20.06 Drivers of Variation in 90-day Episode Payments for Coronary Artery Bypass Grafts (CABG)

Posted on January 25, 2017

V. Guduguntla1,2,5, J. Syrjamaki1,5, C. Ellimoottil1,3,4,5, D. Miller1,3,4,5, P. Theurer1,6, D. Likosky1,7, J. Dupree1,3,4,5  1University Of Michigan,Ann Arbor, MI, USA 2University Of Michigan,Medical School,Ann Arbor, MI, USA 3Institute For Healthcare Policy And Innovation,Ann Arbor, MICHIGAN, USA 4Dow Division Of Health Services Research,Department Of Urology,Ann Arbor, MICHIGAN, USA 5Michigan Value Collaborative,Ann Arbor, MICHIGAN, USA 6The Michigan Society Of Thoracic And Cardiovascular Surgeons Quality Collaborative,Ann Arbor, MICHIGAN, USA 7Section Of Health Services Research And Quality,Department Of Cardiac Surgery,Ann Arbor, MICHIGAN, USA

Introduction:  Coronary Artery Bypass Grafting (CABG) is a common and expensive surgery. Starting in July 2017, CABG will become part of a mandatory Medicare bundled payment program, an alternative payment model where hospitals are paid a fixed amount for the entire care process, including care for 90-days post-discharge. Details on the specific drivers of CABG payment variation are largely unknown, and an improved understanding will be important for policy makers, hospital leaders, and clinicians.

Methods:  We identified patients undergoing CABG at 33 non-federal hospitals in Michigan from 2012 through June 2015 using data from the Michigan Value Collaborative, which includes adjusted claims from Medicare and Michigan’s largest private payer. We calculated 90-day price-standardized, risk-adjusted, total episode payments for each of these patients, and divided hospitals into quartiles based on mean total episode payments. We then disaggregated payments into four components: readmissions, professional, post-acute care, and index hospitalization. Lastly, we compared payment components across hospital quartiles and determined drivers of variation for each component.

Results: We identified a total of 5,910 patients across 33 Michigan hospitals.  The mean age was 68 and 74% were male.  The mean 90-day episode payment for CABG was $48,571 (SD: $20,739; Range: $11,723-$356,850). The highest cost quartile had a mean total episode payment of $45,487 compared to $54,399 for the lowest cost quartile, resulting in a difference of $8,912 or 16.4%. The highest cost quartile hospitals, when compared to the lowest cost quartile hospitals, had greater readmissions (1.35x), professional (1.34x), post-acute care (1.30x), and index hospitalization payments (1.15x) (all p<0.05). The main drivers of this variation are patients with multiple readmissions, increased use of evaluation and management (E&M) services, higher utilization of inpatient rehabilitation, and diagnosis related group distribution, respectively.

Conclusions: Significant variation exists in 90-day CABG episode payments for Medicare and private payer patients in Michigan. These results have implications for policymakers implementing CABG bundled payment programs, hospital administrators leading quality improvement efforts, and clinicians caring for these patients. Specifically, hospitals and clinicians entering bundled payment programs for CABG should work to understand local sources of variation, including multiple readmissions as well as inpatient E&M and post-discharge rehabilitation services. 

17.17 Cluster Analysis of Acute Type A Aortic Dissection Results in a Modified DeBakey Classification

Posted on January 25, 2017

J. L. Philip1, B. Rademacher1, C. B. Goodavish2, P. D. DiMusto3, N. C. De Oliveira2, P. C. Tang2  1University Of Wisconsin,General Surgery,Madison, WI, USA 2University Of Wisconsin,Cardiothoracic Surgery,Madison, WI, USA 3University Of Wisconsin,Vascular Surgery,Madison, WI, USA

Introduction: Acute type A aortic dissection is a surgical emergency. Traditional classifications systems group dissections were based on an evolving therapeutic approach. Using statistical groupings based on dissection morphology, we examined the impact of morphology on presentation and clinical outcomes.

