Relative Lung Perfusion on Ventilation-Perfusion Scans After Double Lung Transplant.

BACKGROUND: Pulmonary blood flow can be assessed on ventilation-perfusion (VQ) scan with relative lung perfusion, with a 55% to 45% (or 10%) right-to-left differential considered normal. We hypothesized that wide perfusion differential on routine VQ studies at 3 mo posttransplant would be associated with an increased risk of death or retransplantation, chronic lung allograft (CLAD), and baseline lung allograft dysfunction. METHODS: We conducted a retrospective cohort study on all patients who underwent double-lung transplant in our program between 2005 and 2016, identifying patients with a wide perfusion differential of >10% on a 3-mo VQ scan. We used Kaplan-Meier estimates and proportional hazards models to assess the association between perfusion differential and time to death or retransplant and time to CLAD onset. We used correlation and linear regression to assess the relationship with lung function at time of scan and with baseline lung allograft dysfunction. RESULTS: Of 340 patients who met inclusion criteria, 169 (49%) had a relative perfusion differential of ≥ 10% on a 3-mo VQ scan. Patients with increased perfusion differential had increased risk of death or retransplantation ( P = 0.011) and CLAD onset ( P = 0.012) after adjustment for other radiographic/endoscopic abnormalities. Increased perfusion differential was associated with lower lung function at time of scan. CONCLUSIONS: Wide lung perfusion differential was common after lung transplant in our cohort and associated with increased risk of death, poor lung function, and CLAD onset. The nature of this abnormality and its use as a predictor of future risk warrant further investigation.

Mismatched perfusion defects on routine ventilation-perfusion scans after lung transplantation.

BACKGROUND: Incidental pulmonary embolism (PE) is a challenging entity with unclear treatment implications. Our program performs routine ventilation-perfusion (VQ) scans at 3-months post-transplant to establish airway and vascular function. We sought to determine the prevalence and prognostic implications of mismatched perfusion defects (MMPD) found on these studies, hypothesizing they would be associated with a benign prognosis. METHODS: We studied VQ scans obtained routinely at 3-months post-transplant from double lung transplant recipients 2005-2016 for studies with MMPD interpreted as high or intermediate probability for PE. We tested the relationship between MMPD and 1-year survival via chi square testing, overall survival via Kaplan Meier analysis with log rank testing and peak forced expiratory volume in 1 second (FEV1) percent predicted via t-testing. RESULTS: Three hundred and seventy-three patients met inclusion criteria, of whom 35 (9%) had VQ scans with MMPDs interpreted by radiologists as high or intermediate probability for PE. Baseline recipient and donor characteristics were similar between groups. Seven patients (20%) in the MMPD group were treated with therapeutic anticoagulation. Patients with MMPD had similar 1-year survival (100% vs. 98%, P = 1.00), overall survival (log rank P = .90) and peak FEV1% predicted (94% [SD 20%] vs. 92% [SD 21%]; P = .58). Anticoagulation did not affect these relationships. CONCLUSION: Mismatched perfusion defects on routine post-transplant VQ scan were not associated with a difference in survival or lung function. A conservative approach to these changes may be a viable option in the absence of other anticoagulation indications.

The clinical utility of a diagnostic imaging algorithm incorporating low-dose perfusion scans in the evaluation of pregnant patients with clinically suspected pulmonary embolism.

PURPOSE OF THE REPORT: The aim of this study was to determine the proportion of pregnant patients with a clinical suspicion of pulmonary embolism and a normal chest radiograph who require further evaluation with perfusion scintigraphy alone compared with both perfusion scintigraphy and computed tomography (CT). PATIENTS AND METHODS: All patients who had a low-dose perfusion lung scan as part of a clinical imaging algorithm to assess for clinically suspected pulmonary embolism in pregnant patients at 3 regional hospitals from September 2009 to February 2011 were retrospectively reviewed. The proportion of patients requiring a low-dose perfusion-only lung scan was compared with the proportion requiring further evaluation with both a low-dose perfusion scan and a CT scan to complete the algorithm. RESULTS: Seventy-four (74) patients were included. Sixty-one (61/74; 82.4%) patients had a normal low-dose perfusion-only scan and did not require further imaging. Thirteen (13/74; 17.6%) patients demonstrated an abnormal perfusion scan and required further imaging with a CT scan. One patient (1/74; 1.4%) was diagnosed with pulmonary embolism. CONCLUSIONS: Our results suggest that for pregnant patients with a normal chest radiograph, pulmonary embolism can be excluded in 82.4% of patients with a low-dose perfusion scan alone.