Digital Volume Pulse Research Articles

Pulse wave analysis as an experimental tool to clinical application: Past and present (Review)

Pulse examination by palpation of a peripheral artery against a bony prominence is the most commonly used and widely accepted method. However this is subjective and thus prone to errors. Although pulse waveform was recorded in the 19th century, it did not gain popularity because of inconvenience in using the recording instruments and the absence of a sound theory to explain the wave forms recorded. Sphygmomanometry for recording blood pressure gained popularity as it was easy to record and had a sound theoretical background. Sphygmomanometry provides two extreme values of blood pressure but does not give a true representation of the blood pressure changes occurring in the entire cardiac cycle. Recently there has been resurgence in the analysis of the graphical recording of the pulse wave. Photoplethysmography is becoming a widely accepted technique in assessing the volume pulse. The whole review is about historical background, non-invasive methods of pulse recording, relation of the digital volume pulse to the pressure pulse and the advantages of recording the pressure pulse.

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

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.

DHA-rich fish oil reverses the detrimental effects of saturated fatty acids on postprandial vascular reactivity

Experimental elevation of nonesterified fatty acids (NEFAs) impairs endothelial function, but the effect of NEFA composition is unknown. The objective was to test the effect of acute elevation of NEFAs enriched with either saturated fatty acids (SFAs) or SFAs with long-chain (LC) n-3 (omega-3) PUFAs on vascular function measured via flow-mediated dilatation (FMD), laser Doppler iontophoresis (LDI), and digital volume pulse (DVP). In 59 subjects (30 men and 29 women), repeated oral fat feeding of either palm stearin (SFA) or palm stearin with DHA-rich fish oil (SFA + LC n-3 PUFA) was performed on 2 separate occasions with continuous heparin infusion to elevate NEFAs for a duration of 60 to 240 min. Vascular function was measured at baseline and at the end of NEFA elevation; venous blood was collected for measurement of lipids and circulating markers of endothelial function. NEFA elevation during consumption of the SFA-rich drinks was associated with a marked impairment of FMD, whereas consumption of SFAs + LC n-3 PUFAs improved FMD response, with a mean (±SEM) difference of 2.06 ± 0.29% (P < 0.001). Positive correlations were found with percentage weight of LC n-3 PUFAs in circulating NEFAs and change in FMD response [Spearman's rho (r(s)) = 0.460, P < 0.001]. LDI measures increased during both treatments (P ≤ 0.026), and there was no change in DVP indexes. The composition of NEFAs can acutely affect FMD. The beneficial effect of LC n-3 PUFAs on postprandial vascular function warrants further investigation but may be mediated by nitric oxide-independent mechanisms. This trial is registered at clinicaltrials.gov as NCT01351324.

Arterial stiffness, central hemodynamics and wave reflection in normal pregnancy and control nonpregnant women

ObjectivesPregnancy is accompanied by different physiological adaptations in the cardiovascular system. However, information on central blood pressures, wave reflection, arterial stiffness in uncomplicated pregnancy compared with nonpregnant women is limited. Study designForty-six women (mean age 28 years) in the third trimester of pregnancy and 45 healthy age- and height-matched controls were evaluated. Arterial stiffness, central hemodynamics and wave reflection was assessed with the use of digital volume pulse analysis and pulse wave analysis. ResultsIn comparison with nonpregnant participants, pregnant women had significantly lower mean (p=0.04) and central systolic (p=0.02) blood pressure, central pulse pressure (p=0.02), augmentation index (p=0.02) and augmentation pressure (p=0.002), whereas their pulse pressure amplification was significantly higher (p=0.001). Similarly, arterial stiffness index was higher in pregnant women than in healthy nonpregnant controls (p=0.006). This index was correlated significantly with central augmentation index and augmentation pressure (r=0.5, p=0.0005 and r=0.52, p=0.0002, respectively) but only in nonpregnant women. ConclusionsHealthy pregnancy is associated with increased pulse pressure amplification as well as diminished wave reflection, which results in lower central augmentation index and augmentation pressure. Women in the third trimester of pregnancy have slightly higher arterial stiffness in comparison with healthy nonpregnant, age- and height-matched controls. The increased value of measures of arterial stiffness might be secondary to a known physiological increase of cardiac output and the amount of circulating blood.

