Regional assessment of carotid artery pulse wave velocity using compressed sensing accelerated high temporal resolution 2D CINE phase contrast cardiovascular magnetic resonance

BACKGROUND

Cardiovascular magnetic resonance (CMR) allows for non-invasive assessment of arterial stiffness by means of measuring pulse wave velocity (PWV). PWV can be calculated from the time shift between two time-resolved flow curves acquired at two locations within an arterial segment. These flow curves can be derived from two-dimensional CINE phase contrast CMR (2D CINE PC CMR). While CMR-derived PWV measurements have proven to be accurate for the aorta, this is more challenging for smaller arteries such as the carotids due to the need for both high spatial and temporal resolution. In this work, we present a novel method that combines retrospectively gated 2D CINE PC CMR, high temporal binning of data and compressed sensing (CS) reconstruction to accomplish a temporal resolution of 4 ms. This enables accurate flow measurements and assessment of PWV in regional carotid artery segments.

METHODS

Retrospectively gated 2D CINE PC CMR data acquired in the carotid artery was binned into cardiac frames of 4 ms length, resulting in an incoherently undersampled ky-t-space with a mean undersampling factor of 5. The images were reconstructed by a non-linear CS reconstruction using total variation over time as a sparsifying transform. PWV values were calculated from flow curves by using foot-to-foot and cross-correlation methods. Our method was validated against ultrasound measurements in a flow phantom setup representing the carotid artery. Additionally, PWV values of two groups of 23 young (30 ± 3 years, 12 [52%] women) and 10 elderly (62 ± 10 years, 5 [50%] women) healthy subjects were compared using the Wilcoxon rank-sum test.

RESULTS

Our proposed method produced very similar flow curves as those measured using ultrasound at 1 ms temporal resolution. Reliable PWV estimation proved possible for transit times down to 7.5 ms. Furthermore, significant differences in PWV values between healthy young and elderly subjects were found (4.7 ± 1.0 m/s and 7.9 ± 2.4 m/s, respectively; p < 0.001) in accordance with literature.

CONCLUSIONS

Retrospectively gated 2D CINE PC CMR with CS allows for high spatiotemporal resolution flow measurements and accurate regional carotid artery PWV calculations. We foresee this technique will be valuable in protocols investigating early development of carotid atherosclerosis.

Hypolipidemic drugs in elderly subjects: Indications and limits

AIMS

Cardiovascular disease is a major cause of death worldwide. Safety and efficacy of lipid lowering therapy have been clearly established for either primary and secondary prevention of cardiovascular events in adults. Nevertheless, the use of hypolipidemic drugs in elderly individuals, especially in the oldest ones, still raises some concerns. Aim of this paper is to review indications and limits of lipid lowering in advanced age, furnishing a practical medical attitude tempered by clinical and geriatric competences.

DATA SYNTHESIS

While figures from randomized controlled trials and from observational studies seem to support the use of lipid lowering drugs for secondary prevention in the elderly, drawing inferences from primary prevention in old populations is far more challenging. Although these pharmacological agents seem to reduce the incidence of cardiovascular events, they do not prolong survival. In addition, there is some doubt about the cost-effectiveness of treatment because of a more delicate balance between benefit and potential adverse reactions. However, lipid-lowering drugs seem largely underutilized in older age, mainly due to safety concerns that must be reconsidered, at least in part, given the somewhat reassuring results deriving from specific cohort surveys.

CONCLUSIONS

Data on the use and on the effects of lipid lowering drugs in elderly populations are incomplete, especially those concerning very old subjects without established cardiovascular disease. Comprehensive guidelines for the management of dyslipidemias in this rapidly-growing population is a urgent need, and treatment should be based, besides the aforementioned considerations, on patient preferences, cognitive function and life expectancy.