Utility of Lung Ventilation -Perfusion SPECT/CT scan in Chronic Thromboembolic Pulmonary Hypertension.

Objectives Ventilation Perfusion lung scan using Tc99m DTPA and Tc99m MAA ( V/Q scan) has an established role in the diagnosis of pulmonary thromboembolism. (PTE) The role of SPECT/CT V/Q scan in PTE is evolving. PTE is recognized as an important cause of Chronic pulmonary hypertension ( CTEPH) amenable to management with anticoagulation and pulmonary thromboendarterectomy. The aim of this study was to analyze the role of VQ SPECT CT in identifying patients with CTEPH and guide management.

Methods Patients with suspected CTEPH who were referred for VQ SPECT CT were included in the study. The results of the VQ SPECT CT scan were reviewed. The SPECT CT V/Q findings were correlated with CT angiogram (CTA ), pulmonary catheter angiogram, echocardiogram, surgical data of pulmonary thromboendarterectomy and clinical outcome.

Results A total of 31 patients (age range 32-78, males 17, females 14) underwent SPECT CT V/Q for suspected CTEPH. Among these 31 patient's, 12 had high probability SPECT V/Q (39%). Nine of the 12 patients with high probability SPECTCT V/Q also showed concordant results on CT angiogram (75% concordance) and 3 were discordant. Pulmonary thromboendarterectomy was performed on 7 out of the 9 patient's with concordant results for CTEPH on both SPECT CT V/Q and CT angiogram, and two patients were considered to be nonsurgical due to comorbidity. Six out of the 7 patients (85%) who underwent thromboendarterectomy showed significant improvement in followup clinical evaluation and pulmonary HTN on echocardiograms. One patient had recurrent pulmonary embolism as a consequence of hypercoagulable state.

Conclusions SPECT CT V/Q has a useful role in identifying patient's with chronic thromboembolic pulmonary hypertension and guiding management for a successful clinical outcome.