Virtual reality in cardiac interventions-New tools or new toys?

Improvementsin medical imaging and a steady increase in computing power are leading to new possibilities in the field of cardiovascular interventions. Interventions can be planned in advance in greater detail, even to the point of simulating procedures. Nevertheless, all techniques are at an early stage of development. It is of utmost importance that tools, especially if they can be used as decision support are intensively validated and their accuracy is demonstrated. In our commentary, we summarize current techniques for impprovements in planning and guiding of procedures, but also critically discuss the downsides of these techniques. Following the work of Kenichi and colleagues, we also discuss necessary steps in advancing new tools and techniques, particularly as they are used in routine clinical practice. We also discuss the role of artificial intelligence, which could play a crucial role in this context in the future.

Partial ring annuloplasty in the management of mitral annular calcification.

Mitral annular calcification (MAC) complicates the management of mitral valve (MV) disease, regardless of its etiology. Strategies to address MV surgery in MAC include two main options with their own pros and cons; respect and resect strategy. Here, we present a case of minimally-invasive MV repair with partial annuloplasty in the management of noncircumferential MAC with respect to strategy. This technique may be an alternative option for rescuing high-risk patients without extensive decalcification.

Transcatheter mitral valve implantation in the ongoing structural heart revolution.

Transcatheter mitral valve implantation (TMVI) has emerged as a less invasive approach potentially surmounting some of the current hurdles associated with transcatheter edge-to-edge repair and high-risk mitral valve surgery. In this review, we aimed to outline the main scenarios in the TMVI field, highlight current and upcoming devices, and describe challenges and clinical results. Finally, we briefly discuss the future perspectives for this emerging field and how TMVI might further advance the field of transcatheter treatments of mitral valve disease.

Right Antero-Lateral Mini-Thoracotomy Surgical Aortic Valve Replacement.

Over the past few decades, the field of minimally invasive cardiac surgery has significantly broadened. Novel surgical and endovascular techniques have been developed for the treatment of aortic valve pathologies. Surgical aortic valve replacement (SAVR) through a right antero-lateral (mini-)thoracotomy (RALT) has gained approval due to its limited postoperative trauma, faster rehabilitation and sufficient pain control. Nevertheless, SAVR RALT has not been adopted by a significant proportion of cardiac surgeons, due, in part, to its technical complexity and steep learning curve. In this review, we discuss the data for minimally invasive aortic valve surgery and describe our operative technique for SAVR RALT.

Body donation as a grateful gift for a long and active life with a Björk-Shiley valve.

An 87-year-old patient donated his body to the Institute of Anatomy and Cell Biology in gratefulness for the longevity of a Björk-Shiley convexo-concave (BSCC) prosthetic aortic valve, implanted 34 years ago. The dissection of the enlarged heart showed no major signs of thrombosis, malignant fibrosis, or any other relevant issue that could potentially lead to valve failure as in other patients. Despite the reported high mortality rate of the earlier designs, especially of the BSCC valves, some patients survived for longer than expected. In more than 34 years after the BSCC valve implantation, the patient was a very active and lively man, working both as full-time and volunteer firefighter. The lifespan of this BSCC valve is among the longest reported.

Surgical explantation of a partially detached cardioband device.

Transcatheter repair systems are becoming increasingly popular as a potential solution for high-risk and inoperable patients with mitral regurgitation. The cardioband (Edwards Lifesciences, Irvine, California) is a transcatheter direct annuloplasty device, based on the concept of an undersized ring annuloplasty. We report a case of minimally invasive surgical explantation of a failed cardioband device 21 months after its implantation. Intraoperatively, it was found that three anchors of the cardioband device were detached from the posterior annulus at P2. In this report, a "cut and unscrew" technique with some tips and tricks is presented for the removal of the device.

Transcatheter aortic valve implantation and its impact on mitral valve geometry and function.

