Safety profiling of genetically engineered Pim-1 kinase overexpression for oncogenicity risk in human c-kit+ cardiac interstitial cells.

Advancement of stem cell-based treatment will involve next-generation approaches to enhance therapeutic efficacy which is often modest, particularly in the context of myocardial regenerative therapy. Our group has previously demonstrated the beneficial effect of genetic modification of cardiac stem cells with Pim-1 kinase overexpression to rejuvenate aged cells as well as potentiate myocardial repair. Despite these encouraging findings, concerns were raised regarding potential for oncogenic risk associated with Pim-1 kinase overexpression. Testing of Pim-1 engineered c-kit+ cardiac interstitial cells (cCIC) derived from heart failure patient samples for indices of oncogenic risk was undertaken using multiple assessments including soft agar colony formation, micronucleation, gamma-Histone 2AX foci, and transcriptome profiling. Collectively, findings demonstrate comparable phenotypic and biological properties of cCIC following Pim-1 overexpression compared with using baseline control cells with no evidence for oncogenic phenotype. Using a highly selective and continuous sensor for quantitative assessment of PIM1 kinase activity revealed a sevenfold increase in Pim-1 engineered vs. control cells. Kinase activity profiling using a panel of sensors for other kinases demonstrates elevation of IKKs), AKT/SGK, CDK1-3, p38, and ERK1/2 in addition to Pim-1 consistent with heightened kinase activity correlating with Pim-1 overexpression that may contribute to Pim-1-mediated effects. Enhancement of cellular survival, proliferation, and other beneficial properties to augment stem cell-mediated repair without oncogenic risk is a feasible, logical, and safe approach to improve efficacy and overcome current limitations inherent to cellular adoptive transfer therapeutic interventions.

Hypoxia Prevents Mitochondrial Dysfunction and Senescence in Human c-Kit+ Cardiac Progenitor Cells.

Senescence-associated dysfunction deleteriously affects biological activities of human c-Kit+ cardiac progenitor cells (hCPCs), particularly under conditions of in vitro culture. In comparison, preservation of self-renewal and decreases in mitochondrial reactive oxygen species (ROS) are characteristics of murine CPCs in vivo that reside within hypoxic niches. Recapitulating hypoxic niche oxygen tension conditions of ∼1% O2 in vitro for expansion of hCPCs rather than typical normoxic cell culture conditions (21% O2 ) could provide significant improvement of functional and biological activities of hCPCs. hCPCs were isolated and expanded under permanent hypoxic (hCPC-1%) or normoxic (hCPC-21%) conditions from left ventricular tissue explants collected during left ventricular assist device implantation. hCPC-1% exhibit increased self-renewal and suppression of senescence characteristics relative to hCPC-21%. Oxidative stress contributed to higher susceptibility to apoptosis, as well as decreased mitochondrial function in hCPC-21%. Hypoxia prevented accumulation of dysfunctional mitochondria, supporting higher oxygen consumption rates and mitochondrial membrane potential. Mitochondrial ROS was an upstream mediator of senescence since treatment of hCPC-1% with mitochondrial inhibitor antimycin A recapitulated mitochondrial dysfunction and senescence observed in hCPC-21%. NAD+ /NADH ratio and autophagic flux, which are key factors for mitochondrial function, were higher in hCPC-1%, but hCPC-21% were highly dependent on BNIP3/NIX-mediated mitophagy to maintain mitochondrial function. Overall, results demonstrate that supraphysiological oxygen tension during in vitro expansion initiates a downward spiral of oxidative stress, mitochondrial dysfunction, and cellular energy imbalance culminating in early proliferation arrest of hCPCs. Senescence is inhibited by preventing ROS through hypoxic culture of hCPCs. Stem Cells 2019;37:555-567.

Cardiac c-Kit Biology Revealed by Inducible Transgenesis.

