusion (67 ± 3 min; p = 0.018), which was paralleled by a numerically lower radiation dose (119 Gy/cm2 vs. 140 Gy/cm2; p = 0.45). No difference was found for contrast agent use (34 ml MVP group vs 35 ml coil group; p = 0.87). At follow-up, reopening of lumbar arteries was seen in nine cases (four after coil embolization; five after MVPs).

CONCLUSION

Both microvascular plugs and coils can be effectively used for preemptive embolization of aneurysm sac side branches before EVAR. Use of plugs offers a benefit in terms of intervention time.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03842930 Registered 15 February 2019.

Prospective Study of Polytetrafluoroethylene-Covered Microplugs and Detachable Coils for Embolization of Pulmonary Arteriovenous Malformations: Technical Results, Procedure Times, and Costs

PURPOSE

To determine time to occlusion and procedure costs of embolization of pulmonary arteriovenous malformations (PAVMs) using a polytetrafluoroethylene-covered microplug compared with embolization using detachable coils.

MATERIALS AND METHODS

In this prospective study, 37 patients (mean age, 39.1 years [SD ± 17.6]) with 82 PAVMs underwent embolization with microplug or detachable coils between April 2019 and January 2023. Technical success, procedure time intervals, and costs were analyzed.

RESULTS

In 37 patients, 82 PAVMs and 101 feeding arteries were successfully treated (microplug, 64; microplug + another device, 5; detachable coils alone, 32). Time from embolic device inserted into the catheter to device deployed and time to occlusion differed significantly between microplug and detachable coil cohorts (P < .0001 for both). Embolization with ≥1 microplug had a significantly shorter occlusion time than embolization with detachable coils (median, 10.0 minutes saved per feeding artery) (P < .0001). Compared with detachable coil embolization, microplug embolization saved a median of 9.0 minutes per feeding artery (P < .0001) and reduced room cost by a median of $429 per feeding artery (P < .0001). Device costs per feeding artery did not differ significantly between microplug ($2,790) and detachable coil embolization ($3,147) (P = .87).

CONCLUSIONS

Compared with coils, microplugs had an equally high technical success rate but significant time to occlusion and room costs savings per feeding artery. Total room cost and device cost together did not differ significantly between microplugs and coils. Microplugs may be considered technically effective and at least cost-neutral for PAVM embolization where clinically appropriate.

Embolization of De Novo Pulmonary Arteriovenous Malformations Using High-Volume Detachable Non-Fibered Coils: Propensity-Matched Comparison to Traditional Coils

Embolization of de novo pulmonary arteriovenous malformations (PAVMs) using high-volume detachable non-fibered (HVDNF) coils was compared to traditional non-HVDNF coils. Persistent-occlusion rates were evaluated. A total of 272 de novo (previously untreated) PAVM treatments were retrospectively stratified into those treated with non-HVDNF coils only (n = 192) and those treated with HVDNF coils with or without other coils (n = 80). Propensity score matching, followed by survival analysis and cost analysis, was performed. The overall persistent-occlusion rate was 86.0% (234/272). Persistent occlusion was achieved in 81.8% of PAVMs using non-HVDNF coils, compared with 96.3% using HVDNF coils (p = 0.0017). The mean follow-up was 30.7 ± 31.9 months versus 14.7 ± 13.4 months, respectively (p < 0.0001). Propensity-matched survival analysis demonstrated PAVMs treated with HVDNF coils recurred significantly less frequently than PAVMs treated with non-HVNDF coils (p = 0.023). The use of HVDNF coils was more expensive than standard coils, however not significantly different for the treatment of complex PAVMs. The use of high-volume detachable non-fibered coils was associated with higher persistent-occlusion rates when compared with non-HVDNF coils. HVDNF coils were more expensive on average; however, cost was similar between groups for the treatment of complex PAVMs.

Retrospective single-arm cohort study of video-assisted thoracic surgery for treatment of idiopathic peripherally located simple type pulmonary arteriovenous malformation in 23 consecutive patients

BACKGROUND

Although case reports of video-assisted thoracic surgery (VATS) for pulmonary arteriovenous malformation (PAVM) have been published, studies analyzing more than 10 cases were limited. A retrospective single-arm cohort study was performed to investigate the efficacy of VATS in 23 consecutive patients with idiopathic peripherally located simple type PAVM.

METHODS

VATS was performed for wedge resection of 24 PAVMs in 23 patients, which included 4 males and 19 females with an age range of 25 to 80 years (mean: 59.6 ± 13.0). Two patients underwent simultaneous resection of lung carcinoma, one by wedge resection and another by lobectomy. Each medical record was analyzed according to the resected specimen, bleeding volume, postsurgical hospital stay length, duration of chest tube placement, and VATS time. The distance between pleural surface/fissure and PAVM was measured on CT, and the influence of this distance on identification of PAVM was investigated.

