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.

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.

Successful treatment of postoperative right ventricular heart failure with the HIA-Medos-assist system in a 2-year-old girl.

One year after total correction of tetralogy of Fallot, reoperation was performed in a 2-year-old infant because of an aneurysm of the right ventricular outflow tract. After removal of the aneurysm, massive right ventricular failure occurred. Maximal medical inotropic support could not reestablish sufficient right ventricular function. Therefore, it was decided to implant the new HIA-Medos system as a right ventricular assist. In the postoperative period, echocardiographic controls showed increasing contractility of the right ventricle. The assist system was removed after 3 days and the infant was discharged in good condition on the 22nd postoperative day.

Headache as the initial manifestation of acute aortic dissection type A.

The most common initial symptom of aortic dissection is chest pain. Other initial symptoms include pain in the neck, throat, abdomen and lower back, syncope, paresis, and dyspnoea. Headache as the initial symptom of aortic dissection has not been described previously. A 61-year-old woman with a history of migraine and arterial hypertension developed continuous bifrontal headache. Two hours later, right-sided thoracic pain and a diastolic murmur were suggestive of aortic dissection that was confirmed by echocardiography and subsequent surgery. The dissection commenced in the ascending aorta and involved all cervical arteries until the base of the skull. Headache as the initial manifestation of aortic dissection was assumed due to either vessel distension or pericarotid plexus ischemia. Aortic dissection has to be considered as a rare differential diagnosis of frontal headache, especially in patients who develop aortic regurgitation or chest pain for the first time.

Centrifugal pumps as left ventricular assist for coronary revascularization on a beating heart.

During recent years, coronary bypass surgery has progressed toward minimizing invasiveness. One important feature of this approach is performing surgery on a beating heart. During the crucial phase of such surgery, the mechanical support of the heart with a left ventricular assist device (LVAD) is a possible option. During the period from October 1, 1994 until June 30, 1997, we employed a centrifugal pump system in 118 cases of coronary artery bypass graft (CABG) procedures with LVAD support (mechanically supported CABG [SUPPCAB]). A total of 179 distal anastomoses with an average of 1.5 +/- 0.5 coronary anastomoses per patient was performed. Three types of pumps were used: 23 BioPump, 87 Isoflow, and 8 Capiox systems. The median time on mechanical support was 44 min (range, 16-116 min). The mean flow rate during support time was 3.5 +/- 0.8 L/min, which results in a calculated flow of 1.7 +/- 0.6 L/min/m2 body surface area (BSA). The average flow was 3.2 +/- 0.8 L/min with the BioPump and 3.7 +/- 0.8 L/min with the Isoflow pump, respectively (p < 0.01). The mean arterial pressure during mechanical support was 75 +/- 12 mm Hg. In 2 patients, the pump system was kept running postoperatively in the ICU. Eight of the patients received operations under resuscitation or in cardiogenic shock. Nine (7.9%) of the patients did not survive the early postoperative phase. For coronary revascularization of the anterolateral and diaphragmatic parts of the heart, the SUPPCAB procedure is feasible with excellent mechanical support of the heart by centrifugal pumps. Especially in high risk cases, this procedure can be recommended.

Splanchnic oxygen transport and lactate metabolism during normothermic cardiopulmonary bypass in humans.

UNLABELLED: The effect of normothermic (36.2 degrees C +/- 0.6 degree C) nonpulsatile cardiopulmonary bypass (CPB) on splanchnic (hepatic) blood flow (SBF), splanchnic oxygen transport (DO2spl) and oxygen consumption (VO2spl), splanchnic lactate uptake and gastric mucosal pH (pHi, gastric tonometry) was studied in 12 adults (New York Heart Association class II, ejection fraction > or = 0.4) undergoing coronary artery surgery. SBF was estimated with the constant-infusion indocyanine green (ICG) technique using a hepatic venous catheter. DO2spl, VO2spl, and splanchnic lactate uptake were calculated using the Fick principle after the induction of anesthesia, during aortic cross-clamping, after CPB, and 2 and 7 h after admission to the intensive care unit (ICU). SBF, DO2spl, and VO2spl did not decrease during CPB but increased after ICU admission, whereas pHi decreased 7 h after ICU admission. Initial ICG extraction was 0.78, which decreased to 0.54 during aortic clamping and remained low thereafter. The increased arterial blood lactate concentrations were not associated with a decreased splanchnic lactate uptake. We conclude that normothermic CPB is not associated with deterioration in the global intestinal oxygen supply. The increase of blood lactate levels and the decrease in ICG extraction, as well as in pHi, are consistent with a systemic inflammatory response to CPB. IMPLICATIONS: This study demonstrated that normothermic cardiopulmonary bypass (at flows > 2.4 L.min-1.m-2) was not associated with deterioration in global intestinal oxygen delivery, which suggests that increased blood lactate concentrations and decreased gastric mucosal pH and indocyanine green extraction are manifestations of a systemic inflammatory response to cardiopulmonary bypass.

