PubMed Health⌕ Search

Biomedical subjects

J Laas

Publications and source records attributed to J Laas.

At least 19 recordsLinked to original sources
PubMed2000

Downstream turbulence and high intensity transient signals (HITS) following aortic valve replacement with Medtronic Hall or St. Jude Medical valve substitutes.

OBJECTIVE: High intensity transient signals (HITS) representing microembolization to the brain have been found to contribute to cognitive impairment and psychoneurological dysfunction in patients carrying a mechanical aortic valve. It is unknown, whether HITS represent gaseous or solid emboli. This animal study evaluates the impact of valve orientation on HITS for two different mechanical valves with both valves implanted in their best and worst orientation, which has been defined in previous studies with respect to downstream turbulence. METHODS: In four pigs a rotation device carrying either a Medtronic Hall (MH) or St. Jude Medical (SJM) valve size 23 mm was implanted. The device allowed rotation of the implanted valves without reopening of the aorta. Approximately 30 min after weaning from extracorporeal circulation, a Doppler probe was placed on both common carotid arteries. In different orientations of the implanted valves (best and worst position), HITS were detected by the Doppler probe and recorded for ten min by a transcranial Doppler sonography device (Medilab Inc., Estenfeld, Germany). RESULTS: HITS showed significant change with rotation for both valve designs. With the major orifice of the MH oriented towards the non-coronary leaflet (optimum position) very low HITS-counts (0.8-1.7/min) were observed. In the worst orientation HITS rose to 43-66/min. For the SJM the HITS count in the optimum position was 23.4-24/min and in the worst orientation 38-48/min. CONCLUSIONS: Valve orientation has an important impact on microembolization to the brain. In the optimum orientation (large orifice facing the non-coronary leaflet) the Medtronic Hall valve showed negligible incidence of HITS. The St. Jude Medical bileaflet valve showed less variation but demonstrated significant HITS counts at any orientation. As the MH in the worst position shows significantly higher turbulent stresses than the SJM but no higher incidence of HITS, a strong correlation between turbulence and HITS was not demonstrated by this study.

Animals↗
PubMed2000

Tilting disc versus bileaflet aortic valve substitutes: intraoperative and postoperative hemodynamic performance in humans.

BACKGROUND AND AIM OF THE STUDY: Due to an asymmetrical/eccentric flow profile at the level of the aortic valve, there is an optimal orientation for each aortic valve design. This study evaluates intraoperative flow dynamics (turbulence and pressure gradient) and follow up results (pressure gradient and left ventricular mass regression) for Medtronic Hall tilting disc (MH) and St. Jude Medical bileaflet (SJM) valves, with both valves in their optimum orientation as defined in previous animal experiments. METHODS: In a randomized prospective study, MH and SJM valves (size > or = 23 mm) were implanted in their optimum orientation in 24 patients with aortic stenosis. Turbulence measurements were performed intraoperatively via a perivascular ultrasound transducer; Reynold's normal stress (RNS) values were calculated as key markers for turbulent stresses. Transvalvular pressure gradients, interventricular septum and posterior wall thickness were measured by transesophageal echocardiography intraoperatively and six months postoperatively. RESULTS: Mean valve size was 23.8 mm in both groups. Intraoperative RNS values (MH 7.5 +/- 2.2 N/m2 versus SJM 9.8 +/- 2.3 N/m2) and pressure gradients (MH 10.0 +/- 2.6 mmHg versus SJM 20.0 +/- 3.4 mmHg) were significantly lower for the tilting disc valve. At six months follow up, pressure gradients were reduced by half for both valves (MH 5.3 +/- 1.7 mmHg; SJM 10.4 +/- 2.3 mmHg), with the difference between the valves being maintained. Left ventricular mass regression was accelerated for MH patients with regard to interventricular septum thickness. CONCLUSION: Our results indicate that the tilting disc mechanism shows superior hemodynamic performance with respect to turbulence and transvalvular pressure gradients compared with the bileaflet mechanism when both valves are implanted in their optimum orientation. This led to significant acceleration of interventricular septum mass regression. The superiority of the tilting disc mechanism is more pronounced in the smaller-sized valves.

