Hemodynamics and Wall Mechanics of Vascular Graft Failure.

Blood vessels are subjected to complex biomechanical loads, primarily from pressure-driven blood flow. Abnormal loading associated with vascular grafts, arising from altered hemodynamics or wall mechanics, can cause acute and progressive vascular failure and end-organ dysfunction. Perturbations to mechanobiological stimuli experienced by vascular cells contribute to remodeling of the vascular wall via activation of mechanosensitive signaling pathways and subsequent changes in gene expression and associated turnover of cells and extracellular matrix. In this review, we outline experimental and computational tools used to quantify metrics of biomechanical loading in vascular grafts and highlight those that show potential in predicting graft failure for diverse disease contexts. We include metrics derived from both fluid and solid mechanics that drive feedback loops between mechanobiological processes and changes in the biomechanical state that govern the natural history of vascular grafts. As illustrative examples, we consider application-specific coronary artery bypass grafts, peripheral vascular grafts, and tissue-engineered vascular grafts for congenital heart surgery as each of these involves unique circulatory environments, loading magnitudes, and graft materials.

Preoperative dental screening prior to cardiac valve surgery and 90-day postoperative mortality.

BACKGROUND: Preoperative dental screening before cardiac valve surgery is widely accepted but its required scope remains unclear. This study evaluates two preoperative dental screening (PDS) approaches, a focused approach (FocA) and a comprehensive approach (CompA), to compare postsurgical 90-day mortality. METHODS: Retrospective cohort analysis was performed on all patients who underwent valve surgery at Brigham and Women's Hospital with FocA and Massachusetts General Hospital with CompA of PDS approach from January 2009 to December 2016. Patients with intravenous drug abuse and systemic infections were excluded. Univariate, multivariable, and subgroup analysis was performed. RESULTS: A total of 1835 patients were included in the study. With FocA 96% of patients (1097/1143) received dental clearance in a single encounter with 3.3% receiving radiographs and undergoing dental extractions. With CompA 35.5% of patients (245/692) received dental clearance in a single encounter, 94.2% received radiographs, and 21.8% underwent dental extractions. There was no significant difference in 90-day mortality when comparing both PDS approach (10% vs 8.4%, P = .257). This remained unchanged in a multivariable model after adjusting for risk factors (odds ratio:1.32 [95%CI:0.91-1.93] [P = .14]). Reoperation due to infection was less in FocA (0.5%) vs CompA (2.6) (P < .001) and postoperative septicemia was increased in the FocA (1.7%) cohort when compared to the CompA (0.7%) (P < .001) patients. CONCLUSIONS: There was no difference in post valve surgery 90-day mortality between patients who underwent a FocA vs CompA of PDS.

Pain management and safety profiles after preoperative vs postoperative thoracic epidural insertion for bilateral lung transplantation.

OBJECTIVE: Thoracic epidural analgesia provides effective pain control after lung transplantation; however, the optimal timing of placement is controversial. We sought to compare pain control and pulmonary and epidural morbidity between patients receiving preoperative vs postoperative epidurals. METHODS: Institutional records were reviewed for patients undergoing a bilateral lung transplant via a bilateral anterior thoracotomy with transverse sternotomy incision between January 2014 and January 2017. Pain control was measured using visual analog scale pain scores (0-10). Pulmonary complications included a composite of pneumonia, prolonged intubation, and reintubation/tracheostomy. RESULTS: Among 103 patients, 72 (70%) had an epidural placed preoperatively and 31 (30%) had an epidural placed within 72 hours posttransplant. There were no differences in the rates of cardiopulmonary bypass (3% vs 0%, P = 0.59); however, patients with a preoperative epidural were less likely to be placed on extracorporeal membrane oxygenation intraoperatively (25% vs 52%, P = 0.01). Pain control was similar at 24 hours (1.2 vs 1.7, P = 0.05); however, patients with a preoperative epidural reported lower pain scores at 48 (1.2 vs 2.1, P = 0.02) and 72 hours posttransplant (0.8 vs 1.7, P = 0.02). There were no differences in primary graft dysfunction (42% vs 56%, P = 0.28), length of mechanical ventilation (19.5 vs 24 hours, P = 0.18), or adverse pulmonary events (33% vs 52%, P = 0.12). No adverse events including epidural hematoma, paralysis, or infection resulted from epidural placement. CONCLUSION: Preoperative thoracic epidural placement provides improved analgesia without increased morbidity following lung transplantation.

