Angiogenic Gene Therapy for Refractory Angina: Results of the EXACT Phase 2 Trial

BACKGROUND

XC001 is a novel adenoviral-5 vector designed to express multiple isoforms of VEGF (vascular endothelial growth factor) and more safely and potently induce angiogenesis. The EXACT trial (Epicardial Delivery of XC001 Gene Therapy for Refractory Angina Coronary Treatment) assessed the safety and preliminary efficacy of XC001 in patients with no option refractory angina.

METHODS

In this single-arm, multicenter, open-label trial, 32 patients with no option refractory angina received a single treatment of XC001 (1×1011 viral particles) via transepicardial delivery.

RESULTS

There were no severe adverse events attributed to the study drug. Twenty expected severe adverse events in 13 patients were related to the surgical procedure. Total exercise duration increased from a mean±SD of 359.9±105.55 seconds at baseline to 448.2±168.45 (3 months), 449.2±175.9 (6 months), and 477.6±174.7 (12 months; +88.3 [95% CI, 37.1-139.5], +84.5 [95% CI, 34.1-134.9], and +115.5 [95% CI, 59.1-171.9]). Total myocardial perfusion deficit on positron emission tomography imaging decreased by 10.2% (95% CI, -3.1% to 23.5%), 14.3% (95% CI, 2.8%-25.7%), and 10.2% (95% CI, -0.8% to -21.2%). Angina frequency decreased from a mean±SD 12.2±12.5 episodes to 5.2±7.2 (3 months), 5.1±7.8 (6 months), and 2.7±4.8 (12 months), with an average decrease of 7.7 (95% CI, 4.1-11.3), 6.6 (95% CI, 3.5-9.7), and 8.8 (4.6-13.0) episodes at 3, 6, and 12 months. Angina class improved in 81% of participants at 6 months.

CONCLUSIONS

XC001 administered via transepicardial delivery is safe and generally well tolerated. Exploratory improvements in total exercise duration, ischemic burden, and subjective measures support a biologic effect sustained to 12 months, warranting further investigation.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT04125732.

Long-Term Survival Following Primary Graft Dysfunction Development in Lung Transplantation

INTRODUCTION

Primary graft dysfunction (PGD) is a known risk factor for early mortality following lung transplant (LT). However, the outcomes of patients who achieve long-term survival following index hospitalization are unknown. We aimed to determine the long-term association of PGD grade 3 (PGD3) in patients without in-hospital mortality.

METHODS

LT recipients were identified from the United Network for Organ Sharing Database. Patients were stratified based on the grade of PGD at 72 h (No PGD, Grade 1/2 or Grade 3). Groups were assessed with comparative statistics. Long-term survival was evaluated using Kaplan-Meier methods and a multivariable shared frailty model including recipient, donor, and transplant characteristics.

RESULTS

The PGD3 group had significantly increased length of stay, dialysis, and treated rejection post-transplant (P < 0.001). Unadjusted survival analysis revealed a significant difference in long-term survival (P < 0.001) between groups; however, following adjustment, PGD3 was not independently associated with long-term survival (hazard ratio: 0.972; 95% confidence interval: 0.862-1.096). Increased mortality was significantly associated with increased recipient age and treated rejection. Decreased mortality was significantly associated with no donor diabetes, bilateral LT as compared to single LT, transplant in 2015-2016 and 2017-2018, and no post-transplant dialysis.

CONCLUSIONS

While PGD3 remains a challenge post LT, PGD3 at 72 h is not independently associated with decreased long-term survival, while complications such as dialysis and rejection are, in patients who survive index hospitalization. Transplant providers should be aggressive in preventing further complications in recipients with severe PGD to minimize the negative association on long-term survival.

Does Size Matter? The Effect of Size of Distal Perfusion Catheter on Acute Limb Ischemia: A Meta-Analysis

Prevention of limb ischemia in patients with venoarterial extracorporeal membrane oxygenation (VA-ECMO) is primarily achieved through the use of distal perfusion catheters (DPC). Our objective was to assess the role of DPC, and specifically the size of the catheter, in reducing the incidence of acute limb ischemia (ALI) through a meta-analysis. Seventeen studies met criteria for analysis. Pooled analysis included a total of 2,040 patients, of which 904 patients received ECMO with DPC and 1,136 patients underwent ECMO without DPC. Compared with ECMO alone, ECMO with DPC, regardless of size, significantly decreased ALI (relative risk [RR]: 0.49, 95% confidence interval [CI]: 0.31-0.77; p = 0.002). When comparing reactive versus prophylactic placement of DPC, prophylactic DPC was associated with significantly decreased ALI (RR: 0.41, 95% CI: 0.24-0.71; p = 0.02). No differences in mortality (RR: 0.89, 95% CI: 0.76-1.03; p = 0.12) and bleeding events (RR: 1.43, 95% CI: 0.41-4.96; p = 0.58) were observed between the two groups. This analysis demonstrates that the placement of DPC, if done prophylactically and regardless of size, is associated with a reduced risk of ALI versus the absence of DPC placement, but is not associated with differences in mortality or bleeding events.

Textbook outcome: A novel metric in heart transplantation outcomes

OBJECTIVE

Assessing heart transplant program quality using short-term survival is insufficient. We define and validate the composite metric textbook outcome and examine its association with overall survival.

METHODS

We identified all primary, isolated adult heart transplants in the United Network for Organ Sharing/Organ Procurement and Transplantation Network Standard Transplant Analysis and Research files from May 1, 2005, to December 31, 2017. Textbook outcome was defined as length of stay 30 days or less; ejection fraction greater than 50% during 1-year follow-up; functional status 80% to 100% at 1 year; freedom from acute rejection, dialysis, and stroke during the index hospitalization; and freedom from graft failure, dialysis, rejection, retransplantation, and mortality during the first year post-transplant. Univariate and multivariate analyses were performed. Factors independently associated with textbook outcome were used to create a predictive nomogram. Conditional survival at 1 year was measured.

RESULTS

A total of 24,620 patients were identified with 11,169 (45.4%, 95% confidence interval, 44.7-46.0) experiencing textbook outcome. Patients with textbook outcome were more likely free from preoperative mechanical support (odds ratio, 3.504, 95% confidence interval, 2.766 to 4.439, P < .001), free from preoperative dialysis (odds ratio, 2.295, 95% confidence interval, 1.868-2.819, P < .001), to be not hospitalized (odds ratio, 1.264, 95% confidence interval, 1.183-1.349, P < .001), to be nondiabetic (odds ratio, 1.187, 95% confidence interval, 1.113-1.266, P < .001), and to be nonsmokers (odds ratio, 1.160, 95% confidence interval,1.097-1.228, P < .001). Patients with textbook outcome have improved long-term survival relative to patients without textbook outcome who survive at least 1 year (hazard ratio for death, 0.547, 95% confidence interval, 0.504-0.593, P < .001).

CONCLUSIONS

Textbook outcome is an alternative means of examining heart transplant outcomes and is associated with long-term survival. The use of textbook outcome as an adjunctive metric provides a holistic view of patient and center outcomes.

What Is the "Right" First Job?

