Emergency coronary angiography with gadolinium in a patient with thyrotoxicosis, pulmonary embolism and persistent right atrial thrombi.
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Contrast Media↗
Biomedical subjects
Martin Misfeld
Publications and source records attributed to Martin Misfeld.
[Reconstructive surgery of the aortic valve: the Ross, David, and Yacoub procedures].
The aortic valve consists of three cusps attached to the wall of the aortic root. During the cardiac cycle, the aortic root undergoes complex movements that precede and aid opening and closing of the aortic valve. The aortic valve cusps themselves form thin-walled pocket-like structures, made from specialized tissue with fibrous, elastic, nervous, and muscular properties. The complex interactions of this tissue with the aortic root and within the cardiac cycle are only incompletely understood yet. In summary, the aortic valve is a complex structure which shows a perfect function in systole and diastole and under a wide range of hemodynamic conditions. No valve prosthesis (so far) can keep up with the function of the native aortic valve. Therefore, surgical techniques have been invented that aim at sparing the aortic valve or replacing it with very similar autologous tissue. Besides the resulting (near) normal valve function, one appealing advantage of these techniques is that oral anticoagulation can be abandoned completely. If the valve cusps themselves are normal, but the aortic root is aneurysmatic or dissected (with or without resulting secondary aortic insufficiency), the aortic valve can be spared by resecting the aortic root tissue and replacing it by a vascular graft. The aortic valve can then be implanted into the vascular graft in a way described by David, or can be remodeled into it (Yacoub technique) - in this case, the graft first needs to be incised at its base so that the three commissures of the valve can be sewn into the three incisions. This way pseudosinuses within the vascular graft are created. The sinuses within the aortic root are considered important for aortic valve function and coronary perfusion. On the other hand, incisions at the base of the vascular graft harbor the potential for redilatation of the aortic root because of a missing circular fixation. Such a fixation is achieved by the David technique. Therefore, there is a great debate in the surgical community which valve-sparing technique is the best and numerous modifications of the original techniques exist. A clear clinical advantage of one technique over the other could not be demonstrated so far, but many authorities advise that the David technique is to be used preferentially in patients with Marfan's syndrome (or other connective tissue disorders) and those with a very wide basal aortic root. If the aortic valve cusps themselves are diseased and cannot be reconstructed, the autologous pulmonary valve is the most physiological substitute. Replacing the aortic valve with the autologous pulmonary valve is named Ross procedure. The defect in the right ventricular outflow tract that is created while harvesting the autograft must be reconstructed during the same procedure; usually, a pulmonary valve allograft is used for this purpose. With all reconstructive surgical techniques and with all autologous replacements there is a risk of reoperation, mainly (besides technical issues) because it is feared that leaving autologous tissue in place leads to recurrence of the original illness. The published results, however, with aortic valve-sparing surgery and with the Ross procedure show that the risk of reoperation appears to be very acceptable. This statement is especially true for the Ross procedure for which more and longer experience exists worldwide. Echocardiographic studies show that the aortic valve function after valve-sparing techniques and - especially - after the Ross procedure is indeed excellent. Therefore, patients with aortic root pathologies or aortic valve diseases should be informed about valve-sparing aortic root reconstructive techniques or the Ross procedure. The choice of technique should be made in close contact between patient, cardiologist, and cardiac surgeon. However, the described techniques require extensive experience within the surgical team.
Aortic Aneurysm↗
Invited commentary.
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Coronary Artery Bypass, Off-Pump↗
Complex reconstruction of the thoracic aorta using a novel stent graft/graft prosthesis.
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Aged↗
Ross procedure in a quadricuspid aortic valve.
A quadricuspid aortic valve is a rare congenital cardiovascular abnormality, and when present, it is associated with aortic valve regurgitation. If aortic valve replacement is required, mechanical or biological prostheses are used. We report the case of a patient with a severely regurgitant quadricuspid aortic valve in whom a Ross procedure was performed.
Aortic Valve↗
In vitro hydrodynamics, cusp-bending deformation, and root distensibility for different types of aortic valve-sparing operations: remodeling, sinus prosthesis, and reimplantation.
