Internal Shunt Research Articles

Initial experience with the AbioCor implantable replacement heart at the University of Louisville.

Potential benefits of heart transplantation are limited by the severe donor organ shortage. The AbioCor implantable replacement heart has been developed as a potential alternative to heart transplantation. We report our initial experience with the AbioCor in a bovine model. A right thoracotomy was performed for access to the heart and great vessels. After initiation of cardiopulmonary bypass, excision of the native ventricles was followed by orthotopic placement of the IRH and complete implantation of the transcutaneous energy transfer coil, controller, and battery pack. Invasive monitoring of IVC, SVC, carotid artery, pulmonary artery, and left atrial (LA) pressures was performed in all animals. Twelve calves have undergone implantation of the AbioCor. There were three early deaths, one from bleeding, one from respiratory failure, and one from neurodysfunction from low flow during CPB. Nine animals have had a normal recovery and survived a mean of 24.5 days (range, 4-48 days). All the animals have demonstrated excellent hemodynamics with the maintenance of normal pressures in the LA, SVC, IVC, pulmonary artery, and aorta. Adjustment of the right-sided internal hydraulic fluid shunt has allowed for control of right-left balance and, thereby, manipulation of left and right side filling pressures. Late morbidity has consisted of neck wound infection and sepsis, pneumonia, and bleeding. Successful orthotopic implantation of all components of the AbioCor has been achieved in a bovine model. This device has demonstrated restoration of normal hemodynamics and excellent function of the atrial hydraulic shunt to achieve right-left balance.

Technical note: external cerebrospinal fluid (CSF) drainage by percutaneous needle punction in newborn children.

External drainage of CSF in children is indicated in acute hydrocephalus e.g. after intraventricular bleeding or infection. In these cases the drainage has to remain in place until physiological CSF circulation is restored or an internal shunt can be inserted. External drainage is mostly performed using a silicon catheter connected to a plastic bag. An external CSF drainage left for several days in situ bears an increasing risk of bacterial infection. In these cases a metal needle minimizes the risk of ventriculitis. For prevention of accompanying infection we implanted a Cytocan port needle with a 20 G diameter in 7 infants. The needle is easily inserted with low risk of complications. By its plastic top angulated at 90 degrees to the needle the system can be fixed to the skin very safely by suture or tape. With this system neither an implantation related intracerebral haemorrhage nor an accompanying ventriculitis was encountered. In two cases a pre-existing ventriculitis was cured by this needle drainage and antibiotic treatment. In five cases an acute hydrocephalus after intraventricular haemorrhage was drained by the port needle system.

Prevention of Spinal Cord Ischemia in an Ovine Model of Abdominal Aortic Aneurysm Treated with a Self-Expanding Stent-Graft

Purpose: To present novel techniques to prevent spinal ischemia during aneurysm creation and chronic bifurcated stent-graft implantation in an ovine model of abdominal aortic aneurysm (AAA). Method: Experimental AAAs were created in 38 sheep. To prevent spinal ischemia, an internal aortic shunt was used during aneurysm creation. In the animals designated to receive bifurcated stent-grafts, a left external iliac-to-internal iliac bypass was performed to revascularize the caudal artery and prevent postdeployment spinal cord ischemia. Specimens were harvested at 1 week, 1, 3, and 6 months, and 1 year. Results: Aneurysms were successfully created without paralysis in 35 animals. Two died due to aspiration pneumonia. Of the 33 animals implanted with endografts, 16 (94%) of 17 with straight devices and 15 (94%) of 16 with bifurcated stent-grafts survived with well-functioning, patent stent-grafts. Paralysis developed in 2 animals after endografting due to technical failures. Conclusions: The use of an internal shunt during aneurysm creation and internal iliac-to-external iliac transposition prior to bifurcated stent-graft deployment prevented spinal ischemia in an ovine AAA model. Chronically deployed stent-grafts were well tolerated.