BACKGROUND: The aim of this study was to evaluate the impact of transcatheter aortic valve implantation (TAVI) on mitral valve geometry and function. METHODS: Eighty-four patients underwent TAVI. Forty-four (52%) patients received a balloon-expandable valve and 40 (48%) were implanted with a self-expandable valve. All patients underwent three-dimensional-volumetric transesophageal echocardiography of the mitral valve before and immediately after TAVI. A dedicated software was used for assisted semiautomatic measurement of mitral annular geometry. RESULTS: During systole, the anterior to posterior (AP) diameter was significantly reduced after the procedure (3.4 ± 0.5 cm vs 3.2 ± 0.5 cm; P < .05). The mitral annular area (10.8 ± 2.8cm2 vs 9.9 ± 2.6cm2 ; P < .05) as well as the tenting area (1.6 ± 0.7 cm2 vs 1.2 ± 0.6 cm2 ; P < .001) measured at mid-systole were reduced after TAVI. Diastolic measures were similar. Patients treated with balloon-expandable valves showed a significantly larger reduction in the AP diameter compared to self-expandable valves (-0.25 cm vs -0.11 cm; P < .05). The reduction of the annular area was higher in the balloon-expandable group (-1.2 ± 1.59 vs -0.22 ± 1.41; P < .05). Grade of mitral regurgitation did improve or remained stable after TAVI. CONCLUSION: TAVI significantly impacts the mitral valve and mitral annular geometry and morphology. The choice of the prosthesis (balloon- vs self-expandable) may be relevant for those changes.

Minimally invasive surgical aortic valve replacement: The RALT approach.

Less-invasive techniques for cardiothoracic surgical procedures are designed to limit surgical trauma, but the technical requirements and preoperative planning are more demanding than those for conventional sternotomy. Patient selection, interdisciplinary collaboration, and surgical skills are key factors for procedural success. Aortic valve replacement is frequently performed through an upper hemisternotomy, but the right anterior minithoracotomy represents an even less traumatic, technical advancement. Preoperative assessment of the ascending aorta in relation to the sternum is mandatory to select patients and the intercostal access site. This description of the surgical technique focuses on the specific procedural details including the obligatory planning with computed tomography and our cannulation strategy. We also sought to define the anatomical ascending aorta-sternal relationship, as it is of utmost importance in preoperative computed tomographic planning.

Sternal Anomalies in Asymptomatic Patients after Median Sternotomy and Potential Influencing Factors.

BACKGROUND: We aimed to assess asymptomatic patients who had open-heart surgery with median sternotomy for potential sternal anomalies (SA), their related patient-specific risk factors, and treatment options for the prevention of SA. METHODS: Multiplanar CT scans (CTs) from 131 asymptomatic consecutive patients were analyzed retrospectively. Of these, 83 underwent CABG (63.4%), and 48 had aortic valve (AV) procedures via median sternotomy. Sternal bone healing was analyzed for SA and their exact location. RESULTS: In total, 49 SA were identified in 42 (32.1%) patients; 65% SA were found in the manubrium (n = 32). Five hundred thirty-two wires were implanted (4.2 ± 0.5 wires/patient), out of which 96.1% (n = 511) were figure 8 wires. There was no difference between normal and abnormal sterna with regard to the number of wires used for sternal closure (4.2 ± 0.5 vs. 4.3 ± 0.6, p = ns). The distance between wire placement to the proximal edge of the manubrium in normal and abnormal sterna was comparable (11.2 ± 4.2 vs. 10.9 ± 4.8 mm, p = ns). Patients who underwent CABG had a significantly higher risk for SA (OR = 2.4, p ≤ 0.05, 95% CI [1.2-4.9]). The use of BIMA (OR = 4.4, p ≤ 0.05, 95% CI [1.1-17.9]) and body mass index (BMI) > 31 kg/m2 (OR = 3.4, p ≤ 0.01, 95% CI [1.4-8.3]) significantly increased the risk of SA. CONCLUSION: At least 30% of patients were at an increased risk for SA after receiving a median sternotomy. CABG, use of BIMA, and a BMI > 30 kg/m2 were potential risk factors for the development of SA and warrant close clinical follow-up. Sternal plate fixation, particularly in the manubrium, could be beneficial in such patients.

Results of mitral valve repair with an adjustable annuloplasty ring 2 years after implantation.

