bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Mutant and Antisense RNA of Phospholamban on SR Ca
2+
-ATPase Activity and Cardiac Myocyte Contractility
Authors: He Huaping , Meyer Markus , Martin Jody L. , McDonough Patrick M. , Ho Peter , Lou Xiaojing , Lew Wilbur Y. W. , Hilal-Dandan Randa , Dillmann Wolfgang H.
Published: June 2012

Background
—The delayed cardiac relaxation in failing hearts has been attributed to a reduced activity of sarcoplasmic reticulum Ca
2+
-ATPase (SERCA2). Phospholamban (PLB) inhibits SERCA2 activity and is therefore a potential target to improve the cardiac performance in heart failure.

Methods and Results
—Mutants of PLB (Adv/mPLB) or antisense RNA of PLB (Adv/asPLB) was expressed in cardiac myocytes by recombinant adenovirus, and their effects on SERCA2 activity and myocyte contractility were studied. One mPLB, K3E/R14E, pentamerized with endogenous PLB in neonatal myocytes and resulted in a 45% increase in the affinity of SERCA2 for Ca
2+
and 27% faster diastolic Ca
2+
decline as determined by SR
45
Ca uptake assays and by indo 1–facilitated Ca
2+
transient measurement, respectively. Edge-detection analysis of adult myocyte contractility showed a 74% increase in fractional shortening, accompanied by 115% increase in velocity of relengthening and 25% decrease in time to half-maximal relengthening. In parallel, infection of neonatal cardiac myocytes by Adv/asPLB decreased the endogenous PLB level by 54%, which was associated with a 35% increase in Ca
2+
affinity of SERCA2 and 21% faster diastolic Ca
2+
decline. However, in adult cardiac myocytes, Adv/asPLB failed to significantly alter the endogenous PLB level, the SERCA2 activity, or most of the contractile parameters.

Conclusions
—K3E/R14E is a dominant negative mutant of PLB that disrupts the structural integrity and function of the endogenous PLB and consequently enhances SERCA2 activity and myocyte contractility. In neonatal myocytes, the decrease in steady-state abundance of PLB by asPLB also leads to increased SERCA2 activity.
Risk Factors, Angiographic Patterns, and Outcomes in Patients With Ventricular Septal Defect Complicating Acute Myocardial Infarction
Authors: Crenshaw Brian S. , Granger Christopher B. , Birnbaum Yochai , Pieper Karen S. , Morris Douglas C. , Kleiman Neal S. , Vahanian Alec , Califf Robert M. , Topol Eric J.
Published: June 2012

Background
—Ventricular septal defect (VSD) complicating acute myocardial infarction has been studied primarily in small, prethrombolytic-era trials. Our goal was to determine clinical predictors and angiographic and clinical outcomes of this complication in the thrombolytic era.

Methods and Results
—We compared enrollment characteristics, angiographic patterns, and outcomes (30-day and 1-year mortality) of patients enrolled in the Global Utilization of Streptokinase and TPA for Occluded Coronary Arteries (GUSTO-I) trial with and without a confirmed diagnosis of VSD. Univariable and multivariable analyses were used to assess relations between enrollment factors and the development of VSD. In all, 84 of the 41 021 patients (0.2%) developed VSD, a smaller percentage than reported in the prethrombolytic era. The median time from symptom onset to VSD diagnosis was 1 day. Enrollment factors most associated with this complication were advanced age, anterior infarction, female sex, and no previous smoking. The infarct artery was more often the left anterior descending and more likely to be totally occluded in patients who developed VSD. Mortality at 30 days was higher in patients with VSDs than in those without this complication (73.8% versus 6.8%,
P
<0.001). Patients with VSDs selected for surgical repair (n=34) had better outcomes than patients treated medically (n=35; 30-day mortality, 47% versus 94%).

Conclusions
—Compared with historical control subjects, patients who undergo thrombolysis within 6 hours of infarction onset may have a reduced risk of later VSD. If patients develop this mechanical complication, however, it typically occurs sooner than described in the prethrombolytic era. Despite improvements in medical therapy and percutaneous and surgical techniques, mortality with this complication remains extremely high.
Fractal Correlation Properties of R-R Interval Dynamics and Mortality in Patients With Depressed Left Ventricular Function After an Acute Myocardial Infarction
Authors: Huikuri Heikki V. , Mäkikallio Timo H. , Peng Chung-Kang , Goldberger Ary L. , Hintze Ulrik , Møller Mogens
Published: June 2012

Background
—Preliminary data suggest that the analysis of R-R interval variability by fractal analysis methods may provide clinically useful information on patients with heart failure. The purpose of this study was to compare the prognostic power of new fractal and traditional measures of R-R interval variability as predictors of death after acute myocardial infarction.

Methods and Results
—Time and frequency domain heart rate (HR) variability measures, along with short- and long-term correlation (fractal) properties of R-R intervals (exponents α
1
and α
2
) and power-law scaling of the power spectra (exponent β), were assessed from 24-hour Holter recordings in 446 survivors of acute myocardial infarction with a depressed left ventricular function (ejection fraction ≤35%). During a mean±SD follow-up period of 685±360 days, 114 patients died (25.6%), with 75 deaths classified as arrhythmic (17.0%) and 28 as nonarrhythmic (6.3%) cardiac deaths. Several traditional and fractal measures of R-R interval variability were significant univariate predictors of all-cause mortality. Reduced short-term scaling exponent α
1
was the most powerful R-R interval variability measure as a predictor of all-cause mortality (α
1
<0.75, relative risk 3.0, 95% confidence interval 2.5 to 4.2,
P
<0.001). It remained an independent predictor of death (
P
<0.001) after adjustment for other postinfarction risk markers, such as age, ejection fraction, NYHA class, and medication. Reduced α
1
predicted both arrhythmic death (
P
<0.001) and nonarrhythmic cardiac death (
P
<0.001).

