Biomedical subjects

A Milano

Publications and source records attributed to A Milano.

At least 91 records · Page 5Linked to original sources

PubMed1992

The Meadox-Gabbay pericardial xenograft: failure of the unicusp principle.

Durability of a new bioprosthesis, the Meadox-Gabbay unileaflet pericardial xenograft, was evaluated by reviewing a series of 12 patients who received this device in the mitral position from 1983 to 1985. Bioprosthetic failure necessitated reoperation in 5 patients 21, 22, 53, 66, and 81 months after placement. Three patients died of cardiac failure after 31, 52, and 70 months; no postmortem examinations were done. In 2 of the 3 patients, an echocardiographic study had shown signs of valvular dysfunction. Pathological examination of five available explants revealed the presence of redundancy and stretching of the single pericardial leaflet in all of them; in one, this lesion alone caused severe prosthetic incompetence. Other pathological findings included cusp and commissural calcification and commissural tears with or without calcification. Histologic examination and electron microscopy showed intrinsic calcification involving both collagen bundles and cellular debris and various degrees of collagen disruption. In this limited series of patients, the Meadox-Gabbay pericardial xenograft demonstrated various modes of failure that markedly impair its durability and render it unsuitable as a cardiac valve substitute.

Adult↗

PubMed1992

Molecular characterization of the genes encoding acetohydroxy acid synthase in the cyanobacterium Spirulina platensis.

The enzyme acetohydroxy acid synthase (AHS), which catalyses the first common step in the biosynthesis of isoleucine, leucine and valine, has been demonstrated to be present in Spirulina platensis in two isoenzymic forms. The complete nucleotide sequences of the genes ilvX and ilvW encoding these two enzymes have been determined. Sequence analysis revealed the presence of two open reading frames, of 1836 and 1737 nucleotides for ilvX and ilvW, respectively. The predicted amino acid sequences of the two isoenzymes, compared with the Synechococcus PCC 7942 AHS enzyme and the large subunits of the Escherichia coli AHSI, II, III isoenzymes, revealed a notable degree of similarity. A small subunit has not been identified for either of the S. platensis AHS isoenzymes. Analysis by Northern blot hybridization demonstrated that the ilvX and ilvW genes are transcribed to give mRNA species of approximately 2.15 kb and 1.95 kb, respectively.

Acetolactate Synthase↗

PubMed1992

Glutaraldehyde-fixed bovine iliac veins used as bioprosthetic conduits: an experimental animal study.

The ideal prosthetic conduit for surgical repair of complex congenital heart disease has yet to be found. Twenty conduits were implanted between the right ventricle and pulmonary artery in growing sheep as follows: four Dacron porcine valve conduits (mean time in place, 142 days); four avalved glutaraldehyde-fixed bovine iliac veins (mean 132 days); and 12 glutaraldehyde-fixed bovine iliac veins containing a porcine valve (mean 180 days). Fifteen conduits were left in place from 167 to 244 days (mean 204 days), and five were explanted earlier (mean 54 days). Pathological study included gross, x-ray, histological, and ultrastructural investigation. Five conduits failed because of infective endocarditis. The valved Dacron conduits showed significant tissue ingrowth and calcification of the valve graft. The valved bovine iliac veins presented calcification at the valve level and vein wall, as well as a valvelike calcific fibrous ridge at the proximal anastomosis with the right ventricle. The avalved bovine iliac veins also presented calcific deposits along the wall and a valvelike calcific ridge at the ventricular anastomosis. Histological and ultrastructural studies of the vein tunica media revealed the phenomena of inflammatory rejection and foreign body reaction with loss of smooth muscle cells (medionecrosis) and fibrotic replacement. In conclusion, bovine iliac veins undergo inflammation with medionecrosis indicating that smooth muscle cell antigenicity is not attenuated by glutaraldehyde fixation.

Animals↗

PubMed1992

Annular enlargement during aortic valve replacement: preliminary results with a simplified technique.

