bluuebunny/crossref_metadata_2025 huggingface dataset:
Signaling Pathways in Reactive Oxygen Species–Induced Cardiomyocyte Apoptosis
Authors: von Harsdorf Rüdiger , Li Pei-Feng , Dietz Rainer
Published: June 2012

Background
—The importance of free radical homeostasis and apoptosis in normal and diseased hearts and their interrelationships are poorly defined. We tested whether reactive oxygen species can trigger apoptosis in cardiomyocytes, and we explored the underlying pathways.

Methods and Results
—A cell culture model of isolated cardiac cells and different reactive oxygen species (ROS)–generating systems were used. Apoptosis became evident when cardiomyocytes were exposed to either H
2
O
2
or superoxide anion (O
2
−
). Both H
2
O
2
- and O
2
−
-induced apoptosis of cardiomyocytes were associated with an increase in p53 protein content, whereas protein levels of Bax and Bcl-2 were unaltered. H
2
O
2
, but not O
2
−
, induced an increase in the protein content of Bad. Furthermore, H
2
O
2
elicited translocation of Bax and Bad from cytosol to mitochondria, where these factors formed heterodimers with Bcl-2, which was followed by the release of cytochrome
c
, activation of CPP32, and cleavage of poly(ADP-ribose) polymerase. Interestingly, this pathway was not activated by O
2
−
. Instead, O
2
−
used Mch2α to promote the apoptotic pathway, as revealed by the activation of Mch2α and the cleavage of its substrate, lamin A.

Conclusions
—Taken together, these results indicate that ROS may play an important pathophysiological role in cardiac diseases characterized by apoptotic cell death and suggest that different ROS-induced activations of the apoptotic cell death program in cardiomyocytes involve distinct signaling pathways.
Effect of Pacing Chamber and Atrioventricular Delay on Acute Systolic Function of Paced Patients With Congestive Heart Failure
Authors: Auricchio Angelo , Stellbrink Christoph , Block Michael , Sack Stefan , Vogt Jürgen , Bakker Patricia , Klein Helmut , Kramer Andrew , Ding Jiang , Salo Rodney , Tockman Bruce , Pochet Thierry , Spinelli Julio
Published: June 2012

Background
—Previous studies of pacing therapy for dilated congestive heart failure (CHF) have not established the relative importance of pacing site, AV delay, and patient heterogeneity on outcome. These variables were compared by a novel technique that evaluated immediate changes in hemodynamic function during brief periods of atrial-synchronous ventricular pacing.

Methods and Results
—Twenty-seven CHF patients with severe left ventricular (LV) systolic dysfunction and LV conduction disorder were implanted with endocardial pacing leads in the right atrium and right ventricle (RV) and an epicardial lead on the LV and instrumented with micromanometer catheters in the LV, aorta, and RV. Patients in normal sinus rhythm were stimulated in the RV, LV, or both ventricles simultaneously (BV) at preselected AV delays in a repeating 5-paced/15-nonpaced beat sequence. Maximum LV pressure derivative (LV+dP/dt) and aortic pulse pressure (PP) changed immediately at pacing onset, increasing at a patient-specific optimal AV delay in 20 patients with wide surface QRS (180±22 ms) and decreasing at short AV delays in 5 patients with narrower QRS (128±12 ms) (
P
<0.0001). Overall, BV and LV pacing increased LV+dP/dt and PP more than RV pacing (
P
<0.01), whereas LV pacing increased LV+dP/dt more than BV pacing (
P
<0.01).

Conclusions
—In this population, CHF patients with sufficiently wide surface QRS benefit from atrial-synchronous ventricular pacing, LV stimulation is required for maximum acute benefit, and the maximum benefit at any site occurs with a patient-specific AV delay.
Angiographic Anatomy of the Inferior Right Atrial Isthmus in Patients With and Without History of Common Atrial Flutter
Authors: Cabrera José Angel , Sanchez-Quintana Damian , Ho Siew Yen , Medina Alfonso , Wanguemert Fernando , Gross Egon , Grillo José , Hernandez Enrique , Anderson Robert H.
Published: June 2012

Background
—Although most ablative procedures undertaken for common atrial flutter target the inferior right atrial isthmus, comparative studies of the morphology of this area are lacking. Our study examines its angiographic anatomy, making correlations with postmortem specimens, to provide a better understanding of the anatomic substrate of this arrhythmia.

Methods and Results
—The gross morphological features and dimensions of the area between the orifice of the inferior caval vein and the attachment of the septal leaflet of the tricuspid valve were determined from angiograms made in 23 patients with documented atrial flutter and 30 control subjects. For comparison, we studied 20 normal heart specimens. When viewed in right anterior oblique projection, 2 morphologically distinct areas were identified. In the specimens, the inferior isthmus measured a mean length of 30±4 mm, not significantly different from the dimensions obtained from angiograms of control subjects. The mean length of the isthmus, however, was greater in patients with common atrial flutter than those without (37±8 versus 28±6 mm). Patients with atrial flutter and structural heart disease had an even longer isthmus than those with flutter alone (39.6±8 versus 33±7 mm). Compared with those without flutter, the atrial diameter was also larger in patients with flutter (57.6±9 versus 48.5±6 mm). Reevaluation carried out at follow-up 10±2 months after ablation did not show any reduction in atrial size, although contractility improved.

Conclusions
—The inferior isthmus and right atrium in patients with common atrial flutter were significantly larger than those in a control population.
Short-Term Effect of Atrial Fibrillation on Atrial Contractile Function in Humans
Authors: Daoud Emile G. , Marcovitz Pamela , Knight Bradley P. , Goyal Rajiva , Man K. Ching , Strickberger S. Adam , Armstrong William F. , Morady Fred
Published: June 2012

Background
—Conversion of chronic atrial fibrillation (AF) is associated with atrial stunning, but the short-term effect of a brief episode of AF on left atrial appendage (LAA) emptying velocity is unknown. The purpose of this study was to determine whether a short episode of AF affects left atrial function and whether verapamil modifies this effect.