We aimed to investigate the safety and medium-term durability of an adjustable mitral annuloplasty ring in patients undergoing surgery for mitral valve regurgitation. Forty-five patients requiring mitral valve repair were enrolled into this prospective, multicentre study between May 2012 and May 2013 in six hospitals in Europe and Israel. Study endpoints evaluated the performance and safety of the device assessed using inter-individual comparisons. Implantation was performed through a sternotomy in ten patients and mini-thoracotomy in 35 patients. The ring was adjusted after declamping and weaning from cardio-pulmonary bypass under echocardiographic guidance if the coaptation surface was not optimal, or in cases of residual mitral regurgitation. Follow-up was performed up to 2 years post-procedure. Mean age was 61 ± 12 years. Ring adjustment was performed in 71% of patients to optimise the results of mitral valve repair. Following the procedure, 11/45 patients (24%) who had had mild residual mitral regurgitation had no mitral regurgitation following ring adjustment. Two patients with severe mitral regurgitation post-procedure had mild regurgitation following ring adjustment. Coaptation length increased significantly after adjustment. One patient died before hospital discharge due to complications unrelated to the adjustable ring. One patient had to undergo re-operation at 39 days post-procedure due to endocarditis. At 2 years of follow-up, 78% of patients had no residual mitral regurgitation and 22% had mild residual mitral regurgitation. Adjustable mitral annuloplasty ring implantation was safe in all patients. Mitral valve repair with the adjustable ring was durable in all patients who reached 2 years follow-up. CLINICAL TRIAL REGISTRATION: NCT01617720.

Use of extracellular matrix patches in cardiac surgery.

A noncellular xenogeneic extracellular matrix derived from the porcine small intestinal submucosa can be used as a new patch material with potential advantages. We review the literature on the use of this material in cardiac surgery.

Image-based ring size prediction for mitral valve repair.

OBJECTIVES: Annuloplasty rings are routinely used in mitral valve repair (MVr). However, accurate annuloplasty ring size selection is essential to obtain a favourable outcome. Moreover, ring sizing can be challenging in some patients and is highly influenced by surgeons' experience. This study investigated the utility of three-dimensional mitral valve (3D-MV) reconstruction models to predict annuloplasty ring size for MVr. METHODS: A total of 150 patients undergoing minimally invasive MVr with annuloplasty ring due to Carpentier type II pathology and who were discharged with none/trace residual mitral regurgitation were included. 3D-MV reconstruction models were created with a semi-automated software package (4D MV Analysis) to quantitate mitral valve geometry. To predict the ring size, univariable and multivariable linear regression analyses were performed. RESULTS: Between 3D-MV reconstruction values and implanted ring sizes, the highest correlation coefficients were provided by commissural width (CW) (0.839; P < 0.001), intertrigonal distance (ITD) (0.796; P < 0.001), annulus area (0.782; P < 0.001), anterior mitral leaflet area (0.767; P < 0.001), anterior-posterior diameter (0.679; P < 0.001) and anterior mitral leaflet length (0.515; P < 0.001). In multivariable regression analysis, only CW and ITD were found to be independent predictors of annuloplasty ring size (R2 = 0.743; P < 0.001). The highest level of agreement was achieved with CW and ITD, and 76.6% of patients received a ring with no >1 ring size difference from the predicted ring sizes. CONCLUSIONS: 3D-MV reconstruction models can support surgeons in the decision-making process for annuloplasty ring sizing. The present study may be a first step towards accurate annuloplasty ring size prediction using multimodal machine learning decision support.

Minimally Invasive Extirpation of Benign Atrial Cardiac Tumors: Clinical Follow-Up and Survival.

OBJECTIVE: Evidence determining the optimal treatment for cardiac tumors is rare. We report our midterm clinical outcome and patient characteristics of our series undergoing atrial tumor removal through a right lateral minithoracotomy (RLMT). METHODS: From 2015 to 2021, 51 patients underwent RLMT for atrial tumor extirpation. Patients receiving concomitant atrioventricular valvular, cryoablation, and/or patent foramen ovale closure surgery were included. Follow-up was performed using standardized questionnaires (mean: 1,041 ± 666 days). Follow-up involved any tumor recurrence, clinical symptoms, and any recurrent arterial embolization. Survival analysis was successfully achieved in all patients. RESULTS: Successful surgical resection was achieved in all patients. Mean cardiopulmonary bypass and cross-clamping times were 75 ± 36 and 41 ± 22 min, respectively. The most common tumor location was the left atrium (n = 42, 82.4%). Mean ventilation time was 12.74 ± 17.23 h, intensive care unit stay ranged from 1 to 1.9 days (median: 1 day). Nineteen patients (37.3%) received concomitant surgery. Histopathological analysis showed 38 myxoma (74.5%), 9 papillary fibroelastoma (17.6%), and 4 thrombus (7.8%). Thirty-day mortality was observed in 1 case (2%). One patient (2%) suffered a stroke postoperatively. No patient had a relapse of cardiac tumor. Three patients (9.7%) showed arterial embolization during follow-up. Thirteen follow-up patients (25.5%) were in New York Heart Association class ≤II. Overall survival was 90.2% at 2 years. CONCLUSIONS: A minimally invasive approach for benign atrial tumor resection is effective, safe, and reproducible. Of the atrial tumors, 74.5% were myxoma and 82% were located in the left atrium. A low 30-day mortality rate with no manifestation of recurrent intracardiac tumor was observed.

