Biomedical subjects

R S Mitchell

Publications and source records attributed to R S Mitchell.

At least 37 records · Page 2Linked to original sources

PubMed1997

Simultaneous abdominal aortic replacement and thoracic stent-graft placement for multilevel aortic disease.

PURPOSE: Patients with aneurysmal disease involving both the descending thoracic and abdominal aorta have historically required simultaneous or sequential conventional operations, but the morbidity rate is high with either approach in these patients, who often exhibit coexisting cardiopulmonary disease. Transluminally placed endovascular grafts have recently been developed for repair of aortic aneurysms, and we have implemented these techniques to eliminate the need for a thoracotomy in patients with multilevel aortic disease. METHODS: Since January 1994, 18 patients have undergone conventional abdominal aortic replacement with endovascular stent-graft placement into the descending thoracic aorta under fluoroscopic guidance through a 10 mm Dacron side limb off the abdominal graft. Abdominal aortic replacement required a tube graft in eight patients and bifurcated grafts in 10 patients. Thoracic stent-grafts (custom fabricated, woven Dacron covered, self-expandable stents) averaged 12.2 +/- 4.2 cm (mean +/- SD) in length. RESULTS: One patient died, resulting in a hospital mortality rate of 6%. No patients required further surgical intervention to treat their aortic disease. Seventeen patients (94%) are currently well 14 +/- 8 months after surgery (range, 3 to 29 months) with completely excluded thoracic aortic disease, no stent migration, and no change in stent configuration documented by serial radiologic examinations. CONCLUSIONS: Simultaneous abdominal aortic replacement and deployment of a thoracic stent-graft can safely exclude multilevel aortic aneurysmal disease and may be a valuable treatment option for these otherwise high-risk patients.

Aged↗

PubMed1997

Traumatic thoracic aortic aneurysm: treatment with endovascular stent-grafts.

PURPOSE: To demonstrate the feasibility and safety of endovascular stent-graft placement for treatment of traumatic aortic aneurysm. MATERIALS AND METHODS: Ten patients with traumatic aortic aneurysm were treated with endovascular stent-grafts. Three patients had an acute traumatic aneurysm; seven had a chronic aneurysm. Stent-grafts were constructed from modified Z-stents covered with woven polyester or expanded polytetrafluoroethylene graft material and were deployed through a 20-24-F delivery sheath in an exposed artery located remotely from the lesion. RESULTS: Stent-graft placement and thrombosis of the aneurysmal sac were successful in all patients. Major complications were encountered in three patients after endovascular treatment. One patient had a peri-graft leak; complete thrombosis of the aneurysmal sac was achieved after coil embolization of the leak. Transposition of the left subclavian artery was necessary to relieve left arm ischemia in another patient. In the third patient, stent placement in the left main stem bronchus was needed to relieve left lung atelectasis. All patients were alive and without complications during the follow-up period (mean, 15 months). CONCLUSION: Transluminal placement of endovascular stent-grafts is a technically feasible method for treatment of traumatic thoracic aortic aneurysm and may be an effective alternative to open-chest surgery.

Accidents, Traffic↗

PubMed1997

Thoracic aortic aneurysm repair with endovascular stent-grafts.

The purpose of the study was to describe the clinical experience is using endoluminal stent-grafts for the treatment of thoracic aortic aneurysms in high-risk patients. Patients with aneurysms of the descending thoracic aorta who were considered high surgical risks underwent evaluation for endoluminal repair. The prosthesis was constructed from Z stents covered with polyester fabric using dimensions based upon preprocedural computed tomography scans and angiography. Through a femoral arteriotomy or left retroperitoneal flank incision, a 22-24 Fr delivery catheter was inserted and advanced through the aorta to the target site under fluoroscopic guidance in the operating suite. The stent-graft prosthesis was deployed at the site of the aneurysm. 44 patients (36 male, 8 female; mean age 36 years) underwent stent-graft repair for thoracic aneurysms (mean diameter 6.3 cm). The deployment was technically successful in all cases, with complete aneurysm thrombosis in 88%. The 30-day perioperative mortality rate was 6.8% and 35-month actuarial survival was 82%. There were no cases of stent migration, surgical conversion or intraprocedural death. Paraplegia occurred in two patients who underwent simultaneous surgical infrarenal aortic aneurysm repair immediately followed by stent-graft placement for a coexisting thoracic aneurysm. The conclusion was that placement of endoluminal stent-grafts for repair of thoracic aortic aneurysms is technically feasible in high-risk patients in whom conventional surgery is contraindicated. Long-term studies are needed to determine protection against aneurysm rupture and patient survival.

