Characterization of Surgical Movements As a Training Tool for Improving Efficiency.

INTRODUCTION: Surgical experience is often reflected by efficient, fluid, and well-calculated movements. For a new trainee, learning these characteristics is possible only by observation as there is no quantification system to define these factors. We analyzed surgeons' hand movements with different experience levels to characterize their movements according to experience. METHODS: Hand motions were recorded by an inertial measurement unit (IMU) mounted on the hands of the surgeons during a simulated surgical procedure. IMU data provided acceleration and Eulerian angles: yaw, roll, and pitch corresponding to hand motions as radial/ulnar deviation, pronation/supination, and extension/flexion, respectively. These variables were graphically depicted and compared between three surgeons. RESULTS: Participants were assigned to three groups based on years of surgical experience: group 1: >15 y; group 2: 3-10 y; and group 3: 0-1 y. Visualization of the roll motion, being the main motion during suturing, showed the clear difference in fluidity and regularity of the movements between the groups, showing minimal wasted movements for group 1. The angle of the roll motion, measured at the minimum, midpoint, and maximum points was significantly different between the groups. As expected, the experienced group completed the procedure first; however, the acceleration was not different between the groups. CONCLUSIONS: Surgeons' hand movements can be easily characterized and quantified by an IMU device for automatic assessment of surgical skills. These characteristics graphically visualize a surgeon's regularity, fluidity, economy, and efficiency. The characteristics of an experienced surgeon can serve as a training model and as a reference tool for trainees.

A Universal Device to Convert a Continuous Flow Assist Device to a Pulsatile Flow Device to Simulate Normal Blood Flow and Pressure Patterns.

BACKGROUND: Continuous follow assist devices (CFAD) are the most commonly used mechanical circulatory support devices. Compared to Pulsatile flow assist devices (PFAD), CFADs deliver a non-physiologic type of flow, which might contribute to complications related to lack of pulsatility in these devices. Moreover, lack of pulsatility complicates the clinical management of these patients who often present with good perfusion but with no palpable pulse and none or a negligible pulse pressure on blood pressure measurement. METHODS AND RESULTS: Presented here is a concept of a universal converter device that can be added inline other CFADs to convert the flow from continuous to pulsatile, simulating a normal flow and pressure pattern. After initial implantation and stabilization with a CFAD, adding this converter might potentially provide the benefits of pulsatile physiologic flow. The device is made of 2 components connected in parallel, working in tandem in user determined cycles. The continuous flow through a specifically positioned openings create a smooth conversion to a pulsatile flow. This device can convert a continuous flow to a physiologic pulsatile flow to achieve a native-like flow pattern and potentially prevent some CFAD complications. CONCLUSION: This paper presents the concept of pulsatility generation and simulation for other assist devices. Such a device can be a universal add-on or a supplemental option for CFADs.

Pretreatment of synthetic vascular grafts with heparin before implantation, a simple technique to reduce the risk of thrombosis.

Thrombosis of synthetic grafts commonly used in cardiovascular surgery is a major complication. We examined whether pretreatment of the graft with heparin reduces the risk of early thrombosis. A circuit was assembled to compare two pairs of shunts simultaneously in the same animal. The study shunts were pretreated with heparin. After 2 hours of circulation, clot formation was evaluated by image analysis techniques. The pretreated grafts had fewer blood clots adhered to the surface by direct visual inspection. The image analysis showed 5 vs. 39 clots, 0.01% vs. 1.8% clotted area, and 62 vs. 5630 clot pixel area between the treated and non-treated grafts respectively, p < 0.05. Pretreatment of the synthetic graft with heparin prior to implantation reduces the risk of early clot formation. This simple practice might be helpful to prevent initial thrombosis of the graft and later occlusion.

Repair of Tetralogy of Fallot in Children Less Than 4 kg Body Weight.

