Search PubMed⌕ Search

Biomedical subjects

A Diegeler

Publications and source records attributed to A Diegeler.

At least 55 records · Page 3Linked to original sources
PubMed1998

Solidus of Earth's deep mantle

The solidus of a pyrolite-like composition, approximating that of the lower mantle, was measured up to 59 gigapascals by using CO2 laser heating in a diamond anvil cell. The solidus temperatures are at least 700 kelvin below the melting temperatures of magnesiowustite, which in the deep mantle has the lowest melting temperatures of the three major components-magnesiowustite, Mg-Si-perovskite, and Ca-Si-perovskite. The solidus in the deep mantle is more than 1500 kelvin above the average present-day geotherm, but at the core-mantle boundary it is near the core temperature. Thus, partial melting of the mantle is possible at the core-mantle boundary.

Journal Article↗
PubMed1998

Minimally invasive coronary artery bypass grafting without cardiopulmonary bypass: early experience and follow-up.

BACKGROUND: There is renewed interest in coronary artery bypass grafting without cardiopulmonary bypass using the anterolateral minithoracotomy approach. We evaluated 209 patients who underwent minimally invasive direct coronary artery bypass grafting using an anterolateral minithoracotomy. The anastomosis was performed under direct vision on the beating heart without using cardiopulmonary bypass. METHODS: The procedure was performed using a 6- to 9-cm left (or right) anterolateral thoracotomy for internal thoracic artery graft harvesting and anastomosis. Different devices were used for local immobilization. In 195 patients a single internal thoracic artery to left anterior descending coronary artery bypass was performed, in 3 patients a single right internal thoracic artery to right coronary artery bypass, and in 11 patients the radial artery was used together with the internal thoracic artery as a T-graft. RESULTS: Conversion to sternotomy or cardiopulmonary bypass was necessary in 10 (4.7%) patients. Intraoperative myocardial infarction was observed in 4 patients (1.9%). Early postoperative redo operation was necessary in 5 patients (2.4%). Mortality was 0.47%. Postoperatively, 191 patients (91.3%) underwent angiography for graft patency control. The overall patency rate was 97.3%. Minor stenosis of the internal thoracic artery graft was observed in 18 patients (9.4%); moderate stenosis was observed in 5 patients (2.6%). Midterm angiographic follow-up after 6 months was performed in 58 patients. The patency rate was 98.2%. One patient with severe symptomatic stenosis (1.7%) underwent reoperation. CONCLUSIONS: With the help of the local immobilization systems off-pump coronary artery bypass grafting was safely performed through a minithoracotomy. The incidence of intraoperative and postoperative complications was low and follow-up showed good results. Thus, minimally invasive direct coronary artery bypass grafting is an excellent technique for arterial revascularization in patients having symptomatic left anterior descending coronary artery disease.

Adult↗
PubMed1998

Comparison of different anticalcification treatments for stentless bioprostheses.

BACKGROUND: New anticalcificant treatments have been developed because tissue calcification is a major contributing factor for bioprosthetic valve failure. METHODS: Aortic valve leaflet and aortic root tissue samples from stentless bioprostheses treated with No-React (Biocor, Belo Horizonte, Brazil), AOA (Medtronic freestyle, Minneapolis, MN), and BiLinx (St. Jude Medical, St. Paul, MN) were compared to a control group by subcutaneous implantation in 60 male weanling Sprague-Dawley rats. RESULTS: Calcium levels were in the range of 0.3 to 2.2 mg/g dry tissue at 3 and 12 weeks in all three treated aortic valve leaflet implants. The BiLinx treatment proved anticalcificant effectiveness on aortic root samples as well. There were statistically significant differences for valve leaflet tissue samples: No-React = AOA < BiLinx < < Control and for aortic root tissue samples: BiLinx < < AOA < Control = No-React. CONCLUSION: Calcification of aortic valve leaflets was significantly reduced by all new anticalcificant treatments. Inhibition of cellular calcification (BiLinx) resulted in additional reduction of aortic root calcification. Maximum anticalcificant properties upon both leaflet and aortic root is important as these are considered a functional unit in stentless bioprostheses.