It is a daunting task to find the "right" first job. However, the foundation of the search is similar to that of the interview and match process for residency and fellowship. Does the job opportunity have the makeup of clinical and research opportunities, case mix, support and culture that will set the trainee up to fulfill his or her early career goals? Does the position seem like a good fit? The variation occurs with (1) the mystery behind it-there are scarce resources available on the topic, and (2) the logistics: where and when to look; the interview process.

Clinical and economic impact of ventricular assist device infections: a real-world claims analysis

BACKGROUND

VAD therapy has revolutionized the treatment of end-stage heart failure, but infections remain an important complication. The objective of this study was to characterize the clinical and economic impacts of VAD-specific infections.

METHODS

A retrospective analysis of a United States claims database identified members ≥ 18 years with a claim for a VAD implant procedure, at least 6 months of pre-implant baseline data, and 12 months of follow-up between 1 June 2016 and 31 December 2019. Cumulative incidence of infection was calculated. Infection and non-infection cohorts were compared regarding mortality, healthcare utilization, and total cost. Regression models were used to identify risk factors associated with infections and mortality.

RESULTS

A total of 2,259 patients with a VAD implant were included, with 369 experiencing infection (12-month cumulative incidence 16.1%). Patients with infection were 2.1 times more likely to die (p < 0.001, 95% CI [1.5-2.9]). The mean 12-month total cost per US patient was $354,339 for the non-infection cohort and $397,546 for the infection cohort, a difference of $43,207 (p < 0.0001).

CONCLUSIONS

VAD infections were associated with higher mortality, more healthcare utilization, and higher total cost. Strategies to minimize VAD-specific infections could lead to improved clinical and economic outcomes.

Intraoperative Embolization during Inferior Vena Cava Tumor Thrombectomy for Renal Cell Carcinoma

Intraoperative tumor thrombus embolization is a potentially lethal complication during inferior vena cava (IVC) thrombectomy for renal cell carcinoma (RCC). Intraoperative embolization is uncommonly encountered because IVC thrombectomy surgical technique is focused on avoiding this complication. Nonetheless, early recognition of embolization is essential so that emergent management can be instituted. When available, cardiopulmonary bypass (CPB) and embolectomy should be considered the gold standard for the management of intraoperative embolization. Several novel endovascular techniques are also available for selective use. We present the case of a 71-year-old female with a right renal mass and level II (retrohepatic) IVC tumor thrombus. During cytoreductive nephrectomy and IVC thrombectomy, tumor embolization was diagnosed during a period of hypotension based on transesophageal echocardiographic finding of new thrombus within the right atrium. This prompted sternotomy, CPB, and pulmonary artery embolectomy. The patient survived this embolization event and has a complete response to systemic therapy 9 months postoperatively. This case serves as the framework for a discussion on management considerations surrounding intraoperative embolization during IVC thrombectomy.

Thoracic retransplantation: Does time to retransplantation matter?

OBJECTIVE

For some individuals, chronic allograft failure is best treated with retransplantation. We sought to determine if time to retransplantation impacts short- and long-term outcomes for heart or lung retransplant recipients with a time to retransplantation more than 1 year.

METHODS

The United Network for Organ Sharing/Organ Procurement and Transplantation Network STAR file was queried for all adult, first-time heart (June 1, 2006, to September 30, 2020) and lung (May 1, 2005, to September 30, 2020) retransplantations with a time to retransplantation of at least 1 year. Patients were grouped according to the tertile of time to retransplantation (tertile 1: 1-7.7 years, tertile 2: 7.7-14.7 years, tertile 3: 14.7+ years; lung: tertile 1: 1-2.8 years, tertile 2: 2.8-5.6 years, tertile 3: 5.6+ years). The primary outcome was survival after retransplantation. Comparative statistics identified differences in groups, and Kaplan-Meier methods and a Cox proportional hazard model were used for survival analysis.

RESULTS

After selection, 908 heart and 871 lung retransplants were identified. Among heart retransplant recipients, tertile 1 was associated with male sex, smoking history, higher listing status, and increased mechanical support pretransplant. Tertile 3 had the highest rate of concomitant kidney transplant; however, the incidence of morbidity and in-hospital mortality was similar among the groups. Unadjusted and adjusted analyses revealed no survival difference among all groups. Regarding lung retransplant recipients, tertile 1 was associated with increased lung allocation score, pretransplant hospitalization, and mechanical support. Unadjusted and adjusted survival analyses revealed decreased survival in tertile 1.

CONCLUSIONS

Time to retransplant does not appear to affect heart recipients with a time to retransplantation of more than 1 year; however, shorter time to retransplantation for prior lung recipients is associated with decreased survival. Potential lung retransplant candidates with a time to retransplantation of less than 2.8 years should be carefully evaluated before retransplantation.

The Association of Persistent Poverty and Outcomes Among Patients Undergoing Cardiac Surgery

INTRODUCTION

We sought to evaluate the association of county-level poverty duration and cardiac surgical outcomes.

METHODS

Patients who underwent coronary artery bypass graft, surgical aortic valve replacement, and mitral valve repair and replacement between 2016 and 2020 were identified using the Medicare Standard Analytical Files Database. County-level poverty data were acquired from the American Community Survey and US Department of Agriculture (1980-2015). High poverty was defined as ≥19.5% of residents in poverty. Patients were stratified into never-high poverty (NHP), intermittent low poverty, intermittent high poverty, and persistent poverty (PP). A mixed-effect hierarchical generalized linear model and Cox regression models that adjusted for patient-level covariates were used to evaluate outcomes.

RESULTS

Among 237,230 patients, 190,659 lived in NHP counties, while 10,273 resided in PP counties. Compared with NHP patients, PP patients were more likely to present at a younger median age (NHP: 75 y versus PP: 74 y), be non-Hispanic Black (5388, 2.9% versus PP: 1030, 10.1%), and live in the south (NHP: 66,012, 34.6% versus PP: 87,815, 76.1%) (all P < 0.001). PP patients also had more nonelective surgical operations (NHP: 58,490, 30.8% versus 3645, 35.6%, P < 0.001). Notably, PP patients had increased odds of 30-d mortality (odds ratio 1.13, 95% confidence interval [CI] 1.02-1.26), 90-d mortality (odds ratio 1.14, 95% CI 1.05-1.24), and risk of long-term mortality (hazard ratio 1.13, 95% CI 1.09-1.19) compared with patients in NHP counties (all P < 0.05).

CONCLUSIONS

County-level poverty was associated with a greater risk of short- and long-term mortality among cardiac surgical patients.

Refractory Hypotension During Implantation of a 70 mL Total Artificial Heart in a Patient With Pectus Excavatum: A Case Report

The Syncardia total artificial heart system is the only commercially approved durable device for treating biventricular heart failure patients awaiting heart transplantation. Conventionally, the Syncardia total artificial heart system is implanted based on the distance from the anterior aspect of the 10th thoracic vertebra to the sternum and the patient's body surface area. However, this criterion does not account for chest wall musculoskeletal deformities. This case report describes a patient with a pectus excavatum who developed compression of the inferior vena cava after Syncardia total artificial heart implantation and how transesophageal echocardiography guided chest wall surgery to accommodate the total artificial heart system.

