Can pulmonary angiography be limited to the most suspicious side if the contralateral side appears normal on the ventilation/perfusion lung scan? Data from PIOPED. Prospective Investigation of Pulmonary Embolism Diagnosis.

PURPOSE

The purpose of this investigation was to determine the frequency of pulmonary embolism (PE) in a single lung that showed a normal ventilation/perfusion (V/Q) lung scan when the V/Q scan on the contralateral side was interpreted as non-high-probability for PE.

METHODS

Data are from the national collaborative study Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED). PE was diagnosed or excluded in all lungs by pulmonary angiography.

RESULTS

Single lungs with no V/Q abnormalities, when the V/Q scan on the contralateral side was interpreted as non-high-probability for PE, showed PE in 2 of 19 (11%) (95% confidence interval [CI], 1 to 33%). If PE was excluded by angiography on the side of the abnormal V/Q scan, then PE on the side of the normal V/Q scan was shown in only 1 of 19 (5%) (95% CI, 0 to 26%).

CONCLUSION

A normal V/Q scan in a single lung, when the contralateral lung was interpreted as non-high-probability for PE, did not completely exclude PE on the apparently normal side. In such lungs, the probability of PE was in the range of low-probability interpretations. If the pulmonary angiogram showed no PE on the side of the abnormal V/Q scan, the probability of PE on the side of the normal V/Q scan satisfied the definition of very low probability for PE. This observation in patients undergoing pulmonary angiography may assist in determining whether the pulmonary angiogram should be bilateral.