Aluminum↗
PubMed1998

Minimally invasive port-access mitral valve surgery.

OBJECTIVES: This study evaluates the feasibility of video-assisted minimally invasive mitral valve surgery by means of the Port-Access system. The aim of the study was to minimize surgical access and to develop a video-assisted surgical technique. METHODS: The Port-Access system allows for closed chest endoluminal aortic clamping, cardioplegic arrest, and decompression of the heart. The mitral valve was either repaired (n = 28) or replaced (n = 23) in 51 patients by means of a minimally invasive approach through a right lateral minithoracotomy and under videoscopic guidance. RESULTS: Mean length of incision was 5.4 +/- 1.8 cm (range 3.8 to 8 cm). Mean duration of operation, cardiopulmonary bypass, and crossclamp time was 196 +/- 53, 133 +/- 52, and 72 +/- 27 minutes, respectively. Median intubation time was 25.5 hours (range 5 to 264 hours). Median duration of intensive care and hospital stay was 2 days (range 1 to 36 days) and 13 days (10 to 36 days), respectively. Hospital mortality was 9.8% (5/51). Overall morbidity was relatively high. In two patients acute retrograde aortic dissection led to conversion of the procedure. At follow-up (261 +/- 13 days), three patients required reoperation for paravalvular leakage. Baseline mean Duke activity index score was 19.3 +/- 11.3 before the operation and increased to 23.2 +/- 10 at 6 weeks' and 24.2 +/- 10.3 at 12 weeks' follow-up, respectively. CONCLUSION: The Port-Access system allows for video-assisted minimally invasive replacement and complex repair of the mitral valve through a right lateral minithoracotomy. However, morbidity and mortality associated with this novel technique were high.

Aged↗
PubMed1998

Transmyocardial laser revascularization using the Holium-YAG laser for treatment of end stage coronary artery disease.

OBJECTIVE: Transmyocardial Laserrevascularization (TMLR) is a treatment for end-stage coronary artery disease, that is not eligible for surgery or PTCA. The experience with TMLR using the Holium YAG laser is presented. METHODS: Transmyocardial Laserrevascularization (TMLR) was performed in 28 patients with end stage coronary artery disease, using a new Holium YAG Laser. All patients were refractory to a maximum of medical treatment. In 16 patients TMLR was used as the sole therapy with a mean of 28 +/- 4 laser created channels (group A). In 12 patients TMLR was combined with coronary artery bypass graft surgery with a mean of 17 +/- 2 channels and 1.3 +/- 0.2 grafts (group B). Preoperative and postoperative examination included angina classification, exercise test and thallium scan. RESULTS: Postoperative demographics were as follows: (a) age 55-71 years (mean 63.9 +/- 6.5 years); (b) Canadian Cardiovascular Society Angina Scale (CCS) mean 3.3 +/- 0.5; (c) ejection fraction 35-71% (mean 54 +/- 13.7%). All patients had an peri- and postoperative course without major complications and a duration of hospitalization of 8.2 +/- 1.9 days. Minor complications were a clinically silent myocardial infarction n = 1, atrial arrhythmia n = 2 and pneumothorax n = 2. A follow-up at 3-12 months was completed in 23 patients (82%). Only one patient died 5 months after surgery (cardiac related death). In all remaining patients CCS had improved with a mean of 1.6 +/- 0.3, P < 0.01. The exercise tolerance test (bicycle) improved in 17 patients with a mean 26.5 +/- 6.5 watt, P < 0.01. The ejection fraction did not significantly improve. The repeated thallium scan did not show an improvement of perfusion in the lasered area to a significant level. Subjective benefit from the treatment was confirmed by 21 patients. CONCLUSION: Based on these results it is concluded that TMLR with the Holium-YAG laser is a safe therapy for the treatment of end stage coronary artery disease. The postoperative clinical results are comparable to that achieved with the CO2-laser in terms of reducing angina symptoms and improving exercise tolerance and quality of life. However. relief of symptoms is not correlated to objective findings of cardiac function.

