In vivo assessment of endothelial function in human lower extremity arteries

Blunted brachial blood flow velocity response to acute mental stress in PTSD females

Post-traumatic stress disorder (PTSD) is associated with increased cardiovascular disease (CVD) risk. Compared with males, females are twice as likely to develop PTSD after trauma exposure, and cardiovascular reactivity to stress is a known risk factor for CVD. We aimed to examine hemodynamic responses to acute mental stress in trauma-exposed females with and without a clinical diagnosis of PTSD. We hypothesized that females with PTSD would have higher heart rate (HR), blood pressure (BP), and lower blood flow velocity (BFV) responsiveness compared with controls. We enrolled 21 females with PTSD and 21 trauma-exposed controls. We continuously measured HR using a three-lead electrocardiogram, BP using finger plethysmography, and brachial BFV using Doppler ultrasound. All variables were recorded during 10 min of supine rest, 5 min of mental arithmetic, and 5 min of recovery. Females with PTSD were older, and had higher BMI and higher resting diastolic BP. Accordingly, age, BMI, and diastolic BP were covariates for all repeated measures analyses. Females with PTSD had a blunted brachial BFV response to mental stress (time × group, p = 0.005) compared with controls, suggesting greater vasoconstriction. HR and BP responses were comparable. In conclusion, our results suggest early impairment of vascular function in premenopausal females with PTSD.

Hydrogel-based therapeutic angiogenesis: An alternative treatment strategy for critical limb ischemia

Critical limb ischemia (CLI) is the most severe clinical manifestation of peripheral arterial disease (PAD), resulting in the total or partial loss of limb function. Although the conventional treatment strategy of CLI (e.g., medical treatment and surgery) can improve blood perfusion and restore limb function, many patients are unsuitable for these strategies and they still face the threats of amputation or death. Therapeutic angiogenesis, as a potential solution for these problems, attempts to manipulate blood vessel growth in vivo for augment perfusion without the help of extra pharmaceutics and surgery. With the rise of interdisciplinary research, regenerative medicine strategies provide new possibilities for treating many clinical diseases. Hydrogel, as an excellent biocompatibility material, is an ideal candidate for delivering bioactive molecules and cells for therapeutic angiogenesis. Besides, hydrogel could precisely deliver, control release, and keep the bioactivity of cargos, making hydrogel-based therapeutic angiogenesis a new strategy for CLI therapy. In this review, we comprehensively discuss the approaches of hydrogel-based strategy for CLI treatment as well as their challenges, and future directions.

A post-market, multi-vessel evaluation of the imaging of peripheral arteries for diagnostic purposeS comparing optical Coherence tomogrApy and iNtravascular ultrasound imaging (SCAN)

Background

Intravascular imaging plays an important part in diagnosis of vascular conditions and providing insight for treatment strategy. Two main imaging modalities are intravascular ultrasound (IVUS) and optical coherence tomography (OCT). The objective of this study was to prove non-inferiority of OCT imaging to IVUS images in matched segments of peripheral vessels in patients with suspected peripheral vascular disease.

Methods

The SCAN study was a prospective, non-inferiority clinical study of matched IVUS and OCT images collected along defined segments of peripheral vessels from twelve subjects (mean age 68 ± 10.3 years; 10 men) displaying symptoms of vascular disease. Luminal diameters were measured by both imaging systems at the distal, middle, and proximal points of the defined segments. Three blinded interventional radiologists evaluated the quality of both imaging modalities in identifying layered structures (3-point grading), plaque (5-point grading), calcification (5-point grading), stent structure (3-point grading), and artifacts (3-point grading) from 240 randomly ordered images. Mean grading scores and luminal diameters were calculated and analyzed with Student’s t-Test and Mann-Whitney-Wilcoxon testing. Intrareader reproducibility was calculated by intraclass correlation (ICC) analysis.

Results

The mean scoring of plaque, calcification, and vascular stent struts by the three readers was significant better in terms of image quality for OCT than IVUS (p < 0.001, p = 0.001, p = 0.004, respectively). The mean scores of vessel wall component visibility and artifacts generated by the two imaging systems were not significantly different (p = 0.19, p = 0.07, respectively). Mean vessel luminal diameter and area at three specific locations within the vessels were not significantly different between the two imaging modalities. No patient injury, adverse effect or device malfunction were noted during the study.

Conclusions

Imaging by OCT provides the physician with better visualization of some vessel and plaque chacteristics, but both IVUS and OCT imaging are safe and effective methods of examining peripheral vessels in order to perform diagnostic assessment of peripheral vessels and provide information necessary for the treatment strategy of peripheral artery disease.

Trial registration

NCT03480685 registered on 29 March 2018.

