摘要:

BackgroundThe use of repeated intravenous infusions of EDTA, which has become known as “chelation therapy,” has been promoted for treating intermittent claudication as well as a wide range of other disorders. Multiple reports of excellent results in large numbers of patients have encouraged the use of this regimen. The lack of well-controlled studies substantiating the benefits of this treatment has limited its use mainly to private clinics. The aim of the study was to assess the benefits of chelation therapy in patients with intermittent claudication.Methods and ResultsA double-blind, randomized, controlled trial included 32 patients with intermittent claudication who were randomized to a treatment group (15) and a control group (17). Main outcome measures were subjective and measured walking distances and ankle/brachial pulse indices. Other outcome measures included lifestyle and subjective parameters of improvement, cardiac function, ECG, renal function, hematology, blood glucose, and lipid biochemistry. No clinically significant differences in main outcome measures between chelation therapy and placebo groups were detected up to 3 months after treatment. Measures of mood state, activities of daily living, and quality of life factors were not consistently affected by chelation therapy. An equal propor-tion (13%) of each group thought that they had received the active agent. The proportion of patients showing an improvement in walking distance was not significantly different between the chelation group (60%) and the control group (59%).ConclusionsChelation therapy has no significant beneficial effects over placebo in patients with intermittent claudication.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundRegional performance of the hypertrophied left ventricle (LV) in hypertrophic cardiomyopathy (HCM) is still incompletely characterized with studies variably reporting that the hypertrophied myocardium is hypokinetic, akinetic, or has normal function. Different imaging modalities (M-mode or two-dimensional echocardiography) and methods of analysis (fixed or floating frame of reference for wall motion analysis) yield different results. We assessed regional function in terms of systolic wall thickening and shortening and related these parameters to end-diastolic thickness using tagged magnetic resonance imaging and the three-dimensional volume-element approach.Methods and ResultsIn 17 patients with HCM and 6 healthy volunteers, four parallel short-axis images with 12 radial tags and two mutually orthogonal long-axis images with four parallel tags were obtained at end diastole and end systole. After the LV endocardial and epicardial borders were traced, three-dimensional volume elements were constructed by connecting two matched planar segments in two adjacent short-axis image planes, accounting for translation, twist, and long-axis short-ening. A total of 72 such volume elements encompassed the entire LV. From each of these elements, end-diastolic thick-ness and systolic function (fractional thickening and circum-ferential shortening) were calculated. The average end-dia-stolic thickness was 15.8±4.2 mm in patients with HCM, which was significantly greater than that in healthy subjects (8.6±2.1 mm,P<.001). Fractional thickening was significantly less in patients with HCM than in healthy subjects (0.31±0.22 versus 0.56±0.23, P<.001). There was a highly significant inverse correlation between fractional thickening and end-diastolic thickness that was independent of the type of hypertrophy or age group. Similar inverse relations were observed between circumferential shortening and end-diastolic wall thickness.ConclusionsThe myocardium in patients with HCM is heterogeneously thickened and the fractional thickening and circumferential shortening of the abnormally thickened myocardium are reduced compared with healthy subjects. The decrease in fractional thickening and shortening is inversely related to the local thickness.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

C-type natriuretic peptide (CNP) is a newly identified peptide that is structurally related to atrial natri-uretic peptide (ANP). Although it has been suggested that CNP is released from the endothelium for the regulation of local vascular tone, no data are available concerning the vasodilatory response to CNP in humans.Methods and ResultsStrain-gauge plethysmography was used to determine the vasodilatory effects of intra-arterially infused CNP compared with the effects of ANP infusion in 11 patients with chronic heart failure (CHF) and 11 age-matched healthy controls. Graded doses of CNP and ANP (8, 16, 32, and 48 pmo.minm−1· dL−1tissue volume) were administered randomly into the nondominant brachial artery, and forearm blood flow (FBF) was measured. No significant changes in systemic blood pressure and heart rate were found during the study. Both the absolute and percent FBF responses to ANP relative to the baseline value were significantly lower in CHF patients than in healthy controls (P<.01), whereas the responses to CNP were similar. The calculated forearm spillover of cyclic GMP (cGMP) was significantly lower in CHF patients receiving the highest dose of ANP (P<.02), whereas changes in cGMP spillover after the equimolar dose of CNP were significantly higher (P<.02), despite the lesser potency of CNP.ConclusionsIn patients with CHF the peripheral vasodilatory effect of ANP is attenuated, but CNP-induced peripheral vasorelaxation is preserved, with CNP being less potent for equimolar doses.