Intraoperative Bypass Graft Flow Measurement With Transit Time Flowmetry: A Clinical Assessment.

BACKGROUND: Guidelines advocate transit time flowmetry (TTFM) for intraoperative graft patency verification during coronary artery bypass graft surgery (CABG), but studies on accuracy and precision of the TTFM technique are few. In an observational study of CABG patients, we analyzed covariation of left internal mammary artery (LIMA) blood flow with TTFM and free flow measurements. METHODS: Covariation of TTFM and free blood flows was evaluated in 60 patients undergoing CABG using the LIMA as one of the conduits. With LIMA flow measurements routinely performed before and after vasodilation, results are based on 120 paired intraoperative measurements. RESULTS: As demonstrated by a combined approach of regression and Bland-Altman analysis for the two flow situations, TTFM was higher than free flow in 64% of measurements, with an overestimation by TTFM of 7.1% ± 16.3% in the overall cohort (prevasodilation), statistically carried by measurements with 4-mm probes (overestimation by 13.3% ± 15.4%, both p < 0.01). In a multiregression analysis, oversizing of the TTFM probe (odds ratio 9.56, 95% confidence interval: 2.03 to 45.10, p = 0.004) and high flows (odds ratio 1.02, 95% confidence interval: 1.01 to 1.04, p < 0.001) were independent determinants of flow overestimation by TTFM, although in the Bland-Altman analysis no systematic overestimation was seen in the postvasodilation situation. In a receiver-operating characteristics analysis, optimal cutoff value as determined from Youden's index for assuming flow overestimation was 68 mL/min. CONCLUSIONS: Overall, with slight overall overestimation of 7.1%, TTFM is an accurate indicator of LIMA blood flow during CABG, with a clinically acceptable precision. Overestimation may be expected with flows greater than 68 mL/min, but most importantly, in situations with oversized TTFM probes.

Race and Sex Disparities in Outcomes of Dialysis Access Maintenance Interventions.

PURPOSE: To determine whether utilization and outcomes of dialysis access maintenance interventions vary by patient race or sex. MATERIALS AND METHODS: Data for this retrospective cohort study of first-time arteriovenous (AV) access recipients were drawn from a 5% sample of Medicare beneficiaries, containing claims from all clinical settings (2009-2014) in 2,693 patients who received their first AV fistula/graft in 2009. Maintenance interventions-angiography, angioplasty, thrombolysis, stent placement, and venous embolization-were identified by corresponding Current Procedural Terminology codes. Outcomes of primary patency (PP), postinterventional primary patency (PIPP), and postinterventional secondary patency (PISP) were calculated with utilization records. Associations between demographic data and patency times were evaluated by a multivariate survival approach, controlling for baseline differences in patient age, comorbid disease, type of dialysis access, and interventionist specialty. RESULTS: AV grafts (AVGs) were created with greater frequency in women (32% vs 23% in men; P < .001) and minority patients (39% in black, 32% in Hispanic, and 29% in Asian patients vs 21% in white patients; P < .001). Women were at greater hazards for loss of PP (hazard ratio [HR], 1.49; 95% confidence interval [CI], 1.09-2.14) and PIPP (HR, 1.42; 95% CI, 1.01-2.00). Black patients were at greater hazards for loss of PP (HR, 1.37; 95% CI, 1.23-1.54) and PISP (HR, 1.29; 95% CI, 1.01-1.65). AVG creation predisposed patients to patency loss in all models (P < .001). CONCLUSIONS: Dialysis access patency rates are lower for women and black patients. More frequent primary AVG creation in women and minority patients additionally predisposes these patients to patency loss.

Adding access blood flow surveillance reduces thrombosis and improves arteriovenous fistula patency: a randomized controlled trial.

