ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundAccessory pathways may be located in close proximity to the His bundle, resulting in a high risk of heart block during attempted surgical or electrical interruption of these pathways. This study reports the prevalence, ECG characteristics, and results of catheter ablation of parahissian accessory pathways. They were defined on the basis of both the presence of a high amplitude (>0.1 mV) of His bundle potential at the ablation site and an exclusion of anteroseptal or midseptal location of the accessory pathway.Methods and ResultsEight patients with a parahissian accessory pathway were identified among 582 consecutive patients who underwent radiofrequency ablation of an acces-sory pathway. They were six males and two females with a mean age of 21±9 years. During maximal preexcitation, the ECG showed a positive delta wave in leads I, II, and aVF in all patients: six had a negative delta wave in leads V1and V2instead of the positivity usually observed in anteroseptal accessory pathways. This pattern had a sensitivity of 75%, a specificity of 96%, a positive predictive value of 86%, and a negative predictive value of 93% for a parahissian location in comparison with a group of 28 patients with anteroseptal accessory pathways. At the successful ablation site, the mean amplitude of the His bundle potential was 0.2±0.1 (0.12 to 0.4 mV). All accessory pathways were successfully ablated without causing heart block using 5 to 20 W of radiofrequency energy.ConclusionsParahissian accessory pathways have a preexcitation pattern that is distinctive from that of anteroseptal accessory pathways. Catheter ablation of these pathways is feasible using low energy with preservation of normal atrio-ventricular conduction.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundThree peptides consisting of amino acids 1-30, 31-67, and 79-98 of the 126–amino acid atrial natriuretic factor prohormone (proANF), which have blood pressure-lowering, diuretic, natriuretic, and/or kaliuretic properties in animals, were investigated to determine if they have similar properties in humans.Methods and ResultsThirty-six healthy, normotensive human volunteers (18 men and 18 women, ages 20 to 58 years) were divided into six similar groups based on age, sex, weight, blood pressure, and heart rate. After a 60-minute baseline period, 100 ng of proANFs 1-30, 31-67, 79-98, or ANF/kg body wt per minute was given intravenously for 60 minutes followed by a 3-hour postinfusion data collection period. Each of the atrial natriuretic peptides decreased systolic and diastolic blood pressures (P<.05), with proANF 31-67 causing the largest decrease. Urine flow increased 4- to 12-fold and was still significantly increased (P<.01) for 2 to 3 hours after stopping the respective infusions of proANFs 1-30, 31-67, and 79-98. Atrial natriuretic factor (ANF) increased urine flow 4- to 11-fold but by 2 hours after infusion was significantly increased in only 1 of 6 subjects. Sodium excretion increased 3-to 8-fold, 3- to 6-fold, 0- to 2-fold (NS), and 3- to 11-fold, respectively, with proANFs 1-30, 31-67, 79-98, and ANF. Natriuretic effects of proANFs 1-30 and 31-67 were significantly prolonged (P<.001) compared with ANF. ProANFs 1-30, 31-67, 79-98, and ANF increased potassium excretion 2- to 3-fold, 0-fold, 3- to 4-fold, and 2-fold, respectively. High-performance gel permeation chromatography followed by the respective radioimmunoassays revealed that proANFs 1-30, 31-67, 79-98, and 68-98, as well as ANF circulate as distinct peptides.ConclusionsProANFs 1-30, 31-67, and 79-98, as well as ANF have significant blood pressure-lowering and diuretic properties. ProANFs 1-30 and 31-67 also have natriuretic properties in humans that are significantly (P<.001) prolonged compared with ANF. ProANF 79-98, although not possessing any natriuretic property, is the strongest stimulator of potassium excretion of the four atrial natriuretic peptides.