RATIONALE: Biological significance of c-Kit as a cardiac stem cell marker and role(s) of c-Kit+ cells in myocardial development or response to pathological injury remain unresolved because of varied and discrepant findings. Alternative experimental models are required to contextualize and reconcile discordant published observations of cardiac c-Kit myocardial biology and provide meaningful insights regarding clinical relevance of c-Kit signaling for translational cell therapy. OBJECTIVE: The main objectives of this study are as follows: demonstrating c-Kit myocardial biology through combined studies of both human and murine cardiac cells; advancing understanding of c-Kit myocardial biology through creation and characterization of a novel, inducible transgenic c-Kit reporter mouse model that overcomes limitations inherent to knock-in reporter models; and providing perspective to reconcile disparate viewpoints on c-Kit biology in the myocardium. METHODS AND RESULTS: In vitro studies confirm a critical role for c-Kit signaling in both cardiomyocytes and cardiac stem cells. Activation of c-Kit receptor promotes cell survival and proliferation in stem cells and cardiomyocytes of either human or murine origin. For creation of the mouse model, the cloned mouse c-Kit promoter drives Histone2B-EGFP (enhanced green fluorescent protein; H2BEGFP) expression in a doxycycline-inducible transgenic reporter line. The combination of c-Kit transgenesis coupled to H2BEGFP readout provides sensitive, specific, inducible, and persistent tracking of c-Kit promoter activation. Tagging efficiency for EGFP+/c-Kit+ cells is similar between our transgenic versus a c-Kit knock-in mouse line, but frequency of c-Kit+ cells in cardiac tissue from the knock-in model is 55% lower than that from our transgenic line. The c-Kit transgenic reporter model reveals intimate association of c-Kit expression with adult myocardial biology. Both cardiac stem cells and a subpopulation of cardiomyocytes express c-Kit in uninjured adult heart, upregulating c-Kit expression in response to pathological stress. CONCLUSIONS: c-Kit myocardial biology is more complex and varied than previously appreciated or documented, demonstrating validity in multiple points of coexisting yet heretofore seemingly irreconcilable published findings.

Percutaneous Repair of Postoperative Mitral Regurgitation After Left Ventricular Assist Device Implant.

Mitral regurgitation commonly improves after implantation of a left ventricular assist device without concomitant valvular repair owing to the mechanical unloading of the left ventricle. However, the development (or persistence) of significant mitral regurgitation after implantation of a left ventricular assist device is associated with adverse clinical events. We present a case of a left ventricular assist device patient who successfully underwent a percutaneous MitraClip procedure for repair of persistent late postoperative mitral insufficiency with demonstrable clinical and hemodynamic improvement.

Empowering human cardiac progenitor cells by P2Y14 nucleotide receptor overexpression.

KEY POINTS: Autologous cardiac progenitor cell (CPC) therapy is a promising approach for treatment of heart failure (HF). There is an unmet need to identify inherent deficits in aged/diseased human CPCs (hCPCs) derived from HF patients in the attempts to augment their regenerative capacity prior to use in the clinical setting. Here we report significant functional correlations between phenotypic properties of hCPCs isolated from cardiac biopsies of HF patients, clinical parameters of patients and expression of the P2Y14 purinergic receptor (P2Y14 R), a crucial detector for extracellular UDP-sugars released during injury/stress. P2Y14 R is downregulated in hCPCs derived from HF patients with lower ejection fraction or diagnosed with diabetes. Augmenting P2Y14 R expression levels in aged/diseased hCPCs antagonizes senescence and improves functional responses. This study introduces purinergic signalling modulation as a potential strategy to rejuvenate and improve phenotypic characteristics of aged/functionally compromised hCPCs prior to transplantation in HF patients. ABSTRACT: Autologous cardiac progenitor cell therapy is a promising alternative approach to current inefficient therapies for heart failure (HF). However, ex vivo expansion and pharmacological/genetic modification of human cardiac progenitor cells (hCPCs) are necessary interventions to rejuvenate aged/diseased cells and improve their regenerative capacities. This study was designed to assess the potential of improving hCPC functional capacity by targeting the P2Y14 purinergic receptor (P2Y14 R), which has been previously reported to induce regenerative and anti-senescence responses in a variety of experimental models. c-Kit+ hCPCs were isolated from cardiac biopsies of multiple HF patients undergoing left ventricular assist device implantation surgery. Significant correlations existed between the expression of P2Y14 R in hCPCs and clinical parameters of HF patients. P2Y14 R was downregulated in hCPCs derived from patients with a relatively lower ejection fraction and patients diagnosed with diabetes. hCPC lines with lower P2Y14 R expression did not respond to P2Y14 R agonist UDP-glucose (UDP-Glu) while hCPCs with higher P2Y14 R expression showed enhanced proliferation in response to UDP-Glu stimulation. Mechanistically, UDP-Glu stimulation enhanced the activation of canonical growth signalling pathways ERK1/2 and AKT. Restoring P2Y14 R expression levels in functionally compromised hCPCs via lentiviral-mediated overexpression improved proliferation, migration and survival under stress stimuli. Additionally, P2Y14 R overexpression reversed senescence-associated morphology and reduced levels of molecular markers of senescence p16INK4a , p53, p21 and mitochondrial reactive oxygen species. Findings from this study unveil novel biological roles of the UDP-sugar receptor P2Y14 in hCPCs and suggest purinergic signalling modulation as a promising strategy to improve phenotypic properties of functionally impaired hCPCs.

