[Control of percutaneous biopsy with CT fluoroscopy]

PURPOSE

Clinical evaluation of CT fluoroscopy and comparison with conventional CT guidance for monitoring of non-pulmonary percutaneous biopsy procedures.

MATERIALS AND METHODS

20 non-pulmonary CT-guided biopsy procedures were prospectively performed either with CT fluoroscopy or with conventional CT guidance. CT fluoroscopy was performed using 120 kV and 50, 70 or 90 mA at a frame-rate of three or six images per second. Number of punctures and biopsies, procedure times, radiation doses and histologic results were analyzed separately for conventional CT guidance and for CT fluoroscopy.

RESULTS

With CT fluoroscopy, yield of biopsies was improved (p = 0.005, t-test) and procedure times were shorter than for conventional CT guidance (11.4 +/- 6.0 vs. 23.6 +/- 13.8 min; p = 0.03, t-test). Analysis of procedure related radiation exposure and histologic outcome showed no significant difference between conventional and fluoroscopic CT-guided procedures (p > 0.05, t-test).

CONCLUSIONS

CT fluoroscopy facilitates guidance of percutaneous biopsy procedures. Compared to conventional CT assistance, procedure times are decreased while yield of biopsies is improved.

Distribution and latency of muscle responses to transcranial magnetic stimulation of motor cortex after spinal cord injury in humans

Noninvasive transcranial magnetic stimulation (TMS) of the motor cortex was used to evoke electromyographic (EMG) responses in persons with spinal cord injury (n = 97) and able-bodied subjects (n = 20, for comparative data). Our goal was to evaluate, for different levels and severity of spinal cord injury, potential differences in the distribution and latency of motor responses in a large sample of muscles affected by the injury. The spinal cord injury (SCI) population was divided into subgroups based upon injury location (cervical, thoracic, and thoracolumbar) and clinical status (motor-complete versus motor-incomplete). Cortical stimuli were delivered while subjects attempted to contract individual muscles, in order to both maximize the probability of a response to TMS and minimize the response latency. Subjects with motor-incomplete injuries to the cervical or thoracic spinal cord were more likely to demonstrate volitional and TMS-evoked contractions in muscles controlling their foot and ankle (i.e., distal lower limb muscles) compared to muscles of the thigh (i.e., proximal lower limb muscles). When TMS did evoke responses in muscles innervated at levels caudal to the spinal cord lesion, response latencies of muscles in the lower limbs were delayed equally for persons with injury to the cervical or thoracic spinal cord, suggesting normal central motor conduction velocity in motor axons caudal to the lesion. In fact, motor response distribution and latencies were essentially indistinguishable for injuries to the cervical or thoracic (at or rostral to T10) levels of the spine. In contrast, motor-incomplete SCI subjects with injuries at the thoracolumbar level showed a higher probability of preserved volitional movements and TMS-evoked contractions in proximal muscles of the lower limb, and absent responses in distal muscles. When responses to TMS were seen in this group, the latencies were not significantly longer than those of able-bodied (AB) subjects, strongly suggestive of "root sparing" as a basis for motor function in subjects with injury at or caudal to the T11 vertebral body. Both the distribution and latency of TMS-evoked responses are consistent with highly focal lesions to the spinal cord in the subjects examined. The pattern of preserved responsiveness predominating in the distal leg muscles is consistent with a greater role of corticospinal tract innervation of these muscles compared to more proximal muscles of the thigh and hip.

[Epiphyseal injuries of the distal tibia. Does MRI provide useful additional information?]

Plain film radiography often underestimates the extent of injury in children with epiphyseal fracture. Especially Salter-Harris V fractures (crush fracture of the epiphyseal plate) are often primarily not detected. MRI of the ankle was performed in 10 children aged 9-17 (mean 14) years with suspected epiphyseal injury using 1.0-T Magnetom Expert. The fractures were classified according to the Salter-Harris-Rang-Odgen classification and compared with the results of plain radiography. In one case MRI could exclude epiphyseal injury; in four cases the MRI findings changed the therapeutic management. The visualisation of the fracture in three orthogonal planes and the possibility of detection of cartilage and ligamentous injury in MR imaging makes this method superior to conventional radiography and CT. With respect to radiation exposure MRI instead of CT should be used for the diagnosis of epiphyseal injuries in children.

