Development of a Novel Large Animal Model of Ischemic Heart Failure Using Autologous Platelet Aggregates

Background

Current animal models of heart failure lack the biomass of thrombus that occurs in patients undergoing myocardial infarction. We propose a novel animal model of ischemic cardiomyopathy developed by sequential direct injections of autologous platelet aggregates into the coronary circulation resulting in development of ischemic cardiac insufficiency.

Methods

Autologous platelets from adult sheep were isolated and aggregated. Aggregated platelets were then injected into the coronary circulation of anesthetized animals under fluoroscopic guidance. Troponin I levels were monitored for first three days after embolization to validate cardiac tissue injury. Progression of heart failure was corroborated by monitoring changes in echo-based assessment of ejection fraction and left ventricular end-systolic and end-diastolic dimensions. Thrombus-based obstruction of coronary artery was confirmed with histopathology review by mepacrine labeling of pre-aggregated platelets.

Results

All experimental animals developed heart failure-like cardiac insufficiency confirmed by elevated levels of troponin I and associated with significant drop in the ejection fraction.

Conclusions

Sequential injections of aggregated platelets into coronary circulation lead to progressive development of ischemic cardiac insufficiency. This phenomenon seems to mimic development of ischemic heart failure seen in human patients and opens multiple research opportunities to fill the existing gap between basic research and clinical practice.

Increased presence of oxidized low-density lipoprotein in the left ventricular blood of subjects with cardiovascular disease

Oxidized LDL (Ox‐LDL) and oxidative stress have been implicated in both atherosclerosis and congestive heart failure (HF) development. Here, we tested whether Ox‐LDL levels in left ventricular blood (LVB) might differ from those of venous peripheral blood (PB), and whether the level might depend on cardiac function. We also tested whether the LDL molecule is likely to have a longer residence time in the left ventricle of HF subjects with low ejection fraction (EF). The aim of this study was to determine Ox‐LDL levels, paraoxonase 1 (PON1) activity, and cholesterol efflux capacity (CEC) of PB and LVB, and correlate these values with LVEF. Sixty‐one HF patients underwent preoperative transthoracic echocardiographic assessment of ventricular function. LVEFs were determined using Simpson's biplane technique. LVB and PB levels of Ox‐LDL were determined, and PON1 activity and plasma cholesterol efflux capacity were measured. A significant increase in the levels of Ox‐LDL in LVB was noted as compared to levels in PB, even when EF was near normal. However, as ejection fraction decreased, the level of Ox‐LDL in PB approached that of the LVB. PON1 activity and cholesterol efflux studies indicated increased oxidative stress in LVB and a decreased ability to promote cholesterol efflux from lipid‐enriched macrophages. The results suggest that LVB is more oxidatively stressed compared to PB, and therefore LV tissue might be affected differently than peripheral tissues. We recently reported that brain natriuretic peptide (BNP), a marker for HF, is induced by Ox‐LDL, so it is possible localized factors within the LV could profoundly affect markers of HF.

Abstract 302: Presence of Oxidized Low-Density Lipoprotein in the Left Ventricular Blood of Subjects with Cardiovascular Diseases

Hypothesis: Oxidized low density lipoprotein (Ox-LDL) has properties that profoundly affect cardiovascular function. We hypothesized that Ox-LDL is likely to be formed in the left ventricular blood (LVB) when the heart is subjected to ischemic conditions and the ejection fraction (EF) is low. We speculated whether “stagnation” of LDL in the LV could result in increased formation of Ox-LDL.

Objective: We studied whether there is an increased level of Ox-LDL in the LVB as opposed to peripheral blood (PB), and whether its presence correlated with the EF. Also we examined whether a higher level of Ox-LDL negatively correlated with the activity of paraoxonase 1 (PON 1).

