Monorail system for percutaneous repositioning of the Greenfield vena caval filter.

The authors describe a technique for removing or repositioning a malpositioned Greenfield inferior vena caval filter. A "monorail" system was used, in which a wire was passed from the femoral vein through the apical hole in the filter and out the internal jugular vein; the wire was held taut from above and below and thus facilitated repositioning or removal of the filter. The technique was used successfully in two cases.

Natural history of the false channel of type A aortic dissection after surgical repair: CT study.

To evaluate the false channel after surgical repair of a type A aortic dissection, postoperative computed tomographic (CT) scans were retrospectively reviewed in 33 patients. Initial CT demonstrated persistence of a double channel distal to the site of surgical repair in 26 patients (79%). In four of these patients serial CT demonstrated enlargement of the false channel, a finding that contributed to the decision to repeat surgery. Progression of thrombus was noted in five patients. Peripheral calcification within the aortic wall of the false channel, presumably located on the "pseudointima," was found in six patients. Because of the progressive nature of type A dissections in the postoperative period, serial CT examinations can provide important information on patients who have undergone surgical correction of a type A dissection.

Safety of 125iodine and 192iridium implants to the canine carotid artery. Long-term results.

Thirty-nine healthy dogs underwent a simulated radical neck dissection followed by implantation of either 125Iodine (125I) or 192Iridium (192Ir) in various dose regimes randomized prospectively from 3,000 to 30,000 rad. Bilateral selective carotid angiography was performed immediately postoperatively and at 6, 12, 18, and 24 months. No significant effects occurred to the animals who received 15,000 rad 125I or 6,000 rad 192Ir. In the higher dosed animals the 125I-treated group fared better than the 192Ir-treated group, probably due to the lower dose rate delivery. Fewer and less serious complications occurred in the 125I-treated group, but this group developed more complications after one year than the Iridium group.

Diagnostic challenges following cardiac transplantation.

It is now almost two decades since the first human cardiac transplantation was performed. Recipients will require close follow-up by their referring physicians outside of the main referral centers. This article is intended to assist the referring physician in choosing the most appropriate diagnostic studies throughout the posttransplant period.

Naturally corrected double-outlet right ventricle with biventricular outflow tract obstruction.

A 5-year-old girl had presyncopal episodes associated with exertion. Diagnostic evaluation revealed a combination of congenital abnormalities: double-outlet right ventricle with apparent "natural correction" of a large subaortic ventricular septal defect and severe biventricular outflow tract obstruction. Intraoperative and postoperative studies confirmed satisfactory relief of the biventricular outflow tract obstruction.

Aortic pseudoaneurysm complicating Takayasu disease: CT appearance.

The CT findings of a patient with Takayasu arteritis and an ascending aortic pseudoaneurysm are presented. Computed tomography demonstrated the nature, location, and extent of the aortic lesion and revealed the ominous finding of a related large hematoma indicating prior aortic rupture.

Digital subtraction angiography of coronary grafts: optimization of technique.

Forty patients who had undergone coronary artery bypass surgery were studied with digital subtraction angiography (DSA) to develop an outpatient screening technique for coronary artery bypass graft visualization. Of 103 grafts in 40 patients, 101 were seen: 95 were clearly patent and in six the stump of an occluded graft was seen. Of 32 grafts seen in 14 patients using intraarterial DSA, only 13 (41%) were demonstrated using intravenous DSA. Intraarterial DSA is an effective screening procedure to determine bypass graft patency. However, volumes of 40-45 ml of 76% contrast medium injected at rates of at least 20 ml/sec must be used for each injection to obtain a diagnostic image, and since each projection is complementary and contributes some information, several injections must be used to complete an examination.

Evaluation of the portable chest roentgenogram for quantitating extravascular lung water in critically ill adults.

The diagnosis of pulmonary edema is frequently made from characteristic findings on the chest roentgenogram that suggest an increase in lung water. Optimal radiographic technique depends on a cooperative upright patient, which is not possible with most critically ill patients. These patients may also have multiple radiographic abnormalities that make interpretation of the chest roentgenogram difficult. The ability of portable chest roentgenograms to accurately identify the presence of excess lung water and monitor changes in lung water has not previously been evaluated in critically ill adults who are intubated and ventilated and in the supine position when the films are exposed. In 12 patients the pulmonary edema seen on portable chest roentgenograms was given a score (0 to 390 points), which was then compared with a determination of extravascular lung water using the thermal-dye indicator dilution technique. A linear correlation was observed (r = 0.51; p less than 0.05; n = 73). Evaluation of a change in radiographic score vs a change in lung water showed no linear correlation (r = 0.1; p greater than 0.05). While portable chest roentgenograms exposed under the conditions described were a useful technique for demonstrating pulmonary edema, they were not accurate in monitoring modest changes in lung water in critically ill patients.

