Routine echocardiography using a standard frequency ultrasound (SFU) probe has insufficient spatial resolution to clearly visualize the parietal pericardium (PP). High frequency ultrasound (HFU) has an enhanced axial resolution. This study aimed to use commercially available high frequency linear probe (HFLP) to evaluate the apical PP thickness (PPT) and pericardial adhesion (PA) in both normal pericardium and/or pericardial diseases.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 received both SFU and HFU to image the apical PP (APP) and pericardial adhesion (PA). Some subjects received CT scans.The apical PPT was measured by HFU and found to be 0.60±0.01 (0.37∼0.87) mm in normal controls, 1.22±0.04 (0.48∼4.53) mm in patients with AA, and 2.91±0.17 (1.13∼9.01) mm in patients with CP. A tiny physiologic effusion was observed in 39.2% of normal individuals. PA was detected in 69.8% of patients with local pericarditis of AA and 97.5% of patients with CP. Visibly thickened visceral pericardium was observed in six CP patients. The apical PPT measurements obtained by HFU correlated well with those obtained by CT in those CP patients. However, CT could only clearly visualize the APP in 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.The apical PPTs measured by HFU in normal controls was 0.40∼1.00 mm, consistent with previous reports from necropsy studies. HFU had a higher resolution in distinguishing local pericarditis of the APP from normal individuals. We found that HFU was superior to CT in imaging APP lesions, as CT failed to visualize 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 findings that 18% of CP patients had normal PPT.Copyright © 2023. Published by Elsevier Inc.