Alternative minimally invasive surgical explantation techniques for failed transcatheter mitral valve repair devices.

Objective: The use of transcatheter mitral valve repair (TMVr) devices is increasing in elderly and high-risk patients. However, the increasing number of patients with recurrent mitral regurgitation (MR) has confronted surgeons with the issue of how to explant the devices and whether the mitral valve should be repaired or replaced. The aim of the study is to summarize our clinical experience with the explantation of different TMVr devices and to provide alternative surgical techniques that can be performed in different clinical scenarios. Methods: A simulator system including a dummy valve representing native valves was used to create video documentation and to develop alternative surgical methods for clip explantation. Moreover, the clip explantation techniques were shown in 2 patients undergoing minimally-invasive mitral valve repair after a failed TMVr. Results: Alternative explantation techniques were described for each TMVr device; 2 techniques for MitraClip and 3 techniques for PASCAL (Precision Transcatheter Valve Repair System), which may be adjusted for each individual according to the underlying valve pathology and the degree of device encapsulation. The patients were discharged without residual MR and remained MR free at the follow-up. Conclusions: Transcatheter edge-to-edge repair devices can be surgically explanted without damaging the MV leaflets. Removal of each device may require a different technique tailored to the degree of device encapsulation and valve pathology. Increasing experience may facilitate repair in patients with recurrent MR after TMVr.

Off-pump surgery for the poor ventricle?

Severely decreased ejection-fraction is an established risk-factor for worse outcome after cardiac surgery. We compare outcomes of off-pump coronary artery bypass grafting (OPCAB) and on-pump CABG (ONCABG) in patients with severely compromised EF. From 2004 to 2009, 478 patients with a decreased EF ≤35% underwent myocardial-revascularization. Patients received either OPCAB (n = 256) or ONCABG (n = 222). Propensity score (PS), including 50 preoperative risk-factors, was used to balance characteristics between groups. PS adjusted logistic regression analysis was performed to assess mortality and major adverse cardiac and cerebrovascular events (MACCE). A composite endpoint for major non-cardiac complications such as respiratory failure, renal failure, rethoracotomy was applied. Complete revascularization (CR) was assumed when the number of distal anastomoses was larger than that of diseased vessels. There was no difference for mortality (2.3 vs. 4.1%; PS-adjusted odds ratio (PS-OR) = 1.05; p = 0.93) and MACCE (13.7 vs. 17.6%; PS-OR = 1.22; p = 0.50) including myocardial-infarction (1.4 vs. 4.9%; PS-OR = 0.39; p = 0.26), low cardiac output (2.3 vs. 4.7%; PS-OR = 0.75; p = 0.72) and stroke (2.3 vs. 2.7%; PS-OR = 0.69; p = 0.66). OPCAB patients presented with a trend to less frequent occurrence of the non-cardiac composite (12.1 vs. 22.1%; PS-OR = 0.54; p = 0.059) including renal dysfunction (PAOR = 0.77; 95% CI 0.31-1.9; p = 0.57), bleeding (PAOR = 0.42; 95% CI 0.14-1.20; p = 0.10) and respiratory failure (PAOR = 0.39; 95% CI 0.05-3.29; p = 0.39). The rate of complete revascularization was similar (92.2 vs. 92.8%; PS-OR = 0.75; p = 0.50). OPCAB in patients with severely decreased EF is safe and feasible. It may even benefit these patients in regard to non-cardiac complications and does not come at cost of less complete revascularization.

Innovations in minimally invasive mitral valve pair.