Conclusions
—Analysis of the fractal characteristics of short-term R-R interval dynamics yields more powerful prognostic information than the traditional measures of HR variability among patients with depressed left ventricular function after an acute myocardial infarction.
The Effect of Endovascular Irradiation on Platelet Recruitment at Sites of Balloon Angioplasty in Pig Coronary Arteries
Authors: Salame Mahomed Y. , Verheye Stefan , Mulkey Stephen P. , Chronos Nicolas A. F. , King Spencer B. , Crocker Ian R. , Robinson Keith A.
Published: June 2012

Background
—Endovascular irradiation (EI) inhibits balloon-induced neointima formation in animals and is now in clinical trials for restenosis prevention. However, little is known of the effect of EI on vessel thrombogenicity due to delayed arterial healing. We investigated EI effects on platelet recruitment in pig coronary arteries.

Methods and Results
—EI was performed using
90
Sr/Y at 0 Gray (Gy), 15Gy, or 30Gy at 2 mm after balloon overstretch injury. At 1 day, 1 week, and 1 month, platelet recruitment and thrombus formation were assessed using autologous
111
In-oxine-platelet labeling and light and scanning electron microscopy. In balloon-injured nonirradiated vessels, there was complete reendothelialization at 1 month, and platelet recruitment was similar to normal uninjured arteries. In irradiated vessels, scanning electron microscopy showed incomplete reendothelialization at 1 month, and these areas demonstrated attachment of activated platelets. Light microscopy of irradiated coronaries showed adherent partially organized thrombi and incomplete resolution of intramural hemorrhages. There was a significant increase in platelet recruitment at 1 month in arteries receiving EI at 15Gy (5.1±2.8×10
6
,
P
=0.02) or 30Gy (12.5±9.9×10
6
,
P
=0.005) compared with nonirradiated controls (2.7±1.5×10
6
); 30Gy was also higher than 15Gy (
P
=0.05). Platelet recruitment was also increased for 30Gy compared with control at 1 day.

Conclusions
—Endovascular irradiation at 15Gy or 30Gy after balloon angioplasty results in incomplete endothelial recovery, impaired resolution of intramural hemorrhage, and a dose-dependent increase in platelet recruitment at 1 month.
Adenovirus-Mediated Gene Transfer of a Secreted Form of Human Macrophage Scavenger Receptor Inhibits Modified Low-Density Lipoprotein Degradation and Foam-Cell Formation in Macrophages
Authors: Laukkanen Johanna , Lehtolainen Pauliina , Gough Peter J. , Greaves David R. , Gordon Siamon , Ylä-Herttuala Seppo
Published: June 2012

Background
—Macrophage scavenger receptors (MSRs) play an important role in the pathogenesis of atherosclerosis. Therefore, local modulation of MSR activity could have a beneficial effect on atherogenesis.

Methods and Results
—We cloned a secreted “decoy” MSR (sMSR) that contains an extracellular portion of the human MSR type AI and constructed an adenoviral vector that directs high-level expression of sMSR in macrophages under the control of the human CD68 promoter. Expression of the sMSR protein inhibited the degradation of
125
I-labeled acetylated LDL and oxidized LDL by murine macrophages up to 90%. sMSRs also reduced acetylated LDL degradation in MSR knockout mouse peritoneal macrophages by 60% to 80%, which suggests that the decoy construct can compete for the uptake mediated via other related scavenger receptors. In addition, sMSRs inhibited foam-cell formation in murine macrophages in the presence of cytochalasin D. The mechanism of inhibition is through ligand binding to the sMSRs, which prevents the ligand binding to MSRs on cell membranes.

Conclusions
—The demonstration that recombinant adenovirus–mediated gene transfer of decoy sMSRs can block foam-cell formation suggests a possible new strategy for gene therapy of atherosclerosis and for the treatment of lipid accumulation after arterial manipulations.
Dose-Dependence of 4-Aminopyridine Plasma Concentrations and Electrophysiological Effects in Dogs
Authors: Nattel Stanley , Matthews Carol , De Blasio Emma , Han Wei , Li Danshi , Yue Lixia
Published: June 2012

Background
—Previous investigators have administered 4-aminopyridine (4AP) to dogs to evaluate the role of transient outward current (
I
to
) in vivo; however, plasma concentrations of 4AP were not measured, and it is therefore uncertain which cardiac ion channels were blocked at the concentrations achieved.

Methods and Results
—We applied high-performance liquid chromatography to measure 4AP concentrations produced by intravenous 4AP administration to dogs. A previously described dose regimen produced plasma concentrations that increased during the maintenance infusion but never exceeded 250 μmol/L and caused significant mortality. Whole-cell patch-clamp experiments on isolated canine myocytes showed that even the maximum 4AP concentrations achieved in vivo failed to alter ventricular
I
to
and had very small effects on atrial
I
to
; however, concentrations achieved in vivo had a strong inhibitory effect on the dog ultrarapid delayed rectifier (
I
Kur.d
), present only in atrial cells. We designed a loading and maintenance infusion regimen to produce stable 4AP plasma concentrations. At concentrations in the range of 25 and 50 μmol/L, 4AP had no effect on ventricular refractory period but increased atrial refractoriness significantly, consistent with the results of voltage clamp studies.

Conclusions
—The interpretation of previous studies using intravenous 4AP administration to inhibit
I
to
in dogs in vivo needs to be reevaluated in light of the fact that the infusion regimens used produce plasma concentrations that are inadequate to affect ventricular
I
to
. Our findings also support the concept that selective inhibition of ultrarapid delayed rectifier current can prolong atrial refractory periods without affecting ventricular refractoriness.
Temporal Repolarization Lability in Hypertrophic Cardiomyopathy Caused by β-Myosin Heavy-Chain Gene Mutations
Authors: Atiga Walter L. , Fananapazir Lameh , McAreavey Dorothea , Calkins Hugh , Berger Ronald D.
Published: June 2012

Background
—Certain genetic mutations associated with hypertrophic cardiomyopathy (HCM) carry an increased risk of sudden death. QT variability identifies patients at a high risk for sudden death from ventricular arrhythmias. We tested whether patients with HCM caused by β-myosin heavy-chain (β-MHC) gene mutations exhibit labile ventricular repolarization using beat-to-beat QT variability analysis.

