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Biomedical subjects

G Bloch

Publications and source records attributed to G Bloch.

At least 91 records · Page 5Linked to original sources
PubMed1989

[Viability of new valvular homografts. Myth or reality?].

Use in cardiac surgery of aortic homografts as a valvular substitute is old and was specially developed in France by F. Fontan. In fact, these first allografts were non-viable and the results, in aortic position, were not better than current bioprosthesis. Renewed interest is related to the important notion of "viability" allowed by an immediate procurement (organ donors), preparation in nutrient medium RPMI with low doses of antibiotics and final storage at -196 degrees C (cryopreservation). We have reviewed our initial experience concerning 32 implanted homografts in children either in reconstruction of the right ventricular outflow tract (in many forms of congenital heart disease) or in aortic position. No mortality was observed. The only failure was due to an initial sizing mistake leading to an aortic valve replacement at 13 months. No late deterioration (mean follow-up: 12.5 months) was detected by echocardiography. These results seem to confirm other larger series (as O'Brien's, Brisbane, Australia). Biologic, histological and immunological assessments of "viable" homografts are discussed. The limits of the technique are reported.

Adolescent↗
PubMed1988

[Aortic subvalvular obstructions. Anatomical forms and surgical treatment of 82 consecutive cases].

The authors report their experience of surgery for subvalvular aortic obstruction in 82 patients aged from 4 to 44 years (mean 15 years). Nearly one-half of the patients presented with symptoms; the others were operated upon for various reasons: gradient exceeding 60 mmHg, development or aggravation of aortic regurgitation, positive exercise test, electrocardiographic or echocardiographic signs of left ventricular repercussions. Nineteen children had previously undergone surgery for another malformation, but the subvalvular aortic obstruction had either been missed during this first operation or had developed subsequently. The diaphragmatic pattern was the most frequent (62 cases); the fibromuscular pattern was less common (9 cases) and the tunnel pattern (6 cases) was regularly associated in this series with hypoplasia of the aortic ring. Obstruction due to faulty insertion of the mitral valve was encountered on 3 occasions. The operative technique for each anatomical pattern is described. Tunnel obstructions did not require primary aortoventriculoplasty without prosthetic valve replacement of apicoaortic conduits. In addition to treatment of associated lesions (including 4 cases of ventricular septal defect), 9 aortic commissurotomies, 6 aortic valvuloplasties and 4 aortic valve replacements were performed. The transaortic gradient was dramatically improved. The aortic regurgitation murmur subsided with or, usually, without valvuloplasty.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Sequence-dependence of the conformational changes induced by the 5-methyl cytosine in synthetic RNA oligomers.

The RNA hexamer containing a 5-methyl cytosine (m5C) r(CGUAm5CG) was studied by 1H and 31P NMR at 500 MHz and 121 MHz, respectively. In contrast to r(CGm5CGCG) which exhibits an atypic duplex structure [(1987) J. Am. Chem. Soc. 109, 2539-2541], r(CGUAm5CG) adopts a classical A-type conformation. This result demonstrates that the influence of the m5C on the conformation of RNA hexamers is sequence-dependent.

5-Methylcytosine↗
PubMed1987

Cardiovascular abnormalities in thoracopagus twins: embryological interpretation and review.

The cardiovascular abnormalities of two sets of thoracopagus twins with conjoined heart and liver are described and compared with 27 well documented cases. An embryological interpretation of the cardiovascular abnormalities is suggested. The common heart in both sets showed a common atrium and two ventricles. In case 1 the great arteries were L. malposed in twin A. In case 2 the great arteries originated from their respective double outlet single ventricle. The systemic and pulmonary veins drained directly into the common atrium in case 1 and indirectly via systemic veins in case 2. The type of cardiovascular abnormalities are complex and discordent from one set to another and in the same set. However among 27 published cases of thoracopagus twins, cardiac union, including atrial union with separate ventricles, or atrial and ventricular union, was encountered in 16 cases. Approximately 90% of them are not suitable for surgical separation because of the high degree of cardiac union and the complexity of cardiovascular abnormalities. Surgical separation could be attempted in only two cases, but at the cost of the life of one of the twins.

Aorta↗
PubMed1987

[Tetralogy of Fallot in adults. Apropos of 43 cases with 38 total corrections].

