Karl-Heinz Labs

Cross-beam vector Doppler ultrasound for angle-independent velocity measurements

Combining Doppler measurements taken along multiple intersecting ultrasound (US) beams is one approach to obtaining angle-independent velocity. Over 30 laboratories and companies have developed such cross-beam systems since the 1970s. Early designs focused on multiple single-element probes. In the late 1980s, combining multiple color Doppler images acquired from linear-array transducers became a popular modality. This was further expanded to include beam steering and the use of subapertures. Often, with each change in design, came a new twist to calculating the velocity. This article presents a review of most proposed cross-beam systems published to date. The emphasis is on the basic design, the approach used to determine the angle-independent velocity, the advantages of the design, and the disadvantages of the design. From this, requirements needed to convert the idea of angle-independent vector Doppler into a commercial system are suggested.

The value of rapid D-dimer testing combined with structured clinical evaluation for the diagnosis of deep vein thrombosis

PURPOSE Large studies have shown that most cases referred for duplex sonography for suspected deep vein thrombosis (DVT) have normal scan results. For medical and economic reasons, a preselection procedure, which allows the detection of true-negative cases before duplex scanning, is required; this procedure should be characterized by a high sensitivity and a high negative predictive value. METHODS In 343 patients (398 lower extremities) with suspected DVT, the DVT probability was clinically assessed, and a whole blood D-dimer agglutination test and a duplex scan were performed. The diagnostic sensitivities of the D-dimer test alone, a high clinical DVT probability alone, and the combination of both were evaluated. RESULTS The sensitivity values for the D-dimer test to diagnose proximal and distal DVTs were 88.7% and 80.9%, the negative predictive values (NPV) were 96.3% and 97.9%, and the specificity and the positive predictive value (PPV) were 54.8% and 49.6% and 26.6% and 8.2%, respectively. The sensitivities of the clinical DVT probability assessment for the diagnosis of proximal and distal DVTs were 83.9% and 66.7%, respectively; the corresponding NPVs were 94.9% and 96.5%, respectively. The specificity was 56.1% and 50.8%, and the PPVs were 26.1% and 7.0%, respectively. The combined use of the results of the clinical probability assessment and the D-dimer test resulted in sensitivities for proximal and distal DVTs of 98.4% and 90.5%, NPVs of 99.3% and 98.6%, a specificity of 43.4% and 38.4%, and PPVs of 24. 3% and 7.6%, respectively. CONCLUSION The combined use of a clinical DVT probability assessment scheme and the D-dimer test largely avoids false negative results, has a high sensitivity and NPV, helps to reduce the costs of DVT diagnosis, and may, in the future, be useful as a preselection procedure before duplex sonography.

Role of Hemostatic Risk Factors for Restenosis in Peripheral Arterial Occlusive Disease After Transluminal Angioplasty

In a prospective study, the role of various hemostatic factors known to be associated with thrombotic risk was investigated in 71 patients with peripheral arterial occlusive disease (PAOD, stages II through IV, Fontaine; aged 68 +/- 13 years). Laboratory investigations were done before; 1, 24, and 48 hours after; and 3 and 6 months after percutaneous transluminal angioplasty (PTA). Thirty of 71 (42.3%) patients developed restenosis (> 50% reduction of the lumen diameter) at the site of PTA within 6 months, verified by color-coded duplex sonography. Significantly increased levels of thrombin-antithrombin III complexes (P < .01), prothrombin fragments 1 + 2 (P < .01), and D-dimers (P < .01) were found 1 hour, as well as 24 to 48 hours, after PTA. Fibrinogen (P < .01) and von Willebrand factor (P < .01) were significantly higher 48 hours after PTA. Restenotic patients as a whole had higher plasma fibrinogen (3.46 +/- 1.12 versus 2.95 +/- 0.62 g/L, P < .01) and C-reactive protein (25.4 +/- 46.7 versus 7.9 +/- 6.9 mg/L, P < .05) at baseline, as well as higher fibrinogen (P < .05) and prothrombin fragments 1 + 2 (P < .01) during months 3 to 6 after PTA. There was a nonsignificant tendency for higher values of von Willebrand factor (206 +/- 98% versus 184 +/- 100%, P = .2) at baseline in patients with restenosis, whereas tissue plasminogen activator, plasminogen activator inhibitor, coagulation screening tests, blood cell counts, and serum lipids showed no significant difference between the two groups. The relative risk for developing restenosis within 6 months while having high fibrinogen (> 2.8 g/L) or C-reactive protein at baseline was 2.80 (95% CI: 1.30-6.02, P < .01) and 1.96 (95% CI: 1.07-3.58, P < .05), respectively. Patients with critical limb ischemia (stage III/IV, Fontaine) had significantly higher fibrinogen and von Willebrand factor at repeated points of time, as well as significantly higher C-reactive protein and lower creatinine clearance at entry. In the logistic regression risk factor analysis, baseline plasma fibrinogen, C-reactive protein concentration, and the severity of the arterial disease were significantly predictive of restenosis. Our results indicate that high procoagulant factors and persistent thrombin generation of the hemostatic system might promote restenosis, particularly in patients with extended atherosclerosis. This finding suggests that new treatment strategies should be taken under consideration for patients with PAOD and PTA.