EXACT Trial: Results of the Phase 1 Dose-Escalation Study

BACKGROUND

New therapies are needed for patients with refractory angina. Encoberminogene rezmadenovec (XC001), a novel adenoviral-5 vector coding for all 3 major isoforms of VEGF (vascular endothelial growth factor), demonstrated enhanced local angiogenesis in preclinical models; however, the maximal tolerated dose and safety of direct epicardial administration remain unknown.

METHODS

In the phase 1 portion of this multicenter, open-label, single-arm, dose-escalation study, patients with refractory angina received increasing doses of encoberminogene rezmadenovec (1×109, 1×1010, 4×1010, and 1×1011 viral particles) to evaluate its safety, tolerability, and preliminary efficacy. Patients had class II to IV angina on maximally tolerated medical therapy, demonstrable ischemia on stress testing, and were angina-limited on exercise treadmill testing. Patients underwent minithoracotomy with epicardial delivery of 15 0.1-mL injections of encoberminogene rezmadenovec. The primary outcome was safety via adverse event monitoring over 6 months. Efficacy assessments included difference from baseline to months 3, 6 (primary), and 12 in total exercise duration, myocardial perfusion deficit using positron emission tomography, angina class, angina frequency, and quality of life.

RESULTS

From June 2, 2020 to June 25, 2021, 12 patients were enrolled into 4 dosing cohorts with 1×1011 viral particle as the highest planned dose. Seventeen serious adverse events were reported in 7 patients; none were related to study drug. Six serious adverse events in 4 patients were related to the thoracotomy, 3 non-serious adverse events were possibly related to study drug. The 2 lowest doses did not demonstrate improvements in total exercise duration, myocardial perfusion deficit, or angina frequency; however, there appeared to be improvements in all parameters with the 2 higher doses.

CONCLUSIONS

Epicardial delivery of encoberminogene rezmadenovec via minithoracotomy is feasible, and up to 1×1011 viral particle appears well tolerated. A dose response was observed across 4 dosing cohorts in total exercise duration, myocardial perfusion deficit, and angina class. The highest dose (1×1011 viral particle) was carried forward into phase 2.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT04125732.

Total artificial heart implantation: supportive care preparedness planning framework

BACKGROUND

The total artificial heart (TAH) is an implanted device approved as a modality to stabilize patients with severe biventricular heart failure or persistent ventricular arrhythmias for evaluation and bridge to transplantation. According to the Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS), about 450 patients received a TAH between 2006 and 2018. Patients being evaluated for a TAH are often critically ill and a TAH offers the best chance at survival. Given the prognostic uncertainty of these patients, there is a crucial need for preparedness planning to help patients and their caregivers plan for living and supporting a loved one with a TAH.

AIM

To describe an approach to preparedness planning and highlight the importance of palliative care.

METHODS

We reviewed the current needs and approaches to preparedness planning for a TAH. We categorized our findings and suggest a guide to maximize conversations with patients and their decision makers.

RESULTS

We identified four critical areas to address: the decision maker, minimal acceptable outcome/maximal acceptable burden, living with the device, and dying with the device. We suggest using a framework of mental and physical outcomes and locations of care as a way to identify minimal acceptable outcome and maximal acceptable burden.

CONCLUSION

Decision making for a TAH is complex. There is an urgency and patients do not always have capacity. Identifying legal decision makers and social support is critical. The surrogate decision makers should be included in preparedness planning including discussions about end-of-life care and treatment discontinuation. Having palliative care as members of the interdisciplinary mechanical circulatory support team can assist in these preparedness conversations.

Mechanical Dyssynchrony of Isolated Left and Right Ventricular Human Myocardium in End-Stage Heart Failure

BACKGROUND

The left and right ventricles of the human heart differ in embryology, shape, thickness, and function. Ventricular dyssynchrony often occurs in cases of heart failure. Our objectives were to assess whether differences in contractile properties exist between the left and right ventricles and to evaluate signs of left/right ventricular mechanical synchrony in isolated healthy and diseased human myocardium.

METHODS

Myocardial left and right ventricular trabeculae were dissected from nonfailing and end-stage failing human hearts. Baseline contractile force and contraction/relaxation kinetics of the left ventricle were compared to those of the right ventricle in the nonfailing group (n=41) and in the failing group (n=29). Correlation analysis was performed to assess the mechanical synchrony between left and right ventricular myocardium isolated from the same heart, in nonfailing (n=41) and failing hearts (n=29).

RESULTS

The failing right ventricular myocardium showed significantly higher developed force (Fdev; P=0.001; d=0.98), prolonged time to peak (P<0.001; d=1.14), and higher rate of force development (P=0.002; d=0.89) and force decline (P=0.003; d=0.82) compared to corresponding left ventricular myocardium. In healthy myocardium, a strong positive relationship was present between the left and right ventricles in time to peak (r=0.58, P<0.001) and maximal kinetic rate of contraction (r=0.63, P<0.001). These coefficients were much weaker, often nearly absent, in failing myocardium.

CONCLUSIONS

At the level of isolated cardiac trabeculae, contractile performance, specifically of contractile kinetics, is correlated in the nonfailing myocardium between the left and right ventricles' but this correlation is significantly weaker, or even absent, in end-stage heart failure, suggesting an interventricular mechanical dyssynchrony.

Allocation changes in heart transplantation: What has really changed?

OBJECTIVE

In 2018, the heart allocation system changed status classifications and broadened geographic distribution. We examined this change at a national level based on the immediate pre- and postchange periods.

METHODS

Using the Scientific Registry of Transplant Recipients database, we identified all adult primary, isolated heart transplants from October 18, 2017, to October 17, 2019. Two time periods were compared: (1) October 18, 2017, to October 17, 2018 (pre); and (2) October 18, 2018, to October 17, 2019 (post). Comparisons were made between groups, and a multivariable logistic regression model was created to identify factors associated with pretransplant temporary mechanical circulatory support. Volume analysis at the regional, state, and center level was also conducted as the primary focus.

RESULTS

A total of 5381 independent heart transplants were identified within the time frame. On unadjusted analysis, there was a significant increase in temporary mechanical circulatory support (pre, 11.1%; post, 36.2%, P < .01) and decrease in waitlist days (pre, 93 days; post, 41 days; P < .01). Distance traveled (nautical miles) (pre, 83; post, 225; P < .01) and ischemic time (hours) (pre, 3.0; post, 3.4; P < .01) were significantly increased. On multivariable analysis, the postallocation time period was independently associated with temporary MCS (odds ratio, 4.463; 95% confidence interval, 3.844-5.183; P < .001). Transplant volumes did not significantly change after the allocation change at a regional, state, and center level.

CONCLUSIONS

Since the planned alteration to the allocation system, there have been changes in the use of temporary mechanical circulatory support as well as distance and ischemic time associated with transplant, but no significant volume changes were observed. Continued observation of outcomes and volume under the new allocation system will be necessary in the upcoming years.

Donor and Recipient Hepatitis C Status Does Not Affect Rejection in Thoracic Transplantation

BACKGROUND

Donors with hepatitis C virus (HCV) have expanded the donor pool for heart and lung transplantation, but concerns have arisen about rejection. We examined the incidence of rejection after heart and lung transplantation in recipients of HCV-positive donors as well as HCV-positive recipients.

