The present series of in vivo experiments in healthy subjects, were performed to investigate wall stiffness in peripheral vessels and how this modality adapts to iterative increments or sustained reductions in local intravascular pressures. Vascular stiffness was measured as changes in arterial and venous diameters, and in arterial flow, during graded increments in distending pressures in the vasculature of an arm or a lower leg. In addition, effects of intravascular pressure elevation on flow characteristics in veins, and on limb pain were elucidated. Arteries and veins were stiffer (i.e. pressure distension was less) in the lower leg than in the arm. The pressure-induced increase in arterial flow was substantially greater in the arm than in the lower leg, indicating a greater stiffness in the arterioles of the lower leg. Prolonged reduction of intravascular pressures in the lower body, induced by 5 wks of sustained horizontal bedrest (BR), decreased stiffness in the leg vasculature. BR increased pressure distension in the tibial artery threefold and in the tibial vein by 86 %. The pressure-induced increase in tibial artery flow was greater post bedrest, indicating reduced stiffness in the arterioles of the lower leg. Intermittent increases of intravascular pressures in one arm (pressure training; PT) during a 5-wk period decreased vascular stiffness. Pressure distension and pressure-induced flow in the brachial artery were reduced by about 50 % by PT. PT reduced pressure distension in arm veins by 30 to 50 %. High intravascular pressures changed venous flow to arterial-like pulsatile patterns, reflecting propagation of pulse waves from the arteries to the veins either via the capillary network or through arteriovenous anastomoses. High vascular pressures induced pain, which was aggravated by BR and attenuated by PT; the results suggest that the pain was predominantly caused by vascular overdistension. In conclusion, vascular wall stiffness constitutes a plastic modality that adapts to meet demands imposed by a change in the prevailing local intravascular pressure. That increased intravascular pressure leads to increased arteriolar wall stiffness supports the notion that local pressure load may serve as a “prime mover” in the development of vascular changes in hypertension. / medicine doktorsexamen QC 20101109

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Atrial fibrillation (AF), the most common cardiac arrhythmia in persons over age 65, is associated with an increased stroke risk necessitating the need for long-term oral anticoagulation for risk reduction. With the introduction of direct thrombin and factor Xa inhibitors in the US since 2010, these novel oral anticoagulants (NOACs) are increasingly being prescribed, replacing the use of warfarin, a vitamin K antagonist. AF catheter ablation (CA), an elective procedure requiring femoral vascular access is a treatment for drug refractory and persistent AF. Bedrest, limb immobilization, and limited head of bed elevation are nursing measures utilized following femoral venous, and sometimes arterial, sheath removal and hemostasis. Limited research is available on the appropriate duration of bedrest to minimize bleeding complications associated with AF ablation in patients who use NOACs. The purpose of this quality improvement project was to compare and evaluate the effect of bedrest duration on post-procedure bleeding outcomes, urinary complaints, and back pain among patients taking NOACs while undergoing AFCA. Thirty patients undergoing elective AFCA on NOACs were orally consented to participate in the study and placed on shortened (8 hours) or prolonged (>8 hours) bedrest following vascular hemostasis. Outcome measurements included bleeding after ambulation, back pain, and urinary complaints. Fifteen patients (50%) were on shortened bedrest and 15 (50%) were on prolonged bedrest. No statistically significant difference in bleeding, urinary complaints, or back pain were found. Since there is no clear advantage to prolonged bedrest for patients on NOACS after an AFCA procedure, clinicians should consider this when deciding on bedrest duration for their patients.