Predictors of an intermediate ventilation/perfusion lung scan in patients with suspected acute pulmonary embolism

An intermediate ventilation/perfusion (V/Q) lung scan lacks diagnostic utility in excluding acute pulmonary embolism (PE).

To identify the potential predictors of an intermediate V/Q lung scan in patients with suspected acute PE.

A review of the medical records of 306 consecutive patients with suspected acute PE, in whom a V/Q lung scan was performed (interpretation using modified Prospective Investigation of Pulmonary Embolism Diagnosis criteria).

A total of 274 patients (89.5%) had a non-intermediate V/Q lung scan: 88 (28.8%) high probability, 149 (48.7%) low probability, and 37 (12.1%) near normal/normal. Thirty-two patients (10.5%) had an intermediate V/Q lung scan. Patients with an intermediate V/Q lung scan presented a significantly greater frequency of age greater than 70 years (81.2 versus 50.4%, P=0.01), previous cardiopulmonary disease (75 versus 46.3%, P=0.003), chronic obstructive pulmonary disease (34.4 versus 15.7%, P=0.01), and chest radiograph evidence of emphysema (18.7 versus 4.7%, P=0.008). We found no other significant differences in the rest of the characteristics studied between patients with an intermediate and a non-intermediate V/Q lung scan.

The possibility of an intermediate V/Q lung scan is higher in elderly patients and in patients with previous cardiopulmonary disease (especially with chronic obstructive pulmonary disease). Emphysema is the only chest radiograph abnormality associated with a greater possibility of an intermediate V/Q lung scan.