Scapulohumeral subluxation and luxation in five alpacas.

INTRODUCTION: The patient histories, findings from clinical examinations, diagnostic imaging techniques, the surgical procedures, complications, necropsy findings and the outcomes from five male or castrated male alpacas with scapulohumeral sub-/luxation are presented. These alpacas each had a history of severe forelimb lameness for one week (n: 1), four weeks (n: 2) and for two-to-three months (n: 2). Two of the five alpacas were euthanized due to severe osteoarthritic changes that developed during the two-to-three months of scapulohumeral luxation. Three alpacas were treated with open reduction and internal stabilisation by placing tension band sutures between one 4,5 mm cortical screw anchored in the scapular neck and two 4,5 mm cortical screws anchored in the greater humeral tubercle, all of them provided with washers. Post-surgery a carpal flexion sling was applied to avoid postoperative weight-bearing. An exercise programme was started after removal of the carpal sling and continued for 12 weeks. In one of the three alpacas an additional non-displaced fracture of the acromion occurred two weeks after surgery. In conclusion, all three treated alpacas had good-to-excellent long-term outcomes and are still alive 123, 15 and 12 months after surgical repair of the scapulohumeral sub-/luxation. As four weeks, or even up to three months elapsed in four of these five alpacas until a definitive diagnosis was made, more education should be provided to alpaca owners that severely lame animals should be presented to a veterinarian with adequate diagnostic possibilities and expertise as soon as possible in order not to compromise treatment success.

INTRODUCTION: Dans cette étude rétrospective, on présente les antécédents des patients, les résultats des examens cliniques, les techniques d'imagerie diagnostique, les procédures chirurgicales, les complications, les résultats de l'autopsie et les résultats finaux de cinq alpagas mâles ou mâles castrés souffrant d'une subluxation ou luxation scapulo-humérale. Ces alpagas présentaient chacun des antécédents de boiterie sévère des membres antérieurs depuis une semaine (n: 1), quatre semaines (n: 2) et deux à trois mois (n: 2). Deux des cinq alpagas ont été euthanasiés en raison des changements arthrosiques graves qui s'étaient développés au cours des deux à trois mois de luxation scapulo-humérale. Trois alpagas ont été traités par réduction ouverte et stabilisation interne en plaçant des sutures à bande de tension entre une vis corticale de 4,5 mm ancrée dans le col de l'omoplate et deux vis corticales de 4,5 mm ancrées dans le tubercule huméral supérieur, toutes munies de rondelles. Après l'opération, une écharpe de flexion du carpe a été mise en place pour éviter la mise en charge postopératoire. Un programme d'exercices a été mis en place après le retrait de l'écharpe carpienne et a été poursuivi pendant 12 semaines. Chez l'un des trois alpagas, une fracture non déplacée de l'acromion s'est produite deux semaines après l'opération. En conclusion, les trois alpagas traités ont eu des résultats à long terme bons à excellents et sont toujours en vie 123, 15 et 12 mois après la réparation chirurgicale de la subluxation scapulo-humérale. Dans la mesure où il s'est écoulé quatre semaines voire jusqu'à trois mois chez quatre de ces cinq alpagas avant qu'un diagnostic définitif ne soit posé, il convient d'informer davantage les propriétaires d'alpagas que les animaux gravement boiteux doivent être présentés à un vétérinaire disposant des possibilités de diagnostic et de l'expertise adéquates le plus rapidement possible afin de ne pas compromettre le succès du traitement.

Ultrasonographic diagnosis of closed pedal bone fractures in bovine claws: An ex-vivo study in slaughterhouse specimens.