Acute Effects of Ginkgo Biloba Extract on Vascular Function and Blood Pressure

We investigated whether a single dose of standardized Ginkgo biloba extract (GBE) can improve vascular function. A randomised controlled crossover trial was conducted on 14 young healthy men, who received GBE or placebo. The digital volume pulse was monitored to measure reflection index (DVP-RI) and stiffness index (DVP-SI) and peripheral augmentation index (pAIx) was assessed using radial pulse wave analysis at baseline and 2, 4 and 6 h after treatment. DVP-SI was slightly higher 2 h following GBE compared to placebo (P < 0.05); other outcome variables were unaffected by treatment.

Association of bone turnover markers and arterial stiffness in pre-dialysis chronic kidney disease (CKD)

Vascular calcification (VC) is highly prevalent in CKD and leads to increased vascular stiffness and cardiovascular disease (CVD). Non-traditional cardiovascular risk factors include abnormal bone turnover and/or dysregulation of the calcification inhibitors, although their relative contribution remains unclear. We investigated the association between bone turnover, the calcification inhibitors (matrix gla protein; MGP and Fetuin-A), and the phosphate regulating hormone; fibroblast growth factor-23 (FGF-23) and arterial stiffness in pre-dialysis CKD patients. One hundred and forty-five patients with CKD stages 1–4 (74 M, 71 F) aged (mean [SD]) 53 [14] years were studied. Bone turnover markers (bone-specific alkaline phosphatase (BALP) and tartrate-resistant acid phosphatase (TRACP)) and MGP, Fetuin-A and FGF-23 were determined. BMD was measured at the lumbar spine (LS), femoral neck (FN), forearm (FARM) and total hip (TH). Arterial stiffness was assessed by contour analysis of digital volume pulse (SI DVP). There was a significant positive correlation between TRACP:BALP ratio and SI DVP ( r = 0.19, p = 0.023). Following multi-linear regression analysis, significant associations were seen between serum BALP ( p = 0.037), TRACP ( p = 0.009) and TRACP:BALP ratio ( p = 0.001) and SI DVP independently of traditional CVD risk factors. No significant relationship between SI DVP and MGP, Fetuin-A and FGF-23 was observed. A significant negative correlation was seen between BMD at the FARM and SI DVP in CKD stage 4 (r = − 0.35, p = 0.024). The association remained significant following correction for age, gender and cardiovascular risk factors ( p = 0.029). Our data suggest a link between imbalances in bone turnover and arterial stiffness in pre-dialysis CKD. Longitudinal studies are needed to evaluate the clinical usefulness of these bone turnover markers as predictors of CVD in CKD.

Association of Arterial Stiffness Indexes, Determined From Digital Volume Pulse Measurement and Cardiovascular Risk Factors in Chronic Kidney Disease

Progression of atherosclerosis with increased arterial stiffness is associated with increased cardiovascular morbidity and mortality in patients with chronic kidney disease (CKD). Compliance index (CI) derived from digital volume pulse (DVP), measuring the relationship between volume and pressure changes in fingertip, can evaluate the local arterial stiffness. The purpose of this study was to measure the stiffness of different arteries and determine the relationships of CI-DVP with clinical characteristics and renal function in CKD patients. This cross-sectional pilot study included 186 CKD and 46 healthy subjects. Evaluation of different arterial stiffness was performed by DVP using dual-channel photoplethysmography and measured as CI (CI-DVP) and pulse wave velocity (PWV)-DVP. CKD patients had lower CI-DVP and higher PWV-DVP than that in the healthy group. There was a trend of stepwise decrease in CI-DVP and increase in PWV-DVP related to the advance of CKD from early to late stage. Decrease of CI-DVP was associated with the increase in number of cardiovascular risk factors. Multivariate linear regression analysis revealed that CI-DVP (B = 4.59, P < 0.01) was independently associated with estimated glomerular filtration rate (eGFR). Male gender, eGFR, and systolic blood pressure (BP) were independent determinants for CI-DVP (B = -0.25, P = 0.01; B = 0.007, P = 0.03; and B = -0.03, P < 0.0001; whole model R(2) = 0.28, P < 0.0001). Our data demonstrate a significant association between CI-DVP, a new surrogate marker of arterial stiffness different from PWV, and renal function and cardiovascular risk factors in CKD patients.