Heart-liver transplantation using the en bloc technique: A single-center experience over two decades.

BACKGROUND: Combined heart-liver transplantation (CHLT) is a definitive therapy reserved for patients with concomitant heart failure and advanced liver disease. A limited number of centers perform CHLT, and even fewer use the en bloc implantation technique. Here we review clinical outcomes and immunoprotective effects following CHLT and describe our institution's more than two decades of experience in performing the en bloc technique. METHODS: All patients who underwent CHLT at our institution between January 2003 and July 2023 were identified. Recipient and donor characteristics, operative details, and clinical outcomes were assessed. Kaplan-Meier analysis was performed to evaluate survival following CHLT. RESULTS: A total of 20 patients underwent CHLT using the en bloc technique at our institution between January 2003 and July 2023. At a median follow-up of 3.8 years for patients who survived the perioperative period (n = 18), estimated survival was 94% at 1 year and 75% at 5 years. There was 100% freedom from acute moderate rejection, acute severe rejection, and chronic rejection in all patients. No patients required retransplantation due to rejection. CONCLUSIONS: CHLT is a definitive therapy reserved for patients with multiorgan dysfunction. At our institution, the en bloc technique is the preferred operative approach, as it minimizes cardiac insult, requires fewer anastomoses, minimizes cold ischemia time, and allows for rapid correction of coagulopathy. Overall survival for this cohort is excellent. Episodes of acute rejection were rare, providing further support for the idea that the liver may serve an immunoprotective role in multiorgan transplantation.

Midterm Outcomes in Type A Aortic Dissection Repair With and Without Malperfusion in a Hybrid Operating Room.

Treatment approach to type A aortic dissection with malperfusion, immediate open aortic repair vs upfront endovascular treatment, remains controversial. From January 2017 to July 2021, 301 consecutive type A repairs were evaluated at our institution. Starting in 2019, all type A aortic dissections were performed in a fixed-fluoroscopy, hybrid operating room. Propensity score matching was used to control baseline patient characteristics between traditional and hybrid operating room approaches. There were 144 patients in the traditional group and 157 in the hybrid group. In the hybrid group, 41% (64/157) underwent intraoperative angiograms, and of those, 58% (37/64) received at least 1 endovascular intervention. Following propensity matching, 125 patients remained in each the traditional and hybrid groups. Thirty-day survival was significantly improved in the hybrid cohort at 96.7% (122/125) as compared to the traditional cohort at 87.2% (109/125) (P = 0.002). There were no significant differences in perioperative paralysis (1.6% vs 1.6%, P > 0.9), new hemodialysis (12% vs 9.6%, P = 0.5), fasciotomy (2.4% vs 5.6%, P = 0.20, and exploratory laparotomy (1.6% vs 4.8%, P = 0.3). The hybrid operating room approach to type A aortic dissection, provides the ability to immediately assess distal malperfusion and perform endovascular interventions at the time of open aortic repair, and is associated with significantly higher 30-day and 2-year survival when compared to a stepwise repair approach in a traditional operating room.

Failure to rescue in the era of the lung allocation score: The impact of center volume.