Methods and Results
—The subjects of this study were 19 patients without structural heart disease undergoing an electrophysiology procedure. In 13 patients, LAA emptying velocity was measured by transesophageal echocardiography in the setting of pharmacological autonomic blockade before, during, and after a short episode of AF. During sinus rhythm, the baseline LAA emptying velocity was measured 5 times and averaged. AF was then induced by rapid right atrial pacing. After either spontaneous or electrical conversion, LAA emptying velocity was measured immediately on resumption of sinus rhythm and every minute thereafter. The mean duration of AF was 15.3±3.8 minutes. The mean baseline emptying velocity was 70±20 cm/s. The first post-AF emptying velocity was 63±20 cm/s (
P
=0.02 versus baseline emptying velocity). The post-AF emptying velocity returned to the baseline emptying velocity value after 3.0 minutes. The mean percent reduction in post-AF emptying velocity was 9.7±21% (range, 15% increase to 56% decrease). A second group of 6 patients were pretreated with verapamil (0.1-mg/kg IV bolus followed by an infusion of 0.005 mg · kg
−1
· min
−1
). In these patients, the first post-AF emptying velocity, 58±14 cm/s, was not significantly different from the pre-AF emptying velocity, 60±13 cm/s (
P
=0.08).

Conclusions
—In humans, several minutes of AF may be sufficient to induce atrial contractile dysfunction after cardioversion. When atrial contractile dysfunction occurs, there is recovery of AF within several minutes. AF-induced contractile dysfunction is attenuated by verapamil and may be at least partially mediated by cellular calcium overload.
Char Syndrome, an Inherited Disorder With Patent Ductus Arteriosus, Maps to Chromosome 6p12-p21
Authors: Satoda Masahiko , Pierpont Mary Ella M. , Diaz George A. , Bornemeier Renee A. , Gelb Bruce D.
Published: June 2012

Background
—Patent ductus arteriosus (PDA) is a relatively common form of congenital heart disease. Although polygenic inheritance has been implicated, no specific gene defects causing PDA have been identified to date. Thus, a positional cloning strategy was undertaken to determine the gene responsible for the Char syndrome, an autosomal dominant disorder characterized by PDA, facial dysmorphism, and hand anomalies.

Methods and Results
—A genome scan was performed with 46 members of 2 unrelated families in which the disease was fully penetrant but the phenotype differed. Significant linkage was achieved with several polymorphic DNA markers mapping to chromosome 6p12-p21 (maximal 2-point LOD score of 8.39 with D6S1638 at θ=0.00). Haplotype analysis identified recombinant events that defined the Char syndrome locus with high probability to a 3.1-cM region between D6S459/D6S1632/D6S1541 and D6S1024.

Conclusions
—A familial syndrome in which PDA is a common feature was mapped to a narrow region of chromosome 6p12-p21. Additional analysis with other families and polymorphic markers as well as evaluation of potential candidate genes should lead to the identification of the Char syndrome gene, which will provide insights into cardiogenesis as well as limb and craniofacial development.
Tissue Inhibition of Angiotensin-Converting Enzyme Activity Stimulates Angiogenesis In Vivo
Authors: Fabre Jean-Etienne , Rivard Alain , Magner Meredith , Silver Marcy , Isner Jeffrey M.
Published: June 2012

Background
—Endothelial cells (ECs) represent the critical cellular element responsible for postnatal angiogenesis. Because ACE inhibitors may favorably affect endothelial function, we investigated the hypothesis that administration of the ACE inhibitor quinaprilat could enhance angiogenesis in vivo.

Methods and Results
—Ten days after resection of 1 femoral artery, New Zealand White (NZW) rabbits were randomly assigned to receive recombinant human vascular endothelial growth factor (rhVEGF) administered as a single intra-arterial injection (n=6), quinaprilat (n=8) or captopril (n=7) administered as a daily subcutaneous injection, or no treatment (controls, n=6). Angiogenesis was monitored in vivo by measurement of blood pressure, vasoreactivity, and resistance in ischemic versus normal limbs at day 10 (D10) and D40; angiographic studies to identify sites of neovascularization were performed at D10 and D40, and morphometric analysis of capillary density in the ischemic limb was performed at necropsy (D40). Both functional and morphological outcomes documented augmented angiogenesis in quinaprilat-treated rabbits similar to that observed for rhVEGF and superior to that observed with either captopril or no drug (controls). Residual ACE activity was equivalent for the captopril and quinaprilat groups in plasma (42.54±0.03% versus 41.53±0.02%,
P
=NS) but not in tissue, where quinaprilat lowered ACE activity significantly (
P
<0.01) compared with captopril (13% versus 61%).

Conclusions
—ACE inhibition with quinaprilat promotes angiogenesis in a rabbit model of hindlimb ischemia. Thus, nonsulfhydryl ACE inhibitors with high tissue affinity may be potentially useful for therapeutic angiogenesis in ischemic tissues. Moreover, previous evidence that ACE inhibition benefits patients with myocardial ischemia may be due in part to augmented collateral development.
Matrix Metalloproteinase Inhibition Attenuates Early Left Ventricular Enlargement After Experimental Myocardial Infarction in Mice
Authors: Rohde Luis E. , Ducharme Anique , Arroyo Luis H. , Aikawa Masanori , Sukhova Galina H. , Lopez-Anaya Arturo , McClure Kim F. , Mitchell Peter G. , Libby Peter , Lee Richard T.
Published: June 2012

Background
—Extracellular matrix synthesis and degradation contribute to the morphological changes that occur after myocardial infarction (MI).