[Mortality and morbidity conference in radiology]

PURPOSE

To establish a morbidity and mortality conference in a radiology department as an instrument of quality assurance.

METHODS

Since April 1995 a monthly conference is held in the radiology department. Complications of invasive diagnostic procedures (angiography and biopsy) and minimal invasive interventions are presented. Cases of morbidity (major complications) and mortality (deceased patients, who were examined or treated in the radiology department before) are discussed. The identification of cases was possible due to a data base that included all such procedures prospectively.

RESULTS

Twenty cases of major complications were identified and discussed during 18 morbidity and mortality conferences in 1996 and 1997. Out of the 9 patients who died in our hospital and previously had an interventional procedure in the radiology department, one case was identified as being procedure-related. An analysis of this case was performed.

CONCLUSION

With a formalised structure of case detection, the morbidity and mortality conference becomes a tool of a complete analysis of complications and a meaningful instrument for the solution of problems concerning procedure-related complications.

[Dosage monitoring as a quality control instrument in digital radiography]

PURPOSE

Automatic image processing procedures ensure a constant image quality. Overexposed images constitute a danger zone on account of a subjectively better image appearance (improved signal-to-noise ratio). We have examined the software "Dose-Monitoring" both for the identification of false exposures and as a quality control tool.

MATERIALS AND METHODS

Firstly the correlation between dose and present IgM (mean grey tone from the crude histogram of a 12-bit image) was examined by exposing phantoms. A further-reaching comparison of the present IgM values of some MTRAs with the department average (nominal IgM) should detect tendencies for over- and underexposure. Finally a dose reduction in 12 forms of X-ray examination was evaluated with regard to IgM course controls (median IgM).

RESULTS

A high correlation (0.987) between dose and mean grey tone (IgM). In some MRTAs tendency for over-/underexposure was detected. The dose reduction of defined types of X-ray examination lead to a trend to lower mean IgM values.

DISCUSSION

Numerous factors have an influence on the IgM value thus making its evaluation difficult, even so it is a suitable parameter for uncovering tendencies to incorrect exposure and for identifying processes requiring optimization.

CONCLUSIONS

The value of this tool lies in the quality assurance of dose fluctuations and a possible dose reduction.

[Bacteremia in intra-arterial angiography, percutaneous transluminal angioplasty and percutaneous transhepatic cholangio-drainage]

PURPOSE

Prospective evaluation of the rate of bacteremia attributed to invasive radiological techniques.

METHODS

Aerobic and anerobic blood cultures were obtained in 100 patients (62 men, 38 women; mean age 65 +/- 14 years) undergoing intra-arterial angiography (N = 50), PTA (N = 30) or percutaneous transhepatic biliary drainage (PTCD; N = 20). Samples were taken before the treatment (T0), immediately after puncture of the vessel or bile duct (T2), and 30 min after the termination of the procedure (T3).

RESULTS

The overall rate of bacteremia was 18%. During diagnostic angiography a 16% rate of temporary bacteremia (no positive T3 samples) was observed. During PTA the rate was 27% (no clinically significant infectious disease) and during PTCD the rate was 10% (5% cholangitis with septicemia). We isolated staphylococci (S. epidermidis: N = 7, S. species: N = 3, S. aureus: N = 1), streptococci (N = 2), Propionibacterium acnes (N = 5), E. coli (N = 1), Enterococcus faecium (N = 1), Enterobacter species (N = 1), and Clostridium perfringens (N = 1). Apart from the one patient with cholangitis no clinical infectious complication occurred.

CONCLUSION

Temporary bacteremia is rather frequent during invasive radiological procedures. Strictly aseptic conditions and antibiotic prophylaxis, specially in case of implantation of a permanent foreign body, is warranted.

[Modelling of radiological services in the context of a hospital information system: does the DICOM standard meet the requirements?]

