Emilie Bollache

Geometry is a major determinant of flow reversal in proximal aorta

The aim of this study is to quantify aortic backward flow (BF) using phase-contrast cardiovascular magnetic resonance (PC-CMR) and to study its associations with age, indexes of arterial stiffness, and geometry. Although PC-CMR blood flow studies showed a simultaneous presence of BF and forward flow (FF) in the ascending aorta (AA), the relationship between aortic flows and aging as well as arterial stiffness and geometry in healthy volunteers has never been reported. We studied 96 healthy subjects [47 women, 39 ± 15 yr old (19-79 yr)]. Aortic stiffness [arch pulse wave velocity (PWVAO), AA distensibility], geometry (AA diameter and arch length), and parameters related to AA BF and FF (volumes, peaks, and onset times) were estimated from CMR. Applanation tonometry carotid-femoral pulse-wave velocity (PWVCF), carotid augmentation index, and time to return of the reflected pressure wave were assessed. Whereas FF parameters remained unchanged, BF onset time shortened significantly (R(2) = 0.18, P < 0.0001) and BF volume and BF-to-FF peaks ratio increased significantly (R(2) = 0.38 and R(2) = 0.44, respectively, P < 0.0001) with aging. These two latter BF indexes were also related to stiffness indexes (PWVCF, R(2) > 0.30; PWVAO, R(2) > 0.24; and distensibility, R(2) > 0.20, P < 0.001), augmentation index (R(2) > 0.20, P < 0.001), and aortic geometry (AA diameter, R(2) > 0.58; and arch length, R(2) > 0.31, P < 0.001). In multivariate analysis, aortic diameter was the strongest independent correlate of BF beyond age effect. In conclusion, AA BF estimated using PC-CMR increased significantly in terms of magnitude and volume and appeared earlier with aging and was mostly determined by aortic geometry. Thus BF indexes could be relevant markers of subclinical arterial wall alterations.

MR and applanation tonometry derived aortic impedance: association with aging and left ventricular remodeling.

We sought to noninvasively estimate aortic impedance indices from MR and tonometric data.

Impaired atrioventricular transport in patients with transposition of the great arteries palliated by atrial switch and preserved systolic right ventricular function: A magnetic resonance imaging study

OBJECTIVES We aimed (1) determine if systemic right ventricle filling parameters influence systemic right ventricle stroke volume in adult patients with D-transposition of the great arteries (D-TGA) palliated by atrial switch, using cardiac magnetic resonance imaging and echocardiography, and (2) to study relationship of these diastolic parameters with exercise performance and BNP, in patients with preserved systolic systemic right ventricle function. DESIGN Single-center, cross-sectional, prospective study. SETTING In patients with D-TGA palliated by atrial switch, diastolic dysfunction of the systemic right ventricle may precede systolic dysfunction. METHODS Forty-five patients with D-TGA and atrial switch and 45 age and sex-matched healthy subjects underwent cardiac magnetic resonance imaging and echocardiography. Filling flow-rates measured by phase-contrast cardiac magnetic resonance imaging were analyzed using customized software to estimate diastolic parameters and compared with exercise performance. RESULTS In D-TGA, early filling of systemic right ventricle was impaired with a lower peak filling rate normalized by filling volume (Ef/FV measured by cardiac magnetic resonance imaging) and a higher early filling peak velocity normalized by early peak myocardial velocity (EUS /Ea measured by echocardiography) compared with controls (P ≤ .04). Stroke volume of systemic right ventricle showed a direct and significant association with pulmonary venous pathway size (respectively r = 0.50, P < .01). Systemic right atrial area and systemic right ventricle mass/volume index measured by cardiac magnetic resonance imaging, as well as Ef/FV were significantly correlated with exercise performances and BNP (P < .01). All correlations were independent of age, gender, body mass index and blood pressure. CONCLUSIONS Systemic right ventricle pre-load and stroke volume depend mainly on intraatrial pathway function. Moreover, systemic right ventricle remodeling and right atrial dysfunction impair systemic right ventricle filling, leading to BNP increase and exercise limitation. Cardiac magnetic resonance imaging should assess systemic right ventricle filling abnormalities in D-TGA patients.

New estimate of valvuloarterial impedance in aortic valve stenosis: A cardiac magnetic resonance study

Valvuloarterial impedance (ZVA), estimating left ventricle (LV) afterload, has been proposed in transthoracic echocardiography (TTE) as a predictor of mortality in aortic valve stenosis (AVS). However, its calculation differs from arterial characteristic impedance (ZC). Our aim was to apply the concept of ZC calculation to estimate ZVA from MR with carotid tonometry and to evaluate these indices through their associations with symptoms, LV diastolic function and aortic stiffness.

Left ventricular-aortic coupling in sickle cell disease underlies diastolic dysfunction

Left ventricular (LV) diastolic dysfunction (DD) is associated with increased mortality in sickle cell disease (SCD) but its mechanisms are not well known, preventing the development of effective therapies. Our hypothesis was that DD in SCD may be due to changes in aortic properties. We studied 31 SCD patients (32±7yrs) and 12 normal controls (29±10yrs) who underwent echocardiography and MRI on the same day. LV diastolic function was assessed from echocardiography. MRI included velocity-encoded images of the aorta to measure ascending aortic cross-sectional area, stroke volume, distensibility, as well as volumes of the forward (FFV) and backward (BFV) blood flow. Compared to controls, SCD patients had increased aortic area, stroke volume, and both FFV and BFV, while distensibility was similar. DD was found in 5/31 patients (16%), in whom the increase in BFV and BFV/FFV ratio was even more pronounced, when compared to the remaining patients. Our findings suggest a potential mechanism of DD in SCD patients. Increased cardiac output induced by chronic anemia might be associated with aortic dilation, which may increase LV afterload (BFV), ultimately leading to LV DD. If confirmed in larger studies, these aortic changes could be targets for specific therapies as a way to prevent the development of DD in SCD.

Pixel-wise absolute pressures in the aortic arch from 3D MRI velocity data and carotid artery applanation tonometry

A pixel-wise method for absolute and local aortic pressures estimation using 3D velocities in MRI and carotid pressure curves to set-up reference pressure values is presented. This method is based on the Navier-Stokes equation and a fast iterative algorithm. Its reliability was demonstrated: 1) in a synthetic phantom by comparison against simplified Bernoulli equation applied at peak velocities, and 2) in a healthy subject and a patient with aortic coarctation, in which absolute pressure distribution within the aortic arch was consistent with established physiopathological knowledge. Such local absolute aortic pressures may be useful in the understanding of hemodynamic changes secondary to cardiovascular alterations. Also, their addition to the already available indices of risk of aortic complications such as dilatation and dissection definition may prove of major clinical usefulness.