Motion estimation in beating heart surgery.

Minimally invasive beating-heart surgery offers substantial benefits for the patient, compared to conventional open surgery. Nevertheless, the motion of the heart poses increased requirements to the surgeon. To support the surgeon, algorithms for an advanced robotic surgery system are proposed, which offer motion compensation of the beating heart. This implies the measurement of heart motion, which can be achieved by tracking natural landmarks. In most cases, the investigated affine tracking scheme can be reduced to an efficient block matching algorithm allowing for realtime tracking of multiple landmarks. Fourier analysis of the motion parameters shows two dominant peaks, which correspond to the heart and respiration rates of the patient. The robustness in case of disturbance or occlusion can be improved by specially developed prediction schemes. Local prediction is well suited for the detection of single tracking outliers. A global prediction scheme takes several landmarks into account simultaneously and is able to bridge longer disturbances. As the heart motion is strongly correlated with the patient's electrocardiogram and respiration pressure signal, this information is included in a novel robust multisensor prediction scheme. Prediction results are compared to those of an artificial neural network and of a linear prediction approach, which shows the superior performance of the proposed algorithms.

Myosplint implant and shape-change procedure: intra- and peri-operative safety and feasibility.

BACKGROUND: In patients with dilated cardiomyopathy (DCM), the heart enlarges, leading to a corresponding increase in ventricular wall stress. To reduce the stress, transventricular tension members (Myosplint, Myocor, Inc.) were implanted to change the left ventricle (LV) effective radius and to reduce the LV wall stress by 20%. We conducted this study to evaluate the intra- and peri-operative safety and feasibility of LV-shape change therapy. METHODS: In 7 patients, all diagnosed with DCM, Myosplints were implanted. New York Heart Association class ranged from III-IV, and LV end-diastolic diameter ranged from 70 to 102 mm. Mitral valve regurgitation was classified as mild in 3 and moderate in 4 cases. Four patients underwent mitral valve annuloplasty. RESULTS: We observed no significant device-related complications, such as thromboembolism, bleeding, device instability, or vascular damage, at 90 days. Early indications in a small patient population demonstrate some improvements in clinical parameters. CONCLUSIONS: From this initial experience, one may conclude that placement of the Myosplint devices can be safely performed without early, significant adverse events. In patients with significant mitral valve incompetence, concomitant mitral valve repair is indicated to realize the full benefit of the procedure. This study also suggests that Myosplints can be safely implanted in combination with mitral valve repair. The long-term effect of each procedure on cardiac function and survival will require further evaluation.

Comparison of two stabilizer concepts for off-pump coronary artery bypass grafting.

BACKGROUND: This study was designed to evaluate the efficacy of two different stabilizer concepts for off-pump coronary artery bypass grafting. METHODS: Between 2000 and 2001, 100 consecutive patients who underwent off-pump coronary artery bypass grafting were randomly assigned to two stabilization systems: the Medtronic Octopus 3 (n = 50) and the Genzyme Immobilizer (n = 50). During operation, two-dimensional cardiac surface motion was assessed by intravital microscopy using orthogonal polarization spectral imaging in 20 vessels at the anterior wall. Postoperative angiography of 47 vessels revealed anastomotic quality. RESULTS: Patient demographics were similar in both groups regarding age, sex, ejection fraction, and New York Heart Association functional class. In 7 patients the randomized Immobilizer was rejected by the surgeon for lateral or posterior wall revascularization and subsequently switched to the Octopus device. Patients received 1.8 +/- 0.7 grafts in the Octopus and 1.6 +/- 0.5 in the Immobilizer group (p = not significant). Two-dimensional cardiac surface motion was significantly less using the Immobilizer (109.7 +/- 32.4 microm versus 423.5 +/- 129.6 microm; p < 0.001). Time required for anastomosis was significantly shorter in the Immobilizer group (11.3 +/- 3.5 versus 14.9 +/- 2.4 minutes; p < 0.001). Postoperative angiography showed no vessel occlusions but two anastomotic stenoses in each group. CONCLUSIONS: Both stabilizers have been shown useful for off-pump coronary artery bypass grafting. The Immobilizer system showed better epicardial immobilization of the anterior wall resulting in shorter anastomosis times. However, because the Octopus 3 handling is more flexible and allows easier access to all vessels, it is the device of choice for posterior wall revascularization in our institution.

