Page 139 - Assessing right ventricular function and the pulmonary circulation in pulmonary hypertension Onno Anthonius Spruijt

assessed by either the Student t test or an appropriate ANOVA followed by the Bonferroni post hoc test for multigroup comparisons. Correlations between 18FLT uptake (k3) and clinical variables were determined by simple linear regression analyses. A P value <0.05 was considered statistically significant. All statistical analyses were performed with Statistical analyses were performed using SPSS for Windows version 20 (IBM Corp., Armonk, NY) and GraphPad Prism for Windows version 5 (GraphPad Software, La Jolla, CA).
Results
Increased Rate of 18FLT Phosphorylation k3 in IPAH Patients
The clinical characteristics of the IPAH patients studied and details of the controls included in this study are summarized in Table 1. We calculated the rates of 18FLT transportation by 2T4k modeling [29] based on the sixty‐minute PET imaging dynamic acquisition. Compared with 18FLT PET uptake in control subjects, 18FLT phosphorylation k3 (Figure 1A) was increased significantly in IPAH patient lungs (0.086±0.034 vs 0.054±0.009; P<0.05). There was variation in k3 within the IPAH group, such that some patients exhibited uptake more than 2‐fold above the control group whereas others were in the range of controls. Further analysis by 3‐dimensional parametric mapping of computed per‐ voxel 18FLT uptake from IPAH patients demonstrated that focal areas of relatively high uptake were distributed unevenly throughout the lung parenchyma (Figure 1B). Two representative IPAH patients with lowest and highest mPAP (Patient A 25mmHg vs Patient B 92mmHg) and PVR (Patient A 134 dyn.s/cm5 vs Patient B 1005dyn.s/cm5) demonstrated this variation (Table 1); computed per‐voxel 18FLT uptake from Patient B showed a distinctive uneven regional pattern of 18FLT signal compared to Patient A.
We next looked at the relationship between lung 18FLT uptake and cardiopulmonary hemodynamics in the IPAH group. There was no correlation between lung 18FLT uptake (phosphorylation rates k3) and mean pulmonary artery pressure (mPAP, r2=0.38, p=0.111) or pulmonary vascular resistance (PVR r2=0.042, p=0.625) (Figure 1C). Interestingly, 18FLT phosphorylation k3 levels were correlated significantly with right ventricular end‐diastolic volume index (r2=0.54, p=0.037), right ventricular end‐systolic volume (r2=0.65, p=0.015), right ventricular ejection fraction (r2=0.51, p=0.048) and the load on the right ventricle (arterial elastance r2=0.50, p=0.048). There was no correlation between k3 and cardiac index (r2=0.05, p=0.604) (Supplement Figure I).
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