Pedal bone fractures are one of the most common fracture locations in adult cattle and can be diagnosed by radiographs in two planes. Most bovine practitioners do not have access to such X-ray machines, but many use ultrasound units on a daily basis, primarily for reproductive medicine. For this reason, in this double-masked, randomized controlled study, we aimed to investigate the suitability of ultrasonographic examination using a 5 MHz linear transducer for diagnosing closed fractures of the pedal bone in cattle. A total of 54 hindlimb claws from slaughtered cattle were prepared and approximately 50% of the claws were artificially fractured. All claws were ultrasonographically examined twice by two examiners to determine the presence or absence of fractures and their locations. Ultrasound results were confirmed using radiographs of the claws as the reference standard method. All fracture locations as determined by ultrasonography were situated within ±2 mm of the radiographically-determined fracture zone. Ultrasound examination yielded a calculated sensitivity of 93%, a specificity of 91% and an inter-rater reliability of 0.77. The intra-rater reliability for the examiners were 0.96 and 0.88. Examiner experience with ultrasound examination and using ultrasound images for diagnosis could have influenced diagnostic accuracy. We conclude that artificially-created pedal bone fractures in ex-vivo bovine claws can be diagnosed using ultrasonography; similar results are expected in live animals. These results should encourage veterinarians to use ultrasonography for diagnosing pedal bone fractures in cattle.

Definition of the safe lower limits of aortic resection during surgical procedures on the thoracoabdominal aorta: use of somatosensory evoked potentials.

The technique of intraoperative monitoring of somatosensory evoked potentials was applied to a canine model of spinal cord ischemia in an attempt to determine the safe lower limits of aortic resection during thoracic aortic surgery. Fifteen animals underwent left thoracotomy with institution of partial left atrial/femoral artery bypass for maintenance of distal aortic perfusion after proximal descending thoracic aortic exclusion. In Group I animals (n = 6, control), no further interventions were performed so that the effect of exclusion of vessels noncritical to spinal cord blood supply could be assessed by measurements of spinal cord blood flow and somatosensory evoked potentials. In Group II animals (n = 8), the level of distal aortic exclusion was progressively lowered until loss of somatosensory evoked potential (critical vessel exclusion) occurred. The effect of critical vessel exclusion on spinal cord blood flow was then assessed. Exclusion of multiple vessels noncritical to spinal cord blood supply (Group I) had no effect on spinal cord blood flow or function (somatosensory evoked potentials). Exclusion of vessels critical to spinal cord blood supply resulted in significant spinal cord ischemia (83.4% flow reduction, probability [p] less than 0.05 versus baseline) and ischemic spinal cord dysfunction (loss of somatosensory evoked potential).(ABSTRACT TRUNCATED AT 250 WORDS)

Noninvasive assessment of treatment of cardiac allograft rejection with indium-111-labeled lymphocytes.

We have shown previously that cardiac allograft rejection can be detected noninvasively with gamma scintigraphy after administration of indium-111 (111In)-labeled lymphocytes. To determine whether this technique could be used to monitor salvage immunosuppressive therapy in reversing rejection, 5 dogs were studied after thoracic heterotopic cardiac transplantation. Initial postoperative immunosuppression was maintained with cyclosporine (10-20 mg/kg/day) and prednisone (1 mg/kg/day) for 7 days after transplantation and then discontinued. Scintigraphy after administration of labeled lymphocytes was performed during initial immunosuppression and every 3 days after its termination. Endomyocardial biopsies were obtained on each day scintigraphy was performed. Once scintigraphic criteria for rejection were met (111In-lymphocyte uptake greater than mean +/- 2SD of normal myocardium), animals were treated with high dose methylprednisolone and cyclosporine. Myocardial 111In-lymphocyte activity compared with that in blood was 0.7 +/- 0.8 during initial immunosuppression, increased to 5.7 +/- 3.5 after termination of therapy (P less than 0.01), and diminished with salvage immunosuppressive therapy to 0.5 +/- 0.8 (P = NS compared with native hearts or allografts during initial immunosuppression). Scintigraphy accurately predicted all but one episode of biopsy-documented rejection and accurately detected reversal of rejection during salvage. Thus, scintigraphy with 111In-labeled lymphocytes should facilitate noninvasive monitoring of antirejection therapy in patients.