Adult↗

PubMed1997

Endovascular stent graft repair of thoracic aortic aneurysms.

UNLABELLED: Aneurysmal disease of the thoracic aorta continues to present vexing challenges to the aortic surgeon. Not only does the incidence of the disease seem to be increasing, but the older population also harbors more comorbidities. In an effort to reduce the perioperative mortality and morbidity, surgeons and interventional radiologists at Stanford University Medical Center devised a less invasive, endovascular stent-graft repair. This report details the results of the first 81 patients, and reviews some other pertinent developments. The stent-graft is composed of interlocked, self-expanding "Z" stents covered with a woven Dacron graft, which can then be introduced through a hollow 27F Teflon sheath under fluoroscopic guidance and deployed across the aneurysm. Aneurysms of the descending thoracic aorta are most easily treated, but distal arch pathology can occasionally be accommodated. A friction seal prevents movement of the stent, and complete exclusion of the aneurysm sac from the circulation is usually possible. Degenerative aneurysms accounted for the majority of the diseased aortas. RESULTS: There were 7 (9% +/- 3%) deaths, 3 directly attributable to the stent-graft procedure, including two strokes presumably from atheroemboli from the aortic arch. Paraplegia occurred in three patients, but in only one with an uncomplicated stent-graft placement without protracted hypotension. Two nonfatal strokes also occurred. There has been only a single instance of documented late graft failure, which resulted in a fatal hemorrhage. Although the long-term durability of the stent-grafts in unknown at this early stage, we believe this technology to be a significantly less morbid treatment for aneurysmal disease of the descending thoracic aorta. Only long-term follow-up will further define its utility.

Aorta, Thoracic↗

PubMed1997

Stent-graft repair of thoracic aortic aneurysms.

Aneurysmal disease of the thoracic aorta continues to be a very challenging management problem for physicians because of the many comorbidities harbored by these patients, as well as the morbidity of the conventional open repair via left thoracotomy. In a combined effort between interventional radiology and cardiovascular surgery, an endovascular stent graft repair has been devised for these patients in an effort to reduce morbidity. This report documents the results in the first 108 patients so treated. The graft itself, custom-made for each individual, is composed of interlocked, self-expanding "Z" stents covered with a woven Dacron graft. Compressed in a loading capsule, the graft can then be advanced through a 27-French (outside diameter; OD) sheath, which is positioned within the aneurysm under fluoroscopic guidance. Relatively normal 2- to 3-cm segments of proximal and distal aorta allow an adequate friction seal to prevent stent graft dislodgement and also provide a hemostatic seal to obliterate aneurysm filling. Complete aneurysm thrombosis was achieved primarily in 103 patients. There were 10 deaths (9.25%) within the first 30 days, four of which were directly attributable to the stent graft procedure. Perioperative strokes occurred in four patients, and there were four instances of paraplegia. There have been two documented stent graft failures in a mean follow-up of 21.8 months (range, 1 to 57 months). Although the long-term durability of this procedure remains unknown, we believe this less invasive endovascular approach will prove to be an effective and less morbid treatment for aneurysmal disease of the descending thoracic aorta.

Aortic Aneurysm, Thoracic↗

PubMed1996

Crystal structure of the coat protein from the GA bacteriophage: model of the unassembled dimer.

