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2.
J Appl Physiol (1985) ; 112(6): 1001-7, 2012 Mar.
Article in English | MEDLINE | ID: mdl-22223455

ABSTRACT

Premenopausal women have a lower risk of cardiovascular disease (CVD) compared with men of a similar age. Furthermore, the regulation of factors that influence CVD appears to differ between the sexes, including control of the autonomic nervous system (ANS) and the renin-angiotensin system. We examined the cardiac ANS response to angiotensin II (Ang II) challenge in healthy subjects to determine whether differences in women and men exist. Thirty-six healthy subjects (21 women, 15 men, age 38 ± 2 years) were studied in a high-salt balance. Heart-rate variability (HRV) was calculated by spectral power analysis [low-frequency (LF) sympathetic modulation, high-frequency (HF) parasympathetic/vagal modulation, and LF:HF as a measure of overall ANS balance]. HRV was assessed at baseline and in response to graded Ang II infusions (3 ng·kg(-1)·min(-1) × 30 min; 6 ng·kg(-1)·min(-1) × 30 min). Cardiac ANS tone did not change significantly in women after each Ang II dose [3 ng·kg(-1)·min(-1) mean change (Δ)LF:HF (mean ± SE) 0.5 ± 0.3, P = 0.8, vs. baseline; 6 ng·kg(-1)·min(-1) ΔLF:HF (mean ± SE) 0.5 ± 0.4, P = 0.4, vs. baseline], whereas men exhibited an unfavorable shift in overall cardiac ANS activity in response to Ang II (ΔLF:HF 2.6 ± 0.2, P = 0.01, vs. baseline; P = 0.02 vs. female response). This imbalance in sympathovagal tone appeared to be largely driven by a withdrawal in cardioprotective vagal activity in response to Ang II challenge [ΔHF normalized units (nu), -5.8 ± 2.9, P = 0.01, vs. baseline; P = 0.006 vs. women] rather than an increase in sympathetic activity (ΔLF nu, -4.5 ± 5.7, P = 0.3, vs. baseline; P = 0.5 vs. women). Premenopausal women maintain cardiac ANS tone in response to Ang II challenge, whereas similarly aged men exhibit an unfavorable shift in cardiovagal activity. Understanding the role of gender in ANS modulation may help guide risk-reduction strategies in high-risk CVD populations.


Subject(s)
Angiotensin II/pharmacology , Autonomic Nervous System/drug effects , Autonomic Nervous System/physiology , Heart/drug effects , Heart/physiology , Renin-Angiotensin System/drug effects , Renin-Angiotensin System/physiology , Adult , Cardiovascular Diseases/physiopathology , Female , Heart Rate/drug effects , Heart Rate/physiology , Hemodynamics/drug effects , Hemodynamics/physiology , Humans , Male , Multivariate Analysis , Regression Analysis , Sex Factors , Vagus Nerve/drug effects , Vagus Nerve/physiology
3.
Circulation ; 104(13): 1489-93, 2001 Sep 25.
Article in English | MEDLINE | ID: mdl-11571241

ABSTRACT

BACKGROUND: Patients with ischemic LV dysfunction are at high risk of sudden death. However, no benefit from prophylactic defibrillator therapy was observed in a group of patients with LV dysfunction undergoing CABG (CABG Patch trial). Thus, the effect of CABG on future risk of sudden death in patients with LV dysfunction is of considerable interest. METHODS AND RESULTS: Mortality and modes of death in 5410 patients with ischemic LV dysfunction who were enrolled in the Studies of Left Ventricular Dysfunction (SOLVD) trials were evaluated. Outcomes of patients with (n=1870, 35%) versus without (n=3540) history of prior CABG were compared, and stratification by baseline ejection fraction (EF) values (<0.25, 0.25 to 0.30, and >0.30) was performed. Prior CABG was associated with a 25% (95% CI, 15% to 36%) reduction in risk of death and a 46% (95% CI, 30% to 58%) reduction in risk of sudden death independent of EF and severity of heart failure symptoms. As baseline EF declined, absolute reduction in risk of sudden death with prior CABG increased (P<0.01). No alteration in risk of death from progressive heart failure was observed with prior CABG. When these results were applied to a group of patients with LV dysfunction who had not undergone prior surgery (Coronary Artery Surgery Study Registry) predicted annual rates of death (8.2%) and sudden death (2.4%) were similar to those observed in the CABG Patch trial (7.9% and 2.3%, respectively). CONCLUSIONS: In patients with ischemic LV dysfunction, prior CABG is associated with a significant independent reduction in mortality. These results appear to account for the lack of benefit from defibrillator therapy in the CABG Patch trial.


