Normal cardiac function in mice with supraphysiological cardiac creatine levels.

Creatine and phosphocreatine levels are decreased in heart failure, and reductions in myocellular phosphocreatine levels predict the severity of the disease and portend adverse outcomes. Previous studies of transgenic mouse models with increased creatine content higher than two times baseline showed the development of heart failure and shortened lifespan. Given phosphocreatine's role in buffering ATP content, we tested the hypothesis whether elevated cardiac creatine content would alter cardiac function under normal physiological conditions. Here, we report the creation of transgenic mice that overexpress the human creatine transporter (CrT) in cardiac muscle under the control of the α-myosin heavy chain promoter. Cardiac transgene expression was quantified by qRT-PCR, and human CrT protein expression was documented on Western blots and immunohistochemistry using a specific anti-CrT antibody. High-energy phosphate metabolites and cardiac function were measured in transgenic animals and compared with age-matched, wild-type controls. Adult transgenic animals showed increases of 5.7- and 4.7-fold in the content of creatine and free ADP, respectively. Phosphocreatine and ATP levels were two times as high in young transgenic animals but declined to control levels by the time the animals reached 8 wk of age. Transgenic mice appeared to be healthy and had normal life spans. Cardiac morphometry, conscious echocardiography, and pressure-volume loop studies demonstrated mild hypertrophy but normal function. Based on our characterization of the human CrT protein expression, creatine and phosphocreatine content, and cardiac morphometry and function, these transgenic mice provide an in vivo model for examining the therapeutic value of elevated creatine content for cardiac pathologies.

Operative and nonoperative management of chronic disseminated intravascular coagulation due to persistent aortic endoleak.

Disseminated intravascular coagulation (DIC) due to endoleak is a rare complication following endovascular aneurysm repair. Two of the four previously reported cases occurred in patients with cirrhosis. We describe three patients with normal liver function who developed DIC due to delayed high-flow (type Ia or III) endoleaks. Two patients underwent successful surgical repair, and the third was managed medically. All three patients had chronic thrombocytopenia prior to developing an endoleak as did the four reported cases in the literature. We propose that thrombocytopenia, like cirrhosis, be considered a risk factor for DIC due to endoleaks in patients undergoing endovascular aneurysm repair.

Endogenous S-nitrosothiols protect against myocardial injury.

Despite substantial evidence that nitric oxide (NO) and/or endogenous S-nitrosothiols (SNOs) exert protective effects in a variety of cardiovascular diseases, the molecular details are largely unknown. Here we show that following left coronary artery ligation, mice with a targeted deletion of the S-nitrosoglutathione reductase gene (GSNOR(-/-)) have reduced myocardial infarct size, preserved ventricular systolic and diastolic function, and maintained tissue oxygenation. These profound physiological effects are associated with increases in myocardial capillary density and S-nitrosylation of the transcription factor hypoxia inducible factor-1alpha (HIF-1alpha) under normoxic conditions. We further show that S-nitrosylated HIF-1alpha binds to the vascular endothelial growth factor (VEGF) gene, thus identifying a role for GSNO in angiogenesis and myocardial protection. These results suggest innovative approaches to modulate angiogenesis and preserve cardiac function.

Population-Based Trends in Amputations and Revascularizations for Peripheral Artery Disease From 1990 to 2009.