Physical training for intermittent claudication: a comparison of structured rehabilitation versus home-based training

In a non-randomized, open-label study results after a structured institution-based peripheral arterial occlusive disease (PAD) rehabilitation program were compared with the results of training at home. Three groups were compared: group 1 (n = 19) PAD rehabilitation; group 2 (n = 19) PAD rehabilitation + clopidogrel 75 mg once daily; group 3 (n = 21) home-based training. The training period was 3 months for all groups, which was followed by a 3-month observation phase (without prescribed training). The rehabilitation program consisted of 3 training hours per week. Background variables, demographics, and baseline claudication distances were comparable between groups. After 3 months of training the absolute claudication distances (ACD) improved by 82.7%, 131.4%, and 5.4% for groups 1, 2 and 3. The initial claudication distances (ICD) changed by 163.8%, 200.6%, and 44.4%, respectively. All changes, except the ACD result for group 3, were statistically significant (p 0.05). Structured training groups (1 and 2) performed significantly better than group 3 (p 0.05). When results from groups 1 and 2 were pooled, ACDs changed from 493.3 218.1 to 1026.0 468.9 m, 546.0 378.8 m [95% CI 417.8 - 674.2 m]; p 0.05. ICDs improved from 175.3 110.8 m to 493.1 326.7 m, 320.8 315.9 m [95% CI 213.9 - 427.7 m]; p 0.05. The difference between the pooled mean results of the structured training groups and the results of group 3 amounted to 474.3 m [95% CI 270.2 - 678.4 m] and 242.4 m [95% CI 99.0 - 385.7 m], for ACD and ICD, respectively. Structured, supervised PAD rehabilitation is a highly efficacious treatment for intermittent claudication and may be regarded as the present gold standard among conservative treatment options.

Reliability of treadmill testing in peripheral arterial disease: a comparison of a constant load with a graded load treadmill protocol

This study aims to evaluate the reliability of repeated graded workload treadmill testing (G-test; 2 mph; 0% grade, increasing 2% every 2 min) and to compare the reliability of a constant workload treadmill protocol (C-test; 2 mph; 12% grade) versus the graded workload treadmill protocol in patients with intermittent claudication, studied longitudinally. A clinical trial investigating an orally stable prostacycline derivative that included 330 patients with intermittent claudication was performed. The trial employed three active treatment groups and one placebo group. Because there were no significant inter-group differences at baseline or after treatment, data from all groups were pooled for the evaluation of treadmill test reliability. Treadmill data were obtained from a 2-week run-in phase where three G-tests were performed, as well as from the beginning and the end of a 3-month double-blind phase where a G-test and a C-test were performed in random order. Treadmill test reliability was described through test process-related and between-subject variances and also using variance-derived parameters such as the reliability coefficient (RC) and the relative precision (RP). A higher value for the RC and a lower value for the RP indicate that the test variability is predominantly due to between-subject variance and not to test process-related variance. Estimates of variance were described for both the maximal or absolute claudication distance (ACD) and the initial claudication distance (ICD) with each treadmill test. Reliability estimates are reported for the total study sample and for patients with baseline claudication distances <300 feet and .300 feet (approximately <100 m; .100 m), as measured with the C-test. The cut-off value was empirically chosen to separate severely diseased from mild to moderately diseased claudicants. Theoretical considerations suggest that reliability measures may differ in these subgroups. With repeated testing during the run-in phase for the measure of ACD, the G-test had an RC of 0.952 and an RP of 21.9%. With the comparison of both test protocols in the entire study population for the measurement of ACD, the G-test had an RC of 0.902 and an RP of 31.3%, while the C-test had an RC of 0.876 and an RP of 35.2%. The results for ICD on the G-test were an RC of 0.809 and an RP of 43.7%, while the C-test had an RC of 0.737 and an RP of 51.3%. The reliability of the ACD measurement for RC and RP was numerically superior to those for the ICD for both protocols. In patients with a baseline ACD <300 feet, the RC for ACD on the G-test was 0.827 and the RP was 41.4%. In contrast, on the C-test the RC decreased to 0.250 and the RP increased to 86.6%. These changes in RC and RP were due to a marked decrease in the between-subject variance, demonstrating the inability of the C-test to separate appropriately the different claudication distances in populations with highly limited baseline claudication distances. During a run-in phase, the G-test has excellent test characteristics. During the longitudinal phase of a trial, the reliability of G-tests and C-tests are comparable in the entire study population. However, in patients with low claudication distances, the G-test should be given preference over the C-test.

