Myocardial Functional Decline During Prolonged Ex Situ Heart Perfusion.

BACKGROUND: Myocardial function declines in a time-dependent fashion during ex situ heart perfusion. Cell death and metabolic alterations may contribute to this phenomenon, limiting the safe perfusion period and the potential of ex situ heart perfusion to expand the donor pool. Our aim was to investigate the etiology of myocardial functional decline in ex situ perfused hearts. METHODS: Cardiac function, apoptosis, effectors and markers of cell death, and metabolic function were assessed in healthy pig hearts perfused for 12 hours. These hearts were perfused in nonworking mode or working mode. RESULTS: Cardiac function declined during ex situ heart perfusion regardless of perfusion mode but was significantly better preserved in the hearts perfused in working mode (11-hour cardiac index/1-hour cardiac index: working mode, 33%; nonworking mode, 10%; p = 0.025). The rate of apoptosis was higher in the ex situ perfused hearts compared with in vivo samples (apoptotic cells: in vivo, 0.13%; working mode, 0.54%; nonworking mode, 0.88%; p < 0.001), but the absolute values were low and out of proportion to the decline in function in either group. Myocardial dysfunction at the end of the perfusion interval was partially rescued by delivery of a pyruvate bolus. CONCLUSIONS: A significant decline in myocardial function occurs over time in hearts preserved ex situ that is out of proportion to the magnitude of myocyte cell death present in dysfunctional hearts. Alterations in myocardial substrate utilization during prolonged ex situ heart perfusion may contribute to this phenomenon and represent an avenue to improve donor heart preservation.

Ex vivo perfusion induces a time- and perfusate-dependent molecular repair response in explanted porcine lungs.

Ex vivo lung perfusion (EVLP) shows promise in ameliorating pretransplant acute lung injury (ALI) and expanding the donor organ pool, but the mechanisms of ex vivo repair remain poorly understood. We aimed to assess the utility of gene expression for characterizing ALI during EVLP. One hundred sixty-nine porcine lung samples were collected in vivo (n = 25), after 0 (n = 11) and 12 (n = 11) hours of cold static preservation (CSP), and after 0 (n = 57), 6 (n = 8), and 12 (n = 57) hours of EVLP, utilizing various ventilation and perfusate strategies. The expression of 53 previously described ALI-related genes was measured and correlated with function and histology. Twenty-eight genes were significantly upregulated and 6 genes downregulated after 12 hours of EVLP. Aggregate gene sets demonstrated differential expression with EVLP (P < .001) but not CSP. Upregulated 28-gene set expression peaked after 6 hours of EVLP, whereas downregulated 6-gene set expression continued to decline after 12 hours. Cellular perfusates demonstrated a greater reduction in downregulated 6-gene set expression vs acellular perfusate (P < .038). Gene set expression correlated with relevant functional and histologic parameters, including P/F ratio (P < .001) and interstitial inflammation (P < .005). Further studies with posttransplant results are warranted to evaluate the clinical significance of this novel molecular approach for assessing organ quality during EVLP.

Metabolically stabilized double-stranded mRNA polyplexes.

The metabolic instability of mRNA currently limits its utility for gene therapy. Compared to plasmid DNA, mRNA is significantly more susceptible to digestion by RNase in the circulation following systemic dosing. To increase mRNA metabolic stability, we hybridized a complementary reverse mRNA with forward mRNA to generate double-stranded mRNA (dsmRNA). RNase A digestion of dsmRNA established a 3000-fold improved metabolic stability compared to single-stranded mRNA (ssmRNA). Formulation of a dsmRNA polyplex using a PEG-peptide further improved the stability by 3000-fold. Hydrodynamic dosing and quantitative bioluminescence imaging of luciferase expression in the liver of mice established the potent transfection efficiency of dsmRNA and dsmRNA polyplexes. However, hybridization of the reverse mRNA against the 5' and 3' UTR of forward mRNA resulted in UTR denaturation and a tenfold loss in expression. Repeat dosing of dsmRNA polyplexes produced an equivalent transient expression, suggesting the lack of an immune response in mice. Co-administration of excess uncapped dsmRNA with a dsmRNA polyplex failed to knock down expression, suggesting that dsmRNA is not a Dicer substrate. Maximal circulatory stability was achieved using a fully complementary dsmRNA polyplex. The results established dsmRNA as a novel metabolically stable and transfection-competent form of mRNA.

