Vladimir Tuka - Academia.edu (original) (raw)

Papers by Vladimir Tuka

Research paper thumbnail of Common carotid wall shear stress and carotid atherosclerosis in end-stage renal disease patients

Physiological research / Academia Scientiarum Bohemoslovaca

Decrease of arterial wall shear stress (WSS) is associated with higher probability of atheroscler... more Decrease of arterial wall shear stress (WSS) is associated with higher probability of atherosclerotic plaque development in many disease conditions. End-stage renal diseases (ESRD) patients suffer from vascular disease frequently, but its nature differs from general population. This study was aimed at proving an association between common carotid wall shear stress and the presence of carotid bifurcation plaques in a group of ESRD patients. ESRD subjects, planned for the creation of a dialysis access and therapy were included. Wall shear rate (WSR) was used as a surrogate of WSS and was analyzed in the common carotid arteries by duplex ultrasonography. Intima media thickness (IMT) was measured at the same site. The presence/absence of carotid bifurcation plaques was recorded. The endothelial function was estimated by the levels of von Willebrand factor (vWf). 35 ESRD patients were included (19 females, 17 diabetics). Atherosclerotic plaque was present in 53 % of bifurcations. Wall sh...

Research paper thumbnail of Prolonged severe toxicity following verapamil ingestion

Research paper thumbnail of Arteriovenous Grafts: Early Ultrasonography Tells Their Fortune

American journal of nephrology, 2015

The patency of arteriovenous grafts (AVG) for hemodialysis is mostly limited by growing stenoses ... more The patency of arteriovenous grafts (AVG) for hemodialysis is mostly limited by growing stenoses that lead to decreasing of blood flow, thromboses and finally to access failure. The aim of this study was to find out if detection of any pathology by duplex Doppler ultrasonography (DDU) early after creation of AVG could identify those with lower survival. We retrospectively enrolled AVG examined by DDU in our center within 40 days after their creation during the last 10 years. The findings were divided into 4 subgroups: (1a) normal finding, (1b) DDU risk factor (low flow volume, medial calcinosis of the feeding artery, presence of intimal hyperplasia in the venous anastomosis), (2a) non-significant or (2b) significant stenosis. The primary outcome measure was the cumulative survival of people with AVGs, and the secondary was the primary (unassisted) survival. All patients underwent DDU surveillance every 3 months with pre-emptive treatment of significant stenoses. Overall, 340 cases w...

Research paper thumbnail of The determinants of blood pressure response to exercise

Cor et Vasa, 2015

ABSTRACT Introduction There is currently no consensus on the definition of normal BP (blood press... more ABSTRACT Introduction There is currently no consensus on the definition of normal BP (blood pressure) increase during exercise and thus of the exaggerated BP response to exercise. The aim of the present study was a description of the relationship between BP and work rate corrected by body weight on cycle ergometer. A secondary objective was to explore the possible components of this relationship. Materials and methods An observational study with retrospective analysis of the BP data acquired during standard stress tests on cycle ergometer was performed. For the analysis each work rate was expressed corrected to the patients' body weight. Results We analysed BP data from a total of 313 stress tests. From the linear regression analysis we found that at the first exercise step systolic BP depends primarily on resting BP (p = 0.001), on W/kg (p = 0.001), on BMI (p = 0.005) and age (p = 0.002) (BP = -25.059 + 0.927∗BPrest + 31.625∗W/kg1 + 0.840∗BMI + 0.235∗age) and diastolic BP depends primarily on resting BP (p = 0.001), and on resting diastolic BP (p = 0.033): BP = 29.790 + 0.583∗BPrest + 0.071∗BPrest. On subsequent steps age did no more influence systolic BP and resting diastolic BP remained the main determinant of diastolic BP. Conclusion The main finding of this study is the confirmation that the exercise blood pressure depends principally on resting blood pressure and work rate and to a lesser amount on BMI and age. In future studies work rate should be corrected by body weight at submaximal levels.