P2Y2 Nucleotide Receptor Prompts Human Cardiac Progenitor Cell Activation by Modulating Hippo Signaling.

RATIONALE: Autologous stem cell therapy using human c-Kit+ cardiac progenitor cells (hCPCs) is a promising therapeutic approach for treatment of heart failure (HF). However, hCPCs derived from aged patients with HF with genetic predispositions and comorbidities of chronic diseases exhibit poor proliferative and migratory capabilities, which impair overall reparative potential for injured myocardium. Therefore, empowering functionally compromised hCPCs with proregenerative molecules ex vivo is crucial for improving the therapeutic outcome in patients with HF. OBJECTIVE: To improve hCPC proliferation and migration responses that are critical for regeneration by targeting proregenerative P2Y2 nucleotide receptor (P2Y2R) activated by extracellular ATP and UTP molecules released following injury/stress. METHODS AND RESULTS: c-Kit+ hCPCs were isolated from cardiac tissue of patients with HF undergoing left ventricular assist device implantation surgery. Correlations between P2 nucleotide receptor expression and hCPC growth kinetics revealed downregulation of select P2 receptors, including P2Y2R, in slow-growing hCPCs compared with fast growers. hCPC proliferation and migration significantly improved by overexpressing or stimulating P2Y2R. Mechanistically, P2Y2R-induced proliferation and migration were dependent on activation of YAP (yes-associated protein)-the downstream effector of Hippo signaling pathway. CONCLUSIONS: Proliferation and migration of functionally impaired hCPCs are enhanced by P2Y2R-mediated YAP activation, revealing a novel link between extracellular nucleotides released during injury/stress and Hippo signaling-a central regulator of cardiac regeneration. Functional correlations exist between hCPC phenotypic properties and P2 purinergic receptor expression. Lack of P2Y2R and other crucial purinergic stress detectors could compromise hCPC responsiveness to presence of extracellular stress signals. These findings set the stage for subsequent studies to assess purinergic signaling modulation as a potential strategy to improve therapeutic outcome for use of hCPCs in patients with HF.

Concurrent Isolation of 3 Distinct Cardiac Stem Cell Populations From a Single Human Heart Biopsy.

