PubMed Health⌕ Search

Biomedical subjects

E H Lieberman

Publications and source records attributed to E H Lieberman.

11 recordsLinked to original sources
PubMed2000

The mode selection trial (MOST) in sinus node dysfunction: design, rationale, and baseline characteristics of the first 1000 patients.

BACKGROUND: More than 200,000 permanent pacemakers will be implanted in the United States in 2000 at a cost of more than $2 billion. Sick sinus syndrome (SSS) will likely account for approximately half of all cases necessitating implantation. Pacemaker technology permits the selection of ventricular (single-chamber) or dual-chamber devices. However, clinical and outcomes data are inadequate to support a clear recommendation that one or the other type of device be used. METHODS: The Mode Selection Trial (MOST) is a single-blind study supported by the National Heart, Lung, and Blood Institute designed to enroll 2000 patients with SSS. All patients will receive a DDDR pacemaker programmed to VVIR or DDDR before implantation. The average time of follow-up will be 3 years. MOST has a >90% power to detect a 25% reduction in the primary end point-nonfatal stroke or total (all cause) mortality-in the DDDR-treated group. Secondary end points will include health-related quality of life and cost effectiveness, atrial fibrillation, and development of pacemaker syndrome. Prespecified subgroups for analysis will include women and the elderly. Enrollment was completed in October 1999, with a total of 2010 patients. RESULTS: The median age of the first 1000 enrolled patients is 74 years, with 25% of patients 80 years or older. Women comprise 49%, and 17% are nonwhite, predominantly black (13%). Before pacemaker implantation, 22% of patients reported a history of congestive heart failure, 11% coronary angioplasty, and 25% coronary bypass surgery. Supraventricular tachycardia including atrial fibrillation was present in 53% of patients. A prior stroke was reported by 12%. Antiarrhythmic therapy was in use in 18% of patients. CONCLUSIONS: MOST will fill the clinical need for carefully designed prospective studies to define the benefits of dual-chamber versus single-chamber ventricular pacing in patients with SSS. The MOST population is typical of the overall pacemaker population in the United States. Thus the final results of MOST should be clinically generalizable.

Aged↗
PubMed1998

Quality of life and clinical outcomes in elderly patients treated with ventricular pacing as compared with dual-chamber pacing. Pacemaker Selection in the Elderly Investigators.

BACKGROUND: Standard clinical practice permits the use of either single-chamber ventricular pacemakers or dual-chamber pacemakers for most patients who require cardiac pacing. Ventricular pacemakers are less expensive, but dual-chamber pacemakers are believed to be more physiologic. However, it is not known whether either type of pacemaker results in superior clinical outcomes. METHODS: The Pacemaker Selection in the Elderly study was a 30-month, single-blind, randomized, controlled comparison of ventricular pacing and dual-chamber pacing in 407 patients 65 years of age or older in 29 centers. Patients received a dual-chamber pacemaker that had been randomly programmed to either ventricular pacing or dual-chamber pacing. The primary end point was health-related quality of life as measured by the 36-item Medical Outcomes Study Short-Form General Health Survey. RESULT: The average age of the patients was 76 years (range, 65 to 96), and 60 percent were men. Quality of life improved significantly after pacemaker implantation (P<0.001), but there were no differences between the two pacing modes in either the quality of life or prespecified clinical outcomes (including cardiovascular events or death). However, 53 patients assigned to ventricular pacing (26 percent) were crossed over to dual-chamber pacing because of symptoms related to the pacemaker syndrome. Patients with sinus-node dysfunction, but not those with atrioventricular block, had moderately better quality of life and cardiovascular functional status with dual-chamber pacing than with ventricular pacing. Trends of borderline statistical significance in clinical end points favoring dual-chamber pacing were observed in patients with sinus-node dysfunction, but not in those with atrioventricular block. CONCLUSION: The implantation of a permanent pacemaker improves health-related quality of life. However, the quality-of-life benefits associated with dual-chamber pacing as compared with ventricular pacing are observed principally in the subgroup of patients with sinus-node dysfunction.

Aged↗
PubMed1997

Noninvasive assessment of endothelium-dependent flow-mediated dilation of the brachial artery.

Coronary atherosclerosis is characterized by an early loss of endothelium-dependent vasodilation. However, the methods of assessing coronary endothelial function are invasive and difficult to repeat over time. Recently, a noninvasive ultrasound method has been widely used to measure flow-mediated dilation in the brachial artery as a surrogate test for endothelial function. We seek to further validate this method of measuring vascular function. The brachial artery diameters and blood flow of 20 normal volunteers (10 males and 10 females) were measured using high resolution (7.5 MHz) ultrasound and strain gauge plethysmography. Flow-mediated endothelium-dependent vasodilation was measured in the brachial artery during reactive hyperemia after 5 minutes of cuff occlusion in the upper arm. The brachial artery diameter increased maximally by 9.7 +/- 4.3% from baseline at 1 min after cuff release and blood flow increased by 1002 +/- 376%. Five min of cuff occlusion was sufficient to achieve 97 +/- 6% of maximal brachial artery dilation and degree of dilation was not different whether the cuff was inflated proximally or distally to the image site. The intraobserver variability in measuring brachial diameters was 2.9% and the variability of the hyperemic response was 1.4%. In young, healthy men and women, the baseline brachial artery diameter was the only factor that was predictive of the flow-mediated vasodilation response. The brachial noninvasive technique has been further validated by the determination of flow-mediated dilation. This method of assessing endothelial function may help to determine the importance of vasodilator dysfunction as a risk factor in the development of atherosclerosis.