OBJECTIVE: To determine trends in amputations and revascularizations for peripheral artery disease (PAD) in a well-defined population. METHODS: A population-based cohort study of Olmsted County, Minnesota, residents with PAD undergoing amputation or revascularization was conducted between January 1, 1990, and December 31, 2009. Population-level 5-year incidence trends for endovascular, open surgical, and hybrid revascularizations and major and minor amputations were determined. Limb-specific outcomes after revascularization, including major adverse limb events and amputation-free survival, were compared between initial surgical and endovascular or hybrid revascularization groups using Kaplan-Meier analysis. RESULTS: We identified 773 residents who underwent 1906 limb-procedures, including 689 open revascularizations, 685 endovascular or hybrid revascularizations, and 220 major amputations. During the 20-year study period, the incidence of endovascular and hybrid revascularizations increased, whereas the incidence of open surgical revascularizations and major amputations decreased. Incidence of revascularizations for chronic limb-threatening ischemia (CLTI) did not change. Among residents with CLTI undergoing their first revascularization on a limb, endovascular revascularization was associated with more major adverse limb events and major amputations compared with surgical revascularization during the ensuing 15 years. CONCLUSION: The rising incidence of endovascular and hybrid revascularizations and the decreasing incidence of open surgical revascularizations for PAD were associated with a decreasing incidence of major amputations in this population between 1990 and 2009, despite a stable incidence of revascularizations for CLTI. With more major adverse limb events and major amputations after endovascular revascularization, these trends suggest that additional emphasis should be placed on improving limb salvage efforts beyond just mode of revascularization.

Dynamic regulation of phosphoinositide 3-kinase-gamma activity and beta-adrenergic receptor trafficking in end-stage human heart failure.

BACKGROUND: Downregulation of beta-adrenergic receptors (betaARs) under conditions of heart failure requires receptor targeting of phosphoinositide 3-kinase (PI3K)-gamma and redistribution of betaARs into endosomal compartments. Because support with a left ventricular assist device (LVAD) results in significant improvement of cardiac function in humans, we investigated the effects of mechanical unloading on regulation of PI3Kgamma activity and intracellular distribution of betaARs. Additionally, we tested whether displacement of PI3Kgamma from activated betaARs would restore agonist responsiveness in failing human cardiomyocytes. METHODS AND RESULTS: To test the role of PI3K on betaAR endocytosis in failing human hearts, we assayed for PI3K activity in human left ventricular samples before and after mechanical unloading (LVAD). Before LVAD, failing human hearts displayed a marked increase in betaAR kinase 1 (betaARK1)-associated PI3K activity that was attributed exclusively to enhanced activity of the PI3Kgamma isoform. Increased betaARK1-coupled PI3K activity in the failing hearts was associated with downregulation of betaARs from the plasma membrane and enhanced sequestration into early and late endosomes compared with unmatched nonfailing controls. Importantly, LVAD support reversed PI3Kgamma activation, normalized the levels of agonist-responsive betaARs at the plasma membrane, and depleted the betaARs from the endosomal compartments without changing the total number of receptors (sum of plasma membrane and early and late endosome receptors). To test whether the competitive displacement of PI3K from the betaAR complex restored receptor responsiveness, we overexpressed the phosphoinositide kinase domain of PI3K (which disrupts betaARK1/PI3K interaction) in primary cultures of failing human cardiomyocytes. Adenoviral-mediated phosphoinositide kinase overexpression significantly increased basal contractility and rapidly reconstituted responsiveness to beta-agonist. CONCLUSIONS: These results suggest a novel paradigm in which human betaARs undergo a process of intracellular sequestration that is dynamically reversed after LVAD support. Importantly, mechanical unloading leads to complete reversal in PI3Kgamma and betaARK1-associated PI3K activation. Furthermore, displacement of active PI3K from betaARK1 restores betaAR responsiveness in failing myocytes.

Inhibition of receptor-localized PI3K preserves cardiac beta-adrenergic receptor function and ameliorates pressure overload heart failure.