RESULTS

In all 23 patients, VATS was successfully performed, and the venous sac was included in each resected specimen. Bleeding volume was less than 10mL in all but one with 1900 mL bleeding volume due to simultaneous lobectomy for carcinoma, not wedge resection of PAVM. Postsurgical hospital stay length, duration of chest tube placement, and VATS time were 5.0 ± 1.4 days, 2.7 ± 0.7 days, and 49.3 ± 39.9 min, respectively. In 21 PAVMs with a distance of 1 mm or less, purple vessel or pleural bulge of PAVM was identified soon after insertion of a thoracoscope. In the remaining 3 PAVMs with a distance of 2.5 mm or more, additional efforts were needed for identification.

CONCLUSION

VATS was found to be a safe and effective to treatment for idiopathic peripherally located simple type PAVM. When the distance between pleural surface/fissure and PAVM was 2.5 mm or more, a plan and strategy for identification of PAVM should be prepared before VATS.

An Update on Embolization for Pulmonary Arteriovenous Malformations

Pulmonary arteriovenous malformations are abnormal connections between a pulmonary artery and a pulmonary vein that can lead to ischemic stroke and brain abscess due to right-to-left shunting of blood. Embolization is currently considered the first treatment option for pulmonary arteriovenous malformations owing to its minimal invasiveness. This review updates the indications and techniques for the embolization of pulmonary arteriovenous malformations and determines the persistence of pulmonary arteriovenous malformations following embolization based on the most recent literature.

The role of interventional radiology in treatment of patients with hereditary hemorrhagic telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) also known as Osler-Weber-Rendu disease is a rare autosomal dominant, multi-organ disorder that leads to formation of abnormal vascular connections resulting in devastating and life-threatening complications. Due to its multisystem character, wide range of clinical manifestations and variable expressivity, HHT remains a diagnostic challenge and requires close cooperation of specialists from various medical fields. Interventional radiology plays a key role in the management of this disease, helping maintain the health of HHT patients and minimize the risk of fatal complications. The aim of this article is to review clinical manifestations, diagnostic guidelines and criteria of HHT as well as to present the means of endovascular therapy in the management of HHT patients.

Diagnosis and Management of Persistent Pulmonary Arterio-venous Malformations following Embolotherapy

Embolotherapy is the primary treatment for pulmonary arterio-venous malformations (PAVMs). Approximately, 2-25% of PAVMs demonstrate persistence following embolization. Early identification and treatment of persistent PAVMs are critical to mitigating life threatening complications. The presence of prior embolic devices and complex angioarchitecture of persistent PAVMs pose technical challenges during repeat embolotherapy. In this article, we review patterns of persistence, factors affecting the persistence, endovascular treatment techniques, and outcomes.

Noncontrast time-resolved pulmonary magnetic resonance angiography with consecutive beam saturation pulse and variable flip angles using three-dimensional fast spin echo: A preliminary study

To develop and validate a novel noncontrast time-resolved magnetic resonance angiography (NC TR-MRA) using consecutive beam pulses with variable flip angles for visualizing hemodynamics in the pulmonary artery, we performed phantom and volunteer studies and applied the novel NC TR-MRA to a 51-year-old woman with pulmonary arteriovenous malformation (PAVM).The novel NC TR-MRA sequence utilized consecutive multiple-beam saturation pulses with variable flip angles considering venous blood T1 relaxation to alter the visualized blood signal length. The flowing blood signal length is suppressed according to the number of beam saturation pulses. NC TR-MRA in each flow phase was assessed by subtracting the images with and without beam saturation pulses. In the flow phantom study, three flow velocities were used to simulate physiological pulmonary arterial blood flow. Signal profiles along the flow direction were evaluated in each flow phase. In the volunteer study, five healthy volunteers were recruited, and NC TR-MRA was applied to evaluate relationships between the flow-saturated time and signal enhancement rates. Four regions of interest (ROIs) were determined on the proximal and distal portions of the right basal artery. A patient with PAVM was included to validate whether a PAVM lesion could be visualized using NC TR-MRA. The visualized flow signal lengths extended proportionally with the number of beam saturation pulses in the steady-flow phantom at all velocities. In the volunteer study, NC TR-MRA images showed signal enhancement from the proximal to distal portions of the right basal artery with increase in the flow-saturated time. Signal enhancement rates in all ROIs were significantly positively correlated with the flow-saturated time (p < 0.001 in all ROIs). Further, the lesion and its hemodynamics could be explicitly visualized in the patient with PAVM. Hence, NC TR-MRA using beam saturation pulse can visualize the hemodynamics of the pulmonary artery and may be useful for diagnosing and following patients with PAVM.

Feasibility of Single-Shot Whole Thoracic Time-Resolved MR Angiography to Evaluate Patients with Multiple Pulmonary Arteriovenous Malformations

OBJECTIVE

To evaluate the feasibility of single-shot whole thoracic time-resolved MR angiography (TR-MRA) to identify the feeding arteries of pulmonary arteriovenous malformations (PAVMs) and reperfusion of the lesion after embolization in patients with multiple PAVMs.

MATERIALS AND METHODS

Nine patients (8 females and 1 male; age range, 23-65 years) with a total of 62 PAVMs who underwent percutaneous embolization for multiple PAVMs and were subsequently followed up using TR-MRA and CT obtained within 6 months from each other were retrospectively reviewed. All imaging analyses were performed by two independent readers blinded to clinical information. The visibility of the feeding arteries on maximum intensity projection (MIP) reconstruction and multiplanar reconstruction (MPR) TR-MRA images was evaluated by comparing them to CT as a reference. The accuracy of TR-MRA for diagnosing reperfusion of the PAVM after embolization was assessed in a subgroup with angiographic confirmation. The reliability between the readers in interpreting the TR-MRA results was analyzed using kappa (κ) statistics.