A CASE OF EXTRACRANIAL INTERNAL CAROTID ARTERY ANEURYSM

A case of extracranial internal carotid artery aneurysm which is relatively rare is presented, together with some review of literatures. A 50-year-old woman was admitted to another hospital because of sudden onset of severe headache and a tumor in the right side of theneck. MRI showed that the neck tumor was neurinoma. The patient was operates on. Intraoperatively, the tumor was found to be an aneurysm of the right internal carotid artery (ICA). The patient was referred to our institution. On 3 D-CT, a saccular aneurysm was located at the right ICA, which was 30×25mm in size with mural thrombus. Brain MRI visualized a cerebral infarction of the right frontal lobe without any abnormal neurological findings. The patient underwent an aneurysmectomy and interposition of saphenous vein graft. The intraoperative carotid stump pressure was 62 mmHg ; however, an outlying internal shunt was placed because of the cerebral infarction and the prolonged clamping time of the right ICA. Intraoperative electroencephalographic monitoring did not show any abnormal changes, and the graft blood flow volume was sufficient. Postoperative course was uneventful and an arteriogram showed no stenosis of the bypass graft. Pathological examination revealed that the aneurysm was true type with disruption of medial elastica and inflammatory cellular infiltration in all layers, which was diagnosed as nonspecific vasculitis.

Profound deficitを呈した急性期頸部内頸動脈閉塞に対する血栓内膜剥離術

Emergency carotid endarterectomy (CEA) was performed in 10 patients with proximal internal carotid artery occlusion associated with profound neurological deficits. All patients visited our clinic within 5 hours from the onset, and flow of the IC was restored 4.9 hours after the onset on average. Of the 10 patients, the outcome was excellent in 3, good in 4, severe disability in 2, and 1 died. For these patients, prevention of distal embolism after CEA is most important.According to the intraoperative findings, namely, whether or not back-flow from the distal IC was demonstrated by arteriotomy of the IC distal to the occlusion, and whether or not clotting existed in the distal IC, the 10 patients were divided into 3 groups.Group A (3 cases): Back-flow from the distal IC was demonstrated and clotting of the distal IC was not demonstrated.Group B (2 cases): Both back-flow from the distal IC and clotting of the distal IC were demonstrated.Group C (5 cases): Back-flow from the distal IC was not demonstrated because of packed clotting in the distal IC.In group A, restoration of the flow will be established without distal embolism by not only CEA but also fibrinolysis followed by percutaneous transluminal angioplasty (PTA). For group B and group C, clotting of the distal IC shoud be removed by forceps or aspiration through the distal tube of the internal shunt during CEA to prevent the distal embolism. At present, it is best to use CEA for patients with proximal IC occlusion to prevent the distal embolism, because it is impossible to know whether or not clotting exsists in the distal IC.

2.1 Minimizing visceral ischemia in the repair of thoracoabdominal aortic aneurysm by using an internal shunt

2.1 Minimizing visceral ischemia in the repair of thoracoabdominal aortic aneurysm by using an internal shunt

Theory of phase locking in simple two-dimensional Josephson junction arrays with small inductances

Several elementary two-dimensional Josephson junction arrays have been investigated mainly analytically with the special emphasis on phase locking. For this purpose, a novel perturbation scheme appropriate for the handling of small loop inductances has been developed and applied to (i) a single SQUID cell, (ii) two cells coupled by an inductive line, and (iii) an externally loaded two-cell configuration with more general internal shunt. While internal in-phase locking within the cells can easily be achieved as long as the normalized ring inductances are small compared to unity, the inter-cell coupling tends to favor an antiphase regime. A mechanism is proposed for circumventing this problem and the boundaries separating both regimes are determined. The influence of an external load is considered as well.

General anaesthesia versus cervical block and perioperative complications in carotid artery surgery

To compare the influence of anaesthetic technique on perioperative complications in patients undergoing carotid endarterectomy. In a retrospective study of 1020 consecutive patients who underwent carotid artery surgery over 10 years, perioperative neurologic and cardiologic complications and the use of an internal carotid artery shunt were compared in 337 patients (33%) treated under general anaesthesia and 683 (67%) under cervical block. The two groups had similar characteristics. The most frequent surgical indication was symptomatic carotid artery disease (91.5%). The remaining patients had asymptomatic severe internal carotid lesions (> 70%). The overall perioperative stroke rate was 1.9%, the death-stroke rate 0.7% and the cardiac complication rate 0.8%. The perioperative stroke rate was higher in the general anaesthesia group than in the cervical block group (3.2% vs 1.3%, p = 0.01). Cardiac complication rates were similar in the two groups. A carotid artery shunt was used in 75 patients (22%) receiving general anaesthesia and in 92 patients (13%) receiving cervical block (p = 0.0004). The causes of stroke in the cervical block group were intraoperative embolism (4 cases, 26%), perioperative thromboembolism (7 cases, 58%) and clamping ischaemia (1 case, 16%). Mechanisms causing stroke in the general anaesthesia group remained unidentified or uncertain. Cervical block anaesthesia yields better perioperative results than general anaesthesia probably because it allows more reliable cerebral monitoring, reducing or even eliminating perioperative strokes related to clamping ischaemia. It facilitates detection of the mechanism underlying intraoperative stroke allowing surgical techniques and intraoperative management to be modified accordingly. Cervical block anaesthesia significantly reduces the need for internal carotid artery shunting.