beta-Adrenergic receptor (betaAR) downregulation and desensitization are hallmarks of the failing heart. However, whether abnormalities in betaAR function are mechanistically linked to the cause of heart failure is not known. We hypothesized that downregulation of cardiac betaARs can be prevented through inhibition of PI3K activity within the receptor complex, because PI3K is necessary for betaAR internalization. Here we show that in genetically modified mice, disrupting the recruitment of PI3K to agonist-activated betaARs in vivo prevents receptor downregulation in response to chronic catecholamine administration and ameliorates the development of heart failure with pressure overload. Disruption of PI3K/betaAR colocalization is required to preserve betaAR signaling, since deletion of a single PI3K isoform (PI3Kgamma knockout) is insufficient to prevent the recruitment of other PI3K isoforms and subsequent betaAR downregulation with catecholamine stress. These data demonstrate a specific role for receptor-localized PI3K in the regulation of betaAR turnover and show that abnormalities in betaAR function are associated with the development of heart failure. Thus, a strategy that blocks the membrane translocation of PI3K and leads to the inhibition of betaAR-localized PI3K activity represents a novel therapeutic approach to restore normal betaAR signaling and preserve cardiac function in the pressure overloaded failing heart.

Adeno-associated viral vectors based on serotype 3b use components of the fibroblast growth factor receptor signaling complex for efficient transduction.

Adeno-associated virus type 3b (AAV3b) has been largely ignored by gene therapists because of the inability of vectors based on this serotype to transduce target tissues efficiently. Here we describe a phenomenon unique to AAV3b in that vectors based on this serotype mediate enhanced transduction in the presence of heparin. Among the many biological functions attributed to heparin, its interaction with, and ability to regulate, several growth factors (GFs) and growth factor receptors (GFRs) has been well characterized. Using GFR-overexpressing cell lines, soluble GFs and heparins, as well as specific GFR inhibitors, we have demonstrated a requirement for fibroblast growth factor receptor-2 (FGFR2) and FGF1 in the heparin-mediated augmentation of AAV3b vector transduction. In contrast to AAV2, we establish that heparin can be used as an adjunct with AAV3b to further increase transduction in a variety of cells and target tissues, additionally suggesting that AAV3b may be an attractive viral vector for clinical use during procedures in which heparin is used. In summary, AAV3b exhibits FGFR2-dependent, markedly enhanced transduction efficiency in the presence of heparin and FGFs, which could make it a useful vector for gene therapy in a variety of human diseases.

Use of custom Dacron branch grafts for "hybrid" aortic debranching during endovascular repair of thoracic and thoracoabdominal aortic aneurysms.

OBJECTIVES: A significant number of patients with thoracic and thoracoabdominal aortic aneurysms are unsuitable for endovascular repair owing to the absence of graft seal zones. "Hybrid" techniques, including open aortic debranching procedures, allow creation of proximal and/or distal landing zones and expand the potential applications of endovascular repair. We report our experience with aortic arch and thoracoabdominal debranching using custom fabricated Dacron branch grafts, which greatly simplify aortic debranching by providing inflow via a single anastomosis and incorporate a side arm for introduction of the stent graft. METHODS: Between November 14, 2005, and December 18, 2006, a total of 53 thoracic endograft procedures were performed at our institution. Of these, 13 (25%) involved either open aortic arch or abdominal debranching to create proximal or distal landing zones for endovascular repair. Patients undergoing arch debranching (n = 7) had aneurysms involving the transverse arch with less than 2 cm of proximal landing zone distal to the innominate artery, necessitating stent graft coverage of both the innominate and left common carotid arteries. Patients undergoing complete abdominal debranching (n = 6) had either thoracoabdominal aortic aneurysms (extent II, n = 1; extent V, n = 3) or visceral button false aneurysms after prior open thoracoabdominal aortic aneurysm repair (n = 2). In all cases, endovascular aneurysm exclusion was performed at the same operation. RESULTS: Mean patient age was 63 +/- 11 years (range 46-83 years); all patients had significant comorbidities, including prior open aortic surgery in 8 (62%). There were no perioperative (30 day) deaths and no permanent neurologic deficits, either cerebrovascular accident or paraparesis/paraplegia. At a mean follow-up of 7.5 +/- 6.0 months, there has been no late mortality and all debranching bypass grafts remain patent without need for further intervention. Computed tomographic scans demonstrate no type I or III endoleaks, and all aneurysms are thrombosed with stable (n = 4) or decreasing aortic dimensions (n = 9). CONCLUSIONS: "Hybrid" aortic debranching using custom fabricated Dacron branch grafts with a single inflow source combined with endovascular aneurysm exclusion appears to be a safe alternative to conventional open repair for thoracoabdominal and arch aneurysms and avoids the need for cardiopulmonary bypass and aortic crossclamping. This technique may be ideally suited to patients with significant comorbidity or prior open aortic surgery. Longer term follow-up is needed to determine the durability of this approach.

