scholarly journals High Frequency of Microvascular Dysfunction in US Outpatient Clinics: A Sign of High Residual Risk? Data from 7,105 Patients

2022 ◽  
Vol 2022 ◽  
pp. 1-9
Author(s):  
Morteza Naghavi ◽  
Stanley Kleis ◽  
Hirofumi Tanaka ◽  
Albert A. Yen ◽  
Ruoyu Zhuang ◽  
...  
Keyword(s):  
Vascular Reactivity ◽  
Reactive Hyperemia ◽  
Microvascular Dysfunction ◽  
Microvascular Function ◽  
Residual Risk ◽  
Outpatient Clinics ◽  
Reactivity Index ◽  
Maximum Temperature ◽  
Thermal Monitoring ◽  
Arterial Tonometry

Previous studies have linked peripheral microvascular dysfunction measured by arterial tonometry to high residual risk in on-statin patients. Digital thermal monitoring (DTM) of microvascular function is a new and simplified technique based on fingertip temperature measurements that has been correlated with the burden of atherosclerosis and its risk factors. Here, we report analyses of DTM data from two large US registries: Registry-I (6,084 cases) and Registry-II (1,021 cases) across 49 US outpatient clinics. DTM tests were performed using a VENDYS device during a 5-minute arm-cuff reactive hyperemia. Fingertip temperature falls during cuff inflation and rebounds after deflation. Adjusted maximum temperature rebound was reported as vascular reactivity index (VRI). VRI distributions were similar in both registries, with mean ± SD of 1.58 ± 0.53 in Registry-I and 1.52 ± 0.43 in Registry-II. In the combined dataset, only 18% had optimal VRI (≥2.0) and 82% were either poor (<1.0) or intermediate (1.0-2.0). Women had slightly higher VRI than men ( 1.62 ± 0.56 vs. 1.54 ± 0.47 , p < 0.001 ). VRI was inversely but mildly correlated with age ( r = − 0.19 , p < 0.001 ). Suboptimal VRI was found in 72% of patients <50 years, 82% of 50-70 years, and 86% of ≥70 years. Blood pressure was not correlated with VRI. In this largest registry of peripheral microvascular function measurements, suboptimal scores were highly frequent among on-treatment patients, possibly suggesting a significant residual risk. Prospective studies are warranted to validate microvascular dysfunction as an indicator of residual risk.

Abstract P253: Relation Between Microvascular Function and Large Artery Stiffness in African American Diabetic Patients

Hypertension ◽  
2017 ◽  
Vol 70 (suppl_1) ◽  
Author(s):  
Ajibola M Adedayo ◽  
Ayobami Eluwole ◽  
Fasika Tedla ◽  
Arye Kremer ◽  
Nicole Mastrogiovanni ◽  
...  
Keyword(s):  
African Americans ◽  
Glycemic Control ◽  
Vascular Complications ◽  
Microvascular Dysfunction ◽  
Microvascular Function ◽  
Reactivity Index ◽  
Entire Group ◽  
Diabetic Patients ◽  
Large Artery ◽  
Artery Stiffness

Rationale: Diabetes is highly prevalent among African Americans and poses a higher risk for vascular complications in this population. Although socioeconomic factors are well known to influence outcomes, true biologic differences in risk factor vulnerability have been suggested. Vascular complications have been traditionally viewed as either macrovascular (myocardial infarction and stroke) or microvascular (retinopathy, nephropathy, and neuropathy). Better glycemic control is known to improve microvascular but not macrovascular complications. In recent years, there has been a growing appreciation that microvascular dysfunction may promote large artery disease and vice versa. Given this notion of vascular “cross-talk” and since subclinical dysfunction is known to precede target organ damage, the objective of this study was to determine whether subclinical microvascular dysfunction is related to large artery stiffness. Methods: A total of 141 patients with type II diabetes were recruited from our outpatient clinics over a 6 month period. Medical information was obtained via patient interview and electronic medical record review including laboratory results. Microvascular function was assessed by the vascular reactivity index (VRI), which assesses changes in digital temperature before and after release of arterial cuff occlusion (VENDYS 5000BC DTM system Endothelix, Inc.). Large artery stiffness was assessed by carotid-femoral pulse wave velocity (PWV) using applanation tonometry (Sphygmocor, Atcor Inc.). Results: Mean age was 60 + 8 years, 64% were female. 80% had hypertension and 90% had dyslipidemia. 15% had chronic kidney disease. Mean HbA1C levels were 8.1 + 2.2%. For the entire group, VRI was significantly correlated with PWV (r=.27, p=.002). On multivariate analysis, VRI was independently associated with PWV (β=-1.0, p=.001) and a trend towards an association with HbA1c (β =.07, p=.09) after adjusting for traditional cardiovascular risk factors. Conclusions: Among African Americans with diabetes, subclinical microvascular dysfunction is significantly correlated to large artery stiffness and possibly to glycemic control. Further study is needed to clarify mediating factors of these relationships.