Successful resection of a symptomatic right ventricular lipoma.

We report the case of a 31-year-old woman with a 4-year history of recurrent palpitations, presenting with an increased frequency of paroxysms caused by ventricular tachycardias during pregnancy. A cardiac tumor of unknown origin infiltrating the right ventricle was diagnosed. Three weeks after prophylactic abrasion the tumor was totally excised with the use of cardiopulmonary bypass including restoration of the right ventricular wall and the tricuspid valve. Histology confirmed diagnosis of a benign cardiac lipoma. The postoperative course was uneventful and the patient was discharged 7 days after surgery. There was no episode of ventricular tachycardias during the 6-month follow-up.

Incorporating robotics into an open-heart program.

The above described clinical series show that after a careful and thorough training program and stepwise introduction of surgical telemanipulation systems, application of telemanipulations is safe and shows acceptable results. Still, OR times are longer than for conventional procedures, and the operation is demanding, and expensive. The main shortcoming is that the procedure is only suitable for a highly selected patient population. However, despite all the clinical experience gathered in various centers, this technique is still evolving and in its beginning. There are some very promising developments that will improve the benefit of telemanipulators. For the first time, the separation of the surgeon from the surgical field facilitates training of surgeons on simulators. This might lead to a higher standard of surgical performance. Progress in sensor technology will make tactile-force feedback available, and new 3 D-visualization systems are designed to provide a better depth perception and higher resolution of the endoscopic image. Virtual stabilizing systems will enable robotic systems to operate on a virtual arrested heart without the need for CPB or mechanical stabilizers. These and other research topics summarized under the term augmented reality will enhance the natural senses and abilities of the surgeon. More and more, automatization will find its way into the OR. Preoperatively collected data about the patient's anatomy will be used to create safety margins, the robotic system will allow for the surgeon's movements, and instruments will be able to find their way to the surgical site without remote control. Because a stepwise approach has led to the clinical results that we and others have now achieved, it is the basis for further step-by-step development of the application of telemanipulation systems in coronary artery bypass grafting, and possibly other endoscopic procedures in cardiac surgery.

Robotically assisted coronary artery bypass surgery with the ZEUS telemanipulator system.

Our goal of minimally invasive coronary bypass surgery is a completely endoscopic operation and anastomosis. Minimally invasive procedures reduce the invasiveness of the operation and therefore the morbidity and length of hospitalization of the patients. A possible solution to the technical problems that accompany manually performed endoscopic anastomoses is telemanipulation, which provides surgeons with the necessary equipment to accomplish totally endoscopic coronary anastomoses. Robotic telemetric systems together with 3-D visualization provide the necessary platform. This article summarizes the current worldwide experience with the ZEUS(TM) system in cardiac surgery and describes the steps from preclinical to endoscopic operation, focusing on the potential limitations of the procedure and the system.

Minimally invasive valve surgery: different techniques and approaches.

Less invasive approaches to cardiac surgical procedures are being developed in an effort to decrease patient morbidity and enhance postoperative recovery in comparison with conventional methods. Although full median sternotomy has been the standard surgical approach to the heart for more than 30 years, minimally invasive techniques using limited incisions are rapidly gaining acceptance. Potential advantages of a small skin incision include less trauma and tissue injury, leading to a less painful and quicker overall recovery, as well as shorter hospital stays for patients. Decreasing the size of the skin incision for minimally invasive valve surgery to significantly less than the cardiac size requires specific access to the valve to be repaired or replaced. Thus, various minimally invasive techniques and approaches have been described for aortic and mitral valve surgery. This article will review the different minimally invasive techniques and approaches, as well as early results and outcomes for aortic and mitral valve surgery.

Early and midterm results after coronary artery bypass grafting with and without cardiopulmonary bypass: which patient population benefits the most?

