Decalcification of the Mitral Annulus: Surgical Experience in 81 Patients.

OBJECTIVE: Mitral valve surgery in the presence of extensive calcification of the mitral annulus is a technical challenge and increases perioperative risk. This study reviews our experience with decalcification of the mitral annulus in patients undergoing mitral valve reconstruction or replacement.

METHODS: From 1995 to 2003, 81 patients (mean age 64 +/- 13 years, 30 male, 51 female) with extensive calcification of the mitral annulus underwent mitral valve repair (n = 42) or replacement (biological n = 20, mechanical n = 19). The mean follow-up was 24 months. Patients presented with a mean EuroSCORE of 7. Concomitant surgical procedures were performed in 62 %. Patient outcomes were retrospectively assessed.

RESULTS: Perioperative survival was 97.5 % (n = 79) and hospital survival was 91.3 % (n = 74). Two-year survival was 88.9 %. Eight patients needed reexploration due to bleeding and five patients required prolonged mechanical ventilation. No perioperative stroke was observed. Freedom from reoperation was 90.2 % (n = 73). Early reoperation for recurrent incompetence was necessary in 3 patients and late reoperation in 5 patients.

CONCLUSIONS: Despite the elevated perioperative risk and the high risk of reoperation with this procedure, decalcification of the annulus and repair/replacement of the mitral valve could be performed with good clinical results.

Author(s): M Dietrich , M Doss , T Aybek , S Martens , M Scherer , G Wimmer-Greinecker, A Moritz

in: Thorac Cardiovasc Surg. 2006 Oct ;54 (7):464-467 17089313

Transapical aortic valve implantation: an animal feasibility study.

BACKGROUND: Percutaneous aortic valve implantation has recently been performed in nonsurgical patients with severe aortic stenosis. Retrograde valve delivery has been problematic because of the size of the delivery system and concomitant peripheral vascular disease. We investigated a minimally invasive approach through the left ventricular apex for antegrade placement of a device-deliverable valve.

METHODS: Transapical aortic valve implantation was performed using a 23-mm equine valve mounted on a stainless steel stent in 24 swine (weight range, 35 to 45 kg). A limited or full sternotomy approach was used to access the apex of the heart. The crimped valve was introduced through a sheath in the left ventricular apex. Fluoroscopy and echocardiography were used for guidance. Deployments were performed on the beating heart either with ventricular unloading using femoral extracorporeal circulation or rapid ventricular pacing.

RESULTS: All valves were successfully delivered at the selected target site with acceptable visualization of the noncalcified aortic annulus. Valve migration occurred during eight deployments (two distal and six retrograde) secondary to persistent cardiac output, unfavorable annular anatomy, and dislodgement by the delivery catheter. Exact positioning of the nonmigrated valves at the aortic annulus was examined by necropsy of all animals at the end of the procedures. Paravalvular leak was noted in 14 of 18 (77.8%) valves remaining in situ.

CONCLUSIONS: The transapical approach was used for the successful antegrade placement of a stented valve, obviating the technical problems associated with a large delivery system transiting the peripheral vascular system. Stent design contributing to paravalvular leak remains problematic.

Author(s): Dewey TM, Walther T, Doss M, Brown D, Ryan WH, Svensson L, Mihaljevic T, Hambrecht R, Schuler G, Wimmer-Greinecker G, Mohr FW, Mack MJ.

in: Ann Thorac Surg. 2006 Jul;82(1):110-6.

PMID: 16798200 [PubMed - indexed for MEDLINE]

Behavior of gaseous microemboli in extracorporeal circuits: Air versus CO2.

Background: Open heart surgery is associated with serious risk of cerebral and peripheral organ dysfunction, attributed in part to air microbubbles generated in or not eliminated from the extracorporeal circuit (ECC). Venous air leakage leads to increased arterial bubble load. CO 2 replacing air in cardiac chambers show faster resorption times, reducing possible cerebral or peripheral organ damage after heart valve interventions. In two models of ECC the effect of air entering closed circuits was demonstrated and compared to the effect of CO 2 entry.

Methods: Fragmentation and dissolution of gas (0.5 mL) was evaluated in an in vitro model of ECC, using ultrasonic bubble detection. Air leakage (10 mL) in the venous line of the ECC was simulated and compared to the effect of the same quantity of CO 2 entering the circuit. Both models used whole blood priming and physiological conditions, verified with blood gas analyses.

Results: Fragmentation and dissolution of gas bubbles injected into a closed ECC could be demonstrated, complete resorption of CO 2 bubbles was observed earlier than complete resorption of room air (5.0+/-0.6 vs. 14.4+/-5.9 min, p=0.0009). CO 2 entering the venous line lead to 40% less arterial bubble load as compared to the same amount of room air entering the circuit (2099+/-991 vs. 3555+/-632, p=0.005).

Conclusions: Current ECC systems fail to eliminate gas entering the circuit, leading rather to microbubble dispersion. CO 2 is much faster resorbed within the circuit than room air. In open heart surgery as valvular operations, CO 2 insufflation into the operative field is protective, as we have demonstrated in our models.

Author(s): S Martens , M Dietrich , M Doss , M Deschka , H Keller , A Moritz

in: Int J Artif Organs. 2006 Jun ;29 (6):578-82 16841286

Transapical approach for sutureless stent-fixed aortic valve implantation: experimental results.

OBJECTIVE: Percutaneous aortic valve implantation has been performed in patients with severe aortic stenosis judged as nonsurgical candidates. We evaluated a facilitated transapical antegrade approach for potential use in surgical high-risk patients.