Methods: We retrospectively reviewed 108 patients who underwent acute type A dissection repair from 2000-2016. Dissection morphology was characterized using 3-dimensional reconstructions of computed tomography scan images based on the true lumen area as a fraction of the total aortic area along the aorta. Two-step cluster analysis was performed to group the dissections.

Results: Cluster analysis resulted in two distinct clusters (silhouette cluster of cohesion and separation = 0.6). Cluster 1 (n=71, 65.7%) was characterized by a dissection extending form the ascending aorta into the abdominal aorta and iliac arteries (table 1). Cluster 2 dissections (n=37, 34.3%) extends from the ascending aorta to the aortic arch with limited extension into the distal arch and descending thoracic aorta. Cluster 2 extends the traditional DeBakey type II definition to include dissections propagating into the arch. Cluster 1 patients had more malperfusion (P=0.002) as well as lower extremity and abdominal pain on presentation (P<0.05). Cluster 2 had a greater number of diseased coronary vessels (P<0.05) and more commonly had previous percutaneous coronary intervention (P<0.05). No differences in age, gender and other major comorbidities were noted. Cluster 1 is characterized by a smaller primary tear area (3.7 vs 6.6 cm2, P=0.009), greater number of secondary tears (1.9 vs 0.5, P<0.001), more dissected non-coronary branches (2.9 vs 0.6, P<0.001) and greater degree of aortic valve insufficiency (P<0.05). Operative variables including cardiopulmonary bypass and cross-clamp time as well as extent of arch repair and type of proximal operations were similar. There were no differences in post-operative complications or survival. Cluster 1 had a significantly higher rate of intervention for distal dissection complications (10% vs 0%, P=0.048).

Conclusions: This study examines clinical presentation and outcomes in acute type A dissection based on morphology using statistical categorization. Cluster 2 acute type A dissections had much less distal aortic dissection involvement and need for distal aortic intervention. Therefore, it is likely reasonable to extend the definition of DeBakey type II dissection to involvement of the distal arch and proximal descending thoracic aorta. The greater area of the primary aortic tear in Cluster 2 with rapid decompression of the false lumen may explain the lesser degree of distal aortic dissection.

17.13 Distal Perfusion Catheters Reduce Vascular Complications Associated with Veno-Arterial ECMO Therapy.

Posted on January 25, 2017

Y. Sanaiha1, G. R. Ramos1, Y. Juo1, J. C. Jimenez1, P. B. Benharash1  1David Geffen School Of Medicine,Division Of General Surgery,Los Angeles, CA, USA

Introduction: Despite advances in cannulation technique, venoarterial (VA) Extracorporeal Membrane Oxygenation (ECMO) is still associated with near 15% incidence of acute limb ischemia (ALI) requiring interventions such as amputation. Distal perfusion catheters (DPCs) have been used to provide antegrade flow to the distal extremity, and can be placed preemptively or in response to signs of limb ischemia. However, the efficacy of DPCs in reducing incidence of vascular complications is not well-established. The present study aims to evaluate the impact of DPC on ALI incidence and mortality.

Methods: The institutional ECMO database was used to identify all adult patients who underwent VA-ECMO between January 2013 to June 2016. Demographic, technical, and clinical outcomes data were collected. Acute limb ischemia was defined as skin mottling on exam, loss of pulses, or tissue loss. Interventions included thombectomy, fasciotomy or amputation.

Results: During the study period, 103 adult ECMO patients met inclusion criteria and were included for analysis. Indications for ECMO were cardiogenic shock in 46.6%, cardiac arrest in 24.3%, post-cardiotomy syndrome in 16.5%, transplant rejection in 4.5%, and severe respiratory failure in 7.8%. 51 patients received DPCs as a preemptive measure and 1 patient received DPC as a therapeutic measure. Overall, 28 (34.1%) patients experienced ALI, with 15 (18.2%) patients requiring surgical intervention. Patients who received DPCs had similar ALI rates compared to those without a DPC (28.8% vs 29.4%, p=NS). Overall mortality with VA-ECMO cannulation was 55% over the study period, while 53% of patients with ALI did not survive to 30 days post-decannulation.

