Influence of Ultra-Low-Dose and Iterative Reconstructions on the Visualization of Orbital Soft Tissues on Maxillofacial CT.

BACKGROUND AND PURPOSE: Dose reduction on CT scans for surgical planning and postoperative evaluation of midface and orbital fractures is an important concern. The purpose of this study was to evaluate the variability of various low-dose and iterative reconstruction techniques on the visualization of orbital soft tissues. MATERIALS AND METHODS: Contrast-to-noise ratios of the optic nerve and inferior rectus muscle and subjective scores of a human cadaver were calculated from CT with a reference dose protocol (CT dose index volume = 36.69 mGy) and a subsequent series of low-dose protocols (LDPs I-4: CT dose index volume = 4.18, 2.64, 0.99, and 0.53 mGy) with filtered back-projection (FBP) and adaptive statistical iterative reconstruction (ASIR)-50, ASIR-100, and model-based iterative reconstruction. The Dunn Multiple Comparison Test was used to compare each combination of protocols (α = .05). RESULTS: Compared with the reference dose protocol with FBP, the following statistically significant differences in contrast-to-noise ratios were shown (all, P ≤ .012) for the following: 1) optic nerve: LDP-I with FBP; LDP-II with FBP and ASIR-50; LDP-III with FBP, ASIR-50, and ASIR-100; and LDP-IV with FBP, ASIR-50, and ASIR-100; and 2) inferior rectus muscle: LDP-II with FBP, LDP-III with FBP and ASIR-50, and LDP-IV with FBP, ASIR-50, and ASIR-100. Model-based iterative reconstruction showed the best contrast-to-noise ratio in all images and provided similar subjective scores for LDP-II. ASIR-50 had no remarkable effect, and ASIR-100, a small effect on subjective scores. CONCLUSIONS: Compared with a reference dose protocol with FBP, model-based iterative reconstruction may show similar diagnostic visibility of orbital soft tissues at a CT dose index volume of 2.64 mGy. Low-dose technology and iterative reconstruction technology may redefine current reference dose levels in maxillofacial CT.

Effects of failure of the right side of the heart and increased pulmonary resistance on mechanical circulatory support with use of the miniaturized HIA-VAD displacement pump system.

This experimental study was designed to assess the influence of failure of the right side of the heart or pulmonary hypertension, or both, on the performance of a novel miniaturized left ventricular assist device. In small-sized dogs (n = 50) ischemic global left ventricular failure was induced and support was provided by the HIA-VAD displacement pump (stroke volume 10 or 25 ml) installed as a left ventricular assist device. In three groups of animals (n = 10 each) pulmonary hypertension was created before induction of global left ventricular failure. During left ventricular assist device support temporary ischemic failure of the right side of the heart was induced in four groups of animals (n = 10 each). In the group subjected to left ventricular failure, support with the left ventricular assist device, and right ventricular failure during left ventricular assist, left atrial pressure and cardiac index were significantly lower than in the group subjected to left ventricular failure and left ventricular assist alone (2 +/- 6 versus 11 +/- 6 mm Hg and 1.6 +/- 0.4 versus 1.0 +/- 0.4 L/(min/m2), respectively, p < 0.05). In the group subjected to pulmonary hypertension, left ventricular failure, and left ventricular support, left atrial pressure dropped to values near zero but cardiac index remained unaltered as compared with results with the same regimen without pulmonary hypertension. However, when right ventricular failure was added (that is, pulmonary hypertension, left ventricular failure, left ventricular support, and right ventricular failure during support with the left ventricular assist device) left atrial pressure dropped to negative values (p < 0.05) and cardiac index progressively deteriorated. When, in an additional group of dogs, biventricular support was installed in the latter regimen, circulation was initially well supported but oxygenation deteriorated in 60% of cases. We conclude that (1) adequate right ventricular function was indispensable during support with the left ventricular assist device, (2) the combination of pulmonary hypertension and right ventricular failure led to the "low left ventricular assist device output syndrome," and (3) biventricular mechanical support in the presence of pulmonary hypertension may be complicated by the alveolar leakage syndrome.