Different Effect of IgA Nephropathy and Polycystic Kidney Disease on Arterial Stiffness

Background: Renal function is a major predictor of vascular function and cardiovascular diseases. Little information exists about the effect of specific renal diseases on vascular function in chronic kidney diseases (CKD). Methods: One hundred and twenty patients (60 with IgA nephropathy, IgAN, and 60 with polycystic kidney disease, PKD) with CKD stages 1–4 were studied and compared. Pulse-wave velocity was measured by the digital volume pulse (DVP) method and stiffness index (SI_DVP) was derived. Results: All CKD (IgAN and PKD) patients had increased SI_DVP compared to controls (10.39 vs. 8.87 ± 1.79 m/s, p = 0.008). PKD patients had increased SI_DVP compared to IgAN and controls (11.14 ± 2.19, 9.66 ± 2.02 and 8.87 ± 1.79 m/s, respectively, p < 0.001). An inverse correlation was found between SI_DVP and glomerular filtration rate in all CKD (IgAN and PKD) patients (p = 0.001) and in IgAN alone (p < 0.01), but not in PKD. With multivariate regression analysis, only age and 24-hour systolic blood pressure exerted independent effects on SI_DVP. Conclusions: Compared to controls, arterial stiffness was increased in CKD patients. However, arterial stiffening was more pronounced in PKD than in IgAN, suggesting that vascular function is not similarly altered in etiologically different CKD groups. The fact that blood pressure was an independent risk factor underscores a therapeutic opportunity.

Plasma leptin levels and digital pulse volume in obese patients without metabolic syndrome — A pilot study

Background The mechanism of obesity leading to endothelial function is complex, and involves many adipokines and inflammatory cytokines. The data is especially lacking in obese patients without metabolic syndrome. We assessed the relationship among endothelial dysfunction, anthropometric indices, adipokines and inflammatory cytokines in this population. Methods Obese patients without metabolic syndrome were included in this study. The plasma resistin, leptin, retinol-binding-protein 4 and inflammatory cytokines were examined. Endothelial function was assessed by a fingertip peripheral arterial tonometry (PAT) device. Data are expressed as the natural logarithm (ln) of the PAT ratio. Endothelial dysfunction was defined by a ln (PAT ratio) < 0.30. Results A total of 35 patients were enrolled, 11 of whom were with endothelial dysfunction. There was a significant difference of ln leptin (p = 0.007), ln [leptin/visceral fat thickness] (p = 0.004) and ln [leptin/subcutaneous fat thickness] (p < 0.001) between patients with and without endothelial dysfunction. Multivariate linear regression analyses showed that ln [leptin/subcutaneous fat thickness] was significantly related to the ln (PAT ratio) (p = 0.002). Using ln [leptin/subcutaneous fat thickness] to detect endothelial dysfunction, the area of receiver operating characteristic curves was 0.843 (p = 0.002). Using 6.10 as a cutoff point, the sensitivity and specificity to determine endothelial dysfunction were 91% and 78%, respectively. Conclusion Abnormal digital vascular function occurs in obese patients without metabolic syndrome. Low plasma leptin/subcutaneous fat ratio is associated with endothelial dysfunction in this population.

Acute effects of elevated NEFA on vascular function: a comparison of SFA and MUFA

There is emerging evidence to show that high levels of NEFA contribute to endothelial dysfunction and impaired insulin sensitivity. However, the impact of NEFA composition remains unclear. A total of ten healthy men consumed test drinks containing 50 g of palm stearin (rich in SFA) or high-oleic sunflower oil (rich in MUFA) on separate occasions; a third day included no fat as a control. The fats were emulsified into chocolate drinks and given as a bolus (approximately 10 g fat) at baseline followed by smaller amounts (approximately 3 g fat) every 30 min throughout the 6 h study day. An intravenous heparin infusion was initiated 2 h after the bolus, which resulted in a three- to fourfold increase in circulating NEFA level from baseline. Mean arterial stiffness as measured by digital volume pulse was higher during the consumption of SFA (P < 0·001) but not MUFA (P = 0·089) compared with the control. Overall insulin and gastric inhibitory peptide response was greater during the consumption of both fats compared with the control (P < 0·001); there was a second insulin peak in response to MUFA unlike SFA. Consumption of SFA resulted in higher levels of soluble intercellular adhesion molecule-1 (sI-CAM) at 330 min than that of MUFA or control (P ≤ 0·048). There was no effect of the test drinks on glucose, total nitrite, plasminogen activator inhibitor-1 or endothelin-1 concentrations. The present study indicates a potential negative impact of elevated NEFA derived from the consumption of SFA on arterial stiffness and sI-CAM levels. More studies are needed to fully investigate the impact of NEFA composition on risk factors for CVD.