Research paper thumbnail of Dialysis needle hemodynamics in arterio-venous fistulae: a technical report

The journal of vascular access

Vascular access is the lifeline for end-stage renal disease patients needing hemodialysis treatme... more Vascular access is the lifeline for end-stage renal disease patients needing hemodialysis treatment. For dialysis treatment two needles are placed into the vascular access. Few studies on needle hemodynamics have been published. We investigated needle hemodynamics by means of Doppler ultrasonography, both in B-mode and in pulsed Doppler mode. Direct visualization of the needles, turbulence around the arterial needle and blood flow jet from the venous needle are presented. Ultrasound investigation of the hemodynamics of the dialysis needles is feasible. The extreme blood flow jet through the arterial needle was directed in all patients to the anterior vessel wall.

Research paper thumbnail of Understanding the dialysis access steal syndrome. A review of the etiologies, diagnosis, prevention and treatment strategies

The journal of vascular access

Distal hypoperfusion ischemic syndrome (DHIS), commonly referred to as hand ischemia or 'stea... more Distal hypoperfusion ischemic syndrome (DHIS), commonly referred to as hand ischemia or 'steal' after dialysis access placement, occurs in 5-10% of cases when the brachial artery is used, or 10 times that of wrist arteriovenous fistulas (AVFs) using the radial artery. It is typically seen in elderly women with diabetes, and may carry severe morbidity including tissue or limb loss if not recognized and treated. Three distinct etiologies include (1) blood flow restriction to the hand from arterial occlusive disease either proximal or distal to the AV access anastomosis, (2) excess blood flow through the AV fistula conduit (true steal), and (3) lack of vascular (arterial) adaptation or collateral flow reserve (ie atherosclerosis) to the increased flow demand from the AV conduit. These three causes of steal may occur alone or in concert. The diagnosis of steal is based on an accurate history and physical examination and confirmed with tests including an arteriogram, duplex Doppl...

Research paper thumbnail of Long-term arterial adaptation to high blood flow in the feeding artery of vascular access for hemodialysis

The Journal of Vascular Access, 2012

Purpose: Arteries continuously respond to changing tissue demands and to hemodynamic conditions b... more Purpose: Arteries continuously respond to changing tissue demands and to hemodynamic conditions by altering their diameter and wall structure. the relatively slow dilatation of the feeding artery of vascular accesses continues at least two years after access creation with a continuous decrease in wall shear rate (WSr), which however, remains highly supra-physiological. the aim of this study was to test the hypothesis that after a longer time period the WSr returns to its baseline value. Methods: In a cross-sectional study patients with arteriovenous fistulae were classified into four groups according to the access vintage (from new access to accesses older than six years). the WSr, cross-sectional area, and mean circumferential wall stress were measured and compared between groups.

Research paper thumbnail of More precise diagnosis of access stenosis: ultrasonography versus angiography

The Journal of Vascular Access, 2012

Patency of mature vascular access for hemodialysis is mostly limited by the growing stenoses lead... more Patency of mature vascular access for hemodialysis is mostly limited by the growing stenoses leading to acute access thrombosis. The therapy of choice is usually percutaneous balloon angioplasty (PTA). However, PTA injures the vessel wall and subsequent re-stenosis develops faster than de novo stenosis. Therefore, the key is in appropriate timing of PTA procedures--as late as possible but before access thrombosis develops. Ultrasonography combines the morphologic and functional access assessment, but the former is less precise than angiography. The aim of this study was to compare ultrasonographic and angiographic measuring of residual diameter as the additional criterion of significant stenoses used in our center. Residual diameter of significant stenoses was measured by B-mode ultrasonography three times in 20 patients. All the patients were indicated for angiography and the residual diameter of the stenoses was re-analyzed by this method. The repeatability of ultrasonographic residual diameter measurements and reproducibility in comparison to angiography were expressed by coefficients of variation (CV). The residual diameter was 1.69 ± 0.05 mm by ultrasound and 1.65 ± 0.59 mm measured by angiography. In the ultrasound repeatability study, CV was 3.17 ± 2.76% and in the reproducibility study CV was 18.0 ± 15.6%. All the stenoses found to be significant by ultrasound were above 65% by angiography and PTA was performed. Ultrasonographic measurement of the residual diameter is stable in experienced hands and is well comparable to angiography results. These findings advocate residual diameter of 2.0 mm as the strong additional criterion of the significant stenoses, which can also be used in ultrasound surveillance of arteriovenous grafts.

