Biomedical subjects

M F O'Brien

Publications and source records attributed to M F O'Brien.

At least 55 records · Page 3Linked to original sources

PubMed1995

Allograft aortic valve replacement: long-term follow-up.

Aortic valve replacement using an allograft aortic valve has been performed on 804 patients. From December 1969 to May 1975, 124 patients received a nonviable allograft valve sterilized by incubation with low-dose antibiotics and stored for weeks by refrigeration at 4 degrees C (series 1). From June 1975 to January 1994, 680 patients received viable allograft valves, now cryopreserved early within 2 hours of collection from transplant recipient donors, 6 hours for multiorgan donor valves and 23 hours (mean) for autopsy valves from donor death. The 30-day mortality was 8.9% +/- 5% (95% confidence limits) for series I and 2.8% +/- 1% (95% confidence limits) for series II. Actuarial patient survival including hospital mortality at 15 years was 56% +/- 5% for series I and 62% +/- 5% for series II. The probability of a thromboembolic event was low, freedom at 15 years being 95% +/- 1% for patients receiving allografts with or without associated coronary bypass procedures and 81% +/- 5% for patients having allografts with other associated procedures (eg, mitral valve operations). Actuarial freedom from endocarditis was similar for the two series, 91% +/- 3% (series I) and 94% +/- 2% (series II) at 15 years. The freedom from valve incompetence, from reoperation for all causes, and from structural deterioration demonstrated clearly the inferiority of the 4 degrees C stored allograft valves. For structural deterioration as identified clinically, at reoperation and at death, freedom from this event at 15 years was 45% +/- 6% for series I and 80% +/- 5% for series II (p value for the difference is 0).(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗

PubMed1995

Composite stentless xenograft for aortic valve replacement: clinical evaluation of function.

At The Prince Charles Hospital, 55 patients have received the composite porcine aortic xenograft (model 300, Cryolife-O'Brien valve; Cryolife International, Atlanta, GA; formerly the Bravo Cardiovascular Inc valve) for aortic valve replacement since December 1992. Associated procedures were required in 50% of patients (coronary artery bypass grafting in 25 patients). Hospital and "late" mortality have been 0%. Follow-up has been 100% complete. The median patient age was 74 years (range, 59 to 88 years). One permanent intraoperative cerebrovascular accident and two early thromboembolic events (both associated with acute atrial fibrillation) have constituted the only three morbid events. Serial echocardiography at 1 week, 6 months, and 1 year has shown a mean gradient of 9 mm Hg. A small number of patients have a "trivial" degree of valve incompetence. No progression of either gradient or incompetence is evident. The clinical state of 54 of these patients is most satisfactory. However, long-term surveillance is necessary to determine the 8- to 10-year durability of this stentless xenograft.

Aged↗

PubMed1995

Root replacement for all allograft aortic valves: preferred technique or too radical?

From November 1985 to January 1994, 146 patients have received a viable cryopreserved allograft for aortic root replacement. The follow-up was complete, with all events included to March 1st, 1994. The median age of patients was 49 years; 83.6% were male. Valve dysfunction (91 patients), primary aortic wall disease (45 patients), and a combination of both (10 patients) were the indications for aortic root replacement. The current operative mortality is 1.7% (three deaths in 172 patients to July 1st, 1994). Four late deaths have occurred, with an 8-year actuarial survival of 85% +/- 8% (95% confidence limits). Endocarditis (two events) and thromboembolism (four events) had a low incidence. Structural deterioration (three events) and reoperation for all causes (nine events) have constituted low morbidity and are compared with the results after non-root allograft implantation techniques. The clinical and echocardiographic evidence indicates that the immediate results of valve function with root replacement are superior. But no statistical difference between aortic root replacement and non-root procedures is apparent at 8 years, indicating that a longer follow-up is required before the answer to the question "preferred technique or too radical" can be answered.