Adult↗
PubMed1998

Less-invasive coronary artery bypass grafting: different techniques and approaches.

OBJECTIVE: The aim of this study was to compare four different techniques for less-invasive coronary artery bypass surgery with and without cardiopulmonary bypass (CPB) in terms of feasibility as well as in terms of the intra- and postoperative course. METHODS: One hundred and fourteen patients were divided into four groups, according to the surgical technique. Group I: minithoracotomy, internal thoracic artery (ITA) harvesting and anastomosis under direct vision using cardiopulmonary bypass (CPB) on the fibrillating heart (n = 31). Group II: sternotomy and beating heart without CPB (n = 13). Group III: MIDCAB with CPB and cardioplegic cardiac arrest using endo-aortic balloon-occlusion, Port Access system (n = 9). Group IV: MIDCAB on the beating heart without CPB (n = 61). In total, 104 single and ten double graft procedures were performed using the radial artery T-graft technique in seven cases (groups III and IV). RESULTS: Harvesting of the ITA graft took 41+/-16.2 min in group I and could be reduced to 31+/-8.3 min in group IV by the use of a specially-designed retractor. Complications were: death (n = 1, group I), myocardial infarction, (n = 1, group I), early occlusion of the graft (n = 1, group IV), early stenosis of the anastomosis (n = 2, groups I and IV), late stenosis of the anastomosis (n = 1, group IV), thrombosis of the femoral vein (n = 1, group III). Postoperative ventilation, ICU and hospital stay were similar among groups. CONCLUSIONS: Based on our results, the following strategy has been developed: MIDCAB without CPB is the preferred technique for one-vessel graft procedures to the left anterior descendens (LAD) or RCA. The Port Access system (with CPB) is reserved as a second option for young patients requiring multiple-vessel grafting to the left coronary circulation (LAD/CX) and as a backup to avoid conversion. Sternotomy and an off-pump technique is used for single-vessel or multiple-vessel graft procedures in selected patients (emergency procedure, acute myocardial infarction, in the very obese).

Algorithms↗
PubMed1998

S-shaped in comparison to L-shaped partial sternotomy for less invasive aortic valve replacement.

OBJECTIVE: Evaluation of less invasive aortic valve replacement to minimize surgical trauma and achieve a better postoperative quality of life. METHODS: Thirty-three patients had aortic valve replacement using a 4-6 cm small incision and partial sternotomy only. Partial sternotomy was performed proximal (16), S-shaped (14) or horizontal (3). Access for cardiopulmonary bypass was via sternotomy (24) or the right femoral vessels (9). Patient age was 58+/-13 years, 21 had aortic stenosis and 12 aortic incompetence. RESULTS: Surgical exposure was sufficient and allowed for uncomplicated AVR in all patients. Mechanical valves (20), conventional bioprostheses (3), stentless bioprostheses (9) or a homograft (1) were implanted. Crossclamp time was not prolonged in comparison to the conventional technique. Intensive care stay and hospital stay were 1 and 10 days, respectively. One patient had to be reoperated for paravalvular leakage, two patients (horizontal sternotomy) had sternal dehiscence. Postoperative pain was low in most patients. CONCLUSION: Less invasive aortic valve replacement is feasible with good functional results. The S-shaped sternotomy approach is advantageous whereas the horizontal sternotomy is no longer performed due to a high rate of instability. This new technique will be further evaluated in comparison to the conventional approach.

Aortic Valve↗
PubMed1998

An experimental approach to quantitative thermal coronary angiography.

