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Transcatheter aortic valve implantation (TAVI) is becoming the standard of care for severe symptomatic aortic stenosis (AS). Yet, some patients with AS are not indicated/eligible for TAVI. Several noninvasive, catheter-based or surgical alternatives exist, and other therapeutic options are emerging. This review provides an overview of non-TAVI options for severe AS. Non-invasive, transcatheter, and alternative surgical strategies are discussed, emphasizing their backgrounds, techniques, and outcomes. Alternative therapies to TAVI, whether device-based or non-device-based, continue to evolve or emerge and provide either alternative treatments or a bridge to TAVI, for patients not meeting indications for, or having contraindications to TAVI. Although TAVI and SAVR are the current dominant therapies, there are still some patients that could benefit in the future from other alternatives. Data on alternative options for such patients are scarce. Many advantages and disadvantages arise when selecting a specific treatment strategy for individual patients. Head-to-head comparison studies could guide physicians toward better patient selection and procedural planning. Awareness of therapeutic options, indications, techniques, and outcomes should enable heart teams to achieve optimized patient selection. Furthermore, it can increase the use of these alternatives to optimize the management of AS among different patient populations. [ABSTRACT FROM AUTHOR]

Robotics-assisted beating heart surgery holds significant potential for application as it can reduce the risks of infection. A crucial requirement in beating heart surgery is the real-time and accurate feedback of the interaction forces between the end-effector and cardiac tissues. The primary challenge is developing a sensorless scheme to separate the beating motion-coupled force (MCF) from the robot dynamic state-coupled force (SCF). Acquiring the accurate beating frequency before surgery is often challenging, which limits the use of conventional force observers. To address these difficulties, this article proposes an online force separation scheme. Specifically, we establish a robot-cardiac tissue coupled model that considers robot dynamics, force generation mechanisms, and heart motion characteristics. Based on this, we design a motion frequency exploration-based force separator (MSEFS), utilizing an online expectation–maximization procedure for the joint estimation of the motion state and frequency parameter. Simulation results demonstrate that the proposed scheme surpasses existing force estimation schemes in performance due to its capability for motion frequency exploration. [ABSTRACT FROM AUTHOR]

While the dilemma of motion tracking and force control in beating-heart surgery is previously addressed using active control architectures and rigid robotic actuators, this work leverages the highly controllable mechanical properties of concentric tube robots for intelligent, design-based force control in minimally invasive cardiac ablation. Briefly, cardiac ablation is the conventional procedure for treating arrhythmia patients, by which exposing the diseased cardiac tissue to Radio-Frequency (RF) energy restores the normal heart rhythm. Yet, the procedure suffers low success rate due to the inability of existing flexible catheters to maintain a consistent, optimal contact force between the tip electrode and the tissue, imposing the need for future repeat surgeries upon disease recurrence. The novelty of our work lies in the development of a statically-balanced compliant mechanism composed of (1) distal bi-stable concentric tubes and (2) a compliant, torsional spring mechanism that provides torque at tubes proximal extremity, resulting in an energy-free catheter with a zero-stiffness tip. This catheter is expected to maintain surgical efficacy and safety despite the chaotic displacement of the heart, by naturally keeping the tip force at an optimal level, not less and not more than the surgical requirement. The presented experimental results of the physical prototype, reflect the feasibility of the proposed design, as well as the robustness of the formulated catheter mathematical models which were uniquely deployed in the selection of the optimal design parameters. [ABSTRACT FROM AUTHOR]

Mitral regurgitation is the most common valvular disease and significant (moderate/severe) mitral regurgitation is found in 2.3% of the population older than 65 years. New transcatheter minimally invasive technologies are being developed to address mitral valve disease in patients deemed too high a risk for conventional open-heart surgery. There are several features of the mitral valve (saddle-shaped noncalcified annulus with irregular leaflet geometry) that make a transcatheter approach to repair or replacing the valve more challenging compared with the aortic valve. Several devices are under investigation for transcatheter mitral valve replacement, and also for mitral valve repair targeting the mitral valve leaflets, chordae tendinae, and mitral annulus. The MitraClip device is the only Food and Drug Administration-approved device to treat mitral regurgitation by targeting the mitral leaflets. There are eight minimally invasive devices being studied in humans that target the mitral annulus, and at least two devices being studied in animal models. There are 5 devices in clinical trials for minimally invasive approaches targeting the chordae tendinae. More than 10 different transcatheter mitral valves are in various stages of development and clinical trials. These transcatheter mitral valves can be delivered either through a transseptal, transapical, transaortic, or left atriotomy approach. It seems likely that transcatheter treatment approaches to mitral valve disease will become more common, at least in the sick and elderly patient population. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the safety and efficacy of the Hanoi ASD procedure, which is totally endoscopic surgery for atrial septal defect (ASD) repair on beating heart. In addition, the present study also aimed to analyze the learning curve for this procedure., Methods: From May 2016 to February 2023, 198 consecutive ASD patients weighing ≥20 kg were enrolled in the retrospective study. The Hanoi ASD procedure includes (1) unilateral or bilateral femoral arterial cannulation; (2) two or three 5 mm trocars and a 15 mm port; (3) ASD repair on beating heart, preventing air embolism with CO 2 insufflation and keeping the left atrium full of blood; and (4) not snaring the inferior vena cava. Cumulative sum (CUSUM) analysis was used to evaluate the cardiopulmonary bypass (CPB) and operation time learning curves. Variables among the learning curve phases were compared., Results: The CPB and operation times were 90 (72 to 115) min and 180 (150 to 220) min, respectively. Total drainage volume was 190 (120 to 290) mL. No endoscopic failure or major complications were complications were excluding factors causing bias, the CUSUM CPBtime analysis for the remaining 131 patients included 3 phases. Phase 1 was the initial learning period (cases 1 to 34), phase 2 represented the technical competence period (cases 35 to 54), and phase 3 was the challenging period (cases 55 to 131)., Conclusions: The Hanoi ASD procedure is safe and feasible for repairing ASD in patients weighing ≥20 kg. According to the learning curve analysis, 34 cases were required to achieve technical efficiency, and 54 cases were required to address highly challenging cases., Competing Interests: Declaration of Conflicting InterestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

