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Biomedical subjects

Volkmar Falk

Publications and source records attributed to Volkmar Falk.

At least 55 records · Page 3Linked to original sources
PubMed2003

Secundum ASD closure using a right lateral minithoracotomy: five-year experience in 122 patients.

BACKGROUND: Surgical closure of secundum atrial septal defect (ASD) is a standard procedure associated with very low mortality and morbidity. We evaluated outcomes in the era of catheter-based interventional closure and minimally invasive techniques. METHODS: From May 1996, February 2002, 177 patients with a body weight of more than 30 kg underwent surgical ASD closure. A right lateral minithoracotomy (LMT) was used in 122 patients and a conventional approach, in 55. Diagnoses included secundum ASD in 106 patients in the LMT group and 40 in the conventional group, sinus venosus ASD in 13 patients in each group, and status post interventional closure in 3 and 2 patients, respectively. Mean age was 37 +/- 17 years in the LMT group and 43 +/- 20 years, in the conventional group and mean body weight was 66 +/- 17 kg and 70 +/- 16 kg, respectively. In the LMT group, femoral cannulation was performed for cardiopulmonary bypass. RESULTS: Direct ASD closure was carried out in 67.2% of patients in the LMT group and 58.2% of those in the conventional group. The remaining patients had pericardial patch closure. There was one death: A patient in the conventional group who required explantation of an Amplatzer device because of infection died postoperatively. Average stay in the intensive care unit was 1.2 +/- 0.5 days. Two patients required reoperation for residual ASD after direct closure; 1 sustained a temporary neurological deficit that resolved completely. On postoperative echocardiography, a minimal residual shunt was seen in only 3 patients. All patients were in good clinical condition with improved functional status at discharge from the hospital. CONCLUSIONS: Secundum ASD closure by LMT has become as standard and safe an operation as the conventional technique and achieves good perioperative results and satisfactory long-term outcomes. Thus LMT is an attractive option for patients who are not suitable for closure using catheter-based devices.

Adolescent↗
PubMed2003

Limitations for manual and telemanipulator-assisted motion tracking--implications for endoscopic beating-heart surgery.

BACKGROUND: Surgical performance is limited by human factors. Beating-heart surgery requires full dexterity and motion tracking. Currently techniques for total endoscopic beating-heart bypass grafting using telemanipulation systems are being developed. The aim of this study was to assess the limitations for manual and telemanipulator-assisted motion tracking using the da Vinci telemanipulator system. METHODS: To simulate beating-heart conditions an endoscopic trainer was developed. Twenty subjects were asked to touch targets manually and with telemanipulator assistance with different patterns of increasing index of difficulty (resting model, unstabilized, and stabilized model with a frequency of 35, 60, and 90 beats per minute). In addition one task was performed using different scaling ratios on a resting model. The times between hits as well as errors were electronically recorded. RESULTS: There was no significant impact of various frequencies and amplitudes for manual tracking. The average values for the delay (k(m)[ms]) and information-processing (c(m) [ms/bit]) constants for the manual tasks were 201 ms and 86 ms/bit respectively. Both the delay constant (k(t) = 630 ms; p < 0.0005) and the information-processing constant (c(t) = 250 ms/bit; p < 0.0005) were increased for the telemanipulator-assisted tasks at rest. When working on moving targets telemanipulator-assisted tracking required significantly more time and led to more errors. At a frequency of 90 beats per minute telemanipulator-assisted tracking became more difficult. CONCLUSIONS: Endoscopic beating-heart bypass grafting requires optimal stabilization to avoid inaccuracies due to incomplete motion tracking. At higher frequencies telemanipulator-assisted tracking became more difficult, demonstrating the technical limits of current telemanipulator technology.

Cardiac Surgical Procedures↗
PubMed2003

Facilitated endoscopic beating heart coronary artery bypass grafting using a magnetic coupling device.