METHODS: A pericardial xenograft fixed within a 23-mm stent (Cribier-Edwards aortic prosthesis, Edwards Inc., Irvine, CA, USA) was implanted using a transapical approach in fifteen 35-45 kg pigs. A limited or a full sternotomy was used to transapically introduce a crimped valve through a 24-F sheath. Deployments were performed on the beating heart either with ventricular unloading using femoro-femoral cardiopulmonary bypass (CPB) or rapid ventricular pacing (RVP), all under fluoroscopic and echocardiographic visualization.

RESULTS: All valves were successfully deployed at the target site with acceptable visualization of the noncalcified annulus. Valve migration occurred in six procedures (three distal and three retrograde) secondary to inadequate reduction of ventricular output, unfavorable annular anatomy, excessive crimping of the valve, and dislodgement by the delivery balloon. Exact positioning of the valve into the target area was confirmed by autopsy at the end of the procedures. Paravalvular leak was noted in five implants.

CONCLUSIONS: The transapical approach provides a safe, accurate, and effective route for facilitated antegrade delivery of a stent-fixed valve. Advanced stent design will lead to better stability of the implant and may minimize the risk of paravalvular leakage in future. Identifying the appropriate population for human feasibility trials remains a challenge.

Author(s): Walther T, Dewey T, Wimmer-Greinecker G, Doss M, Hambrecht R, Schuler G, Mohr FW, Mack M

in: Eur J Cardiothorac Surg. 2006 May;29(5):703-8. Epub 2006 Apr 5.

This paper was presented at the Annual Meeting of the European Society of Thoracic Surgeons N^o13, Barcelona , Spain (25. Sept. 2005)

PMID: 16600616 [PubMed - indexed for MEDLINE]

Stentless bioprostheses improve postoperative coronary flow more than stented prostheses after valve replacement for aortic stenosis.

OBJECTIVE: In some randomized studies, stentless aortic valves have demonstrated hemodynamic advantages in comparison with stented prostheses. The effect of more physiologic flow dynamics on coronary artery flow has not been investigated yet. This study compares coronary perfusion after aortic valve replacement with stented or stentless porcine bioprostheses in a prospective randomized study.

METHODS: A total of 24 patients (73 +/- 6 years) referred for treatment of aortic stenosis were randomized to aortic valve replacement with stented (Medtronic Mosaic; (Medtronic Inc, Minneapolis, Minn) or stentless (Medtronic Freestyle; Medtronic Inc) prostheses. Coronary flow was measured by means of magnetic resonance imaging preoperatively, 5 days after the operation, and 6 months postoperatively, then with evaluation of coronary flow reserve. Echocardiography was performed to quantify transvalvular gradients and left ventricular mass regression.

RESULTS: Coronary flow increased in both groups significantly.

Author(s): Farhad Bakhtiary, Mirko Schiemann, Omer Dzemali, Thomas Wittlinger, Mirko Doss, Hans Ackermann, Anton Moritz, Peter Kleine

in: J Thorac Cardiovasc Surg. 2006 Apr ;131 (4):883-8 16580448

Impact of mechanical and biological aortic valve replacement on coronary perfusion: a prospective, randomized study.

BACKGROUND AND AIM OF THE STUDY: Coronary perfusion is impaired in patients with aortic stenosis (AS). Aortic valve replacement (AVR) leads to improvement, but not complete restoration, of coronary flow. Previous studies have shown that postoperative coronary flow rate and coronary reserve in mechanical valves is dependent on valve design and orientation. The study aim was to investigate acute changes in coronary perfusion in patients undergoing mechanical or biological valve replacement in a prospective, randomized clinical study.

METHODS: Forty patients undergoing AVR for AS underwent MRI scanning to measure coronary flow preoperatively and at five days after surgery. Patients scheduled for mechanical AVR (n = 20) were randomized to a tilting disc (Medtronic Hall) or bileaflet (Medtronic ADVANTAGE) prosthesis; the biological-valve group (n = 20) received a stented (Medtronic Mosaic) or stentless (Medtronic Freestyle) valve. Valve sizes were comparable in all groups. Patients also underwent echocardiography both preoperatively and postoperatively to measure transvalvular pressure gradients. The rate-pressure product (RPP) was calculated as a marker of myocardial oxygen demand and cardiac workload.

RESULTS: The mean preoperative coronary flow rate was 90 +/- 32 ml/min, and this increased after AVR in all patients. The rise in the mechanical-valve groups was comparable for the two tested valves, whereas in the biological-valve groups a significantly higher increase for stentless valves was present (p < 0.05). Mean pressure gradients for the Hall and ADVANTAGE valves were equal; for biological valves, the Mosaic demonstrated a higher mean gradient (19 +/- 6 mmHg) than the Freestyle (10 +/- 4 mmHg) (p < 0.05). The RPP was lower for ADVANTAGE (mechanical group) and for Freestyle valves (biological group).

CONCLUSION: Coronary artery flow was increased following AVR in all valve groups. The rise was significantly more distinct for Medtronic Freestyle stentless valves compared to the three other valve substitutes. As the stentless design also demonstrated superior hemodynamics and a lower myocardial oxygen demand with lower pressure gradients and lower RPP, this may have a positive impact on the clinical long-term outcome of this valve.

Author(s): Farhad Bakhtiary MD, Nasreddin Abolmaali MD, Omer Dzemali MD, Thomas Wittlinger MD, Mirko Doss MD, Anton Moritz MD, Peter Kleine MD

in: J Heart Valve Dis. 2006 Jan;15(1):5-11; discussion 11

 

PMID: 16480006 [PubMed - indexed for MEDLINE]

Automatic connector devices for proximal anastomoses do not decrease embolic debris compared with conventional anastomoses in CABG.