METHODS

Adults undergoing heart and lung transplantation from March 31, 2015 to December 31, 2019 were identified in the United Network for Organ Sharing/Organ Transplantation and Procurement Network Standard Transplant Analysis and Research file. Patients were stratified as donor-recipient HCV negative, donor positive, and recipient positive. Comparative statistics and a multilevel logistic regression model were used.

RESULTS

Meeting the criteria were 10 624 heart transplant recipients. Donor-positive recipients were significantly associated with older age, blood group O, and shorter waitlist time. No significant differences existed with regards to treatment for rejection in the first year (negative, 19.5%; donor positive, 22.3%; recipient positive, 19.5%; P = .45) or other outcomes. On regression analysis HCV status was not associated with treated rejection; however center variability was significantly associated with treated rejection (median odds ratio, 2.18). Similarly, 9917 lung transplant recipients were identified. Donor-positive recipients were more commonly White and had obstructive disease and lower lung allocation scores. Both unadjusted (negative, 22.1%; donor positive, 23.0%; recipient positive, 18.6%; P = .43) and adjusted analyses failed to demonstrate a significant association between HCV status and treatment for rejection, whereas center variability remained significantly associated with treatment for rejection (median odds ratio, 2.41).

CONCLUSIONS

Use of HCV donors has expanded the donor pool for heart and lung transplantation. HCV donor status was not associated with treatment for rejection in the first year, but center variability played a role in the incidence and treatment of rejection.

Quantification of Cardiac Adipose Tissue in Failing and Nonfailing Human Myocardium

Background

Because body mass index (BMI) is generally used clinically to define obesity and to estimate body adiposity, BMI likely is positively correlated with epicardial adipose tissue (EAT) level. Based on echocardiography, previous outcomes on this matter have varied from almost absent to rather strong correlations between BMI and EAT. The purpose of our study was to unambiguously examine EAT content and determine if correlations exist between EAT content and BMI, cause of heart failure, or contractile force.

Methods and Results

We qualitatively scored 150 human hearts ex vivo on EAT distribution. From each heart, multiple photographs of the heart were taken, and both atrial and ventricular adipose tissue levels were semiquantitatively scored. Main findings include a generally higher EAT content on nonfailing hearts compared with end‐stage failing hearts (atrial adipose tissue level 5.70±0.13 vs. 5.00±0.12, P<0.001; ventricular adipose tissue level 5.14±0.16 vs. 4.57±0.12, P=0.0048). The results also suggest that EAT quantity is not strongly correlated with BMI in nonfailing (atrial adipose tissue level r=0.069, ventricular adipose tissue level r=0.14) or failing (atrial adipose tissue level r=−0.022, ventricular adipose tissue level r=0.051) hearts. Atrial EAT is closely correlated with ventricular EAT in both nonfailing (r=0.92, P<0.001) and failing (r=0.87, P<0.001) hearts.

Conclusions

EAT volume appears to be inversely proportional to severity of or length of time with heart failure based on our findings. Based on a lack of correlation with BMI, it is incorrect to assume high EAT volume given high body fat percentage.

Trends in Donation After Circulatory Death in Lung Transplantation in the United States: Impact Of Era

Background: Use of lungs donated after circulatory death (DCD) has expanded, but changes in donor/recipient characteristics and comparison to brain dead donors (DBD) has not been studied. We examined the evolution of the use of DCD lungs for transplantation and compare outcomes to DBD lungs.

Methods: The SRTR database was used to construct three 5-year intervals. Perioperative variables and survival were compared by era and for DCD vs. DBD. Geographic variation was estimated using recipient permanent address.

Results: 728 DCD and 27,205 DBD lung transplants were identified. DCD volume increased from Era 1 (n = 73) to Era 3 (n = 528), representing 1.1% and 4.2% of lung transplants. Proportionally more DCD recipients were in ICU or on ECMO pre-transplant, and had shorter waitlist times. DCD donors were older, had lower PaO2/FiO2 ratios compared to DBD, more likely to be bilateral, had longer ischemic time, length of stay, post-op dialysis, and increased use of lung perfusion. There was no difference in overall survival. Geographically, use was heterogeneous.

Conclusion: DCD utilization is low but increasing. Despite increasing ischemic time and transplantation into sicker patients, survival is similar, which supports further DCD use in lung transplantation. DCD lung transplantation presents an opportunity to continue to expand the donor pool.

HVAD to HeartMate 3 left ventricular assist device exchange: Best practices recommendations

The HeartWare HVAD System (Medtronic) is a durable implantable left ventricular assist device that has been implanted in approximately 20,000 patients worldwide for bridge to transplant and destination therapy indications. In December 2020, Medtronic issued an Urgent Medical Device Communication informing clinicians of a critical device malfunction in which the HVAD may experience a delay or failure to restart after elective or accidental discontinuation of pump operation. Moreover, evolving retrospective comparative effectiveness studies of patients supported with the HVAD demonstrated a significantly higher risk of stroke and all-cause mortality when compared with a newer generation of a commercially available durable left ventricular assist device. Considering the totality of this new information on HVAD performance and the availability of an alternate commercially available device, Medtronic halted the sale and distribution of the HVAD System in June 2021. The decision to remove the HVAD from commercial distribution now requires the use of the HeartMate 3 left ventricular assist system (Abbott, Inc) if a patient previously implanted with an HVAD requires a pump exchange. The goal of this document is to review important differences in the design of the HVAD and HeartMate 3 that are relevant to the medical management of patients supported with these devices, and to assess the technical aspects of an HVAD-to-HeartMate 3 exchange. This document provides the best available evidence that supports best practices.

Bullectomy used to treat a patient with pulmonary vesicles related to COVID-19: A case report

BACKGROUND

The corona virus disease 2019 (COVID-19) has been a pandemic for more than one year and estimated to affect the whole world in the near future.

CASE SUMMARY

Here we reported that one COVID-19 patient with vesicles was treated by bullectomy. The patient’s perioperative laboratory tests were analyzed. The pathological findings of bullectomy were described and compared with those of common bulla cases.

CONCLUSION

This patient with vesicles underwent bullectomy and had a poor prognosis. He showed diffuse alveolar damage and extensive necrosis in bullectomy specimen. We hope our report will be of interest for clinicians who will treat COVID-19 patients in the future.

Lung transplantation in the septuagenarian can be successfully performed though long-term results impacted by diseases of aging

BACKGROUND

Advanced age is considered a risk factor for lung transplantation (LTX). We sought to evaluate the long-term outcomes of LTX in the septuagenarian.

METHODS

LTX recipients in the UNOS transplant registry (May 1, 2005 to June 12, 2020) were stratified into 18-59, 60-69, and > = 70 years of age. Recipient and transplant characteristics were evaluated for survival, cause of death (COD), length of stay (LOS), and complications. A Kaplan-Meier analysis examined long-term survival for all patients stratified by age, specifically looking at cause of death.