Repeated endomyocardial biopsy without complication in an infant after heart transplantation.

Endomyocardial biopsy is necessary for accurate diagnosis of rejection after heart transplantation. This case illustrates the safe use of repeated endomyocardial biopsies in an infant after heart transplantation.

Protective effects of various preservation solutions on cultured endothelial cells.

Vascular endothelium represents the first target in organ preservation and plays an important role in reperfusion injury. Bovine aortic endothelial cells were cultivated and the most commonly used preservation solutions, such as University of Wisconsin HTK (Brettschneider's histidine-tryptophane-ketoglutarate), and Euro-Collins solutions were tested on the endothelial monolayer. In addition, one group of cultivated cells was preserved with cold saline solution, and endothelial monolayers grown in culture medium were used as controls. The quality of preservation was assessed after 24, 48, and 72 hours of cold storage. Reperfusion was simulated and its effects were observed by reincubation in culture medium at 37 degrees C for 6 hours. The total number of cells, cell viability (determined using trypan blue exclusion), and morphologic alterations were determined. Prostacyclin release was evaluated as a biochemical marker. University of Wisconsin solution maintains more than 99% cell viability after rewarming after both 24 and 48 hours of cold storage. After 72 hours, 86.7% of cells were still viable. Preservation with HTK and Euro-Collins solution allowed cell survival for only 24 hours (96.7%, HTK; 49.9%, Euro-Collins), with no viable cells seen after 48 hours. The cold saline-preserved sample showed 57.8% viable cells after 24 hours and 29.7% after 48 hours. No viable cells were detectable after 72 hours. Light microscopy revealed several patterns of both structural damage and intracellular change (nucleus and cytoplasm) in the endothelial monolayer after preservation with HTK, Euro-Collins solution, and cold saline solution. No morphologic alterations were seen in the University of Wisconsin solution group for as long as 72 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Left ventricular assist with an axial flow pump (Hemopump): clinical application.

Eighteen patients suffering from acute left heart failure were selected as candidates for Hemopump support. In 6 patients, peripheral atheromatosis prevented insertion of the device. Of the remaining 12 patients, 9 had postcardiotomy shock, 2 had acute rejection after orthotopic heart transplantation, and 1 had acute myocardial infarction complicated by a large postinfarction ventricular septal defect. During Hemopump support, hemodynamics recovered in all patients. Major complications were related to mechanical pump failure, such as fracture of the drive cable and expulsion of the cannula out of the ventricle, or to hemolysis of variable degree. Seven patients (58%) survived and were discharged from the hospital: the 2 patients bridged to heart transplantation and 5 of the 9 postcardiotomy patients, including 1 who could not be weaned but later underwent successful transplantation. The patient with the postinfarction ventricular septal defect died after removal of the device because of hemolysis. These results indicate that the Hemopump is a relatively noninvasive and efficacious left ventricular system of moderate power.

Intramyocardial hematoma mimicking abnormal left ventricular trabeculation.

Intramyocardial hematoma may present as a tumor or pseudoaneurysm on echocardiography. A 68-year-old man was admitted with a subacute posterior wall infarction complicated by ventricular fibrillation. Echocardiography showed isolated left ventricular abnormal trabeculations, a finding suggesting an associated skeletal muscle disorder, in the lateral wall. At cardiac surgery, performed 6 weeks later because of severe 3-vessel disease, an intramyocardial hematoma of the lateral wall was excised, and myocardial and skeletal muscle biopsies were taken, which showed neither isolated left ventricular abnormal trabeculations nor skeletal muscle disorder. Postoperatively, echocardiography revealed no abnormal trabeculations.

Coronary sinus endothelin-1 concentrations after cardioplegic cardiac arrest.

