Biomedical subjects
Publications and source records attributed to I Maurer.
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The effect of chronic left ventricular pressure overload on the activities of mitochondrial respiratory chain enzymes was investigated in myocardial biopsies from the left ventricular apex of 13 patients undergoing aortic valve replacement for aortic valve stenosis. Transvalvular pressure gradients measured by left-sided heart catheterization ranged from 52 to 100 mmHg. The specific activity of mitochondrial respiratory chain enzyme complexes I+III (antimycin A sensitive NADH cytochrome c oxidoreductase) and the myocardial concentrations of coenzyme Q10 (CoQ10) increased significantly (P < 0.05) with increasing aortic valve pressure gradient. In contrast, the specific activities of complex IV (cytochrome c oxidase), succinate dehydrogenase, and citrate synthase, a mitochondrial matrix enzyme, showed no significant correlation with the pressure gradient. Since CoQ10 is the rate-limiting compound of the activity of complexes I+III but not of cytochrome c oxidase, succinate dehydrogenase, or citrate synthase, these data suggest that the increase in the activity of complexes I+III is due to the increase in CoQ10 content.
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Conventional biologic and mechanical prostheses have important limitations with regard to their hemodynamic characteristics and long-term durability. We evaluated the hemodynamic function of a stentless porcine aortic prosthesis in 10 patients by invasive pressure measurements and angiography with videodensitometry 8 +/- 4 days after operation, as well as by Doppler echocardiography 35 +/- 15 months after valve replacement. The early postoperative invasive study revealed a mean gradient of 8 +/- 6 mm Hg across the prosthesis, no regurgitation in eight patients, and mild regurgitation, defined as less than 20% regurgitant fraction, in the remaining two patients. The late postoperative Doppler echocardiographic study revealed a mean gradient across the aortic prosthesis of 6 +/- 3 mm Hg, mean Doppler-derived valve orifice area of 1.8 +/- 0.6 cm2, and color Doppler flow velocity mapping suggested no regurgitation in eight patients and mild regurgitation in two patients corresponding to early postoperative angiography. None of the 10 patients received anticoagulation therapy. The clinical course of all patients was without incident. This stentless aortic bioprosthesis may offer hemodynamic advantage; however, further studies are needed to allow comparison with conventional mechanical and biologic prostheses.
A case of mitral valve reconstruction with replacement of the chordae tendineae by polytetrafluoroethylene (PTFE) sutures is described in a 52-year-old man. 21 days after operation mitral valve insufficiency due to rupture of a natural chorda led to reoperation with mitral valve replacement. The cardiac valve tissue was examined both macroscopically and microscopically. It showed a proliferation of fibroblasts. However, there was no endothelial cell layer detectable. To the best of our knowledge our case is the first report of the histological changes in human cardiac valvular tissue after implantation of PTFE sutures.
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We describe a simple, reproducible technique of achieving more normal left ventricular function after mitral valve replacement. Polytetrafluoroethylene (PTFE) sutures are used as chordae tendineae to restore the integrity between the mechanical valve and papillary muscles and thus the left ventricular wall.
The anatomy of valsalva's sinus is such that it decreases the mechanical stress on the leaflets of the aortic valve. Artificial stents impair the hemodynamic performance of an aortic bioprosthesis and lead to unphysiological functional stresses and may also shorten their durability. Therefore a semi-supported xenograft was developed which can be attached with an one-suture row in subcoronary position. This facilitates surgery considerably. Moreover, the commissures can be attached directly to the patient's aortic wall. The semi-supported valve was successfully implanted in a 69 years old patient with a combined aortic valve lesion. Postoperative invasive investigations, including angiography and videodensitometry, showed a normal performance of the valve and a normal anatomy of the aortic root.
Vasopressin binding sites could be clearly demonstrated in the cochlea. Membrane staining was mainly limited to the apical and ciliar membranes of the cochlear and vestibular hair cells, and hence to membranes in which adenylate cyclase activity could not be demonstrated. In addition to V2-vasopressin receptors that mediate hormonal signals by adenylate cyclase activation and cAMP release, in V1-vasopressin-receptors extracellular vasopressin signal is mediated by the breakdown of inositol phosphates and the release of inositol-triphosphates and diacylglycerol. Inositol triphosphates were found to be responsible for the intracellular mobilization of calcium. The localization of vasopressin binding sites at the hair cell membranes, therefore, suggests that vasopressin contributes to the breakdown and release of phospholipid messenger molecules and is thus probably involved in cochlear and vestibular signal transduction.
The effects of isoflurane (1 MAC) and enflurane (1 MAC) on cerebral blood flow and cerebral oxygen consumption were studied in 20 male patients without intracranial disease undergoing coronary artery bypass surgery (mean age 57 and 59 years respectively). The aim of the study was to investigate whether both agents diminish autoregulation of cerebral blood flow and CO2 reactivity of cerebral blood vessels. Patients were randomly assigned to one of two groups (10 patients each) receiving either isoflurane 1.15 vol.% or enflurane 1.68 vol.% endexpiratory. Measurements were performed and blood samples were taken in the awake state (I); 15 min after achievement of steady-state conditions with 1.68 vol.% enflurane or 1.5 vol.% isoflurane without blood pressure support (II); during norepinephrine-induced hypertension at a cerebral perfusion pressure of 110 mmHg (III); and during controlled hyperventilation at a PaCO2 of 27 mmHg and normotension (IV). Cerebral blood flow was measured by the argon wash-in technique. Isoflurane and enflurane produced a significant drop in cardiac index and cerebral perfusion pressure and reduced cerebral blood flow significantly by 35% and 39% respectively. Cerebral oxygen consumption was also significantly decreased by 49% (isoflurane) and 50% (enflurane). Induced hypertension with norepinephrine increased cerebral blood flow significantly by 32% (isoflurane) and 26% (enflurane), while hypocapnia reduced cerebral blood flow significantly by 26% (isoflurane) and 29% (enflurane).(ABSTRACT TRUNCATED AT 250 WORDS)
A fourteen year old boy with Rubinstein-Taybi-syndrome presented with a severe congenital subvalvular fibrous aortic stenosis with associated aortic regurgitation. Transthoracic echocardiographic imaging and left heart angiography showed a transvalvular peak systolic pressure gradient of 90 mmHg and a regurgitant fraction of 30%. The surgical treatment consisted of resection of the subvalvular fibrous tissue and subsequent aortic valvuloplasty. Intraoperative transesophageal echocardiography revealed a wide systolic opening of the aortic valve and good coaptation of the aortic valve leaflets in diastole. Two-dimensional color-coded and contrast echocardiography were successfully used to confirm a satisfactory reconstruction. Transesophageal echocardiography therefore represents a valuable tool in the assessment of the morphologic and haemodynamic status, especially in rare cases of congenital heart disease in older children.