Comprehensive Assessment of Peripheral Artery Disease Using Magnetic Resonance Imaging, Angiography, and Spectroscopy

Exercise-stimulated arterial transit time in calf muscles measured by dynamic contrast-enhanced magnetic resonance imaging

The primary goal of this study was to evaluate arterial transit time (ATT) in exercise-stimulated calf muscles as a promising indicator of muscle function. Following plantar flexion, ATT was measured by dynamic contrast-enhanced (DCE) MRI in young and elderly healthy subjects and patients with peripheral artery disease (PAD). In the young healthy subjects, gastrocnemius ATT decreased significantly (P < 0.01) from 4.3 ± 1.5 to 2.4 ± 0.4 sec when exercise load increased from 4 lbs to 16 lbs. For the same load of 4 lbs, gastrocnemius ATT was lower in the elderly healthy subjects (3.2 ± 1.1 sec; P = 0.08) and in the PAD patients (2.4 ± 1.2 sec; P = 0.02) than in the young healthy subjects. While the sensitivity of the exercise-stimulated ATT is diagnostically useful, it poses a challenge for arterial spin labeling (ASL), a noncontrast MRI method for measuring muscle perfusion. As a secondary goal of this study, we assessed the impact of ATT on ASL-measured perfusion with ASL data of multiple post labeling delays (PLDs) acquired from a healthy subject. Perfusion varied substantially with PLD in the activated gastrocnemius, which can be attributed to the ATT variability as verified by a simulation. In conclusion, muscle ATT is sensitive to exercise intensity, and it potentially reflects the functional impact of aging and PAD on calf muscles. For precise measurement of exercise-stimulated muscle perfusion, it is recommended that ATT be considered when quantifying muscle ASL data.

The role of lipid dysregulation and vascular risk factors in glaucomatous retrobulbar circulation

The aim of this study was to evaluate selected lipid-related and vascular factors and their effect on retrobulbar hemodynamics in glaucoma. Fifty-six patients with primary open angle glaucoma (POAG) [POAG group; mean age 68.32 years (SD±0.21)] and 54 patients in control group [CG, mean age 68.1 years (SD±5.34)] were examined. Peak systolic velocity, end-diastolic velocity, mean velocity, pulsatility index, and resistive index of the ophthalmic artery, the central retinal artery and the posterior ciliary arteries were measured by Color Doppler Imaging. Selected lipid-related, systemic and local vascular parameters were evaluated. Statistical methods included Shapiro-Wilk, Student-t and Mann-Whitney U tests, and Spearman rank correlations. In POAG group systolic arterial blood pressure, diastolic arterial blood pressure, total cholesterol, low density lipoprotein cholesterol (LDL-ch), and intraocular pressure were significantly higher; while ocular perfusion pressure, high density lipoprotein cholesterol (HDL-ch) and diastolic ocular perfusion pressure were significantly lower (p≤0.05). Color Doppler Imaging confirmed blood flow abnormalities in all investigated arteries. In addition, significant correlations of HDL-ch, LDL-ch and triglycerides (TG) with peak systolic velocity, end-diastolic velocity and mean velocity were found in individual arteries (p≤0.05). Also, significant associations of systolic arterial blood pressure, ocular perfusion pressure, systolic oclular perfusion pressure and diastolic ocular perfusion pressure with peak systolic velocity, end-diastolic velocity, mean velocity and resistive index were revealed in the posterior ciliary arteries (p≤0.05). Dysregulation of lipid-related and vascular factors, as well as statistical correlation between the above and retrobulbar blood flow indices, might imply their role in vasoconstrictive processes during glaucomatous endotheliopathy.