PROBLEM

The data model given in the DICOM standard is examined under the aspect of system integration. Semantic properties of the IODs (information object definitions) and their relationships are investigated.

METHOD

Starting from the entities defined in Part 3 of the DICOM standard, we explored how the classes defined there can be integrated into a common data model of the electronic patient record implemented by the HIS (Hospital Information System). Based on the IODs we investigated the definitions and semantics of entities being relevant for structured recording of image data.

RESULTS

Because semantic definitions are incomplete, a proposal is made for the core domain of structured radiologic service recording. Its definition of semantics goes beyond the application domain of radiologic imaging to avoid structural conflicts during HIS/RIS/PACS integration. Differentiation between treatment and billing provides an independent temporal mapping of services concerning medical and billing aspects. Two groups of radiologic services are distinguished: radiologic imaging and additional services.

CONCLUSION

The incomplete definition of IOD semantics leads to potential conflicts during system integration. Complete covering of this topic is necessary for implementation of the electronic patient record.

[Radiation exposure during thoracic radiography at the intensive care unit. Dose accumulation and risk of radiation-induced cancer in long-term therapy]

PURPOSE

Assessment of the additional morbidity risk due to repeated bedside chest radiography according to ICRP 60 during intensive care.

MATERIAL AND METHODS

Ventral surface doses were recorded by thermoluminescence dosimetry in 2 man and 7 women, mean age 36 +/- 12 years, mean height 169 +/- 5 cm, mean weight 74 +/- 8 kg, receiving long-term ventilation therapy due to Adult Respiratory Distress Syndrome (ARDS).

RESULTS

From 18 to 126 days duration of therapy 9 patients received a total of 348 bedside chest radiographs, mean 39 +/- 22 radiographs per patient. 217 chest radiographs yielded 217 surface doses and 217 gonadal doses. Patient's mean surface dose varies between at least 0.31 +/- 0.12 mGy and at most 0.56 +/- 0.09 mGy. The surface dose representing gonadal exposure is less than 0.03 mGy per exposure. The mean effective dose is about 0.15 mSv per exposure. The cumulative effective dose Heff ranges between 2.49 mSv and 14.09 mSv, thus estimating the additional individual cancer risk ranges between 0.01% and 0.07%.

CONCLUSION

In comparison with the decreased prognosis of severely ill long-term ventilated patients the additional morbidity risk due to chest radiographs is a negligible quantity.

Correlation of flow velocity measurements by magnetic resonance phase contrast imaging and intravascular Doppler ultrasound

RATIONALE AND OBJECTIVES

The authors compare the magnetic resonance (MR) phase contrast flow velocity measurements in varying concentric stenoses with invasive measurements obtained with a Doppler guidewire.

METHODS

Flow velocity measurements were obtained using a calibrated 0.018 inch 12 MHz Doppler guidewire and a 1.0 T MR imaging system in a pulsatile hydraulic model with variable arterial stenoses. Velocity measurements were performed proximal, intrastenotic, and distal to the stenoses. The cross-sectional area of stenosis was calculated from the data of both methods. For MR imaging measurements, fast low-angle shot two-dimensional phase contrast sequences with different velocity encodings were used.

RESULTS

Phase contrast flow measurements correlated well (r = 0.95, Pearson) with Doppler guidewire-based flow velocity data. Generally, flow velocities obtained with MR imaging were lower when compared with the Doppler-based data (P < or = 0.001, Wilcoxon matched pairs test). However, the ratios and the calculated cross-sectional area of stenoses showed a high correlation (r = 0.96) with the predefined area of stenoses.

CONCLUSIONS

The assessment of flow alterations in vitro due to variable stenoses using MR phase contrast flow measurements is very well correlated with the Doppler guidewire. Consequently, these results required in vivo measurements of atherosclerotic lesions to evaluate the clinical impact.

[Postoperative imaging of synthetic coronary artery bypass graft patency by means of CT angiography]

PURPOSE

CT angiography was performed in 12 patients with insufficient autologous graft situations to evaluate postoperative patency and situation of the proximal, distal and coronary artery anastomoses of synthetic Perma-Flow coronary artery bypass grafts.

