bluuebunny/crossref_metadata_2025_split huggingface dataset:
Abnormal vasomotor changes early after coronary angioplasty. A quantitative arteriographic study of their time course.
Authors: el-Tamimi H , Davies G J , Hackett D , Sritara P , Bertrand O , Crea F , Maseri A 
Published: June 2012

BACKGROUND
To study the impact of percutaneous transluminal coronary angioplasty (PTCA) on coronary vasomotion, we prospectively analyzed spontaneous changes in coronary diameter and the response to the cold pressor test and intracoronary nitroglycerin in 11 patients subjected to successful single-vessel PTCA.

METHODS AND RESULTS
All antianginal medications were stopped 48 hours before each study. The minimum diameter of the PTCA segment and the diameter of a distal segment in the angioplastied vessel and of a segment in a control vessel not manipulated by the balloon catheter or guide wire were measured by computerized edge detection immediately before PTCA and 5 minutes after, 4 hours after, and 8 days after PTCA. At 4 hours, PTCA and distal segments were constricted by 38 +/- 9% and 16 +/- 5%, respectively, compared with the values at 5 minutes (p less than 0.01). Before angioplasty, the cold pressor test caused vasoconstriction of PTCA and distal segments by 23 +/- 6% (p less than 0.0001) and 15 +/- 4% (p less than 0.008), respectively, but no constrictor response was elicited at 5 minutes or 4 hours after angioplasty. Eight days after PTCA, the basal coronary diameters were similar to those observed 5 minutes after PTCA and the response to the cold pressor test was similar to that observed before PTCA. All segments dilated significantly with nitroglycerin at all times, and no vasoconstriction changes were found in the control segments.

CONCLUSIONS
Four hours after PTCA, transient spontaneous vasoconstriction of the PTCA and distal segments occurs, which is so intense that the cold pressor test does not cause any further constriction. These abnormalities resolve within 8 days of PTCA.
Differential effects of heptanol, potassium, and tetrodotoxin on reentrant ventricular tachycardia around a fixed obstacle in anisotropic myocardium.
Authors: Brugada J , Mont L , Boersma L , Kirchhof C , Allessie M A 
Published: June 2012

BACKGROUND
The aim of this study was to test the hypothesis that electrical uncoupling and depression of the fast sodium channels have differential effects on propagation of the electrical impulse relative to the fiber orientation.

METHODS AND RESULTS
In a model of reentrant ventricular tachycardia (VT) (mean cycle length, 144 +/- 13 msec) around a ring of anisotropic myocardium in 10 Langendorff-perfused rabbit hearts, the effects of extracellular K+ concentration [( K+]o) and heptanol were studied. [K+]o and heptanol each had a dose-dependent effect on VT cycle length. However, high [K+]o slowed the VT mainly by depressing longitudinal conduction, whereas heptanol preferentially depressed transverse conduction. The ratio between longitudinal and transverse conduction velocities progressively decreased with high [K+]o and progressively increased with heptanol. Heptanol terminated VT at a mean concentration of 3.5 +/- 0.5 mM. The cycle length before termination was 446 +/- 120 msec (p less than 0.001). In eight of 10 experiments, termination occurred by failure of conduction during transverse propagation. VT terminated at a mean [K+]o of 11.6 +/- 1.8 mM. The cycle length before termination was 493 +/- 341 msec (p less than 0.01). In seven of 10 cases, termination occurred by failure of conduction during longitudinal propagation. In the remaining five episodes (two with heptanol and three with high [K+]o), termination occurred by collision of the reentrant beat with an antidromic impulse being reflected within the ring. In a separate series of six hearts, tetrodotoxin was administered during VT. Like high [K+]o, tetrodotoxin prolonged the cycle length of the VT by preferentially slowing longitudinal conduction, and VT was terminated by longitudinal block.

