Spanish Randomized Controlled Trial Demonstrates that Surveillance Methods Prevent Thrombosis and Increase Assisted Patency Rate in Native Arteriovenous Fistulas
An abstract presented at the recent Congress of Vascular Access Society in Barcelona, Spain corroborated evidence found by others that surveillance methods do prevent thrombosis and increase assisted patency in arteriovenous fistulas. The investigators at eight Madrid hospitals used two complementary second generation surveillance methods, Doppler Ultrasound (DU) and Ultrasound Dilution (UDM) to assess native arteriovenous fistulas.
Over three years, 105 hemodialysis patients were monitored in the experimental group; 104 hemodialysis patients were monitored in a control group. DU and UDM were performed in the experimental group every three months. When flow was ≤ 500 ml/min, there was a 25% decrease in QA (access blood flow), or a hemodynamically significant stenosis was found, the patient was referred for fistulography, surgery or close clinical surveillance observation. Thrombosis rate, assisted primary patency rate, primary patency rate and secondary patency rate were measured in all patients.
The study reported a significant reduction in thrombosis rate after two years in the group with surveillance (0.027 thrombosis/patient/year versus control group 0.081 thrombosis/patient/year). The assisted primary patency was higher in the QA group, but there was no significant difference in the non-assisted primary patency rates between the two groups. The study also demonstrated a non significant improvement in the secondary patency rate in the experimental group.
The team of fifteen clinicians that participated in the study concluded that surveillance with Doppler ultrasound and indicator dilution QA prevents thrombosis and increases assisted primary patency rates in arteriovenous fistulas.
Aragoncilla I et al, "Second Generation Surveillance Methods Prevent Thrombosis and Increase Assisted Patency Rate in Native Arteriovenous Fistulae. A Randomized Clinical Trial," J Vasc Access Abstracts 15:20 9th Congress of Vascular Access Society, 15-18 April 2015 Barcelona Spain (Transonic Reference # HD10276A)
Tessitore N et al, "Adding access blood flow surveillance to clinical monitoring reduces thrombosis rates and costs, and improves fistula patency in the short term: a controlled cohort study," Nephrol Dial Transplant. 2008 Nov;23(11):3578-84. (Transonic Reference # 7639A)
Studies Spotlight Need for Clot Prediction Capability during Extracorporeal Life Support
The ELSA Monitor provides quantitative assessment of oxygenator clotting and thereby predicts increased thrombotic risk to the patient, and diminished oxygenator performance.
Bleeding and thrombosis remain the primary complications of extracorporeal life support (ELS) and are the most frequent causes of death and morbidity. In a 2015 study, bleeding and thrombosis was analyzed from 2,036 ELS patients less than 19 years old from eight tertiary centers. In patients without a diaphragmatic hernia (87%), survival was reduced by 33% if a thrombosis developed from clots in the circuit, the oxygenator, or from hemolysis. The study underscores the critical value of Transonic's ELSA Monitor's oxygenator blood volume measurement capability to help detect clots developing in the oxygenator.
A study from George Washington Medical School "Precision and Accuracy of the New Transonic ELSA Monitor to Quantify Oxygenator Blood Volume (in-vivo and in-vitro studies)" just presented at the 2015 PAS Annual meeting verifies the ELSA's capability to detect the formation of clots in the ELS circuit by trending oxygenator blood volumes with the monitor. It concluded that the ELSA Monitor demonstrated high precision in measuring decrease in oxygenator volume in the ECMO circuit using the injection of a small volume of saline and the ELSA monitor would be a valuable tool to identify early clot formation in ECMO circuits and allow device change outs before they become clinically emergent.
Said MM, Mikesell GT, Rivera O, Khodayar Rais-Bahrami K, "Precision and Accuracy of the New Transonic ELSA Monitor to Quantify Oxygenator Blood Volume (in-vivo and in-vitro studies)," 2015 PAS Annual Meeting and Eastern SPR Annual Meeting. (Transonic Reference # ELS10230V)
Said MM, Mikesell GT, Rivera O, Khodayar Rais-Bahrami K, "Influence of central hemodynamics and dual-lumen catheter positioning on recirculation in neonatal veno-venous ECMO," 2015 PAS Annual Meeting and Eastern SPR Annual Meeting. (Transonic Reference # ELS10231V)
Sick Kids’ Surgeons Find Aortic Blood Flow Measurements Predict Pulmonary Artery Banding Outcomes
Surgeons at Toronto’s Sick Kids hospital reviewed 12 children who underwent Pulmonary Artery Banding (PAB) to evaluate the clinical utility of intraoperative aortic blood flow measurements on clinical outcome. PAB is used to restrict pulmonary flow in order to provide adequate systemic flow in children who face surgery to correct a congenital defect. Increasing aortic flow allows the child to grow and be a safer candidate for follow-up surgery.
