Video-assisted thoracic surgery S7 segmentectomy: use of virtual reality surgical planning and simulated reality intraoperative modelling

Preoperative planning and perioperative guidance are crucial in anatomical sublobar pulmonary resections. Preoperative virtual reality visualization of the computed tomography scan and intraoperative guidance through a soft-tissue dynamic lung model (simulated reality) can provide better insights into patient-specific anatomy for the surgical team. Using these imaging techniques, we present a right-sided video-assisted thoracoscopic surgery segment 7 resection.

Ex vivo lung perfusion: a procedural guide

Available donor organs for lung transplantation are scarce. Ex vivo lung perfusion provides a platform to preserve, assess, and recondition donor lungs and can thereby aid in enlarging the donor pool. This video tutorial discusses the indications, preparation, and surgical technique for and the initiation, maintenance and termination of the ex vivo lung perfusion procedure.

Virtual Reality Simulator versus Conventional Advanced Life Support Training for Cardiopulmonary Resuscitation Post-Cardiac Surgery: A Randomized Controlled Trial

External chest compressions are often ineffective for patients arresting after cardiac surgery, for whom emergency resternotomy may be required. A single-blinded randomized controlled trial (RCT) was performed, with participants being randomized to a virtual reality (VR) Cardiac Surgical Unit Advanced Life Support (CSU-ALS) simulator training arm or a conventional classroom CSU-ALS training arm. Twenty-eight cardiothoracic surgery (CTS) residents were included and subsequently assessed in a moulage scenario in groups of two, either participating as a leader or surgeon. The primary binary outcomes were two time targets: (1) delivering three stacked shocks within 1 min and (2) resternotomy within 5 min. Secondary outcomes were the number of protocol mistakes made and a questionnaire after the VR simulator. The conventional training group administered stacked shocks within 1 min in 43% (n = 6) of cases, and none in the VR group reached this target, missing it by an average of 25 s. The resternotomy time target was reached in 100% of the cases (n = 14) in the conventional training group and in 83% of the cases (n = 10) in the VR group. The VR group made 11 mistakes in total versus 15 for those who underwent conventional training. Participants reported that the VR simulator was useful and easy to use. The results show that the VR simulator can provide adequate CSU-ALS training. Moreover, VR training results in fewer mistakes suggesting that repetitive practice in an immersive environment improves skills.

Comparative study of male and female patients undergoing surgical aortic valve replacement

BACKGROUND

Sex does have an effect on disease perception and outcomes after cardiac surgery.

OBJECTIVES

The aim of this study was to quantify the differences in cardiovascular risk profiles within an age-matched cohort and assess the long-term survival differences in males and females who underwent surgical aortic valve replacement (SAVR) with or without concomitant coronary artery bypass surgery.

METHODS

All-comers patients who underwent SAVR with or without coronary artery bypass surgery were included. Characteristics, clinical features and survival up to 30 years were compared between female and male patients. Propensity matching and age matching using propensity scores were used to compare both groups.

RESULTS

During the total study period between 1987 and 2017, there were 3462 patients {mean age 66.8 [standard deviation (SD): 11.1] years, 37.1% female} who underwent SAVR with or without coronary artery bypass surgery at our institution. In general, female patients were older than male patients (69.1 (SD : 10.3) versus 65.5 (SD : 11.3), respectively). In the age-matched cohort, female patients were less likely to have multiple comorbidities and undergo concomitant coronary artery bypass surgery. Twenty-year survival following the index procedure was higher in age-matched female patients (27.1%) compared to male patients (24.4%) in the overall cohort (P = 0.018).

CONCLUSIONS

Substantial sex differences in cardiovascular risk profile exist. However, when SAVR with or without coronary artery bypass surgery is performed, extended long-term mortality is comparable between males and females. More research regarding sex-dimorphic mechanisms of aortic stenosis and coronary atherosclerosis would promote more awareness in terms of sex-specific risk factors after cardiac surgery and contribute to more guided personalized surgery in the future.

Preoperative visualization of congenital lung abnormalities: hybridizing artificial intelligence and virtual reality

OBJECTIVES

When surgical resection is indicated for a congenital lung abnormality (CLA), lobectomy is often preferred over segmentectomy, mostly because the latter is associated with more residual disease. Presumably, this occurs in children because sublobar surgery often does not adhere to anatomical borders (wedge resection instead of segmentectomy), thus increasing the risk of residual disease. This study investigated the feasibility of identifying eligible cases for anatomical segmentectomy by combining virtual reality (VR) and artificial intelligence (AI).

METHODS

Semi-automated segmentation of bronchovascular structures and lesions were visualized with VR and AI technology. Two specialists independently evaluated via a questionnaire the informative value of regular computed tomography versus three-dimensional (3D) VR images.

