Coupling of the right ventricle to its load is considered to be one of the main determinants of symptomatology and outcome in pulmonary arterial hypertension (PAH). To maintain right ventricular (RV) - pulmonary arterial coupling the right ventricle reacts with adaptation and eventually maladaptation as disease progresses. Among various maladaptive mechanism, RV dyssynchrony, has been described as a relevant determinant of RV function, exercise capacity and outcome in PAH. However, association of load-independent RV function with RV dyssynchrony remains unknown.
We analyzed PAH patients from the Right Heart I study (ClinicalTrials.gov identifier: NCT03403868) with available 2D speckle-tracking echocardiography between January 2016 and March 2019. RV dyssynchrony was defined as the standard deviation (SD) of the times to peak-systolic strain for the four mid-basal RV segments corrected to Bazett’s formula. Load independent RV function was assessed due to acquisition of pressure-volume loops with single-beat measure of end-systolic elastance (Ees), arterial elastance (Ea) and the ratio of Ees/Ea (defines RV- pulmonary arterial coupling). Association between load independent pressure-volume loop indices and RV dyssynchrony were evaluated with Spearman correlation coefficient and multivariate linear regression analysis.
Thirty-three patients with PAH (idiopathic [n = 26; 79.8%]) were enrolled. The median RV dyssynchrony was 53 ms [interquartile range (IQR): 33–95 ms], Ees was 0.53 mmHg/ml [IQR:
0.30–0.76 mmHg/ml], Ea was 0.80 mm Hg/ml [IQR: 0.49–1.10 mmHg/ml] and Ees/Ea was 0.71[IQR: 0.38–1.04]. Ea showed a significant correlation with RV dyssynchrony, albeit Ees or Ees/Ea not. In multivariate linear regression (including Ea, Ees and Ees/Ea) Ea remained independently associated with RV dyssynchrony.
In conclusion, Ea as a load-independent measure of afterload emerged as a determinate of RV dyssynchrony in advanced and severe PAH. The reduction of afterload might be the key strategy to improve RV dyssynchrony, which has to be explored in dedicated studies.