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.

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.

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.

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.

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.

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.

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.

[Percutaneous "high risk" angioplasty with prophylactic cardiopulmonary support. High risk PTCA with mechanical circulatory support]. / Die perkutane "Hochrisiko" -Angioplastie unter prophylaktischem Kardiopulmonalen Support. Hochrisiko PTCA mit mechanischer Kreislaufassistenz.

With improved technology and development of several mechanical assist devices, the indications of percutaneous transluminal coronary revascularization have been extended. In 39 patients (30 men, mean age = 60.1 +/- 8.1 years) with angina pectoris or heart failure, with poor operative risk-benefit ratio and ejection fraction < 35% and/or target vessel supplying > 50% of the viable myocardium, we performed assisted percutaneous transluminal coronary revascularization. Intraortic balloon counterpulsation (n = 16), extracorporal circulation (n = 21), or hemopump (n = 2) were used for mechanical support. Complete 6-week follow up was possible in 27 patients. An improvement of left-ventricular function (patients with EF < or = 35% demonstrated an improvement: 27 +/- 7 vs 36 +/- 10%, p < 0.05), heart failure (patients with EF < or = 35% demonstrated an improvement of maximal oxygen uptake: 14 +/- 4 vs 17 +/- 4 ml/kg/min; p < 0.05) and a marked improvement of angina (23/38 demonstrated CCS-improvement of at least one class) was found. Hospital mortality was as low as 2.6%. Major postinterventional complications included nonfatal myocardial infarction (n = 2), fatal retroperitoneal bleeding (n = 1), pulmonary edema (n = 1), nonfatal ventricular fibrillation (n = 1), cerebrovascular event without residual (n = 1), and deep vein thrombosis (n = 4). In conclusion, assisted percutaneous revascularization was successful in a high risk subset of patients with increased surgical risk and/or poor ventricular function.

[Surgical coronary revascularization of the beating heart]. / Chirurgische Koronarrevaskularisation am schlagenden Herzen.

Despite the fact that all the progress in technology, surgical technique and pathophysiological knowledge has made aortocoronary bypass surgery a safe routine procedure, there are certain clinical settings where an alternative approach seems to be advantageous. In 50 patients with age ranging from 51 to 74 years with advanced coronary heart disease and poor left ventricular (LV) function, as well as in patients with good LV function and single or double vessel disease not amenable for PTCA and in patients with acute ischemia or recent myocardial infarction, we performed coronary artery bypass grafting (CABG) without cardioplegic arrest during a short period of left ventricular unloading by means of a left ventricular assist device (LVAD). During LVAD support we administered Esmolol to decrease the heart rate and to keep the heart flaccid to facilitate easier peripheral anastomosis on a breathing heart. Preoperative ejection fraction ranged from 15 to 56%. In two patients of the acute MI-group, we continued the left ventricular mechanical support postoperatively, one of them survived. We performed on average 1,4 distal anastomoses and used in 34 cases the left internal mammary artery. All but three patients survived the procedure in stable conditions and could leave intensive care after a mean stay of 1.5 days. There were no perioperative myocardial infarctions. In our view, CABG during LVAD support without heart lung machine and cardioplegia is a safe and life saving procedure. No ischemic damage is applied to the heart and it can be recommended for cautions use in select patients.

[Acute and chronic mechanical circulatory support]. / Akute und chronische mechanische Kreislaufassistenz.