There are four groups of RNA bacteriophages with distinct antigenic and physicochemical properties due to differences in surface residues of the viral coat proteins. Coat proteins also play a role as translational repressor during the viral life cycle, binding an RNA hairpin within the genome. In this study, the first crystal structure of the coat protein from a Group II phage GA is reported and compared to the Group I MS2 coat protein. The structure of the GA dimer was determined at 2.8 A resolution (R-factor = 0.20). The overall folding pattern of the coat protein is similar to the Group I MS2 coat protein in the intact virus (Golmohammadi R, Valegård K, Fridborg K, Liljas L. 1993, J Mol Biol 234:620-639) or as an unassembled dimer (Ni Cz, Syed R, Kodandapani R. Wickersham J, Peabody DS, Ely KR, 1995, Structure 3:255-263). The structures differ in the FG loops and in the first turn of the alpha A helix. GA and MS2 coat proteins differ in sequence at 49 of 129 amino acid residues. Sequence differences that contribute to distinct immunological and physical properties of the proteins are found at the surface of the intact virus in the AB and FG loops. There are six differences in potential RNA contact residues within the RNA-binding site located in an antiparallel beta-sheet across the dimer interface. Three differences involve residues in the center of this concave site: Lys/Arg 83, Ser/Asn 87, and Asp/Glu 89. Residue 87 was shown by molecular genetics to define RNA-binding specificity by GA or MS2 coat protein (Lim F. Spingola M, Peabody DS, 1994, J Biol Chem 269:9006-9010). This sequence difference reflects recognition of the nucleotide at position -5 in the unpaired loop of the translational operators bound by these coat proteins. In GA, the nucleotide at this position is a purine whereas in MS2, it is a pyrimidine.

Amino Acid Sequence↗

PubMed1996

Endoluminal aortic grafting: a preliminary animal study of graft-healing.

Our purpose was to evaluate the placement, long term performance, and healing of a transluminally delivered endoluminal graft and attachment system, in an animal model using large adult sheep. Nineteen sheep in the weight range of 105-125 kg were entered into this study. Under fluoroscopic guidance in anesthetized animals, an endoluminal delivery system was inserted through a common femoral arteriotomy into the infrarenal aorta, and the graft and attachment system were deployed. Fixation of the proximal and distal ends of the graft to the aortic wall was achieved by hooks on the self expanding attachment system, and seated by balloon expansion. Explantation of the prosthesis was performed prior to euthanasia at 1-, 3-, and 6-month intervals. Aortograms were obtained before and after implantation and before explantation for evaluation of placement, patency, anastomotic seal, migration, and graft infolding. In situ gross examination of the prosthesis under anesthesia prior to sacrifice was performed in all animals. Histologic sections were obtained from both attachment sites ("anastomoses"), from the midgraft and hook insertion sites, and from normal aorta inferior and superior to the endoluminal prosthesis. Scanning electron microscopy was performed randomly on specimens derived from the superior and inferior anastomotic sites at each time point. Selected intervals of healing were 1 month (N=5), 3 months (N=5), and 6 months (N=8). One sheep was euthanized at 1 week due to paraplegia. At all intervals, all prostheses were patent, were well incorporated at the aortic wall-anastomotic sites, and were without mural thrombus. The attachment hooks penetrated the aortic adventitia in all animals. There was no graft migration. At one month, initial pannus formation covered the anastomoses and the entire luminal graft, yet the endothelial-like surface coverage was incomplete. At 3 months and at 6 months, the anastomoses and luminal surfaces displayed more uniform pannus and endothelial-like surface coverage. We conclude that this endoluminal delivery system, passed through a femoral arteriotomy, can effectively deploy an endoluminal graft with self expanding attachment system having consistent patency, secure fixation, and incorporation of the anastomoses with the aortic wall in this animal model.

Animals↗

PubMed1996

Twenty-year clinical experience with porcine bioprostheses.