Conclusion: This study is one of the largest retrospective cohort studies examining efficacy of DPC in reducing the incidence of ALI. Patients receiving DPCs were found to have a similar incidence of ALI. Development of ALI was not significantly associated with increased mortality. Methods to continuouly assess distal blood flow are needed even in the presence of DPCs.  Establishemnt of selection criteria for the use of DPCs may improve outcomes.

 

 

17.12 Long-Term Follow Up of Activity Levels and Lifestyle Choices After Esophagectomy

Posted on January 25, 2017

Z. El-Zein1, S. Barnett1, J. Lin1, W. Lynch1, R. Reddy1, A. Chang1, M. Orringer1, P. Carrott1  1University Of Michigan,Section Of Thoracic Surgery,Ann Arbor, MI, USA

Introduction: We aimed to determine if preoperative counseling for esophagectomy patients led to durable smoking cessation, routine exercise for years after surgery, and lower postoperative complication rates. 

Methods:  Of 789 patients identified as long-term survivors from a prospectively-collected esophagectomy database, 393 (49.8%) were contacted and agreed to receive a survey of long-term lifestyle changes. Of 294/393 (74.8%) patients who returned the completed survey, 239 (81.3%) underwent esophagectomy for cancer (median follow-up 5.5 years) and 55 (18.7%) for benign disease (median follow-up 9.2 years). Each group was analyzed using descriptive statistics and Chi-square where appropriate.

Results: In the cancer population, 35/239 (14.6%) were smokers at preoperative counseling and 14/35 (40%) smoked following surgery (P<0.01). With regard to exercise, 177/239 (74.1%) reported counseling preoperatively and 62/239 (25.9%) reported no counseling. The median exercise frequency for the counseled group was 5 vs. 2 days/week for the “non-counseled” group preoperatively (p<0.0001) and 4 vs. 3 days/week postoperatively (P=0.02). Currently, 117/177 (66.1%) in the counseled group exercise regularly (2+ days/week for 30+ minutes) compared to 31/62 (50%) from the “non-counseled” group (p=0.02). In the cancer population, preoperative smokers had higher pneumonia rates than non-smokers (11.4% vs. 3.9%, P=0.06). The documented exercise-counseled group had a significantly lower pneumonia rate than the non-counseled group (3.2% vs. 11.5%, P=0.01). In the benign population, there was no significant reduction in smoking rates and no significant difference in exercise frequency or complication rates between the counseled and non-counseled groups. 

Conclusion: Preoperative interventions before a major operation such as an esophagectomy due to cancer lead to an increase in activity level, permanent changes in lifestyle habits, and lower postoperative complication rates.

 

17.11 Survival outcomes in octogenarians with early stage, non-small cell lung cancer in the recent era

Posted on January 25, 2017

W. M. Whited1, E. Schumer1, J. Trivedi1, M. Bousamra1, V. Van Berkel1  1University Of Louisville,Department Of Cardiovascular And Thoracic Surgery,Louisville, KY, USA

Introduction:
This study aims to examine survival differences in elderly patients with early stage (I and II), non-small cell lung carcinoma (NSCLC) undergoing pulmonary resection.

Methods:
The national Surveillance, Epidemiology, and End Results database was queried for lung cancer patients between 1998 and 2010.  Age at diagnosis for all patients and those undergoing surgical resection were compared by year between patients <80 and >80 years.  Using Kaplan-Meier analysis, survival was compared between age subgroups (<70, 70-79, and >80 years) stratified by cancer stage for patients with early stage, NSCLC who underwent surgical resection.

Results:

41,680 patients age 18 years or greater were identified with early stage, NSCLC.  Of these, 29, 580 patients underwent pulmonary resection.  The proportion of patients older than 80 out of all patients who underwent resection for early stage, NSCLC demonstrates an upward trend since 1998 from 180 patients (9.1%) to 278 patients (11.4%).  Survival comparison stratified by stage for patients <70, 70-79, and >80 years is shown in Figure 1.   Five year survival for patients with stage I, NSCLC, ages <70, 70-79, and >80 years, respectively, is 62%, 45%, and 28% (p<0.001).  Five year survival for patients with stage II, NSCLC, ages <70, 70-79, and >80 years, respectively, is 43%, 23%, and 17% (p<0.001). There were similar trends in survival when stratified by sex and histology.  

