Three-dimensional regional evaluation of right ventricular myocardial work from cine computed tomography: A pilot...

Evaluating regional variations in right ventricular (RV) performance can be challenging, particularly in patients with significant impairments due to the need for 3D spatial coverage with high spatial resolution. ECG-gated cineCT can fully visualize the RV and be used to quantify regional strain with high spatial resolution. However, strain is influenced by loading conditions. Myocardial work (MW)-measured clinically as the ventricular pressure-strain loop area-is considered a more comprehensive metric due to its independence of preload and afterload. In this study, we sought to develop regional RV MW assessments in 3D with high spatial resolution by combining cineCT-derived regional strain with RV pressure waveforms from right heart catheterization (RHC).

Regional MW is not measured in the right ventricle (RV) due to a lack of high spatial resolution regional strain (RS) estimates throughout the ventricle. We present a cineCT-based approach to evaluate regional RV performance and demonstrate its ability to phenotype three complex populations: end-stage LV failure (HF), chronic thromboembolic pulmonary hypertension (CTEPH), and repaired tetralogy of Fallot (rTOF).

Forty-nine patients (19 HF, 11 CTEPH, 19 rTOF) underwent cineCT and RHC. RS was estimated as the regional change in the endocardial surface from full-cycle ECG-gated cineCT and combined with RHC pressure waveforms to create regional pressure-strain loops; endocardial MW was measured as the loop area. Detailed, 3D mapping of RS and MW enabled spatial visualization of strain and work strength, and phenotyping of patients.

HF patients demonstrated more overall impaired strain and work compared to the CTEPH and rTOF cohorts. For example, the HF patients had more akinetic areas (median: 9%) than CTEPH (median: < 1%, p = 0.02) and rTOF (median: 1%, p < 0.01) and performed more low work (median: 69%) than the rTOF cohort (median: 38%, p < 0.01). The CTEPH cohort had more impairment in the septal wall; < 1% of the free wall and 16% of the septal wall performed negative work. The rTOF cohort demonstrated a wide distribution of strain and work, ranging from hypokinetic to hyperkinetic strain and low to medium-high work. Impaired strain (-0.15 ≤ RS) and negative work were strongly-to-very strongly correlated with RVEF (R = -0.89, p < 0.01; R = -0.70, p < 0.01, respectively), while impaired work (MW ≤ 5 mmHg) was moderately correlated with RVEF (R = -0.53, p < 0.01).

Regional RV MW maps can be derived from clinical CT and RHC studies and can provide patient-specific phenotyping of RV function in complex heart disease patients.