Methods and Results
—We tested the hypothesis that inhibition of matrix metalloproteinases (MMPs) attenuates left ventricular remodeling in experimental MI. Seventy-one male FVB mice that survived ligation of the left anterior coronary artery were randomized to a broad-spectrum MMP inhibitor (CP-471,474) or placebo by gavage. Echocardiographic studies were performed before randomization (within 24 hours of surgery) and 4 days later and included short-axis imaging at the midpapillary and apical levels. Infarction as defined by wall motion abnormality was achieved in 79% of the procedures (n=56), and mortality rate during the 4-day protocol was 23% (9 of 36 on treatment vs 7 of 35 on placebo;
P
=NS). Baseline end-diastolic and end-systolic dimensions and areas were similar (
P
=NS) between treated and placebo groups. At follow-up, infarcted mice allocated to MMP inhibitor had significantly smaller increases in end-systolic and end-diastolic dimensions and areas at both midpapillary and apical levels compared with infarcted mice allocated to placebo (all
P
<0.05). In addition, infarcted animals that received MMP inhibitor had no change in fractional shortening (−3±13%), whereas animals that received placebo had a decrease in fractional shortening (−12±12%) (
P
<0.05). In an analysis stratified by baseline end-diastolic area, the effects of MMP inhibition on the changes in end-systolic area and end-diastolic area were most prominent in animals that had more initial left ventricular dilatation (both
P
<0.05).

Conclusions
—–Administration of an MMP inhibitor attenuates early left ventricular dilation after experimental MI in mice. Further studies in genetically altered mice and other models will improve understanding of the role of MMPs in left ventricular remodeling.
Novel Mechanism for Endothelial Dysfunction
Authors: Ito Akira , Tsao Philip S. , Adimoolam Shanthi , Kimoto Masumi , Ogawa Tadashi , Cooke John P.
Published: June 2012

Background
—Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase (NOS). Plasma levels of ADMA are elevated in individuals with hypercholesterolemia or atherosclerosis. We postulated that reduced degradation of ADMA may play a role in the accumulation of ADMA in these individuals. Accordingly, we studied the effects of oxidized LDL (oxLDL) or tumor necrosis factor-α (TNF-α) on the accumulation of ADMA by transformed human umbilical vein endothelial cells (ECV304) and on the enzyme dimethylarginine dimethylaminohydrolase (DDAH), which degrades ADMA.

Methods and Results
—ECV304 were incubated with or without native LDL (100 μg/mL), oxLDL (100 μg/mL), or TNF-α (250 U/mL) for 48 hours. The concentration of ADMA in the conditioned medium was determined by high-performance liquid chromatography. Western blotting was performed to evaluate DDAH expression. We assayed DDAH activity by determining
l
-citrulline formation from ADMA. The addition of oxLDL or TNF-α to ECV304 significantly increased the level of ADMA in the conditioned medium. The effect of oxLDL or TNF-α was not due to a change in DDAH expression but rather to the reduction of DDAH activity. To determine whether dysregulation of DDAH also occurred in vivo, New Zealand White rabbits were fed normal chow or a high-cholesterol diet. Hypercholesterolemia significantly reduced aortic, renal, and hepatic DDAH activity.

Conclusions
—These results suggest that the endothelial vasodilator dysfunction observed in hypercholesterolemia may be due to reduced degradation of ADMA, the endogenous inhibitor of NOS.
Expression of Lectinlike Oxidized Low-Density Lipoprotein Receptor-1 in Human Atherosclerotic Lesions
Authors: Kataoka Hiroharu , Kume Noriaki , Miyamoto Susumu , Minami Manabu , Moriwaki Hideaki , Murase Takatoshi , Sawamura Tatsuya , Masaki Tomoh , Hashimoto Nobuo , Kita Toru
Published: June 2012

Background
—Oxidized LDL (Ox-LDL) seems to play key roles in atherogenesis. Lectinlike Ox-LDL receptor-1 (LOX-1) is a recently identified cell-surface receptor for Ox-LDL. The relationship of this novel receptor for Ox-LDL to atherogenesis, however, has not yet been clarified. In this study, we explored the expression of LOX-1 in the atherosclerotic lesions of human carotid arteries.

Methods and Results
—Using carotid endarterectomy specimens obtained from 21 patients and 2 samples of normal human aortas, we examined LOX-1 expression by reverse transcription–polymerase chain reaction and immunohistochemistry. In aortas without atherosclerosis, LOX-1 expression was undetectable by immunohistochemistry and negligible by reverse transcription–polymerase chain reaction. In carotid arteries, luminal endothelial cells covering early atherosclerotic lesions were more frequently positive for LOX-1 expression than those in advanced atherosclerotic lesions. Endothelial cells in the intimal neovasculature of advanced lesions also expressed LOX-1. In addition, macrophages and smooth muscle cells in the intima of advanced atherosclerotic plaques were positive for LOX-1 expression.

Conclusions
—LOX-1 may play important roles in Ox-LDL uptake and subsequent functional alteration in the luminal endothelium in early atherosclerotic lesions and in intimal neovascular endothelial cells in advanced plaques. Furthermore, LOX-1 may also be involved in Ox-LDL uptake and subsequent foam cell transformation in macrophages and smooth muscle cells in the atherosclerotic intima.
Human Coronary Arteriolar Dilation to Bradykinin Depends on Membrane Hyperpolarization
Authors: Miura Hiroto , Liu Yanping , Gutterman David D.
Published: June 2012

Background
—K
+
channel activation in vascular smooth muscle cells (VSMCs) plays a key role in regulating vascular tone. It has been proposed that endothelium-derived hyperpolarizing factor (EDHF) contributes to microvascular dilation more than nitric oxide (NO) does. Whether hyperpolarization is important for coronary arteriolar dilation in humans is not known. Bradykinin (BK), an endogenous vasoactive substance, is released from ischemic myocardium and regulates coronary resistance. Therefore, we tested the effects of inhibiting NO synthase, cyclooxygenase, and K
+
channels on the changes in diameter and membrane potential (Em) in response to BK in isolated human coronary microvessels.

