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Markus Aschwanden

Publications and source records attributed to Markus Aschwanden.

At least 19 recordsLinked to original sources
PubMed2007

Effect of silver-threads-containing compression stockings on the cutaneous microcirculation: a double-blind, randomized cross-over study.

Recently silver fiber-containing compression stockings for the use in patients with chronic venous insufficiency (CVI) were introduced to the market. In order to gain some first insight into the effects of these new fabrics on the cutaneous microcirculation, a double-blind, randomized cross-over trial was performed in 10 healthy volunteers. A 3 days run-in phase preceded the (2 x10 days) treatment phases and was used to assess the reproducibility of the primary endpoint, which was the transcutaneous partial oxygen pressure (tcpO(2)) measured at a probe temperature of 44 degrees C in the perimalleolar region of the reference leg in supine and dependent leg positions. Coefficients of variation for double measured tcpO(2) values were 4.2% (3.1 SD) and 5.8% (6.0 SD) for the leg in supine and dependent position. The intra-individual comparison of the effects from both treatment phases (value end of treatment - start of treatment) resulted in a negative tcpO(2) net balance for the regular hosiery (-0.93 (2.7 SD) mmHg, supine; -1.1 (3.5 SD) mmHg, dependent) but a positive net balance for the silver fibers containing stockings (0.25 (4.0 SD) mmHg, supine; 1.7 (3.9 SD) mmHg, dependent). The inter-treatment differences were statistically significant for the leg in a dependent position. The trial provides first evidence that interweaving silver threads into regular compression stockings may result in a positive effect regarding the nutritive skin perfusion.

Adult↗
PubMed2006

Calf muscles imaged at BOLD MR: correlation with TcPO2 and flowmetry measurements during ischemia and reactive hyperemia--initial experience.

PURPOSE: To prospectively compare the blood oxygen level-dependent (BOLD) magnetic resonance (MR) signal intensity of calf muscle during ischemia and reactive hyperemia with laser Doppler flowmetry (LDF) and transcutaneous oxygen pressure (TcPo2) measurements, two parameters routinely used to evaluate peripheral arterial occlusive disease. MATERIALS AND METHODS: The study was institutional review board approved; all volunteers gave informed consent. Fifteen healthy volunteers (eight male, seven female; mean age, 33.0 years +/- 6.1 [standard deviation]) underwent LDF, TcPo2 measurement, and BOLD MR imaging of the calf during ischemia and reactive hyperemia. The BOLD signal intensity of the gastrocnemius muscle was measured at 1.5-T single-shot multiecho gradient-echo echo-planar imaging. Time to half ischemia minimum (THIM), time to half hyperemia peak (THHP), and time to peak (TTP) after cuff deflation were measured with each method. Correlation coefficients (CCs) for associations of BOLD response with LDF and TcPo2 time courses were calculated. Student t testing of key BOLD MR, LDF, and TcPo2 measurement parameters was performed. RESULTS: During ischemia, normalized LDF and TcPo2 measurements decreased similarly to BOLD MR signal intensity (CCs: 0.86 and 0.96 for associations with LDF and TcPo2 measurements, respectively). Mean THIM values were 136.0, 82.5, and 121.3 seconds for BOLD MR, LDF (P < .01), and TcPo2 (P > .05) measurements, respectively. During early reactive hyperemia, LDF and TcPo2 measurements increased rapidly to peak values, similarly to BOLD MR signal intensity (CCs: 0.81 and 0.78, respectively). Mean THHP values were 26.0, 12.5, and 44.0 seconds for BOLD MR, LDF (P < .01), and TcPo2 (P < .01) measurements, respectively. Mean TTP values were 48.7, 47.5, and 98.0 seconds for BOLD MR, LDF (P > .05), and TcPo2 (P < .01) measurements, respectively. CONCLUSION: BOLD MR imaging of calf muscles-depending on underlying key parameters-has moderate to good correlation with LDF and TcPo2 measurements during ischemia and reactive hyperemia.