Arachnoid cysts in adults: experience with internal shunts to the subdural compartment.

Twelve patients (10 males, 2 females) with symptomatic arachnoid cysts of the middle cranial fossa (9 patients) or overlying the frontal cortex (3 patients) were included. Under local anesthesia, an internal shunt was implanted from the cyst to the subdural compartment. Postoperative computed tomography scans showed volume reduction in eight patients. Permanent clinical improvement was also seen in eight patients. In the remaining four, the improvement was only temporary or partial, necessitating additional surgery in three patients. Complications (two subdural hematomas, one subdural infusion), were observed in three patients, all with large cysts. The complications were treated without sequelae. Internal shunts may be tried in adults as the first treatment for this condition.

Arachnoid cysts of the left temporal fossa: impaired preoperative cognition and postoperative improvement.

Thirteen adult patients were operated on for symptomatic arachnoid cysts in the left temporal fossa; seven with an internal shunt procedure during local anaesthesia, and five with a craniotomy with fenestration of the cyst to the basal cisterns. In one patient, an initial internal shunt was transformed to a cystoperitoneal shunt. After surgery, all patients experienced relief of symptoms. Reduction of cyst volume occurred in 11 patients. The patients were tested for brain asymmetries related to language and verbal memory before and after operation, with a dichotic listening technique with simultaneous presentation of different auditory stimuli to the two ears. In the preoperative memory test, the patients showed impaired total recall compared with healthy control subjects, and recall from the right ear was significantly impaired. The patients also performed poorly in a forced attention task consisting of dichotic presentations of consonant-vowel syllables. In addition to clinical improvement, the surgical procedures led to improvements in both dichotic perception and memory. Overall memory performance was enhanced, mainly because of improved recall from the right ear. This normalisation of memory function was found as early as four hours after the operation. The results indicate that arachnoid cysts in the left temporal fossa may impair cognitive function, that neuropsychological tests are necessary to disclose these impairments, and that cognitive improvement occurs after surgery.

Minimally Invasive Neurosurgery Using CRW-3 Stereotaxy

The Cosman-Roberts-Wells (CRW-3) scanner independent stereotactic system is a recent arc-radius design developed from the Brown-Roberts-Wells system. The results of 74 supratentorial non-basal tumor suspect cases treated with this second generation computed tomography (CT) guided stereotactic apparatus are presented. Using a simple stereotactic target classification coupled with biopsy, trephine or mini-craniotomy, it has been possible to biopsy, excise and develop new strategies using microneurosurgical techniques with extremely low morbidity.

Pearson near-total laryngectomy: a reproducible speaking shunt.

Since 1980, Pearson and his associates at the Mayo Clinic have accrued an increasing number of patients whom they have treated with what is now designated as a "near-total" laryngectomy rather than a total laryngectomy. Despite the positive reports of the value of this procedure in providing speech by an internal shunt, the use of this total laryngectomy alternative has not gained wide acceptance. We report our experience with treating 11 patients during a 3-year period using the near-total laryngectomy. Between September 1989 and September 1992, 11 patients with the following anatomic lesions were offered and accepted the option of the near-total laryngectomy: (1) T3 or early T4 glottic squamous cell carcinoma that did not involve the interarytenoid space or the vocal process of the opposite arytenoid; (2) T3 supraglottic squamous cell carcinoma with a fixed vocal cord in which a supraglottic laryngectomy could not be performed; (3) T2, T3 pyriform sinus squamous cell carcinomas; (4) radiotherapy failure early glottic lesions in which a vertical hemilaryngectomy for salvage was not able to be performed and met the requirements in (1); and (5) large hypopharyngeal lesions in which the larynx would be sacrificed to prevent aspiration but was not involved with tumor. Nine of 11 patients (82%) attained successful speech in an average of 5.3 months. Two of the 11 patients required a completion laryngectomy, both due to wound complications. All but two of the patients received postoperative radiotherapy. Of the nine successful speakers, five have had an occasional droplet of fluid through the shunt; three have been on a permanent basis and two transient. Eighty-nine percent of the speaking patients (8 of 9) are alive without disease, a mean of 25.5 months after therapy completion. The near-total laryngectomy can be performed outside the Mayo Clinic with creditable results, with 82% of the patients attaining successful speech, an average of 5.3 months postoperatively. Eighty-nine percent of the speakers have had a mean disease-free survival of 25.5 months. Analysis of larger series from multiple institutions in conjunction with voice analyses of these patients compared to those with tracheoesophageal punctures is needed to confirm our initial enthusiasm for this procedure.

