circulation2010-02-16

(Circulation. 2010;121:742-749.)
© 2010 American Heart Association, Inc.

abstract 1 of 7
Congenital Heart Disease
Noninvasive Creation of an Atrial Septal Defect by Histotripsy in a Canine Model
Zhen Xu, PhD; Gabe Owens, MD, PhD; David Gordon, MD; Charles Cain, PhD; Achi Ludomirsky, MD
From the Departments of Biomedical Engineering (Z.X.), Pediatric Cardiology (G.O.), Pathology (D.G.), and Biomedical Engineering (C.C.), University of Michigan, Ann Arbor, and Department of Pediatric Cardiology, New York University, New York (A.L.).
Correspondence to Zhen Xu, 2200 Bonisteel Blvd, Room 1107 Gerstacker, Ann Arbor, MI 48109. E-mail zhenx@umich.edu
Received June 24, 2009; accepted December 15, 2009.
Background— The primary objective of this study was to develop an image-guided, noninvasive procedure to create or enlarge an atrial septal defect for the treatment of neonates with hypoplastic left heart syndrome and an intact or restrictive atrial septum. Histotripsy is an innovative ultrasonic technique that produces nonthermal, mechanical tissue fractionation through the use of high-intensity ultrasound pulses. This article reports the pilot in vivo study to create an atrial septal defect through the use of extracardiac application of histotripsy in an open-chest canine model.
Methods and Results— In 10 canines, the atrial septum was exposed to histotripsy by an ultrasound transducer positioned outside the heart. Ultrasound pulses of 6-microsecond duration at a peak negative pressure of 15 MPa and a pulse repetition frequency of 3.3 kHz were generated by a 1-MHz focused transducer. The procedure was guided and monitored by real-time ultrasound imaging. In 9 of 10 canines, an atrial septal defect was produced, and shunting across the atrial septum was visualized. Pathology of the hearts showed atrial septal defects with minimal damage to surrounding tissue. No damage was found on the epicardial surface of the heart or other structures.
Conclusions— Under real-time ultrasound guidance, atrial septal defects were successfully created with extracardiac histotripsy in a live canine model. Although further studies in an intact animal model are needed, these results provide promise of histotripsy becoming a valuable clinical tool.

abstract 2 of 7
Epidemiology and Prevention
Association of Diet, Exercise, and Smoking Modification With Risk of Early Cardiovascular Events After Acute Coronary Syndromes
Clara K. Chow, MBBS, FRACP, PhD; Sanjit Jolly, MD, MSc, FRCPC; Purnima Rao-Melacini, MSc; Keith A.A. Fox, BSc (Hons), MB, ChB, FRCP, FESC, F***; Sonia S. Anand, MD, PhD, FRCPc; Salim Yusuf, DPhil, FRCPC, FRSC
From the Population Health Research Institute (C.K.C., S.J., P.R.-M., S.S.A., S.Y.) and Departments of Medicine (C.K.C., S.S.A., S.Y.) and Epidemiology (S.S.A.), McMaster University, and Hamilton Health Sciences (C.K.C., S.J., P.R.-M., S.S.A., S.Y.), Hamilton, Ontario, Canada; The George Institute for International Health, University of Sydney, Sydney, New South Wales, Australia (C.K.C.); and Centre for Cardiovascular Science, University of Edinburgh, Royal Infirmary of Edinburgh, Edinburgh, United Kingdom (K.A.A.F.).
Correspondence to Dr Clara K. Chow, Hamilton General Hospital, 237 Barton St E, Hamilton, Ontario, L8L 2X2, Canada. E-mail cchow@george.org.au or clara.chow@phri.ca
Received July 6, 2009; accepted November 3, 2009.
Background— Although preventive drug therapy is a priority after acute coronary syndrome, less is known about adherence to behavioral recommendations. The aim of this study was to examine the influence of adherence to behavioral recommendations in the short term on risk of cardiovascular events.
