Incidence of Pulmonary Embolism Diagnosed by Ventilation and Perfusion Scan After Indeterminate CT Pulmonary Angiography

Investigators studied the incidence of pulmonary embolism (PE) diagnosed by ventilation and perfusion (VQ) scan after suboptimal computed tomography pulmonary angiography (CTPA). They retrospectively analyzed data from one academic institution that used modified prospective investigation of pulmonary embolism diagnosis (PIOPED) or prospective investigative study of acute pulmonary embolism diagnosis (PISAPED) criteria to diagnose pulmonary embolism. Of 300 consecutive CTPA studies, 122 were determined to be “suboptimal,” and the patients then proceeded to VQ scan. Of these, 98% were negative for PE. An alternative diagnosis was made in 28% of suboptimal CTPA cases (59% pneumonia). On review, contrast injection timing was the factor responsi…