Adolescent↗

PubMed1995

The Cryolife-O'Brien composite aortic stentless xenograft: surgical technique of implantation.

The Cryolife-O'Brien (Cryolife International, Atlanta, GA; formerly the Bravo Cardiovascular Inc valve) stentless porcine aortic xenograft (model 300) is a composite valve of three noncoronary leaflets, symmetric in configuration with a broad coaptive leaflet surface. Because the valve has only a superior aortic wall cuff, a single continuous suture line of 3/0 Prolene provides a rapid, safe implantation. The ideal recipients are elderly patients, who benefit from a short cardiopulmonary bypass period and whose degenerative calcific valves are generally symmetric. The step-by-step technique of implantation is outlined, as are the principles of maintaining symmetry during implantation. The stentless valve has been used for aortic valve replacement in 55 elderly patients, with no deaths and minimal morbidity.

Aged↗

PubMed1995

Allograft aortic root replacement: standardization and simplification of technique.

A variety of surgical techniques for implantation of an allograft aortic valve have been described. Compounding this confusion, the host pathologic processes necessitating aortic valve or root replacement are many, often associated with asymmetry of the aortic root and valve annulus. These complexities can now be negated by routinely performing allograft aortic root replacement with pedicle coronary artery reimplantation in all situations. This procedure is described in a simple step-by-step manner that makes it amenable to all cardiac surgeons independent of experience.

Anastomosis, Surgical↗

PubMed1995

The Medtronic Intact xenograft: an analysis of 342 patients over a seven-year follow-up period.

Three hundred forty-two patients from December 1985 to January 1993 received 352 Medtronic Intact porcine xenograft valves (zero-pressure glutaraldehyde-fixed with toluidine blue anticalcification agent). The follow-up was 99.4% complete with a mean of 3.14 years (3 months to 7.9 years). The mean patient age was 64 years (range, 16 to 82 years) and the median age was 67 years. There were 14 aortic valve replacement patients (11.9%) and 62 mitral valve replacement patients (29.2%) who preoperatively were in New York Heart Association class IV to V. The hospital mortality was 8.4% +/- 2.9% (aortic valve replacement, 5.9%; mitral valve replacement, 9.4%; tricuspid valve replacement, 7.6%). Actuarial patient survival at 7 years was 65% +/- 5% (aortic valve replacement, 77% +/- 5%; mitral valve replacement, 63% +/- 5%). At 7 years, the freedom from thromboembolism was 74% +/- 4%, freedom from endocarditis 93% +/- 2%, and freedom from reoperation 90% +/- 3%. Reoperation was required for endocarditis (7 patients), periprosthetic leak (6), and 2 of 3 cases of structural deterioration. The actuarial freedom from structural deterioration at 5 years was 97% +/- 3%. The combined incidence of all important morbid valve-related events was analyzed with an actuarial freedom at 7 years of 63% +/- 3%. The durability of the Medtronic Intact is at least equal to that of other porcine bioprostheses. The relevant important time-frame of 7 to 12 years of follow-up has just begun, and possibly the reoperation rate for intrinsic value failure and the low incidence of calcification in the elderly patient may be showing improved characteristics of this valve. No stronger inferences are possible at this stage of the 7-year follow-up.

Actuarial Analysis↗

PubMed1995

The prevalence of infective endocarditis after aortic valve replacement.