RESULTS

Feeding arteries were visible on the original MIP images of TR-MRA in 82.3% (51/62) and 85.5% (53/62) of readers 1 and 2, respectively. Using the MPR, the rates increased to 93.5% (58/62) and 95.2% (59/62), respectively (κ = 0.760 and 0.792, respectively). Factors for invisibility were the course of feeding arteries in the anteroposterior plane, proximity to large enhancing vessels, adjacency to the chest wall, pulsation of the heart, and small feeding arteries. Thirty-seven PAVMs in five patients had angiographic confirmation of reperfusion status after embolization (32 occlusions and 5 reperfusions). TR-MRA showed 100% (5/5) sensitivity and 100% (32/32, including three cases in which the feeding arteries were not visible on TR-MRA) specificity for both readers.

CONCLUSION

Single-shot whole thoracic TR-MRA with MPR showed good visibility of the feeding arteries of PAVMs and high accuracy in diagnosing reperfusion after embolization. Single-shot whole thoracic TR-MRA may be a feasible method for the follow-up of patients with multiple PAVMs.

Angiographic features of pulmonary arteriovenous malformations: a new imaging classification system, BRAND, to guide embolisation

AIM

To introduce a new classification system for pulmonary arteriovenous malformations (PAVMs) based on the BRanches, ANgles and Diameter of the feeding artery (BRAND), which is intended provide a better understanding of the vascular structure of PAVMs and facilitate the selection of therapeutic strategies for embolisation.

MATERIALS AND METHODS

Twenty-one patients with PAVMs from 2005 to 2020 were reviewed retrospectively. According to angiographic morphology, classified the PAVMs using the BRAND classification.

RESULTS

A total of 41 PAVMs were treated with transcatheter embolisation. Based on the BRAND classification, there were four branches (9.8%), four acute angles (9.8%), and 32 occlusion sites >4 mm in diameter (78%). A total of 30 PAVMs (73.2%) were treated with occluders and plugs while the rest were embolised with coils (26.8%). Immediate technical success was achieved in all patients. In feeding arteries with acute angles, balloon-assisted tracking and trans-septal puncture techniques were used to facilitate the advancement of delivery systems. All origins of branches were preserved. Mean SaO₂ increased significantly from 79.5 ± 7.5% before embolisation to 92 ± 5.3% after embolisation (p<0.05). During a median follow-up of 5.4 years, two patients (9.5%) developed new PAVMs and required a second procedure. One patient (4.8%) underwent repeat embolisation due to the reperfusion of previously embolised PAVMs with coils.

CONCLUSIONS

BRAND classification is well suited to address the challenging feeding arteries of PAVMs and allow precise placement of the delivery system, leading to minimal procedural risk and high success rates.

Comparison of Feeding-Artery-Only versus Nidus-Plus-Feeding-Artery Embolization of Pulmonary Arteriovenous Malformations

PURPOSE

To compare coil embolotherapy outcomes of feeding-artery-only versus nidus-plus-feeding-artery technique for treating pulmonary arteriovenous malformations (PAVMs).

MATERIALS AND METHODS

A total of 219 treatment-naïve PAVMs embolized in 90 patients at a single center from 2008 to 2018 met inclusion criteria for retrospective evaluation. Of the patients, 87% had a diagnosis of hereditary hemorrhagic telangiectasia (HHT). Feeding artery (FA) diameters ≥2 mm were treated. Coil embolization techniques were classified on the basis of embolic deployment zone: (i) distal feeding artery (DFA) technique (coil-to-nidus distance ≤ 1 cm) or (ii) nidus plus feeding artery (NiFA) technique. Successful embolization predictors were assessed using a multivariate linear regression model with input from patient- and PAVM-specific variables.

RESULTS

Treatment success was achieved in 192 of 219 PAVMs (87.7%) over a mean follow-up period of 19 months. Statistically significant predictors of success in the linear regression model included simple angioarchitecture, NiFA embolization technique, and shorter follow-up duration. Stratified by technique, success rates were 99 of 105 (94.3%) and 93 of 114 (81.6%) PAVMs for NiFA and DFA, respectively (P = .007). On average, NiFA-embolized PAVMs had a larger FA diameter (3.6 mm vs 2.7 mm, P < .001) and comprised more complex PAVMs (48% vs 22%, P < .001) than DFA. Treatment success was not significantly associated with sac size or FA diameter.

CONCLUSIONS

Coil embolization of both the nidus and FA was associated with a higher persistent occlusion rate than FA embolization alone.

Evaluation of percutaneous transcatheter embolization for pulmonary arteriovenous malformations

BACKGROUND

The purpose of this study was to assess the safety and efficacy of percutaneous transcatheter embolization (TCE) for the treatment of pulmonary arteriovenous malformations (PAVMs).