Research paper thumbnail of PO11-306 Hypercholesterolemia Prevents Vessel Adaptation in Extremely High Flow Conditions in Hemodialyzed Patients

Atherosclerosis Supplements, 2007

Research paper thumbnail of Creation of dialysis vascular access with normal flow increases BNP levels

European Journal of Heart Failure Supplements, 2008

Research paper thumbnail of Stent Graft or Balloon Angioplasty Alone for Dialysis-Access Grafts

New England Journal of Medicine, 2010

Haskal et al.(Feb. 11 issue) 1 report prolonged vascular access with the use of a stent graft amo... more Haskal et al.(Feb. 11 issue) 1 report prolonged vascular access with the use of a stent graft among patients undergoing balloon angioplasty for failing dialysis-access grafts. Despite the impressive results, some aspects of the work need additional discussion.

Research paper thumbnail of Diabetes and distal access location are associated with higher wall shear rate in feeding artery of PTFE grafts

Nephrology Dialysis Transplantation, 2006

Background. Surgical creation of permanent vascular access for haemodialysis leads to considerabl... more Background. Surgical creation of permanent vascular access for haemodialysis leads to considerable haemodynamic changes. They could be implicated in the pathogenesis of access complications, which limit access survival, especially in diabetics. Physiologically, the relation between arterial diameter and blood velocity is maintained by wall shear stress (WSS), which is directly related to both blood viscosity and wall shear rate (WSR ¼ blood velocity/internal diameter). Because of methodological difficulties, WSR is used as a measure of WSS. Extremely high values of WSS might induce hypercoagulable states, which might contribute to access thrombosis. We performed a study, which was aimed to (i) describe WSR values in feeding arteries of various polytetrafluoroethylene access types and (ii) prove that diabetic patients have higher WSR than non-diabetics. Methods. A linear-array 11 MHz probe of SONOS 5500 (Phillips, USA) was used to obtain blood velocity and internal diameter in the feeding arteries of radial or brachial polytetrafluoroethylene grafts. WSR was calculated as 4 Â blood velocity/internal diameter. We compared observed values of WSR according to feeding artery (radial vs brachial artery) and according to diabetic status using unpaired t-test. Results. We included 106 patients (58 non-diabetic and 48 diabetic) in the study. WSR was significantly higher in radial arteries compared with brachial arteries independent of diabetes status. Diabetic subjects had significantly higher WSR in both radial and brachial arteries. Conclusions. Diabetes mellitus and distal vascular access creation are associated with higher WSR in the feeding artery. This could be of relevance in the pathogenesis of access complications, e.g. thrombosis, and thus lower patency rates in diabetic patients.

Research paper thumbnail of Haemodialysis access via tissue-engineered vascular graft

The Lancet, 2009

Todd McAllister and colleagues' Article (April 25, p 1440)1 on t... more Todd McAllister and colleagues' Article (April 25, p 1440)1 on the use of autologous tissue-engineered vascular grafts in patients on haemodialysis is a seminal paper on the use of bioengineered tissue in clinical medicine. But we were somewhat surprised by the frequency of ...

Research paper thumbnail of Regular ultrasonographic screening significantly prolongs patency of PTFE grafts

Kidney International, 2005

Research paper thumbnail of Local Hemodynamics of the Vascular Access for Hemodialysis

Kidney and Blood Pressure Research, 2009

Vascular access is called Achilles' heel of hemodialysis because it is associated with a ... more Vascular access is called Achilles' heel of hemodialysis because it is associated with a substantial morbidity. A permanent vascular access is created either by a direct connection of the patient's own artery and vein or by the interposition of a graft. Arteriolar beds are bypassed, which leads to a substantial increase in arterial (and venous) flow and the vessels adapt to it by a complex of interesting processes. These are reviewed together with some pathophysiological mechanisms of access complications.