Subject(s)
Coronary Artery Bypass , Myocardial Ischemia/mortality , Risk Assessment/statistics & numerical data , Ventricular Dysfunction, Left/mortality , Adult , Aged , Aged, 80 and over , Death, Sudden, Cardiac/etiology , Female , Humans , Male , Middle Aged , Myocardial Ischemia/complications , Preoperative Care , Ventricular Dysfunction, Left/complications
5.
Pacing Clin Electrophysiol ; 24(4 Pt 1): 526-34, 2001 Apr.
Article in English | MEDLINE | ID: mdl-11341097

ABSTRACT

This article contains the results of an attempt by appointed members of the North American Society of Pacing and Electrophysiology to define the research frontier in electrophysiology and suggest areas of study as an aid in setting the research agenda.


Subject(s)
Arrhythmias, Cardiac/physiopathology , Defibrillators, Implantable , Electrocardiography , Electrophysiology , Pacemaker, Artificial , Arrhythmias, Cardiac/diagnosis , Arrhythmias, Cardiac/therapy , Humans , Research
6.
N Engl J Med ; 344(18): 1351-7, 2001 May 03.
Article in English | MEDLINE | ID: mdl-11333991

ABSTRACT

BACKGROUND: Black patients with heart failure have a poorer prognosis than white patients, a difference that has not been adequately explained. Whether racial differences in the response to drug treatment contribute to differences in outcome is unclear. To address this issue, we pooled and analyzed data from the Studies of Left Ventricular Dysfunction (SOLVD) prevention and treatment trials, two large, randomized trials comparing enalapril with placebo in patients with left ventricular dysfunction. METHODS: We used a matched-cohort design in which up to four white patients were matched with each black patient according to trial, treatment assignment, sex, left ventricular ejection fraction, and age. A total of 1196 white patients (580 from the prevention trial and 616 from the treatment trial) were matched with 800 black patients (404 from the prevention trial and 396 from the treatment trial). The average duration of follow-up was 35 months in the prevention trial and 33 months in the treatment trial. RESULTS: The black patients and the matched white patients had similar demographic and clinical characteristics, but the black patients had higher rates of death from any cause (12.2 vs. 9.7 per 100 person-years) and of hospitalization for heart failure (13.2 vs. 7.7 per 100 person-years). Despite similar doses of drug in the two groups, enalapril therapy, as compared with placebo, was associated with a 44 percent reduction (95 percent confidence interval, 27 to 57 percent) in the risk of hospitalization for heart failure among the white patients (P<0.001) but with no significant reduction among black patients (P=0.74). At one year, enalapril therapy was associated with significant reductions from base line in systolic blood pressure (by a mean [+/-SD] of 5.0+/-17.1 mm Hg) and diastolic blood pressure (3.6+/-10.6 mm Hg) among the white patients, but not among the black patients. No significant change in the risk of death was observed in association with enalapril therapy in either group. CONCLUSIONS: Enalapril therapy is associated with a significant reduction in the risk of hospitalization for heart failure among white patients with left ventricular dysfunction, but not among similar black patients. This finding underscores the need for additional research on the efficacy of therapies for heart failure in black patients.


Subject(s)
Angiotensin-Converting Enzyme Inhibitors/therapeutic use , Black People , Enalapril/therapeutic use , Heart Failure/drug therapy , Heart Failure/ethnology , Ventricular Dysfunction, Left/drug therapy , White People , Adult , Aged , Cohort Studies , Female , Heart Failure/prevention & control , Hospitalization/statistics & numerical data , Humans , Male , Middle Aged , Mortality , Randomized Controlled Trials as Topic , Stroke Volume , Treatment Outcome , Ventricular Dysfunction, Left/ethnology , Ventricular Dysfunction, Left/prevention & control
7.
Circulation ; 103(16): 2066-71, 2001 Apr 24.
Article in English | MEDLINE | ID: mdl-11319196