PURPOSE: Stenosis is the main cause of arteriovenous fistula (AVF) failure. It is still unclear whether surveillance based on vascular access blood flow (QA) enhances AVF function and longevity. METHODS: We conducted a three-year follow-up randomized, controlled, multicenter, open-label trial to compare QA-based surveillance and pre-emptive repair of subclinical stenosis with standard monitoring/surveillance techniques in prevalent mature AVFs. AVFs were randomized to either the control group (surveillance based on classic alarm criteria; n = 104) or to the QA group (QA measured quarterly using Doppler ultrasound [M-Turbo®] and ultrasound dilution [Transonic®] added to classic surveillance; n = 103).The criteria for intervention in the QA group were: 25% reduction in QA, QA<500 mL/min or significant stenosis with hemodynamic repercussion (peak systolic velocity [PSV] more than 400 cm/sc or PSV pre-stenosis/stenosis higher than 3). RESULTS: At the end of follow-up we observed a significant reduction in the thrombosis rate in the QA group (0.025 thrombosis/patient/year in the QA group vs. 0.086 thrombosis/patient/year in the control group [p = 0.007]). There was a significant improvement in the thrombosis-free patency rate (HR, 0.30; 95% CI, 0.11-0.82; p = 0.011) and in the secondary patency rate in the QA group (HR, 0.49; 95% CI, 0.26-0.93; p = 0.030), with no differences in the primary patency rate between the groups (HR, 0.98; 95% CI, 0.57-1.61; p = 0.935).There was greater need for a central venous catheter and more hospitalizations associated with vascular access in the control group (p = 0.034/p = 0.029).Total vascular access-related costs were higher in the control group (€227.194 vs. €133.807; p = 0.029). CONCLUSIONS: QA-based surveillance combining Doppler ultrasound and ultrasound dilution reduces the frequency of thrombosis, is cost effective, and improves thrombosis free and secondary patency in autologous AVF.

Quantitative assessment technique of HyperEye medical system angiography for coronary artery bypass grafting.

PURPOSE: The HyperEye Medical System (HEMS) uses indocyanine green (ICG) to visualize blood vessels in coronary artery bypass grafting (CABG). We performed quantitative HEMS assessment to detect grafts at risk of occlusion. METHODS: We assessed the HEMS angiograms of 177 grafts from 69 patients who underwent CABG and compared the results with those of fluoroscopic coronary angiography, by measuring the increasing rate of ICG intensity, average acceleration value, and time to peak luminance intensity. RESULTS: Grafts in the patent and failed groups showed significant differences in their increasing rate of intensity and average acceleration value. The average accelerations value of ICG intensity of internal thoracic artery (ITA) and saphenous vein (SV) grafts were 112.3 and 144.9 intensity/s2 in the patent group, and 71.0 and 91.8 intensity/s2 in the failed group. The time to peak luminance intensity was 1.7 and 1.4 s in the patent group and 2.3 and 1.9 s in the failed group; these values were not significantly different. CONCLUSION: Significant reductions in the ICG intensity rate and average acceleration value can occur in failed grafts. Therefore, quantifiable changes in ICG intensity may help detect minute changes in blood flow.

Novel modular anastomotic valve device for hemodialysis vascular access: preliminary computational hemodynamic assessment.

PURPOSE: Arteriovenous graft patency is limited by terminal occlusion caused by intimal hyperplasia (IH). Motivated by evidence that flow disturbances promote IH progression, a modular anastomotic valve device (MAVD) was designed to isolate the graft from the circulation between dialysis periods (closed position) and enable vascular access during dialysis (open position). The objective of this study was to perform a preliminary computational assessment of the device ability to normalize venous flow between dialysis periods and potentially limit IH development and thrombogenesis. METHODS: Computational fluid dynamics simulations were performed to compare flow and wall shear stress (WSS) in a native vein and MAVD prototypes featuring anastomotic angles of 90° and 30°. Low WSS (LWSS) regions prone to IH development were characterized in terms of temporal shear magnitude (TSM), oscillatory shear index (OSI), and relative residence time (RRT). Thrombogenic potential was assessed by investigating the loading history of fluid particles traveling through the device. RESULTS: The closed MAVD exhibited the same flow characteristics as the native vein (0.3% difference in pressure drop, 3.5% difference in surface-averaged WSS). The open MAVD generated five LWSS regions (TSM <0.5 Pa) exhibiting different degrees of flow reversal (surface-averaged OSI: 0.03-0.36) and stagnation (max RRT: 2.50-37.16). Reduction in anastomotic angle resulted in the suppression of three LWSS regions and overall reductions in flow reversal (surface-averaged OSI <0.21) and stagnation (max RRT <18.05). CONCLUSIONS: This study suggests the ability of the MAVD to normalize venous flow between dialysis periods while generating the typical hemodynamics of end-to-side vein-graft anastomoses during dialysis.

