Pressure Volume Loop Analysis of the Right Ventricle in Heart Failure With Computed Tomography

Abstract

Right ventricular (RV) function is an important marker of mortality in chronic left-sided heart failure. Right ventricular function is particularly important for patients receiving left ventricular assist devices as it is a predictor of postoperative RV failure. RV stroke work index (RVSWI), the area enclosed by a pressure–volume (PV) loop, is prognostic of RV failure. However, clinical RVSWI approximates RVSWI as the product of thermodilution-derived stroke volume and the pulmonary pressure gradient. This ignores the energetic contribution of regurgitant flow and does not allow for advanced energetic measures, such as pressure–volume area and efficiency. Estimating RVSWI from forward flow may underestimate the underlying RV function. We created single-beat PV loops by combining data from cine computed tomography (CT) and right heart catheterization in 44 heart failure patients, tested the approximations made by clinical RVSWI and found it to underestimate PV loop RVSWI, primarily due to regurgitant flow in tricuspid regurgitation. The ability of RVSWI to predict post-operative RV failure improved when the single-beat approach was used. Further, RV pressure–volume area and efficiency measures were obtained and show broad agreement with other functional measures. Future work is needed to investigate the utility of these PV metrics in a clinical setting.

3D regional evaluation of right ventricular myocardial work from cineCT

“…HF patients who receive an LVAD are at risk of RV failure after implantation (25). RV size and stroke work index (SWI) have been shown to predict post-LVAD RV failure (8,9). However, the HF patient pairs shown in Figure 3 had similar RV volumetry but different outcomes post-LVAD implantation.…”

“…However, the HF patient pairs shown in Figure 3 had similar RV volumetry but different outcomes post-LVAD implantation. Previous literature has demonstrated that the difference in pre-operative free wall and septal wall strain is predictive of RV failure after LVAD implantation (10). Therefore, MW CT may be useful in stratifying risk in HF patients seeking advanced therapies.…”

“…Second, patients did not undergo RHC and CT imaging simultaneously. However, recent work in our group has shown that combining non-simultaneous RV pressure with CT volumes to estimate stroke work index in our HF cohort compares favorably to clinical estimates (9). Third, we utilized the pressure waveform as a surrogate for myocardial stress.…”

“…Further, CT imaging can be performed in patients with implanted devices as well as very sick patients who can only tolerate short scan times. We have demonstrated how CT imaging of RV function improves evaluation of heart failure patients undergoing LVAD implantation (8)(9)(10). We have also used CT imaging to estimate regional strain throughout the RV and demonstrated that strain mapping can be used to capture regional dysfunction in adults with congenital heart disease (ACHD) (11).…”