Aged↗
PubMed1999

Orientation of tilting disc and bileaflet aortic valve substitutes for optimal hemodynamics.

Procedures for implantation of mechanical aortic valves have to consider eccentric flow in the aortic root. We describe how to optimize orientation of tilting disc (Medtronic Hall) and bileaflet (St. Jude Medical) valves. In tilting disc valves, an asymmetric design faces an asymmetric flow. Hemodynamic performance of this valve type, regarding turbulence and pressure gradients, is close to normal physiology and superior to the bileaflet valve design. This difference is more pronounced the smaller the valve size.

Aortic Valve↗
PubMed1998

[Increased acceptance of the International Normalized Ratio (INR) as a monitoring parameter of oral anticoagulation therapy in Germany. GELIA Study Group].

In 1994 the German Cardiac Society recommended the International Normalized Ratio (INR) instead of "Quick's test" for the long-term management of oral anticoagulation therapy. Parallel cardiac surgical centers in Germany and Switzerland started patient recruitment for the GELIA study (German Experience with Low Intensity Anticoagulation). By the end of 1996, 862 consecutive patients with mechanical heart valve replacement had been enrolled. According to the protocol of the GELIA study, intensity of anticoagulation, methods used to control the oral anticoagulation therapy as well as other factors relevant for the anticoagulation management are reported every three months. The so far accumulated data material of the GELIA study seemed, therefore, appropriate to analyze potential changes in the acceptance of INR during the time period 1993-1996. Potential differences in the anticoagulation management were analyzed separately according to the time of enrollment of patients and changes during the follow up period, e. g., a switch from "Quick's test" to INR. Taking the time of enrollment into account, the percentage of patients who had INR-controlled oral anticoagulation therapy increased from 0% (1993), 14.3% (1994), 63.2% (1995) to 74.2% in 1996. During the follow up, there was a change from "Quick's test" to INR controls in 7 patients (1994; 2.1%), 67 patients (1995; 10.5%) and 142 patients (1996; 17.3%) with a consequent increase of INR controlled patients to a total of 34.2% in 1994, 52.0% in 1995, and 73.9% in 1996.

Administration, Oral↗
PubMed1998

Medtronic Hall versus St. Jude Medical mechanical aortic valve: downstream turbulences with respect to rotation in pigs.

BACKGROUND AND AIMS OF THE STUDY: Turbulences downstream of mechanical aortic valves are known to contribute to most valve-related complications such as thrombosis, embolization or damage to blood components. In vitro studies have demonstrated the impact of the orientation of prostheses on transvalvular energy loss. This study evaluates the influence of valve orientation on turbulences in the supravalvular aorta in pigs. METHODS: A rotation device which could carry a Medtronic Hall (MH) or St. Jude Medical (SJM) aortic valve prosthesis (23 mm) was constructed and implanted into four healthy pigs. Turbulence measurements using pulsed Doppler ultrasonography were carried out 3 cm downstream of the valve, while the prostheses were rotated in 45 degrees steps. Reynold's normal stress values (RNS) were calculated as key markers for turbulent stresses. RESULTS: Turbulences downstream of MH and SJM valves demonstrated a significant change with rotation. The MH valve showed minimum RNSmean values with orientation of the large orifice to the right posterior aortic wall, which is the area of highest velocities during ejection. With this orientation, aortic flow almost complied with physiologic conditions. Increase of turbulence was observed with any other position. The SJM valve revealed significant turbulent flow at any orientation. Minimum RNSmean values were also measured with one orifice facing the right posterior wall of the aorta. CONCLUSION: With optimum orientation (major orifice facing the right posterior aortic wall) the MH valve matches the aortic flow pattern to near-normal physiology. The flow patterns of the SJM valve are less susceptible to rotation, but cannot attain the optimum RNS values of the MH prosthesis.

Animals↗
PubMed1996

Hydrodynamic function of tilting disc prostheses and bileaflet valves in double valve replacement.