INTRODUCCIÓN. La revascularización miocárdica quirúrgica con el corazón latiendo y sin el empleo de circulación extracorpórea es una potencial estrategia para la disminución de la mortalidad y morbilidad en los pacientes con cardiopatía isquémica. El objetivo de esta investigación fue describir los resultados de la revascularización miocárdica quirúrgica con corazón latiendo, con circulación extracorpórea (CEC) o sin ella. MÉTODOS. Se realizó un estudio descriptivo, longitudinal y prospectivo, de tipo serie de casos, cuya muestra estuvo conformada por 159 pacientes, a los cuales se les realizó revascularización miocárdica con el corazón latiendo (143 sin CEC y 16 con CEC) en el Hospital «Hermanos Ameijeiras», en el año 2007. RESULTADOS. La media de edad de los 159 pacientes operados fue de 63,9 años. Hubo predominio del sexo masculino (74,2 %), piel blanca (81,1 %), angina de esfuerzo estable crónica (86,8 %), dislipidemia (84,3 %), hipertensión arterial (81,2 %), uso de dos o más fármacos antiisquémicos (83,0 %), clase funcional III (64,2 %), ritmo cardíaco sinusal (98,1 %), lesión de tronco asociado a enfermedad multivaso (54,1 %) y acceso por esternotomía (93,1 %). Se encontraron diferencias estadísticamente significativas en favor de los pacientes en los que no se usó la CEC en cuanto a revascularización completa (p = 0,006), fármacos inotrópicos (p = 0,000), hemoderivados (p = 0,022), tiempo quirúrgico (p = 0,000) y anestésico (p = 0,000), uso de balón de contrapulso (p = 0,001), extubación mediana (p = 0,003) y estadía en la unidad de cuidados intensivos (p = 0,011). La mortalidad global fue del 5,0 %, más significativa cuando se usó la CEC (p = 0,001), e igual ocurrió al comparar ambas técnicas en relación con sepsis respiratoria, disfunción renal, derrame pleural, bajo gasto cardíaco, hemorragia posoperatoria y diabetes mellitas descompensada. CONCLUSIONES. Concluimos que el uso de la circulación extracorpórea como ayuda en la revascularización miocárdica con el corazón latiendo arrojó resultados insatisfactorios.INTRODUCTION. The surgical myocardial revascularization with beating heart and without extracorporeal circulation (ECC) is a potential strategy to decrease the mortality and the morbidity in patients presenting with ischemic heart disease. The objective of present research was to describe the results of surgical myocardial revascularization with beating heart, with or without ECC. METHODS. A prospective, longitudinal and descriptive study was conducted of cases series type where the sample included 159 patients underwent beating heart myocardial revascularization (143 without ECC and 16 with EEC) en the "Hermanos Ameijeiras" Clinical Surgical Hospital in 2007. RESULTS. The mean age of the 159 patients operated on was of 63,9 years. There was predominance of male sex (74,2%), white race (81,1%), chronic and stable exertion angina (86,8%), dyslipidemia (84,3%), high blood pressure (81,2%), use of two or more anti-ischemia drugs (83,0%), III functional class (64,2%), sinus cardiac rhythm (98,1%), trunk lesion associated to multi-vessel disease (54,1%) and sternotomy approach (93,1%). There were statistically significant differences in favor of the patients without ECC as regards the complete revascularization (p = 0,006), inotropic drugs (p = 0,000), haemoderivatives (p = 0,022), surgical time (p = 0,000) and anesthetics (p = 0,000), use of contrapulsation balloon (p = 0,001), medium extubation (p = 0,003) and intensive care unit stay (p = 0,011). The overall mortality was of 5,0%, more significant when ECC was used (p = 0,001) and similar when both techniques were compared in relation to respiratory sepsis, renal dysfunction, pleural effusion, low cardiac output, postoperative hemorrhage and decompensation of diabetes mellitus. CONCLUSIONS. We conclude that the use of extracorporeal circulation as help in beating heart myocardial revascularization yielded unsatisfactory results.

