Effects of Systemic and Device-Related Complications in Patients Bridged to Transplantation With Left Ventricular Assist Devices

BACKGROUND

The use of left ventricular assist devices (LVADs) as a bridge to heart transplantation has increased rapidly over the last 2 decades. We aim to explore the effect of pretransplant systemic and device-related complications on posttransplant survival for patients bridged with LVADs.

MATERIALS AND METHODS

The United Network of Organ Sharing (Organ Procurement and Transplantation Network) database was queried for all adult heart transplant recipients (aged ≥ 18 y) transplanted from April 1, 2015, to June 31, 2018. Device-related complications included thrombosis, device infection, device malfunction, life-threatening arrhythmia, and other device complications. Systemic complications included a new dialysis need or ventilator dependence between the time of listing and transplantation, transfusion, or systemic infection requiring treatment with intravenous antibiotics within 2 wk of transplantation.

RESULTS

A total of 2131 patients were identified as requiring LVAD support before transplantation. LVAD patients had high rates of preoperative systemic complications (53%) and high rates of device-related complications (42.7% experienced at least one device-related complication). Kaplan-Meier analysis revealed a significantly decreased 1-y survival for LVAD patients bridged to transplantation who experienced a pretransplant systemic complication (P = 0.041). Interestingly, preoperative device-related complications had no effect on 1-y posttransplantation survival (P = 0.93). Multivariate Cox modeling revealed that systemic complications were associated with a significantly increased risk of posttransplant mortality for LVAD patients (hazard ratio 1.45; P = 0.033).

CONCLUSIONS

Recipients who suffered a systemic complication while awaiting heart transplantation experienced higher short-term mortality rates. Device-related complications do not appear to impact posttransplantation outcomes.

Impact of the New Pulmonary Hypertension Definition on Heart Transplant Outcomes: Expanding the Hemodynamic Risk Profile

BACKGROUND

At the recent 6th World Symposium on Pulmonary Hypertension (PH), the definition of PH was redefined to include lower pulmonary artery pressures in the setting of elevated pulmonary vascular resistance (PVR). However, the relevance of this change to subjects with PH due to left-heart disease as well as the preoperative assessment of heart transplant (HT) recipients is unknown.

METHODS

The United Network for Organ Sharing database was queried to identify adult recipients who underwent primary HT from 1996 to 2015. Recipients were subdivided into those with mean pulmonary artery pressure (mPAP) < 25 mm Hg and ≥ 25 mm Hg. Exploratory univariable analysis was undertaken to identify candidate risk factors associated with 30-day and 1-year survival (conditional on 30-day survival) in recipients with mPAP < 25 mm Hg, and subsequently, parsimonious multivariable Cox proportional hazards models were constructed to assess the independent association with PVR.

RESULTS

Over the study period, 32,465 patients underwent HT, including 12,257 (38%) with mPAP < 25 mm Hg. The median age was 55 years (interquartile range, 47-62) and the median PVR was 1.5 Wood units (WU) (interquartile range, 1-2.2) in recipients with mPAP < 25 mm Hg. After controlling for confounders, PVR was independently associated with increased risk for 30-day mortality (hazard ratio, 1.16; 95% CI, 1.05-1.27; P < .01), but not conditional 1-year mortality (hazard ratio, 1.03; 95% CI, 0.94-1.12; P = .55). PVR ≥ 3 WU was associated with an absolute 1.9% increase in 30-day mortality in those with mPAP < 25 mm Hg, a similar risk to recipients with PVR ≥ 3 WU and mPAP ≥ 25 mm Hg.

CONCLUSIONS

Elevated PVR remains associated with a significant increase in the hazard for 30-day mortality after cardiac transplantation, even in the setting of lower pulmonary artery pressures. These data support the validity of the new definition of pulmonary hypertension.

Children's Heart Assessment Tool for Transplantation (CHAT) Score: A Novel Risk Score Predicts Survival After Pediatric Heart Transplantation

BACKGROUND

Given the shortage of donor organs in pediatric heart transplantation (HTx), pretransplant risk stratification may assist in organ allocation and recipient optimization. We sought to construct a scoring system to preoperatively stratify a patient's risk of one-year mortality after HTx.

METHODS

The United Network for Organ Sharing database was queried for pediatric (<18 years) patients undergoing HTx between 2000 and 2016. The population was randomly divided in a 4:1 fashion into derivation and validation cohorts. A multivariable logistic regression model for one-year mortality was constructed within the derivation cohort. Points were then assigned to independent predictors ( P < .05) based on relative odds ratios (ORs). Risk groups were established based on easily applicable, whole-integer score cutoffs.

RESULTS

A total of 5,700 patients underwent HTx; one-year mortality was 10.7%. There was a similar distribution of variables between derivation (n = 4,560) and validation (n = 1,140) cohorts. Of the 12 covariates included in the final model, nine were allotted point values. The low-risk (score 0-9), intermediate-risk (10-20), and high-risk (>20) groups had a 5.18%, 10%, and 28% risk of one-year mortality ( P < .001), respectively. Both intermediate-risk (OR = 2.46, 95% confidence interval [95% CI]: 1.93-3.15; P < .001) and high-risk (OR = 9.24, 95% CI: 6.92-12.35; P < .001) scores were associated with an increased risk of one-year mortality when compared to the low-risk group.

CONCLUSIONS

The Children's Heart Assessment Tool for Transplantation score represents a pediatric-specific, recipient-based system to predict one-year mortality after HTx. Its use could assist providers in identification of patients at highest risk of poor outcomes and may aid in pretransplant optimization of these children.