Methods and Results
—We measured the QT variability index and heart rate–QT interval coherence from Holter monitor recordings in 36 patients with HCM caused by known β-MHC gene mutations and in 26 age- and sex-matched controls. There were 7 distinct β-MHC gene mutations in these 36 patients; 9 patients had HCM caused by the malignant Arg
403
Gln mutation and 8 patients had HCM caused by the more benign Leu
908
Val mutation. The QT variability index was higher in HCM patients than in controls (−1.24±0.17 versus −1.58±0.38,
P
<0.01), and the greatest abnormality was detected in patients with the Arg
403
Gln mutation (−0.99±0.49 versus −1.46±0.43 in controls,
P
<0.05). In keeping with this finding, coherence was lower for the entire HCM group than for controls (
P
<0.001). Coherence was also significantly lower in patients with the Arg
403
Gln mutation compared with controls (
P
<0.05).

Conclusions
—These findings suggest that (1) patients with HCM caused by β-MHC gene mutations exhibit labile repolarization quantified by QT variability analysis and, hence, may be more at risk for sudden death from ventricular arrhythmias, and (2) indices of QT variability may be particularly abnormal in patients with β-MHC gene mutations that are associated with a poor prognosis.
Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy
Authors: Corrado Domenico , Fontaine Guy , Marcus Frank I. , McKenna William J. , Nava Andrea , Thiene Gaetano , Wichter Thomas
Published: June 2012

Abstract
—Arrhythmogenic right ventricular (RV) dysplasia/cardiomyopathy (ARVD/C) is a heart muscle disease characterized by peculiar RV involvement and electrical instability that precipitates ventricular arrhythmias and sudden death. The purpose of the present consensus report of the Study Group on ARVD/C of the Working Groups on Myocardial and Pericardial Disease and Arrhythmias of the European Society of Cardiology and of the Scientific Council on Cardiomyopathies of the World Heart Federation is to review the considerable progress in our understanding of the etiopathogenesis, morbid anatomy, and clinical presentation of ARVD/C since it first was described in 1977. The present article focuses on important but still unanswered issues, mostly regarding risk stratification, clinical outcome, and management of affected patients. Because ARVD/C is relatively uncommon and any one center may have experience with only a few patients, an international registry is being established to accumulate information and enhance the numbers of patients that can be analyzed and thus answer pending questions. The registry also will facilitate pathological, molecular, and genetics research on the causes and pathogenesis of the ARVD/C. Furthermore, availability of an international database will enhance awareness of this largely unrecognized condition among the medical community. Physicians are encouraged to enroll patients in the International Registry of ARVD/C.
Determinants of Coronary Remodeling in Transplant Coronary Disease
Authors: Schwarzacher Severin P. , Uren Neal G. , Ward Michael R. , Schwarzkopf Anne , Giannetti Nadia , Hunt Sharon , Fitzgerald Peter J. , Oesterle Stephen N. , Yeung Alan C.
Published: June 2012

Background
—Coronary remodeling plays a significant role in lumen loss in transplant allograft vasculopathy (TxCAD), but the determinants of remodeling are unknown. We assessed the relationship between remodeling and plaque topography, coronary compliance, and blood flow in TxCAD.

Methods and Results
—One artery in each of 27 transplant patients was investigated with simultaneous intravascular ultrasound and coronary flow measurements (basal and hyperemic by Doppler flow wire). At 4 to 8 different cross sections (mean 5.1±1.2), plaque topography (concentric or eccentric) was determined, and total vessel area, lumen area, and intimal/medial area (IMA) were measured. Mean remodeling ratio (vessel area/IMA) in eccentric lesions (E, n=28) was significantly larger than that in concentric lesions (C, n=70) (E 5.87±0.93 versus C 3.58±0.62;
P
<0.001), despite similar IMA (E 3.89±0.68 versus C 3.90±0.41;
P
=NS) and distribution of imaged segments. Remodeling ratio was consistently larger in eccentric lesions in all 3 vessel segments when analyzed separately, and mean remodeling ratio for each artery was larger in vessels with predominantly eccentric lesions. Coronary compliance ([Δ lumen area/diastolic lumen area]/Δ mean arterial pressure×10
3
) was also significantly greater in eccentric lesions versus concentric lesions (proximal 1.00±0.39 versus 0.22±0.04; mid 0.71±0.17 versus 0.21±0.10; distal 0.43±0.13 versus 0.01±0.08; all
P
<0.01). Coronary flow reserve was also significantly higher in coronary arteries with primarily eccentric lesions (E 2.49±0.64 versus C 1.87±0.28;
P
<0.01).

Conclusions
—Vessel remodeling in transplant vasculopathy is significantly greater in eccentric lesions than in concentric lesions, possibly due to greater coronary compliance and resistive vessel function.
Myofilament Calcium Regulation in Human Myocardium
Authors: Hajjar Roger J. , Schwinger Robert H.G. , Schmidt Ulrich , Kim Catherine S. , Lebeche Djamel , Doye Angelia A. , Gwathmey Judith K.
Published: June 2012

Background
—We investigated whether decreased myofilament calcium contractile activation may, in part, contribute to heart failure.