Replacement valve endocarditis occurred in 3.7% of 2443 patients who underwent primary or redo aortic valve replacements at The Prince Charles Hospital between December 31, 1969 and January 1, 1992, based on a cross-sectional follow-up in 1992 which was 98.8% complete. Because some patients had re-replacements during the study period, a total of 2686 operations were considered for analysis. A variety of replacement devices were used, including 571 allografts (21%), 1152 xenografts (43%), and 880 mechanical valves (36%). Insertion of an allograft valve resulted in a constant risk of endocarditis which, by multivariable hazard function analysis, negated the effect of any early-phase factors (p < 0.0001). With other replacement devices, the risk of infection peaked early after operation (9 weeks) and then gave way to a constant risk. Compared with the risk associated with allograft valves, constant risk was higher when the replacement device was a Carpentier-Edwards xenograft (n = 1021, p = 0.02) and lower when a St. Jude Medical mechanical valve was used (n = 505, p = 0.05). In nonallograft recipients, the presence of active preoperative endocarditis (p < 0.0001) or a concomitant synthetic synthetic aortic root replacement (p = 0.0006) increased the magnitude of the early peaking risk. Regardless of replacement device, constant risk was increased in patients with renal dysfunction (p = 0.01), in younger patients 0.04). When preoperative endocarditis was caused by Staphylococcus aureus, culture-positive postoperative wound infection was associated with increased risk of replacement valve infection (p < 0.001) and when it occurred, the same organism was usually responsible (86%). Identification of patients at increased risk for replacement valve infection may lead to reduced morbidity through strategies such as selective use of replacement devices and antimicrobial prophylaxis.

Aortic Valve↗

PubMed1995

A posterolateral microsurgical approach to extreme-lateral lumbar disc herniation.

Extreme-lateral lumbar disc herniations present a surgical challenge because the conventional posterior approach requires bone resection for complete visualization of the pathology. The authors have identified constant anatomical landmarks in cadaveric dissections that facilitate access to the intervertebral foramen when combined with a posterolateral approach, as described by Watkins, for lumbar spinal fusion. The authors describe a technique that allows rapid localization and safe excision of these extreme-lateral lumbar disc herniations without the need for bone resection.

Cadaver↗

PubMed1994

Posterior spinal fusion supplemented with only allograft bone in paralytic scoliosis. Does it work?

STUDY DESIGN: The authors prospectively evaluated 40 patients with paralytic scoliosis treated from 1985 to 1990 with bilateral posterior segmental instrumentation, facet fusions, local bone graft, and allograft (mostly fresh frozen) bone supplementation only. OBJECTIVES: The authors report the fusion results for these patients, and any complications referable to the use of bank bone. SUMMARY OF BACKGROUND DATA: Acceptable correction was obtained and maintained in the coronal and sagittal planes for all but two patients (the third patient with a pseudarthrosis had not lost correction). The definite pseudarthrosis rate was 7.5%. One patient had a deep wound infection. METHODS: The radiographs were graded as definitely solid, definitely a pseudarthrosis, or no instrumentation failure but difficult to visualize the whole fusion mass. The patients selected for fusion without autogenous harvesting were especially frail and had reduced pulmonary and nutritional reserve. Follow-up ranged from 2 + 2 years to 7 + 6 years, with an average of 3 + 9 years. RESULTS: In the 40 surgical patients, there were three known pseudarthroses. In 28 patients, there was a definite fusion. In the remaining nine patients (five with flaccid disease, four with spastic disease), the quality of their bone precluded definitive determination, but there was no obvious instrumentation failure or loss of correction. CONCLUSION: This study suggests that allograft bone graft is a suitable substitute for autogenous bone graft harvesting in select patients with paralysis in whom autogenous harvesting is not feasible.

Adolescent↗

PubMed1994

Astrocyte response and transforming growth factor-beta localization in acute spinal cord injury.

