bluuebunny/crossref_metadata_2025 huggingface dataset:
The Insertion Allele of the ACE Gene I/D Polymorphism
Authors: Panahloo Arshia , Andrès Christine , Mohamed-Ali Vidya , Gould Mairi M. , Talmud Phillipa , Humphries Steve E. , Yudkin John S.
Published: June 2012

Background
The insertion/deletion (ID) polymorphism of the angiotensin-converting enzyme (ACE) gene has been associated with increased coronary heart disease (CHD), although the mechanism of this association is not apparent. We tested the hypothesis that the deletion allele of the ACE gene is associated with insulin resistance.

Methods and Results
We related ACE genotype to components of the insulin-resistance syndrome in 103 non–insulin-dependent diabetic (NIDDM) and 533 nondiabetic white subjects. NIDDM subjects with the DD genotype had significantly lower levels of specific insulin (DD 38.6, ID 57.1, and II 87.4 pmol · L
−1
by ANOVA,
P
=.011). Non–insulin-treated subjects with the DD genotype had increased insulin sensitivity by HOMA % (DD 56.4%, II 29.4%,
P
=.027) and lower levels of des 31,32 proinsulin (DD 3.3, II 7.6 pmol · L
−1
,
P
=.012) compared with II subjects. There were no differences in prevalence of CHD or levels of blood pressure, serum lipids, or plasminogen activator inhibitor–1 (PAI-1) activity between the three ACE genotypes. In nondiabetic subjects there were no differences in insulin sensitivity, levels of insulin-like molecules, blood pressure, PAI-1, serum lipids, or CHD prevalence between the three ACE genotypes.

Conclusions
We conclude that increased cardiovascular risk of the DD genotype is not mediated through insulin resistance or abnormalities in fibrinolysis. Conversely, we report an increased sensitivity in NIDDM subjects with the ACE DD genotype.
Role of Endogenous Bradykinin in Human Coronary Vasomotor Control
Authors: Groves Peter , Kurz Sabine , Just Hanjörg , Drexler Helmut
Published: June 2012

Background
Bradykinin is a potent vasodilator that acts through B
2
kinin receptors to stimulate the release of endothelium-derived nitric oxide, prostacyclin, and hyperpolarizing factor. In this study, we investigated the contribution of endogenous bradykinin to vasomotor control in the human coronary circulation.

Methods and Results
The selective bradykinin B
2
receptor antagonist HOE 140 was infused into the left main coronary artery (200 μg/min for 15 minutes) in 15 patients without significant coronary stenoses. Epicardial responses were evaluated by quantitative coronary blood flow with a Doppler flow-velocity wire. Flow-dependent dilation (n=10; intracoronary papaverine) and acetylcholine responses (n=5) were assessed before and after HOE 140. After HOE 140, there was a reduction in luminal area in the proximal (
P
<.001), mid (
P
<.001), and distal (
P
<.05) coronary arteries. HOE 140 led to an increase in coronary vascular resistance (
P
<.001) and a decrease in coronary blood flow (
P
<.001). After bradykinin B
2
receptor blockade, there was a reduction in flow-dependent dilation (23.4±6.9% to 3.9±6.0%,
P
<.001), the extent of which correlated with the degree of basal vasoconstriction after HOE 140 in the same vessel segment (
P
<.05). Acetylcholine responses were unchanged after HOE 140.

Conclusions
The results of this study demonstrate for the first time a role for endogenous bradykinin in mediating normal vasomotor responses in resistance and epicardial coronary vessels under basal and flow-stimulated conditions in the human coronary circulation.
Modulation of Endothelium-Dependent Flow-Mediated Dilatation of the Brachial Artery by Sex and Menstrual Cycle
Authors: Hashimoto Masayoshi , Akishita Masahiro , Eto Masato , Ishikawa Michiro , Kozaki Koichi , Toba Kenji , Sagara Yoko , Taketani Yuji , Orimo Hajime , Ouchi Yasuyoshi
Published: June 2012

Background
Estrogen has been reported to augment endothelium-dependent vasodilatation. The role of endogenous ovarian hormones in modulating endothelium-dependent vasodilatation, however, remains to be determined. The purpose of the present study was to investigate the effects of sex and menstrual cycle on endothelium-dependent flow-mediated vasodilatation.

Methods and Results
Seventeen female volunteers 25.1±0.8 years old and 17 age-matched male volunteers were examined. We measured brachial artery diameters noninvasively using a 7.5-MHz ultrasound machine at rest, during reactive hyperemia, and after sublingual nitroglycerin administration. All female subjects were studied three times each, in three different phases of one menstrual cycle (M, menstrual phase; F, follicular phase; and L, luteal phase). Flow-mediated diameter (D) increase (%FMD; ΔD/D×100) in M, when serum estradiol level was low (121.9±12.5 pmol/L), was 11.22±0.58%, and the value was comparable to that in male subjects (10.60±0.75%). %FMD increased in F (18.20±0.81%,
P
<.01 versus M) and L (17.53±0.74%,
P
<.01 versus M), when serum estradiol level was high (F, 632.0±74.5 and L, 533.8±33.4 pmol/L,
P
<.01 versus M). Endothelium-independent vasodilatation by nitroglycerin increased in both F and L. However, the increment was smaller than that of %FMD.