Methods and Results
—Arterioles (97±4 μm; n=120) dissected from human right atrial appendages (n=78) were cannulated at a distending pressure of 60 mm Hg and zero flow. Changes in vessel diameter (video microscopy) and VSMC Em (glass microelectrodes) were measured simultaneously. In vessels constricted and depolarized (Em; −50±3 to −28±2 mV) with endothelin-1 (ET), dilation to BK was associated with greater membrane hyperpolarization (−48±3 mV at 10
−6
mol/L) than dilation to sodium nitroprusside (SNP) (−34±2 mV at 10
−4
mol/L) for similar degrees of dilation. Treatment with
N
ω
-nitro-
l
-arginine methyl ester (L-NAME; 10
−4
mol/L), an NO synthase inhibitor, partially decreased dilation to BK (maximum dilation 61±10% versus control 92±4%;
P
<0.05). Charybdotoxin (CTX; 10
−8
mol/L), a large-conductance Ca
2+
-activated K
+
channel blocker, or apamin (10
−7
mol/L), a small-conductance Ca
2+
-activated K
+
channel blocker, inhibited both dilation (CTX 22±6% and apamin 45±10% versus control 69±6%;
P
<0.05) and membrane hyperpolarization (CTX −31±2 mV and apamin −37±2 mV versus control –44±2 mV;
P
<0.05) to BK, whereas glibenclamide (10
−6
mol/L), an ATP-sensitive K
+
channel blocker, was without effect.

Conclusions
—Vasodilation of human coronary arterioles to BK is largely dependent on membrane hyperpolarization by Ca
2+
-activated K
+
channel activation, with apparently less of a role for endothelium-derived NO. This suggests a role for K
+
channel activation in regulating human coronary arteriolar tone.
Familial Hypertrophic Cardiomyopathy in Maine Coon Cats
Authors: Kittleson Mark D. , Meurs Kathryn M. , Munro Marcia J. , Kittleson Judith A. , Liu Si-Kwang , Pion Paul D. , Towbin Jeffrey A.
Published: June 2012

Background
—A naturally occurring animal model of familial hypertrophic cardiomyopathy (FHCM) is lacking. We identified a family of Maine coon cats with HCM and developed a colony to determine mode of inheritance, phenotypic expression, and natural history of the disease.

Methods and Results
—A proband was identified, and related cats were bred to produce a colony. Affected and unaffected cats were bred to determine the mode of inheritance. Echocardiography was used to identify affected offspring and determine phenotypic expression. Echocardiograms were repeated serially to determine the natural history of the disease. Of 22 offspring from breeding affected to unaffected cats, 12 (55%) were affected. When affected cats were bred to affected cats, 4 (45%) of the 9 were affected, 2 (22%) unaffected, and 3 (33%) stillborn. Findings were consistent with an autosomal dominant mode of inheritance with 100% penetrance, with the stillborns representing lethal homozygotes that died in utero. Affected cats usually did not have phenotypic evidence of HCM before 6 months of age, developed HCM during adolescence, and developed severe HCM during young adulthood. Papillary muscle hypertrophy that produced midcavitary obstruction and systolic anterior motion of the mitral valve was the most consistent manifestation of HCM. Cats died suddenly (n=5) or of heart failure (n=3). Histopathology of the myocardium revealed myocardial fiber disarray, intramural coronary arteriosclerosis, and interstitial fibrosis.

Conclusions
—HCM in this family of Maine coon cats closely resembles the human form of FHCM and should prove a valuable tool for studying the gross, cellular, and molecular pathophysiology of the disease.
Safety and Efficacy of a Soluble P75 Tumor Necrosis Factor Receptor (Enbrel, Etanercept) in Patients With Advanced Heart Failure
Authors: Deswal Anita , Bozkurt Biykem , Seta Yukihiro , Parilti-Eiswirth Semahat , Hayes F. Ann , Blosch Consuelo , Mann Douglas L.
Published: June 2012

Background
—Although previous studies suggested that TNF may contribute to heart failure progression, it is unclear whether antagonizing TNF is beneficial in heart failure patients.

Methods and Results
—Eighteen NYHA class III heart failure patients were randomized into a double-blind dose-escalation study to examine the safety and potential efficacy of etanercept, a specific TNF antagonist (Enbrel). Patients received placebo (6 patients) or an escalating dose (1, 4, or 10 mg/m
2
) of etanercept (12 patients) given as a single intravenous infusion. Safety parameters and patient functional status were assessed at baseline and at days 1, 2, 7, and 14. There were no significant side effects or clinically significant changes in laboratory indices. There was, however, a decrease in TNF bioactivity and a significant overall increase in quality-of-life scores, 6-minute walk distance, and ejection fraction in the cohort that received 4 or 10 mg/m
2
of etanercept; there was no significant change in these parameters in the placebo group.

Conclusions
—A single intravenous infusion of etanercept was safe and well tolerated in patients with NYHA class III heart failure. These studies provide provisional evidence that suggests that etanercept is sufficient to lower levels of biologically active TNF and may lead to improvement in the functional status of patients with heart failure.
Long-Term Ascorbic Acid Administration Reverses Endothelial Vasomotor Dysfunction in Patients With Coronary Artery Disease
Authors: Gokce Noyan , Keaney John F. , Frei Balz , Holbrook Monika , Olesiak Mariusz , Zachariah Benoy J. , Leeuwenburgh Christiaan , Heinecke Jay W. , Vita Joseph A.
Published: June 2012

Background
—Loss of endothelium-derived nitric oxide (EDNO) contributes to the clinical expression of coronary artery disease (CAD). Increased oxidative stress has been linked to impaired endothelial vasomotor function in atherosclerosis, and recent studies demonstrated that short-term ascorbic acid treatment improves endothelial function.