Methods: Following the Institutional Review Board (IRB) approval, 62 HF patients were enrolled in the study. All patients underwent pre-operative transthoracic echocardiographic assessment of ventricular function. Left ventricular ejection fractions were determined using the Simpsons bi-plane technique. 2ml of LVB and 5ml of PB samples were taken before coronary artery bypass surgery, or a surgery with replacement of mitral, aortic or tricuspid valve. Blood level of Ox-LDL was determined by ELISA (Mercodia), and PON 1 activity was determined by the rate of conversion of its substrate p-nitrophenyl acetate into p-nitrophenol.

Results: The result showed significant increase in Ox-LDL in LVB as compared to PB (p=0.032) in HF subjects even when EF was near normal. There was no significant increase in subjects with lower EF. In contrast, Ox-LDL levels increased in the PB of subjects with lower EF and reached those of LVB. We also noticed that there was a statistically significant negative correlation between EF and Ox-LDL levels in both LVB and PB (p < 0.05). The activity of PON1, an antioxidant enzyme that protects LDL from oxidation showed decreased levels both in LV blood as well as in PB with decreased EF. It was observed that there was a statistically significant difference in PON1 levels between LV and PB of subjects having EF>60% (p = 0.03). Conclusions: In conclusion the results suggest that there might be oxidative stress associated with LVB even when the EF is not compromised. In contrast, the increase in PB Ox-LDL with poor EF might suggest that the low blood flow to peripheral tissues and end organs also might contribute to increased oxidative stress. The results also might suggest that persistent oxidative stress could have affected the clearance mechanisms of Ox-LDL.

Induction of brain natriuretic peptide and monocyte chemotactic protein-1 gene expression by oxidized low-density lipoprotein: relevance to ischemic heart failure

Brain natriuretic peptide (BNP) and monocyte chemotactic protein-1 (MCP-1) are biomarkers of heart failure (HF). The aim of the present study was to determine the role of oxidized low-density lipoprotein (Ox-LDL) in the induction of these biomarkers and the signaling pathways involved in vitro. Incubation of HL-1 cardiomyocytes and human myocytes with Ox-LDL induced the expression of BNP and MCP-1 genes, while native LDL had no effect. When peroxides associated with Ox-LDL were reduced to hydroxides, the ability to induce BNP and MCP-1 gene expression was abolished. Furthermore, exposure of HL-1 cells to ischemic conditions alone had no effect on BNP gene expression, while ischemia followed by reperfusion resulted in increased expression of BNP gene. Inhibitors of ERK and JNK inhibited the induction of BNP. Signaling array results suggested that the induction of both MAPK and NF-κB pathways is involved in the induction of BNP by Ox-LDL. These results suggest that Ox-LDL or peroxidized lipids formed in oxidatively stressed myocytes during ischemia-reperfusion injury may play a role in the induction of BNP and MCP-1.

Abstract P334: Comparative Effectiveness of Left Ventricular Assist Devices as a Bridge to Heart Transplantation

Left ventricular assist devices (LVAD) have evolved to be more frequently utilized in patients with advanced congestive heart failure as a bridge to heart transplantation. In the era of limited healthcare resources and diminishing funding for innovative technologies, there is little data to evaluate the comparative effectiveness of LVADs in comparison to more conventional heart failure therapies leading to heart transplantation without mechanical circulatory support.

Objective . To evaluate the clinical outcomes, complications, length of stay, financial impact and satisfaction of patients with advanced heart failure undergoing heart transplantation as part of a comprehensive heart failure program with or without LVAD as a bridge to transplant (BTT).

Methods We retrospectively reviewed 25 patients undergoing heart transplantation from 2009–2010 (12 patients without LVAD, 13 with LVAD as BTT). Inpatient hospital, financial and clinic records were reviewed to evaluate length of stay, morbidity, mortality, DRG assignment, insurance status, charges and cost, reimbursement and patient satisfaction. All patients received surveys assessing their satisfaction with the mechanical circulatory support and transplant program.