Methods and Results— The study population included 18 809 patients from 41 countries enrolled in the Organization to Assess Strategies in Acute Ischemic Syndromes (OASIS) 5 randomized clinical trial. At the 30-day follow-up, patients reported adherence to diet, physical activity, and smoking cessation. Cardiovascular events (myocardial infarction, stroke, cardiovascular death) and all-cause mortality were documented to 6 months. About one third of smokers persisted in smoking. Adherence to neither diet nor exercise recommendations was reported by 28.5%, adherence to either diet or exercise by 41.6%, and adherence to both by 29.9%. In contrast, 96.1% of subjects reported antiplatelet use, 78.9% reported statin use, and 72.4% reported angiotensin-converting enzyme/angiotensin receptor blocker use. Quitting smoking was associated with a decreased risk of myocardial infarction compared with persistent smoking (odds ratio, 0.57; 95% confidence interval, 0.36 to 0.89). Diet and exercise adherence was associated with a decreased risk of myocardial infarction compared with nonadherence (odds ratio, 0.52; 95% confidence interval, 0.4 to 0.69). Patients who reported persistent smoking and nonadherence to diet and exercise had a 3.8-fold (95% confidence interval, 2.5 to 5.9) increased risk of myocardial infarction/stroke/death compared with never smokers who modified diet and exercise.
Conclusions— Adherence to behavioral advice (diet, exercise, and smoking cessation) after acute coronary syndrome was associated with a substantially lower risk of recurrent cardiovascular events. These findings suggest that behavioral modification should be given priority similar to other preventive medications immediately after acute coronary syndrome.

abstract 3 of 7
Exercise Physiology
Regular Exercise Training Prevents Aortic Valve Disease in Low-Density Lipoprotein–Receptor–Deficient Mice
Yasuharu Matsumoto, MD, PhD*; Volker Adams, PhD*; Saskia Jacob, MS; Norman Mangner, MD; Gerhard Schuler, MD; Axel Linke, MD
From the University of Leipzig–Heart Center Leipzig, Department of Cardiology, Leipzig, Germany.
Correspondence to Yasuharu Matsumoto, MD, PhD, FAHA, FESC, or Volker Adams, PhD, Department of Cardiology, Heart Center Leipzig, University of Leipzig, Strümpellstrasse 39, D-04289 Leipzig, Germany. E-mail yasuharu@muj.biglobe.ne.jp or adav@medizin.uni-leipzig.de
Received July 8, 2009; accepted December 10, 2009.
Background— Regular exercise training (ET) slows the progression of atherosclerotic lesions, reduces oxidative stress, and increases nitric oxide bioavailability, all of which may be expected to improve degenerative aortic valve disease.
Methods and Results— Four-week-old low-density lipoprotein–receptor–deficient mice (n=94) were randomly divided into 4 groups: Group 1 (control group), normal diet plus sedentary activity; group 2 (cholesterol group), cholesterol diet plus sedentary activity; group 3 (regular ET group), cholesterol diet plus regular ET (60 min/day, 5 days/week) for 16 weeks; and group 4 (occasional exercise group), cholesterol diet plus occasional ET (1 day/week) for 16 weeks. At 20 weeks of age, histological analysis was performed. A significant increase in aortic valve thickness was evident in the cholesterol group compared with the control group. Importantly, regular but not occasional ET significantly reduced aortic valve thickness compared with the cholesterol group (control 31.3±3.0 µm, cholesterol 50.1±3.4 µm, regular exercise 30.4±1.2 µm, and occasional exercise 48.9±3.2 µm). Immunohistochemistry revealed that a cholesterol diet disrupted and regular ET preserved endothelial integrity on the aortic valve surface. Furthermore, serum myeloperoxidase, accumulation of macrophages and oxidized low-density lipoprotein, in situ superoxide, activated myofibroblasts/osteoblast phenotypes, and mineralization were increased in the cholesterol group but were decreased by regular ET. Polymerase chain reaction revealed increased messenger RNA expression for -smooth muscle actin, bone morphogenetic protein-2, runt-related transcription factor-2, and alkaline phosphatase in the cholesterol group, whereas these were diminished by regular ET. Moreover, regular ET significantly increased circulating levels of fetuin-A compared with the cholesterol group.
