Non-Invasive Assessment of Arterial Stiffness: Pulse Wave Velocity, Pulse Wave Analysis and Carotid Cross-Sectional Distensibility: Comparison between Methods.

Background: The stiffening of large elastic arteries is currently estimated in research and clinical practice by propagative and non-propagative models, as well as parameters derived from aortic pulse waveform analysis. Methods: Common carotid compliance and distensibility were measured by simultaneously recording the diameter and pressure changes during the cardiac cycle. The aortic and upper arm arterial distensibility was estimated by measuring carotid−femoral and carotid−radial pulse wave velocity (PWV), respectively. The augmentation index and blood pressure amplification were derived from the analysis of central pulse waveforms, recorded by applanation tonometry directly from the common carotid artery. Results: 75 volunteers were enrolled in this study (50 females, average age 53.5 years). A significant inverse correlation was found between carotid distensibility and carotid−femoral PWV (r = −0.75; p < 0.001), augmentation index (r = −0.63; p < 0.001) and central pulse pressure (r = −0.59; p < 0.001). A strong correlation was found also between the total slope of the diameter/pressure rate carotid curves and aortic distensibility, quantified from the inverse of the square of carotid−femoral PWV (r = 0.67). No correlation was found between carotid distensibility and carotid−radial PWV. Conclusions: This study showed a close correlation between carotid−femoral PWV, evaluating aortic stiffness by using the propagative method, and local carotid cross-sectional distensibility.

Assessment of 18F-Florbetaben Amyloid PET Imaging in Patients with Suspected Alzheimer's Disease and Isolated Increase in Cerebrospinal Fluid Tau Proteins.

BACKGROUND/OBJECTIVE: The aim of this study was to assess, in routine, the rates with which an amyloid deposition was documented by 18F-florbetaben PET in patients with suspected Alzheimer's disease (AD) but with isolated increases in cerebrospinal fluid (CSF) tau-protein concentrations, and the subsequent impact of these PET results on medical management. METHODS: This prospective study included 34 patients with mild neurocognitive disorders (MND) and suspected AD (73±9 years, 16 women) and with abnormal CSF concentrations in total-tau (T-tau) and/or phosphorylated-tau (P-tau) proteins but normal Aß42 concentration and Aß42/Aß40 ratio. These patients were referred to 8F-florbetaben PET from which the PET-related changes in the confidence for AD diagnosis (low, intermediate, or high) and treatments were reported. RESULTS: The PET examinations were positive for amyloid deposition (brain amyloid plaque load, BAPL score >1) in none of the 9 patients with an increase in only T-tau proteins and in 8 among the 25 (32%) with an increase in P-tau proteins (one BAPL score of 2 and seven BAPL scores of 3). Knowledge of the PET results was associated with subsequent changes in diagnostic confidence in 44% of patients (15/34) and in the intention-to-treat with a cholinesterase inhibitor drug in 18% (6/34). CONCLUSION: In patients with suspected AD and isolated increase in CSF tau protein concentrations, an amyloid deposition is documented by 18F-florbetaben PET in as much as one third of cases when the concentration of P-tau is abnormal, and PET results are associated with significant further changes in medical management.

Pulse wave velocity assessment by external noninvasive devices and phase-contrast magnetic resonance imaging in the obese.

Carotid-femoral pulse wave velocity (PWV) is considered the gold-standard measurement of arterial stiffness. Obesity, however, can render inaccurate the measurement of PWV by external noninvasive devices. Phase-contrast MRI allows the determination of aortic PWV in multiple aortic locations with intra-arterial distance measurements, as well as the assessment of aortic mechanical properties. The purpose of this study was to assess the reliability of external carotid-femoral PWV values measured by well-validated external devices in comparison with MRI acquisitions of PWV and aortic mechanical properties in a population of obese subjects. PWV was measured with PulsePen and Complior II devices in 32 volunteers (18 men and 14 women), aged 46 to 65 years (mean: 55.7+/-5.1 years), presenting with isolated abdominal obesity, with a waist circumference >102 cm for men and >88 cm for women, and a body mass index between 27 and 35. These results were then compared with MRI PWV values and cross-sectional MRI thoracic aorta distensibility values. MRI PWV values were positively correlated with PWV measured by both PulsePen (r=0.47; P=0.005) and Complior (r=0.43; P=0.01). Aortic cross-sectional stiffness was positively correlated with PulsePen PWV (r=0.42; P=0.02). The same trend was also observed with Complior PWV (r=0.33; P=0.06). This is the first study comparing transcutaneous PWV measurements with MRI aortic elastic properties in obese subjects. Our results indicate that, for body mass index values < or =35 kg m(-2), PWV measured externally with Complior or PulsePen validly reflect values obtained directly in the thoracic aorta through MRI.