Adult↗
PubMed2006

Blood oxygenation level-dependent magnetic resonance imaging of the skeletal muscle in patients with peripheral arterial occlusive disease.

BACKGROUND: Blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) has been used to measure T2* changes in skeletal muscle tissue of healthy volunteers. The BOLD effect is assumed to primarily reflect changes in blood oxygenation at the tissue level. We compared the calf muscle BOLD response of patients with peripheral arterial occlusive disease (PAOD) to that of an age-matched non-PAOD group during postischemic reactive hyperemia. METHODS AND RESULTS: PAOD patients (n=17) with symptoms of intermittent calf claudication and an age-matched non-PAOD group (n=11) underwent T2*-weighted single-shot multiecho planar imaging on a whole-body magnetic resonance scanner at 1.5 T. Muscle BOLD MRI of the calf was performed during reactive hyperemia provoked by a cuff-compression paradigm. T2* maps were generated with an automated fitting procedure. Maximal T2* change (deltaT2*(max)) and time to peak to reach deltaT2*(max) for gastrocnemius, soleus, tibial anterior, and peroneal muscle were evaluated. Compared with the non-PAOD group, patients revealed significantly lower deltaT2*(max)-values, with a mean of 7.3+/-5.3% versus 13.1+/-5.6% (P<0.001), and significantly delayed time-to-peak values, with a mean of 109.3+/-79.3 versus 32.2+/-13.3 seconds (P<0.001). CONCLUSIONS: T2* time courses of the muscle BOLD MRI signal during postocclusive reactive hyperemia revealed statistically significant differences in the key parameters (deltaT2*(max); time to peak) in PAOD patients compared with age-matched non-PAOD controls.

Aged↗
PubMed2006

Intraarterial MR angiography and DSA in patients with peripheral arterial occlusive disease: prospective comparison.

PURPOSE: To prospectively evaluate the accuracy of intraarterial magnetic resonance (MR) angiography in the depiction of significant stenoses and occlusions, with intraarterial digital subtraction angiography (DSA) serving as the reference standard. MATERIALS AND METHODS: Approval of the local ethics committee and informed consent were obtained. Twenty patients (11 men; nine women; age range, 48-86 years; mean age, 69.5 years+/-11.2 [standard deviation]) with symptomatic peripheral arterial occlusive disease (PAOD) were prospectively enrolled. After percutaneous transluminal angioplasty (PTA), intraarterial MR angiography was performed in the thigh and the calf with a 1.5-T MR imager in two consecutive runs. Intraarterial MR angiography was performed with a low-dose injection protocol (ie, two 20-mL injections of a 50-mmol gadolinium-based contrast agent). Moderate stenoses (luminal narrowing 50%) or vessel occlusions; 95% confidence intervals (CIs) were calculated for sensitivity and specificity. RESULTS: Intraarterial DSA revealed 78 moderate stenoses, 57 significant stenoses, and 28 occlusions. Sensitivity, specificity, and accuracy of intraarterial MR angiography in the characterization of significant stenoses or occlusions were 92% (95% CI: 72%, 99%), 94% (95% CI: 82%, 98%), and 93%, respectively, in femoropopliteal arteries and 93% (95% CI: 83%, 98%), 71% (95% CI: 51%, 86%), and 86%, respectively, in infrapopliteal arteries. The main artifact observed with intraarterial MR angiography was venous contamination (12%). CONCLUSION: Intraarterial MR angiography is an accurate method used to depict significant stenoses and occlusions in lower extremity arteries with a low-dose injection protocol.

Aged↗
PubMed2006

Fluoroscopic contrast-enhanced MR angiography with a magnetization-prepared steady-state free precession technique in peripheral arterial occlusive disease.