Variation in Platelet Transfusion Practices in Cardiac Surgery

Objective

Although the morbidity associated with red blood cell transfusion in cardiac surgery has been well described, the impacts of platelet transfusion are less clearly understood. Given the conflicting results of prior studies, we sought to investigate the impact of platelet transfusion on outcomes after cardiac surgery across institutions in Maryland.

Methods

Using a multiinstitutional statewide database created by the Maryland Cardiac Surgery Quality Initiative, we retrospectively analyzed data from 10,478 patients undergoing isolated coronary artery bypass across 10 centers. Platelet transfusion practices were compared between institutions. Multivariate logistic regression model was used to analyze the association between platelet transfusion and 30-day mortality and postoperative complications.

Results

Rates of platelet transfusion varied between institutions from 4.4% to 24.7% ( P < 0.001), a difference that remained statistically significant in propensity score–matched cohorts. Among patients on preoperative antiplatelet therapy, transfusion rates varied from 8.5% to 46.4% ( P < 0.001). There was no statistically significant relationship between case volume and transfusion rates ( P = 0.815). In multivariate logistic regression, platelet transfusion was associated with increased risk of 30-day mortality (OR 2.43, P = 0.008), postoperative pneumonia (OR 2.21, P = 0.004), prolonged intubation (OR 2.05, P < 0.001), and readmission (OR 1.43, P = 0.039).

Conclusions

Significant variation existed in platelet transfusion rates between institutions, even after controlling for various risk factors. This variation may be associated with increased mortality and length of stay. Further study is warranted to better understand risks associated with platelet transfusion. Standardizing practice may help reduce risk and conserve resources.

Comparing Frailty Markers in Predicting Poor Outcomes after Transcatheter Aortic Valve Replacement

INTRODUCTION

Frailty is an important component of risk prognostication in transcatheter aortic valve replacement (TAVR). Objective markers of frailty, including sarcopenia, the modified Frailty Index (mFI), and albumin levels, have emerged, but little is known how such markers compare to each other in predicting outcomes after TAVR. We sought to define and compare these markers in predicting long-term outcomes after TAVR.

METHODS

Patients who underwent TAVR at our institution from 2011 to 2016 were included. Indexed cross-sectional areas of the lumbosacral muscles on preoperative computed tomography scans were used to assess sarcopenia. Optimal cutoffs for sarcopenia were defined using a statistically validated method. mFI was calculated using an 11-point scale of clinical characteristics. The primary outcome was 2-year all-cause mortality. Adjusted survival analysis was used to analyze outcomes.

RESULTS

A total of 381 patients were included in this study. Sarcopenia of the psoas muscles was associated with an increased risk of mortality on univariate (HR: 2.3, P = 0.01) and multivariate (HR: 2.5, P = 0.01) analysis. Sarcopenia of the paravertebral muscles was associated with increased risk of mortality only on univariate analysis (HR: 2.1, P = 0.03). Increased preoperative albumin levels were associated with decreased risk of mortality on univariate (HR: 0.3, P < 0.01) and multivariate analysis (HR: 0.3, P < 0.01). The (mFI) was not associated with mortality on univariate or multivariate analysis.

DISCUSSION

Novel cutoffs for sarcopenia of the psoas muscles were determined and associated with decreased survival after TAVR. Sarcopenia and albumin levels may be better tools for risk prediction than mFI in TAVR.

Size Mismatching Increases Mortality After Lung Transplantation in Preadolescent Patients

BACKGROUND

The effect of size mismatch between donor and recipient in pediatric lung transplantation (PLTx) is currently unknown. Previous studies in adults have suggested that oversized allografts are associated with improved outcomes after lung transplantation. We investigated this relationship to quantify its effect on posttransplant outcomes in children.

METHODS

The United Network of Organ Sharing database was queried for preadolescent (age <13 years) patients undergoing PLTx. Donor-to-recipient height, weight, and predictive total lung capacity (pTLC; ages 4 to 13; pTLC = 0.160 x exp[0.021 x height]) ratios were calculated. Exploratory analysis was performed to identify disjoint intervals at which survival was statistically different. Patients were categorized as well-matched, undersized, or oversized. Multivariate Cox proportional hazard regression modeling assessed the adjusted effect of mismatching on mortality. Survival analysis was performed using the Kaplan-Meier method.

RESULTS

The analysis included 540 children. One-year mortality was higher with a height mismatch of 5% or less (hazard ratio [HR], 2.97; p = 0.001) and above 5% (HR, 2.22; p = 0.009). Similarly, 1-year mortality was worse with weight mismatch of 10% or less (HR, 1.99; p = 0.035) and above 10% (HR, 2.04; p = 0.028). On unadjusted analysis, a pTLC ratio of less than 0.9 was associated with worse survival (p = 0.017). This finding persisted after multivariate risk adjustment (HR, 2.93; p = 0.02). Contrary to findings in adults, an oversized allograft (pTLC ratio > 1.1) was not associated with improved survival (HR, 1.95; p = 0.147).

CONCLUSIONS

In preadolescent children undergoing PLTx, size mismatching is associated with increased death. Our findings differ from studies in adults, which demonstrated improved survival associated with oversized allografts. Accordingly, well-matched allografts should be prioritized when assessing donor-recipient pairs for transplantation.