Conclusions— In the low-density lipoprotein–receptor–deficient mouse, regular ET prevents aortic valve sclerosis by numerous mechanisms, including preservation of endothelial integrity, reduction in inflammation and oxidative stress, and inhibition of the osteogenic pathway.

abstract 4 of 7
Heart Failure
Extensible Behavior of Titin in the Miniswine Left Ventricle
Martin M. LeWinter, MD; Joseph Popper, BS; Mark McNabb, BS; Lori Nyland, MS; Stephen B. Bell, BS; Henk Granzier, PhD
From the Cardiology Unit, University of Vermont College of Medicine, Burlington (M.M.L., L.N., S.B.B.), and Department of Molecular and Cellular Biology and Molecular Cardiovascular Research Program, University of Arizona, Tucson (J.P., M.M., H.G.).
Correspondence to Martin M. LeWinter, MD, Cardiology Unit, Fletcher Allen Health Care, 111 Colchester Ave, Burlington, VT 05401. E-mail martin.lewinter@vtmednet.org
Received February 18, 2009; accepted December 10, 2009.
Background— The sarcomeric protein titin is a molecular spring responsible for passive tension and restoring forces of cardiomyocytes. Extension of titin as a function of sarcomere length (SL) has been studied in rodents, which predominantly express the smaller, stiffer N2B titin isoform. Large mammals coexpress roughly equal proportions of N2B and N2BA titin, the larger, more compliant isoform. We hypothesized that extension of titin in relation to SL differs in large mammals and that this difference is functionally important.
Methods and Results— We characterized the filling pressure–SL relation in diastolic-arrested miniswine left ventricles. SL was 2.15 to 2.25 µm at a filling pressure of 0 mm Hg and reached a maximum of 2.50 µm with overfilling. In the normal filling pressure range, SL ranged from 2.32 to 2.40 µm. We assessed titin extension as a function of SL using immunoelectron microscopy, which allowed delineation of the behavior of specific spring segments. The major isoform difference was that the N2B-Us segment extended 4-fold more as a function of SL in N2B compared with N2BA titin. Using this segment, we estimated sarcomeric force development with a worm-like chain model and found that N2B develops markedly greater force than N2BA titin. The resulting force with coexpression of N2B and N2BA titin is intermediate.
Conclusions— In light of murine studies showing that operating SLs are shorter than in miniswine, our results indicate that coexpression of the 2 titin isoforms in large mammals allows longer SLs without the development of excessive diastolic tension.

abstract 5 of 7
Imaging
Molecular Magnetic Resonance Imaging of Myocardial Angiogenesis After Acute Myocardial Infarction
Marlies Oostendorp, PhD; Kim Douma, PhD; Allard Wagenaar, BSc; Jos M.G.M. Slenter, BEng; Tilman M. Hackeng, PhD; Marc A.M.J. van Zandvoort, PhD; Mark J. Post, MD, PhD; Walter H. Backes, PhD
From the Departments of Radiology (M.O., K.D., J.M.G.M.S., W.H.B.), Physiology (A.W., M.J.P.), Biochemistry (T.M.H.), and Biomedical Engineering (K.D., M.A.M.J.v.Z., M.J.P.), and Cardiovascular Research Institute Maastricht (M.O., K.D., A.W., J.M.G.M.S., T.M.H., M.A.M.J.v.Z., M.J.P., W.H.B.), Maastricht University Medical Centre, Maastricht, The Netherlands; Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands (M.J.P.); and Institute for Molecular Cardiovascular Research, Universitaetsklinikum Aachen, Aachen, Germany (M.A.M.J.v.Z.).
