Biomedical subjects

Axel Nötzold

Publications and source records attributed to Axel Nötzold.

4 recordsLinked to original sources

PubMed2006

Microemboli in aortic valve replacement.

Microembolic signals (MES) can be detected in many recipients of mechanical aortic valve prostheses by transcranial Doppler ultrasound. The nature and etiology of these MES have remained unclear for a long time. The solid and gaseous nature of MES are discussed, as well as whether or not MES may reflect artifacts. Recently, the gaseous nature of these MES has been widely established. To understand the physics of bubble formation related to mechanical heart valve prostheses, it is necessary to discuss the different types of cavitation occurring at the prostheses and the conditions leading to the degassing of blood. We describe the history of transcranial Doppler ultrasound-techniques and the current techniques in the measurement of these signals. Furthermore, the possible clinical impact of MES, as well as strategies for the design of new prostheses and surgical alternatives to diminish their load are discussed.

Aortic Valve↗

PubMed2005

In-vitro study on the relationship between progressive sinotubular junction dilatation and aortic regurgitation for several stentless aortic valve substitutes.

OBJECTIVE: Stentless aortic valves are widely used due to their excellent hemodynamic properties. However, if the subcoronary implantation technique is used later dilatation of the sinotubular junction (STJ) can cause regurgitation. The aim of the study was to determine the dilatation tolerance of two commercially available stentless xenografts and fresh aortic and pulmonary roots against such dilatation. METHODS: Four groups each comprising five specimens of fresh porcine aortic roots, pulmonary roots, Medtronic freestyle or Toronto SPV Xenografts were tested in a mock circulation using a special device for gradually increasing the diameter of the sinotubular junction. The smallest diameter D(r) where regurgitation occurs was measured and correlated with the starting diameter D(a) and expressed as per cent values. Opening and closing patterns were obtained by a high speed camera and flow characteristics were determined. RESULTS: The highest dilatation tolerance of STJ was found in the fresh porcine aortic roots (165%+/-10) followed by fresh pulmonary roots (146%+/-12), the Freestyle (143%+/-4) and the SPV (132%+/-5) bioprostheses. All differences were significant with P< or =0.05 except that between the fresh pulmonary roots and the two commercial available bioprostheses. CONCLUSIONS: Our results indicate that aortic homografts provide higher resistance against regurgitation induced by dilatation of the STJ than an autograft or the stentless xenografts, Freestyle xenograft followed by the Toronto SPV. The use of the full-root technique should be considered if aortic dilatation seems to be likely.

Aortic Valve↗

PubMed2004

Emergency endovascular stent-grafting for life-threatening acute type B aortic dissections.

BACKGROUND: There is still a considerable controversy regarding optimal treatment for patients with acute type B aortic dissection. Patients with complicated disease are particularly challenging for cardiovascular treatment. Early surgery for acute dissections of the descending aorta with life-threatening complications is known to carry a high mortality. Endovascular stent grafting is developing as an alternative treatment mainly for chronic stages of type B aortic dissection. It is not clear whether endovascular stent grafting is safe and effective in emergency treatment of acute type B aortic dissection. METHODS: In 10 patients (7 men, 3 women; mean age, 59.2 years; range, 46 to 65 years), endovascular stent grafting was performed within 11.0 +/- 5.9 hours (range, 4 to 24 hours) of diagnosis of complications. Indications for acute intervention included contained rupture, hematothorax, life-threatening malperfusion, and refractory pain. Using a retrograde endovascular route after surgical exposure of the femoral artery, self-expanding stent prostheses consisting of polyester-covered Nitinol (Talent, World Medical; mean diameter, 40 +/- 4 mm; length, 10 cm) were placed into the descending aorta distal to the subclavian artery. Before discharge and on follow-up visits, imaging of the aorta was performed using computed tomography. RESULTS: In 9 of 10 patients (90%), the primary entry could be completely occluded with the endovascular stent. Early mortality was 20% (2 of 10): 1 patient died after disruption of the intimal layer distal to the stent, and 1 patient died in hemorrhagic shock after surgical fenestration of the abdominal aorta for persistent malperfusion. Three patients (30%) required consecutive surgical treatment: indications included acute development of retrograde type A aortic dissection, acute stent dislocation by fractured wires and secondary leakage, and late formation of an aneurysm of the descending aorta 6 months after endovascular stent grafting. There were no surgical or late deaths. CONCLUSIONS: Our experience provides some evidence that early mortality of life-threatening acute type B aortic dissection may be reduced by emergency endovascular stent grafting and that this form of treatment is a promising therapeutic option. Refinements, especially in stent design and application, may further improve the prognosis of patients in the life-threatening situation of complicated acute type B aortic dissection.

Acute Disease↗

PubMed2002

Early elevation of S-100B protein in blood after cardiac surgery is not a predictor of ischemic cerebral injury.

BACKGROUND: We hypothesized that early changes in S-100B levels after cardiac surgery are nonspecific and mostly reflect damage to tissues outside the brain rather than ischemic brain damage. METHODS: We measured serum levels of S-100B at several times perioperatively in 21 patients undergoing cardiac surgery. In addition, we measured levels of neuron specific enolase (NSE), glial fibrillary acidic protein (GFAP), creatine kinase (CK), the cardiac isoenzyme of CK (CK-MB), and myoglobin (MB) in these patients. RESULTS: Early increases in serum S-100B concentration were significantly (p<0.01) correlated with increases in markers of tissue injury outside the brain: S-100B/CK: r(2)=0.69; S-100B/CK-MB: r(2)=0.64; S-100B/myoglobin: r(2)=0.60; S-100B/NSE: r(2)=0.51; CK/NSE: r(2)=0.60; CK-MB/NSE: r(2)=0.59; and myoglobin/NSE: r(2)=0.54. CONCLUSIONS: Our findings indicate that increases in S-100B in the early phase after cardiac surgery are not due to release of S-100B from brain alone but also from tissue outside the brain.

Aged↗