Detection of rejection of canine orthotopic cardiac allografts with indium-111 lymphocytes and gamma scintigraphy.

Previous studies have demonstrated the feasibility of detecting canine heterotopic cardiac allograft rejection scintigraphically after administration of 111In lymphocytes. To determine whether the approach is capable of detecting rejection in orthotopic cardiac transplants in which labeled lymphocytes circulating in the blood pool may reduce sensitivity, the present study was performed in which canine orthotopic cardiac transplants were evaluated in vivo. Immunosuppression was maintained with cyclosporine A (10-20 mg/kg/day) and prednisone (1 mg/kg/day) for 2 wk after transplantation. Subsequently, therapy was tapered. Five successful allografts were evaluated scintigraphically every 3 days after administration of 100-350 microCi 111In autologous lymphocytes. Correction for labeled lymphocytes circulating in the blood pool, but not actively sequestered in the allografts was accomplished by administering 3-6 mCi 99mTc autologous erythrocytes and employing a previously validated blood-pool activity correction technique. Cardiac infiltration of labeled lymphocytes was quantified as percent indium excess (%IE), scintigraphically detectable 111In in the transplant compared with that in blood, and results were compared with those of concomitantly performed endomyocardial biopsy. Scintigraphic %IE for hearts not undergoing rejection manifest histologically was 0.7 +/- 0.4. Percent IE for rejecting hearts was 6.8 +/- 4.0 (p less than 0.05). Scintigraphy detected each episode of rejection detected by biopsy. Scintigraphic criteria for rejection (%IE greater than 2 s.d. above normal) were not manifest in any study in which biopsies did not show rejection. Since scintigraphic results with 111In-labeled lymphocytes were concordant with biopsy results in orthotopic cardiac transplants, noninvasive detection of graft rejection in patients should be attainable with the approach developed.

Monitoring of somatosensory evoked potentials during surgical procedures on the thoracoabdominal aorta. IV. Clinical observations and results.

Thirty-three patients undergoing operations on the descending thoracic or thoracoabdominal aorta were monitored to evaluate causes and effects of spinal cord ischemia as manifested by changes in somatosensory evoked potentials. Maintenance of distal aortic perfusion pressure (greater than 60 mm Hg) by either shunt or bypass techniques in 17 patients resulted in preservation of somatosensory evoked potentials and a normal postoperative neurologic status, irrespective of the interval of thoracic cross-clamping (range 23 to 105 minutes). In 16 other patients in whom cross-clamp time ranged from 16 to 124 minutes, evoked potential loss was observed because of failure to provide distal perfusion (n = 8), inadequate maintenance of distal perfusion pressure (less than 60 mm Hg) despite shunt/bypass (n = 6), or interruption of critical intercostal arteries (n = 2). Incidence of paraplegia in the entire group was 15.1% (5/33) and was limited to only those patients in whom evoked potential loss occurred (5/16, 31.2%) (p = 0.02). Loss of somatosensory evoked potentials for more than 30 minutes resulted in a 71.2% (5/7) incidence of paraplegia, whereas no neurologic deficit was noted in patients (0/26) in whom evoked potential loss was either prevented or limited in duration to 30 minutes (p less than 0.001 versus loss for more than 30 minutes). Intraoperative monitoring of somatosensory evoked potentials is a sensitive indicator of spinal cord ischemia. Simple aortic cross-clamping, failure to maintain distal perfusion pressure above 60 mm Hg, and inability to reimplant critical intercostals in a timely fashion result in a high rate of paraplegia if duration of spinal cord ischemia as measured by somatosensory evoked potentials exceeds 30 minutes. Routine evoked potential monitoring during thoracoabdominal procedures appears useful in assessing the adequacy of spinal cord perfusion. Furthermore, it can alert the surgeon to the necessity for critical intercostal artery reimplantation as well as the need for adjustment or regulation of distal aortic perfusion.

