Calf rEF: Impact of Calf Muscle Pump Dysfunction With Reduced Ejection Fraction on All-Cause Mortality

OBJECTIVE

To evaluate mortality outcomes by varying degrees of reduced calf muscle pump (CMP) ejection fraction (EF).

PATIENTS AND METHODS

Consecutive adult patients who underwent venous air plethysmography testing at the Mayo Clinic Gonda Vascular Laboratory (January 1, 2012, through December 31, 2022) were divided into groups based on CMP EF for the assessment of all-cause mortality. Other venous physiology included measures of valvular incompetence and clinical venous disease (CEAP [clinical presentation, etiology, anatomy, and pathophysiology] score). Mortality rates were calculated using the Kaplan-Meier method.

RESULTS

During the study, 5913 patients met the inclusion criteria. During 2.84-year median follow-up, there were 431 deaths. Mortality rates increased with decreasing CMP EF. Compared with EF of 50% or higher, the hazard ratios (95% CIs) for mortality were as follows: EF of 40% to 49%, 1.4 (1.0 to 2.0); EF of 30% to 39%, 1.6 (1.2 to 2.4); EF of 20% to 29%, 1.7 (1.2 to 2.4); EF of 10% to 19%, 2.4 (1.7 to 3.3) (log-rank P≤.001). Although measures of venous valvular incompetence did not independently predict outcomes, venous disease severity assessed by CEAP score was predictive. After adjusting for several clinical covariates, both CMP EF and clinical venous disease severity assessed by CEAP score remained independent predictors of mortality.

CONCLUSION

Mortality rates are higher in patients with reduced CMP EF and seem to increase with each 10% decrement in CMP EF. The mortality mechanism does not seem to be impacted by venous valvular incompetence and may represent variables intrinsic to muscular physiology.

Artificial intelligence of arterial Doppler waveforms to predict major adverse outcomes among patients with diabetes mellitus

OBJECTIVE

Patients with diabetes mellitus (DM) are at increased risk for peripheral artery disease (PAD) and its complications. Arterial calcification and non-compressibility may limit test interpretation in this population. Developing tools capable of identifying PAD and predicting major adverse cardiac event (MACE) and limb event (MALE) outcomes among patients with DM would be clinically useful. Deep neural network analysis of resting Doppler arterial waveforms was used to detect PAD among patients with DM and to identify those at greatest risk for major adverse outcome events.

METHODS

Consecutive patients with DM undergoing lower limb arterial testing (April 1, 2015-December 30, 2020) were randomly allocated to training, validation, and testing subsets (60%, 20%, and 20%). Deep neural networks were trained on resting posterior tibial arterial Doppler waveforms to predict all-cause mortality, MACE, and MALE at 5 years using quartiles based on the distribution of the prediction score.

RESULTS

Among 11,384 total patients, 4211 patients with DM met study criteria (mean age, 68.6 ± 11.9 years; 32.0% female). After allocating the training and validation subsets, the final test subset included 856 patients. During follow-up, there were 262 deaths, 319 MACE, and 99 MALE. Patients in the upper quartile of prediction based on deep neural network analysis of the posterior tibial artery waveform provided independent prediction of death (hazard ratio [HR], 3.58; 95% confidence interval [CI], 2.31-5.56), MACE (HR, 2.06; 95% CI, 1.49-2.91), and MALE (HR, 13.50; 95% CI, 5.83-31.27).

CONCLUSIONS

An artificial intelligence enabled analysis of a resting Doppler arterial waveform permits identification of major adverse outcomes including all-cause mortality, MACE, and MALE among patients with DM.

Artificial Intelligence of Arterial Doppler Waveforms to Predict Major Adverse Outcomes Among Patients Evaluated for Peripheral Artery Disease

BACKGROUND

Patients with peripheral artery disease are at increased risk for major adverse cardiac events, major adverse limb events, and all-cause death. Developing tools capable of identifying those patients with peripheral artery disease at greatest risk for major adverse events is the first step for outcome prevention. This study aimed to determine whether computer-assisted analysis of a resting Doppler waveform using deep neural networks can accurately identify patients with peripheral artery disease at greatest risk for adverse outcome events.

METHODS AND RESULTS

Consecutive patients (April 1, 2015, to December 31, 2020) undergoing ankle-brachial index testing were included. Patients were randomly allocated to training, validation, and testing subsets (60%/20%/20%). Deep neural networks were trained on resting posterior tibial arterial Doppler waveforms to predict major adverse cardiac events, major adverse limb events, and all-cause death at 5 years. Patients were then analyzed in groups based on the quartiles of each prediction score in the training set. Among 11 384 total patients, 10 437 patients met study inclusion criteria (mean age, 65.8±14.8 years; 40.6% women). The test subset included 2084 patients. During 5 years of follow-up, there were 447 deaths, 585 major adverse cardiac events, and 161 MALE events. After adjusting for age, sex, and Charlson comorbidity index, deep neural network analysis of the posterior tibial artery waveform provided independent prediction of death (hazard ratio [HR], 2.44 [95% CI, 1.78-3.34]), major adverse cardiac events (HR, 1.97 [95% CI, 1.49-2.61]), and major adverse limb events (HR, 11.03 [95% CI, 5.43-22.39]) at 5 years.

CONCLUSIONS

An artificial intelligence-enabled analysis of Doppler arterial waveforms enables identification of major adverse outcomes among patients with peripheral artery disease, which may promote early adoption and adherence of risk factor modification.

Artificial intelligence for the evaluation of peripheral artery disease using arterial Doppler waveforms to predict abnormal ankle-brachial index

BACKGROUND

Patients with peripheral artery disease (PAD) are at increased risk for major adverse limb and cardiac events including mortality. Developing screening tools capable of accurate PAD identification is a necessary first step for strategies of adverse outcome prevention. This study aimed to determine whether machine analysis of a resting Doppler waveform using deep neural networks can accurately identify patients with PAD.

METHODS

Consecutive patients (4/1/2015 - 12/31/2020) undergoing rest and postexercise ankle-brachial index (ABI) testing were included. Patients were randomly allocated to training, validation, and testing subsets (70%/15%/15%). Deep neural networks were trained on resting posterior tibial arterial Doppler waveforms to predict normal (> 0.9) or PAD (⩽ 0.9) using rest and postexercise ABI. A separate dataset of 151 patients who underwent testing during a period after the model had been created and validated (1/1/2021 - 3/31/2021) was used for secondary validation. Area under the receiver operating characteristic curves (AUC) were constructed to evaluate test performance.

RESULTS

Among 11,748 total patients, 3432 patients met study criteria: 1941 with PAD (mean age 69 ± 12 years) and 1491 without PAD (64 ± 14 years). The predictive model with highest performance identified PAD with an AUC 0.94 (CI = 0.92-0.96), sensitivity 0.83, specificity 0.88, accuracy 0.85, and positive predictive value (PPV) 0.90. Results were similar for the validation dataset: AUC 0.94 (CI = 0.91-0.98), sensitivity 0.91, specificity 0.85, accuracy 0.89, and PPV 0.89 (postexercise ABI comparison).

CONCLUSION

An artificial intelligence-enabled analysis of a resting Doppler arterial waveform permits identification of PAD at a clinically relevant performance level.

The Post-thrombotic Syndrome-Prevention and Treatment: VAS-European Independent Foundation in Angiology/Vascular Medicine Position Paper

Importance

The post-thrombotic syndrome (PTS) is the most common long-term complication of deep vein thrombosis (DVT), occurring in up to 40–50% of cases. There are limited evidence-based approaches for PTS clinical management.

