Angular (Gothic) aortic arch leads to enhanced systolic wave reflection, central aortic stiffness, and increased left ventricular mass late after aortic coarctation repair: evaluation with magnetic resonance flow mapping.

OBJECTIVE: We sought to investigate the mechanism whereby a particular deformity of the aortic arch, an angulated Gothic shape, might lead to hypertension late after anatomically successful repair of aortic coarctation. METHODS: Fifty-five normotensive patients with anatomically successful repair of aortic coarctation and either a Gothic (angulated) or a Romanesque (smooth and rounded) arch were studied with magnetic resonance angiography and flow mapping in both the ascending and descending aortas. Systolic waveforms, central aortic stiffness, and pulse velocity were measured. We hypothesized that arch angulation would result in enhanced systolic wave reflection with loss of energy across the aortic arch, as well as increased central aortic stiffness. RESULTS: Twenty patients were found to have a Gothic, and 35 a Romanesque, arch. Patients with a Gothic arch showed markedly augmented systolic wave reflection (12 +/- 6 vs 5 +/- 0.3 mL, P < .001) and greater loss of systolic wave height in the distal aorta (30% +/- 16% vs 22% +/- 12%, P < .01) compared with that of subjects with a Romanesque arch. Pulse wave velocity was also increased with a Gothic arch (5.6 +/- 1.1 vs 4.1 +/- 1 m/s, P < .0001), as well as left ventricular mass index (85 +/- 15 vs 77 +/- 20 g/m2). Patients with a Romanesque arch had increased aortic stiffness compared with that of control subjects (stiffness beta-index, 3.9 +/- 0.9 vs 2.9 +/- 1; P = .03). CONCLUSIONS: Angulated Gothic aortic arch is associated with increased systolic wave reflection, as well as increased central aortic stiffness and left ventricular mass index. These findings explain (at least in part) the association between this pattern of arch geometry and late hypertension at rest and on exercise in subjects after coarctation repair.

Increased central aortic stiffness and left ventricular mass in normotensive young subjects after successful coarctation repair.

BACKGROUND: Hypertension occurs in 20% to 40% of survivors of anatomically successful repair of aortic coarctation (CoA). The aim of the present study was to examine the role of central aortic function in this setting. METHODS: Forty normotensive asymptomatic subjects with successful CoA repair (age 12 +/- 8 years) and 20 age- and sex-matched control subjects underwent detailed magnetic resonance imaging investigation of the thoracic aorta and left ventricle. Aortic distensibility, compliance, and stiffness beta index were calculated in the central (precoarctation) and descending (postcoarctation) aorta. Aortic pulse wave velocity was measured and left ventricular mass was calculated. RESULTS: Compared to control subjects, CoA subjects had markedly decreased central aortic distensibility (2.8 +/- 0.7 vs 4.2 +/- 0.5 mm Hg(-1) x 10(-3), P < .001) and compliance (1.7 +/- 0.3 vs 2.5 +/- 0.6 mm2 mm Hg(-1), P < .001) and increased stiffness beta index (5.2 +/- 1 vs 2.5 +/- 0.6, P < .001). Pulse wave velocity was also significantly increased in the CoA subjects (4.7 +/- 1.3 vs 3.3 +/- 0.6 m/sec, P < .001). Left ventricular mass index was higher in the CoA subjects (84 +/-11 vs 73 +/-10 g/m2, P = .01) and correlated significantly with aortic stiffness beta index (r2 = 0.8, P < .0001). By contrast, descending aortic characteristics were similar in the CoA and control subjects. CONCLUSION: Central aortic stiffness is markedly increased and associated with increased left ventricular mass in normotensive young subjects after successful early repair of CoA.

Interobserver variability in assessing segmental function can be reduced by combining visual analysis of CMR cine sequences with corresponding parametric images of myocardial contraction.

OBJECTIVE: To evaluate if color-coded parametric images could help subjective visual analysis and improve interobserver agreement in the evaluation of segmental contraction (SC) in CMR. BACKGROUND: Routine evaluation of SC in CMR remains mostly based on visual analysis of cine loops and subsequent interobserver variability remains a potential drawback. MATERIALS AND METHODS: Three short axis cine loops were obtained in 33 subjects (18 myocardial infarction, 15 control), and 528 segments were analyzed. From each cine loop a single static parametric image resuming wall motion information was generated using Factor Analysis of Medical Image Sequences. Three readers (R1, R2, R3) scored left ventricular SC in 4 classes in 2 steps: visual assessment of cine loops alone and by combining cine loops with the corresponding parametric image. Reference segmental scores were obtained by consensus. Global contraction indexes were calculated in each step of the analysis. RESULTS: When parametric images were combined with cine loop assessment, interobserver agreement was enhanced for paired readers: R1-R2: kappa = 0.66 (combined analysis) vs. kappa = 0.60 (cine alone); R2-R3: kappa = 0.67 vs. kappa = 0.65; R3-R1: kappa = 0.71 vs. kappa = 0.67 and absolute agreement with consensus was higher for the 3 readers: R1: 91% vs. 85%; R2: 87% vs. 83% and R3: 94% vs. 89%. When considering global wall motion indexes, interobserver agreement was also enhanced: R1 vs. R2 : r = 0.91 vs. 0.85; R2 vs. R3: 0.95 vs. 0.91; R3 vs R1: 0.98 vs. 0.91. CONCLUSION: Adding a color-coded static parametric image to routine subjective visual assessment of SC reduces interobserver variability.

Calculation of left ventricle relative pressure distribution in MRI using acceleration data.

Measurements of pressure variations within the cardiac chambers could provide important information for clinical assessments of cardiovascular function. In this work an MRI method for evaluating spatial distributions of intracardiac relative pressure is presented. We first calculated pressure gradients from MR maps of blood acceleration by applying the NS equation. We then used an original algorithm to compute pressure distribution in a region of interest (ROI) by minimizing the pressure gradient curl so that the result in a given pixel is independent of the integration path. The method was assessed in five healthy volunteers by means of MR 2D maps of the blood acceleration in the left ventricle (LV) during ejection and filling phases. The pressure variations calculated from acceleration mapping fit the known physiological variations better than those based on velocity maps acquired in the same volunteers. Furthermore, the optimization algorithm presented here produced the same results as iterative algorithms proposed by other authors, but in much less time and without requiring adjustable parameters or boundary conditions.

Estimation of left ventricular performance through temporal pressure variations measured by MR velocity and acceleration mappings.

PURPOSE: To describe a method for assessing pressure variation vs. time (dp/dt) using blood flow acceleration measured by MRI, and to demonstrate its applicability in estimating left ventricular (LV) function. MATERIALS AND METHODS: The method was tested in vitro using a pulsatile phantom, and a strong correlation was found between transducer and MRI determinations of dp/dt (r = 0.98). Selected aortic flow parameters were then measured in 10 patients and the results were compared with transducer measurements of the LV dp/dt. RESULTS: The correlation coefficients for the reference estimations of global myocardial function and MRI were 0.59 for aortic velocity, 0.74 for aortic acceleration, and 0.86 for aortic dp/dt. CONCLUSION: MR measurements of velocity and acceleration within the ascending aorta offer a noninvasive method for determining indices, such as the aortic dp/dt, that are closely correlated with the global myocardial contractility function.