RATIONALE: The relative actions and synergism between distinct myocardial-derived stem cell populations remain obscure. Ongoing debates on optimal cell population(s) for treatment of heart failure prompted implementation of a protocol for isolation of multiple stem cell populations from a single myocardial tissue sample to develop new insights for achieving myocardial regeneration. OBJECTIVE: Establish a robust cardiac stem cell isolation and culture protocol to consistently generate 3 distinct stem cell populations from a single human heart biopsy. METHODS AND RESULTS: Isolation of 3 endogenous cardiac stem cell populations was performed from human heart samples routinely discarded during implantation of a left ventricular assist device. Tissue explants were mechanically minced into 1 mm3 pieces to minimize time exposure to collagenase digestion and preserve cell viability. Centrifugation removes large cardiomyocytes and tissue debris producing a single cell suspension that is sorted using magnetic-activated cell sorting technology. Initial sorting is based on tyrosine-protein kinase Kit (c-Kit) expression that enriches for 2 c-Kit+ cell populations yielding a mixture of cardiac progenitor cells and endothelial progenitor cells. Flowthrough c-Kit- mesenchymal stem cells are positively selected by surface expression of markers CD90 and CD105. After 1 week of culture, the c-Kit+ population is further enriched by selection for a CD133+ endothelial progenitor cell population. Persistence of respective cell surface markers in vitro is confirmed both by flow cytometry and immunocytochemistry. CONCLUSIONS: Three distinct cardiac cell populations with individualized phenotypic properties consistent with cardiac progenitor cells, endothelial progenitor cells, and mesenchymal stem cells can be successfully concurrently isolated and expanded from a single tissue sample derived from human heart failure patients.

Factors Related to Pump Thrombosis With the Heartmate II Left Ventricular Assist Device.

BACKGROUND: Recent reports suggested that HeartMate II (HMII) thrombosis rates may be higher in implants after 2011. We characterize events at HMII centers (>100 HMII implants) whose device thrombosis rates are equivalent or lower than reported by INTERMACS. METHODS: Seven centers pooled implants from 2011 through June 2013 to examine pump thrombus and identify characteristics and clinical strategies that potentially mitigate the risk. A total of 666 patients (age 59 ± 13 years; 81% male) were studied (support duration: 13.7 ± 8.3 months, cumulative: 759 patient years). Median target INR was 2.25 (range 2.0 to 2.5), and median pump speed was 9200 rpm (range 8600 to 9600). Pump thrombus was suspected with clinical evidence (e.g., hemolysis, positive ramp test) requiring intervention (e.g., anticoagulation therapy, pump exchange) or patient death. RESULTS: Suspected pump thrombus occurred in 24/666 (3.6%) patients within three months of implant. At six months, 38/666 (5.7%) had suspected pump thrombus including 24 (3.6%) resulting in pump exchange or death. Stroke (hemorrhagic: 0.049, and ischemic: 0.048 events/patient year) and survival (six months: 88 ± 1%; 1 year: 81 ± 2%) were consistent with national averages. Suspected pump thrombus patients were younger (55 ± 13 vs. 59 ± 13, p = 0.046) and had more females (31.6% vs. 18.3%, p = 0.054). There was no difference in indication, etiology of heart failure, or body size. CONCLUSIONS: This analysis demonstrates low HMII thrombus events. Minimization of risk factors by uniform implant techniques and consistent post-op management may reduce device thrombosis. A larger scale multicenter evaluation may better elucidate the difference in thrombus events between centers.

Safety of Prothombin Complex Concentrate to Control Excess Bleeding During Continuous Flow LVAD Insertion.

In cardiovascular surgery, hemostatic complexities require the provision of blood products to control bleeding as well as the use of a number of hemostatic agents, some of which cause significant morbidity. Among these agents is prothrombin complex concentrates (PCC), however there is no clear consensus on PCC use in cardiovascular surgery. To investigate the safety of PCC in patients undergoing left ventricular assist device (LVAD) placement, we reviewed our single institution experience to examine the incidence of thromboembolic events and a variety of hospital markers including morbidity and mortality. A retrospective review was conducted of patients who underwent LVAD placement between January 2010 and October 2012. Patients who received intraoperative PCC constituted the PCC group (n = 41) and those who did not constituted the non-PCC group (n = 27). The overall incidence of thromboembolic events at 3 months postoperative was 12 (29.3%) in the PCC group compared with six (22.2%) in the non-PCC group, respectively (p > 0.05). Morbidity did not differ between groups and one patient in the PCC group died. The intraoperative use of PCC in LVAD insertion does not appear to be associated with a significant increase in thromboembolic events; however, larger randomized trials are needed to confirm these findings.