Adult↗
PubMed1996

Flow-induced vasodilation of the human brachial artery is impaired in patients <40 years of age with coronary artery disease.

The objective of this study was to determine whether abnormal flow-induced endothelium-dependent vasodilation in the brachial artery identifies young patients with coronary artery disease (CAD). High-resolution ultrasonography was used to measure vascular reactivity in a peripheral conduit vessel, the brachial artery, in 14 young men with CAD and in 11 age-matched, healthy, male volunteers. Endothelium-dependent vasodilation was determined by measuring the change in brachial artery diameter during increases in flow induced by reactive hyperemia. Endothelium-independent vasodilation was assessed by administration of sublingual nitroglycerin. To ascertain whether flow-mediated vasodilation in humans is mediated by endothelium-derived nitric oxide, brachial artery diameter was measured during reactive hyperemia, before and during administration of the nitric oxide synthase antagonist NG-monomethyl-L-arginine (L-NMMA). Brachial artery diameter was also measured during intraarterial infusion of acetylcholine and nitroprusside before and after administration of L-NMMA. Flow-induced vasodilation was less in patients with CAD than in healthy volunteers (1.3 +/- 1.1% vs 6.2 +/- 0.7%, p <0.05). Nitroglycerin increased brachial artery diameter similarly in each subject group (11.3 +/- 1.0% vs 15.8 +/- 1.2%, p =0.05). L-NMMA inhibited flow-mediated vasodilation and the vasodilative response to acetylcholine, but did not affect the response to nitroprusside. It is concluded that abnormal flow-induced endothelium-dependent vasodilation occurs in the brachial artery of young patients with CAD.

Acetylcholine↗
PubMed1995

Close relation of endothelial function in the human coronary and peripheral circulations.

OBJECTIVES: The relation between endothelium-dependent vasodilator function in the brachial and coronary arteries was determined in the same subjects. BACKGROUND: Coronary artery endothelial dysfunction precedes the development of overt atherosclerosis and is important in its pathogenesis. A noninvasive assessment of endothelial function in a peripheral conduit vessel, the brachial artery, was recently described, but the relation between brachial artery function and coronary artery vasodilator function has not been explored. METHODS: In 50 patients referred to the catheterization laboratory for the evaluation of coronary artery disease (mean age +/- SD 56 +/- 10 years), the coronary vasomotor response to serial intracoronary infusions of the endothelium-dependent agonist acetylcholine (10(-8) to 10(-6) mol/liter), was studied. Endothelium-dependent vasodilation was also assessed in the brachial artery by measuring the change in brachial artery diameter in response to reactive hyperemia. RESULTS: Patients with coronary artery endothelial dysfunction manifested as vasoconstriction in response to acetylcholine had significantly impaired flow-mediated vasodilation in the brachial artery compared with that of patients with normal coronary endothelial function (4.8 +/- 5.5% vs. 10.8 +/- 7.6%, p < 0.01). Patients with coronary artery disease also had an attenuated brachial artery vasodilator response compared with that of patients with angiographically smooth coronary arteries (4.5 +/- 4.6% vs. 9.7 +/- 8.1%, p < 0.02). By multivariate analysis, the strongest predictors of reduced brachial dilator responses to flow were baseline brachial artery diameter (p < 0.001), coronary endothelial dysfunction (p = 0.003), the presence of coronary artery disease (p = 0.007) and cigarette smoking (p = 0.016). The brachial artery vasodilator response to sublingual nitroglycerin was independent of coronary endothelial responses or the presence of coronary artery disease. The positive predictive value of abnormal brachial dilation ( < 3%) in predicting coronary endothelial dysfunction is 95%. CONCLUSIONS: This study demonstrated a close relation between coronary artery endothelium-dependent vasomotor responses to acetylcholine and flow-mediated vasodilation in the brachial artery. This noninvasive method may become a useful surrogate in assessing the predisposition to atherosclerosis in patients with cardiac risk factors.

Acetylcholine↗
PubMed1994

Estrogen improves endothelium-dependent, flow-mediated vasodilation in postmenopausal women.