Objective: Emboli generated during cardiac surgery have been associated with aortic clamping and manipulation. Proximal anastomotic devices are thought to be less traumatic by eliminating partial clamping, potentially resulting in fewer adverse outcomes. Intra-aortic filtration has been shown to effectively capture particulate debris. We compared the amount of debris released using intra-aortic filtration and the clinical outcomes between conventionally handsewn and automated proximal anastomoses.

Methods: Seventy-seven patients undergoing primary coronary artery bypass grafting with cardiopulmonary bypass were enrolled in a prospective randomized study. Patients were assigned to the anastomotic device Group I (Symmetry^TM Aortic Connector, n=39) or the conventional handsewn anastomosis control Group II (n=38). Proximal anastomoses were performed before cardiopulmonary bypass in both groups. Intra-aortic Filter 1 (EMBOL-X^TM) was deployed prior to partial clamping or puncturing the aorta for device application and removed after the proximal anastomosis was completed. Prior to cross-clamp removal, a second filter was inserted (Filter 2). A core laboratory performed quantitative and histologic analyses of the debris captured. Clinical outcomes included adverse events, neurocognitive test scores, graft patency, and mortality.

Results: Preoperative variables and risk factors were not significantly different between Groups I and II (EuroSCORE 3.9±2.6 vs. 4.2±2.5). Filter analyses showed no significant difference between Groups I and II in Filter 1 or 2 for either surface area of particles or total number of particles (P>0.05). There was a significant decrease between Filters 1 and 2 in both Groups for surface area of particles (Group I: 18.5±23.8 mm² vs. 10.7±16.3 mm², P=0.017; Group II: 15.0±15.4 mm² vs. 6.9±.6.5 mm², P=0.004), and for total number of particles in Group II (8.6±3.7 vs. 7.1±2.4, P=0.023). No significant differences were observed between Group I (device) and Group II (control) outcomes for myocardial infarction, neurocognitive deficit, stroke, length of stay, graft occlusion, or mortality.

Conclusions: The application of proximal aortic connectors without partial clamping does not reduce particulate emboli or affect clinical outcomes compared with conventional anastomoses. Cross-clamping during cardiopulmonary bypass produces less particulate debris than conventional or automated proximal anastomoses performed off-pump, suggesting a major source of emboli is the anastomotic process.

Author(s): Martens S, Dietrich M, Herzog C, Doss M, Schneider G, Moritz A,
Wimmer-Greinecker G.

in: Eur J Cardiothorac Surg. 2004 Jun;25(6):993-1000.

PMID: 15145000 [PubMed - indexed for MEDLINE]

Echocardiographic assessment in minimally invasive mitral valve surgery.

BACKGROUND: Due to limited exposure, removal of intracavitary air and visual assessment of cardiac function during minimally invasive procedures are not always possible. We analysed the utility of intraoperative transesophageal echocardiography (TEE) and postoperative transthoracic echocardiographic (TTE) in minimally invasive mitral valve (MV) procedures.

MATERIAL/METHODS: We evaluated data from 163 consecutive patients undergoing isolated minimally invasive MV replacement (n=40) or repair (n=123) via small right anterolateral thoracotomy (121 complex mitral procedures). Cardioplegic arrest was achieved using either endoaortic (n=23) or transthoracic aortic clamp (n=140). In addition to preoperative TTE, TEE was used intraoperatively before and after cardiopulmonary bypass (CPB). Postoperative TTE was performed to monitor valve function at 3 and 12 months, and at 5-year follow-up.

RESULTS: Pre-CPB TEE was useful to assess valve dysfunction and assist in placement of the arterial and venous cannulas. During CPB, placement and positioning of the endoclamp were guided effectively in all but 4 patients, in whom recurrent balloon migration necessitated secondary transthoracic aortic clamping. TEE detected one acute retrograde aortic dissection and one circumflex artery occlusion. After 18.7+/-10.6 months follow-up, all patients except three improved symptomatically and had consistently good valve function.

CONCLUSIONS: Intraoperative TEE is essential for minimally invasive MV surgery, because it allows immediate control of valve function before and after surgery. It is useful to detect unexpected complications requiring immediate remedy. Postoperative echocardiographic results show that minimally invasive MV surgery is a good alternative to conventional surgery even in complex MV repairs.

Author(s): Aybek T, Doss M, Abdel-Rahman U, Simon A, Miskovic A, Risteski PS, Dogan S, Moritz A.

in: Med Sci Monit. 2005 Apr;11(4):MT27-32. Epub 2005 Mar 24

PMID: 15795704 [PubMed - indexed for MEDLINE]

Valve opening and closing dynamics after different aortic valve-sparing operations.

BACKGROUND AND AIM OF THE STUDY: Aortic valve resuspension for ascending aortic aneurysm repair is associated with removal of the sinus of Valsalva. This may cause changes in leaflet motion and thus impact on long-term durability. The opening and closing characteristics of the aortic valve leaflets after reimplantation were studied using a published technique and a modification to create a ‘neosinus’, and the results compared to those of an age-matched control group.

METHODS: Between September 1995 and March 2002, 25 patients underwent normal aortic root reconstruction (group A), while in a further 21 patients the modified neosinus technique was used (group B). In both groups, the native valve was preserved and suspended inside a tubular prosthesis, with reimplantation of the coronary arteries. Transthoracic and transesophageal studies of aortic valve dynamics were performed intraoperatively, before hospital discharge, and at one year after surgery in all patients; the data were compared with those from a separate group of 25 matched control individuals (group C).