Role of TGF-ß Signaling in Remodeling of Noncoronary Artery Aneurysms in Kawasaki Disease.

Coronary artery aneurysms (CAA) remain an important complication of Kawasaki disease (KD), the most common form of pediatric acquired heart disease in developed countries. Potentially life-threatening CAA develop in 25% of untreated children and 5% of children treated with high-dose intravenous immunoglobulin during the acute phase of the self-limited vasculitis. Noncoronary artery aneurysms (NCAA) in extraparenchymal, muscular arteries occur in a minority of patients with KD who also have CAA, yet little is understood about their formation and remodeling. We postulated that activation of the transforming growth factor-ß (TGF-ß) pathway in KD may influence formation and remodeling of aneurysms in iliac, femoral, and axillary arteries, the most common sites for NCAA. We studied a resected axillary artery from one adult and endarterectomy tissue from the femoral artery from a second adult, both with a history of CAA and NCAA following KD in infancy. Histology of the axillary artery aneurysm revealed destruction of the internal elastic lamina and recanalization of organized thrombus, while the endarterectomy specimen showed dense calcification and luminal myofibroblastic proliferation. Immunohistochemistry for molecules in the TGF-ß signaling pathway revealed increased expression of TGF-ß2, TGF-ß receptor 2, and phosphorylated SMAD3. These findings suggest ongoing tissue remodeling of the aneurysms decades after the acute injury and demonstrate the importance of the TGF-ß signaling pathway in this process.

Functional Effect of Pim1 Depends upon Intracellular Localization in Human Cardiac Progenitor Cells.

Human cardiac progenitor cells (hCPC) improve heart function after autologous transfer in heart failure patients. Regenerative potential of hCPCs is severely limited with age, requiring genetic modification to enhance therapeutic potential. A legacy of work from our laboratory with Pim1 kinase reveals effects on proliferation, survival, metabolism, and rejuvenation of hCPCs in vitro and in vivo. We demonstrate that subcellular targeting of Pim1 bolsters the distinct cardioprotective effects of this kinase in hCPCs to increase proliferation and survival, and antagonize cellular senescence. Adult hCPCs isolated from patients undergoing left ventricular assist device implantation were engineered to overexpress Pim1 throughout the cell (PimWT) or targeted to either mitochondrial (Mito-Pim1) or nuclear (Nuc-Pim1) compartments. Nuc-Pim1 enhances stem cell youthfulness associated with decreased senescence-associated ß-galactosidase activity, preserved telomere length, reduced expression of p16 and p53, and up-regulation of nucleostemin relative to PimWT hCPCs. Alternately, Mito-Pim1 enhances survival by increasing expression of Bcl-2 and Bcl-XL and decreasing cell death after H2O2 treatment, thereby preserving mitochondrial integrity superior to PimWT. Mito-Pim1 increases the proliferation rate by up-regulation of cell cycle modulators Cyclin D, CDK4, and phospho-Rb. Optimal stem cell traits such as proliferation, survival, and increased youthful properties of aged hCPCs are enhanced after targeted Pim1 localization to mitochondrial or nuclear compartments. Targeted Pim1 overexpression in hCPCs allows for selection of the desired phenotypic properties to overcome patient variability and improve specific stem cell characteristics.

Principles of HeartMate II implantation to avoid pump malposition and migration.

Proper left ventricular assist device (LVAD) insertion will help maximize LVAD flow and may reduce adverse events such as right heart failure and pump thrombosis. Although no standardized insertion technique has been universally accepted, the goals are: unobstructed inflow cannula, unobstructed outflow graft with avoidance of right ventricular compression, and prevention of pump migration. To achieve these objectives for the HeartMate II LVAD, we delineate four principles: proper pump pocket creation, optimized positioning of inflow cannula and outflow graft, proper pump position in the body, and fixation. These basic principles are easy to implement and have been beneficial in our patients, assuring long-term unobstructed LVAD flow.