Monitoring of somatosensory evoked potentials during surgical procedures on the thoracoabdominal aorta. I. Relationship of aortic cross-clamp duration, changes in somatosensory evoked potentials, and incidence of neurologic dysfunction.

To determine if intraoperative monitoring of somatosensory evoked potentials detects spinal cord ischemia, we subjected 21 dogs to aortic cross-clamping distal to the left subclavian artery. Group I animals (short-term studies, n = 6) demonstrated decay and loss of somatosensory evoked potentials at 8.5 +/- 1.1 minutes after aortic cross-clamping. During loss of somatosensory evoked potentials, significant decreases in spinal cord blood flow occurred in cord segments below T6. Significant reactive hyperemia occurred without normalization of somatosensory evoked potentials after reperfusion. Fifteen Group II animals (long-term studies) were studied to determine the relationship between duration of spinal cord ischemia (evoked potential loss) and subsequent incidence of paraplegia. Extension of aortic cross-clamping for 5 minutes after loss of somatosensory evoked potentials in six dogs resulted in no paraplegia (mean cross-clamp time 12.7 +/- 0.6 minutes). Prolongation of aortic cross-clamping for 10 minutes after evoked potential loss in nine dogs (mean cross-clamp time 17.6 +/- 0.6 minutes) resulted in a 67% (6/9) incidence of paraplegia 7 days postoperatively (p = 0.02 versus 10 minutes of aortic cross-clamping). These findings demonstrate that simple aortic cross-clamping uniformly results in spinal cord ischemia and that such ischemia is detectable by monitoring of somatosensory evoked potentials. Duration of ischemia, as measured by the time of evoked potential loss during the cross-clamp interval, is related to the incidence of postoperative neurologic injury.

Monitoring of somatosensory evoked potentials during surgical procedures on the thoracoabdominal aorta. II. Use of somatosensory evoked potentials to assess adequacy of distal aortic bypass and perfusion after thoracic aortic cross-clamping.

Pulsatile left atrial-femoral artery bypass was instituted after aortic cross-clamping distal to the left subclavian artery in a canine experimental model to determine the relationship of distal aortic perfusion pressure with spinal cord blood flow and somatosensory evoked potentials. In six animals (Group I) distal aortic perfusion pressure was maintained at 100 mm Hg throughout a 1 hour interval of aortic cross-clamping. During this period, somatosensory evoked potentials and spinal cord blood flow (radioactive microspheres) showed no significant change from baseline. In six other dogs (Group II) distal aortic perfusion pressure was initially maintained at 100 mm Hg after aortic cross-clamping and then progressively decreased to 70, 40, and 25 mm Hg. Somatosensory evoked potentials and spinal cord blood flow were preserved at baseline levels for all distal perfusion pressures greater than 70 mm Hg. At 40 mm Hg, abnormalities in amplitude of the somatosensory evoked potentials were noted in all animals with progression to complete loss of evoked potential activity at lower perfusion pressures. Maintenance of adequate somatosensory spinal cord conduction after thoracic aortic cross-clamping is dependent on a critical level of distal aortic perfusion that can be accomplished by use of an adjunct such as pulsatile left atrial-femoral artery bypass. The critical level of distal aortic perfusion pressure to maintain normal somatosensory evoked potentials and spinal cord blood flow in this canine experimental study was 70 mm Hg or greater. Because inadequate distal aortic perfusion can be easily detected by monitoring of somatosensory evoked potentials, these techniques should prove helpful in evaluating the effectiveness of distal perfusion techniques during clinical aortic cross-clamping for procedures on the thoracoabdominal aorta.

Preservation of myocardial ATP. Comparison of blood vs crystalloid cardioplegia.