Objective

To provide an expert consensus for PTS diagnosis, prevention, and treatment.

Evidence-Review

MEDLINE, Cochrane Database review, and GOOGLE SCHOLAR were searched with the terms “post-thrombotic syndrome” and “post-phlebitic syndrome” used in titles and abstracts up to September 2020.

Filters Were

English, Controlled Clinical Trial / Systematic Review / Meta-Analysis / Guideline. The relevant literature regarding PTS diagnosis, prevention and treatment was reviewed and summarized by the evidence synthesis team. On the basis of this review, a panel of 15 practicing angiology/vascular medicine specialists assessed the appropriateness of several items regarding PTS management on a Likert-9 point scale, according to the RAND/UCLA method, with a two-round modified Delphi method.

Findings

The panelists rated the following as appropriate for diagnosis: 1-the Villalta scale; 2- pre-existing venous insufficiency evaluation; 3-assessment 3–6 months after diagnosis of iliofemoral or femoro-popliteal DVT, and afterwards periodically, according to a personalized schedule depending on the presence or absence of clinically relevant PTS. The items rated as appropriate for symptom relief and prevention were: 1- graduated compression stockings (GCS) or elastic bandages for symptomatic relief in acute DVT, either iliofemoral, popliteal or calf; 2-thigh-length GCS (30–40 mmHg at the ankle) after ilio-femoral DVT; 3- knee-length GCS (30–40 mmHg at the ankle) after popliteal DVT; 4-GCS for different length of times according to the severity of periodically assessed PTS; 5-catheter-directed thrombolysis, with or without mechanical thrombectomy, in patients with iliofemoral obstruction, severe symptoms, and low risk of bleeding. The items rated as appropriate for treatment were: 1- thigh-length GCS (30–40 mmHg at the ankle) after iliofemoral DVT; 2-compression therapy for ulcer treatment; 3- exercise training. The role of endovascular treatment (angioplasty and/or stenting) was rated as uncertain, but it could be considered for severe PTS only in case of stenosis or occlusion above the inguinal ligament, followed by oral anticoagulation.

Conclusions and Relevance

This position paper can help practicing clinicians in PTS management.

Major adverse events associated with inducible cardiac ischemia during treadmill exercise testing for peripheral artery disease

BACKGROUND

The coexistence of coronary artery disease and peripheral artery disease (PAD) is well-established. Whether myocardial ischemia by electrocardiography during treadmill testing to evaluate PAD severity is associated with adverse cardiac and limb events has not been established. The aim of the current study is to assess the risk of major adverse cardiac events (MACE), major adverse limb events (MALE), and all-cause mortality in patients with evidence of myocardial ischemia on ECG compared with those without ischemia in patients undergoing treadmill testing for PAD evaluation.

METHODS

Patients undergoing treadmill exercise ankle-brachial index (ABI) evaluation (January 1, 2003, to December 31, 2006) were identified using the Mayo Clinic Gonda Vascular Laboratory database. Patients with ischemia by electrocardiogram (ECG) were age and sex matched to patients without ischemia. Outcomes were compared by ECG category.

RESULTS

Of 4128 patients who underwent treadmill exercise, 170 (4.1%) had inducible myocardial ischemia by ECG. These were matched with 340 patients without ischemia. The positive ECG group had a higher percentage of diabetes mellitus (31.2% vs 21.8%; P = .02), carotid artery disease (22.4% vs 13.2%; P = .009), exercise-induced angina (14.1% vs 2.9%; P < .0001), and dyspnea (60.6% vs 35.6%; P < .0001). While the resting ABI was similar, the postexercise ABI was lower in the positive ECG group (0.5 vs 0.7; P = .04). After a median follow-up of 8 years, MACE were significantly greater in the positive ECG group (62.4% vs 46.5%; P < .001). MALE were significantly less frequent (17.1% vs 23.2%; P = .02), without an increased risk of amputation. In multivariable analysis, inducible ischemia was associated with higher incidence of MACE (hazard ratio, 1.65; 95% confidence interval, 1.25-2.16; P < .001) and lower incidence of MALE (hazard ratio, 0.51; 95% confidence interval, 0.31-0.84; P < .05).

CONCLUSIONS

ECG monitoring during vascular treadmill testing identified a subset of patients with more frequent MACE but less MALE.

Usability of a Digital Registry to Promote Secondary Prevention for Peripheral Artery Disease Patients

Objective

To evaluate usability of a quality improvement tool that promotes guideline-based care for patients with peripheral arterial disease (PAD).

Patients and Methods

The study was conducted from July 19, 2018, to August 21, 2019. We compared the usability of a PAD cohort knowledge solution (CKS) with standard management supported by an electronic health record (EHR). Two scenarios were developed for usability evaluation; the first for the PAD-CKS while the second evaluated standard EHR workflow. Providers were asked to provide opinions about the PAD-CKS tool and to generate a System Usability Scale (SUS) score. Metrics analyzed included time required, number of mouse clicks, and number of keystrokes.

Results

Usability evaluations were completed by 11 providers. SUS for the PAD-CKS was excellent at 89.6. Time required to complete 21 tasks in the CKS was 4 minutes compared with 12 minutes for standard EHR workflow (median, P = .002). Completion of CKS tasks required 34 clicks compared with 148 clicks for the EHR (median, P = .002). Keystrokes for CKS task completion was 8 compared with 72 for EHR (median, P = .004). Providers indicated that overall they found the tool easy to use and the PAD mortality risk score useful.

Conclusions

Usability evaluation of the PAD-CKS tool demonstrated time savings, a high SUS score, and a reduction of mouse clicks and keystrokes for task completion compared to standard workflow using the EHR. Provider feedback regarding the strengths and weaknesses also created opportunities for iterative improvement of the PAD-CKS tool.

Determinants of Bone Material Strength and Cortical Porosity in Patients with Type 2 Diabetes Mellitus

CONTEXT

Reduced bone material strength index (BMSi) and increased cortical porosity (CtPo) have emerged as potentially contributing to fracture risk in type 2 diabetes mellitus (T2DM) patients.

OBJECTIVE

To determine whether BMSi or CtPo are related to other diabetic complications.

DESIGN

Cross-sectional observational study.

SETTING

Subjects recruited from a random sample of southeast Minnesota residents.

PARTICIPANTS

A total of 171 T2DM patients (mean age, 68.8 years) and 108 age-matched nondiabetic controls (mean age, 67.3 years).

MAIN MEASURES

Bone material strength index was measured using microindentation, skin advanced glycation end-products (AGEs) measured using autofluorescence, high-resolution peripheral quantitative computed tomography at the distal radius and tibia, assessment of diabetic microvascular complications including urine microalbuminuria, retinopathy, neuropathy, and vascular disease (ankle brachial index and transcutaneous oxygen tension [TcPO2]). All analyses were adjusted for age, sex, and body mass index.

RESULTS

Skin AGEs were negatively correlated with the BMSi in both T2DM (r = -0.30, P < 0.001) and control (r = -0.23, P = 0.020) subjects. In relating diabetic complications to CtPo, we found that T2DM patients with clinically significant peripheral vascular disease (TcPO2 ≤ 40 mm Hg) had higher (+21.0%, P = 0.031) CtPo at the distal tibia as compared to controls; in these subjects, CtPo was negatively correlated with TcPO2 at both the distal tibia (r = -0.39, P = 0.041) and radius (r = -0.41, P = 0.029).

CONCLUSIONS

Our findings demonstrate that bone material properties are related to AGE accumulation regardless of diabetes status, while CtPo in T2DM patients is linked to TcPO2, a measure of microvascular blood flow.