Methods and Results
—In a randomized, double-blind, placebo-controlled study, we examined the effects of single-dose (2 g PO) and long-term (500 mg/d) ascorbic acid treatment on EDNO-dependent flow-mediated dilation of the brachial artery in patients with angiographically established CAD. Flow-mediated dilation was examined by high-resolution vascular ultrasound at baseline, 2 hours after the single dose, and 30 days after long-term treatment in 46 patients with CAD. Flow-mediated dilation improved from 6.6±3.5% to 10.1±5.2% after single-dose treatment, and the effect was sustained after long-term treatment (9.0±3.7%), whereas flow-mediated dilation was 8.6±4.7% at baseline and remained unchanged after single-dose (7.8±4.4%) and long-term (7.9±4.5%) treatment with placebo (
P
=0.005 by repeated-measures ANOVA). Plasma ascorbic acid concentrations increased from 41.4±12.9 to 115.9±34.2 μmol/L after single-dose treatment and to 95.0±36.1 μmol/L after long-term treatment (
P
<0.001).

Conclusions
—In patients with CAD, long-term ascorbic acid treatment has a sustained beneficial effect on EDNO action. Because endothelial dysfunction may contribute to the pathogenesis of cardiovascular events, this study indicates that ascorbic acid treatment may benefit patients with CAD.
Visualization and Functional Assessment of Proximal and Middle Left Anterior Descending Coronary Stenoses in Humans With Magnetic Resonance Imaging
Authors: Hundley W. Gregory , Hamilton Craig A. , Clarke Geoffrey D. , Hillis L. David , Herrington David M. , Lange Richard A. , Applegate Robert J. , Thomas Mark S. , Payne Jerri , Link Kerry M. , Peshock Ronald M.
Published: June 2012

Background
—Coronary artery bypass grafting improves survival in patients with >70% luminal diameter narrowing of the 3 major epicardial coronary arteries, particularly if there is involvement of the proximal portion of the left anterior descending (LAD) coronary artery. Measurement of coronary flow reserve can be used to identify functionally important luminal narrowing of the LAD artery. Although magnetic resonance imaging (MRI) has been used to visualize coronary arteries and to measure flow reserve noninvasively, the utility of MRI for detecting significant LAD stenoses is unknown.

Methods and Results
—Thirty subjects (23 men, 7 women, age 36 to 77 years) underwent MRI visualization of the left main and LAD coronary arteries as well as measurement of flow in the proximal, middle, or distal LAD both at rest and after intravenous adenosine (140 μg/kg per minute). Immediately thereafter, contrast coronary angiography and when feasible, intracoronary Doppler assessments of coronary flow reserve, were performed. There was a statistically significant correlation between MRI assessments of coronary flow reserve and (a) assessments of coronary arterial stenosis severity by quantitative coronary angiography and (b) invasive measurements of coronary flow reserve (
P
<0.0001 for both). In comparison to computer-assisted quantitative coronary angiography, the sensitivity and specificity of MRI for identifying a stenosis >70% in the distal left main or proximal/middle LAD arteries was 100% and 83%, respectively.

Conclusions
—Noninvasive MRI measures of coronary flow reserve correlated well with similar measures obtained with the use of intracoronary Doppler flow wires and predicted significant coronary stenoses (>70%) with a high degree of sensitivity and specificity. MRI-based measurement of coronary flow reserve may prove useful for identification of patients likely to obtain a survival benefit from coronary artery bypass grafting.
Restenosis Following Angioplasty in the Swine Coronary Artery Is Inhibited By an Orally Active PDGF-Receptor Tyrosine Kinase Inhibitor, RPR101511A
Authors: Bilder Glenda , Wentz Tara , Leadley Robert , Amin Dilip , Byan Lisa , O’Conner Betsey , Needle Saul , Galczenski Helen , Bostwick Jeffery , Kasiewski Charles , Myers Michael , Spada Alfred , Merkel Linda , Ly Cuong , Persons Paul , Page Kenneth , Perrone Mark , Dunwiddie Christopher
Published: June 2012

Background
—Platelet-derived growth factor (PDGF), a purported mediator of arterial response to injury, stimulates proliferation, chemotaxis, and matrix production by activation of its membrane receptor tyrosine kinase. Because these activities underlie restenosis, inhibition of the PDGF-receptor tyrosine kinase (PDGFr-TK) is postulated to decrease restenosis.

Methods and Results
—RPR101511A is a novel compound which selectively and potently inhibits the cell-free and in situ PDGFr-TK and PDGFr-dependent proliferation and chemotaxis in vascular smooth muscle cells (VSMC). To evaluate the effect of RPR101511A (30 mg · kg
−1
· d
−1
BID for 28 days following PTCA) on coronary restenosis, PTCA was performed in hypercholesterolemic minipigs whose left anterior descending (LAD) coronary artery had been injured by overdilation and denudation, yielding a previously existing lesion. Angiographically determined prePTCA minimal lumen diameters (MLD) were similar in vehicle and RPR101511A-treated pigs (1.98±0.09 versus 2.01±0.08 mm) and increased to the same extent in the 2 groups following successful PTCA (2.30±0.06 versus 2.52±0.13). At termination, there was an average 50% loss of gain in the vehicle-treated group but no loss of gain with RPR101511A (2.16±0.05 versus 2.59±0.11,
P
<0.001). Morphometric analysis of the LAD showed that RPR101511A caused a significant decrease in total intimal/medial ratio (0.96±0.58 versus 0.67±0.09,
P
<0.05).