Examining Hemodialysis Reliable Outflow catheter performance and cost in hemodialysis access.

BACKGROUND: The Hemodialysis Reliable Outflow (HeRO) vascular access device is a hybrid polytetrafluoroethylene graft-stent construct designed to address central venous occlusive disease. Although initial experience has demonstrated excellent mid-term patency rates, subsequent studies have led to external validity questions. The purpose of this study was to examine a single center experience with this vascular access device in challenging access cases with associated costs. METHODS: A retrospective study representing the authors' cumulative HeRO vascular access device experience was undertaken. The primary endpoint was graft failure or death, with secondary endpoints including secondary intervention rates and cost. RESULTS: Forty-one patients with 15,579 HeRO days and a mean of 12.7 ± 1.5 mo with the vascular access device were available for analysis. Secondary patency was 81.6% at 6 mo and 53.7% at 12 mo. The reintervention rate was 2.84 procedures per HeRO vascular access device year. Associated HeRO costs related to subsequent procedures were estimated at $34,713.63 per patient/y. CONCLUSIONS: These data on the patency and primary outcome data diverge significantly from initial multicenter studies and represent a real-world application of this technology. It is costly to maintain patency. Use of HeRO vascular access devices should be judicious with outcome expectations reduced.

Cost-effectiveness of antiplatelet therapy to prolong primary patency of hemodialysis graft.

INTRODUCTION: The Dialysis Access Consortium (DAC) study group previously reported that treatment with extended-release dipyridamole plus aspirin (DASA) resulted in a significant but clinically modest improvement in primary unassisted arteriovenous graft (AVG) patency. Utilizing DAC published data, the objective of this study is to evaluate the cost effectiveness of antiplatelet interventions aimed at preventing loss of primary AVG patency in hemodialysis (HD) patients. METHODS: We performed a cost-utility analysis, using a decision analysis tree model with a 12-month time horizon and a third party payer perspective. Interventions included DASA with and without concurrent aspirin, aspirin alone, and no prophylaxis. The modeled population was defined as adult (≥ 18 years of age) end-stage renal disease (ESRD) patients who had undergone placement of a new AVG in the United States. The outcomes were costs, quality-adjusted life-years (QALY), incremental cost-effectiveness ratios, and net monetary benefit. Probabilities were based upon published studies performed by the DAC Study Group while costs of medications and procedures were drawn from public sources. Utilities of health states were derived from published reports and the Short Form 6D (SF-6D) instrument. RESULTS: Aspirin alone is the most cost effective strategy for AVG pharmacologic prophylaxis, as compared to no prophylaxis or DASA with or without concurrent aspirin. The results are robust on multiple scenario analyses using both deterministic and Monte Carlo probabilistic sensitivity analyses. Accounting for both costs and QALY, using aspirin alone to prevent AVG thrombosis can potentially reduce healthcare costs by $24,679,412 per year compared to no aspirin use, at a willingness-to-pay of $50,000/ QALY. CONCLUSIONS: Aspirin monotherapy compared favorably to other strategies based on cost per QALY. Our findings support the use of aspirin prophylaxis in HD patients with a new AVG who do not have a contraindication to aspirin.

Evaluation of a policy of selective drug-eluting stent implantation for patients at high risk of restenosis.

Drug-eluting stent (DES) deployment during percutaneous coronary intervention (PCI) has reduced target-vessel revascularisation rates (TVR). The selective use of DES in patients at highest risk of restenosis may allay concerns about universal compliance of dual antiplatelet therapy for one year, and potentially reduce costs. If this strategy achieved acceptably low TVR rates, such an approach could be attractive. Late clinical outcomes were examined in 2115 consecutive patients (mean age 63±12 years, 75% male, 22% diabetics) who underwent PCI in the first three years from October 2003, after commencing the following selective criteria for DES use: left main stenosis; ostial lesions of major epicardial arteries; proximal LAD lesions; lesions≥20mm in length with vessel diameter≤3.0mm; lesions in vessels≤2.5mm; diabetics with vessel(s)≤3.0mm; and in-stent restenosis. Among patients undergoing PCI, 2075 (98%) patients received stents (29%≥1 DES and 71% bare metal stent [BMS]), and among those who received DES, there was a 92% compliance with these criteria. There were no differences in clinical outcomes between the two stent groups except for definite stent thrombosis, which occurred in 2% after DES, and 0.6% after BMS at one year (p=0.002). With BMS, large coronary arteries (≥3.5mm), intermediate (3-3.49mm) and small arteries (<3mm) in diameter had a TVR rate at one year of 3.6%, 7.2% and 8.2% respectively (p=0.005). It is possible to use selective criteria for DES while maintaining low TVR rates. The TVR rate with BMS was low in those with stent diameters≥3.5mm. The higher DES stent thrombosis rate reflects first generation DES use, though whether routine second generation DES use reduces these rates needs confirmation.