Flow determination using computed tomography: application to aortic dissection. Part I.

The CT method of flow determination evaluated in this study was based on the application of contrast enhancement dynamics. In order to characterize flow, such parameters as mean transit time, rise time, peak CT value, curve width and variance, and others were derived from the venoarterial indicator dilution curves using a perfect mixers-in-series model of curve fitting analysis and a bolus injection of contrast medium. The technique was first validated in a steady state phantom model that simulated in vivo conditions of right-sided mixing closely by the introduction of a number of mixers. A series of flows through small tubes was measured. Good correlation was obtained (r = .85). For a fixed number of mixers, the central second moment of the primary peak of the indicator dilution curve or variance decreased with increasing flow and peak CT value increased. Applied to the clinical situation, this method would allow characterization of blood flow using an intravenous bolus of contrast.

Flow determination using computed tomography: application to aortic dissection. Part II.

Dynamic CT is not only useful in imaging an aortic dissection but may provide additional information concerning the hemodynamic significance of differing flow patterns in the false channel compared with the true channel. Once validated, the computed tomographic (CT) method of flow determination (See Part I) was applied to an experimental animal model with a surgically created aortic dissection. Good correlation was obtained for the flow estimates of cardiac output derived for the true and false channel (r = .82). The shapes of the curves, however, were distinct, reflecting different flow patterns for the true and false channels. Curve parameters, such as peak CT number (P = .0001), variance (P = .006), and, in particular, the number of mixers (a parameter used to quantify the degree of mixing) (P = .0001), demonstrated significant differences between the two channels of the dissection. The curve parameters derived can therefore be used to differentiate the true and false channels and may then predict the long-term outcome of the false channel, and the aortic branches derived from it.

Quantitative evaluation of left ventricular function using computed tomography.

Computed tomography (CT) provides a noninvasive technique with high resolution cross-sectional tomographic images which allow volume measurements of an object, independent of its geometric configuration. A phantom of known volume with controllable periodic motion was used to validate the CT method of volume determination. A good correlation (P less than 0.05) was achieved. Missing angle reconstruction algorithms for gating were applied to estimate left ventricular volumes and ejection fraction in an experimental animal, and the results compared with a standard angiographic method. Left ventricular volumes correlated poorly, whereas the ejection fraction obtained correlated well (r = 0.9). The discrepancies may be attributed in part to the CT method in which difficulties were recognized in defining the left ventricular borders at the base of the heart and partial volume effect, and in part to inaccuracies in the standard angiographic method. Once validated, this method has been applied to the animal model in the form of a pilot study.

Safety of 125iodine and 192iridium implants to the canine carotid artery: preliminary report.

Thirty-nine healthy dogs underwent a simulated radical neck dissection followed by implantation of either 125Iodine (125I) or 192Iridium (192Ir) in various dose regimes randomized prospectively from 3,000 to 30,000 rad. Bilateral selective carotid angiography was performed immediately postoperatively and at six months and one year. No significant effects occurred to the animals who received 15,000 rad 125I or 6,000 rad 192Ir. In the higher dosed animals the 125I treated group fared better than the 192Ir treated group, probably due to the lower dose rate delivery. All surviving animals will be maintained an additional year to determine the late effects of brachytherapy irradiation to the carotid artery.

Heart-lung transplantation: the postoperative chest radiograph.

The postoperative chest radiographs of 10 patients who had undergone heart-lung transplantation at Stanford University Medical Center were evaluated and compared with those of 10 consecutive cardiac transplantation patients and 10 consecutive coronary artery bypass graft patients. In the second week after surgery, we observed an interstitial radiographic pattern in the heart-lung transplantation patients but not in the other two patient populations. This pattern, which did not correspond with any clinical evidence of infection, rejection, fluid overload, or oxygen toxicity, may represent the reimplantation response described in dogs and primates following transplantation of a single lung. This response may be related to the interruption of bronchial circulation, the denervation of both lungs, and the lymphatic interruption that occur during transplantation. It may also be related to the obligatory period of ischemia that is incurred during implantation.

