Ventilation perfusion lung scans in the management of suspected pulmonary embolism

The purpose of the study was twofold: (a) to relate the degree of clinical suspicion of pulmonary embolism (PE) to the findings of isotope ventilation-perfusion (V/Q) scans, and (b) to determine the extent to which the scan results influence patient management. A questionnaire was completed by the requesting clinician before V/Q scanning in 60 consecutive in-patients in whom PE had, with varying degrees of probability, been considered possible. Retrospectively, the case notes were reviewed to determine whether or not the patients were anticoagulated when discharged. Prior to scanning, PE was considered probable or almost certain in 35 (58 per cent) patients and unlikely or very unlikely in 25 (42 per cent) patients. Thirty-seven (62 per cent) scans were confidently reported positive or negative for PE; in the remaining 23 (38 per cent) cases, the scan report was necessarily inconclusive. The clinical assessment was supported by the scan result in 23/25 (92 per cent) patients in whom PE was felt unlikely or very unlikely, but in only 14/35 (40 per cent) in whom this diagnosis was felt probable or almost certain. Twenty (33 per cent) patients were already anticoagulated when scanned; this treatment was initiated in nine (15 per cent) and discontinued in eight (13 per cent) in the light of the scan result. Isotope V/Q scans are not always useful in confidently confirming or excluding the presence of PE. Nevertheless, the scan reports, even when necessarily guarded and somewhat at variance with the clinical assessment of the probability of PE, strongly influence clinicians in their decisions as to whether to anticoagulate their patients.