John B. C. Dick

Two-dimensional flow quantitative MRI of aortic arch blood flow patterns: Effect of age, sex, and presence of carotid atheromatous disease on prevalence of spiral blood flow.

To determine the effect of age, sex, and presence of carotid atheromatous disease on the presence of aortic spiral blood flow pattern using two‐dimensional flow quantitative magnetic resonance imaging (MRI).

Spiral Laminar Flow Prosthetic Bypass Graft: Medium-Term Results From a First-In-Man Structured Registry Study

BACKGROUND A number of surgical strategies and graft enhancements have been trialled to improve the performance of prosthetic grafts. Neointimal hyperplasia may, in part, be a normal cellular response to an abnormal (turbulent) flow environment. This first-in-many study assesses the safety and medium-term patency performance of a new graft designed to induce stable laminar flow through the distal anastomosis. METHOD Forty patients who required an infrainguinal bypass graft were recruited/registered from a number of centers in Belgium and The Netherlands. Thirty-nine received a Spiral Laminar Flow graft as part of a standard treatment protocol (23 above-the-knee and 16 below-the-knee bypasses). Kaplan-Meier analyses were used to calculate primary and secondary patency rates. RESULTS The 12-, 24-, and 30-month primary patency rates were 86%, 81%, and 81% for above-the-knee bypasses and 73%, 57%, and 57% for below-the-knee bypasses, respectively. In the case of secondary patency rates, numbers were unchanged for above-the-knee bypasses and were 86%, 64%, and 64%, respectively, for below-the-knee bypasses. There were no amputations in the study population. CONCLUSION This first-in-man series shows potential for the idea of spiral flow-enhanced prosthetic grafts. As always, randomized studies are required to explore the role of different enhanced prosthetic grafts.

Statin therapy increases vascular sensitivity to angiotensin II in hypercholesterolaemic patients

Introduction Cross-talk between various cardiovascular risk factors has been suggested by a number of studies. This study examines the interaction between hypercholesterolaemia and the renin-angiotensin system in vivo in man. Methods We performed a randomised, placebo-controlled, double-blind crossover study on 40 hypercholesterolaemic patients, comparing cholesterol-lowering therapy with a statin for six months versus placebo. Brachial artery function was assessed by bilateral venous occlusion plethysmography using intra-arterial infusions of the endothelial-dependent vasoconstrictors, angiotensin I (Ang I) and angiotensin II (Ang II), to measure vascular angiotensin-converting enzyme (ACE) and Ang II receptor response respectively. The endothelial-independent vasoconstrictor, noradrenaline, was used as a control vasoconstrictor. Results were analysed by multiple analysis of variance and statistical significance Cholesterol-lowering treatment with a statin was taken as a p value <0.05. Results Cholesterol-lowering treatment with alstatin significantly reduced the mean total cholesterol level to 5.71 mmol/L vs. 7.57 mmol/L on placebo (p<0.0001). Hypercholesterolaemia significantly increased the vasoconstriction response to noradrenaline (placebo versus statin treatment; p=0.046). In hypercholesterolaemia, there was a strong trend towards a reduction in the vasoconstriction response to Ang I (placebo versus statin treatment; p=0.089). In hypercholesterolaemia, the vasoconstriction response to Ang II was significantly reduced (placebo versus statin treatment; p=0.01). Conclusions Our in vivo results show that, unlike some other previous work, hypercholesterolaemia is associated with down-regulation of the vasoconstrictor response to Ang II and that statin therapy up-regulates the local vasoconstrictor response to Ang II. The possibility now arises that, in man, statins alter the balance between AT1-receptors and AT2-receptors.