The impact of lung perfusion scintigraphy in the emergency management of patients with suspected pulmonary embolism.

Objective: Pulmonary Embolism (PE) is an emergency condition that requires immediate treatment. As the symptoms and the risk factors are nonspecific, PE differential diagnosis is often required. Even if angio-CT is considered the gold standard for PE diagnosis, the frequent allergic condition and/or chronic renal failure of patients make, in most cases, not possible the use of contrast enhancement in emergency with even more increasing use of Lung Perfusion Scintigraphy (LPS), as a simple and fast examination with no preparation/contraindication. The aim of our study is to highlight the role of LPS in the management of patients (pts) with suspected PE admitted to our hospital as an emergency in the "on-call" 24 hours (hrs) service.

Materials And Method: We retrospectively revised 2166 LPS performed for suspected PE from January 2012 to December 2016, of which 1730 were urgent. LPS was performed according to the EANM guidelines in the 4 standard projections. The relation between symptoms, risk factors, dosage of D-dimers, other imaging diagnostic tools and LPS results were evaluated by contingency tables and Odds Ratio (OR).

Results: The origin unit of pts was: emergency (56.7%), pneumology (10.8%), neurology (4.8%), internal medicine (6.5%), surgery (5.2%), cardiology (3.3%) and other departments (11.2%). 59.3% of the examinations were performed during the on-call 24 hrs service. Symptoms were chest pain in 39%, dyspnea in 75%, cough in 22%. In 34% were present two symptoms, while 10% were asymptomatic. D-dimer dosage before LPS was increased in 97% (>500 ug/L). 55.5% had only one risk factor, 18.7% had two or more risk factors. 75.5% of pts had previously performed another diagnostic exam (Chest X-ray in 57%, chest CT in 8.4%, both in 10.1%) while 24.5% did not undergo previous diagnostic exam. The Chest X-ray and/or chest CT resulted negative in 25.4%, suspected for PE in 24.4%, non-specific with pleural effusion in 18.8% and non-specific with inflammatory interstitial diseases in 31.4%. LSP resulted positive for PE in 17% and then treated; LPS resulted negative in the remnant 83%. LPS results were associated with those of CT and Rx (χ=17.5 P=0.001). LPS resulted positive in 13.8% with negative Chest X-ray and/or CT, in 23.4% with suspected PE, in 15.2% with pleural effusion and in 14.7% with inflammatory interstitial diseases. Furthermore LPS resulted positive in 17.32% without previous diagnostic exam. The increased value of D-Dimers (>500ng/ml) observed in 97% was not predictive of PE (OR=0.598 P=0.152). A similar result was observed for cough (OR=1.146 P=0.395) and chest pain (OR=0.927 P=0.601). Conversely, dyspnea appeared to be a significant symptom of PE (OR=1.596 P=0.003). The presence of risk factors is not predictor of PE detected by LPS (OR=1.297 P=0.089).

Conclusion: LPS has a key role in the early diagnosis but even more in the exclusion of PE, optimizing the management of pts who do not require admission to intensive care unit with high costs and limited availability. LPS confirms to be a simple, quick and inexpensive examination. It does not require preparation and has no side effect so it can be performed in all types of pts including pregnant women, politraumatized and complicated patients, with great impact on resource optimization for intensive care units. Our multi-year and large-scale experience related to a metropolitan area suggests that, to date, given the great demand and relevance of this examination, Nuclear Medicine Units must necessarily be organized in order to provide LPS as emergency in on-call 24 hrs service.