The impact of the catechol-O-methyltransferase genotype on the acute responsiveness of vascular reactivity to a green tea extract

The beneficial effects of green tea catechins, such as the proposed improvement in endothelial function, may be influenced by phase II metabolism during and after absorption. The methylation enzyme, catechol-O-methyltransferase (COMT), has a missense mutation rs4680 (G to A), proposed to result in a 40 % reduction in enzyme activity. In the present pilot study, twenty subjects (ten of each homozygous COMT genotype) were recruited. Green tea extract capsules (836 mg green tea catechins) were given in a fasted state, and a high-carbohydrate breakfast was given after 60 min. Blood samples and vascular function measurements were taken at regular intervals. The change in digital volume pulse stiffness index (SI) from baseline was shown to be different between genotype groups at 120 and 240 min, with a lower SI in the GG individuals (P ≤ 0·044). The change in blood pressure from baseline also differed between genotype groups, with a greater increase in systolic (P = 0·023) and diastolic (P = 0·034) blood pressure at 120 min in the GG group. The GG [corrected] group was shown to have a greater increase in insulin concentrations at 120 min (P = 0·019) and 180 min (P = 0·008) compared with baseline, despite similar glucose profiles. No genotypic differences were found in vascular reactivity measured using laser Doppler iontophoresis, total nitrite, lipids, plasma total antioxidant capacity or inflammatory markers after ingestion of the green tea extract. In conclusion, SI and insulin response to the glucose load differed between the COMT genotype groups, and this may be suggestive of a green tea extract and genotype interaction.

Vascular Function in Preeclampsia. Analysis of Digital Volume Pulse by Photoplethysmography

Vascular Function in Preeclampsia. Analysis of Digital Volume Pulse by Photoplethysmography

Novel application of parameters in waveform contour analysis for assessing arterial stiffness in aged and atherosclerotic subjects

Objective Although contour analysis of pulse waves has been proposed as a non-invasive means in assessing arterial stiffness in atherosclerosis, accurate determination of the conventional parameters is usually precluded by distorted waveforms in the aged and atherosclerotic objects. We aimed at testing reliable indices in these patient populations. Methods Digital volume pulse (DVP) curve was obtained from 428 subjects recruited from a health screening program at a single medical center from January 2007 to July 2008. Demographic data, blood pressure, and conventional parameters for contour analysis including pulse wave velocity (PWV), crest time (CT), stiffness index (SI), and reflection index (RI) were recorded. Two indices including normalized crest time (NCT) and crest time ratio (CTR) were also analysed and compared with the known parameters. Results Though ambiguity of dicrotic notch precluded an accurate determination of the two key conventional parameters for assessing arterial stiffness (i.e. SI and RI), NCT and CTR were unaffected because the sum of CT and T DVP (i.e. the duration between the systolic and diastolic peak) tended to remain constant. NCT and CTR also correlated significantly with age, systolic and diastolic blood pressure, PWV, SI and RI (all P < 0.01). Conclusion NCT and CTR not only showed significant positive correlations with the conventional parameters for assessment of atherosclerosis (i.e. SI, RI, and PWV), but they also are of particular value in assessing degree of arterial stiffness in subjects with indiscernible peak of diastolic wave that precludes the use of conventional parameters in waveform contour analysis.

A New Two-Pulse Synthesis Model for Digital Volume Pulse Signal Analysis

Analysis of digital volume pulse (DVP) signal measured by photoplethysmograph (PPG) technique is a low cost non-invasive method of obtaining vital information related to arterial conditions. In this paper, we present a new two-pulse synthesis (TPS) model for deriving arterial parameters, useful for noninvasive assessment of human vascular health. The model is based on the use of Rayleigh function. Relevance of the proposed model is established by applying it on a sample set of 113 PPG signals, obtained form healthy and treated hypertensive subjects. The TPS model compares well with the conventional methods in determining parameters such as pulse transit time or foot-to-foot delay (D), reflection index (RI), stiffness index (SI) and pulse wave velocity (PWV). A new parameter, viz. differential pulse spread (DPS) has also been introduced for DVP signals using the model. The differential pulse spread provides a new dimension to estimate the process of arterial degeneration.

