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Original Research |
1 Hospital Clinica Alemana, Santiago, Chile.
2 Klinik und Poliklinik fur Radiologie der Johannes-Gutenberg-Universität
Mainz, Mainz, Germany.
3 Hospital Clinico de la Universidad Catolica, Servicio Radiologia, Santiago,
Chile.
4 Krankenhaus der Barmherziegen Bruder, Universität Wien, Vienna,
Austria.
5 Bayer HealthCare, Montville, New Jersey, 07045.
6 Present address: Symbiotic Pharma Research, Pine Brook, NJ.
7 EPIX Pharmaceuticals, 4 Maguire Rd., Lexington, MA 02421.
Received April 20, 2007;
accepted after revision July 3, 2007.
Address correspondence to E. C. Parsons, Jr.
(eparsons{at}epixpharma.com).
Abstract
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SUBJECTS AND METHODS. A total of 185 adult patients with known or suspected pedal arterial disease were randomized in a group receiving 0.03 mmol/kg and a group receiving 0.05 mmol/kg of gadofosveset for MR angiography of the pedal arteries. Gadofosveset-enhanced and unenhanced time-of-flight MR angiograms were compared with conventional angiograms, the standard of reference, for the presence of vascular stenosis. All patients underwent drug safety analysis.
RESULTS. For each of three blinded readers, the specificity (21-35%) of gadofosveset-enhanced MR angiography was a statistically significant (p < 0.010) improvement over that of unenhanced MR angiography in the detection of clinically significant (> 50%) stenosis. The sensitivities of the two techniques were similar. For all blinded readers of MR angiograms, sensitivity, specificity, and accuracy were higher with use of the 0.03-mmol/kg dose of gadofosveset than with the 0.05-mmol/kg dose. In the 0.03-mmol/kg group, 28% of patients reported a total of 50 adverse events, 96% of which were reported as mild or moderate. In the 0.05-mmol/kg group, 28% of patients reported a total of 55 adverse events, 98% of which were reported as mild or moderate. No patients died; one patient left the study because of myocardial infarction considered unrelated to the study drug.
CONCLUSION. Because of markedly better efficacy than no contrast agent and a minimal and transient side-effect profile, 0.03 mmol/kg of gadofosveset was found safe and effective for MR angiography of patients with pedal arterial disease.
Keywords: angiography • arteries • contrast media • MR angiography • pedal artery • peripheral arterial disease • vascular studies
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Gadofosveset (Vasovist, EPIX Pharmaceuticals) is a gadolinium-based blood-pool contrast agent that reversibly binds to albumin in the blood. Better MR angiographic results in a variety of vascular beds have been reported [9-11] with gadofosveset than with no contrast agent. Results of a previous dose-ranging phase 2 study [10] showed a significant dose response for gadofosveset and that 0.03 mmol/kg was the most clinically appropriate dose for MR angiography of the abdomen. The purpose of this study was to establish the diagnostic value of gadofosveset in MR angiography of the pedal arteries.
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Patient Selection
Enrolled in the study were patients 18 years or older with known or
suspected pedal arterial disease diagnosed on the basis of physical
examination findings or medical history and who were scheduled for an
angiographic examination, including pedal evaluation. The MR and conventional
angiographic studies were performed within 3-30 days of each other. Patients
must not have undergone surgery or percutaneous transluminal angioplasty of
the target vessels between enrollment and completion of the imaging studies.
No patients with preexisting stents or grafts in the limb to be imaged were
included. Patients were excluded from the study if they had had a major
cardiovascular event, such as myocardial infarction or stroke, within 30 days
before study randomization. To avoid use of the contrast agent in patients
with severe renal insufficiency, patients were excluded if they had a serum
creatinine concentration greater than 2.0 mg/dL or a history of abnormal renal
function, such as renal transplantation or hemodialysis. Pregnant or lactating
women were not included. Other exclusion criteria were a history of
hemoglobinopathy or any specific MRI exclusion criterion, such as
claustrophobia, involuntary motion disorder, and presence of a metallic
implant. Patients also were excluded if they had a hypersensitivity to
gadolinium-based contrast agents or had previously received gadofosveset.
Patients could not have received iodine or other contrast agents within 3 days
before or after gadofosveset administration.
Contrast Agent
Gadofosveset trisodium is a gadolinium-based small molecule (molecular
weight, 975.77 Da) blood-pool contrast agent. It has been shown 88%
noncovalently bound to albumin in 4.5% human serum albumin in vitro. The
binding sequesters most of the drug in the vascular space, extends the
half-life with respect to nonbinding agents, and increases relaxivity to
approximately five times that of gadopentetate dimeglumine at 1.5 T
[12]. Gadofosveset is
primarily renally excreted
[13].