CONCLUSIONS
During reentrant VT, electrical uncoupling of cells by heptanol or modification of active membrane properties by high [K+]o or tetrodotoxin has a differential depressing effect on propagation of the impulse relative to the fiber orientation.
Efficacy of permanent pacing in the management of high-risk patients with long QT syndrome.
Authors: Moss A J , Liu J E , Gottlieb S , Locati E H , Schwartz P J , Robinson J L 
Published: June 2012

BACKGROUND
From the international long QT syndrome (LQTS) study, 30 patients with corrected QT interval (QTc) of more than 0.44 second 1/2 were identified who had permanent pacemakers implanted for management of recurrent syncope or aborted cardiac arrest.

METHODS AND RESULTS
Pacemakers were implanted on average 7 years after the onset of the first syncopal episode. Most of the patients were female (87%), the average age at implantation was 19 +/- 13 years, the mean QTc was 0.55 +/- 0.08 second, and 57% were receiving antiadrenergic treatment for LQTS when the pacemaker was placed. Using birth as the time origin, the median cardiac event rate was significantly (p less than 0.001) reduced by pacing from 0.5 to 0 events per patient per year, with 21 patients experiencing no cardiac events during an average pacemaker follow-up of 49 months per patient. In 10 patients in whom the demand atrial pacing rate was faster than the intrinsic sinus rate, the average heart rate was increased 23 beats/min (from 58 to 81 beats/min) with pacing with reduction in the QT interval from 0.59 seconds to 0.46 seconds.

CONCLUSIONS
The beneficial effects of pacing in high-risk LQTS patients probably relate to the prevention of bradycardia, pauses, and the shortening of long QT intervals--factors that are known to be arrhythmogenic in this syndrome. Permanent cardiac pacing reduces the rate of recurrent syncopal events in high-risk LQTS patients, but it does not provide complete protection.
Unsuspected echocardiographic abnormality in the long QT syndrome. Diagnostic, prognostic, and pathogenetic implications.
Authors: Nador F , Beria G , De Ferrari G M , Stramba-Badiale M , Locati E H , Lotto A , Schwartz P J 
Published: June 2012

BACKGROUND
The idiopathic long QT syndrome (LQTS) is characterized by electrocardiographic abnormalities and by a high incidence of lethal arrhythmias. The present case/control study demonstrates the frequent occurrence of unusual and specific ventricular wall motion abnormalities in LQTS and their association with history of syncope or cardiac arrest. These anomalies were present in 23 of 42 LQTS patients (55%) and in two of 42 healthy controls (5%, p less than 0.0001) matched for age, sex, height, and weight.

METHODS AND RESULTS
Two new measurements were developed to assess quantitatively the abnormalities observed. The first, Th1/2, is an index of the rapidity of the early contraction phase; the second, TSTh, is an index of the presence of a slow movement in the late thickening phase. Th1/2 was smaller in LQTS patients (15.0 +/- 4.1 versus 19.9 +/- 3.9% of the cardiac cycle, p less than 0.001), indicating that they reach half-maximal systolic contraction more rapidly than controls. TSTh was greater in LQTS patients (9.37 +/- 6.82 versus 2.88 +/- 4.46%, p less than 0.001), indicating that they spend more time at a very low thickening rate. A peculiar double peak pattern of late thickening was present in 11 patients and in no controls. These abnormalities were more frequent in symptomatic than in asymptomatic patients (20 of 26, 77%, versus three of 16, 19%, p less than 0.005; relative risk, 2.75). They were not affected by beta-blockade or by left cardiac sympathetic denervation. The same echocardiographic abnormalities were produced by right stellectomy in nine of nine anesthetized dogs, were not dependent on cycle length, and were not modified by subsequent left stellectomy.

CONCLUSIONS
This study demonstrates a previously unsuspected abnormality in the ventricular contraction pattern of LQTS patients and, for the first time, provides evidence that a noninvasively detected cardiac abnormality is associated with a higher risk for syncope/cardiac arrest. The experimental reproduction of this echocardiographic abnormality by right stellectomy indicates that this newly found clinical characteristic of LQTS does not contradict the "sympathetic imbalance" hypothesis.
Endothelium-dependent vasodilation is attenuated in patients with heart failure.
Authors: Kubo S H , Rector T S , Bank A J , Williams R E , Heifetz S M 
Published: June 2012

BACKGROUND
Endothelial cells produce a number of substances, collectively termed endothelium-derived relaxing factor (EDRF), that promote local relaxation of vascular smooth muscle. Although studies have demonstrated defects in endothelium-dependent vasodilation in animal models of hypertension, atherosclerosis, and heart failure, there are only limited data from human subjects because of the difficulty in obtaining fresh vascular segments.

