Biventricular myocardial adaptation in patients with repaired tetralogy of Fallot: Mechanistic insights from magnetic resonance imaging tissue phase mapping

Interaction between the left ventricular ejection fraction and left ventricular strain and its relationship with coronary stenosis

BACKGROUND

Coronary artery stenosis (CAS) is the most common type of heart disease and the leading cause of death in both men and women globally. CAS occurs when the arteries that supply blood to the heart muscle harden and become narrower due to plaque buildup - cholesterol and other material - on their inner walls. As a result, the heart muscle cannot receive the blood or oxygen it needs. Most heart attacks happen when a blood clot suddenly cuts off the hearts' blood supply, causing permanent heart damage.

AIM

To analyze the relationship between the left ventricular ejection fraction (LVEF), left ventricular strain (LVS), and coronary stenosis.

METHODS

A total of 190 participants were enrolled in this trail. The control group comprised 93 healthy individuals, and observation group comprised 97 patients with coronary heart disease who were hospitalized between July 2020 and September 2021. Coronary lesions were assessed using the Gensini score, and the LVEF and LVS were measured using magnetic resonance imaging (MRI). The interaction between the LVEF and LVS was examined using a linear regression model. The relationship between LVEF and coronary stenosis was examined using Spearman’s correlation.

RESULTS

The LVEF of the observation group was lower than that of the control group. The left ventricular end-systolic volume (LVESV) and left ventricular end-diastolic volume (LVEDV) of the observation group were significantly higher than those of the control group (P < 0.05). The longitudinal and circumferential strains (LS, CS) of the observation group were significantly higher than those of the control group; however, the radial strain (RS) of the observation group was significantly lower than that of the control group (P < 0.05). LVS, LS, and CS were significantly negatively correlated with the LVEF, and RS was positively correlated with the LVEF. There were significant differences in the LVEF, LVESV, and LVEDV of patients with different Gensini scores; the LVEF significantly decreased and the LVESV and LVEDV increased with increasing Gensini scores (P < 0.05). In the observation group, the LVEF was negatively correlated and the LVESV and LVEDV were positively correlated with coronary stenosis (P < 0.05).

CONCLUSION

The LVEF measured using MRI is significantly linearly correlated with LVS and negatively correlated with coronary stenosis.

Right Ventricular Remodeling Assessed by MRI in Duchenne Muscular Dystrophy

BACKGROUND

In Duchenne muscular dystrophy (DMD), the right ventricle (RV) tends to be relatively well preserved, but characterization remains difficult due to its complex architecture. Tissue phase mapping (TPM) is a phase contrast cine MRI technique that allows for multidirectional assessment of myocardial velocities.

PURPOSE

To use TPM to elucidate relationships between myocardial structure, function, and clinical variables in DMD.

STUDY TYPE

Retrospective.

SUBJECTS

A total of 20 patients with muscular dystrophy (median age: 16 years); 18 age-matched normal controls (median age: 15 years).

FIELD STRENGTH/SEQUENCE

Three-directional velocity encoded cine gradient echo sequence (TPM) at 1.5 T, balanced steady-state free procession (bSSFP), T1 mapping with extracellular volume (ECV), and late gadolinium enhancement (LGE).

ASSESSMENT

TPM in basal, mid, and apical short-axis planes was performed as part of a standard MRI study with collection of clinical data. Radial, circumferential, and longitudinal velocities (Vr, Vφ, and Vz, respectively) and corresponding time to peak (TTP) velocities were quantified from TPM and used to calculate RV twist as well as intraventricular and interventricular dyssynchrony. The correlations between TPM velocities, myocardial structure/function, and clinical variables were assessed.

STATISTICAL TEST

Unpaired t-test, Wilcoxon rank-sum test, Bland-Altman analyses were used for comparisons between DMD patients and controls and between DMD subgroups. Pearson's test was used for correlations (r). Significance level: P < 0.05.

RESULTS

Compared to controls, DMD patients had preserved RV ejection fraction (RVEF 53% ± 8%) but significantly increased interventricular dyssynchrony (Vφ: 0.49 ± 0.21 vs. 0.72 ± 0.17). Within the DMD cohort, RV dyssynchrony significantly increased with lower LV ejection fraction (intraventricular Vr and Vz: r = -0.49; interventricular Vz: r = 0.48). In addition, RV intraventricular dyssynchrony significantly increased with older age (Vz: r = 0.67).

DATA CONCLUSION

RV remodeling in DMD occurs in the context of preserved RVEF. Within DMD, this abnormal RV deformation is associated with older age and decreased LVEF.

EVIDENCE LEVEL

4.

TECHNICAL EFFICACY

Stage 2.

Differential Adaptation of Biventricular Myocardial Kinetic Energy in Patients With Repaired Tetralogy of Fallot Assessed by MR Tissue Phase Mapping

BACKGROUND

The myocardial kinetic energy (KE) and its association with pulmonary regurgitation (PR) have yet to be investigated in repaired tetralogy of Fallot (rTOF) patients.

PURPOSE

To evaluate the adaptation of myocardial KE in rTOF patients by tissue phase mapping (TPM).

STUDY TYPE

Prospective.

POPULATION

A total of 49 rTOF patients (23 ± 5 years old; male = 32), 47 normal controls (22 ± 1 year old; male = 29).

FIELD STRENGTH/SEQUENCE

3-T/2D dark-blood three-directional velocity-encoded gradient-echo sequence.

ASSESSMENT

Left and right ventricle (LV, RV) myocardial KE in radial (KE_r ), circumferential (KE_ø ), longitudinal (KE_z ) directions. The proportions of KE in each direction to the sum of all KE (KE_røz ): %KE_r , %KE_ø , %KE_z . PR fraction.

STATISTICAL TEST

Student's t test, multivariable regression. Statistical significance: P < 0.05.

RESULTS

In rTOF group, LV KE_z remained normal in systole (P = 0.565) and diastole (P = 0.210), whereas diastolic LV %KE_z (62% ± 14% vs. 72% ± 7%) and systolic LV %KE_ø (9% ± 6% vs. 20% ± 7%) were significantly decreased. The KE_r and %KE_r of both ventricles significantly increased in the rTOF group (RV in diastole: 6 ± 3 vs. 3 ± 1 μJ and 54% ± 13% vs. 27% ± 7%). The rTOF group exhibited significantly higher RV/LV ratios of %KE_r (systole: 1.3 ± 0.3 vs. 1.0 ± 0.3) and %KE_ø (systole: 1.6 ± 0.8 vs. 1.0 ± 0.3) and significantly lower ratios of %KE_z in systole (0.7 ± 0.2 vs. 1.0 ± 0.1) and diastole (0.5 ± 0.2 vs. 0.9 ± 0.1). In multivariable regression analysis, the RV peak systolic KE_røz , RV systolic KE_z , and LV diastolic %KE_ø were independently associated with PR fraction in the rTOF group (adjusted R²  = 0.479).

DATA CONCLUSION

In rTOF patients, the adaptation of the KE proportion occurred earlier than that of the KE amplitude, and the biventricular balance of %KE was disrupted. PR may cause differential KE adaptation in RV and LV. TPM-derived KE may be useful in investigation of myocardial adaptation in rTOF patients.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 3.