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Biomedical subjects

H Antretter

Publications and source records attributed to H Antretter.

At least 19 recordsLinked to original sources
PubMed1998

Atrial natriuretic peptide-induced release of cyclic guanosine monophosphate by coronary bypass grafts.

BACKGROUND: Superior long-term patency rates of the internal mammary artery (IMA) versus saphenous vein (SV) after coronary artery bypass grafting are well documented. Higher production rates of vasodilating and platelet-inhibiting mediators (prostacyclin and nitric oxide) by the IMA seem to have a major impact on its long-term durability and resistance to coronary artery graft disease. For the right gastroepiploic artery (RGEA) marked release of protective mediators is reported as well. The vasodilating effect of cyclic guanosine monophosphate (cGMP) released after stimulation by atrial natriuretic peptide might serve as another graft protective system. The aim of the present study was to determine cGMP release by IMA, RGEA, and SV after atrial natriuretic peptide challenge. METHODS: Samples of human IMA (n = 19), RGEA (n = 7), and SV (n = 18) discarded during coronary artery bypass grafting were stimulated with 10(-6) mol/L atrial natriuretic peptide after a resting phase in nutrient medium. Release of cGMP was determined by 125-iodide radioimmunoassay. RESULTS: Basal cGMP production rates of the IMA (759.9 +/- 277.0 fmol/cm2) and RGEA (739.9 +/- 186.0 fmol/cm2) were higher than production rates of SV (281.2 +/- 64.0 fmol/cm2). Application of atrial natriuretic peptide led to a statistically significant increase of cGMP release in IMA grafts (1,939.3 +/- 778.0 fmol/cm2), whereas RGEA (618.4 +/- 141.3 fmol/cm2) and SV (221.7 +/- 64.5 fmol/cm2) remained at basal levels (p < 0.05). CONCLUSIONS: From these data we conclude that the IMA in comparison with the RGEA and SV produces more extracellular cGMP when stimulated by atrial natriuretic peptide. This effect might support the cGMP-mediated protective properties of nitric oxide and could underline the extraordinary suitability of the IMA as a bypass conduit.

Abdominal Muscles↗
PubMed1998

Stimulated prostacyclin release by conduits used for coronary artery bypass grafting.

A direct comparison of the three coronary artery bypass conduits internal mammary artery (IMA), right gastroepiploic artery (RGEA), and saphenous vein (SV) concerning arachidonic acid (AA) stimulated release of the vasodilating and platelet inhibiting mediator prostacyclin was the aim of the present study. Pieces of saphenous vein (n = 16), right gastroepiploic artery (n = 8), and internal mammary artery (n = 19) were obtained from patients undergoing coronary artery bypass grafting. After a resting phase of 30 min in HEPES medium arachidonic acid (AA) was added in order to stimulate prostacyclin release. Time-dependent production of the stable prostacyclin metabolite 6-keto-prostaglandin F1 alpha was determined following stimulation. Under basal conditions the IMA (12.4 ng/cm2) and RGEA (12.0 ng/cm2) released more prostacyclin than saphenous vein (4.0 ng/cm2). After AA stimulation 6-keto-prostaglandin F1 alpha release at 30 min was as follows: IMA 806.0 ng/cm2, RGEA 35.9 ng/cm2, SV 82.3 ng/cm2 (p < 0.0001 within grafts, p < 0.0001 between grafts, ANOVA for repeated measures). The internal mammary artery in comparison with the right gastroepiploic artery and saphenous vein seems to be better protected against local thrombotic events and development of coronary artery graft disease with the aid of the vasodilating and platelet inhibiting mediator prostacyclin.

Arachidonic Acid↗
PubMed1996

Spinal cord protection in descending and thoracoabdominal aortic surgery--the role of distal perfusion.