Pathophysiology of chronic peripheral ischemia: new perspectives

Peripheral arterial disease (PAD) affects individuals particularly over 65 years old in the more advanced countries. Hemodynamic, inflammatory, and oxidative mechanisms interact in the pathophysiological scenario of this chronic arterial disease. We discuss the hemodynamic, muscle tissue, and oxidative stress (OxS) conditions related to chronic ischemia of the peripheral arteries. This review summarizes the results of evaluating both metabolic and oxidative markers, and also therapy to counteract OxS. In conclusion, we believe different pathways should be highlighted to discover new drugs to treat patients suffering from PAD.

Reproducibility and validity of a novel invasive method of assessing peripheral microvascular vasomotor function

In healthy arteries, blood flow is regulated by microvascular tone assessed by changes in blood flow volume and vascular resistance to endothelium-dependent and -independent vasodilators. We developed a novel method of using intravascular ultrasound (IVUS) and a Doppler flow wire to measure changes in blood flow volume and vascular resistance of the profunda arterial bed. We assessed the variability over 6 months in measuring microvascular endothelium-dependent dilation to acetylcholine and endothelium-independent dilation to adenosine in 20 subjects who were part of a larger study of Gulf War Illness without obstructive peripheral artery disease. Vasomotor function was assessed by Infusions of control (dextrose), acetylcholine (10^-6M), adenosine (50μg), and nitroglycerin (25μg/ml). 400 IVUS and 240 flow velocity images were measured a mean 6 (SD = 2) months apart blind to measurement and infusion stage. The mean (SD) baseline profunda flow was 227 (172) ml/min and vascular resistance 4.6 x 10⁴ (2.4 x 10⁴) dynes-s/cm⁵. The intraclass correlation coefficients for 6-month variability for vascular function were excellent (range 0.827–0.995). Bland-Altman analyses showed mean differences of less than 2% for microvascular endothelium-dependent function (flow volume and resistance) and less than 1% for macrovascular endothelium-dependent function with acceptable limits of agreement. In 49 subjects assessing concurrent validity of the technique against atherosclerosis risk factors, we observed greater impairment in microvascular endothelium-dependent function per year of age (flow volume = -1.4% (p = 0.018), vascular resistance = 1.5% (p = 0.015)) and current smoking (flow volume = -36.7% (p = .006), vascular resistance = 50.0% (p<0.001)). This novel method of assessing microvascular vasomotor function had acceptable measurement reproducibility and validity.

The LargPAD Trial: Phase IIA evaluation of l-arginine infusion in patients with peripheral arterial disease

OBJECTIVE

Endothelial function is improved by l-arginine (l-arg) supplementation in preclinical and clinical studies of mildly diseased vasculature; however, endothelial function and responsiveness to l-arg in severely diseased arteries is not known. Our objective was to evaluate the acute effects of catheter-directed l-arg delivery in patients with chronic lower extremity ischemia secondary to peripheral arterial disease.

METHODS

The study enrolled 22 patients (45% male) with peripheral arterial disease (mean age, 62 years) requiring lower extremity angiography. Endothelium-dependent relaxation of patent but atherosclerotic superficial femoral arteries was measured using a combination of intravascular ultrasound (IVUS) imaging and a Doppler FloWire (Volcano Corporation, Rancho Cordova, Calif) during the infusion of incremental acetylcholine (10^-6 to 10^-4 molar concentration) doses. Patients received 50 mg (n = 3), 100 mg (n = 10), or 500 mg (n = 9) l-arg intra-arterially, followed by repeat endothelium-dependent relaxation measurement (limb volumetric flow). IVUS-derived virtual histology of the culprit vessel was also obtained. Endothelium-independent relaxation was measured using a nitroglycerin infusion. Levels of nitrogen oxides and arginine metabolites were measured by chemiluminescence and mass spectrometry, respectively.

RESULTS

Patients tolerated limb l-arg infusion well. Serum arginine and ornithine levels increased by 43.6% ± 13.0% and 23.2% ± 10.3%, respectively (P < .005), and serum nitrogen oxides increased by 85% (P < .0001) after l-arg infusion. Average vessel area increased by 6.8% ± 1.3% with l-arg infusion (acetylcholine 10^-4; P < .0001). Limb volumetric flow increased in all patients and was greater with l-arg supplementation by 130.9 ± 17.6, 136.9 ± 18.6, and 172.1 ± 24.8 mL/min, respectively, for each cohort. Maximal effects were seen with l-arg at 100 mg (32.8%). Arterial smooth muscle responsiveness to nitroglycerin was intact in all vessels (endothelium-independent relaxation, 137% ± 28% volume flow increase). IVUS-derived virtual histology indicated plaque volume was 14 ± 1.3 mm³/cm, and plaque stratification revealed a predominantly fibrous morphology (46.4%; necrotic core, 28.4%; calcium, 17.4%; fibrolipid, 6.6%). Plaque morphology did not correlate with l-arg responsiveness.

CONCLUSIONS

Despite extensive atherosclerosis, endothelial function in diseased lower extremity human arteries can be enhanced by l-arg infusion secondary to increased nitric oxide bioactivity. Further studies of l-arg as a therapeutic modality in patients with endothelial dysfunction (ie, acute limb ischemia) are warranted.