A Novel Risk Score to Predict New Onset Atrial Fibrillation in Patients Undergoing Isolated Coronary Artery Bypass Grafting

BACKGROUND

Atrial fibrillation (AF) is common after cardiac surgery and contributes to increased morbidity and mortality. Our objective was to derive and validate a predictive model for AF after CABG in patients, incorporating novel echocardiographic and laboratory values.

METHODS

We retrospectively reviewed patients at our institution without preexisting dysrhythmia who underwent on-pump, isolated CABG from 2011-2015. The primary outcome was new onset AF lasting >1 hour on continuous telemetry or requiring medical treatment. Patients with a preoperative echocardiographic measurement of left atrial diameter were included in a risk model, and were randomly divided into derivation (80%) and validation (20%) cohorts. The predictors of AF after CABG (PAFAC) score was derived from a multivariable logistic regression model by multiplying the adjusted odds ratios of significant risk factors (P < .05) by a factor of 4 to derive an integer point system.

RESULTS

1307 patients underwent isolated CABG, including 762/1307 patients with a preoperative left atrial diameter measurement. 209/762 patients (27%) developed new onset AF including 165/611 (27%) in the derivation cohort. We identified four risk factors independently associated with postoperative AF which comprised the PAFAC score: age > 60 years (5 points), White race (5 points), baseline GFR < 90 mL/min (4 points) and left atrial diameter > 4.5 cm (4 points). Scores ranged from 0-18. The PAFAC score was then applied to the validation cohort and predicted incidence of AF strongly correlated with observed incidence (r = 0.92).

CONCLUSION

The PAFAC score is easy to calculate and can be used upon ICU admission to reliably identify patients at high risk of developing AF after isolated CABG.

Surgical Closure of Patent Ductus Arteriosus in Premature Neonates Weighing Less Than 1,000 grams: Contemporary Outcomes

Objective:

The safety of surgical closure of patent ductus arteriosus (PDA) in very low birth weight premature neonates has been questioned because of associated morbidities. However, these studies are vulnerable to significant bias as surgical ligation has historically been utilized as “rescue” therapy. The objective of this study was to review our institutions’ outcomes of surgical PDA ligation.

Methods:

All neonates with operative weight of ≤1.00 kg undergoing surgical PDA ligation from 2003 to 2015 were analyzed. Records were queried to identify surgical complications, perioperative morbidity, and mortality. Outcomes included pre- and postoperative ventilator requirements, pre- and postoperative inotropic support, acute kidney injury, surgical complications, and 30-day mortality.

Results:

One hundred sixty-six preterm neonates underwent surgical ligation. One hundred twenty-one (70.3%) had failed indomethacin closure. One hundred sixty-four (98.8%) patients required mechanical ventilation prior to surgery. At 17 postoperative days, freedom from the ventilator reached 50%. Of 109 (66.4%) patients requiring prolonged preoperative inotropic support, 59 (54.1%) were liberated from inotropes by postoperative day 1. Surgical morbidity was encountered in four neonates (2.4%): two (1.2%) patients had a postoperative pneumothorax requiring tube thoracostomy, one (0.6%) patient had a recurrent laryngeal nerve injury, and one (0.6%) patient had significant intraoperative bleeding. The 30-day all-cause mortality was 1.8% (n = 3); no deaths occurred intraoperatively.

Conclusion:

In this retrospective investigation, surgical PDA closure was associated with low 30-day mortality and minimal morbidity and resulted in rapid discontinuation of inotropic support and weaning from mechanical ventilation. Given the safety of this intervention, surgical PDA ligation merits consideration in the management strategy of the preterm neonate with a PDA.

Diastolic dysfunction is common and predicts outcome after cardiac surgery

Background

Diastolic dysfunction (DD) identified on echocardiography predicts mortality after cardiac surgery, however the most useful diastolic parameters for assessment and the association of DD with prolonged mechanical ventilation, ICU re-admission, and hospital length of stay are not established.

Methods

We included patients that underwent coronary artery bypass grafting (CABG), aortic valve replacement (AVR) or a combined procedure (CAB-AVR) from 2010 to 2016, and who had preoperative transthoracic echocardiography (TTE) at our institution within 6 months of the operation. Diastolic function was graded using the transmitral E and A waves and the septal tissue Doppler velocity. We performed logistic regression to assess the association of grade of DD with a composite endpoint of death, prolonged mechanical ventilation, ICU readmission during hospitalization, and hospital length of stay longer than 14 days.

Results

Between 2010 and 2016, 577 patients were eligible for inclusion. DD was common, with 42% of the cohort manifesting grade II or grade III DD. Rates of death and prolonged ventilation increased across grades of DD and across quartiles of increasing LV filling pressure, assessed by the E/e’ ratio. Adjusting for age, sex, procedure, systolic and diastolic function, both systolic (odds ratio 0.68 95% CI 0.55–0.85 per inter-quartile increase in LVEF) and diastolic function (odds ratio 1.31 95% CI 1.04–1.66 per increasing DD grade) both independently predicted outcome.

Conclusion

Diastolic dysfunction is common among patients undergoing cardiac surgery and is associated with death, prolonged mechanical ventilation, and prolonged hospital and ICU length of stay independent of systolic dysfunction.

Traumatically Brain-Injured Donors and the Impact on Lung Transplantation Survival

BACKGROUND

Concern has been raised over inferior lung transplantation survival associated with traumatic brain injury (TBI) organ donors. Our purpose was to explore the relationship between TBI donors and lung transplantation survival in the lung allocation score (LAS) era.