BACKGROUND: For the past 25 years, porcine valves have been the most widely implanted bioprosthesis, thereby becoming the standard for comparison with newer bioprosthetic valves. METHODS: We retrospectively analyzed 2,879 patients who underwent aortic (AVR; n = 1,594) or mitral (MVR; n = 1,285) valve replacement between 1971 and 1990. Follow-up was 97% complete and extended to 20 years (total, 17,976 patient-years). Patient age ranged from 16 to 94 years; mean age in patients who underwent AVR was 60 +/- 15 (+/- standard deviation) years; that for patients who underwent MVR was 58 +/- 13 years. RESULTS: The operative mortality rates were 7% +/- 1% (70% confidence limits) for AVR and 10% +/- 1% for MVR. Actuarial estimates of freedom from structural valve deterioration at 10 and 15 years were 78% +/- 2% (SE) and 49% +/- 4%, respectively, for the AVR subgroup; and 69% +/- 2% and 32% +/- 4%, respectively, for the MVR subgroup (AVR > MVR; p < 0.05). Estimates of freedom from reoperation at 10 and 15 years were 76% +/- 2% and 53% +/- 4%, respectively, for the AVR subgroup and 70% +/- 2% and 33% +/- 4%, respectively, for the MVR subgroup (AVR > MVR; p < 0.05). Estimates of freedom from thromboembolism at 10 and 15 years were 92% +/- 1% and 87% +/- 2%, respectively, for the AVR subgroup and 86% +/- 1% and 77% +/- 3%, respectively, for the MVR subgroup (AVR > MVR; p < 0.05). Estimates of freedom from anticoagulant-related hemorrhage at 10 and 15 years were both 96% +/- 1% for the AVR subgroup and 93% +/- 1% and 90% +/- 2%, respectively, for the MVR subgroup (AVR > MVR; p < 0.05). Estimates of freedom from valve-related mortality at 10 and 15 years were 86% +/- 1% and 78% +/- 3%, respectively, for the AVR subgroup and 84% +/- 2% and 70% +/- 4%, respectively, for the MVR subgroup (p = not significant). Multivariate analysis (Cox model) showed younger age, later year of operation, and valve site (MVR > AVR) to be significant risk factors for structural valve deterioration. Younger age, later year of operation, valve site (MVR > AVR), and renal insufficiency were the significant, independent risk factors for reoperation. Multivariate analysis revealed that higher New York Heart Association functional class, longer cardiopulmonary bypass time, congestive heart failure, renal insufficiency, and longer cross-clamp time were significant risk factors for valve-related mortality. Valve manufacturer did not emerge as a factor in any analysis. CONCLUSIONS: These long-term results with porcine bioprostheses were satisfactory, particularly in older patients and those undergoing AVR. As expected, younger age was a significant risk factor for structural valve deterioration and reoperation in both groups. Surprisingly, the durability of porcine bioprosthetic valves has not improved over time, which possibly can be attributed to more enhanced postoperative surveillance and earlier reintervention. These first-generation Hancock and Carpentier-Edwards porcine bioprostheses achieved similar long-term performance.

Actuarial Analysis↗

PubMed1996

Accuracy of biplane and multiplane transesophageal echocardiography in diagnosis of typical acute aortic dissection and intramural hematoma.

OBJECTIVES: The purpose of this study was to evaluate the diagnostic accuracy of biplane and multiplane transesophageal echocardiography in patients with suspected aortic dissection, including intramural hematoma. BACKGROUND: Transesophageal echocardiography is a useful technique for rapid bedside evaluation of patients with suspected acute aortic dissection. The sensitivity of transesophageal echocardiography is high, but the diagnostic accuracy of biplane and multiplane transesophageal echocardiography for dissection and intramural hematoma is less well defined. METHODS: We studied 112 consecutive patients at a major referral center who had undergone biplane or multiplane transesophageal echocardiography to identify aortic dissection. The presence, absence and type of aortic dissection (type A or B, typical dissection or intramural hematoma) were confirmed by operation or autopsy in 60 patients and by other imaging techniques in all. The accuracy of transesophageal echocardiography for ancillary findings of aortic dissection (intimal flap, fenestration and thrombosis) was assessed in the 60 patients with available surgical data. RESULTS: Of the 112 patients, aortic dissection was present in 49 (44%); 10 of these had intramural hematoma (5 with and 5 without involvement of the ascending aorta). Of the remaining 63 patients without dissection, 33 (29%) had aortic aneurysm and 30 (27%) had neither dissection nor aneurysm. The overall sensitivity and specificity of transesophageal echocardiography for the presence of dissection were 98% and 95%, respectively. The specificity for type A and type B dissection was 97% and 99%, respectively. The sensitivity and specificity for intramural hematoma was 90% and 99%, respectively. The accuracy of transesophageal echocardiography for diagnosis of acute significant aortic regurgitation and pericardial tamponade was 100%. CONCLUSIONS: Biplane and multiplane transesophageal echocardiography are highly accurate for prospective identification of the presence and site of aortic dissection, its ancillary findings and major complications in a large series of patients with varied aortic pathology. Intramural hematoma carries a high complication rate and should be treated identically with aortic dissection.