Calcium and vitamin D modulate postprandial vascular function: A pilot dose–response study

Background Calcium and vitamin D may modulate postprandial endothelial function. Subjects and Methods Seven lean, young males completed a single blind randomized crossover design where they consumed three breakfast meals containing varying calcium and vitamin D (meal 1 ∼200 mg/15 IU, meal 2 ∼450 mg/140 IU, and meal 3 ∼700 mg/265 IU). Stiffness index (SI), reflective index (RI) and pulse rate (PR) were serially assessed from the digital volume pulse by photoplethysmography (Pulse Trace PT-1000, Micro Medical, UK). Results Incremental areas under the curve over 3 h (Δ) were analyzed by repeated measures ANOVA. ΔPTH was significantly less suppressed with meal A than with meal B and C ( P = 0.003). In contrast, ΔRI was significantly more suppressed following meal A than with either meal B or C ( P = 0.021). ΔSI did not change with meal ingestion and there was no difference in the rise of Δglucose, Δinsulin and ΔPR between meals. Conclusion Higher calcium and vitamin D at breakfast prevented the fall in postprandial vascular tone without changes in glucose or insulin.

Elevated augmentation index derived from peripheral arterial tonometry is associated with abnormal ventricular–vascular coupling

Although typically derived from the contour of arterial pressure waveform, augmentation index (AIx) may also be derived from the digital pulse volume waveform using finger plethysmography (peripheral arterial tonometry, PAT). Little is known regarding the physiologic correlates of AIx derived from PAT. In this study, we investigated the relation of PAT-AIx with measures of ventricular-vascular coupling. Pulse volume waves were measured via PAT and used to derive AIx. Using 2-dimensional echocardiography, effective arterial elastance index (EaI) was estimated as end-systolic pressure/stroke volume index. Left ventricular (LV) end-systolic elastance index (E(LV)I) was calculated as end-systolic pressure/end-systolic volume index. Ventricular-vascular coupling ratio was defined as EaI/E(LV)I. Given the bi-directional nature of ventricular-vascular uncoupling as measured by echocardiography, patients were separated into three groups: low EaI/E(LV)I (<0.6, n = 21), optimal EaI/E(LV)I (mean 0.6-1.2, n = 16) and high EaI/E(LV)I (>1.2, n = 10). Adjusting for potential confounders (age, mean arterial pressure, height and heart rate), patients with optimal EaI/E(LV)I had lower AIx (1 +/- 4%, P<0.05) compared to those with low EaI/E(LV)I (13 +/- 4%) and high EaI/E(LV)I (19 +/- 5%). Abnormal ventricular-vascular coupling, arising from either increased effective arterial elastance or increased ventricular elastance, is associated with increased AIx as measured by PAT. Additional research is needed to examine other vascular correlates of PAT-AIx.

CORRELATION OF SMALL ARTERIAL STIFFNESS WITH TARGET ORGAN DAMAGE IN HYPERTENSION: PP.11.443

Background: We have developed a novel Compliance Index (CI) as a marker for small artery stiffness. This study tried to study the correlation of CI with target organ damage (TOD) in hypertension. Methods: This study recruited 59 consecutive patients (mean age 66 ± 10 years, 39 men) with essential hypertension regularly treated with anti-hypertensive agents for at least for 1 year in a hypertensive clinic. All of the patients did not have diabetes mellitus and vascular complications. CI was measured by our new developed photoplethysmography system as the area under the curve of digital volume pulse divided by pulse pressure. Pulse wave velocity (PWV) measured by applanation tonometry was used for large arterial stiffness. Clearance of creatinine (Ccr) calculated from 24 urine was used for renal function and echocardiography was used for assessment of left ventricular function. TOD was defined as renal insufficiency (Ccr <60 ml/min) or presence of diastolic dysfunction by echocardiography. Results: There were 8 (14%) patients with renal insufficiency. CI was significantly lower in patients with renal insufficiency but not PWV. There were 16 (27%) patients with diastolic dysfunction. CI was lower and left ventricular mass index was higher in patients with diastolic dysfunction. Antihypertensive agents were not different between patients with or without TOD. CI was gradually decreased from patients without TOD, with one TOD, to patients with two TOD (3.18 ± 1.19 U, 2.04 ± 0.78 U, 1.49 ± 0.44 U; p < 0.001) but not PWV. Conclusion: Small but not large arterial stiffness was significant correlated with TOD. CI could be a marker for degree of TOD in regular treated hypertensive patients.