METHODS

Bypass grafts were evaluated postoperatively with spiral CT of the mediastinum. At a flow rate of 3 ml/s, 120 ml of contrast material were applied over a cubital vein. Slice thickness was 3 mm, maximum pitch factor 2 and image reconstruction was performed at 2 mm increment. Shaded surface displays were analysed together with axial scans for bypass evaluation.

RESULTS

8 out of 12 synthetic bypasses proved to be patent. One bypass was completely occluded and in three patients the distal portions of the grafts were occluded. Coronary angiography performed in one case confirmed complete bypass occlusion. Due to the occlusions, 8 distal and 12 proximal anastomoses were visible. Only 8 out of 19 side-to-side coronary artery anastomoses could be sufficiently well imaged with this technique.

CONCLUSIONS

CT angiography is suitable for postoperative screening of synthetic coronary bypasses to determine the patency and anastomotic situations. Coronary artery anastomoses however are not sufficiently imaged and coronary angiography continues to be required.

[Pitfalls when using a contrast media injector in MRI]

PURPOSE

Using a power injector to applicate Gd-DTPA we found a contrast enhancement of the pyelo-caliceal system even in the native studies, and hence we analysed pitfalls when using power injectors in MRI.

MATERIAL AND METHODS

We used a power injector Spectris (MedRad, Maastricht, Netherlands). In vitro artifacts were achieved by the mixture of contrast media and saline solution. We substituted contrast media by red water, NaCl by clear water.

RESULTS

Using power injectors in MRI, some pitfalls must be avoided, which can render investigations useless, especially dynamic contrast-enhanced investigations.

CONCLUSION

In our study we showed an easy way to overcome some pitfalls and use a power injector in MRI in a diagnostically helpful way. The simple use of valves inhibits the mixture of contrast media and saline solution.

[Magnetic resonance phlebography (MRP) of the abdomen and pelvis]

PURPOSE

To evaluate the image quality of magnetic resonance venography (MRV) of pelvic and abdominal veins.

METHODS

A retrospective analysis of all MRV between 1993 and 1996 was conducted. A 2D-FLASH-TOF without breath hold and with arterial presaturation was used. All venous segments have been assessed for the quality of visualisation and an overall image quality was determined. 43% of our patients had malignant disease and phlebothrombosis had already been diagnosed in 64%.

RESULTS

126 examinations and 1696 venous segments were analysed. The overall quality of the examination was good, however one examination was non diagnostic because of motion artefacts. Vessels along the vertical axis were good visualised in over 90%. Most important reasons for insufficient visualisation were breathing, motion and metal artefacts as well as compression and displacement of veins due to tumour disease.

CONCLUSIONS

Magnetic resonance venography without breath hold TOF technique is practical and robust for routine clinical applications.

[Standardized enteroclysis. Monitoring of intra-lumen pressure in 3 different patient groups]

PURPOSE

Monitoring of intraluminal pressure in standardized enteroclysis.

MATERIAL AND METHODS

Pressure monitoring with a double-lumen tube during fluoroscopy-guided adjustment of contrast media instillation rate due to small bowel motility and contrast media transport of 67 patients. Stratification according to patient data and findings in enteroclysis: Crohn's disease (n = 12), non-inflammatory disease (n = 35) and irritable bowel syndrome (n = 20).

RESULTS

The amount, instillation period and rate of contrast media and distension media were not statistically different within the study population. Crohn's disease patients showed elevated intraluminal pressure at the end of the distension phase (47.94 +/- 10.42 cm H2O versus 38.03 +/- 10.08 and 39.55 +/- 9.74 cm H2O, respectively, P = 0.0099), as well as at the end of the examination (48.59 +/- 10.42 cm H2O versus 39.66 +/- 6.52 and 35.67 +/- 8.28 cm H2O, P = 0.0002). In comparison with both other patient groups, maximum intraluminal pressure in Crohn's disease is higher and totals 51.75 +/- 9.94 cm H2O versus 43.00 +/- 6.20 and 39.55 +/- 9.74 cm H2O, P = 0.0010. Patients with Crohn's disease require a longer instillation period of distension media (28.05 +/- 12.82 min, not statistically significant).