BACKGROUND: Suturing of a coronary anastomosis in totally endoscopic coronary artery bypass grafting on the beating heart is technically demanding. The potential benefits of the endoscopic Magnetic Vascular Positioner device (Ventrica, Inc, Fremont, Calif) to facilitate construction of a coronary anastomosis in a closed chest environment were evaluated. METHODS: Totally endoscopic coronary artery bypass grafting on the beating heart was performed in 8 foxhound-beagle inbred dogs with the da Vinci telemanipulation system (Intuitive Surgical, Mountain View, Calif). A prototype of the endoscopic Magnetic Vascular Positioner device was used to facilitate construction of the coronary anastomosis. One pair of magnets was inserted in the internal thoracic artery and left anterior descending artery using robotic instruments to guide and place the endoscopic delivery platform. All animals underwent angiography; gross inspection of the anastomotic site was performed after excision of the hearts. RESULTS: The procedure was accomplished in all animals in 169 minutes (155-190 minutes). Dissection of the left anterior descending coronary artery (6.5 minutes; 1-20 minutes), positioning of the stabilizer (8.5 minutes; 7-16 minutes), placement of occlusion tapes (6 minutes, 3-10 minutes), and arteriotomy 5.5 minutes (3-30 minutes) was achieved without problems. By use of the Magnetic Vascular Positioner device, the anastomosis at the graft site was performed with the graft still in situ. Except for 1 premature deployment, all other deployments were easily accomplished in 3 minutes (1-28 minutes). The following adverse events were encountered: bleeding from the right ventricle caused by occlusion tape (1), anastomotic leakage on reperfusion requiring repair stitches (2), and anastomotic occlusion as a result of thrombus (1). All except 1 animal with a patent graft and anastomosis survived the procedure. The overall patency was 7 of 8. DISCUSSION: The combination of robotic technology allowing for dexterous manipulation in a closed chest environment and a simple yet effective and timesaving technique for anastomotic coupling may facilitate beating heart totally endoscopic coronary artery bypass grafting.

Anastomosis, Surgical↗
PubMed2003

Magnetic vascular coupling for distal anastomosis in coronary artery bypass grafting: a multicenter trial.

OBJECTIVE: The hand-sewn anastomosis is the "gold standard" for performing coronary artery bypass grafts. However, performing a hand-sewn anastomosis is more demanding and time-consuming when used in less invasive approaches such as small access, totally endoscopic or beating heart surgery. In conjunction with attempts to reduce the surgical trauma of coronary artery bypass grafts by using these less invasive approaches, alternative methods for constructing distal anastomoses should be explored. These data report on predischarge angiographic findings and 30-day clinical follow up of patients who have received a new distal anastomotic device. METHODS: In a multicenter trial, 32 patients (mean age: 65 +/- 9 years; 85% men) requiring multivessel coronary artery bypass surgery had 1 of the anastomoses performed using a novel anastomotic technology. The Magnetic Vascular Positioner System was used in 1 of the bypass grafts and the other bypasses were completed by conventional hand-sewn technique. The Magnetic Vascular Positioner System consists of 4 magnetic, gold-plated implants and 2 delivery devices that facilitate the creation of a functional end-to-side anastomosis. A predischarge angiogram was performed to evaluate graft patency. RESULTS: There were no device-related major adverse events. The application of the Magnetic Vascular Positioner device was successful in 32 of 41 cases (78%). Nine patients were intended for treatment but did not receive the Magnetic Vascular Positioner System. In 5 of the cases the coronary artery was too small; 1 case had a posterior wall plaque in the target artery; and 3 patients had a nonhemostatic anastomosis after coupling of the port and were subsequently converted to hand-sewn anastomoses. The median total Magnetic Vascular Positioner anastomotic time was 137 seconds with a range from 65 to 370 seconds. Overall patency rate of the Magnetic Vascular Positioner anastomosis was 93.5% versus 91.7% (P = not significant) in hand-sewn grafts. One patient (3.1%) died due to low cardiac output but had patent grafts at autopsy. One myocardial infarction (3.1%) occurred the day after a percutaneous transluminal coronary angioplasty of a hand-sewn graft. One prolonged mechanical ventilation (3.1%) was required because of pneumonia and adult respiratory distress syndrome. CONCLUSIONS: Magnetic vascular coupling in coronary surgery is safe and effective and has acceptable early patency rates. This new technique may facilitate beating heart and minimally invasive coronary artery bypass grafts.

Adult↗
PubMed2003

Robotic coronary artery bypass grafting (CABG)--the Leipzig experience.