ABSTRACT

BACKGROUND: Electrical storm, multiple temporally related episodes of ventricular tachycardia (VT) or ventricular fibrillation (VF), is a frequent problem among recipients of implantable cardioverter defibrillators (ICDs). However, insufficient data exist regarding its prognostic significance. METHODS AND RESULTS: This analysis includes 457 patients who received an ICD in the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial and who were followed for 31 +/- 13 months. Electrical storm was defined as > or = 3 separate episodes of VT/VF within 24 hours. Characteristics and survival of patients surviving electrical storm (n = 90), those with VT/VF unrelated to electrical storm (n = 184), and the remaining patients (n = 183) were compared. The 3 groups differed in terms of ejection fraction, index arrhythmia, revascularization status, and baseline medication use. Survival was evaluated using time-dependent Cox modeling. Electrical storm occurred 9.2 +/- 11.5 months after ICD implantation, and most episodes (86%) were due to VT. Electrical storm was a significant risk factor for subsequent death, independent of ejection fraction and other prognostic variables (relative risk [RR], 2.4; 95% confidence interval [CI], 1.3 to 4.2; P = 0.003), but VT/VF unrelated to electrical storm was not (RR, 1.0; 95% CI, 0.6 to 1.7; P = 0.9). The risk of death was greatest 3 months after electrical storm (RR, 5.4; 95% Cl, 2.4 to 12.3; P = 0.0001) and diminished beyond this time (RR, 1.9; 95% CI, 1.0 to 3.6; P=0.04). CONCLUSIONS: Electrical storm is an important, independent marker for subsequent death among ICD recipients, particularly in the first 3 months after its occurrence. However, the development of VT/VF unrelated to electrical storm does not seem to be associated with an increased risk of subsequent death.


Subject(s)
Anti-Arrhythmia Agents , Defibrillators, Implantable , Tachycardia, Ventricular/mortality , Ventricular Fibrillation/mortality , Aged , Anti-Arrhythmia Agents/therapeutic use , Cardiac Pacing, Artificial , Clinical Trials as Topic/statistics & numerical data , Defibrillators, Implantable/statistics & numerical data , Electric Countershock , Female , Follow-Up Studies , Humans , Male , Middle Aged , Multivariate Analysis , Prognosis , Proportional Hazards Models , Risk Assessment , Risk Factors , Survival Rate , Tachycardia, Ventricular/diagnosis , Tachycardia, Ventricular/therapy , Ventricular Fibrillation/diagnosis , Ventricular Fibrillation/therapy
8.
Am Heart J ; 141(1): 99-104, 2001 Jan.
Article in English | MEDLINE | ID: mdl-11136493

ABSTRACT

OBJECTIVE: Our purpose was to evaluate whether baseline characteristics predictive of implantable cardioverter defibrillator (ICD) efficacy in the Canadian Implantable Defibrillator Study (CIDS) are predictive in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial. BACKGROUND: ICD therapy is superior to antiarrhythmic drug use in patients with life-threatening arrhythmias. However, identification of subgroups most likely to benefit from ICD therapy may be useful. Data from CIDS suggest that 3 characteristics (age > or =70 years, ejection fraction [EF] < or =0.35, and New York Heart Association class >II) can be combined to reliably categorize patients as likely (> or =2 characteristics) versus unlikely to benefit (<2 characteristics) from ICD therapy. METHODS: The utility of the CIDS categorization of ICD efficacy was assessed by Kaplan-Meier analysis and Cox hazards modeling. The accuracy of the CIDS score was formally tested by evaluating for interaction between categorization of benefit and treatment in a Cox model. RESULTS: ICD therapy was associated with a significantly lower risk of death in the 320 patients categorized as likely to benefit (relative risk [RR] 0.57, 95% confidence interval [CI] 0.37-0.88, P =.01) and a trend toward a lower risk of death in the 689 patients categorized as unlikely to benefit (RR 0.70, 95% CI 0.48-1.03, P =.07). Categorization of benefit was imperfect, as evidenced by a lack of statistical interaction (P =.5). Although 32 of the 42 deaths prevented by ICD therapy in AVID were in patients categorized as likely to benefit, all 42 of these patients had EF values < or =0.35. Neither advanced age nor poorer functional class predicted ICD efficacy in AVID. CONCLUSION: Of the 3 characteristics identified to predict ICD efficacy in CIDS, only depressed EF predicted ICD efficacy in AVID. Thus physicians faced with limited resources might elect to consider ICD therapy over antiarrhythmic drug use in patients with severely depressed EF values.