IV injection of 0.03-0.05 mmol/kg body weight of gadofosveset was determined to be safe, well tolerated, and effective in phase 1 and 2 clinical trials [10, 14, 15]. In this trial, patients received either 0.03 or 0.05 mmol/kg according to a predetermined randomization scheme. Each patient received an injection of the appropriate volume of drug administered over 25 seconds. The dose was followed by a 30-mL saline flush. Dynamic acquisitions were initiated by an automated timing protocol or by the timing of a bolus of not more than 10% of the specified dose of gadofosveset. If these methods were not available, the imaging delay was determined by the patient's history or a delay empirically determined in previous studies (65 seconds for < 60 kg body weight, 55 seconds for > 60 kg body weight).
Imaging
Digital subtraction angiography was performed according to individual
institutional standards. Imaging of the pedal arteries in at least two views
was required. Lateral and anteroposterior views included at least from the
tibiotalar junction to the metatarsophalangeal junction with an image
intensifier matrix of at least 1,024 x 1,024 or cut images. Imaging was
to be extended at least 20 seconds beyond the time the contrast agent was
expected to arrive in the foot. Additional views were obtained if medically
necessary.
MRI was performed with 1.0- to 1.5-T field strength MRI systems with approved and commercially available hardware and software. Before gadofosveset administration, unenhanced (baseline) MR angiograms were obtained according to the standard sequence at each institution or a sequence recommended by the vendor of the MRI system. Approximately one half of the patients in each dose group were imaged with a typical 2D time-of-flight sequence. The other half were imaged with a 3D hybrid or phase-contrast method. Before gadofosveset injection, a subtraction mask was obtained with the imaging parameters specified for the dynamic images.
After gadofosveset injection, dynamic and steady-state imaging was performed with a 3D spoiled gradient-recalled echo technique. Dynamic images were acquired as a sagittal slab, 256 x 320 pixels in plane, 170 x 260 mm field of view with 35-36 partitions interpolated to 70-72 slices set to less than 1.8 mm acquired (< 0.9 mm reconstructed). The contrast parameters were TR/TE, 6-7/minimum with a flip angle of 25°. Reduced-phase field of view gave 167-208 phase steps for an acquisition time of approximately 45 seconds. Two phases (time points) were acquired. The second phase began immediately after the first. One of the allowed timing methods was used to time the start of the dynamic image acquisition.
Steady-state images were acquired as a sagittal slab, 320 x 320 pixels in plane, 280 x 210 field of view, 80 partitions interpolated to 160 slices set to 0.8 mm acquired (0.4 mm reconstructed). The contrast parameters were 18/1.9 with a flip angle of 30°. One fat-suppression pulse per TR and 240 phase steps were used for an acquisition time of approximately 6 minutes. Courser resolution was used in a few cases in which gradient strength did not allow submillimeter slice thickness. Acquisition of steady-state images began within 15 minutes of gadofosveset administration.
Safety Monitoring
After baseline documentation, patients were monitored for at least 72 and
up to 96 hours after administration of gadofosveset. Monitoring included
physical examination findings, vital signs, pulse oximetry values, ECG, and
results of clinical laboratory tests (including hematologic studies, clinical
chemistry, coagulation studies, anaphylaxis panel, and urinalysis).
All reports of adverse events (AEs) were recorded according to International Conference on Harmonisation guidelines. The principal investigators at each study site identified AEs regardless of causal relation to the study drug. Onset, duration, severity, and outcome of all AEs were recorded. All AEs were assessed by the principal investigator, who assigned a severity score of mild (did not cause significant discomfort to the patient or change in activities of daily living), moderate (low level of inconvenience to the patient; patient to continue with activities of daily living), or severe (substantially interfered with activities of daily living). Serious (potentially life-threatening) AEs were to be noted and reported. The principal investigator assessed the likelihood (unlikely to be related, possibly related, and probably related) that an AE was related to the administration of gadofosveset. All study monitoring and AE reporting followed good clinical practice guidelines.