A simplified technique has been used to enlarge the aortic annulus in a series of 13 patients undergoing aortic valve replacement. The procedure basically consists of extending the aortotomy incision into the aortic annulus by dividing the commissure between the left and noncoronary sinuses, without involving the anterior mitral leaflet. Wide opening of the commissure is obtained and the resulting defect is closed, preferably using a patch of bovine pericardium sutured to the mitral annulus and aortic wall. This technique is simple, reproducible, avoids opening of the left atrium (reducing the potential bleeding sites), allows insertion of a prosthesis at least two sizes larger than the original annulus, and is also applicable in cases of mitral-aortic valve replacement. Our preliminary results are satisfactory and seem to demonstrate that in many patients, even in the young age group, more complex procedures are often unnecessary when enlargement of the aortic annulus is required.

Adult↗

PubMed1992

Structural organization of pBC1, a cryptic plasmid from Bacillus coagulans.

The complete nucleotide sequence of the Bacillus coagulans plasmid pBC1 was determined. The sequence revealed an open reading frame encoding a polypeptide of 259 amino acids. This open reading frame shows sequence similarity to genes coding for replication-associated proteins in a group of gram-positive bacterial plasmids known to replicate via single-stranded intermediates. A region required for replication in cis, when the intact replicon is supplied in trans, was identified as well.

Amino Acid Sequence↗

PubMed1992

Durability of glutaraldehyde-fixed pericardial valve prostheses: clinical and animal experimental studies.

Bovine pericardium has been widely employed as a xenograft tissue for the manufacture of bioprosthetic valve substitutes. Early three-leaflet valve models showed poor tissue preservation and shortcomings in valve design, which accounted for tissue wear and prosthesis failure due to cuspal tear. Reducing the number of cusps in the unicusp pericardial valve has proved unsuccessful due to stretching of the single pericardial leaflet with consequent valvular incompetence. The new generation of pericardial xenografts present basic changes in valve design and optimal tissue preservation after industrial processing, with no evidence of leaflet tear at medium term follow up. However, clinical experience is limited and, similarly to porcine xenografts, dystrophic calcification still appears to be a major problem.

Adult↗

PubMed1992

Original expectations of the Hancock valve and 20 years of clinical reality.

The standard (glutaraldehyde-preserved) Hancock porcine bioprosthesis was introduced into clinical practice in order to provide surgeons with a cardiac valve substitute which would be nonthrombogenic and therefore would not require anticoagulation, and would be durable, anatomically suitable, and noiseless. In the present report we have reviewed our long-term experience with Hancock porcine valve recipients in order to verify the original expectations of this bioprosthesis have been met.

Adolescent↗

PubMed1992

Heart valve replacement with the Sorin tilting-disc prosthesis. A 10-year experience.

From 1978 to 1988, 697 patients with a mean age of 48 +/- 11 years (range 5 to 75 years) received a Sorin tilting-disc prosthesis; 358 had had aortic valve replacement, 247 mitral valve replacement, and 92 mitral and aortic valve replacement. Operative mortality rates were 7.8%, 11.3%, and 10.8%, respectively, in the three groups. Cumulative duration of follow-up is 1650 patient-years for aortic valve replacement (maximum follow-up 11.4 years), 963 patient-years for mitral valve replacement (maximum follow-up 9.9 years) and 328 patient-years for mitral and aortic valve replacement (maximum follow-up 9.4 years). Actuarial survival at 9 years is 72% +/- 4% after mitral valve replacement, 70% +/- 3% after aortic valve replacement, and 50% +/- 12% after mitral and aortic valve replacement, and actuarial freedom from valve-related deaths is 97% +/- 2% after mitral valve replacement, 92% +/- 2% after aortic valve replacement, and 62% +/- 15% after mitral and aortic valve replacement. Thromboembolic events occurred in 21 patients with aortic valve replacement (1.3% +/- 0.2%/pt-yr), in 12 with mitral valve replacement (1.2% +/- 0.3% pt-yr), and in seven with mitral and aortic valve replacement (2.1% +/- 0.8%), with one case of prosthetic thrombosis in each group; actuarial freedom from thromboembolism at 9 years is 92% +/- 3% after mitral valve replacement, 91% +/- 3% after aortic valve replacement, and 74% +/- 16% after mitral and aortic valve replacement. Anticoagulant-related hemorrhage was observed in 15 patients after aortic valve replacement (0.9% +/- 0.2%/pt-yr), in 9 after mitral valve replacement (0.9% +/- 0.3%/pt-yr), and in 6 with mitral and aortic valve replacement (0.9% +/- 0.5%/pt-yr); actuarial freedom from this complication at 9 years is 94% +/- 2% after aortic valve replacement, 91% +/- 4% after mitral valve replacement, and 68% +/- 16% after mitral and aortic valve replacement. Actuarial freedom from reoperation at 9 years is 97% +/- 2% after mitral and aortic valve replacement, 92% +/- 4% after mitral valve replacement, and 89% +/- 3% after aortic valve replacement, with no cases of mechanical fracture. The Sorin valve has shown a satisfactory long-term overall performance, comparable with other mechanical prostheses, and an excellent durability that renders it a reliable heart valve substitute for the mitral and aortic positions.