OBJECTIVE: To determine the energy loss attributable to prosthetic valve size and design in double valve replacement, energy consumption of mitral valves (size #25 to #29), of two different designs (Bjork Shiley tilting disc and Carbomedics bileaflet valves), in combination with a small (#21) and large sized (#27) aortic prosthesis, were analyzed in a flow simulator. METHODS: A pulsatile flow simulator was used to reproduce physiological ventricular dynamics and to match the input and output impedances of the human left ventricle. Hydrodynamic performance was determined as stroke work, closing work and leak work for each combination of valves at low flow (5 liters per minute) and high flow (9 liters per minute) conditions. RESULTS: At low flow no decrease of energy requirement was found with the use of a mitral valve larger than #25. At high flow the #27 and #29 mitral valves required less energy compared to a #25 mitral valve, in combination with a large aortic prosthesis. The #29 mitral prosthesis revealed similar results as the #27. With the use of a large aortic prosthesis a remarkable reduction of total flow work was shown. These results were found in both designs. In comparison of the two designs, tilting disc valves required more energy for stroke and closure of the valve, although less energy for leakage. In total, energy requirements were higher for tilting disc valves. COMMENTS: A hydrodynamic advantage for the use of a mitral valve larger than #25 was found only with the combination of a large aortic prosthesis and high flow. Hydrodynamic data favor the use of bileaflet prosthesis especially for a patient who is expected to exercise.

Aortic Valve↗
PubMed1994

Efficient tissue gluing in aortic dissection.

The authors' method for uniting the dissected aortic wall layers with the help of gelatine-resorcinol adhesive is described focusing on special instruments used in this conjunction.

Aortic Dissection↗
PubMed1994

Malperfusion of the thoracoabdominal vasculature in aortic dissection.

Ischemic damage to vital organs supplied by the thoracoabdominal aorta greatly increases the overall risk of aortic dissection. Of 320 patients operated upon for aortic dissection since 1985, 33 (10.3%) underwent operations directed at the relief of malperfusion (15/158 acute type A; 9/18 acute type B; 4/78 chronic type A; 5/66 chronic type B). Organs affected were the kidneys in 32; the bowel in 20; and the spinal cord in 1, while critical lower extremity ischemia was present in 11 patients. In total, 64 vascular areas were affected. Fenestration of the dissecting membrane with or without infrarenal grafting was the procedure performed most frequently in 25, followed by replacement of the descending or thoracoabdominal aorta in 6, and bypass grafting or direct revascularization of individual side branches in 6. Six other operations targeted at the affected organs were done. Twenty-four patients underwent one-stage operation for malperfusion; in 11, early reoperation after primary aortic repair was necessary, while 2 patients were operated electively. Ten of 33 patients died in hospital, 7 of malperfusion-induced complications. Of three late deaths, one was related to sequelae of malperfusion. We conclude that immediate diagnosis and prompt relief of malperfusion offer the best prospects for patient survival. Membrane fenestration appears to be the method of choice for treating malperfusion in most patients, and must be directed to the level of aortic and/or side branch obstruction.

Aortic Dissection↗
PubMed1994

Hydrodynamic performance of Carbomedics valves in double valve replacement.

Most patients undergoing double valve replacements have reduced myocardial capacity. However, little is known about the influence of valve sizes on myocardial energy consumption in double valve replacement. This study was designed to supply hydrodynamic data for the proper selection of sizes in double valve replacement. A mock loop system was used to measure the energy consumption of CarboMedics valves at conditions resembling rest (5 L/min) and moderate exercise (9 L/min). All combinations of aortic valves size #21 to #27 with mitral prosthesis sizes #25 to #29 were tested separately. Larger size aortic prostheses revealed remarkably less energy consumption up to size #27. Under high flow (9 L/min) this effect was more pronounced. In contrast, mitral valve prosthesis sizes #25 to #29 had similar hydrodynamic data. At low flow conditions (5 L/min) no significant benefit was found with the use of a larger mitral valve. Only a reduction of less than 10 percent of total energy consumption could be achieved with the use of a mitral valve larger than #25 at 9 L/min flow. In conclusion there is no hydrodynamic reason for using a valve larger than #25 in the mitral position for patients who exercise moderately. Continuous reduction of cardiac work can be expected with the use of the largest possible aortic prosthesis up to size #27 at rest and at moderate exercise.

