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Tissue Phase Mapping for Assessment of Biventricular Myocardial Motion in Pediatric Patients with Repaired Tetralogy of Fallot1Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States, 2Feinberg School of Medicine, Northwestern University, Chicago, IL, United States, 3Department of Medical Imaging, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, IL, United States, 4Department of Pediatrics, Division of Pediatric Cardiology, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, IL, United States, 5Department of Pediatrics, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States, 6Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Chicago, IL, United States
Synopsis
The purpose of this study was to assess regional biventricular myocardial function in pediatric patients with repaired tetralogy of Fallot (TOF) by tissue phase mapping (TPM). Segmental left (LV) and right ventricular (RV) peak velocities were calculated in systole and diastole based on an extended AHA 16+10-segment model. Inter-ventricular dyssynchrony was quantified from the correlation between global LV and RV radial, long-axis and circumferential velocity time courses. Compared to age-matched healthy controls, TOF patients exhibited reduced long-axis peak velocities in systole and diastole as well as increased inter-ventricular dyssynchrony for radial and circumferential myocardial motion.
Introduction
Tetralogy
of Fallot (TOF)
is the most common cyanotic congenital heart disease, which is usually
surgically repaired during the first year of life. However, residual anatomic
and functional abnormalities are very common requiring life-long surveillance
and further treatment.1-4 Some of the most frequent abnormalities are
right ventricular (RV) dilation and dysfunction from pulmonary regurgitation as
well as left ventricular (LV) dysfunction. Standard imaging assessments4 based on simplified global parameters5-7 may not reflect regional myocardial abnormalities
or ventricular interactions. A more comprehensive evaluation of regional motion
and biventricular interaction might be beneficial. In
this context, tissue phase mapping (TPM) is
a well-established technique to quantify regional myocardial velocities,8-13 but has only recently been applied in children.14-16 The goal of this study was to test the
feasibility of TPM in pediatric patients with repaired tetralogy of Fallot to
quantify regional LV/RV myocardial velocities and to obtain biventricular
functional information.Methods
Five pediatric TOF patients (13+/-3y, 3f) and ten age-matched controls (15+/-3y [p=0.11], 6f) underwent standard CMR (1.5T Siemens Aera) including k-t accelerated (R=5) TPM using a black-blood prepared phase-contrast sequence with 3-directional velocity encoding8,10,17 in short-axis orientation (base, mid, apex; each in one breath-hold; in-plane resolution = (1.5-2.4 mm)2; temporal resolution = 21-25 ms; flip angle = 10° or 15°; venc = 25 cm/s in all directions). A single observer contoured LV and RV endo-/epicardial borders for calculation of time-resolved radial (vr), circumferential (vΦ), and long-axis (vz) LV/RV velocities over the cardiac cycle. For all components and slices pixelwise velocities (Fig. 1) were averaged over each ventricle to obtain global velocity time courses (Fig. 2). To assess the synchrony/dyssynchrony between LV and RV function, the cross-correlation coefficient (cc) between global LV and RV velocity time courses (i.e. averaged over base, mid, apex) was calculated for all 3 velocity components. The resulting cc is a measure of inter-ventricular dyssynchrony (cc=1: completely synchronous LV and RV motion, reduced cc = increased dyssynchony). For regional analysis pixelwise radial and long-axis velocities were also mapped onto an extended AHA model (16 segments for LV, 10 segments for RV,11 Fig. 3) to obtain segmental velocity time courses. Systolic and diastolic peak velocities and times to peak (TTP) velocity were calculated for each segment.Results
Figure 1 depicts systolic and diastolic LV/RV long-axis velocities in a TOF patient compared to a healthy control showing reduced velocities in the patient. Global velocity time courses for LV and RV appeared more synchronous for controls than patients (Fig. 2). This inter-ventricular synchrony was quantitatively assessed by calculating correlation coefficients, which were significantly reduced in patients for radial and circumferential velocities (Tab. 1). Figure 3 shows results for the regional analysis with reduced long-axis peak velocities in patients in systole and diastole. Considering global values (Tab. 2), radial peak velocities as well as radial and long-axis TTPs were similar, but LV/RV long-axis peak velocities were significantly reduced in TOF patients compared to controls.Discussion and Conclusion
Our pilot study shows that biventricular TPM analysis is feasible in pediatric TOF patients and demonstrates significant differences in regional ventricular function compared to control subjects. TOF patients exhibited reduced long-axis peak velocities, consistent with previous studies in young adults,12,13 and increased inter-ventricular dyssynchrony for radial and circumferential velocities. Larger studies are warranted to further characterize regional cardiac function in pediatric TOF patients and to potentially correlate these findings with clinical outcomes.Acknowledgements
Grant support by the National Institute of Heart, Lung and Blood Disorders (NHLBI) R01 HL 117888.References
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