Transplantation of Hearts Donated after Circulatory Death.

Cardiac transplantation has become limited by a critical shortage of suitable organs from brain-dead donors. Reports describing the successful clinical transplantation of hearts donated after circulatory death (DCD) have recently emerged. Hearts from DCD donors suffer significant ischemic injury prior to organ procurement; therefore, the traditional approach to the transplantation of hearts from brain-dead donors is not applicable to the DCD context. Advances in our understanding of ischemic post-conditioning have facilitated the development of DCD heart resuscitation strategies that can be used to minimize ischemia-reperfusion injury at the time of organ procurement. The availability of a clinically approved ex situ heart perfusion device now allows DCD heart preservation in a normothermic beating state and minimizes exposure to incremental cold ischemia. This technology also facilitates assessments of organ viability to be undertaken prior to transplantation, thereby minimizing the risk of primary graft dysfunction. The application of a tailored approach to DCD heart transplantation that focuses on organ resuscitation at the time of procurement, ex situ preservation, and pre-transplant assessments of organ viability has facilitated the successful clinical application of DCD heart transplantation. The transplantation of hearts from DCD donors is now a clinical reality. Investigating ways to optimize the resuscitation, preservation, evaluation, and long-term outcomes is vital to ensure a broader application of DCD heart transplantation in the future.

Steroids Limit Myocardial Edema During Ex Vivo Perfusion of Hearts Donated After Circulatory Death.

BACKGROUND: Normothermic ex vivo heart perfusion (EVHP) has been shown to improve the preservation of hearts donated after circulatory arrest and to facilitate clinical successful transplantation. Steroids are added to the perfusate solution in current clinical EVHP protocols; however, the impact of this approach on donor heart preservation has not been previously investigated. We sought to determine the impact of steroids on the inflammatory response and development of myocardial edema during EVHP. METHODS: Thirteen pigs were anesthetized, mechanical ventilation was discontinued, and a hypoxemic cardiac arrest ensued. A 15-minute warm-ischemic standoff period was observed, and then hearts were resuscitated with a cardioplegic solution. Donor hearts were then perfused ex vivo in a normothermic beating state for 6 hours with 500 mg of methylprednisolone (steroid: n = 5) or without (control: n = 8). RESULTS: The addition of steroids to the perfusate solution reduced the generation of proinflammatory cytokines (interleukin-6, -8, -1ß, and tumor necrosis factor-α) and the development of myocardial edema during EVHP (percentage of weight gain: control = 26% ± 7% versus steroid = 16% ± 10%, p = 0.049). Electron microscopy suggested less endothelial cell edema in the steroid group (injury score: control = 1.8 ± 0.2 versus steroid = 1.2 ± 0.2, p = 0.06), whereas perfusate troponin-I (control = 11.9 ± 1.9 ng/mL versus steroid = 9.5 ± 2.4 ng/mL, p = 0.448) and myocardial function were comparable between the groups. CONCLUSIONS: The addition of methylprednisolone to the perfusion solution minimizes the generation of proinflammatory cytokines and development of myocardial edema during normothermic ex vivo perfusion of hearts donated after circulatory arrest.

Negative pressure ventilation decreases inflammation and lung edema during normothermic ex-vivo lung perfusion.

BACKGROUND: Normothermic ex-vivo lung perfusion (EVLP) using positive pressure ventilation (PPV) and both acellular and red blood cell (RBC)-based perfusate solutions have increased the rate of donor organ utilization. We sought to determine whether a negative pressure ventilation (NPV) strategy would improve donor lung assessment during EVLP. METHODS: Thirty-two pig lungs were perfused ex vivo for 12 hours in a normothermic state, and were allocated equally to 4 groups according to the mode of ventilation (positive pressure ventilation [PPV] vs NPV) and perfusate composition (acellular vs RBC). The impact of ventilation strategy on the preservation of 6 unutilized human donor lungs was also evaluated. Physiologic parameters, cytokine profiles, lung injury, bullae and edema formation were compared between treatment groups. RESULTS: Perfused lungs demonstrated acceptable oxygenation (partial pressure of arterial oxygen/fraction of inspired oxygen ratio >350 mm Hg) and physiologic parameters. However, there was less generation of pro-inflammatory cytokines (tumor necrosis factor-α, interleukin-6 and interleukin-8) in human and pig lungs perfused, irrespective of perfusate solution used, when comparing NPV with PPV (p < 0.05), and a reduction in bullae formation with an NPV modality (p = 0.02). Pig lungs developed less edema with NPV (p < 0.01), and EVLP using an acellular perfusate solution had greater edema formation, irrespective of ventilation strategy (p = 0.01). Interestingly, human lungs perfused with NPV developed negative edema, or "drying" (p < 0.01), and lower composite acute lung injury (p < 0.01). CONCLUSIONS: Utilization of an NPV strategy during extended EVLP is associated with significantly less inflammation, and lung injury, irrespective of perfusate solution composition.