RESULTS: The valve opening velocity was 61.3+/-20.1, 46.3+/-8 and 29.2+/-9.8 cm/s in groups A, B and C, respectively (group A versus B, p = 0.003; A versus C, p <0.0001; B versus C, p <0.0001). Closing velocity was increased to 57.5+/-23 and 43.8+/-7 cm/s in groups A and B, compared to 23.6+/-7 cm/s in group C (A versus B, p = 0.012; A versus C, p <0.0001; B versus C, p = 0.0002). In seven group A patients, the leaflets touched the prosthetic wall during systole. Slow systolic closing displacement (SCD) amounted to 7.3+/-6 % of maximal opening in group A and 12.6+/-5 % in group B (p = 0.05), compared to 21.1+/-8.3% in group C (group A versus group C, p <0.0001; B versus C, p = 0.002).

CONCLUSION: Reimplantation of the natural aortic valve in a prosthetic graft causes abnormally high opening and closing speeds, with possibly increased stress. The study results showed lower valve opening and closure dynamics after the creation of a sinus bulge compared to the conventional reimplantation technique. However, mid-term clinical observations showed favorable valve competence for both types of repair. Further long-term follow up is necessary to prove whether more physiological leaflet dynamics lead to improved durability.

Author(s): Aybek T, Sotiriou M, Wohleke T, Miskovic A, Simon A, Doss M, Dogan S, Wimmer-Greinecker G, Moritz A.

in: J Heart Valve Dis. 2005 Jan;14(1):114-20.

PMID: 15700445 [PubMed - indexed for MEDLINE]

Thoracic aortic stenting: indications and results.

AIM: Determination of the conditions for good acute and long term results of interventional therapy of lesions of the thoracic aorta using stent-grafts.

PATIENTS, MATERIAL AND METHODS: 51 patients with aneurysm of the thoracic aorta (type B dissections) covered rupture and aortobronchial fistula were evaluated. All cases were discussed in an interdisciplinary conference consisting of thoracic surgeon and interventional radiologist. Primarily, 20 patients were operated and 31 were treated by intervention. For all a multidetector row CT angiography was ordered prior to the discussion. All procedures were performed in a DSA suite under general anaesthesia. In 29 patients Talent LPS trade mark tube grafts and in four patients an Excluder trade mark graft was implanted.

RESULTS: 29 patients had an aneurysm of the thoracic aorta, 21 a type B dissection, 19 a perforation and one patient had an aortobronchial fistula. The follow up was 13.4 months. In 29 patients the stent-graft implantation was successful, in 2 patients stent-graft delivery failed due to severe calcification and kincking of both common iliac arteries. One patient had an iliacal dissection after stent-graft delivery which was treated successfully by surgery. In two patients CT angiographic control detected endoleaks, which were treated with a second stent-graft placement. One patient with an acute perforation of the descending aorta died due to cardiac failure prior to stent-graft implantation. Any neurological complication did not occur.

CONCLUSION: Percutaneous treatment of lesions of the descending thoracic aorta using stent-grafts is a safe and feasible alternative treatment to surgical repair. Prior to the a multidetector row CT angiography is necessary for exact planning of the endo-luminal treatment.

Author(s): Thalhammer A, Balzer J, Doss M, Jacobi V, Vogl T.

in: Hamostaseologie. 2004 Aug;24(3):157-61

PMID: 15314699 [PubMed - indexed for MEDLINE]

Improved cerebral protection through replacement of residual intracavital air by carbon dioxide: a porcine model using diffusion-weighted magnetic resonance imaging.

BACKGROUND: Major risk of central or peripheral organ damage is attributed to air embolism from incompletely de-aired cardiac chambers after cardiac operations. Replacement of air by carbon dioxide insufflation into the thoracic cavity is widely used. Diffusion-weighted magnetic resonance imaging of the brain detects ischemia within minutes after onset. The reversibility of ischemia in cerebral tissue after massive gaseous emboli has not yet been described.

METHODS: After selective catheterization of a common carotid artery in 15 pigs, boli of 1 mL/kg body weight of air (n = 5) or carbon dioxide (n = 5, “low dose”) were applied. Five pigs received 2 mL/kg body weight of carbon dioxide (“high dose”). Diffusion-weighted magnetic resonance imaging of the brain was performed 2, 5, 10, 15, and 25 minutes after embolization.

RESULTS: All animals of the “air” group showed important circulatory reactions leading to death of 2 animals. In the whole group, diffusion-weighted magnetic resonance imaging revealed irreversible hyperintense signals in both hemispheres. In the low-dose group, no change in signal intensity was observed in 2 pigs, and 3 others showed reversible changes in signal intensity, without important circulatory reactions. In 3 animals of the high-dose group, hyperintense signals were reversible, but 2 others presented with bilateral, irreversible signals in diffusion-weighted magnetic resonance imaging, accompanied by minor circulatory reactions.

CONCLUSION: In contrast to the dramatic effect of air emboli, identical quantities of carbon dioxide injected into cerebral arteries of the pigs were not associated with major clinical symptoms. The early reversibility of ischemic reactions visualized in diffusion-weighted magnetic resonance imaging encourages the use of carbon dioxide insufflation as a protective method in cardiac surgery.

Author(s): Martens S, Theisen A, Balzer JO, Dietrich M, Graubitz K, Scherer M, Schmitz C,
Doss M, Moritz A.

in: J Thorac Cardiovasc Surg. 2004 Jan;127(1):51-6.

PMID: 14752412 [PubMed - indexed for MEDLINE]

Urgent thoracic aortal dissection and aneurysm: treatment with stent-graft implantation in an angiographic suite.

The aim of this study was to evaluate the feasibility of endoluminal stent-graft placement in an angiographic suite for the treatment of emergent type-B aortic dissections and ruptured thoracic aortal aneurysms.

Twenty-six patients with either urgent type-B dissection (n=8) or aneurysms (n=18) of the descending thoracic aorta were chosen for stent-graft implantation. All patients received a multidetector-row CT in: performed in a fully equipped digital subtraction angiography (DSA) suite under general anesthesia. In 20 patients Talent LPS tube grafts and in 4 patients an Excluder graft were used. Access was achieved via surgical cut-down in the left (n=7) or right (n=19) groin. Sealing was successful in 24 patients. The proximal covered portion of the stent graft was placed across the left subclavian artery in 2 patients. Procedural success was achieved in 23 of 24 patients. One patient required a second stent-graft placement before the aneurysm was sealed. One patient with an acute perforation of the descending aorta died due to cardiac failure prior to stent-graft implantation. In 1 patient stent-graft delivery failed due to severe calcification of both common iliac arteries. Endoluminal treatment of both urgent type-B aortic dissections and thoracic aortal aneurysms with stent graft is an attractive alternative treatment to surgical repair.

The placement of stent grafts in an angiographic suite is a safe and feasible method with good clinical effectiveness and, so far, good clinical outcome.

Author(s): Balzer JO, Doss M, Thalhammer A, Fieguth HG, Moritz A, Vogl TJ.

in: Eur Radiol. 2003 Oct;13(10):2249-58. Epub 2003 May 14.

PMID: 12748810 [PubMed - indexed for MEDLINE]

Ultrafast computed tomography for quality control of automated proximal anastomoses.

BACKGROUND: The Symmetry aortic connector uses a nitinol implant to create proximal anastomoses with saphenous vein grafts. Multiple detector-row cardiac computed tomography (MDCT) is used as a noninvasive method of quality control at our institution.

METHODS: In 50 elective coronary artery bypass grafting patients who participated in a randomized trial comparing automated with conventionally hand-sewn proximal anastomoses, MDC T was performed on postoperative day 5. Fifty-three automated Symmetry anastomoses were created in 34 patients (group 1). Twenty-five conventionally hand-sewn anastomoses created in 16 patients served as controls (group 2). Graft patency and the presence or absence of high-grade stenosis at the proximal anastomotic site were evaluated.

RESULTS: In group 1, 2 (3.8%) of the grafts were found occluded at MDCT or coronary angiography, and no further relevant stenosis was observed. In group 2, at postoperative MDCT all grafts were found patent without significant narrowing of the proximal anastomotic site.

CONCLUSIONS: The feasibility of proximal anastomoses using the Symmetry device has been reported. Patency control with invasive angiography has been performed by other groups. With MDCT, noninvasive evaluation of proximal anastomotic quality and graft patency is possible, even if nitinol is implanted.

Author(s): Martens S, Herzog C, Dietrich M, Doss M, Wimmer-Greinecker G, Moritz A.

in: Heart Surg Forum. 2003;6(6):E170-3.

PMID: 14722005 [PubMed - indexed for MEDLINE]

Do surface modifying additives (SMA) influence blood loss and thrombogenicity in conventional cardiopulmonary bypass for coronary artery bypass grafting?

Xardiopulmonary bypass (CPB) leads to activation of the coagulation and fibrinolytic cascades, partially associated with foreign surface contact. Hemorrhage and the need for blood products is associated with rising cost and increased risk of infection. Treatment with surface modifying additives (SMA) has been shown to reduce thrombogenicity and improve biocompatibility. 76 elective CABG-patients were randomly assigned to surface modifying additives (group I, n=39) or untreated circuits that were otherwise identical (group II, n=37). Measurements of coagulation activity and fibrinolysis, platelet count and function were made. The postoperative blood loss and blood product replacement was also assessed. Thrombin formation measured by prothrombin fragments 1+2 (5.7+/-0.4 nmol/l vs. 5.6+/-0.4 nmol/l), fibrinolytic activity measured by plasmin-antiplasmin complex (1752.6+/-216.8 microg/l vs.1180.0+/-74.8 microg/l) and the postoperative platelet count and function did not differ significantly between the two groups. Blood loss and transfusion requirements were slightly lower in the SMA group. The treatment of extracorporeal surfaces with surface modifying additives does not appear to reduce coagulation disorders and bleeding after conventional CPB.

Author(s): Martens S, Matheis G, Wimmer-Greinecker G, Scherer M, Doss M, Moritz A.

in: Cardiovasc Surg. 2003 Apr;11(2):159-63.

PMID: 12664053 [PubMed - indexed for MEDLINE]

Minimally invasive versus conventional aortic valve replacement: a prospective randomized trail

BACKGROUND AND AIM OF THE STUDY: A prospective randomized study was performed to compare conventional with minimally invasive aortic valve replacement (AVR).

METHODS: Forty consecutive patients scheduled for elective aortic valve surgery were prospectively randomized either to the conventional group (group A, complete median sternotomy) or minimally invasive group (group B, partial upper sternotomy). Intraoperative and postoperative clinical data, and markers of myocardial and cerebral protection were determined. Neuropsychological tests were carried out to quantify psychological disorders.

RESULTS: Operative time and cardiopulmonary bypass time were slightly longer in group B, but not significantly so. No significant inter-group differences were found for postoperative pain scores and respiratory function. Chest tube drainage was significantly less in group B (495 +/- 165 versus 240 +/- 69 ml, p = 0.008). Creatine kinase (CK), CK-MB and troponin T levels were similar in both groups. Neither S-100B protein nor neuron-specific enolase levels differed significantly between groups at all sampling times. There were no strokes in the entire cohort. None of the neuropsychological tests yielded significant inter-group differences between conventional and minimally invasive surgery. C

CONCLUSION: The safety and reliability of AVR via a partial upper sternotomy is reported. Minimally invasive AVR can be performed with only slightly longer operative times, good cosmetic results and significantly less blood loss. A limited surgical access affected neither the patients’ neurological outcome nor the efficacy of myocardial protection.