Subject(s)
Anti-Arrhythmia Agents/therapeutic use , Arrhythmias, Cardiac/mortality , Arrhythmias, Cardiac/therapy , Defibrillators, Implantable , Patient Selection , Aged , Female , Forecasting , Humans , Male , Middle Aged , Reproducibility of Results , Survival Rate
9.
Expert Opin Investig Drugs ; 9(2): 415-28, 2000 Feb.
Article in English | MEDLINE | ID: mdl-11060685

ABSTRACT

beta-Blockers have emerged as an important therapy in patients with symptomatic left ventricular systolic dysfunction. Early studies demonstrated that beta-blocker therapy improved left ventricular function, reduced neurohumoral activity and reduced heart failure symptoms in these patients. While none of these small studies demonstrated a significant benefit in terms of overall survival, several meta-analyses suggested that beta-blocker therapy could, in fact, reduce mortality in patients with left ventricular systolic dysfunction and mild to moderate heart failure symptoms (New York Heart Association class II or III). Three large, recently completed, trials have confirmed the benefit of beta-blockade in these patients. This report reviews some of the initial clinical studies of beta-blockade in heart failure, examines the findings of the three large multicentre trials and other relevant research. Finally, ongoing trials designed to assess the relative efficacy of different beta-blockers and evaluate the utility of beta-blockade in specific subsets of patients with heart failure are discussed.


Subject(s)
Adrenergic beta-Antagonists/therapeutic use , Heart Failure/drug therapy , Ventricular Dysfunction, Left/drug therapy , Clinical Trials as Topic , Humans
10.
J Am Coll Cardiol ; 35(7): 1753-9, 2000 Jun.
Article in English | MEDLINE | ID: mdl-10841221

ABSTRACT

OBJECTIVES: The study evaluated the relationship between light-to-moderate alcohol consumption and prognosis in patients with left ventricular (LV) systolic dysfunction. BACKGROUND: Although chronic consumption of large amounts of alcohol can lead to cardiomyopathy, the effects of light-to-moderate alcohol consumption in patients with LV dysfunction are unknown. METHODS: The relationship between light-to-moderate alcohol consumption and prognosis was assessed in participants in the Studies of Left Ventricular Dysfunction (SOLVD), all of whom had ejection fraction values < or = 0.35. Baseline characteristics and event rates of patients who consumed 1 to 14 drinks per week (light-to-moderate drinkers, n = 2,594) were compared with those of patients who reported no alcohol consumption (nondrinkers, n = 3,719). The association between light-to-moderate alcohol consumption and prognosis was evaluated using Cox proportional hazards analysis, controlling for baseline differences and important covariates. RESULTS: Mortality rates were lower among light-to-moderate drinkers than among nondrinkers (7.2 vs. 9.4 deaths/100 person-years, p < 0.001). Among patients with ischemic LV dysfunction, light-to-moderate alcohol consumption was independently associated with a reduced risk of all-cause mortality (RR [relative risk] 0.85, p = 0.01), particularly for death from myocardial infarction (RR 0.55, p < 0.001). The risks of cardiovascular death, death from progressive heart failure, arrhythmic death, and hospitalization for heart failure were similar for light-to-moderate drinkers and nondrinkers in this group. Among patients with nonischemic LV dysfunction, light-to-moderate alcohol consumption had no significant effect on mortality (RR 0.93, p = 0.5). CONCLUSIONS: Light-to-moderate alcohol consumption is not associated with an adverse prognosis in patients with LV systolic dysfunction, and it may reduce the risk of fatal myocardial infarction in patients with ischemic LV dysfunction.


Subject(s)
Alcohol Drinking , Ventricular Dysfunction, Left/mortality , Cause of Death , Female , Humans , Male , Middle Aged , Prognosis , Retrospective Studies
11.
J Interv Card Electrophysiol ; 4(1): 231-9, 2000 Apr.
Article in English | MEDLINE | ID: mdl-10729839

ABSTRACT

Prior clinical research indicates that conduction slowing is the primary mechanism leading to the spontaneous termination of reentrant tachycardia in humans. Yet, some experimental models indicate that cycle length oscillations and enhanced conduction are important prerequisites. The role of oscillations in conduction times and enhanced conduction in the spontaneous termination of human reentrant tachycardia has not been adequately investigated. The electrophysiologic features preceding the spontaneous termination of orthodromic atrioventricular (AV) reciprocating tachycardia (RT) were evaluated in 21 patients, each of whom had a sustained (>60 seconds) and a spontaneously terminating (>/=10 beats and

Subject(s)
Heart Conduction System/physiopathology , Tachycardia, Atrioventricular Nodal Reentry/physiopathology , Tachycardia, Paroxysmal/physiopathology , Adult , Aged , Electrocardiography , Female , Humans , Male , Middle Aged
12.
J Am Coll Cardiol ; 35(3): 681-9, 2000 Mar 01.
Article in English | MEDLINE | ID: mdl-10716471