CONCLUSION

Intraluminal pressure differs in standardized enteroclysis with fluoroscopy-guided instillation rate adjustment. Irrespective of stenosis or acute inflammation, patients with Crohn's disease show a higher intraluminal pressure compared to patients with non-inflammatory disease or irritable bowel syndrome.

Local intravascular drug delivery: in vitro comparison of three catheter systems

PURPOSE

The aim of this in vitro study was to compare different catheter systems for local drug delivery with respect to the penetration depth of a biotin marker solution delivered into the vessel wall.

METHODS

Post-mortem carotid arteries from pigs were locally infused with a biotin solution using three different catheter systems. With all catheters (microporous balloon catheter, hydrogel-coated balloon catheter, and spiral balloon catheter) we used the same pressure of 405 kPa (4 atm) and infusion times of 60, 90, and 300 sec. After infusion the arteries were histologically prepared and stained using a biotin-specific method. With a light microscope an observer, blinded to the catheter type, scored the amount of biotin within the vessel wall, measured as staining intensity, and the penetration depth of the biotin.

RESULTS

Delivery with the hydrogel-coated balloon catheter was limited to the intima and the innermost parts of the media. The spiral balloon and microporous balloon catheter showed both a deeper penetration and a larger amount of delivered biotin compared with the hydrogel catheter, with a slightly deeper penetration using the microporous catheter. The penetration depth showed a correlation with infusion time for the spiral balloon and microporous catheters, but not for the hydrogel-coated catheter.

CONCLUSION

Different catheter designs lead to different patterns of local drug delivery. The differences in penetration depth and amount of the substance delivered to the vessel wall should be known and might be useful for targeting specific areas within the vessel wall.

An upper body exercise system incorporating resistive exercise and neuromuscular electrical stimulation (NMS)

A device is described which combines arm crank ergometry and neuromuscular electrical stimulation (NMS) delivered at different phases of the crank cycle. Details of the device including circuit schematics are shown. The device was evaluated by non-paralyzed subjects for its operational safety and by tetraplegic subjects for its effectiveness as a muscle-strengthening tool. All subjects showed improvement in one or more of their manual muscle scores. The most dramatic increased motor score occurred in the triceps muscle group. There was an average increase in the manual muscle score of 1.1 +/- 0.2 for the left triceps and 0.7 +/- 0.1 for the right triceps after eight weeks of NMS assisted exercise. No adverse effects were experienced and it appears to meet safety considerations necessary for this group of individuals. Preliminary observations indicate that an eight-week exercise protocol that utilizes this device can be beneficial for this population.

The precise determination of vascular lumen and stent diameters: correlation among calibrated angiography, intravascular ultrasound, and pressure-fixed specimens

PURPOSE

Luminal diameters measured in vivo by calibrated-catheter angiography and by intravascular ultrasound were correlated with those obtained from pressure-fixed histologic cross-sections to determine the accuracy of both methods.

METHODS

Angiographic and endosonographic diameter measurements were performed in the center of stents placed in the iliac arteries of 10 miniature pigs and were compared with luminal and stent diameters in postmortem, pressure-fixed, histologic cross-sections from identical locations.

RESULTS

Compared with histologic diameters, magnification-corrected angiographic measurements still magnified vascular luminal diameters by 0.7 +/- 0.71 mm (r = 0.41, Pearson; p < 0.003, Wilcoxon, matched pairs), whereas intravascular ultrasound measurements proved to be almost identical to the histologic lumina (r = 0.95, Pearson; p > 0. 5, Wilcoxon, matched pairs). Similarly, stent diameters correlated well between endosonographic and histologic measurements (r = 0.91; p = 0.002), and less well between angiographic and histologic diameters (r = 0.62; p = 0.002).

CONCLUSION

Since calibrated angiography still overestimates vascular lumina, endosonography is the preferred technique for accurate in vivo measurements.