[Noninvasive assessment of functional competence of the radial artery as a possible vascular graft for coronary artery bypass grafting].

Described herein is a variant of surgical treatment of a patient presenting with type A aortic dissection extending to the brachiocephalic branches accompanied by thrombosis of the false channel of the latter. In the rare cases in dissection and thrombosis of the brachiocephalic branches for adequate protection of the body (systemic protection) it is necessary to use bidirectional arterial perfusion under the conditions of moderate hyperthermia: through a preliminarily sewn into the carotid artery prosthesis - perfusion of the brain, through cannulated aortic arch or femoral artery - body perfusion.

Assessment of platelet function by whole blood impedance aggregometry in coronary artery bypass grafting patients on acetylsalicylic acid treatment may prompt a switch to dual antiplatelet therapy.

Residual platelet reactivity (RPR) following coronary artery bypass grafting (CABG) might be related to thrombotic complications and major ischemic cardiac events. The aim of this study was to evaluate the changes in platelet reactivity monitored pre- and postoperatively using multiple-electrode aggregometry (MEA) and to propose an alternative therapeutic approach in a subgroup of patients with postoperative RPR. Ninety-nine patients undergoing elective CABG were enrolled in the study, of whom 41 (41.4%) were diabetic. Preoperatively, all patients received 100 mg acetylsalicylic acid (ASA), with 47 of 99 (47.4%) patients receiving an additional 75 mg clopidogrel (CLO). The blood samples were drawn the day before surgery, and on the first and 4th postoperative day. Platelet count and fibrinogen level were documented, as well as type and daily dose of antiplatelet therapy (APT) received pre- and postoperatively. Multiple-electrode aggregometry using tests based on arachidonic acid (ASPI test) and adenosine diphosphate (ADP test) was performed on the day before and 4 days after surgery. Preoperatively, we detected 31 of 99 (31.3%) patients with RPR (ASPI > 30 AUC). Platelet count correlated with both the ASPI (P = 0.03) and ADP (0.002) tests. Fibrinogen correlated with ADP test values (P < 0.001) and was found to have a higher level in the diabetic subgroup (P = 0.01). In comparison with preoperative results, we detected higher values of ASPI test postoperatively (P = 0.04), with 46 of 99 (46.5%) patients having RPR despite a higher dose of 300 mg ASA being administered. Postoperatively, diabetic patients had higher ASPI test values (P = 0.01), and a higher proportion of patients with RPR compared with the nondiabetic subgroup (58.5 vs 38%, P = 0.04). The subgroup of patients with detected ASPI >30 AUC at the 4th postoperative day consequently received as a part of our clinical routine an additional 75 mg CLO per day, in terms of platelet inhibition optimization. Multiple-electrode aggregometry can recognize patients with RPR during both the pre- and post-CABG period. Postoperatively administered ASA (300 mg) did not sufficiently inhibit platelet aggregation in 46.5% of post-CABG patients. In this group of patients a switch to dual APT should be considered.

Targeted duplex ultrasound in a one-stop dialysis vascular access assessment clinic.