METHODS

We queried the United Network for Organ Sharing Scientific Registry of Transplant Recipients and identified all adult (≥18 years) lung transplantations performed from May 4, 2005, to December 31, 2015. Recipients were dichotomized based on donor cause of death, TBI versus non-TBI, propensity score across eight variables (final LAS, intensive care unit admission before transplantation, extracorporeal membrane oxygenation before transplantation, donor age 50 years or older, cytomegalovirus antibody recipient^-/donor⁺, ischemia time, annual center transplantation volume, single versus double lung transplantation), and matched 1:1 without replacement. Our primary outcomes were survival at 1, 3, and 5 years by Kaplan-Meier method.

RESULTS

A total of 17,610 patients underwent isolated lung transplantation over the study period at 75 different transplantation centers. TBI was the leading cause of death in the donor population: 47% of all donors. Propensity score matching generated 6,782 well-matched donor TBI versus non-TBI pairs (all covariate p > 0.2). Risk-adjusted survival was similar between recipients of TBI donors versus non-TBI donors at 1 year (86% versus 86%, log-rank p = 0.27), 3 years (68% versus 68%, log-rank p = 0.47), and 5 years (55% versus 54%, log-rank p = 0.40).

CONCLUSIONS

In the largest analysis of TBI donors and the impact on lung transplantation survival to date, we found similar survival out to 5 years in lung transplant recipients of TBI versus non-TBI donors, alleviating concerns over continued transplantation with this unique donor population.

Imatinib Is Protective Against Ischemia-Reperfusion Injury in an Ex Vivo Rabbit Model of Lung Injury

BACKGROUND

Ischemia-reperfusion injury is characterized by an increase in oxidative stress and leads to significant morbidity and death. The tyrosine kinase c-Abl is activated by oxidative stress and mediates processes that affect endothelial barrier function. We hypothesized treatment with the c-Abl inhibitor imatinib would be protective against ischemia-reperfusion injury in our ex vivo rabbit model.

METHODS

Heart-lung blocs were harvested from rabbits and stored in cold in Perfadex (Vitrolife, Englewood, CO) for 18 hours. Blocs were reperfused for 2 hours in an ex vivo circuit with donor rabbit blood alone (untreated group, n = 7) or donor rabbit blood and 4 mg imatinib (treatment group, n = 10). Serial clinical variables measured every 15 minutes (arterial oxygen and carbon dioxide tension and mean pulmonary artery pressures) and biochemistry of tissue samples before and after reperfusion were assessed.

RESULTS

Compared with untreated lungs, imatinib treatment improved physiologic parameters, including oxygen, carbon dioxide, and pulmonary artery pressures. Imatinib-treated lungs had less vascular barrier dysfunction as quantified by wet-to-dry weight ratios and bronchoalveolar lavage protein concentrations. Treated lungs showed less inflammation as measured by bronchoalveolar lavage myeloperoxidase assay, less mitochondrial reactive oxygen species production, and increased antioxidant catalase levels. Finally, imatinib protected lungs from DNA damage and p53 upregulation.

CONCLUSIONS

Imatinib treatment significantly improved the physiologic performance of reperfused lungs and biochemical indicators associated with reperfusion injury in this ex vivo model. Further study is necessary to elucidate the mechanism of tyrosine kinase inhibition in lungs exposed to ischemia and reperfusion.

Blood utilization in revision versus first-time cardiac surgery: an update in the era of patient blood management

BACKGROUND

Relative to first-time (primary) cardiac surgery, revision cardiac surgery is associated with increased transfusion requirements, but studies comparing these cohorts were performed before patient blood management (PBM) and blood conservation measures were commonplace. The current study was performed as an update to determine if this finding is still evident in the PBM era.

STUDY DESIGN AND METHODS

Primary and revision cardiac surgery cases were compared in a retrospective database analysis at a single tertiary care referral center. Two groups of patients were assessed: 1) those having isolated coronary artery bypass (CAB) or valve surgery and 2) all other cardiac surgeries. Intraoperative and whole hospital transfusion requirements were assessed for the four major blood components.

RESULTS

Compared to the primary cardiac surgery patients, the revision surgery patients required approximately twofold more transfused units intraoperatively (p < 0.0001) and approximately two- to threefold more transfused units for the whole hospital stay (p < 0.0001). Intraoperative massive transfusion (>10 red blood cell [RBC] units) was substantially more frequent with revision versus primary cardiac surgery (2.6% vs. 0.1% [p < 0.0001] for isolated CAB or valve and 6.1% vs. 1.9% [p < 0.0001] for all other cardiac surgeries). Revision surgery was an independent risk factor for both moderate (6-10 RBC units) and massive intraoperative transfusion.

CONCLUSIONS

In the era of PBM, with restrictive transfusion strategies and a variety of methods for blood conservation, revision cardiac surgery patients continue to have substantially greater transfusion requirements relative to primary cardiac surgery patients. This difference in transfusion requirement was greater than what has been previously reported in the pre-PBM era.

Impaired Renal Function Should Not Be a Barrier to Transplantation in Patients With Cystic Fibrosis

BACKGROUND

Previous studies have demonstrated an association between pretransplantation renal dysfunction (PRD) and increased mortality after lung transplantation (LT). The purpose of this study was to determine whether PRD impacts survival after LT in patients with cystic fibrosis (CF).

METHODS

We queried the United Network for Organ Sharing (UNOS) database to identify all adult (≥18 years) recipients with CF who underwent isolated LT from May 4, 2005 to December 31, 2014. We separated recipients into those with and those without PRD (glomerular filtration rate [GFR] ≤60 mL/min). We excluded patients who required dialysis before transplantation. Kaplan-Meier analysis was used to assess unadjusted survival differences. Cox proportional hazards modeling was then performed across 26 variables to assess the risk-adjusted impact of PRD on 1-, 3-, and 5-year mortality.