STUDY DESIGN: An experimental histologic and immunohistological investigation of acute spinal cord injury was performed in a rat model. OBJECTIVE: This study determined (1) the immediate cellular and molecular responses within the spinal cord that result from a clinically relevant compression injury, (2) the acute astrocytic response to injury using the astrocyte specific GFAP antibody, and (3) the temporal pattern of cellular and extracellular localization of transforming growth factor-beta 1 (TGF-beta 1) within the spinal cord injury zone immediately after injury. SUMMARY OF BACKGROUND DATA: Ultimate neurologic outcome from spinal cord injury results from both the primary mechanical trauma and a subsequent cascade of cellular and molecular events that are termed the secondary injury. Efforts aimed at improving neurologic outcome may depend on the manipulation of cellular and molecular mechanisms that are responsible for propagating this secondary injury cascade. Astrocytes and TGF-beta are two potentially key components of this secondary injury. METHODS: Twenty-one Sprague-Dawley adult rats underwent open thoracic spinal cord injuries using the Allen weight-drop technique. Spinal cord specimens were harvested at 0, 1, 2, 4, 8, 24, and 72 hours after injury for histologic and immunohistochemical evaluation. Harvesting of injured and surrounding uninjured cord was performed before sectioning in sagittal and transverse planes. These paraffin-embedded sections were stained with polyclonal antibodies against glial fibrillary acidic protein (GFAP, an astrocytic cytoskeleton marker) and TGF-beta 1. RESULTS: A complex astrocytic response to the spinal cord injury was found within 24 hours of injury. Both the geographic and temporal patterns of astrocyte localization suggest a role in the regulation of spinal cord injury propagation. High concentrations of extracellular TGF-beta were seen immediately after injury within the hematoma at the zone of impact. Subsequently, intracellular TGF-beta was seen in astrocytic nuclei and cytoplasm, intramedullary and extramedullary capillary endothelial cells, and in motor neurons. CONCLUSIONS: The neurologic outcome in patients with SCI results in part from a secondary injury whose cellular and molecular mechanisms are poorly understood. This study suggests that both astrocytes and TGF-beta are involved in the regulation of spinal cord secondary injury. An improved understanding of their specific roles may result in novel treatments to improve the outcome from SCI.

Acute Disease↗

PubMed1994

Recognition and treatment of the proximal thoracic curve in adolescent idiopathic scoliosis treated with Cotrel-Dubousset instrumentation.

STUDY DESIGN: A retrospective radiographic and clinical review of a consecutive series of patients with adolescent idiopathic scoliosis (AIS) instrumented/fused with Cotrel-Dubousset instrumentation (CDI) was undertaken. OBJECTIVE: The authors determined criteria when the upper thoracic curve should be instrumented/fused in AIS treated with CDI and assessed the results of surgical treatment. SUMMARY OF BACKGROUND DATA: Failure to recognize and include the upper left thoracic curve in the instrumentation/fusion of a lower right thoracic idiopathic scoliosis may produce shoulder imbalance and coronal decompensation. Patients with an elevated left shoulder clinically or a positive T1 tilt radiographically usually require instrumentation/fusion of the proximal thoracic curve. However, the upper left thoracic curve may be structural and require inclusion in the instrumentation/fusion when the shoulders clinically are level or even if the right shoulder is elevated preoperatively when using CDI. METHODS: The authors compared 27 patients with AIS with structural upper thoracic curves that were instrumented with CDI to T2 (Group I) to 27 patients with King Type III curves treated with CDI that did not have the upper thoracic curve instrumented/fused (Group II). RESULTS: The distinguishing Group I preoperative criteria indicating a structural upper thoracic curve included a proximal thoracic curve greater than 30 degrees that corrected to no better than 20 degrees on sidebending; > or = Grade I rotation or > or = 1 cm translation present at the apex of this curve; any elevation of the left shoulder or tilt of T1 into the concavity of the upper thoracic curve; or when the transitional vertebra between the two curves is at T6 or below. CONCLUSIONS: When these aforementioned criteria are present and surgical correction with CDI is planned, we recommend extending the instrumentation up to T2 to produce level shoulders and maintain coronal balance.

Adolescent↗

PubMed1994

Preoperative spinal canal investigation in adolescent idiopathic scoliosis curves > or = 70 degrees.