[Reactive thymus dysplasia following therapy for ACTH-producing tumors]

Surgical or conservative treatment of ACTH-producing tumors results in acute drop of the previously excessively high cortisol levels. The following associated pathophysiological changes also occur in the organism's recovery from stress, such as trauma, operation or chemotherapy of tumors. Both cases result in a regeneration of the immune system, which might even be exalted. The corresponding radiographic feature is the "rebound" enlargement of the thymus occurring about six months after remission of hypercortisolism. Histological examination reveals benign thymus hyperplasia. Especially in cases of still unknown primary tumor the appearance of this anterior mediastinal mass can lead to misdiagnosis. We present the cases of two patients with diffuse thymic hyperplasia following surgical and medical correction of hypercortisolism. One patient suffered from classic Cushing's disease responding to transsphenoidal resection of an ACTH-secreting pituitary microadenoma. Six months later CT of the chest incidentally demonstrated an anterior mediastinal mass known as thymic hyperplasia. The second patient presented with an ectopic, still unkown source of ACTH-production. Six months after medical correction of hypercortisolism CT of the thorax showed an enlargement of the anterior mediastinum. Thymectomy was performed in order to exclude thymus carcinoid. Histological examination revealed benign thymus hyperplasia with negative immunostaining.

CONCLUSION

Radiologists and clinicians should be familiar with the pathophysiological changes resulting from precipitously dropping cortisol levels in order to prevent diagnostic errors and unnecessary operations.

Local intraarterial thrombolysis: in vitro comparison of various infusion catheters

PURPOSE

Catheters are compared in vitro to evaluate the efficacy of thrombolysis during urokinase infusion within the thrombus.

METHODS

Six catheters were introduced individually into human thrombus within a stenotic flow model. Urokinase was infused continuously into the thrombus. To quantify the efficacy of thrombolysis, pressure gradients were recorded proximal and distal to the thrombus and during the course of infusion. Uniformity of lysis was assessed radiographically.

RESULTS

The fastest and most homogeneous thrombolysis was achieved with the EDM and the straight-flush catheter, shown by decreasing transthrombotic pressure gradients. All other catheter designs showed less homogeneous and delayed thrombolysis (p </= 0.001, Friedmann-Test, Schaich-Hamerle). There was no significant difference in the efficacy of thrombus dissolution between the EDM and the straight-flush catheter (Wilcoxon, matched pairs, p > 0.7).

CONCLUSION

The EDM catheter and the straight flush catheter achieved the most homogeneous and fastest thrombolysis, apparently due to the best urokinase distribution within the thrombus.

Evaluation of a training program for persons with SCI paraplegia using the Parastep 1 ambulation system: part 1. Ambulation performance and anthropometric measures

OBJECTIVE

To describe performance parameters and effects on anthropometric measures in spinal cord injured subjects training with the Parastep 1 system.

DESIGN

Before-after trial.

SETTING

Human spinal cord injury applied research laboratory.

PARTICIPANTS

Thirteen men and 3 women with thoracic (T4-T11) motor-complete spinal cord injury: mean age, 28.8yrs; mean duration postinjury, 3.8yrs.

INTERVENTION

Thirty-two functional neuromuscular stimulation ambulation training sessions using a commercially available system (Parastep-1). The hybrid system consists of a microprocessor-controlled stimulator and a modified walking frame with finger-operated switches that permit the user to control the stimulation parameters and activate the stepping.

OUTCOME MEASURES

Distance walked, time spent standing and walking, pace, circumferential (shoulders, chest, abdomen, waist, hips, upper arm, thigh, and calf) and skinfold (chest, triceps, axilla, subscapular, supraillium, abdomen, and thigh) measurements, body weight, thigh cross-sectional area, and calculated lean tissue.

RESULTS

Statistically significant changes in distance, time standing and walking, and pace were found. Increases in thigh and calf girth, thigh cross-sectional area, and calculated lean tissue, as well as a decrease in thigh skinfold measure, were all statistically significant.

CONCLUSIONS

The Parastep 1 system enables persons with thoracic-level spinal cord injuries to stand and ambulate short distances but with a high degree of performance variability across individuals. The factors that influence this variability have not been completely identified.