Rejuvenation of human cardiac progenitor cells with Pim-1 kinase.

RATIONALE: Myocardial function is enhanced by adoptive transfer of human cardiac progenitor cells (hCPCs) into a pathologically challenged heart. However, advanced age, comorbidities, and myocardial injury in patients with heart failure constrain the proliferation, survival, and regenerative capacity of hCPCs. Rejuvenation of senescent hCPCs will improve the outcome of regenerative therapy for a substantial patient population possessing functionally impaired stem cells. OBJECTIVE: Reverse phenotypic and functional senescence of hCPCs by ex vivo modification with Pim-1. METHODS AND RESULTS: C-kit-positive hCPCs were isolated from heart biopsy samples of patients undergoing left ventricular assist device implantation. Growth kinetics, telomere lengths, and expression of cell cycle regulators showed significant variation between hCPC isolated from multiple patients. Telomere length was significantly decreased in hCPC with slow-growth kinetics concomitant with decreased proliferation and upregulation of senescent markers compared with hCPC with fast-growth kinetics. Desirable youthful characteristics were conferred on hCPCs by genetic modification using Pim-1 kinase, including increases in proliferation, telomere length, survival, and decreased expression of senescence markers. CONCLUSIONS: Senescence characteristics of hCPCs are ameliorated by Pim-1 kinase resulting in rejuvenation of phenotypic and functional properties. hCPCs show improved cellular properties resulting from Pim-1 modification, but benefits were more pronounced in hCPC with slow-growth kinetics relative to hCPC with fast-growth kinetics. With the majority of patients with heart failure presenting advanced age, infirmity, and impaired regenerative capacity, the use of Pim-1 modification should be incorporated into cell-based therapeutic approaches to broaden inclusion criteria and address limitations associated with the senescent phenotype of aged hCPC.

Human cardiac progenitor cells engineered with Pim-I kinase enhance myocardial repair.

OBJECTIVES: The goal of this study was to demonstrate the enhancement of human cardiac progenitor cell (hCPC) reparative and regenerative potential by genetic modification for the treatment of myocardial infarction. BACKGROUND: Regenerative potential of stem cells to repair acute infarction is limited. Improved hCPC survival, proliferation, and differentiation into functional myocardium will increase efficacy and advance translational implementation of cardiac regeneration. METHODS: hCPCs isolated from the myocardium of heart failure patients undergoing left ventricular assist device implantation were engineered to express green fluorescent protein (hCPCe) or Pim-1-GFP (hCPCeP). Functional tests of hCPC regenerative potential were performed with immunocompromised mice by using intramyocardial adoptive transfer injection after infarction. Myocardial structure and function were monitored by echocardiographic and hemodynamic assessment for 20 weeks after delivery. hCPCe and hCPCeP expressing luciferase were observed by using bioluminescence imaging to noninvasively track persistence. RESULTS: hCPCeP exhibited augmentation of reparative potential relative to hCPCe control cells, as shown by significantly increased proliferation coupled with amelioration of infarction injury and increased hemodynamic performance at 20 weeks post-transplantation. Concurrent with enhanced cardiac structure and function, hCPCeP demonstrated increased cellular engraftment and differentiation with improved vasculature and reduced infarct size. Enhanced persistence of hCPCeP versus hCPCe was revealed by bioluminescence imaging at up to 8 weeks post-delivery. CONCLUSIONS: Genetic engineering of hCPCs with Pim-1 enhanced repair of damaged myocardium. Ex vivo gene delivery to modify stem cells has emerged as a viable option addressing current limitations in the field. This study demonstrates that efficacy of hCPCs from the failing myocardium can be safely and significantly enhanced through expression of Pim-1 kinase, setting the stage for use of engineered cells in pre-clinical settings.

