ISSN:0009-7322    

出版商:OVID    

年代:1999

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundThe incremental prognostic value of post-stress left ventricular ejection fraction (EF) and volume over perfusion has not been investigated.70 mL had high death rates (7.9%/year; P<0.02). Multivariate Cox proportional hazards regression showed that perfusion variables and ESV were independent predictors of overall coronary events, whereas EF and ESV demonstrated incremental prognostic values over prescan and perfusion information in predicting cardiac death and cardiac death or myocardial infarction.ConclusionsPost-stress EF and ESV by gated-SPECT have incremental prognostic values over prescan and perfusion information in predicting cardiac death, and they provide clinically useful risk stratification. (Circulation. 1999;100:1035-1042.)

ISSN:0009-7322    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundCardiac complications are important causes of morbidity after noncardiac surgery. The purpose of this prospective cohort study was to develop and validate an index for risk of cardiac complications.or=to3 of these factors were 0.5%, 1.3%, 4%, and 9%, respectively, in the derivation cohort and 0.4%, 0.9%, 7%, and 11%, respectively, among 1422 patients in the validation cohort. Receiver operating characteristic curve analysis in the validation cohort indicated that the diagnostic performance of the Revised Cardiac Risk Index was superior to other published risk-prediction indexes.ConclusionsIn stable patients undergoing nonurgent major noncardiac surgery, this index can identify patients at higher risk for complications. This index may be useful for identification of candidates for further risk stratification with noninvasive technologies or other management strategies, as well as low-risk patients in whom additional evaluation is unlikely to be helpful. (Circulation. 1999;100:1043-1049.)

ISSN:0009-7322    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundIn vitro, the flavonoid components of red wine and purple grape juice are powerful antioxidants that induce endothelium-dependent vasodilation of vascular rings derived from rat aortas and human coronary arteries. Although improved endothelial function and inhibition of LDL oxidation may be potential mechanisms by which red wine and flavonoids reduce cardiovascular risk, the in vivo effects of grape products on endothelial function and LDL oxidation have not been investigated. This study assessed the effects of ingesting purple grape juice on endothelial function and LDL susceptibility to oxidation in patients with coronary artery disease (CAD).Methods and Results-Fifteen adults with angiographically documented CAD ingested 7.7 +/- 1.2 mL [middle dot] kg-1[middle dot] d-1of purple grape juice for 14 days. Flow-mediated vasodilation (FMD) was measured using high-resolution brachial artery ultrasonography. Susceptibility of LDL particles to oxidation was determined from the rate of conjugated diene formation after exposure to copper chloride. At baseline, FMD was impaired (2.2 +/- 2.9%). After ingestion of grape juice, FMD increased to 6.4 +/- 4.7% (P=0.003). In a linear regression model that included age, artery diameter, lipid values, and use of lipid-lowering and antioxidant therapies, the effect of grape juice on FMD remained significant (mean change 4.2 +/- 4.4%, P<0.001). After ingestion of grape juice, lag time increased by 34.5% (P=0.015).ConclusionsShort-term ingestion of purple grape juice improves FMD and reduces LDL susceptibility to oxidation in CAD patients. Improved endothelium-dependent vasodilation and prevention of LDL oxidation are potential mechanisms by which flavonoids in purple grape products may prevent cardiovascular events, independent of alcohol content. (Circulation. 1999;100:1050-1055.)