Aortic Valve↗
PubMed1994

Complicated Cogan's syndrome with aortic insufficiency and coronary stenosis.

We describe a case of Cogan's syndrome in a 19-year-old woman with tinnitus, deafness, interstitial keratitis, and complicating aortic insufficiency and coronary stenosis. Serological testing revealed IgG and IgA antibodies against Chlamydia trachomatis. In spite of very high antibody titers there was no direct evidence for C. trachomatis in her urogenital smears or in biopsies of her aortic adventitia, and therefore these findings are of uncertain significance. Reconstruction of the aortic valve and bypass surgery for an ostial stenosis of the left coronary artery were necessary. Ten months after starting cyclosporine treatment her course was stable and cochlear implant surgery was successfully performed.

Adult↗
PubMed1994

Risk of replacement of descending aorta with a standardized left heart bypass technique.

Replacement of the descending aorta for aneurysms (51%) and dissection (49%) was performed in 132 patients with a highly standardized left heart vortex-pump bypass. No adjuncts other than staged aortic clamping and intercostal artery reconnection were used to reduce spinal cord injury in extensive involvement. Four patients (3%) died early, two of cardiac cause, and nine (7%) died late. Complications of vital organ function occurred in eight patients, two having reversible renal failure and six spinal cord injury that was permanent in three (2.3%). Cord injury occurred only in replacement beyond thoracic segment 8 and could not be completely avoided despite distal intercostal artery reconnection in two cases; in the other four cases such vessels either did not appear worth reconnecting or were sacrificed in emergency operations. We conclude that left heart bypass effectively unloads the proximal circulation during aortic occlusion while maintaining adequate perfusion of distal vital organs as evidenced by low rates of early mortality and renal failure. The remaining risk of spinal cord damage may be lowered by more aggressive reconnection of all distal intercostal arteries and by extending the permissible cord ischemic period by means of hypothermia.

Adult↗
PubMed1993

Comparison of transthoracic and transesophageal echocardiography for detection of abnormalities of prosthetic and bioprosthetic valves in the mitral and aortic positions.

Two-dimensional echocardiography is the diagnostic procedure of choice for evaluation of prosthetic valve abnormalities. However, transthoracic echocardiography (TTE) may be limited owing to acoustic shadowing and poor acoustic windows. Some of these limitations may be overcome by transesophageal echocardiography (TEE). One hundred twenty-six patients with 148 prosthetic valves (113 bioprostheses and 35 mechanical devices) were studied by M-mode and 2-dimensional TTE and TEE. Prosthetic valve morphology was confirmed by surgery or autopsy in all cases; 124 prostheses were classified as diseased (33 endocarditis, 8 thrombi, and 83 degeneration defined as leaflet thickening > 3 mm with restricted motion) and 24 as normal. Prosthetic valve endocarditis and thrombi were correctly identified by TTE in 12 of 33 (36%) and 1 of 8 (13%) prostheses, respectively, but could be diagnosed by TEE in 27 of 33 (82%; p < 0.001) and 8 of 8 (100%; p < 0.01), respectively. Compared with TTE, TEE had a higher sensitivity for morphologic prosthetic valve abnormalities in patients with either bioprostheses (88 [87%] vs 66 [65%] of 101 prostheses; p < 0.01) or mechanical devices (19 [83%] vs 5 [22%] of 23 prostheses; p < 0.01) and in patients with a prosthesis in either the aortic (49 [77%] vs 32 [50%] of 64; p < 0.01) or mitral (58 [97%] vs 39 [65%] of 60; p < 0.001) position. Overall, sensitivity and specificity were 57 and 63%, respectively, for TTE, and 86 and 88%, respectively, for TEE.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Valve↗
PubMed1993

High incidence of aneurysm formation following patch plasty repair of coarctation.