ABSTRACT

OBJECTIVES: The present analysis examines the prognostic implications of moderate renal insufficiency in patients with asymptomatic and symptomatic left ventricular systolic dysfunction. BACKGROUND: Chronic elevations in intracardiac filling pressures may lead to progressive ventricular dilation and heart failure progression. The ability to maintain fluid balance and prevent increased intracardiac filling pressures is critically dependent on the adequacy of renal function. METHODS: This is a retrospective analysis of the Studies of Left Ventricular Dysfunction (SOLVD) Trials, in which moderate renal insufficiency is defined as a baseline creatinine clearance <60 ml/min, as estimated from the Cockroft-Gault equation. RESULTS: In the SOLVD Prevention Trial, multivariate analyses demonstrated moderate renal insufficiency to be associated with an increased risk for all-cause mortality (Relative Risk [RR] 1.41; p = 0.001), largely explained by an increased risk for pump-failure death (RR 1.68; p = 0.007) and the combined end point death or hospitalization for heart failure (RR 1.33; p = 0.001). Likewise, in the Treatment Trial, multivariate analyses demonstrated moderate renal insufficiency to be associated with an increased risk for all-cause mortality (RR 1.41; p = 0.001), also largely explained by an increased risk for pump-failure death (RR 1.49; p = 0.007) and the combined end point death or hospitalization for heart failure (RR 1.45; p = 0.001). CONCLUSIONS: Even moderate degrees of renal insufficiency are independently associated with an increased risk for all-cause mortality in patients with heart failure, largely explained by an increased risk of heart failure progression. These data suggest that, rather than simply being a marker of the severity of underlying disease, the adequacy of renal function may be a primary determinant of compensation in patients with heart failure, and therapy capable of improving renal function may delay disease progression.


Subject(s)
Renal Insufficiency/etiology , Ventricular Dysfunction, Left/complications , Aged , Angiotensin-Converting Enzyme Inhibitors/therapeutic use , Cause of Death , Creatinine/metabolism , Disease Progression , Enalapril/therapeutic use , Female , Heart Failure/mortality , Heart Failure/physiopathology , Heart Failure/prevention & control , Humans , Male , Middle Aged , Prognosis , Renal Insufficiency/metabolism , Risk Factors , Stroke Volume , Survival Rate , Ventricular Dysfunction, Left/drug therapy , Ventricular Dysfunction, Left/physiopathology
13.
Congest Heart Fail ; 6(4): 215-219, 2000.
Article in English | MEDLINE | ID: mdl-12147955

ABSTRACT

ACE inhibitors are standard therapy for treating both symptomatic and asymptomatic patients with left ventricular dysfunction. However, recent clinical trials have shown that beta blockers further reduce mortality in patients with symptomatic heart failure treated with ACE inhibitors. However, the evidence in support of adding beta blockers to ACE inhibitor therapy in patients with asymptomatic left ventricular dysfunction is less certain. The mechanisms by which ACE inhibitors and beta blockers may exert benefit in patients with heart failure are discussed, and studies assessing the association of beta blockade with outcome in patients with mild heart failure receiving ACE inhibitor therapy are reviewed. (c)2000 by CHF, Inc.

14.
Am J Cardiol ; 84(3): 252-7, 1999 Aug 01.
Article in English | MEDLINE | ID: mdl-10496431

ABSTRACT

We conducted a retrospective analysis of the Studies Of Left Ventricular Dysfunction (SOLVD) trials to assess the predictive value of the baseline white blood cell (WBC) count on mortality. Mortality was higher in participants with a baseline WBC count >7,000 compared to those with a baseline WBC < or =7,000 (27% vs 21%, p <0.0001). After controlling for important covariates, each increase in WBC count of 1,000/mm3 was significantly associated with an increased risk of all-cause mortality (relative risk [RR] 1.05, p <0.001). Overall, compared with a baseline WBC count < or =7,000, a baseline WBC count >7,000 was significantly associated with an increased risk of all-cause mortality (RR 1.22, p = 0.001). In participants with ischemic left ventricular (LV) dysfunction, a WBC count >7,000 remained significantly associated with an increased risk of all-cause mortality (RR 1.26, p <0.001), whereas in participants with nonischemic LV dysfunction there was no relation between WBC count and mortality (RR 1.08, p = 0.5). Thus, baseline WBC is an independent predictor of mortality in patients with LV dysfunction, specifically in those with ischemic cardiomyopathy.