ISSN:0009-7322    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundWe investigated the effects of candesartan (an angiotensin II antagonist) alone, enalapril alone, and their combination on exercise tolerance, ventricular function, quality of life (QOL), neurohormone levels, and tolerability in congestive heart failure (CHF).Methods and Results-Seven hundred sixty-eight patients in New York Heart Association functional class (NYHA-FC) II to IV with ejection fraction (EF) <0.40 and a 6-minute walk distance (6MWD) <500 m received either candesartan (4, 8, or 16 mg), candesartan (4 or 8 mg) plus 20 mg of enalapril, or 20 mg of enalapril for 43 weeks. There were no differences among groups with regard to 6MWD, NYHA-FC, or QOL. EF increased (P=NS) more with candesartan-plus-enalapril therapy (0.025 +/- 0.004) than with candesartan alone (0.015 +/- 0.004) or enalapril alone(0.015 +/- 0.005). End-diastolic (EDV) and end-systolic (ESV) volumes increased less with combination therapy (EDV 8 +/- 4 mL; ESV 1 +/- 4 mL; P<0.01) than with candesartan alone (EDV 27 +/- 4 mL; ESV 18 +/- 3 mL) or enalapril alone (EDV 23 +/- 7 mL; ESV 14 +/- 6 mL). Blood pressure decreased with combination therapy (6 +/- 1/4 +/- 1 mm Hg) compared with candesartan or enalapril alone (P<0.05). Aldosterone decreased (P<0.05) with combination therapy (23.2 +/- 5.3 pg/mL) at 17 but not 43 weeks compared with candesartan (0.7 +/- 7.8 pg/mL) or enalapril (-0.8 +/- 11.3 pg/mL). Brain natriuretic peptide decreased with combination therapy (5.8 +/- 2.7 pmol/L; P<0.01) compared with candesartan (4.4 +/- 3.8 pmol/L) and enalapril alone (4.0 +/- 5.0 pmol/L).ConclusionsCandesartan alone was as effective, safe, and tolerable as enalapril. The combination of candesartan and enalapril was more beneficial for preventing left ventricular remodeling than either candesartan or enalapril alone. (Circulation. 1999;100:1056-1064.)

ISSN:0009-7322    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundRespiratory gas exchange measurements in patients with chronic heart failure (CHF) at rest and during exercise commonly reveal prominent slow oscillations in ventilation (VE), measured oxygen uptake (VO2), and carbon dioxide production (VCO2), whose origin is not clear. Voluntary simulation of periodic breathing (PB) in normals has been reported to generate a different pattern of oscillations in gas exchange from that seen in spontaneous PB. This necessitates hypothesizing that PB is caused by a primary oscillation in tissue metabolism or in cardiac output.Methods and Results-We developed an automated method by which normal controls could be guided to breathe according to a PB pattern. The resultant metabolic oscillations closely matched those seen in spontaneous PB and had several interesting properties. At low workloads (including rest), the oscillations in VO2were as prominent as those in VEin both spontaneous PB (alphaVO2/alphaVE=0.92 +/- 0.04) and voluntary PB (0.93 +/- 0.07). However, at increased workload, the oscillations in VO2because less prominent than those in VE0.05 at low, intermediate, and high workloads). Furthermore, VO2peaked before VEin both spontaneous and voluntary PB. This time delay varied from 6.4 +/- 0.4 s at low ventilation, to 11.3 +/- 0.9 s at high ventilation (P<0.0001).ConclusionsThe magnitude and phase pattern of oscillations in gas exchange of spontaneous PB can be obtained by adequately matched voluntary PB. Therefore, the gas exchange features of PB are explicable by primary ventilatory oscillation. (Circulation. 1999;100;1065-1070.)

ISSN:0009-7322    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundThe goal of this study was to assess the prognostic value of ambulatory versus clinic blood pressure measurement and to relate cardiovascular risk to ambulatory systolic and diastolic blood pressure levels.Methods and Results-The study population consisted of 688 patients 51 +/- 11 years of age who had undergone pretreatment 24-hour intra-arterial ambulatory blood pressure monitoring on the basis of elevated clinic blood pressure. A total of 157 first events were recorded during a 9.2 +/- 4.1-year follow-up period. The predictive value of a regression model containing age, sex, race, body mass index, smoking, diabetes mellitus, fasting cholesterol level, and previous history of cardiovascular disease was significantly improved by the addition of any ambulatory systolic or diastolic blood pressure parameter (whether 24-hour, daytime, or nighttime mean) or pulse pressure, whereas inclusion of baseline clinic blood pressure variables did not enhance the prediction of events. The most predictive models contained the ambulatory systolic blood pressure parameters. In the model containing 24-hour mean ambulatory systolic blood pressure (P=0.001), age (P<0.001), male sex (P<0.001), South Asian origin (P=0.008), diabetes mellitus (P=0.05), and previous cardiovascular disease (P<0.001) were additional independent predictors of events. Whereas 24-hour ambulatory systolic blood pressure was linearly related to the incidence of both coronary and cerebrovascular events, 24-hour ambulatory diastolic blood pressure exhibited a positive linear relationship with cerebrovascular events but a curvilinear relationship with coronary events.ConclusionsAmbulatory blood pressure is superior to clinic measurement for the assessment of cardiovascular risk; there is no reduction in coronary risk at lower levels of ambulatory diastolic blood pressure. (Circulation. 1999;100:1071-1076.)