Technical and anatomical limitations as well as human factors complicate endoscopic coronary bypass surgery. Computer-enhanced telemanipulation systems overcome some of these shortcomings by restoring the dexterity and precision of a distant operator (surgeon) within a confined space. Endoscopic coronary artery bypass grafting (CABG) has evolved from a merely experimental approach to a clinical concept. Although CABG was initially exclusively performed on the arrested heart, adjunct technologies such as endoscopic vacuum-assisted stabilizers now allow a closed-chest, beating-heart procedure. The development of anastomotic devices, and further refinements in telemanipulator technology, optical systems, and image-guided augmented-reality scenarios will greatly facilitate endoscopic bypass grafting in the future.

Coronary Artery Bypass↗
PubMed2003

Mitral valve repair in patients with end stage cardiomyopathy: who benefits?

OBJECTIVE: Patients with end stage cardiomyopathy frequently present with additional severe mitral regurgitation. We analyzed the outcome of mitral valve reconstruction in this high risk patient group. METHODS: Sixty-six patients with significant mitral regurgitation and an ejection fraction (EF) below 30% (dilated cardiomyopathy=53, ischemic cardiomyopathy (ICM)=13) were retrospectively evaluated from 07/96 and 02/02. All received annuloplasty ring implantation and additional repair (n=4) if required. Mean follow-up was 28+/-18 months. RESULTS: Mitral valve repair (MVR) was technically feasible in all patients. Intraoperative transesophageal echocardiography (TEE) revealed none (n=60) or only trivial (n=6) residual mitral regurgitation. Thirty day mortality was 6.1%. Actuarial survival after 1 and 5 years was 86+/-4 and 66+/-8%, respectively. During follow-up seven patients were transplanted due to lack of clinical improvement after 10+/-7 months (range 1-23). Echocardiography revealed a significant improvement in EF (25+/-10.5% pre-op, 34+/-15% post-op) and a slight decrease in left ventricular end-diastolic diameter (69+/-10 mm pre-op, 67+/-13 mm follow up). Patients were in NYHA functional -class 3 (median) preoperatively and in class 2 at long term-follow-up. Gender, left ventricular enddiastolic diameter, preoperative ejection fraction or type of surgical approach (sternotomy, right lateral minithoracotomy) had no significant influence on patient outcome. Patients with ICM or patients older than 60 years showed an increased risk for clinical events both early post-operatively and at long-term follow-up. CONCLUSION: MVR can be performed with low perioperative morbidity and mortality even in patients with advanced heart failure, modifying selection criteria for potential candidates may further improve long term outcome.

Adult↗
PubMed2003

Totally endoscopic multivessel coronary artery bypass surgery using the da Vinci surgical system: a feasibility study on cadaveric models.

BACKGROUND: The aim of the study was to develop a totally endoscopic coronary artery bypass procedure for the treatment of multivessel disease (MVTECAB). METHODS: Procedure development was conducted on 6 human cadavers with the da Vinci Surgical System. For aortic clamping, a transthoracic aortic clamp was applied. The proximal anastomoses of vein grafts were created transthoracically with the Corlink automated anastomosis device. The target vessels on the heart were exposed with a modified endoscopically applicable Starfish vacuum device. In 1 cadaver, the endo-sling and endoscopic fan retractors were studied for exposure support. RESULTS: Harvesting of bilateral internal thoracic arteries was easily accomplished. Aortic clamping was easier from the right side. In the left-side approach, the proximal anastomoses were completed without leakage in all 3 cadavers. One incorrect deployment occurred, and the deployment needed to be redone. In the right-si d e approach, 1 proximal anastomosis was performed without leakage, and another needed to be repaired for incorrect deployment. The fan retractors either covered too much of the targeted area of the heart surface or did not provide good manipulation capabilities. The endo-sling enabled atraumatic exposure of the target vessels. The modified Starfish performed sufficiently for exposing target vessels. Problems were found with epicardial fat clogging the Starfish suction chamber and with bending of the suction tube neck, both of which resulted in a loss of tissue contact. Two of the cadavers approached from the left side were completely revascularized with 3 grafts, and 4 anastomoses were performed on the third cadaver. Triple-vessel revascularization was performed in the cadavers approached from the right side. CONCLUSION: This study demonstrates the feasibility of performing an MVTECAB on the arrested heart with the da Vinci Surgical System. Further procedure development is necessary to optimize the synergistic effects of the technologies used and to introduce this operation into clinical practice.

Cadaver↗
PubMed2003

Computer-enhanced endoscopic coronary artery bypass grafting: the da Vinci experience.

Anatomical and technical limitations as well as human factors render endoscopic coronary artery bypass surgery difficult. The da Vinci telemanipulator overcomes some of these shortcomings by restoring the dexterity and precision of a distant operator within the confined space in a closed-chest environment. Using the da Vinci system, total endoscopic coronary artery bypass grafting has evolved from a merely experimental surgical approach to a clinically applicable treatment option. Initially exclusively performed on the arrested heart, adjunct technologies such as endoscopic vacuum-assisted stabilizers now allow a single-vessel closed-chest beating heart procedure in selected patients. Despite the technical progress, endoscopic multivessel bypass grafting has yet to be achieved. The development of endoscopically applicable anastomotic devices and heart-positioning devices along with further refinements in telemanipulator technology, better optical systems, and image guided augmented reality scenarios may facilitate endoscopic bypass grafting in the future.

Cardiac Surgical Procedures↗
PubMed2002

Left ventricular reverse remodeling after surgical therapy for aortic stenosis: correlation to Renin-Angiotensin system gene expression.

BACKGROUND: Surgical therapy for aortic stenosis leads to reverse remodeling, with normalization of left ventricular hypertrophy (LVH). The aim of this study was to examine Renin-Angiotensin system (RAS) gene expression in this setting. METHODS: Growing sheep (n=44) underwent supracoronary aortic banding for controlled induction of LVH at the age of 6 to 8 months (A=baseline). Surgical revision to completely release the pressure gradient was performed 8.3+/-1 months later (B). The animals were sacrificed after another 10.1+/-2 months (C). Along with hemodynamic measurements, subtractive hybridization and competitive polymerase chain reaction were applied to quantify mRNA expression for angiotensin-converting enzyme (ACE) and angiotensin receptors 1 and 2 (AT1-R and AT2-R). RESULTS: Left ventricular mass index was 82+/-21 g (A), 150+/-33 g (B), and 78+/-18 g (C), P<0.01. Left ventricular function and cardiac index remained stable. Myocardial fiber diameter was 11.3+/-0.8 (A), 15.9+/-1.2 (B), and 11.4+/-1 (C) microm, P<0.01. Gene expression was as follows: ACE 0.8+/-0.05 (A), 1.3+/-0.08 (B), and 0.9+/-0.06 (C), P<0.01; AT1-R 0.7+/-0.06 (A), 0.9+/-0.07 (B), and 0.3+/-0.04 (C), P<0.01; AT2-R 0.5+/-0.05 (A), 0.2+/-0.04 (B), and 0.5+/-0.05 (C), P<0.01. CONCLUSION: LVH in aortic stenosis coincides with significant alterations of the RAS. Surgical therapy leads to reverse remodeling, which is paralleled by regression of RAS gene expression.

Animals↗
PubMed2002

Comparison of stenting with minimally invasive bypass surgery for stenosis of the left anterior descending coronary artery.

BACKGROUND: Minimally invasive bypass surgery and coronary-artery stenting are both accepted treatments for isolated stenosis of the proximal left anterior descending coronary artery. We compared the clinical outcomes after these two procedures. METHODS: A total of 220 symptomatic patients with high-grade lesions in the proximal left anterior descending coronary artery were randomly assigned to treatment--110 to surgery and 110 to stenting. The combined clinical end point was freedom from major adverse cardiac events, such as death from cardiac causes, myocardial infarction, and the need for repeated revascularization of the target lesion within six months. RESULTS: A major adverse cardiac event occurred in 31 percent of patients after stenting, as compared with 15 percent in the surgery group (P=0.02). The difference was predominantly due to a higher rate of repeated revascularization of the target vessel for restenosis after stenting (29 percent vs. 8 percent, P=0.003). The combined rates of death and myocardial infarction did not differ significantly between groups (3 percent in the stenting group and 6 percent in the surgery group, P=0.50). Adverse events occurred more frequently after surgery. The percentage of patients free from angina after six months was 79 percent in the surgery group, as compared with 62 percent in the stenting group (P=0.03). CONCLUSIONS: In patients with isolated high-grade lesions of the proximal left anterior descending artery, both minimally invasive bypass surgery and stenting are effective. Stenting yields excellent short-term results with fewer periprocedural adverse events, but surgery is superior with regard to the need for repeated intervention in the target vessel and freedom from angina at six months of follow-up.

Angioplasty, Balloon, Coronary↗
PubMed2002

[Arterial revascularization of coronary vessels].

UNLABELLED: ARTERIAL GRAFTS: Atherosclerosis is the major cause of late vein graft failure and has led to the use of arterial grafts. The use of the left internal thoracic artery (ITA) is associated with improved survival which has been proven in numerous studies. Recent studies have also demonstrated a survival benefit of double over single ITA graft use. Especially in younger patients bilateral ITA grafting is recommended. SURGICAL TECHNIQUE: In terms of dissection of the graft, the technique of skeletizing the artery seems beneficial especially in diabetics to decrease the likelihood of mediastinitis. The radial artery is mainly used as a T graft in order to achieve complete arterial revascularization. RESULTS: While patency rates seem superior as compared to vein grafts, a survival benefit has yet to be proven. Irrespective of graft type, in-situ-grafts have a superior patency as opposed to free grafts. As has long been demonstrated with vein grafts, patency of arterial grafts also depends on the size of the recipient vessel. Grafts to the distal circumflex and distal right coronary artery have worse patency rates than grafts to the LAD. Conflicting results exist concerning the gastroepiploic artery; its use can only be recommended if the vessel is of good caliber. All other arterial conduits are used infrequently and there are no data to draw any meaningful conclusion for routine use. Arterial revascularization on the beating heart is feasible and short and midterm follow-up data are encouraging. CONCLUSION: Our current policy is to perform complete arterial revascularization in all patients under the age of 70 using bilateral ITAs and radial arteries.

Arteries↗
PubMed2002

Endoscopic internal thoracic artery dissection leads to significant reduction of pain after minimally invasive direct coronary artery bypass graft surgery.

BACKGROUND: The aim of this study was to evaluate postoperative pain levels after endoscopic versus conventional internal thoracic artery (ITA) dissection for minimally invasive direct coronary artery bypass graft surgery (MIDCABG) surgery. Results were compared with pain levels associated with conventional cardiac bypass operations through a median sternotomy. METHODS: Of 190 patients included in this prospective study, 24 patients had endoscopic ITA takedown (MIDCABG-endo) using the da Vinci telemanipulator followed by a manual coronary anastomosis through a left minithoracotomy. A conventional MIDCABG operation (MIDCABG-conv) was performed in 73 patients with ITA preparation under direct vision. Postoperative pain levels after conventional CABG through a median sternotomy (CABG-conv, n = 93) served as controls. A standarized questionnaire including visual analog scale (VAS) was used for prospective pain assessment from POD 1 to 7. RESULTS: Pain levels (VAS) declined in all groups from POD 1 to 7. Overall pain levels were significantly lower in the MIDCABG-endo group as compared with MIDCABG-conv and CABG-conv groups, respectively (p < 0.001, general linear model). There was no significant difference between the MIDCABG-conv and CABG-conv (p = not significant, general linear model) groups. Furthermore, patients after MIDCABG-endo required fewer nonsteroidal anti-inflammatory drugs and opioid medications, postoperatively. CONCLUSIONS: An endoscopic ITA takedown in MIDCABG surgery leads to significantly reduced postoperative pain levels possibly because of less rib retraction.

Aged↗
PubMed2002

Up-regulation of Bcl-2 through hyperbaric pressure transfection of TGF-beta1 ameliorates ischemia-reperfusion injury in rat cardiac allografts.