RESULTS

A total of 27632 recipients were identified. As recipients aged, we found a decrease in proportion of cystic fibrosis and an increase in restrictive disease while obstructive disease peaked in the 60-69yo cohort (p<0.001). Septuagenarians had higher rates of single LTX, male gender and white race (p<0.001). Older recipients had significantly longer donor recovery distances traveled with paradoxical shorter ischemic times, shorter hospital LOS and were transplanted at higher volume centers. There was no difference with in-hospital mortality among groups (p = 0.5). Acute rejection during initial hospitalization, rejection within 1 year, and post-transplant dialysis incidence decreased with age. Graft failure was a common COD in younger patients while malignancy and cardio/cerebrovascular diseases were common COD in > = 70yo.

CONCLUSION

Select septuagenarian LTX candidates may be safely transplanted with relatively few complications. Immunosenescence and conditions of the aged are likely contributing factors to the decreased rejection and graft failure observations. Septuagenarians should not be excluded from LTX consideration based solely on age. Transplantation in septuagenarians should only be done in very selected patients (screened for malignancies and atherosclerotic disease) and these recipients should be carefully followed after transplantation because of these risk factors. This article is protected by copyright. All rights reserved.

Thoracic transplantation during the COVID-19 pandemic

The worldwide pandemic caused by COVID-19, resulting from the infection by betacoronarvirus SARS-CoV-2, has dramatically altered healthcare worldwide. Due to the highly contagious nature of SARS-CoV2, coupled with hospitals and intensive care units being overwhelmed, numerous transplant programs either slowed or shut down completely. While there have been isolated reports of COVID-19 in transplant recipients, no study to date has examined how COVID-19 affected actual transplant patterns and outcomes in the United States. Of particular importance is the impact of COVID-19 on mortality in waitlisted patients and transplant recipients. Using the Scientific Registry of Transplant Recipients (SRTR) dataset we compared waitlist and transplant characteristics from 3/2019-8/2019 to 3/2020-8/2020, as well as COVID-19 associated mortality in patients with prior heart or lung transplant or those active on the waitlist. Overall, there was an initial decrease in transplant volume in April 2020; however, volumes have normalized since then, with comparable outcomes to similar calendar months in 2019. Additionally, there were no significant changes in post-transplant outcomes or waiting list mortality. Given the ongoing COVID-19 pandemic it would be beneficial to maintain current practices for thoracic transplantation, to continue to provide this life-saving therapy to those in need. This article is protected by copyright. All rights reserved.

Insights into early postoperative acute kidney injury following lung transplantation

BACKGROUND

Acute kidney injury (AKI) is a common complication after lung transplantation (LT) and is associated with higher cost and mortality. We sought to evaluate the incidence of postoperative AKI, defined as AKI within 14 days of transplant, and identify associated perioperative factors.

METHODS

We conducted a single-center, retrospective review of 153 lung transplant recipients. Postoperative AKI was determined using the RIFLE (Risk, Injury, Failure, Loss, End Stage) criteria. Perioperative covariates and their association with postoperative AKI were analyzed using Cox proportional hazards. Kaplan-Meier survival curves were constructed to evaluate patient survival at one year and data finalization. A subanalysis was performed evaluating factors associated with early AKI (within 48 hours of transplant) and late AKI.

RESULTS

Postoperative AKI occurred in 36.6% of patients with 51.8% of cases occurring within 48 hours of LT. Recipient race, transplant type, cardiopulmonary support, and red blood cell administration were associated with postoperative AKI. Survival was significantly lower in patients with postoperative AKI following LT.

CONCLUSIONS

Postoperative AKI within 2 weeks of lung transplant is associated with lower short- and long-term survival. Perioperative factors associated with postoperative AKI may be potential points of intervention to minimize AKI development in the future. This article is protected by copyright. All rights reserved.

Epicardial delivery of XC001 gene therapy for refractory angina coronary treatment (The EXACT Trial): Rationale, design, and clinical considerations

BACKGROUND

Patients with refractory angina (RA) have poor quality of life and new therapies are needed. XC001 is a novel adenoviral vector expressing multiple isoforms of vascular endothelial growth factor (VEGF) promoting an enhanced local angiogenic effect.

METHODS

The Epicardial Delivery of XC001 Gene Therapy for Refractory Angina Coronary Treatment (EXACT) trial is a 6-month (with 6-month extension) phase 1/2, first-in-human, multicenter, open-label, single-arm, dose-escalation study to evaluate the safety, tolerability, and preliminary efficacy of XC001 in patients with RA. The trial will enroll 33 patients in an initial (n = 12) ascending dose-escalation phase (1 × 10⁹, 1 × 10¹⁰, 4 × 10¹⁰, and 1 × 10¹¹ viral particles), followed by phase 2 (n = 21) assessing the highest tolerated dose. Patients must have stable Canadian Cardiovascular Society (CCS) class II-IV angina on maximally tolerated medical therapy without options for conventional revascularization, demonstrable ischemia on stress testing, and angina limiting exercise tolerance. XC001 will be delivered directly to ischemic myocardium via surgical transthoracic epicardial access. The primary outcome is safety via adverse event monitoring through 6 months. Efficacy assessments include difference from baseline to month 6 in time to 1 mm of ST segment depression, time to angina, and total exercise duration; myocardial blood flow at rest, and stress and coronary flow reserve by positron emission tomography; quality of life; CCS functional class; and angina frequency.

CONCLUSIONS

The EXACT trial will determine whether direct intramyocardial administration of XC001 in patients with RA is safe and evaluate its effect on exercise tolerance, myocardial perfusion, angina and physical activity, informing future clinical investigation.

CLINICAL TRIAL REGISTRATION

NCT04125732.

Safety of direct oral anticoagulants in solid organ transplant recipients: A meta-analysis

There is limited evidence comparing direct oral anticoagulants (DOACs) and warfarin in solid organ transplant (SOT) recipients. We performed a pooled analysis to study the safety and efficacy of DOACs in this patient population. We searched PubMed, Embase, and Scopus databases using the search terms "heart transplant" or "lung transplant" or "liver transplant" or "kidney transplant" or "pancreas transplant" and "direct oral anticoagulant" for literature search. Random effects model with Mantel-Haenszel method was used to pool the outcomes. Pooled analysis included 489 patients, of which 259 patients received DOACs and 230 patients received warfarin. When compared to warfarin, the use of DOACs was associated with decreased risk of composite bleed (RR .49, 95% CI .32-.76, p = .002). There were no differences in rates of major bleeding (RR .55, 95% CI .20-1.49, p = .24) or venous thromboembolism (RR .65, 95% CI .25-1.70, p = .38) between the two groups. Evidence from pooled analysis suggests that DOACs are comparable to warfarin in terms of safety in SOT recipients. Further research is warranted to conclusively determine whether DOACs are safe alternatives to warfarin for anticoagulation in SOT recipients.