OBJECTIVE: To assess the effect of estrogen replacement therapy on endothelium-dependent vasodilation in postmenopausal women. DESIGN: Double-blind, placebo-controlled, crossover trial. SETTING: University medical center. PATIENTS: 13 postmenopausal women aged 44 to 69 years (average age, 55 +/- 7 years). INTERVENTION: Patients were randomly assigned to receive placebo, oral estradiol at a dose of 1 mg/d, and oral estradiol at a dose of 2 mg/d. Each treatment phase lasted 9 weeks. MEASUREMENTS: High-resolution ultrasonography was used to measure vascular reactivity in a peripheral conduit vessel, the brachial artery. Endothelium-dependent vasodilation was determined by measuring the change in brachial artery diameter during increases in flow induced by reactive hyperemia. Endothelium-independent vasodilation was measured after sublingual nitroglycerin was administered. RESULTS: Flow-mediated, endothelium-dependent vasodilation of the brachial artery was greater when patients received estradiol (13.5% and 11.6% for 1-mg and 2-mg doses, respectively) than when patients received placebo (6.8%; P < 0.05 for each dose compared with placebo). In contrast, estrogen administration had no effect on endothelium-independent vasodilation as assessed by sublingual nitroglycerin. CONCLUSION: Short-term estrogen replacement therapy improves flow-mediated endothelium-dependent vasodilation in postmenopausal women. This improvement may be mediated by a direct effect of estrogen on vascular function or may be induced through modification of lipoprotein metabolism.

Administration, Oral↗
PubMed1994

Refractory hypoxemia in inferior myocardial infarction from right-to-left shunting through a patent foramen ovale: a case report and review of the literature.

Right ventricular (RV) infarction is a well-recognized complication of some acute inferior myocardial infarctions. Recently, there have been numerous case reports of RV infarctions complicated by severe refractory hypoxemia secondary to right-to-left shunting through a patent foramen ovale. An additional case missed by transthoracic echocardiography and cardiac catheterization is reported and the English literature on the subject is reviewed.

Aged↗
PubMed1993

Computational structural analysis based on intravascular ultrasound imaging before in vitro angioplasty: prediction of plaque fracture locations.

OBJECTIVES: This in vitro study was designed to test the hypothesis that a structural analysis based on intravascular ultrasound images of atherosclerotic vessels obtained before angioplasty can be used to predict plaque fracture locations and balloon pressures required to cause fracture. BACKGROUND: Intravascular ultrasound imaging performed before interventional procedures has potential for providing information useful for guiding therapeutic strategies. METHODS: Intravascular imaging was performed on 16 atherosclerotic human iliac vessel segments obtained freshly at autopsy; balloon angioplasty was then performed with 1-min inflations at 2 atm, increasing in 2-atm increments until fracture of the lumen surface occurred. Fracture locations were confirmed by histopathologic examination. Structural analysis of these images was performed with a large strain finite element analysis of the image that calculated the distribution of stress in the vessel with 2 atm of lumen pressure. RESULTS: Structural analysis demonstrated a total of 30 high circumferential stress regions in the vessels (mean 1.9 high stress regions/vessel). A total of 18 plaque fractures occurred in the 16 vessel segments. Of the 17 fractures that occurred in the 15 specimens with regions of high circumferential stress, 14 (82%) occurred at a high stress region (p < 0.0001). However, there was no significant relation between the peak stresses estimated by structural analysis and the ultimate balloon inflation pressure required to cause fracture. CONCLUSIONS: Structural analysis based on intravascular ultrasound imaging performed before in vitro balloon angioplasty can predict the locations of plaque fracture that usually accompany angioplasty. However, these data suggest that intravascular ultrasound may not be useful for predicting the ultimate balloon inflation pressure necessary to cause fracture, possibly because of the variable fracture properties and microscopic structure of atherosclerotic tissues.

Angioplasty, Balloon↗
PubMed1991

S-nitrosocysteine inhibition of human platelet secretion is correlated with increases in platelet cGMP levels.

Platelet inhibition by exogenous and endogenous nitrovasodilators has been shown to be associated with increases in cGMP, but proof of a role for cGMP in this process is lacking. We therefore studied the effects of cGMP and guanylate cyclase stimulation on human platelet secretion by pharmacologically modulating intraplatelet cGMP levels. The endothelium-derived relaxing factor (EDRF)-like activator of guanylate cyclase, S-nitrosocysteine (SNOC), led to a dose-dependent inhibition of secretion in intact human platelets (IC50 = 10(-6) M). The cGMP phosphodiesterase inhibitor M&B 22,948 augmented SNOC-induced inhibition of secretion through elevations in cGMP without affecting cAMP levels (from 50% to 81% inhibition versus control, p = 0.02). Methylene blue reversed the inhibitory effects of SNOC on platelet secretion (p = 0.03). Dibutyryl-cGMP and 8-bromo-cGMP also significantly inhibited secretion in this system. Incubation of platelets with exogenous cGMP to achieve intraplatelet cGMP levels comparable to those after SNOC treatment resulted in similar degrees of inhibition of secretion (32% inhibition versus control, p = 0.01) and was also potentiated by M&B 22,948 (from 32% to 68% inhibition, p = 0.003). In addition, a highly significant correlation between intraplatelet cGMP levels and the degree of inhibition of secretion was demonstrable in these studies (r = 0.94, p = 0.016). These data demonstrate that elevation of intraplatelet cGMP levels by the EDRF-like compound SNOC is correlated with inhibition of human platelet secretion.

Blood Platelets↗