BACKGROUND: We present our early and midterm results with off-pump coronary artery bypass grafting (OPCAB) on the beating heart and with conventional coronary artery bypass grafting (CABG) and compare patient outcomes for both procedures. METHODS: Between November 1997 and April 2001, OPCAB was performed in 330 patients. The results were compared with those of a matched population of 330 patients who had undergone CABG during the same period. Specific postoperative outcomes were evaluated for patient subgroups with multimorbidity, with impaired ventricular function, of an older age, and of a young age without comorbidities. Midterm results and quality-of-life (QOL) scores for patients were obtained by follow-up. RESULTS: In the overall series, OPCAB resulted in signifi- cantly shorter surgery times (P =.008), ventilation times (P <.001), intensive care unit (ICU) stays (P <.001), and hospital stays (P =.006). OPCAB also resulted in less postoperative inotropic medication (P =.041), lower transfusion rates (P <.001), fewer postoperative myocardial infarctions (P =.038), and lower hospital mortality rates (P =.024). Among the patient subgroups, patients with multimorbidities were the only subgroup to show a significant reduction in hospital mortality after OPCAB surgery (P =.048). Times of postoperative ventilation, ICU stay, and hospitalization were significantly reduced for all patient subgroups (P <.05). After mean followup times of 43.8 months (OPCAB) and 44.8 months (CABG), QOL scores, midterm complication rates, and mortality rates were not significantly different among the groups. CONCLUSION: OPCAB surgery improved postoperative recovery for the entire patient population without compromising midterm outcome. Compared with conventional CABG, high-risk patients with multimorbidity particularly profit from avoiding cardiopulmonary bypass and show significantly lower hospital mortality.

Identification and characterization of cells with high angiogenic potential and transitional phenotype in calcific aortic valve.

Recent data suggest that angiogenesis plays an important role in the pathogenesis of valvular disease. However, the cellular mechanisms underlying this process remain unknown. This study aimed at identifying and characterizing the cellular components responsible for pathological neovascularization in calcific aortic valves (CAV). Immunohistochemical analysis of uncultured CAV tissues revealed that smooth muscle alpha-actin (alpha-SMA)-positive cells, which coexpressed Tie-2 and vascular endothelial growth factor receptor-2 (VEGFR-2), can be identified prior to the initiation of capillary-like tube formation. In a second step, leaflets of CAV and non-calcific aortic valves (NCAV) were cultured and the cells involved in capillary-like tube formation were isolated. The majority of these cells displayed the same phenotype as non-cultured cells identified in CAV tissues, i.e., expression of alpha-SMA, Tie-2, and VEGFR-2. In comparison to cells isolated from cultures of NCAV leaflets, these cells showed enhanced angiogenic activity as demonstrated by migration and tube assays. The coexpression of VEGFR-2 and Tie-2 together with alpha-SMA suggests both endothelial and mesenchymal properties of the angiogenically activated cells involved in valvular neovascularization. Hence, our findings might provide new insights into the process of pathological angiogenesis in cardiac valves.

Internal cardioversion shortens periods of postoperative atrial fibrillation: results of a prospective, multicenter trial.

AIM OF THE STUDY: Atrial fibrillation (AF) commonly occurs following open heart surgery especially in the high-risk group of old patients with reduced left ventricular function. Via Syncrus heart wires implanted on the left and right atrium internal cardioversion shocks can be applied. This prospective nonrandomized multicenter study compares duration of AF periods and clinical outcome in patients treated with Syncrus wires to a control group treated conventionally. METHODS: In 88 patients Syncrus heart wires were implanted. Upon detection of AF antiarrhythmic medication was started for at least 6 hours followed by internal cardioversion. The results of this treatment were compared to a control group of 86 patients with an identical risk profile. RESULTS: In the Syncrus group 53.4% of patients suffered from postoperative AF compared with 50.0% in the control group. Internal cardioversion led to restoration of sinus rhythm in 60% of patients at the first series of shocks (mean energy 7.7 +/- 1.3 J) and 95.8% with the second series (mean energy 8.6 +/- 0.5 J). Length of AF periods was 12.4 +/- 7.2 hours in the Syncrus group versus 42.9 +/- 19.6 hours in control patients. CONCLUSIONS: Internal cardioversion using Syncrus heart wires demonstrated effectiveness in treating postoperative AF. Especially, length of AF periods could be diminished by the system with the expectation of reduction in hospital length of stay.