BACKGROUND: Failure to Rescue (FTR) is a valuable surgical quality improvement metric. The aim of this study is to assess the relationship between center volume and FTR following lung transplantation. METHODS: Using the database of the United Network for Organ Sharing (UNOS) all adult, primary, isolated lung recipients in the United States between May 2005 and March 2016 were identified. FTR was defined as operative mortality after any of five specific complications. FTR was compared across terciles of transplantation centers stratified based on operative volume. RESULTS: 17,185 lung recipients met study criteria. The composite FTR rate (Death following at least one complication) was 20.7%. Following stratification by volume, FTR rates increased from high to middle tercile centers (19.3% vs. 23.0%). Multivariate logistic regression models suggested an independent relationship between higher center volume and lower FTR rates (p < 0.001). CONCLUSION: Higher volume lung transplantation centers have lower rates of failure to rescue.

Failure to Rescue Contributes to Center-Level Differences in Mortality After Lung Transplantation.

BACKGROUND: The clinical response to postoperative complications after lung transplantation (LTx) may contribute to mortality differences among transplantation centers. The ability to avoid mortality after a complication-failure to rescue (FTR)-may be an effective quality metric in LTx. METHODS: The United Network for Organ Sharing database was queried for adult, first-time, lung-only transplantations from May 2005 to December 2015. Transplantation centers were stratified into equal-sized terciles on the basis of observed operative mortality rates. Several postoperative complications were identified, including stroke, acute rejection, acute kidney injury requiring hemodialysis, airway dehiscence, and extracorporeal membrane oxygenation 72 hours after surgery. Rates of FTR were calculated as the number of operative mortalities in patients who had complications divided by the number of patients who had any postoperative complications. RESULTS: Our study population included 16,411 LTx operations performed at 69 transplantation centers. LTx centers were stratified into terciles with average perioperative mortality of 4.0% for low-mortality centers, 6.9% for intermediate-mortality centers, and 12.4% for high-mortality centers. Low-mortality centers had slightly lower complication rates (low, 15.0% vs intermediate, 17.1% vs high, 19.1%; P < .001). Differences in FTR rate were significantly more pronounced (low, 14.9% vs intermediate, 23.9% vs high, 34.2%; P < .001). Multivariable logistic regression and generalized linear models demonstrated an independent association between high FTR rates and high mortality in LTx (P < .001). CONCLUSIONS: Differences in rates of FTR contribute significantly to per-center variability in mortality after LTx. FTR can serve as a quality metric to identify opportunities for improvement in management of perioperative adverse events.

Cardiac Surgery Trainees as "Skin-to-Skin" Operating Surgeons: Midterm Outcomes.

BACKGROUND: We have previously demonstrated that cardiac surgery trainees can safely perform operations "skin-to-skin" with adequate attending surgeon supervision. METHODS: We used 100 consecutive cases (82 coronary artery bypass grafts, 9 aortic valve replacements, 7 coronary artery bypass grafts plus aortic valve replacements, 2 others) performed by residents (group R) to match 1:1 by procedure to nonconsecutive cases done by a single attending surgeon (group A) from July 2014 to October 2016. Patients were stratified based on whether the attending surgeon or trainee performed every critical step of the operation skin-to-skin. Outcomes included death, major morbidity, and readmission. RESULTS: Patients in the two groups were similar with respect to demographic characteristics and comorbidities. The median follow-up time for patients in this study was 28 months (interquartile range: 23 to 35 months). There were seven deaths (3.5%; four in group A, three in group R, p = 0.7). Of the 43 patients (21.5%) who were readmitted during the study term, 27 patients (13.5%) were readmitted for causes related to the operation (11 in group A, 16 in group R, p = 0.02). The most common reasons for readmissions related to the operation were chest pain (n = 11), pleural effusion that required drainage (n = 8), pneumonia (n = 4), and unstable angina that required percutaneous coronary intervention (n = 3). No statistically significant differences were found in reasons for readmission between group A and group R. CONCLUSIONS: The equivalence of postoperative outcomes previously demonstrated at 30 days persists at midterm follow-up. Our data indicate that trainees can be educated in operative cardiac surgery under the current paradigm without sacrificing outcome quality. It is reasonable to expect academic programs to continue providing trainees with experience as primary operating surgeons.

Lung Transplantation From Donation After Circulatory Death: United States and Single-Center Experience.