scholarly journals Raynaud Phenomenon in Systemic Sclerosis: Does Digital Thermal Monitoring Correlate to Specific Nailfold Videocapillaroscopy Abnormalities?

2020 ◽  
pp. jrheum.191371
Author(s):  
Julie Thomas ◽  
Mislav Radic ◽  
Jordan R. Tucker ◽  
Rebecca Overbury ◽  
Tracy M. Frech
Keyword(s):  
Systemic Sclerosis ◽  
Vascular Function ◽  
Vascular Reactivity ◽  
Clinical Care ◽  
Density Measurement ◽  
Nonparametric Tests ◽  
Reactivity Index ◽  
Thermal Monitoring ◽  
Nailfold Videocapillaroscopy ◽  
Raynaud Phenomenon

Objective Early diagnosis of systemic sclerosis (SSc) is imperative, and Raynaud phenomenon (RP) is an important component of progressive vasculopathy. Nailfold videocapillaroscopy (NVC) is a well-established tool that can quantify structural vascular abnormalities. Digital thermal monitoring (DTM) assesses microvascular functional dysfunction related to thermoregulation. In this study, we investigated the correlation of NVC patterns and DTM variables in patients with SSc. Methods Patients with SSc according to the 2013 American College of Rheumatology/European League Against Rheumatism criteria who consented and enrolled in the clinical care registry had NVC and DTM performed. For NVC, the number of capillaries (density), measurement of apical diameter (dimension), presence or absence of hemorrhages, and number of abnormal shapes were assessed to categorize 3 different qualitative patterns: early, active, and late. For DTM, Doppler ultrasound hyperemic, low frequency, blood velocity of radial artery, and fingertip vascular function were assessed, and a vascular reactivity index (VRI) measurement was automated. Statistical evaluation was performed by nonparametric tests to assess the correlation of NVC and VRI. Results Thirty-one SSc subjects with interpretable NVC and DTM performed on the same day were included in the study. VRI was progressively higher in SSc patients with early, active, and late NVC patterns of microangiopathy (P < 0.0001). There was a significant negative correlation between VRI and microhemorrhages scores (r = –0.363, P = 0.044). Conclusion Our study suggests that more advanced vasculopathy correlates to reduced microvascular function as detected by DTM and more advanced structural abnormalities detected by NVC. NVC and DTM may provide different aspects of vasculopathy quantification and complement each other as investigative tools.

scholarly journals Serum Adipocyte Fatty Acid-Binding Protein Level is Negatively Associated with Vascular Reactivity Index Measured by Digital Thermal Monitoring in Kidney Transplant Patients

Metabolites ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 159 ◽  
Author(s):  
Tai-Li Chen ◽  
Ming-Che Lee ◽  
Ching-Chung Ho ◽  
Bang-Gee Hsu ◽  
Jen-Pi Tsai
Keyword(s):  
Fatty Acid ◽  
Endothelial Function ◽  
Kidney Transplant ◽  
Vascular Reactivity ◽  
Fatty Acid Binding Protein ◽  
Reactivity Index ◽  
Thermal Monitoring ◽  
Fatty Acid Binding ◽  
Negatively Associated ◽  
Acid Binding Protein