METHODS AND RESULTS
To address the hypothesis that endothelium-dependent vasodilation is attenuated in patients with heart failure, we measured forearm blood flow responses to the intra-arterial administration of methacholine, a known stimulus of EDRF release through muscarinic receptors. In 14 normal subjects, a dosage range of methacholine increased forearm blood flow by 5.26 +/- 0.63, 10.50 +/- 0.63, and 13.22 +/- 0.86 ml/min/100 ml forearm volume (FAV); these responses were 1.98 +/- 0.46, 5.48 +/- 0.79, and 8.50 +/- 1.53 ml/min/100 ml FAV in 14 patients with heart failure. When pooled over all doses, the responses were strikingly less in the patients with heart failure (5.32 +/- 0.31 versus 9.52 +/- 0.60 ml/min/100 ml FAV; p = 0.0003). In a second study, the average difference in forearm blood flow responses between patients with heart failure and normal subjects with methacholine was significantly greater than the average difference between the groups with nitroprusside (4.04 +/- 1.10 versus 2.20 +/- 0.71 ml/min/100 ml FAV; p = 0.04). The decreased methacholine responses in the patients with heart failure were not related to age (r = 0.39; p = NS) or etiology because there was no difference in the responses between patients with ischemic heart disease and those with idiopathic cardiomyopathy.

CONCLUSIONS
These data suggest that endothelium-dependent vasodilation is attenuated in patients with heart failure. Although the mechanisms of the decreased endothelium-dependent responses in heart failure are not known, this impaired local vasodilation may contribute to abnormalities in vasoconstriction that are characteristic of heart failure.
Antithrombotic efficacy of recombinant tick anticoagulant peptide. A potent inhibitor of coagulation factor Xa in a primate model of arterial thrombosis.
Authors: Schaffer L W , Davidson J T , Vlasuk G P , Siegl P K 
Published: June 2012

BACKGROUND
Tick anticoagulant peptide is a specific, potent inhibitor of blood coagulation factor Xa. The effects of recombinant tick anticoagulant peptide (rTAP) and standard heparin (SH) were compared in an anesthetized baboon model of arterial thrombosis where platelet deposition onto a Dacron vascular graft segment of an arteriovenous (AV) shunt was studied.

METHODS AND RESULTS
Animals were randomized to receive systemic administration of SH (10 or 100 U/kg i.v. bolus followed by 0.4 or 1.0 U/kg/min i.v. infusion, respectively) or rTAP (6.25, 12.5, or 25.0 micrograms/kg/min i.v. infusion). rTAP, but not SH, caused a significant (p less than 0.05), dose-dependent reduction of indium-111 labeled platelet and iodine-125 labeled fibrin (ogen) deposition onto the graft. Deposition was not significantly increased from baseline values during infusion of 12.5 or 25.0 micrograms/kg/min of rTAP. Blood flow was maintained at 64 +/- 9, 95 +/- 2, or 97 +/- 2% of baseline following infusion of 6.25, 12.5, or 25.0 micrograms/kg/min of rTAP, respectively. Both SH and rTAP significantly (p less than 0.05) decreased the systemic fibrinopeptide A (FPA) elevation during exposure to the Dacron graft. rTAP was fully antithrombotic at APTT values of 42.6 +/- 2.4 seconds (less than twofold basal value), while SH had no antithrombotic efficacy despite APTT values greater than 150 seconds (greater than fivefold basal value).