Conclusion:

The number of elderly patients diagnosed with NSCLC is increasing, particularly those >80 years; therefore, there is an increasing number of older patients undergoing surgical resection.  While surgical resection in octogenarians for stage I, NSCLC is feasible, elderly patients have poor overall survival and should be fully informed of alternatives to surgical intervention. 

 

15.16 Outcomes and Costs for Thoracoscopic Alone Versus Robotic Assisted Thoracoscopic Procedures

Posted on January 25, 2017

M. Eby1, J. Parreco1, R. Martinez1, R. Kozol1  1University Of Miami,General Surgery,Miami, FL, USA

Introduction:
Previous studies have shown the benefits of thoracoscopic procedures in regards to less postoperative pain, faster recovery, and less overall cost when compared to open surgery. However, the comparison of thoracoscopic alone versus robotic assisted thoracoscopic procedures is less well known. The purpose of this study was to compare overall outcomes and costs associated with thoracoscopic alone versus robotic assisted thoracoscopic procedures.

Methods:
The Nationwide Readmission Database (NRD) was queried for all patients with admissions with elective thoracoscopic and robotic assisted thoracoscopic procedures in 2013. The most common diagnoses with total costs were calculated. Multivariate logistic regression was then implemented using patient comorbidities and demographics as well as hospital characteristics to determine the odds ratios (OR) of outcomes.

Results:
During the study period, 24,707 patients underwent thoracoscopic procedures with 2,837 (11.5%) being robotic assisted and 21,870 (88.5%) thoracoscopic alone. The mean robotic assisted total admission cost was $25,409.16 SD+/-21,523.75 while the mean total thoracoscopic alone was $19,470.92 SD+/-20,380.66 (p<0.01, 95% CI 5,133.20 to 6,743.29). The mean cost of readmissions for robotic assisted was $23,467.70 SD+/-32,578.80 while the mean cost of readmissions for thoracoscopic alone was $23,759.56 SD+/-35,416.83 (p=0.85, 95% CI -3,312.41 to 2,728.70). The most common primary diagnosis for patients undergoing robotic assisted thoracoscopic procedures was malignant neoplasm of upper lobe, bronchus or lung at 777 patients (27.4%) with a mean total admission cost of $27,160.17 (+/-20,299.65). This was also the most common primary diagnosis for patients undergoing thoracoscopic alone procedures with 4,932 patients (22.6%) and a mean total admission cost of $22,382.38 (+/-17,882.993). The OR for mortality in thoracoscopic alone patients was 1.28 (p=0.08, 95% CI 0.97 to 1.68) and the OR for readmission was 1.12 (p=0.03, 95% CI 1.01 to 1.24).

Conclusion:

Initial admission costs are higher in patients undergoing robotic assisted thoracoscopic procedures compared to thoracoscopic alone. However, readmission costs are similar and readmissions occur at a higher rate in patients undergoing thoracoscopic alone procedures. Therefore, with lower readmission rates and equivalent overall survival, robotic assisted thoracoscopic procedures prove to be beneficial and potentially superior in both patient outcomes and reduction in net health care costs when compared to thoracoscopic alone.

15.13 Understanding Resource Utilization in Congenital Heart Disease

Posted on January 25, 2017

A. Eckhauser1, J. Marietta3, N. Pinto2, M. Puchalski2  1University Of Utah,Cardiothoracic Surgery/Surgery,Salt Lake City, UT, USA 2University Of Utah,Cardiology/Pediatrics,Salt Lake City, UT, USA 3Primary Children’s Hospital,Salt Lake City, UT, USA

Introduction:  Resource utilization and the cost of caring for patients with congenital heart disease (CHD) is largely unknown and often inferred from administrative data. How these costs are broken down into components by operating room, nursing care, rooming, and pharmacy can be used to help better understand opportunities to improve care. We sought to evaluate these costs in three common congenital heart surgeries.