Adipocyte fatty acid-binding protein (A-FABP) is abundantly found in mature adipocytes and is involved in cardiovascular disease. Our aim is to investigate the association between serum A-FABP levels and endothelial function among kidney transplant (KT) patients. Fasting blood samples were obtained from 80 KT patients. Serum A-FABP levels were measured using a commercially available enzyme immunoassay kit. Endothelial function and vascular reactivity index (VRI) were measured using digital thermal monitoring test. In this study, VRI < 1.0, VRI 1.0–1.9, and VRI ≥ 2.0 were defined as poor, intermediate, and good vascular reactivity, respectively. There were 12 (15.0%), 30 (37.5%), and 38 (47.5%) KT patients categorized as having poor, intermediate, and good vascular reactivity, respectively. Increased serum levels of alkaline phosphatase (p = 0.012), γ-glutamyltranspeptidase (GGT; p = 0.032), and A-FABP (p < 0.001) were associated with decreased vascular reactivity. Multivariable forward stepwise linear regression analysis revealed that age (β = −0.283, adjusted R2 change = 0.072; p = 0.003) and serum log-A-FABP level (β = −0.514, adjusted R2 change = 0.268; p < 0.001) were significantly associated with VRI values in KT patients. We concluded that serum fasting A-FABP level is negatively associated with VRI values and plays a role in endothelial dysfunction of KT patients.

Sensitivity of Digital Thermal Monitoring Parameters to Reactive Hyperemia

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Mohammad W. Akhtar ◽  
Stanley J. Kleis ◽  
Ralph W. Metcalfe ◽  
Morteza Naghavi
Keyword(s):  
Blood Flow ◽  
Flow Rate ◽  
Vascular Reactivity ◽  
Early Stage ◽  
Reactive Hyperemia ◽  
Assessment Tools ◽  
Functional Evaluation ◽  
Thermal Monitoring ◽  
Essential Components ◽  
Baseline Flow

Both structural and functional evaluations of the endothelium exist in order to diagnose cardiovascular disease (CVD) in its asymptomatic stages. Vascular reactivity, a functional evaluation of the endothelium in response to factors such as occlusion, cold, and stress, in addition to plasma markers, is the most widely accepted test and has been found to be a better predictor of the health of the endothelium than structural assessment tools such as coronary calcium scores or carotid intima-media thickness. Among the vascular reactivity assessment techniques available, digital thermal monitoring (DTM) is a noninvasive technique that measures the recovery of fingertip temperature after 2–5 min of brachial occlusion. On release of occlusion, the finger temperature responds to the amount of blood flow rate overshoot referred to as reactive hyperemia (RH), which has been shown to correlate with vascular health. Recent clinical trials have confirmed the potential importance of DTM as an early stage predictor of CVD. Numerical simulations of a finger were carried out to establish the relationship between DTM and RH. The model finger consisted of essential components including bone, tissue, major blood vessels (macrovasculature), skin, and microvasculature. The macrovasculature was represented by a pair of arteries and veins, while the microvasculature was represented by a porous medium. The time-dependent Navier–Stokes and energy equations were numerically solved to describe the temperature distribution in and around the finger. The blood flow waveform postocclusion, an input to the numerical model, was modeled as an instantaneous overshoot in flow rate (RH) followed by an exponential decay back to baseline flow rate. Simulation results were similar to clinically measured fingertip temperature profiles in terms of basic shape, temperature variations, and time delays at time scales associated with both heat conduction and blood perfusion. The DTM parameters currently in clinical use were evaluated and their sensitivity to RH was established. Among the parameters presented, temperature rebound (TR) was shown to have the best correlation with the level of RH with good sensitivity for the range of flow rates studied. It was shown that both TR and the equilibrium start temperature (representing the baseline flow rate) are necessary to identify the amount of RH and, thus, to establish criteria for predicting the state of specific patient’s cardiovascular health.

scholarly journals Interrelationships among noninvasive measures of postischemic macro- and microvascular reactivity

2008 ◽  
Vol 105 (2) ◽  
pp. 427-432 ◽  
Author(s):  
Mandeep Dhindsa ◽  
Shawn M. Sommerlad ◽  
Allison E. DeVan ◽  
Jill N. Barnes ◽  
Jun Sugawara ◽  
...  
Keyword(s):  
Shear Stress ◽  
Vascular Reactivity ◽  
Reactive Hyperemia ◽  
Clinical Importance ◽  
Physiological Mechanisms ◽  
Arterial Tonometry ◽  
Flow Mediated Dilatation ◽  
Two Measures ◽  
Hyperemic Flow ◽  
Apparently Healthy