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Coronary flow reserve (CFR), the functional index of stenosis severity more frequently used in the catheterization laboratory, is greatly affected by the hemodynamic conditions at the time of measurement and cannot be applied in the immediate assessment of the outcome of coronary interventions. The aim of the present study was to establish the feasibility and reproducibility of the assessment of the slope of the instantaneous diastolic relation between coronary flow velocity and aortic pressure during maximal hyperemia (IHDVPS) using a spectral analysis of the intracoronary Doppler signal, to assess the sensitivity and specificity of this index in the detection of flow-limiting coronary stenoses in comparison with CFR, and to study the possibility of deter-mining the zero-flow pressure from the intercept of the velocity-pressure relation on the pressure axis during a con-trolled cardiac arrest.Methods and ResultsThe instantaneous peak coronary flow velocity measured after intracoronary papaverine with a Doppler guidewire was plotted against the simultaneously measured aortic pressure, and the slope of the velocity-pressure relation in the phase of progressive diastolic velocity decrease was calculated during four consecutive beats. In nine normal arteries, a controlled diastolic cardiac arrest was induced by an intracoronary bolus injection of 3 mg adenosine. The IHDVPS could be assessed in 79 of 95 patients (83%), with a moderate intraobserver variability (0.4±11% after independent selection of different beats during maximal hyperemia). The IHDVPS showed no significant correlation with heart rate, mean diastolic aortic pressure, type of vessel studied, and cross-sectional area at the site of the velocity recording. The IHDVPS was significantly lower in arteries with.30% diameter stenosis than in normal or near-normal arteries (0.71±0.48 versus 1.73±0.80 cm · s−1· mm Hg−1,P<.0000002). In the stenosis group, both IHDVPS and CFR were significantly correlated with the minimal luminal cross-sectional area (r=.46,P<.05 andr=.62,P<.002, respectively). The study of the velocity-pressure relation during long diastolic pauses showed a curvilinear relation between velocity and pressure in the lower pressure range, with an upward concavity to the velocity axis and no intercept with the pressure axis in most cases.ConclusionsThe IHDVPS can distinguish between arteries with and without coronary stenoses and has a significant inverse correlation with the severity of the stenosis. Under the stable hemodynamic conditions of this study, the IHDVPS and CFR had similar sensitivities and specificities in distinguishing normal and stenotic vessels and demonstrated similar correlation with minimal luminal cross-sectional area. The curvilinearity of the velocity-pressure relation during long diastolic pauses, possibly due to a significant reduction of luminal cross-sectional area at low pressures, complicates the use of the flow velocity-pressure relation for the assessment of the zero-flow pressure.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundAging decreases cardiac β–adrenergic responsiveness in model systems and in humans in vivo. The purpose of this study was to comprehensively evaluate the age-related changes in the β-receptor-G protein-adenylyl cyclase complex in nonfailing human hearts.Methods and ResultsTwenty-six nonfailing explanted human hearts aged 1 to 71 years were obtained from organ donors and subjected to pharmacological investigation of β-adrenergic neuroeffector systems. When the population was subdivided into the 13 youngest and 13 oldest subjects, total β-receptor density assessed by maximum [125I]ICYP binding (βmax) was reduced in older hearts by 37% in left ventricles and 31 % in right ventricles (bothP<.05), and the downregulation was confined to the β1subtype (r= −.78 left ventricle β1density versus donor age). Older donor hearts exhibited a 3- to 4-fold rightward shift of ICYP-isoproterenol (ISO) competition curves and demonstrated 43% fewer receptors in a high-affinity agonist binding state (P<.05). Older hearts exhibited decreased adenylyl cyclase stimulation by ISO, by zinterol (β2-agonist), and by the G protein–sensitive probes forskolin, Gpp(NH)p, and NaF. In contrast, there was no change in response to manganese, a specific activator of the adenylyl cyclase catalytic subunit. Toxin-catalyzed ADP ribosylation in membranes prepared from older versus younger hearts revealed a 29% to 30% reduction (P<.05) with cholera toxin (Gβs) but no difference with pertussis toxin (Gβi). The systolic contractile response of isolated right ventricular trabeculae to ISO was decreased by 46%, with a 10-fold increase in ISO EC50in older relative to younger donor hearts.ConclusionsThere is a profound decrease in cardiac β-adrenergic responsiveness with aging. This occurs by multiple mechanisms including downregulation and decreased agonist binding of β1-receptors, uncoupling of β2-receptors, and abnormal G protein-mediated signal transduction.