Methods and Results
—Calcium concentration required for 50% activation and Hill coefficient for fibers from nonfailing and failing human hearts at pH 7.1 were not different. Maximum calcium-activated force (F
max
) was also not different. However, at pH 6.8 and 6.9, differences were seen in myofilament calcium activation between nonfailing and failing hearts. At lower pH, failing myocardium was shifted left on the calcium axis compared with nonfailing myocardium, which suggested an increase in myofilament calcium responsiveness. Increased inorganic phosphate concentration decreased maximal force development by 56% in nonfailing and 36% in failing myocardium and shifted the calcium-force relationship by 2.01±0.22 versus 0.86±0.13 μmol/L, respectively (
P
<0.05). Addition of cAMP resulted in a 0.56 μmol/L shift toward higher intracellular calcium concentrations in nonfailing myocardium and a 1.04 μmol/L shift in failing myocardium. Protein kinase A in the presence of cAMP resulted in a further rightward shift in nonfailing human myocardium but did not further shift the calcium-force relationship in fibers from failing hearts. cGMP also resulted in a greater decrease in myofilament calcium sensitivity in fibers from failing hearts.

Conclusions—
We propose that changes at the level of the thin myofilaments result in differential responses to changes in the intracellular milieu in nonfailing versus failing myocardium.
Modulation of Functionally Active Endothelin-Converting Enzyme by Chronic Neutral Endopeptidase Inhibition in Experimental Atherosclerosis
Authors: Grantham J. Aaron , Schirger John A. , Wennberg Paul W. , Sandberg Sharon , Heublein Denise M. , Subkowski Thomas , Burnett John C.
Published: June 2012

Background
—Endothelin-converting enzyme-1 (ECE-1) processes big endothelin-1 (ET-1) to ET-1, a peptide implicated in atheroma formation. ECE-1 exists in 2 isoforms (ECE-1α and ECE-1β), the result of alternative splicing of a common gene. Neutral endopeptidase (NEP) is a genetically distinct metallopeptidase that degrades the natriuretic peptides. These peptides mediate antiproliferative and vasodilating actions. We sought to demonstrate the distribution of the 2 ECE-1 isoforms in experimental atherosclerosis, to determine the effects of chronic NEP-I on plasma cGMP concentrations, vascular wall ECE-1 activity, and ET-1 concentration, and to correlate these actions with atheroma formation. Our hypothesis was that chronic NEP-I, in association with augmented cGMP, would inhibit ECE-1 conversion of big ET-1 to active ET-1, thus reducing tissue ET-1 concentrations and associated atheroma formation.

Methods and Results
—Cholesterol-fed New Zealand White rabbits (n=8, 1% cholesterol diet) and NEP-I–treated cholesterol-fed New Zealand White rabbits (n=8; candoxatril, 30 mg/kg per day, Pfizer) were euthanized after 8 weeks of feeding. ECE-1α and ECE-1β immunoreactivity was present in the aortas of both groups. Compared with control values, plasma cGMP concentrations were increased (2.8±0.6 versus 8.4±1.2 pmol/mL,
P
<0.05), ECE-1 activity was attenuated (68±3% versus 32±8%,
P
<0.05), aortic tissue ET-1 concentrations were reduced (4.6±0.5 versus 3.2±0.3 pg/mg protein,
P
<0.05), and atheroma formation was attenuated (62±6% versus 34±5%,
P
<0.01) by NEP-I.

Conclusions
—These studies suggest that ECE-1 is present and functionally active in the vascular wall in atherosclerosis. Inhibition of ECE-1 by NEP-I represents a novel approach to interruption of the endothelin system in this cardiovascular disease state.
Application of cDNA Microarrays in Determining Molecular Phenotype in Cardiac Growth, Development, and Response to Injury
Authors: Sehl Patricia D. , Tai Julie T. N. , Hillan Kenneth J. , Brown Lesley A. , Goddard Audrey , Yang Renhui , Jin Hongkui , Lowe David G.
Published: June 2012

Background
—Normal myocardial development and the tissue response to cardiac stress are accompanied by marked changes in gene expression; however, the extent of these changes and their significance remain to be fully explored. We used cDNA microarrays for gene expression profiling in rat cardiac tissue samples to study developmental transitions and the response to myocardial infarction (MI).

Methods and Results
—Microarrays with rat cDNAs for 86 known genes and 989 anonymous cDNAs obtained by molecular subtraction (representational difference analysis) of mRNA from sham-operated and 6-week post-MI samples were used in 2-color hybridization experiments. Twelve known genes previously associated with myocardial development were identified together with 10 uncharacterized expressed sequence tags and 36 genes not previously associated with cardiac development. After MI, genes associated with myocardial stress and wound healing exhibited differences in magnitude and expression kinetics, and 14 genes not previously associated with MI were identified. In situ hybridization revealed mRNA localization characteristic of wound healing and vascular and cardiomyocyte reactivity.

Conclusions
—Tissue analysis of gene expression with cDNA microarrays provides a measure of transcriptional or posttranscriptional regulation and cellular recruitment. Our results demonstrate the complexity of gene regulation in the developing myocardium and show that cDNA microarrays can be used to monitor the evolution of the cardiac stress–inducible phenotype.
Basic Fibroblast Growth Factor Increases Tissue Factor Expression in Circulating Monocytes and in Vascular Wall
Authors: Corseaux Delphine , Meurice Thibaud , Six Isabelle , Rugeri Lucia , Ezekowitz Michael D. , Rouvier Philippe , Bordet Régis , Bauters Christophe , Jude Brigitte
Published: June 2012

Background
—Basic fibroblast growth factor (bFGF) promotes vascular repair and angiogenesis and can induce in vitro tissue factor (TF), a potent agent initiating thrombogenesis, which probably plays a role in angiogenesis. We investigated whether bFGF administration induced TF expression by monocytes and vascular cells.