METHODS

Forty-three consecutive patients (n = 17 males; n = 26 females) with 72 untreated PAVMs underwent coil and/or plug embolization between January 2010 and February 2018. The mean patient age was 42 ± 14 years (range 19-71 years). The median size of the feeding artery was 7.9 ± 2.9 mm (range 3.5-14.0 mm). The arterial blood gas level and cardiac function of all patients were analysed. The technical success rate, recanalization rate, and complications were evaluated. Computed tomography angiography (CTA) examinations were scheduled for 12 months after treatment and every 2-4 years thereafter.

RESULTS

Twenty-five PAVMs were treated with coils alone, twenty-one were treated with plugs alone, and twenty-six were treated with both coils and plugs. The technical success rate was 100%. There were no complications during operation. However, one patient (2.3%) had pulmonary thrombosis and embolism post-operation. The patients' pre-operative and post-operative PaO₂ and SaO₂ levels were significantly different (p < 0.01). A comparison of the New York Heart Association (NYHA) grade before and after embolization in all patients showed a significant decrease in the post-operative grade (p < 0.01). The 72 PAVMs were divided into three groups (coils only group [n = 25], plugs only group [n = 21], and coils/plugs combined group [n = 26]). After 12 months of follow-up, there were seven reperfusion PAVMs in the coil group, seven reperfusion PAVMs in the plug group, and 1 reperfusion PAVM in the combined group. There were significant differences between the two groups and the combined group.

CONCLUSION

Percutaneous TCE is safe and effective for the treatment of PAVMs. A combination of coils and vascular plugs may be useful for preventing recanalization after the embolization of PAVMs.

Pulmonary arteriovenous malformation (PAVM) embolization: prediction of angiographically-confirmed recanalization according to PAVM Diameter changes on CT

Background

To assess pulmonary arteriovenous malformation (PAVM) recanalization after embolization based on PAVM diameter changes on computed tomography (CT), with pulmonary angiography used as a gold standard.

Methods

A retrospective review was done of patients from 2008 to 2019 with a PAVM treated with endovascular embolization. The treatment outcome was determined by conventional angiography. Follow-up pulmonary angiography was performed when recanalization was suspected on CT, or embolization of all lesions in multiple PAVM patients could not be completed in a single session. Patients who had no preprocedural or follow-up CT were excluded. Draining vein, feeding artery, and venous sac diameter were measured on CT, and diameter reduction rates were compared with the widely-used, binary 70 % criteria.

Results

Forty-one patients with 114 PAVMs were treated during the study period. Eight patients with 50 PAVMs met the inclusion criteria. Mean vein, artery, and venous sac diameter reduction rates were as follows: 59.2 ± 9.3 %, 47.5 ± 10.6 %, and 62.6 ± 13.2 %, respectively, in the occluded group and 5.4 ± 19.5 %, 11.3 ± 17.7 %, and 26.8 ± 14.2 %, respectively, in the recanalized group. The area under the receiver operating characteristic curves for PAVM recanalization for the draining vein was 1.00, showing a better result than the artery (0.97) and sac (0.99). Patients showed > 42 % draining vein diameter reduction in the occluded group and < 32 % in the recanalized group. The widely-used 70 % criteria showed low specificity for predicting recanalization (draining vein, 7.3 %; venous sac, 41.7 %) but 100 % sensitivity for both the draining vein and venous sac.

Conclusions

The widely-used 70 % binary criteria showed limited performance in predicting outcomes in this angiographically-confirmed case series. Further investigations are warranted to establish a strategy for detecting recanalization after PAVM embolization.

Location of embolization affects patency after coil embolization for pulmonary arteriovenous malformations: importance of time-resolved magnetic resonance angiography for diagnosis of patency

OBJECTIVES

This study aimed to assess the diagnostic accuracy of computed tomography (CT) and time-resolved magnetic resonance angiography (TR-MRA) for patency after coil embolization of pulmonary arteriovenous malformations (PAVMs) and identify factors affecting patency.

METHODS

Data from the records of 205 patients with 378 untreated PAVMs were retrospectively analyzed. Differences in proportional reduction of the sac or draining vein on CT between occluded and patent PAVMs were examined, and receiver operating characteristic analysis was performed to assess the accuracy of CT using digital subtraction angiography (DSA) as the definitive diagnostic modality. The accuracy of TR-MRA was also assessed in comparison to DSA. Potential factors affecting patency, including sex, age, number of PAVMs, location of PAVMs, type of PAVM, and location of embolization, were evaluated.

RESULTS

The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of CT were 82%, 81%, 77%, 85%, and 82%, respectively, when the reduction rate threshold was set to 55%, which led to the highest diagnostic accuracy. The sensitivity, specificity, PPV, NPV, and accuracy of TR-MRA were 89%, 95%, 89%, 95%, and 93%, respectively. On both univariable and multivariable analyses, embolization of the distal position to the last normal branch of the pulmonary artery was a factor that significantly affected the prevention of patency.

CONCLUSIONS

TR-MRA appears to be an appropriate method for follow-up examinations due to its high accuracy for the diagnosis of patency after coil embolization of PAVMs. The location of embolization is a factor affecting patency.

