BACKGROUND: Solitary pulmonary microembolism is rarely discussed as a distinct
diagnostic entity. The purpose of this investigation was to determine the prevalence
and clinical significance of embolism limited to subsegmental branches in a group
of patients discharged from hospital on anticoagulants with a diagnosis of pulmonary
embolism based on ventilation-perfusion imaging followed by selective angiography.
MATERIAL AND METHODS: Of 29 consecutive patients with classic signs of
pulmonary embolism at angiography, we identified a subgroup of 5 patients with
sub-segmental embolism, which was solitary in all cases.
RESULTS: Clinical presentation included chest pain (2/5), shortness of
breath (2/5, or hypoxemia (1/5). Chest X-rays were normal (2/5), or showed pulmonary
oedema (1/5) or atelectasis with (1/5), or without (1/5) pleural effusion. VQ
imaging patterns included small subsegmental mismatch (1/5), one segment mismatch
(1/5), single (1/5) or triple (2/5) match. The site and size of the microemboli
found at angiography were incompatible with the location and severity of symptoms
in 4/5 (80%) patients, and with location and extent of Chest X-ray findings and
with VQ patterns in all patients. VQ abnormalities were either either disproportionably
larger or were non congruent with the vascular territory compromised by the subsegmental
embolus.
CONCLUSIONS: Sub-segmental pulmonary micro-emboli were always solitary,
and not uncommon, comprising 17% of all patients with pulmonary embolism. The
location and size of the emboli were inconsistent with clinical, Chest X-ray and
scintigraphic findings, suggesting that isolated microemboli are a serendipitous
finding, of no clinical significance