BACKGROUND: Data from animal experiments demonstrate that endothelin-1 is released into the coronary circulation during myocardial ischaemia and reperfusion, indicating that endothelin-1 may contribute to the pathophysiology of ischaemia and reperfusion. The aim of this study was to investigate the release of endothelin-1 into the coronary circulation during reperfusion of the human heart after hypothermic cardioplegic cardiac arrest. METHODS: Endothelin-1 was measured in arterial, central venous and coronary sinus blood in 19 patients undergoing elective uncomplicated coronary artery bypass grafting before aortic crossclamping and 1, 5, 10 and 20 min after aortic declamping. RESULTS: Endothelin-1 concentrations showed a slight non-significant increase over baseline values 1, 5, 10 and 20 min after aortic declamping. Endothelin-1 concentrations were not significantly higher in coronary sinus blood than in arterial blood at any time point measured, indicating no net release of endothelin-1 by the heart. CONCLUSIONS: Our results did not demonstrate endothelin-1 release into the coronary circulation after myocardial ischemia and reperfusion associated with hypothermic cardioplegic cardiac arrest.

Autograft aortic valve replacement with downsized pulmonary allograft for right ventricular outflow tract reconstruction.

A three-week-old neonate underwent aortic valve replacement with a pulmonary autograft (Ross procedure). The right ventricular outflow tract was reconstructed with a downsized pulmonary allograft. The surgical technique is presented. Six months after operation the girl is doing well and both the autograft and allograft function are excellent.

Pathophysiological considerations concerning uni- and biventricular mechanical cardiac assist.

Mechanical assisted circulation by the means of cardiac assist devices is a routine procedure in modern cardiac surgery and cardiology. We investigated the impact of mechanical unloading on regional myocardial "stunning" and the influence of assisted circulation on left heart and right heart failure persevered by an ultimate addition of pulmonary hypertension in experimental set ups. We found that mechanical unloading either during ischemia or in the early reperfusion phase attenuates stunning and enhances the return of synchronous heart performance. In our global dysfunction model we showed that the right heart is dispensable. Sufficient inflow to the left heart is provided unless pulmonary hypertension is present. Also additional left heart support can not overcome the deleterious situation and in select cases only additional right heart support can prevent the "low LVAD output" syndrome. We conclude that mechanical assisted circulation and mechanical unloading are beneficial in case of regional and global dysfunction persevered by pulmonary hypertension, however, the knowledge about interactions of assist systems and the circulation has to be improved in order to optimize clinical assist device performance.

Pre-clinical evaluation of a novel, pneumatic, ventricular assist device (Medos HIA-VAD) under pathophysiological conditions.

To evaluate a new cardiac assist system, the Medos HIA-VAD, we studied the effects of mechanical unloading on regional and global myocardial dysfunction. As a model for the regional temporary contractile dysfunction we chose an anesthetized, open chest preparation in sheep. We occluded the diagonal coronary artery for 15 minutes and reperfused for 90 minutes. Hemodynamic parameters and wall thickening were monitored. Unloading with the 60-ml Medos HIA-VAD was performed either during ischemia (group II) or during reperfusion (group III). The recovery of non-uniformity indicated by post-ejection wall thickening was significantly faster (p < 0.05) in both groups if compared to the non-assisted group (group I) (all groups n = 4). Recovery of systolic wall thickening in the postischemic region in group I was only 76 +/- 12%, while it was 103 +/- 11% and 92 +/- 11% in groups II and III, respectively (p < 0.05). In a canine model of global left ventricular failure, we occluded the left anterior descending coronary artery for 20 min, and after 5 minutes of reperfusion, the circumflex artery for 45 min (group I, n = 5). After 5 min of CX occlusion in group II we performed assisted circulation for 90 min with the 10-ml (n = 5) and the 25-ml (n = 5) Medos HIA-VAD. In group I, no dog survived, in group II, all survived 4 hours of reperfusion (n = 10). Lactate at the end of the experiment was 1.1 +/- 0.9 mmol/L (10-ml, and 1.1 +/- 0.2 mmol/L (25-ml) (p > 0.05 vs. base line). We conclude that the Medos HIA-VAD is a reliable assist device that enhances myocardial recovery and allows sufficient peripheral circulation in the case of cardiogenic shock.