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundAlthough coronary angioplasty is increasingly applied in the treatment of multivessel disease and a broadening range of vessel size, the influence of vessel size itself on the late results of intervention is unresolved. An influence of vessel size on late outcome would carry implications for the application and evaluation of interventional devices, which are selectively used in larger or smaller vessels. The purpose of the present study was to investigate the influence of vessel size on both the restenosis process and late angiographic outcome in a large homogeneous patient group after successful percutaneous transluminal coronary angioplasty (PTCA).Methods and ResultsThe study population comprised 3072 patients with 3736 successfully dilated native primary coronary artery lesions and satisfactory quantitative angiographic analysis in multiple identical projections before and after PTCA and at a 6-month follow-up. Late luminal loss, minimal luminal diameter (MLD) at follow-up, and net luminal gain, as well as percent diameter stenosis at follow-up, net gain in percent diameter stenosis, restenosis rates (according to three definitions), and net gain index, were all compared among nine equally sized groups (noniles) according to vessel size. A direct influence of vessel size on continuous measures of late result was also evaluated by linear regression. These evaluations provided conflicting information with no consistent influence of vessel size emerging. To elucidate the independent influ-ence of vessel size on the restenosis process (late loss) and late angiographic outcome (MLD at follow-up), multiple linear regression analysis was performed taking into account luminal gain, preprocedural MLD, and lesion location. In this manner, vessel size was found to be exert a significantly positive influence on MLD at follow-up (P<.0001) and an equally negative effect on loss. Correcting for vessel size by using percent stenosis measurements led to an anticipated neutralization of this influence. Lesion location in the left anterior descending coronary artery was found to be independently associated with greater loss and smaller MLD at follow-up (P<.0001).ConclusionsIncreasing coronary vessel size was found to be independently predictive of decreasing late luminal loss and increasing follow-up MLD after successful balloon angioplasty. Apparently superior or inferior late angiographic results of new interventional devices may thus be explained in part by preferential use in larger or smaller vessels, respec-tively. Devices that can safely optimize the short-term result of intervention may realize their ultimate long-term value in larger coronary vessels.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundCoronary stenting in conjunction with coronary angioplasty is a valuable tool for treatment of severe coronary dissection and is effective in reducing the frequency of restenoses. Evidence is increasing that the lumen gain within the stent is negatively correlated with the rate of subacute closures and restenoses. Since the assessment of radiolucent coronary stents and complex lumen morphologies by angiography is limited, we hypothesized that the use of a balloon catheter with integrated intravascular ultrasound (IVUS) facility for stent deployment and guidance of its expansion could improve the acute lumen gain without relevant procedural prolongation.Methods and ResultsDeployment of a single Palmaz-Schatz coronary stent with the combined imaging balloon catheter alone was successful in 18 of 20 patients eligible for this study. Corresponding measurements of minimal lumen diameter (MLD) by angiography and IVUS could be performed in 16 patients, revealing a close correlation between the two methods within the reference segments (3.10±0.38 and 3.08±0.43 mm,r=.79). Despite an adequate angiographic result in most patients after stent deployment, IVUS showed smaller MLD within the stented segment (2.15±0.23 mm) compared with angiography (2.63±0.26 mm,P<.0001) with a poor correlation (r=.27). To achieve IVUS criteria for optimal stent expansion (ratio of 0.9 between IVUS-assessed cross-sectional area of stent and reference segment), an average of three additional balloon inflations with higher pressure and/or a larger balloon diameter were performed without adverse effects in 15 of 16 patients who initially did not fulfill these criteria. This resulted in a significant increase in stent MLD to 2.63±0.27 mm (IVUS,P<.0001 versus initial MLD) and 2.89±0.32 mm (angiography,P<.0002 versus initial MLD) and a better correlation between the two methods (r=.60). The IVUS guidance led to a 40±15% increase of the minimal stent cross-sectional area with an additional time consumption of 21 minutes on average.ConclusionsThis study demonstrates the application of a combined imaging balloon catheter for delivery and ultrasound- guided expansion of Palmaz-Schatz coronary stents. IVUS offered a comprehensive insight into the stented coronary segments, revealing a substantial overestimation of stent dimensions by angiography. IVUS guidance led to a significant improvement of stent expansion. This additional lumen gain, which was not discernible by angiography in most patients, might result in a reduction of subacute stent thromboses as well as restenoses.