Video and robotic-assisted minimally invasive mitral valve surgery: a comparison of the Port-Access and transthoracic clamp techniques.

BACKGROUND: In order to assess different surgical techniques for video-assisted minimally invasive mitral valve surgery, a retrospective study was undertaken comparing the Port-Access system (Cardiovations, Ethicon Inc, Somerville, NJ) and the transthoracic clamp technique. METHODS: In 120 patients mitral valve surgery was performed through a small right minithoracotomy using either the Port-Access endovascular cardiopulmonary bypass system (Port-Access, n = 60) or the transthoracic clamp technique (MICRO, n = 60). Mean patient age was 61.5 +/- 10.5 years (81 patients with isolated mitral valve insufficiency, 39 patients with combined mitral valve disease). RESULTS: Eighty-one (67.5%) patients underwent mitral valve repair and 39 (32.5%) patients had valve replacement. Mean time of surgery was 4.5 +/- 3.5 and 4.1 +/- 3.2 hours (p = 0.07), aortic cross-clamp time 89 +/- 69 and 78 +/- 65 minutes (p = 0.08), mean intensive care unit stay 1.5 +/- 2.1 and 1.6 +/- 2.5 days (p = ns), and hospital stay 9.0 +/- 10.5 and 9.2 +/- 9.7 days (p = ns) in the Port-Access and MICRO groups, respectively. In the Port-Access group, there were 6 reexplorations for bleeding, one perforation of the right ventricle with the endopulmonary vent, and 2 reconstructions of the femoral artery necessary after femoral cannulation, compared to one reexploration for bleeding in the MICRO group. There was only one minor paravalvular leak after replacement and 2 cases of residual greater than or equal to grade II mitral valve regurgitation after mitral valve repair in the Port-Access group, necessitating reoperation. In both groups, there was no mortality, no cerebrovascular accident, no aortic dissection, and no conversion to sternotomy. CONCLUSIONS: Minimally invasive mitral valve surgery has become a standard approach for isolated mitral valve operations at our institution. The MICRO technique tends to shorten the time of surgery and aortic cross-clamping and reduces perioperative costs by simplifying the operative procedure.

Evaluation of acute traumatic changes of the coronary artery wall after robotically assisted endoscopic coronary artery bypass grafting.

BACKGROUND: There is concern that the technical limitations of robotic systems used in endoscopic coronary artery bypass grafting (CABG) may lead to increased trauma of the anastomotic site. To examine this issue, we compared the acute traumatic changes of the coronary artery wall caused by conventional manual suturing and robotically assisted suturing for anastomoses using the ZEUS telemanipulator (Computer Motion Inc., Goleta, CA) in a laboratory setting. METHODS: Coronary artery bypass grafting was performed on isolated porcine hearts. Fifteen anastomoses (with harvested porcine right coronary artery (RCA) segments) were carried out using the ZEUS microsurgical telemanipulator (group Z), while 15 further anastomoses were performed with a conventional manual technique (group M) using Gore-Tex CV-8 suture material. Specimens were taken from each anastomotic site and from native parts of the left anterior descending artery (LAD) (control group). Morphological changes of the cellular and fibrous components of the lamina intima and lamina media, and the shape and maximum diameter of the puncture mark, were examined by light microscopy (LM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Vascular endothelial damage and denudation were graded on a score from 1 to 5. RESULTS: In each group, 14 specimens were evaluated. SEM findings showed a significantly higher degree of endothelial denudation in group Z and group M compared to the control group, while group Z was significantly more affected than group M. Likewise, the maximum diameter of the puncture mark was significantly larger in group Z than in group M. TEM and LM studies supported these results. In addition, LM revealed that in five specimens of group Z the shape of the stitch through the artery wall was not cylindrical, as in the other cases, but was asymmetrical and displayed a superficial furrow on the side of the vascular lumen. CONCLUSION: The results indicate that there is an increased incidence of damage to the coronary artery wall caused by the microsurgical telemanipulator. Further studies are necessary to determine whether the differences between conventional and robotic-assisted suturing techniques will have an effect on the long-term outcome of coronary artery bypass grafting.