Calf muscle pump function as a predictor of all-cause mortality

Calf muscle pump (CMP) promotes venous return from the lower extremity and contributes to preload and cardiac output. Impaired CMP function may reflect a measure of frailty or cumulative disease burden or may impede cardiac function. The study objective was to test the hypothesis that impaired CMP negatively impacts survival. Consecutive adult patients who underwent venous strain gauge plethysmography at the Mayo Clinic Gonda Vascular Laboratory (January 1, 1998 - December 31, 2011) were assessed for overall survival. Patients with venous incompetence, venous obstruction or unilateral calf pump dysfunction were excluded. Risk of mortality was assessed with Cox proportional hazard ratios and after adjusting for Charlson Comorbidity Index variables. Over the study period, 2728 patients were included in the analysis. Compared to patients with normal CMP, those with impaired CMP were older (p < 0.001), predominantly female (p = 0.01) and had higher mean Charlson scores (p < 0.001). Patients with impaired CMP had a higher mortality rate at 5 (8.9% vs 2.4%), 10 (17.5% vs 5.9%), and 15 years (22.8% vs 8.3%) compared to those with normal CMP (p < 0.001 for each comparison). Of patients with heart failure, those with impaired CMP had worse survival at each 5-year increment compared to those with normal CMP (p < 0.05 at each increment). In conclusion, impaired CMP appears to be an independent predictor of poor outcomes after adjusting for variables within the Charlson Comorbidity Index. The association between impaired CMP, heart failure, and mortality may represent a negative impact on circulatory function or a surrogate measure of frailty.

SUN-381 Cortical Porosity Is Associated with Peripheral Small Vessel Disease in Adult Patients with Type 2 Diabetes

Patients with Type 2 Diabetes (T2D) are at higher fracture risk despite having relatively normal or even increased BMD by DXA. Increased cortical porosity has emerged as a potential factor contributing to fragility fractures in T2D. However, there is conflicting evidence whether T2D patients have increased cortical porosity. We hypothesized that microvascular complications have an important role in cortical porosity. Thus, we performed high-resolution peripheral quantitative computed tomography imaging at the distal radius and tibia to evaluate bone microarchitecture in men with T2DM age ≥ 50 yrs or postmenopausal women with T2DM and nondiabetic controls. Comprehensive diabetic complications were assessed in all patients including urine microalbuminuria, retinopathy, neuropathy (touch, temperature, and vibration sensation), ankle brachial index (ABI) and transcutaneous oxygen tension (TcPO2). Percent differences between groups were obtained from linear regression models adjusting for age, BMI, and sex. Relationships between variables were assessed using adjusted Spearman correlations. A total of 164 T2D patients (mean age 68.9 ±7.8 yrs.; 56.7% men; HbA1C=7.7 ±0.9%; mean diabetes duration 15.2 yrs.) and 107 nondiabetic controls (mean age 67.3±8.8 yrs.; 42.1% men; HbA1C =5.4 ±0.3%) were recruited to the study. Overall, there was a trend for increased cortical porosity at the distal tibia in the T2D group (+12.2%; p=0.063) compared with nondiabetic controls. Of note, TcPO2 was negatively correlated with cortical porosity at the distal radius (r= -0.17; p= 0.039) and distal tibia (r= -0.15; p= 0.073). In particular, the Low TcPO2 (≤40 mmHg) group (n=29) had greater cortical porosity at the distal tibia (+19.6 %; p=0.037) compared with the High TcPO2 (>40 mmHg) group (n=133). In addition, the low TcPO2 group had a significant increase in cortical porosity in the distal tibia (+24.8% p=0.020) compared with nondiabetic controls. In conclusion, this is the first evidence in humans indicating that TcPO2, a measure of microvascular blood flow, is linked to cortical porosity in the distal radius and tibia in T2D patients. Our findings may explain the conflicting findings regarding cortical porosity in T2D because only T2D patients with impaired microvascular blood flow have increased cortical porosity. Collectively, our data indicate that cortical porosity is a microvascular complication of longstanding T2D.

P2491Physiologic assessment for coronary artery disease with myocardial perfusion imaging is clinically more relevant when selecting diabetic with high risk features

Background

Based on previously published data, routine myocardial perfusion imaging in diabetics is not recommended. Selecting patients with diabetes and high risk cardiovascular features could be important to improve the yield of physiologic assessment of the coronary arteries disease and subsequently patient outcome.

Purpose

We posed the question whether nuclear stress testing has a better yield by selecting diabetic individuals with known vascular disease.

Methods

We analyzed records for 15,392 diabetics from 1996 to 2009 with and without vascular disease. Vascular disease is defined as carotid vascular disease, abdominal aortic aneurysm, or peripheral arterial disease. There was 2457 myocardial perfusion studies performed within 2 years of the vascular evaluation. We studied the results of these stress testing in each group and evaluated for the presence of myocardial ischemia. Multivariate Cox proportional regression was used to calculate hazard ratios (HR) with 95% confidence intervals after adjusting for age, gender.

Results

Of those who underwent myocardial perfusion studies 1819 were diabetic with vascular disease group A (mean age 67.8, 70.5% female) and 638 were diabetic without vascular disease group B (mean age 64.5 years, 67.1% female). There was at least one reversible defect suggest myocardial ischemia in 225 and 758 studies in group A and B respectively. Comparing outcome based on the presence of myocardial ischemia in group A without vascular disease, those with vascular disease did have an increased risk of myocardial infarction (adjusted HR: 1.630, 95% CI: 1.281–2.074) and death (adjusted HR: 1.646, 95% CI: 1.413–1.918).

Conclusion

Myocardial perfusion imaging is a reasonable test in patients with diabetes and vascular disease. The presence of myocardial ischemia is more common and is associated with worse cardiovascular outcome.

Acknowledgement/Funding

None

Association of Ankle-Brachial Indices With Limb Revascularization or Amputation in Patients With Peripheral Artery Disease

IMPORTANCE

The prevalence and morbidity of peripheral artery disease (PAD) are high, with limb outcomes including revascularization and amputation. In community-dwelling patients with PAD, the role of noninvasive evaluation for risk assessment and rates of limb outcomes have not been established to date.

OBJECTIVE

To evaluate whether ankle-brachial indices are associated with limb outcomes in community-dwelling patients with PAD.

DESIGN, SETTING, AND PARTICIPANTS

A population-based, observational, test-based cohort study of patients was performed from January 1, 1998, to December 31, 2014. Data analysis was conducted from July 15 to December 15, 2017. Participants included a community-based cohort of 1413 patients with PAD from Olmsted County, Minnesota, identified by validated algorithms deployed to electronic health records. Automated algorithms identified limb outcomes used to build Cox proportional hazards regression models. Ankle-brachial indices and presence of poorly compressible arteries were electronically identified from digital data sets. Guideline-recommended management strategies within 6 months of diagnosis were also electronically retrieved, including therapy with statins, antiplatelet agents, angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers, and smoking abstention.

MAIN OUTCOMES AND MEASURES

Ankle-brachial index (index ≤0.9 indicates PAD; <.05, severe PAD; and ≥1.40, poorly compressible arteries) and limb revascularization or amputation.

