Assessment of operability by means of CTPA and perfusion SPECT in patients with chronic thromboembolic pulmonary hypertension

Background

Chronic thromboembolic pulmonary hypertension (CTEPH) can potentially be cured by pulmonary thrombendarterectomy (PEA), the criteria for differentiation between operable and non-operable patients are not standardized.

Purpose

To retrospectively evaluate the value of rigidly registered computed tomography pulmonary angiography (CTPA) and single photon emission CT (SPECT) in differentiating for PEA.

Material and Methods

Forty-nine patients with CTEPH (21 men; age, 58 ± 13 years) were evaluated by an interdisciplinary expert board using all available diagnostic information and their consensus statement as gold standard. For SPECT a lobe based perfusion score was visually assessed using the score of 0 (lack of perfusion) to 1 (normal perfusion) calculating percentage of vascular obstruction (PVO). By CTPA, vascular obstruction index (OI) of central, peripheral, and global PA-bed were determined. The accuracy of the alignment between CTPA and SPECT was determined by fusion score (FS) ranging from 1 (no alignment) to 5 (exact alignment). Angiography provided PA pressure (PAP), pulmonary vascular resistance (PVR), and PA wedge pressure (PAWP). Receiver operating characteristics (ROC) analysis was performed.

Results

Twenty-nine patients were considered surgically amenable, and 20 patients were inoperable. Mean PAP, PVR, and PAWP were 48 ± 11 mmHg, 868 ± 461 dynes*sec*cm^–5, and 11 ± 5 mmHg, without differences between surgical and non-surgical patients (P > 0.5). In all patients accurate registration was reached (FS = 4.1 ± 0.7; range, 2–5). PVO and central OI separated PEA-amenable patients (P ≤ 0.001) resulting in the area under the curve of 0.828 (cutoff for PVO: 37.8% with a sensitivity of 82% and specificity of 79%) and 0.755 (cutoff for central OI: 29% with a sensitivity and specificity of 86.2% and 79%) for operability.

Conclusion

An accurate interpretation of rigidly registered CTPA and perfusion SPECT may contribute to stratification of operability in patients with CTEPH.

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