A Case of Muscle Contraction-Induced Ischemic Limb Hyperemia in a Patient with Peripheral Arterial Disease during Incremental Repeat Isometric Knee Extensor Workloads

Background: To determine whether muscle contraction-induced leg blood flow (LBF) during exercise may be altered in a patient with an ischemic limb due to peripheral arterial disease (PAD) compared with the non-PAD limb. Case Presentation: A 66-year-old male patient with intermittent claudication due to PAD in the right leg (ankle brachial pressure index, 0.69) showed complete obstruction in both common iliac arteries including internal/external segments with collaterals above the femoral artery and popliteal artery with collaterals, and in the healthy left non-PAD-leg (1.06). He attempted unilateral repeat isometric knee extensions at a target contraction rhythm with each leg at incremental contraction intensities (5%, 10%, and 30% of maximum voluntary contraction [MVC] for 3 min at each intensity). Blood velocity/flow (Doppler ultrasound) in the femoral artery, blood pressure, and leg vascular conductance (LVC) were measured. Isometric thigh MVC strength pre-exercise was similar between the PAD-leg (48.0 kg) and non-PAD-leg (48.7 kg). Pre-exercise LBF (ml/min) was also similar between the PAD-leg (316) and non-PAD-leg (327). Blood pressure increases were similar during exercise. Average exercising LBF in ml/min in the last 1 min at each intensity was higher in the PAD-leg than the non-PAD-leg: 1087 vs. 471 at 5%, 2097 vs. 712 at 10%, and 2656 vs. 1517 at 30% MVC with a close positive linear relationship between LBF and %MVC in the non-PAD-leg (r = 0.999, P < 0.01), in agreement with previous findings, but less significant in the PAD-leg (r = 0.879, P = NS), indicating intense vasodilation (increasing LVC) in the PAD-leg compared with the non-PAD-leg. Conclusion: Knee extensor exercising LBF in the femoral artery was dissimilar between the PAD-leg and non-PAD-leg at the same exercise intensity, even though pre-exercising LBF was the same. Further research on the time-course in hemodynamics during leg exercise in PAD might potentially provide insight for the cardiovascular adjustment in severity of arteriosclerosis, stenosis and/or collaterals reserve.

Impact of Revascularization on the Distal to Proximal Pressure Ratio in Case of Multiple Coronary Stenoses

Objective: In order to take a decision about the revascularization approach to be adopted, it is of fundamental importance to determine whether coronary artery stenoses induce ischemia or not. An index, named (Fractional Flow Reserve), based on pressure measurements has been proposed to this aim and is usually interpreted in terms of flows. The objective of this work is to compute simultaneously pressures and flow rates in the coronary network of patients with three-vessel disease, in order to study more precisely the relationship between these two quantities. Approach: 22 patients have been included in the study. Some pressure and flow rate measurements were collected during by-pass surgery. These clinical data allow determining parameters for a patient’s specific model, based on the electric/hydraulic analogy. Collateral pathways are included in the model, as well as the severity of the disease and the impact of revascularization. Main Results: For patients with stenoses on LAD, LCx, LMCA and occlusion of the RCA, the flow rate delivered to the right territory is of course a function of the aortic pressure, the left stenoses severity, and the pressure distal to the thrombosis. But it mainly depends on the capillary and collateral resistances, and on the proportion between them. Abnormal microvascular hemodynamics, may be present in patients with non-hemodynamic significant lesions as assessed by the pressure ratio. Complete revascularization with the 3 grafts is demonstrated to be fully justified. The direction of collateral flows may be reversed, depending on the pressure gradient. In any case, they remain low and become negligible when the 3 grafts are operating. Significance: Surgical decision based only on pressure measurements may miss some real hemodynamic problems due to the considered stenosis. This risk is even greater in case of serial stenoses.

Effect of arteriosclerotic intracranial arterial vessel wall enhancement on downstream collateral flow

Background:The effect of arteriosclerotic intracranial arterial vessel wall enhancement(IAVWE)on downstream collateral flow found in vessel wall imaging(VWI)is not clear.Regardless of the mechanism underlying IAVWE on VWI,damage to the patient’s nervous system caused by IAVWE is likely achieved by affecting downstream cerebral blood flow.The present study aimed to investigate the effect of arteriosclerotic IAVWE on downstream collateral flow.Methods:The present study recruited 63 consecutive patients at the Second Hospital of Hebei Medical University from January 2021 to November 2021 with underlying atherosclerotic diseases and unilateral middle cerebral artery(MCA)M1-segment stenosis who underwent an magnetic resonance scan within 3 days of symptom onset.The patients were divided into 4 groups according to IAVWE and the stenosis ratio(Group 1,n=17;Group 2,n=19;Group 3,n=13;Group 4,n=14),and downstream collateral flow was analyzed using three-dimensional pseudocontinuous arterial spin labeling(3D-pCASL)and RAPID software.The National Institutes of Health Stroke Scale(NIHSS)scores of the patients were also recorded.Two-factor multivariate analysis of variance using Pillai’s trace was used as the main statistical method.Results:No statistically significant difference was found in baseline demographic characteristics among the groups.IAVWE,but not the stenosis ratio,had a statistically significant significance on the late-arriving retrograde flow proportion(LARFP),hypoperfusion intensity ratio(HIR),and NIHSS scores(F=20.941,P<0.001,Pillai’s trace statistic=0.567).The between-subject effects test showed that IAVWE had a significant effect on the three dependent variables:LARFP(R^(2)=0.088,F=10.899,P=0.002),HIR(R^(2)=0.234,F=29.354,P<0.001),and NIHSS(R^(2)=114.339,F=33.338,P<0.001).Conclusions:Arteriosclerotic IAVWE significantly reduced downstream collateral flow and affected relevant neurological deficits.It was an independent factor affecting downstream collateral flow and NIHSS scores,which should be a focus of future studies.Trial Registration:ChiCTR.org.cn,ChiCTR2100053661.