Research paper thumbnail of Creation of dialysis vascular access with normal flow increases brain natriuretic peptide levels

International Urology and Nephrology, 2009

Background Chronic heart failure is very common in hemodialyzed patients due to several factors s... more Background Chronic heart failure is very common in hemodialyzed patients due to several factors such as intermittent volume overload, anemia, and hypertension. Dialysis access flow is usually considered to have a minor effect. We hypothesized that creation of dialysis access with ''normal'' flow would lead to elevation of B-type natriuretic peptide (BNP), which is a sensitive marker of heart failure. Methods We included subjects with a newly created, well-functioning vascular access and normal left ventricular ejection fraction. They were examined before access creation (baseline), then again 6 weeks and 6 months after the surgery. Only subjects with access flow (Qa) \ 1500 ml/min were included. Changes of BNP levels and their relation to access flow were studied.

Research paper thumbnail of Surprisingly delayed escalation of severe verapamil poisoning

European Journal of Emergency Medicine, 2009

We present a case report of intoxication by a potentially lethal dose of sustained-release verapa... more We present a case report of intoxication by a potentially lethal dose of sustained-release verapamil with delayed escalation of complications. The patient was hospitalized 1.5 h after an attempted suicide with a very high dose of verapamil sustained-release (7.2 g). On admission the plasma concentrations were extremely high (3600 ng/l). Heart rate and blood pressure declined slowly with a surprising sudden escalation on the third day coupled with hemodynamic collapse and loss of consciousness. Complete recovery was achieved in spite of 2 h of extreme hypotension. We outline the clinical course, a need for massive bowel irrigation in case of sustained-release medication, the timing of a temporary pacing and the effect of centralization of circulation even on invasively measured blood pressure.

Research paper thumbnail of Factors Associated with Impaired Arterial Adaptation to Chronically High Wall Shear Rate in the Feeding Artery of PTFE Grafts

American Journal of Nephrology, 2008

The feeding artery of dialysis vascular access is subjected to unusually high wall shear stress (... more The feeding artery of dialysis vascular access is subjected to unusually high wall shear stress (WSS), a hemodynamic factor leading to vasodilatation, for at least several months after access creation. Physiologically, high WSS leads to compensatory endothelium-dependent vasodilatation. We supposed that the dilatation of the feeding artery continues to lower WSS during longer time period after access creation and that this process is limited by risk factors of endothelial dysfunction. We examined the feeding artery of vascular accesses within 3 months, 1 and 2 years after access creation. By ultrasonography, we obtained internal diameter and blood velocity in the feeding arteries. We calculated wall shear rate (WSR). We examined 75 patients. Internal diameter rose from 3.9 +/- 0.1 mm (3 months) to 4.3 +/- 0.2 mm within the first year and to 4.6 +/- 0.2 mm within the second. Similarly, mean WSR decreased from 1,839 +/- 117 to 1,629 +/- 123 s(-1) and to 1,159 +/- 109 s(-1), respectively. The vasodilatation was limited by diabetes mellitus, hypercholesterolemia and hypertriglyceridemia. The feeding artery continues to dilate 2 years after access creation, with a simultaneous decrease in WSR. This process is dampened in patients with diabetes mellitus and dyslipidemia.

Research paper thumbnail of Vascular Access Surveillance: No Benefit?

American Journal of Kidney Diseases, 2008

No abstract is available. To read the body of this article, please view the Full Text online. ...... more No abstract is available. To read the body of this article, please view the Full Text online. ... © 2008 National Kidney Foundation, Inc. Published by Elsevier Inc All rights reserved. ... Visit SciVerse ScienceDirect to see if you have access via your institution. ... Advertisements on this site ...