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundSerotonin may contract human large coronary arteries through two 5-hydroxtryptamine (5-HT) receptors, 5-HT1-like and 5 -HT2.These 5-HT1-like receptors resemble both cloned 5-HT1Dreceptor subtypes, 5-HT1Dαand 5 -HT1DβAlthough these subtypes have similar pharmacology, 5-HT1Dαreceptors appear to have lower affinity for ketanserin than 5-HT1Dαreceptors. We assessed the relative participation of 5-HT1-like and 5-HT2receptors and attempted to identify whether vasoconstrictor 5-HT1-like receptors are 5 1HT1Dαor 5-.HT1Dβ.Methods and ResultsEpicardial coronary arteries were dissected from the hearts of29 patients (including 1 healthy donor) undergoing heart transplant operation. Endothelium-denuded strips were set up to contract at 37°C. To assess the relative contributions of 5-HT2-like and 5-HT2receptors, we blocked the latter with ketanserin (0.1 to 1.0 μmol/L) and ketanserin-resistant receptors with methiothepin (0.1 μmol/ L). Concentration-effect curves for 5-HT, in the absence and presence of ketanserin, were analyzed by using a model for two receptor subtypes. The fractional contributions of 5-HT1-like and 5 -HT2receptors to the maximum effect of 5 -HT, f1and f2, were estimated in arteries from 28 patients: f1(0.71±0.20, mean±SD) was significantly larger than f2(0.29±0.20) (P<.0001). Using [3H]-serotonin to label transfected and ex-pressed receptors, we verified that ketanserin has lower affinity for 5-HT1Dβ(pK1-log Ki, mol/L] less than 5.0) than for 5-HTlDα(pKi=7.1±0.1) receptors. A concentration of ketanserin (1 μmol/L) that would occupy more than 90% of 5-HT1Dαreceptors failed to block 5-HT-induced contractions (4 patients). The 5-HT1-like receptor stimulant sumatriptan evoked maximal contractions that matched f1and was equipotent with 5-HT through 5-HT1-like receptors (8 patients). No systematic influence of disease, atheroma, or therapy on f1and f2was detected.ConclusionsCoronary artery contractile 5-HT1-like receptors resemble cloned 5-HT1Dβreceptors and predominate over 5-HT2receptors in mediating serotonin-evoked contractions. Sumatriptan contracts coronary arteries as a full agonist through 5-HT1-like receptors.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundIn vitro, animal and epidemiological studies suggest that lipoprotein oxidation may play an important role in atherosclerosis. Antioxidants may protect against lipoprotein oxidation and in that way inhibit atherosclerosis and its clinical sequelae. To investigate this possibility, we examined the association between levels of several antioxidants and myocardial infarction using serum specimens collected 7 to 14 years before the onset of myocardial infarction.Methods and ResultsA nested case-control design was used. Cases and control subjects were selected from the 25 802 persons who had donated 15 mL of blood in 1974 for a serum bank. Cases comprised 123 persons with a subsequent first diagnosis of myocardial infarction who ranged from 23 through 58 years of age in 1974 and who had had their first diagnosis of myocardial infarction during 1981 to 1988. Two groups of control subjects matched to the cases for sex and age were selected from donors to the serum bank, one from those with hospital admissions during the same period and the other from the total group of donors. Sera were assayed for four carot-A enoids (β-carotene, lycopene, lutein, and zeaxanthin), α-to-copherol, and cholesterol. Because associations with these serum nutrients showed similar trends whether based on hospital or community controls, the two control groups were combined. There was a significantly increasing risk for subse-quent myocardial infarction with decreasing levels of (β-caro-tene in 1974 (Pvalue for trend,.02) and a suggestive trend with decreasing levels of lutein (P=.09). When the results were stratified by smoking status, the excess risk of myocardial infarction associated with low serum levels of carotenoids was limited to smokers. A protective association with higher levels of α-tocopherol was suggested only among persons with high levels of serum cholesterol.ConclusionsLow serum levels of carotenoids were associ-ated with an increased risk of subsequent myocardial infarc-tion among smokers.