Conclusions
Endothelium-dependent vasodilatation varies during the menstrual cycle. The endogenous estradiol may be involved in this menstrual cycle–related vasodilatation.
Lysophosphatidylcholine Inhibits Endothelium-Dependent Hyperpolarization and
N
ω
-Nitro-
l
-Arginine/IndomethacinResistant Endothelium-Dependent Relaxation in the Porcine Coronary Artery
Authors: Eizawa Hiroshi , Yui Yoshiki , Inoue Reiko , Kosuga Kunihiko , Hattori Ryuichi , Aoyama Takeshi , Sasayama Shigetake
Published: June 2012

Background
Oxidized LDL and lysophosphatidylcholine (LPC) have been reported to inhibit the endothelium-dependent relaxation (EDR) mediated by nitric oxide. Recently, a new vasorelaxing factor, endothelium-derived hyperpolarizing factor (EDHF), which hyperpolarizes and relaxes the porcine coronary artery in the presence of
N
ω
-nitro-
l
-arginine (NNA) and indomethacin (IM), has been reported. We examined whether LPC also inhibits both the EDHF-mediated relaxation and membrane hyperpolarization of the porcine coronary artery.

Methods and Results
EDHF was evaluated as the bradykinin- or A23187-induced relaxation of the porcine coronary artery contracted by prostaglandin F
2α
in the presence of NNA and IM. We also directly measured the membrane potential of the porcine coronary artery. The effects of LPC on both relaxation and membrane hyperpolarization were investigated. At concentrations of 0 to 20 μmol/L, LPC dose-dependently inhibited the NNA/IM-resistant EDR induced by bradykinin and A23187, and the relaxation was reversible after the absorption of LPC with albumin. LPC also inhibited the bradykinin- and A23187-induced hyperpolarization of the porcine coronary artery.

Conclusions
In the present study, LPC was found to inhibit not only nitric oxide–mediated but also EDHF-mediated relaxation of the porcine coronary artery. Our findings suggest a new regulatory mechanism in the atherosclerotic coronary artery.
Effects of Ischemia on Left Ventricular Apex Rotation
Authors: Gibbons Kroeker Carol A. , Tyberg John V. , Beyar Rafael
Published: June 2012

Background
Left ventricular (LV) twist has been defined as the counterclockwise rotation of the ventricular apex with respect to the base during systole. We recently showed that, since base rotation is minimal, measurement of apex rotation reflects the dynamics of LV twist. Since ischemia is known to affect endocardial and epicardial fiber force and shortening and therefore the transmural balance of torsional moments, we hypothesized that ischemia has a significant effect on apex-rotation amplitude and on untwisting during the isovolumic relaxation (IVR) period.

Methods and Results
With an optical device coupled to the LV apex, apex rotation was recorded simultaneously with LV pressure, ECG, LV segment length, and minor-axis diameters in 16 open-chest dogs. Ischemia was caused by a 1- to 2-minute snare occlusion of either the left anterior descending (LAD) or circumflex (LCx) arteries. LAD ischemia had a pronounced effect on apex rotation: an increase in apex-rotation amplitude attributed to subendocardial dysfunction at 10 seconds of ischemia; maximum apex rotation occurring later (during the IVR period) throughout the ischemia; a paradoxical relaxation pattern of initial untwisting followed by twisting and untwisting during the IVR period with ischemia; and a decrease in the amplitude of apex rotation with ischemia, possibly due to transmural dysfunction. LCx occlusion had similar effects on apex rotation, except that apex-rotation amplitude was not increased at 10 seconds of occlusion and the amplitude of apex rotation did not decrease with severe ischemia. Under control preischemic conditions, a linear relationship between apex rotation and segment length was observed during ejection and a different, steeper relationship during IVR. With regionally ischemic segments, this relationship became nonlinear for both ejection and IVR.

Conclusions
Both LAD and LCx ischemia had profound effects on the dynamics of apex rotation. A paradoxical relaxation pattern occurred with ischemia. We suggest that these observations are due to changes in the dynamic transmural balance of torsional moments that determine LV twist.
Cardioversion of Nonrheumatic Atrial Fibrillation
Authors: Collins Laura J. , Silverman David I. , Douglas Pamela S. , Manning Warren J.
Published: June 2012

Background
The use of warfarin anticoagulation for several weeks before cardioversion results in a 90% reduction in the incidence of cardioversion-related thromboembolism. The mechanism of this benefit, however, is unknown; it has been widely attributed to organization and adherence of atrial thrombi, a finding observed among pathological studies of patients with rheumatic valvular disease.

Methods and Results
Serial transesophageal echocardiography was performed in 14 patients with nonrheumatic atrial fibrillation after identification of atrial thrombi on initial transesophageal study. All patients received warfarin anticoagulation and were followed clinically for signs of thromboembolism. Eighteen atrial thrombi were identified on initial transesophageal study, including 14 thrombi confined to the left atrial appendage, 2 in the body of the left atrium, 1 in the right atrial appendage, and 1 in the body of the right atrium. Thrombus size varied from 5 to 20 mm, and 6 were considered mobile. After a median of 4 weeks of warfarin, 16 of 18 atrial thrombi (89%; 95% CI, 73% to 100%) had completely resolved on transesophageal echocardiographic study. In addition, no new thrombi were identified on follow-up study, and no patient had a clinical thromboembolic event between studies.

Conclusions
These data strongly support the hypothesis that among patients with nonrheumatic atrial fibrillation, the mechanism of clinical benefit with 3 to 4 weeks of warfarin before cardioversion is related to thrombus resolution and prevention of new thrombus formation rather than thrombus organization.
Bradykinin-Induced Vasodilation Is Impaired at the Atherosclerotic Site but Is Preserved at the Spastic Site of Human Coronary Arteries In Vivo
Authors: Kuga Takeshi , Egashira Kensuke , Mohri Masahiro , Tsutsui Hiroyuki , Harasawa Yasuhiko , Urabe Yoshitoshi , Ando Shinichi , Shimokawa Hiroaki , Takeshita Akira
Published: June 2012

Background
Bradykinin causes endothelium-dependent vasodilation of isolated human coronary arteries in vitro. However, the effect of bradykinin on vasomotion of human coronary arteries in vivo has not been studied. The aim of this study was to examine whether bradykinin-induced vasodilation is altered at the atherosclerotic or spastic site of human coronary arteries in vivo.