Standard of Reference
Digital radiographs were transmitted to a central imaging facility. Some
institutions provided additional views on film, and these images were
digitized for blinded reading. All images were read at a central location by
board-certified practicing radiologists. Two independent readers blinded to
patient information aside from the images interpreted the radiographs. The
following four vessels were evaluated: distal posterior tibial artery, medial
plantar artery, lateral plantar artery, and dorsal plantar artery. The readers
identified stenosed regions, noted the location of the most stenosed area on
an anatomic diagram, and measured the normal and stenotic diameters using
digital calipers. Readers were allowed to deem a vessel uninterpretable if the
images were not sufficient to make a determination. For the purposes of the
primary analysis, clinically significant disease in each segment was defined
as stenosis of 50% or more of the diameter of the vessel. A third blinded
reader (the adjudicator) evaluated all vessels on which the first two readers
disagreed about either interpretability or presence or absence of clinically
significant disease. Each vessel was thus assigned a diagnosis based on the
agreement of at least two of the three blinded readers' interpretations of the
conventional angiograms.
MRI Readers
All readers of MR angiograms were board-certified practicing radiologists
and were blinded to patient information. Unenhanced and contrast-enhanced
images were separately presented and evaluated according to a block
randomization scheme that ensured that at least one fourth of all image data
sets separated the two data sets representing a given patient. Images were
processed and displayed on a workstation (Advantage Windows, GE Healthcare).
Readers were provided source images and maximum intensity projections of 3D
data sets. For the contrast-enhanced examinations, dynamic contrast-enhanced
and steady-state data sets were shown together, as were subtraction images
(contrast-enhanced minus unenhanced mask for dynamic contrast-enhanced MR
angiography). Readers were allowed to perform further postprocessing,
including subvolume maximum intensity projections and oblique reformations, on
any data set.
Quantitative image evaluation was performed in the same manner as for the conventional angiographic evaluations. The readers first determined whether the images were interpretable. A patient's side was considered uninterpretable if two or more vessels were uninterpretable. If the side was interpretable, the readers measured the degree of maximum stenosis in each interpretable vessel to assess the presence or absence of disease in that vessel. Measurements were performed on source or reformatted images with on-screen digital calipers. The blinded readers were not asked to measure stenosis when it was less than 10%. The minimum cross-sectional diameter at the level of stenosis and the diameter of the most normal adjacent arterial segment were measured. After the stenosis measurement, readers rated their overall diagnostic confidence on a per-side basis using a 5-point scale (1, not confident; 2, somewhat not confident; 3, uncertain; 4, somewhat confident; 5, very confident) [16].
Analysis and Statistical Methods
The primary analysis was performed to determine sensitivity, specificity,
and overall accuracy in the detection of clinically significant stenosis in
the pedal arteries on gadofosveset-enhanced MR angiography and unenhanced MR
angiography in comparison with the adjudicated conventional angiographic
standard. Sensitivity was defined as the number of correctly identified
diseased vessels divided by the total number of diseased vessels. Specificity
was defined as the number of correctly identified normal vessels divided by
the total number of normal vessels. Accuracy was defined as the number of
correctly identified vessels (abnormal or normal) divided by the total number
of vessels with a reference diagnosis. All MR angiograms on which vessels were
uninterpretable were considered inaccurate for the purposes of determining
sensitivity, specificity, and accuracy. That is, if a vessel was deemed
uninterpretable by a blinded reader of an MR angiogram and was diagnosed as
diseased with conventional angiography, the MR angiographic finding for the
vessel was counted as false negative. However, if the vessel was considered
not clinically significant with conventional angiography, the MR angiographic
finding for the vessel was counted as false positive. Statistical comparisons
between gadofosveset-enhanced MR angiography and unenhanced MR angiography
were performed with sensitivity, specificity, and accuracy for each reader.
Statistical significance was assessed with a cluster-corrected McNemar's test,
which is used to account for correlations within the vessels of each subject
[17].
The 0.05- and 0.03-mmol/kg groups were considered separately in all analyses, and the groups were compared with respect to the primary analysis. The 95% CIs for the difference between contrast-enhanced results were calculated. This calculation involved a cluster correction on the variance estimates before estimation of the differences between the unpaired groups. The secondary analyses were to be performed on the dose group that had superior performance or on the lower dose if the performances were similar.
The agreement between readers of conventional angiograms was assessed by
computation of the sensitivity (agreement for the presence of 
50%
stenosis), specificity (agreement for the absence of 50% stenosis), and
accuracy (overall agreement) of interpretation of each reader versus the
other. The two readers thus were evaluated in reference to the other's
diagnosis.