Conclusions
—RPR101511A, which acts by inhibition of the PDGFr-TK, completely prevented angiographic loss of gain following PTCA and significantly reduced histological intimal hyperplasia.
Prospective Evaluation of the Angiotensin-Converting Enzyme Insertion/Deletion Polymorphism and the Risk of Stroke
Authors: Zee Robert Y.L. , Ridker Paul M. , Stampfer Meir J. , Hennekens Charles H. , Lindpaintner Klaus
Published: June 2012

Background
—The
D/I
polymorphism of the
ACE
gene has been studied in relation to a variety of cardiovascular disorders, including stroke. A number of small studies have been conducted, with inconsistent results. We investigated the association between
ACE
genotype and the incidence of stroke in a large, prospective, matched case-control sample from the Physicians’ Health Study.

Methods and Results
—In the Physicians’ Health Study, 348 subjects who had been apparently healthy at enrollment suffered a stroke during 12 years of follow-up, as determined from medical records and autopsy. A total of 348 cases were matched by age, time of randomization, and smoking habit to an equal number of controls (who had remained free of stroke). The
D/I
polymorphism was determined by polymerase chain reaction. Data were analyzed for the entire nested case-control sample, and also among a subgroup without a history of hypertension or diabetes mellitus, considered to be at low conventional risk (207 cases and 280 controls). All observed genotype frequencies were in Hardy-Weinberg equilibrium. The relative risk associated with the
D
allele was 1.11 (95% CI, 0.90 to 1.37;
P
=0.35), assuming an additive model in the matched analysis. Additional analyses assuming dominant or recessive effects of the
D
allele, as well as the analysis after stratification for low-risk status, showed no material as a statistically significant association.

Conclusions
—The results of this large, prospective study indicate that the
ACE D/I
gene polymorphism is not associated with subsequent risk of stroke.
Amelioration by Quinapril of Myocardial Infarction Induced by Coronary Occlusion/Reperfusion in a Rabbit Model of Atherosclerosis
Authors: Hoshida Shiro , Yamashita Nobushige , Kawahara Kiminori , Kuzuya Tsunehiko , Hori Masatsugu
Published: June 2012

Background
—The increased severity of the myocardial injury produced by coronary occlusion-reperfusion in models of atherosclerosis is associated with an increase in leukocyte accumulation in the ischemic myocardium. Expression of P-selectin, an adhesion molecule involved in the interaction between leukocytes and endothelium, is increased in atherosclerotic vessels. Long-term angiotensin-converting enzyme (ACE) inhibition has been shown to reduce atherosclerotic vascular change in experimental models.

Methods and Results
—We examined changes in the size of the infarct resulting from coronary occlusion/reperfusion in normally fed and cholesterol-fed rabbits that were chronically treated with quinapril. Infarct size was significantly larger in the cholesterol-fed versus normally fed rabbits. ACE activity in the ischemic and nonischemic myocardium was significantly reduced by quinapril. Chronic quinapril administration significantly ameliorated the increased myocardial injury in cholesterol-fed rabbits. Quinapril administration markedly increased the myocardial cGMP content and reduced the myeloperoxidase activity in the border region of the ischemic myocardium in cholesterol-fed rabbits. The enhanced expression of P-selectin in myocardial tissue of cholesterol-fed rabbits was also effectively reduced by quinapril treatment. The above effects of quinapril were eliminated by blockade of bradykinin B
2
receptors or inhibition of nitric oxide synthesis.

Conclusions
—Chronic quinapril treatment ameliorated the severity of myocardial injury produced by coronary occlusion/reperfusion in cholesterol-fed rabbits, possibly because of reversal of the enhanced interaction between leukocytes and endothelium in the ischemic myocardium via a bradykinin-related pathway.
RGS4 Inhibits G-Protein Signaling in Cardiomyocytes
Authors: Tamirisa Praveen , Blumer Kendall J. , Muslin Anthony J.
Published: June 2012

Background
—RGS family members are GTPase-activating proteins for heterotrimeric G
q
and G
i
proteins.
RGS
genes are expressed in heart tissue and in cultured cardiomyocytes. There is evidence that altered
RGS
gene expression may contribute to the pathogenesis of cardiac hypertrophy and failure.

Methods and Results
—We investigated the ability of RGS proteins to block G-protein signaling in vivo by using a cultured cardiomyocyte transfection system. Endothelin-1, angiotensin II, and phenylephrine signal through G
q
or G
i
family members and promote the hypertrophy of cardiomyocytes. We found that phenylephrine-mediated and endothelin-1–mediated induction of the atrial natriuretic factor and myosin light chain-2 genes was inhibited in cells that were transfected with RGS4. Phenylephrine-mediated gene induction was not inhibited in cells that were transfected with N128A-RGS4, a point mutant form that lacks GTPase-activating protein activity. Phenylephrine-mediated myofilament organization and cell growth were also blocked in cells by RGS4.

Conclusions
—These results demonstrate that RGS protein can inhibit G-protein–mediated signaling in vivo and suggest that increased expression of RGS protein may be a counterregulatory mechanism to inhibit G protein signaling.
Magnetic Resonance Imaging and Invasive Evaluation of Development of Heart Failure in Transgenic Mice With Myocardial Expression of Tumor Necrosis Factor-α
Authors: Franco Fatima , Thomas Gail D. , Giroir Brett , Bryant Debora , Bullock M. Craig , Chwialkowski Michael C. , Victor Ronald G. , Peshock Ronald M.
Published: June 2012

Background
—Transgenic mice expressing tumor necrosis factor-α (TNF-α) in cardiac myocytes develop dilated cardiomyopathy, but the temporal progression to cardiac dysfunction is not well characterized. We asked (1) Does magnetic resonance imaging (MRI) provide a reproducible assessment of cardiac output in mice that correlates with invasive measurements obtained with thermodilution? (2) What is the time course of left ventricular (LV) remodeling in transgenic mice with myocardial expression of TNF-α?

