REGIONAL ALTERATIONS IN LUNG VENTILATION IN END-STAGE PRIMARY PULMONARY-HYPERTENSION - CORRELATION BETWEEN CT AND SCINTIGRAPHY

OBJECTIVE. The purpose of this study was to correlate scintigraphic fi ndings of regional alterations in lung ventilation and perfusion with regional variations in CT attenuation in patients with primary pulmona ry hypertension. SUBJECTS AND METHODS. Chest CT scans and ventilation- perfusion scans obtained within 24 hr of each other in 18 patients wit h primary pulmonary hypertension referred for lung transplantation wer e reviewed. The lungs were divided into eight regions (left/right, sup erior/inferior relative to the carina, and anterior/posterior relative to the trachea). CT scans were evaluated and areas of parenchymal inh omogeneities were tabulated for the eight regions. Areas of reverse mi smatch (perfusion without ventilation) were established by blinded ana lysis of planar scintigraphic studies in six projections using Tc-99m- labeled DTPA-aerosol and macroaggregated albumin for the eight regions and then were correlated with the CT findings. RESULTS. Abnormal find ings on ventilation scans and reverse ventilation-perfusion mismatches indicating an inadequate hypoxic vasoconstriction reflex were found i n 91 regions in all 18 patients. Nonuniform parenchymal CT density was found in 12 patients, There was a significant correlation (p = .009) of scintigraphic reverse mismatches with abnormal CT density in 38 reg ions in 11 patients, In one patient, there was no scintigraphic correl ation with abnormal CT attenuation. The specificity of abnormal CT den sity for scintigraphic reverse mismatches was 81%, with a sensitivity of 42%. CONCLUSION. Scintigraphic reverse mismatches indicate a high p revalence of significant pulmonary arterial shunting in patients with ventilatory defects. Increased relative CT attenuation in areas of imp aired ventilation as shown on the ventilation scans is amplified in pr imary pulmonary hypertension by an inadequate hypoxic vasoconstriction reflex. This finding does not signify underlying infiltrative lung di sease and correlates with regions with reverse mismatches.