Mitroflow aortic bioprosthesis 5-year follow-up: north american prospective multicenter study.

BACKGROUND: The Mitroflow valve (Sorin Group, Milan, Italy) has been in use since 1982 and has shown long-term durability in large studies from European centers but has not been studied for long-term hemodynamics in large standardized multicenter trials. This study sought to assess the hemodynamics of the Mitroflow valve by extending the duration of follow-up in an ongoing prospective multicenter trial conducted in North America. METHODS: Six sites participated in this midterm study requiring annual follow-up and echocardiographic evaluation using a standardized transthoracic echocardiography acquisition protocol. RESULTS: There were 276 patients enrolled (age 74±8 years) and 54% were in New York Heart Association (NYHA) functional class III-IV. Follow-up from the time of valve implantation had a mean of 4.0±1.7 years with a cumulative follow-up of 1,102 patient-years. At 5 years of follow-up, 99% of patients were free of moderate or severe aortic regurgitation and 94% were in NYHA functional class I or II. Between baseline and 5 years, mean gradients increased an average of 0.4 to 4.3 mm Hg. The change in effective orifice area was appreciably small (-0.1 to -0.3 cm2) after 5 years. There were 57 deaths (4 early and 53 late) and 9 valve explants. CONCLUSIONS: The Mitroflow valve implanted in the aortic position has shown to be hemodynamically stable over a 5-year follow-up in an elderly population with a high prevalence of comorbid conditions.

A North American, prospective, multicenter assessment of the Mitroflow aortic pericardial prosthesis.

BACKGROUND: The aim of the Mitroflow aortic pericardial valve study was to prospectively assess performance of the Mitroflow prosthesis among North American patients. METHODS: The study was conducted between November 2003 and December 2007 on patients requiring aortic valve replacement. The study cohort consisted of 689 patients (391 male, 298 female), with a mean age of 74.3 +/- 8.4 years, and 46.6% of whom were New York Heart Association (NYHA) class I/II preoperatively. Patients were followed at 3 to 6 months and yearly until study closure. Mean follow-up was 25.7 +/- 12 months, and total follow-up was 1,474.4 patient-years, with a maximum of 48.7 months. RESULTS: Postoperatively, more than 97% of evaluated patients were NYHA class I/II. At 3 years, 131 patients had died, for an actuarial survival of 79.1%; and the 3-year actuarial freedom from valve-related death, valve explant, all valve reoperation, and structural valve dysfunction was 97.0%, 98.1%, 97.9%, and 99.2%, respectively. Other valve-related complications included prosthetic valve endocarditis (1.4% per patient-year), thromboembolic episodes (1.3% per patient-year), major embolism (0.5% per patient-year), perivalvular leak (0.6% per patient-year), and major anticoagulation-related bleeding (0.6% per patient-year). Echocardiograms at 1 year showed mean pressure gradients averaged from 7.3 +/- 1.8 mm Hg to 13.4 +/- 5.1 mm Hg, and peak gradients averaged from 14.3 +/- 4.7 mm Hg to 26.0 +/- 9.2 mm Hg for valve sizes 27 to 19. Aortic regurgitation in patients was absent/trace (90.2%) or mild (8.7%); none was severe. CONCLUSIONS: The early results of this study show a low incidence of valve-related adverse events and excellent hemodynamic performance. Continued follow-up is needed to determine if long-term durability in North American patients is comparable to that in previous reports on the durability of the Mitroflow valve.

A 20-year experience with urgent percutaneous cardiopulmonary bypass for salvage of potential survivors of refractory cardiovascular collapse.