Results There were 14 males and 11 females (avg age 54 ).In the non- LVAD group, 9 patients fell into DRG 1 ,3 were in DRG 2;in the LVAD group, 10 patients fell in DRG 1, 3 patients were in DRG 2.Complications occurring in the LVAD patients included pneumonia (2),CVA, depression, rejection and bowel perforation ;in the non-LVAD patients pneumonia, pulmonary embolus, aspergillosis, peri-rectal abscess and failure to thrive; Mortality at 1 year occurred in 2 patients after LVAD; 1 patient after transplant without LVAD. All patients responded that they were very satisfied with the advanced heart failure program whether they received LVAD prior to transplant or not

Conclusions Transplant recipients with advanced heart failure have comparable clinical outcomes after transplant whether they required LVAD implantation prior to transplant. Perioperative care algorithms focused on reduction of common post-operative complications resulting in significant financial impact (ie pulmonary), should be developed to address these issues.

The use of extracorporeal membrane oxygenation in severe necrotizing soft tissue infections complicated by septic shock

Necrotizing soft tissue infections remain a challenging clinical problem. Delays in diagnosis, incomplete débridement of necrotic tissues, and the hemodynamic instability and end-organ failure associated with overwhelming sepsis all contribute to significant mortality. Extracorporeal support is a well-established tool to support profound cardiopulmonary failure. To broaden the indications for use, we present two cases of young adults with necrotizing soft tissue infections who sustained sepsis-induced hemodynamic collapse and required extracorporeal support to facilitate adequate tissue débridement as a bridge to recovery.

Anterior wall viability and low ejection fraction predict functional improvement after CABG

BACKGROUND

Absence of myocardial hyperenhancement on cardiac magnetic resonance imaging (CMR) predicts functional improvement after coronary artery bypass graft surgery (CABG). However, not all patients with absence of hyperenhancement improve their left ventricular ejection fraction (LVEF) after CABG. We sought to identify other characteristics associated with improvement in LVEF after CABG.

METHODS

Preoperative CMR was obtained in 95 patients who underwent CABG from 2003 to 2007 at The Ohio State University Medical Center. Follow-up LVEF was assessed by echocardiogram between 3 wk and 2 y postoperatively (mean: 7±0.5 mo). Improvement in LVEF was defined as a postoperative increase in LVEF≥10%. CMR and clinical factors were analyzed for predictors of functional improvement.

RESULTS

Mean age was 61±1 y with 79 males. LVEF improved from 28%±2% preoperatively, to 38%±2% postoperatively (P<0.0001). Forty-three patients improved their LVEF. Patients who improved their LVEF had a lower preoperative LVEF (P=0.0001) and higher anterior wall viability (P=0.03). Preoperative LVEF (odds ratio 0.89, 95% CI 0.83-0.95, P=0.001) and left ventricular end systolic volume index (odds ratio 0.97, 95% CI 0.95-0.99, P=0.015) were predictors of improvement in LVEF by multivariable logistic regression analysis.

CONCLUSIONS

Recruitment of viable non functioning myocardium of the anterior wall is responsible for the improvement in ejection fraction. Low LVEF, non-remodeled left ventricle, and anterior wall viability predict improvement in ejection fraction after CABG. These criteria may help clinicians select patients who would benefit from surgical revascularization.

Medial necrosis in aortic root aneurysm after repair of tetralogy of Fallot

Aneurysmal dilatation of the aortic root occurs in some patients with tetralogy of Fallot (TOF) late after repair. It can lead to aortic valve insufficiency and rarely to aortic rupture or dissection. Aortic valve or aortic surgery is rarely performed in this group of patients. We present a case of aneurysmal dilatation of the ascending aorta treated with aortic valve sparing root replacement 43 years after the TOF repair. Histological examination of the aortic wall revealed medial necrosis. The implications of those finding and the timing of surgery are discussed.