BACKGROUND: Many duplex detectable factors have been shown to correlate with upper limb arteriovenous fistula (AVF) outcomes, and many practitioners now request preoperative duplex vessel mapping routinely before AVF surgery. We report outcomes from a "one stop" AVF assessment clinic in which the operating surgeons perform their own targeted preoperative ultrasound examinations. METHODS: All patients undergoing assessment for formation of a new AVF were included in this prospective observational study. A plan was made for surgery based on the results of the physical examination performed by the surgeon and then reviewed in light of the findings from a targeted duplex ultrasound (DUS) that was performed by the surgeon in the clinic on portable ultrasound equipment. Ultimate choice of surgical site and the influence of the DUS were recorded along with postoperative outcomes. RESULTS: In all, 39 patients were included. Four (10%) of the patients received a more distal AVF and eight (20%) were converted to more proximal AVF because of unexpected adverse findings after targeted DUS. In one patient, no site could be confidently selected by physical examination alone. There was a 13% early failure rate with cumulative patency rates of 86% and 73% at 3 and 6 months, respectively. CONCLUSION: Targeted DUS identified findings that might adversely affect fistula function in one of four patients in this series, whereas one in 10 patients was able to have more distal fistulae formed because of improved confidence in the quality of distal vessels. Early failure and patency rates are comparable with those in units using formal routine ultrasound. These results would suggest that routine targeted DUS, performed quickly by surgeons in an outpatient clinic, can alter surgical planning in one of the three patients and is therefore advocated as a quick, relatively inexpensive and important adjunct to AVF planning.

[Clinical-pharmacoeconomical aspects of ß-adrenoblockers use in patients with ischemic heart disease undergoing coronary artery bypass grafting].

Aim of this study was to assess clinical and pharmacoeconomic effects of long term use of adrenoblockers in patients with ischemic heart disease (IHD) undergoing coronary artery bypass grafting. Patients with IHD (n=294) were included in open, prospective, randomized clinical trial. The follow up period was 3 years. It was noted that long term use of bisoprolol in comparison with atenolol and metoprolol was characterized by more pronounced increase of exercise tolerance, lower rate of angina recurrence and lower expenses for treatment of patients with IHD.

In vivo assessment of the effects of ginsenoside Rb1 on intimal hyperplasia in ApoE knockout mice.

OBJECTIVE: This study investigated the effects of ginsenoside Rb1 (Rb1) on injury-induced intimal hyperplasia in ApoE knock out (ApoE -/-) mice. We also examined the value of an ultrasound micro-image system in dynamic monitoring of lumen diameter and flow velocity. METHODS: After guide wire injury of the distal left common carotid artery (CCA), ApoE-/- mice were treated with intraperitoneal infusion of normal saline (NS), homocysteine (Hcy), ginsenoside Rb1 (Rb1), or Hcy+Rb1 for 4 wk. Bilateral CCA luminal diameters and flow velocities were measured with an ultrasound micro-image system before surgery and weekly afterwards. Following the final ultrasound, CCAs were harvested and analyzed for intima-medium thickness ratios. RESULTS: Progressive reduction in luminal diameters and increase in flow velocity of the injured left distal CCA segment were observed using ultrasound micro-imaging system in all groups compared with the relatively stable left proximal CCA and right CCA. The NS and Hcy groups had significantly higher degree of diameter reduction compared with the Rb1 and Rb1+Hcy groups. The ultrasound findings were consistent with histology analyses at 4 wk post-op. CONCLUSIONS: The study suggested that Rb1 attenuated the effects of Hcy on injured carotid arteries of ApoE -/- mice. The study also showed that ultrasound micro-image system was a reliable tool in monitoring luminal reduction after injury in a murine model. This study establishes a fundamental step of in vivo monitoring of the therapeutic effects of agents in a murine model without sacrificing the animals.

Economic analysis of angiography and preemptive angioplasty to prevent hemodialysis-access thrombosis.

OBJECTIVES: We sought to determine the economic value of early angiography and prophylactic angioplasty to prevent hemodialysis-access thrombosis. BACKGROUND: End stage renal disease consumes more than 6% of the Medicare budget. There is a need to understand the financial impact of each component of care. METHODS: We conducted an observational economic analysis of a closed cohort of 818 hemodialysis patients, of whom 560 were referred for 1437 consecutive radiographic procedures during an 8-year period. Patient-level, bottom-up microcosting methods provided supply and personnel costs before and after expansion of an angiographic referral program. RESULTS: The rate of referral for malfunctioning but nonthrombosed hemodialysis accesses increased from 18.8 +/- 8.8 to 48.3 +/- 11.9 angiographic procedures per 100 patient-years (P < 0.001), which was associated with a decline in access thrombosis from 27.6 to 22.0 events per 100 patient-years (P = 0.029) and a net cost of $34,586 per 100 patient-years. The incremental cost-effectiveness ratio for invasive surveillance was $6,177 per thrombosis event avoided. The angiographic program expanded at the same time that the proportion of autogenous fistulas increased from 28.3% +/- 11.3% to 59.7% +/- 10.7% of total referrals (P = 0.0001). On multivariable logistic regression analysis, the expanded angiography program (P = 0.001) and the proportion of autogenous fistulas (P = 0.0001) were both independently associated with the reduction in access thrombosis. CONCLUSIONS: Given the incremental costs and the relatively modest benefits in preventing access thrombosis, preemptive angiographic management may represent a less efficient use of healthcare resources than increasing the number of patients with autogenous fistulas. (c) 2009 Wiley-Liss, Inc.