The records of 43 patients older than 18 years presenting with tetralogy of Fallot were retrospectively examined to determine the semiological characteristics of the disease in adults. One or more palliative operations had previously been performed in 27 patients. Full correction was carried out in 38 patients with results described below. Tetralogy of Fallot has the following characteristics in adults as compared with children: clinically, heart failure, attacks of angina, haemoptysis and sequelae of previous complications are more frequent; at electrocardiography, right atrial hypertrophy, right bundle disorders of conduction and ventricular extrasystoles are also more frequent; radiology shows that cardiomegaly is no longer exceptional; haemodynamic studies demonstrate an increase in right atrial and right ventricular end-diastolic pressures. These characteristics indicate a deterioration of haemodynamic adjustment to the disease with age. The operative morbidity mostly consisted of haemorrhages (55% of the patients), more frequent in subjects with permeable anastomoses (p less than 0.01), and heart failure (50% of the patients) the frequency of which increased with the subject's age, the duration of the operation and the use of an infundibulo-pulmonary prosthesis (p less than 0.05). The operative mortality (18%) depended on the extent of the pulmonary stenosis and on the presence of a previous anastomosis (p = 0.04). An analysis of the causes of death reported in the literature showed that in adults the presence of an anastomosis constitutes a separate risk factor in complete repair. The excellent long-term results of corrective surgery concerning cardiac function and survival suggest that except for those rare cases where the operative risk is very high all adults with tetralogy of Fallot should undergo complete repair.

Adult↗
PubMed1987

[Endocarditis of the pulmonary valve complicating interventricular communication. Echocardiographic detection].

A 29-year old woman known to have Roger's disease was hospitalized for streptococcal endocarditis with pulmonary embolism and cerebral vascular accident. Echocardiography demonstrated vegetations on the pulmonary valve, and this was confirmed at surgery. Pulmonary valve endocarditis is a rare lesion sometimes occurring as a complication of congenital malformations with ventricular septal defect. Its prognosis is governed not so much by bacterial resistance or haemodynamic repercussions as by the risk of septic pulmonary embolism or systemic embolism. Prophylaxis is essential to avoid this dangerous complication.

Adult↗
PubMed1987

[Repeated valvular replacements. Apropos of 64 cases].

In a series of 833 operations with implantation of 1011 prosthetic valves there were 64 reoperations on 44 patients, an incidence of 7.6%. In almost 50% of the cases, reoperation was motivated by desinsertion. The incidence of desinsertions increased with the number of reoperations. In 40% of the cases, desinsertion was caused by endocarditis. The degeneration of bioprosthetic valves was rapid in children. Thromboembolic accidents occurred in patients with mitral valve mechanical prosthesis. Peri-operative mortality due to left ventricular dysfunction was 9%. Mortality rate was high after reoperation for endocarditis on a desinserted prosthetic valve. Surveillance and prevention of bacterial endocarditis remain of paramount importance.

Adolescent↗
PubMed1986

[Aortocoronary bypass. Development of technics and indications over a 10-year period].

During the 1973-1983 period considerable changes have taken place in the techniques and indications of coronary bypass. In a homogeneous series of 3095 patients operated upon by the same group, changes in techniques have been: the introduction in routine coronary bypass of the membrane oxygenator which provides optimal biological conditions and the prolonged circulatory assistance so necessary to high risk patients, and the application to coronary bypass of microsurgical techniques enabling surgeons to perform multiple anastomoses on small vessels easily and safely. Changes in indications have been characterized by a progressive decrease in operations on patients with one-vessel lesions and normal left ventricular function to the benefit of those with multiple-vessel lesions and altered left ventricular function. As a result, the complete revascularization rate and the number of anastomoses have increased continuously. These two categories of changes have not modified the overall in-patient mortality rate, but there has been a significant increase in peri-operative necrosis.

Cardiomyopathies↗
PubMed1985

[Collateral pulmonary circulation in Fallot's tetralogy].

An angiographic study of 231 patients with tetralogy of Fallot (TOF) in both neonatal and adult age groups (0 to 49 years) was in this condition. Cases of pulmonary atresia with ventricular septal defect were excluded. Two types of collateral pulmonary circulation were observed: the most common form is the result of distal intrapulmonary anastomosis between systemic parietal, mammary and bronchial vessels with the pulmonary arteries. This type of collateral circulation represents an evolutive stage of TOF and is directly related to age and to the degree of hypoxia; the other, oa rare and probably congenital form (1.7 p. 100 of cases) observed even in young children, consisting of proximal anastomoses between systemic vessels arising from the aorta (1 to 3 vessels) and the pulmonary arterial tree. The rare forms of TOF with single pulmonary arteries acquired after palliative or congenital anastomoses (1.4 p. 100) have both types of collateral circulation. Preoperative diagnosis of the collateral pulmonary circulation requires opacification of the aorta especially of the descending thoracic segment and its branches, completed in cases of an absent pulmonary artery by wedged pulmonary venous opacification. The haemodynamic effects of this collateral circulation on the pulmonary bed to a variable degree of histological change. This may partially explain some of the poor surgical results of repair of TOF and, in view of recent progress in cardiopulmonary bypass techniques in children, incite to earlier surgical correction of this condition.

