Evaluation of Pericardial Thickening and Adhesion Using High-Frequency Ultrasound.

Background: Routine echocardiography using a standard-frequency ultrasound probe has insufficient spatial resolution to clearly visualize the parietal pericardium (PP). High-frequency ultrasound (HFU) has enhanced axial resolution. The aim of this study was to use a commercially available high-frequency linear probe to evaluate apical PP thickness (PPT) and pericardial adhesion in both normal pericardium and pericardial diseases.

Methods: From April 2002 to March 2022, 227 healthy individuals, 205 patients with apical aneurysm (AA) and 80 patients with chronic constrictive pericarditis (CP) were recruited to participate in this study. All subjects underwent both standard-frequency ultrasound and HFU to image the apical PP (APP) and pericardial adhesion. Some subjects underwent computed tomography (CT).

Results: Apical PPT was measured using HFU and found to be 0.60 ± 0.01 mm (0.37-0.87 mm) in normal control subjects, 1.22 ± 0.04 mm (0.48-4.53 mm) in patients with AA, and 2.91 ± 0.17 mm (1.13-9.01 mm) in patients with CP. Tiny physiologic effusions were observed in 39.2% of normal individuals. Pericardial adhesion was detected in 69.8% of patients with local pericarditis due to AA and 97.5% of patients with CP. Visibly thickened visceral pericardium was observed in six patients with CP. Apical PPT measurements obtained by HFU correlated well with those obtained by CT in those patients with CP. However, CT could clearly visualize the APP in only 45% of normal individuals and 37% of patients with AA. In 10 patients with CP, both HFU and CT demonstrated equal ability to visualize the very thickened APP.

Conclusions: Apical PPT measured using HFU in normal control subjects ranged from 0.37 to 0.87 mm, consistent with previous reports from necropsy studies. HFU had higher resolution in distinguishing local pericarditis of the AA from normal individuals. HFU was superior to CT in imaging APP lesions, as CT failed to visualize the APP in more than half of both normal individuals and patients with AA. The fact that all 80 patients with CP in our study had significantly thickened APP raises doubt regarding the previously reported finding that 18% of patients with CP had normal PPT.