Myocardial deformation in patients with a single left ventricle using 2D cardiovascular magnetic resonance feature tracking: a case–control study

Ventricular dysfunction is a well-known complication in single ventricle patients in Fontan circulation. As studies exclusively examining patients with a single left ventricle (SLV) are sparse, we assessed left ventricular (LV) function in SLV patients by using 2D-cardiovascular magnetic resonance (CMR) feature tracking (2D-CMR-FT) and 2D-speckle tracking echocardiography (2D-STE). 54 SLV patients (11.4, 3.1-38.1 years) and 35 age-matched controls (12.3, 6.3-25.8 years) were included. LV global longitudinal, circumferential and radial strain (GLS, GCS, GRS) and strain rate (GLSR, GCSR, GRSR) were measured using 2D-CMR-FT. LV volumes, ejection fraction (LVEF) and mass were determined from short axis images. 2D-STE was applied in patients to measure peak systolic GLS and GLSR. In a subgroup analysis, we compared double inlet left ventricle (DILV) with tricuspid atresia (TA) patients. The population consisted of 19 DILV patients, 24 TA patients and 11 patients with diverse diagnoses. 52 patients were in NYHA class I and 2 patients were in class II. Most SLV patients had a normal systolic function but median LVEF in patients was lower compared to controls (55.6% vs. 61.2%, p = 0.0001). 2D-CMR-FT demonstrated reduced GLS, GCS and GCSR values in patients compared to controls. LVEF correlated with GS values in patients (p < 0.05). There was no significant difference between GLS values from 2D-CMR-FT and 2D-STE in the patient group. LVEF, LV volumes, GS and GSR (from 2D-CMR-FT) were not significantly different between DILV and TA patients. Although most SLV patients had a preserved EF derived by CMR, our results suggest that, LV deformation and function may behave differently in SLV patients compared to healthy subjects

Abnormal torsion and helical flow patterns of the neo-aorta in hypoplastic left heart syndrome assessed with 4D-flow MRI.

BackgroundThe Norwood procedure is the first stage of correction for patients with hypoplastic left heart syndrome (HLHS) and may lead to an abnormal neoaortic anatomy. We prospectively studied the neoaorta's fluid dynamics and the abnormal twist of the neoaorta by MRI examinations of HLHS patients in Fontan circulation. This study for the first time investigates the hypothesis that the neoaorta twist is associated with increased helical flow patterns, which may lead to an increased workload for the systemic right ventricle (RV) and ultimately to RV hypertrophy.MethodsA group of forty-two HLHS patients with a median age of 4.9 (2.9-17.0) years, at NYHA I was studied along with a control group of eleven subjects with healthy hearts and a median age of 12.1 (4.0-41.6). All subjects underwent MRI of the thoracic aorta including ECG-gated 2D balanced SSFP cine for an axial slice stack and 4D-flow MRI for a sagittal volume slab covering the thoracic aorta. The twist of the neoaortic arch was quantified by the effective geometric torsion, defined as the product of curvature and geometric torsion. Fluid dynamics and geometry in the neoaorta, including the flow helicity index, were evaluated using an in-house analysis software (MeVisLab-based). Myocardial mass of the systemic ventricle at end-diastole was estimated by planimetry of the short-axis stack.ResultsCompared to the control group, the neoaorta in the HLHS patients shows an increased twist (P=0.04) and higher peak helicity density (P=0.03). The maximum helicity density was correlated with maximum effective torsion of the ascending neoaorta (P<0.001). The degree of maximum twist correlated with the increase in RV myocardial mass (P<0.01).ConclusionsThis study shows that the abnormal twist of the neoaortic arch in HLHS patients is associated with abnormal helical flow patterns, which may contribute to increased RV afterload and may adversely affect the systemic RV by stimulation of myocardial hypertrophy. These findings suggest that further improvements of surgical aortic reconstruction, guided by insights from 4D-flow MRI, could lead to better neoaortic fluid dynamics in patients with HLHS

MRI-based comprehensive analysis of vascular anatomy and hemodynamics.

BackgroundStandardized methods for mapping the complex blood flow in vessels are essential for processing the large data volume acquired from 4D Flow MRI. We present a method for systematic and efficient analysis of anatomy and flow in large human blood vessels. To attain the best outcomes in cardiac surgery, vascular modifications that lead to secondary flow patterns such as vortices should be avoided. In this work, attention was paid to the undesired cancelation of vortices with opposite directions of rotation, known as Dean flow patterns, using hemodynamic parameters such as circulation and helicity density.MethodsOur approach is based on the multiplanar reconstruction (MPR) of a multi-dimensional feature-space along the blood vessel's centerline. Hemodynamic parameters and anatomic information were determined in-plane from the reconstructed feature-space and from the blood vessel's centerline. A modified calculation of circulation and helicity density and novel parameters for quantifying Dean flow were developed. To test the model performance, we applied our methods to three test cases.ResultsComprehensive information on position, magnitude and interrelation of vascular anatomy and hemodynamics were extracted from 4D Flow MRI datasets. The results show that the Dean flow patterns can be efficiently assessed using the novel parameters.ConclusionsOur approach to comprehensively and simultaneously quantify multiple parameters of vascular anatomy and hemodynamics from 4D Flow MRI provides new insights to map complex hemodynamic conditions