Thermal coronary angiography is a noninvasive but not yet quantitative method to intraoperatively assess graft patency in CABG surgery. Aim of this study was to quantify graft flow by measuring perfusion-induced myocardial temperature changes over time. Saphenous vein grafts to the left anterior descending artery were perfused at flow rates of 16-105 ml/min with warm saline. A thermal scanner with a 256 x 256 focal-plane array detector providing a spatial resolution of 1.2 mrad was used. The resulting temperature curves were averaged and a non-linear fit procedure was performed to calculate the time constant (tau) at each flow rate. An increase of myocardial temperature along the LAD with different flow rates could be demonstrated. There was an excellent correlation between the calculated time constant and actual flow (r = 0.96, p < 0.0002). By determining the time constant for different flow rates an estimate of actual graft flow is possible using thermal coronary angiography. Clinical studies have to show if the time constant can be used as a predictor of graft flow in patients.

Animals↗
PubMed1998

Changes of leukocyte subsets in coronary artery bypass surgery: cardiopulmonary bypass versus 'off-pump' techniques.

BACKGROUND: The use of cardiopulmonary bypass (CPB) in coronary bypass grafting is associated with a generalized inflammatory response. This negative impact of CPB may be avoided by using new surgical techniques recently introduced to perform coronary bypass grafting 'off-pump', i.e. without CPB. METHODS: Since the specific effects of CPB on the immunorelevant cells have still not been fully investigated, we measured the changes in leukocyte subsets of the circulating blood in patients who underwent coronary bypass surgery with a conventional sternotomy approach and CPB (group A, n = 10), in patients who underwent the same surgical procedure but without CPB (group B, n = 10), and in patients who underwent a minimally invasively performed single bypass to the left anterior descending artery (LAD) (group C, n = 10). RESULTS: Leukocyte subsets showed a similar change during and after coronary bypass grafting in all three groups. The total number of leukocytes was increased soon after reperfusion in the CPB group. A similar but delayed increase was observed in both off-pump groups. Changes in lymphocyte subsets and T-lymphocyte subsets were similar in all three groups, with a drop of lymphocytes during the first 24 postoperative hours mainly caused by a drop of T4-helper cells. CONCLUSION: The results indicate a reaction of the leukocyte subsets to coronary bypass surgery which is more related to the surgical trauma in general than to CPB in particular.

Aged↗
PubMed1997

Thermal coronary angiography for intraoperative testing of coronary patency in congenital heart defects.

Intraoperative thermal coronary angiography was successfully applied in 9 patients who underwent operative correction of congenital heart defects: arterial switch operation for transposition of the great arteries (n = 5), Ross operation for valvar aortic stenosis with regurgitation (n = 3), and aortic implantation of the left coronary artery for anomalous connection of the left coronary artery to the pulmonary artery (n = 1). Intraoperative thermal coronary angiography allows early detection and surgical correction of coronary ostial obstruction.

Coronary Angiography↗
PubMed1997

Instantaneous subaortic outflow obstruction after volume reduction in hearts with univentricular atrioventricular connection and discordant ventriculoarterial connection.

OBJECTIVE: To study the phenomenon of potential subaortic outflow obstruction after surgical volume unloading of the heart in patients with univentricular atrioventricular connection, discordant ventriculoarterial connection, and bulboventricular foramen (BVF)-dependent systemic flow. MATERIAL AND METHODS: Intraoperative transesophageal echocardiography was used in five patients with tricuspid atresia (N = 3) or double-inlet left ventricle (N = 2) with rudimentary right ventricle and BVF who were scheduled to undergo a bidirectional cavopulmonary anastomosis (N = 3) or completion of the Fontan procedure after previous banding of the pulmonary artery (N = 2). The BVF diameter was measured in two orthogonal views, and the area was calculated by using the formula for an ellipse. Left ventricular posterior wall thickness and left ventricular internal diameter were also measured. Intraoperative prerepair and postrepair gradients across the BVF were measured by echocardiography. RESULTS: Volume unloading of the left ventricle resulted in instantaneous contraction of left ventricular size (decrease of median left ventricular internal diameter from 38 to 34 mm and increase of median left ventricular posterior wall thickness from 5 to 7 mm), decrease of median BVF area index (from 1.82 to 1.55 cm2/m2), and development of a median gradient of 60 mm Hg across the BVF. At a mean follow-up of 19.6 months, all patients were clinically well and had no echocardiographic evidence of BVF obstruction. CONCLUSION: In hearts with univentricular atrioventricular connection, discordant ventriculoarterial connection, and BVF-dependent systemic flow, a decrease in ventricular volume is associated with an instantaneous alteration in ventricular geometry, diminution in BVF size, and potential for subaortic outflow obstruction. Intraoperative transesophageal echocardiography is of paramount importance in excluding development of subaortic outflow obstruction in this setting.

