Marc A. Pfeffer

Bio: Marc A. Pfeffer is an academic researcher from Brigham and Women's Hospital. The author has contributed to research in topics: Heart failure & Myocardial infarction. The author has an hindex of 166, co-authored 765 publications receiving 133043 citations. Previous affiliations of Marc A. Pfeffer include Partners HealthCare & University of Miami.

Utilizing the integrated difference of two survival functions to quantify the treatment contrast for designing, monitoring, and analyzing a comparative clinical study.

Abstract: Background Consider a comparative, randomized clinical study with a specific event time as the primary end point. In the presence of censoring, standard methods of summarizing the treatment difference are based on Kaplan-Meier curves, the logrank test, and the point and interval estimates via Cox's procedure. Moreover, for designing and monitoring the study, one usually utilizes an event-driven scheme to determine the sample sizes and interim analysis time points. Purpose When the proportional hazards (PHs) assumption is violated, the logrank test may not have sufficient power to detect the difference between two event time distributions. The resulting hazard ratio estimate is difficult, if not impossible, to interpret as a treatment contrast. When the event rates are low, the corresponding interval estimate for the 'hazard ratio' can be quite large due to the fact that the interval length depends on the observed numbers of events. This may indicate that there is not enough information for making inferences about the treatment comparison even when there is no difference between two groups. This situation is quite common for a postmarketing safety study. We need an alternative way to quantify the group difference. Methods Instead of quantifying the treatment group difference using the hazard ratio, we consider an easily interpretable and model-free parameter, the integrated survival rate difference over a prespecified time interval, as an alternative. We present the inference procedures for such a treatment contrast. This approach is purely nonparametric and does not need any model assumption such as the PHs. Moreover, when we deal with equivalence or noninferiority studies and the event rates are low, our procedure would provide more information about the treatment difference. We used a cardiovascular trial data set to illustrate our approach. Results The results using the integrated event rate differences have a heuristic interpretation for the treatment difference even when the PHs assumption is not valid. When the event rates are low, for example, for the cardiovascular study discussed in this article, the procedure for the integrated event rate difference provides tight interval estimates in contrast to those based on the event-driven inference method. Limitations The design of a trial with the integrated event rate difference may be more complicated than that using the event-driven procedure. One may use simulation to determine the sample size and the estimated duration of the study. Conclusions The procedure discussed in this article can be a useful alternative to the standard PHs method in the survival analysis.

Alterations of cardiac performance in rats with established spontaneous hypertension

Abstract: To characterize intact cardiac performance during the progression from moderate to severe left ventricular hypertrophy, peak pumping ability, maximal pressure-generating capacity and passive pressure-volume relations were determined in ether-anesthetized 6 and 18 month old female spontaneously hypertensive rats, in 18 month old male spontaneously hypertensive rats and in sex- and age-matched normotensive rats. Ejection phase indexes of young female hypertensive rats were comparable with those of age-matched normotensive rats. Both groups ejected the same peak stroke volumes from similar end-diastolic volumes so that their indexes of ejection fraction were identical. However, in old female and male hypertensive rats, these characteristics of ventricular performance were greatly diminished. A reduced peak stroke volume was ejected from a normal end-diastolic volume in old female hypertensive rats and from a significantly larger end-diastolic volume in old male hypertensive rats, so that ejection fraction indexes were moderately and substantially reduced, respectively. Maximal pressure developed during an aortic occlusion was always significantly greater in hypertensive rats. Despite elevated systemic arterial blood pressures, young female hypertensive rats ejected a normal stroke volume from a normal end-diastolic volume. Even though the severity of hypertension did not further progress with age, cardiac mass increased, yet systolic function decreased in old hypertensive rats. Therefore, hypertrophic growth of the left ventricle in the hypertensive rat is associated with both a compensated and a depressed phase of cardiac performance.

Impact of candesartan on nonfatal myocardial infarction and cardiovascular death in patients with heart failure.