ROC curves were constructed with the qualitative diagnoses. The five qualitative measures of disease state were separately considered the positive diagnostic threshold, and sensitivity versus 1 minus specificity was plotted for each reader MR of angiograms. The average and SD of the numeric confidence of diagnosis metric were computed for each MR angiography reader. Mean confidence scores and 95% CIs were calculated using the t statistic for each reader and each MR angiographic technique.
Counts and percentages of adverse events were tabulated. Also noted were changes in vital signs, laboratory results, physical examination findings, and ECG measurements. For ECG recordings, changes from baseline for the PR interval, QRS complex, QT interval, QTc interval, and ST segment were summarized with descriptive statistics and interpreted by an independent cardiologist. Any out-of-range results were noted as adverse events, according to International Conference on Harmonisation reporting standards.
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Efficacy
One hundred eighty patients completed the study, that is, underwent
gadofosveset-enhanced MR angiography and conventional angiography and thus
were included in the evaluation of efficacy. Their demographic statistics did
not differ notably from those of the whole population who received
gadofosveset. Among the 180 patients, 93 were in the 0.03-mmol/kg dose group
and 87 were in the 0.05-mmol/kg dose group. Both dose groups were similar with
respect to demographic characteristics. Fourteen patients in each dose group
were imaged with 1-T magnets, and performance was similar to those of the
whole population.
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In the primary efficacy analysis, the results were similar in the two dose
groups. Accuracy and specificity increased over those for unenhanced MR
angiography for all readers for both dose groups. Except for the accuracy of
reader B at the 0.03-mmol/kg dose, these increases were statistically
significant (p 
0.011). The changes in sensitivity were generally
inconsistent and not statistically significant. At the 0.03-mmol/kg dose,
reader A had a strongly significant increase in sensitivity at the cost of a
smaller increase in specificity compared with the other two readers. The
primary results are summarized in Table
2.
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Each of the two readers of conventional angiograms were evaluated for sensitivity, specificity, and accuracy of diagnosis with the other held to be the standard of reference. This analysis was used to evaluate the correspondence between readers of conventional angiograms in a diagnostic task equivalent to the primary MR angiography end point. These results are summarized in Table 3.
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ROC curves of the five qualitative diagnostic scores were constructed separately for the two dose groups. The results are shown in Figure 1A, 1B. Uninterpretable vessels for each reader were excluded from this analysis. The increased diagnostic power of the contrast-enhanced images is apparent in both groups, but neither dose was clearly superior to the other.
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Also in the 0.03-mmol/kg dose group, the number of examinations with uninterpretable segments decreased with the use of contrast material. For two of the three readers of MR angiograms, this rate was lower than for either reader of conventional angiograms (Table 4). Furthermore, the confidence expressed in diagnoses of interpreted segments was significantly higher for readers A and B using contrast-enhanced MR angiography as opposed to unenhanced MR angiography (Table 5). Reader C had equivalent confidence in both MR angiographic techniques but chose to interpret the percentage stenosis in the fewest segments.
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Safety
One hundred eighty-five patients were enrolled in the study. Of these, 96
received 0.03 mmol/kg of gadofosveset, and 89 were given 0.05 mmol/kg of
gadofosveset. There were no notable differences in the safety profiles of the
two dose groups.
In the 0.03-mmol/kg dose group no patient died, experienced serious AEs, or withdrew from the study because of AEs. Twenty-seven (28%) of the patients in this group reported 50 AEs during the study, and 19 (20%) reported 30 AEs the investigator considered possibly or probably related to the study drug. Among the 50 AEs reported by this group, 48 (96%) were mild or moderate in severity. Two patients reported a total of two AEs that were severe, and neither severe AE was considered treatment related. The most common treatment-related AEs were paresthesia (7%), dysgeusia (4%), vasodilation (3%), dry mouth (2%), and feeling cold (2%). Most (77%) of the treatment-related AEs occurred within 5 minutes after gadofosveset administration, and most of them resolved spontaneously within 15 minutes. In this dose group, 58% of the AEs were reported within 1 hour after gadofosveset injection, and 62% resolved within 1 hour of onset.
In the 0.05-mmol/kg dose group, 25 (28%) of the patients reported 55 AEs, and 21 (24%) reported 37 AEs that the investigator considered possibly or probably related to the study drug. Fifty-four (98%) of the AEs reported for this group were mild or moderate in severity. One patient reported one AE that was severe and led to the patient's withdrawal from the study, but the AE was not considered treatment related. This severe event (myocardial infarction) was the only AE reported to be serious, and no patient died. The most common treatment-related AEs were nausea, burning sensation, and paresthesia (4% each) and pruritus and vasodilatation (3% each). Taken together, the overall AE profile was similar to that previously reported for gadofosveset [9, 11].
