Assessment of Takayasu's arteritis activity by ultrasound localization microscopy.

BACKGROUND: Ultrasound localization microscopy (ULM) based on ultrafast ultrasound imaging of circulating microbubbles (MB) can image microvascular blood flows in vivo up to the micron scale. Takayasu arteritis (TA) has an increased vascularisation of the thickened arterial wall when active. We aimed to perform vasa vasorum ULM of the carotid wall and demonstrate that ULM can provide imaging markers to assess the TA activity. METHODS: Patients with TA were consecutively included with assessment of activity by the National Institute of Health criteria: 5 had active TA (median age 35.8 [24.5-46.0] years) and 11 had quiescent TA (37.2 [31.7-47.3] years). ULM was performed using a 6.4 MHz probe and a dedicated imaging sequence (plane waves with 8 angles, frame rate 500 Hz), coupled with the intravenous injection of MB. Individual MB were localised at a subwavelength scale then tracked, allowing the reconstruction of the vasa vasorum flow anatomy and velocity. FINDINGS: ULM allowed to show microvessels and to measure their flow velocity within the arterial wall. The number of MB detected per second in the wall was 121 [80-146] in active cases vs. 10 [6-15] in quiescent cases (p = 0.0005), with a mean velocity of 40.5 [39.0-42.9] mm.s-1 in active cases. INTERPRETATION: ULM allows visualisation of microvessels within the thickened carotid wall in TA, with significantly greater MB density in active cases. ULM provides a precise visualisation in vivo of the vasa vasorum and gives access to the arterial wall vascularisation quantification. FUNDING: French Society of Cardiology. ART (Technological Research Accelerator) biomedical ultrasound program of INSERM, France.

Methods: Aortic wall deformation assessment by ultrafast ultrasound imaging: Application to bicuspid aortic valve associated aortopathy.

Purpose: Aortic maximal rate of systolic distention (MRSD) is a prognosis factor of ascending aorta dilatation with magnetic resonance imaging. Its calculation requires precise continuous tracking of the aortic diameter over the cardiac cycle, which is not feasible by focused ultrasound. We aimed to develop an automatic aortic acquisition using ultrafast ultrasound imaging (UUI) to provide access to the aortic MRSD. Methods: A phased array probe and developed sequences at 2000 frames/s were used. A created interface automatically tracked the anterior and posterior aortic walls over the cardiac cycle. Tissue Doppler allowed a precise estimation of the walls' movements. MRSD was the maximum derivative of the aortic diameter curve over time. To assess its feasibility, 34 patients with bicuspid aortic valve (BAV) and 31 controls were consecutively included to evaluate the BAV-associated aortopathy at the sinus of Valsalva, the tubular ascending aorta, and the aortic arch. Results: UUI acquisitions and the dedicated interface allow tracking of the aortic diameter and calculating the MRSD for the BAV patients and controls (mean age of 34 vs. 43 years, p = 0.120). A trend toward lower deformation in the different aortic segments was observed, as expected. Still, only the MRSD with UUI was significantly different at the sinus of Valsalva in this small series: (0.61 .103.s-1 [0.37-0.72] for BAV patients vs. 0.92 .103.s-1 [0.72-1.02] for controls, p = 0.025). Conclusion: Aortic deformation evaluated with UUI deserves attention with a simple and automated measurement technique that could assess the segmental aortic injury associated with BAV.

Diastolic Function Assessment of Left and Right Ventricles by MRI in Systemic Sclerosis Patients.

BACKGROUND: Heart involvement is frequent although often clinically silent in systemic sclerosis (SSc) patients. Early identification of cardiac involvement can be improved by noninvasive methods such as MRI, in addition to transthoracic echocardiography (TTE). PURPOSE: To assess the ability of phase-contrast (PC)-MRI to detect subclinical left (LV) and right (RV) ventricular diastolic dysfunction in SSc patients. STUDY TYPE: Prospective. POPULATION: Thirty-five consecutive SSc patients (49 ± 14 years) and 35 sex- and age-matched healthy controls (48.6 ± 13.5 years) who underwent TTE and MRI in the same week. FIELD STRENGTH/SEQUENCE: 5 T/PC-MRI using a breath-hold velocity-encoded gradient echo sequence. ASSESSMENT: LV TTE (E/E') and LV and RV PC-MRI indices of diastolic function (LV early and late transmitral [EM , EfM , AM , AfM ] and RV transtricuspid [ET , EfT , AT , AfT ] peak filling flow velocities and flow rates, as well as LV [ E M ' ] and RV [ E T ' ] peak longitudinal myocardial velocities during diastole) were measured. STATISTICAL TESTS: Two-tailed t-test, Wilcoxon test, or Fischer test for comparison of variables between SSc and healthy control groups; sensitivity, specificity, receiver-operating-characteristic (ROC) area under the curve (AUC) to assess discriminative ability of variables. A P-value <0.05 was considered statistically significant. RESULTS: TTE LV E/E' and MRI EM / E M ' and ET / E T ' were significantly higher in SSc patients than in controls (8.27 ± 1.25 vs. 6.70 ± 1.66; 9.43 ± 2.7 vs. 6.51 ± 1.50; 6.51 [4.70-10.40] vs. 4.13 [3.22-5.75], respectively) and separated SSc patients and healthy controls with good sensitivity (68%, 71%, and 80%), specificity (85%, 94%, and 62%), and AUC (0.787, 0.807, and 0.765). LV EfM was significantly higher in SSc patients than in controls (347.1 ± 113.7 vs. 284.7 ± 94.6) as RVAfT (277 [231-355] vs. 220 [154-253] mL/sec) with impaired relaxation pattern (EfT /AfT , 0.95 [0.87-1.21] vs. 1.12 [0.93-1.47]). DATA CONCLUSION: MRI was able to detect LV and RV diastolic dysfunction in SSc patients with good accuracy in the absence of LV systolic dysfunction at echocardiography. Use of MRI can allow to better assess the early impact of myocardial fibrosis related to SSc. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY STAGE: 2.