Actuarial Analysis↗

PubMed1991

Molecular cloning and expression of Spirulina platensis acetohydroxy acid synthase genes in Escherichia coli.

The coding sequence for Spirulina platensis acetohydroxy acid synthase (AHAS, EC 4.1.3.18) is shown to be contained within a 4.2 Kb ClaI fragment (ilvX) that has been cloned from a recombinant lambda library. This fragment was able to complement a suitable mutant of Escherichia coli when inserted into the ClaI site of plasmid pAT153 in either orientation, demonstrating that transcription of ilvX originated within the cloned fragment. The probe used for hybridization experiments was the corresponding gene from Anabaena sp. PCC7120. The same probe allowed us to identify a second putative gene encoding AHAS in the S. platensis genomic library.

Acetolactate Synthase↗

PubMed1991

Failure of Hancock pericardial xenografts: is prophylactic bioprosthetic replacement justified?

The incidence of major valve-related complications was evaluated in a series of patients in whom the Hancock pericardial xenograft was used for aortic (AVR; n = 84), mitral (MVR; n = 17) and mitral-aortic (MAVR; n = 13) valve replacement. At 7 years actuarial survival is 66% +/- 8% after AVR, 64% +/- 13% after MVR, and 41% +/- 15% after MAVR, whereas actuarial freedom from valve-related death is 79% +/- 7% after AVR, 78% +/- 13% after MVR, and 81% +/- 12% after MAVR. Actuarial freedom from thromboemboli and anticoagulant-related hemorrhage at 7 years is 93% +/- 4% and 98% +/- 2% after AVR and 83% +/- 10% and 88% +/- 11% after MVR; no such complications occurred after MAVR. Structural valve deterioration determined at reoperation, at autopsy, or by clinical investigation was observed in 34 patients with AVR (10.0 +/- 0.2%/patient-year), in 10 with MVR (10.6 +/- 3.3%/patient-year), and in 9 with MAVR (16.6 +/- 5.5%/patient-year). After AVR, 19 patients underwent reoperation and 2 died before reoperation; 4 patients with MVR underwent reoperation, and 7 patients with MAVR underwent reoperation and 1 died before reoperation. Seventy-eight percent of the current survivors (13 patients with AVR, 7 with MVR, and 1 with MAVR) have clinical evidence of valve failure. At 7 years actuarial freedom from structural deterioration of the Hancock pericardial xenograft is 25% +/- 7% after AVR, 29% +/- 14% after MVR, and 0% after MAVR.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

Influence of type of prosthesis on late results after combined mitral-aortic valve replacement.

The influence of type of prosthesis on the late outcome of patients with combined mitral-aortic valve replacement was analyzed by comparing, at a 14-year follow-up, patients receiving two biological prostheses (group 1; n = 135), two mechanical prostheses (group 2; n = 221), or a mechanical prosthesis in the aortic position and a bioprosthesis in the mitral position (group 3; n = 97). No difference was found among the three groups in terms of actuarial survival and incidence of and freedom from valve-related deaths, thromboemboli, and hemorrhages. Patients with biological prostheses had a significantly greater incidence of structural valve deterioration, reoperations, and overall complications when compared with patients with only mechanical prostheses. The results of an extended follow-up of patients with combined mitral-aortic valve replacement indicate that mechanical prostheses perform better in the long-term owing to their superior durability when compared with biological valves. The use of bioprostheses should be confined to old patients with limited life expectancy because of their cardiac disease, provided that anticoagulants are not used. Combination of mechanical and biological prostheses in the same patient should be avoided because the advantages of each type of prosthesis are lost.