BACKGROUND: Lung transplants from donation after circulatory death (DCD) have been scarcely used in the United States. Concerns about the warm ischemic injury, resource mal-utilization due to the uncertain timing of death, and public scrutiny may be some factors involved. METHODS: Survival for recipients of a donation after brain death (DBD) versus DCD was analyzed by using the United Network for Organ Sharing and our institutional database. A propensity-matching and Cox regression analysis was performed for 25 characteristics. Primary graft dysfunction metrics were compared. RESULTS: A total of 389 of 20,905 lung transplantations (2%) were performed by using DCDs in the United States, and 15 of 128 (12%) at our institution. Five and 10-year survival for DBDs was 55% and 30% and 59% and 33% for DCDs, respectively. Propensity-matched analysis of 311 DBD/DCD pairs did not demonstrate any difference in survival. On Cox regression, DCD was not associated with impaired survival. Male sex, Karnofsky class greater than 50, double lung transplantation, and transplantation year were predictors of improved survival. Age, creatinine, pulmonary fibrosis, retransplantation, extracorporeal membrane oxygenation, allocation score, and donor age were predictors of worse survival. Primary graft dysfunction at time 0 was worse for recipients of DCDs (p = 0.005) but equivalent at 24, 48, and 72 hours. CONCLUSIONS: DCD lung transplants remain underused in the United States. Nevertheless, survival is similar to DBD. Primary graft dysfunction metrics for DCDs are worse than DBDs on intensive care arrival but improved subsequently.

Comparative Histology of Aortic Dilatation Associated With Bileaflet Versus Trileaflet Aortic Valves.

BACKGROUND: A more aggressive posture toward resection of the dilated aorta has been advocated when associated with bicuspid aortic valve (BAV), based on the notion that aortic material properties are weaker in this setting despite scant data to support or refute this position. The hypothesis that histologic abnormality reflects aortic wall strength was tested by comparing aortas from patients with BAV and trileaflet aortic valve. METHODS: Resected aortas associated with BAV (n = 60) and trileaflet aortic valve (n = 24) were compared with normal diameter aortas from patients undergoing cardiac transplantation (n = 16) by five histologic criteria: elastic fiber loss (graded 0-4), smooth muscle cell loss (graded 0-4), medial proteoglycan accumulation (graded 0-3), medial fibrosis (graded 0-3), and atherosclerosis (graded 0-3). Patients with known connective tissue disorders, systemic inflammatory conditions, dissection, or prior heart surgery were excluded. RESULTS: Patients with BAV were a decade younger and more often had functional stenosis. The extent of elastic fiber loss, smooth muscle cell loss, medial fibrosis, and atherosclerosis was more severe in trileaflet aortic valve than BAV when considered across all diameters and when stratified to those between 4 and 5 cm. CONCLUSIONS: More severe histologic abnormalities associated with trileaflet aortic valve compared with BAV, especially when stratified by diameter, do not support a more aggressive approach to surgical intervention for dilatation associated with BAV. Indeed, if based on histologic diagnosis alone, our findings are suggestive that the converse might be true. Additionally, the lack of correlation between aortic diameter and histologic abnormality in the setting of BAV highlights the inadequacy of diameter alone as a criterion for aortic resection.

Pulmonary valve replacement through a left minithoracotomy: an alternate approach.

We present a case of an isolated pulmonary valve endocarditis in a 23-year-old woman with a history of heavy oxycodone abuse. She presented with fever and positive cultures for methicillin-sensitive Staphylococcus aureus. A transesophageal echocardiogram demonstrated a 3-cm vegetation of the pulmonary valve. Antibiotic therapy was started but she continued to have fever and the vegetation size did not change. In view of ongoing fever and risk of embolization, a left minithoracotomy was performed, and the pulmonary valve was replaced with a bioprosthesis using warm cardiopulmonary bypass, with a beating-heart technique. The patient had an uneventful postoperative course and was discharged home. To the best of our knowledge, this is the first case of a pulmonary valve replacement through this approach.