Acute Disease↗

PubMed1996

Port-access coronary artery bypass grafting: a proposed surgical method.

Minimally invasive surgical methods have been developed to provide patients the benefits of open operations with decreased pain and suffering. We have developed a system that allows the performance of cardiopulmonary bypass and myocardial protection with cardioplegic arrest without sternotomy or thoracotomy. In a canine model, we successfully used this system to anastomose the internal thoracic artery to the left anterior descending coronary artery in nine of 10 animals. The left internal thoracic artery was dissected from the chest wall, and the pericardium was opened with the use of thoracoscopic techniques and single lung ventilation. The heart was arrested with a cold blood cardioplegic solution delivered through the central lumen of a balloon occlusion catheter (Endoaortic Clamp; Heartport, Inc., Redwood City, Calif.) in the ascending aorta, and cardiopulmonary bypass was maintained with femorofemoral bypass. An operating microscope modified to allow introduction of the 3.5x magnification objective into the chest was positioned through a 10 mm port over the site of the anastomosis. The anastomosis was performed with modified surgical instruments introduced through additional 5 mm ports. In the cadaver model (n = 7) the internal thoracic artery was harvested and the pericardium opened by means of similar techniques. A precise arteriotomy was made with microvascular thoracoscopic instruments under the modified microscope on four cadavers. In three other cadavers we assessed the exposure provided by a small anterior incision (4 to 6 cm) over the fourth intercostal space. This anterior port can assist in dissection of the distal internal thoracic artery and provides direct access to the left anterior descending, circumflex, and posterior descending arteries. We have demonstrated the potential feasibility of grafting the internal thoracic artery to coronary arteries with the heart arrested and protected, without a major thoracotomy or sternotomy.

Anastomosis, Surgical↗

PubMed1996

Endovascular stent-graft repair of thoracic aortic aneurysms.

Conventional repair of aneurysms of the descending thoracic aorta entails thoracotomy and graft interposition. For elderly patients and those with previous operations, obesity, respiratory insufficiency, or other comorbidities, such a procedure entails significant mortality and morbidity. Transluminal stent-graft placement offers an alternative approach with potentially less morbidity and quicker recovery; however, the effectiveness and durability of stent-grafts remain uncertain. METHODS: Since July 1992, thoracic aortic stent-grafts have been placed in 44 patients with a variety of pathologic conditions. Each graft was individually constructed from self- expanding, stainless-steel Z stents covered with a woven Dacron polyester fabric graft. Craft dimensions were determined from spiral computed tomographic scans. All implants were performed in the operating theater under fluoroscopic and transesophageal echocardiographic guidance. Follow-up was by computed tomography and contrast angiography in all cases. PATIENT DATA: There were 36 men and 8 women. Mean age was 66 years (range 35 to 88 years). Mean aneurysmal diameter was 6.3 cm (range 4.0 to 9.4 cm). Etiologies included 23 degenerative aneurysms, four posttraumatic aneurysms, four pseudoaneurysms, and one chronic aortic dissection. RESULTS: There were three early deaths (<30 days) and two late deaths. One early death resulted from graft failure. There were two instances of paraparesis or paraplegia, with one associated early death. A single stent was deployed in 27 patients, two stents were required in 14 patients, and three stents were required in three patients. In 23 patients, vascular access was attained through the femoral artery; abdominal aortic access, either native or graft, was necessary in the remaining 21 patients. Twelve grafts were placed in conjunction with open abdominal aortic surgical procedures. Mean follow-up (98% complete) was 12.6 months (range 1 to 34 months). One late death occurred from aneurysmal expansion and rupture in a patient with a persistent midgraft leak. The second late death may have resulted from aneurysmal rupture. Immediate thrombosis was achieved in 36 patients, and late thrombosis was achieved in three others. Failure to achieve complete aneurysmal thrombosis occurred in five patients, however, and one individual (previously noted) died of aneurysmal expansion and rupture; the remaining four are being carefully monitored. Only one patient has required conversion of the stent to an open procedure; a contained rupture of the false lumen of a chronic dissection eventually necessitated total descending thoracic aortic exclusion. CONCLUSIONS: These early results support the hypothesis that endovascular stent-graft placement may be a safe and durable treatment for selected patients with aneurysmal disease of the descending thoracic aorta. Large introducer size (26F outer diameter) and relatively limited angulation capability, as well as imprecise deployment techniques, currently limit its applicability. Distal embolization and stent migration have not been observed. Failure to achieve complete aneurysmal thrombosis may allow continued aneurysmal expansion and rupture. Further follow-up is clearly necessary to evaluate the true long-term effectiveness of this procedure.