Background: Cardiac surgery using cardiopulmonary bypass (CPB) is associated with some adverse postoperative complications caused by an altered immune response. An alternative approach to cardiac surgery, operating without the use of CPB (i.e. off-pump surgery), seems to display less adverse impacts on the immune response. Patients and Methods: Peripheral blood lymphocytes in 40 patients undergoing cardiac surgery either with CPB (“on-pump”) or without CPB (“off-pump”) were followed using flow cytometry. The samples of peripheral blood were taken at five intervals: preoperatively, after termination of the surgery, on the first, on the third and on the seventh postoperative day, respectively. Results: The most substantial changes appeared on the first postoperative day in both subgroups of patients. While the percentage of both total T cells and CD4+ T cells were decreased, the percentage of HLA-DR+ activated lymphocytes was increased. These changes were more profound in the “on-pump” subgroup compared to the “off-pump” subgroup. Conclusion: Our results may suggest that the “off-pump” surgical approach reveals less adverse impact on adaptive immune responses.

Objectives: The use of cardiopulmonary bypass (CPB) during coronary artery bypass graft surgery (CABG) is associated with a systemic inflammatory response, resulting in altered microcirculation. The aim of this study was to evaluate whether beating heart surgery can preserve the microcirculation. Methods: Sublingual microcirculation was characterized by a Sidestream Darkfield Imaging Microscope during off-pump (OPCABG) and on-pump (ONCABG) surgery. Microcirculatory parameters were evaluated during eight precise perioperative time points. Results: The quality of the microcirculation decreased during early ONCABG. OPCABG resulted in a significantly better microcirculation compared to ONCABG for three of six parameters during surgery. However, by the end of surgery and postoperatively, the microcirculatory parameters were no different between the groups. Conclusions: While the results do not show a marked preservation of the microcirculation during and after OPCABG compared to ONCABG, they coincide with the body temperature fluctuations of each group during and after surgery. Our work suggests that active warming could impact the microcirculation parameters. [ABSTRACT FROM AUTHOR]

The off-pump literature is divided into three eras: the "early phase" with results favouring off-pump surgery supported with randomized control trials (RCTs) mainly from Bristol, UK; an "intermediate phase" dominated by the results of the ROOBY trial and finally a more "contemporary phase" whereby the off/on-pump argument is unsettled. Although the literature has failed to project an overall superiority of off-pump versus on-pump surgery, nevertheless, small randomized control trials and large meta-analysis studies are concluding that the incidence of a stroke is less than 1 % when an aortic off-pump techniques (especially the non-touch technique) are advocated in patients with diseased ascending aorta. Furthermore, off-pump combined with hybrid procedures may lead to a reduction of adverse outcome in the aged high-risk population with concomitant poor left ventricular function and co-morbidities.The current review attempts to bring an insight onto the last ten years knowledge on the on/off-pump debate, with an aim to draw some clear conclusions in order to allow practitioners to reflect on the subject. [ABSTRACT FROM AUTHOR]

Most surgeons perform coronary bypass surgery with the aid of cardiopulmonary bypass, which inflicts a massive systemic inflammatory response to the body leading to adverse clinical outcome. In an attempt to make CABG less invasive, interest have been diverted to the off pump technique.The current review attempts to bring an insight onto the last ten years knowledge on the off-pump impact in end organ function, with an aim to draw some clear conclusions in order to allow practitioners to reflect on the subject. [ABSTRACT FROM AUTHOR]

Robotic-assisted heart surgeries do not allow autonomous compensation of cardiac motion. This paper tackles this problem, based on a robotic control architecture that relies on force feedback, without requiring vision data. The algorithm merges two cascade loops. The inner one is based on the Kalman active observer (AOB) for model-reference adaptive control and the outer one based on a model predictive control (MPC) approach generates control references for beating heart motion compensation. A 4-DoF surgical robot generates desired surgical forces and a 3-DoF robot equipped with an ex vivo heart at the end-effector reproduces realistic heart motion. [ABSTRACT FROM AUTHOR]