Long chain n − 3 PUFA-rich meal reduced postprandial measures of arterial stiffness

The consumption of long chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) is known to be cardio-protective. Data on the influence of LC n-3 PUFA on arterial stiffness in the postprandial state is limited. The aim of this study was to investigate the acute effects of a LC n-3 PUFA-rich meal on measures of arterial stiffness. Twenty-five healthy subjects (12 men, 13 women) received a control and a LC n-3 PUFA-rich meal on two occasions in a random order. Arterial stiffness was measured at baseline, 30, 60, 90, 120, 180 and 240 min after meal consumption by pulse wave analysis and digital volume pulse to derive an augmentation index and a stiffness index respectively. Blood samples were taken for measurement of lipids, glucose and insulin. Consumption of the LC n-3 PUFA-rich meal had an attenuating effect on augmentation index (P=0.02) and stiffness index (P=0.03) compared with the control meal. A significant treatment effect (P=0.036) was seen for plasma non-esterified fatty acids concentrations. These data indicate that acute LC n-3 PUFA-rich meal consumption can improve postprandial arterial stiffness. This has important implications for the beneficial properties of LC n-3 PUFA and cardiovascular risk reduction.

Assessment of endothelial function by non-invasive peripheral arterial tonometry predicts late cardiovascular adverse events

There is growing need for the identification of novel non-invasive methodologies for the identification of individuals at risk for adverse cardiovascular (CV) events. We examined whether endothelial dysfunction, as detected by non-invasive peripheral arterial tonometry (EndoPAT), can predict late CV events. Reactive hyperaemia (RH) was induced following upper arm occlusion of systolic blood pressure in 270 outpatients (54 +/- 12 years, 48% female). The natural logarithmic scaled RH index (L_RHI) was calculated from the ratio between the digital pulse volume during RH and at baseline. The patients were followed for CV adverse events (AE: cardiac death, myocardial infarction, revascularization or cardiac hospitalization) during a 7-year follow-up (inter-quartile range = 4.4-8). Cox models were used to estimate the association of EndoPAT results with AE adjusted for age. During the follow-up, AE occurred in 86 patients (31%). Seven-year AE rate was 48% in patients with L_RHI < 0.4 vs. 28% in those with L_RHI >or= 0.4 (P = 0.03). Additional univariate predictors of AE were advancing age (P = 0.02) and prior coronary bypass surgery (P = 0.01). The traditional Framingham risk score was not higher in patients with AE. Multivariate analysis identified L_RHI < 0.4 as an independent predictor of AE (P = 0.03). A low RH signal detected by EndoPAT, consistent with endothelial dysfunction, was associated with higher AE rate during follow-up. L_RHI was an independent predictor of AE. Non-invasive assessment of peripheral vascular function may be useful for the identification of patients at risk for cardiac AEs.

Ischemic steal syndrome following arm arteriovenous fistula for hemodialysis

Arteriovenous fistulae in the arm are commonly used for hemodialysis in end-stage renal disease. Although physiological steal with reverse flow in the artery distal to the fistula is common, hand ischemia or infarction are rare. The ischemic steal syndrome (hand or forearm ischemia) is usually a result of arterial disease proximal or distal to the fistula and/or poor collateral supply to the hand. The diagnosis is primarily clinical; however, markedly reduced digital pressures and pulse volume recordings support the diagnosis. Management requires imaging for focal stenoses or disease in arteries proximal and distal to the fistula from the aorta to the hand. We present a case caused by subclavian artery occlusion that was initially missed due to focusing investigation only on the fistula. We describe the percutaneous treatments and surgical revisions that attempt to restore flow to the hand without compromising the fistula.