Structure-Activity Relationship of PEGylated Polylysine Peptides as Scavenger Receptor Inhibitors for Non-Viral Gene Delivery.

PEGylated polylysine peptides of the general structure PEG30 kDa-Cys-Trp-LysN (N = 10 to 30) were used to form fully condensed plasmid DNA (pGL3) polyplexes at a ratio of 1 nmol of peptide per µg of DNA (ranging from N:P 3:1 to 10:1 depending on Lys repeat). Co-administration of 5 to 80 nmols of excess PEG-peptide with fully formed polyplexes inhibited the liver uptake of (125)I-pGL3-polyplexes. The percent inhibition was dependent on the PEG-peptide dose and was saturable, consistent with inhibition of scavenger receptors. The scavenger receptor inhibition potency of PEG-peptides was dependent on the length of the Lys repeat, which increased 10-fold when comparing PEG30 kDa-Cys-Trp-Lys10 (IC50 of 20.2 µM) with PEG30 kDa-Cys-Trp-Lys25 (IC50 of 2.1 µM). We hypothesize that PEG-peptides inhibit scavenger receptors by spontaneously forming small 40 to 60 nm albumin nanoparticles that bind to and saturate the receptor. Scavenger receptor inhibition delayed the metabolism of pGL3-polyplexes, resulting in efficient gene expression in liver hepatocytes following delayed hydrodynamic dosing. PEG-peptides represent a new class of scavenger inhibitors that will likely have broad utility in blocking unwanted liver uptake and metabolism of a variety of nanoparticles.

Dual antiplatelet therapy use by Canadian cardiac surgeons.

BACKGROUND: Dual antiplatelet therapy is the cornerstone treatment for patients with acute coronary syndrome. Recent Canadian Guidelines recommend the use of dual antiplatelet therapy for 1 year after coronary artery bypass grafting in patients with acute coronary syndrome, but considerable variability remains. METHODS: We performed a survey of 75 Canadian cardiac surgeons to assess the use of dual antiplatelet therapy. RESULTS: Whereas 58.6% of respondents indicated that the benefits of dual antiplatelet therapy were seen irrespective of how patients were managed after acute coronary syndrome, 36.2% believed that the benefits of dual antiplatelet therapy were limited to those treated medically or percutaneously. In regard to the timing of dual antiplatelet therapy administration, 57% of respondents indicated that dual antiplatelet therapy should be given upstream in the emergency department, whereas 36.2% responded that dual antiplatelet therapy should be given only once the coronary anatomy has been defined. The majority surveyed (81%) weighed bleeding risk as being more important than ischemic risk reduction. In stable patients after acute coronary syndrome, the majority of surgeons would wait approximately 4 days after the last dose of P2Y12 antagonist before coronary artery bypass grafting. Only 44.6% indicated that they routinely use dual antiplatelet therapy postrevascularization in the setting of acute coronary syndrome. Rather, most surgeons use dual antiplatelet therapy for select patients, such as those with a stented vessel without a bypass graft, endarterectomy, or off-pump coronary artery bypass grafting. CONCLUSIONS: Cardiac surgeons exhibit variation in their attitudes and practice patterns toward dual antiplatelet therapy after coronary artery bypass grafting, and in approximately half of cases, their practice does not adhere to current guideline recommendations. New trials focusing on coronary artery bypass grafting cases in their primary analysis and educational initiatives for surgeons that focus on guideline recommendations may be warranted.

The utility of cardiac biomarkers and echocardiography for the early detection of bevacizumab- and sunitinib-mediated cardiotoxicity.

