Main pulmonary arterial distensibility - Different presentation between chronic pulmonary hypertension and acute pulmonary embolism

Background: The main pulmonary arterial (PA) distensibility in patients with pulmonary hypertension (PH) and pulmonary embolism (PE) is uncertain. Methods and Results: We enrolled 45 patients with echocardiographic signs of PH and without imaging evidence of PE, and another 45 who were found by multidetector-row computed tomography to have PE. Fifty normal patients served as a control group. The PA distensibility was calculated from the change in main PA diameter between diastole and systole, as the maximal systolic diameter minus the minimal diastolic diameter divided by the minimal diastolic diameter. The PA distensibility is lowest in PH (6.0±2.7%), followed by PE (12.9±3.4%) and then the normal controls (25.9±5.7%). Statistical analysis of data obtained from patients with PE or PH reveals that a PA distensibility of >8.3% could be used to identify PE with a sensitivity of 83% and a specificity of 82%. After a 3-month anticoagulation, 22 of 45 PE patients had complete resolution of thrombus; 23 had residual thrombus. The PE patients, regardless of residual thrombus presence, had significant improvement of PA distensibility after a 3-month anticoagulation, although the diameters of main PA did not shrink. Conclusion: PA distensibility is a method to distinguish acute PE from chronic PH.