Methods and Results
The effect of bradykinin on vasomotion of epicardial coronary arteries was evaluated in 8 patients with normal coronary arteries (control group), 14 patients with organic coronary stenosis (coronary artery disease [CAD] group), and 8 patients with vasospastic angina (VSA group). Changes in the diameter of epicardial coronary artery were assessed by quantitative coronary arteriography. Intracoronary administration of bradykinin at graded doses (60, 200, and 600 ng) dilated epicardial coronary arteries without altering arterial pressure or heart rate in all patients of either group. In the control group, vasomotor responses of the site where acetylcholine caused dilation were compared with the responses of the site where acetylcholine caused constriction. The magnitudes of bradykinin-induced dilation at the site with acetylcholine-induced dilation (mean±SD: 6±6%, 11±9%, and 15±9%) were comparable to that (3±6%, 8±8%, and 13±9%) at the site with acetylcholine-induced constriction. In the CAD group, vasomotor responses of the stenotic site (% diameter stenosis, 15% to 50%) and nonstenotic site were examined. The bradykinin-induced dilation at the stenotic site (0±4%, 3±8%, and 5±9%) was significantly less (
P
<.01) than at the nonstenotic site (3±4%, 8±6%, and 16±11%) and in the control group. Coronary vasodilation with nitrate at the stenotic site (20±11%) was comparable to that at the nonstenotic site (22±16%) and in the control group (21±10%). In the VSA group, vasomotor responses of the site with acetylcholine-induced spasm and the site without spasm were examined. The bradykinin-induced vasodilation at the spastic site (5±5%, 16±15%, and 33±17%) was comparable to that at the nonspastic site (4±8%, 12±14%, and 21±9%). Nitrate-induced dilation was comparable at the spastic site (51±19%) and the nonspastic site (32±13%). The ratio of bradykinin-induced vasodilation to nitrate-induced vasodilation at the spastic site was comparable to the control group.

Conclusions
These results suggest that bradykinin causes vasodilation of human epicardial coronary arteries in vivo and that bradykinin-induced endothelium-dependent vasodilation is impaired at the stenotic site but is preserved at the angiographically normal site where endothelium-dependent vasodilation by acetylcholine is impaired and at the spastic site.
Early and Late Quantitative Angiographic Results of Vein Graft Lesions Treated by Excimer Laser With Adjunctive Balloon Angioplasty
Authors: Strauss Bradley H. , Natarajan Madhu K. , Batchelor Wayne B. , Yardley David E. , Bittl John A. , Sanborn Timothy A. , Power John A. , Watson Linley E. , Moothart Richard , Tcheng James E. , Chisholm Robert J.
Published: June 2012

Background
Percutaneous excimer laser coronary angioplasty (PELCA) has been approved for treatment of diseased saphenous vein bypass grafts. However, detailed and complete quantitative angiographic analysis of immediate procedural and late follow-up results has not been performed.

Methods and Results
PELCA using the CVX-300 excimer laser system was performed in 125 bypass lesions (mean graft age, 96±53 months; range, 2 to 240 months) in 106 consecutive patients at eight centers. Quantitative analyses of the procedural and follow-up angiograms were done with the Cardiac Measurement System. Stand-alone PELCA was done in 21 lesions (17%). Lesions were located at the ostium (20%), body (67%), or distal anastomosis (13%). The graft reference diameter was 3.26±0.79 mm (mean±SD). Minimal lumen diameter increased from 1.09±0.52 mm before treatment to 1.61±0.69 mm after laser and 2.18±0.63 mm after adjunctive balloon dilation (
P
<.001) but had declined at follow-up to 1.40±1.17 mm. Dissections were evident in 45% of lesions after laser treatment (types A and B, 27%; types C through F, 18%), including 7% occlusions. Angiographic success (≤50% diameter stenosis [% DS]) was 54% after laser and 91% after adjunctive PTCA, with an overall clinical success rate of 89%. In-hospital complications were death, 0.9%; myocardial infarction (Q-wave and non–Q-wave), 4.5%; and bypass surgery, 0.9%. Independent predictors of % DS after laser were reference diameter, lesion length, and minimal lumen diameter before laser. At angiographic follow-up in 83% of eligible patients, the restenosis rate per lesion (DS >50%) was 52%, including 23 occlusions (24%). The only independent predictor of increased % DS at follow-up was lesion symmetry. Logistic regression indicated that smaller reference diameter was an independent predictor of late occlusion. Overall 1-year mortality was 8.6%. Actuarial event-free survival (freedom from death, myocardial infarction, bypass surgery, or target vessel percutaneous transluminal coronary angioplasty) was 48.2% at 1 year.

Conclusions
Excimer laser angioplasty with adjunctive balloon angioplasty can be safely and successfully performed in diseased, old saphenous vein bypass graft lesions considered at high risk for reintervention. The extent of laser ablation remains limited by the diameter and effectiveness of the catheters. Late restenosis and, in particular, total occlusion mitigate the early benefits of the procedure. Other approaches such as the routine use of additional anticoagulation (eg, warfarin) should be considered to reduce the risk of late occlusions and restenosis after laser angioplasty of bypass grafts.
Evidence Against Reinnervation of Cardiac Vagal Afferents After Human Orthotopic Cardiac Transplantation
Authors: Arrowood James A. , Goudreau Evelyne , Minisi Anthony J. , Davis Annette B. , Mohanty Pramod K.
Published: June 2012

Background
Orthotopic cardiac transplantation results in total cardiac denervation. Recent studies in humans suggest that reinnervation of cardiac sympathetic nerves (cardiac efferents) may occur after cardiac transplantation. We hypothesized that reinnervation of cardiac afferents may occur as well. To test this hypothesis, we investigated reflex responses produced by stimulation of ventricular chemosensory endings subserved by vagal afferents (cardiac depressor reflex).