Mitral valve (MV) insufficiency is the second most common heart valve disease represented in cardiac surgery. The gold standard therapy is surgical repair of the valve. Today, most centers prefer a minimally invasive approach through a right-sided mini-thoracotomy. Despite the small access, there is still the need to use cardiopulmonary bypass (CPB), and the operation has to be performed on the arrested heart. New devices have been developed to optimize the results of surgical repair by implementing mechanisms for post-implantation adjustment on the beating heart or the avoidance of CPB. Early attempts with adjustable mitral annuloplasty rings go back to the early 1990s. Only a few devices are available on the market. Recently, a mitral valve adjustable annuloplasty ring was CE-marked and is under further clinical investigation. In addition, a sutureless annuloplasty band to be implanted on the beating heart is under preclinical and initial clinical investigation for transatrial and transfemoral transcatheter implantation. Furthermore, new neochord systems are being developed, which allow for functional length adjustment on the beating heart after implantation. Some devices were developed for percutaneous MV repair implanted into the coronary sinus to reshape the posterior MV annulus. Other percutaneous devices are directly fixed to the posterior annulus to alter its shape. Several disadvantages have been observed preventing a broad clinical use of some of these devices. There is a continuous effort to develop innovative techniques to optimize MV repair and to decrease invasiveness.

The arch remodelling stent for DeBakey I acute aortic dissection: experience with 100 implantations.

OBJECTIVES: A novel hybrid non-covered stent was developed to treat malperfusion and prevent aneurysm formation following hemiarch procedure for DeBakey I acute aortic dissection (AAD). The present analysis investigates the performance of the device in 100 consecutive implantations. METHODS: Between 2018 and 2021, 100 patients underwent surgical repair of DeBakey I AAD with implantation of a non-covered stent in the arch and descending aorta. The primary entry tear was located in the root or the ascending aorta. Clinical and imaging data were collected and analysed retrospectively. The endpoints of the study were 30-day mortality, neurological outcome and need of additional procedures due to postoperative malperfusion. Technical success was assessed in the first postoperative computed tomography in regard to the induction of false lumen thrombosis in the descending aorta. RESULTS: The median age was 61 (54-73) years. Preoperative malperfusion was present in 46 (46%) patients. The primary arterial cannulation strategy was the right axillary artery and an open distal anastomosis was performed in a median caudal circulatory arrest of 40 (34-52) min. In 48% of cases, a 55-40 tapered stent was implanted. The 30-day mortality was 18%, and the operation-related new postoperative neurological deficit was present in 8%. Technical success was achieved in 76% of patients. CONCLUSIONS: The novel non-covered stent can be safely applied to complement aortic repair with the hemiarch procedure for DeBakey I AAD. The expansion of the true lumen through the device may prevent postoperative malperfusion and induces positive vascular remodelling with the thrombosis of the false lumen.

Periareolar endoscopic minimally invasive cardiac surgery: postoperative scar assessment analysis.

OBJECTIVES: The standard approach for minimally invasive cardiac surgery (MICS) for repair of the atrioventricular valves is a right lateral minithoracotomy. In this study, we report our experience with a periareolar endoscopic approach, which aims at an optimal cosmetic outcome while preserving optimal clinical outcomes. METHODS: All patients underwent periareolar endoscopic MICS using high-definition three-dimensional endoscopic visualization without additional rib-spreading. Patients presented with degenerative and/or functional mitral regurgitation. Patients undergoing concomitant tricuspid valve surgery, cryo-ablation, patent foramen ovale closure, left atrial appendage occlusion and/or left atrial myxoma extirpation were included. This descriptive article analysed the aesthetic and functional outcome of the periareolar scar using 5 most common and clinimetrically sound scar assessment scales. For statistical analysis of the scar assessment grading scales, box and whisker plots were calculated depicting median, interquartile range and high and low range data points. RESULTS: Median scar assessment scale scores for n = 100 male patients (response rate 100/109; 91.7%) were 2 [1, 4], 7.5 [6, 9], 11 [8, 14], 3 [2, 3] and 10 [9, 11] for the Vancouver scar scale, Manchester scar scale, patient scar assessment scale, Stony brook scar evaluation scale and Dermatology Quality of Life Index scale, respectively. Ninety-seven patients received mitral valve repair, 7 mitral valve replacement, whereas 5 had left atrial myxoma extirpation. Concomitant tricuspid annuloplasty, cryo-ablation, left atrial appendage occlusion and patent foramen ovale closure surgery were performed in 12, 29, 5 and 8 patients, respectively. Median procedure, cardiopulmonary bypass and cross-clamp times were 169.5 [154.3, 189.3], 111.5 [97, 127], and 68.5 [58.8, 81] min, respectively. CONCLUSIONS: Periareolar endoscopic MICS is safe and cosmetically appealing. It is feasible and allows for complex mitral valve repair, mitral valve replacement and concomitant surgery. Data from 5 scar assessment scales suggest that this technique delivers patient-satisfying results regarding functional and cosmetic outcomes.