OBJECTIVE: Preserving aortic valve cusps during operations for aortic root pathology theoretically offers several advantages over alternative prosthetic valve-bearing conduits. Functional properties of different valve-sparing techniques under defined conditions are not well studied. METHODS: Fresh porcine aortic roots were investigated in a pulsatile flow simulator, either native root or after different types of valve-sparing procedures (remodeling, sinus prosthesis, and reimplantation). Functional parameters, such as transvalvular pressure gradient, closing volume, cusp-bending deformation, and distensibility at different levels of the root were analyzed. RESULTS: The mean pressure gradient was highest in reimplantation techniques (8.4 +/- 1.8 mm Hg) compared with sinus prostheses (7.2 +/- 0.9 mm Hg, P = .01) and remodeling techniques (6.8 +/- 1.0 mm Hg, P = .002), mirror imaging the closing volume (reimplantation, 1.5 +/- 0.4 mL; sinus prostheses, 2.3 +/- 0.7 mL [P < .001]; remodeling, 3.4 +/- 1.1 mL [P < .001]). Bending deformation indices increased significantly from remodeling (0.45 +/- 0.05) and sinus prostheses (0.58 +/- 0.06) to reimplantation techniques (0.73 +/- 0.09). Dynamic changes in area of all techniques were decreased at the sinotubular junction and the commissural and sinus levels when compared with those seen in native roots but increased at the annular level for techniques with unfixed annulus (remodeling and modified sinus prosthesis). CONCLUSIONS: In vitro the various aortic valve-sparing operations differed characteristically in their ability to spare valve function, none of them completely meeting native valve behavior. The remodeling techniques exhibited valve dynamics closest to those of the native aortic root. The more the aortic valve is fixed with noncompliant prosthetic material, the more the native root dynamics are impaired.
Animals↗
Myocardial redox state during coronary artery bypass grafting assessed with microdialysis.
PURPOSE: Microdialysis allows the biochemical analysis of interstitial fluids of nearly every organ as a bedside procedure. This technique could be useful to reveal data about the myocardial metabolism during cardiopulmonary bypass in human coronary artery bypass graft (CABG) surgery. METHODS: In 17 patients undergoing CABG a myocardial microdialysis catheter (CMA 70, CMA/Microdialysis AB, Sweden) was inserted in the apical region of the beating heart. Microdialysis measurements were performed at timed intervals before, during, and after cardiopulmonary bypass (CPB). The concentrations of lactate and pyruvate were analyzed semi-continuously. RESULTS: During CPB the myocardial lactate-pyruvate-ratio (LPR) rose from an initial 11 (8-15) to 33 (29-41) ( P<0.01). After CPB the LPR decreased to 4 (3-7) at the end of observation ( P<0.05). The pyruvate concentration showed an immediate increase from 34 (30-42) microM at the end of CPB to 181 (147-234) microM after removal of the cross-clamp with subsequent increase during reperfusion ( P<0.01). Plasma lactate and pyruvate showed no essential changes during the study. CONCLUSION: Using the microdialysis technique it was possible to analyze myocardial metabolic changes during CABG. The course of myocardial LPR as a sensitive indicator of the myocardial redox state showed profound changes during and after CPB. We propose the microdialysis technique as an additional monitoring tool in CABG.
Aged↗
Strategies for the reduction of cerebral microembolism during transmyocardial laser revascularization.
BACKGROUND AND OBJECTIVES: During transmyocardial laser revascularization (TMLR), multiple microembolic signals (MES) can be detected in cerebral arteries. We sought to characterize composition and clinical relevance of these MES and to evaluate strategies to reduce cerebral microembolization during TMLR. STUDY DESIGN/MATERIALS AND METHODS: TMLR was performed in pigs. Laser energy was set to 4-10 J (group A) or 80 J (group B). Oxygen concentration was varied between 21 and 100%. MES were recorded in the ophthalmic artery. Brain and spinal cord were investigated histologically after 10 days. RESULTS: More MES could be detected during high- compared to low-energy laser procedures. Ventilation with 100% oxygen reduced the number of MES. No lesions were found on histology. CONCLUSIONS: The number of MES depends on the laser energy. Laser-induces cavitation-effects lead to an additional release of nitrogen bubbles. Thus, the microembolic load can be reduced by ventilation with 100% oxygen and by decreasing the laser energy.
Animals↗
A novel, form-stable, anatomically curved vascular prosthesis for replacement of the thoracic aorta.
PURPOSE: Current replacement of the thoracic aorta performed with straight vascular prostheses may cause kinking, potentially affecting hemodynamics and promoting vortices and thrombus formation. A novel vascular prosthesis, resistant to pressure-related shape deformation, was designed to imitate the curved anatomy of the thoracic aorta. DESCRIPTION: A woven velour prosthesis was trimmed with cross-sutures along a marked line, resulting in a curved-shaped anatomic form, and was compared with conventional straight and thermally fixed curved grafts. The vascular prostheses were fixed at both ends at various base distances (8, 10, 12, 14, and 16 cm) and pressurized. To imitate the neck vessels an abutment was fixed at the upper convexity of the grafts. Radius of curvature or depth of kinking was measured at different pressures (100, 125, and 150 mm Hg). Pressure gradients and flow profiles were further analyzed in an aortic arch glass model. EVALUATION: When pressurized the straight and the thermally fixed protheses showed double kinking before and behind the abutment at all pressures and distances. Kinking depth increased with increasing pressure and less base distance. Transkinking pressure gradients increased with the degree of kinking. In a glass model flow profiles showed postkinking turbulences and vortex formation. The newly designed vascular prosthesis showed no kinking and remained form stable at all test conditions. CONCLUSIONS: This novel curved vascular prosthesis for replacement of the thoracic aorta demonstrates form stability compared with conventional straight and thermally fixed vascular prostheses in an aortic arch model, with smaller pressure gradients and flow disturbances.