The clinical importance of vascular reactivity as an early marker of atherosclerosis has been well established, and a number of established and emerging techniques have been employed to provide measurements of peripheral vascular reactivity. However, relations between these methodologies are unclear as each technique evaluates different physiological aspects related to micro- and macrovascular reactive hyperemia. To address this question, a total of 40 apparently healthy normotensive adults, 19–68 yr old, underwent 5 min of forearm suprasystolic cuff-induced ischemia followed by postischemic measurements. Measurements of vascular reactivity included 1) flow-mediated dilatation (FMD), 2) changes in pulse wave velocity between the brachial and radial artery (ΔPWV), 3) hyperemic shear stress, 4) reactive hyperemic flow, 5) reactive hyperemia index (RHI) assessed by fingertip arterial tonometry, 6) fingertip temperature rebound (TR), and 7) skin reactive hyperemia. FMD was significantly and positively associated with RHI ( r = 0.47) and TR ( r = 0.45) (both P < 0.01) but not with reactive hyperemic flow or hyperemic shear stress. There was no correlation between two measures of macrovascular reactivity (FMD and ΔPWV). Skin reactive hyperemia was significantly associated with RHI ( r = 0.55) and reactive hyperemic flow ( r = 0.35) (both P < 0.05). There was a significant association between reactive hyperemia and RHI ( r = 0.30; P < 0.05). In more than 75% of cases, vascular reactivity measures were not significantly associated. We concluded that associations among different measures of peripheral micro- and macrovascular reactivity were modest at best. These results suggest that different physiological mechanisms may be involved in changing different measures of vascular reactivity.

scholarly journals Reproducibility and normalization of reactive hyperemia using laser speckle contrast imaging

PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0244795
Author(s):  
Behnia Rezazadeh Shirazi ◽  
Rudy J. Valentine ◽  
James A. Lang
Keyword(s):  
Reactive Hyperemia ◽  
Intraclass Correlation ◽  
Microvascular Dysfunction ◽  
Microvascular Function ◽  
Rate Of Change ◽  
Laser Speckle ◽  
Maximal Flow ◽  
Contrast Imaging ◽  
Laser Speckle Contrast Imaging ◽  
Speckle Contrast

Background Impaired perfusion indices signal potential microvascular dysfunction preceding atherosclerosis and other cardiometabolic pathologies. Post-occlusive reactive hyperemia (PORH), a vasodilatory response following a mechanically induced ischemia, is a transient increase in perfusion and can assess microvascular function. The greatest blood flow change corresponding to the first minute of hyperemia (represented by time-to-peak, hyperemic velocity, AUC within 1st min) has been shown to indicate microvascular dysfunction. However, the reproducibility of these temporal kinetic indices of the PORH response is unknown. Our aim was to examine the inter- and intra-day reproducibility and standardization of reactive hyperemia, with emphasis on the kinetic indices of PORH, using laser speckle contrast imaging (LSCI) technique. Methods and results Seventeen healthy adults (age = 24 ± 3 years) completed three PORH bouts over two lab visits. LSCI region of interest was a standardized 10 cm region on the dominant ventral forearm. A 5-min brachial artery occlusion period induced by inflating an arm cuff to 200 mmHg, preceded a 4-min hyperemic period. Inter- and intra-day reliability and reproducibility of cutaneous vascular conductance (LSCI flux / mean arterial pressure) were determined using intraclass correlation (ICC) and coefficient of variation (CV%). Maximal flow and area under the curve standardized to zero perfusion showed intra- and inter-day reliability (ICC > 0.70). Time to maximal flow (TMF) was not reproducible (inter-day CV = 18%). However, alternative kinetic indices such as 1-min AUC and overshoot rate-of-change (ORC), represented as a piecewise function (at 5s, 10s, 15s, and 20s into hyperemia), were reproducible (CV< 11%). Biological zero was a reliable normalization point. Conclusion PORH measured with LSCI is a reliable assessment of microvascular function. However, TMF or its derived hyperemic velocity are not recommended for longitudinal assessment. Piecewise ORC and 1-min AUC are reliable alternatives to assess the kinetic response of PORH.