RESULTS

Five asymptomatic, non-operated cases were selected. Bronchovascular segmentation, volume calculation and image visualization in the VR environment were successful in all cases. Based on the computed tomography images, assignment of the CLA lesion to specific lung segments matched between the consulted specialists in only 1 out of the cases. Based on the three 3D VR images, however, the localization matched in 3 of the 5 cases. If the patients would have been operated, adding the 3D VR tool to the preoperative workup would have resulted in changing the surgical strategy (i.e. lobectomy versus segmentectomy) in 4 cases.

CONCLUSIONS

This study demonstrated the technical feasibility of a hybridized AI-VR visualization of segment-level lung anatomy in patients with CLA. Further exploration of the value of 3D VR in identifying eligible cases for anatomical segmentectomy is therefore warranted.

The current status of stem cell-based therapies during ex vivo graft perfusion: An integrated review of four organs

The use of extended criteria donor grafts is a promising strategy to increase the number of organ transplantations and reduce waitlist mortality. However, these organs are often compromised and/or damaged, are more susceptible to preservation injury, and are at risk for developing post-transplant complications. Ex vivo organ perfusion is a novel technology to preserve donor organs while providing oxygen and nutrients at distinct perfusion temperatures. This preservation method allows to resuscitate grafts and optimize function with therapeutic interventions prior to solid organ transplantation. Stem cell-based therapies are increasingly explored for their ability to promote regeneration and reduce the inflammatory response associated with in vivo reperfusion. The aim of this review is to describe the current state of stem cell-based therapies during ex vivo organ perfusion for the kidney, liver, lung, and heart. We discuss different strategies, including type of cells, route of administration, mechanisms of action, efficacy, and safety. The progress made within lung transplantation justifies the initiation of clinical trials, whereas more research is likely required for the kidney, liver, and heart to progress into clinical application. We emphasize the need for standardization of methodology to increase comparability between future (clinical) studies.

Essential Surgical Plan Modifications After Virtual Reality Planning in 50 Consecutive Segmentectomies

BACKGROUND

Lately, an increased interest in pulmonary segmentectomy is observed. Segmental border identification is extremely difficult on 2D computed tomography (CT). Preoperative application of virtual reality (VR) can provide better insight in patient-specific anatomy. The aim of our study was to investigate the added clinical value of 3D-VR using PulmoVR for preoperative planning.

METHODS

Patients with indication for pulmonary segmentectomy were included between June 2020 and September 2021 at the Erasmus Medical Center, Rotterdam, The Netherlands. CT-scans were (semi)automatically segmented to visualize lung segments, segmental arteries, veins, and bronchi. Three surgeons made a surgical plan based on the conventional CT-scan and subsequently analyzed the VR visualization. Primary outcome was the incidence of critical (ensuring radical resection) preoperative plan modifications. Secondary, data on observed anatomical variation and perioperative (oncological) outcomes were collected.

RESULTS

A total of 50 patients (median age at surgery 65 years (interquartile range 17.25 years)) with indication for pulmonary segmentectomy were included. After supplemental VR visualization, the surgical plan was adjusted in 52%; the tumor was localized in a different segment in 14%, more lung-sparing resection was planned in 10% and extended segmentectomy, including one lobectomy, was planned in 28%. Pathologic examination confirmed radical resection in 49 patients (98%).

CONCLUSIONS

3D-VR has shown added clinical value in our first 50 VR-guided segmentectomies, since 52% change of plan with 98% radical resection was observed. Furthermore, 3D-VR visualization of the bronchovasculature including various anatomical variations provided a better insight in the patient-specific anatomy, providing lung-sparing possibilities with more certainty.

Virtual Reality in the Preoperative Planning of Adult Aortic Surgery: A Feasibility Study

Background: Complex aortic anatomy needs careful preoperative planning in which a patient-tailored approach with novel immersive techniques could serve as a valuable addition to current preoperative imaging. This pilot study aimed to investigate the technical feasibility of virtual reality (VR) as an additional imaging tool for preoperative planning in ascending aortic surgery. Methods: Ten cardiothoracic surgeons were presented with six patients who had each undergone a recent repair of the ascending aorta. Two-dimensional computed tomography images of each patient were assessed prior to the VR session. After three-dimensional (3D) VR rendering and 3D segmentation of the ascending aorta and aortic arch, the reconstructions were analyzed by each surgeon in VR via a head-mounted display. Each cardiothoracic surgeon completed a questionnaire after each planning procedure. The results of their assessments were compared to the performed operations. The primary endpoint of the present study was a change of surgical approach from open to clamped distal anastomosis, and vice versa. Results: Compared with conventional imaging, 80% of surgeons found that VR prepared them better for surgery. In 33% of cases (two out of six), the preoperative decision was adjusted due to the 3D VR-based evaluation of the anatomy. Surgeons rated CardioVR usefulness, user-friendliness, and satisfaction with median scores of 3.8 (IQR: 3.5–4.1), 4.2 (IQR: 3.8–4.6,) and 4.1 (IQR: 3.8–4.7) on a five-point Likert scale, respectively. Conclusions: Three-dimensional VR imaging was associated with improved anatomical understanding among surgeons and could be helpful in the future preoperative planning of ascending aortic surgery.