Subject(s)
Leukocyte Count , Myocardial Ischemia/complications , Ventricular Dysfunction, Left/blood , Ventricular Dysfunction, Left/mortality , Aged , Analysis of Variance , Female , Humans , Male , Middle Aged , Myocardial Ischemia/blood , Myocardial Ischemia/mortality , Retrospective Studies , Risk , Risk Factors , Ventricular Dysfunction, Left/etiology
15.
Am J Cardiol ; 84(3): 299-303, 1999 Aug 01.
Article in English | MEDLINE | ID: mdl-10496439

ABSTRACT

Left ventricular (LV) systolic dysfunction, as indicated by a reduced LV ejection fraction (EF) is a potent predictor of cardiovascular mortality. Radionuclide angiography accurately and reproducibly assesses LVEF; however, echocardiography is used more frequently in clinical practice. Whether these methods predict similar mortality has not been fully investigated. We performed a retrospective analysis of patients with baseline radionuclide angiographic (RNA; n = 4,330) and echocardiographic (echo; n = 1,376) based EFs < or =0.35 who were enrolled in the Studies Of Left Ventricular Dysfunction (SOLVD) to address this hypothesis. After adjusting for important prognostic variables, the risk of death (RR 1.15; 95% confidence interval 1.01 to 1.30; p = 0.03) and of cardiovascular death (RR 1.15; 95% confidence interval 1.01 to 1.32; p = 0.04) was higher for patients with ECG-based EFs. To compare the 2 techniques across a range of EF values, we divided the cohort into tertiles of EF. The adjusted risk estimates for all-cause and cardiovascular mortality were similar within each tertile. Of note, the mortality difference in patients with echo- versus RNA-based EFs was most prominent in women. Further, patients with echo-based EFs had significantly higher mortality at sites where this technique was less frequently used to assess the EF. Thus, for a given EF < or =0.35, an echo-based value was associated with a higher risk of death compared with the RNA-based method of measurement. These data suggest that EF values determined by echocardiography and radionuclide angiography predict different mortality and this may, in part, be related to technical proficiency as well as patient characteristics.


Subject(s)
Echocardiography , Radionuclide Ventriculography , Ventricular Dysfunction, Left/diagnostic imaging , Ventricular Dysfunction, Left/mortality , Adult , Aged , Aged, 80 and over , Cause of Death , Female , Humans , Male , Middle Aged , Predictive Value of Tests , Retrospective Studies , Risk , Stroke Volume , Ventricular Dysfunction, Left/physiopathology
16.
J Am Coll Cardiol ; 34(2): 325-33, 1999 Aug.
Article in English | MEDLINE | ID: mdl-10440140

ABSTRACT

OBJECTIVES: To evaluate whether use of beta-adrenergic blocking agents, alone or in combination with specific antiarrhythmic therapy, is associated with improved survival in persons with ventricular fibrillation (VF) or symptomatic ventricular tachycardia (VT). BACKGROUND: The ability of beta-blockers to alter the mortality of patients with VF or VT receiving contemporary medical management is not well defined. METHODS: Survival of 1,016 randomized and 2,101 eligible, nonrandomized patients with VF or symptomatic VT followed in the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial through December 31, 1996 was assessed using Cox proportional hazards analysis. RESULTS: The 817 (28%) patients discharged from hospital receiving beta-blockers had less ventricular dysfunction, fewer symptoms of heart failure and a different pattern of medication use compared with patients not receiving beta-blockers. Before adjustment for important prognostic variables, beta-blockade was not significantly associated with survival in randomized or in eligible, nonrandomized patients treated with specific antiarrhythmic therapy. After adjustment, beta-blockade remained unrelated to survival in randomized or in eligible, nonrandomized patients treated with amiodarone alone (n = 1142; adjusted relative risk [RR] = 0.96; 95% confidence interval [CI] 0.64-1.45; p = 0.85) or a defibrillator alone (n = 1347; adjusted RR = 0.88; 95% CI 0.55 to 1.40; p = 0.58). In contrast, beta-blockade was independently associated with improved survival in eligible, nonrandomized patients who were not treated with specific antiarrhythmic therapy (n = 412; adjusted RR = 0.47; 95% CI 0.25 to 0.88; p = 0.018). CONCLUSIONS: Beta-blocker use was independently associated with improved survival in patients with VF or symptomatic VT who were not treated with specific antiarrhythmic therapy, but a protective effect was not prominent in patients already receiving amiodarone or a defibrillator.