ISSN:0009-7322    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundLong-QT syndrome is a monogenic disorder that produces cardiac arrhythmias and can lead to sudden death. At least 5 loci and 4 known genes exist in which mutations have been shown to be responsible for the disease. The potassium channel gene KCNQ1, previously named KVLQT1, on chromosome 11p15.5 is one of these.Methods and Results-We initially analyzed one family using microsatellite markers and found linkage to KCNQ1. Mutation detection showed a G to C change in the last base of exon 6 (1032 G[right arrow]C) that does not alter the coded alanine. Restriction digest analysis in the family showed that only affected individuals carried the mutation. A previous report suggested that a G to A substitution at the same position may act as a splice mutation in KCNQ1, but no data was given to support this hypothesis nor was the transcription product identified. We have shown by reverse-transcription polymerase chain reaction that 2 smaller bands were produced for the KCNQ1 gene transcripts in addition to the normal-sized transcripts when lymphocytes of affected individuals were analyzed. Sequencing these transcripts showed a loss of exon 7 in one and exons 6 and 7 in the other, but an in-frame transcript was left in each instance. We examined other families in whom long-QT syndrome was diagnosed and found another unreported splice-site mutation, 922-1 G[right arrow]C, in the acceptor site of intron 5, and 2 of the previously reported 1032 G[right arrow]A mutations. All these showed a loss of exons 6 and 7 in the mutant transcripts, validating the proposal that a consensus sequence is affected in the exonic mutations and that the integrity of the base at position 1032 is essential for correct processing of the transcript.ConclusionsThe 6 cases already reported in the literature with the 1032 G[right arrow]A transition, the novel 1032 G[right arrow]C transversion, and a recent G[right arrow]T transversion at the same base show that codon 344 is the second most frequently mutated after codon 341, suggesting at least two hotspots for mutations in KCNQ1.(Circulation. 1999;100:1077-1084.)

ISSN:0009-7322    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundThe age-related decline in maximal oxygen consumption is attenuated by habitual aerobic exercise. However, the relative effects of training on central and peripheral responses to exercise in older subjects are not known. The present study assessed the contribution of central and peripheral responses to the age-associated decline in peak oxygen consumption and compared the effect of exercise training in healthy older and younger subjects.Methods and Results-Ten older and 13 younger men underwent invasive measurement of central and peripheral cardiovascular responses during an upright, staged cycle exercise test before and after a 3-month period of exercise training with cycle ergometry. At baseline, cardiac output and AV oxygen difference during exercise were significantly lower in older subjects. With training, the older and younger groups increased maximal oxygen consumption by 17.8% and 20.2%, respectively. Peak cardiac output was unchanged in both groups. Systemic AV oxygen difference increased 14.4% in the older group and 14.3% in the younger group and accounted for changes in peak oxygen consumption. Peak leg blood flow increased by 50% in older subjects, whereas the younger group showed no significant change. There was no change in peak leg oxygen extraction in the older group, but in the younger group, leg AV oxygen difference increased by 15.4%.ConclusionsThese findings suggest that the age-related decline in maximal oxygen consumption results from a reversible deconditioning effect on the distribution of cardiac output to exercising muscle and an age-related reduction in cardiac output reserve. (Circulation. 1999;100:1085-1094.)

ISSN:0009-7322    

出版商:OVID    

年代:1999

数据来源: OVID