RESULTS

Of 1413 patients, 633 (44.8%) were women; mean (SD) age was 70.8 (13.3) years. A total of 283 patients (20.0%) had severe PAD (ankle-brachial indices <0.5) and 350 (24.8%) had poorly compressible arteries (ankle-brachial indices ≥1.4); 780 (55.2%) individuals with less than severe disease formed the reference group. Only 32 of 283 patients (11.3%) with severe disease and 68 of 350 patients (19.4%) with poorly compressible arteries were receiving 4 guideline-recommended management strategies. In the severe disease subgroup, the 1-year event rate for revascularization was 32.4% (90 events); in individuals with poorly compressible arteries, the 1-year amputation rate was 13.9% (47 events). In models adjusted for age, sex, and critical limb ischemia, poorly compressible arteries were associated with amputation (hazard ratio [HR], 3.12; 95% CI, 2.16-4.50; P < .001) but not revascularization (HR, 0.91; 95% CI, 0.69-1.20; P = .49). In contrast, severe disease was associated with revascularization (HR, 2.69; 95% CI, 2.15-3.37; P < .001) but not amputation (HR, 1.30; 95% CI, 0.82-2.07; P = .27).

CONCLUSIONS AND RELEVANCE

Community-dwelling patients with severe PAD or poorly compressible arteries have high rates of revascularization or limb loss, respectively. Guideline-recommended management strategies for secondary risk prevention are underused in the community.

Leveraging the Electronic Health Record to Create an Automated Real-Time Prognostic Tool for Peripheral Arterial Disease

Background Automated individualized risk prediction tools linked to electronic health records ( EHR s) are not available for management of patients with peripheral arterial disease. The goal of this study was to create a prognostic tool for patients with peripheral arterial disease using data elements automatically extracted from an EHR to enable real-time and individualized risk prediction at the point of care. Methods and Results A previously validated phenotyping algorithm was deployed to an EHR linked to the Rochester Epidemiology Project to identify peripheral arterial disease cases from Olmsted County, MN, for the years 1998 to 2011. The study cohort was composed of 1676 patients: 593 patients died over 5-year follow-up. The c-statistic for survival in the overall data set was 0.76 (95% confidence interval [CI], 0.74-0.78), and the c-statistic across 10 cross-validation data sets was 0.75 (95% CI, 0.73-0.77). Stratification of cases demonstrated increasing mortality risk by subgroup (low: hazard ratio, 0.35 [95% CI, 0.21-0.58]; intermediate-high: hazard ratio, 2.98 [95% CI, 2.37-3.74]; high: hazard ratio, 8.44 [95% CI, 6.66-10.70], all P<0.0001 versus the reference subgroup). An equation for risk calculation was derived from Cox model parameters and β estimates. Big data infrastructure enabled deployment of the real-time risk calculator to the point of care via the EHR . Conclusions This study demonstrates that electronic tools can be deployed to EHR s to create automated real-time risk calculators to predict survival of patients with peripheral arterial disease. Moreover, the prognostic model developed may be translated to patient care as an automated and individualized real-time risk calculator deployed at the point of care.

Innovative Informatics Approaches for Peripheral Artery Disease: Current State and Provider Survey of Strategies for Improving Guideline-Based Care

OBJECTIVE

To quantify compliance with guideline recommendations for secondary prevention in peripheral artery disease (PAD) using natural language processing (NLP) tools deployed to an electronic health record (EHR) and investigate provider opinions regarding clinical decision support (CDS) to promote improved implementation of these strategies.

PATIENTS AND METHODS

Natural language processing was used for automated identification of moderate to severe PAD cases from narrative clinical notes of an EHR of patients seen in consultation from May 13, 2015, to July 27, 2015. Guideline-recommended strategies assessed within 6 months of PAD diagnosis included therapy with statins, antiplatelet agents, angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, and smoking abstention. Subsequently, a provider survey was used to assess provider knowledge regarding PAD clinical practice guidelines, comfort in recommending secondary prevention strategies, and potential role for CDS.

RESULTS

Among 73 moderate to severe PAD cases identified by NLP, only 12 (16%) were on 4 guideline-recommended strategies. A total of 207 of 760 (27%) providers responded to the survey; of these 141 (68%) were generalists and 66 (32%) were specialists. Although 183 providers (88%) managed patients with PAD, 51 (25%) indicated they were uncomfortable doing so; 138 providers (67%) favored the development of a CDS system tailored for their practice and 146 (71%) agreed that an automated EHR-derived mortality risk score calculator for patients with PAD would be helpful.

CONCLUSION

Natural language processing tools can identify cases from EHRs to support quality metric studies. Findings of this pilot study demonstrate gaps in application of guideline-recommended strategies for secondary risk prevention for patients with moderate to severe PAD. Providers strongly support the development of CDS systems tailored to assist them in providing evidence-based care to patients with PAD at the point of care.

Discrepancies in Prevalence of Peripheral Arterial Disease between Lower Extremities at Rest and Postexercise

Background  Lower extremity peripheral arterial disease (PAD) is a common medical condition causing substantial morbidity. Limited data exist on whether discrepancies in PAD prevalence exist between the lower extremities using resting ankle-brachial indices (ABIs) and postexercise pressures. Objective  We predicted the prevalence of PAD between the lower extremities. Methods and Results  Consecutive patients who had undergone a noninvasive arterial lower extremity study at Mayo Clinic, Rochester, MN, between January 1996 and December 2012 with suspected PAD were retrospectively reviewed. We identified 12,312 consecutive patients who underwent an arterial lower extremity and an exercise treadmill study. Prevalence of PAD was assessed at rest and after exercise using two criteria: a resting ABI ≤ 0.90 and a postexercise pressure decrease of > 30 mm Hg. Mean age was 67 ± 12 years and there were 4,780 (39%) women studied. At rest, we found a higher prevalence of PAD on the left extremity (27.4%) compared with the right (24.6%) ( p  < 0.0001). After exercise, we found a higher prevalence of PAD on the right extremity (25.1%) compared with the left (19.0%) ( p  < 0.0001). These discrepancies between the prevalence of PAD at rest and after exercise were present in women and men. Conclusion  Using validated criteria of a resting ABI of ≤ 0.90 and postexercise ankle pressure decrease > 30 mm Hg, our results suggest that there is a significantly higher prevalence of PAD in the left lower extremity at rest, in contrast to a greater prevalence of abnormal postexercise testing in the right lower extremity. The reason(s) of these discrepancies remain to be studied.

Peri-procedural use of anticoagulants in radiology: an evidence-based review

Peri-procedural anticoagulant management hinges on the balance of hemorrhagic and thrombotic complications. The radiologist is tasked with accurately assessing the hemorrhagic risk for patients undergoing procedures, taking into account procedural bleeding rates, underlying coagulopathy based on lab tests, and use of anticoagulants. The purpose of this article is to provide a contemporary review of commonly used anticoagulants and, incorporating published evidence, review their management related to image-guided procedures.

Peripheral arterial disease preoperatively may predict graft failure and mortality in kidney transplant recipients

Patients with end-stage renal disease undergoing kidney transplant often have diffuse atherosclerosis and high cardiovascular morbidity and mortality rates. We analyzed the correlation of peripheral arterial disease (PAD), here quantified by an abnormal ankle–brachial index (ABI) measured within the 5 years prior to kidney transplant, with graft failure and mortality rates (primary end points) after adjusting for known cardiovascular risk factors (age, sex, smoking history, hypertension, diabetes, stroke, known coronary artery disease or heart failure, years of dialysis). Of 1055 patients in our transplant population, 819 had arterial studies within the 5 years prior to transplant. Secondary end points included myocardial infarction; cerebrovascular accident; and limb ischemia, gangrene, or amputation. Low ABI was an independent and significant predictor of organ failure (OR, 2.77 (95% CI, 1.68–4.58), p<0.001), secondary end points (HR, 1.39 (95% CI, 0.97–1.99), p<0.076), and death (HR, 1.84 (95% CI, 1.26–2.68), p=0.002). PAD was common in this population: of 819 kidney transplant recipients, 46% had PAD. Low ABI was associated with a threefold greater risk of graft failure, a twofold greater risk of death after transplant, and a threefold greater risk of secondary end points. Screening for PAD is important in this patient population because of the potential impact on long-term outcomes.