"Real world" thoracic endografting: results with the Gore TAG device 2 years after U.S. FDA approval.

BACKGROUND: The Gore TAG thoracic endoprosthesis (W. L. Gore and Associates, Flagstaff, AZ) was approved by the U.S. Food and Drug Administration (FDA) for the treatment of thoracic aortic aneurysms on March 23, 2005, and remains the only FDA approved thoracic device to date. We present our experience with the TAG device for the 2 years post-approval to better characterize "real world" use and results outside the clinical trial setting. METHODS: Between March 23, 2005, and March 23, 2007, n = 91 thoracic endograft procedures were performed at our institution. Of these, n = 83 (91%) utilized the TAG device and form the basis of this report. Indications for endovascular repair were: fusiform or saccular aneurysm (n = 43; 52%), acute or chronic dissection (n = 30; 36%), acute or chronic traumatic transection (n = 7; 8%), and false aneurysm after prior aortic surgery (n = 3; 4%). A "hybrid" approach involving carotid-carotid bypass (n = 2), stage I elephant trunk procedure (n = 3), aortic arch debranching (n = 7), or complete visceral debranching (n = 5) was required in 20% of patients to create an adequate landing zone. RESULTS: Primary technical success rate was 98.8% (n = 82/83). Thirty-day rates of mortality and permanent stroke were both 3.6% (n = 3 each). Permanent paraparesis/paraplegia rate was 2.4% (n = 2). The 30-day rate of vascular or device-related complications requiring additional endovascular or open procedures was 7.2% (n = 6). During a mean duration of follow-up of 14 +/- 8 months (range 0-28), there was one late death from aneurysm rupture (1.2%) and one late conversion to open repair (1.2%). CONCLUSIONS: "Real world" utilization of the TAG device includes high rates of off-label use (nearly 50%) and "hybrid" techniques (20%) for the treatment of multiple pathologic entities of the thoracic and thoracoabdominal aorta. Regardless, short to mid-term results appear promising. Longer follow-up is needed to determine the durability of this approach.

Minitransseptal versus left atrial approach to the mitral valve: a comparison of outcomes.

BACKGROUND: Approaches to the mitral valve include left atriotomy (LA) through the interatrial groove and transseptal approach (TS) through the right atrium. Left atriotomy is more commonly used, but TS offers better mitral visualization in difficult cases. While TS has been associated with more atrial arrhythmias, heart block, and difficulty in repair, strong data are lacking. METHODS: Retrospective chart review was conducted of 531 consecutive patients undergoing a mitral valve procedure through sternotomy by a single surgeon between 1989 and 2003. Of these, 273 were performed through the standard LA approach and 258 by a "minitransseptal" approach consisting of a 6-cm vertical incision in the interatrial septum without incising the roof of the right or left atria. RESULTS: Subset analysis of isolated mitral procedures showed no significant differences in cross-clamp time or total bypass time. Although significantly more TS patients required new pacemakers (10.5% TS versus 5.1% LA) or had new junctional rhythm (8.7% TS versus 4.2% LA), TS patients also had more concomitant valve procedures and redo sternotomies. Multivariate analysis showed that the incidence of new pacemakers was linked most strongly with redo procedures, but TS was not an independent predictor of needing a new pacemaker, new junctional rhythm, or new atrial fibrillation. CONCLUSIONS: The minitransseptal approach can provide excellent mitral valve exposure in difficult cases without any significant increase in junctional rhythm, atrial fibrillation, or new pacemaker requirements.