Author(s): Dogan S, Dzemali O, Wimmer-Greinecker G, Derra P, Doss M, Khan MF, Aybek T, Kleine P, Moritz A.

in: J Heart Valve Dis. 2003 Jan;12(1):76-80.

Optimal carbon dioxide application for organ protection in cardiac surgery.

BACKGROUND: Cardiac surgery is associated with an important risk of central or peripheral organ damage, attributed in part to air embolism from incompletely deaired cardiac chambers. Insufflation of carbon dioxide into the thoracic cavity is widely used for organ protection in cardiac surgery.

METHODS: In patients operated on through a sternotomy, the gas was insufflated through a standard cardioplegia line (group I, n = 10) or a Jackson-Pratt drain (group II, n = 10), with flow rates of 2, 4, and 6 L/min. In patients undergoing mitral valve surgery through a right anterolateral minithoracotomy, application through a gas port (group III, n = 10) was compared with application through a Veress needle (group IV, n = 10). In groups I and IV measurements were repeated with a gauze sponge to divert the gas stream.

RESULTS: At a flow of 2 L/min, carbon dioxide levels in the thoracic cavity reached 52% +/- 30% in group I and increased to 81% +/- 27% when a gauze sponge was used. In group II a level of 91% +/- 5% was achieved. In minimally invasive procedures carbon dioxide levels reached 92% +/- 6% in group III and 60% +/- 25% in group IV without a gauze sponge and 97% +/- 2% in group IV with a gauze sponge. Increasing flow rates from 2 to 6 L/min decreased carbon dioxide levels in the thoracic cavity. Arterial blood gas analysis did not reveal critical levels of partial pressure of carbon dioxide at any time.

CONCLUSIONS: For optimized carbon dioxide concentrations during cardiac procedures, jet effects in the thoracic cavity have to be avoided. The highest levels were achieved with infusion lines covered by a gauze sponge or a perforated drain for conventional operations and a sponge-covered Veress needle or a gas port for minimally invasive approaches.

Author(s): Martens S, Dietrich M, Doss M, Wimmer-Greinecker G, Moritz A.
in: The Journal of Thoracic and Cardiovascular Surgery, 2002 Aug;124(2):387-91.

PMID: 12167800 [PubMed - indexed for MEDLINE]

Erfolgreiche Reoperation eines rupturierten Aortenbogenaneurysmas bei Takayasu Arteriitis.

Takayasu’s disease is an inflammatory arteriopathy that often progresses to stenosis or aneurysms of the large arteries of the aortic arch. In this connection aneurysms of the ascending aorta are rare. We report the case of a 33 years old female with a ruptured aneurysm of the ascending aorta complicated by a former operation of a truncobycarotidal bypass and severe sclerosis. After ascending aorta and aortic arch replacement was performed in deep hypothermia circulatory arrest we could discharge the patient in good condition on the 11. postoperative day.

Author(s): Wohleke T, Martens S, Doss M, Wimmer-Greinecker G, Moritz A.
in: VASA 2002; 31: 132 –135
[Article is in German]

The Heartflo Device for Distal coronary anastomoses: Clinical experience in 60 Patients.

Background. The Heartflo anastomotic device automates the suturing process with simultaneous delivery of 10 standard polypropylene sutures through the graft and the coronary vessel wall to construct the anastomosis. We performed clinical testing in 60 patients undergoing coronary artery bypass grafting.

Methods. One automated distal coronary anastomosis was initially placed in each patient, the other anastomoses were created with standard running sutures. After a “flat foot”-shaped prototype was deployed in 30 patients (group I), the design of the foot was modified and deployment of the new device performed in the next 30 patients (group II).

Results. In group I, automated anastomoses were completed in 16 patients (53%) using 1.7 ± 1 additional stitches. In 26 group II patients (86%), a hemostatic anastomosis using 1.2 ± 1 additional stitches was achieved. Anastomoses were completed in 19.0 ± 3 minutes in group I and in 15.6 ± 2 minutes in group II.

Conclusions. We have shown the feasability of coronary anastomoses using the Heartflo device. The modified version improved tissue capture, resulting in a higher rate of completed anastomoses. Because anastomotic time is still prolonged, an easier suture management is mandatory in the next developmental step.

Author(s): Martens S, Dietrich M, Doss M, Moritz A, Wimmer Greinecker G.
in: Ann Thorac Surg 2002;74:1139-43

Biventricular pacing for weaning from extracorporeal circulation in heart failure.

Resynchronization of the intra- and interventricular conduction by biventricular pacing has been suggested in patients with end-stage heart failure. We present a case in which extracorporeal circulation could only be weaned after placement of an additional left ventricular pacing wire. Biventricular stimulation led to normal motion of the anterior wall and a previously bulging interventricular septum; this improved the hemodynamic situation significantly.

Author(s): Kleine P, Doss M, Aybek T, Wimmer-Greinecker G, Moritz A.
in: The Annals of Thoracic Surgery, 2002 Mar;73(3):960-2.

PMID: 11899211 [PubMed - indexed for MEDLINE]

Sutured coronary artery grafting utilizing the heartflo anastomosis device- first clinical experiences.

BACKGROUND: The Heartflo device was developed to facilitate consistency in distal coronary anastomosis quality. The device automates the suturing process during the anastomosis procedure via simultaneous delivery of ten standard 7-0 polypropylene sutures through the graft and the coronary vessel wall.