RESULTS

Isolated LT was performed on 1,830 patients with CF; 17 patients were excluded because of pretransplantation dialysis. Eighty-two of 1,813 patients (4.5%) had PRD (GFR ≤60 mL/min). Kaplan-Meier analysis revealed no survival differences between PRD and non-PRD groups at 1 year (85.3% versus 89.5%; log-rank p = 0.23), 3 years (71.0% versus 72.5%; p = 0.57), or 5 years (63.3% versus 59.8%; p = 0.95). After risk adjustment, PRD was not independently associated with an increased hazard for mortality at 1 year (hazard ratio [HR], 1.38 [95% confidence interval [CI], 0.74-2.58]; p = 0.31), 3 years (HR, 1.44 [95% CI, 0.92-2.24]; p = 0.11), or 5 years (HR, 1.30 [95% CI, 0.86-1.94]; p = 0.29).

CONCLUSIONS

Although PRD has historically served as a relative contraindication to LT, our study is the first to suggest that among CF recipients, PRD was not associated with increased hazard for mortality out to 5 years after LT.

A Novel Risk Score to Predict the Need for Nutrition Support After Cardiac Surgery

BACKGROUND

In specific patients, early postoperative nutrition mitigates malnutrition-related morbidity and mortality. The goal of this study was to develop and validate a prediction score designed to stratify patients immediately after cardiac surgery according to risk for nutrition support (NS).

METHODS

We identified adult cardiac surgery patients at our institution in 2012 requiring postoperative NS, enteral or parenteral. Using multivariable logistic regression modeling, we developed a Johns Hopkins Hospital Nutrition Support (JHH NS) score from relative odds ratios generated by variables that independently predicted the need for NS. The JHH NS score was then prospectively validated using all patients undergoing cardiac surgery in 2015.

RESULTS

Among 1,056 patients in the derivation cohort, 87 (8%) required postoperative NS. Seven variables were identified on multivariable analysis as independent predictors of NS need and were used to create the JHH NS score. Scores ranged from 0 to 36. Each 1-point increase in the JHH NS score was associated with a 20% increase in the risk of requiring NS (odds ratio 1.20, p < 0.001). The c-statistic of the regression model for NS was 0.85. In all, 115 of 1,336 patients (8.6%) in the validation cohort required NS. Observed rates of NS in the validation group correlated positively with predicted rates (r = 0.89).

CONCLUSIONS

The JHH NS score reliably stratified patients at risk for the need for postoperative NS. This easily calculable and highly predictive screening tool may expedite timing of initiation of NS in patients at high risk for not being able to physically take in adequate nutrition.

Selective Localization of a Novel Dendrimer Nanoparticle in Myocardial Ischemia-Reperfusion Injury

BACKGROUND

Dendrimer nanoparticle therapies represent promising new approaches to drug delivery, particularly in diseases associated with inflammatory injury. However, their application has not been fully explored in models of acute myocardial ischemia (MI) and reperfusion injury.

METHODS

White male New Zealand rabbits underwent left thoracotomy with 30-minute temporary left anterior descending artery occlusion and MI confirmed by electrocardiography and histology (MI rabbits, n = 9), or left thoracotomy and pericardial opening for 30 minutes but no left anterior descending artery occlusion (control [C] rabbits, n = 9) rabbits. Following the 30-minute period, a dendrimer (generation 6 dendrimer conjugated to cyanine-5 fluorescent dye [G6-Cy5], 6.7 nm diameter) was administered intravenously and the chest closed in layers. Animals were sacrificed at 3 hours (3 MI, 3 C), 24 hours (3 MI, 3 C), or 48 hours (3 MI, 3 C) postsurgery.

RESULTS

As compared to controls, MI rabbits had twofold G6-Cy5 uptake in the myocardial anterior wall as compared to the same region in nonischemic control rabbits at 24 hours postsurgery (6.01 ± 0.57 μg/g versus 2.85 ± 0.85 μg/g; p = 0.04). This trend was also present at 48 hours (6.38 ± 1.53 μg/g versus 3.95 ± 0.60 μg/g, p = 0.21) and was qualitatively evident on confocal microscopy. G6-Cy5 half-life in serum was approximately 12 hours, with 22% of the injected G6-Cy5 dose remaining at 48 hours.

CONCLUSIONS

This study demonstrates for the first time that dendrimer nanodevices selectively localize in ischemic as compared to healthy myocardium. This indicates that dendrimer nanodevices are promising agents to deliver drugs specifically to the ischemic myocardium to attenuate the injury. Subsequent studies will assess the efficacy of a dendrimer-drug conjugate in ameliorating reperfusion injury following MI.

Simulated Regionalization of Heart and Lung Transplantation in the United States

We simulated the impact of regionalization of isolated heart and lung transplantation within United Network for Organ Sharing (UNOS) regions. Overall, 12 594 orthotopic heart transplantation (OHT) patients across 135 centers and 12 300 orthotopic lung transplantation (OLT) patients across 67 centers were included in the study. An algorithm was constructed that "closed" the lowest volume center in a region and referred its patients to the highest volume center. In the unadjusted analysis, referred patients were assigned the highest volume center's 1-year mortality rate, and the difference in deaths per region before and after closure was computed. An adjusted analysis was performed using multivariable logistic regression using recipient and donor variables. The primary outcome was the potential number of lives saved at 1 year after transplant. In adjusted OHT analysis, 10 lives were saved (95% confidence interval [CI] 9-11) after one center closure and 240 lives were saved (95% CI 209-272) after up to five center closures per region, with the latter resulting in 1624 total patient referrals (13.2% of OHT patients). For OLT, lives saved ranged from 29 (95% CI 26-32) after one center closure per region to 240 (95% CI 224-256) after up to five regional closures, but the latter resulted in 2999 referrals (24.4% of OLT patients). Increased referral distances would severely limit access to care for rural and resource-limited populations.