Preservation of myocardial high-energy phosphates correlates with the heart's ability to resume normal function following aortic crossclamping (AXC). The ability of the canine myocardium to synthesize and maintain ATP during 180 minutes of AXC was evaluated in 12 hearts subjected to either blood or crystalloid cardioplegic arrest. Group 1 hearts were arrested by infusion of 750 ml of blood potassium cardioplegia (BKC) solution into the aortic root initially and every 30 minutes, as were group 2 (six) hearts but with a crystalloid cardioplegia (CC) solution. Transmural left ventricular biopsy specimens were obtained for ATP analysis prior to AXC (control), before and after cardioplegia injections 2, 4, and 6, prior to unclamping (180 minutes of AXC), and 30 minutes following reperfusion. ATP levels increased significantly above control (p less than 0.005) during the 180 minutes of AXC immediately following infusion of BKC. At the end of 180 minutes of AXC and following 30 minutes of reperfusion, ATP was noted to be normal in this group (p = NS). In contrast, ATP levels fell significantly (p less than 0.005) during the period of aortic cross-clamping in the crystalloid cardioplegia group and did not return to normal even after 30 minutes of reperfusion (p less than 0.005). We concluded that BKC, by presenting the arrested myocyte with adequate oxygen and substrate, allows for synthesis and preservation of myocardial ATP during periods of AXC as long as three hours. In this respect, it should be regarded as superior to CC, which permits a statistically significant depletion of ATP (p less than 0.005) uncorrected, even after 30 minutes of reperfusion in the beating, nonworking state.

Preoperative three-dimensional reconstruction of the heart and great vessels in patients with congenital heart disease. Technique and initial results.

Magnetic resonance images have been obtained preoperatively in six patients with congenital heart disease. Contiguous sequences of electrocardiogram-triggered spin-echo images have been reconstructed in three-dimensional form to define the size and anatomic relationships to the great vessels and internal cardiac structures. Findings of magnetic resonance imaging were corroborated by angiographic and sector-scan echocardiographic studies and at operation. Individual scan slices were manually edited to separate the heart and great vessels from the blood within them and from extracardiac structures. Surface reconstruction software originally developed for craniofacial and orthopedic surgical planning was adapted for processing of cardiac magnetic resonance image sequences. Preoperative three-dimensional magnetic resonance imaging reconstructions were obtained in patients with aortic coarctation with ventricular septal defect, hypoplastic left ventricle, pulmonary artery atresia with ventricular septal defect, atrial septal defect, partial atrioventricular canal defect with anomalous pulmonary venous drainage, and tetralogy of Fallot with peripheral pulmonary artery stenosis. The reconstructions showed anatomic findings consistent with two-dimensional magnetic resonance imaging, echocardiography, cineangiography, and intraoperative findings. The three-dimensional images have a format that is familiar and consistent with the gross intraoperative appearance of the heart and great vessels. These three-dimensional images can facilitate the interpretation of magnetic resonance scan findings for cardiac surgeons without the sacrifice of significant clinical information.

Percutaneous cardiopulmonary bypass with a synchronous pulsatile pump combines effective unloading with ease of application.

Percutaneous total cardiopulmonary bypass offers the advantage of rapid, simple implementation without the need for thoracic incision and provides the ability to support both left and right ventricular failure as well as pulmonary insufficiency. Previous studies using roller pump percutaneous bypass were only partially successful because of the inability to effectively unload the left ventricle. In the present experiment we attempted to determine in a normal canine model whether use of synchronous pulsatile pumping for percutaneous bypass could overcome this problem. Fourteen dogs were placed on percutaneous bypass for 1 hour. A roller pump was used in seven and a synchronous pulsatile pump with an electrocardiogram triggering mechanism in the other seven. All animals were maintained on percutaneous bypass for 1 hour. In the pulsatile pump group there was a significantly greater percent decrease from baseline in tension-time index (-56.3% versus -19.1%, p less than 0.01) and in myocardial oxygen consumption (-45.8% versus +2.1%, p less than 0.05) and a significantly greater percent increase in the endocardial/epicardial blood flow ratio (27.6% versus -6.5%, p less than 0.01) than in the roller pump group. These results show that superior unloading can be achieved by percutaneous pulsatile bypass compared with percutaneous roller pump bypass. The findings suggest that percutaneous total cardiopulmonary bypass with a synchronous pulsatile pump offers a relatively simple but effective method for providing appropriate patients with temporary hemodynamic stability before cardiac catheterization or medical or surgical revascularization.