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Cocaine use has been associated with arterial occlusion resulting from plateletrich thrombi and with an accelerated, often atypical atherosclerotic lesion that could be ascribed to platelet activation and platelet α-granule release.Methods and ResultsUsing a flow cytometric method to quantitate the percent of circulating activated platelets in whole blood (those that express the α-granule membrane protein P-selectin), we found that 5 of 25 samples from 12 long-term cocaine users had a baseline level of circulating activated platelets >3 SD (range, 19% to 60%) above the mean (4.4±3.7%, mean±1 SD) for 85 nonusers (sample n=130). This subset resulted in a significantly higher mean baseline level of circulating activated platelets (11.8±14.4%) for all cocaine users (P=.01). By contrast, cocaine and its metabolites, at concentrations documented as obtainable during in vivo cocaine use (10−7to 10−5mol/L), had no effect on in vitro platelet activation or aggregation, either directly or in concert with platelet agonists. However, in experiments in which cocaine users received blinded infusions of placebo or cocaine, the mean percent of circulating activated platelets rose significantly (P<.05) after infusion of either placebo (peak 77±31%) or cocaine (peak 65 ±28%), the latter at doses resulting in peak plasma cocaine levels averaging < 10−6mol/L.ConclusionsLong-term cocaine use in some subjects is intermittently associated with high basal levels of circulating platelets that have undergone α-granule release. The inability of cocaine and its metabolites at concentrations of 10−7kto 10−5mol/L to cause platelet P-selectin expression in vitro in this study, coupled with the acute increase in circulating activated platelets observed in vivo after either cocaine or placebo infusion, suggests that in vivo platelet α-granule release associated with cocaine use may occur through indirect rather than direct effects of the drug.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundExercise and pharmacological stress echocar-diography have emerged as convenient alternatives to myocardial scintigraphy. The objective of this study was to compare in the same patients the diagnostic values of exercise, dobutamine, and dipyridamole stress echocardiography tests for detection of myocardial ischemia.Methods and ResultsWe performed exercise (maximal treadmill Bruce protocol), dobutamine (up to 40 μg/kg per minute) and dipyridamole (up to 0.84 mg/kg over 10 minutes) stress echocardiography tests, in random sequence and on separate days, in 136 consecutive patients. All patients underwent coronary angiography. Significant coronary artery disease was defined by quantitative coronary angiography as a lesion with a diameter stenosis ≥50%. A stress echocardiogram was considered positive when new or worsening of preexisting wall motion abnormality was observed. Most of the patients (94%) were receiving the same antianginal medication for each stress test; 59 patients were receiving concomitant β-blocker therapy. The prevalence of coronary artery disease was 87.5%, with 108 patients having one-vessel coronary artery disease. Peak heart rate and systolic blood pressure were higher with exercise than with dobutamine or dipyridamole (P<.01). Sensitivity of exercise, dobutamine, and dipyridamole stress echocardiography was 88%, 82%, and 74% (dipyridamole versus exercise,P<.01), respectively. Specificity was 82%, 77%, and 94%, respectively. The overall accuracy was 87%, 82%, and 77% (dipyridamole versus exercise,P<.01), respectively. The accuracy of dipyridamole was higher (P=.02) in the group of patients not receiving β-blockers (84%) than in the patients receiving β-blocker therapy (66%), whereas the accuracy of exercise and dobutamine were only slightly higher in the patients not receiving, β-blockers. Significant side effects occurred in 3%, 11%, and 1% of patients during exercise, dobutamine, and dipyridamole tests, respectively.ConclusionsDespite the different hemodynamic effects, exercise, dobutamine, and dipyridamole echocardiography have high overall diagnostic values. In this group of patients with a predominance of one-vessel coronary artery disease, the overall diagnostic accuracy of stress echocardiography tests was higher for exercise than for dobutamine or dipyridamole. Concomitant β-blocker therapy significantly decreased the accuracy of the dipyridamole stress echocardiography test. Pharmacological stress testing (dipyridamole without β-blockers) can therefore be used as an efficient option for detection of myocardial ischemia in patients who are unable or poorly motivated to exercise adequately.