BACKGROUND: Oxidative stress after ischemia-reperfusion of cardiac allografts leads to activation of cardiomyocytes and production of cytokines. Bcl-2, an inhibitor of the apoptotic pathway, also has strong antioxidant properties. Ischemia-reperfusion injury after transplantation leads to decreased bcl-2 and increased tumor necrosis factor (TNF)-alpha levels. Transforming growth factor (TGF)-beta1 is known to attenuate ischemia-reperfusion injury and inhibits apoptosis of myofibroblasts. We hypothesize that TGF-beta1, prevents bcl-2 cleavage and increased TNF-alpha production. METHODS: Rat PVG donor hearts were heterotopically transplanted into ACI recipients. Donor hearts were procured and assigned to groups: (1) intracoronary TGF-beta1 (200 ng/ml) perfusion and pressure at 78 psi for 45 minutes (n = 4); (2) intracoronary TGF-beta1 perfusion and incubation for 45 minutes without pressure (n = 4), (3) saline perfusion and incubation for 45 minutes without pressure (n = 4). Hearts were procured 4 hours after transplantation and analyzed by reverse transcriptase-polymerase chain reaction for bcl-2 mRNA expression, ELISA for TNF-alpha, and for myeloperoxidase activity (MPO). RESULTS: Bcl-2 decreased in untreated animals (bcl-2:G3PDH ratio = 0.85 +/- 0.73 vs 1.16 +/- 0.11, not significant [NS]), whereas TNF-alpha increased to 669.99 +/- 127.09 vs 276.84 +/- 73.65 pg/mg total protein in controls (p < 0.003). In TGF-beta(1) pressure-treated hearts, bcl-2 was up-regulated (2.49 +/- 0.6 vs 1.16 +/- 0.11, controls, p < 0.005), whereas TNF-alpha was unchanged (396.1 +/- 100.38 vs 276.84 +/- 73.65 pg/mg, NS). Hearts treated with TGF-beta1 and pressure showed significant up-regulation of bcl-2 compared with hearts treated with TGF-beta1 without pressure (2.49 +/- 0.6 vs 1.17 +/- 0.6, p < 0.02). MPO showed no differences. CONCLUSIONS: Bcl-2 is down-regulated and TNF-alpha up-regulated in this model of ischemia-reperfusion injury. Furthermore, TGF-beta1 is linked to this process and ameliorates reperfusion injury by up-regulating bcl-2 and inhibiting TNF-alpha. Therapeutic overexpression of myocardial TGF-beta1 may be clinically useful to control ischemia-reperfusion injury associated with cardiac transplantation.

Animals↗
PubMed2002

Experimental evaluation and early clinical results of a new low-profile bileaflet aortic valve.

We performed an experimental and clinical evaluation of a new low-profile bileaflet aortic valve (Regent, St. Jude Medical Inc., St. Paul, MN, U.S.A.). Common valve sizes were experimentally tested for leakage volume, pressure drop, and transvalvular hemodynamics using a pulse duplicator. Thirty patients (mean age 60 +/- 7 years, predominant valve stenosis n = 25) received the Regent prosthesis for initial clinical evaluation. In vitro evaluation revealed equivalent leakage volumes, larger performance indices (0.552 versus 0.513), and lower pressure drops in comparison to SJM hemodynamic plus valve controls. Clinically, 21 mm (n = 9), 23 mm (n = 12), and 25 mm (n = 9) valves were implanted with no significant perioperative complications. Echocardiography revealed low transvalvular flow velocities (2.2 +/- 0.4 m/s) and low pressure gradients (20 +/- 6 mm Hg) postoperatively and at 6 months follow-up. In vitro testing and early clinical results are promising; however, long-term performance has to be proven.

Aged↗
PubMed2002

Hemodynamic evaluation of stentless mitral valve replacement.

The purpose of this study was to evaluate the perioperative and postoperative hemodynamic function of recently introduced stentless mitral valves (SMVs). Forty-two selected patients who had received the SMV since 1997 had preoperative, postoperative, and follow-up transthoracic echocardiographic (TTE) examinations. Transesophageal echocardiography (TEE) was applied routinely during the operation as well as postoperatively if indicated. Adequate SMV function was seen in all patients perioperatively. Echocardiographic prediction of valve size and of papillary muscle distances was correct in 37 of 42 patients. Transvalvular blood flow velocities were 1.6 +/- 0.2 m/s postoperatively versus 1.8 +/- 0.3 m/s at 1 year and 1.7 +/- 0.3 m/s at 3-year follow-up. Mean transvalvular gradients were 4.3 +/- 1.6, 3.8 +/- 1.9, and 4.7 +/- 1.1 mm Hg, respectively. TEE and TTE are extremely useful to assist SMV implantation as well as for regular follow-up evaluation. The hemodynamic function after SMV implantation with preservation of the annulo-ventricular continuity is promising.

Aged↗