Methods and Results
—We studied TF expression in normally fed (n=16) and cholesterol-fed (2% for 6 weeks, n=16) rabbits. Animals were then randomized to receive intravenous bFGF (2.5 μg twice weekly for 3 weeks) or saline injections. TF expression was evaluated in mononuclear cells from arterial blood and in aortic sections by an immunohistochemical assay using a monoclonal anti-rabbit TF antibody (activator protein 1). Monocyte TF expression was increased by bFGF administration in both normal and hypercholesterolemic rabbits (129±45 versus 19±3 mU TF/1000 monocytes,
P
<0.05, and 31±12 versus 7±1 mU TF/1000 monocytes,
P
<0.005, respectively) and was further increased by stimulation of monocytes by endotoxin in vitro. TF expression was lower in hypercholesterolemic rabbits than in normal rabbits. In the media of the vascular wall, bFGF induced strong TF expression in normal rabbits and only weak TF expression in hypercholesterolemic ones.

Conclusions
—This study demonstrates that systemic administration of bFGF induces an impressive increase of TF expression in circulating monocytes and in the vascular wall in normal and to a lower extent in hypercholesterolemic rabbits. The significance of this observation in terms of inducing thrombosis in vivo needs clarification.
Short-Term Effects of Rapid Pacing on mRNA Level of Voltage-Dependent K
+
Channels in Rat Atrium
Authors: Yamashita Takeshi , Murakawa Yuji , Hayami Noriyuki , Fukui Ei-ichi , Kasaoka Yuji , Inoue Masashi , Omata Masao
Published: June 2012

Background
—Atrial fibrillation causes electrophysiological changes of the atrium, thereby facilitating its maintenance. Although the expression of ion channels is modulated in chronic atrial fibrillation, it is yet unknown whether paroxysmal atrial fibrillation can also lead to electrical remodeling by affecting gene expression.

Methods and Results
—To examine the short-term effects of rapid pacing on the mRNA level of voltage-dependent K
+
channels, high-rate atrial pacing was performed in Sprague-Dawley rat hearts. Total RNA was prepared from the atrial appendages from 0 to 8 hours after the onset of pacing, and mRNA levels of Kv1.2, Kv1.4, Kv1.5, Kv2.1, Kv4.2, Kv4.3, erg, KvLQT1, and minK were determined by RNase protection assay. Among these 9 genes, the mRNA level of the Kv1.5 channel immediately and transiently increased, with bimodal peaks at 0.5 and 2 hours after the onset of pacing. Conversely, the pacing gradually and progressively decreased the mRNA levels of the Kv4.2 and Kv4.3 channels. The increase of Kv1.5 and the decrease of Kv4.2 and Kv4.3 mRNA levels were both rate dependent. In correspondence with the changes in the mRNA level, Kv1.5 channel protein transiently increased in the membrane fraction of the atrium during a 2- to 8-hour pacing period. Electrophysiological findings that the shortening of the action potential produced by 4-hour pacing was almost abolished by a low concentration of 4-aminopyridine implied that the increased Kv1.5 protein was functioning.

Conclusions
—Even short-term high-rate atrial excitation could differentially alter the mRNA levels of Kv1.5, Kv4.2, and Kv4.3 in a rate-dependent manner. In particular, increased Kv1.5 gene expression, having a transient nature, implied the possible biochemical electrical remodeling unique to paroxysmal tachycardia.
Differential Effects of the Cyclin-Dependent Kinase Inhibitors p27
Kip1
, p21
Cip1
, and p16
Ink4
on Vascular Smooth Muscle Cell Proliferation
Authors: Tanner Felix C. , Boehm Manfred , Akyürek Levent M. , San Hong , Yang Zhi-Yong , Tashiro Jun , Nabel Gary J. , Nabel Elizabeth G.
Published: June 2012

Background
—The cyclin-dependent kinase inhibitors (CKIs) have different patterns of expression in vascular diseases. The Kip/Cip CKIs, p27
Kip1
and p21
Cip1
, are upregulated during arterial repair and negatively regulate the growth of vascular smooth muscle cells (VSMCs). In contrast, the Ink CKI, p16
Ink4
, is not expressed in vascular lesions. We hypothesized that a variation in the inactivation of cdk2 and cdk4 during the G
1
phase of the cell cycle by p27
Kip1
, p21
Cip1
, and p16
Ink4
leads to different effects on VSMC growth in vitro and in vivo.

Methods and Results
—The expression of p27
Kip1
and p21
Cip1
in serum-stimulated VSMCs inactivated cdk2 and cdk4, leading to G
1
growth arrest. p16
Ink4
inhibited cdk4, but not cdk2, kinase activity, producing partial inhibition of VSMC growth in vitro. In an in vivo model of vascular injury, overexpression of p27
Kip1
reduced intimal VSMC proliferation by 52% (
P
<0.01) and the intima/media area ratio by 51% (
P
<0.005) after vascular injury and gene transfer to pig arteries, when compared with control arteries. p16
Ink4
was a weak inhibitor of intimal VSMC proliferation in injured arteries (
P
=NS), and it did not significantly reduce intima/media area ratios (
P
=NS), which is consistent with its minor effects on VSMC growth in vitro.

Conclusions
—p27
Kip1
and p21
Cip1
are potent inhibitors of VSMC growth compared with p16
Ink4
because of their different molecular mechanisms of cyclin-dependent kinase inhibition in the G
1
phase of the cell cycle. These findings have important implications for our understanding of the pathophysiology of vascular proliferative diseases and for the development of molecular therapies.
Noninvasive, Transthoracic, Low-Frequency Ultrasound Augments Thrombolysis in a Canine Model of Acute Myocardial Infarction
Authors: Siegel Robert J. , Atar Shaul , Fishbein Michael C. , Brasch Andrea V. , Peterson Thomas M. , Nagai Tomoo , Pal Dharmendra , Nishioka Toshihiko , Chae Jang-Seong , Birnbaum Yochai , Zanelli Claudio , Luo Huai
Published: June 2012

Background
—Limitations of coronary thrombolysis include the time to reperfusion, patency rate, and bleeding. We evaluated the use of noninvasive transcutaneous ultrasound to augment coronary thrombolysis.

