Computed axial tomography evidence of left atrial enlargement: A predictor of elevated pulmonary capillary wedge pressure in pulmonary hypertension

Background: One of the commonest causes of pulmonary hypertension (PH) is left heart dysfunction associated with elevated pulmonary capillary wedge pressure (PCWP). In contrast, the pathology of pulmonary arterial hypertension (PAH) originates in the pulmonary vascular bed. Accurate diagnosis of PAH requires right heart catheterization (RHC) with normal PCWP. This study examines the role of computed tomography of the chest (CT chest) in evaluating left atrial (LA) size as an indicator of elevated PCWP in patients undergoing PH evaluation. Methods: CT chest and RHC data were reviewed in 37 subjects at the Baylor PH Center. Both subjective estimates and objective measurements of left atrial size from the CT chest were recorded separately by 3 investigators. Patients were categorized as Group I (small-normal LA) and Group II (large LA) and RHC results compared.The objective and subjective measurements were compared by receiver operator characteristic (ROC). Results: The mean PCWP was 12 ± 6 mmHg in Group I and 21 ± 7 mmHg in Group II (P = 0.001). The estimated LA area was 19.4 ± 4.9 cm² in Group I and 39.9 ± 7.6 cm² in Group II (mean ± SD; P < 0.001). The estimated LA area, corrected for the chest wall length, was 0.78 ± 0.19 cm² and 1.65 ± 0.26 cm² in Groups I and II, respectively (P < 0.001). Significant correlations were found between uncorrected PCWP and LA area (R = 0.45, P = 0.005), corrected PCWP and LA area (R = 0.47, P = 0.003), and the subjective observer impression of LA enlargement and measured PCWP (R = 0.51, P = 0.01). Conclusion: In this pilot study, enlarged LA area on the CT chest was associated with an elevated PCWP on RHC. For patients undergoing PH evaluation, increased LA area on CT chest could suggest left heart dysfunction in patients as a possible cause of PH.