Evaluation of a training program for persons with SCI paraplegia using the Parastep 1 ambulation system: part 3. Lack of effect on bone mineral density

OBJECTIVE

To determine if the bone mineral density loss seen after spinal cord injury (SCI) is reversed by a walking program using the Parastep 1 system.

DESIGN

Before-after trial.

SETTING

Human SCI applied research laboratory.

PARTICIPANTS

Thirteen men and 3 women with thoracic motor- and sensory-complete SCI, mean age 28.8yrs, mean duration postinjury 3.8yrs.

INTERVENTION

Thirty-two functional neuromuscular stimulation (FNS) ambulation training sessions using a commercially available system (Parastep 1). This system consists of a microprocessor-controlled stimulator and a modified walking frame with finger-operated switches that permit the user to control the stimulation parameters and activate the stepping.

OUTCOME MEASURE

Bone mineral density at the femoral head, neck, and Ward's triangle measured using a Lunar DP3 dual-photon densitometer.

RESULTS

No significant change in bone mineral density was found using repeated measures analyses of variance.

CONCLUSIONS

Axial loading combined with muscle stimulation and resistive exercise does not result in significant changes in bone mineral density in persons with complete paraplegia.

Evaluation of a training program for persons with SCI paraplegia using the Parastep 1 ambulation system: part 2. Effects on physiological responses to peak arm ergometry

OBJECTIVE

To examine the task-nonspecific effects of functional neuromuscular stimulation (FNS)-assisted ambulation training on the physiological responses of persons with paraplegia to upper extremity exercise challenge.

DESIGN

Before-after trial.

SETTING

Human spinal cord injury (SCI) applied research laboratory.

PARTICIPANTS

Twelve men and three women with motor- and sensory-complete thoracic-level SCI (T4-T11), mean age 28.2 +/- 6.8yrs (range, 21.1 to 45.2yrs), mean injury duration 3.7 +/- 3.0yrs (range, 7 to 8.8yrs).

INTERVENTION

Thirty-two sessions of FNS ambulation training using a commercial six-channel system (Parastep 1). This system is composed of a microprocessor-controlled electrical stimulation unit and a walking frame outfitted with finger switches that allow the user to independently control the system and stimulation parameters.

OUTCOME MEASURES

Peak and subpeak physiological responses to arm ergometry testing and upper extremity strength measures, obtained before and after the FNS ambulation training.

RESULTS

Statistically significant increases in peak values for time to fatigue, peak power output, and peak VO2 (all p < .001). Heart rate was significantly lower throughout subpeak levels of arm ergometry after the ambulation training (p < .05). Values of upper extremity strength were not significantly altered after training.

CONCLUSIONS

FNS ambulation by persons with SCI paraplegia results in task-nonspecific training adaptations. Central cardiovascular adaptations were indicated as the primary source of these beneficial alterations in exercise responses.

Evaluation of a training program for persons with SCI paraplegia using the Parastep 1 ambulation system: part 4. Effect on physical self-concept and depression

OBJECTIVE

To determine whether persons with spinal cord injury (SCI) paraplegia who participated in an electrical stimulation walking program experienced changes in measures of physical self-concept and depression.

DESIGN

Before-after trial.

SETTING

Human SCI applied research laboratory.

PARTICIPANTS

Volunteer sample of 12 men and 3 women with SCI paraplegia, mean age 28.75 +/- 6.6yrs and mean duration of injury 3.8 +/- 3.2yrs.

INTERVENTION

Thirty-two FNS ambulation training sessions using a commercially available system (Parastep 1). The hybrid system consists of a microprocessor-controlled stimulator and a modified walking frame with finger-operated switches that permit the user to control the stimulation parameters and activate the stepping.

OUTCOME MEASURES

The Tennessee Self-Concept Scale (TSCS) and the Beck Depression Inventory (BDI) were administered before and after training. Only the Physical Self subscale of the TSCS was analyzed. After training, individual interviews were performed to assess participants' subjective reactions to the training program.

RESULTS

A repeated measures analysis of variance indicated that desired directional and statistically significant changes occurred on the Physical Self subscale of the TSCS (F(1,14) = 8.54, p < .011) and on the BDI (F(1,14) = 5.42, p < .035).