Discordant Diagnosis of Lower Extremity Peripheral Artery Disease Using American Heart Association Postexercise Guidelines

To determine whether postexercise criteria for peripheral artery disease (PAD) diagnosis recommended by the American Heart Association (AHA) identifies the same group of PAD patients.Diagnosis of PAD is performed using ankle-brachial index at rest (resting-ABI). When resting-ABI is not contributive, an AHA scientific statement recommend to use 1 of 2 following criteria: a postexercise ABI decrease of greater than 20% or a postexercise ankle pressure decrease of greater than 30 mm Hg.Between 1996 and 2012, 31,663 consecutive patients underwent lower-extremity arterial study at Mayo Clinic. Among them, only unique patients who had exercise treadmill testing were analyzed. In this retrospective analysis, resting-ABI, postexercise ABI, and postexercise decrease of ankle pressure measured at 1-minute were measured in each patient. We conducted an analysis of agreement between postexercise criteria expressing the agreement separately for the positive and the negative ratings. Twelve thousand three hundred twelve consecutive patients were studied with a mean age of 67 ± 12 years, 61% male. According to resting-ABI, 4317 (35%) patients had PAD. In the whole population, if a clinician diagnoses "PAD" with 1 postexercise criterion, the probability that other clinicians would also diagnose "PAD" is 74.3%. If a clinician diagnoses "no PAD", the probability that other clinicians would also diagnose "no PAD" is 82.4%. In the patients to be of potential benefit from treadmill test when the resting-ABI > 0.90, if a clinician diagnoses "PAD" with 1 postexercise criterion, the probability that other clinicians would also diagnose "PAD" is 58.4% whereas if a clinician diagnoses "no PAD," the probability that other clinicians would also diagnose "no PAD" is 87.5%.Postexercise criteria do not identify the same group of PAD patients. In our opinion, postexercise criteria to define PAD deserve additional study.

Application of exercise transcutaneous oxygen pressure measurements for detection of proximal lower extremity arterial disease: a case report

Proximal claudication is secondary to ischemia caused by peripheral artery disease (PAD), whereas proximal pseudo-claudication is secondary to other disease processes such as hip arthritis, spinal stenosis, neuropathy, and so forth. The differentiation between the two can be challenging. Exercise transcutaneous oxygen pressure measurement (exercise-TcPO2) allows noninvasive detection of flow-reducing lesions in the proximal arteries and tributaries of the lower extremity arterial tree. We present the first case report in the United States using an exercise-TcPO2 algorithm. A 71-year-old diabetic patient with proximal left-sided and right-calf claudication with indeterminate ankle-brachial indices underwent an exercise-TcPO2 study before and after endovascular intervention. Four TcPO2 probes were placed: one at chest level (reference probe), one on each buttock, and one on the symptomatic calf. The Delta from Resting Oxygen Pressure (DROP) index was calculated at each probe site using a previously validated protocol. Proximal left- and right-calf ischemia were confirmed by the initial exercise-TcPO2, and, after endovascular treatment of the left iliac artery lesion, improvements in proximal exercise-TcPO2 values were found. These data suggest that exercise-TcPO2 can be useful in PAD evaluation in patients with non-compressible arteries and/or proximal claudication.

Disease location is associated with survival in patients with peripheral arterial disease

BACKGROUND

We investigated whether disease location influences survival in patients with peripheral arterial disease.

METHODS AND RESULTS

Patients (n = 12,731; mean age, 67.5 ± 12.7 years; 57.4% male) who underwent outpatient noninvasive lower extremity arterial evaluation were followed up for 5.9 ± 3.1 years for all-cause mortality. Peripheral arterial disease (n = 8930) was defined as a resting or postexercise ankle-brachial index (ABI) ≤ 0.90, and normal ABI (n = 3,801) was defined as a resting and postexercise ABI of 1.00 to 1.30. Presence or absence of disease at the proximal location or distal location was determined on the basis of Doppler signals in leg arteries; 42% had no PD or DD, 45% had proximal (14% postexercise PD only), 30% had distal disease, 17% had both proximal and distal disease, 28% had proximal only and 14% had distal only. We performed multivariable logistic regression to identify factors associated with disease location, and Cox proportional hazard regression to assess the respective effects of proximal or distal disease on survival. Older age, male sex, diabetes, heart failure, and critical limb ischemia were associated with distal disease, whereas female sex, smoking, hypertension, dyslipidemia, coronary heart disease, cerebrovascular disease, chronic obstructive pulmonary disease, and critical limb ischemia were associated with proximal disease. Over a mean follow-up of 5.9 ± 3.1 years, 3039 patients (23.9%) died. After adjustment for potential confounders, the hazard ratios (HRs) of death associated with PD only and DD only were 1.3 (1.3 to 1.4) and 1.5 (1.4 to 1.6), respectively. After additional adjustment for resting ABI, there was no significant association between proximal disease and death, whereas the association of distal disease with death remained significant (HR, 1.2; 95% CI, 1.1 to 1.3).

CONCLUSIONS

In patients with peripheral arterial disease, proximal and distal disease locations were associated with distinctive risk factor and comorbidity profiles. Distal disease was associated with worse survival even after adjustment for risk factors, comorbidities, and resting ABI.

External iliac vein thrombosis in an athletic cyclist with a history of external iliac artery endofibrosis and thrombosis

External iliac artery endofibrosis describes an intimal subendothelial fibrosis leading to wall thickening and stenosis that has been described in high-performance athletes. There are anatomical, mechanical, and probably metabolic factors that may contribute to this pathology. Ankle-brachial index (ABI) measurement with exercise testing, duplex ultrasound, computed tomography (CT) or magnetic resonance (MR) angiogram, and ultimately arteriography help to make the diagnosis. Management can be conservative, but most cases require surgical intervention. External iliac vein stenosis and thrombosis in cyclists has rarely been described in the literature. We report a case of extensive left lower limb deep venous thrombosis (DVT) including the external iliac vein diagnosed in a 57-year-old athletic cyclist with a history of external iliac artery thrombosis.

Predicting superficial venous incompetence with strain gauge plethysmography

Background

With currently available effective interventional methods to treat superficial venous insufficiency, it becomes particularly important to have a simple and reliable method to evaluate the location and severity of venous reflux. To date, there are few studies that evaluated plethysmography with and without tourniquet application to differentiate superficial from deep venous incompetence.

Objectives

To determine if strain gauge plethysmography (SGP) with and without tourniquet application can be used to distinguish between the superficial and deep venous components of venous incompetence.

Methods

We conducted a prospective study using SGP with and without tourniquet application and duplex ultrasound (duplex US) to assess the severity and location of venous incompetence in 62 patients (85 limbs, 42 women, with an age range of 32–81 years) referred to our vascular laboratory for haemodynamic evaluation. Based on duplex US results, patients were diagnosed with superficial (SVI), deep and superficial (mixed) and deep vein incompetence (DVI).

Results

Mixed incompetence was the most common type. Twenty-three out of 33 limbs in the SVI group normalized their refill rate (RR) with tourniquet application (69.6%). Normalization of the RR with tourniquet application was less common in the mixed ( n: 17 out of 40, 42.5%) and DVI ( n: 2 out of 6, 33.3%) groups.