The digital heart-lung unit: applications of exponential technology

Exponential technologies such as virtual reality (VR), computational modelling, and additive manufacturing have emerged in the field of cardiology and cardiothoracic surgery. An increasing number of publications that evaluate the clinical role of these technologies are becoming available. Moreover, there is an increase in the number of hospitals and departments that have implemented digital and exponential solutions in clinical workflow. In our centre, we have adopted various exponential technologies in order to improve clinical pre-procedural workflow, patient care, and training and education. In order to provide our view and approach on the implementation of these technologies, in this article, we provide an overview of the currently applied modalities including immersive VR, three-dimensional (3D) computational modelling, VR-based simulations, and additive manufacturing (3D printing). Moreover, we present the potential of these applications in cardiovascular and cardiothoracic medicine, and additionally, we will provide key facilitators, challenges, and recommendations to adopting these technologies in clinical practice.

Ki67 (MIB-1) as a Prognostic Marker for Clinical Decision Making Before Extended Pleurectomy Decortication in Malignant Pleural Mesothelioma

Introduction

The role of surgery for early stage malignant pleural mesothelioma (MPM) remains controversial. Current expert opinion is only to treat patients surgically as part of multimodality therapy. It is still challenging to identify patients who will not benefit from surgery. We specifically evaluated tumor-related parameters in combination with clinical parameters to identify prognostic markers for survival.

Methods

Clinical data of 27 consecutive patients with MPM treated with extended pleurectomy and decortication within a multimodality approach were collected and analyzed. Several tumor (immuno-)histopathologic characteristics were determined on resected tumor material, among which MTAP and Ki67 (MIB-1). Univariable and multivariable analyses served to correlate clinical and tumor-related parameters to overall survival (OS) and progression-free survival (PFS).

Results

The median PFS (mPFS) was 15.3, and the median OS (mOS) was 26.5 months. Patients with a Ki67 score greater than 10% had a significantly shorter PFS (mPFS = 8.81 versus 25.35 mo, p = 0.001) and OS (mOS 19.7 versus 44.5 mo, p = 0.002) than those with a Ki67 score less than or equal to 10. Receiver operating characteristic curve analysis for Ki67 revealed an area under the curve of 0.756 with a sensitivity of 90% and specificity of 71% for a cutoff of 10% for Ki67. Patients with loss of MTAP had a significantly shorter mPFS (9 versus 21.1 mo, p = 0.014) and mOS (19.7 versus 42.6 mo, p = 0.047) than those without MTAP loss.

Conclusions

In our study, Ki67 was prognostic for OS and PFS in patients with MPM treated with extended pleurectomy/decortication in a multimodality approach. Determination of Ki67 before surgery combined with specific clinical parameters could assist in clinical decision making by identifying patients, with high Ki67, who are unlikely to benefit from surgery.

A nationwide population-based cohort study of surgical care for patients with superior sulcus tumors: Results from the Dutch Lung Cancer Audit for Surgery (DLCA-S)

OBJECTIVES

Data on national patterns of care for patients with superior sulcus tumors (SST) is currently lacking. We investigated the distribution of surgical care and outcome for patients with SST in the Netherlands.

MATERIAL AND METHODS

Data was retrieved from the Dutch Lung Cancer Audit for Surgery (DLCA-S) for all patients undergoing resection for clinical stage IIB-IV SST from 2012 to 2019. Because DLCA-S is not linked to survival data, survival for a separate cohort (2015-2017) was obtained from the Netherlands Cancer Registry (NCR).