OBJECTIVE: The objective of our study was to evaluate the feasibility of intraarterial (IA) near-real-time contrast-enhanced MR angiography (CE-MRA) with a frame rate of 1.3 frames per second in seven patients with lower extremity peripheral arterial occlusive disease (PAOD). For optimized background suppression, a modified 2D steady-state free precession (SSFP) technique with magnetization preparation and mask subtraction was developed. The femoropopliteal and infrapopliteal arteries were covered in two separate steps. Acceptable contrast-to-noise ratios were obtained, and road maps were reconstructed from the same data set. CONCLUSION: Mastering IA near-real-time CE-MRA, including road map reconstruction, with an SSFP technique in the lower extremity of patients with PAOD is an important building block toward successfully performing endovascular catheter MR-guided interventions.

Aged↗
PubMed2005

Intraarterial versus IV gadolinium injections for MR angiography: quantitative and qualitative assessment of the infrainguinal arteries.

OBJECTIVE: Our purpose was to quantitatively and qualitatively compare 3D intraarterial (IA) gadolinium-enhanced MR angiography (IA MRA) versus the standard of reference of MR angiography, 3D IV gadolinium-enhanced MR angiography (IV MRA), in patients with peripheral arterial occlusive disease (PAOD) for use during catheter-based MR-guided endovascular interventions. CONCLUSION: IA MRA provides image quality of the infrainguinal arteries in PAOD patients comparable to IV MRA with a significantly improved assessment of the infrapopliteal arteries due to reduced venous contamination. Further benefits of IA MRA include usage of only very low doses of gadolinium and simplified bolus timing.

Aged↗
PubMed2004

Lower extremity: low-dose contrast agent intraarterial MR angiography in patients--initial results.

Institutional review board approval and patient consent were obtained. A low-dose injection protocol for intraarterial three-dimensional (3D) gadolinium-enhanced magnetic resonance (MR) angiography was derived from femoral flow phantom studies and prospectively evaluated in patients with peripheral arterial occlusive disease (PAOD). All MR angiograms were obtained at 1.5 T with a T1-weighted gradient-echo sequence. MR angiograms of a gadolinium dilution series (0.8-200.0 mmol/L) were acquired in a femoral phantom at different flow rates. Signal-to-noise ratios (SNRs) above the 75% threshold of the measured maximum were considered optimal. The lowest optimal concentration was injected intraarterially in nine patients to obtain 3D MR angiograms of the thigh and calf station. Contrast-to-noise ratios (CNRs) were calculated for four arterial segments. The low optimal concentration of 50 mmol/L (20-mL bolus volume), about 5% of the total permissible dose, showed SNRs larger than the 75% threshold in the phantom study. In patients, this concentration led to high-spatial-resolution angiograms with mean CNRs of 70.0 +/- 14.5 (+/- standard deviation) for the superficial femoral artery and 47.5 +/- 13.4 at the infrapopliteal level. Low-dose contrast agent intraarterial 3D MR angiography showed high arterial enhancement, enabling assessment of lower extremity arteries in patients with PAOD and multiple injections--a crucial precondition for MR-guided endovascular interventions.

Aged↗
PubMed2004

Infragenual cuff-compression reduces venous contamination in contrast-enhanced MR angiography of the calf.

PURPOSE: To reduce venous contamination at the calf level in three-dimensional contrast-enhanced MR angiography (CE-MRA) by applying continuous infragenual cuff-compression. MATERIALS AND METHODS: Ten patients with clinically relevant peripheral arterial occlusive disease (PAOD) underwent dynamic three-dimensional CE-MRA of the calf. Six consecutive measurements were acquired with the first measurement serving as mask. Cuff-compression of 50 mmHg was attached below the knee. To allow intra-individual comparison, compression was applied unilaterally. The cuff was inflated three minutes before scanning and was continued throughout the MRA session. Venous contamination and arterial visualization scores were ranked using a five-point rating scale. Contrast-to-noise ratios (CNRs) of superficial enhancing calf-veins on the uncompressed and compressed calf sides were evaluated. An asymmetry index (AI) defined by CNR(mean) (uncompressed)/CNR(mean) (compressed) was introduced to describe the ratio in venous contrast agent supply between both sides quantitatively. RESULTS: Three-dimensional CE-MRA of the calves demonstrated significantly lower superficial venous contamination scores (P < 0.004) and clearly improved arterial visualization (P < 0.009) on the compressed side. Additionally, AI values were larger than 1 (P < 0.02), indicating a higher contrast agent supply in the superficial veins on the uncompressed side. CONCLUSION: Infragenual cuff-compression minimizes venous overlay in three-dimensional CE-MRA at calf level by reduction of contrast agent supply in the superficial veins.