STUDY DESIGN: This is a prospective evaluation of a consecutive series of patients with adolescent idiopathic scoliosis (AIS) with curves > or = 70 degrees. OBJECTIVE: The authors investigated the possibility that large curve size may constitute an atypical presentation of idiopathic scoliosis suggestive of underlying neurologic pathology, which would warrant preoperative investigation. SUMMARY OF BACKGROUND DATA: The potential for intraspinal pathology to cause scoliosis is well accepted. The incidence of spinal canal abnormalities in congenital or atypical scoliosis may be as high as 30-60%. Identification of clinical neurologic deficits, congenital abnormalities, or atypical features of scoliosis are often helpful in identifying the subpopulation of scoliosis patients at risk for spinal canal pathology. METHODS: Thirty-three consecutive patients with large (> or = 70 degrees) adolescent idiopathic scoliosis (AIS) and without evidence of neurologic or congenital abnormalities, were evaluated with either computed tomography/myelogram (n = 3) or magnetic resonance imaging (n = 30) to assess the entire spinal canal. RESULTS: None of the studies revealed any pathology of the neuraxis, and all 33 patients were treated with surgery without any neurologic sequelae. CONCLUSIONS: Preoperative investigation of the central neuraxis is not mandatory in large (> or = 70 degrees) but otherwise typical AIS curves. These large curves do not appear to suggest associated spinal canal anomalies.

Adolescent↗

PubMed1994

Donor-specific immune response after aortic valve allografting in the rat.

The allospecific immune response in rats to a major histocompatibility complex-disparate aortic valve allograft was investigated using three in vitro assays. In each assay, DA strain (RT-1a) rats served as allograft recipient and syngeneic donor, Lewis strain (RT-1l) rats were allogeneic donors, and Buffalo (RT-1b) rats provided third-party control cells. Mixed lymphocyte cultures using spleen cells demonstrated donor-specific stimulation indices of 3.04 +/- 0.44, 4.14 +/- 0.62, and 6.32 +/- 0.60 at 7, 14, and 28 days, respectively, after aortic valve allografting; 8.19 +/- 2.91, 8.51 +/- 1.25, and 10.80 +/- 0.53 after skin allografting; and 1.84 +/- 0.56, 1.82 +/- 0.38, and 1.82 +/- 0.53 after aortic valve isografting. Limiting dilution analysis of splenocytes showed a donor-specific cytotoxic T lymphocyte precursor frequency at 7, 14, and 28 days of 1:6,853, 1:4,714, and 1:1,964 after aortic valve allografting; 1:4,181, 1:1,611, and 1:1,018 after skin allografting; and 1:14,517, 1:11,882, and 1:10,995 after aortic valve isografting. Flow cytometry detected an increase in the level of donor-specific anti-T cell antibodies in both valve and skin allograft recipients but not in isografted animals. Aortic valve allografting from Lewis into DA rats elicits allospecific cellular and humoral immune responses similar in magnitude to skin allografting but somewhat slower in onset. Investigation of the immune response to aortic allografts in humans is warranted, as donor-specific T cells, antibodies, or both may damage the allograft.

Animals↗

PubMed1994

Intracanalicular osteochondroma producing spinal cord compression in hereditary multiple exostoses.

Spinal cord compression is an unusual but potentially catastrophic manifestation of hereditary multiple exostoses (HMEs). Isolated, osteochondromas are usually of little significance. However, if they are located near neurologic structures, they may cause irritation due to mechanical compression. In patients with HMEs who present with neck or back pain, and particularly in those who have neurologic symptoms in the upper or lower extremities, a diagnosis of intracanalicular osteochondroma should be presumed until proven otherwise. Prompt diagnosis and surgical excision affords the best prognosis for these patients who have spinal cord compression secondary to intracanalicular osteochondroma.

Adolescent↗

PubMed1994

A local community's approach to breastfeeding promotion.

An understanding of theories of group development and the program planning process are critical to any community group's effective functioning. This paper describes the developmental stages experienced by a multi-agency, multi-disciplinary regional breastfeeding committee. The stages of forming, storming, norming, performing, and adjourning devised by Tuckman and Jensen are clearly evident in the growth of this group and can be useful to any other group. The basis for the group's decision-making regarding tasks and activities are addressed by the three health promotion planning approaches: education, policy development, and environmental support. This paper outlines the steps utilized by the committee to develop a series of breastfeeding promotion factsheets as one of its major activities.