Management of platelet-directed pharmacotherapy in patients with atherosclerotic coronary artery disease undergoing elective endoscopic gastrointestinal procedures.

The periprocedural management of patients with atherosclerotic coronary heart disease, including those who have heart disease and those who are undergoing percutaneous coronary intervention and stent placement who might require temporary interruption of platelet-directed pharmacotherapy for the purpose of an elective endoscopic gastrointestinal procedure, is a common clinical scenario in daily practice. Herein, we summarize the available information that can be employed for making management decisions and provide general guidance for risk assessment.

[Assessment of the course of ischemic heart disease after placement of stents with drug covering and uncovered metal stents: data of 3 years follow-up].

The placement of sirolimus-eluting stents decreases the frequency of repeat revascularization procedures in patients undergoing percutaneous coronary intervention (PCI) in randomized clinical trials. However, there is uncertainty about the effectiveness of sirolimus-eluting stents, and increasing concern about their safety in routine clinical practice. From the prof. Samko PCI laboratory in Moscow, Russia, we identified 426 patients, who received either bare-metal stents alone or sirolimus-eluting stents alone during an index PCI procedure between March 1, 2002, and September 31, 2004.The primary outcomes of the study were the rates of target-lesion revascularization, myocardial infarction, death, late stent thrombosis. The 3-year rate of target-lesion revascularization was significantly lower among patients who received sirolimus-eluting stents than among those who received bare-metal stents (3.1% vs. 19 %, p=0.001). The 3-year mortality rate was not different between the bare-metal stent group and the sirolimus eluting stent group (5.9% vs. 7.2%, p=0.68), the 3-year rate of all ARC late stent thrombosis was similar in the two groups (5.9% and 7.2%, respectively; p=0.95). Sirolimus-eluting stents are effective in reducing the need for target-vessel revascularization without significantly increased rates of death, late stent thrombosis, myocardial infarction.

Intraoperative coronary graft assessment.

PURPOSE OF REVIEW: Intraoperative graft assessment in coronary artery bypass grafting is infrequently performed. Nevertheless, studies show an immediate graft closure rate of 5-9% and a 1-year closure rate of 20-30%. RECENT FINDINGS: Coronary angiography is the 'gold standard' for graft assessment yet has been seldom employed because of logistical problems and image quality. Two methods, transit time flow measurement and intraoperative fluorescence imaging are simple, safe, and expeditious. Intraoperative graft failure detection rates of 2-5% have been reported. SUMMARY: Early graft occlusion occurs frequently after coronary artery bypass grafting. Two relatively simple but underutilized methods of intraoperative graft assessment have been shown to be predictive of graft failure. Wider use of these techniques as well as wider availability of hybrid operating rooms, which will allow intraoperative coronary angiography, may reduce graft failure.

Embolic protection: the FilterWire EZ Embolic Protection System.

The field of interventional cardiology has grown dramatically over the past 30 years, including recent advances in the area of peripheral vascular intervention. The phenomenon of no-reflow, characterized by a reduction in coronary blood flow during vascular intervention, has been associated with adverse outcomes in both saphenous vein graft and carotid artery interventions. Distal embolic protection devices, such as the FilterWire EZ System, have been shown to reduce the incidence of no-reflow and adverse cardiac events in patients undergoing saphenous vein graft interventions. Recently approved indications for the FilterWire EZ System include carotid artery stenting. With the definite reduction in adverse events from the use of distal protection, future advancements will focus on improved deliverability of such devices.