Robotically-assisted coronary artery surgery with and without cardiopulmonary bypass - from first clinical use to endoscopic operation.

BACKGROUND: Recently, the ZEUS(tm) Robotic Surgical System has been introduced to increase the precision of endoscopic cardiac surgery. This study investigated its clinical use for endoscopic coronary artery bypass grafting. MATERIAL/METHODS: Between 1998 and 2001, 41 patients with single and multivessel disease were operated on using the ZEUS(tm) system. The robotic system was introduced step by step into clinical practice. Initially, the system was used only for endoscopic internal mammary artery (IMA) harvest (n=12), later for coronary anastomoses on the arrested (n=13) or beating heart after median sternotomy (n=6), and finally for endoscopic coronary bypass grafting on either the arrested (n=2) or beating heart (n=8). RESULTS: Endoscopic IMA harvest ranged from 48 to 110 min and was completed in all cases. In the sternotomy group, the robotic anastomosis time averaged 21 min on the arrested and 25 min on the beating heart, respectively (n.s.). In the endoscopic cases, the average time for endoscopic anastomosis was 41 min on the arrested and 36.5 min on the beating heart (n.s.), with an overall duration of surgery between 4.0 and 8.0 hours. One endoscopic case was intraoperatively converted to a MIDCAB procedure with manual anastomosis. The total patency rate of all graft anastomoses, confirmed by early postoperative angiographic control, was 97%. One patient underwent reoperation with an uneventful postoperative course. CONCLUSIONS: The present study demonstrates the feasibility of endoscopic coronary revascularization using a computer-assisted surgical robotic system on the arrested and beating heart in selected patients.

Minimally invasive direct coronary artery bypass grafting (MIDCAB) and off-pump coronary artery bypass grafting (OPCAB): two techniques for beating heart surgery.

OBJECTIVE: Coronary bypass surgery can be performed less invasively by avoiding cardiopulmonary bypass (CPB). We present our experiences with beating heart bypass surgery performed through a minithoracotomy or sternotomy. METHODS: From May 1997 to September 1999, 340 patients were included in a prospective study. Of these patients, 111 (group 1) underwent minimally invasive direct coronary artery bypass grafting (MIDCAB) through an antero-lateral minithoracotomy, and 229 (group 2) had off-pump coronary artery bypass grafting (OPCAB) through a full sternotomy. A pressure stabilizer was used for MIDCAB and a suction stabilizer for OPCAB surgery. Early postoperative angiography was performed on 48% of patients in group 1 and 45% of those in group 2. Statistical analysis was applied to compare the variables from both groups and a probability value of less than 0.05 was considered significant. RESULTS: In all MIDCAB grafts, revascularization was performed by a single left internal mammary artery (LIMA) graft to the left anterior descending coronary artery (LAD). This procedure was completed in 96.4% of patients without CPB. Conversion to sternotomy was necessary for one patient (0.9%). In the OPCAB group, an average of 1.7 grafts per patient were revascularized, of which 98 were single, 99 double, and 32 triple. Of the OPCAB group, 12% of patients were redo operations and 17% had severe comorbidities. Conversion to CPB was necessary for 10 patients (4.4%) because of hemodynamic instability. No cerebrovascular accident (CVA) was seen in any group. There were no hospital deaths in the MIDCAB group, but there were three deaths (1.3%) in the OPCAB group. Age, previous bypass surgery, and severe comorbidities did not influence early mortality. Early postoperative reoperation due to graft failure was necessary for three patients (2.7%) after MIDCAB and for three patients (1.3%) after OPCAB. Confirmed by angiography, the early postoperative total graft patency rate was 96.2% in the MIDCAB group and 96.6% in the OPCAB group; the perfect patency rate (no stenosis greater than 50%) was 92.4% and 93.1%, respectively. CONCLUSIONS: Coronary bypass surgery without the use of CPB is feasible and safe, and offers good early results. Nevertheless, MIDCAB grafting is a challenging technique and should only be performed in selected patients with favorable coronary anatomy. On the other hand, with the sternotomy approach, exposure of all vessels was well tolerated and made complete revascularization feasible. OPCAB can be performed safely even on high-risk patients.