RESULTS

In the study period, 181 patients had SST surgery, representing 1.03% (181/17488) of all lung cancer pulmonary resections. For 2015-2017, the SST resection rate was 14.4% (79/549), and patients with stage IIB/III SST treated with trimodality had a 3-year overall survival of 67.4%. 63.5% of patients were male, and median age was 60 years. Almost 3/4 of tumors were right sided. Surgery was performed in 20 hospitals, with average number of annual resections ranging from ≤ 1 (n = 17) to 9 (n = 1). 39.8% of resections were performed in 1 center and 63.5% in the 3 most active centers. 12.7% of resections were extended (e.g. vertebral resection). 85.1% of resections were complete (R0). Morbidity and 30-day mortality were 51.4% and 3.3% respectively. Despite treating patients with a higher ECOG performance score and more extended resections, the highest volume center had rates of morbidity/mortality, and length of hospital stay that were comparable to those of the medium volume (n = 2) and low-volume centers (n = 1).

CONCLUSION

In the Netherlands, surgery for SST accounts for about 1% of all lung cancer pulmonary resections, the number of SST resections/hospital/year varies widely, with most centers performing an average of ≤ 1/year. Morbidity and mortality are acceptable and survival compares favourably with the literature. Although further centralisation is possible, it is unknown whether this will improve outcomes.

Weaning from cardiopulmonary bypass, decannulation, and closure

In 1952, John Gibbon performed the first successful cardiac procedure using cardiopulmonary bypass, which turned out to be one of the most important clinical advances of that year. Cardiopulmonary bypass has also been described as "One of the most impressive evidences of the role of investigative surgery in the history of medicine in the persevering efforts of Dr. Gibbon for more than 20 years, which finally culminated in a practical heart-lung machine," at the first John H. Gibbon, Jr, Lecture at the annual meeting of the American College of Surgeons [1]. Due to the subsequent advancement of cardiopulmonary bypass, many patients with complex heart disease requiring surgical care undergo cardiac surgery while the other organs remain adequately oxygenated and perfused.

Conventional open harvesting of the radial artery as a conduit for coronary artery bypass grafting

This video tutorial summarizes the main steps of the conventional open surgical technique for harvesting the radial artery as a coronary artery bypass graft, taking anatomic and surgical aspects into account.

Surgical setup for cardiopulmonary bypass through central cannulation

The introduction of cardiopulmonary bypass was one of the most important clinical advances of 1952. In that year, John Gibbon performed the first successful cardiac surgery using cardiopulmonary bypass. The procedure has been described as "One of the most impressive evidences of the role of investigative surgery in the history of medicine in the persevering efforts of Dr. Gibbon for more than 20 years, which finally culminated in a practical heart-lung machine", at the first John H. Gibbon, Jr. Lecture at the annual meeting of the American College of Surgeons. Due to on-going advancements in cardiopulmonary bypass, many patients with complex heart disease requiring surgical care undergo cardiac surgery while the other organs remain adequately oxygenated and perfused. This tutorial discusses the access, surgical technique, and initiation of cardiopulmonary bypass through central cannulation and describes the safeguards and pitfalls.

Intimal aortic atherosclerosis in cardiac surgery: surgical strategies to prevent embolic stroke

 

OBJECTIVES

Although the incidence of perioperative stroke after cardiac surgery gradually decreased over the last decades, there is much variation between centres. This review aimed to create a concise overview of the evidence on possible surgical strategies to prevent embolic stroke in patients with intimal aortic atherosclerosis.

METHODS

The PubMed and EMBASE databases were searched for studies on surgical management of aortic atherosclerosis and the association with perioperative stroke in cardiac surgery, including specific searches on the most common types of surgery. Articles were screened with emphasis on studies comparing multiple strategies and studies reporting on the patients’ severity of aortic atherosclerosis. The main findings were summarized in a figure, with a grade of the corresponding level of evidence.

RESULTS

Regarding embolic stroke risk, aortic atherosclerosis of the tunica intima is most relevant. Although several strategies in general cardiac surgery seem to be beneficial in severe disease, none have conclusively been proven most effective. Off-pump surgery in coronary artery bypass grafting should be preferred with severe atherosclerosis, if the required expertise is present. Although transcatheter aortic valve replacement is used as an alternative to surgery in patients with a porcelain aorta, the risk profile concerning intimal atherosclerosis remains poorly defined.

CONCLUSIONS

A tailored approach that uses the discussed alternative strategies in carefully selected patients is best suited to reduce the risk of perioperative stroke without compromising other outcomes. More research is needed, especially on the perioperative stroke risk in patients with moderate aortic atherosclerosis.

Differences in baseline characteristics and outcomes of bicuspid and tricuspid aortic valves in surgical aortic valve replacement

OBJECTIVES

Patients with bicuspid aortic valve (BAV) comprise a substantial portion of patients undergoing surgical aortic valve replacement (SAVR). Our goal was to quantify the prevalence of BAV in the current SAVR ± coronary artery bypass grafting (CABG) population, assess differences in cardiovascular risk profiles and assess differences in long-term survival in patients with BAV compared to patients with tricuspid aortic valve (TAV).