Conclusion

SGP with tourniquet application is a simple and fast technique that can identify patients with SVI, based on RR improvement, who probably would benefit more from ablation procedures. Further studies evaluating impact of SGP with tourniquet test results on clinical outcome of SVI invasive treatment are warranted

Successful iliac vein and inferior vena cava stenting ameliorates venous claudication and improves venous outflow, calf muscle pump function, and clinical status in post-thrombotic syndrome

OBJECTIVES

Stent therapy has been proposed as an effective treatment of chronic iliofemoral (I-F) and inferior vena cava (IVC) thrombosis. The purpose of this study was to determine the effects of technically successful stenting in consecutive patients with advanced CVD (CEAP3-6 +/- venous claudication) for chronic obliteration of the I-F (+/-IVC) trunks, on the venous hemodynamics of the limb, the walking capacity, and the clinical status of CVD. These patients had previously failed to improve with conservative treatment entailing compression and/or wound care for at least 12 months.

METHODS

The presence of venous claudication was assessed by > or =3 independent examiners. The CEAP clinical classification was used to determine the severity of CVD. Outflow obstruction [Outflow Fraction at 1- and 4-second (OF1 and OF4) in %], venous reflux [Venous Filling Index (VFI) in mL/100 mL/s], calf muscle pump function [Ejection Fraction (EF) in %] and hypertension [Residual Venous Fraction (RVF) in %], were examined before and after successful venous stenting in 16 patients (23 limbs), 6 females, 10 males, median age 42 years; range, 31-77 yearas, left/right limbs 14/9, using strain gauge plethysmography; 7/16 of these had thrombosis extending to the IVC. Contralateral limbs to those stented without prior I-F +/- IVC thrombosis, nor infrainguinal clots on duplex, were used as control limbs (n = 9). Excluded were patients with stent occlusion or stenoses, peripheral arterial disease (ABI <1.0), symptomatic cardiac disease, unrelated causes of walking impairment, and malignancy. Preinterventional data (< or =30 days) were compared with those after endovascular therapy (8.4 months; interquartile range [IQR], 3-11.8 months). Nonparametric analysis was applied.

RESULTS

Compared with the control group, limbs with I-F +/- IVC thrombosis before stenting had reduced venous outflow (OF4) and calf muscle pump function (EF), worse CEAP clinical class, and increased RVF (all, P < 0.05). At 8.4 months (IQR, 3-11.8 months) after successful I-F (+/-IVC) stenting, venous outflow (OF1, OF4) and calf muscle pump function (EF) had both improved (P < 0.001) and the RVF had decreased (P < 0.001), at the expense of venous reflux, which had increased further (increase of median VFI by 24%; P = 0.002); the CEAP status had also improved (P < 0.05) from a median class C3 (range, C3-C6; IQR, C3-C5) [distribution, C6: 6; C4: 4; C3: 13] before intervention to C2 (range, C2-C6; IQR, C2-C4.5) [distribution, C6: 1; C5: 5; C4: 4; C2: 13] after intervention. At this follow up (8.4 months median), venous outflow (OF1, OF4), calf muscle pump function (EF), and RVF of the stented limbs did not differ significantly from those of the control; significantly worse (P < 0.025) were the amount of venous reflux (VFI), and the CEAP clinical class, despite the improvement with stenting. Incapacitating venous claudication noted in 62.5% (10 of 16, 95% CI, 35.8%-89.1%) of patients (15 of 23 limbs; 65.2%, 95% CI, 44.2%-86.3%) before stenting was eliminated in all after stenting (P < 0.001).

CONCLUSIONS

Successful I-F (+/-IVC) stenting in limbs with venous outflow obstruction and complicated CVD (C3-C6) ameliorates venous claudication, normalizes outflow, and enhances calf muscle pump function, compounded by a significant clinical improvement of CVD. The significant increase in the amount of venous reflux of the stented limbs indicates that elastic or inelastic compression support of the successfully stented limbs would be pivotal in preventing disease progression.

Hemodynamic impairment, venous segmental disease, and clinical severity scoring in limbs with Klippel-Trenaunay syndrome

BACKGROUND

Klippel-Trenaunay syndrome (KTS) is a complex congenital anomaly featuring two or more of the following: (1) capillary malformations (port-wine stains), (2) soft tissue or bony hypertrophy (or both), and (3) varicose veins or venous malformations. With the purpose of determining the actual significance of venous impairment in patients with KTS, we quantified the venous valvular competency and calf muscle pump function and examined their effect on clinical severity.

METHODS

Included were patients with near-normal function of affected limb(s) and minimal/small foot hypertrophy. Excluded were those with deep venous hypoplasia, aplasia or thrombosis, lymphedema, limb length discrepancy (>2.5 cm), peripheral arterial (ankle-brachial index <1.0), or cardiac disease and walking impairment. Venous duplex scanning, ascending venography, magnetic resonance imaging, strain gauge plethysmography, and a bone scanogram were performed. We studied eight men and seven women aged 15 to 51 years (median, 24 years). The KTS involved 17 limbs (unilateral in 13 patients and bilateral in 2). Contralateral limbs in patients with unilateral KTS acted as controls (n = 13). Venous clinical severity was graded according to the CEAP and venous clinical severity score (VCSS), and reflux complexity was classified according to the venous segmental disease score. Outflow obstruction (outflow fraction at 1 and 4 seconds; OF(1) and OF(4), respectively), reflux (venous filling index), calf muscle pump function (ejection fraction), and hypertension (residual volume fraction) were determined in both limbs with strain gauge plethysmography. Data, reported as median and interquartile range, were analyzed with the Mann-Whitney test.

RESULTS

Varicose veins or venous malformations occurred in the medial, posterior, or anterolateral limb segments of the ankle (7/17, 7/17, and 9/17), calf (10/17, 8/17, and 12/17), knee (9/17, 8/17, and 8/17), and thigh (10/17, 6/17, and 8/17, respectively). Venous malformations occupied the subcutaneous space (17/17) and extended into the subfascial space in 6 (35.3%) of 17 limbs. Abnormal reflux (>0.5 seconds) was distributed in the great (64.7%; 11/17) and small (5.9%; 1/17) saphenous veins and the common femoral (23.5%; 4/17), femoral (41.1%; 7/17), popliteal (29.4%; 5/17), perforator (70.6%; 12/17), and axial calf (35.3%; 6/17) veins. There was no difference in the OF(1) and OF(4) between the affected limbs and the controls. Limbs with KTS had a fivefold greater venous filling index (0.133-0.46 mL . 100 mL(-1) . s(-1); 0.258 mL . 100 mL(-1) . s(-1)) than the controls (0.034-0.055 mL . 100 mL(-1) . s(-1); 0.046 mL . 100 mL(-1) . s(-1); P < .0001), and this was linked to a higher venous segmental disease score (3 [2-4] vs 0 [0-1]; P < .0001). Limbs with KTS had half the ejection fraction (20.8%; 12.3%-24%) of the controls (39.3%; 30.9%-64.6%) and twice as high a residual venous fraction (77% [69.6%-84.5%] vs 40.9% [20.6%-60%]; both P < .004). Patients complained of swelling (100%; 15/15), aching (100%; 15/15), pain (93.3%; 14/15) and heaviness (100%; 15/15), tiredness (66.7%; 10/15), and tightness (33.3%; 5/15) of the limb(s) with KTS. Limbs with KTS had a worse (1) venous clinical severity by 11 VCSS points (11 [8-12] vs 0 [0-1]) and (2) clinical status by 3 CEAP classes (C3 [C3-C4] vs C0 [C0-C2]) than the control limbs (both P < .0001).

