Blood flow assessment technology in aortic surgery: a narrative review.

Background and Objective: Blood flow assessment is an emerging technique that allows for assessment of hemodynamics in the heart and blood vessels. Recent advances in cardiovascular imaging technologies have made it possible for this technique to be more accessible to clinicians and researchers. Blood flow assessment typically refers to two techniques: measurement-based flow visualization using echocardiography or four-dimensional flow magnetic resonance imaging (4D flow MRI), and computer-based flow simulation based on computational fluid dynamics modeling. Using these methods, blood flow patterns can be visualized and quantitative measurements of mechanical stress on the walls of the ventricles and blood vessels, most notably the aorta, can be made. Thus, blood flow assessment has been enhancing the understanding of cardiac and aortic diseases; however, its introduction to clinical practice has been negligible yet. In this article, we aim to discuss the clinical applications and future directions of blood flow assessment in aortic surgery. We then provide our unique perspective on the technique's translational impact on the surgical management of aortic disease. Methods: Articles from the PubMed database and Google Scholar regarding blood flow assessment in aortic surgery were reviewed. For the initial search, articles published between 2013 and 2023 were prioritized, including original articles, clinical trials, case reports, and reviews. Following the initial search, additional articles were considered based on manual searches of the references from the retrieved literature. Key Content and Findings: In aortic root pathology and ascending aortic aneurysms, blood flow assessment can elucidate postoperative hemodynamic changes after surgical reconfiguration of the aortic valve complex or ascending aorta. In cases of aortic dissection, analysis of blood flow can predict future aortic dilatation. For complicated congenital aortic anomalies, surgeons may use preoperative imaging to perform "virtual surgery", in which blood flow assessment can predict postoperative hemodynamics for different surgical reconstructions and assist in procedural planning even before entering the operating room. Conclusions: Blood flow assessment and computational modeling can evaluate hemodynamics and flow patterns by visualizing blood flow and calculating biomechanical forces in patients with aortic disease. We anticipate that blood flow assessment will become an essential tool in the treatment planning and understanding of the progression of aortic disease.

Significance of isolated postoperative atrial fibrillation in thoracic aortic aneurysm repair.

OBJECTIVE: Although postoperative atrial fibrillation has been shown to be associated with worse survival after thoracic aortic surgery, its effect on outcomes independently from other postoperative complications is not well understood. METHODS: This is a single-center retrospective study of patients who underwent open thoracic aortic aneurysm repair between March 2005 and March 2021. Postoperative atrial fibrillation was defined as new-onset atrial fibrillation that developed during the index hospital stay. Patients with preoperative atrial fibrillation were excluded. Postoperative major complications included reoperation for bleeding, respiratory failure, acute renal failure, and stroke. Variables associated with postoperative atrial fibrillation were analyzed with multivariable regression. Survival of patients without major complications was compared between patients without atrial fibrillation and patients with postoperative atrial fibrillation after propensity score matching for baseline and intraoperative characteristics. RESULTS: Of 1454 patients, 520 (35.8%) were observed to have postoperative atrial fibrillation. Patients with postoperative atrial fibrillation had a higher rate of postoperative major complications than those without atrial fibrillation (20.2% vs 12.2%, P < .001). Ten-year survival was 82.0% in patients with postoperative atrial fibrillation and 87.0% in patients without atrial fibrillation (P = .008). In the cohort of patients without complications, 10-year survival was similar between patients with and without postoperative atrial fibrillation after propensity score matching (83.6% vs 83.8%, P = .75). CONCLUSIONS: Postoperative atrial fibrillation is common after open proximal thoracic aortic aneurysm repair. Although development of major postoperative complications is associated with postoperative atrial fibrillation and decreased long-term survival, isolated postoperative atrial fibrillation does not appear to influence long-term survival.

Temporal correlation between postreperfusion complement deposition and severe primary graft dysfunction in lung allografts.

Growing evidence implicates complement in the pathogenesis of primary graft dysfunction (PGD). We hypothesized that early complement activation postreperfusion could predispose to severe PGD grade 3 (PGD-3) at 72 hours, which is associated with worst posttransplant outcomes. Consecutive lung transplant patients (n = 253) from January 2018 through June 2023 underwent timed open allograft biopsies at the end of cold ischemia (internal control) and 30 minutes postreperfusion. PGD-3 at 72 hours occurred in 14% (35/253) of patients; 17% (44/253) revealed positive C4d staining on postreperfusion allograft biopsy, and no biopsy-related complications were encountered. Significantly more patients with PGD-3 at 72 hours had positive C4d staining at 30 minutes postreperfusion compared with those without (51% vs 12%, P < .001). Conversely, patients with positive C4d staining were significantly more likely to develop PGD-3 at 72 hours (41% vs 8%, P < .001) and experienced worse long-term outcomes. In multivariate logistic regression, positive C4d staining remained highly predictive of PGD-3 (odds ratio 7.92, 95% confidence interval 2.97-21.1, P < .001). Hence, early complement deposition in allografts is highly predictive of PGD-3 at 72 hours. Our data support future studies to evaluate the role of complement inhibition in patients with early postreperfusion complement activation to mitigate PGD and improve transplant outcomes.

Analysis of socioeconomic and demographic factors on post-treatment outcomes for metastatic spinal tumors.

OBJECTIVE: Sociodemographic factors may play a role in incidence and treatment of metastatic spinal tumors, as there is a delay in diagnosis and increased incidence of relevant primaries. There has yet to be a detailed analysis of the impact of sociodemographic factors on surgical outcomes for spinal metastases. We sought to examine the influence of socioeconomic factors on outcomes for patients with metastatic spinal tumors. METHODS: Two hundred and sixty-three patients who underwent surgery for metastatic spinal tumors were identified. Sociodemographic characteristics were then collected and assigned to patients based on their ZIP code. The Chi-square test and the Mann-Whitney-U test were used for binary and continuous variables, respectively. Multivariate regression models were also used to control for age, smoking status, body mass index, and Charlson Comorbidity Index. RESULTS: Males had significantly lower rates of post-treatment complication compared to females (22.7 % vs 39.3 %, p = 0.0052), and those in high educational attainment ZIP codes had significantly shorter length of stay (LOS) compared to low educational attainment ZIP codes (9.3 days vs 12.2 days, p = 0.0058). Multivariate regression revealed that living in a high percentage white ZIP code and being male significantly decreased risk of post-treatment complication by 19 % (p = 0.042) and 14 % (p = 0.032), respectively. Living in a high educational attainment ZIP code decreased LOS by 3 days (p = 0.019). CONCLUSIONS: Males had significantly lower rates of post-treatment complication. Patients in high percentage white areas also had decreased rate of post-treatment complications. Patients living in areas with high educational attainment had shorter length of stay.

Postreperfusion Pulmonary Artery Pressure Indicates Primary Graft Dysfunction After Lung Transplant.

BACKGROUND: Primary graft dysfunction is a risk factor of early mortality after lung transplant. Models identifying patients at high risk for primary graft dysfunction are limited. We hypothesize high postreperfusion systolic pulmonary artery pressure is a clinical marker for primary graft dysfunction. METHODS: This is a retrospective review of 158 consecutive lung transplants performed at a single academic center from January 2020 through July 2022. Only bilateral lung transplants were included and patients with pretransplant extracorporeal life support were excluded. RESULTS: Primary graft dysfunction occurred in 42.3% (n = 30). Patients with primary graft dysfunction had higher postreperfusion systolic pulmonary artery pressure (41 ± 9.1 mm Hg) than those without (31.5 ± 8.8 mm Hg) (P < .001). Logistic regression showed postreperfusion systolic pulmonary artery pressure is a predictor for primary graft dysfunction (odds ratio 1.14, 95% CI 1.06-1.24, P < .001). Postreperfusion systolic pulmonary artery pressure of 37 mm Hg was optimal for predicting primary graft dysfunction by Youden index. The receiver operating characteristic curve of postreperfusion systolic pulmonary artery pressure at 37 mm Hg (sensitivity 0.77, specificity 0.78, area under the curve 0.81), was superior to the prereperfusion pressure curve at 36 mm Hg (sensitivity 0.77, specificity 0.39, area under the curve 0.57) (P < .01). CONCLUSIONS: Elevated postreperfusion systolic pulmonary artery pressure after lung transplant is predictive of primary graft dysfunction. Postreperfusion systolic pulmonary artery pressure is more indicative of primary graft dysfunction than prereperfusion systolic pulmonary artery pressure. Using postreperfusion systolic pulmonary artery pressure as a positive signal of primary graft dysfunction allows earlier intervention, which could improve outcomes.

Low-molecular-weight Heparin (enoxaparin) versus unfractionated heparin for venous thromboembolism prophylaxis in patients undergoing craniotomy.

OBJECTIVE: To explore the difference in post-operative DVT, PE, and ICH complications following administration of prophylactic UFH or enoxaparin in patients undergoing craniotomy. METHODS: A retrospective chart review was conducted for 542 patients at our institution receiving either 5000units/0.5 mL UFH (BID or TID; 180 patients) or single daily 40 mg/0.4 mL enoxaparin (362 patients) following craniotomy. Multivariate linear regression models were developed comparing rates of postoperative DVT, PE, and reoperation for bleeding in patients given enoxaparin versus UFH prophylaxis while controlling for age at surgery, history of VTE, surgery duration, number of post-operative hospital days, reoperation, post-operative infections, and reason for surgery (tumor type, genetics, etc.). Mann Whitney U tests were subsequently performed comparing rates of postoperative DVT, PE, and ICH for each group. RESULTS: Patients receiving prophylactic enoxaparin, when compared to UFH, exhibited similar rates of postoperative DVT (22 % vs 20.6 %, p = 0.86), PE (9.7 % vs 8.9 %, p = 0.86), and reoperation for bleeding (0.4 % vs 0.2 %, p = 0.58), while controlling for the factors described above. CONCLUSION: In patients undergoing craniotomy, rates for DVT, PE, and ICH were similar between patients treated with either prophylactic enoxaparin or UFH. Further studies are needed to understand whether a certain subset of patients demonstrate improved benefit from either prophylactic anticoagulant.

Neurologic, functional, and survival outcomes following surgical management of metastatic breast cancer to the spine.

OBJECTIVE: Metastatic spinal tumors commonly arise from primary breast cancer. We assessed outcomes and identified associated variables for patients who underwent surgical management for spinal metastases of breast cancer. METHODS: We retrospectively reviewed patients surgically treated for spinal metastases of breast cancer. Neurologic and functional outcomes were analyzed via Frankel scale and Karnofksy Performance Status (KPS) scores, respectively. Variables associated with Frankel and KPS scores after surgery were identified. Multivariable analysis was used to assess predictors for postoperative survival. RESULTS: Forty-nine patients were identified. There was no significant difference in Frankel scores postoperatively and at last follow-up. KPS scores (P = 0.002) significantly improved at last follow-up. Preoperative non-ambulation and postprocedural complications were associated with non-ambulation postoperatively. Postprocedural complications and disease-free interval (DFI) < 24 and < 60 months were associated with functional impairment at last follow-up. Current smoking status at the time of surgery (P = 0.021) and triple negative (negative immunohistochemistry for estrogen receptor, progesterone receptor, and HER2) breast cancer (P = 0.038) were significantly associated with shortened postoperative survival. CONCLUSION: When indicated, surgery for spinal metastases of breast cancer leads to preservation of neurologic status and long-term functional improvement. Preoperative ambulatory status and postprocedural complications were associated with ambulatory status after surgery, while postprocedural complications and shortened DFI were associated with functional status after surgery.Current smoking status at the time of surgery and triple negative breast cancer are negative predictors for postoperative survival after metastatic breast cancer to the spine.

Visual Outcomes After Treatment for Sporadic Optic Pathway Gliomas in Pediatric Patients: A Systematic Review.

OBJECTIVE: Optic pathway gliomas (OPGs) typically occur in the first decade of life and 40%-50% are not associated with neurofibromatosis 1 (NF1) (sporadic). Management strategies are often patient specific because of the variable and unpredictable course. No study has summarized the effect of treatment strategies on visual outcomes in the subset of pediatric patients with sporadic OPG. METHODS: We conducted a systematic review to determine the nature of visual outcomes in pediatric patients with sporadic, non-NF1-associated OPG using the PubMed, Embase, Scopus, Cochrane, and CINAHL Plus databases. Visual outcomes were categorized as improved, unchanged, or deteriorated. RESULTS: Of 1316 results, 31 articles were included. Treatment indications are unknown with full clinical detail. A total of 45.2% (14/31) reported deteriorated outcomes after treatment, 35.5% (11/31) no change, and 19.4% (6/31) improvement. Of radiotherapy studies, 50.0% (4/8) found no change, 37.5% (3/8) deterioration, and 12.5% (1/8) improvement. Of chemotherapy studies, 35.7% (5/14) each showed improvement and deterioration, whereas 28.6% (4/14) showed no change. Of surgical studies, 62.5% (5/8) indicated deterioration, and 37/5% (3/8) indicated no change. The singular study examining observation reported deterioration in visual outcomes. Factors associated with poor visual outcomes included signs and symptoms of visual decline at presentation, involvement of the intraorbital optic nerve, and intracranial hypertension requiring surgery. Causality cannot be determined from systematic review. CONCLUSIONS: Most studies showed that vision in pediatric patients with sporadic OPG is stable to poor after observation, chemotherapy, radiotherapy, or surgery. Chemotherapy may be associated with most favorable visual outcomes.

The role of preoperative embolization in the treatment of spinal metastases from renal cell carcinoma.

BACKGROUND: One strategy to reduce extensive intraoperative bleeding for patients undergoing surgery for metastatic renal cell carcinoma (RCC) to the spine is preoperative embolization. Prior studies have shown mixed results. The objective of this study is to evaluate the efficacy of preoperative embolization in patients undergoing spine surgery for metastatic RCC with consideration of multiple confounders. We aim to assess blood loss and other outcomes reflective of functional status and postoperative complications. METHODS: A retrospective chart review was conducted for 43 patients that underwent surgery for metastatic spinal RCC and either received preoperative embolization (n = 29) or did not (n = 14). Mann Whitney tests were run for initial analyses. Multivariate regression models were then used to predict outcomes while controlling for multiple demographic and preoperative variables. RESULTS: Mann Whitney tests revealed a significant difference between the mean age of patients undergoing preoperative embolization in comparison to those that did not (59.2 years versus 52.4 years; p = 0.044). We found that preoperative embolization was not significantly associated with decreased blood loss (2257 mL versus 2000 mL; p = 0.97). There were also no significant differences between groups in post-procedural complications (34.5% versus 14.3%; p = 0.097), last follow-up Nurick score (ß = 0.72, p = 0.18; 2.1 versus 1.6) or operative duration (ß = 28, p = 0.66; 408 min versus 353 min). The female gender was found to be significantly associated with higher last follow-up Nurick scores (ß = 1.24, p = 0.033). CONCLUSION: We observed no differences in blood loss or other outcomes between patients undergoing preoperative embolization and those that did not.

Unfractionated Heparin TID Dosing Regimen Is Associated With a Lower Rate of Pulmonary Embolism When Compared With BID Dosing in Patients Undergoing Craniotomy.

BACKGROUND: Venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE), and intracranial hemorrhage (ICH) may complicate the post-operative course of patients undergoing craniotomy. While prophylaxis with unfractionated heparin (UFH) has been shown to reduce VTE rates, twice-daily (BID) and three-times-daily (TID) UFH dosing regimens have not been compared in neurosurgical procedures. The objective of this study was to explore the association between UFH dosing regimen and rates of VTE and ICH in craniotomy patients. METHODS: A retrospective chart review was conducted for 159 patients at Northwestern University receiving 5000 units/0.5 mL UFH injections either BID (n = 132) or TID (n = 27). General linear regression models were run to predict rates of DVT, PE, and reoperation due to bleeding from UFH dosing regimen while controlling for age at surgery, sex, VTE history, craniotomy for tumor resection, surgery duration, length of stay, reoperation, infections, and IDH/MGMT mutations. RESULTS: Receiving UFH TID was significantly associated with a lower rate of PE when compared with receiving UFH BID (ß = -0.121, P = 0.044; TID rate = 0%, BID rate = 10.6%). UFH TID also showed a trend toward lower rates of DVT (ß = -0.0893, P = 0.295; TID rate = 18.5%, BID rate = 21.2%) when compared with UFH BID. UFH TID showed no significant difference in rate of reoperation for bleeding when compared to UFH BID (ß = -0.00623, P = 0.725; TID rate = 0%, BID rate = 0.8%). CONCLUSIONS: UFH TID dosing is associated with lower rates of PE when compared with BID dosing in patients undergoing craniotomy.

Does gender bias affect outcomes in mitral valve surgery for degenerative mitral regurgitation?

OBJECTIVES: This study was conducted to determine if gender bias explains the worse outcomes in women than in men who undergo mitral valve surgery for degenerative mitral regurgitation. METHODS: Patients who underwent mitral valve surgery for degenerative mitral regurgitation with or without concomitant ablation surgery for atrial fibrillation were identified from the Cardiovascular Research Database of the Clinical Trial Unit of the Bluhm Cardiovascular Institute at Northwestern Memorial Hospital and were defined according to the Society of Thoracic Surgery National Adult Cardiac Surgery Database. Of the 1004 patients (33% female, mean age 62.1 ± 12.4 years; 67% male, mean age 60.1 ± 12.4 years) who met this criteria, propensity score matching was utilized to compare sex-related differences. RESULTS: Propensity score matching of 540 patients (270 females, mean age 61.0 ± 12.2; 270 males, mean age 60.9 ± 12.3) demonstrated that 98% of mitral valve surgery performed in both groups was mitral valve repair and 2% was mitral valve replacement. Preoperative CHA2DS2-VASc scores were higher in women and fewer women were discharged directly to their homes. Before surgery, women had smaller left heart chambers, lower cardiac outputs, higher diastolic filling pressures and higher volume responsiveness than men. However, preoperative left ventricular and right ventricular strain values, which are normally higher in women, were similar in the 2 groups, indicating worse global strain in women prior to surgery. CONCLUSIONS: The worse outcomes reported in women compared to men undergoing surgery for degenerative mitral regurgitation are misleading and not based on gender bias except in terms of referral patterns. Men and women who present with the same type and degree of mitral valve disease and similar comorbidities receive the same types of surgical procedures and experience similar postoperative outcomes. Speckle-tracking echocardiography to assess global longitudinal strain of the left and right ventricles should be utilized to monitor for myocardial dysfunction related to chronic mitral regurgitation.