CONCLUSIONS
The demonstrated antithrombotic effect of rTAP in the absence of alterations in primary hemostasis suggests that controlling thrombin generation through inhibition of factor Xa may be a novel and effective pharmacological approach in the prevention of high-shear arterial thrombosis.
Predictors of in-hospital mortality after DC catheter ablation of atrioventricular junction. Results of a prospective, international, multicenter study.
Authors: Evans G T , Scheinman M M , Bardy G , Borggrefe M , Brugada P , Fisher J , Fontaine G , Huang S K , Huang W H , Josephson M 
Published: June 2012

BACKGROUND
The Catheter Ablation Registry was the first international, multicenter, prospective study of the safety and efficacy of catheter ablation.

METHODS AND RESULTS
From August 1987 through March 1990, the study comprised 136 patients in whom only DC energy was used in attempted production of third-degree atrioventricular block to treat uncontrollable supraventricular tachycardias. Eight patients died during hospitalization for ablation. In seven (5.1%), the ablation may have contributed to their deaths. Causes of death included ventricular fibrillation (five patients, three with polymorphic ventricular tachycardia), progressive heart failure (one patient), and respiratory failure (two patients, one dying after resuscitation from ventricular fibrillation). Compared with survivors, patients who died were more likely to have had prior aborted sudden death (38% versus 2%, p less than 0.05), congestive heart failure (88% versus 22%, p less than 0.001), cardiomyopathy (50% versus 16%, p less than 0.05), lower baseline systolic blood pressure (106 versus 138 mm Hg, p less than 0.001), prolonged baseline and postablation corrected QT interval (p less than 0.01), and markedly reduced ejection fraction (27% versus 52%, p less than 0.001). Ablation successfully produced third-degree atrioventricular block in 88% of the patients who died and in 83% of survivors.

CONCLUSIONS
Catheter ablation of the atrioventricular junction with DC energy carries a significant, previously unrecognized risk of death (5.1%), particularly from lethal arrhythmias, when applied to patients with severe left ventricular dysfunction. Great care should be taken in these seriously ill patients to guard against postablation ventricular arrhythmias.
Three-dimensional reconstruction of human coronary and peripheral arteries from images recorded during two-dimensional intravascular ultrasound examination.
Authors: Rosenfield K , Losordo D W , Ramaswamy K , Pastore J O , Langevin R E , Razvi S , Kosowsky B D , Isner J M 
Published: June 2012

BACKGROUND
Intravascular ultrasound provides high-resolution images of vascular lumen, plaque, and subjacent structures in the vessel wall; current instrumentation, however, limits the operator to viewing a single, tomographic, two-dimensional image at any one time. Comparative analysis of serial two-dimensional images requires repeated review of the video playback recorded during the two-dimensional examination, followed by a "mind's eye" type of imagined reconstruction.

METHODS AND RESULTS
Computer-based, automated three-dimensional reconstruction was used to generate a tangible format with which to assess and compare a "stacked" series of two-dimensional images. Three-dimensional representations were prepared from sequential images obtained during intravascular ultrasound examination in 52 patients, 50 of whom were studied before and/or after percutaneous revascularization. Conventional two-dimensional ultrasound images were acquired by means of a systematic, timed pullback of the ultrasound catheter through the respective vascular segments. Images were then assembled in automated fashion to create a three-dimensional depiction of the vessel lumen and wall. Computer-enhanced three-dimensional reconstructions were generated in both sagittal and cylindrical formats. The sagittal format resulted in a longitudinal profile similar to that obtained during angiographic examination; in contrast to angiography, however, the sagittal reconstruction offered 360 degrees of limitless orthogonal views of the plaque and arterial wall as well as the vascular lumen. The cylindrical format yielded a composite view of a given vascular segment, and a hemisected version of the cylindrical reconstruction enabled en face inspection of the reconstructed luminal surface. Sagittal reconstructions facilitated analysis of dissections and plaque fractures resulting from percutaneous revascularization, and the hemisected cylindrical reconstructions enhanced analysis of endovascular prostheses.