Medos/HIA-assist system: first experiences with mechanical circulatory assist in infants and children.

The Medos/HIA-System is a new pneumatically driven system for mechanical circulatory assist. The system is characterized by excellent efficiency at high heart rates and is available with three ventricles of 10, 25 and 60ml stroke volume. It can be used as left-, right- or biventricular assist device. Our preliminary experiences with this novel system for support of infants and children are reported.

Haemodynamic changes in patients undergoing high-risk PTCA under protection of transfemoral heart- lung machine support with centrifugal pumps.

Patients with a high risk for myocardial revascularization by cardiological or surgical means can be supported during high-risk PTCA with mechanical circulatory support (supp HR-PTCA). Between November 1994 and June 1997 we performed 28 supp HR-PTCA's under protection of a heart-lung machine (HLM) with femoro - femoral cannulation under regional anesthesia. We approached 2.8+/-1.5 stenoses and 1.7+/-0.6 vessels per patient. Primary success rate was 95 percent of the treated vessels. During unloading, pulmonary artery mean pressure fell to 42+/-29% of the starting value, and LVEDP was decreased to 36+/-42%. Mechanical unloading also resulted in a significant reduction of left ventricular volumes (unloaded LVEDVI and LVESVI represent 76.8% and 76.6% of pre-unloaded values, respectively, p<0.05). All patients except one survived the procedure and could be discharged from the hospital. Femoro-femoral cardio-pulmonary bypass under regional anesthesia provides sufficient protection for high risk PTCA procedures and enables high risk patients to benefit from coronary revascularization.

Mechanical unloading properties of axial flow pumps and their effect on myocardial stunning.

Postischemic myocardial dysfunction affects morbidity and mortality in patients with coronary artery disease. It is known that mechanical unloading of the left heart ventricle can positively influence postischemic myocardial dysfunction. In this respect we tested two miniaturised axial flow pumps, i.e. the 14-F and the 21-F Hemopump. An experimental study was carried out on 30 open chest sheep where regional myocardial wall motion was followed using sonomicrometry in a preparation of transient coronary artery occlusion. Only the larger 21-F Hemopump showed hemodynamically significant unloading of the left ventricle. Furthermore, as far as stunning is concerned, systolic wall thickening recovered better when this type of pump was used during reperfusion. Also postejection thickening, which is an indication of diastolic postischemic dysfunction, is reduced significantly in the postischemic area (ANOVA, p < 0.05). Thus, the 21F Hemopump, but not the 14F Hemopump, provides adequate mechanical unloading in order to beneficially influence myocardial stunning.

A new pneumatic pump for extracorporeal circulation: TPP (true pulsatile pump). Experimental and first clinical results.

A pulsatile, membrane type pump, TPP, was developed for use in routine cardiac surgery. The artificial ventricle consists of a polycarbonate housing with an inlet and outlet polyurethane tricuspid valve. The membrane is actuated hydraulically. For pre-clinical studies, we designed a study in sheep. After a pump run of 6 hours the animals were allowed to recover and sacrificed after 72 hours. All clinical parameters returned to normal values (p > 0.05 vs. control values). During pump run we found elevated free plasma hemoglobine. However, these values returned to normal until the end of the observation period. Thereafter, the device was used in ten routine cardiac surgery procedures. All patients survived the procedure and were discharged from hospital. The postoperative course of lab parameters (kidney, liver and blood count) was no different to routine cardiac surgical procedures. This pulsatile pump system can thus be safely employed in cardiac surgery.

Cardiac transplantation: current results at the Texas heart institute.