Generation-6 hydroxyl PAMAM dendrimers improve CNS penetration from intravenous administration in a large animal brain injury model

Hypothermic circulatory arrest (HCA) provides neuroprotection during cardiac surgery but entails an ischemic period that can lead to excitotoxicity, neuroinflammation, and subsequent neurologic injury. Hydroxyl polyamidoamine (PAMAM) dendrimers target activated microglia and damaged neurons in the injured brain, and deliver therapeutics in small and large animal models. We investigated the effect of dendrimer size on brain uptake and explored the pharmacokinetics in a clinically-relevant canine model of HCA-induced brain injury. Generation 6 (G6, ~6.7nm) dendrimers showed extended blood circulation times and increased accumulation in the injured brain compared to generation 4 dendrimers (G4, ~4.3nm), which were undetectable in the brain by 48h after final administration. High levels of G6 dendrimers were found in cerebrospinal fluid (CSF) of injured animals with a CSF/serum ratio of ~20% at peak, a ratio higher than that of many neurologic pharmacotherapies already in clinical use. Brain penetration (measured by drug CSF/serum level) of G6 dendrimers correlated with the severity of neuroinflammation observed. G6 dendrimers also showed decreased renal clearance rate, slightly increased liver and spleen uptake compared to G4 dendrimers. These results, in a large animal model, may offer insights into the potential clinical translation of dendrimers.

Risk Factors for De Novo Malignancy Following Lung Transplantation

Risk factors for non-skin cancer de novo malignancy (DNM) after lung transplantation have yet to be identified. We queried the United Network for Organ Sharing database for all adult lung transplant patients between 1989 and 2012. Standardized incidence ratios (SIRs) were computed by comparing the data to Surveillance, Epidemiology, and End Results Program data after excluding skin squamous/basal cell carcinomas. We identified 18 093 adult lung transplant patients; median follow-up time was 1086 days (interquartile range 436-2070). DNMs occurred in 1306 patients, with incidences of 1.4%, 4.6%, and 7.9% at 1, 3, and 5 years, respectively. The overall cancer incidence was elevated compared with that of the general US population (SIR 3.26, 95% confidence interval [CI]: 2.95-3.60). The most common cancer types were lung cancer (26.2% of all malignancies, SIR 6.49, 95% CI: 5.04-8.45) and lymphoproliferative disease (20.0%, SIR 14.14, 95% CI: 9.45-22.04). Predictors of DNM following lung transplantation were age (hazard ratio [HR] 1.03, 95% CI: 1.02-1.05, p < 0.001), male gender (HR 1.20, 95% CI: 1.02-1.42, p = 0.03), disease etiology (not cystic fibrosis, idiopathic pulmonary fibrosis or interstitial lung disease, HR 0.59, 95% CI 0.37-0.97, p = 0.04) and single-lung transplantation (HR 1.64, 95% CI: 1.34-2.01, p < 0.001). Significant interactions between donor or recipient smoking and single-lung transplantation were noted. On multivariable survival analysis, DNMs were associated with an increased risk of mortality (HR 1.44, 95% CI: 1.10-1.88, p = 0.009).

Accumulation and cellular localization of nanoparticles in an ex vivo model of acute lung injury

BACKGROUND

The benefit of nanomedicine in mitigating acute lung injury (ALI) is currently unknown. Therefore, we introduced the generation IV polyamidoamine dendrimers with neutral surface property (dendrimer) into our established ex vivo animal model and sought to determine their biodistribution to define their cellular uptake profile and to evaluate their potential as a drug delivery candidate for the treatment of ischemia-reperfusion-induced ALI.

METHODS

Eight rabbit heart-lung blocks were harvested and exposed to 18 h of cold ischemia. The heart-lung blocks were then reperfused with rabbit donor blood. Dendrimer was conjugated to fluorescein isothiocyanate (D-FITC) for localization and quantification studies. D-FITC (30 mg or 150 mg) was injected into the bypass circuit and baseline, 1- and 2-h tissue samples were obtained to determine percent uptake. Low (10×) and high (40×) magnification images were obtained using confocal microscopy to confirm the accumulation and to determine the cellular targets of the dendrimer.

RESULTS

Four heart-lung blocks were exposed to 30 mg and four to 150 mg of D-FITC. After adjusting for dry weight, the mean uptake in the 30 and 150 mg samples after 2 h of reperfusion were 0.79 ± 0.16% and 0.39 ± 0.22% of perfused doses, respectively. Confocal imaging demonstrated dendrimer uptake in epithelial cells and macrophages.

CONCLUSIONS

Fluorescently tagged dendrimers demonstrated injury-dependent tissue accumulation in a variety of different cell types. This unique approach will allow conjugation to and delivery of multiple agents with the potential of mitigating ALI injury while avoiding systemic toxicity.