Adult↗

PubMed1996

Aortic dissection: percutaneous management of ischemic complications with endovascular stents and balloon fenestration.

PURPOSE: The purpose of this study was to evaluate endovascular stenting (EVS) and balloon fenestration (BF) of intimal flaps for the management of lower extremity, renal, and visceral ischemia in acute or chronic aortic dissection. METHODS: Twenty-two patients (16 male, 6 female) with a median age of 53 years (range 35 to 77 years) underwent percutaneous treatment for peripheral ischemic complications of 12 type A (five acute, seven chronic) and 10 type B (nine acute, one chronic) aortic dissections. RESULTS: Ten patients had leg ischemia, 13 had renal ischemia, and 6 had visceral ischemia. Sixteen patients were treated with EVS including 11 with renal, 6 with lower extremity, 2 with superior mesenteric artery, and 2 with aortic stents. Three patients had BF of the intimal flap, and three had BF in combination with EVS. Revascularization with clinical success was achieved in all 22 patients. Two patients died 3 days and 13.4 months after the procedure was performed, respectively. Of the remaining 20 patients, 1 is lost to follow-up, and 19 have persistent relief of clinical symptoms. Mean follow-up time is 13.7 months (range 1.1 to 46.5 months). One case was complicated by guidewire-induced perinephric hematoma. CONCLUSION: EVS and BF provide a safe and effective percutaneous method for managing peripheral ischemic complications of aortic dissection.

Acute Disease↗

PubMed1996

True lumen obliteration in complicated aortic dissection: endovascular treatment.

PURPOSE: To evaluate endovascular treatment of ischemic complications caused by true lumen obliteration in aortic dissection. MATERIALS AND METHODS: Endovascular techniques were used to treat true lumen obliteration in 11 patients with complicated aortic dissection. In all cases, the true lumen was compressed to a paper-thin sliver by the expanded false lumen. Two patients had Stanford type A (chronic) and nine had type B (six acute, three chronic) dissections. Obliteration of the true lumen was associated with branch vessel ischemia that included renal (n = 7), mesenteric (n = 6), and lower-extremity (n = 6) arterial compromise. Two patients were treated with aortic stents, four with balloon fenestration of the intimal flap, and three with both stent placement and fenestration. In two patients, ischemic complications caused by true lumen obliteration could not be treated with endovascular techniques. RESULTS: Revascularization was technically successful with relief of clinical symptoms in nine patients. Revascularization was unsuccessful in one patient in whom surgical revascularization of the superior mesenteric artery was necessary and in one in whom hypertension was managed medically. One patient developed thrombosis of a renal artery in which a stent had been placed. The 30-day mortality rate was 9%, and the mean follow-up was 10.1 months (range, 2 weeks to 39 months). CONCLUSION: True lumen obliteration can be safely and effectively treated with endovascular stent placement and balloon fenestration.

Aortic Dissection↗

PubMed1996

Port-access coronary artery bypass with cardioplegic arrest: acute and chronic canine studies.

