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.

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.

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.

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.

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.