Abstract P37: Evidence of Impaired Vascular Reactivity Following Dust Exposure in Participants in the World Trade Center Medical Monitoring and Treatment Program

2011 ◽  
Vol 4 (suppl_2) ◽  
Author(s):  
Simonette T Sawit ◽  
Mary Ann McLaughlin ◽  
Ana Garcia Alvarez ◽  
Dewan Kazi Fahima ◽  
Cynara Maceda ◽  
...  
Keyword(s):  
Treatment Program ◽  
Vascular Reactivity ◽  
Reactive Hyperemia ◽  
Medical Monitoring ◽  
Volume Changes ◽  
Peripheral Arterial Tonometry ◽  
Pulse Volume ◽  
Arterial Tonometry ◽  
Digital Pulse ◽  
Peripheral Arterial

INTRODUCTION: Exposure to particulate matter (PM) has been investigated as an additional risk factor for cardiovascular disease (CVD). It is likely that different mechanisms, including vascular dysfunction, are responsible for acute and chronic toxic effects. In participants of the Law Enforcement Cardiovascular Screening Program (LECS), a subset of the WTC Medical Monitoring and Treatment Program, we look to characterize the relationship between PM exposure and vascular reactivity (surrogate for endothelial function), as measured by peripheral arterial tonometry (PAT). METHODS: PAT, a system comprised of a finger probe to assess digital volume changes accompanying pulse waves, was used. Digital pulse volume changes during reactive hyperemia was assessed in 60 patients with either high (n=33) or low (n=27) PM exposure. PAT index, a measure of reactive hyperemia, was calculated as the ratio of the digital pulse volume during reactive hyperemia divided by that at baseline. All data were prospectively obtained. We define highest inhaled PM exposure as occurring on 9/11/2001, and lower inhaled PM exposure as occurring on or after 9/13/2001. A PAT index of 1.67 or less was considered to represent abnormal vascular reactivity. RESULTS: Mean age was 49 years (range 45-53), 83% were male. There were no significant differences in baseline characteristics, including CVD risk factors. Median PAT was 1.87 (1.30-2.75) for subjects with lower exposure and 1.68 (1.15-3.22) for subjects with highest exposure to PM. Of subjects with highest exposure to PM, 68% (17/33) had a PAT index 1.67 or less, compared with 32% (8/27), of subjects with lower exposure (p value=0.17). The odds of having abnormal PAT index to normal PAT index was 2.1 times higher in subjects with highest exposure compared to those with lower exposure to PM (95%CI 0.7-6.2). CONCLUSION: We observe a trend correlating highest WTC inhaled PM exposure with abnormal vascular reactivity as measured by peripheral arterial tonometry index of 1.67 or less. The clinical impact of this finding, in this pilot study, requires further investigation.

scholarly journals New Indices of Endothelial Function Measured by Digital Thermal Monitoring of Vascular Reactivity: Data from 6084 Patients Registry

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Morteza Naghavi ◽  
Albert A. Yen ◽  
Alex W. H. Lin ◽  
Hirofumi Tanaka ◽  
Stanley Kleis
Keyword(s):  
Blood Pressure ◽  
Endothelial Function ◽  
Diastolic Blood Pressure ◽  
Vascular Reactivity ◽  
Cardiovascular Health ◽  
Patient Characteristics ◽  
Reactivity Index ◽  
Thermal Monitoring ◽  
Reactivity Measurement ◽  
Large Patient

Background. Endothelial function is viewed as a barometer of cardiovascular health and plays a central role in vascular reactivity. Several studies showed digital thermal monitoring (DTM) as a simple noninvasive method to measure vascular reactivity that is correlated with atherosclerosis risk factors and coronary artery disease. Objectives. To further evaluate the relations between patient characteristics and DTM indices in a large patient registry. Methods. DTM measures were correlated with age, sex, heart rate, and systolic and diastolic blood pressure in 6084 patients from 18 clinics. Results. DTM vascular reactivity index (VRI) was normally distributed and inversely correlated with age (r=-0.21, p<0.0001). Thirteen percent of VRI tests were categorized as poor vascular reactivity (VRI < 1.0), 70 percent as intermediate (1.0 ≤ VRI < 2.0), and 17 percent as good (VRI ≥ 2.0). Poor VRI (<1.0) was noted in 6% of <50 y, 10% of 50–70 y, and 18% of ≥70 y. In multiple linear regression analyses, age, sex, and diastolic blood pressure were significant but weak predictors of VRI. Conclusions. As the largest database of finger-based vascular reactivity measurement, this report adds to prior findings that VRI is a meaningful physiological marker and reflects a high level of residual risk found in patients currently under care.

scholarly journals Clinical Bedside Tools to Assess Systemic Sclerosis Vasculopathy: Can digital thermal monitoring and sublingual microscopy identify patients with digital ulcers?