KEY POINTS

• Diagnosis of patency after coil embolization for pulmonary arteriovenous malformations (PAVMs) is important because a patent PAVM can lead to neurologic complications. • The diagnostic accuracies of CT with a cutoff value of 55% and TR-MRA were 82% and 93%, respectively. • The positioning of the coils relative to the sac and the last normal branch of the artery was significant for preventing PAVM patency.

Comparison of Contrast Enhanced Magnetic Resonance Angiography to Computed Tomography in Detecting Pulmonary Arteriovenous Malformations

Background: Computed tomography (CT) is considered the imaging modality of choice to diagnose pulmonary arteriovenous malformations PAVMs. The drawback of this technique is that it requires ionizing radiation. Magnetic resonance (MR) imaging does not have the limitation, but little is known about the performance of MR compared to CT for the detection of PAVMs. The aim of this study is to investigate the sensitivity of contrast-enhanced MR angiography (CE-MRA) in the detection of PAVMs with feeding artery diameters (FAD) > 2 mm. Methods: Patients with a grade 2 or 3 shunt on screening transthoracic contrast echocardiography (TTCE) were asked to participate. Included patients underwent chest CT and CE-MRA. CT was considered the reference standard. CT and CE-MRA scans were anonymized and assessed for the presence of PAVMs with FAD > 2 mm by one and two readers respectively. Data analysis was performed on per patient and per PAVM basis. Results: Fifty-three patients were included. 105 PAVMs were detected on CT, 45 with a FAD ≥ 2 mm. In per patient analysis, sensitivity and specificity of CE-MRA were 92% and 97% respectively for reader 1 and 92% and 62% for reader 2. Negative and positive predictive value (NPV/PPV) were 93% and 96% for R1 and 90% and 67% for R2. In per PAVM analysis, sensitivity, specificity, NPV and PPV were 96%, 99%, 100% and 86% for R1 and 93%, 96%, 100% and 56% for R2, respectively. Conclusions: CE-MRA has excellent sensitivity and NPV for detection of PAVMs with FAD ≥ 2 mm and can therefore be used to detect these PAVMs. We are hopeful that future advancements in CE-MRA technology will reduce false positive rates and allow for more broad use of CE-MRA in PAVM diagnosis and management.

[Pulmonary arteriovenous shunt - a rare cause of recurrent stroke due to paradoxical embolism]

Paradoxical embolism is one of the mechanisms of ischemic stroke in patients younger than 45 years of age, due to opening between the right and left chambers of the heart through a patent foramen ovale, an atrial or ventricular septal defect, pulmonary arteriovenous malformations (PAVMs), etc. The PAVMs are structurally abnormal vessels that provide direct capillary-free communication between the pulmonary and systemic circulations, and hence an anatomic "right-to-left" shunt. Most pulmonary malformations are congenital and associated with hereditary hemorrhagic telangiectasia (Rendu-Osler-Weber disease). This publication highlights the issues of pathogenesis, clinical presentation, diagnosis and treatment of this pathology, and also describes a clinical case in which multiple PAVMs caused repeated ischemic strokes.

Migrated coil expectorated 12 years after embolization of pulmonary arteriovenous malformation, due probably to abscess formation around the coil

Pulmonary arteriovenous malformations (PAVMs) are rare vascular structures providing direct capillary-free communications between pulmonary arteries and veins. Embolotherapy is indicated as a front-line therapy. We report an unusual long-term complication of coil embolization for a 44-year-old woman with hereditary hemorrhagic telangiectasia (HHT) who had repeatedly undergone the procedures for her PAVMs. She expectorated the coil which had been placed 12 years earlier and migrated to the bronchus according to the chest radiogram and bronchoscopy. Histology of the resected lung segment suggested the cavity communicating with the bronchus was the consequence of abscess formation around the coils. Even after technically successful embolization to PAVMs, long term follow-up should be necessary paying attention to the symptoms and imaging to avoid massive hemoptysis and subsequent emergency surgery.

Approach to Pulmonary Arteriovenous Malformations: A Comprehensive Update

Pulmonary arteriovenous malformations (PAVMs) are abnormal direct vascular communications between pulmonary arteries and veins which create high-flow right-to-left shunts. They are most frequently congenital, usually in the setting of hereditary hemorrhagic telangiectasia (HHT). PAVMs may be asymptomatic or present with a wide variety of clinical manifestations such as dyspnea, hypoxemia, or chest pain. Even when asymptomatic, presence of PAVMs increases patients' risk of serious, potentially preventable complications including stroke or brain abscess. Transcatheter embolotherapy is considered the gold standard for treatment of PAVMs. Though previous guidelines have been published regarding the management of PAVMs, several aspects of PAVM screening and management remain debated among the experts, suggesting the need for thorough reexamination of the current literature. The authors of this review present an updated approach to the diagnostic workup and management of PAVMs, with an emphasis on areas of controversy, based on the latest literature and our institutional experience.

Pulmonary arteriovenous malformation exhibiting recanalization >10 years after coil embolization: Two case reports

RATIONALE

Some patients with pulmonary arteriovenous malformation (PAVM) present with hypoxemia and life-threatening complications, including stroke and cerebral abscess. Catheter embolization is currently the preferred treatment for PAVM. However, previous studies have revealed that the incidence of PAVM recanalization is approximately 10% 5 to 7 years after embolization. In contrast, there are no studies where recanalization has occurred over 10 years after embolization.