Research paper thumbnail of Common carotid wall shear stress and carotid atherosclerosis in end-stage renal disease patients

Physiological research / Academia Scientiarum Bohemoslovaca

Decrease of arterial wall shear stress (WSS) is associated with higher probability of atheroscler... more Decrease of arterial wall shear stress (WSS) is associated with higher probability of atherosclerotic plaque development in many disease conditions. End-stage renal diseases (ESRD) patients suffer from vascular disease frequently, but its nature differs from general population. This study was aimed at proving an association between common carotid wall shear stress and the presence of carotid bifurcation plaques in a group of ESRD patients. ESRD subjects, planned for the creation of a dialysis access and therapy were included. Wall shear rate (WSR) was used as a surrogate of WSS and was analyzed in the common carotid arteries by duplex ultrasonography. Intima media thickness (IMT) was measured at the same site. The presence/absence of carotid bifurcation plaques was recorded. The endothelial function was estimated by the levels of von Willebrand factor (vWf). 35 ESRD patients were included (19 females, 17 diabetics). Atherosclerotic plaque was present in 53 % of bifurcations. Wall sh...

Research paper thumbnail of Prolonged severe toxicity following verapamil ingestion

Research paper thumbnail of Arteriovenous Grafts: Early Ultrasonography Tells Their Fortune

American journal of nephrology, 2015

The patency of arteriovenous grafts (AVG) for hemodialysis is mostly limited by growing stenoses ... more The patency of arteriovenous grafts (AVG) for hemodialysis is mostly limited by growing stenoses that lead to decreasing of blood flow, thromboses and finally to access failure. The aim of this study was to find out if detection of any pathology by duplex Doppler ultrasonography (DDU) early after creation of AVG could identify those with lower survival. We retrospectively enrolled AVG examined by DDU in our center within 40 days after their creation during the last 10 years. The findings were divided into 4 subgroups: (1a) normal finding, (1b) DDU risk factor (low flow volume, medial calcinosis of the feeding artery, presence of intimal hyperplasia in the venous anastomosis), (2a) non-significant or (2b) significant stenosis. The primary outcome measure was the cumulative survival of people with AVGs, and the secondary was the primary (unassisted) survival. All patients underwent DDU surveillance every 3 months with pre-emptive treatment of significant stenoses. Overall, 340 cases w...

Research paper thumbnail of The determinants of blood pressure response to exercise

Cor et Vasa, 2015

ABSTRACT Introduction There is currently no consensus on the definition of normal BP (blood press... more ABSTRACT Introduction There is currently no consensus on the definition of normal BP (blood pressure) increase during exercise and thus of the exaggerated BP response to exercise. The aim of the present study was a description of the relationship between BP and work rate corrected by body weight on cycle ergometer. A secondary objective was to explore the possible components of this relationship. Materials and methods An observational study with retrospective analysis of the BP data acquired during standard stress tests on cycle ergometer was performed. For the analysis each work rate was expressed corrected to the patients' body weight. Results We analysed BP data from a total of 313 stress tests. From the linear regression analysis we found that at the first exercise step systolic BP depends primarily on resting BP (p = 0.001), on W/kg (p = 0.001), on BMI (p = 0.005) and age (p = 0.002) (BP = -25.059 + 0.927∗BPrest + 31.625∗W/kg1 + 0.840∗BMI + 0.235∗age) and diastolic BP depends primarily on resting BP (p = 0.001), and on resting diastolic BP (p = 0.033): BP = 29.790 + 0.583∗BPrest + 0.071∗BPrest. On subsequent steps age did no more influence systolic BP and resting diastolic BP remained the main determinant of diastolic BP. Conclusion The main finding of this study is the confirmation that the exercise blood pressure depends principally on resting blood pressure and work rate and to a lesser amount on BMI and age. In future studies work rate should be corrected by body weight at submaximal levels.