Abstract: ContextAngiotensin-converting enzyme (ACE) inhibitors reduce the risk of myocardial infarction (MI), but it is not known whether angiotensin receptor blockers have the same effect.ObjectiveTo assess the impact of the angiotensin receptor blocker candesartan on MI and other coronary events in patients with heart failure.Design, Setting, and ParticipantsThe Candesartan in Heart Failure: Assessment of Reduction in Mortality and Morbidity (CHARM) program, a randomized, placebo-controlled study enrolling patients (mean age, 66 [SD, 11] years) with New York Heart Association class II to IV symptoms who were randomly allocated to receive candesartan (target dose, 32 mg once daily) or matching placebo given in addition to optimal therapy for heart failure. Patients were enrolled from March 1999 through March 2001. Of 7599 patients allocated, 4004 (53%) had experienced a previous MI, and 1808 (24%) currently had angina. At baseline, 3125 (41%) were receiving an ACE inhibitor; 4203 (55%), a β-blocker; 3153 (42%), a lipid-lowering drug; 4246 (56%), aspirin; and 6286 (83%), a diuretic.Main Outcome MeasureThe primary outcome of the present analysis was the composite of cardiovascular death or nonfatal MI in patients with heart failure receiving candesartan or placebo.ResultsDuring the median follow-up of 37.7 months, the primary outcome of cardiovascular death or nonfatal MI was significantly reduced in the candesartan group (775 patients [20.4%]) vs the placebo group (868 [22.9%]) (hazard ratio [HR], 0.87; 95% confidence interval [CI], 0.79-0.96; P = .004; number needed to treat [NNT], 40). Nonfatal MI alone was also significantly reduced in the candesartan group (116 [3.1%]) vs the placebo group (148 [3.9%]) (HR, 0.77; 95% CI, 0.60-0.98; P = .03; NNT, 118). The secondary outcome of fatal MI, sudden death, or nonfatal MI was significantly reduced with candesartan (459 [12.1%]) vs placebo (522 [13.8%]) (HR, 0.86; 95% CI, 0.75-0.97; P = .02; NNT, 59). Risk reductions in cardiovascular death or nonfatal MI were similar across predetermined subgroups and the component CHARM trials. There was no impact on hospitalizations for unstable angina or coronary revascularization procedures with candesartan.ConclusionIn patients with heart failure, candesartan significantly reduces the risk of the composite outcome of cardiovascular death or nonfatal MI.

The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: the JNC 7 report.

Abstract: "The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure" provides a new guideline for hypertension prevention and management. The following are the key messages(1) In persons older than 50 years, systolic blood pressure (BP) of more than 140 mm Hg is a much more important cardiovascular disease (CVD) risk factor than diastolic BP; (2) The risk of CVD, beginning at 115/75 mm Hg, doubles with each increment of 20/10 mm Hg; individuals who are normotensive at 55 years of age have a 90% lifetime risk for developing hypertension; (3) Individuals with a systolic BP of 120 to 139 mm Hg or a diastolic BP of 80 to 89 mm Hg should be considered as prehypertensive and require health-promoting lifestyle modifications to prevent CVD; (4) Thiazide-type diuretics should be used in drug treatment for most patients with uncomplicated hypertension, either alone or combined with drugs from other classes. Certain high-risk conditions are compelling indications for the initial use of other antihypertensive drug classes (angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, β-blockers, calcium channel blockers); (5) Most patients with hypertension will require 2 or more antihypertensive medications to achieve goal BP (<140/90 mm Hg, or <130/80 mm Hg for patients with diabetes or chronic kidney disease); (6) If BP is more than 20/10 mm Hg above goal BP, consideration should be given to initiating therapy with 2 agents, 1 of which usually should be a thiazide-type diuretic; and (7) The most effective therapy prescribed by the most careful clinician will control hypertension only if patients are motivated. Motivation improves when patients have positive experiences with and trust in the clinician. Empathy builds trust and is a potent motivator. Finally, in presenting these guidelines, the committee recognizes that the responsible physician's judgment remains paramount.

Cochrane Handbook for Systematic Reviews of Interventions

Abstract: The Cochrane Handbook for Systematic Reviews of Interventions is the official document that describes in detail the process of preparing and maintaining Cochrane systematic reviews on the effects of healthcare interventions.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

A New Equation to Estimate Glomerular Filtration Rate

Abstract: The Modification of Diet in Renal Disease (MDRD) Study equation underestimates glomerular filtration rate (GFR) in patients with mild kidney disease. Levey and associates therefore developed and va...

Lifetime Prevalence and Age-of-Onset Distributions of DSM-IV Disorders in the National Comorbidity Survey Replication

Abstract: Context Little is known about lifetime prevalence or age of onset of DSM-IV disorders. Objective To estimate lifetime prevalence and age-of-onset distributions of DSM-IV disorders in the recently completed National Comorbidity Survey Replication. Design and Setting Nationally representative face-to-face household survey conducted between February 2001 and April 2003 using the fully structured World Health Organization World Mental Health Survey version of the Composite International Diagnostic Interview. Participants Nine thousand two hundred eighty-two English-speaking respondents aged 18 years and older. Main Outcome Measures Lifetime DSM-IV anxiety, mood, impulse-control, and substance use disorders. Results Lifetime prevalence estimates are as follows: anxiety disorders, 28.8%; mood disorders, 20.8%; impulse-control disorders, 24.8%; substance use disorders, 14.6%; any disorder, 46.4%. Median age of onset is much earlier for anxiety (11 years) and impulse-control (11 years) disorders than for substance use (20 years) and mood (30 years) disorders. Half of all lifetime cases start by age 14 years and three fourths by age 24 years. Later onsets are mostly of comorbid conditions, with estimated lifetime risk of any disorder at age 75 years (50.8%) only slightly higher than observed lifetime prevalence (46.4%). Lifetime prevalence estimates are higher in recent cohorts than in earlier cohorts and have fairly stable intercohort differences across the life course that vary in substantively plausible ways among sociodemographic subgroups. Conclusions About half of Americans will meet the criteria for a DSM-IV disorder sometime in their life, with first onset usually in childhood or adolescence. Interventions aimed at prevention or early treatment need to focus on youth.