Aged↗
PubMed2004

Effects of probucol versus aspirin and versus brachytherapy on restenosis after femoropopliteal angioplasty: the PAB randomized multicenter trial.

PURPOSE: To evaluate the effect of probucol and/or of endovascular brachytherapy (EVBT) on restenosis after percutaneous transluminal angioplasty (PTA) of femoropopliteal arteries. METHODS: A total of 335 patients (206 men; mean age 72+/-9 years) with intermittent claudication were randomized according to a 2x2 factorial design to 1 of the 4 groups: probucol, placebo, EVBT, and EVBT+probucol. Probucol (1 g/d) or placebo were given in double-blinded fashion 1 month before and for 6 months after PTA. Gamma irradiation (192Iridium, 14 Gy, 5-mm reference depth) was randomly applied in an unblinded manner from a noncentered endoluminal catheter. All patients received aspirin (100 mg/d). Primary endpoint was restenosis (>50% diameter reduction) detected by duplex ultrasound 6 months after PTA. Secondary endpoints included clinical and hemodynamic assessment. RESULTS: Restenosis in patients undergoing EVBT was 17% (23/133) versus 35% (50/142) in patients without EVBT (p<0.001); in patients treated with probucol versus placebo, the rates were 23% (31/135) and 30% (43/140, p<0.001). Three quarters (77%, 102/133) of patients were free of claudication after EVBT therapy versus 61% (87/142) without EVBT (p<0.05). Need for target vessel revascularization was 6% (8/133) with EVBT versus 14% (20/142) without EVBT (p<0.01). Late thrombotic occlusions occurred in 4% (6/133), exclusively in patients treated with EVBT after stent implantation. CONCLUSIONS: Endovascular brachytherapy significantly reduces restenosis, improves symptoms, and reduces reinterventions after PTA of femoropopliteal arteries. Probucol reduces restenosis but has no additive effect when combined with brachytherapy.

Aged↗
PubMed2003

Late acute thrombotic occlusion after endovascular brachytherapy and stenting of femoropopliteal arteries.

OBJECTIVES: The aim of this article is to underline the importance of this complication after endovascular brachytherapy (EVBT) and intravascular stenting of the femoropopliteal arteries occurring in a running randomized trial. BACKGROUND: Endovascular brachytherapy has been proposed as a promising treatment modality to reduce restenosis after angioplasty. However, the phenomenon of late acute thrombotic occlusion (LATO) in patients receiving EVBT after stenting is of major concern. METHODS: In an ongoing prospective multicenter trial, patients were randomized to undergo EVBT (iridium 192; 14 Gy at a depth of the radius of the vessel +2 mm) after percutaneous recanalization of femoropopliteal obstructions. Of the 204 patients who completed the six months follow-up, 94 were randomized to EVBT. RESULTS: Late acute thrombotic occlusion occurred exclusively in 6 of 22 patients (27%) receiving EVBT after intravascular stenting and always in concomitance with reduction of antithrombotic drug prevention (clopidogrel). Conversely, none of the 13 patients with stents and without EVBT (0%; p < 0.05) and none of the 72 patients (0%; p < 0.01) undergoing EVBT after simple balloon angioplasty presented LATO. CONCLUSIONS: Late thrombotic occlusion occurs not only in patients undergoing EVBT after percutaneous coronary recanalization but also after stenting of the femoropopliteal arteries and may compromise the benefits of endovascular radiation. The fact that all our cases with LATO occurred concomitantly with stopping clopidogrel may indicate a possible rebound mechanism. An intensive and prolonged antithrombotic prevention is probably indicated in these patients.