CONCLUSIONS

Venous disease in limbs with KTS is a major source of morbidity in affected patients. Limbs with KTS are characterized by complex reflux patterns, severe valvular incompetence, calf muscle pump impairment, and venous hypertension, thus explaining the advanced clinical severity (VCSS) and CEAP grade.

Enhanced endothelin-converting enzyme immunoreactivity in early atherosclerosis

Endothelin-1 (ET-1) is a 21-amino-acid local and circulating factor whose plasma concentrations are increased in advanced atherosclerosis. ET-1 is cleaved from a prohormone (big ET-1) by endothelin-converting enzymes (ECEs) into the biologically active mature form which mediates vasoconstriction and cell proliferation. This study was designed to test by immunohistochemistry the hypothesis that ECE is present locally in the neointima of atherosclerotic vessels. Two groups of rabbits, control (n = 6) and cholesterol-fed (1% cholesterol diet for 8 weeks; n = 6) were sacrificed. Aortas were excised and divided for determination of tissue ET-1 concentration by RIA and immunohistochemical analysis of ECE. Vascular wall ET-1 was increased in the atherosclerotic aorta (6.1 +/- 0.8 vs. 9.8 +/- 0.9 pg/mg protein; p < 0.05), whereas circulating ET-1 concentrations were similar in the two groups (3.8 +/- 0.4 vs. 2.4 +/- 1.4 pg/ml). Immunostaining revealed the presence of ECE in endothelial and vascular smooth-muscle cells of the control group. Enhanced ECE immunoreactivity was present in atherosclerotic aortas, particularly in the neointimal macrophages and smooth-muscle cells. We conclude that local vascular wall, but not circulating ET-1, is increased in early atherosclerosis. In addition, ECE immunoreactivity is increased in early atherosclerosis and may therefore contribute to the generation of local ET-1 in early experimental atherosclerosis. These studies provide important insights into the regulation of ET-1 in early atherosclerosis, which may contribute to the elucidation of factors involved in the progression of atherosclerosis.

Modulation of functionally active endothelin-converting enzyme by chronic neutral endopeptidase inhibition in experimental atherosclerosis

BACKGROUND

Endothelin-converting enzyme-1 (ECE-1) processes big endothelin-1 (ET-1) to ET-1, a peptide implicated in atheroma formation. ECE-1 exists in 2 isoforms (ECE-1alpha and ECE-1beta), the result of alternative splicing of a common gene. Neutral endopeptidase (NEP) is a genetically distinct metallopeptidase that degrades the natriuretic peptides. These peptides mediate antiproliferative and vasodilating actions. We sought to demonstrate the distribution of the 2 ECE-1 isoforms in experimental atherosclerosis, to determine the effects of chronic NEP-I on plasma cGMP concentrations, vascular wall ECE-1 activity, and ET-1 concentration, and to correlate these actions with atheroma formation. Our hypothesis was that chronic NEP-I, in association with augmented cGMP, would inhibit ECE-1 conversion of big ET-1 to active ET-1, thus reducing tissue ET-1 concentrations and associated atheroma formation.

METHODS AND RESULTS

Cholesterol-fed New Zealand White rabbits (n=8, 1% cholesterol diet) and NEP-I-treated cholesterol-fed New Zealand White rabbits (n=8; candoxatril, 30 mg/kg per day, Pfizer) were euthanized after 8 weeks of feeding. ECE-1alpha and ECE-1beta immunoreactivity was present in the aortas of both groups. Compared with control values, plasma cGMP concentrations were increased (2.8+/-0.6 versus 8.4+/-1.2 pmol/mL, P<0.05), ECE-1 activity was attenuated (68+/-3% versus 32+/-8%, P<0. 05), aortic tissue ET-1 concentrations were reduced (4.6+/-0.5 versus 3.2+/-0.3 pg/mg protein, P<0.05), and atheroma formation was attenuated (62+/-6% versus 34+/-5%, P<0.01) by NEP-I.

CONCLUSIONS

These studies suggest that ECE-1 is present and functionally active in the vascular wall in atherosclerosis. Inhibition of ECE-1 by NEP-I represents a novel approach to interruption of the endothelin system in this cardiovascular disease state.

Vascular actions of brain natriuretic peptide: modulation by atherosclerosis and neutral endopeptidase inhibition

OBJECTIVES

We sought to define the vascular actions of the cardiac hormone brain natriuretic peptide (BNP) on cellular proliferation and cyclic guanosine monophosphate (cGMP) in human aortic vascular smooth muscle cells (HAVSMCs). Secondly, we investigated BNP and acetylcholine (ACh) vasorelaxations in aortic rings from normal and atherosclerotic rabbits in the presence and absence of long-term oral inhibition of neutral endopeptidase (NEP).

BACKGROUND

The vascular actions of BNP are not well defined, despite the presence of its receptor in vascular smooth muscle and the upregulation of NEP, the ectoenzyme that degrades BNP, in the vascular wall in atherosclerosis.

METHODS

HAVSMCs stimulated with fetal calf serum (FCS) were pulsed with bromodeoxyuridine (BrdU) with and without BNP. The HAVSMCs were incubated in the presence and absence of BNP to assess cGMP. Vasorelaxations to BNP and ACh were assessed in rings in normal and atherosclerotic rabbits in the presence and absence of long-term oral inhibition of NEP, together with assessment of atheroma formation.

RESULTS

FCS-stimulated BrdU uptake in HAVSMCs was suppressed with BNP. BNP potentiated cGMP in HAVSMCs. BNP resulted in potent vasorelaxation in normal isolated aortic rings, which were impaired in atherosclerotic versus normal rabbits and preserved with NEP inhibition, which also decreased atheroma formation. Relaxations to ACh, which were also impaired in atherosclerosis, were preserved with inhibition of NEP.

CONCLUSIONS

We conclude that BNP potently inhibits vascular smooth muscle cell proliferation and potentiates the generation of cGMP. BNP potently relaxes the normal rabbit aorta, and this response is impaired in atherosclerosis but preserved with inhibition of NEP, together with a reduction in atheroma formation and preservation of relaxations to ACh.

Further attenuation of endothelium-dependent relaxation imparted by natriuretic peptide receptor antagonism

Nitric oxide (NO) is an important endothelium-derived relaxing factor that functions via activation of soluble guanylyl cyclase and cGMP generation in vascular smooth muscle. Recently, studies have described the synthesis and secretion of C-type natriuretic peptide (CNP) from endothelial cells. This peptide also mediates relaxation via cGMP but through activation of particulate guanylyl cyclase. We tested the hypothesis that endothelium-dependent relaxations to acetylcholine or bradykinin in isolated canine coronary arteries involve both releases of NO and CNP. Rings of canine coronary arteries were incubated with either inhibitors of NO production (N(G)-monomethyl-L-arginine, L-NMMA) or the natriuretic peptide receptor antagonist HS-142-1. CNP caused concentration-dependent relaxations of rings with and without endothelium. These relaxations were attenuated by HS-142-1. Relaxations to acetylcholine and bradykinin were attenuated by L-NMMA alone but not attenuated by HS-142-1 alone. Coinhibition with L-NMMA and HS-142-1 significantly inhibited acetylcholine- and bradykinin-induced relaxation to a magnitude greater than either inhibitor alone. In summary, a novel interaction between the NO and the natriuretic peptide system is demonstrated by increased attenuation of endothelium-dependent relaxations to acetylcholine and bradykinin when both NO synthase and natriuretic peptide receptors are inhibited. These investigations support the concept of release of multiple endothelium-derived factors in response to acetylcholine- and bradykinin-receptor stimulation in endothelial cells, which may include CNP, as well as NO.

