Page 57 - Assessing right ventricular function and the pulmonary circulation in pulmonary hypertension Onno Anthonius Spruijt

including RVFAC, TAPSE, RVMPI, and more recently RVGLS [3, 12, 13, 18]. In our study, RVFAC emerged as a stronger correlate of outcome than either TAPSE or RVMPI. In a recent study, we showed that RVFAC was more closely related to RVEF than TAPSE [19]. Moreover, we showed that an RVFAC of 25%corresponded best to an RVEF of 35%, a commonly chosen threshold for moderate RV dysfunction in CMR imaging studies of patients with PAH [14, 15]. In comparison to RVFAC, TAPSE has the advantage of reproducibility but does not take into account the radial component of RV contraction [20]. Although RVMPI combines information of both systolic and diastolic function, in different studies it has not appeared to carry stronger prognostic value than RVFAC, TAPSE, or RVGLS [18, 21]. Although not yet proven, this may be in part due to pseudo-normalization of RVMPI values, which can occur in patients with severe dysfunction. As shown in the recent study of Fine et al. [18], RVGLS emerged as the best metric of RV function compared with RVFAC and TAPSE in PAH; ongoing studies are currently validating the findings in independent cohorts. One of the most important contributions of our study was to prove the independent contribution to RA size [22]. In fact, in contrast to studies on atrial remodeling in left heart failure, there have been a limited number of studies addressing atrial remodeling or atrial function in PAH [7, 8, 23]. Bustamante- Labarta et al. [7] were the first to suggest an association between RA size and outcome in 25 patients with PAH. In the study of Raymond et al. [8], in 81 patients with NYHA functional class III or IV PAH, there was a trend for an independent association between RA area indexed to height and the composite endpoint of death or transplantation (p=0.106). In the recent study of Kane et al. [23], severe RA enlargement assessed qualitatively were also predictive of survival when corrected for age, sex, and functional class. Mechanistically, RA size is strongly associated with RAP, and tricuspid regurgitation severity can therefore provide important information on adverse ventricular remodeling. However, further studies are needed to provide better normative indexed thresholds of RA size. In addition to changes in RA remodeling, we showed that RA function was significantly impaired in patients with PAH. Although the change affected both passive and atrial components of atrial function, better prognostic information was provided by active atrial emptying. The association between active RAEF and RAP, as well as TAPSE, is not surprising because RAP may be an indirect metric of RA afterload and TAPSE may limit the extent of active RAEF as the atria cannot contract if the ventricle has a limited annular excursion. As a marker of outcome, active RAEF has the potential disadvantage of lower reproducibility compared with maximal RA size; in addition it is more collinearly related with metrics of RV systolic function, which may limit its incremental value in multivariate models. Conversely, RA size was more related to RV end-systolic dimensions, which
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