Methods and Results
—Transgenic mice from 2 different lineages with differing amounts of myocardial TNF-α expression [lineage 1 (L1) and lineage 2 (L2)] and littermate controls (LC) were studied. In protocol 1, cardiac output (CO) and stroke volume (SV) were measured by MRI and thermodilution (TD) in 15 mice (3 L1, 4 L2, 8 LC). In protocol 2, 23 mice (7 L1, 8 L2, 8 LC) were scanned at 1 month of life and every 4 weeks thereafter. In both protocols, cine-MRI was performed with the use of a 1.5-T clinical system (1.5-mm slices, 195×195 μm in-plane resolution). MRI CO and SV correlated well with TD [CO
TD
(mL/min)=0.94*CO
MRI
+0.72,
r
=0.84; SV
TD
(μL)=1.01*SV
MRI
−1.07,
r
=0.94]. Serial MRI studies showed significant increase in LV mass and volumes over time and a significant decrease in ejection fraction in transgenic mice when compared with littermate controls. Compared with lineage 2, lineage 1 showed significantly larger LV mass and volumes and significantly lower ejection fraction.

Conclusions
—MRI assessment of cardiac function in mice correlates well with invasive measurements. Serial MRI studies in the TNF-α mouse model demonstrate that the rate of progression and severity of LV dysfunction are dependent on the degree of TNF-α overexpression.
Protein Kinase A (PKA)-Dependent Troponin-I Phosphorylation and PKA Regulatory Subunits Are Decreased in Human Dilated Cardiomyopathy
Authors: Zakhary Daniel R. , Moravec Christine S. , Stewart Robert W. , Bond Meredith
Published: June 2012

Background
—Most studies indicate that failing human hearts have greater baseline myofibrillar Ca
2+
sensitivity of tension development than nonfailing hearts. Phosphorylation of cardiac troponin I (TnI) by cAMP-dependent protein kinase (PKA) decreases the affinity of the troponin complex for Ca
2+
, thus altering the Ca
2+
sensitivity of force production. We tested the hypothesis that PKA-dependent TnI phosphorylation is altered in the failing human heart and investigated changes in PKA regulatory subunits as a potential mechanism.

Methods and Results
—Using in vitro back-phosphorylation with [γ-
32
P]ATP, we demonstrated a significant (
P
<0.05) ≈25% reduction in baseline PKA-dependent TnI phosphorylation in human hearts with dilated cardiomyopathy (DCM) compared with nonfailing (NF) human hearts. There was no significant difference in cAMP content or maximal PKA activity between DCM and NF hearts, but expression of the regulatory subunits of PKA-I (RI) and PKA-II (RII) was significantly decreased in DCM versus NF hearts (RI by ≈40%,
P
<0.05; RII by ≈30%,
P
<0.01).

Conclusions
—PKA activity is regulated at the substrate level through interactions of PKA regulatory subunits with A-kinase anchoring proteins. The reduced baseline PKA-dependent phosphorylation of TnI in DCM may be due to decreased expression of RI and RII and consequently reduced anchoring of PKA holoenzyme. These findings provide new evidence of deficiencies in downstream regulation of the β-adrenergic pathway in the failing human heart and may account for increased baseline myofibrillar Ca
2+
sensitivity.
Low Penetrance in the Long-QT Syndrome
Authors: Priori Silvia G. , Napolitano Carlo , Schwartz Peter J.
Published: June 2012

Background
—It is still currently held that most patients affected by the long-QT syndrome (LQTS) show QT interval prolongation or clinical symptoms. This is reflected by the assumption in linkage studies of a penetrance of 90%. We had previously suggested that a larger-than-anticipated number of LQTS patients might be affected without showing clinical signs. We have now exploited the availability of molecular diagnosis to test this hypothesis.

Methods and Results
—We identified 9 families with “sporadic” cases of LQTS, ie, families in which, besides the proband, none of the family members had clinical signs of the disease. Mutation screening by conventional single-strand conformational polymorphism and sequencing was performed on DNA of probands and family members to identify mutation carriers. Of 46 family members considered on clinical grounds to be nonaffected, 15 (33%) were found instead to be gene carriers. Penetrance was found to be 25%. In these families, conventional clinical diagnostic criteria had a sensitivity of only 38% in correctly identifying carriers of the genetic defect.

Conclusions
—This study demonstrates that in some families, LQTS may appear with a very low penetrance, a finding with multiple clinical implications. The family members considered to be normal and found to be silent gene carriers are unexpectedly at risk of generating affected offspring and also of developing torsade de pointes if exposed to either cardiac or noncardiac drugs that block potassium channels. It is no longer acceptable to exclude LQTS among family members of definitely affected patients on purely clinical grounds. Conversely, it now appears appropriate to perform molecular screening in all family members of genotyped patients.
Influence of Low HDL on Progression of Coronary Artery Disease and Response to Fluvastatin Therapy
Authors: Ballantyne Christie M. , Herd J. Alan , Ferlic Laura L. , Dunn J. Kay , Farmer John A. , Jones Peter H. , Schein Jeffrey R. , Gotto Antonio M.
Published: June 2012

Background
—Patients with coronary artery disease (CAD) commonly have low HDL cholesterol (HDL-C) and mildly elevated LDL cholesterol (LDL-C), leading to uncertainty as to whether the appropriate goal of therapy should be lowering LDL-C or raising HDL-C.