METHODS

Patients who underwent SAVR with or without concomitant CABG and who had a surgical report denoting the relevant valvular anatomy were eligible and included. Prevalence, predictors and outcomes for patients with BAV were analysed and compared to those patients with TAV. Matched patients with BAV and TAV were compared using a propensity score matching strategy and an age matching strategy.

RESULTS

A total of 3723 patients, 3145 of whom (mean age 66.6 ± 11.4 years; 37.4% women) had an operative report describing their aortic valvular morphology, underwent SAVR ± CABG between 1987 and 2016. The overall prevalence of patients with BAV was 19.3% (607). Patients with BAV were younger than patients with TAV (60.6 ± 12.1 vs 68.0 ± 10.7, respectively). In the age-matched cohort, patients with BAV were less likely to have comorbidities, among others diabetes (P = 0.001), hypertension (P < 0.001) and hypercholesterolaemia (P = 0.003), compared to patients with TAV. Twenty-year survival following the index procedure was higher in patients with BAV (14.8%) compared to those with TAV (12.9%) in the age-matched cohort (P = 0.015).

CONCLUSIONS

Substantial differences in the cardiovascular risk profile exist in patients with BAV and TAV. Long-term survival after SAVR in patients with BAV is satisfactory.

Epipleural surgical block and ultrasound-guided erector spinae plane block for analgesia in VATS

Thoracic surgery is still associated with severe postoperative pain. In this video tutorial, we present 2 techniques that could be used as an additional method in a multimodal postoperative analgesia strategy for video-assisted thoracic surgery. We present the combination of an epipleural surgical infiltration of a local anesthetic with an ultrasound-guided erector spinae plane block.

Outcomes of surgical aortic valve replacement over three decades

OBJECTIVE

The study objective was to analyze temporal changes in baseline and procedural characteristics and long-term survival of patients undergoing surgical aortic valve replacement over a 30-year period.

METHODS

A retrospective analysis of patients undergoing surgical aortic valve replacement between 1987 and 2016 in the Erasmus Medical Center (Rotterdam, The Netherlands) was conducted. Patient baseline and procedural characteristics were analyzed in periods according to the date of surgical aortic valve replacement (period A: 1987-1996; B: 1997-2006; C: 2007-2016). Survival status was determined using the Dutch National Death Registry. Relative survival was obtained by comparing the survival after surgical aortic valve replacement with the survival of the age-, sex-, and year-matched general population.

RESULTS

Between 1987 and 2016, 4404 patients underwent SAVR. From period A to C, the mean age increased from 63.9 ± 11.2 years to 66.2 ± 12.3 years (P < .001), and the prevalence of diabetes mellitus, hypertension, hypercholesterolemia, previous myocardial infarction, and previous stroke at baseline increased (P values for trend for all < .001). The prevalence of concomitant procedures increased from 42.4% in period A to 48.3% in period C (P = .004). Bioprosthesis use increased significantly (18.8% in period A vs 67.1% in period C, P < .001). Mean survival after surgical aortic valve replacement was 13.8 years. Relative survival at 20 years in the overall cohort was 60.4% (95% confidence interval, 55.9-65.2) and 73.8% (95% confidence interval, 67.1-81.1) in patients undergoing isolated primary surgical aortic valve replacement.

CONCLUSIONS

Patient complexity has been continuously increasing over the last 30 years, yet long-term survival after surgical aortic valve replacement remains high compared with the age-, sex-, and year-matched general population.

Asymptomatic Patients with Severe Aortic Stenosis and the Impact of Intervention

Objectives the exact timing of aortic valve replacement (AVR) in asymptomatic patients with severe aortic stenosis (AS) remains a matter of debate. Therefore, we described the natural history of asymptomatic patients with severe AS, and the effect of AVR on long-term survival. Methods: Asymptomatic patients who were found to have severe AS between June 2006 and May 2009 were included. Severe aortic stenosis was defined as peak aortic jet velocity Vmax ≥ 4.0 m/s or aortic valve area (AVA) ≤ 1 cm². Development of symptoms, the incidence of AVR, and all-cause mortality were assessed. Results: A total of 59 asymptomatic patients with severe AS were followed, with a mean follow-up of 8.9 ± 0.4 years. A total of 51 (86.4%) patients developed AS related symptoms, and subsequently 46 patients underwent AVR. The mean 1-year, 2-year, 5-year, and 10-year overall survival rates were higher in patients receiving AVR compared to those who did not undergo AVR during follow-up (100%, 93.5%, 89.1%, and 69.4%, versus 92.3%, 84.6%, 65.8%, and 28.2%, respectively; p < 0.001). Asymptomatic patients with severe AS receiving AVR during follow-up showed an incremental benefit in survival of up to 31.9 months compared to conservatively managed patients (p = 0.002). Conclusions: The majority of asymptomatic patients turn symptomatic during follow-up. AVR during follow-up is associated with better survival in asymptomatic severe AS patients.