Methods and Results
Two cardiac transplant groups were studied: an “early” group (n=18, <24 months after transplant) and a “late” group (n=18, >43 months after transplant); these groups were compared with a control group with intact innervation (n=18). The reflex response of the recipient sinus node (RSN) in the remnant right atrium, which remains innervated after transplantation, was observed during selective right coronary artery (RCA) and left coronary artery (LCA) injection of the radiographic contrast agent meglumine diatrizoate, which is known to stimulate ventricular chemosensory endings. A decrease in the rate of the RSN was expected if reinnervation of chemosensory endings had occurred and the afferent limb of the cardiac depressor reflex was intact. With injection, the RSN rate of both transplant groups did not decrease but increased (early: LCA, 7.2±1.4 beats per minute; RCA, 6.3±1.3 beats per minute; late: LCA, 5.9±1.0 beats per minute; RCA, 6.0±0.9 beats per minute) compared with the expected decrease in control patients (LCA, −20.8±2.5 beats per minute; RCA, −18.0±4.0 beats per minute;
P
<.001 versus transplants). Decreases in mean arterial pressure in the transplant groups (early: LCA, −11.3±1.4 mm Hg; RCA, −10.0±1.6 mm Hg; late: LCA, −13.0±1.6 mm Hg; RCA, −9.1±1.5 mm Hg) were less than those observed in the control group (LCA, −19.8±2.2 mm Hg; RCA, −18.7±4.0 mm Hg;
P
<.05 versus transplants).

Conclusions
The results suggest that reinnervation of ventricular chemosensory endings subserved by vagal afferents in cardiac transplant patients does not occur up to 74 months after transplantation.
Mechanism of Repetitive Monomorphic Ventricular Tachycardia
Authors: Lerman Bruce B. , Stein Kenneth , Engelstein Erica D. , Battleman David S. , Lippman Neal , Bei Dong , Catanzaro Daniel
Published: June 2012

Background
The most common form of idiopathic ventricular tachycardia (VT) is repetitive monomorphic VT (RMVT), which is characterized by frequent ventricular ectopy and salvos of nonsustained VT with intervening sinus rhythm. Unlike most other forms of idiopathic VT, this tachycardia typically occurs at rest and is nonsustained. The mechanism of RMVT is undefined. Because of a common site of origin, the right ventricular outflow tract (RVOT), we hypothesized that RMVT is mechanistically related to paroxysmal sustained, exercise-induced VT, which has been shown to be consistent with cAMP-mediated triggered activity. Therefore, in this study, we sought to identify (1) the mechanism of RMVT at the cellular level by using electropharmacological probes known to activate either stimulatory or inhibitory G proteins and thereby modify intracellular cAMP levels, (2) potential autonomic triggers of RMVT through analysis of heart rate variability, and (3) whether well-characterized somatic activating mutations in the stimulatory G protein, Gα
s
, underlie RMVT.

Methods and Results
Twelve patients with RMVT underwent electrophysiological study. Sustained monomorphic VT was reproducibly initiated and terminated with programmed stimulation and/or isoproterenol infusion in 11 of the 12 patients (the other patient had incessant RMVT). Induction of VT demonstrated cycle length dependence and was facilitated by rapid atrial or ventricular pacing. Termination of VT occurred in response to interventions that either lowered stimulated levels of intracellular cAMP (and thus decreased intracellular Ca
2+
)—ie, adenosine (12 of 12), vagal maneuvers or edrophonium (8 of 9), and β-blockade (3 of 5)—or directly decreased the slow-inward calcium current—ie, verapamil (10 of 12). Analysis of heart rate variability during 24-hour ambulatory monitoring in 7 patients showed that the sinus heart rate is increased and accelerates before nonsustained VT (
P
<.05), whereas high-frequency heart rate variability is unchanged. These findings are consistent with transient increases in sympathetic tone preceding nonsustained VT. Finally, myocardial biopsy samples were obtained from the site of origin of the VT (typically the RVOT) and from the right ventricular apex from 9 patients. Genomic DNA was extracted from each biopsy sample, and three exons of Gα
s
in which activating mutations have previously been described were amplified by polymerase chain reaction. All sequences from these regions were found to be identical to that of control.

Conclusions
Although the arrhythmia occurs at rest, the constellation of findings in idiopathic VT that is characterized by RMVT is consistent with the mechanism of cAMP-mediated triggered activity. Therefore, the spectrum of VT resulting from this mechanism includes not only paroxysmal exercise-induced VT but also RMVT.
In Utero Placement of Aortopulmonary Shunts
Authors: Reddy V. Mohan , Meyrick Barbara , Wong Jackson , Khoor Andras , Liddicoat John R. , Hanley Frank L. , Fineman Jeffrey R.
Published: June 2012

Background
The development of pulmonary hypertension and its associated increased vascular reactivity is a common accompaniment of congenital heart disease with increased pulmonary blood flow. Although the morphology of the pulmonary vascular changes is well described, the mechanisms of vascular remodeling and increased reactivity remain incompletely understood.

Methods and Results
To elucidate these mechanisms, we established an accurate and reliable experimental model of pulmonary hypertension with increased pulmonary blood flow. An aortopulmonary shunt was created with an 8.0-mm expanded polytetrafluoroethylene vascular graft in 11 late-gestation fetal lambs. At 1 month of age, shunted lambs had a pulmonary–to–systemic blood flow ratio of 2.2±1.2. Compared with 11 age-matched control lambs, mean pulmonary arterial pressure (44.8±11.7 versus 16.2±2.9 mm Hg) and the ratio of pulmonary to systemic arterial pressure were significantly increased (
P
<.05). Pulmonary vascular resistance was not significantly increased. The pulmonary vasoconstricting response to the infusion of
U46619
(a thromboxane A
2
mimic) or acute alveolar hypoxia also was augmented in the shunted lambs. Morphometric analysis of the barium-filled pulmonary artery bed revealed medial hypertrophy, abnormal extension of muscle distally into the walls of the intra-acinar arteries, and increased numbers of barium-filled intra-acinar arteries.