The use of distal perfusion in descending thoracic and thoracoabdominal aortic surgery remains a controversial issue. Few mainly retrospective studies which directly compare simple clamping with distal perfusion are available. The aim of the present study was such a comparison in an own series of descending and thoracoabdominal aortic replacement. The records of 29 patients who underwent descending or thoracoabdominal aortic replacement between 1988 and 1994 were retrospectively reviewed. Patients were divided into two groups. Group I consisted of 14 patients who received aortic replacement using simple clamping, group II was represented by 15 patients who were operated with distal perfusion techniques. In group II left heart bypass with a centrifugal pump was used in 3 patients, and partial cardiopulmonary bypass with a roller pump in 12 patients. The paraplegia/paraparesis rate was 28.6% in group I and 0.0% in group II (p = 0.0258). There were no statistically significant differences regarding surgical revision for bleeding (14.3% in group I, 14.0% in group II), postoperative renal failure (14.3% in group I 13.3% in group II), postoperative ventilator dependence (9.0 days in group I, 11.2 days in group II), rate of postoperative multisystem organ failure (26.7% in group I, 33.3% in group II), length of stay in the ICU (13.6 days in group I and 13.9 days in group II), and 30-day mortality (21.4% in group I and 33.3% in group II). Methods of distal perfusion in comparison to simple clamping can lead to a lower paraplegia/paraparesis rate in descending and thoracoabdominal aortic surgery.

Adult↗
PubMed1996

[A new cardiac pacemaker stimulation technology (autocapture) allows, with unchanged life expectancy, reduction of generator size by half].

Energy delivery (stimulation amplitude) of a pacemaker should be adjusted to the depolarisation threshold of the heart, which is a nonconstant magnitude. As programming of the stimulation amplitude is time-consuming, many pacemakers are never adjusted to the measured threshold referring to energy delivery. The unnecessary energy loss subsequently reduces the longevity of the implanted devices and remains the weak point of modern pacemakers. Autocapture function (automatic stimulation threshold search, subsequently automatic amplitude regulation 0.3 V above measured threshold, evoked response detection to verify the efficacy of every stimulus and back up pulse in case of loss of capture) is for the first time realized in an extremely small, rate adaptive, multiprogrammable single chamber pacemaker (Microny SR+ 2425T). The pulse generator was tested in a multicentric, european clinical investigation study. These pacemakers were implanted in 8 patients (5 male, 3 female) between December 1994 and April 1995. Automatic measurement of Autocapture threshold revealed 0.7 +/- 0.15 V at implantation, 1.5 +/- 0.3 V after 1 month, 1.3 +/- 0.14 V after 6 months and 1.3 +/- 0.14 V 1 year after implantation. A safety margin of 0.3 V is added to the threshold value to secure capture, therefore mean stimulation amplitude is 1.6 V after 12 months implantation time. The Autocapture feature minimizes current drain and that means that this extremely small generator provides a comparable life as the twice as large common generators used at present time.

Aged↗
PubMed1995

Reperfusion after cardioplegic cardiac arrest--effects on intracoronary leucocyte elastase release and oxygen free radical mediated lipid peroxidation.

In experimental animal models reperfusion of ischaemic myocardium causes sequestration of leucocytes within the coronary circulation. Leucocytes contribute to postischaemic myocardial injury by releasing proteolytic enzymes and by generating oxygen free radicals. The aim of this study was to investigate whether leucocytes also contribute to myocardial injury following ischaemia and reperfusion associated with cardioplegic cardiac arrest. Therefore, we studied the release of the proteolytic enzyme elastase and oxygen free radical initiated myocardial lipid peroxidation in coronary sinus blood during reperfusion after cardioplegic cardiac arrest. The elastase-alpha-1-proteinase inhibitor complex and malondialdehyde (a byproduct of myocardial lipid peroxidation) were measured in arterial, central venous and coronary sinus blood samples in 19 patients undergoing elective coronary artery bypass grafting before aortic crossclamping and 1, 5, 10 and 20 m in after aortic declamping. Malondialdehyde concentrations did not increase significantly during the study period, whereas elastase concentrations showed a significant increase during cardiopulmonary bypass in arterial, central venous as well as coronary sinus blood. Neither elastase nor malondialdehyde concentrations in coronary sinus blood differed significantly from arterial or central venous blood at any time point measured. Our data demonstrated increased elastase concentrations during cardiopulmonary bypass, but we did not find enhance intracoronary elastase release or myocardial during cardiopulmonary bypass, but we did not find enhanced intracoronary elastase release or myocardial lipid peroxidation. Our data suggest that patients are sufficiently protected from leucocyte mediated ischaemia reperfusion injury during uncomplicated coronary artery bypass grafting with cardioplegic arrest.