PATIENT CONCERNS

Herein, we report 2 cases diagnosed with cerebral embolism due to PAVM recanalization 13 years and 30 years after catheter treatment, in case I and II, respectively.

DIAGNOSES

Both cases were diagnosed with PAVM recanalization on chest computed tomography (CT) examination performed after cerebral embolism development. Furthermore, pulmonary artery angiography revealed blood flow from the pulmonary artery to the vein in the PAVM, confirming PAVM recanalization.

INTERVENTIONS

Coil re-embolization was performed for the all recanalized PAVM.

OUTCOMES

All the target lesions were successfully re-embolized in both cases. However, in case I, the second recanalization of embolized PAVM was confirmed 1 year after coil re-embolization. Consequently, the third embolization was performed in case I. In contrast to case I, the patient in case II was followed up without recanalization for 2 years after embolization.

LESSONS

We described the first 2 cases diagnosed with PAVM recanalization >10 years after the first catheter embolization. These cases suggest that patients with PAVMs should undergo life-long follow-up after catheter embolization.

Pulmonary arteriovenous malformations: what the interventional radiologist needs to know

Pulmonary arteriovenous malformations (PAVMs) or fistulas are rare direct pathological connections between pulmonary arterial and venous circulation. Most of PAVMs are congenital and closely associated with hereditary hemorrhagic telangiectasia, but acquired PAVMs have also been described in the literature. Diagnosis of PAVMs is a priority for clinicians, in order to prevent potentially fatal events such as cerebrovascular stroke, systemic septic embolization, hemoptysis and hemothorax. In this scenario, the radiologist plays a key role in both diagnostic and therapeutic workups of PAVMs: Chest X-ray, computed tomography and magnetic resonance are effective tools for PAVMs identification and confirmation of the suspected diagnosis. Furthermore, imaging modalities provide most of the elements for PAVMs classification according to their angioarchitecture (simple and complex) and help the clinicians in establishing which lesion requires prompt treatment and which one will benefit of imaging follow-up alone. Endovascular management of PAVMs has grown up as the first-line treatment in respect of surgery during last decades, showing lower risk of intra- and post-procedural complications and offering a wide number of treatment options and materials, ensuring effective management in virtually any clinical situation; interventional treatment aims to exclude PAVMs from pulmonary circulation, and specific technique and embolic agents should be selected according to pre-treatment imaging, in order to obtain the best procedural outcome. This paper proposes a review of the clinical and radiological features that a radiologist needs to know for PAVMs diagnosis and proper management, also showing an overview of the most common endovascular treatment strategies and embolization materials.

Update on MR imaging of the pulmonary vasculature

Magnetic resonance imaging (MRI) plays an increasingly important role in the non-invasive evaluation of the pulmonary vasculature. MR angiographic (MRA) techniques provide morphological information, while MR perfusion techniques provide functional information of the pulmonary vasculature. Contrast-enhanced MRA can be performed at high spatial resolution using 3D T1-weighted spoiled gradient echo sequence or at high temporal resolution using time-resolved techniques. Non-contrast MRA can be performed using 3D steady state free precession, double inversion fast spin echo, time of flight or phase contrast sequences. MR perfusion can be done using dynamic contrast-enhanced technique or using non-contrast techniques such as arterial spin labelling and time-resolved imaging of lungs during free breathing with Fourier decomposition analysis. MRI is used in the evaluation of acute and chronic pulmonary embolism, pulmonary hypertension and other vascular abnormalities, congenital anomalies and neoplasms. In this article, we review the different MR techniques used in the evaluation of pulmonary vasculature and its clinical applications.

Patients with in-situ metallic coils and Amplatzer vascular plugs used to treat pulmonary arteriovenous malformations since 1984 can safely undergo magnetic resonance imaging

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.

MVP™ Micro Vascular Plug Systems for the Treatment of Pulmonary Arteriovenous Malformations

PURPOSE

To describe our institutional experience with MVP™ micro vascular plug systems for the treatment of pulmonary arteriovenous malformations (PAVMs).

MATERIALS AND METHODS

We performed a retrospective medical record review of 52 patients with 119 PAVMs treated exclusively with MVP™ systems (69 procedures/153 MVP™ systems) between July 2014 and July 2018. All patients had PAVMs with feeding artery diameters ≥ 2 mm. MVP™ systems were deployed according to physician preference. We collected patient demographic information; procedural data (including size of feeding artery, size and number of embolics used per PAVM, fluoroscopy time, contrast administration), technical success rates, complications, and persistence. Persistence was assessed using computed tomography angiography (CTA) performed 1-3 months and 3-5 years after embolization per clinical protocol.

RESULTS

All procedures were technically successful without major complications. Mean feeding artery diameter was 3.3 ± 1.2 mm. Mean fluoroscopy time per procedure and contrast volume administered per procedure were 35 ± 16 min and 217 ± 101 mL, respectively. A mean of 1.3 ± 0.8 MVP™ systems was used per PAVM. There were no instances of persistence during a mean follow-up time of 328 ± 258 days (range 26 to 914 days).