Planned Versus Unplanned Reexplorations for Bleeding: A Comparison of Morbidity and Mortality

BACKGROUND

Mediastinal reexplorations for bleeding are associated with significant morbidity and mortality. This study hypothesized that bleeding patients who undergo delayed chest closure after an initial operation experience similar outcomes in comparison with patients who have initial chest closure and later require an unplanned reexploration.

METHODS

This study included all patients in the Johns Hopkins University School of Medicine (Baltimore, MD) institutional Society of Thoracic Surgeons (STS) database who underwent cardiac surgical procedures or thoracic transplantation from 2011 to June 2014, had an intraoperative red blood cell transfusion requirement of 2 units or more, and required mediastinal reexploration for bleeding. Reexplorations were classified as planned (temporary chest closure for a planned "second look") or unplanned (initial sternal closure and subsequent reexploration). The two groups were then propensity matched. The primary outcome was 30-day mortality. Secondary outcomes were major complication rates, hospital length of stay, duration of mechanical ventilation, and incidence of postoperative pneumonia and cardiac arrest.

RESULTS

Among 3,293 patients, 110 (3.3%) met inclusion criteria and required mediastinal reexploration for bleeding. This group included 62 planned (56%) and 48 unplanned (44%) reexplorations. After propensity matching 30 pairs of patients across 16 variables, operative mortality rates were comparable (37% vs 37%; p = 1.00) between unplanned and planned reexploration cohorts. There were no differences in rates of deep sternal wound infection, renal failure, postoperative hospital length of stay, pneumonia, or cardiac arrest, with the exception of a higher rate of prolonged intubation (93% vs 53%; p < 0.01) in the planned reexploration group.

CONCLUSIONS

Delayed sternal closure is a safe alternative to initial definitive chest closure when concern exists for postoperative bleeding.

Incidence of late atrial fibrillation in bilateral lung versus heart transplants

BACKGROUND

We compared the incidence of late-onset atrial fibrillation in orthotopic heart transplant recipients and bilateral orthotopic lung transplant recipients.

METHODS

We reviewed the records of all heart and lung transplant operations carried out in our institution between 1995 and 2015. We performed 1:1 propensity-matching based on patient age, sex, body mass index, and hypertension. Our primary outcome, late-onset atrial fibrillation, was defined as atrial fibrillation occurring after discharge following hospitalization for transplantation.

RESULTS

Over the study period, 397 orthotopic heart transplants and 240 bilateral orthotopic lung transplants were performed. Propensity matching resulted in 173 pairs who were matched with respect to age, sex, body mass index, and preoperative hypertension. The median follow-up was 5.3 years for heart transplant patients and 3.1 years for lung transplant patients. Late-onset atrial fibrillation occurred in 11 heart transplant patients (5 of whom had biopsy-proven evidence of rejection) and 19 lung transplant patients (2 of whom had biopsy-proven evidence of rejection). On Kaplan-Meier analysis, the probability of late-onset atrial fibrillation at 5 years was 4.3% for heart transplant patients vs. 13.9% for lung transplant patients (log-rank p = 0.01).

CONCLUSIONS

We documented an increased probability of late-onset atrial fibrillation among bilateral orthotopic lung transplant patients compared to orthotopic heart transplant patients. This was a hypothesis-generating study that suggests a potential role for cardiac autonomic innervation in the genesis of atrial fibrillation.

Phase of Care Mortality Analysis: A Unique Method for Comparing Mortality Differences Among Transcatheter Aortic Valve Replacement and Surgical Aortic Valve Replacement Patients

The objective of this study is based on the phase of care mortality analysis (POCMA), an effective tool to evaluate the root cause of in-hospital mortality in cardiac surgery patients. POCMA has not been used to compare operative mortalities among transcatheter aortic valve replacement (TAVR) and surgical aortic valve replacement (SAVR) populations, and may provide insight that could affect patient safety initiatives and improve outcomes in aortic valve surgery. We included patients who underwent TAVR or isolated SAVR between 2011 and March 31, 2015 and did not survive the index hospitalization. A multidisciplinary heart team made POCMA assignments as part of the weekly morbidity and mortality conference, pinpointing the phase of care and subcategory that directly caused or had the greatest effect on each mortality. During the study period, 240 patients underwent TAVR and 530 underwent SAVR. Unadjusted mortality rates were significantly higher in the TAVR group, 5.0% (n = 12) compared with SAVR, 1.9% (n = 10) (P = 0.016). TAVR deaths by phase of care are as follows: 0 for preoperative, 9 (72.8%) for intraoperative, 2 (18.2%) for postoperative intensive care unit, and 1 (9.1%) for postoperative floor. By comparison, 4 (40%) SAVR deaths had a root cause in the preoperative phase, 1 (10%) in the intraoperative phase, and 5 (50%) in the postoperative intensive care unit phase. POCMA is a novel method of categorizing in-hospital mortalities. Our single institution review revealed that patients who underwent TAVR more often expired because of intraoperative technical issues, whereas SAVR deaths were typically the result of patient selection or postoperative complications.

Differential outcomes of type A dissection with malperfusion according to affected organ system

BACKGROUND

The management of malperfusion in patients with acute Stanford type A aortic dissection is controversial. We sought to determine the rate of resolution of malperfusion following primary repair of the dissection and to identify anatomic sites of malperfusion that may require additional management.

METHODS

We reviewed the hospital records of patients who presented to our institution with acute type A aortic dissection. Patient demographics, operative details and post-operative course were retrospectively extracted from our institutional electronic database. Depending upon the anatomic site, malperfusion was identified by a combination of radiographic and clinical definitions. Data were analyzed using standard univariable and multivariable methods.