The reliability of leg circumference assessment: a comparison of spring tape measurements and optoelectronic volumetry

The purpose of this study was to compare the reliability of repeated spring tape measurements with optoelectronic volumeter measurements for the assessment of lower leg circumferences. The limb circumferences at mid-calf and ankle level of both legs were measured three times using a spring tape measure as well as an optoelectronic volumeter. In all, 30 healthy volunteers participated in the study. Test reliability and repeatability were described through the process-related and between-subject variances and variance-derived parameters such as the reliability coefficient (intraclass correlation coefficient, RC), the relative precision (RP), and the coefficient of repeatability (CR). A higher value for the RC and a lower value for the RP indicate that the test variability is predominantly due to between-subject variance and not to test process-related variance. RCs for both methods, independent of whether measurements were taken at calf or at ankle level, always exceeded 0.95. RPs were in the same order of magnitude for both methods but lower for measurements at calf than at ankle level (range: RPcalf 6.36-8.74%; range: RPankle 12.49-18.56%). CRs for both methods were low and of comparable magnitude (CR range: 4.8-7.7), although slightly smaller for the spring tape. When measurement results from the spring tape and the volumeter were compared, results achieved with the volumeter were significantly longer than those from the spring tape (p, 0.05). Results from both methods were linearly in good agreement and there was no proportional bias; differences shown were due to a significant constant bias regarding the volumeter. Circumference measurements taken by spring tape and by optoelectronic volumetry are both characterized by a comparably high reliability. However, these methods cannot be used in an interchangeable way because a constant bias exists for volumetry, resulting in significantly larger circumferences compared with those measured using the spring tape.

A new rotational thrombectomy catheter: System design and first clinical experiences

AbstractPurpose: To describe a new catheter for the percutaneous mechanical removal of fresh and organized thrombi, and to assess its efficacy and safety in vitro and in vivo. Methods: The catheter consists of a coated stainless steel spiral that rotates at 40,000 rpm over a guidewire inside the whole length of an 8 Fr, single-lumen, polyurethane catheter, driving a dual-blade cutting crown. Abraded occlusion material is sucked into the catheter head through distal side holes and transported by the spiral into a reservoir at the proximal end. The efficacy of the device was tested in arterial models and fresh bovine carotid arteries (n=72). In a clinical pilot study 10 patients (8 women, 2 men; mean age 70.6 ±10.1 years) with occlusions of the superficial femoral artery (2–12 cm, mean 5.8 cm), not older than 4 weeks, underwent thrombectomy with the new catheter. Results: In arterial models and bovine cadaver arteries the catheter completely removed fresh thrombi. Occlusion material of higher consistency was cut into particles of 100–500 μm and transported outside. Thrombectomy was successful and vessel patency restored in all 10 patients. The ankle/brachial pressure index significantly (p<0.0005) increased from 0.41±0.18 before intervention to 0.88±0.15 after 48 hr and to 0.84±0.20 after 3 months. Two reocclusions occurred within 14 days after the intervention. Conclusion: Thrombectomy with the new device appears to be feasible and safe in patients with acute and subacute occlusions of the femoropopliteal artery.