Advances in the non-invasive assessment of vascular dysfunction in metabolic syndrome and diabetes: Focus on endothelium, carotid mechanics and renal vessels

AIM

The present paper is a selective review on the methodology and clinical significance of techniques to assess specifically endothelial function, carotid mechanics and renal vascular function, particularly in the light of vascular dysfunction in metabolic syndrome and type 2 diabetes.

DATA SYNTHESIS

Endothelial dysfunction appears to be earlier detectable in the microcirculation of patients with altered glucose metabolism, while it attains significance in the macrocirculation at more advanced disease stages. Smooth muscle cell dysfunction is now increasingly recognized to play a role both in the development of endothelial dysfunction and abnormal arterial distensibility. Furthermore, impaired glucose metabolism affects carotid mechanics through medial calcification, structural changes in extracellular matrix due to advanced glycation and modification of the collagen/elastin material stiffness. The assessment of renal vascular function by dynamic ultrasound or magnetic resonance imaging has recently emerged as an appealing target for identifying subtle vascular alterations responsible for the development of diabetic nephropathy.

CONCLUSIONS

Vascular dysfunction represents a major mechanism for the development of cardiovascular disease in patients with abnormal glucose metabolism. Hence, the currently available non-invasive techniques to assess early structural and vascular abnormalities merit recommendation in this population, although their predictive value and sensitivity to monitor treatment-induced changes have not yet been established and are still under investigation.

Bilateral photoplethysmography for arterial steal detection in arteriovenous fistula using a fractional-order decision-making quantizer

As inflow and outflow stenoses worsen, both flow resistance and pressure increase in the stenotic vascular access. During dialysis, when blood flow decreases, it may retrograde from the peripheral artery through the palmar arch to the arterial anastomosis site. Arterial steal syndrome (ASS) causes distal hypoperfusion, resulting in hand ischemia or extremity pain and edema. Hence, this study proposes the bilateral photoplethysmography (PPG) for ASS detection in arteriovenous fistulas. The decision-making quantizer utilizes the fractional-order feature extraction method and a non-cooperative game (NCG) framework to evaluate the ASS risk level. Bilateral asynchronous PPG signals have significant differences in the rise time and amplitude in relation to the degree of stenosis. The fractional-order self-synchronization error formulation is a feature extraction method used to quantify bilateral differences in blood flow changes between the dexter and sinister PPG signals. The NCG model as a method of decision-making is then employed to evaluate the ASS risk level. Using an acoustic Doppler measurement, the resistive (Res) index is also used to evaluate the vascular access stenosis at the arterial anastomosis site. In contrast with alternative methods including the high-sensitivity C-reactive protein level or Res index, our experimental results indicate that the proposed decision-making quantizer is more efficient in preventing ASS during hemodialysis treatment.

A prospective evaluation of using IVUS during percutaneous superficial femoral artery interventions

BACKGROUND

The outcomes of endovascular interventions of the superficial femoral artery (SFA) are variable. Completion angiography is typically performed to confirm satisfactory outcomes after SFA angioplasty and/or stenting. However, two-dimensional angiography may not accurately reflect the extent of residual stenosis. We sought to determine whether intravascular ultrasound (IVUS) can help with residual disease assessment and procedure outcome.

METHODS

Patients with anticipated SFA disease were prospectively recruited to the study. Patients with primary SFA disease on diagnostic angiography were included. After SFA endovascular intervention with angioplasty and/or stenting, a completion angiogram was performed to confirm satisfactory results before IVUS evaluation. IVUS-detected maximal residual stenosis, maximal residual lesion volume, and number of nonconsecutive posttreatment SFA segments with >50% residual stenosis were evaluated. Periprocedural ankle-brachial indexes (ABIs), Short Form 36 (SF-36) surveys, and Walking Impairment Questionnaires were also collected.

RESULTS

Fifty-nine patients were prospectively enrolled. Thirty-three received angioplasty only, and 26 received angioplasty and stenting. All patients were men, mean age was 67 years, and major comorbidities included coronary artery disease (53%), active smoking (56%), hypertension (88%), and diabetes (68%). The angioplasty-only cohort had more nonconsecutive areas of >50% residual stenosis (P = 0.004), greater residual stenosis (P = 0.03), and smaller minimal lumen diameters after treatment (P = 0.01) than the angioplasty and stenting cohort. However, there was no significant difference in ABI between the 2 groups and no difference in ABI improvement after intervention. Sixty-four percent of all patients demonstrated a >0.2 increase in postintervention ABI. Improvement in ABI at 1 month after procedure significantly correlated with postintervention SF-36 survey physical scores (r = 0.435, P = 0.007).

CONCLUSIONS

IVUS evaluation provides more-accurate intraprocedural insight on the extent of residual stenosis after SFA interventions. Future studies are warranted to determine whether IVUS-guided postangioplasty and/or stenting can impact long-term interventional outcome.