Acute Disease↗
PubMed2003

Dialysis access-associated steal syndrome: the intraoperative use of duplex ultrasound scan.

Dialysis access-associated steal syndrome (DASS) is an uncommon but serious complication after the creation of an arteriovenous shunt for hemodialysis and is related to an excess perfusion of the fistula. Several surgical options have been described for DASS correction. To achieve an adequate distribution of the blood flow towards the fistula and the hand, intraoperative duplex ultrasound scan monitoring was used in this preliminary communication to control the surgical reduction of volume flow through the fistula. The shunt flow was not estimated with direct insonation of the shunt but calculated from the difference of the bilateral subclavian artery volume flow rates. This new technique has several advantages over a direct shunt evaluation that are discussed in this report. Three patients with DASS are described in whom the technique was successfully applied and led to a normalization of the hand perfusion and to the maintenance of a long-term patency of the fistula.

Aged↗
PubMed2002

Reproducibility of constant-load treadmill testing with various treadmill protocols and predictability of treadmill test results in patients with intermittent claudication.

BACKGROUND: Most trials on the reliability of constant-load treadmill testing use one pair of treadmill settings (speed, grade) only. The question of whether the results can be applied to tests with different settings is left open. Also, claudication distances measured with differing settings are not comparable, rendering the comparison of the results from different trials difficult. This study evaluates the reliability of constant-load testing with various workloads and compares them with claudication distances achieved with walking at normal speed on level ground but also evaluates whether metabolic equivalent (MET) normalization can be used to translate the results of different treadmill tests into each other. METHODS: Fifteen patients with claudication underwent repeated treadmill testing with different treadmill settings, including speeds of 2.0, 3.2, and 4.0 km/h (1.25, 2.0, and 2.5 mph, respectively) and grades of 0% and 12%. The walking capacity was also tested on level ground with a speed chosen by the individual patient. Results of virtual treadmill tests with all possible combinations of the speeds and the grades used were predicted from real tests, with MET normalization. The relationship between real and predicted claudication distances was tested with regression modeling. RESULTS: Reliability coefficients (RCs) for the absolute claudication distance (ACD) were superior to RCs for the initial claudication distance. RCs for ACD ranged between 0.61 and 0.95, with increasing values found with increasing workloads. The best coefficients for the regression of measured on predicted claudication distances were achieved with a model on the basis of a power function (r = 0.963). The model was only appropriate for the prediction of group mean results from clinical trials but cannot be applied to single patient data. For proof of concept, the model was tested with six published studies in which the claudication distances of a patient sample were double treadmill tested with different workloads. The result of the second test was predicted from the first test, and estimated and measured claudication distances were compared. The mean difference (all trials) was 7.9%, whereas the maximum difference amounted to 16.5%. CONCLUSION: For an optimal treadmill test reliability, higher workloads should be used and ACD should be preferred over initial claudication distance. MET normalization provides the basis for the comparability of treadmill test results achieved with different test conditions.

Aged↗
PubMed2002

Factor VII deficiency and a copper metabolism disorder in a patient with Klippel-Trenaunay syndrome.

We report on a patient with Klippel-Trenaunay (KT) syndrome, a factor VII deficiency and a copper metabolism disorder. The KT syndrome involved the left leg and, histologically, the liver. Dermatological examination, duplex ultrasonography and a skin and liver biopsy verified the KT syndrome. A long prothrombin time prompted clotting studies revealing a factor VII deficiency while the other factors were in the normal range. Further laboratory examinations showed a copper metabolism disorder similar to Wilson's disease with a low serum ceruloplasmin level, elevated copper concentration in the urine and increased copper deposition in the liver. Neither liver cirrhosis nor a Kayser-Fleischer corneal ring was present. Sequencing analysis of the Wilson's disease gene ATB7B showed no mutations. The occurrence of these three uncommon pathologies in a single patient has not been described to date, which may suggest a mutation in a hypothetical common regulatory gene leading to this unusual phenotype.

Adult↗