METHODS: In 30 elective coronary artery bypass patients, one distal anastomosis was intentionally performed with the anastomosis device. Device success was stated if a patent anastomosis with a minimal flow of 50 ml/min resulted, additional stitches were counted if bleeding occurred.

RESULTS: 4 cases of device failure occurred in the first 5 patients. The subsequent patients were operated without any mechanical problems. In 16 patients (53 %), a patent anastomosis with a mean flow of 75 +/- 6 ml/min using 1.7 +/- 0.3 additional stitches was achieved. Anastomoses were completed in 19.0 +/- 0.7 min; postoperative course was uneventful in all patients.

CONCLUSIONS: We have shown that coronary anastomoses are feasible using the Heartflo device, representing a promising step on the way to automated coronary anastomoses. Its application is still limited by the size and tissue quality of the target vessel and difficult suture management during the anastomosis procedure.

Author(s): Martens S, Doss M, Moritz A, Wimmer-Greinecker G.

in: The Thoracic and Cardiovascular Surgeon,Vol. 50, February 2002: 1 – 5

PMID: 11847595 [PubMed - indexed for MEDLINE]

Five year experience with valve sparing surgery for aortic root aneurysms.

BACKGROUND: The aim of this study was to analyze the mid-term results of aortic root reconstruction.

METHODS: Between September 1995 and March 2001, 32 patients (25 males, 7 females, median age 58 +/- 21 years) underwent aortic root reconstruction as described by T. David. Indications for operation were aortic insufficiency with ascending aortic aneurysm in 27 patients, and acute aortic dissection (Stanford type A) in 5 patients. In all patients the native valve was preserved and suspended inside a tubular prosthesis with reimplantation of the coronary arteries. In 10 patients the classic reconstruction technique was modified by shaping a “Neosinus.”

RESULTS: There was one perioperative death due to myocardial infarction. Two patients suffered a stroke. 26 patients were followed up 12 months postoperatively. 22 out of 26 patients were in NYHA functional class I, 2 patients in class II and the remaining 2 in class III. Three patients died in the postoperative period. Six patients had trivial AR, 4 mild and 1 moderate regurgitation. There were no thromboembolic events during follow up. The mean transvalvular gradient was 3.5 +/- 2.2 mmHg. Compared to a normal cohort of patients (n = 20), resuspended aortic valves opened (26.4 +/- 5.8 vs. 61.3 +/- 22.1 cm/sec, p < 0.0001) and closed (22.8+/- 6.9 vs. 57.9 +/- 22.3) at a higher speeds and also showed shorter opening (0.053 +/- 0.12 vs. 0.023 +/- 0.09 sec, p < 0.0001) and closing times (0.051 +/- 0.07 vs. 0.23 +/- 0.07 cm/sec) of the aortic leaflets.

CONCLUSIONS: Aortic valve reimplantation is a reliable technique able to reduce long term complications when compared to conventional composite graft replacement of the aortic root. Altered leaflet opening and closing dynamics do not impair midterm durability.

This paper was presented at the 30th Annual Meeting of the German Society for Thoracic and Cardiovascular Surgery in Leipzig, February 17th – 21th 2001

Author(s): Aybek T, Wohleke T, Simon A, Doss M, Moritz A.

in: The Thoracic and Cardiovascular Surgeon,Vol. 50, February 2002: 35 – 40
PMID: 11847602 [PubMed - indexed for MEDLINE]

Interventional versus surgical closure of atrial and ventricular septal defects.

Author(s): Moritz A, Doss M, Dogan S, Aybek T, Wimmer-Greinecker G.

in: Journal of Interventional Cardiology, Vol. 13, No. 6, December 2000: 503 – 506

Bridge to Recovery in a patient with isolated right ventricular cardiomyopathy.

A 50 year old patient with an aneurysm of the ascending aorta and an isolated right ventricular cardiomyopathy developed postcardiotomy right heart failure. A right heart bypass using a centrifugal pump and subsequently a Thoratec-assist-device as bridge to transplant were implanted. Despite poor right ventricular function, weaning off the assist-device was possible after a period of 54 days.

Author(s): Hemmer W, Beyer M, Hannekum A, Doss M.
in: Cardiovascular Engineering Vol.5, No.1, March 2000: 19 – 20

Leaflet escape in a Tekna and an original Duromedics bileaflet valve.

We report a case of leaflet escape in an Edwards-TEKNA bileaflet valve, in the mitral position. The examination findings of the explanted valve are compared with a similar case of leaflet escape in an original Edward-Duromedics prosthesis. Based on our findings alone, it is not certain whether the TEKNA valve continues to have a higher risk for fracture.

Of about 20,000 original Edwards – Duromedics bileaflet valves ( Baxter Healthcare Corp , Santa Ana , CA ) ( models 3160 and 9120 ) implanted from 1982 to 1988 , 12 cases of leaflet embolization from the mitral position were reported [ 1 ] . The prosthesis was subsequently withdrawn from the market and reintroduced after modifications as the revised Edwards – Duromedics or TEKNA valve ( models 3160R , 3200 and 9120R , and 9200 ) in June 1990. In recent years , we had to carry out two emergency reoperations due to leaflet embolization of Duromedics prostheses. We report a case of a fractured TEKNA prosthesis as well as the case of a fractured original Duromedics prosthesis.