Mitral valve repair is the preferred surgical treatment for mitral regurgitation. Cardiac surgeons must increasingly pursue high-quality mitral valve repair, which ensures excellent long-term outcomes. Intraoperative assessment of a competency of the repaired mitral valve before closure of the atrium is an important step in accomplishing successful mitral valve repair. Saline test is the most simple and popular method to evaluate the repaired valve. In addition, an 'Ink test' can provide confirmation of the surface of coaptation, which is often insufficient in the assessment of saline test. There are sometimes differences between the findings of the leakage test in an arrested heart and the echocardiographic findings after surgery. Assessment of the mitral valve in an arrested heart may not accurately reflect its function in a contractile heart. Assessment of the valve on the beating heart induced by antegrade or retrograde coronary artery perfusion can provide a more physiological assessment of the repaired valve. Perfusion techniques during beating heart surgery mainly include antegrade coronary artery perfusion without aortic cross-clamping, and retrograde coronary artery perfusion via the coronary sinus with aortic cross-clamping. It is the most important point for the former approach to avoid air embolism with such precaution as CO insufflation, left ventricular venting, and transesophageal echocardiography, and for the latter approach to maintain high perfusion flow rate of coronary sinus and adequate venting. Leakage test during mitral valve repair increasingly takes an important role in successful mitral valve reconstruction. [ABSTRACT FROM AUTHOR]

Abstract: Controlling the interaction between robots and living soft tissues has become an important issue as the number of robotic systems inside the operating room increases. Many researches have been done on force control to help surgeons during medical procedures, such as physiological motion compensation and tele-operation systems with haptic feedback. In order to increase the performance of such controllers, this work presents a novel force control scheme using Active Observer (AOB) based on a viscoelastic interaction model. The control scheme has shown to be stable through theoretical analysis and its performance was evaluated by in vitro experiments. In order to evaluate how the force control scheme behaves under the presence of physiological motion, experiments considering breathing and beating heart disturbances are presented. The proposed control scheme presented a stable behavior in both static and moving environment. The viscoelastic AOB presented a compensation ratio of 87% for the breathing motion and 79% for the beating heart motion. [Copyright &y& Elsevier]

Objective: Conventional coronary artery bypass grafting (CABG) using cardiopulmonary bypass and cardiac arrest is associated with higher mortality and morbidity rates in acute coronary syndrome (ACS) patients undergoing surgery. Although off-pump CABG (OPCAB) is beneficial for high-risk patients, its efficacy for ACS is unknown, with on-pump beating CABG an adjunctive method. We investigated the effects of OPCAB and on-pump beating CABG for ACS. Methods: We evaluated 121 consecutive patients with ACS (91 males, 30 females; mean age 69.5 ± 10.3 years) who underwent CABG since 2000. Seventy-five had unstable angina (UA) and 46 acute myocardial infarction (AMI) [non-ST elevation (NSTEMI): 22, ST elevation (STEMI): 24]. We assessed CABG for acute coronary syndrome under our primary OPCAB strategy, and compared perioperative status between UA and AMI patients. Results: (1) Sixty-five (87 %) with UA underwent OPCAB, 8 on-pump beating CABG, and 2 conventional CABG. Conversion from OPCAB was seen in 4 patients. In-hospital mortality was 1.3 %. (2) All UA patients who had intra-aortic balloon pumping (IABP) underwent OPCAB. No patients with preoperative IABP experienced conversion from OPCAB. (3) In AMI patients, hospital mortality was higher (8.9 %) and the ratios for OPCAB, on-pump beating CABG, and conventional CABG were 39, 57, and 4 %, respectively. Mortality was exclusively seen in patients with STEMI who underwent conventional CABG. Conclusions: OPCAB might have beneficial effects for ACS patients with UA, while IABP was found essential for completing OPCAB. In AMI patients, on-pump beating CABG might be reasonable for avoiding conversion from OPCAB and ischemic perfusion injury. [ABSTRACT FROM AUTHOR]

Recently, model-based visual tracking techniques using endoscopic images have been proposed for estimating beating heart motion and thus actively compensating motion in robot-assisted minimally invasive surgery. However, most existing methods suffer the problems of computation burden with increasing size of target region and number of parameters, and also limited capability to handle partial occlusions. In this paper, an overlapped thin-plate spline approach is proposed. By dividing the target region into overlapped sub-regions, overall computational burden is greatly reduced and robustness against environment disturbances is improved. With the proposed tracking scheme, 3 D coordinates of point of interest on beating heart surfaces can be extracted and used to compensate heart motion by a surgical robot, which presents a step further towards successful robotic beating heart surgery using a model-based visual tracking technique. The performance of the proposed tracking method is demonstrated through experiments on phantom data and in vivo videos recorded by the da Vinci surgical platform. [ABSTRACT FROM AUTHOR]