Correspondence to Walter H. Backes, Department of Radiology, Maastricht University Medical Centre (MUMC+), P. Debyelaan 25, PO Box 5800, 6202 AZ Maastricht, The Netherlands. E-mail w.backes@mumc.nl
Received June 25, 2009; accepted December 18, 2009.
Background— Angiogenesis is a natural mechanism to restore perfusion to the ischemic myocardium after acute myocardial infarction (MI). Therapeutic angiogenesis is being explored as a novel treatment for MI patients; however, sensitive, noninvasive in vivo measures of therapeutic efficacy are lacking and need to be developed. Here, a molecular magnetic resonance imaging method is presented to noninvasively image angiogenic activity in vivo in a murine model of MI with cyclic Asn-Gly-Arg (cNGR)–labeled paramagnetic quantum dots (pQDs). The tripeptide cNGR homes specifically to CD13, an aminopeptidase that is strongly upregulated during myocardial angiogenesis.
Methods and Results— Acute MI was induced in male Swiss mice via permanent ligation of the left anterior descending coronary artery. Molecular magnetic resonance imaging was performed 7 days after surgery and up to 2 hours after intravenous contrast agent administration. Injection of cNGR-pQDs resulted in a strong negative contrast that was located mainly in the infarcted myocardium. This negative contrast was significantly less in MI mice injected with unlabeled pQDs and in sham-operated mice injected with cNGR-pQDs. Validation with ex vivo 2-photon laser scanning microscopy revealed a strong colocalization of cNGR-pQDs with vascular endothelial cells, whereas unlabeled pQDs were mostly extravasated and diffused through the tissue. Additionally, 2-photon laser scanning microscopy demonstrated significant microvascular remodeling in the infarct/border zones compared with remote myocardium.
Conclusions— cNGR-pQDs allow selective, noninvasive detection of angiogenic activity in the infarcted heart with the use of in vivo molecular magnetic resonance imaging and ex vivo 2-photon laser scanning microscopy.

abstract 6 of 7
Interventional Cardiology
Intracoronary Eptifibatide Bolus Administration During Percutaneous Coronary Revascularization for Acute Coronary Syndromes With Evaluation of Platelet Glycoprotein IIb/IIIa Receptor Occupancy and Platelet Function
The Intracoronary Eptifibatide (ICE) Trial
Albert J. Deibele, MD; Lisa K. Jennings, PhD; James E. Tcheng, MD; Cathy Neva, RN, CCRC; Angela D. Earhart, BS; C. Michael Gibson, MS, MD
From the Duluth Clinic, Division of Cardiology, Duluth, Minn (A.J.D., C.N.); University of Tennessee, Vascular Biology Center of Excellence, Memphis (L.K.J., A.D.E.); Duke University Medical Center, Division of Cardiology, Durham, NC (J.E.T.); and Beth Israel Deaconess Medical Center, Division of Cardiology, Boston, Mass (C.M.G.).
Reprint requests to C. Michael Gibson, MS, MD, 350 Longwood Ave, First Floor, Boston, MA 02115. E-mail mgibson@perfuse.org
Received June 1, 2009; accepted November 23, 2009.
Background— Eptifibatide reduces major adverse cardiac events in patients with acute coronary syndromes undergoing percutaneous coronary intervention (PCI). Intracoronary bolus administration of eptifibatide may result in higher levels of platelet glycoprotein IIb/IIIa receptor occupancy in the local coronary bed, disaggregate thrombus in the epicardial artery and microvasculature, and thereby improve coronary flow.