Altered microRNA and mRNA profiles during heart failure in the human sinoatrial node

Heart failure (HF) is frequently accompanied with the sinoatrial node (SAN) dysfunction, which causes tachy-brady arrhythmias and increased mortality. MicroRNA (miR) alterations are associated with HF progression. However, the transcriptome of HF human SAN, and its role in HF-associated remodeling of ion channels, transporters, and receptors responsible for SAN automaticity and conduction impairments is unknown. We conducted comprehensive high-throughput transcriptomic analysis of pure human SAN primary pacemaker tissue and neighboring right atrial tissue from human transplanted HF hearts (n = 10) and non-failing (nHF) donor hearts (n = 9), using next-generation sequencing. Overall, 47 miRs and 832 mRNAs related to multiple signaling pathways, including cardiac diseases, tachy-brady arrhythmias and fibrosis, were significantly altered in HF SAN. Of the altered miRs, 27 are predicted to regulate mRNAs of major ion channels and neurotransmitter receptors which are involved in SAN automaticity (e.g. HCN1, HCN4, SLC8A1) and intranodal conduction (e.g. SCN5A, SCN8A) or both (e.g. KCNJ3, KCNJ5). Luciferase reporter assays were used to validate interactions of miRs with predicted mRNA targets. In conclusion, our study provides a profile of altered miRs in HF human SAN, and a novel transcriptome blueprint to identify molecular targets for SAN dysfunction and arrhythmia treatments in HF.

MG53 suppresses NFκB activation to mitigate age-related heart failure

Aging is associated with chronic oxidative stress and inflammation that impact the tissue repair and regeneration capacity. MG53 is a TRIM family protein that facilitates repair of cell membrane injury in a redox-dependent manner. Here we demonstrate that the expression of MG53 is reduced in failing human heart and aging mouse heart, concomitant with elevated NFκB activation. We evaluate the safety and efficacy of longitudinal, systemic administration of recombinant human MG53 (rhMG53) protein in aged mice. Echocardiography and pressure-volume loop measurements reveal beneficial effects of rhMG53 treatment in improving heart function of aging mice. Biochemical and histological studies demonstrate the cardioprotective effects of rhMG53 are linked to suppression of NFκB-mediated inflammation, reducing apoptotic cell death and oxidative stress in the aged heart. Repetitive administrations of rhMG53 in aged mice do not have adverse effects on major vital organ functions. These findings support the therapeutic value of rhMG53 in treating age-related decline in cardiac function.

Impact of etiology on force and kinetics of left ventricular end-stage failing human myocardium

BACKGROUND

Heart failure (HF) is associated with highly significant morbidity, mortality, and health care costs. Despite the significant advances in therapies and prevention, HF remains associated with poor clinical outcomes. Understanding the contractile force and kinetic changes at the level of cardiac muscle during end-stage HF in consideration of underlying etiology would be beneficial in developing targeted therapies that can help improve cardiac performance.

OBJECTIVE

Investigate the impact of the primary etiology of HF (ischemic or non-ischemic) on left ventricular (LV) human myocardium force and kinetics of contraction and relaxation under near-physiological conditions.

METHODS AND RESULTS

Contractile and kinetic parameters were assessed in LV intact trabeculae isolated from control non-failing (NF; n = 58) and end-stage failing ischemic (FI; n = 16) and non-ischemic (FNI; n = 38) human myocardium under baseline conditions, length-dependent activation, frequency-dependent activation, and response to the β-adrenergic stimulation. At baseline, there were no significant differences in contractile force between the three groups; however, kinetics were impaired in failing myocardium with significant slowing down of relaxation kinetics in FNI compared to NF myocardium. Length-dependent activation was preserved and virtually identical in all groups. Frequency-dependent activation was clearly seen in NF myocardium (positive force frequency relationship [FFR]), while significantly impaired in both FI and FNI myocardium (negative FFR). Likewise, β-adrenergic regulation of contraction was significantly impaired in both HF groups.

CONCLUSIONS

End-stage failing myocardium exhibited impaired kinetics under baseline conditions as well as with the three contractile regulatory mechanisms. The pattern of these kinetic impairments in relation to NF myocardium was mainly impacted by etiology with a marked slowing down of kinetics in FNI myocardium. These findings suggest that not only force development, but also kinetics should be considered as a therapeutic target for improving cardiac performance and thus treatment of HF.

Efficient precise in vivo base editing in adult dystrophic mice

Recent advances in base editing have created an exciting opportunity to precisely correct disease-causing mutations. However, the large size of base editors and their inherited off-target activities pose challenges for in vivo base editing. Moreover, the requirement of a protospacer adjacent motif (PAM) nearby the mutation site further limits the targeting feasibility. Here we modify the NG-targeting adenine base editor (iABE-NGA) to overcome these challenges and demonstrate the high efficiency to precisely edit a Duchenne muscular dystrophy (DMD) mutation in adult mice. Systemic delivery of AAV9-iABE-NGA results in dystrophin restoration and functional improvement. At 10 months after AAV9-iABE-NGA treatment, a near complete rescue of dystrophin is measured in mdx4cv mouse hearts with up to 15% rescue in skeletal muscle fibers. The off-target activities remains low and no obvious toxicity is detected. This study highlights the promise of permanent base editing using iABE-NGA for the treatment of monogenic diseases.

Impact of thoracotomy approach on right ventricular failure and length of stay in left ventricular assist device implants: an intermacs registry analysis

INTRODUCTION

Traditionally, implantation of Left Ventricular Assist Devices (LVADs) is performed via median sternotomy. Recently, less invasive thoracotomy approaches are growing in popularity as they involve less surgical trauma, potentially less bleeding, and may preserve right ventricular function. We hypothesized implantation of LVADs via thoracotomy has less perioperative right ventricular failure (RVF) and shorter postoperative length of stay (LOS).

METHODS

Continuous flow LVAD implants from Intermacs between February 6, 2014 - December 31, 2018 were identified. Patients implanted via thoracotomy were propensity matched in a 1:1 ratio with patients implanted via sternotomy. Outcomes were compared between sternotomy and thoracotomy approach and by device type (axial, centrifugal-flow with hybrid levitation (CF-HL), centrifugal-flow with full magnetic levitation devices (CF-FML)). The primary outcome was time to first moderate or severe RVF. Secondary outcomes included survival and LOS.

RESULTS

Overall 978 thoracotomy patients were matched with 978 sternotomy patients. Over the study period, 242 thoracotomy patients and 219 sternotomy patients developed RVF with no significant difference in time to first moderate to severe RVF by surgical approach overall (p = 0.27) or within CF-HL (p = 0.36) or CF-FML devices (p = 0.25). Survival did not differ by implant technique (150 deaths in thoracotomy group, 154 deaths in sternotomy group; p = 0.58). However, sternotomy approach was associated with a significantly shorter LOS (17 Vs 18 days, p = 0.009).

CONCLUSION

As compared to sternotomy, implantation of continuous flow LVADs via thoracotomy approach does not reduce moderate to severe RVF or improve survival but does reduce post-operative LOS. Device type did not influence outcomes and most centers did a small volume of thoracotomy implants.

Fibroblast-Specific Proteotranscriptomes Reveal Distinct Fibrotic Signatures of Human Sinoatrial Node in Nonfailing and Failing Hearts

BACKGROUND

Up to 50% of the adult human sinoatrial node (SAN) is composed of dense connective tissue. Cardiac diseases including heart failure (HF) may increase fibrosis within the SAN pacemaker complex, leading to impaired automaticity and conduction of electric activity to the atria. Unlike the role of cardiac fibroblasts in pathologic fibrotic remodeling and tissue repair, nothing is known about fibroblasts that maintain the inherently fibrotic SAN environment.

