Page 66 - Assessing right ventricular function and the pulmonary circulation in pulmonary hypertension Onno Anthonius Spruijt

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the Tricuspid Annular Plane Systolic Excursion (TAPSE). TAPSE describes the absolute longitudinal movement of the lateral tricuspid annulus towards the apex and is a widely applied measure of RV function. TAPSE can also be measured with cMRI. Although the complex geometry of the RV makes measurements of RV function using uni-dimensional measurements difficult, TAPSE shows a reasonably good correlation with RVEF [28, 29]. When measured at baseline, TAPSE has important prognostic value and the measurement is also sensitive to changes in RV function during follow-up [30, 31]. However, because longitudinal shortening reaches a floor level during progressive RV failure, a determination of transverse shortening is preferred when RV function is monitored in end- stage PH [32].
Flattening or even shifting of the inter ventricular septum from right to left is frequently seen in PH and is due to a delay in the time to peak shortening of the RV compared to the LV [33]. A frequently applied method to quantify bowing of the inter ventricular septum is the eccentricity index (EI), which can be obtained with ECHO and cMRI. EI is measured in a short-axis view of the LV cavity at end-systole or end-diastole and is defined as the ratio of the LV diameter parallel to the inter ventricular septum and the LV diameter perpendicular to the inter ventricular septum. Normally the EI is around 1 and EI increases with bowing of the inter ventricular septum. It has been shown that Bosentan treatment decreased the end-systolic EI in PAH patients [17, 18, 20]. Improvement of diastolic EI was seen in PAH patients who received Sildenafil in addition to prostanoids [34].
An important aspect in the pathogenesis of PH is hypertrophy of the RV wall. With cMRI it is possible to obtain RV mass as well as LV mass including trabeculae. The increase in RV mass due to the increase in afterload is believed to have a protective effect on the RV since it reduces wall stress following the law of Laplace. Wilkins et al compared the adding of Sildenafil or Bosentan to first line monotherapy and found a reduction of RV mass when Sildenafil was added, but not Bosentan [20]. A reduction of RV mass with Sildenafil has also been described in other studies [21, 35] and has been suggested to be related to intrinsic effects on the heart, in addition to vasodilating effects [9]. No change in RV mass was decribed with Ambrisentan [19].
The myocardial performance index, also known as the Tei index, describes global RV function and integrates systolic and diastolic function. The Tei index is measured by the ratio of isovolumic time intervals (isovolumic relaxation time plus isovolumic contraction time) and the ejection time, so that a deterioration of RV function results in an increase in Tei index. Tei index can be assessed with Doppler-ECHO without the need of making geometric assumptions. It has been shown that in PAH patients, Tei index decreases with Bosentan [17, 18, 36, 37] and with intravenous epoprostenol