Abstract: The rapid motion of the heart presents a significant challenge to the surgeon during intracardiac beating heart procedures. We present a 3D ultrasound-guided motion compensation system that assists the surgeon by synchronizing instrument motion with the heart. The system utilizes the fact that certain intracardiac structures, like the mitral valve annulus, have trajectories that are largely constrained to translation along one axis. This allows the development of a real-time 3D ultrasound tissue tracker that we integrate with a 1 degree-of-freedom (DOF) actuated surgical instrument and predictive filter to devise a motion tracking system adapted to mitral valve annuloplasty. In vivo experiments demonstrate that the system provides highly accurate tracking (1.0mm error) with 70% less error than manual tracking attempts. [Copyright &y& Elsevier]

Robotics tool enables the surgeon to conduct the operation on the beating heart during the off-pump coronary artery graft bypass surgery. The robotic tool actively cancels the relative motion between the point of intersect (POI) on the surface of the heart and surgical tool, which allows the surgeon to operate as if the heart is stationary. The nonlinear nature of the beating heart motion disables the conventional feedback controller and pose difficulty to the robot tool. We apply Granger causality to analyze simultaneously measured electrocardiography (ECG) and 3D heart motion data. The extracted interdependency between the different sets of time series reveals the feasiblity for the improved prediction of the heart motion. In this paper, we propose an adaptive multivariate vector autoregressive (MVAR) prognosis-based model following (MF) control algorithm. Using this method, the prediction part takes advantage of the ECG signal, which contains the nonstationary heart rate dynamics significantly correlated with the heart motion. In addition, the control part automatically incorporates the feedforward path to enhance the tracking of the abrupt change and occasional abnormality in heart motion. The comparative experiment results for evaluating the proposed algorithm are reported by using the vivo collected data. The results indicate that MVAR-based MF improves the control accuracy by 0.2 mm and achieves better tracking performance by capturing more nonlinear characteristics of the heart motion, and following the heart motion better with sufficient details. [ABSTRACT FROM AUTHOR]

This study has been conducted in an effort to establish metabolic and inflammatory responses of the myocardium during aortic valve surgery on the beating heart with CPB and continuous coronary sinus perfusion with normothermic blood. Twenty patients, divided into two groups, participated in this study. Conventional aortic valvular operations were performed on first 10 patients, while the second group, consisting of 10 patients as well, was subjected to the operations with CPB on the beating heart with continuously perfusion with blood through coronary sinus. There were total of 14 biological and 6 mechanical valves implanted in aortic position. In this study, cardiac markers and inflammatory mediators IL-8 and TNF, were measured preoperatively and postoperatively. Metabolic changes were documented based on the levels of CK-MB, troponin I, myoglobin and LDH. Inflammatory factors we measured through IL-8 and TNF. All measurements were taken in 6 hour intervals during the initial 48 hours following the operations. The patients of "the beating heart" group had significantly lower dose of markers and cytokines in comparison to those who had undergone the conventional valvular operation. The elimination of the adverse effects of global ischemia produced from reperfusion injury and the similarity to the physiological condition, suggests that the revival of the beating heart procedure is more reasonable. This procedure of valvular surgery on the beating heart can be one of the good surgical options for the high-risk valvular patients.

Robotic-assisted beating heart surgery aims to allow surgeons to operate on a beating heart without stabilizers as if the heart is stationary. The robot actively cancels heart motion by closely following a point of interest (POI) on the heart surface—a process called active relative motion canceling. Due to the high bandwidth of the POI motion, it is necessary to supply the controller with an estimate of the immediate future of the POI motion over a prediction horizon in order to achieve sufficient tracking accuracy. In this paper, two least-squares-based prediction algorithms, using an adaptive filter to generate future position estimates, are implemented and studied. The first method assumes a linear system relation between the consecutive samples in the prediction horizon. On the contrary, the second method performs this parametrization independently for each point over the whole the horizon. The effects of predictor parameters and variations in heart rate on tracking performance are studied with constant and varying heart rate data. The predictors are evaluated using a three-degree-of-freedom (DOF) test bed and prerecorded in vivo motion data. Then, the one-step prediction and tracking performances of the presented approaches are compared with an extended Kalman filter predictor. Finally, the essential features of the proposed prediction algorithms are summarized. [ABSTRACT FROM AUTHOR]

Off-pump Coronary Artery Bypass Graft (CABG) surgery outperforms traditional on-pump surgery because the assisted robotic tools can alleviate the relative motion between the beating heart and robotic tools. Therefore, it is possible for the surgeon to operate on the beating heart and thus lessens post surgery complications for the patients. Due to the highly irregular and non-stationary nature of heart motion, it is critical that the beating heart motion is predicted in the model-based track control procedures. It is technically preferable to model heart motion in a nonlinear way because the characteristic analysis of 3D heart motion data through Bi-spectral analysis and Fourier methods demonstrates the involved nonlinearity of heart motion. We propose an adaptive nonlinear heart motion model based on the Volterra Series in this paper. We also design a fast lattice structure to achieve computational-efficiency for realtime online predictions. We argue that the quadratic term of the Volterra Series can improve the prediction accuracy by covering sharp change points and including the motion with sufficient detail. The experiment results indicate that the adaptive nonlinear heart motion prediction algorithm outperforms the autoregressive (AR) and the time-varying Fourier-series models in terms of the root mean square of the prediction error and the prediction error in extreme cases. [ABSTRACT FROM AUTHOR]