Adult↗

PubMed1991

Extended follow-up of the standard Hancock porcine bioprosthesis.

We have reviewed 665 patients in whom the standard Hancock porcine bioprosthesis (HPB) was used for aortic (AVR = 173), mitral (MVR = 437), and mitral and aortic (MAVR = 55) valve replacement in the time interval from 1970 to 1983. After AVR, HPB-related deaths occurred in 24 patients (1.7% +/- 0.4% per patient-year); 11 had thromboembolic episodes (0.8% +/- 0.2% per patient-year), 6 hemorrhages related to anticoagulants (0.4% +/- 0.2% per patient-year), 9 endocarditis (0.7% +/- 0.2% per patient-year), 7 prosthetic leak (0.5% +/- 0.1% per patient-year), and 59 structural deterioration (4.3% +/- 0.6% per patient-year). At 16 years, actuarial survival is 40% +/- 6%, freedom from thromboembolic episodes 89% +/- 4%, from hemorrhages 90% +/- 5%, from endocarditis 94% +/- 2%, from prosthetic leak 95% +/- 2%, and from structural deterioration 36% +/- 6%. After MVR, HPB-related deaths occurred in 64 patients (1.6% +/- 0.2% per patient-year); 68 had thromboembolic episodes (1.7% +/- 0.2% per patient-year), 28 hemorrhages (0.7% +/- 0.1% per patient-year), 12 endocarditis (0.3% +/- 0.1% per patient-year), 9 prosthetic leak (0.2% +/- 0.1% per patient-year), and 158 structural deterioration (4.0% +/- 0.3% per patient-year). At 18 years, actuarial survival is 33% +/- 4%, freedom from thromboembolic episodes 57% +/- 13%, from hemorrhages 81% +/- 6%, from endocarditis 91% +/- 4%, from prosthetic leak 98% +/- 1%, and from structural deterioration 18% +/- 5%.(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗

PubMed1991

The risk of reoperation in patients with bioprosthetic valves.

The risk of operative mortality in patients undergoing a first reoperation for bioprosthetic failure was assessed in a series of patients reoperated upon during the last two decades (1970-1990). A total of 330 such patients underwent replacement of 351 bioprostheses: 88 had aortic; 221 mitral; and 21 mitral and aortic bioprosthetic replacement. Indication for reoperation was in most cases structural valve deterioration (87%), followed by periprosthetic leak (7%) and endocarditis (6%). The operative mortality was significantly higher in patients who preoperatively were in New York Heart Association Functional Class IV or had a lower left ventricular function, in those reoperated because of prosthetic infection, and in those reoperated on an emergency basis. Structural valve deterioration was associated to a substantially low risk; operative mortality has improved in recent years, regardless of the indication for reoperation, partly due to the increasing experience and improved surgical techniques. Our results indicate that in recipients of bioprosthetic valves, careful follow-up with closer surveillance of valve and cardiac function and earlier prosthetic replacement might contribute to reducing the risk of reoperation.

Adolescent↗

PubMed1991

[Follow-up using echocardiography and ambulatory electrocardiography of patients after excision of intracardiac myxoma].

From November 1968 to May 1990, 56 patients, 19 male and 37 female (mean age 49 +/- 14 years) underwent excision of an intracardiac myxoma (M). M was located into the left atrium in 48 (86%), the right atrium in 6 (11%), and the right ventricle in 2 (3.5%). Operation consisted of excision of the tumor together with its base of attachment. There were 2 early (3.5%) and 2 late (3.7%) deaths. Actuarial survival at 20 years is 91 +/- 4%. Non-invasive reevaluation has been carried out in 44 patients (84%), 39 with left atrial M, 4 with right atrial M, and 1 with right ventricular M. 2-D echocardiography ruled out tumor recurrence in all patients and showed, in those with left atrial M, a reduction in the size of the atrial chamber; on the contrary, left ventricular systolic diameter, diastolic diameter and ejection fraction were unmodified. In 7 patients (15.9%) a residual mild mitral insufficiency was disclosed. In 34 patients 24-hour electrocardiographic monitoring reevaluation showed a low incidence of major supraventricular arrhythmias, late postoperatively (short runs of paroxysmal supraventricular tachycardia in 3 patients, and atrial ectopic rhythm in 1). All these patients had undergone tumor excision by biatrial approach. Based on our results, we conclude that excision of intracardiac myxomas is curative and long-term survival is excellent. Non-invasive reevaluation of patients by 2-D echocardiography and 24-hour electrocardiographic monitoring is mandatory in order to promptly disclose possible complications, particularly tumor recurrence and arrhythmias.