CONCLUSIONS

Subsequent to the ambulation training program there were statistically significant increases in physical self-concept scores and decreases in depression scores.

Evaluation of a training program for persons with SCI paraplegia using the Parastep 1 ambulation system: part 5. Lower extremity blood flow and hyperemic responses to occlusion are augmented by ambulation training

OBJECTIVE

To test whether 12 weeks of exercise conditioning using functional neuromuscular stimulation (FNS) ambulation alters the resting lower extremity blood flow and hyperemic responses to vascular occlusion in subjects with paraplegia, and to determine whether an association exists between limb flow and lower extremity fat-free mass.

DESIGN

Pretest, posttest.

SETTING

Academic medical center.

PARTICIPANTS

Subjects with chronic neurologically complete paraplegia.

INTERVENTION

Thirty-two sessions of microprocessor-controlled ambulation using electrically stimulated contractions of lower extremity muscles and a rolling walker.

OUTCOME MEASURES

Subjects underwent quantitative Doppler ultrasound examination of the common femoral artery (CFA) before and after training. End-diastolic arterial images and arterial flow-velocity profiles obtained at rest and after 5 minutes of suprasystolic thigh occlusion were computer-digitized for analysis of heart rate (HR), CFA peak systolic velocity (PSV), CFA cross-sectional area (CSA), flow velocity integral (FVI), pulse volume (PV), and CFA (arterial) inflow volume (AIV).

RESULTS

Significant effects of training on CSA (p < .0001), FVI (p < .05), computed PV (p < .001), and computed AIV (p < .01) were observed. Resting HR was lower following training (p < .05). The change for resting PSV approached but did not reach significance (p = .083). Analysis of postocclusion PV and AIV showed significant effects for conditioning status (p values < .01), postcompression time (p values < .0001), and their interaction (p values < .01). At 1 minute after occlusion, the posttraining AIV response was 78.2% greater in absolute magnitude and 17.4% more robust when expressed as a percentage change from its resting value than before training. Significant correlations were found between thigh fat free mass and both AIV and PV (p values < .05).

CONCLUSION

Exercise training using FNS ambulation increases the resting lower extremity AIV in individuals with paraplegia and augments the hyperemic response to vascular occlusion. Improved posttraining blood flow is attributable both to vascular structural changes and upregulation of vascular flow control mechanisms. Limb mass is associated with the volume of arterial blood flow.

Magnetic resonance imaging and signal-averaged electrocardiography in patients with repetitive monomorphic ventricular tachycardia and otherwise normal electrocardiogram

Early or localized forms of arrhythmogenic right ventricular dysplasia (ARVD) have been proposed as the arrhythmogenic substrate of repetitive monomorphic ventricular tachycardia (RMVT) originating in the right ventricular outflow tract in patients without any underlying cardiac abnormality on clinical examination and echocardiography. To further examine this hypothesis, magnetic resonance imaging (MRI) and signal-averaged electrocardiography (SAECG) were performed on 23 patients with RMVT and normal 12-lead standard ECG of conducted sinus beats. MRI was performed using ECG-gated turbo spin-echo images of the heart in order to detect signs of early or localized forms of ARVD, such as localized wall thickness reductions, signal intensity increase indicating adipose tissue infiltrates, and regional bulgings or aneurysms. MRI was normal in 22 (96%) of 23 study patients. In the remaining patient (4%), MRI demonstrated signal intensity increase in the intraventricular septum but not in the right ventricular outflow tract. Time-domain analysis of the SAECG was normal in 21 (91%) of 23 patients and revealed ventricular late potentials in 2 study patients (9%). Frequency-domain analysis of the SAECG was normal in 22 (96%) of 23 patients and revealed ventricular late potentials in one study patient (4%). We conclude that normal MRI findings of the heart and absence of ventricular late potentials in the SAECG in most patients with RMVT and otherwise normal ECG do not support the hypothesis that early or localized forms of ARVD create the arrhythmogenic substrate in the majority of these patients.