Research paper thumbnail of Dialysis needle hemodynamics in arterio-venous fistulae: a technical report

The journal of vascular access

Vascular access is the lifeline for end-stage renal disease patients needing hemodialysis treatme... more Vascular access is the lifeline for end-stage renal disease patients needing hemodialysis treatment. For dialysis treatment two needles are placed into the vascular access. Few studies on needle hemodynamics have been published. We investigated needle hemodynamics by means of Doppler ultrasonography, both in B-mode and in pulsed Doppler mode. Direct visualization of the needles, turbulence around the arterial needle and blood flow jet from the venous needle are presented. Ultrasound investigation of the hemodynamics of the dialysis needles is feasible. The extreme blood flow jet through the arterial needle was directed in all patients to the anterior vessel wall.

Research paper thumbnail of Understanding the dialysis access steal syndrome. A review of the etiologies, diagnosis, prevention and treatment strategies

The journal of vascular access

Distal hypoperfusion ischemic syndrome (DHIS), commonly referred to as hand ischemia or 'stea... more Distal hypoperfusion ischemic syndrome (DHIS), commonly referred to as hand ischemia or 'steal' after dialysis access placement, occurs in 5-10% of cases when the brachial artery is used, or 10 times that of wrist arteriovenous fistulas (AVFs) using the radial artery. It is typically seen in elderly women with diabetes, and may carry severe morbidity including tissue or limb loss if not recognized and treated. Three distinct etiologies include (1) blood flow restriction to the hand from arterial occlusive disease either proximal or distal to the AV access anastomosis, (2) excess blood flow through the AV fistula conduit (true steal), and (3) lack of vascular (arterial) adaptation or collateral flow reserve (ie atherosclerosis) to the increased flow demand from the AV conduit. These three causes of steal may occur alone or in concert. The diagnosis of steal is based on an accurate history and physical examination and confirmed with tests including an arteriogram, duplex Doppl...

Research paper thumbnail of Long-term arterial adaptation to high blood flow in the feeding artery of vascular access for hemodialysis

The Journal of Vascular Access, 2012

Purpose: Arteries continuously respond to changing tissue demands and to hemodynamic conditions b... more Purpose: Arteries continuously respond to changing tissue demands and to hemodynamic conditions by altering their diameter and wall structure. the relatively slow dilatation of the feeding artery of vascular accesses continues at least two years after access creation with a continuous decrease in wall shear rate (WSr), which however, remains highly supra-physiological. the aim of this study was to test the hypothesis that after a longer time period the WSr returns to its baseline value. Methods: In a cross-sectional study patients with arteriovenous fistulae were classified into four groups according to the access vintage (from new access to accesses older than six years). the WSr, cross-sectional area, and mean circumferential wall stress were measured and compared between groups.

Research paper thumbnail of More precise diagnosis of access stenosis: ultrasonography versus angiography

The Journal of Vascular Access, 2012

Patency of mature vascular access for hemodialysis is mostly limited by the growing stenoses lead... more Patency of mature vascular access for hemodialysis is mostly limited by the growing stenoses leading to acute access thrombosis. The therapy of choice is usually percutaneous balloon angioplasty (PTA). However, PTA injures the vessel wall and subsequent re-stenosis develops faster than de novo stenosis. Therefore, the key is in appropriate timing of PTA procedures--as late as possible but before access thrombosis develops. Ultrasonography combines the morphologic and functional access assessment, but the former is less precise than angiography. The aim of this study was to compare ultrasonographic and angiographic measuring of residual diameter as the additional criterion of significant stenoses used in our center. Residual diameter of significant stenoses was measured by B-mode ultrasonography three times in 20 patients. All the patients were indicated for angiography and the residual diameter of the stenoses was re-analyzed by this method. The repeatability of ultrasonographic residual diameter measurements and reproducibility in comparison to angiography were expressed by coefficients of variation (CV). The residual diameter was 1.69 ± 0.05 mm by ultrasound and 1.65 ± 0.59 mm measured by angiography. In the ultrasound repeatability study, CV was 3.17 ± 2.76% and in the reproducibility study CV was 18.0 ± 15.6%. All the stenoses found to be significant by ultrasound were above 65% by angiography and PTA was performed. Ultrasonographic measurement of the residual diameter is stable in experienced hands and is well comparable to angiography results. These findings advocate residual diameter of 2.0 mm as the strong additional criterion of the significant stenoses, which can also be used in ultrasound surveillance of arteriovenous grafts.