Immersive 3D virtual reality imaging in planning minimally invasive and complex adult cardiac surgery

Aims

Increased complexity in cardiac surgery over the last decades necessitates more precise preoperative planning to minimize operating time, to limit the risk of complications during surgery and to aim for the best possible patient outcome. Novel, more realistic, and more immersive techniques, such as three-dimensional (3D) virtual reality (VR) could potentially contribute to the preoperative planning phase. This study shows our initial experience on the implementation of immersive VR technology as a complementary research-based imaging tool for preoperative planning in cardiothoracic surgery. In addition, essentials to set up and implement a VR platform are described.

Methods

Six patients who underwent cardiac surgery at the Erasmus Medical Center, Rotterdam, The Netherlands, between March 2020 and August 2020, were included, based on request by the surgeon and availability of computed tomography images. After 3D VR rendering and 3D segmentation of specific structures, the reconstruction was analysed via a head mount display. All participating surgeons (n = 5) filled out a questionnaire to evaluate the use of VR as preoperative planning tool for surgery.

Conclusion

Our study demonstrates that immersive 3D VR visualization of anatomy might be beneficial as a supplementary preoperative planning tool for cardiothoracic surgery, and further research on this topic may be considered to implement this innovative tool in daily clinical practice.

Lay summary

Over the past decades, surgery on the heart and vessels is becoming more and more complex, necessitating more precise and accurate preoperative planning. Nowadays, operative planning is feasible on flat, two-dimensional computer screens, however, requiring a lot of spatial and three-dimensional (3D) thinking of the surgeon. Since immersive 3D virtual reality (VR) is an upcoming imaging technique with promising results in other fields of surgery, we aimed in this study to explore the additional value of this technique in heart surgery. Our surgeons planned six different heart operations by visualizing computed tomography scans with a dedicated VR headset, enabling them to visualize the patient's anatomy in an immersive and 3D environment. The outcomes of this preliminary study are positive, with a much more reality-like simulation for the surgeon. In such, VR could potentially be beneficial as a preoperative planning tool for complex heart surgery.

Technique of surgical aortic valve implantation using single interrupted annular sutures

The introduction of the first surgical prosthetic heart valves in the early 1960s made effective treatment of aortic valve disease possible. The goal of surgical aortic valve replacement is to replace the diseased aortic valve with a properly functioning, sufficiently large prosthesis while avoiding intraoperative complications such as conduction disturbances, coronary artery occlusion, or paravalvular leaks. Although most commonly, non-everting pledgeted mattress sutures are used to implant the prosthesis during surgical aortic valve replacement , interrupted single sutures without pledgets can be a useful alternative, especially in patients with a small tissue annulus, because they theoretically maximize the orifice available for flow. This tutorial discusses the surgical technique of surgical aortic valve replacement using interrupted single annular sutures.

Electrical activation of sinus venosus myocardium and expression patterns of RhoA and Isl-1 in the chick embryo

Electrical Activity and RhoA in the Embryo.

INTRODUCTION

Myocardium at the venous pole (sinus venosus) of the heart has gained clinical interest as arrhythmias can be initiated from this area. During development, sinus venosus myocardium is incorporated to the primary heart tube and expresses different markers than primary myocardium. We aimed to elucidate the development of sinus venosus myocardium, including the sinoatrial node (SAN), by studying expression patterns of RhoA in relation to other markers, and by studying electrical activation patterns of the developing sinus venosus myocardium.

METHODS AND RESULTS

Expression of RhoA, myocardial markers cTnI and Nkx2.5, transcription factors Isl-1 and Tbx18, and cation channel HCN4 were examined in sequential stages in chick embryos. Electrical activation patterns were studied using microelectrodes and optical mapping. Embryonic sinus venosus myocardium is cTnI and HCN4 positive, Nkx2.5 negative, complemented by distinct patterns of Isl-1 and Tbx18. During development, initial myocardium-wide expression of RhoA becomes restricted to right-sided sinus venosus myocardium, comprising the SAN. Electrophysiological measurements revealed initial capacity of both atria to show electrical activity that in time shifts to a right-sided dominance, coinciding with persistence of RhoA, Tbx18, and HCN4 and absence of Nkx2.5 expression in the definitive SAN.

