Abstract
Background: Precapillary pulmonary hypertension (PrecapPH), characterised by obliteration of the pulmonary arteries, alters ventilation (V)-perfusion (Q) relationships. Limited studies have explored the non-invasive quantification of VQ heterogeneity using single photon emission computed tomography (SPECT) in PrecapPH.
Objective: We measured and compared SPECT-derived VQ heterogeneity in health and PrecapPH. The influence of posture on cranial-caudal V and Q gradients were also assessed.
Methods: Regional V and Q were quantified in supine and upright positions in: 1. Healthy controls (n = 13), 2. Pulmonary arterial hypertension (PAH) (n = 10) and 3. Chronic thromboembolic pulmonary hypertension (CTEPH) (n = 8). Measures of VQ heterogeneity (log SDQ, logSDV) were derived from normalized VQ counts at each voxel. The influence of posture on cranial-caudal V and Q gradients were measured.
Results: The distributions of log SDQ for controls, PAH and CTEPH were (0.16±0.03, 0.22±0.03, 0.26±0.06: p<0.0001) and of logSDV (0.17±0.03, 0.21±0.06, 0.31±0.15: p<0.003) respectively. Postural change resulted in significant redistribution of regional perfusion in controls but was attenuated in both PAH and CTEPH (3.01±3.09 vs 0.26±1.60 vs 0.27±0.61 normalized perfusion/cm, p=0.01, respectively). In contrast, redistribution of regional ventilation was not significantly different across all 3 groups (p=0.76).
Conclusion: Wider heterogeneity in ventilation and perfusion in CTEPH is due to non-homogenous obstruction of pulmonary vascular bed. Quantification of VQ heterogeneity using SPECT can provide insights into the pathophysiological sequalae pulmonary vascular obstruction.
- Copyright ©ERS 2015