Conclusions
In utero placement of aortopulmonary shunts reproduces the aberrant hemodynamic state of children with congenital heart disease with left-to-right shunts; postnatal pulmonary hypertension, increased pulmonary blood flow, and vascular remodeling. In addition, the lambs have a unique paradoxical increase in pulmonary vascular volume that attenuates an increase in pulmonary vascular resistance. This experimental preparation provides a useful and consistent model for the study of the pathogenesis of pulmonary hypertension.
Vulnerability of Pulmonary Capillaries in Heart Disease
Authors: West John B. , Mathieu-Costello Odile
Published: June 2012

Abstract
The pulmonary blood-gas barrier presents a dilemma. It must be extremely thin for efficient gas exchange. However, it also needs to be immensely strong because the stresses in the pulmonary capillary wall become extremely high when the capillary pressure rises. Stress failure of the capillaries occurs in several pathological conditions. It causes high-permeability edema as in neurogenic pulmonary edema or high-altitude pulmonary edema; alveolar hemorrhage, which occurs in all galloping racehorses; or a combination of the two as in severe congestive heart failure. The vulnerability of the capillary wall to increased mechanical stress has not previously been sufficiently appreciated.
Endogenous and Exogenous Nitric Oxide Protect Against Intracoronary Thrombosis and Reocclusion After Thrombolysis
Authors: Yao Sheng-Kun , Akhtar Salman , Scott-Burden Timothy , Ober Judy C. , Golino Paolo , Buja L. Maximilian , Casscells Ward , Willerson James T.
Published: June 2012

Background
Nitric oxide (NO), an endothelium-derived relaxing factor, plays an important role in regulating platelet activation. We evaluated the effect of NO in a canine model of intracoronary thrombosis, thrombolysis, and reocclusion.

Methods and Results
Before thrombosis was induced, 34 anesthetized dogs were treated with a continuous intracoronary infusion of saline (n=8);
N

G

-nitro-
l
-arginine (L-NNA, n=8), an inhibitor of NO synthetase;
l
-arginine (n=7), the precursor for NO; or sodium nitroprusside (SNP, n=11), an NO donor. Ten minutes after the infusion was begun, an electric current of 150 μA was applied to the endothelium of coronary arteries to induce thrombosis. Occlusive thrombi developed in all dogs in the saline group (38±4 minutes) and the L-NNA group (30±6 minutes), in 6 of 7 dogs in the
l
-arginine group (81±18 minutes), and in 6 of 11 dogs in the SNP group (102±21 minutes) (
P
<.01). The time to thrombus was prolonged by
l
-arginine (
P
<.05) and SNP (
P
<.01). After 3 hours of thrombus formation in coronary arteries, tissue plasminogen activator and heparin were administered intravenously. Thrombi were lysed in 4 (of 8) dogs in the saline group (71±8 minutes), in 4 (of 8) dogs in the L-NNA group (72±8 minutes), in 4 (of 6) dogs in the
l
-arginine group (50±14 minutes), and in 4 (of 6) dogs in the SNP group (49±11 minutes) (
P
>.05). After thrombolysis, coronary artery reocclusion developed in all reperfused dogs in the saline group (30±8 minutes) and in the L-NNA group (48±12 minutes), in 3 (of 4) reperfused dogs in the
l
-arginine group (123±26 minutes), and in 3 (of 4) reperfused dogs in the SNP group (128±19 minutes) (
P
<.01). The ex vivo platelet aggregation induced by collagen was inhibited after in vivo treatment with
l
-arginine or SNP.

Conclusions
Increasing NO production or giving an NO donor may inhibit platelet aggregation and delay intracoronary thrombus formation and reocclusion after thrombolysis.
Attenuation of the Synthesis of Plasminogen Activator Inhibitor Type 1 by Niacin
Authors: Brown Steven L. , Sobel Burton E. , Fujii Satoshi
Published: June 2012

Background
Plasminogen activator inhibitor type 1 (PAI-1), the primary physiological inhibitor of endogenous plasminogen activators, has been implicated as a potentiating factor in atherogenesis as well as in coronary thrombosis. We and others have observed attenuation of PAI-1 expression by gemfibrozil both in vivo and in vitro.

Methods and Results
To determine whether other lipid-lowering agents with different mechanisms of action exert similar effects, we exposed Hep G2 cells, a highly differentiated human hepatoma cell line, to selected concentrations of niacin. Accumulation of PAI-1 protein, assayed with an ELISA, decreased in conditioned media by 72% in 48 hours in a specific, concentration-dependent fashion. Metabolic labeling experiments demonstrated a decrease in the rate of PAI-1 synthesis. Northern blot analysis demonstrated a preceding, parallel, and specific decrease in the concentration of PAI-1 mRNA. Niacin attenuated the increased PAI-1 synthesis induced by mediators released from thrombi as well. Thus, with 4.25 ng/mL transforming growth factor-β
1
, PAI-1 accumulation increased 4.5-fold in conditioned media in 48 hours. However, niacin attenuated the increase by 65%. Again, both the rate of PAI-1 synthesis and PAI-1 mRNA were reduced. The increased plasma PAI-1 activity and PAI-1 mRNA in liver induced by dexamethasone (0.8 mg IP) in vivo in rats were attenuated by 3 weeks of pretreatment with niacin.