Mechanical circulatory support and mechanical unloading of the left ventricle become more and more routine in clinical treatment regimens of both acute and chronic heart failure. Along with increasing availability of different cardiac assist systems one can adjust the degree of support according to the clinical situation. We report about our experience in the period between January 1994 and May 1995 with following assist systems: Hemopump, centrifugal pumps, Medos, HIAVAD and Novacor. We implanted those devices in 21 patients out of following indications: postinfarct--cardiac failure (CF), postcardiotomy CF, elective postcardiotomy support, myocarditis CF and "bridge" to transplant. Ten patients survived the period of mechanical support and could be weaned successfully. Circulatory support was sufficient in all cases, indication, time of implantation, anticoagulation and prevention of infections are discussed.

Left-ventricular unloading with a new pulsatile assist device: the HIA-VAD system and its influence on myocardial stunning.

To assess the mechanical unloading properties of a new pneumatic cardiac assist device (60 ml Medos HIA-VAD) and its possible influence on recovery from myocardial stunning we performed a study in 12 anaesthetized sheep. After left thoracotomy measuring transducers were placed and the assist device connected between the left-atrial appendage and the descending thoracic aorta. Global hemodynamics were measured before and after unloading was performed. Myocardial stunning was induced by transient occlusion of a coronary artery for 15 minutes and regional myocardial wall thickening was measured. A group without unloading served as controls (group I, n = 4). In a second group unloading was performed during the last ten minutes of ischemia (group II, n = 4) and in a third group unloading was performed for 30 minutes starting after ten minutes of reperfusion (group III, n = 4). After starting the Medos HIA-VAD, significant unloading could be demonstrated: left-ventricular dP/dtmax decreased significantly (p < 0.05) to 54% and 61% in groups II and III and left-atrial pressure to 50% and 71%, respectively. Systolic and mean arterial pressure did not change significantly (p > 0.05), while the diastolic pressure increased (p < 0.05) to 134% and 138% in groups II and III. After mechanical unloading whether during ischemia or during reperfusion systolic wall thickening in the postischemic area recovered to 103% and 92% of preischemic control in groups II and III, respectively. Recovery was incomplete in the non-unloaded controls (76%) (p < 0.05 versus groups II and III). Post-ejection thickening, a diastolic measure of stunning, diminished significantly after unloading in both protocols (p < 0.05 for groups II and III versus group I). We conclude that mechanical unloading with the 60 ml Medos HIA-VAD significantly improves recovery from myocardial stunning.

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.

Reperfusion after cardioplegic cardiac arrest--effects on intracoronary leucocyte elastase release and oxygen free radical mediated lipid peroxidation.

In experimental animal models reperfusion of ischaemic myocardium causes sequestration of leucocytes within the coronary circulation. Leucocytes contribute to postischaemic myocardial injury by releasing proteolytic enzymes and by generating oxygen free radicals. The aim of this study was to investigate whether leucocytes also contribute to myocardial injury following ischaemia and reperfusion associated with cardioplegic cardiac arrest. Therefore, we studied the release of the proteolytic enzyme elastase and oxygen free radical initiated myocardial lipid peroxidation in coronary sinus blood during reperfusion after cardioplegic cardiac arrest. The elastase-alpha-1-proteinase inhibitor complex and malondialdehyde (a byproduct of myocardial lipid peroxidation) were measured in arterial, central venous and coronary sinus blood samples in 19 patients undergoing elective coronary artery bypass grafting before aortic crossclamping and 1, 5, 10 and 20 m in after aortic declamping. Malondialdehyde concentrations did not increase significantly during the study period, whereas elastase concentrations showed a significant increase during cardiopulmonary bypass in arterial, central venous as well as coronary sinus blood. Neither elastase nor malondialdehyde concentrations in coronary sinus blood differed significantly from arterial or central venous blood at any time point measured. Our data demonstrated increased elastase concentrations during cardiopulmonary bypass, but we did not find enhance intracoronary elastase release or myocardial during cardiopulmonary bypass, but we did not find enhanced intracoronary elastase release or myocardial lipid peroxidation. Our data suggest that patients are sufficiently protected from leucocyte mediated ischaemia reperfusion injury during uncomplicated coronary artery bypass grafting with cardioplegic arrest.