RESULTS

Between 1997-2013, 101 patients underwent repair of an acute type A dissection. Thirty-day mortality was 14.9% (15/101); there were five intraoperative deaths. There was no difference in 30-day mortality between patients with or without malperfusion (15.4% vs. 14.7%, P=0.93). Twenty-five patients (24.7%), who survived surgery, presented with 31 sites of malperfusion. Anatomic sites included extremities [14], renal [10], cerebral [5] and intestinal [2]. Of these 31 sites, malperfusion resolved in 18 (58.1%) with primary aortic repair. Renal malperfusion resolved radiographically in 80.0%, with no difference in the incidence of insufficiency (44.0% vs. 35.2%; P=0.44) or dialysis (20.0% vs. 15.5%; P=0.61) between malperfusion and non-malperfusion patients. Extremity malperfusion resolved postoperatively in six out of 14 patients. Of the remaining eight, concomitant revascularization was performed in four, one had an amputation and three required postoperative interventions. Advanced patient age (OR: 1.06, 95% CI: 1.01-1.12, P=0.02) was an independent predictor of 30-day mortality, while preoperative malperfusion was not (OR: 0.77, 95% CI: 0.18-3.31, P=0.73).

CONCLUSIONS

Malperfusion complicating acute type A dissection can be managed in many patients by aortic replacement alone with low overall mortality. Most cases of renal and cerebral malperfusion resolved following aortic surgery. Revascularization was frequently necessary in patients with extremity malperfusion. Patients presenting with intestinal ischemia had very poor outcomes. A patient-specific approach is recommended in such complex patients.

Predictors of Late-Onset Atrial Fibrillation Following Isolated Mitral Valve Repairs in Patients With Preserved Ejection Fraction

BACKGROUND

We sought to determine the incidence of and risk factors for late-onset atrial fibrillation (LOAF) in patients with preserved ejection fractions undergoing mitral valve repair

METHODS

We included patients undergoing isolated mitral valve repair (MVR) for degenerative disease between 1997-2014 at our institution with EF ≥60%. Patients who had AF preoperatively were excluded from the final analysis. Our primary outcome, LOAF, was defined as AF occurring after discharge following MVR (≥9 days).

RESULTS

223 patients were included in the study with a mean follow-up of 4.8 ± 4.6 years. A total of 25 patients developed LOAF, and freedom from LOAF was 93.9% at one year, and 87.3% at five years. Patients developing LOAF were of similar mean age (58 vs. 63 years in controls, p = 0.08) and had similar preoperative comorbidities, but did show a trend toward larger left atrial diameter (5.1 vs. 4.7 cm, p = 0.11). After risk adjustment with Cox regression analysis, only increasing left atrial size was associated with LOAF (HR 1.63, p = 0.04). On follow-up, 29 patients (10.8%) developed moderate or greater mitral regurgitation at a mean of 2.2 years. Using a mixed-effects model, we were unable to detect an association between recurrent mitral regurgitation following MVR and LOAF (OR 1.36, p = 0.42).

CONCLUSIONS

LOAF occurs in about 13% of preserved ejection fraction patients undergoing MVR by five years. Increasing left atrial diameter is an independent predictor of LOAF. Concomitant anti-arrhythmic procedures may warrant further investigation in patients with preserved ejection fraction and enlarged left atria undergoing MVR. doi: 10.1111/jocs.12774 (J Card Surg 2016;31:486-492).

Surgical repair of aortic dissection 16 years post-Ross procedure

The Ross procedure is an excellent choice for younger patients in need of aortic valve replacement. While patients have benefited from superior survival rates associated with this procedure, complications related to aortic root dilatation and degeneration of the autograft may be encountered later in life. These challenges may be exacerbated in those with underlying connective tissue abnormalities, a phenomenon commonly observed in the bicuspid aortic valve population. In this report, we present the case of a patient who presented with an aortic dissection 16 years after a Ross procedure for aortic insufficiency in the setting of a bicuspid aortic valve, and review the existing literature related to this adverse event.

Managing mitral regurgitation: focus on the MitraClip device

Based on the principle of surgical edge-to-edge mitral valve repair (MVR), the MitraClip percutaneous MVR technique has emerged as a minimally invasive option for MVR. This catheter-based system has been widely demonstrated to be safe, although inferior to surgical MVR. Studies examining patients with ≥3+ mitral regurgitation (MR) show that, for all patients treated, freedom from death, surgery, or MR ≥3+ is in the 75%–80% range 1 year following MitraClip implantation. Despite its inferiority to surgical therapy, in high-risk surgical patients, data suggest that the MitraClip system can be employed safely and that it can result in symptomatic improvement in the majority of patients, while not precluding future surgical options. MitraClip therapy also appears to reduce heart failure readmissions in the high-risk cohort, which may lead to an economic benefit. Ongoing study is needed to clarify the impact of percutaneous mitral valve clipping on long-term survival in high-risk populations, as well as its role in other patient populations, such as those with functional MR.

Malperfusion syndromes in aortic dissections

Aortic dissection remains a challenging clinical scenario, especially when complicated by peripheral malperfusion. Improvements in medical imaging have furthered understanding of the pathophysiology of malperfusion events in association with aortic dissection, including the elucidation of different mechanisms of branch vessel obstruction. Despite these advances, malperfusion syndrome remains a deadly entity with significant mortality. This review presents the latest knowledge regarding the pathogenesis of aortic dissection complicated by malperfusion syndrome, and discusses the diagnostic and therapeutic guidelines for management of this vicious entity.