Methods and Results
—Patients in the Lipoprotein and Coronary Atherosclerosis Study (LCAS) had mildly to moderately elevated LDL-C; many also had low HDL-C, providing an opportunity to compare angiographic progression and the benefits of the HMG-CoA reductase inhibitor fluvastatin in patients with low versus patients with higher HDL-C. Of the 339 patients with biochemical and angiographic data, 68 had baseline HDL-C <0.91 mmol/L (35 mg/dL), mean 0.82±0.06 mmol/L (31.7±2.2 mg/dL), versus 1.23±0.29 mmol/L (47.4±11.2 mg/dL) in patients with baseline HDL-C ≥0.91 mmol/L. Among patients on placebo, those with low HDL-C had significantly more angiographic progression than those with higher HDL-C. Fluvastatin significantly reduced progression among low–HDL-C patients: 0.065±0.036 mm versus 0.274±0.045 mm in placebo patients (
P
=0.0004); respective minimum lumen diameter decreases among higher–HDL-C patients were 0.036±0.021 mm and 0.083±0.019 mm (
P
=0.09). The treatment effect of fluvastatin on minimum lumen diameter change was significantly greater among low–HDL-C patients than among higher–HDL-C patients (
P
=0.01); among low–HDL-C patients, fluvastatin patients had improved event-free survival compared with placebo patients.

Conclusions
—Although the predominant lipid-modifying effect of fluvastatin is to decrease LDL-C, patients with low HDL-C received the greatest angiographic and clinical benefit.
Neurohumoral Prediction of Benefit From Carvedilol in Ischemic Left Ventricular Dysfunction
Authors: Richards A. M. , Doughty R. , Nicholls M. G. , Macmahon S. , Ikram H. , Sharpe N. , Espiner E. A. , Frampton C. , Yandle T. G.
Published: June 2012

Background
—Plasma neurohormones were analyzed for prediction of adverse outcomes and response to treatment in 415 patients with ischemic left ventricular dysfunction randomly assigned to receive carvedilol or placebo.

Methods and Results
—Atrial natriuretic peptide, brain natriuretic peptide (BNP), or norepinephrine (NE) levels above the group median were associated with increased mortality rates and heart failure. On multivariate analysis, both BNP and NE interacted with treatment to predict death or heart failure independent of age, New York Heart Association class, and left ventricular ejection fraction. For placebo, supramedian levels of BNP were associated with 3-fold the mortality rate of inframedian levels (20/104; 19% vs 6/99; 6%;
P
<0.01). For carvedilol, mortality rate was comparable in these 2 subgroups (12/109; 11% vs 8/94; 9%; NS). Corresponding rates for heart failure were 29/104 (28%) versus 3/99 (3%;
P
<0.001) for placebo and 16/109 (15%) versus 7/94 (7%; NS) for carvedilol. High NE levels did not predict additional benefit from carvedilol, which significantly reduced heart failure admissions only in those with NE levels below the median (13.1% to 4.0%;
P
<0.01). In the 23% of the study population with supramedian BNP but inframedian levels of NE, carvedilol reduced hospital admission with heart failure by >90% (
P
<0.001).

Conclusions
—Carvedilol reduced mortality rates and heart failure in those with higher pretreatment BNP levels but lesser activation of plasma NE. Neurohumoral profiling may guide introduction of β-blockade in heart failure.
Cardioprotective Effect of Angiotensin-Converting Enzyme Inhibition Against Hypoxia/Reoxygenation Injury in Cultured Rat Cardiac Myocytes
Authors: Matoba Satoaki , Tatsumi Tetsuya , Keira Natsuya , Kawahara Akira , Akashi Kazuko , Kobara Miyuki , Asayama Jun , Nakagawa Masao
Published: June 2012

Background
—Although ACE inhibitors can protect myocardium against ischemia/reperfusion injury, the mechanisms of this effect have not yet been characterized at the cellular level. The present study was designed to examine whether an ACE inhibitor, cilazaprilat, directly protects cardiac myocytes against hypoxia/reoxygenation (H/R) injury.

Methods and Results
—Neonatal rat cardiac myocytes in primary culture were exposed to hypoxia for 5.5 hours and subsequently reoxygenated for 1 hour. Myocyte injury was determined by the release of creatine kinase (CK). Both cilazaprilat and bradykinin significantly inhibited CK release after H/R in a dose-dependent fashion and preserved myocyte ATP content during H/R, whereas CV-11974, an angiotensin II receptor antagonist, and angiotensin II did not. The protective effect of cilazaprilat was significantly inhibited by Hoe 140 (a bradykinin B
2
receptor antagonist),
N
G
-monomethyl-
l
-arginine monoacetate (L-NMMA) (an NO synthase inhibitor), and methylene blue (a soluble guanylate cyclase inhibitor) but not by staurosporine (a protein kinase C inhibitor), aminoguanidine (an inhibitor of inducible NO synthase), or indomethacin (a cyclooxygenase inhibitor). Cilazaprilat significantly enhanced bradykinin production in the culture media of myocytes after 5.5 hours of hypoxia but not in that of nonmyocytes. In addition, cilazaprilat markedly enhanced the cGMP content in myocytes during hypoxia, and this augmentation in cGMP could be blunted by L-NMMA and methylene blue but not by aminoguanidine.

Conclusions
—The present study demonstrates that cilazaprilat can directly protect myocytes against H/R injury, primarily as a result of an accumulation of bradykinin and the attendant production of NO induced by constitutive NO synthase in hypoxic myocytes in an autocrine/paracrine fashion. NO modulates guanylate cyclase and cGMP synthesis in myocytes, which may contribute to the preservation of energy metabolism and cardioprotection against H/R injury.