Methods:  We evaluated overall costs for 3 common congenital heart defects- complete atrioventricular canal (AVC), coarctation of the aorta (AA) and D-transposition of the great arteries (DTGA) using linking to a statewide database (1997-2012) of inpatient discharge and vital records thru age 5.  For the subset of patients operated on at our tertiary care center from 2012-2016 we obtained costs associated with the initial surgery using an activity based accounting system that broke down cost components for the index hospitalization and stratified these costs based on major comorbidities to understand resource use. 

Results:  The 1yr-costs for the AVC cohort were $86,271 ± 112,900 (n=213), AA $57,788 ± 84,036 (n=465) and DTGA $108,840 ± 98,768 (n=169) with an additional 18, 10, and 7% respectively added through year 5.  The total average cost at our center for the initial surgical hospitalization for AVC repair was $24,318 ± 22,007, for AA $35,207 ± 32,840 and for DTGA $56,516 ± 28,427.  Figure 1 displays major contributors to surgical costs and differences based on major comorbidities within each cohort for the initial surgical hospitalization. Prematurity had the most profound increase in cost in patients with DTGA.  Trisomy 21 in patients with AVC actually led to a decrease in utilization.

Conclusion:  The majority of hospital costs associated with caring for children with CHD occur in the first year of repair and are related to the surgical hospitalization.  Risk factors such as prematurity and operative strategy can have profound effects on total cost that vary significantly by type of CHD.  Using such data to explore this effect can help to identify leverage points to improve the value of care delivered to these patients.
 

01.05 Statins Reduce Thoracic Aortic Aneurysm Growth in Marfan Syndrome Mice

Posted on January 25, 2017

M. P. Fischbein1  1Stanford University,Cardiothoracic Surgery,Palo Alto, CA, USA

Introduction: Systematically dissect the prenylation pathway to better define the mechanism behind the beneficial effect of statins on aneurysm reduction in MFS and anticipate this will help elucidate the pathophysiology of aneurysm formation.  

Methods: Fbn1C1039G/+ mice (4 week old) were treated subcutaneously with either (a) Pravastatin (PS) (HMG-Co Reductase inhibitor) (100 mg/kg per day); (b) Manumycin A (MA) (FPT inhibitor) (2.5 mg/kg/every other day); (c) Perillyl Alcohol (PA) (GGPT-1 and -2 inhibitor) (5.0 mg/kg/every other day); or (d) vehicle control Fbn1C1039G/+ mice from age 4-8 weeks. Aortic dimensions were measured with transthoracic echo.

Results:  PS and MA significantly reduced aneurysm growth compared to vehicle control (PS:1.57 ± 0.03 mm; MA: 1.55 ± 0.06 mm; vehicle: 1.77 ± 0.05 mm, respectively: p < 0.05). There was no significant difference between PS and MA treated groups. In contrast, PA did not significantly decrease aneurysm size (PA: 1.81 ± 0.06 mm). Elastin staining illustrated reduced elastin breakdown in MA treated mice compared to vehicle control treated groups (MA: 2.2 ± 0.3, vehicle: 4.2 ± 0.6, respectively: p < 0.05). After identifying that the Ras pathway is important, we measured the relative expression of pRaf-1 and pErk1/2, downstream enzymes in transforming growth factor- β (TGF-β) signaling pathway with WES. Although elevated in control Marfan mice, both pRaf-1 and pErk 1/2 were significantly reduced in MA treated mice, corresponding with a reduction in aneurysm growth (pRaf-1: MA: 5.1 ± 1.3, vehicle: 8.8 ± 0.8, p = 0.08, pErk1/2: MA: 2.3 ± 0.1, vehicle: 3.2 ± 0.1, p < 0.05, respectively