Carotid Stiffness Assessment With Ultrafast Ultrasound Imaging in Case of Bicuspid Aortic Valve.

AIMS: To compare the carotid stiffness and flow parameters by ultrafast ultrasound imaging (UF), in bicuspid aortic valve (BAV) patients to first-degree relatives (controls). METHODS: BAV patients (n = 92) and controls (n = 48) were consecutively included at a reference center for BAV. Aortic valve and ascending aorta were evaluated by echocardiography. Common carotid arteries were evaluated by UF with a linear probe. A high frame rate (2,000 frames/s) was used to measure the pulse wave velocity (PWV). The arterial diameter change over the cardiac cycle was obtained by UF-Doppler imaging. This allowed us to measure the distensibility and the maximal rate of systolic distension (MRSD). The wall shear stress (WSS) was measured based on the same acquisitions, by analyzing blood flow velocities close to the carotid walls. RESULTS: BAV patients had significantly larger aortic diameters (p < 0.001) at the Valsalva sinus and at the tubular ascending aorta but no larger carotid diameters. No significant differences were found in carotid stiffness parameters (distensibility, MRSD, and PWV), even though these patients had a higher aortic stiffness. Carotid stiffness correlated linearly with age and similar slopes were obtained for BAV patients and controls. No difference in carotid WSS was found between BAV patients and controls. CONCLUSION: Our results clearly show that the carotid stiffness and flow parameters are not altered in case of BAV compared with controls.

Arterial Stiffness Assessment by Shear Wave Elastography and Ultrafast Pulse Wave Imaging: Comparison with Reference Techniques in Normotensives and Hypertensives.

Shear wave elastography and ultrafast imaging of the carotid artery pulse wave were performed in 27 normotensive participants and 29 age- and sex-matched patients with essential hypertension, and compared with reference techniques: carotid-femoral pulse wave velocity (cfPWV) determined via arterial tonometry and carotid stiffness (carPWV) determined via echotracking. Shear wave speed in the carotid anterior (a-SWS) and posterior (p-SWS) walls were assessed throughout the cardiac cycle. Ultrafast PWV was measured in early systole (ufPWV-FW) and in end-systole (dicrotic notch, ufPWV-DN). Shear wave speed in the carotid anterior appeared to be the best candidate to evaluate arterial stiffness from ultrafast imaging. In univariate analysis, a-SWS was associated with carPWV (r = 0.56, p = 0.003) and carotid-to-femoral PWV (r = 0.66, p < 0.001). In multivariate analysis, a-SWS was independently associated with age (R²â€¯= 0.14, p = 0.02) and blood pressure (R²â€¯= 0.21, p = 0.004). Moreover, a-SWS increased with blood pressure throughout the cardiac cycle and did not differ between normotensive participants and patients with essential hypertension when compared at similar blood pressures.

Quantitative assessment of arterial wall biomechanical properties using shear wave imaging.

A new ultrasound-based technique is proposed to assess the arterial stiffness: the radiation force of an ultrasonic beam focused on the arterial wall induces a transient shear wave (∼10 ms) whose propagation is tracked by ultrafast imaging. The large and high-frequency content (100 to 1500 Hz) of the induced wave enables studying the wave dispersion, which is shown experimentally in vitro and numerically to be linked to arterial wall stiffness and geometry. The proposed method is applied in vivo. By repeating the acquisition up to 10 times per second (theoretical maximal frame rate is ∼100 Hz), it is possible to assess in vivo the arterial wall elasticity dynamics: shear modulus of a healthy volunteer carotid wall is shown to vary strongly during the cardiac cycle and measured to be 130 ± 15 kPa in systole and 80 ± 10 kPa in diastole.