CONCLUSIONS
This preliminary experience demonstrates that computer-based three-dimensional reconstruction may further augment the use of intravascular ultrasound in assessing vascular pathology and guiding interventional therapy.
Hemostatic effects of tranexamic acid and desmopressin during cardiac surgery.
Authors: Horrow J C , Van Riper D F , Strong M D , Brodsky I , Parmet J L 
Published: June 2012

BACKGROUND
Desmopressin-induced release of tissue plasminogen activator from endothelial cells may explain the absence of its hemostatic effect in patients undergoing cardiac surgery. Prior administration of the antifibrinolytic drug tranexamic acid might unmask such an effect, and combination therapy might thereby improve postoperative hemostasis.

METHODS AND RESULTS
A double-blinded design randomly allocated 163 adult patients undergoing coronary revascularization, valve replacement, both procedures, or repair of atrial septal defect to four treatment groups: placebo, tranexamic acid given as 10 mg/kg over 30 minutes followed by 1 mg.kg-1.hr-1 for 12 hours initiated before skin incision, desmopressin given as 0.3 micrograms/kg over 20 minutes after protamine infusion, and both drugs. One surgeon performed all operations. Blood loss consisted of mediastinal tube drainage over 12 hours. Follow-up visits sought evidence of myocardial infarction and stroke. Desmopressin decreased neither the 12-hour blood loss nor the amount of homologous red cells transfused. Tranexamic acid alone significantly reduced 12-hour blood loss, by 30% (mean, 318 versus 453 ml; p less than 0.0001), without enhancement by desmopressin. Tranexamic acid also decreased the proportion of patients receiving homologous blood within 12 hours of operation (8% versus 21%, p = 0.024) and within 5 days of operation (22% versus 41%, p = 0.011).

CONCLUSIONS
Desmopressin exerts no hemostatic effect, with or without prior administration of antifibrinolytic drug. Prophylactic tranexamic acid alone appears economical and safe in decreasing blood loss and transfusion requirement after cardiac surgery.
First-pass entry of nonionic contrast agent into the myocardial extravascular space. Effects on radiographic estimates of transit time and blood volume.
Authors: Canty J M , Judd R M , Brody A S , Klocke F J 
Published: June 2012

BACKGROUND
Almost all x-ray-based techniques intended to assess regional myocardial perfusion from myocardial concentration-time curves following the administration of soluble contrast agents assume that these agents behave as intravascular indicators and can therefore provide measurements of intravascular transit time and intramyocardial blood volume.

METHODS AND RESULTS
We tested this assumption by comparing a conventional nonionic contrast agent (ioversol) to a particulate emulsion (ethiodol) that remained in the vascular space in closed-chest dogs during pharmacological vasodilation. Using fast computed tomography (CT), pairs of myocardial CT intensity-time curves were obtained following sequential bolus aortic administration of the two contrast agents. The emulsion (particle size less than 3 microns) was almost completely washed out of the myocardial region of interest within a few seconds, as would be anticipated for a vascular indicator. At the onset of recirculation, CT intensity for ethiodol fell to 5 +/- 1% (SEM) of peak values in normally perfused areas and to 10 +/- 4% of peak values in an area in which flow had been reduced by 50% by a chronically implanted coronary artery occluder (p = NS). In comparison, the diffusible nonionic contrast agent ioversol showed substantial intramyocardial retention at the onset of recirculation. At the time of recirculation, CT intensities for ioversol averaged 36 +/- 2% of peak values in normally perfused nonstenotic areas and 54 +/- 4% of peak values in stenotic areas (p less than 0.01). Using residue function analysis for a diffusible indicator, first-pass extractions of the conventional nonionic agent averaged 33 +/- 2% in normally perfused areas and 50 +/- 3% in stenotic areas (p less than 0.01). Because of the significant first-pass myocardial retention of ioversol, both mean myocardial appearance time and intramyocardial blood volume were consistently overestimated.

CONCLUSIONS
Soluble radiographic contrast agents, like other small molecules, enter the interstitial space to a degree, which is important because it affects estimates of myocardial perfusion based on transit time and intramyocardial blood volume. Indicator dilution models intended to quantify myocardial perfusion with conventional radiographic contrast agents need to account for this extravascular exchange.