Subject(s)
Adrenergic beta-Antagonists/therapeutic use , Defibrillators, Implantable , Tachycardia, Ventricular/therapy , Ventricular Fibrillation/therapy , Aged , Amiodarone/therapeutic use , Anti-Arrhythmia Agents/therapeutic use , Combined Modality Therapy , Female , Humans , Male , Middle Aged , Risk Factors , Survival Rate , Tachycardia, Ventricular/drug therapy , Tachycardia, Ventricular/mortality , Ventricular Fibrillation/drug therapy , Ventricular Fibrillation/mortality
17.
Control Clin Trials ; 20(4): 319-27, 1999 Aug.
Article in English | MEDLINE | ID: mdl-10440559

ABSTRACT

Lack of concealment of allocation in randomized clinical trials can invite selection bias, which is the preferential enrollment of specific patients into one treatment group over another. For example, patients more likely to respond may be enrolled only when the next treatment to be assigned is known to be the active treatment, and patients less likely to respond may be enrolled only when the next treatment to be assigned is known to be the control. Despite the fact that selection bias can compromise both the internal and external validity of trials, little methodology has been developed for its detection. An investigator may test the success of the randomization by comparing baseline characteristics across treatment groups, but such test is limited by the potential inability of the measured baseline variables to predict response. A new method for detecting selections bias, based on response data only, is developed for the case in which a small block size, and either unmasking of treatment codes or an open-label design, have compromised the concealment of allocation. This new method complements baseline comparisons, and is sensitive to detect selection bias even in situations in which baseline comparisons are not.


Subject(s)
Randomized Controlled Trials as Topic/statistics & numerical data , Selection Bias , Computer Simulation , Data Collection/statistics & numerical data , Humans , Reproducibility of Results
18.
J Cardiovasc Pharmacol ; 34(1): 1-6, 1999 Jul.
Article in English | MEDLINE | ID: mdl-10413059

ABSTRACT

In vitro studies indicate that nitric oxide synthase (NOS) inhibitors alter sinus node automaticity. Moreover, whereas the systemic delivery of N(G)-monomethyl-L-arginine (L-NMMA), a NOS inhibitor, results in sinus bradycardia and arterial hypertension, its intracoronary administration has little effect on sinus heart rate. Therefore whether L-NMMA directly alters sinus node function in humans is not known. By using a crossover design, we evaluated the effect of intracoronary L-NMMA (20 micromol/min x 10 min) on corrected sinus node recovery time (CSNRT), heart rate, mean arterial blood pressure, electrocardiographic intervals, and coronary artery blood flow in nine men and 13 women aged 48+/-12 years. All were in sinus rhythm and had normal baseline CSNRTs. Baseline measurements were made during a dextrose infusion, and then L-NMMA was administered, and these parameters remeasured. In 11 patients, the infusions were near the origin of the sinus node artery (Concordant), whereas in the remaining 11, they were into the opposite coronary circulation (Discordant). After L-NMMA, significant prolongations in CSNRT were seen in Concordant (p < 0.001) and Discordant patients (p < 0.05), but were most pronounced in the Concordant group (p < 0.05). Although a significant reduction in coronary artery blood flow and nonsignificant changes in blood pressure and heart rate were observed after L-NMMA, these changes were not related to changes in CSNRT (r2 < or = 0.2; p > or = 0.2). These data support the notion that NO is a modifier of human sinus node automaticity.


Subject(s)
Electrocardiography/drug effects , Enzyme Inhibitors/pharmacology , Nitric Oxide Synthase/antagonists & inhibitors , Sinoatrial Node/drug effects , omega-N-Methylarginine/administration & dosage , omega-N-Methylarginine/pharmacology , Blood Pressure/drug effects , Coronary Vessels , Cross-Over Studies , Female , Heart Rate/drug effects , Humans , Infusions, Intra-Arterial , Male , Middle Aged
19.
J Am Coll Cardiol ; 33(4): 916-23, 1999 Mar 15.
Article in English | MEDLINE | ID: mdl-10091816

