Grading of pulmonary right-to-left shunt with transthoracic contrast echocardiography: Does it predict the indication for embolotherapy?

Rationale: Pulmonary arteriovenous malformations (PAVMs) are associated with severe neurologic complications in patients with hereditary hemorrhagic telangiectasia (HHT). Therefore, screening is warranted. Transthoracic contrast echocardiography (TTCE) can effectively detect a pulmonary right-to-left shunt (RLS). Objectives: To determine prospectively the predictive value of TTCE grading to detect PAVMs on high-resolution CT (HRCT) scans of the chest and the indication for embolotherapy. Methods: Three hundred seventeen patients, referred for possible HHT, were screened for PAVMs. Patients who underwent both chest HRCT scanning and TTCE were included in the study (n = 281). For the purposes of this study we used a 3-point grading scale, and shunt grades 3 and 4 according to the classification model of Barzilai et al were combined. Embolotherapy was performed of all PAVMs judged large enough for treatment. Results: Echocardiographic criteria for a pulmonary RLS were present in 105 patients (41%) [mean (± SD) age, 43.7 ± 15.7 years; female gender, 63%]. Chest HRCT scan findings were positive in 55 patients (52%) in this group. The positive predictive value of shunt grade for the presence of PAVMs on chest HRCT scans was 22.9% for grade 1 (n = 35), 34.8% for grade 2 (n = 23), and 83.0% for grade 3 (n = 47), respectively. None of the patients with PAVMs seen on chest HRCT scans and a TTCE grade 1 (n = 8) or 2 (n = 8) were candidates for embolotherapy. Of 39 patients with TTCE grade 3 and PAVMs seen on chest HRCT scans, 26 patients (67%) underwent embolotherapy. Conclusion: An increased echocardiographic shunt grade correlates with an increased probability of PAVMs seen on chest HRCT scans. Only patients with a TTCE grade 3 displayed PAVMs on chest HRCT scans that were large enough for embolotherapy.