Adjunctive left ventricular unloading during myocardial reperfusion plays a major role in minimizing myocardial infarct size.

Although prompt institution of reperfusion following coronary artery occlusion has been shown to limit myocardial infarct size, significant "reperfusion injury" may result. We investigated in a canine model whether maintenance of the left ventricle in an unloaded state during the initial reperfusion period following acute myocardial ischemia would result in greater limitation of infarct size or modify the development of reperfusion injury. Group I (control, n = 6) underwent 6 hours of occlusion of the left anterior descending coronary artery without further intervention. In both Group II (n = 6) and Group III (n = 6), the snare was released after 2 hours and hearts were reperfused for 4 hours. In Group III only, the left ventricle was maintained in an unloaded state throughout the entire reperfusion interval via pulsatile left atrial-femoral artery bypass. The results showed that reperfusion of the left ventricle in an unloaded state resulted in significantly improved limitation of both infarct size (area of infarct/area at risk = 16.6% for Group III versus 72.0% for Group I and 55.4% for Group II, p less than 0.001) and area of microvascular damage (area of microvascular damage/area at risk = 4.8% for Group III versus 30.6% for Group II, p less than 0.001). These results indicate that although myocardial reperfusion of the type provided by thrombolysis and/or angioplasty techniques does result in limitation of infarct size when compared to no reperfusion, this limitation is not optimal unless the left ventricle is unloaded during the initial reperfusion period.

Monitoring of somatosensory evoked potentials during surgical procedures on the thoracoabdominal aorta. III. Intraoperative identification of vessels critical to spinal cord blood supply.

Somatosensory evoked potentials were used to locate intercostal arteries critical to spinal cord blood flow in nine dogs. To mimic a clinical situation, the proximal descending thoracic aorta (left subclavian artery to T7) was excluded with cross-clamps, and partial pulsatile left atrial-femoral artery bypass was instituted to maintain distal aortic pressure at 100 mm Hg. Progressively lower aortic segments were excluded (T7-10, T10-L1, L1-3, L3-6, L6-7) until loss of somatosensory evolved potentials occurred. Spinal cord blood flow measurements at the time of evoked potential loss revealed significant ischemia (p less than 0.02 versus baseline) in the excluded segment in seven animals but normal spinal cord blood flow in the remainder of the cord. Upon reperfusion, significant reactive hyperemia (p less than 0.02) was noted only in previously ischemic cord segments. Two animals exhibited no change in somatosensory evoked potentials or spinal cord blood flow despite exclusion of the entire thoracoabdominal aorta, presumably as a result of spinal collaterals. Loss of somatosensory evoked potentials despite adequate distal perfusion indicates that critical intercostal vessels have been excluded from systemic and bypass circulations. Use of evoked potential measurements in both experimental and clinical situations provides a means for assessing adequacy of spinal cord blood flow during cross-clamping and can alert the surgeon to the need for reimplantation of critical intercostal arteries during surgical resection of the thoracoabdominal aorta.

Time course of effective interventional left heart assist for limitation of evolving myocardial infarction.