CONCLUSION

Results show an initially bilateral electrical potential of sinus venosus myocardium evolving into a right-sided activation pattern during development, and suggest a role for RhoA in conduction system development. We hypothesize an initial sinus venosus-wide capacity to generate pacemaker signals, becoming confined to the definitive SAN. Lack of differentiation toward a chamber phenotype would explain ectopic pacemaker foci.

Cardiac malformations in Pdgfralpha mutant embryos are associated with increased expression of WT1 and Nkx2.5 in the second heart field

Platelet-derived growth factor receptor alpha (Pdgfralpha) identifies cardiac progenitor cells in the posterior part of the second heart field. We aim to elucidate the role of Pdgfralpha in this region. Hearts of Pdgfralpha-deficient mouse embryos (E9.5-E14.5) showed cardiac malformations consisting of atrial and sinus venosus myocardium hypoplasia, including venous valves and sinoatrial node. In vivo staining for Nkx2.5 showed increased myocardial expression in Pdgfralpha mutants, confirmed by Western blot analysis. Due to hypoplasia of the primary atrial septum, mesenchymal cap, and dorsal mesenchymal protrusion, the atrioventricular septal complex failed to fuse. Impaired epicardial development and severe blebbing coincided with diminished migration of epicardium-derived cells and myocardial thinning, which could be linked to increased WT1 and altered alpha4-integrin expression. Our data provide novel insight for a possible role for Pdgfralpha in transduction pathways that lead to repression of Nkx2.5 and WT1 during development of posterior heart field-derived cardiac structures.

Epicardium-derived cells enhance proliferation, cellular maturation and alignment of cardiomyocytes

During heart development, cells from the proepicardial organ spread over the naked heart tube to form the epicardium. From here, epicardium-derived cells (EPDCs) migrate into the myocardium. EPDCs proved to be indispensable for the formation of the ventricular compact zone and myocardial maturation, by largely unknown mechanisms. In this study we investigated in vitro how EPDCs affect cardiomyocyte proliferation, cellular alignment and contraction, as well as the expression and cellular distribution of proteins involved in myocardial maturation. Embryonic quail EPDCs induced proliferation of neonatal mouse cardiomyocytes. This required cell-cell interactions, as proliferation was not observed in transwell cocultures. Western blot analysis showed elevated levels of electrical and mechanical junctions (connexin43, N-cadherin), sarcomeric proteins (Troponin-I, alpha-actinin), extracellular matrix (collagen I and periostin) in cocultures of EPDCs and cardiomyocytes. Immunohistochemistry indicated more membrane-bound expression of Cx43, N-cadherin, the mechanotransduction molecule focal adhesion kinase, and higher expression of the sarcoplasmic reticulum Ca(2+) ATPase (SERCA2a). Newly developed software for analysis of directionality in immunofluorescent stainings showed a quantitatively determined enhanced cellular alignment of cardiomyocytes. This was functionally related to increased contraction. The in vitro effects of EPDCs on cardiomyocytes were confirmed in three reciprocal in vivo models for EPDC-depletion (chicken and mice) in which downregulation of myocardial N-cadherin, Cx43, and FAK were observed. In conclusion, direct interaction of EPDCs with cardiomyocytes induced proliferation, correct mechanical and electrical coupling of cardiomyocytes, ECM-deposition and concurrent establishment of cellular array. These findings implicate that EPDCs are ideal candidates as adjuvant cells for cardiomyocyte integration during cardiac (stem) cell therapy.

Podoplanin deficient mice show a RhoA-related hypoplasia of the sinus venosus myocardium including the sinoatrial node

We investigated the role of podoplanin in development of the sinus venosus myocardium comprising the sinoatrial node, dorsal atrial wall, and primary atrial septum as well as the myocardium of the cardinal and pulmonary veins. We analyzed podoplanin wild-type and knockout mouse embryos between embryonic day 9.5-15.5 using immunohistochemical marker podoplanin; sinoatrial-node marker HCN4; myocardial markers MLC-2a, Nkx2.5, as well as Cx43; coelomic marker WT-1; and epithelial-to-mesenchymal transformation markers E-cadherin and RhoA. Three-dimensional reconstructions were made and myocardial morphometry was performed. Podoplanin mutants showed hypoplasia of the sinoatrial node, primary atrial septum, and dorsal atrial wall. Myocardium lining the wall of the cardinal and pulmonary veins was thin and perforated. Impaired myocardial formation is correlated with abnormal epithelial-to-mesenchymal transformation of the coelomic epithelium due to up-regulated E-cadherin and down-regulated RhoA, which are controlled by podoplanin. Our results demonstrate an important role for podoplanin in development of sinus venosus myocardium.

