Background: Untreated pulmonary arteriovenous malformations (PAVMs) can present with life-threatening complications. Agitated saline solution transthoracic contrast echocardiography (TTCE) has been recommended as the screening test of choice for PAVMs in hereditary hemorrhagic telangiectasia (HHT). A TTCE grading system has been proposed but not validated. The aim of this study was to determine the positive predictive value (PPV) of TTCE grades for the presence of PAVMs on CT.
Methods: A blinded retrospective review was conducted. All patients screened at the Toronto HHT Center (June 2002 to September 2004) with positive TTCE results were included. TTCE results were scored for delay (number of cardiac cycles) before appearance of microcavitations in the left atrium and graded for intensity of opacification. Grade 1 indicates minimal left ventricular opacification, grade 2 indicates moderate opacification, grade 3 indicates extensive opacification without outlining the endocardium, and grade 4 indicates extensive opacification with endocardial definition. Thoracic CT was performed in all patients, and results were scored as positive, negative, or indeterminate for PAVMs.
Results: Of 155 patients screened for PAVMs, 104 had positive TTCE results. Complete data were available for 90 patients (87%). Mean age was 45 years; 62% were female. Seventeen percent of patients screened and 27% of patients with positive TTCE results had CT detectable PAVMs. There was a significant association between TTCE grade and presence of PAVMs on CT (p < 0.0001). The PPV of grades 1, 2, 3, and 4 were 0.02 (95% confidence interval, 0.00 to 0.06), 0.25 (95% confidence interval, 0.06 to 0.44), 0.56 (95% confidence interval, 0.23 to 0.88), and 1.0 (95% confidence interval, 1.0 to 1.0), respectively.
Conclusions: Increased shunt grade predicts increased probability of PAVMs and may be used to guide decisions in the screening algorithm for PAVMs.