In this paper, control strategies for an active stabilizer dedicated to beating heart coronary artery bypass grafting are investigated. The active stabilizer, which consists of a piezoactuated compliant mechanism, has to be controlled to compensate for the displacements induced by the beating heart in order to provide the surgeon with a locally motionless myocardium surface. Three controllers, including different levels of prior knowledge about the heart motion, are presented. Their performance with respect to modeling uncertainties, arising unknown interactions of the stabilizer with its positioning mechanism, and the heart, is studied through simulations, as well as laboratory and in vivo experiments. Finally, the selection of the most adequate control scheme and the performance of the device from a clinical point of view are discussed. [ABSTRACT FROM AUTHOR]

Purpose: Tracking of beating heart motion in a robotic surgery system is required for complex cardiovascular interventions. Methods: A heart surface motion tracking method is developed, including a stochastic physics-based heart surface model and an efficient reconstruction algorithm. The algorithm uses the constraints provided by the model that exploits the physical characteristics of the heart. The main advantage of the model is that it is more realistic than most standard heart models. Additionally, no explicit matching between the measurements and the model is required. The application of meshless methods significantly reduces the complexity of physics-based tracking. Results: Based on the stochastic physical model of the heart surface, this approach considers the motion of the intervention area and is robust to occlusions and reflections. The tracking algorithm is evaluated in simulations and experiments on an artificial heart. Providing higher accuracy than the standard model-based methods, it successfully copes with occlusions and provides high performance even when all measurements are not available. Conclusions: Combining the physical and stochastic description of the heart surface motion ensures physically correct and accurate prediction. Automatic initialization of the physics-based cardiac motion tracking enables system evaluation in a clinical environment. [ABSTRACT FROM AUTHOR]

The manipulation of fast-moving, delicate tissues in beating heart procedures presents a considerable challenge to the surgeon. A robotic force tracking system can assist the surgeon by applying precise contact forces to the beating heart during surgical manipulation. Standard force control approaches cannot safely attain the required bandwidth for this application due to vibratory modes within the robot structure. These vibrations are a limitation even for single degree-of-freedom systems that drive long surgical instruments. These bandwidth limitations can be overcome by the incorporation of feed-forward motion terms in the control law. For intracardiac procedures, the required motion estimates can be derived from 3-D ultrasound imaging. Dynamic analysis shows that a force controller with feed-forward motion terms can provide safe and accurate force tracking for contact with structures within the beating heart. In vivo validation confirms that this approach confers a 50% reduction in force fluctuations when compared with a standard force controller and a 75% reduction in fluctuations when compared with manual attempts to maintain the same force. [ABSTRACT FROM PUBLISHER]

This paper presents a novel miniature uniaxial force sensor for use within a beating heart during mitral valve annuloplasty. The sensor measures 5.5 mm in diameter and 12 mm in length and provides a hollow core to pass instrumentation. A soft elastomer flexure design maintains a waterproof seal. Fiber optic transduction eliminates electrical circuitry within the heart, and acetal components minimize ultrasound-imaging artifacts. Calibration uses a nonlinear viscoelastic method, and in vitro tests demonstrate a 0-4-N force range with rms errors of 0.13 N (<3.2%). In vivo tests provide the first endocardial measurements of tissue-minimally invasive surgery instrument interaction forces in a beating heart. [ABSTRACT FROM AUTHOR]

A correlation between perfusion modality and vascular dilation induced by endothelial nitric oxide (NO) release has been pointed out in the literature; nevertheless, only a few studies deal with the analysis of patients treated by cardiac surgery. The aim of this work is to analyze endothelial NO release in patients undergoing cardiac surgery under continuous flow cardiopulmonary bypass (CPB) or pulsatile perfusion. Pulsatile devices approved for clinical CPB do not accurately reproduce the physiological flow waveform provided by the left ventricle while, on the other hand, it is important to analyze pulsatile perfusion under both physiological flow waveform and pulsatile flow CPB. Physiological pulsatile perfusion (supplied by the left ventricle) was examined in this study. A total of 16 patients undergoing cardiac surgery were enrolled in the study and divided into two groups: 8 patients were put on continuous flow CPB while the others underwent beating heart surgery. Venous blood samples were withdrawn to quantify endothelial NO release through its bioactive forms in blood. Plasma was used for the chemiluminescent detection of nitrite (NO2 -) and nitrate (NO3 -), and the cellular component for electron spin resonance detection of nitrosylhemoglobin. Significant reduction in the intraoperative concentration with respect to the preoperative was observed only in the continuous group for both NO2 - and NOx (NO2 - + NO3 -) concentration (p=0.003 and p=0.016, respectively). A significant difference in the intraoperative nitrite concentration was also observed between the groups (p=0.006). Nitrosylhemoglobin concentration, although not instrumentally detectable, resulted as negligible with respect to the other NO metabolites. Despite the small number of patients belonging to each group, this significant reduction of NO2 - concentration under continuous flow CPB revealed a strong dependence on endothelial NO release and plasma nitrite concentration on perfusion modality. [ABSTRACT FROM AUTHOR]