Research paper thumbnail of PO11-306 Hypercholesterolemia Prevents Vessel Adaptation in Extremely High Flow Conditions in Hemodialyzed Patients

Atherosclerosis Supplements, 2007

Research paper thumbnail of Creation of dialysis vascular access with normal flow increases BNP levels

European Journal of Heart Failure Supplements, 2008

Research paper thumbnail of Stent Graft or Balloon Angioplasty Alone for Dialysis-Access Grafts

New England Journal of Medicine, 2010

Haskal et al.(Feb. 11 issue) 1 report prolonged vascular access with the use of a stent graft amo... more Haskal et al.(Feb. 11 issue) 1 report prolonged vascular access with the use of a stent graft among patients undergoing balloon angioplasty for failing dialysis-access grafts. Despite the impressive results, some aspects of the work need additional discussion.

Research paper thumbnail of Diabetes and distal access location are associated with higher wall shear rate in feeding artery of PTFE grafts

Nephrology Dialysis Transplantation, 2006

Background. Surgical creation of permanent vascular access for haemodialysis leads to considerabl... more Background. Surgical creation of permanent vascular access for haemodialysis leads to considerable haemodynamic changes. They could be implicated in the pathogenesis of access complications, which limit access survival, especially in diabetics. Physiologically, the relation between arterial diameter and blood velocity is maintained by wall shear stress (WSS), which is directly related to both blood viscosity and wall shear rate (WSR ¼ blood velocity/internal diameter). Because of methodological difficulties, WSR is used as a measure of WSS. Extremely high values of WSS might induce hypercoagulable states, which might contribute to access thrombosis. We performed a study, which was aimed to (i) describe WSR values in feeding arteries of various polytetrafluoroethylene access types and (ii) prove that diabetic patients have higher WSR than non-diabetics. Methods. A linear-array 11 MHz probe of SONOS 5500 (Phillips, USA) was used to obtain blood velocity and internal diameter in the feeding arteries of radial or brachial polytetrafluoroethylene grafts. WSR was calculated as 4 Â blood velocity/internal diameter. We compared observed values of WSR according to feeding artery (radial vs brachial artery) and according to diabetic status using unpaired t-test. Results. We included 106 patients (58 non-diabetic and 48 diabetic) in the study. WSR was significantly higher in radial arteries compared with brachial arteries independent of diabetes status. Diabetic subjects had significantly higher WSR in both radial and brachial arteries. Conclusions. Diabetes mellitus and distal vascular access creation are associated with higher WSR in the feeding artery. This could be of relevance in the pathogenesis of access complications, e.g. thrombosis, and thus lower patency rates in diabetic patients.

Research paper thumbnail of Haemodialysis access via tissue-engineered vascular graft

The Lancet, 2009

Todd McAllister and colleagues' Article (April 25, p 1440)1 on t... more Todd McAllister and colleagues' Article (April 25, p 1440)1 on the use of autologous tissue-engineered vascular grafts in patients on haemodialysis is a seminal paper on the use of bioengineered tissue in clinical medicine. But we were somewhat surprised by the frequency of ...

Research paper thumbnail of Regular ultrasonographic screening significantly prolongs patency of PTFE grafts

Kidney International, 2005

Research paper thumbnail of Local Hemodynamics of the Vascular Access for Hemodialysis

Kidney and Blood Pressure Research, 2009

Vascular access is called Achilles' heel of hemodialysis because it is associated with a ... more Vascular access is called Achilles' heel of hemodialysis because it is associated with a substantial morbidity. A permanent vascular access is created either by a direct connection of the patient's own artery and vein or by the interposition of a graft. Arteriolar beds are bypassed, which leads to a substantial increase in arterial (and venous) flow and the vessels adapt to it by a complex of interesting processes. These are reviewed together with some pathophysiological mechanisms of access complications.