Minimally invasive mitral valve surgery after failed transcatheter mitral valve repair in an intermediate-risk cohort.

OBJECTIVES: Although clinical experience with transcatheter mitral valve interventions is rapidly increasing, there is still a lack of evidence regarding surgical treatment options for the management of recurrent mitral regurgitation (MR). This study provides guidance for a minimally invasive surgical approach following failed transcatheter mitral valve repair, which is based on the underlying mitral valve (MV) pathology and the type of intervention. METHODS: A total of 46 patients who underwent minimally invasive MV surgery due to recurrent or residual MR after transcatheter edge-to-edge repair or direct interventional annuloplasty between October 2014 and March 2021 were included. RESULTS: The median age of the patients was 78 [interquartile range, 71-82] years and the EuroSCORE II was 4.41 [interquartile range, 2.66-6.55]. At the index procedure, edge-to-edge repair had been performed in 45 (97.8%) patients and direct annuloplasty in 1 patient. All patients with functional MR at the index procedure (n = 36) underwent MV replacement. Of the patients with degenerative MR (n = 10), 5 patients were eligible for MV repair after removal of the MitraClip. The 1-year survival following surgical treatment was 81.3% and 75.0% in patients with functional and degenerative MR, respectively. No residual MR greater than mild during follow-up was observed in patients who underwent MV repair. CONCLUSIONS: Minimally invasive surgery following failed transcatheter mitral valve repair is feasible and safe, with promising midterm survival. The surgical management should be tailored to the underlying valve pathology at the index procedure, the extent of damage of the MV leaflets and the type of previous intervention.

Experience with a standardized protocol to predict successful explantation of left ventricular assist devices.

OBJECTIVE: Patients with a continuous-flow left ventricular assist device may show recovery of myocardial function with unloading. Identifying candidates for and predicting clinical and hemodynamic stability after left ventricular assist device explantation remain challenging. METHODS: Retrospective analysis of patients who underwent evaluation for left ventricular assist device explantation following a standardized protocol from January 2016 to March 2020. Patients who met screening criteria underwent echocardiography under "baseline," "minimal net flow," and "pump stop" conditions. If the protocol criteria were met, right heart catheterization with left ventricular assist device stoppage and occlusion of the outflow graft with a balloon catheter were performed. In patients with pulmonary capillary wedge pressure less than 16 mm Hg, explantation was performed under "pump stop" conditions. RESULTS: A total of 544 patients were screened. Of these, 57 (10.5%) underwent a total of 73 echocardiography under "baseline" "minimal net flow" and "pump stop" conditions and 46 underwent left ventricular assist device stoppage and occlusion of the outflow graft with balloon catheter maneuvers. Complications during the procedure were rare. Ultimately, 21 patients (3.9%) underwent explantation. The left ventricular ejection fraction at baseline was 55.5% ± 6.5%. The mean pulmonary capillary wedge pressure was 8.1 ± 2.6 mm Hg and increased to 10.7 ± 2.9 mm Hg under left ventricular assist device stoppage and occlusion of the outflow graft with a balloon catheter. A nonischemic cause of cardiomyopathy was more likely to be found in patients who underwent explantation (20/21 patients [95%], P = .020). The survival 1 year after explantation was 95.2%, with 1 death occurring 222 days after left ventricular assist device explantation. At follow-up (median 24.9 months [interquartile range, 16.4-43.1 months]), patients were in New York Heart Association class 1 (61.9%), 2 (28.6%), and 3 (9.5%). CONCLUSIONS: Our 4-year experience with a standardized protocol for left ventricular assist device explantation showed a low rate of adverse events. If all criteria are met, explantation can be performed safely and with an excellent survival and functional class.