Surgery for malignant involvement of the superior vena cava : W.W. Lai, M.H. Wu, N.S. Chou, M.Y. Lin, Y.L. Tsong. National Cheng-Kung University Hospital, Tainan, Taiwan, R.O.C.

This study reviews surgical operations on seven patients with intrathoracic tumors involving the superior vena cava (SVC). Among these patients, five were found to have advanced bronchogenic carcinoma; one was found to have thyroid carcinoma; and another was found to have thymic carcinoma. The incidence of SVC involvement in resectable lung cancer patients at the National Cheng-Kung University Hospital was 5.8% (5/85). Total excision of SVC was done in three patients and three different prostheses (ringed GoreTex, woven Dacron and pericardial tube graft) were interposed. Four patients underwent partial excision and repair: one by direct suture and three by autologous pericardial patch. A temporary SVC-right atrium internal shunt was used in two of these seven patients. The mean time of SVC cross-clamping in five patients was 20 minutes (10-28 minutes), and the mean value of the central venous pressure at the time of SVC cross-clamping was 34 mmHg (18-54 mmHg). There were no operative deaths or neurologic sequels. Venography or computed tomography obtained 7-100 days after surgery demonstrated all but one to be patent. In conclusion, SVC reconstruction with concomitant tumor resection can be performed if a patient fulfills the following criteria: 1) there is no distant metastasis; 2) a radiosensitive or chemotherapy-effective tumor has been ruled out; and 3) total SVC occlusion or prominent collateral circulation should be avoided.

A Case of Carotid Body Tumor : The Usefulness of Internal Shunt Device

A Case of Carotid Body Tumor : The Usefulness of Internal Shunt Device

New side-holed sheath for intraaortic balloon pumping to maintain limb perfusion

We developed a new side-holed shunt sheath for inserting intraaortic balloon pumps to maintain lower limb perfusion in patients with stenotic and tortuous aortoiliac arteries. This sheath has a large internal diameter and several side holes, which act as an internal shunt. It was useful and effective in 11 patients with severe aortoiliac occlusive lesions who required assistance by intraaortic balloon pumping.

The use of internal shunts for quench protection

The quench protection by subdivision of the winding with use of the internal shunts for two solenoids was realized. The bores of the coils are 0.55 m and 0.7 m. Maximum stored energy is 0.15 MJ for the first coil, and it is 1.6 MJ for the another one. Heating of shunts and their effect on the temperature of the conductor were measured. The normal zone propagation in the windings was investigated. The acceleration of filling of the winding by a normal zone across axial and radial directions has been observed. That leads to more uniform heating of the winding. The problem on the internal shunt resistance and its optimum value is discussed.

単一のチームによる頸動脈内膜剥離術の手術成績

We performed 79 carotid endarterectomies in 72 patients in the last 7 years. This report describes surgical results, complications and follow-up in those endarterectomies. We used internal shunts under barbiturate brain protection in all cases. The mean time for shunt insertion and removal is 3 minutes and 4.5 minutes, respectively. We used surgical microscope and removed plaques as a whole block. The surgical mortality was 2.8% (2 cases) and major morbidity was 2.8% (2 cases). The cause of operative death in two cases was rupture of the suture, which resulted in blood loss and subsequent fatal infarction. One case of major infarction was caused by temporary occlusion of the carotid artery. The bilateral vertebral arteries of this case were occluded, and collaterals were from the carotid artery through the stenotic part. The other case of major infarction was caused by inappropriate collection of the intimal flap and inappropriate usage of the large-sized internal shunt. The follow-up disclosed only one case of infarction occurred in the surgical side, because the patient failed to take anti-platelet drugs. Two cases developed symptomatic restenosis of the endarterectomy site because of myointimal hyperplasia. Complication of endarterectomy can be avoided by careful intra- and postoperative care.