Case reports

Case 1
A 37 – year-old man was admitted to our Department of Cardiology , with acute onset of severe pulmonary edema and low cardiac output. He had undergone mitral valve replacement with a TEKNA prosthesis ( model 9120R , size 27 mm ) 3 years earlier. Severe mitral regurgitation was diagnosed. The intraoperative findings confirmed an absent posterior mitral valve leaflet. After complete excision of the valve , the left ventricle was palpated in an attempt to retrieve embolized fragments of the leaflet. However , this was unsuccessful. The old valve was replaced by a 29 – mm Medtronic Hall prosthesis ( Medtronic Inc , Minneapolis , MN ) . A search for the remaining embolized leaflet particles was undertaken. By computed tomography , one particle was localized at the aortic bifurcation and another in the left common iliac artery. Both were removed via a transperitoneal approach. They were found to be nearly identical in size , confirming that the leaflet had been broken in half ( Fig 1A , B ) . All parts of the explanted valve were returned to the manufacturing company. The patient made a good recovery.

(Fig 1. Central fracture of a leaflet ( case 1 ) , showing both fragments.)

Case 2
A 64 – year-old man who had undergone mitral valve replacement with a Duromedics prosthesis ( model 9120 , size 31 mm ) in 1986 was admitted to our Department of Cardiology with signs of fulminant pulmonary edema. Cardiac catheterization demonstrated severe mitral regurgitation and a critical stenosis of the right coronary artery. Intraoperatively , the mitral valve prosthesis showed a missing posterior leaflet. The valve was replaced by a 25 – mm Medtronic Hall prosthesis and the patient received a saphenous vein graft to the right coronary artery. Similar to the first case , no periphery pulse deficit gave us an indication to the location of embolization. A foreign body was located in the left common iliac artery by computed tomography and clearly identified in the proximal external iliac artery by B – mode ultrasonic examination. The leaflet was recovered via a retroperitoneal approach. The fracture had occured at one of the pivot balls ( Fig 2 ) . The patient made an uneventful recovery postoperatively. The explanted valve fragments were again sent to the manufacturing firm for inspection.

(Fig 2. Recovered leaflet from second patient ; fracture in the region of the pivoting system.)

Examination of the explanted valve fragments

Case 1
A region of pyrolytic carbon loss , approximately 2 mm in length and 80 ( mu ) m in depth , was observed on the seating lip , which coincided with the location of the central fracture of the leaflet. This pyrolytic carbon loss appeared to be primarily the result of impact as opposed to cavitation or erosion , which are usually related to material quality and flow.

Case 2
Contrary to case 1 , the second case showed a fracture at the leaflet’s pivoting system. Substantial damage in the form of severe pitting on the corresponding pivot slot edge was present.

Comment
Cavitation has been recognized as the reason for the series of valve failures in the Edwards – Duromedics prosthesis. Typical forms of damage attributed to cavitation are pitting and microcracking , which can later give rise to complete fractures , eg , of leaflets. The original Duromedics valve was shown to be more susceptible to cavitation than other comparable bileaflet valves. This was attributed to high velocities on valve closure , especially in surfaces of the inflow side. Cavitation also seems to be promoted by the seating lip , found in Duromedics valves , which halts leaflet movement and can cause high – velocity pressure jets [ 2 and 3 ] . The experience gained from the original Duromedics valve led to several modifications , especially aimed at reducing the valve – closing velocity and the forces of cavitation. The radius of the seating lip was changed , a shock absorber was integrated into the sewing ring , and minor changes of the pivoting joints and the porosity of the material were initiated [ 4 ] . In vitro investigations showed higher cavitation thresholds for the TEKNA valve , comparable with the results for other bileaflet valves [ 5 ] . These findings , however , were not confirmed by all authors. The manufacturing firm reported three cases of leaflet escape for the revised model in 1996 [ 6 ] ; the explanted valves did not show changes typical for cavitation. As a possible reason for valve failure , we must also consider small irregularities in the structure of the material used. Pyrolytic carbon is a very hard but also very brittle substance. Therefore , its surface can be damaged by improper handling , eg , contact with a metallic tool. The currently available clinical data on the TEKNA valve do not show a high risk for fracture. Valve defects , typical for cavitation , have so far not been reported. These early results will have to be confirmed by the clinical course of the coming years.

REFERENCES:

1. Radlick PH. Suspension of marketing Edwards Duromedics bileaflet valve models 3160 and 9120, all sizes. Baxter, Important product information, Santa Ana, CA, 1988:1-2..

2. G. Richard, A. Beavan and P. Strzepa, Cavitation threshold ranking and erosion characteristics of bileaflet heart valve prostheses. J Heart Valve Dis 3 Suppl I (1994), pp. 94-103.

3. G.X. Guo, T.H. Chiang, R.C. Quijano and N.H.C. Hwang, The closing velocity of mechanical heart valve leaflets. Med Eng Phys 16 (1994), pp. 458-464.

4. A. Moritz, W. Klepvtko, S. Rodler et al., Six-year follow-up after heart valve replacement with the Edwards Duromedics bileaflet prosthesis. Eur J Cardiothorac Surg 7 (1993), pp. 84-90.

5. C. Kingsbury, R. Kafesjian, G. Guo et al., Cavitation threshold with respect to dP/dt: evaluation in 29 mm bileaflet, pyrolitic carbon heart valves. Int J Artif Organs 16 (1993), pp. 515-520.

6. Edwards TEKNA bileaflet valve clinical report, June 1996. Baxter Healthcare Corporation, Santa Ana, CA, 1996.. (REcor) Address reprint requests to Dr Hemmer, Sana Herzchirurgische Klinik, Herdweg 2, D-70174 Stuttgart, Germany

Author(s): Hemmer W, Doss M, Hannekum A, Kapfer X.

in: Annals of Thoracic Surgery 2000 Mar;69(3):942-4.

Links:

PMID: 10750795 [PubMed - indexed for MEDLINE]