Two (2%) of the patients in the 0.03-mmol/kg group had blood chemistry, hematologic, and urinalysis values during the MR angiography monitoring period that were considered AEs, although none of these AEs was judged serious. The two patients had a total of three clinically significant laboratory values. Increased neutrophil count and increased WBC count occurred in the same patient, and hypoglycemia was reported for the other patient. There were no clinically concerning trends in any of these values over time. Three (3%) of the patients in the 0.05-mmol/kg group had blood chemistry, hematologic, and urinalysis values during the MR angiography monitoring period that were considered AEs, although none of the events was judged serious. These three patients had a total of eight clinically significant laboratory values, and no single event was reported by more than one patient.
For both dose groups, no individual changes in vital signs were considered serious or related to gadofosveset. Isolated patients had abnormal ECG readings. In the 0.03-mmol/kg group, one (1%) of the patients reported one clinically significant event of ventricular extrasystole unlikely related to the study drug. In the 0.05-mmol/kg group, four patients reported a total of four clinically significant events, none of them considered related to the study drug. No clinically significant trends in ECG results were discerned.
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The two doses of gadofosveset had similar advantages over no contrast agent. Higher sensitivity, specificity, and accuracy were observed in the 0.03-mmol/kg dose group, but the differences between diagnoses with and without contrast enhancement were similar in the two dose groups. Because the dose groups had independent patient populations, the trend may be systematic, but it may also be due to increased extravasation at the higher dose. Phase 2 studies showed a decrease in contrast efficacy beyond 0.05 mmol/kg [10] in the aortoiliac vessel bed, presumably because the albumin in plasma becomes saturated and more gadofosveset leaks into the extravascular space. In either case, there does not appear to be an advantage to the higher dose.
The blinded reading and analysis of image data were prospectively designed to extract the diagnostically relevant information from the images. The blinded readings were conducted by three independent readers of MR angiograms to compare contrast-enhanced and unenhanced techniques and by two separate readers of conventional angiograms to establish the standard of reference with a third reader, the adjudicator, to resolve diagnostic disagreements. All image readers were blinded to clinical information about the patients and therefore provided an assessment of the diagnostic imaging procedure alone. Because two readers of conventional angiograms interpreted all angiograms, a comparison between the two readers was also available. This condition allowed comparison of the primary end points with the conventional angiographic agreement, which necessarily limited the accuracy of the standard of reference.
Gadofosveset-enhanced MR angiography was clinically and statistically superior to unenhanced MR angiography, primarily because of a large increase in specificity. Generating clinically useful MR images in low-flow blood vessels is a well-recognized problem of unenhanced time-of-flight MR angiography. For example, Pipe [18] estimated that flow slower than a few centimeters per second can produce loss of signal intensity of a vessel that can be confused with stenosis or occlusion. The very low specificity of unenhanced MR angiography in this study (average, 33% for the 0.03-mmol/kg dose) most likely reflects an increased tendency to deem disease present owing to the absence of apparent signal intensity of vessels on unenhanced MR angiograms. Because contrast-enhanced MR angiography does not depend on blood velocity for signal intensity, contrast-enhanced imaging overcame this problem in slow-flow vessels.
For our patient population, specificity, which reflects the probability of correctly identifying nondiseased vessels, is particularly important. In most cases, the purpose of pedal angiography is not identification of patients with disease but surgical planning, in particular the search for normal pedal vessels for limb-saving bypass surgery. Thus the average 30% increase in specificity of contrast-enhanced MR angiography over unenhanced MR angiography in the 0.03-mmol/kg dose group, which translates into increased ability to correctly identify a potentially limb-sparing target pedal vessel, is the most clinically relevant finding of the study.
The specificity of contrast-enhanced MR angiography (average, 63% for the 0.03-mmol/kg dose) may at first seem low. However, catheter angiography, though the clinically accepted preoperative diagnostic examination, is known to have somewhat lower accuracy in pedal vessels than in other vessel beds. For example, a study [19] in which unenhanced MR angiography was compared with catheter angiography and intraoperative conventional angiography showed that using traditional catheter angiography, radiologists erroneously classified 44% of the normal vessels as abnormal. In a study with a diabetic population, Kreitner et al. [8] found that in 38% of the patients, MR angiography revealed patent pedal vessels suitable for grafting that were not seen on catheter angiography. A follow-up study by the same group [7] showed a limb salvage rate of 89.5% at 36 months in patients with graftable vessels not identified with catheter angiography. The investigators argued that with conventional angiography, these vessels had been incorrectly classified as abnormal. In the present study, the two individual readers of conventional angiograms reflected these effects in their limited agreement. Combining the data from Tables 2 and 3 shows the agreement of the two readers of conventional angiograms was similar to the results achieved by MR angiography readers against the standard of reference for diseased vessels (sensitivity) and slightly better for nondiseased vessels (specificity). The results of the previous studies suggested that the specificity for gadofosveset-enhanced MR angiography is clinically acceptable because it likely includes a number of vessels incorrectly given false-positive diagnoses on the basis of findings on conventional angiography.