Renal actions of synthetic dendroaspis natriuretic peptide

BACKGROUND

Dendroaspis natriuretic peptide (DNP), recently isolated from the venom of the green Mamba snake Dendroaspis angusticeps, is a 38 amino acid peptide containing a 17 amino acid disulfide ring structure similar to that of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP). DNP-like immunoreactivity (DNP-LI) was reported to be present in human plasma and atrial myocardium and to be elevated in human congestive heart failure. Although previously named DNP, it remains unknown if DNP is natriuretic or if is it present in canine plasma, urine, and atrial myocardium.

METHOD

Studies were performed in vivo in anesthetized dogs (N = 6) using intravenous infusion of synthetic DNP at 10 and 50 ng/kg/min. Employing a sensitive and specific radioimmunoassay for DNP, the presence of DNP-like peptide was assessed in the canine plasma and urine before, during, and following the administration of exogenous synthetic DNP. Additionally, we performed immunohistochemical studies using the indirect immunoperoxidase method with polyclonal DNP antiserum in normal atrial myocardium (N = 10). Atrial concentrations of DNP-LI were also assessed.

RESULTS

We report that DNP is markedly natriuretic and diuretic, which, like ANP and BNP, is associated with the increase in urinary and plasma cGMP. DNP-like peptide is also detected in canine plasma, urine, and atrial myocardium.

CONCLUSION

These studies establish that DNP is a potent natriuretic and diuretic peptide with tubular actions linked to cGMP and that DNP may play a physiological role in the regulation of sodium excretion.

Presence of Dendroaspis natriuretic peptide-like immunoreactivity in human plasma and its increase during human heart failure

OBJECTIVE

To determine whether Dendroaspis natriuretic peptide (DNP), a novel peptide isolated from the venom of the Dendroaspis angusticeps snake that contains a 17-amino acid disulfide ring structure similar to that in atrial, brain, and C-type natriuretic peptides, is present in normal human plasma and myocardium and whether, like the other natriuretic peptides, DNP-like immunoreactivity (DNP-LI) is activated in human congestive heart failure (CHF).

MATERIAL AND METHODS

Circulating DNP-LI was assessed in 19 normal human subjects and 19 patients with CHF (New York Heart Association class III or IV) with a specific and sensitive radioimmunoassay for DNP with no cross-reactivity with the other natriuretic peptides. Immunohistochemical studies that used polyclonal rabbit anti-DNP antiserum were performed on human atrial myocardial tissue obtained from four patients with end-stage CHF who were undergoing cardiac transplantation and from three donor hearts at the time of transplantation.

RESULTS

We report that DNP-LI circulates in normal human plasma and is present in the normal atrial myocardium. In addition, DNP-LI is increased in the plasma of patients with CHF.

CONCLUSION

This study demonstrates, for the first time, the presence of a DNP-like peptide in normal human plasma and in the atrial myocardium. Additionally, these studies demonstrate increased plasma DNP-LI in human CHF. These results support the possible existence of an additional new natriuretic peptide in humans, which may have a role in the neurohumoral activation that characterizes human CHF.

Effects of aging per se on arterial stiffness: systemic and regional compliance in beagles

Although previous studies have suggested that aging results in an increase in vascular stiffness, diseases that increase in prevalence with advanced age may have confounded the results of some of this past research. The purpose of this investigation was to determine whether aging per se results in reduced arterial compliance by using animals that are resistant to atherosclerosis and do not develop hypertension or hyperlipidemias with advanced age. We evaluated systemic and regional (femoral) arterial compliance in older (110 +/- 8 months old) and in younger (27 +/- 2 months old) female beagle dogs by using a computer-based assessment of the diastolic decay of arterial pressure waveforms and a modified Windkessel model of the circulation. Although systemic arterial pressure was very similar in both age groups, cardiac output was 29% lower (p = 0.03) and systemic vascular resistance was 24% higher (p = 0.02) in the older dogs. Moreover, there was an age-related reduction in systemic arterial compliance, derived both from the exponential decay in the arterial pulse (C1) (p = 0.05) and that derived from the oscillatory component of the diastolic pulse wave (C2) (p = 0.04). By contrast, although femoral vascular resistance was 25% higher in the older dogs (p = 0.04), regional (femoral) vascular compliance measured after femoral arterial occlusion was also 25% reduced but was not significantly changed with age (p = 0.14). These results demonstrate that systemic arterial compliance is reduced with age in dogs, extending this finding to animals without age-related diseases that frequently occur in older human beings. Regional compliance, evaluated in the isolated femoral vascular bed, also tends to be reduced with age, but variability in this parameter in dogs reduces the significance of this finding.

Role for the endogenous natriuretic peptide system in the control of basal coronary vascular tone in dogs

1. While the natriuretic peptides (atrial, brain and C-type) mediate potent endothelium-independent vasorelaxing actions in vitro, the role of the endogenous natriuretic peptide system in vascular regulation in vivo remains unclear. 2. HS-142-1 is a novel natriuretic peptide receptor antagonist derived from a fungus named Aureobasidium sp. which selectively blocks particulate guanylate cyclase-linked natriuretic peptide A and B receptors that bind atrial, brain and C-type natriuretic peptide, and thus attenuates the generation of cGMP. 3. To characterize the vascular actions of the endogenous natriuretic peptide system in the control of basal coronary and systemic haemodynamics, six normal male mongrel anaesthetized dogs were studied while a second group of five dogs served as a control. HS-142-1 was given as an intravenous bolus at 3 mg/kg and was studied over five 20 min periods. 4. No significant difference after HS-142-1 was observed in mean arterial pressure, heart rate, cardiac output, right atrial pressure, pulmonary capillary wedge pressure or systemic vascular resistance compared with control. In contrast, a significant increase in coronary vascular resistance and decrease in coronary blood flow were observed which were different from the baseline values and the responses of the control group. 5. These studies demonstrate that HS-142-1 produces vasoconstriction in the coronary circulation. We conclude that the endogenous natriuretic peptide system, which is of cardiac and endothelial cell origin, is an important regulator of basal coronary vascular tone.

Aging and vasoreactivity: in vivo responses in the beagle hindlimb

The purpose of this investigation was to determine whether vasodilator responses are attenuated and whether vasoconstriction is augmented with age in resistance vessels in the hindlimb of the dog. We examined blood flow (FAF) and pressure (FAP) responses in the femoral arterial system in older (109 +/- 8-mo-old) and younger mature (31 +/- 3-mo-old) female beagles during pentobarbital anesthesia. Vasodilator responses were evaluated during the intra-arterial administration of acetylcholine (ACh), which produces endothelium-dependent vasodilation, and albuterol, which mediates relaxation in vascular smooth muscle via beta-adrenoceptors. The vasoconstrictor response to phenylephrine (PE), an alpha-adrenergic agonist, was also examined. ACh and albuterol each induced dose-dependent vasodilation in the older and in the younger dogs. Resultant changes in neither FAF nor FAP were affected by age in response to either of these vasodilator substances. Likewise, reductions in femoral vascular resistance (FVR) in response to ACh or to albuterol were not age dependent. Vasodilation following induced hindlimb ischemia resulted in similar increases in FAF in both groups, but produced a greater reduction in FAP in older vs. younger dogs (P = 0.05). Similarly, FVR decreased more in the older beagles (P = 0.02). Vasoconstriction mediated by PE resulted in similar reductions in FAF in both age groups, but the increase in FAP was less at several PE doses in older vs. younger dogs (P < 0.05). However, increases in FVR in response to PE were not statistically different in the younger and older beagles.(ABSTRACT TRUNCATED AT 250 WORDS)