We reviewed our experience of surgical repair of Tetralogy of Fallot (TOF) in children weighing less than or equal to 4 kg to compare outcome of early palliation versus complete repair as the initial surgical approach. Seventy-six patients, weighing ≤ 4 kg, with TOF surgery between January 2005 and September 2013 were included in this single-center retrospective study. Twenty-five patients who underwent initial shunt procedure followed by later full repair were compared to 51 patients who had primary full repair for differences in baseline characteristics and outcomes. Shunt group patients had lower body weight, 2.76 ± 0.69 versus 3.11 ± 0.65 (kg), p = 0.03, and lower preoperative oxygen saturations, 82 ± 7 versus 90 ± 6 (%), p = 0.0001, than full repair group. A higher number of surgical procedures per patient was recorded in shunt patients, 2.29 ± 0.59 versus 1.27 ± 0.49, p = 0.00002. Thirteen of 51 patients in the full repair group required a repeat surgery. Catheterization procedures were performed in 12 patients in shunt and in 15 patients in full repair group, with interventional angioplasty in three and 11, respectively, p ≥ 0.05. Two patients, both in the shunt group, died after the surgery. Early full repair had longer hospital stay but significantly less hospitalizations 1.95 ± 1.3 versus 2.5 ± 1.4, p = 0.03. Initial complete repair of TOF in small children yielded favorable outcome with significantly less surgical procedures and subsequent hospitalizations. Cath laboratory re-interventions for residual defects were similar after both surgical approaches, and type of initial surgery does not predict freedom from re-intervention.

The neonatal hypoplastic aortic arch: decisions and more decisions.

Neonatal patients with hypoplasia of the aortic arch constitute a heterogeneous group with a wide spectrum of severity. The milder end of the spectrum comprises patients with aortic coarctation and isthmus hypoplasia. At the other end of the spectrum are patients with severe transverse arch hypoplasia or hypoplastic left heart syndrome. The aim of this paper is to discuss the various strategies and surgical approaches available for this group of patients, focusing on the surgical decisions that influence individual patient management. Many of the things discussed are applicable to any neonatal arch problem. We also describe and discuss in detail our surgical technique for patients who undergo neonatal repair of a hypoplastic aortic arch via median sternotomy.

In vivo quantification of clot formation in extracorporeal circuits.

Clot formation is a common complication in extracorporeal circuits. In this paper we describe a novel method for clot formation analysis using image processing. We assembled a closed extracorporeal circuit and circulated blood at varying speeds. Blood filters were placed in downstream of the flow, and clotting agents were added to the circuit. Digital images of the filter were subsequently taken, and image analysis was applied to calculate the density of the clot. Our results show a significant correlation between the cumulative size of the clots, the density measure of the clot based on image analysis, and flow duration in the system.

Localization of coronary bypass targets in hard-to-see coronary arteries.

BACKGROUND: Precise identification of coronary arteries and selection of anastomotic sites are critical stages of coronary bypass surgery. Visualization of coronary arteries is occasionally challenging when the heart is covered with a thick layer of fat or scar tissue. In this paper, we review the methods to localize the coronary arteries during coronary surgery. METHODS: Prior publications were searched to summarize all available methods for localization of coronary arteries during coronary surgery. RESULTS: Five clinically recognized and three experimental techniques from the literature review are reviewed and summarized. CONCLUSIONS: Knowledge of various techniques of coronary artery identification in hard-to-see coronary arteries is an important asset in coronary surgery and especially useful during the most critical option of the most common heart surgery.

Biventricular pacing improves left ventricular function by 2-D strain in right ventricular failure.

BACKGROUND: We used speckle-tracking echocardiography to test the hypothesis that regional left ventricular (LV) strain would improve during optimized biventricular pacing (BiVP) in acute right ventricular (RV) pressure overload (PO). MATERIALS AND METHODS: Complete heart block and RVPO were induced in five open-chest fully anesthetized pigs. BiVP was optimized by adjusting atrioventricular and interventricular delays to maximize cardiac output derived from an aortic flow probe. LV short axis views were obtained during atrio-RV pacing (RVP), atrio-LV pacing (LVP), and BiVP. Intraventricular synchrony was assessed by comparing speckle-tracking echocardiography-derived time to peak (TTP) strain in the anterior septal (AS) and posterior wall segments. Segmental function was assessed using radial strain. RESULTS: Cardiac output was higher with optimized (RV first) BiVP than with LVP (0.96 ± 0.26 L/min versus 0.89 ± 0.27 L/min; P = 0.05). AS TTP strain (502 ± 19 ms) during LVP was prolonged versus BiVP (392 ± 58 ms) and versus RVP (390 ± 53 ms) (P = 0.0018). AS TTP strain during LVP was prolonged versus posterior (502 ± 19 ms versus 396 ± 72 ms, P = 0.0011). No significant difference in TTP strain in these segments was seen with BiVP or RVP. Posterior strain (20% ± 5%) increased 66% versus AS strain (12% ± 6%) during BiVP (P = 0.0029). A similar increase occurred during RVP (posterior 20% ± 3% versus AS 12% ± 7%, P = 0.0002). Posterior strain did not increase during LVP. CONCLUSIONS: BiVP and RVP restore intraventricular LV synchrony and increase regional function versus LVP during RVPO. RV pre-excitation unloads the RV and reduces the duration of AS contraction, facilitating synchrony of all LV segments and increasing free wall LV contraction.