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundTo discern whether hypertriglyceridemia (hyper-TG, TG >95th percentile) and hypoalphalipoproteinemia (hypoalpha, high-density lipoprotein [HDL-C] 10th percentile) are jointly transmitted in families, we studied 385 probands with marked elevations in TG or cholesterol levels (TG or cholesterol >99th percentile in a previous visit) and their 2072 first-degree relatives in the Lipid Research Clinics' Family Study. Repeat TG measurement, with exclusion criterion of TG ≤95th percentile, resulted in 162 probands with hyper-TG.Methods and ResultsWhen the proband demonstrated the conjoint trait (CT; ie, TG >95th percentile, HDL-C 10th percentile, n=82), an average of 10.6% of first-degree relatives conjointly expressed hyper-TG and hypoalpha in contrast to only 4.1% of first-degree relatives of a proband who expressed high TG levels with normal HDL-C levels (TG >95th percentile, HDL-C >10th percentile, n=80). Hyper-TG was expressed in 24.2% of first-degree relatives of probands with CT. However, hyper-TG was expressed in only 14.4% of first-degree relatives of probands with hyper-TG alone. CT probands and their family members tended to have more reported cardiac events and symptoms (P=.02 and.09, respectively) than those subjects associated with hyper-TG alone.ConclusionsThe differences in HDL-C-TG abnormalities between families related to hyper-TG probands with or without hypoalpha indicate that bottom decile HDL-C is not simply secondary to hyper-TG. A familial interaction is suggested between HDL-C and TG levels consistent with the transmission of hyper-TG and hypoalpha among first-degree relatives. Among subjects and their families with hyper-TG, those who in addition have low HDL-C demonstrate a tendency for more coronary artery disease than do those with normal HDL-C levels.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

BackgroundDespite the significant role that dyslipidemia is believed to play in the development of cardiovascular disease in diabetes, most studies examining diabetic dyslipidemia in the United States have not been population based, and very little data are available for African Americans with diabetes. We used data from a national survey to compare the effect of diabetes on lipid concentrations in African-American and white men and women. In addition, we examined other factors related to lipid concentrations and controlled for these factors in our analyses.Methods and ResultsThe Second National Health and Nutrition Examination Survey included a representative sam-ple of 4177 African Americans and whites in the US civilian noninstitutionalized population 20 to 74 years old. These persons were classified as having non-insulin-dependent dia-betes mellitus (NIDDM) (n=720) or as being nondiabetic (n=3457) based on an oral glucose tolerance test and medical history of diabetes. Subjects were given an interview and physical examination that included measurement of serum lipoproteins, body mass index, body fat distribution, dietary fat intake, alcohol consumption, frequency of smoking, and use of medications. By uivariate analysis, a worse profile of mean cholesterol, triglycerides, and high-density lipoprotein cholesterol levels was generally apparent in NIDDM than in nondiabetic subjects, regardless of race or sex; a similar pattern was found for the prevalence of abnormal concentrations of these lipids. Lipid profiles appeared to be worse in whites with NIDDM than in African Americans. For mean total and low-density lipoprotein cholesterol, concentrations tended to be worse in women with NIDDM than in men. When other factors significantly affecting lipid levels were adjusted by multivariate analysis, we found that in all race/sex groups, total cholesterol was higher in NIDDM than in nondiabetic subjects but differences were not significant (P=.54), triglyceride concentrations were significantly higher in NIDDM subjects (P<.0001), and high-density lipoprotein cholesterol concentrations were lower in NIDDM subjects (P=.003). An interaction of diabetes with race was found for low-density lipo-protein cholesterol (P=.0001), where concentrations were substantially lower in NIDDM than in nondiabetic subjects among African Americans (P<.01) but slightly higher in NIDDM subjects among whites (P=.33). For other lipids, no differential effect of NIDDM was found by race or sex.ConclusionsIn African-American and white men and women in the United States, NIDDM is associated with a pattern of dyslipidemia that may potentiate the atherosclerotic process. Diabetic treatment should include aggressive treatment of dyslipidemia to reduce this increased risk.

ISSN:0009-7322    

出版商:OVID    

年代:1994

数据来源: OVID