The clinical value of dynamic pulmonary perfusion imaging combination with V/Q scan in patients with acute pulmonary embolism

Introduction: To explore the clinical value of dynamic pulmonary perfusion imaging (DPPI) in the assessment of hemodynamic changes in patients with acute pulmonary embolism (APE).

Methods: From June 2020 to June 2021, a retrospective analysis was made on 243 consecutive patients who suspected or had previous PE. The diagnostic criteria of APE referred to the guidelines for the diagnosis and treatment of APE developed by the ESC. Patients with previous PE, primary pulmonary hypertension, chronic lung disease, and arthritis involving the pulmonary artery were excluded. Finally, 107 patients (47 males and 60 females, aged 24-86 years, mean 60.3±15.5 years) were enrolled in this study. DPPI was performed by ^99mTc-MAA injection, and routine lung ventilation /perfusion scans (V/Q) were also performed. The lung equilibrium time (LET) was calculated by drawing the region of interest of DPPI (the time unit: second). The percent of pulmonary perfusion defects (PPD%) was estimated by pulmonary perfusion imaging. According to the clinical diagnosis, the patients were divided into the APE group and the non-APE group. The differences of LET and echocardiographic parameters (tricuspid regurgitation maximum velocity, tricuspid valve peak systolic gradient, PASP, RV size) between the two groups were compared. To analyze the efficacy of V/Q alone, and a combination of V/Q with DPPI for diagnosis of PE. According to PPD%, the APE patients were divided into mild (PPD%<20%), moderate (20%~40%), and severe groups (PPD%>40%), and the differences of LET and echocardiographic parameters among the three groups were compared.

Results: Forty-three patients were clinically diagnosed as APE and 64 patients were non-APE. There was no significant difference in age, sex, and BMI between the two groups. The incidence of lower limb venous thrombosis (12.0% vs. 4.7%, P = 0.001) and D-dimer (735ug/L vs. 260ug/L, P = 0.003) in the PE group were significantly higher than those in the non-PE group. The LET (32.4 sec vs. 24.5sec, P = 0.003) of the APE group was significantly longer than that of the non-APE group, and the PPD% (18% vs. 0%, P = 0.001) of the APE group was significantly higher than that of the non-APE group. A moderate correlation between LET and PPD was found (r = 0.284, P =0.003). However, there was no significant difference in echocardiographic parameters between the two groups. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of V/Q in the diagnosis of PE were 88.4%, 64.1%, 73.8%, 70.4%, and 77.3%, respectively. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of V/Q combined with DPPI (LET >24.3 sec) in the diagnosis of PE were 93.0%, 71.9%, 80.4%, 69.0%, and 93.9%, respectively.

Table1. The Diagnostic efficacy of simple V/Q scan and combination of V/Q and DPPI to detect PE.

Conclusions: DPPI is a safe, effective, and non-invasive imaging method for evaluating pulmonary artery hemodynamics. A combination of LET and V/Q scans could improve the diagnostic efficacy of PE.