Conclusions
These results suggest that niacin, by decreasing PAI-1 expression, may potentiate fibrinolysis, thereby decreasing the stimulation of atherogenesis by clot-associated mitogens associated with microthrombi. Furthermore, the results imply that a pathogenetic link may exist between intracellular lipid metabolism and regulation of expression of fibrinolytic system components.
Additive Effects of Combined Angiotensin-Converting Enzyme Inhibition and Angiotensin II Antagonism on Blood Pressure and Renin Release in Sodium-Depleted Normotensives
Authors: Azizi Michel , Chatellier Gilles , Guyene Thanh-Tam , Murieta-Geoffroy Dalia , Ménard Joël
Published: June 2012

Background
Angiotensin-converting enzyme (ACE) inhibitors do not decrease plasma angiotensin (Ang) II levels 24 hours after drug intake to the same extent as at peak. This intermittent partial “escape” is explained either by a renin-mediated reactive rise in plasma Ang I or by non–ACE-dependent Ang II generation. We therefore tested the hypothesis that a combination of ACE inhibition and Ang II blockade may have additive biological and hemodynamic effects.

Methods and Results
In a single-dose, double-blind, randomized, four-way, crossover study, an Ang II antagonist (losartan 50 mg), an ACE inhibitor (captopril 50 mg), their combination, and matched placebos were orally administered to 12 normotensive male volunteers maintained in mild sodium depletion. When captopril 50 mg and losartan 50 mg were given alone, the magnitude of their effects on blood pressure, plasma active renin, Ang I, and aldosterone was similar, whereas the kinetics of their effects were different, reflecting differences in drug pharmacokinetics. The losartan-captopril combination completely suppressed the rise in plasma Ang II induced by losartan 2 hours after drug intake (3.3±3.6 pg/mL versus 20.3±19.1 pg/mL, respectively,
P
<.05). Six hours after drug intake, the losartan-captopril combination induced a significantly greater decrease in mean blood pressure than that produced by either losartan or captopril alone (73±7 mm Hg versus 79±8 mm Hg versus 81±7 mm Hg, respectively,
P
<.05). The maximum placebo-subtracted falls in mean blood pressure for the losartan-captopril combination, captopril 50 mg, and losartan 50 mg were 14±5 mm Hg, 10±3 mm Hg, and 9±6 mm Hg, respectively (F2.22=3.45,
P
<.05). The duration of the mean blood pressure fall was not prolonged by the combination. After combined losartan-captopril administration, the area under the plasma active renin versus time curve (0 to 24 hours) was significantly increased when compared with either losartan or captopril alone (6404±2961 pg · h · mL
−1
versus 3105±1461 pg · h · mL
−1
versus 2092±867 pg · h · mL
−1
, respectively,
P
<.05). The combination had no additive effects on plasma aldosterone decrease when compared with either losartan or captopril alone (58±17% versus 51±20% versus 53±21%, respectively, NS).

Conclusions
The combined administration of a standard single oral dose of an ACE inhibitor and an Ang II antagonist to mildly sodium-depleted normal subjects (1) had a major additive effect on plasma renin rise, (2) induced an additional mean blood pressure reduction, and (3) had no additive effect on plasma aldosterone fall.
Myocardial Protection by Na
+
-H
+
Exchange Inhibition in Ischemic, Reperfused Porcine Hearts
Authors: Klein Hermann H. , Pich Sibylle , Bohle Rainer M. , Wollenweber Jutta , Nebendahl Klaus
Published: June 2012

Background
Studies in isolated myocytes and isolated heart preparations have suggested that Na
+
-H
+
exchange is an important mechanism for myocardial ischemia–reperfusion injury. This study was undertaken to determine whether inhibition of Na
+
-H
+
exchange limits infarct size and improves regional systolic shortening in regional ischemia and reperfusion in intact pigs.

Methods and Results
The left anterior descending coronary artery was occluded in 18 anesthetized and thoracotomized pigs for 45 minutes and then reperfused for 24 hours. As main end points of this study, regional systolic shortening (sonomicrometry) and infarct size (percentage of infarcted to ischemic myocardium) were determined at the end of the experiments. Infarcted myocardium was assessed by histochemistry (tetrazolium stain) and by quantitative histology of one heart slice. The Na
+
-H
+
exchange inhibitor Hoe 694 was administered intravenously at a dose of 3 mg/kg in 6 pigs each either 10 minutes before ischemia (group A) or 10 minutes before the onset of reperfusion (group B). Six pigs served as controls (group C). Treatment with Hoe 694 before ischemia decreased histochemical infarct size from 65±18% (control group) to 13±8% (
P
<.01) and histological infarct size from 49±20% (control group) to 14±4% (
P
<.01). Histochemical (55±19%) and histological (42±15%) infarct sizes of group B were insignificantly reduced by 15%. Myocardial protection in group A was associated with an attenuated contracture after 10 minutes of reperfusion and an improved regional systolic shortening after 24 hours of reperfusion (group A, 25±12%; control group, 6±5%;
P
=.01). These parameters remained unaffected in group B.

Conclusions
This study clearly demonstrates that Na
+
-H
+
exchange is an important mechanism for cell death in myocardial ischemia and reperfusion in intact pigs; thus, inhibition of this exchange system may prove a promising new strategy in the clinical treatment of myocardial ischemia and reperfusion.
Infarct Salvage With Liposomal Prostaglandin E
1
Administered by Intravenous Bolus Immediately Before Reperfusion in a Canine Infarction-Reperfusion Model
Authors: Smalling Richard W. , Feld Steven , Ramanna Nagendra , Amirian James , Felli Patty , Vaughn William K. , Swenson Christine , Janoff Andrew
Published: June 2012

Background
Prostaglandin E
1
(PGE
1
) inhibits leukocyte and platelet function and reduces infarct size during left atrial infusion. Intravenous liposomal PGE
1
(TLC C-53) accelerates thrombolysis and prevents reocclusion in canine coronary thrombosis. We tested the hypothesis that intravenous TLC C-53 would attenuate reperfusion injury in a canine infarction-reperfusion model.