Repair of aortic coarctation was performed in 152 adolescent and adult patients (mean age 28.5 years, range 14-67 years). Ninety patients were treated with patch plasty, 33 with end-to-end anastomosis, 18 with interposition of a tubular graft, 6 with prosthetic bypass and 5 with direct plasty. There were two (1.3%) early and ten (6.6%) late deaths after 2.9 to 11.8 (mean 6.6) years. Of the remaining 140 patients, 129 (92.1%) were reexamined with computed tomography and angiography after 1.5 to 17.2 (mean 9.1) years postoperatively. In 27 patients (35.1%) of the patch plasty group significant dilatation at the operative site was observed and reoperation for aneurysm formation was required in 15 patients (19.5%). Resection of the intimal crest did not increase the probability of aneurysm formation, whereas Dacron as patch material and late hypertension had a significant influence. Six of the ten late deaths occurred in the patch plasty group. Rupture of an aneurysm at the operative site was proved in two of these patients, and three patients died suddenly for unknown reasons. In the other groups significant dilatation was observed in 13 patients and 3 local aneurysms required reoperation (2 after end-to-end anastomosis and 1 after direct plasty). We conclude that patch plasty repair of coarctation should be abandoned in adults. End-to-end anastomosis is advisable only if possible without excessive tension. Reoperation with interposition of a tubular graft on left heart bypass proved to be a safe method.

Adolescent↗
PubMed1993

Three-dimensional vascular imaging--an additional diagnostic tool.

Angiography is still the standard for imaging of vascular structures. However, since the number of projections is limited, complex pathoanatomy may not be sufficiently visible. This study presents two patients in whom 3D reconstruction from Spiral CT data revealed combined vascular lesions undisclosed by angiography. In one case the combination of coarctation and chronic dissection type B, in another the combination of two aneurysms of the celiac trunk in series was disclosed. We conclude that 3D reconstruction can be a valuable asset in the diagnosis of complex vascular pathoanatomy.

Adult↗
PubMed1993

A case of coronary stenosis developing after successful aortic valve repair in Cogan's syndrome.

Cogan's syndrome has been described as entity of progressive deafness and interstitial keratitis with variable cardiovascular involvement leading to aortic insufficiency or orificial stenosis of coronary or aortic arch vessels. So far, aortic valve replacement either with mechanical or biological prosthesis was favored for correction of the valvular lesion. A patient with primary successful aortic valve repair followed by coronary revascularization for left coronary ostial stenosis occurring after the first operation is presented.

Adult↗
PubMed1993

[Surgical aspects of fulminant pulmonary embolism].

Fulminant pulmonary embolism associated with cardiac arrest has an extremely high mortality. The feasibility of pulmonary embolectomy initiated during resuscitation is still under discussion. Between January 1975 and October 1992, embolectomy was performed in 34 patients, 21 to 79 years of age. Diagnosis was established primarily by indirect parameters (medical history, ECG, blood gas analyses, Swan-Ganz catheter in 22 cases). Only in 12 instances, imaging techniques as angiography, ventilation perfusion mismatch, and transesophageal echocardiography were performed. Fifteen patients did not require resuscitation (group A); 6 had to be resuscitated and underwent surgery after reestablishing circulation with catecholamines (group B); 13 patients were connected to extracorporeal circulation during continuous cardiopulmonary resuscitation (30 to 210 minutes) (group C). Embolectomy was performed using extracorporeal circulation with the heart beating (n = 8), or fibrillating (n = 15), or using cardioplegia (n = 11). Twenty-two patients received a caval clip or ligature at the end of the procedure. Fifteen patients (44%) died early postoperatively. The mortality rates for groups A, B, and C were 33%, 66% and 46%, respectively. Nine patients died of right heart failure, 4 of brain death, and 2 of septical complications. Of the surviving patients, only one had ischemic brain damage. In two cases a recurrent pulmonary embolism occurred after a follow-up of 16 years (mean follow-up 4.9 years). We conclude, that even with subtotal obstruction of the pulmonary artery, effective cardiopulmonary resuscitation with maintenance of uncompromised brain function is possible. In emergency situations, the decision to operate may be based only on clinical features without imaging diagnostic procedures.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