Comparative recognition of left ventricular thrombi by echocardiography and cineangiography.

Studies performed in 47 patients, 11 of whom underwent surgery for aneurysmectomy and 36 of whom underwent cardiac transplantation, were reviewed to assess the diagnostic accuracies of cross sectional echocardiography and cineangiography in detecting left ventricular mural thrombi and the effect of anticoagulation treatment on the incidence of such thrombi. Cross sectional echocardiography in 37 patients and cineangiography in 26 (16 patients were examined by both methods) were analysed independently by sets of two observers experienced in the respective methods. All four observers were blinded to the pathological or surgical findings regarding mural thrombus. Mural thrombus was confirmed by pathological investigation in 14 of 47 (30%) cases; 11 of these 14 patients had intra-aneurysmal thrombi. The negative predictive value was quite good for both methods, but cross sectional echocardiography had a superior positive predictive value. This was due both to detailed soft tissue resolution by cross sectional echocardiography and to overdetection of mural thrombi by cineangiography in cases of aneurysms without mural thrombi. Mural thrombi were present in three of 20 patients with preceding anticoagulation and in 10 of 19 patients without anticoagulation. The results emphasise that cross sectional echocardiography is more reliable than cineangiography in recognising thrombi.

A high frame-rate digital subtraction angiography imaging technique for evaluation of aortofemoral runoff.

Intravenous digital subtraction angiography was used to obtain a complete aortofemoral runoff examination of high diagnostic quality in a single patient session in eight patients. Using a 9-inch (22.9-cm) image intensifier, oblique and posteroanterior projections were obtained from the level of the aortic bifurcation to the tibial artery trifurcation. This technique is based upon the administration of one-half of the usual dose of contrast agent combined with a high frame-rate imaging technique and postacquisition integration to increase the signal-to-noise ratio. It is easily performed on an outpatient basis, lowers patient risk, and allows a significant savings of time, film, and cost compared with the conventional intra-arterial aortofemoral runoff examination.

Validation of a CT method for flow determination. Work in progress.

The dynamic computed tomographic (DCT) method of flow determination is based on the application of venoarterial indicator dilution curves as they reflect flow. Using a simple model consisting of a tube and a single mixing chamber, experimental parameters were optimized in a controlled manner to achieve ideal mixing for flow determination. Under these ideal conditions, and using 16 consecutive 3-second scans of an 8-mm thick section, tube diameters of 8 mm and 20 mm, and flow range of 0.7-2.7 liters per minute, the accuracy of the CT method of flow determination was good (17% error). There was a correlation coefficient of 0.85 between measured flow (FM) and calculated flow (FC), and the paired t-test for FM and FC indicated that there was no statistically significant difference (P = .25). The DCT method of flow determination has been validated in this experiment preliminary to its application to flow characterization in blood vessels in the animal model.

Aortic dissection: CT and angiographic comparisons.

Computed tomography and aortography were compared in a retrospective study of 35 patients with aortic dissection of type A (n = 17) and type B (n = 18). Based on classical diagnostic criteria such as evidence of two channels, intimal flaps and displaced intimal calcification, computed tomography was able to confirm the presence and type of aortic dissection in 32 patients. Dynamic computed tomography was used in 20 cases. When bolus technique was applied appropriately (16/20), computed tomography clearly differentiated the two channels and identified each by its time density characteristics. In 5 of the 35 patients included, the aortographic diagnosis was equivocal because no definite second channel was identified. In these, CT was helpful to confirm the diagnosis showing the presence of an intimal flap, displaced intimal calcification and clot in the false channel. It was noted that classical signs of differentiation of the true and false channels by their relationship to intimal calcification and by the anatomic relationship of the two identified channels to each other at different levels of the aorta are not without exceptions. It is concluded that dynamic computed tomography represents a valuable alternative to aortography and is preferred in chronic dissection and follow-up examinations and for the initial workup of patients with a mediastinal mass. However, when a roadmap of the aortic branches is required prior to surgical intervention, aortography remains the procedure of choice.

Combined azygous vein and subclavian artery injury in blunt chest trauma.

Blunt chest trauma resulting in azygous vein injury with associated mediastinal widening is described. Emergency operative intervention was required, and subsequent arteriography revealed initial transection of the subclavian artery requiring repair. The potential significance of mediastinal venous bleeding and the importance of arteriography in diagnosing occult arterial injury in this setting are emphasized.