BACKGROUND: Our goal is to perform minimally invasive coronary artery bypass grafting without sacrificing the benefits of myocardial protection with cardioplegia. METHODS: Twenty-three dogs underwent acute studies and 4 dogs underwent survival studies. The left internal mammary artery was taken down using a thoracoscope. Cardiopulmonary bypass was conducted via femoral cannulas and using an endovascular balloon catheter for ascending aortic occlusion, root venting, and delivery of antegrade blood cardioplegia. Pulmonary artery venting was achieved with a jugular vein catheter. An internal mammary artery-to-coronary artery anastomosis was performed using a microscope through a 10 mm port. RESULTS: All animals were weaned from cardiopulmonary bypass in sinus rhythm without inotropes. Cardiopulmonary bypass duration was 104 +/- 28 minutes and aortic clamp duration was 61 +/- 22 minutes. Cardiac output and pulmonary artery occlusion pressure were unchanged. The internal mammary artery was anastomosed to the left anterior descending artery (25) or the first diagonal (2) with patency shown in 25 of 27. One dog in the survival study had a very short internal mammary artery pedicle under tension and was euthanized for excessive postoperative hemorrhage. Three weeks postoperatively the remaining dogs had angiographically patent anastomoses, normal transthoracic echocardiograms, and histologically normal healing and patent grafts. CONCLUSIONS: Endovascular cardiopulmonary bypass using a balloon catheter is effective in arresting and protecting the heart to allow thoracoscopic internal mammary artery-to-coronary artery anastomosis.

Animals↗

PubMed1996

MR and cerebrospinal fluid enzymes as sensitive indicators of subclinical cerebral injury after open-heart valve replacement surgery.

PURPOSE: To evaluate MR imaging and lumbar cerebrospinal fluid enzymes as potential sensitive indicators of cerebral injury after open-heart valve replacement surgery. METHODS: Thirty-four patients with cardiac valvular disease were prospectively entered into this study and then underwent valve replacement or repair under cardiopulmonary bypass using a membrane oxygenator. In 26 patients, MR head images were obtained 12 to 24 hours before surgery; repeat MR images were obtained between 1 and 2 weeks after surgery. In 18 patients, lumbar puncture cerebrospinal fluid was analyzed 24 to 48 hours after surgery; the analyses included measurement of lactic dehydrogenase, creatine phosphokinase, adenylate kinase, and neuron-specific enolase. RESULTS: After surgery, MR imaging showed new ischemic lesions in 15 (58%) of 26 patients: 7 with deep white matter hyperintense lesions; 5 with brain stem, caudate, cerebellar, or thalamic/basal ganglia infarcts; 1 with intraparenchymal hemorrhage; 1 with a subdural hematoma and cortical infarct; and 1 with a corpus callosum lesion consistent with calcium or air. These new ischemic lesions seen on MR images were associated with a focal neurologic deficit in only 4 (27%) of the 15 patients. Neuron-specific enolase and lactic dehydrogenase were abnormally elevated after surgery in 5 (28%) of 18 patients. Adenylate kinase and creatine phosphokinase (brain isozymes) were elevated in one (67%) of the patients. Two (40%) of the five patients with abnormally high neuron-specific enolase or lactic dehydrogenase after surgery also showed a new focal neurologic deficit. CONCLUSIONS: MR imaging is a sensitive measure of subclinical cerebral ischemia after cardiac valve replacement under cardiopulmonary bypass. Cerebrospinal fluid neuron-specific enolase and lactic dehydrogenase are less sensitive than MR imaging for detecting subclinical cerebral ischemia, but these values were elevated after surgery more frequently than was adenylate kinase in our patients.

Adenylate Kinase↗

PubMed1995

Surgical management of aortic dissection during a 30-year period.