The first series of cardiac transplants at the Texas Heart Institute began in May of 1968 but was discontinued because of the complications of infection and rejection. A second series of cardiac transplants was initiated in July of 1982 after the introduction of the immunosuppressant drug, cyclosporine. By August of 1984, 30 patients had undergone orthotopic cardiac transplantation for end-stage cardiac disease. Of the patients in this series, four have died of rejection, two of infectious complications, and one of an unknown cause. The remainder have all returned to Class I New York Heart Association (NYHA) cardiac status. All patients were reviewed in detail for suitability of cardiac transplantation and presented to a cardiac transplant review board. All transplanted patients were functional Class IV. Donor hearts were obtained locally or by long-distance procurement. Ten of the hearts were obtained from an average distance of 250 miles from Houston. Donors ranged in age from 16 to 37 years. Requirements were normal cardiac function with minimal use of inotropic support, no history of cardiac disease, absence of cardiac arrest and absence of active infection. Although only one of the patients in the initial group of transplants survived 1 year, to date there have been 11 survivors for more than 1 year in the current series. Advances in cardiac transplantation have resulted in an improved prognosis for the terminal cardiomyopathic patients requiring transplantation. The use of cyclosporine, an immunosuppressant that spares the nonspecific immune system, has been helpful in allowing patients to survive infections. The use of the drug must be carefully monitored, however, because of its numerous toxicities.

[Possibilities for saving homologous blood in heart surgery]. / Möglichkeiten des Fremdblutsparens in der Herzchirurgie.

The risks of blood transfusion in context with the increasing number of operative open-heart procedures and the linked increased demand for blood products present a challenge to find methods of saving homologous blood. On the one hand there is increasingly less blood at the surgeon's disposal and on the other hand there is the threat of infectious complications with viruses of the HIV or the hepatitis group, as well as allergic reactions. At present we are developing the concept of blood saving as a programme which should work without excess demands on the staff and which can be adjusted to the needs of the individual patient. The programme consists of the following components: preoperative self donation, use of cell saver, acceptance of e relatively low hematocrit, medication to alter the coagulation process and blood-less priming.

Use of left-ventricular assist with the Hemopump in cardiac surgery.

From July 1989 to May 1992 16 patients received circulatory support with a Hemopump assist device in the Department of Cardiac Surgery of the Katholieke Universiteit Leuven. The mean age of those patients was 56 +/- 13 years (ranging from 23 to 72 years). The mean time of assisted circulation was 60 +/- 46 h (ranging from 2 to 168 h). Group I consists of 13 patients who received the device after postcardiotomy cardiac failure (survival 38%). Group II includes 1 patient who received the pump prior to repair of a large postinfarction ventricular septal defect (survival 10%). Group III consists of 2 patients for whom the Hemopump was used as a bridge to cardiac retransplantation. Both are still alive (survival 100%). If the 21-F Hemopump is implanted following a critical indication it can be used rather successfully for mechanical circulatory support.

Mechanical unloading with a miniaturized axial flow pump (hemopump): an experimental study.

A family of miniaturized axial flow pumps has been developed, including the Hemopump, the 14-F, and the 21-F HP, which were especially designed for cardiological use. We designed an experimental set-up to study the unloading properties of these devices in a model of regional stunning in an anesthetized, open thorax preparation in sheep. Stunning was caused by 15-min occlusion of the diagonal branch of the left anterior descending coronary artery with subsequent 90 min of reperfusion. Regional myocardial function was assessed by sonomicrometry. A control group was compared with 2 groups with either mechanical unloading during part of ischemia (Group 2) or the early phase of reperfusion (Group 3). In either unloading protocol, both Hemopumps were used. It was shown that recovery from asynchrony was significantly faster in Groups 2 and 3 if unloading was performed with the 21-F HP compared with control Group 1 and the groups using the 14-F HP (p > 0.05). Thus, mechanical unloading with the 21-F Hemopump enhances recovery from stunning whereas unloading with the 14-F HP has only minor effects on hemodynamics and no effects on recovery.