OBJECTIVE: In-hospital cardiac arrest or refractory shock carries a high mortality despite the use of advanced resuscitative measures. We have implemented an in-hospital, nurse-based, continuously available, percutaneous, venoarterial cardiopulmonary bypass system, also known as extracorporeal life support (ECLS), as an adjunct to resuscitation when initial measures are ineffective. METHODS: In 1986, a system for the rapid initiation of ECLS, was created in which trained critical care nurses primed an ECLS circuit and in-house physicians percutaneously placed required cannulas. From a prospective registry, we assessed long-term survival (LTS) (> or =30 days, cardiopulmonary support weaned), short-term survival (<30 days, CPS weaned), or death on CPS. RESULTS: One hundred fifty patients (age, 57 +/- 17 years) were urgently started on CPS for cardiac arrest (n = 127; witnessed, n = 124; unwitnessed, n = 3) and refractory shock (n = 23). Sixty-nine patients were weaned from CPS, and 81 could not be weaned. Overall, 39 (26.0%) patients achieved LTS with a subsequent Kaplan-Meier median survival of 9.5 years. Duration of CPS was 32 +/- 38 hours for LTS and 21 +/- 38 hours for non-LTS. LTS occurred in 29 (23.4%) of 124 patients started on CPS for witnessed cardiac arrest and 11 (47.8%) of 23 for refractory shock (P < .05). Among patients with CPS initiated in the cardiac catheterization laboratory, LTS was seen in 24 (50.0%) of 48 versus 15 (14.7%) of 102 in patients with CPS initiated in other locations (P < .001). Cardiopulmonary resuscitation times greater than or equal to 30 minutes were associated with lower LTS (P < .05). The most common cause of death during CPS was refractory cardiac dysfunction (39.5%), and the most common cause associated with short-term survival was neurologic/pulmonary dysfunction (53.6%). Seven patients were bridged to a left ventricular assist device, and 1 subsequently underwent heart transplantation. Multivariate analysis revealed only cardiac catheterization laboratory site of initiation as a significant independent predictor of LTS (P < .01). When dividing the 20-year experience in tertiles, recent recipients have had more common prearrest insertion. Rates of long-term survival have not changed. CONCLUSION: Of patients started on CPS, 46% were weaned, and 26.0% were long-time survivors. Rapid initiation of CPS permits LTS for some inpatients with cardiovascular collapse when initial advanced resuscitation fails. Strategies to improve end-organ function associated with use of CPS should lead to greater LTS. This practical application of inexpensive available technology should be more widely used.

Improved mechanical reliability of the HeartMate XVE left ventricular assist system.

BACKGROUND: The HeartMate XVE left ventricular assist device is a valuable treatment option for patients with end-stage heart failure. During the past several years, the XVE has undergone a series of design enhancements to improve reliability. We compared the reliability of the two most recent design iterations of the XVE pump (stitch modification to the inflow valve assembly and new inflow valve housing redesign) to the earlier VE version. METHODS: A retrospective evaluation of device reliability was performed for 268 devices implanted in 245 patients (VE: n = 167 devices, 147 patients, implant dates October 16, 1998, to December 19, 2003; XVE: n = 101 devices, 98 patients, implant dates August 1, 2002, to April 14, 2004). RESULTS: Median duration of device support for the VE and XVE was 159 days (range, 0 to 1,206 days) and 229 days (range, 0 to 693 days), respectively (p = 0.495). Significantly fewer major device malfunctions occurred within the XVE group as compared with the VE group (6 versus 36, respectively; p = 0.0003). The number of major device malfunctions per patient-year of support for inflow valve dysfunction, bearing wear, and other failures for the VE and XVE were 0.2 versus 0.04 (p = 0.006), 0.16 versus 0.01 (p = 0.005), and 0.06 versus 0.04 (p = 1.000), respectively. The freedom from major device malfunction at 1 year was 76% +/- 6% for the VE and 97% +/- 2% for the XVE device (p < 0.001). The freedom from death as a result of major device malfunction at 1 year was 97% +/- 2% for the VE and 98% +/- 2% for the XVE (p = 0.698). CONCLUSIONS: Design enhancements to the HeartMate XVE have significantly reduced the incidence of major device malfunctions compared with the earlier VE model because of a reduction in failure modes from bearing wear and inlet valve dysfunction. Further follow-up is necessary to establish the long-term durability of the most recent XVE pump version.