BACKGROUND: Certain recent studies have demonstrated improved surgical outcome in patients with aortic dissection. We analyzed the surgical survival rates of patients with acute aortic dissections and the late prognosis of those with aortic dissection during a 30-year period. METHODS AND RESULTS: Between 1963 and 1992, 360 patients (256 men and 104 women; mean +/- 1 SD age, 57 +/- 14 years) underwent surgery for aortic dissection: 174 patients had an acute type A (AcA), 46 an acute type B (AcB), 106 a chronic type A (ChA), and 34 a chronic type B (ChB) aortic dissection. The overall operative mortality rate was 24 +/- 8% (26 +/- 3% for AcA, 39 +/- 8% for AcB, 17 +/- 4% for ChA, and 15 +/- 6% for ChB, [+/- 70% confidence limit]). The operative mortality rates for patients with acute aortic dissection (AcA or AcB) were assessed for five time "windows": 1963 to 1972 (42 +/- 8%), 1973 to 1977 (37 +/- 8%), 1978 to 1982 (15 +/- 6%), 1983 to 1987 (27 +/- 6%), and 1988 to 1992 (26 +/- 6%). Logistic regression analysis suggested that the low operative mortality rate during the 1978-to-1982 interval occurred by chance. Multivariate analysis showed earlier operative year, hypertension, cardiac tamponade, renal dysfunction, and older age were independent determinants of operative death. Actuarial survival rates (including early deaths) after 5, 10, and 15 years for AcA patients were 55%, 37%, and 24%; for AcB, 48%, 29%, and 11%; for ChA, 65%, 45%, and 27%; and for ChB, 59%, 45%, and 27%. Multivariate analysis revealed that older age and previous operation were significant predictors for late death. Freedom from reoperation for all patients was 84%, 67%, and 57% at 5, 10, and 15 years, respectively. CONCLUSIONS: Although the operative mortality rate decreased over time for patients with aortic dissection, the risk for those with acute aortic dissection during the last 10 years (1983 to 1992) is probably more realistic than that observed in the preceding 5-year interval (1978 to 1982). The operative mortality rates for patients with chronic aortic dissection have remained relatively static. Earlier diagnosis of acute aortic dissection before development of cardiac tamponade and renal impairment is critical to improve the operative salvage rate. Long-term outcome still is not optimal, which emphasizes the need for better serial postoperative aortic imaging surveillance and medical follow-up and blood pressure control.

Adult↗

PubMed1995

Co-crystallization of an ETS domain (PU.1) in complex with DNA. Engineering the length of both protein and oligonucleotide.

The PU.1 transcription factor is a member of the ets gene family of regulatory proteins. These molecules play a role in normal development and also have been implicated in malignant processes such as the development of erythroid leukemia. The Ets proteins share a conserved DNA-binding domain (the ETS domain) that recognizes a purine-rich sequence with the core sequence: 5'-C/AGGAA/T-3'. This domain binds to DNA as a monomer, unlike many other DNA-binding proteins. The ETS domain of the PU.1 transcription factor has been crystallized in complex with a 16-base pair oligonucleotide that contains the recognition sequence. The crystals formed in the space group C2 with a = 89.1, b = 101.9, c = 55.6 A, and beta = 111.2 degrees and diffract to at least 2.3 A. There are two complexes in the asymmetric unit. Production of large usable crystals was dependent on the length of both protein and DNA components, the use of oligonucleotides with unpaired A and T bases at the termini, and the presence of polyethylene glycol and zinc acetate in the crystallization solutions. This is the first ETS domain to be crystallized, and the strategy used to crystallize this complex may be useful for other members of the ets family.

Amino Acid Sequence↗

PubMed1995

Crystallization of the MS2 translational repressor alone and complexed to bromouridine.

The coat protein from the MS2 bacteriophage plays a dual role by encapsidating viral RNA and also by binding RNA as a translational repressor. In order to study the isolated dimer in a conformation not influenced by capsid interactions, a mutant molecule was crystallized that is defective in capsid assembly but is an active repressor. The unassembled dimer crystallized in the space group P21212 with a = 76.2, b = 55.7, and c = 28.4 A. In these crystals, monomers were related by twofold symmetry. When this dimer was co-crystallized with 5-bromouridine, crystals formed in space group R3 with a = b = 155.9 A, c = 29.9 A, gamma = 120 degrees; the dimer was the asymmetric unit.

Bromodeoxyuridine↗