Adolescent↗
PubMed1985

[Date of surgery in congenital cardiopathies].

The appropriate time for surgical intervention in congenital cardiopathies is chosen as a function of several imperatives; psychological and family reasons militate in favour of an early intervention. In particular, in cardiopathies accompanied by pulmonary arterial hypertension (serious VSD, arterial transpositions with VSD, etc.) there is a risk of irreversible obstructive pulmonary arterial disease in the first months of life in some cases. This risk, added to those of cardiac insufficiency, prompts early intervention. The progressive risks of cyanotic cardiopathies: risks of intravascular thrombosis and of cerebral abscess have contributed to these cardiopathies being operated upon earlier than was done some years ago. The decision to be taken remains difficult for complex cardiopathies. Coarctations of the aorta are usually operated upon before the age of 4 years in order to avoid the risk of permanently fixed arterial hypertension and premature vascular degeneration. The operative indications in aortic stenoses are now guided not only by clinical data but also by an assessment of the haemodynamic tolerance by ultrasonography and exertion tests.

Adolescent↗
PubMed1984

Long-term evaluation of bioprosthetic valves: 615 consecutive cases.

From January 1975 to September 1983, 615 patients underwent valve replacement using 698 bioprosthetic valves for selected indications. This group represents the third of all patients having valve replacement during the same period. Children younger than 15 years were excluded. The mean pre-operative functional class was 2.9. The early mortality rate was less than 5% and the follow-up range 3 months to 9 years (3.2 yrs). The symptomatic improvement was attested by a mean post-operative functional class of 1.4. In a linear study the following rates of valve related complications were noted: thromboembolism 4.6%, endocarditis 2.5%, primary tissue valve degeneration 1.1%, paraprosthetic leak 2.5%. In an actuarial study, at 8 years, 83% of patients were free from any valve failure. The probability rates of complications were the following: thromboembolic events 8%, endocarditis 5%, degeneration 3%, reoperation 7%. The probability of survival at 8 yrs was 69% and the probability rates of late mortality were noted as follow: cardiac related mortality 27%, valve-related mortality 4%. Despite an expected increasing rate of degeneration, the results warrant the use of bioprostheses in a selected group of patients.

Actuarial Analysis↗
PubMed1984

[Surgical treatment of aortic subvalvular obstruction. Experimental study of a new approach].

The aortic subvalvular region is difficult to approach. The results after resection through a pure transaortic approach are often unsatisfactory. An aorto-septal approach derived from the Konno-Rastan aortoventriculoplasty was experimented in animals. This technique involves opening the ascending aorta and the pulmonary infundibulum, section of the aortic annulus at the left anterior commissure and incising the muscular interventricular septum. The results of this aorto-septal approach show: - that the whole left ventricular ejection tract can be exposed; - that the incision can be closed without damage to the heart, i.e. creation of atrioventricular block, and with reconstruction of an intact interventricular septum and a normally functioning aortic valve. This approach could therefore be used for the treatment of diffuse subvalvular aortic stenosis: - subaortic fibromuscular tunnel without hypoplasia of the aortic ring (one personal case has already been reported); - severe forms of hypertrophic obstructive cardiomyopathy with asymmetric septal hypertrophy.

Animals↗
PubMed1984

[Surgical treatment of valve prosthesis endocarditis].

Between 1972 and 1982, 27 patients underwent 29 prosthetic valve replacements for infective endocarditis. Fourteen cases (48%) were operated in the acute infectious phase. Most patients (71%) had signs of cardiac failure and surgery was often performed as an emergency (78%). Twelve aortic valve prostheses (10 mechanical + 2 bioprostheses) and 2 mitral bioprostheses were infected. Four patients (29%) died in the postoperative period; all were in functional Class IV and were reoperated as an emergency. The infection only persisted in 1 patient (7%). Three patients died during follow-up (3 year survival: 46%). Three replacement prostheses developed perivalvular leaks (21%) and 2 were reoperated. Fifteen cases (52%) were operated after the acute infection for secondary lesions. These lesions affected an aortic valve prosthesis in 14 cases (9 mechanical and 5 bioprostheses) and 1 mechanical mitral valve prosthesis. Operative mortality was nil. Three patients died during follow-up (3 year survival: 67%). Five replacement prostheses developed perivalvular leaks (33%) and 3 had to be reoperated. These results show: that the high operative mortality (29%) in the group operated during the acute infectious phase is related to the preoperative haemodynamic condition and not to persistence of the infection (only 1 case); secondly, recurrent perivalvular leaks were common in both groups due to the fragility of the tissues and were the main cause of late mortality.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