Evaluation of pulmonary perfusion and ventilation in suspected chronic thromboembolic pulmonary hypertension via phase-resolved functional lung magnetic resonance imaging: correlations with hemodynamics and cardiopulmonary function

Abstract

Background: Phase-resolved functional lung (PREFUL) magnetic resonance imaging (MRI) is a reliable, noninvasive method for assessing pulmonary ventilation and perfusion. However, the differences in subgroups of patients with chronic pulmonary embolism (CPE) have not been thoroughly investigated, and there may be significant clinical value in examining noninvasive methods for evaluating hemodynamics and right heart function in patients with CPE. This study aimed to evaluate pulmonary perfusion and ventilation in patients with suspected chronic thromboembolic pulmonary hypertension (CTEPH) via PREFUL MRI and further determined the correlations of these findings with right heart catheterization (RHC), right heart function indicators, and pulmonary function test results.

Methods: A retrospective analysis was performed on patients with suspected CTEPH who were referred to our center between June 2020 and September 2022. All patients underwent RHC or echocardiography, pulmonary angiography (PA), ventilation-perfusion (V/Q) lung scan, or CTPA, with PREFUL MRI being conducted within 2 weeks of these tests. The diagnoses of CTEPH and chronic thromboembolic pulmonary disease (CTED) were established through multidisciplinary team discussions. Mean parameter values from five PREFUL MRI slices were calculated, including normalized perfusion (Q_N), exclusive perfusion defect percentage (QDP_exc), total perfusion defect percentage (QDP_tot), regional ventilation (RV), exclusive ventilation defect percentage (VDP_exc), total ventilation defect percentage (VDP_tot), and ventilation/perfusion match defect percentage (VQM_def). Clinical correlations were assessed through the comparison of PREFUL MRI parameters with hemodynamic data, right heart function indicators, and pulmonary function parameters.

Results: In total, 42 patients (26 men and 16 women; mean age 53.5±13.5 years) with suspected CTEPH were analyzed: 31 had CTEPH and 11 had CTED. Significant differences between the two groups were found in Q_N, QDP_exc, QDP_tot, RV, and VDP_exc. VQM_def demonstrated the best diagnostic performance among all parameters, with a sensitivity of 87%, specificity of 91%, and accuracy of 88%. Q_N, QDP_exc, and QDP_tot were correlated with mean pulmonary arterial pressure (mPAP; r=-0.490, r=0.539, and r=0.534, respectively; all P values <0.01). QDP_exc and QDP_tot were correlated with pulmonary vascular resistance (r=0.369 and r=0.362, respectively; P<0.05). Q_N, QDP_exc, and QDP_tot also were significantly correlated with right heart function indicators (all P values <0.01). RV was negatively correlated with percent predicted single-breath diffusing capacity of the lung for carbon monoxide (DLCO SB %pred; r=-0.588; P<0.001), and VDP_tot was negatively correlated with the ratio of forced expiratory volume in 1 s to forced vital capacity (parameter expressed as a percentage of the predicted value) (r=-0.379; P=0.027).

Conclusions: Quantitative parameters obtained from PREFUL MRI were correlated with hemodynamic status and cardiopulmonary function in patients with CTEPH or CTED. PREFUL MRI perfusion parameters demonstrated strong diagnostic performance for CTEPH, indicating their clinical potential.

Keywords: Chronic thromboembolic pulmonary hypertension (CTEPH); hemodynamics; phase-resolved functional lung (PREFUL); pulmonary function test.

Figure 1

PREFUL MRI of a 58-year-old man with CTEPH. Five coronal slices, centered at the level of the tracheal bifurcation, are presented from anterior to posterior (displayed from left to right, respectively). The global defect percentages for this patient were as follows: RV =16.7%, Q_N =4.4%, QDP_exc =29.9%, QDP_tot =32.7%, VDP_exc =18.3%, VDP_tot =21.1%, VQM_def =2.8%, and VQM_non-def =49.0%. CTEPH, chronic thromboembolic pulmonary hypertension; MRI, magnetic resonance imaging; PREFUL, phase-resolved functional lung; Q_N, normalized perfusion; QDP_exc, exclusive perfusion defect percentage; QDP_tot, total perfusion defect percentage; RV, regional ventilation; VDP_exc, exclusive ventilation defect percentage; VDP_tot, total ventilation defect percentage; VQM_def, ventilation/perfusion match defect percentage; VQM_non-def, ventilation-perfusion match nondefect percentage.

Figure 2

PREFUL MRI of a 50-year-old man with CTED. The global defect percentages for this patient were as follows: RV =15.9%, Q_N =6.1%, QDP_exc =19.9%, QDP_tot =19.9%, VDP_exc =2.0%, VDP_tot =2.0%, VQM_def =0%, and VQM_non-def =78.1%. CTED, chronic thromboembolic pulmonary disease; MRI, magnetic resonance imaging; PREFUL, phase-resolved functional lung; Q_N, normalized perfusion; QDP_exc, exclusive perfusion defect percentage; QDP_tot, total perfusion defect percentage; RV, regional ventilation; VDP_exc, exclusive ventilation defect percentage; VDP_tot, total ventilation defect percentage; VQM_def, ventilation/perfusion match defect percentage; VQM_non-def, ventilation-perfusion match nondefect percentage.

Figure 3

Other results from the patient in Figure 1 (A,B) and images from the patient in Figure 2 (C,D). (A) Pulmonary angiogram revealed an eccentric filling defect in the main pulmonary artery (arrow). (B) Flow-volume loop indicated mild ventilatory dysfunction and mild diffusion impairment, with a negative bronchodilator test. The premedication pulmonary function test results were as follows: FVC %predicted =86.2%, FEV₁ %predicted =74.5%, FEV₁/FVC %predicted =84.7%, and DLCO SB %predicted =65.6%. (C) Maximum intensity projection of the pulmonary artery indicated filling defects in the right lower lobe pulmonary artery (arrow), with complete occlusion of the lumen. (D) Flow-volume loop demonstrated normal lung function. FVC %predicted, percent predicted forced vital capacity; FEV₁ %predicted, percent predicted forced expiratory volume in 1 s; DLCO SB %predicted, percent predicted single-breath diffusing capacity of the lung for carbon monoxide.

Figure 4

ROC curve comparison of various PREFUL MRI parameters. The areas AUCs of Q_N, QDP_exc, QDP_tot, VDP_tot, and VQM_def were 0.85, 0.87, 0.87, 0.71, and 0.91, respectively. AUC, area under the curve; MRI, magnetic resonance imaging; PREFUL, phase-resolved functional lung; Q_N, normalized perfusion; QDP_exc, exclusive perfusion defect percentage; QDP_tot, total perfusion defect percentage; ROC, receiver operating characteristic; VDP_tot, total ventilation defect percentage; VQM_def, ventilation/perfusion match defect percentage.