How useful are acceleration- and deceleration-based doppler indices? A trial on patients with percutaneous transluminal angioplasty

The usefulness of indices commonly used in Doppler sonography is limited; the aim of this study was to investigate if inclusion of systolic acceleration and deceleration patterns in Doppler indices will result in practical diagnostic advantages. Systolic delay time index (SDTI) and height-width index (HWI) are compared to Goslings pulsatility index (PI) and to PI-based damping factors (DF) in patients with isolated lesions in the distal superficial femoral artery before and after percutaneous transluminal angioplasty (PTA). Before PTA, all indices distal to the lesion differ significantly from proximal indices. After successful PTA, none of the indices is able to detect the PTA outcome with sufficient sensitivity. The additionally defined curve broadening index (CBI) shows a 100% sensitivity for detecting PTA success in the examined patient population.

Effect of Aspirin Versus Clopidogrel on Walking Exercise Performance in Intermittent Claudication: A Double-Blind Randomized Multicenter Trial

Background This study sought to determine possible effects of different antiplatelet therapies on walking exercise performance in intermittent claudication. Aspirin, in contrast to clopidogrel, interferes with processes that increase collateral conductance in an ischemic animal model. Methods and Results Patients with stable intermittent claudication were recruited from 21 centers in Switzerland and Germany and randomized to either aspirin or clopidogrel treatment. They participated in a 3-month rehabilitation program (electronically monitored, home-based, 1-hour daily walking sessions at a speed of approximately 120 steps/min). Walking distance was assessed by treadmill tests (3.2 km/h; 12% grade) at baseline and after 12 weeks. A total of 229 of 259 patients with a mean age of 66.2±7.7 years completed the study according to the protocol. A total of 24.5% were females, 20.1% diabetics, and 85.6% were active/ex-smokers. The baseline characteristics were a median (interquartile range) ankle/brachial index of 0.69 (0.57±0.8), an initial claudication distance (ICD) of 98 m (70 to 151 m), and an absolute claudication distance (ACD) of 162 m (113 to 302 m). Training resulted in a median increase of initial claudication distance by 33.5 m (33.3%) in the clopidogrel group and 29 m (33.9%) in the aspirin group. The values for absolute claudication distance were 60.5 m (34.9%) and 75 m (35.3%), respectively (pICD=0.42 and pACD=0.66). Conclusions Treatment with aspirin did not show a difference in initial claudication distance or absolute claudication distance improvements compared with clopidogrel after a 3-month walking rehabilitation program. (J Am Heart Assoc. 2012;1:51-56.) Clinical Trial Registration URL: http://www.ClinicalTrials.gov. Unique identifier: NCT00189618, URL: https://EudraCT.ema.europa.eu, Unique identifier: 2004-005041-35

Assessment of Collateral Perfusion: A Pharmacodynamic Study with Bulflomedil Hydrochloride:

The aim of the study was to assess the influence of Buflomedil hydrochloride on collat eral function. Ten patients with isolated superficial femoral occlusions were investigated twice by duplex sonography with measurement sites at the common femoral artery (CF) and the popliteal artery (PA). After the second scan 200 mg of Buflomedil hydrochloride were infused; the infusion was followed by a third duplex examination. Endpoints assessed included the arterial diameter (DCF, DPA), the systolic peak velocity (Vmax), the mean velocity of the maximum envelope (Vmean m.e.), the intensity weighted time average mean velocity (Vmean i.w.), the maximum reverse flow velocity (Vrev), the end- diastolic velocity (Venddiast), the calculated volume flow (Q), the pulsatility and the resistance indices (PI, RI), and PI and RI based segmental damping factors (DFPI, DFRI). For the CF measurement site the infusion of Buflomedil hydrochloride resulted in a signif icant reduction in Vrev and PI (p < 0.05), whereas trends in the opposite direction (increase) were observed for both measures of Vmean and for Q (0.1<p<0.05). No significant changes were reported for the PA measurement site. DFPI numerically decrcased (0.1 <p<0.05). The pattern of changes suggest that Buflomedil hydrochloride induces collateral vasodilation and thus improves collateral function.