Breast Feeding↗

PubMed1994

Evoked potential monitoring of the upper extremities during thoracic and lumbar spinal deformity surgery: a prospective study.

We prospectively investigated the usefulness of somatosensory evoked potential (SEP) monitoring to detect clinically significant peripheral nerve or brachial plexus compression in the upper extremities during spinal deformity surgery. All patients had bilateral median and ulnar nerve SEPs evaluated as a baseline, both intermittently throughout the surgical procedure and at termination of surgery. This information was correlated with pre- and postoperative upper extremity neurologic examinations. Twenty-five upper extremities in 21 patients had intraoperative SEP changes consisting of at least a 60% decline in amplitude or a 10% increase in latency. On many occasions, repositioning of the upper extremities improved the SEP responses to acceptable baselines. Overall, SEP monitoring of the upper extremities was 78% sensitive for detecting upper extremity sensory deficits, 100% sensitive for detecting combined sensory and motor deficits, and 98.5% specific for predicting normal postoperative upper extremity function. We recommend the simultaneous electrophysiologic monitoring of the upper and lower extremities during spinal surgery to allow identification of brachial plexus and/or peripheral nerve stretch/compression that may be amenable to intraoperative correction.

Adolescent↗

PubMed1993

The role of fusion and instrumentation in the treatment of degenerative spondylolisthesis with spinal stenosis.

Between February 1985 and March 1990 44 patients with degenerative spondylolisthesis underwent primary surgery for spinal stenosis (in all cases the decompression preserved the facets bilaterally without discectomy) and were studied prospectively. Forty-three patients have been followed for > or = 2 years and are the basis of this study. There were three treatment groups: group I, no fusion (nine patients); group II, transverse process fusion with autogenous iliac bone graft without instrumentation (11 initial patients, with one lost to follow-up for a total of 10); and group III, transverse process fusion with autogenous iliac crest bone graft and instrumentation (24 patients, 18 with one-level pedicle fixation and six with two-level fixation). A higher proportion of group III subjects had a successful fusion compared with group II (p = 0.002). There was significantly more spondylolisthesis progression in groups I and II than in group III (p = 0.001). A higher proportion of "spondylolisthesis unchanged subjects" reported they were helped by the surgery than those whose spondylolisthesis progressed postoperatively (p < 0.01).

Aged↗

PubMed1993

An analysis of risk factors for death and mode-specific death after aortic valve replacement with allograft, xenograft, and mechanical valves.

From September 1967 to January 1990, a total of 2100 patients underwent 2366 aortic valve replacements with a variety of allograft, xenograft, and mechanical valves. Concomitant procedures were performed in 764 patients. Actuarial survival at 12 years was 59.6% (70% confidence limits 57.8% to 61.4%). Hazard function for death was highest immediately after operation, falling to merge with a slowly rising phase of risk at approximately 3 months. Actuarial freedom from sudden death at 12 years was 88.0% (70% confidence limits 86.7% to 89.3%). The shape of the hazard function for sudden death was similar to that for death. Actuarial freedom from death with cardiac failure at 12 years was 87.9% (70% confidence limits 86.5% to 89.2%). The shape of the hazard function for death with cardiac failure was also similar to that for death. Risk factor analysis revealed the important deleterious impact on long-term survival resulting from impaired left ventricular structure and function because of aortic valve disease. No current-era valve used in this study (allograft, xenograft, or mechanical) was a risk factor for death. Both aortic wall disease and endocarditis necessitating aortic valve replacement substantially decreased long-term patient survival. Aortic valve replacement is advisable much earlier in the natural history of aortic valve disease before secondary left ventricular damage occurs.

Actuarial Analysis↗