Management of intracranial hemorrhage in a child with a left ventricular assist device.

Pediatric patients bridged to heart transplant with LVADs require chronic anticoagulation and are at increased risk of hemorrhagic complications, including intracranial hemorrhage. In this population, intracranial hemorrhage is often fatal. We report a case of successful management of a five-yr-old-boy with DCM on an LVAD who developed a subdural hematoma. We initially chose medical management, weighing the patient's high risk of thromboembolism from anticoagulation reversal against the risk of his chronic subdural hematoma. When head CT showed expansion of the hemorrhage with increasing midline shift, we chose prompt surgical evacuation of the hematoma with partial reversal of anticoagulation, given the increased risk of acute deterioration. The patient ultimately received an orthotopic heart transplant and was discharged with no permanent neurological complications. This represents a case of a pediatric patient on an LVAD who survived a potentially fatal subdural hematoma and was successfully bridged to cardiac transplantation.

Utilizing the Fourth Dimension for Patient Education in Cardiovascular Surgery.

The complex 3-dimensional (3D) anatomy of the cardiovascular system presents a steep learning obstacle to patients in understanding cardiovascular diseases and surgical procedures. Although 3D printed models have become popular in surgical education, 2D cross-sections remain standard in clinical practice owing to costs and availability. In this report, we demonstrate how the free 3D modeling software Meshmixer can be used to add a fourth dimension to patient education by exploiting interactive 3D modeling. This report serves as proof of concept for the feasibility and potential utility of interactive 3D modeling as an inexpensive tool for cardiovascular surgery patient education.

Effect of Blood Flow on Cardiac Morphogenesis and Formation of Congenital Heart Defects.

Congenital heart disease (CHD) affects about 1 in 100 newborns and its causes are multifactorial. In the embryo, blood flow within the heart and vasculature is essential for proper heart development, with abnormal blood flow leading to CHD. Here, we discuss how blood flow (hemodynamics) affects heart development from embryonic to fetal stages, and how abnormal blood flow solely can lead to CHD. We emphasize studies performed using avian models of heart development, because those models allow for hemodynamic interventions, in vivo imaging, and follow up, while they closely recapitulate heart defects observed in humans. We conclude with recommendations on investigations that must be performed to bridge the gaps in understanding how blood flow alone, or together with other factors, contributes to CHD.

Developing and optimizing a chronic cyanotic swine model.

BACKGROUND: Pulmonary artery (PA)-left atrial (LA) shunt models in piglets have been described, but technical details critical to limit morbidity/mortality and promote study of chronic cyanosis are lacking. Accordingly, we describe our experience with an optimized technique. MATERIALS AND METHODS: In 25 6- to 8-wk-old Yorkshire piglets, a beveled, 8 mm, polytetrafluoroethylene tube graft was anastomosed to the PA and LA. Systemic pressure was maintained at >60 mmHg. Saturation targets were met by adjusting a Teflon band on the graft and distal PA. The target oxygen saturation (SO(2)) was 85% on a 50% fraction of inspired oxygen (FiO(2)). If the SO(2) was <75% on a 50% FiO(2), the graft was constricted to achieve a SO(2) ≥ 90% on a 100% FiO(2) and 75%-80% on a 21% FiO(2). Complications affecting mortality were neutralized with a stepwise strategy to minimize risk. RESULTS: Thrombosis, blood loss, and arrhythmia were determinants of survival. Protocol optimization over time increased survival while assuring chronic cyanosis. Survival approached 90%, with a SO(2) of 80% to 90%, 3 to 5 wk postoperatively. Complications included bleeding, excessive hypoxemia, uncontrolled shunt flow, arrhythmias, and thrombosis. CONCLUSIONS: Refinement of surgical technique, shunt adjustment via graft banding, and thrombotic and arrhythmia prophylaxis are the keys to success with this model.