Research paper thumbnail of Creation of dialysis vascular access with normal flow increases brain natriuretic peptide levels

International Urology and Nephrology, 2009

Background Chronic heart failure is very common in hemodialyzed patients due to several factors s... more Background Chronic heart failure is very common in hemodialyzed patients due to several factors such as intermittent volume overload, anemia, and hypertension. Dialysis access flow is usually considered to have a minor effect. We hypothesized that creation of dialysis access with ''normal'' flow would lead to elevation of B-type natriuretic peptide (BNP), which is a sensitive marker of heart failure. Methods We included subjects with a newly created, well-functioning vascular access and normal left ventricular ejection fraction. They were examined before access creation (baseline), then again 6 weeks and 6 months after the surgery. Only subjects with access flow (Qa) \ 1500 ml/min were included. Changes of BNP levels and their relation to access flow were studied.

Research paper thumbnail of Surprisingly delayed escalation of severe verapamil poisoning

European Journal of Emergency Medicine, 2009

We present a case report of intoxication by a potentially lethal dose of sustained-release verapa... more We present a case report of intoxication by a potentially lethal dose of sustained-release verapamil with delayed escalation of complications. The patient was hospitalized 1.5 h after an attempted suicide with a very high dose of verapamil sustained-release (7.2 g). On admission the plasma concentrations were extremely high (3600 ng/l). Heart rate and blood pressure declined slowly with a surprising sudden escalation on the third day coupled with hemodynamic collapse and loss of consciousness. Complete recovery was achieved in spite of 2 h of extreme hypotension. We outline the clinical course, a need for massive bowel irrigation in case of sustained-release medication, the timing of a temporary pacing and the effect of centralization of circulation even on invasively measured blood pressure.

Research paper thumbnail of Factors Associated with Impaired Arterial Adaptation to Chronically High Wall Shear Rate in the Feeding Artery of PTFE Grafts

American Journal of Nephrology, 2008

The feeding artery of dialysis vascular access is subjected to unusually high wall shear stress (... more The feeding artery of dialysis vascular access is subjected to unusually high wall shear stress (WSS), a hemodynamic factor leading to vasodilatation, for at least several months after access creation. Physiologically, high WSS leads to compensatory endothelium-dependent vasodilatation. We supposed that the dilatation of the feeding artery continues to lower WSS during longer time period after access creation and that this process is limited by risk factors of endothelial dysfunction. We examined the feeding artery of vascular accesses within 3 months, 1 and 2 years after access creation. By ultrasonography, we obtained internal diameter and blood velocity in the feeding arteries. We calculated wall shear rate (WSR). We examined 75 patients. Internal diameter rose from 3.9 +/- 0.1 mm (3 months) to 4.3 +/- 0.2 mm within the first year and to 4.6 +/- 0.2 mm within the second. Similarly, mean WSR decreased from 1,839 +/- 117 to 1,629 +/- 123 s(-1) and to 1,159 +/- 109 s(-1), respectively. The vasodilatation was limited by diabetes mellitus, hypercholesterolemia and hypertriglyceridemia. The feeding artery continues to dilate 2 years after access creation, with a simultaneous decrease in WSR. This process is dampened in patients with diabetes mellitus and dyslipidemia.

Research paper thumbnail of Vascular Access Surveillance: No Benefit?

American Journal of Kidney Diseases, 2008

No abstract is available. To read the body of this article, please view the Full Text online. ...... more No abstract is available. To read the body of this article, please view the Full Text online. ... © 2008 National Kidney Foundation, Inc. Published by Elsevier Inc All rights reserved. ... Visit SciVerse ScienceDirect to see if you have access via your institution. ... Advertisements on this site ...