Right Ventricular Inefficiency in Repaired Tetralogy of Fallot: Proof of Concept for Energy Calculations From Cardiac MRI Data

Abstract

Repaired tetralogy of Fallot (rTOF) patients develop right ventricular (RV) dilatation and dysfunction. To prevent their demise, pulmonary valve replacement is necessary, though appropriate timing for it is challenged by a paucity of reliable diagnostic parameters. In this pilot study, we hypothesized that stroke work (SW) and energy calculations would delineate the inefficiency of RV performance in rTOF. RV SW was calculated for both an rTOF and a normal subject by utilizing RV pressure and volume measurements obtained during cardiac catheterization and MRI studies. Energy transfer rate and ratio were computed at the main pulmonary artery (PA). Compared to the normal RV, the rTOF RV had higher operating pressure, lower computed SW (0.078 J vs. 0.115 J for normal), and higher negative energy transfer at the PA (0.044 J vs. 0.002 J for normal). Furthermore, the energy transfer ratio was nearly twice as high for the normal RV (1.06) as for the rTOF RV (0.56). RV SW and energy transfer ratio delineate important operational efficiency differences in blood flow from the RV to the PA between rTOF and normal subjects. Our pilot data suggest that the rTOF RV is significantly less efficient than normal.

Impact of Acute Pulmonary Embolization on Arterial Stiffening and Right Ventricular Function in Dogs

“…Our results also demonstrate good agreement between the novel energy analysis proposed by Das et al 15 and the elastance ratio method ( η vv ). While both the SW produced by the RV and the net energy E net transferred to the blood flow increased after embolization, the ratio E net /SW showed a 36% (non significant) decrease, similar to η vv .…”

“…PA pressure from RHC and flow data from 2D PC images also were combined to calculate E net using the formulation proposed by Das et al 15 : $$E_{\text{net}}=\underset{0}{\overset{T}{\int }}\left(p+\frac{1}{2}\rho v^2\right)\mathit{Qdt}$$ where p , v , and Q are, respectively, time-dependent pressure, velocity, and flow rate in the main PA, ρ is blood density and T is the heartbeat duration.…”

“…Sanz et al 30 assessed RV–PA coupling non-invasively using a simplified model that includes measurements from MRI only. Also, Das et al 15 have proposed that the efficiency of the RV can be estimated by the ratio of the net energy transferred to the blood pool in one heartbeat to the stroke work. This energy approach can be used along with η vv to assess RV performance in PAH.…”

Computational modeling and engineering in pediatric and congenital heart disease

“…Recent studies applying engineering to ToF have correlated energy loss with cardiac performance, suggesting new clinical indices that may be used to better predict the timing of surgical intervention. [68–70] Further investigation is needed in larger patient cohorts. Shape analysis has also been applied in the context of ToF to determine factors related to timing of pulmonary valve replacement, showing significant correlations between regurgitation severity and RV dilation.…”

Non-invasive evaluation of energy loss in the pulmonary arteries using 4D phase contrast MR measurement: a proof of concept

“…Recently, energy-based endpoints have been investigated in our research group [8-10] to help determine timing for surgical interventions. In particular, BSA indexed RV stroke work (SW I ) and energy transfer ratio ( e MPA ) between the RV and main PA (MPA) were proposed in our previous study to evaluate the hemodynamic status of the RV and the PA for repaired CHD patients.…”