Methods and Results
Twenty-one open-chest dogs were randomized to receive a 10-minute intravenous infusion of either liposome diluent (placebo), free PGE
1
(2 μg/kg), or TLC C-53 (2 μg/kg PGE
1
) after 2 hours of left anterior descending (LAD) occlusion just before reperfusion. Hemodynamic assessment, regional myocardial blood flow determination with radioactive microspheres, myocardial leukocyte infiltration by myeloperoxidase assay, and estimation of infarct size using triphenyl tetrazolium chloride staining were performed. Regional fractional shortening was measured with sonomicrometer crystals implanted in the midmyocardium. Infarct size as a percentage of the risk region was significantly reduced (
P
<.05) with TLC C-53 (37.9±17.4%) compared with PGE
1
(56.7±13.9%) or placebo (58.0±9.9%) infusion. Infarct salvage with TLC C-53 was independent of collateral blood flow by ANCOVA. There was a dramatic reduction in myeloperoxidase activity in the infarct, risk, and border regions of dogs treated with TLC C-53 compared with placebo. Enzyme activity was also significantly reduced (
P
<.05) in the infarct zone with TLC C-53 (0.11±0.1 U/100 mg) treatment compared with PGE
1
(0.38±0.3 U/100 mg). No significant differences in regional myocardial blood flow or myocardial function among treatment groups were identified, although there was a trend toward improved function in the TLC C-53 dogs.

Conclusions
Bolus intravenous administration of TLC C-53 immediately before reperfusion results in reduced leukocyte infiltration and substantial infarct salvage. TLC C-53 may be useful in limiting reperfusion injury during treatment of acute myocardial infarction.
Beneficial Effects of Inhibition of Angiotensin-Converting Enzyme on Ischemic Myocardium During Coronary Hypoperfusion in Dogs
Authors: Kitakaze Masafumi , Minamino Tetsuo , Node Koichi , Komamura Kazuo , Shinozaki Yoshiro , Mori Hidezo , Kosaka Hiroaki , Inoue Michitoshi , Hori Masatsugu , Kamada Takenobu
Published: June 2012

Background
Angiotensin-converting enzyme (ACE) produces angiotensin II, causing vasoconstriction of coronary arteries and reduction of coronary blood flow. The present study was undertaken to test the hypothesis that an ACE inhibitor increases coronary blood flow and improves myocardial metabolic and contractile functions of ischemic myocardium.

Methods and Results
In 65 open-chest dogs, the left anterior descending coronary artery was perfused through an extracorporeal bypass tube from the left carotid artery. When cilazaprilat (3 μg/kg per minute) was infused into the bypass tube for 10 minutes after reduction of coronary blood flow due to partial occlusion of the bypass tube, coronary blood flow increased from 30±1 to 43±2 mL/100 g per minute despite there being no changes in coronary perfusion pressure (43±1 mm Hg). The ratio of myocardial endocardial flow to epicardial flow increased during an infusion of cilazaprilat. Both fractional shortening and lactate extraction ratio of the perfused area were increased (fractional shortening: 4.1±0.6% to 8.9±0.6%,
P
<.001; lactate extraction ratio: −55.7±3.3% to −36.7±3.9%,
P
<.001). During an infusion of cilazaprilat, the bradykinin concentration of coronary venous blood was markedly increased. The increased coronary blood flow due to cilazaprilat was attenuated by HOE-140 (an inhibitor of bradykinin receptors; coronary blood flow: 35±2 mL/100 g per minute), and by
N
ω
-nitro-
l
-arginine methyl ester (an inhibitor of nitric oxide synthase; coronary blood flow: 34±2 mL/100 g per minute). Intracoronary administration of bradykinin mimicked the beneficial effects of cilazaprilat. Cyclic GMP content of the coronary artery was increased by cilazaprilat compared with the untreated condition in the ischemic myocardium. In the denervated hearts, the increased coronary blood flow due to cilazaprilat was not attenuated. On the other hand, CV11974, an inhibitor of angiotensin II receptors, slightly increased coronary blood flow to 34±2 from 30±1 mL/100 g per minute.

Conclusions
We conclude that an inhibitor of ACE can increase coronary blood flow and ameliorate myocardial ischemia, primarily due to accumulation of bradykinin and production of nitric oxide from the ischemic myocardium. Inhibition of angiotensin II production due to inhibition of ACE partially contributes to coronary vasodilation in the ischemic myocardium.
Investigation of Coronary Vessels in Microscopic Dimensions by Two- and Three-dimensional NMR Microscopic Imaging in the Isolated Rat Heart
Authors: Bauer Wolfgang R. , Hiller Karl-Heinz , Roder Fridtjof , Neubauer Stefan , Fuchs Alexander , Große Boes Christoph , Lutz Rene , Gaudron Peter , Hu Kai , Haase Axel , Ertl Georg
Published: June 2012

Background
Nuclear magnetic resonance (NMR) imaging of macroscopic coronary vessels is rapidly advancing, whereas little attention has focused on development of NMR techniques for investigation of coronary microvessels. Such techniques would be of particular importance, since conventional methods to visualize coronary microvessels have specific limitations. The aim of our study was to develop two- and three-dimensional (2D and 3D) high-resolution imaging of coronary microvessels. Quantitative analysis of vessel size was performed in tomograms and applied to evaluate the vasoconstrictor effect of endothelin 1.

