Page 162 - Assessing right ventricular function and the pulmonary circulation in pulmonary hypertension Onno Anthonius Spruijt

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Native T1-values between IPAH, PAH-SSc and CTEPH patients
A recent study of Ntusi et al [18] found increased native T1-values of the total myocardium in no-PH systemic sclerosis patients compared to controls. We found no differences in native T1-values between IPAH, PAH-SSc and CTEPH patients. The presence of myocardial fibrosis found in these different forms of precapillary PH differ between studies. No differences in myocardial fibrosis of RV free wall tissue were found between controls, IPAH and PAH-SSc patients [21], while others found an increased amount of myocardial fibrosis in PAH patients compared to no-PH controls [22]. Ntusi et al. [18] included both limited cutaneous (lcSSc) and diffuse cutaneous systemic sclerosis (dcSSc) patients, while in our study we only included patients with lcSSc. It is known that cardiac involvement of systemic sclerosis is much higher in dcSSc patients compared to lcSSc patients [31], which can explain the differences in results.
Limitations
We could not assess native T1-values of the total RV free wall, since in most patients the RV free wall was too thin to avoid partial volume effects. Only the inferior part of the RV free wall could be accurately assessed in all patients. Although we did not assess the total RV free wall, large variances in native T1-values between different regions of the RV free wall are not expected in a pressure overloaded RV.
Our study is a retrospective analysis and we included both treatment naïve and treated PH patients. From our data we cannot rule out any treatment effects on the measured native T1-values.
The control subjects were significantly younger compared to PH patients. It is known that age can influence native T1-values of the myocardium, with higher native T1-values found at a younger age [11]. Since native T1-values of the interventricular insertion regions were significantly increased in PH patients compared to control subjects, this only strengthens our findings.
The MOLLI technique as we applied is known to slightly underestimate native T1 values at higher heart rates [32]. The main conclusions in this study rely on regional differences, and are therefore not affected. Moreover, heart rates were not different between patients and controls. Another potential confounder is the effect of the T2 relaxation time: the absolute T1 values obtained with the MOLLI technique defer from their actual values in tissues with short T2 [33]. Whether or not T2- changes play a role in our study, is still to be explored. A technique such as SASHA [34] is more accurate, however, the values obtained with this SACHA technique show a larger variability and the MOLLI method performs more precisely [35].