Development of a novel large animal model of ischemic heart failure using autologous platelet aggregates

BACKGROUND

Current animal models of heart failure lack the biomass of thrombus that occurs in patients undergoing myocardial infarction. We propose a novel animal model of ischemic cardiomyopathy developed by sequential direct injections of autologous platelet aggregates into the coronary circulation resulting in development of ischemic cardiac insufficiency.

METHODS

Autologous platelets from adult sheep were isolated and aggregated. Aggregated platelets were then injected into the coronary circulation of anesthetized animals under fluoroscopic guidance. Troponin I levels were monitored for first three days after embolization to validate cardiac tissue injury. Progression of heart failure was corroborated by monitoring changes in echo-based assessment of ejection fraction and left ventricular end-systolic and end-diastolic dimensions. Thrombus-based obstruction of coronary artery was confirmed with histopathology review by mepacrine labeling of pre-aggregated platelets.

RESULTS

All experimental animals developed heart failure-like cardiac insufficiency confirmed by elevated levels of troponin I and associated with significant drop in the ejection fraction.

CONCLUSIONS

Sequential injections of aggregated platelets into coronary circulation lead to progressive development of ischemic cardiac insufficiency. This phenomenon seems to mimic development of ischemic heart failure seen in human patients and opens multiple research opportunities to fill the existing gap between basic research and clinical practice.

Toward a definitive, totally thoracoscopic procedure for atrial fibrillation

PURPOSE

Evolution of anti-arrhythmia surgery beyond the Cox maze III has been hampered by the difficulty in implementing a complete lesion set in a truly minimally invasive approach. In this study, we introduce a true port-access procedure that addresses both autonomic and anatomic sources of atrial fibrillation, with real-time verification of all technical endpoints.

DESCRIPTION

A total of 32 patients with persistent or longstanding persistent atrial fibrillation underwent the totally thoracoscopic anti-arrhythmia procedure incorporating pulmonary vein isolation, mapping of epicardial autonomics, extended linear ablations across critical segments of atrial substrate, and ligation of the left atrial appendage. All aspects of the procedure were confirmed with intraoperative electrophysiologic testing.

EVALUATION

With 1 week of continuous rhythm surveillance at 3, 6, and 13 months postoperatively in all patients, 21 of 24 patients with 6-month follow-up are in sinus rhythm with no anti-arrhythmia medications.

CONCLUSIONS

An anti-arrhythmia operation that is highly effective in patients with advanced forms of atrial fibrillation can be safely performed through a totally port-access approach.

Vacuum-assisted apical suction devices induce passive electrical changes consistent with myocardial ischemia during off-pump coronary artery bypass graft surgery

OBJECTIVE

Off-pump coronary artery bypass graft surgery is common therapy to completely revascularize diseased hearts. In order to graft posterior arteries in this procedure, the heart must be lifted from the chest cavity and manipulated to expose the surgical field using an apical suction device. This suction device may cause unwanted myocardial ischemia.

METHODS

In this observational study, we measured myocardial electrical impedance, a parameter that responds to myocardial ischemia, as well as ST-segment changes during off-pump coronary artery bypass graft surgery in 12 patients with two-vessel coronary artery disease undergoing revascularisation of the left anterior descending and the posterior descending coronary arteries. During the posterior descending artery revascularisation phase of the procedure the apical suction device was oriented over the electrodes used to measure myocardial electrical impedance, thus allowing us the opportunity to assess myocardial ischemia in this region of the heart.

RESULTS

In these 12 patients, myocardial electrical impedance progressively increased under the suction device during posterior coronary artery revascularisation, suggesting that myocardial ischemia developed in this region of the myocardium. ST-segment changes were negligible while the heart was vertically displaced (and the suction device attached), but increased immediately when the heart was returned to the neutral anatomical position.

CONCLUSION

Our data suggest that the apical suction device may cause ischemia while the heart is vertically displaced and electrically disconnected from the body. Under these conditions, ST-segment changes may not detect myocardial ischemia. Myocardial electrical impedance has the potential to reliably detect intraoperative myocardial ischemia under these circumstances.