Conclusion: Statins reduce aortic aneurysm growth in Fbn1C1039G/+ Marfan mice by decreasing both Ras activation and downstream ERK signaling

 

01.02 Decreased Coronary Arteriolar Response to KCa channel Opener after CP/CPB in Diabetic Patients

Posted on January 25, 2017

Y. Liu1, V. Cole1, F. W. Sellke1, J. Feng1  1Rhode Island Hospital,Cardiothoracic/Surgery,Providence, RI, USA

Introduction: We have found recently that diabetes is associated with inactivation of endothelial KCa channels, which may contribute to endothelial dysfunction in diabetic patients at baseline.  In the current study, we further investigated the effects of cardioplegic ischemia and reperfusion (CP) and CPB (cardiopulmonary bypass) on coronary arteriolar responses to the calcium-activated potassium channel (KCa) opener NS309 in diabetic and non-diabetic patients undergoing coronary artery bypass grafting (CABG).

Methods: The protein expression/localization of KCa channels in the harvested  atrial tissue were assayed by Western blotting and immunohistochemistry. Coronary arterioles from the harvested right atrial tissues were dissected pre- and post-CP/CPB from diabetic and non-diabetic patients (n = 5-6/group) undergoing CABG surgery. In-vitro relaxation response of pre-contracted arterioles was examined in the presence of the selective small (SKCa) and intermediate (IKCa) conductance KCa opener NS309 (10-9-10-5 M) and other vasodilatory agents.

Results: There were no significant differences in the total protein levels of IKCa, and SKCa between diabetic and non-diabetic groups or between pre- and post-CP/CPB (P>0.05). The relaxation response to NS309 post-CP/CPB was significantly decreased in diabetic and non-diabetic groups compared to their pre-CP/CPB responses, respectively (P<0.05). Furthermore, this decrease was greater in the diabetic group than that of non-diabetic group (P<0.05).

Conclusion: Our data suggest that diabetes further inactivates KCa channels of coronary microvasculature early after CP/CPB and CABG surgery. This alteration may contribute to post-operative endothelial dysfunction in diabetic patients after cardiac surgery.

 

01.11 Modulation of the NFκB Pathway by Alcohol in Ischemic Myocardium

Posted on January 25, 2017

L. A. Scrimgeour1, B. A. Potz1, F. W. Sellke1  1Brown University School Of Medicine,Cardiothoracic Surgery,Providence, RI, USA

Introduction:

Studies suggest low alcohol consumption can be cardioprotective but it remains unclear how this effect is modulated. The Nuclear Factor kappa-B (NFκB) pathway functions to regulate the expression of genes involved in a wide variety of cellular processes involved inflammation and stress. Therefore, we used a swine model of metabolic syndrome induced by a high fat diet to investigate the effects of red wine versus vodka on NFκB signaling in chronically ischemic myocardium.

Methods:

Yorkshire swine were given a high-fat diet for four weeks, and then an ameroid constrictor was placed on the left circumflex artery. They continued on the high fat diet and were subdivided into three groups with supplementation of wine or vodka for 7 weeks; hypercholesterolemic diet alone (CON, n=8), hypercholesterolemic diet with vodka (hypercholesterolemic vodka [HCV], n=8), and hypercholesterolemic diet with wine (hypercholesterolemic wine [HCW], n=8). Animals underwent euthanasia and ischemic myocardium was harvested for analysis. This tissue was analyzed via Western blot. Protein density data were normalized to GAPDH and reported as fold-change values +/- standard error of the mean compared to control (CON) samples.

Results:

Administration of alcohol was associated with decreased expression of IKKα, IKKB and and phosphorylated IκBα in the ischemic myocardium compared to the control group. Alcohol administration was associated with an increase in NFκB in the ischemic myocardium compared to the control group [Figure 1].

Conclusions:

In the setting of myocardial ischemia, alcohol appears to modulate the NFκB pathway. This was demonstrated by the decreased expression of IKKα after alcohol administration, which decreased phosphorylation of IκBα. When less IκBα is phosphorylated, it remains bound to and inhibits NFkB from passage into the nucleus and upregulating of a variety of genes. Many of these gene products further promote inflammation and contribute to the adaptive response of tissues such as the myocardium in response to the stress of ischemia. This study provides a mechanism by which alcohol may have a protective effect on the heart.