Adolescent↗

PubMed1990

Surgical excision of intracardiac myxomas: a 20-year follow-up.

Since November 1968, 54 patients have undergone excision of an intracardiac myxoma, which was located in the left atrium in 46 (85%), in the right atrium in 6 (11%), and in the right ventricle in 2 (4%). There were 35 female and 19 male patients with a mean age of 48 +/- 14 years (range, 7 to 68 years). Four patients were asymptomatic; the others were seen mostly with exertional dyspnea, palpitation, signs of systemic illness, and syncopal episodes. Before operation, embolic episodes occurred in 13 patients with a left atrial myxoma. There were two early (3.7%) and two late deaths (3.8). Actuarial survival at 20 years is 91% +/- 4%, and most of the current survivors are asymptomatic at a mean follow-up of 6.5 +/- 5 years (range, 0.2 year to 20 years). Noninvasive reevaluation was performed with echocardiographic studies in 44 patients and 24-hour electrocardiographic monitoring in 34. No instances of tumor recurrence were observed, and there was a low incidence of major supraventricular arrhythmias late postoperatively. We conclude that excision of intracardiac myxomas is curative and long-term survival is excellent. The transseptal approach provides adequate exposure and allows complete removal of the tumor regardless of its location.

Adolescent↗

PubMed1990

Influence of prosthetic design on durability of the Liotta porcine valve in the mitral position.

From March 1979 to December 1984, the Liotta low-profile porcine bioprosthesis was employed for mitral valve replacement in 71 patients to avoid potential left ventricle-prosthesis mismatch occasionally observed with the standard, high-profile, Hancock porcine xenograft. Follow-up of 61 operative survivors showed at 10 years an actuarial survival of 67% +/- 7%, freedom from thromboemboli of 96% +/- 2%, freedom from structural deterioration of 63% +/- 11% and freedom from all Liotta bioprosthesis-related complications of 53% +/- 10%. Complications related to excessive protrusion of the stent into the left ventricular cavity were eliminated with the Liotta bioprosthesis; the peculiar stent configuration, however, was responsible for an increased rate of structural deterioration requiring reoperation in 10 patients (2.8% +/- 0.9%/patient-year) at a mean interval of 76 +/- 18 months after mitral valve replacement (range, 45 to 106 months). Common findings in all explants were cusp prolapse, cusp tears, and commissural rupture related to various degrees of tissue calcification, constantly leading to severe prosthetic incompetence. As also shown experimentally, such structural changes have been attributed to increased systolic stresses on the closed cusps, favored by excessive reduction of the stent height. Our experience shows that the Liotta bioprosthesis used for mitral valve replacement does not provide any clear-cut advantage over standard porcine bioprostheses and that its long-term durability appears affected by the unique prosthetic design.

Adult↗

PubMed1990

Right atrial myxoma originating from the inferior vena cava.

A patient undergoing successful excision of a right atrial myxoma arising from the inferior vena cava is reported. The rarity of this case prompted a review of the literature in which only 2 other patients with a right atrial myxoma originating from inferior vena cava tissue were found.

Adult↗

PubMed1990

Left atrial myxoma: excision guided by transesophageal cross-sectional echocardiography.

We present a patient with a left atrial myxoma in whom the intraoperative use of transesophageal cross-sectional echocardiography proved helpful in selecting the most appropriate surgical approach, thus allowing expeditious and complete excision of the tumor. This technique, which permits continuous monitoring of cardiac function throughout open heart procedures, appears particularly valuable in patients with intracardiac masses.

Echocardiography↗