Ventricular kinetic energy may provide a novel noninvasive way to assess ventricular performance in patients with repaired tetralogy of Fallot

Abstract

Objective: Ventricular kinetic energy measurements may provide a novel imaging biomarker of declining ventricular efficiency in patients with repaired tetralogy of Fallot. Our purpose was to assess differences in ventricular kinetic energy with 4-dimensional flow magnetic resonance imaging between patients with repaired tetralogy of Fallot and healthy volunteers.

Methods: Cardiac magnetic resonance, including 4-dimensional flow magnetic resonance imaging, was performed at rest in 10 subjects with repaired tetralogy of Fallot and 9 healthy volunteers using clinical 1.5T and 3T magnetic resonance imaging scanners. Right and left ventricular kinetic energy (KERV and KELV), main pulmonary artery flow (QMPA), and aortic flow (QAO) were quantified using 4-dimensional flow magnetic resonance imaging data. Right and left ventricular size and function were measured using standard cardiac magnetic resonance techniques. Differences in peak systolic KERV and KELV in addition to the QMPA/KERV and QAO/KELV ratios between groups were assessed. Kinetic energy indices were compared with conventional cardiac magnetic resonance parameters.

Results: Peak systolic KERV and KELV were higher in patients with repaired tetralogy of Fallot (6.06 ± 2.27 mJ and 3.55 ± 2.12 mJ, respectively) than in healthy volunteers (5.47 ± 2.52 mJ and 2.48 ± 0.75 mJ, respectively), but were not statistically significant (P = .65 and P = .47, respectively). The QMPA/KERV and QAO/KELV ratios were lower in patients with repaired tetralogy of Fallot (7.53 ± 5.37 mL/[cycle mJ] and 9.65 ± 6.61 mL/[cycle mJ], respectively) than in healthy volunteers (19.33 ± 18.52 mL/[cycle mJ] and 35.98 ± 7.66 mL/[cycle mJ], respectively; P < .05). QMPA/KERV and QAO/KELV were weakly correlated to ventricular size and function.

Conclusions: Greater ventricular kinetic energy is necessary to generate flow in the pulmonary and aortic circulations in repaired tetralogy of Fallot. Quantification of ventricular kinetic energy in patients with repaired tetralogy of Fallot is a new observation. Future studies are needed to determine whether changes in ventricular kinetic energy can provide earlier evidence of ventricular dysfunction and guide future medical and surgical interventions.

Figure 1

[A-B]. Healthy Volunteer RV Kinetic energy maps in a long axis orientation. The figures demonstrate the KE values of each voxel of blood in the segmented plane where the highest KE values are marked in red. Note that highest kinetic energies are seen along the RV outflow tract during systole and along the RV inner curvature during diastole. [C-D]. rTOF RV Kinetic energy maps oriented along the RV outflow tract. Note that highest kinetic energies are seen along the RV outflow tract during systole and diastole due to the presence of pulmonic regurgitation in this patient.

Figure 2

[A] Peak systolic KE_RV and KE_LV comparison between subjects with rTOF and healthy volunteers. Differences in KE_RV (P = .65) and KE_LV (P = .47) are not statistically significant. [B] Ratios of outflow to peak systolic ventricular KE as markers for ventricular-vascular efficiency. Q_MPA/KE_RV was significantly lower in rTOF than in healthy volunteers (P = .015). Q_Ao/KE_LV was also significantly lower in rTOF than in healthy volunteers (P = .0003). KE, Kinetic energy; rTOF, repaired tetralogy of Fallot; LV, left ventricular; RV, right ventricular; Q_mpa, main pulmonary artery flow; KE_RV, right ventricular kinetic energy; Q_ao, aortic flow; KE_LV, left ventricular kinetic energy.