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundMechanisms and electropharmacological characteristics in adult patients with atrial tachycardia (AT) are not well described. We proposed that a combination of electropharmacological characteristics, recording of monophasic action potential, and effects of radiofrequency ablation could further determine the mechanisms and achieve a new classification in adults with various types of AT because they were important in regard to the correlation between mecha-nisms and pathophysiology, clinical syndrome, and responses to specific pharmacological or nonpharmacological therapies.Methods and ResultsThirty-six patients (11 female, 25 male; mean age, 57±13 years) with AT were referred for electropharmacological studies and radiofrequency ablation. Resetting response pattern, entrainment phenomenon, recording of monophasic action potential, serial drug test, response to Valsalva maneuver, endocardial mapping technique, and radiofrequency ablation were performed. Seven patients had automatic AT provocable with isoproterenol; neither initiation nor termination was related to programmed electrical stimulation. The other 29 patients had AT initiated or terminated by electrical stimulation and mechanisms related to triggered activity or reentry; nine of them needed isopro-terenol to facilitate initiation of AT, associated with delayed afterdepolarization in monophasic action potential. All responded to adenosine (15 to 60 μg/kg) and Valsalva maneuver. Dipyridamole terminated AT and decreased the slope of afterdepolarization. Afterdepolarization was not found in the patients with automatic or reentrant AT. In 40 of 41 (98%), AT was ablated successfully, with late recurrence in 2 of 40 (5%) (follow-up, 18±4 months).ConclusionsThis study demonstrates the diverse mechanisms and electropharmacological characteristics of AT in adults. Furthermore, radiofrequency ablation of various types of AT could achieve high success and low recurrence rates.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundThe purpose of this study was to evaluate electrode temperatures obtained using a radiofrequency ablation system that incorporates closed loop feedback control to achieve preset target electrode temperatures and to determine if closed loop temperature control results in a lower incidence of developing a coagulum.Methods and ResultsTwo hundred seventy patients underwent catheter ablation of atrioventricular nodal reentrant tachycardia, an accessory pathway, and/or the atrioventricular junction using an ablation system incorporating closed loop feedback control. Forty-five patients underwent catheter ablation in the power control mode in which power output was fixed, and 225 patients underwent catheter ablation in the temperature control mode. A coagulum occurred during 0.8% of radiofrequency applications in the temperature control mode versus 2.2% in the power control mode (P<.01). Electrode temperatures were within 10°C of the targeted temperature during 35% of applications in the temperature control mode. Ability to achieve the targeted electrode temperature was related to the target, with radiofrequency energy applications at the atrioventricular junction resulting in the highest temperatures (70±12°C) and those for ablation of the atrioventricular node the lowest (59±11°C,P<.001), using a maximum of 50 W of power for both. Electrode temperatures were higher during ablation of left free wall and posteroseptal pathways than during ablation of right free wall and septal pathways. The mean and minimum temperatures associated with success were 64±12°C and 44°C, respectively. Overall, the electrode temperatures at successful and unsuccessful ablation sites did not differ (P>.05).ConclusionsTemperature monitoring with closed loop control of power output facilitates radiofrequency catheter ablation procedures by minimizing the probability of developing a coagulum while ensuring maximum lesion formation.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundPulmonary hypertension results in increased morbidity and mortality in children after surgical repair of congenital heart defects. Various vasodilators have been unsuccessful in providing preferential pulmonary vasodilation in these patients. Identification of a more preferential pulmonary vasodilator would improve the assessment, management, and outcome of these children. To determine whether ATP-MgCl2is a preferential pulmonary vasodilator in children with pulmonary hypertension secondary to congenital heart defects, ATP-MgCl2was administered during routine cardiac catheterization, and the effects were compared with tolazoline. In addition, ATP-MgCl2was infused intravenously during episodes of postoperative pulmonary hypertension.Methods and ResultsDuring cardiac catheterization in 28 children, the effect of ATP-MgCl2on the pulmonary artery pressure (PAP) and pulmonary vascular resistance index (Rp) was compared with tolazoline. ATP-MgCl2(0.1 mg of ATP per kilogram per minute) decreased mean PAP by 24% (P<.05) and Rpby 47% (P<.05) without changing mean systemic arterial pressure or systemic vascular resistance. These effects were comparable to those of tolazoline (1 mg/kg). ATP-MgCl2produced no significant side effects; tolazoline caused tachycardia, nausea, and vomiting. After cardiac surgery in 7 patients, ATP-MgCl2decreased PAP by 14% (P<.05) and systemic arterial pressure by 6% (P<.05) and eliminated pulmonary hypertensive crises in 3 of 3 patients.ConclusionsATP-MgCl2is a safe, effective, and preferential pulmonary vasodilator in children with pulmonary hypertension secondary to congenital heart defects. It is useful for evaluating pulmonary vasoreactivity during cardiac catheterization and for treating pulmonary hypertension after cardiac surgery.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID