High-resolution spatiotemporal changes in dominant frequency and structural organization during persistent atrial fibrillation.

OBJECTIVE: Analyze changes in frequency activity and structural organization that occur over time with persistent atrial fibrillation (AF). BACKGROUND: Little is known about the frequency characteristics of the epicardium during transition from paroxysmal to persistent AF. Accurate identification of areas of high dominant frequency (DF) is often hampered by limited spatial resolution. Improvements in electrode arrays provide high spatiotemporal resolution, allowing for characterization of the changes that occur during this transition. METHODS: AF was induced in adult Yorkshire swine by atrial tachypacing. DF mapping was performed using personalized mapping arrays. Histological analysis and late gadolinium enhanced magnetic resonance imaging were performed to determine structural differences in fibrosis. RESULTS: The left atrial epicardium was associated with a significant increase in DF in persistent AF (6.5 ± 0.2 vs. 7.4 ± 0.5 Hz, P = 0.03). The organization index (OI) significantly decreased during persistent AF in both the left atria (0.3 ± 0.03 vs. 0.2 ± 0.03, P = 0.01) and right atria (0.33 ± 0.04 vs. 0.23 ± 0.02, P = 0.02). MRI analysis demonstrated increased ECV values in persistent AF (0.19 vs 0.34, paroxysmal vs persistent, P = 0.05). Tissue sections from the atria showed increase in fibrosis in pigs with persistent AF compared to paroxysmal AF. Staining demonstrated decreased myocardial fiber alignment and loss of anisotropy in persistent AF tissue. CONCLUSIONS: Changes in tissue organization and fibrosis are observed in the porcine model of persistent AF. Alterations in frequency activity and organization index can be captured with high resolution using flexible electrode arrays.

An automated line-clearing chest tube system after cardiac surgery.

Objective: To complete the first in-human study of the automated line clearance Thoraguard chest tube system. The study focuses on the viability and efficacy of the device in comparison with conventional models as well as secondary matters such as patient experience and ease of use. Methods: This was a single-center, prospective, open-label study involving adult patients (n = 27) who underwent nonemergent, first-time, cardiac surgery. Patients received automated clearance chest tubes for surgical drainage in both the mediastinal and pleural spaces. The control group was retrospective (n = 80); individuals received conventional chest tubes placed and secured in locations determined at the surgeon's discretion. Results: The automated-clearance tubes exhibited a similar drainage profile at 1, 3, 6, 12, and 24 hours compared with the conventional chest tubes. The final output at the time of tube removal was also similar (1150 [750-1590] vs 1289 [766.3-1890] mL, respectively, P = .76). The number of patients readmitted for drainage of an effusion was similar in both groups (1/27 [3.7%] vs 3/80 [3.75%], P > .99). Conclusions: This study has shown that the Centese Thoraguard chest tube system is a viable option for surgical chest drainage and effective when used in routine cardiac surgery operations.

Biodegradable external wrapping promotes favorable adaptation in an ovine vein graft model.

Vein grafts, the most commonly used conduits in multi-vessel coronary artery bypass grafting surgery, have high intermediate- and long-term failure rates. The abrupt and marked increase in hemodynamic loads on the vein graft is a known contributor to failure. Recent computational modeling suggests that veins can more successfully adapt to an increase in mechanical load if the rate of loading is gradual. Applying an external wrap or support at the time of surgery is one way to reduce the transmural load, and this approach has improved performance relative to an unsupported vein graft in several animal studies. Yet, a clinical trial in humans has shown benefits and drawbacks, and mechanisms by which an external wrap affects vein graft adaptation remain unknown. This study aims to elucidate such mechanisms using a multimodal experimental and computational data collection pipeline. We quantify morphometry using magnetic resonance imaging, mechanics using biaxial testing, hemodynamics using computational fluid dynamics, structure using histology, and transcriptional changes using bulk RNA-sequencing in an ovine carotid-jugular interposition vein graft model, without and with an external biodegradable wrap that allows loads to increase gradually. We show that a biodegradable external wrap promotes luminal uniformity, physiological wall shear stress, and a consistent vein graft phenotype, namely, it prevents over-distension, over-thickening, intimal hyperplasia, and inflammation, and it preserves mechanotransduction. These mechanobiological insights into vein graft adaptation in the presence of an external support can inform computational growth and remodeling models of external support and facilitate design and manufacturing of next-generation external wrapping devices. STATEMENT OF SIGNIFICANCE: External mechanical support is emerging as a promising technology to prevent vein graft failure following coronary bypass graft surgery. While variants of this technology are currently under investigation in clinical trials, the fundamental mechanisms of adaptation remain poorly understood. We employ an ovine carotid-jugular interposition vein graft model, with and without an external biodegradable wrap to provide mechanical support, and probe vein graft adaptation using a multimodal experimental and computational data collection pipeline. We quantify morphometry using magnetic resonance imaging, mechanics using biaxial testing, fluid flow using computational fluid dynamics, vascular composition and structure using histology, and transcriptional changes using bulk RNA sequencing. We show that the wrap mitigates vein graft failure by promoting multiple adaptive mechanisms (across biological scales).

Diminishing Basic Science Research Experience Among United States Cardiothoracic Surgery Trainees.

INTRODUCTION: There is growing concern regarding the attrition of surgeon-scientists. To understand the decline of basic science research (BSR), it is essential to examine trends in research conducted by trainees. We hypothesized that, over recent decades, cardiothoracic (CT) surgery trainees have published fewer BSR articles. MATERIALS AND METHODS: CT surgeons at United States training institutions in 2020 who completed training in the past three decades, excluding international trainees, were analyzed (1991-2000: n = 148; 2001-2010: n = 228; 2011-2020: n = 247). Publication records were obtained from Scopus. Articles with medical subject heading terms involving molecular/cellular or animal research were classified as BSR using the National Institutes of Health iCite Translation module. Data were analyzed using Fisher's exact test or the Wilcoxon rank-sum test. RESULTS: While the proportion of surgeons who published a first-author paper during training remained stable over the past two decades (178/228 [78.1%] versus 189/247 [76.5%], P = 0.7427), the proportion who published a first-author BSR paper decreased significantly (135/228 [59.2%] versus 96/247 [38.9%], P < 0.0001). Among surgeons who published a first-author paper in training, the total papers published by each trainee did not change over the past two decades (3.5 versus 3.3 first-author papers per 10 y of training, P = 0.8819). However, the number of BSR papers published during training decreased significantly (1.7 versus 0.8 first-author papers per 10 y of training, P < 0.0001). CONCLUSIONS: CT surgery trainees are publishing fewer BSR papers. Additional efforts are needed to increase exposure of trainees to BSR and reaffirm that BSR is a valuable and worthwhile pursuit for academic surgeons.

Electrophysiologic Conservation of Epicardial Conduction Dynamics After Myocardial Infarction and Natural Heart Regeneration in Newborn Piglets.

Newborn mammals, including piglets, exhibit natural heart regeneration after myocardial infarction (MI) on postnatal day 1 (P1), but this ability is lost by postnatal day 7 (P7). The electrophysiologic properties of this naturally regenerated myocardium have not been examined. We hypothesized that epicardial conduction is preserved after P1 MI in piglets. Yorkshire-Landrace piglets underwent left anterior descending coronary artery ligation at age P1 (n = 6) or P7 (n = 7), After 7 weeks, cardiac magnetic resonance imaging was performed with late gadolinium enhancement for analysis of fibrosis. Epicardial conduction mapping was performed using custom 3D-printed high-resolution mapping arrays. Age- and weight-matched healthy pigs served as controls (n = 6). At the study endpoint, left ventricular (LV) ejection fraction was similar for controls and P1 pigs (46.4 ± 3.0% vs. 40.3 ± 4.9%, p = 0.132), but significantly depressed for P7 pigs (30.2 ± 6.6%, p < 0.001 vs. control). The percentage of LV myocardial volume consisting of fibrotic scar was 1.0 ± 0.4% in controls, 9.9 ± 4.4% in P1 pigs (p = 0.002 vs. control), and 17.3 ± 4.6% in P7 pigs (p < 0.001 vs. control, p = 0.007 vs. P1). Isochrone activation maps and apex activation time were similar between controls and P1 pigs (9.4 ± 1.6 vs. 7.8 ± 0.9 ms, p = 0.649), but significantly prolonged in P7 pigs (21.3 ± 5.1 ms, p < 0.001 vs. control, p < 0.001 vs. P1). Conduction velocity was similar between controls and P1 pigs (1.0 ± 0.2 vs. 1.1 ± 0.4 mm/ms, p = 0.852), but slower in P7 pigs (0.7 ± 0.2 mm/ms, p = 0.129 vs. control, p = 0.052 vs. P1). Overall, our data suggest that epicardial conduction dynamics are conserved in the setting of natural heart regeneration in piglets after P1 MI.

Characteristics of Integrated Thoracic Surgery Residency Matriculants: A Survey of Program Directors.

BACKGROUND: The 6-year Integrated Thoracic Surgery (I-6) residency programs have evolved over the past decade. Despite the rising number of programs, there are minimal data published about the criteria utilized by program directors to select candidates. We analyze the characteristics and qualities of successful matriculants using the American Association of Medical College's (AAMC) data reports and survey responses from program directors. METHODS: Using a survey administered through the RedCap service, program directors were asked to rate the importance of a variety of factors in their evaluations of candidates. The AAMC data reports from 2018 to 2020 provided information on the mean matriculant research productivity, United States Medical Licensing Examination (USMLE) step 1 scores, and step 2 clinical knowledge (CK) scores. RESULTS: Responses were received from 19 of 33 I-6 programs (58%). Program directors consistently rated interview performance as a very important factor in their evaluation of applicants. Matching into the specialty is becoming more competitive, with mean USMLE step 1, step 2 CK, and research productivity increasing over the past few years; matriculants had mean step 1 and step 2 CK scores of 247.3 and 254.2, respectively, in the 2020 match. CONCLUSIONS: Thoracic surgery program directors place high value on applicant interview performance, letters of recommendation, and professionalism. Program directors agree that a forthcoming pass/fail USMLE step 1 score report will lead to closer scrutiny of other factors during the decision-making process and may cause future evaluation of applicants to be heavily reliant on letters of recommendation and medical school pedigree.

Trends in Diversity in Integrated Cardiothoracic Surgery Residencies.

BACKGROUND: Integrated cardiothoracic surgery residencies began 2006 to address workforce shortages in cardiothoracic surgery. As more attention has been given to racial and gender disparities, our goal was to examine trends in diversity among integrated cardiothoracic residents. METHODS: All US accredited integrated cardiothoracic programs that had accepted residents through 2020 were included. A resident list was collected through online websites and direct institutional contact. Gender, race, and year of entry were recorded. Linear regression models were used to evaluate racial and gender trends over time. RESULTS: From 2006 through 2020, 321 residents were accepted into integrated cardiothoracic training programs. Men comprised 72% (232/321) of the cohort. The racial distribution was 66.4% White (213/321), 26.2% Asian (84/321), 5.3% Hispanic (17/321), and 2.2% African American (7/321). Over the study period the time slope for Whites was -2.95 (P < .01), indicating an approximately 3% decrease each year. The time slope for Asians was 1.60 (P < .01), whereas the time slope did not change significantly for African Americans (0.10, P = .94) or Hispanics (0.13, P = .91). Adjusting for the number of integrated programs each year as a covariate did not change trends for any race. The time slope did not change significantly over the time period for men (-0.25, P = .71). CONCLUSIONS: Gender and racial diversity have not improved over time in integrated cardiothoracic residencies. Institutions should strive to recruit medical students from underrepresented backgrounds and increase their focus on gender diversity.