The recent introduction of novel anticancer therapies, including bevacizumab (BVZ) and sunitinib (SNT), is associated with an increased risk of cardiotoxicity. However, early identification of left ventricular (LV) systolic dysfunction may facilitate dose modification and avoid the development of advanced heart failure. Using a murine model of BVZ- and SNT-mediated cardiotoxicity, we investigated whether cardiac biomarkers and/or tissue velocity imaging (TVI) using echocardiography can detect early changes in cardiac function, before a decrease in LV ejection fraction is identified. A total of 75 wild-type C57Bl/6 male mice were treated with either 0.9% saline, BVZ, or SNT. Serial monitoring of blood pressure, high-sensitivity troponin I, and echocardiographic indexes were performed over a 14-day study period, after which the mice were euthanized for histological and biochemical analyses. Mice treated with either BVZ or SNT developed systemic hypertension as early as day 7, which increased by day 14. Cardiac biomarkers, specifically high-sensitivity troponin I, were not predictive of early LV systolic dysfunction. Although conventional LV ejection fraction values decreased at day 13 in mice treated with either BVZ or SNT, TVI confirmed early LV systolic dysfunction at day 8. Histological and biochemical analysis demonstrated loss of cellular integrity, increased oxidative stress, and increased cardiac apoptosis in mice treated with BVZ or SNT therapy at day 14. In a murine model of BVZ- or SNT-mediated cardiomyopathy, noninvasive assessment by TVI detected early LV systolic dysfunction before alterations in conventional echocardiographic indexes.

Vocal Cord Paralysis After Thoracic Aortic Surgery: Incidence and Impact on Clinical Outcomes.

BACKGROUND: Vocal cord paralysis (VCP) is a serious complication associated with thoracic aortic surgery; however, there is a paucity of literature regarding the incidence and impact of VCP on postoperative outcomes. We sought to determine the incidence of VCP and its impact on clinical outcomes in patients who underwent thoracic aortic repair at our center. METHODS: A retrospective chart review was conducted on all patients who underwent thoracic aortic surgery between January 2009 and September 2012. RESULTS: A total of 259 patients underwent a thoracic aortic procedure during the study period. Vocal cord paralysis was diagnosed in 12 (5%) patients, a median of 6 [3 to 21] days after extubation. The incidence was 1%, 0%, 20%, and 25% in those undergoing an open ascending, hemiarch, total arch, or descending aortic procedure, respectively. Patients with VCP had an increased incidence of pneumonia (58% vs 17%, p = 0.003), readmission to the intensive care unit for respiratory failure (17% vs 2%, p = 0.047), and longer hospital length of stay (18 [11 to 43] days versus 9 [6 to 15] days, p = 0.002). A propensity-matched analysis confirmed a higher incidence of pneumonia (58% vs 17%, p = 0.020) and longer hospital length of stay (18 [11 to 43] vs 10 [7 to 14] days, p = 0.015) in patients suffering VCP. CONCLUSIONS: Vocal cord paralysis is a common complication in patients undergoing open surgery of the aortic arch and descending aorta, and is associated with significant morbidity. Further research may be warranted to determine if early fiberoptic examination and consideration of a vocal cord medialization procedure may mitigate the morbidity associated with VCP.

Type A aortic dissection complicated by an aorto-right atrial fistula.

A 63-year-old male underwent an ascending aortic replacement for an acute type A dissection. Nine days later a fistulous communication between the right coronary sinus and right atrium was identified and surgically repaired. We present a literature review, including the clinical presentation, diagnosis, and surgical management of this rare complication.

Knowledge, attitudes, and practice patterns in surgical management of bicuspid aortopathy: a survey of 100 cardiac surgeons.

