Afterload dependence of right ventricular myocardial strain

Background: Right ventricular (RV) free wall strain (RVFWS) is a feasible method for quantitation and follow-up of RV function and may have benefits over traditional markers such as fractional area change. However, like all ejection phase parameters, RVFWS is difficult to assess in the presence of changing afterload. The aim of this study was to compare RVFWS and traditional RV function parameters for tracking progress of RV function in patients with pulmonary arterial hypertension (PAH) over a range of pulmonary artery systolic pressure (PASPs).

Methods: Sequential echocardiograms were collected retrospectively at two time points between 2005 and 2015 in 187 patients (71% women; mean age, 63 ± 14 years) undergoing pulmonary vasodilator therapy for group 1 PAH. Patients were either studied during PAH therapy (n = 111) or before and after treatment initiation (n = 76). Standard measurements of RV and left ventricular function and PASP were performed, and speckle-tracking strain was used to calculate RVFWS. The linear response of RVFWS to afterload (PASP) was assessed using a standard regression equation. Because it is unclear if the response might be nonlinear, a quadratic association (PASP squared) was also used in the regression model.

Results: At visit 1, patients with PAH showed impaired functional capacity (mean 6-min walk distance, 371 ± 131 m), increased PASP (mean, 54 ± 26 mm Hg), and borderline RVFWS (mean, 18 ± 6%). Patients before PAH therapy showed more pronounced reduction in 6-min walk distance (mean, 302 ± 136 m) and RVFWS (mean, 16 ± 5%). RVFWS at baseline was associated with PASP (R² = 0.25, P = .001), RV end-diastolic area (R² = 0.36, P < .001), and fractional area change (R² = 0.21, P < .001). Change in RVFWS was more strongly associated with ΔPASP (std β = -0.20, P = .02) than ΔPASP squared (std β = 0.11, P = .20). RVFWS showed strength over fractional area change for sequential RV assessment over a range of PASP changes.

Conclusions: Afterload changes should be taken into account in the evaluation of RVFWS during PAH follow-up, with the relationship to PASP likely to be linear.