Methods and Results
—In 24 dogs, a thrombotic occlusion of the left anterior descending coronary artery was induced and documented by 12-lead ECG and coronary angiography. After ≥60 minutes of occlusion, tissue-type plasminogen activator (t-PA; 1.42 mg/kg) was given intravenously over 90 minutes. A total of 12 of the 24 dogs had concomitant transcutaneous application of low-frequency ultrasound (27 kHz) over the chest. At 90 minutes, the mean TIMI grade flow in the t-PA alone group was 0.92±1.4 compared with 2.42±1.9 in the t-PA plus ultrasound group (
P
=0.006). TIMI 2 to 3 flow was present in 4 of 12 cases receiving t-PA alone compared with 10 of 12 cases receiving t-PA plus ultrasound (
P
=0.003). At 180 minutes, mean TIMI grade flow was 0.75±1.4 in the t-PA alone group versus 2.58±0.9 in the t-PA plus ultrasound group (
P
=0.001). Pathological examination confirmed the angiographic patency rate and did not reveal injury secondary to ultrasound in the skin, soft tissues, heart, or lungs.

Conclusions
—In vivo, the noninvasive transthoracic application of low-frequency ultrasound (1) greatly augments the efficacy of t-PA–mediated thrombolysis, (2) seems safe, and (3) has substantial potential as a noninvasive adjunct to improve coronary patency without increasing the risk of bleeding.
Reducing Cardiac Filling Pressure Lowers Norepinephrine Spillover in Patients With Chronic Heart Failure
Authors: Azevedo Eduardo R. , Newton Gary E. , Floras John S. , Parker John D.
Published: June 2012

Background
—We studied the cardiac sympathetic response to selective unloading of cardiopulmonary baroreceptors in subjects with normal left ventricular (LV) function and congestive heart failure (CHF).

Methods and Results
—Eight patients with normal LV function (age 57±5 years, ejection fraction 58±2%) and 8 patients with CHF (age 60±2 years; ejection fraction 19±2%) were studied. Instrumentation consisted of an arterial line, a pulmonary artery catheter, and a coronary sinus thermodilution catheter. The radiotracer technique was used for measurement of cardiac norepinephrine spillover (CANESP) and total-body norepinephrine spillover. Lower-body negative pressure (LBNP) was applied at 2 levels: nonhypotensive and hypotensive LBNP. Nonhypotensive LBNP reduced filling pressures significantly in both groups. Arterial pressure did not change. This reduction in filling pressures caused a significant reduction in CANESP in the CHF group (from 167±53 to 125±37 pmol/min,
P
<0.05) but no change in the normal LV function group. Hypotensive LBNP caused a significant increase in CANESP in the normal group (73±13 vs 122±27 pmol/min,
P
<0.05) but no significant change in those with CHF.

Conclusions
—We conclude that selective reduction in filling pressures lowers cardiac norepinephrine spillover in patients with CHF. These findings suggest that a goal of CHF management should be to reduce cardiac filling pressures while avoiding systemic hypotension.
Insertion/Deletion Polymorphism in the Angiotensin-Converting Enzyme Gene Affects Heart Weight
Authors: Nakahara Ken-ichi , Matsushita Satoru , Matsuoka Hiroko , Inamatsu Takashi , Nishinaga Masanori , Yonawa Masahiko , Aono Tadashi , Arai Tomio , Ezaki Yukiyoshi , Orimo Hajime
Published: June 2012

Background
—Angiotensin (Ang) II, a major regulatory factor for left ventricular mass, is generated from Ang I by ACE. ACE levels are associated with an insertion/deletion (I/D) polymorphism in the ACE gene. The ACE polymorphism should result in varied Ang II concentrations and hence affect left ventricular mass. We therefore investigated whether ACE genotype is a predictor of heart weight.

Methods and Results
—From 693 consecutive patients autopsied between 1994 and 1998 in our hospital, patients with valvular disease, myocardial infarction, or cardiomyopathy were excluded. The remaining 443 autopsy patients were the subjects of our study. The heart weight at autopsy was corrected for body surface area. Genomic DNA was purified from the kidney, and ACE genotype was determined by polymerase chain reaction. Heart weight in the DD genotype (249.9±49.9 g/m
2
) was significantly higher than that in the ID (230.0±51.2 g/m
2
;
P
<0.05) and II (226.8±49.8 g/m
2
;
P
<0.01) genotypes. Heart weight was also positively related to age (
r
=0.145,
P
<0.0001) and coronary stenosis index (
r
=0.147,
P
=0.0019). Multiple regression analysis showed that a history of hypertension (
P
<0.0001), age (
P
=0.0001), and DD genotype (
P
=0.0154) were independent predictors of heart weight.

Conclusions
—ACE genotype predicts cardiac mass; however, it was less effective than epigenetic factors such as hypertension or age.
Oxidized Low-Density Lipoproteins Inhibit Endothelial Cell Proliferation by Suppressing Basic Fibroblast Growth Factor Expression
Authors: Chen Chu-Huang , Jiang Wei , Via David P. , Luo Sherry , Li Tz-Rung , Lee Yuan-Teh , Henry Philip D.
Published: June 2012

Background
—Hyperlipidemia inhibits proliferation of endothelial cells (ECs) in culture and angiogenesis in vivo and in arterial explants. Elucidation of the mechanisms may suggest novel therapies against atherosclerosis.

Methods and Results
—Basic fibroblast growth factor (bFGF) expression and mitogenic effects were assessed in bovine aortic ECs incubated with oxidized LDL (ox-LDL). Compared with native LDL and lipoprotein-free controls, ox-LDL reduced bFGF mRNA levels in a time- and concentration-dependent manner, 100 μg/mL producing a maximum reduction of 40% to 50% within 24 to 48 hours. There were commensurate reductions in intracellular and extracellular bFGF concentrations, DNA and total RNA syntheses, and cell replication. FGF receptor 1 and β-actin mRNA levels were unchanged. Ox-LDL accelerated bFGF mRNA degradation in actinomycin D–treated cells. However, inhibition of bFGF expression by ox-LDL was attenuated by cyclohexamide, indicating a requirement for continuous new protein synthesis for posttranscriptional destabilization. Reduced syntheses of DNA and total RNA were completely restored by bFGF but not by vascular endothelial growth factor. Inhibition of total RNA synthesis achieved by exposing cells to a bFGF-neutralizing antibody was similar in magnitude to that induced by ox-LDL.

