Diagnostic Yield of Rescreening Adults for Pulmonary Arteriovenous Malformations

Executive summary of the 14th HHT international scientific conference

Hereditary Hemorrhagic Telangiectasia (HHT) is an autosomal dominant vascular disorder characterized by small, dilated clustered vessels (telangiectasias) and by larger visceral arteriovenous malformations (AVMs), which directly connect the feeding arteries with the draining veins. These lesions are fragile, prone to rupture, and lead to recurrent epistaxis and/or internal hemorrhage among other complications. Germline heterozygous loss-of-function (LOF) mutations in Bone Morphogenic Protein 9 (BMP9) and BMP10 signaling pathway genes (endoglin-ENG, activin like kinase 1 ACVRL1 aka ALK1, and SMAD4) cause different subtypes of HHT (HHT1, HHT2 and HHT-juvenile polyposis (JP)) and have a worldwide combined incidence of about 1:5000. Expert clinicians and international scientists gathered in Cascais, Portugal from September 29th to October 2nd, 2022 to present the latest scientific research in the HHT field and novel treatment strategies for people living with HHT. During the largest HHT scientific conference yet, participants included 293 in person and 46 virtually. An impressive 209 abstracts were accepted to the meeting and 59 were selected for oral presentations. The remaining 150 abstracts were presented during judged poster sessions. This review article summarizes the basic and clinical abstracts selected as oral presentations with their new observations and discoveries as well as surrounding discussion and debate. Two discussion-based workshops were also held during the conference, each focusing on mechanisms and clinical perspectives in either AVM formation and progression or current and future therapies for HHT. Our hope is that this paper will represent the current progress and the remaining unanswered questions surrounding HHT, in order to serve as an update for those within the field and an invitation to those scientists and clinicians as yet outside of the field of HHT.

Evolution of Pulmonary Arteriovenous Malformations: The Role of Contrast Echocardiography

BACKGROUND

Pulmonary arteriovenous malformations (PAVMs) are direct connections between the pulmonary artery and the pulmonary vein, mostly associated with hereditary hemorrhagic telangiectasia (HHT). PAVMs can lead to severe neurologic complications such as stroke and brain abscess. The risk of complications decreases after embolization. Therefore, screening for PAVMs using transthoracic contrast echocardiography (TTCE) is recommended, including a rescreening interval of 5 years.

RESEARCH QUESTION

Is extension of the interval for rescreening patients without a pulmonary right-to-left shunt (RLS) of up to 10 years appropriate?

STUDY DESIGN AND METHODS

Adult patients with HHT with 5- or 10-year follow-up TTCE, or both, were included. Patients who underwent PAVM embolization in the past or at baseline were excluded. The RLS grades and presence of a treatable PAVM were compared with baseline.

RESULTS

In total, 387 patients (median age, 45 years [interquartile range, 33-54 years]; 56% women) involving 5- and 10-year follow-up data in 363 and 166 patients, respectively, were included. None of the patients (n = 148) without a pulmonary RLS at baseline demonstrated a treatable PAVM after 5 and 10 years. Of the patients with a pulmonary RLS at baseline, 20 patients (9%) and three patients (3%) demonstrated a treatable PAVM at the 5- and 10-year follow-up, respectively. In most patients, the RLS grade remained stable over time.

INTERPRETATION

On the basis of the results of this retrospective study, we believe that the rescreening interval for patients with HHT without a pulmonary RLS at initial screening may be extended to 10 years. Those with a pulmonary RLS should be rescreened every 5 years because treatable PAVMs can evolve.

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.

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.

Postembolotherapy Pulmonary Arteriovenous Malformation Follow-Up: A Role for Graded Transthoracic Contrast Echocardiography Prior to High-Resolution Chest CT Scan

BACKGROUND

High-resolution chest CT (HRCT) scan is recommended after pulmonary arteriovenous malformation (PAVM) embolotherapy to assess for PAVM persistence and untreated PAVM growth. Graded transthoracic contrast echocardiography (TTCE) predicts the need for embolotherapy in PAVM screening. This study sought to determine whether postembolotherapy graded TTCE can similarly predict the need for repeat embolotherapy.

METHODS

Thirty-two patients (8 men and 24 women; mean age, 51.1 ± 12.6 years) with prior PAVM embolotherapy and follow-up HRCT scan were prospectively enrolled. Patients underwent graded TTCE using a validated three-point quantitative grading scale. TTCE grade and HRCT findings were compared.

RESULTS

Median time between most recent HRCT scan and TTCE was 7 days (interquartile range, 0-272 days). Thirty patients (94%) had no PAVMs requiring repeat embolotherapy on HRCT scan. Two patients (6%) had PAVMs requiring repeat embolotherapy (feeding artery [FA] ≥ 3 mm), one with untreated PAVM growth and one with treated PAVM persistence. TTCE was positive in 88% of patients (n = 28). All patients (n = 4, 12%) with negative TTCE had no visible PAVMs on HRCT scan. Nine patients (32%) had grade 1 shunt, 10 (35%) had grade 2 shunt, and nine (32%) had grade 3 shunt. No patients with grade 1 shunt had PAVMs amenable to repeat embolotherapy on HRCT scan. All patients (n = 2) with PAVMs requiring repeat embolotherapy (FA ≥ 3 mm) had grade 3 shunt. TTCE grade was significantly associated with PAVM FA diameter (P < .001).

CONCLUSIONS

Postembolotherapy graded TTCE can predict the need for repeat embolotherapy on HRCT scan. Patients with negative TTCE and grade 1 shunt may not require HRCT follow-up and can potentially be followed with serial graded TTCE.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT02936349; URL: www.clinicaltrials.gov.