 

01.20 Influence of Diabetic Treatment on Substrate Selection in a Ex-vivo Coronary Artery Bypass Model

Posted on January 25, 2017

C. T. Holmes1, N. Clarke1, L. Powell1, M. E. Jessen1, M. Peltz1  1University Of Texas Southwestern Medical Center,Department Of Cardiovascular And Thoracic Surgery,Dallas, TX, USA

Introduction:   Coronary artery bypass grafting remains the standard of care for treatment of multivessel coronary artery disease, particularly in diabetic patients.  The influence of diabetic therapies on myocardial substrate selection under these conditions are unknown but may be important to ensure optimal outcomes after cardiac surgery. We hypothesized metformin and insulin  alter myocardial substrate selection during cardiac surgery and may effect reperfusion cardiac function.

Methods:

Groups of rat hearts (n=4 per group) were perfused under 3 conditions: Normokalemia, Cardioplegia or Bypass. Normokalemia groups were perfused with Krebs-Heinseleit buffer in the presence of no additives (Control), 500mM metformin (Metformin), 10 units/L insulin (Insulin), or both insulin and metformin (Metformin + Insulin).  Cardioplegia animals were perfused with the same additives for 30 minutes with potassium modified buffer (20mM) to simulate cardioplegic arrest. Bypass groups containing the same additives were treated with three 22-minute ischemic intervals followed by a 3-minute interval of perfusion with cardioplegia buffer and 30 minutes of normokalemic reperfusion to simulate conditions encountered during coronary artery bypass grafting.  Perfusion buffer with physiological concentrations of fatty acids (.35mM), ketones (.17mM), lactate (1.2mM), pyruvate (.12mM), and glucose (5.5mM) with different Carbon-13 (13C) labelling patterns was used for all conditions. 13C NMR spectra were obtained. Fractional substrate oxidation was determined by glutamate isotopomer analysis . Myocardial efficiency (rate*pressure/oxygen consumption) was measured in Bypass groups. Groups were compared by one-way analysis of variance or t-tests.

Results:

During cardioplegia, fatty acid oxidation was decreased for all additives. Ketone oxidation in this condition was increased with all additives except for metformin.  Fatty acid oxidation was increased in all groups with a corresponding decrease in endogenous substrate oxidation when additive was included in the perfusion buffer.  See Figure. Myocardial efficiency was not different for each additive compared to the stabilization period.

Conclusion:

Conditions encountered during cardiac surgery result in alterations in myocardial substrate oxidation profiles resulting in a reduction in fatty acid oxidation during potassium cardioplegia but increased fatty acid oxidation after reperfusion. These alterations in substrate oxidation did not affect myocardial efficiency in otherwise normal hearts.
 

01.16 Alterations in Mitochondrial DNA Density in Right Ventricular Failure and Recovery

Posted on January 25, 2017

J. Winward1, M. E. Bowen1, H. Li1, S. H. McKellar1  1University Of Utah,Cardiothoracic Surgery,Salt Lake City, UT, USA

Introduction:
Increasing evidence indicates that abnormal energy metabolism plays a leading role in right ventricular failure (RVF), but the specific role in RVF and RV recovery (RVR) is unknown. Our analyses showed failed fatty acid oxidation (FAO) and changes in hypoxia markers in RVF and RVR. These observations led us to hypothesize that the buildup of FAO precursors was the result of insufficient mitochondrial (MT) biogenesis. Our objective was to discover how MT biogenesis is altered in RVF and RVR cardiomyoctes compared to healthy controls in a rabbit model.

Methods:
Fifteen rabbits were assigned to one of three groups—control, RVF, and RVR—and RV tissue samples were taken from each rabbit’s RV. MT gene expression and transcriptional variance were measured via RT-PCR and RNA sequencing. Immunoblotting of MT biogenesis activators was also performed.