METHODS

Intact SAN pacemaker complex was dissected from cardioplegically arrested explanted nonfailing hearts (non-HF; n=22; 48.7±3.1 years of age) and human failing hearts (n=16; 54.9±2.6 years of age). Connective tissue content was quantified from Masson trichrome-stained head-center and center-tail SAN sections. Expression of extracellular matrix proteins, including collagens 1 and 3A1, CILP1 (cartilage intermediate layer protein 1), and POSTN (periostin), and fibroblast and myofibroblast numbers were quantified by in situ and in vitro immunolabeling. Fibroblasts from the central intramural SAN pacemaker compartment (≈10×5×2 mm³) and right atria were isolated, cultured, passaged once, and treated ± transforming growth factor β1 and subjected to comprehensive high-throughput next-generation sequencing of whole transcriptome, microRNA, and proteomic analyses.

RESULTS

Intranodal fibrotic content was significantly higher in SAN pacemaker complex from HF versus non-HF hearts (57.7±2.6% versus 44.0±1.2%; P<0.0001). Proliferating phosphorylated histone 3⁺/vimentin⁺/CD31^- (cluster of differentiation 31) fibroblasts were higher in HF SAN. Vimentin⁺/α-smooth muscle actin⁺/CD31^- myofibroblasts along with increased interstitial POSTN expression were found only in HF SAN. RNA sequencing and proteomic analyses identified unique differences in mRNA, long noncoding RNA, microRNA, and proteomic profiles between non-HF and HF SAN and right atria fibroblasts and transforming growth factor β1-induced myofibroblasts. Specifically, proteins and signaling pathways associated with extracellular matrix flexibility, stiffness, focal adhesion, and metabolism were altered in HF SAN fibroblasts compared with non-HF SAN.

CONCLUSIONS

This study revealed increased SAN-specific fibrosis with presence of myofibroblasts, CILP1, and POSTN-positive interstitial fibrosis only in HF versus non-HF human hearts. Comprehensive proteotranscriptomic profiles of SAN fibroblasts identified upregulation of genes and proteins promoting stiffer SAN extracellular matrix in HF hearts. Fibroblast-specific profiles generated by our proteotranscriptomic analyses of the human SAN provide a comprehensive framework for future studies to investigate the role of SAN-specific fibrosis in cardiac rhythm regulation and arrhythmias.

Two-Year Follow Up of the LATERAL Clinical Trial: A Focus on Adverse Events

BACKGROUND

The LATERAL trial validated the safety and efficacy of the thoracotomy approach for implantation of the HeartWare HVAD System, leading to Food and Drug Administration approval. We sought to analyze 24-month adverse event (AE) rates, including a temporal analysis of the risk profile, associated with the thoracotomy approach for the HVAD system.

METHODS

AEs from the LATERAL trial were evaluated over 2 years postimplant. Data was obtained from the Interagency Registry for Mechanically Assisted Circulatory Support database for 144 enrolled United States and Canadian patients. Temporal AE profiles were expressed as events per patient year.

RESULTS

During 162.5 patient years of support, there were 25 driveline infections (0.15 events per patient year), 50 gastrointestinal bleeds (0.31 events per patient year), and 21 strokes (0.13 events per patient year). Longitudinal AE analysis at follow-up intervals of <30 and 30 to 180 days, and 6 to 12 and 12 to 24 months revealed the highest AE rate at <30 days, with a decrease in total AEs within the first 6 months. After 6 months, most AE rates either stabilized or decreased through 2 years, including a 95% overall freedom from disabling stroke.

CONCLUSIONS

Two-year follow-up of the LATERAL trial revealed a favorable morbidity profile in patients supported with the HVAD system, as AE rates were more likely to occur in the first 30 days postimplant, and overall AE rates were significantly reduced after 6 months. Importantly, 2-year freedom from disabling stroke was 95%. These data further support the improving AE profile of patients on long-term HVAD support. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02268942.

Evaluating the Impact of Pulmonary Artery Obstruction After Lung Transplant Surgery: A Systematic Review and Meta-analysis

BACKGROUND

Pulmonary artery obstruction is an uncommon but significant complication after lung transplantation. Although numerous reports have documented its occurrence, the hemodynamic parameters associated with its presentation and diagnostic considerations remain ill-defined. This systematic review summarizes evidence in the literature surrounding pulmonary artery obstruction after lung transplantation surgery.

METHODS

Databases were searched for all articles and abstracts reporting on pulmonary artery obstruction. Data collected included the number of patients studied, patient characteristics, incidences of pulmonary artery obstruction, and timing and imaging modality used for diagnosis.

RESULTS

Thirty-four full-text citations were included in this review. The point prevalence of pulmonary artery obstruction was 3.66%. The peak pulmonary artery velocity associated with obstruction was found to be 2.60 ± 0.58 m/s. The diameter of the obstructed pulmonary artery predictive of poor outcomes was noted to be 0.78 ± 0.40 cm. The majority of diagnoses were made in the late postoperative period using pulmonary angiogram and transesophageal echocardiography. Overall, 76% of patients (47 of 62) required emergent procedural reintervention, and 23% of patients (14 of 62) diagnosed with pulmonary artery obstruction died during their hospital stay.

CONCLUSIONS

This systematic review underscores the importance of identifying pulmonary artery obstruction immediately after lung transplant surgery. The clinical implications of these results warrant the development of identification and management strategies for early detection of irregularities in pulmonary artery anastomosis in lung transplant patients.

Expert Consensus Paper: Lateral Thoracotomy for Centrifugal Ventricular Assist Device Implant

BACKGROUND

The increasing prevalence of heart failure has led to the expanded use of left ventricle assist devices (VADs) for end-stage heart failure patients worldwide. Technological improvements witnessed the development of miniaturized VADs and their implantation through less traumatic non-full sternotomy approaches using a lateral thoracotomy (LT). Although adoption of the LT approach is steadily growing, a lack of consensus remains regarding patient selection, details of the surgical technique, and perioperative management. Furthermore, the current literature does not offer prospective randomized studies or evidence-based guidelines for LT-VAD implantation.

METHODS

A worldwide group of LT-VAD experts was convened to discuss these key topics openly. After a PubMed search and review with all authors, a consensus was reached and an expert consensus paper on LT-VAD implantation was developed.

RESULTS

This document aims to guide clinicians in the selection of patients suitable for LT approaches and preoperative optimization. Details of operative techniques are described, with an overview of hemisternotomy and bilateral thoracotomy approaches. A review of the best surgical practices for placement of the pump, inflow cannula, and outflow graft provides advice on the best surgical strategies to avoid device malpositioning while optimizing VAD function. Experts' opinions on cardiopulmonary bypass, postoperative management, and approaches for pump exchange and explant are presented. This review also emphasizes the critical need for multidisciplinary teams and specific training.

CONCLUSIONS

This expert consensus review provides a compact guide to LT for VAD implantation, from patient selection through intraoperative tips and postoperative management.

Unmasking Arrhythmogenic Hubs of Reentry Driving Persistent Atrial Fibrillation for Patient-Specific Treatment

Background

Atrial fibrillation (AF) driver mechanisms are obscured to clinical multielectrode mapping approaches that provide partial, surface‐only visualization of unstable 3‐dimensional atrial conduction. We hypothesized that transient modulation of refractoriness by pharmacologic challenge during multielectrode mapping improves visualization of hidden paths of reentrant AF drivers for targeted ablation.