Pulmonary vein, dorsal atrial wall and atrial septum abnormalities in podoplanin knockout mice with disturbed posterior heart field contribution

The developing sinus venosus myocardium, derived from the posterior heart field, contributes to the atrial septum, the posterior atrial wall, the sino-atrial node, and myocardium lining the pulmonary and cardinal veins, all expressing podoplanin, a coelomic and myocardial marker. We compared development and differentiation of the myocardium and vascular wall of the pulmonary veins (PV), left atrial dorsal wall, and atrial septum in wild type with podoplanin knockout mouse embryos (E10.5-E18.5) by 3D reconstruction and immunohistochemistry. Expression of Nkx2.5 in the pulmonary venous myocardium changes from mosaic to positive during development pointing out a high proliferative rate compared with Nkx2.5 negative myocardium of the sino-atrial node and cardinal veins. In mutants, myocardium of the PVs, dorsal atrial wall and atrial septum was hypoplastic. The atrial septum and right-sided wall of the PV almost lacked interposed mesenchyme. Extension of smooth muscle cells into the left atrial body was diminished. We conclude that myocardium of the PVs, dorsal atrial wall, and atrial septum, as well as the smooth muscle cells, are derived from the posterior heart field regulated by podoplanin.

Cardiac malformations and myocardial abnormalities in podoplanin knockout mouse embryos: Correlation with abnormal epicardial development

Epicardium and epicardium-derived cells have been shown to be necessary for myocardial differentiation. To elucidate the function of podoplanin in epicardial development and myocardial differentiation, we analyzed podoplanin knockout mouse embryos between embryonic day (E) 9.5 and E15.5 using immunohistochemical differentiation markers, morphometry, and three-dimensional reconstructions. Podoplanin null mice have an increased embryonic lethality, possibly of cardiac origin. Our study reveals impairment in the development of the proepicardial organ, epicardial adhesion, and spreading and migration of the epicardium-derived cells. Mutant embryos show a hypoplastic and perforated compact and septal myocardium, hypoplastic atrioventricular cushions resulting in atrioventricular valve abnormalities, as well as coronary artery abnormalities. The epicardial pathology is correlated with reduced epithelial-mesenchymal transformation caused by up-regulation of E-cadherin, normally down-regulated by podoplanin. Our results demonstrate a role for podoplanin in normal cardiac development based on epicardial-myocardial interaction. Abnormal epicardial differentiation and reduced epithelial-mesenchymal transformation result in deficient epicardium-derived cells leading to myocardial pathology and cardiac anomalies.

Development of the cardiac conduction system and the possible relation to predilection sites of arrhythmogenesis

The cardiac conduction system (CCS) encompasses a complex system responsible for the coordinated contraction of the heart. In the developing heart, as well as in the adult heart, tissues of the (putative) CCS are characterized by different properties than the surrounding working myocardium, which can be observed on a histological level, as well as by the expression patterns of several immunohistological and molecular markers. In recent years, many markers have been studied that have helped to elucidate the processes involved in CCS development. It has become clear that multiple genes, cells and their interactions are involved in this complex process. In this article, an overview of the current knowledge of CCS development is supplied. Furthermore, several controversies regarding conduction system development are discussed, as well as the possible significance of embryologic development of the CCS for the development of arrhythmias later in life.

Nkx2.5-negative myocardium of the posterior heart field and its correlation with podoplanin expression in cells from the developing cardiac pacemaking and conduction system

Recent advances in the study of cardiac development have shown the relevance of addition of myocardium to the primary myocardial heart tube. In wild-type mouse embryos (E9.5-15.5), we have studied the myocardium at the venous pole of the heart using immunohistochemistry and 3D reconstructions of expression patterns of MLC-2a, Nkx2.5, and podoplanin, a novel coelomic and myocardial marker. Podoplanin-positive coelomic epithelium was continuous with adjacent podoplanin- and MLC-2a-positive myocardium that formed a conspicuous band along the left cardinal vein extending through the base of the atrial septum to the posterior myocardium of the atrioventricular canal, the atrioventricular nodal region, and the His-Purkinje system. Later on, podoplanin expression was also found in the myocardium surrounding the pulmonary vein. On the right side, podoplanin-positive cells were seen along the right cardinal vein, which during development persisted in the sinoatrial node and part of the venous valves. In the MLC-2a- and podoplanin-positive myocardium, Nkx2.5 expression was absent in the sinoatrial node and the wall of the cardinal veins. There was a mosaic positivity in the wall of the common pulmonary vein and the atrioventricular conduction system as opposed to the overall Nkx2.5 expression seen in the chamber myocardium. We conclude that we have found podoplanin as a marker that links a novel Nkx2.5-negative sinus venosus myocardial area, which we refer to as the posterior heart field, with the cardiac conduction system.