2021 ◽  
pp. jrheum.201234
Author(s):  
Tracy M. Frech ◽  
Zhining Ou ◽  
Angela P. Presson
Keyword(s):  
Systemic Sclerosis ◽  
Vascular Reactivity ◽  
Rank Correlation ◽  
Boundary Region ◽  
Reactivity Index ◽  
Clinical Feature ◽  
Digital Ulcers ◽  
Thermal Monitoring ◽  
Irreversible Damage ◽  
Cross Sectional

Objective Sublingual microscopy assesses systemic sclerosis (SSc) vasculopathy. Digital thermal monitoring (DTM) may identify patients at risk for digital ulcer (DU). The purpose of this analysis was to assess sublingual microscopy and DTM in SSc patients with and with no previous DU in order to determine the utility of these clinical tools. Methods SSc registry patients with clinical data had both DTM and sublingual microscopy on the same day were included in this cross-sectional analysis. DTM quantifies vascular reactivity index (VRI). Sublingual microscopy measures longitudinal red blood cell fraction (RBC fract) and perfused boundary region (PBR). We evaluated the pairwise association between VRI, RBCfract and PBR in a monotonic relationship using Spearman’s rank correlation in the DU subset. Correlation coefficients (rs) and their 95% confidence intervals (CIs) were reported. Results Ninety patients were included; 29 had digital pits and/or active DU and 61 never had a DU. The only significant clinical feature associated with DU was modified Rodnan skin score (p=0.003) with DU being higher. The VRI was lower in patients with DU (p=0.01). The higher RBCfract the lower PBR (rs =- 0.71, 95% CI: -0.86, -0.47, p<0.001). VRI was not associated with RBCfract or PBR (p=0.24 or 0.55, respectively) in the DU patients. Conclusion DTM is a useful tool for assessing SSc-DU. While sublingual microscopy measurements did not significantly correlate to VRI in SSc-DU patients, a longitudinal study may be more helpful in capturing vasculopathy activity prior to possibly irreversible damage.

scholarly journals Evidence of microvascular dysfunction in patients with cystic fibrosis

2016 ◽  
Vol 310 (11) ◽  
pp. H1479-H1485 ◽  
Author(s):  
Paula Rodriguez-Miguelez ◽  
Jeffrey Thomas ◽  
Nichole Seigler ◽  
Reva Crandall ◽  
Kathleen T. McKie ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Exercise Capacity ◽  
Reactive Hyperemia ◽  
Clinical Manifestations ◽  
Microvascular Dysfunction ◽  
Forced Expiratory Volume ◽  
Microvascular Function ◽  
Doppler Imaging ◽  
Control Subjects ◽  
Positive Correlations

Cystic fibrosis (CF) is a genetic, multisystemic disorder with broad clinical manifestations apart from the well-characterized pulmonary dysfunction. Recent findings have described impairment in conduit vessel function in patients with CF; however, whether microvascular function is affected in this population has yet to be elucidated. Using laser-Doppler imaging, we evaluated microvascular function through postocclusive reactive hyperemia (PORH), local thermal hyperemia (LTH), and iontophoresis with acetylcholine (ACh). PORH [518 ± 174% (CF) and 801 ± 125% (control), P = 0.039], LTH [1,338 ± 436% (CF) and 1,574 ± 620% (control), P = 0.045], and iontophoresis with ACh [416 ± 140% (CF) and 617 ± 143% (control), P = 0.032] were significantly lower in patients with CF than control subjects. In addition, the ratio of PORH to LTH was significantly ( P = 0.043) lower in patients with CF (55.3 ± 5.1%) than control subjects (68.8 ± 3.1%). Significant positive correlations between LTH and forced expiratory volume in 1 s (%predicted) ( r = 0.441, P = 0.013) and between the PORH-to-LTH ratio and exercise capacity ( r = 0.350, P = 0.049) were observed. These data provide evidence of microvascular dysfunction in patients with CF compared with control subjects. In addition, our data demonstrate a complex relationship between microvascular function and classical markers of disease severity (i.e., pulmonary function and exercise capacity) in CF.

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