Methods and Results
Angiographic imaging was performed on an 11.75-T magnet by 2D and 3D gradient-echo pulse sequences. In tomograms, the validity of this method in providing correct vessel size was tested by phantom experiments. Experiments were carried out in the isolated constant-pressure–perfused rat heart with continuous registration of coronary flow and left ventricular pressure. NMR pulse sequences were pressure-triggered in mid diastole. Four groups of hearts were studied. In group 1 (n=20), 2D imaging perpendicular and parallel to the long axis of the heart was performed. Cross sections of vessels with diameter >140 μm were clearly detectable. In group 2 (control, n=5) and group 3 (n=13), tomograms perpendicular to the long axis were obtained before and after administration of vehicle (group 2) and 200 pmol endothelin 1 bolus (group 3). Vehicle had no effect on vessel cross section. Endothelin 1, which decreased global coronary flow by 47%, reduced vessel cross section by 38±19%. A weak but, on average, significant inverse correlation between area of cross section and vessel size was found. In group 4 (n=10), 3D imaging was performed in 7 normal hearts and 3 hearts with anterior myocardial infarction. A 3D image of the entire coronary artery tree was obtained, revealing excellent agreement with anatomic studies. In infarcted rat hearts, occlusion of the left coronary artery was demonstrated.

Conclusions
Visualization and quantification of coronary microvessels are feasible by NMR microscopy. NMR microscopy bears the potential of becoming a powerful tool for the investigation of the coronary microcirculation.
Alterations in Intracellular Calcium Handling Associated With the Inverse Force-Frequency Relation in Human Dilated Cardiomyopathy
Authors: Pieske Burkert , Kretschmann Bodo , Meyer Markus , Holubarsch Christian , Weirich Jörg , Posival Herbert , Minami Kazatomo , Just Hanjörg , Hasenfuss Gerd
Published: June 2012

Background
The present study was performed to test the hypothesis that the altered force-frequency relation in human failing dilated cardiomyopathy may be attributed to alterations in intracellular calcium handling.

Methods and Results
The force-frequency relation was investigated in isometrically contracting ventricular muscle strip preparations from 5 nonfailing human hearts and 7 hearts with end-stage failing dilated cardiomyopathy. Intracellular calcium cycling was measured simultaneously by use of the bioluminescent photoprotein aequorin. Stimulation frequency was increased stepwise from 15 to 180 beats per minute (37°C). In nonfailing myocardium, twitch tension and aequorin light emission rose with increasing rates of stimulation. Maximum average twitch tension was reached at 150 min
−1
and was increased to 212±34% (
P
<.05) of the value at 15 min
−1
. Aequorin light emission was lowest at 15 min
−1
and was maximally increased at 180 min
−1
to 218±39% (
P
<.01). In the failing myocardium, average isometric tension was maximum at 60 min
−1
(106±7% of the basal value at 15 min
−1
,
P
=NS) and then decreased continuously to 62±9% of the basal value at 180 min
−1
(
P
<.002). In the failing myocardium, aequorin light emission was highest at 15 min
−1
. At 180 min
−1
, it was decreased to 71±7% of the basal value (
P
<.01). Including both failing and nonfailing myocardium, there was a close correlation between the frequencies at which aequorin light emission and isometric tension were maximum (
r
=.92; n=19;
P
<.001). Action potential duration decreased similarly with increasing stimulation frequencies in nonfailing and end-stage failing myocardium. Sarcoplasmic reticulum
45
Ca
2+
uptake, measured in homogenates from the same hearts, was significantly reduced in failing myocardium (3.60±0.51 versus 1.94±0.18 (nmol/L) · min
−1
· mg protein
−1
,
P
<.005).

Conclusions
These data indicate that the altered force-frequency relation of the failing human myocardium results from disturbed excitation-contraction coupling with decreased calcium cycling at higher rates of stimulation.
Repolarizing K
+
Currents in Nonfailing Human Hearts
Authors: Konarzewska Hanna , Peeters George A. , Sanguinetti Michael C.
Published: June 2012

Background
Studies of cardiac K
+
channels from animal models have documented tissue-dependent and species-dependent diversity in the types and properties of K
+
channels responsible for the repolarization of cardiac action potentials. Recent reports of human ventricular K
+
currents emphasized differences in transient outward K
+
current (I
to1
) recorded from left ventricular (LV) subendocardial and subepicardial myocytes. These myocytes are usually isolated only from the LV free wall. The surface of the interventricular septum is continuous with the endocardium of both ventricular chambers. However, the septum contracts in unison with the left ventricle and therefore might have electric properties consonant with this function. In this study, we compare the characteristics of human cardiac K
+
currents (I
to1
and inward rectifier K
+
current [I
K1
]) of myocytes isolated from either the LV subepicardium or subendocardium of the right ventricular (RV) septum.

Methods and Results
Subendocardial tissues were obtained during routine biopsies of the right interventricular septum of seven heart transplant recipients. Subepicardial tissues were obtained from five patients with normal LV function during open heart surgery. I
K1
amplitude was the same in myocytes isolated from both regions. Delayed rectifier K
+
currents were small or absent in these cells. I
to1
was only slightly larger in LV subepicardial versus RV septal subendocardial myocytes. For example, at +60 mV, I
to1
was 7.2±0.4 pA/pF (n=33) in subepicardial cells compared with 6.0±0.5 pA/pF (n=36) in subendocardial cells. All characteristics of I
to1
examined, including the voltage dependence of activation and inactivation, rate of inactivation, and percent decline of peak current during repetitive pulsing, were similar in myocytes isolated from both regions. These findings are in contrast to previous studies that demonstrated that I
to1
of subendocardial myocytes isolated from the LV free wall of human hearts was smaller and that recovery from inactivation of this current was much slower compared with that observed in subepicardial myocytes.

Conclusions
We conclude that the major repolarizing K
+
currents in normal human ventricular myocytes are I
K1
and I
to1
and that the properties of I
to1
of subendocardial cells isolated from the right interventricular septum are more similar to subepicardial cells than to subendocardial cells of the LV free wall. The similar electric properties shared by myocytes from these two regions may be functionally important inasmuch as the right side of the interventricular septum functions as an extension of the subepicardium of the left ventricle during the contractile cycle.