A CONTRALATERAL EXTERNAL CAROTID-MIDDLE CEREBRAL ARTERY BYPASS OPERATION

In the treatment of head and neck carcinoma involving the carotid artery, resection of the carotid artery and direct reconstruction using a vein graft has commonly been employed to reduce the incidence of cerebral ischemic complications. But the procedure of carotid grafting itself carries the risk of preventing complete tumor clearance. And contamination due to salivary fistula, particulary in cases of meso or hypopharyngeal carcinoma, may result in graft rupture or thrombosis. To overcome these difficulties, the authors have developed a new surgical procedure, namely, a contralateral external carotid-middle cerebral artery bypass operation. This bypass system is designed at directly supplying the cerebral hemisphere on the carotid ligation side through a vein graft running entirely outside the cervical operative field. The vein graft is anastomosed end-to side to the external carotid artery of the opposite side. Then it is placed subcutaneously in front of the auricle, above the zygomatic arch, frontal subgaleal space and anastomosed end-to side to the recipient artery, the ascending branch of the middle cerebral artery, in the Broca area of the carotid ligation side. The neck is incised almost the same manner as in parotidectomy, with a slightly longer cervical extension, and the scalp by bilateral coronal incision of Sutta. A frontotemporal osteoplastic craniotomy of the involved side is performed. The length of the saphenous vein used is about 50cm. This surgical procedure requires no transient internal or external shunt. The common carotid artery can be ligated safely after confirming good post-anastomotic bypass flow using an electro-magnetic blood flow meter. Since 1990, four patients have undergone this surgery and none has developed serious neurological post-operative complications.

頭蓋外椎骨動脈(VA)起始部狭窄病変に対する血行再建術

Thirty-three vertebral artery (VA) reconstructions were reviewed. Twenty-three patients were symptomatic because of vertebrobasilar ischemic disorder. Various reconstructive techniques were used: VA transposition to common carotid artery (VA·CA) (22), VA·CA+carotid endarterectomy (CEA) (3), VA transposition to subclavian artery (VA·SA) (2), external carotid-vertebral artery anastomosis (ECA-VA) (4), and vertebral artery endarterectomy (VAE) (2). Postoperative arteriograms were obtained in all the patients with 9%occlusion and 91%excellent results (patency rates: VA·CA 20/22 (91%), VA·CA+CEA 3/3 (100%), VA·SA 2/2 (100%), ECA-VA 3/4 (75%), VAE 2/2 (100%). Clinical results were the following: improvement 15/23 (65%) and no exacerbation in symptomatic group, but in asymptomatic group exacerbation was noted in 3 cases of VA·CA+CEA. The conclusions are as follows: (1) VA reconstruction, especially VA·CA, in carefully selected patients, is a safe and effective procedure. (2) The use of internal shunt during crossclamping of CA in surgery of VA·CA for the protection of temporary ischemia is occasionally advised. (3) Temporary ischemia due to the vertebral artery clamping is generally well tolerated in proximal VA reconstructive surgery. (4), In performing a combined reconstructive surgery of VA and CA in one single procedure, special technical care is needed to prevent embolic complication.

Monitoring Electrophysiologic Function during Carotid Endarterectomy

There is no consensus as to the most appropriate monitor for detecting ischemia during carotid endarterectomy. Accordingly, simultaneous 16-channel continuous electroencephalogram (EEG) and somatosensory evoked potential (SSEP) monitoring were performed in 64 normocapnic patients undergoing carotid endarterectomy and anesthetized with isoflurane or halothane-nitrous oxide (supplemented with fentanyl). Recordings were obtained before, during, and for 15 min after cross-clamping of the internal carotid artery. Internal shunt was not used in any patient, regardless of EEG and SSEP changes. Significant amplitude reduction in the cortical component of the primary negative peak (greater than 50%) in SSEP occurred in 6 patients, and an increase in central conduction time (CCT) (greater than 1 ms) occurred in 5 patients. Major EEG changes occurred in 6 patients, 4 of whom also had SSEP changes. Two patients had transient neurologic deficits postoperatively, with both having SSEP changes (amplitude reduction greater than 50%), whereas one had EEG changes. Based on these observations, the relative sensitivity and specificity for EEG and SSEP (amplitude reduction greater than 50%) in detecting postoperative neurologic deficits were 50% and 92% for EEG and 100% and 94% for SSEP, respectively, differences that were not statistically significant. Regarding SSEP, the use of latency change (CCT) as a criterion was associated with a sensitivity of 0% (P = 0.046 from sensitivity of amplitude) and a specificity of 87% (P = 0.17 from specificity of amplitude).(ABSTRACT TRUNCATED AT 250 WORDS)