Biomedical subjects

Stephan Jacobs

Publications and source records attributed to Stephan Jacobs.

9 recordsLinked to original sources

PubMed2006

Modeling of temperature mapping for quantitative dynamic infrared coronary angiography for intraoperative graft patency control.

OBJECTIVES: Intraoperative application of thermal coronary angiography based on dynamic infrared imaging leads to useful qualitative information concerning coronary artery bypass graft flow and anatomy. Additional quantitative flow estimation is desirable to detect graft failures. The aim of this study was to develop a heat-transfer model for quantitative flow estimation in an experimental setup. The first clinical results in coronary artery bypass grafting are reported. METHODS: Dynamic infrared imaging was applied in pig hearts to collect video data of the rewarming process of the left anterior descending artery supplied by antegrade perfusion. For mathematic description, we used the dynamic enthalpy balance for open systems, and a Laplace transformation was carried out. Therefore the time constant tau was calculated by performing a nonlinear fit procedure on the averaged dynamic temperature curves recorded over a left anterior descending artery segment. Subsequently, left internal thoracic artery-left anterior descending artery bypass graft flow was assessed intraoperatively. Effective left anterior descending artery flow was determined by using a transit-time flowmeter. RESULTS: Tau is a system constant and changes depending on the flow and the system capacity. Assuming system capacity to be constant, tau only depends on the flow. It follows from the differential equation that there is a potential relation between tau and the flow. An excellent comparison (R2 = 0.968, P <.005) was demonstrated. By using the algorithms, quantitative flow estimation in pig hearts was possible. For clinical application, the formulas were applied to intraoperatively derived dynamic temperature curves with a good comparison to the actual left internal thoracic artery-left anterior descending artery flow. CONCLUSION: The developed heat-transfer model allows for precise measurement of graft flow by using dynamic infrared imaging and can be applied for noninvasive graft flow estimation in beating-heart surgery.

Animals↗

PubMed2006

Surgical PACS for the digital operating room. Systems engineering and specification of user requirements.

For better integration of surgical assist systems into the operating room, a common communication and processing plattform that is based on the users needs is needed. The development of such a system, a Surgical Picture Aquisition and Communication System (S-PACS), according the systems engineering cycle is oulined in this paper. The first two steps (concept and specification) for the engineering of the S-PACS are discussed.A method for the systematic integration of the users needs', the Quality Function Deployment (QFD), is presented. The properties of QFD for the underlying problem and first results are discussed. Finally, this leads to a first definition of an S-PACS system.

Computer Simulation↗

PubMed2005

Comparison of bare-metal stenting with minimally invasive bypass surgery for stenosis of the left anterior descending coronary artery: a 5-year follow-up.

BACKGROUND: Randomized trials comparing stenting with minimally invasive direct coronary artery bypass surgery in patients with isolated proximal left anterior descending lesions have shown a significantly higher reintervention rate for stenting and similar results for mortality and reinfarction at short-term follow-up. Long-term follow-up data are sparse. METHODS AND RESULTS: Patients with isolated proximal left anterior descending stenosis were randomized to either surgery (n=110) or bare-metal stenting (n=110). At 5 years, follow-up data were obtained with respect to the primary end point of death, reinfarction, or repeated target vessel revascularization. Clinical symptoms were assessed by the Canadian Cardiovascular Society (CCS) classification. Follow-up information was completed for 216 patients (98.2%), and mean follow-up was 5.6+/-1.2 years. With respect to mortality (surgery, 12%; stenting, 10%; P=0.54) and reinfarctions (surgery, 7%; stenting, 5%; P=0.46), there were no differences between treatment strategies. The need for repeated target vessel revascularization was significantly higher after stenting (32%) compared with surgery (10%; P<0.001). Clinical symptoms improved significantly in both treatment groups compared with baseline; however, there was a favorable trend for surgery (stenting: CCS, 2.6+/-0.9 to 0.5+/-0.8, P<0.001; surgery: CCS, 2.6+/-0.9 to 0.3+/-0.6, P<0.001; P=0.05, stenting versus surgery). CONCLUSIONS: At the 5-year follow-up, minimally invasive bypass surgery and bare-metal stenting showed similar results for the end points of mortality and reinfarctions. However, the reintervention rate is higher after stenting, and the relief in clinical symptoms is slightly better after surgery.

Aged↗

PubMed2005

Redo minimally invasive direct coronary artery bypass grafting.

BACKGROUND: Conventional redo coronary artery bypass grafting is associated with an increased risk of mortality and morbidity as a result of manipulation of patent grafts, mediastinitis, and the presence of pericardial adhesions. Minimally invasive direct coronary artery bypass grafting may be an alternative approach in selected patients. METHODS: From January 1997 to October 2003, 46 patients (mean age, 66 +/- 7.4 years) underwent minimally invasive direct coronary artery bypass grafting using the left internal thoracic artery to the left anterior descending artery on the beating heart as a reoperation. Patients after previous cardiac operation by means of median sternotomy without use of the left internal thoracic artery presenting with a significant left anterior descending artery stenosis ("culprit lesion") were included. Predicted mortality was 13.6% (range, 2.4% to 72.8%) as calculated by the logistic Euroscore; ejection fraction was 0.531 (range, 0.14 to 0.81). Surgical results were analyzed for mortality, morbidity, duration of the procedure, hospital stay, and event-free survival. RESULTS: Mean operating time was 103 +/- 34 minutes. There were two in-hospital deaths (4.6%), one for malignant ventricular arrhythmia (Euroscore, 60.9%) and the second as a result of severe gastrointestinal bleeding (Euroscore, 29.2%). One patient (2.3%) was successfully reoperated on because of perianastomotic hematoma using the same approach after 6 days. Patients were discharged after 9.4 +/- 2.6 days. There were no other serious adverse events, no stroke, and no myocardial infarction. During follow-up (37 +/- 21 months, complete in 92.1%), 1 patient experienced angina and 6 patients died. The actuarial 4-year survival is 74.8% (95% confidence interval, 51% to 92%), and the actuarial 4-year event-free survival including freedom from angina, major adverse cardiac events, and reintervention is 81% (95% confidence interval, 54% to 97%). CONCLUSIONS: Minimally invasive direct coronary artery bypass grafting can be considered as an alternative approach for redo coronary artery bypass grafting in selected patients.

Aged↗

PubMed2005

Facilitated MIDCAB using a magnetic coupling device.

A 59-year-old male with chronic occlusion of the left anterior descending coronary artery underwent a minimally invasive direct coronary artery bypass procedure using the second generation of a magnetic anastomotic coupling device. Postoperative angiogram demonstrated excellent patency and flow.

Anastomosis, Surgical↗

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

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

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↗