CONCLUSIONS

For PAVMs with feeding artery diameters of 2 to 7.9 mm (mean 3.3 ± 1.2 mm), MVP™ systems are safe and effective given their high technical success rates and lack of persistence. Further prospective work will be required to elucidate the advantages and disadvantages of these MVP™ systems for PAVM embolization.

LEVEL OF EVIDENCE

Level III.

Where is the Origin of the Last Normal Branch from Feeding Artery of Pulmonary Arteriovenous Malformations?

Purpose

Reperfusion via pulmonary-to-pulmonary arterial anastomoses is known as one type of recurrence of pulmonary arteriovenous malformations (PAVMs) after embolization. It is important to occlude the fistulous portion beyond the origin of the last normal branch from feeding artery of PAVMs to prevent recurrence. In this study, we evaluate the origin of the last normal branch by CT as well as its visibility on pulmonary arteriography (PAG).

Materials and Methods

We reviewed forty patients with 77 PAVMs who underwent coil embolization between October 2007 and December 2017. All patients underwent MDCT before embolization. Axial and MPR CT lung images were reviewed with special interests in the origin of the last normal branch from feeding artery of PAVMs. The origin was classified into three portions, including sac, junction (portion just proximal to the sac) and proximal feeder (more than 5 mm proximal to the sac). We also evaluated whether PAG can depict the normal branches detected by MDCT.

Results

MDCT showed that the last normal branch originated from sac in 30 PAVMs (39.0%), junction in 39 (50.6%), and proximal feeder in 8 (10.4%).On selective PAG, the last normal branch could be visualized in 30 PAVMs (39.0%), although it could not be visualized due to high-flow shunt in the other 47 PAVMs.

Conclusions

Selective PAG frequently fails to demonstrate the last normal branch from feeding artery of PAVMs, which often originates from the sac. Pretherapeutic evaluation of CT images of the last normal branch is important to prevent reperfusion of PAVMs.

Level of Evidence

Level 3, local non-random sample.

Covered Stents in the Treatment of Pulmonary Arteriovenous Malformations

Seven patients with pulmonary arteriovenous malformations (PAVMs) not well suited to coil and/or plug treatment were treated with expanded polytetrafluoroethylene-covered stents. Mean diameter of treated arteries was 6 mm. Complete technical success was achieved in 7 of 8 PAVMs, 6 using only covered stents and 1 using both a covered and a bare stent owing to endoleak. In 1 patient, the parent vessel was sacrificed after identification of additional feeding vessels following stent graft placement. In 6 patients with median imaging follow-up of 8 months (range, 1-121 months), all stent grafts were patent, and all treated PAVMs were completely excluded without persistence.

Time-resolved magnetic resonance angiography as a follow-up method for visceral artery aneurysm treated with coil-embolisation

Purpose

The purpose of this study is to assess the feasibility and usefulness of time-resolved magnetic resonance angiography (TR-MRA) for follow-up of visceral artery aneurysms (VAAs) after embolotherapy.

Material and methods

Twenty-one VAAs (11 splenic, six renal, three internal iliac, and one superior pancreaticoduodenal artery aneurysms) in 18 patients (median age, 64 years; range, 36-88 years) previously treated by embolisation with platinum coils, were evaluated. The mean size of the aneurysm was 10.5 cm³ (range, 0.3-132 cm³). Among them, 19 lesions were treated by aneurysmal packing with or without distal-to-proximal embolisation. For the remaining two lesions, distal-to-proximal embolization alone was performed. The mean observation period after embolotherapy was 35 weeks (range, 4-216). All patients underwent TR-MRA following an intravenous bolus injection of gadolinium chelate. Recanalisation was diagnosed when any portion of the aneurysmal sac was enhanced in the arterial phase.

Results

On TR-MRA, two lesions were diagnosed as recanalised. They were confirmed by transcatheter arteriography and re-treated by embolotherapy. For the remaining 19 lesions, there were no findings of recanalisation on TR-MRA.

Conclusions

TR-MRA appears to be a feasible method for follow-up examination of VAAs treated by embolotherapy.

Utility of second-generation single-energy metal artifact reduction in helical lung computed tomography for patients with pulmonary arteriovenous malformation after coil embolization

PURPOSE

The quality of images acquired using single-energy metal artifact reduction (SEMAR) on helical lung computed tomography (CT) in patients with pulmonary arteriovenous malformation (PAVM) after coil embolization was retrospectively evaluated.

MATERIALS AND METHODS

CT images were reconstructed with and without SEMAR. Twenty-seven lesions [20 patients (2 males, 18 females), mean age 61.2 ± 11.0 years; number of embolization coils, 9.8 ± 5.0] on contrast-enhanced CT and 18 lesions of non-enhanced lung CT concurrently performed were evaluated. Regions of interest were positioned around the coils and mean standard deviation value was compared as noise index. Two radiologists visually evaluated metallic coil artifacts using a four-point scale: 4 = minimal; 3 = mild; 2 = strong; 1 = extensive.