Computational fluid dynamics: a primer for congenital heart disease clinicians.

Computational fluid dynamics has become an important tool for studying blood flow dynamics. As an in-silico collection of methods, computational fluid dynamics is noninvasive and provides numerical values for the most important parameters of blood flow, such as velocity and pressure that are crucial in hemodynamic studies. In this primer, we briefly explain the basic theory and workflow of the two most commonly applied computational fluid dynamics techniques used in the congenital heart disease literature: the finite element method and the finite volume method. We define important terminology and include specific examples of how using these methods can answer important clinical questions in congenital cardiac surgery planning and perioperative patient management.

The Cavoatrial Anastomosis Procedure in Anomalous Connection of Superior Vena Cava to Left Atrium.

Anomalous connection of the superior vena cava to the morphologic left atrium is a rare congenital systemic venous abnormality. As opposed to pulmonary venous anomalies, the significant right-to-left shunt in these patients warrants a correction early in life. Optimal repair technique for combined pulmonary and systemic venous anomalies is not defined yet. Herein, we describe a neonate with such a diagnosis treated with cavoatrial anastomosis, known as Warden procedure with excellent results.

Mechanical Concepts Applied in Congenital Heart Disease and Cardiac Surgery.

All biological processes are governed by principles of physics that dictate the pathophysiology and even the treatment of congenital heart diseases. In this review, basic concepts such as flow, pressure, resistance, and velocity are introduced, followed by more complex laws that describe the relationship between these variables and the disease processes. Finally, physical phenomena such as turbulence, steal and runoff phenomenon, and energy loss are discussed. By application of these principles, one can accurately quantify modifications undertaken to treat diseases, for example, the size of a patch that augments a vessel and the angle of an anastomosis to allow a certain flow.

Preoperative aspirin administration improves oxygenation in patients undergoing coronary artery bypass grafting.

OBJECTIVES: Release of thromboxane (Tx) A(2) by platelets may be one of multiple factors that are responsible for lung injury after cardiopulmonary bypass, leading to pulmonary vasoconstriction and impaired oxygenation. In experimental models, the inhibition of Tx receptor or its production improved lung function. The use of aspirin, which is used widely in the treatment of ischemic heart disease because of its antiplatelet activity, is usually discontinued a week before the patient undergoes the operation to restore normal platelet hemostatic function. The purpose of this study was to determine the relationship between the time of cessation of aspirin before coronary artery bypass surgery, and postoperative oxygenation and bleeding. DESIGN: A prospective clinical study comparing the effect of aspirin on postoperative oxygenation in patients who had been treated or had not been treated with aspirin. SETTING: Tx levels in the pericardial fluid, oxygenation, and bleeding were compared between the two groups. PATIENTS: Thirty-two patients with coronary artery disease who were undergoing coronary artery bypass grafting. Fourteen of these patients received aspirin until the day of the operation, whereas 18 patients stopped receiving aspirin at least 1 week before undergoing the operation. MAIN RESULTS: Mean (+/- SD) Tx levels in the pericardial fluid were significantly lower in the aspirin group (117 +/- 47 pg/mL) compared to those in the control group (1,306 +/- 2,048 pg/mL; p = 0.02). The duration of ventilation after the operation was significantly longer in the nonaspirin group (9.6 +/- 5.6 h vs 3.8 +/- 1.4 h, respectively; p = 0.0004). Po(2) reached a higher level while patients breathed 100% O(2) in the aspirin group (235 +/- 54 mm Hg vs 176 +/- 27 mm Hg, respectively; p = 0.001). The mean amount of bleeding during the first 24 h after surgery was increased in the aspirin group (710 +/- 202 mL) compared with the nonaspirin group (539 +/- 143 mL; p = 0.01), but these patients did not require more transfusions. CONCLUSIONS: The administration of aspirin until the operation may improve oxygenation with only a slight increase in bleeding. This improvement is probably mediated by antiplatelet activity and Tx inhibition by aspirin.

Stuck bioprosthetic aortic valve--a new entity? A case report.

We describe herein a case of bioprosthetic valve malfunction, which closely imitates a stuck valve. Although the term "stuck" was used originally for the immovable mechanical valve leaflets, the echocardiographic manifestation of this malfunction is similar to those of a mechanical one. The clinical presentation of the stuck bioprosthesis is, however, far more benign than a stuck mechanical valve. Familiarity with this entity is important.