Results:
MT DNA density decreased during RVF with fold changes of RVF=0.75 (p=0.22) returning to RVR=1.06 (p=0.84). Further division of the RVF group into compensated RVF (cRVF) and decompensated RVF (dRVF) revealed that MT density was qualitatively greater in cRVF (FC=0.88, p=0.58) than in dRVF (FC=0.62, p=0.26). RNA sequencing revealed significantly increased transcription of HIF in RVF when compared to the control (FC=0.93; p<0.04) and RVR (FC=0.90; p<0.03). However, the rate of transcription of downstream activators of MT biogenesis (i.e. PGC-1-α, NRF-1, NRF-2, Akt3, Perm-1, TFAM, VEGF, and AMPK) was not significantly altered between the groups. Despite its unaltered transcription, immunoblotting of activated AMPK revealed a significant fold increase in RVF (1.50) and RVR (1.61) compared to the control (1.06) (p=0.01). 

Conclusion:
Our data qualitatively suggest that MT DNA density decreases in a manner directly proportion to the severity of RVF, and that it increases in RVR.  Other studies show similar findings in human subjects. Additionally, the increased transcription of HIF in the RVF samples leads us to hypothesize that hypoxia plays a significant role in the MT pathogenesis of RVF. The discrepancy between the rate of transcription and the enzyme activation of AMPK, in conjunction with the altered MT DNA density in RVF and RVR despite the unchanged rate of transcription of upstream MT biogenesis regulatory enzymes, leads us to hypothesize that the functionality rather than the quantity of MT biogenesis regulators is leading to the variance in MT DNA density, as seen with the increased levels of the activated AMPK protein in RVF and RVR, despite its unaltered rates of transcription. Further research investigating the alterations of MT biogenesis markers at the transcriptional and translational level, and hypoxia’s role therein, is warranted.
 

01.15 Proof of Concept: Magnetic Chest Tube Positioning System

Posted on January 25, 2017

D. Laan1, D. Vu1, M. Hernandez1, J. Aho1, H. Schiller1  1Mayo Clinic,General Surgery,Rochester, MN, USA

Introduction: Chest tubes can serve as life-saving adjuncts in trauma. Unfortunately, suboptimal positioning frequently complicates tube placement and can lead to impaired function. Magnets have been shown to successfully guide and direct small catheters, but this technology has never been shown to be efficacious in chest tube positioning. We sought to demonstrate, in a deceased porcine model, the utility of a 2-magnet system in directing the intra-thoracic position of a chest tube (Figure 1).

Methods: In recently deceased cross-bred domestic swine we tested magnetic positioning of  a chest tube  The operator held one magnet on the outside of the chest.  The second magnet was introduced through a catheter to the distal tip of the chest tube.  The operator was then tasked with moving the tube to distinct pre-marked intrathoracic locations under blinded conditions. This was achieved by taking advantage of the magnetic force between the two magnets. The experiment was video-recorded through an open sternotomy incision to determine success of tube positioning. Five chest tube positioning maneuvers were attempted with this system. An attempt at chest tube positioning with no magnet (standard of care) to premarked intrathoracic locations was attempted as a control.

Results:The chest tube positioning system was successful in directing a chest tube from one pre-marked location to another on 4 of 5 attempts. The system demonstrated an ability to move the tube in the cephalad-caudad axis and the anterior-posterior axis. Magnetic coupling between the 2 magnet ends was confirmed at a distance of 10cm in this model. The control chest tube with no magnet failed to navigate intrathoracically from one pre-marked location to the next with 0 of 5 attempts successful.

Conclusion:Positional flaws in chest tube placement are common. We demonstrate the 2-magnet system’s efficacy as an alternative to the traditional hand-guided method under simulated placement conditions.  The pull between two magnets can be effective with up to 10cm separating magnet ends. Furthermore, we have shown with some reproducibility that a magnetic chest tube positioning system may be superior to the current standard of care technique of chest tube placement. Further study is needed to develop this emerging technology.

 

 

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