Previous work has shown that if pulsatile left atrial-femoral artery bypass is instituted after occlusion of the left anterior descending coronary artery for from 15 minutes to 2 hours, it can significantly limit the size of the infarct resulting 4 hours later. This study investigated whether pulsatile left atrial-femoral artery bypass begun after more clinically pertinent periods of initial ischemia can still significantly limit infarct expansion. After baseline measurements of hemodynamics, tension-time index, and regional myocardial blood flow in 73 open-chest, adult dogs, the left anterior descending coronary artery was ligated for 15 minutes or 1, 2, 4, or 6 hours of unprotected ischemia. In the five control groups, the initial ischemic period was merely extended for another 4 hours. In the five experimental groups, the animals were placed on pulsatile left atrial-femoral artery bypass for another 4 hours after the initial ischemic period. At the end of each procedure, gentian violet was used to identify the area at risk of infarction, and triphenyltetrazolium chloride was used to delineate the area of infarct. The results showed a significant reduction in the area of infarct as a percentage of the area at risk in each bypass group compared with its control group for all ischemic periods of less than 6 hours. These findings suggest that the maximum permissible ischemic time delay for myocardial salvage by pulsatile left atrial-femoral artery bypass is one which is pertinent in a clinical setting. The results justify continued attempts to develop appropriate techniques for percutaneous application of this modality to patients with an evolving myocardial infarction.

Left atrium-to-femoral artery bypass: effectiveness in reduction of acute experimental myocardial infarction.

The effects of prompt institution of left atrium-to-femoral artery (LA-FA) bypass on myocardial infarct area (AI) as a percentage of myocardial area at risk for infarction (AR) during a 4 hour period following ligation of the left anterior descending coronary artery (LAD) were studied in 26 dogs. Following LAD ligation, baseline measurements of myocardial tension-time index (TTI) and regional myocardial blood flow (RMBF) were obtained. Group I (controls, n = 16) received no further support. Group II (LA-FA bypass, n = 10) underwent left ventricular unloading via LA-FA bypass beginning 15 minutes after coronary occlusion. Four hours after LAD occlusion, measurements of TTI and RMBF were repeated in both groups. Just before sacrifice, gentian violet was injected into the aortic root to delineate the AR. The hearts were then removed and sectioned transversely through the left ventricle (LV) and septum. The AR (that ventricular area not perfused by gentian violet) was measured by planimetry and compared to the AI as identified by incubation of heart slices in triphenyltetrazolium chloride dye. In comparisons of control versus LA-FA bypass groups, both AI/LV (21.6% versus 10.4%) and AI/AR ratios (73.7% versus 21.8%) were significantly reduced in the bypass group (p less than 0.005). Mortality in the control group (5/16, 31.2%) was significantly greater (p less than 0.005) than in the bypass group (0/10, 0%). Mean TTI over the 4 hour ischemic period was essentially unchanged in the control group as compared to a reduction of 62.8% in the bypass group (p less than 0.005). Furthermore, RMBF at 4 hours was significantly improved in all regions of the LV in hearts undergoing LA-FA bypass when compared with control hearts (p = 0.025). These results demonstrate by a consistent method that prompt institution of LA-FA bypass significantly reduces the mortality associated with acute coronary artery occlusion, as well as the total AI and AI/AR. The protective mechanisms provided by LA-FA bypass probably include the highly significant reduction of LV work and the opening of new bridge collateral blood vessels with redistribution of blood flow to the ischemic region.

Aortic dissection in a cardiac allograft recipient: a case report.

Ascending aortic dissection is rare in cardiac allograft recipients. Only two patients with dissection arising from the native aorta have been reported previously and, unfortunately, the diagnosis was made postmortem in each instance. We report the first case of successful surgical treatment of aortic dissection confined to the donor aorta in a recipient of an orthotopic cardiac allograft.

Prevention of early failure of stapled gastric partitions in treatment of morbid obesity.