Conclusions
—Cytotoxic effects of ox-LDL on ECs are attributable in part to suppression of bFGF expression.
Treatment of In-Stent Restenosis With Excimer Laser Coronary Angioplasty Versus Rotational Atherectomy
Authors: Mehran Roxana , Dangas George , Mintz Gary S. , Waksman Ron , Abizaid Alexandre , Satler Lowell F. , Pichard Augusto D. , Kent Kenneth M. , Lansky Alexandra J. , Stone Gregg W. , Leon Martin B.
Published: June 2012

Background
—Atheroablation yields improved clinical results for balloon angioplasty (percutaneous transluminal coronary angioplasty, PTCA) in the treatment of diffuse in-stent restenosis (ISR).

Methods and Results
—We compared the mechanisms and clinical results of excimer laser coronary angioplasty (ELCA) versus rotational atherectomy (RA), both followed by adjunct PTCA; 119 patients (158 ISR lesions) were treated with ELCA+PTCA and 130 patients (161 ISR lesions) were treated with RA+PTCA. Quantitative coronary angiographic and planar intravascular ultrasound (IVUS) measurements were performed routinely. In addition, volumetric IVUS analysis to compare the mechanisms of lumen enlargement was performed in 28 patients with 30 lesions (16 ELCA+PTCA, 14 RA+PTCA). There were no significant between-group differences in preintervention or final postintervention quantitative coronary angiographic or planar IVUS measurements of luminal dimensions. Angiographic success and major in-hospital complications with the 2 techniques were also similar. Volumetric IVUS analysis showed significantly greater reduction in intimal hyperplasia volume after RA than after ELCA (43±14 versus 19±10 mm
3
,
P
<0.001) because of a significantly higher ablation efficiency (90±10% versus 76±12%,
P
=0.004). However, both interventional strategies had similar long-term clinical outcome; 1-year target lesion revascularization rate was 26% with ELCA+PTCA versus 28% with RA+PTCA (
P
=NS).

Conclusions
—Despite certain differences in the mechanisms of lumen enlargement, both ELCA+PTCA and RA+PTCA can be used to treat diffuse ISR with similar clinical results.
Single Low-Dose Administration of Human Recombinant Hepatocyte Growth Factor Attenuates Intimal Hyperplasia in a Balloon-Injured Rabbit Iliac Artery Model
Authors: Yasuda Satoshi , Noguchi Teruo , Gohda Masahiro , Arai Takashi , Tsutsui Nobumasa , Matsuda Takehisa , Nonogi Hiroshi
Published: June 2012

Background
—Previous studies have shown that repeated systemic administration of human recombinant hepatocyte growth factor (hrHGF) in mg/kg levels modulates the wound-healing process in various diseases. Recently, HGF has been characterized as one of the most potent endothelial-cell–specific growth factors. We tested our hypothesis that local delivery of hrHGF, even at low μg/kg levels (≥2 orders of magnitude lower than systemically administered doses), might attenuate neointimal hyperplasia in response to vascular injury via accelerated reendothelialization.

Methods and Results
—The iliac artery was denuded in 16 New Zealand White rabbits (3 kg), followed by administration, via a drug delivery catheter, of either hrHGF (10 μg; n=11) or control vehicle (n=5) over 20 minutes. In pilot studies using this device, the drug permeated into the medial tissues, where it persisted for ≥24 hours. Four weeks after the local delivery of hrHGF, computer-assisted morphometric analysis revealed significant reduction in the intimal area (hrHGF, 0.37±0.21 versus control, 0.68±0.16 mm
2
, mean±SD;
P
<0.05) but no change in the medial area (hrHGF, 1.03±0.21 versus control, 1.10±0.52 mm
2
). Scanning electron microscopy revealed extensive endothelialization with regular and confluent endothelial cell layer regeneration in the hrHGF-treated vessels.

Conclusions
—Accelerated endothelialization after local delivery of hrHGF, a novel and potent endothelial cell mitogen, effectively attenuates neointimal proliferation even after single low-dose administration. This observation could have potential therapeutic implications in the prevention of restenosis after angioplasty.
High Levels of Platelet Inhibition With Abciximab Despite Heightened Platelet Activation and Aggregation During Thrombolysis for Acute Myocardial Infarction
Authors: Coulter Stephanie A. , Cannon Christopher P. , Ault Kenneth A. , Antman Elliott M. , Van de Werf Frans , Adgey A. A. Jennifer , Gibson C. Michael , Giugliano Robert P. , Mascelli Mary A. , Scherer Joel , Barnathan Elliot S. , Braunwald Eugene , Kleiman Neal S.
Published: June 2012

Background
—We evaluated platelet activation and aggregation in patients with acute myocardial infarction (AMI) treated with thrombolytic therapy alone or with reduced-dose thrombolysis and concomitant abciximab.