Vision Outcomes for Pediatric Patients With Optic Pathway Gliomas Associated With Neurofibromatosis Type I: A Systematic Review of the Clinical Evidence.

Children with neurofibromatosis type I (NF1) have a higher predisposition for low-grade astrocytomas of the optic pathway, commonly referred to as optic pathway gliomas (OPGs). OPGs can result in visual deterioration. Treatment outcomes in OPG-NF1 management are often reported around tumor stabilization. We sought to compare vision outcomes associated with different OPG treatment strategies to inform about this important functional metric. A meta-analysis exploring the different modalities to treat children with OPG-NF1 was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines using multiple databases. Of the 113 articles identified in the search, 23 full text articles, representing 564 patients, were included for review. These articles included retrospective, prospective, and randomized controlled studies on observation (n=9), chemotherapy (n=19), radiation therapy (n=6), and surgery (n=7). Of the patients undergoing observation, 87% (60/69) demonstrated stable acuity. In the chemotherapy studies, 27.3% (72/264) demonstrated improved acuity/visual field and/or visual-evoked potential amplitudes, 39.4% (104/264) stable acuity, and 33.3% (88/264) deterioration. Both the radiation and surgical treatments reported worsening acuity at 90.9% (10/11) and 73.3% (11/15), respectively. Causal associations are not known. Indications for and timing of treatment choice warrant larger scale study to provide further understanding.

Physicochemical mechanotransduction alters nuclear shape and mechanics via heterochromatin formation.

The nucleus houses, organizes, and protects chromatin to ensure genome integrity and proper gene expression, but how the nucleus adapts mechanically to changes in the extracellular environment is poorly understood. Recent studies have revealed that extracellular physical stresses induce chromatin compaction via mechanotransductive processes. We report that increased extracellular multivalent cations lead to increased heterochromatin levels through activation of mechanosensitive ion channels (MSCs), without large-scale cell stretching. In cells with perturbed chromatin or lamins, this increase in heterochromatin suppresses nuclear blebbing associated with nuclear rupture and DNA damage. Through micromanipulation force measurements, we show that this increase in heterochromatin increases chromatin-based nuclear rigidity, which protects nuclear morphology and function. In addition, transduction of elevated extracellular cations rescues nuclear morphology in model and patient cells of human diseases, including progeria and the breast cancer model cell line MDA-MB-231. We conclude that nuclear mechanics, morphology, and function can be modulated by cell sensing of the extracellular environment through MSCs and consequent changes to histone modification state and chromatin-based nuclear rigidity.

Physicochemical mechanotransduction alters nuclear shape and mechanics via heterochromatin formation.

The nucleus houses, organizes, and protects chromatin to ensure genome integrity and proper gene expression, but how the nucleus adapts mechanically to changes in the extracellular environment is poorly understood. Recent studies have revealed that extracellular physical stresses induce chromatin compaction via mechanotransductive processes. We report that increased extracellular multivalent cations lead to increased heterochromatin levels through activation of mechanosensitive ion channels, without large-scale cell stretching. In cells with perturbed chromatin or lamins, this increase in heterochromatin suppresses nuclear blebbing associated with nuclear rupture and DNA damage. Through micromanipulation force measurements, we show that this increase in heterochromatin increases chromatin-based nuclear rigidity, which protects nuclear morphology and function. In addition, transduction of elevated extracellular cations rescues nuclear morphology in model and patient cells of human diseases, including progeria and the breast cancer model cell line MDA-MB-231. We conclude that nuclear mechanics, morphology, and function can be modulated by cell sensing of the extracellular environment through mechanosensitive ion channels and consequent changes to histone modification state and chromatin-based nuclear rigidity.