Aorta, Thoracic↗
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↗
Intramyocardial oxygen monitoring in coronary artery bypass surgery.
OBJECTIVE: In coronary artery bypass surgery various parameters have been used to monitor patients clinical status. Direct monitoring of myocardial oxygenation can be performed by measuring intramyocardial partial oxygen tension pressure (p ti O2). This study was performed to determine the perioperative time course of this parameter in correlation to standard monitoring parameters. METHODS: Twenty-three patients underwent standard coronary artery bypass grafting (CABG). A special polarographic microprobes was inserted into the myocardium in the distribution zone of the left anterior descending artery which was one of the target vessels of myocardial revascularization. Intramyocardial p ti O2 was monitored intra- and up to 12 hours postoperatively. Values were correlated to hemodynamic, oxygenation and procedure associated parameters. RESULTS: Myocardial oxygenation during CABG is characterized by a significant decrease of p ti O2 during cross-clamping and a significant increase after removal of the cross-clamp. The postoperative time course of p ti O2 shows a steady increase of p ti O2 in the first 12 postoperative hours investigated. Preoperative ejection fraction as well as cardio-pulmonary bypass time does not seem to have an influence on the postoperative p ti O2 in these patients. Various standard monitoring parameters show complex influence on intramyocardial p ti O2- CONCLUSIONS: Determination of intramyocardial partial oxygen pressure in patients undergoing bypass surgery shows characteristic changes. Changes in p ti O2 as a direct online parameter of myocardial oxygenation occur immediately after procedures that influence myocardial perfusion and therefore, may help to detect potential complications earlier than standard monitoring parameters in cardiac surgery.
Aged↗
Specific regional and directional contractile responses of aortic cusp tissue.
BACKGROUND AND AIM OF THE STUDY: The control of valve size and function is a dynamic process that may be modulated by vasoactive factors. The exact response of different regions of the cusp tissue with regard to extent and direction could influence valve shape, function and response to stress. METHODS: Porcine aortic valve cusps were cut into either circumferential (basal, belly and coapting edge) or radial (left, center and right) strips. Together with an intact cusp orientated circumferentially, specimens were set up in isolated organ baths. RESULTS: In response to 90 mM KCI, the belly of the cusp (0.66 +/- 0.05 mN; p <0.05) was significantly more responsive than either the basal region (0.41 +/- 0.06 mN) or the coapting edge (0.31 +/- 0.03 mN) and all three regions of radially orientated strips (left: 0.13 +/- 0.02 mN; center: 0.23 +/- 0.04 mN; right: 0.11 +/- 0.03 mN). All strips showed contraction to endothelin-1 (10(-9) to 10(-7) M). When corrected for weight, the responses of the basal (15.2 +/- 1.8 mN/g) and belly (11.3 +/- 1.5 mN/g) regions were significantly greater than that of the coapting edge (8.4 +/- 1.0 mN/g; p <0.05) and the intact cusp (7.1 +/- 1.9 mN/g, n = 7, p <0.05). In the radially orientated tissue, responses to endothelin-1 were similar in all three regions (left: 3.4 +/- 1.0 mN/g; center: 3.2 +/- 0.5 mN/g; right: 2.3 +/- 0.9 mN/g). CONCLUSION: The contractile ability of valve cusps occurs preferentially in the circumferential direction. The enhanced contraction of the basal region may have important implications for the management of stresses experienced by the hinge of the valve. In addition, these findings may be relevant in designing tissue for valve repair by cusp extension or for the tissue engineering of a whole valve.
Animals↗
Warning hint of a hidden early left main stem bifurcation during antegrade cardioplegia.
The short left main trunk with early bifurcation is a common variation of the left coronary anatomy and is easily overlooked during antegrade selective cardioplegia resulting in the risk of single branch perfusion. We describe an obvious characteristic sign to detect this pitfall during blood cardioplegia.
Coronary Vessels↗
Ischemic non-septal interventricular communication.