Off-pump totally endoscopic coronary artery bypass grafting is a milestone for cardiac surgery, and still a technical challenge. Indeed, the fast and complex cardiac motion makes this operating method technically demanding. Therefore, several robotic systems have been designed to assist the surgeons by compensating for the cardiac motion and providing a virtually motionless operating area. In the proposed systems, the servoing schemes often take advantage of a prediction algorithm that supplies the controller with some future heart motion. This prediction enlarges the control-loop bandwidth, thus allowing a better motion compensation. Obviously, improving the prediction accuracy will lead to better motion-compensation results. Thus, a current challenge in computer-assisted cardiac surgery research is the design of efficient heart-motion-prediction algorithms. In this paper, a detailed survey of the main existing prediction approaches is given and a classification is provided. Then, a novel prediction technique based on amplitude modulation is proposed, and compared with other techniques using in vivo collected datasets. A final discussion summarizes the main features of all the proposed approaches. [ABSTRACT FROM AUTHOR]

Dynamic cardiac magnetic resonance imaging (MR) and computed tomography (CT) provide cardiologists and cardiac surgeons with high-quality 4-D images for diagnosis and therapy, yet the effective use of these high-quality anatomical models remains a challenge. Ultrasound (US) is a flexible imaging tool, but the US images produced are often difficult to interpret unless they are placed within their proper 3-D anatomical context. The ability to correlate real-time 3-D US volumes (RT3D US) with dynamic MR/CT images would offer a significant contribution to improve the quality of cardiac procedures. In this paper, we present a rapid two-step method for registering RT3D US to high-quality dynamic 3-D MR/CT images of the beating heart. This technique overcomes some major limitations of image registration (such as the correct registration result not necessarily occurring at the maximum of the mutual information (MI) metric) using the MI metric. We demonstrate the effectiveness of our method in a dynamic heart phantom (DHP) study and a human subject study. The achieved mean target registration error of CT+US images in the phantom study is 2.59 mm. Validation using human MR/US volumes shows a target registration error of 1.76 mm. We anticipate that this technique will substantially improve the quality of cardiac diagnosis and therapies. [ABSTRACT FROM AUTHOR]

We describe complete emergency arterial coronary artery bypass grafting performed on the beating heart of a 73-year-old man with situs inversus totalis and triple-vessel disease. The right internal mammary artery was anastomosed to the left anterior descending artery in situ. The first and second obtuse marginal branches of the circumflex coronary and the posterior descending branch of the right coronary artery were sequentially revascularized using the left internal mammary and radial arteries in situ. The only abnormality was that the position of the heart mirrored that of a normal heart. Beating heart surgery appears to be as safe in patients with dextrocardia as in the general population. However, the position of the surgeon must be reconsidered for optimal handling of stabilizers and to facilitate access to anastomosis sites. Understanding mirror-image coronary arterial anatomy is important for successful surgical outcomes among patients with dextrocardia. [ABSTRACT FROM AUTHOR]

Two-dimensional ultrasound (US) is widely used in minimally invasive cardiac procedures due to its convenience of use and noninvasive nature. However, the low quality of US images often limits their utility as a means for guiding procedures, since it is often difficult to relate the images to their anatomical context. To improve the interpretability of the US images while maintaining US as a flexible anatomical and functional real-time imaging modality, we describe a multimodality image navigation system that integrates 2D US images with their 3D context by registering them to high quality preoperative models based on magnetic resonance imaging (MRi) or computed tomography (CT) images. The mapping from such a model to the patient is completed using spatial and temporal registrations. Spatial registration is performed by a two-step rapid registration method that first approximately aligns the two images as a starting point to an automatic registration procedure. Temporal alignment is performed with the aid of electrocardiograph (ECG) signals and a latency compensation method. Registration accuracy is measured by calculating the TRE. Results show that the error between the US and preoperative images of a beating heart phantom is 1.7 ± 0.4 mm, with a similar performance being observed in in vivo animal experiments. [ABSTRACT FROM AUTHOR]