ABSTRACT

OBJECTIVES: This analysis was performed to assess whether beta-adrenergic blocking agent use is associated with reduced mortality in the Studies of Left Ventricular Dysfunction (SOLVD) and to determine if this relationship is altered by angiotensin-converting enzyme (ACE) inhibitor use. BACKGROUND: The ability of beta-blockers to alter mortality in patients with asymptomatic left ventricular dysfunction is not well defined. Furthermore, the effect of beta-blocker use, in addition to an ACE inhibitor, on these patients has not been fully addressed. METHODS: This retrospective analysis evaluated the association of baseline beta-blocker use with mortality in 4,223 mostly asymptomatic Prevention trial patients, and 2,567 symptomatic Treatment trial patients. RESULTS: The 1,015 (24%) Prevention trial patients and 197 (8%) Treatment trial patients receiving beta-blockers had fewer symptoms, higher ejection fractions and different use of medications than patients not receiving beta-blockers. On univariate analysis, beta-blocker use was associated with significantly lower mortality than nonuse in both trials. Moreover, a synergistic reduction in mortality with use of both a beta-blocker and enalapril was suggested in the Prevention trial. After adjusting for important prognostic variables with Cox multivariate analysis, the association of beta-adrenergic blocking agent use with reduced mortality remained significant for Prevention trial patients receiving enalapril. Lower rates of arrhythmic and pump failure death and risk of death or hospitalization for heart failure were observed. CONCLUSIONS: The combination of a beta-blocker and enalapril was associated with a synergistic reduction in the risk of death in the SOLVD Prevention trial.


Subject(s)
Adrenergic beta-Antagonists/therapeutic use , Systole/drug effects , Ventricular Dysfunction, Left/drug therapy , Adrenergic beta-Antagonists/adverse effects , Adult , Aged , Angiotensin-Converting Enzyme Inhibitors/adverse effects , Angiotensin-Converting Enzyme Inhibitors/therapeutic use , Cause of Death , Drug Therapy, Combination , Enalapril/adverse effects , Enalapril/therapeutic use , Female , Hemodynamics/drug effects , Humans , Male , Middle Aged , Retrospective Studies , Survival Rate , Ventricular Dysfunction, Left/diagnosis , Ventricular Dysfunction, Left/mortality , Ventricular Function, Left/drug effects
20.
J Am Coll Cardiol ; 33(4): 951-8, 1999 Mar 15.
Article in English | MEDLINE | ID: mdl-10091821

ABSTRACT

OBJECTIVES: The purpose of this study was to evaluate the relationship of baseline pulse pressure and mean arterial pressure to mortality in patients with left ventricular dysfunction. BACKGROUND: Increased conduit vessel stiffness increases pulse pressure and pulsatile load, potentially contributing to adverse outcomes in patients with left ventricular dysfunction. METHODS: Pulse and mean arterial pressure were analyzed for their effect on mortality, adjusting for other modifiers of risk, using Cox proportional hazards regression analysis of data collected from 6,781 patients randomized into the Studies of Left Ventricular Dysfunction trials. RESULTS: Pulse and mean arterial pressure were related positively to each other, age, ejection fraction and prevalence of diabetes and hypertension and inversely to prior myocardial infarction and beta-adrenergic blocking agent use. Higher pulse pressure was associated with increased prevalence of female gender, greater calcium channel blocking agent, digoxin and diuretic use, lower heart rate and a higher rate of reported smoking history. Higher mean arterial pressure was associated with higher heart rate, lower calcium channel blocker and digoxin use and lower New York Heart Association functional class. Over a 61-month follow-up 1,582 deaths (1,397 cardiovascular) occurred. In a multivariate analysis adjusting for the above covariates and treatment assignment, higher pulse pressure remained an independent predictor of total and cardiovascular mortality (total mortality relative risk, 1.05 per 10 mm Hg increment; 95% confidence interval, 1.01 to 1.10; p = 0.02). Mean arterial pressure was inversely related to total and cardiovascular mortality (total mortality relative risk, 0.89; 95% confidence interval, 0.85 to 0.94; p <0.0001). CONCLUSIONS: One noninvasive blood pressure measurement provides two independent prognostic factors for survival. Increased conduit vessel stiffness, as assessed by pulse pressure, may contribute to increased mortality in patients with left ventricular dysfunction, independent of mean arterial pressure.


Subject(s)
Blood Pressure/drug effects , Sphygmomanometers , Ventricular Dysfunction, Left/diagnosis , Adult , Aged , Angiotensin-Converting Enzyme Inhibitors/therapeutic use , Double-Blind Method , Enalapril/therapeutic use , Female , Humans , Male , Middle Aged , Myocardial Contraction/drug effects , Prognosis , Pulsatile Flow/drug effects , Survival Rate , Ventricular Dysfunction, Left/drug therapy , Ventricular Dysfunction, Left/mortality , Ventricular Function, Left/drug effects
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