Methods and Results— Patients undergoing PCI for an acute coronary syndrome were randomized to either intracoronary or intravenous bolus administration of eptifibatide. The primary end point was the local glycoprotein IIb/IIIa receptor occupancy measured in the coronary sinus. There were no angiographic, electrophysiological, or other adverse findings attributable to intracoronary eptifibatide. Platelet glycoprotein IIb/IIIa receptor occupancy was significantly greater with intracoronary versus intravenous administration: first bolus, 94±9% versus 51±15% (P<0.001); and second bolus, 99±2% versus 91±4% (P=0.001), respectively. Microvascular perfusion was significantly improved as measured by the corrected thrombolysis in myocardial infarction frame count (cTFC) with intracoronary versus intravenous administration: pre-PCI, 36 (median) (25th and 75th percentiles, 16 and 64) versus 31 (25th and 75th percentiles, 23 and 45; P=0.8); and post-PCI, 18 (25th and 75th percentiles, 10 and 22) versus 25 (25th and 75th percentiles, 22 and 35; P=0.007), respectively. The only multivariate predictor associated with a post-PCI cTFC rank score was the first bolus glycoprotein IIb/IIIa receptor occupancy (P<0.001).
Conclusions— Intracoronary bolus administration of eptifibatide during PCI in patients with acute coronary syndromes results in higher local platelet glycoprotein IIb/IIIa receptor occupancy, which is associated with improved microvascular perfusion demonstrated by an improved cTFC.

abstract 7 of 7
Vascular Medicine
Reduction of AMP-Activated Protein Kinase 2 Increases Endoplasmic Reticulum Stress and Atherosclerosis In Vivo
Yunzhou Dong, PhD*; Miao Zhang, MD, PhD*; Bin Liang, MD, PhD; Zhonglin Xie, MD, PhD; Zhengxing Zhao, MSc; Sima Asfa, MSc; Hyoung Chul Choi, MD, PhD; Ming-Hui Zou, MD, PhD
From the Division of Endocrinology and Diabetes, Department of Medicine, University of Oklahoma Health Science Center, Oklahoma City (Y.D., M.Z., B.L., Z.X., Z.Z., S.A., M.-H.Z.), and Department of Pharmacology, College of Medicine, Yeungnam University, Daegu, Korea (H.C.C.).
Correspondence to Ming-Hui Zou, MD, PhD, Department of Medicine and Endocrinology, University of Oklahoma Health Science Center, Oklahoma City, OK 73104. E-mail ming-hui-zou@ouhsc.edu
Received April 9, 2009; accepted December 11, 2009.
Background— Aberrant endoplasmic reticulum (ER) stress is associated with several cardiovascular diseases, including atherosclerosis. The mechanism by which aberrant ER stress develops is poorly understood. This study investigated whether dysfunction of AMP-activated protein kinase (AMPK) causes aberrant ER stress and atherosclerosis in vivo.
Methods and Results— Human umbilical vein endothelial cells and mouse aortic endothelial cells from AMPK-deficient mice were used to assess the level of ER stress with Western blotting. Reduction of AMPK 2 expression significantly increased the level of ER stress in human umbilical vein endothelial cells. In addition, mouse aortic endothelial cells from AMPK 2 knockout (AMPK 2–/–) mice had higher expression of markers of ER stress and increased levels of intracellular Ca2+. These phenotypes were abolished by adenovirally overexpressing constitutively active AMPK mutants (Ad-AMPK-CA) or by transfecting sarcoendoplasmic reticulum calcium ATPase (SERCA). Inhibition of SERCA induced ER stress in endothelial cells. Furthermore, reduction of AMPK expression suppressed SERCA activity. In addition, SERCA activity was significantly reduced concomitantly with increased oxidation of SERCA in mouse aortic endothelial cells from AMPK 2–/– mice. Both of these phenotypes were abolished by adenovirally overexpressing Ad-AMPK-CA. Furthermore, Tempol, which restored SERCA activity and decreased oxidized SERCA levels, markedly reduced the level of ER stress in mouse aortic endothelial cells from AMPK 2–/– mice. Finally, oral administration of tauroursodeoxycholic acid, a chemical chaperone that inhibits ER stress, significantly reduced both ER stress and aortic lesion development in low-density lipoprotein receptor– and AMPK 2-deficient mice.
Conclusion— These results suggest that AMPK functions as a physiological suppressor of ER stress by maintaining SERCA activity and intracellular Ca2+ homeostasis.