Figure 2

[A] Peak systolic KE_RV and KE_LV comparison between subjects with rTOF and healthy volunteers. Differences in KE_RV (P = .65) and KE_LV (P = .47) are not statistically significant. [B] Ratios of outflow to peak systolic ventricular KE as markers for ventricular-vascular efficiency. Q_MPA/KE_RV was significantly lower in rTOF than in healthy volunteers (P = .015). Q_Ao/KE_LV was also significantly lower in rTOF than in healthy volunteers (P = .0003). KE, Kinetic energy; rTOF, repaired tetralogy of Fallot; LV, left ventricular; RV, right ventricular; Q_mpa, main pulmonary artery flow; KE_RV, right ventricular kinetic energy; Q_ao, aortic flow; KE_LV, left ventricular kinetic energy.

Figure 3

[A] RVEDVI versus ventricular efficiency. [B] RVEF versus ventricular efficiency. [C] LVEDVI versus ventricular efficiency. [D] LVEF versus ventricular efficiency. There is a moderately positive correlation between ventricular efficiency and RVEDVI in subjects with rTOF (r = 0.68, P = .03) demonstrated by the red boxes in A. However, the other comparisons did not reach statistical significance. RVEDVI, Right ventricular end-diastolic volume index; Qmpa, main pulmonary artery flow; KERV, right ventricular kinetic energy; rTOF, repaired tetralogy of Fallot; RVEF, right ventricular ejection fraction; LVEDVI, left ventricular end-diastolic volume index; Qao, aortic flow; KELV, left ventricular kinetic energy; LVEF, left ventricular ejection fraction.

Figure 3

[A] RVEDVI versus ventricular efficiency. [B] RVEF versus ventricular efficiency. [C] LVEDVI versus ventricular efficiency. [D] LVEF versus ventricular efficiency. There is a moderately positive correlation between ventricular efficiency and RVEDVI in subjects with rTOF (r = 0.68, P = .03) demonstrated by the red boxes in A. However, the other comparisons did not reach statistical significance. RVEDVI, Right ventricular end-diastolic volume index; Qmpa, main pulmonary artery flow; KERV, right ventricular kinetic energy; rTOF, repaired tetralogy of Fallot; RVEF, right ventricular ejection fraction; LVEDVI, left ventricular end-diastolic volume index; Qao, aortic flow; KELV, left ventricular kinetic energy; LVEF, left ventricular ejection fraction.

Figure 3

[A] RVEDVI versus ventricular efficiency. [B] RVEF versus ventricular efficiency. [C] LVEDVI versus ventricular efficiency. [D] LVEF versus ventricular efficiency. There is a moderately positive correlation between ventricular efficiency and RVEDVI in subjects with rTOF (r = 0.68, P = .03) demonstrated by the red boxes in A. However, the other comparisons did not reach statistical significance. RVEDVI, Right ventricular end-diastolic volume index; Qmpa, main pulmonary artery flow; KERV, right ventricular kinetic energy; rTOF, repaired tetralogy of Fallot; RVEF, right ventricular ejection fraction; LVEDVI, left ventricular end-diastolic volume index; Qao, aortic flow; KELV, left ventricular kinetic energy; LVEF, left ventricular ejection fraction.

Figure 3

[A] RVEDVI versus ventricular efficiency. [B] RVEF versus ventricular efficiency. [C] LVEDVI versus ventricular efficiency. [D] LVEF versus ventricular efficiency. There is a moderately positive correlation between ventricular efficiency and RVEDVI in subjects with rTOF (r = 0.68, P = .03) demonstrated by the red boxes in A. However, the other comparisons did not reach statistical significance. RVEDVI, Right ventricular end-diastolic volume index; Qmpa, main pulmonary artery flow; KERV, right ventricular kinetic energy; rTOF, repaired tetralogy of Fallot; RVEF, right ventricular ejection fraction; LVEDVI, left ventricular end-diastolic volume index; Qao, aortic flow; KELV, left ventricular kinetic energy; LVEF, left ventricular ejection fraction.