Two-dimensional or 3-D visual guidance is often used for minimally invasive cardiac surgery and diagnosis. This visual guidance suffers from several drawbacks such as limited field of view, loss of signal from time to time, and in some cases, difficulty of interpretation. These limitations become more evident in beating-heart procedures when the surgeon has to perform a surgical procedure in the presence of heart motion. In this paper, we propose dynamic 3-D virtual fixtures (DVFs) to augment the visual guidance system with haptic feedback, to provide the surgeon with more helpful guidance by constraining the surgeon's hand motions thereby protecting sensitive structures. DVFs can be generated from preoperative dynamic magnetic resonance (MR) or computed tomograph (CT) images and then mapped to the patient during surgery. We have validated the feasibility of the proposed method on several simulated surgical tasks using a volunteer's cardiac image dataset. Validation results show that the integration of visual and haptic guidance can permit a user to perform surgical tasks more easily and with reduced error rate. We believe this is the first work presented in the field of virtual fixtures that explicitly considers heart motion. [ABSTRACT FROM AUTHOR]

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Minimally invasive techniques have had limited application in congenital cardiac surgery, primarily due to the complexity of the defects, small working area, and the fact that most defects require exposure to intracardiac structures. Advances in cannula design and instrumentation have allowed application of minimal incision techniques but in most cases, cardiopulmonary bypass is still required. Image guided surgery, which uses noninvasive imaging to guide intracardiac procedures, holds the promise of permitting performance of reconstructive surgery in the beating heart in children. [ABSTRACT FROM AUTHOR]

Abstract: Background: Heart positioning during beating heart surgery produces significant haemodynamic compromise either when a deep pericardial stitch (DPS) or apical suction devices (ApSDs) are used. In this study the two techniques’ haemodynamic performance and effect on intracardiac structures were compared through transoesophageal echocardiography (TEE) obtained volume measurements and three-dimensional ventricular and mitral valve computer reconstructions. Methods: Sequential 0° to 180° TEE images of the left heart were obtained in 10 patients undergoing beating heart surgery. Measurements with both techniques in three different positions were obtained: at baseline, the heart elevated to access its inferior surface and the heart elevated and rotated to access its lateral surface. Three-dimensional computer reconstructions of the mitral valve and the left heart were generated. Ventricular volume measurements were used to calculate stroke volume, ejection fraction and differences from baseline. An analysis of variance between each technique in all three positions was performed. Results: Central venous, left atrial and pulmonary artery pressures were significantly increased with either technique during positioning. Both techniques significantly affected left ventricular function decreasing stroke volume and ejection fraction. In the vertical and rotated position, the ApSD produced a significant decrease from baseline both in stroke volume (DPS: 32.8±18.7 vs ApSD: 55.46±21.7; p =0.02) and in ejection fraction (DPS: 19.3±10.5 vs ApSD: 40.9±24.6; p =0.02). The three-dimensional reconstructions demonstrated significant distortion of the atrioventricular geometry and the mitral valve, which was more pronounced with the DPS. Conclusion: Both techniques produce variable degrees of deformation with associated cardiac dysfunction and haemodynamic instability. Cardiac function is impeded more with an ApSD with the heart elevated and rotated. [Copyright &y& Elsevier]

This paper focuses on the development of control algorithms for intelligent robotic tools that assist off-pump coronary artery bypass graft (CABG) surgery. In the robotic-assisted CABG surgery, the surgeon operates on the beating heart using intelligent robotic instruments. Robotic tools actively cancel the relative motion between the surgical instruments and the point of interest on the beating heart, dynamically stabilizing the heart for the operation. This algorithm is called active relative motion canceling (ARMC). Here, a model-based intelligent ARMC algorithm employing biological signals, such as electrocardiogram, to achieve effective motion cancellation is proposed. Finally, experimental results of the algorithm on a 3-degree-of-freedom robotic test-bed system are reported. [ABSTRACT FROM PUBLISHER]

Cardiopulmonary bypass (CPB) has been suggested to be a cause of complex systemic inflammatory response that significantly contributes to several adverse postoperative complications. In the last few years, off‐pump coronary artery bypass grafting (OPCAB) has gained widespread attention as an alternative technique to conventional on‐pump coronary artery bypass grafting (ONCAB). However, a degree of uncertainty regarding the relative merits of ONCAB and OPCAB continues to be a significant issue. Surgeons supporting off‐pump surgery, state that the avoidance of the CPB leads to significantly reduced myocardial ischemia‐reperfusion injury, postoperative systemic inflammatory response and other biological derangements, a feature that may improve the clinical outcomes. However, perfection in perioperative care, surgical technique and methods of attenuating the untoward effects of CPB has resulted in better clinical outcome of ONCAB as well. Possible reasons of these controversial opinions are that high‐quality studies have not comprehensively examined relevant patient outcomes and have enrolled a limited range of patients. Some studies may have been too small to detect clinically important differences in patient outcomes between these two modalities. We present a review of the available scientific interpretation of the literature on OPCAB with regard to safety, hemodynamic changes, inflammation, myocardial preservation and oxidative stress. We also sought to determine from different reported retrospective and randomized control studies, the initial and the long‐term benefits of this approach, despite the substantial learning curve associated with OPCAB. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]