Adult↗
PubMed1995

[Bioprosthesis degeneration and reoperation in the aortic and mitral position].

In agreement with our experiences from our first study 15 patients (8 men, 7 women) underwent reoperation because of degeneration of bioprosthetic valves implanted in aortic or mitral position during the last 24 months. At reoperation 4 patients had a more complex cardiac procedure (double valve replacement, double valve replacement with bypass grafting, valve replacement with enlargement of the valvular area). There was no acute operation and only 1 patient was serious symptomatic preoperatively (NYHA IV). We revealed a mean implantation time of 126.4 months +/- 32.2 (median 130) for all bioprostheses without a significant difference in implant time regarding to aortic or mitral position. At reoperation bypass time (p = 0.001) and aortic clamp time (p = 0.011) was significantly longer compared to the first operation. There was no perioperative death, all patients are still alive and in good condition (8 of them NYHA I, 7 NYHA II). The early change of tissue degenerated bioprostheses can be carried out under elective conditions with improved postoperative outcome: mortality and morbidity remains acceptable low. In our group incremental risk factors for early mortality are severely affected patients with low functional status (NYHA IV) and acute operation. Preoperative coronary angiography remains essential for evaluation of concomitant coronary artery disease.

Adult↗
PubMed1995

[Standards in pediatric pacemaker therapy].

Despite differences between pediatric and adult pacing have narrowed, implantation procedures in children require special considerations. Patients are physically smaller, they often suffer from complex cardiac defects necessitating further open heart surgery procedures. As there are no pacemakers and only some electrodes designed specially for pediatric pacing, selection of appropriate systems is important. At this time we care for 18 patients with a mean age of 11.5 +/- 6.5 years (= 138.6 +/- 78.4 months, range 10 to 280 months). 50% of them received a permanent pacemaker because of surgically induced heart block, 33.3% because of congenital complete heart block and 16.7% because of sick sinus syndrome. Mean age at first pacemaker implantation was 57 +/- 42 months (Range 0 to 120 months). 72.2% of these children had their first pacing system implanted in the abdominal wall with an epicardial electrode, 27.8% had endovenous endocardial electrodes with subpectoral generator placement. 72.2% of our patients had already revisions of their pacing systems, mean longevity time of pulse generators were 36.8 +/- 21.8 months. Upgrading from single chamber pacing to physiological AV-sequential dual chamber pacing was performed at a mean age of 9.0 +/- 2.8 years (= 108.3 +/- 33.9 months, range 66 to 154 months). By reviewing our patient data we want to discuss present standards and guidelines of surgical pacemaker therapy in children and how to prevent potential complications.

Adolescent↗
PubMed1994

[Successful resuscitation in severe hypothermia following near-drowning].

A six-year-old boy fell into an ice-cold mountain stream and was immediately washed away. He was rescued 65 min later, 6 1/2 km downstream, seemingly lifeless with a rectal temperature of 16.4 degrees C. He was flown by helicopter to the surgical clinic of Innsbruck University, while resuscitation measures were undertaken by an accompanying doctor. After cannulation of the femoral artery and vein, extracorporeal circulation (ECC) with a child-size oxygenator was started and the blood rewarmed over 96 min in steps of 3 degrees C. Once circulatory stability and adequate cardiac output had been achieved ECC was gradually discontinued while the patient was still slightly hypothermic. Ten months after the accident the boy is restored to health, except for minimal residual neurological signs. There is a high chance for full neurological recovery.

Brain Damage, Chronic↗