The possible systematic inaccuracy of the conventional angiography standard was a limitation of our study design. As a result, the specificity of both unenhanced and contrast-enhanced MR angiography may have been underestimated. The difference in specificity is among vessels visualized on conventional angiography, but the success rate of MR angiography among patent vessels that are radiographically occult cannot be directly determined. Furthermore, this limitation may give an apparent sensitivity advantage to the inferior technique, and this advantage may be the reason for the inability to discriminate a sensitivity difference. Perhaps only a follow-up study such as the aforementioned [7] can resolve such a difference.
This study was limited in two important respects. First, we did not compare gadofosveset with extracellular contrast agents for MR angiography. Second, we did not separately evaluate the advantage of imaging in the steady state. Contrast-enhanced MR angiography with extracellular agents in the pedal vessels has been shown effective, but concerns about extravasation and venous contamination make single-station high-resolution imaging difficult [20]. Pedal MR angiography therefore has been studied with careful bolus timing and various bolus chase techniques [4]. These techniques cannot extend the time window available for imaging the vasculature. Gadofosveset, however, remains in the blood with minimal extravasation for a period of time that allows higher-resolution imaging, enabling discrimination of arteries and vessels depicted with computerized image segmentation [21, 22]. Because high-resolution steady-state images were provided, this advantage was partly available to the readers in this study, but the relative advantage of these images and computerized segmentation methods that may increase their utility remains to be studied.
Gadofosveset continued to have only mild and transient side effects. Among treatment-related adverse events, none was severe, and the most common was paresthesia. Nephrogenic systemic fibrosis has been associated with high-dose MR angiography in renally compromised patients, and we excluded such patients from the study. Although no cases of nephrogenic systemic fibrosis associated with gadofosveset have been reported, we recommend the usual caution in imaging of renally compromised patients.
The study was a benchmark comparison of gadofosveset MR angiography of the pedal arteries with conventional and MR angiography without contrast enhancement. The amount of diagnostically relevant information greatly improved with the use of gadofosveset. This finding is apparent in the diagnostic specificity, the rate of interpretable examinations, the ROC curves of qualitative diagnosis among interpretable images, and the overall diagnostic confidence. The efficacy results of this study coupled with the acceptable and transient side-effect profile indicate that MR angiography with a single IV bolus injection of 0.03 mmol/kg of gadofosveset is safe, more effective than unenhanced MR angiography alone, and similar to conventional angiography in terms of utility in the diagnosis of clinically important vascular lesions in the pedal arterial region.
Acknowledgments
The following investigators contributed substantially to the study: Anibal
Agustin Damonte, Instituto Cardiovascular de Rosario, Rosario, Argentina; Jan
Beran, Liberec City Hospital, Liberec, Czech Republic; Geoffery Parker, Royal
Prince Albert Hospital, Sydney, New South Wales, Australia; Jan Zizka, Charles
University Hospital, Hradec Králové, Czech Republic; Bernd
Tombach, Universitätsklinikum Münster, Münster, Germany; Manuel
Fernandez, Clinica Las Condes, Santiago de Chile; Sigifredo
Chavarria-Nuñez, Hospital Clinica del Parque, Chihuahua, Mexico; Peter
Reimer, Klinikum Karlsruhe, Karlsruhe, Germany; Bryan Hardy, Health Science
Center, Winnipeg, MB, Canada; Jeffrey Maki, VA Puget Sound Health Care System,
Seattle, WA; William Corse, Central Montgomery Medical Center, Lansdale, PA;
Brian Davison, Brigham and Women's Hospital, Boston, MA; Amit Mehta,
Massachusetts General Hospital, Boston, MA; Christoph Binkert, Brigham and
Women's Hospital, Boston, MA; Steven Whitmoyer, Abington Memorial Hospital,
Abington, PA; Brian Polesuk, Central Montgomery Medical Center, Lansdale,
PA.
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