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Aged↗
Intramyocardial partial oxygen pressure in patients undergoing transmyocardial laser revascularization and bypass surgery.
OBJECTIVE: Numerous investigations could not clarify the exact mechanism of transmyocardial laser revascularization (TMLR). The aim of this study was to investigate, whether TMLR leads to an increase of myocardial oxygenation in comparison to patients undergoing coronary artery bypass grafting (CABG). DESIGN: Twelve patients (TMLR group) underwent TMLR alone with an 800 W CO2 laser through a left anterior thoracotomy. Seventeen patients (CABG group) underwent standard CABG. Myocardial oxygenation was determined by measuring intramyocardial partial oxygen pressure (ptiO2 ). PtiO2 was measured online and mean values at 1, 24, 32, and 48 h postoperatively were compared with baseline before intervention. Parameters influencing ptiO2 (arterial pO2, hemodynamic parameters, hemoglobin) were recorded. RESULTS: Mean baseline ptiO2 was significantly lower in the TMLR group compared with the CABG group (p < 0.05). In both groups ptiO2 increased significantly in the postoperative course, whereby ptiO2 in the TMLR group was significantly lower compared with the CABG group. CONCLUSION: Although the exact mechanism of action of TMLR remains unclear, ptiO2 and thus oxygen supply in the myocardium increased in patients undergoing TMLR at least in the early postoperative course. However, ptiO2 increased to a lesser extent compared with CABG.
Aged↗
Localization of immunoreactive endothelin and characterization of its receptors in aortic cusps.
BACKGROUND AND AIM OF THE STUDY: Aortic valve cusp tissue has been shown to have contractile properties in response to a range of common vasoactive agents. Of these, endothelin (ET) is both the most potent and efficacious. METHODS: In an attempt to define the mechanism of action and localization of ET, the response of porcine aortic valve cusps to ET and the selective ET(B) receptor agonist sarafotoxin 6c (S6c) was examined, in the presence and absence of ET(A) and ET(B) receptor antagonists. An attempt was made, using immunocytochemical techniques, to localize ET in cusp tissue. RESULTS: Addition of 90 mM KCl produced a mean contractile response of 1.02+/-0.09 mN (n = 27). ET (10- to 10(-7)M) produced a concentration-dependent contraction of aortic valve cusps, with a maximum response of 116.7+/-12.7% (n = 6) of that obtained with 90 mM KCl. In a similar manner, 10(-5)M of the selective ET(A) receptor antagonist BQ123 (n = 4) and 10(-5)M of the selective ET(B) receptor antagonist BQ788 (n = 4) each partially inhibited the effect of ET. The ET(B)-selective agonist S6c (10(-9) to 10(-7)M) also induced a concentration-dependent contraction of valve cusps (n = 4), with a maximum response of 99.1+/-11.1%. This response was completely inhibited by 10(-5)M BQ788 (n = 4). Immunoreactive ET was localized to the endothelial cells that lined both the ventricular and aortic side of the cusps. CONCLUSION: These results show that aortic valve cusps contract to ET via an action at both ET(A) and ET(B) receptors. The presence of immunoreactive ET in the endothelial cells of the cusps also suggests that it might play a role in valve function. Further studies are required to elucidate the role of these receptors in the physiology and pathophysiology of the aortic valve.
Analysis of Variance↗
The influence of a nonlinear resistance element upon in vitro aortic pressure tracings and aortic valve motions.
In vitro testing of biological heart valves requires pressure and flow waveforms closely simulating natural conditions, which are mainly influenced by the characteristics of the vascular system. Simulation of the arterial function in artificial circulations was mostly performed by the useful Windkessel model but sometimes failed by generating inadequate systolic pressures. The integration of a novel nonlinear resistance element may improve the Windkessel function. Native porcine aortic valves were studied in a mock circulation with a novel nonlinear resistance element combined with the Windkessel compared with an aperture plate resistance. Pressure and flow measurements were performed at varying heart rates and stroke volumes and analyzed in the time and frequency domain. Aortic valve motions were evaluated using high speed video recording. With the classical afterload configuration including an aperture plate resistance, the pressure tracings showed a nonphysiologic decrease of pressure during systole after early peak pressure. By integration of the novel nonlinear resistance, peak systolic pressure occured later, peak pressure was higher, and the pressure waveform was more physiologically shaped. Leaflet motions of the aortic valves were less oscillatory and compared well with in vivo characteristics. In conclusion, a novel nonlinear resistance element in a mock circulation has the potential to provide more physiologic aortic pressure waveforms as influencing aortic valve dynamics and thus may be a helpful tool for investigation of biological heart valves.
Animals↗