RESULTS

Noise index was significantly improved with SEMAR versus without SEMAR (median [interquartile range]; 194.4 [161.6-211.9] Hounsfield units [HU] vs. 243.9 [220.4-286.0] HU; p < 0.001). Visual score was significantly improved with SEMAR versus without SEMAR (Reader 1, 3 [3] vs.1 [1]; Reader 2, 3 [3] vs.1 [1]; p < 0.001). Significant differences were similarly demonstrated on lung CT (p < 0.001).

CONCLUSION

SEMAR provided clear chest CT images in patients who underwent PAVM coil embolization.

Usefulness of Hydrogel-Coated Coils in Embolization of Pulmonary Arteriovenous Malformations

Purpose

To evaluate the usefulness of hydrogel-coated coils for preventing recanalization after coil embolization of pulmonary arteriovenous malformations (PAVMs).

Materials and Methods

Thirty-seven consecutive patients with 57 untreated PAVMs underwent coil embolization with hydrogel-coated coils between January 2013 and Jun 2017. The mean age was 49 years (range 9–83 years), and there were seven male patients and 30 female patients. The median size of the feeding artery was 3.7 mm (range 1.5–6.1 mm), and the median size of the venous sac was 9.3 mm (range 2.6–36.6 mm). For all PAVM, embolization was attempted using 0.018-in. hydrogel-coated coils with or without other coils (0.0135–0.018-in. bare platinum coils and fibered platinum coils). Technical success rate, recanalization rate, and complications were evaluated. Technical success was defined as completion of embolization using hydrogel-coated coils. Recanalization was evaluated with time-resolved magnetic resonance angiography and/or pulmonary angiography.

Results

In 56 of 57 PAVMs, embolization was successfully performed with hydrogel-coated coils. Therefore, the technical success rate was 98% (56/57). The number of PAVMs at risk was 56, 42, 18, and 12 at 0, 12, 24, and 36 months, respectively. There was no recanalization with a mean follow-up period of 19 months (range 2–47 months) in 56 PAVMs embolized with hydrogel-coated coils. There were no major complications. As a minor complication, local pain was observed in 8 of 43 sessions (19%) after embolization.

Conclusions

Hydrogel-coated coils may be useful for preventing recanalization after the embolization of PAVMs.

First use of Micro Vascular Plugs in Australia: Endovascular treatment of pulmonary arteriovenous malformation

This report describes the first Australian experience with the Micro Vascular Plug System (MVP), as a permanent embolic device for the treatment of pulmonary arteriovenous malformations (PAVMs). MVPs deployed in small vessels between 2 mm and 5 mm are demonstrated to be feasible, safe and effective treatment for PAVMs.

Screening children for pulmonary arteriovenous malformations: Evaluation of 18 years of experience

BACKGROUND

Hereditary Hemorrhagic Telangiectasia (HHT) is an autosomal dominant disease with multi-systemic vascular dysplasia. Early diagnosis through screening is important to prevent serious complications. How best to screen children of affected parents for pulmonary arteriovenous malformations (PAVMs) is often subject to debate. Transthoracic contrast echocardiogram (TTCE) is considered optimal in screening for PAVMs in adults. Guidelines for the screening of children are not specific, reflecting the lack of scientific evidence on the best method to use.

OBJECTIVE

Aims of this study are (i) to evaluate our current screening method, consisting of history, physical examination, pulse oximetry, and chest radiography and (ii) to assess whether postponing more invasive screening for PAVMs until adulthood is safe.

METHODS

This is a prospective observational cohort study using a patient database.

RESULTS

Over a period of 18 years (mean follow-up 9.21 years, SD 4.72 years), 436 children from HHT families were screened consecutively. A total of 175/436 (40%) children had a diagnosis of HHT. PAVMs were detected in 39/175 (22%) children, 33/39 requiring treatment by embolotherapy. None of the screened children suffered any PAVM-associated complications with this screening method.

CONCLUSION

This study shows that a conservative screening method during childhood is sufficient to detect large PAVMs and protect children with HHT for PAVM-related complications. Postponing TTCE and subsequent chest CT scanning until adulthood to detect any smaller PAVMs does not appear to be associated with major risk.

ACR Appropriateness Criteria Clinically Suspected Pulmonary Arteriovenous Malformation

Pulmonary arteriovenous malformations are often included in the differential diagnosis of common clinical presentations, including hypoxemia, hemoptysis, brain abscesses, and paradoxical stroke, as well as affecting 30% to 50% of patients with hereditary hemorrhagic telangiectasia (HHT). Various imaging studies are used in the diagnostic and screening settings, which have been reviewed by the ACR Appropriateness Criteria Vascular Imaging Panel. Pulmonary arteriovenous malformation screening in patients with HHT is commonly performed with transthoracic echocardiographic bubble study, followed by CT for positive cases. Although transthoracic echocardiographic bubble studies and radionuclide perfusion detect right-to-left shunts, they do not provide all of the information needed for treatment planning and may remain positive after embolization. Pulmonary angiography is appropriate for preintervention planning but not as an initial test. MR angiography has a potential role in younger patients with HHT who may require lifelong surveillance, despite lower spatial resolution compared with CT. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every three years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.