Anastomosis, Surgical↗
PubMed1997

Stentless valve replacement in the small aortic root.

Despite the variety of different artificial heart valves available, no ideal prosthesis for the small aortic root has yet been identified. The aim of this study was to evaluate the haemodynamic performance and clinical outcome after stentless aortic valve replacement. A total of 70 patients with a small aortic root underwent Toronto (n = 61) or Freestyle (n = 9) stentless aortic valve replacement. All but three patients had aortic stenosis. Mean (s.d.) age at operation was 71.2(7.9) years. The mean annular diameter was 21.4(1.2) mm. Using controlled oversizing adjusting valve size to the sinotubular junction diameter, a 23-mm prosthesis was implanted in 23 patients and a 25-mm prosthesis in 47 patients. The maximum pressure gradient was 19.1(6.8) mmHg and effective valve orifice area was 1.47(0.27) cm2. At discharge and at follow-up, all patients were in New York Heart Association class I or II. At follow-up there was a significant reduction in pressure gradients, an increase in effective valve orifice areas, and decrease of pre-existing left ventricular hypertrophy. In conclusion, with controlled oversizing a gain in prosthesis size of 2 to 4 mm can be achieved. Implantation of oversized stentless valves leads to improved haemodynamics and to left ventricular remodelling in patients with a small aortic root.

Aged↗
PubMed1997

Budd-Chiari syndrome as late complication of secundum atrial septal defect closure.

A young adult patient, in whom 20 years previously a secundum atrial septal defect had been closed surgically, presented with symptoms of a Budd-Chiari syndrome, cirrhosis of the liver, ascites, and edema of the lower legs. The inferior vena cava-right atrial junction was obstructed by a calcified Teflon patch and shrinkage of the surrounding tissue. Augmentation of the inferior vena cava-right atrial junction with a Gore-Tex patch resulted in unobstructed inflow into the right atrium.

Adult↗
PubMed1997

Influence of short-term ischemia on segmental spinal cord reflex functions in cats.

In the lumbar spinal cord in cats, microcirculatory (laser Doppler flowmetry) and segmental neurophysiological parameters [monosynaptic reflexes of a flexor and extensor, polysynaptic reflexes from a cutaneous nerve, and the cord dorsum potential (CDP)] were determined in context with ischemias of 1-10 min. Ischemias were achieved by aortic snare occlusion of the descending aorta and were pooled into deep and moderate ones (0-20% and 20-50% residual spinal cord blood flow). Three phases of reaction to ischemia were defined: a period of decreasing responses, a period of delay until recovery, and a recovery period from beginning to completeness of recovery. Although the period of decreasing responses was relatively constant, the delay until recovery could be correlated with duration and depth of ischemia. The recovery period depended mainly on the duration of ischemia. For 2-6-min ischemias, the correlation between depth and duration of ischemia to the delay until recovery or to the recovery period tended to be linear. The period of decreasing responses, the delay until recovery, and the recovery period of mono- and polysynaptic reflexes behaved in a comparable way and demonstrated similar susceptibility to ischemia. The CDP turned out to be the most stable response, indicating a higher resistance of the first-order interneurons to ischemia than of motor neurons.

Animals↗