OBJECTIVE: Clinical practice guidelines have been established for surgical management of the aorta in bicuspid aortic valve disease. We hypothesized that surgeons' knowledge of and attitudes toward bicuspid aortic valve aortopathy influence their surgical approaches. METHODS: We surveyed cardiac surgeons to probe the knowledge of, attitudes toward, and surgical management of bicuspid aortopathy. A total of 100 Canadian adult cardiac surgeons participated. RESULTS: Fifty-two percent of surgeons believed that the mechanism underlying aortic dilation in those with bicuspid aortic valve was due to an inherent genetic abnormality of the aorta, whereas only 2% believed that altered valve-related processes were involved in this process. Only a minority (15%) believed that bicuspid valve leaflet fusion type is associated with a unique pattern of aortic dilatation aortic phenotype. Sixty-five percent of surgeons recommended echocardiographic screening of first-degree relatives of patients with bicuspid aortic valve. Most surgeons (61%) elected to replace the aorta when the diameter is 45 mm or greater at the time of valve surgery. Fifty-five percent of surgeons surveyed suggested that in the absence of concomitant valvular disease, they would recommend ascending aortic replacement at a threshold of 50 mm or greater. Approximately one third of surgeons suggested that they would elect to replace a mildly dilated ascending aorta (40 mm) at the time of valve surgery. The most common surgical approach (61%) for combined valve and aortic surgery was aortic valve replacement and supracoronary replacement of the ascending aorta, and only a minority suggested the use of deep hypothermic circulatory arrest and open distal anastomosis. More aggressive approaches were favored with greater surgeon experience, and when circulatory arrest was chosen, the majority (68%) suggested they would use antegrade cerebral perfusion. In the setting of aortic insufficiency and a dilated aorta, 42% of surgeons suggested that they would perform valve-sparing surgery. Of note, 40% of respondents used an index measure of aortic size to body surface area in addition to absolute aortic diameter in assessing the threshold for intervention. CONCLUSIONS: This large survey uncovered significant gaps in the knowledge and attitudes of surgeons toward the diagnosis and management of bicuspid aortopathy, many of which were at odds with current guideline recommendations. Efforts to promote knowledge translation in this area are strongly encouraged.

A cardioprotective preservation strategy employing ex vivo heart perfusion facilitates successful transplant of donor hearts after cardiocirculatory death.

BACKGROUND: Ex vivo heart perfusion (EVHP) has been proposed as a means to facilitate the resuscitation of donor hearts after cardiocirculatory death (DCD) and increase the donor pool. However, the current approach to clinical EVHP may exacerbate myocardial injury and impair function after transplant. Therefore, we sought to determine if a cardioprotective EVHP strategy that eliminates myocardial exposure to hypothermic hyperkalemia cardioplegia and minimizes cold ischemia could facilitate successful DCD heart transplantation. METHODS: Anesthetized pigs sustained a hypoxic cardiac arrest and a 15-minute warm ischemic standoff period. Strategy 1 hearts (S1, n = 9) underwent initial reperfusion with a cold hyperkalemic cardioplegia, normothermic EVHP, and transplantation after a cold hyperkalemic cardioplegic arrest (current EVHP strategy). Strategy 2 hearts (S2, n = 8) underwent initial reperfusion with a tepid adenosine-lidocaine cardioplegia, normothermic EVHP, and transplantation with continuous myocardial perfusion (cardioprotective EVHP strategy). RESULTS: At completion of EVHP, S2 hearts exhibited less weight gain (9.7 ± 6.7 [S2] vs 21.2 ± 6.7 [S1] g/hour, p = 0.008) and less troponin-I release into the coronary sinus effluent (4.2 ± 1.3 [S2] vs 6.3 ± 1.5 [S1] ng/ml; p = 0.014). Mass spectrometry analysis of oxidized pleural in post-transplant myocardium revealed less oxidative stress in S2 hearts. At 30 minutes after wean from cardiopulmonary bypass, post-transplant systolic (pre-load recruitable stroke work: 33.5 ± 1.3 [S2] vs 19.7 ± 10.9 [S1], p = 0.043) and diastolic (isovolumic relaxation constant: 42.9 ± 6.7 [S2] vs 65.2 ± 21.1 [S1], p = 0.020) function were superior in S2 hearts. CONCLUSION: In this experimental model of DCD, an EVHP strategy using initial reperfusion with a tepid adenosine-lidocaine cardioplegia and continuous myocardial perfusion minimizes myocardial injury and improves short-term post-transplant function compared with the current EVHP strategy using cold hyperkalemic cardioplegia before organ procurement and transplantation.

Laparoscopic nephroureterectomy in a patient with a left ventricular assist device.

Left ventricular assist device (LVAD) therapy is an established treatment option for select patients with advanced heart failure. Advances in technology and patient management have resulted in improved post-implant outcomes. Consequently, more patients with LVADs are presenting for evaluation and care of non-cardiac surgical disease. However, there is a paucity of literature regarding the optimal perioperative and surgical management of such patients. We present the case of a 71-year-old male with a HeartMate II (Thoratec Corporation, Pleasanton, CA) LVAD, who underwent a laparoscopic left nephroureterectomy for an upper urinary tract transitional cell carcinoma. His perioperative course was uneventful due to the multidisciplinary efforts of cardiac surgery, cardiac anesthesia, nephrology and urology. To our knowledge, this is the first reported case of a laparoscopic nephroureterectomy in a patient with a HeartMate II LVAD.