Methods and Results
—The study was performed in 20 control subjects and 51 patients with AMI before and after reperfusion with either alteplase or reteplase or reduced doses of these agents with concomitant abciximab. Platelet activation was assayed by platelet surface expression of P-selectin. Turbidometric platelet aggregation in response to ADP was measured in patients before thrombolytic therapy and 90 minutes and 24 hours after the beginning of thrombolytic therapy. P-selectin expression was greater at baseline in patients than normal control subjects (30.4% versus 9.8%,
P
<0.0001) but was identical between the 2 groups after stimulation with ADP (64.4% versus 69.3%,
P
=0.37). However, at 24 hours, basal P-selectin expression declined in patients (
P
=0.0025 versus baseline), whereas ADP-stimulated P-selectin expression was lower in patients than in control subjects (48% versus 69%,
P
=0.0004). When combined with reduced doses of either alteplase or reteplase, abciximab achieved 91% and 83% inhibition of 5 and 20 μmol/L ADP–induced platelet aggregation, which decreased to 46% and 40%, respectively, at 24 hours. No appreciable difference in the platelet inhibition profile of abciximab was observed between the 2 thrombolytics.

Conclusions
—Platelet activation and aggregation are heightened in the setting of thrombolysis for AMI. Despite this enhanced level of platelet activation, abciximab, combined with a reduced-dose thrombolytic, inhibited platelet aggregation similarly to the level reported in elective settings.
Early Potent Antithrombotic Effect With Combined Aspirin and a Loading Dose of Clopidogrel on Experimental Arterial Thrombogenesis in Humans
Authors: Cadroy Yves , Bossavy Jean-Pierre , Thalamas Claire , Sagnard Luc , Sakariassen Kjell , Boneu Bernard
Published: June 2012

Background
—We conducted a double-blind, randomized, crossover study to assess the antithrombotic effects of the combination of aspirin (acetylsalicylic acid, ASA) and clopidogrel, with or without a loading dose, versus ASA alone in a model of arterial thrombosis in humans.

Methods and Results
—Eighteen male volunteers received the following 3 regimens for 10 days separated by a 1-month period: (1) 325 mg ASA daily, (2) 325 mg ASA+75 mg clopidogrel daily, (3) 325 mg ASA daily+300-mg clopidogrel loading dose on day 1 and +75 mg clopidogrel per day on days 2 to 10. The antithrombotic effect was measured 1.5, 6, and 24 hours after drug intake on day 1 and 6 hours after drug intake on day 10. Arterial thrombus formation was induced ex vivo by exposing a collagen-coated coverslip in a parallel-plate perfusion chamber to native blood for 3 minutes at an arterial wall shear rate. Without a loading dose, clopidogrel+ASA developed an antithrombotic effect within 6 hours after the first intake. It was superior to that produced by ASA, but it was moderate (
P
≤0.03). However, with the loading dose, the antithrombotic effect of clopidogrel+ASA appeared within 90 minutes, and after 6 hours it was comparable to that on day 10. On day 10, clopidogrel+ASA decreased platelet thrombus formation by ≈70%, and the effect was significantly more potent than that produced by ASA alone (
P
<0.001).

Conclusions
—This study confirms the synergistic antithrombotic effects of a combined ASA and clopidogrel therapy and shows the early benefit obtained with a loading dose of clopidogrel.
Antisense to LOX-1 Inhibits Oxidized LDL–Mediated Upregulation of Monocyte Chemoattractant Protein-1 and Monocyte Adhesion to Human Coronary Artery Endothelial Cells
Authors: Li Dayuan , Mehta Jawahar L.
Published: June 2012

Background
—We have recently demonstrated a lectin-like receptor for oxidized (ox)-LDL (LOX-1) in human coronary artery endothelial cells (HCAECs). This receptor is upregulated by ox-LDL. The present study examined the significance of LOX-1 in monocyte adhesion to HCAECs and endothelial injury in response to ox-LDL.

Methods and Results
—HCAECs were incubated in the presence of antisense oligodeoxynucleotides to the 5′-coding sequence of the human
LOX-1
gene (0.5 μm/L). Basal LOX-1 mRNA and protein were suppressed by antisense LOX-1. Ox-LDL–mediated upregulation of LOX-1 was also suppressed by antisense LOX-1. Incubation of HCAECs with ox-LDL (40 μg/mL) for 24 hours markedly increased monocyte chemoattractant protein-1 (MCP-1) mRNA and protein expression as well as monocyte adhesion to HCAECs (
P
<0.01). After 48 hours of preincubation of HCAECs with antisense LOX-1, ox-LDL–mediated upregulation of MCP-1 and monocyte adhesion to HCAECs both were suppressed (
P
<0.01), whereas sense LOX-1 had no effect. Whereas antisense or sense LOX-1 alone (both 0.5 nmol/L) did not injure the cells, antisense LOX-1, but not sense LOX-1, reduced ox-LDL–mediated HCAEC injury, determined as LDH release (
P
<0.01). Activation of mitogen-activated protein kinase (MAPK) may play a critical role in signal transduction in ox-LDL–mediated alteration in MCP-1 expression, since antisense LOX-1, but not the sense LOX-1, completely inhibited the ox-LDL–induced MAPK activation.

Conclusions
—These observations with the first use of a specific antisense to human LOX-1 mRNA suggest that LOX-1 is a key factor in ox-LDL–mediated monocyte adhesion to HCAECs.
Mapping and Ablation of Left Atrial Flutters
Authors: Jaïs Pierre , Shah Dipen C. , Haïssaguerre Michel , Hocini Mélèze , Peng Jing Tian , Takahashi Atsushi , Garrigue Stéphane , Le Métayer Philippe , Clémenty Jacques
Published: June 2012

Background
—Typical right atrial isthmus–dependent flutters have been described in detail, but very little is known about left atrial (LA) flutters.

Methods and Results
—We performed conventional and 3D mapping of the LA for 22 patients with atypical flutters. Complete maps in 17 patients demonstrated macroreentrant circuits (n=15) with 1 to 3 loops rotating around the mitral annulus, the pulmonary veins, and a zone of block or a silent area. In 2 patients, a small reentry circuit with a zone of markedly slow conduction was identified. Linear ablation performed across the most accessible part of the circuit cured 16 patients (73%) with a follow-up of 15±7 months.

Conclusions
—LA reentrant tachycardias are related to individually varying circuits and are amenable to mapping guided radiofrequency ablation.