Baseline aortic and PA flow measurements were performed directly with an 8- or 10 - mm Transonic Flowprobe. After banding, a repeat aortic flow measurement was made. Aortic flow, intraoperative hemodynamics, and clinical outcomes were analyzed to determine the potential predictive utility of intraoperative variables on postoperative outcomes. The group found that aortic flow increased after PAB and the efficacy of the PAB procedure was found to be directly related to the percentage increase in aortic blood flow measured intraoperatively.
The change in the aortic blood flow was identified as a new, physiologically based parameter to help predict PAB outcome.
- An increase in aortic blood flow of less than 20% may foreshadow PAB failure.
- An increase in aortic blood flow of more than 40% indicated good outcomes despite relatively loose PAB.
Kotani Y, Coles M, D Desai N, Honjo O, Caldarone CA, Coles JG, Van Arsdell GS, "The Utility of Aortic Blood Flow Measurements in the Prediction of Pulmonary Artery Banding Outcome," Ann Thorac Surg. 2015 Apr 15. (Transonic Reference: 10278AH)
Transonic True Flow Showcased in Forbes HeartAssist5 Article
A February Forbes Magazine article entitled “An Engineering Feat Gives Hearts Extra Life” by contributor Nicole Fisher heralds Transonic’s implantable Flowprobe in the HeartAssist5 as a “one-of-a-kind technology” that provides data that makes remote monitoring of the LVAD patient so valuable. The author writes, “With the release of their new HeartAssist5 heart pump, ReliantHeart is making real-time, personalized feedback possible for the millions of Americans suffering from heart failure. The new technology allows for real-time, remote monitoring of implantable devices, years of added life for patients, and flexibility to travel without a physician nearby.” The implantable Transonic Flowprobe is called a revolutionary aspect of the HeartAssist5. Reliant Heart’s CEO Roger Ford says this ability to see patient-specific trends remotely in real time not only helps all patients improve quality of life, but the longevity of the HeartAssist5 creates a life support system, far beyond the “bridge” that the LVAD was originally created to be.
The article also cites a recent study where researchers found that platelets flowing through the HeartAssist5 are exposed to significantly lower cumulative shear stress levels than in competitive devices tested. Ultimately, this means that the ReliantHeart product allows for what the CEO calls “a more physiologically normal cardiac output, including the pulse.” Already approved to market in Europe for patients awaiting a heart transplant and as a destination therapy for patients who are not candidates for cardiac transplantation, the Heart Assist5 was implanted in March in a patient at the University of Chicago Medicine as part of a FDA clinical trial being conducted by ReliantHeart, Inc.
To read the full article go to:
Chiu WC et al, “Thromboresistance comparison of the HeartMate II ventricular assist device with the device thrombogenicity emulation- optimized HeartAssist 5 VAD.” J Biomech Eng. 2014 Feb;136(2):021014.
Uterine BF Study in the Rat Sheds Light on the Effect of Exercise during Pregnancy
The effect of hypertension and diabetes on maternal circulation during pregnancy is of increasing interest. To learn more about their effects, a research group from the College of Health Sciences, Midwestern University, Downers Grove, Ill, studied the effect of pregnancy on the uterine vasoconstrictor response to exercise in Sprague-Dawley rats. Previous studies had examined the decrease in blood flow to the uterus during treadmill exercise in non pregnant rats and rabbits. The group hypothesized that the rats, like the rabbits, would exhibit first a robust uterine vasoconstrictor response to short-term treadmill exercise which would attenuate in late pregnancy. They measured uterine blood flow with Transonic 0.5 - 0.7 mm PSB perivascular ultrasound transit time flowprobes in non pregnant and then in late pregnant rats during five minutes of treadmill exercise.
The data gathered indicated that treadmill exercise triggers a reduction in uterine artery blood flow and vascular conductance in the rat. The degree of the response is blunted, but not eliminated during late gestation, thus protecting oxygen delivery to the fetus during exercise performed during late gestation. These findings were similar to those found earlier using the rabbit model.
To read the full (free) publication go to http://www.ncbi.nlm.nih.gov/pubmed/25804264.
Lashley CJ et al, "Effect of pregnancy on the uterine vasoconstrictor response to exercise in rats," Physiol Rep. 2015 Mar;3(3). (Transonic Reference 10274A)
O'Hagan KP, Alberts JA, "Uterine artery blood flow and renal sympathetic nerve activity during exercise in rabbit pregnancy," Am J Physiol Regul Integr Comp Physiol. 2003 Nov;285(5):R1135-44. (Transonic Reference # 2689A).