Clinical observations and data obtained in animal experiments indicate that the gastric partition is most susceptible to the stresses of solid food boluses between the second and sixth postoperative weeks, predisposing the operation to early failure. Tensiometer studies indicate that by the sixth to the eighth postoperative week, the staple line is as strong as uninjured stomach. Liquid diet restriction for eight weeks after gastric partitioning reduces the incidence of early operative failure. Until safe and effective methods of increasing staple line strength are established, all patients having gastric partitioning should be restricted to a liquid diet for eight weeks after operation.

'Pulsatile' left atrial-femoral artery bypass. A new method of preventing extension of myocardial infarction.

A left atrial-femoral artery (LA-FA) bypass system was designed to deliver synchronous pulsatile blood flow. We compared it with nonpulsatile LA-FA bypass in its effectiveness to limit infarct extension after ligation of the left anterior descending coronary artery at its origin in 35 dogs. Nonpulsatile LA-FA bypass resulted in a 70% reduction in the size of infarct. The addition of synchronous diastolic counterpulsation (P-LA-FA) further reduced the size of infarct, when compared with that in controls (95%) or animals that underwent LA-FA bypass (83%). Both LA-FA and P-LA-FA bypasses limited infarct extension and reduced mortality after acute coronary occlusion through effective unloading of the left ventricle. The addition of diastolic counterpulsation to LA-FA bypass led to further significant infarct reduction, when compared with LA-FA bypass alone. These effects were most likely secondary to improvements in myocardial blood flow distribution.

Evolving concepts in prevention of spinal cord injury during operations on the descending thoracic and thoracoabdominal aorta.

Spinal cord injury following operations on the descending thoracic or thoracoabdominal aorta remains a major problem. In certain subsets of patients, the risk of postoperative spinal cord injury is substantial. Although several adjuncts have been employed clinically to eliminate or reduce the frequency of this complication, none have proven to be completely effective. An important reason for this is the failure of these techniques to reliably and noninvasively localize the level of origin of arteries from the aorta that are critical to spinal cord circulation. Since postoperative spinal cord injury most likely results from ischemia or hypoxia of the lower segment of spinal cord, use of adjunctive techniques to preserve spinal cord function during aortic clamping by perfusing the distal aorta adequately with or without systemic hypothermia should be considered. To practically implement this, partial cardiopulmonary bypass for distal perfusion when the critical intercostal or lumbar arteries originate from the aorta distal to the excluded segment, and total cardiopulmonary bypass with systemic hypothermia and implantation of intercostal and lumbar arteries when these arteries originate from the excluded segment, can be used. In addition, whenever possible, intraoperative monitoring of spinal cord function should be performed.

Noninvasive three-dimensional reconstruction of the heart and great vessels by ECG-gated magnetic resonance imaging: a new diagnostic modality.

We have developed a new method of computer image processing that allows true three-dimensional (3-D) images of the heart and great vessels to be reconstructed from standard ECG-gated two-dimensional magnetic resonance (MR) images. Contiguous 5-mm thick MR images of the thorax from the level of the cardiac apex to the aortic arch were obtained in 4 normal volunteers and 3 patients with congenital heart disease: 1 with pseudotruncus arteriosus and 1 with a ventricular septal defect, each with Eisenmenger's complex, and 1 with aortic coarctation. Each image could be obtained at up to seven different intervals throughout the cardiac cycle with ECG gating. The scanning procedure is noninvasive and requires no contrast material. Using standard software, images from each interval in the cardiac cycle were edited to isolate pertinent cardiac and great vessel structures. High-resolution 3-D reconstructions were formed for each interval by stacking the edited images. Sequential projection of 3-D reconstructions from each interval yields four-dimensional (includes time) cine views. Both 3-D and cine views can be obtained from any axis or divided in any plane to allow accurate, noninvasive assessment of cardiac and great vessel anatomy, chamber volumes, and regional and global wall motion. Noninvasive 3-D reconstruction of the heart and great vessels provides accurate anatomical data not available from standard cardiac catheterization or other noninvasive diagnostic procedures, and aids in the preoperative planning of the procedure to correct complex congenital malformations.