Methods and Results

Pharmacologic challenge with adenosine was tested in ex vivo human hearts with a history of AF and cardiac diseases by multielectrode and high‐resolution subsurface near‐infrared optical mapping, integrated with 3‐dimensional structural imaging and heart‐specific computational simulations. Adenosine challenge was also studied on acutely terminated AF drivers in 10 patients with persistent AF. Ex vivo, adenosine stabilized reentrant driver paths within arrhythmogenic fibrotic hubs and improved visualization of reentrant paths, previously seen as focal or unstable breakthrough activation pattern, for targeted AF ablation. Computational simulations suggested that shortening of atrial refractoriness by adenosine may (1) improve driver stability by annihilating spatially unstable functional blocks and tightening reentrant circuits around fibrotic substrates, thus unmasking the common reentrant path; and (2) destabilize already stable reentrant drivers along fibrotic substrates by accelerating competing fibrillatory wavelets or secondary drivers. In patients with persistent AF, adenosine challenge unmasked hidden common reentry paths (9/15 AF drivers, 41±26% to 68±25% visualization), but worsened visualization of previously visible reentry paths (6/15, 74±14% to 34±12%). AF driver ablation led to acute termination of AF.

Conclusions

Our ex vivo to in vivo human translational study suggests that transiently altering atrial refractoriness can stabilize reentrant paths and unmask arrhythmogenic hubs to guide targeted AF driver ablation treatment.

Early COVID-19 infection after lung transplantation

COVID-19, the clinical syndrome caused by the novel coronavirus, SARS-CoV-2, continues to rapidly spread, leading to significant stressors on global healthcare infrastructure. The manifestations of COVID-19 in solid organ transplant recipients are only beginning to be understood with cases reported to date in transplant recipients on chronic immunosuppression. Herein, we report the first case of COVID-19 in a lung transplant recipient in the immediate posttransplant period, and we describe the epidemiologic challenges in identifying the source of infection in this unique situation.

Optical Mapping-Validated Machine Learning Improves Atrial Fibrillation Driver Detection by Multi-Electrode Mapping

BACKGROUND

Atrial fibrillation (AF) can be maintained by localized intramural reentrant drivers. However, AF driver detection by clinical surface-only multielectrode mapping (MEM) has relied on subjective interpretation of activation maps. We hypothesized that application of machine learning to electrogram frequency spectra may accurately automate driver detection by MEM and add some objectivity to the interpretation of MEM findings.

METHODS

Temporally and spatially stable single AF drivers were mapped simultaneously in explanted human atria (n=11) by subsurface near-infrared optical mapping (NIOM; 0.3 mm² resolution) and 64-electrode MEM (higher density or lower density with 3 and 9 mm² resolution, respectively). Unipolar MEM and NIOM recordings were processed by Fourier transform analysis into 28 407 total Fourier spectra. Thirty-five features for machine learning were extracted from each Fourier spectrum.

RESULTS

Targeted driver ablation and NIOM activation maps efficiently defined the center and periphery of AF driver preferential tracks and provided validated annotations for driver versus nondriver electrodes in MEM arrays. Compared with analysis of single electrogram frequency features, averaging the features from each of the 8 neighboring electrodes, significantly improved classification of AF driver electrograms. The classification metrics increased when less strict annotation, including driver periphery electrodes, were added to driver center annotation. Notably, f1-score for the binary classification of higher-density catheter data set was significantly higher than that of lower-density catheter (0.81±0.02 versus 0.66±0.04, P<0.05). The trained algorithm correctly highlighted 86% of driver regions with higher density but only 80% with lower-density MEM arrays (81% for lower-density+higher-density arrays together).

CONCLUSIONS

The machine learning model pretrained on Fourier spectrum features allows efficient classification of electrograms recordings as AF driver or nondriver compared with the NIOM gold-standard. Future application of NIOM-validated machine learning approach may improve the accuracy of AF driver detection for targeted ablation treatment in patients.

Cost-Effectiveness of Thoracotomy Approach for the Implantation of a Centrifugal Left Ventricular Assist Device

This study reports the first analysis regarding cost-effectiveness of left ventricular assist device (LVAD) implantation via thoracotomy. Cost-effectiveness of LVADs implanted via the traditional surgical approach of sternotomy has been improved through the years because of technological advances, along with understanding the importance of patient selection and postimplant management have on positively affecting outcomes. Given the positive clinical outcomes of the thoracotomy approach, we seek to study the cost-effectiveness of a centrifugal LVAD via this less invasive approach. We developed a Markov model. Survival and quality of life inputs (QALY) for the LVAD arm were based on data from the LATERAL clinical trial. For the Medical Management arm, survival was derived from the Seattle Heart Failure Model. The heart transplant probability was derived from INTERMACS. Survival after heart transplantation used International Society for Heart and Lung Transplantation data. Cost inputs were calculated based on Medicare data and past literature. The incremental cost-effectiveness ratio was found to be $64,632 per quality adjusted life year and $57,891 per life year in the bridge to transplant indication. These results demonstrate further improvement in the overall cost-effectiveness of LVAD therapy and confirm implantation of LVADs via a less invasive approach as being cost-effective.

Pegylated-Catalase Is Protective in Lung Ischemic Injury and Oxidative Stress

BACKGROUND

Lung transplant ischemia-reperfusion injury is typified by toxic metabolites and oxygen free radicals leading to worse graft function. Catalase is an enzyme involved in oxidative-stress detoxification. We hypothesize that direct delivery of highly concentrated polyethylene glycol-catalase (PEG-CAT) during normothermic ex vivo lung perfusion (EVLP) significantly reduces ischemia-reperfusion injury.

METHODS

To demonstrate protection, primary culture porcine endothelial cells were treated with PEG-CAT (0 to 1250 U/mL) in a model of oxidative stress (400 μM H₂o₂). In vivo, rat lungs were subjected to 0 hours or 1 hour of warm ischemic injury and 2 hours of EVLP with or without PEG-CAT. Perfusate was collected throughout the perfusion duration and tissue was collected at the end. Tissue and perfusate underwent analysis for markers of apoptosis and a biometric signature of lung health.

RESULTS

Uptake of PEG-CAT into primary endothelial cells was demonstrated with Alexa Fluor 488-labeled PEG-CAT. Oxidatively stressed cells pretreated with PEG-CAT had significantly decreased cytotoxicity and caspase 3/7 activity and increased cell viability and cell membrane integrity. In a rat model of warm ischemia with EVLP, PEG-CAT improved allograft viability as measured by indications of cell membrane integrity (lactate dehydrogenase and hyaluronic acid), presence of vasoconstrictive peptides (endothelin-1 and big endothelin-1) released from endothelial cells, and reduced apoptosis (terminal deoxynucleotidyl transferase dUTP nick-end labeling).

CONCLUSIONS

In vitro and ex vivo, PEG-CAT protects against oxidative stress-induced cytotoxicity, maintains cellular metabolism, and mitigates lung ischemia-reperfusion in an experimental model. Together, these data suggest that PEG-CAT is a potential therapeutic target for donor organs at risk for ischemia-reperfusion injury.