Efficacy and safety of digoxin alone and in combination with low-dose diltiazem or betaxolol to control ventricular rate in chronic atrial fibrillation

A Comparison of Rate Control Agents for the Treatment of Atrial Fibrillation: Follow-Up Investigation of the AFFIRM Study

There are limited data from randomized controlled trials comparing rate control agents in atrial fibrillation. Patient-level data from the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) trial was used to compare outcomes in patients randomized to the rate control arm who were treated with a single rate control agent at baseline. The rate control agents used were beta-blockers, non-dihydropyridine calcium channel blockers, and digoxin. The independent variable for this analysis was the initial study drug used and the dependent variables were time to first hospitalization and time to death from any cause. We analyzed 1,144 out of 2,027 participants assigned to the rate control group who were on a single rate control agent at the start of the trial. There were 485 (42.5%) participants in the beta-blocker group, 344 (30%) in the calcium channel blocker group, and 315 (27.5%) in the digoxin group. All hospitalization and all-cause mortality occurred in 55.9% and 12.5% of those in the beta-blocker group, 58.4% and 16.7% in the calcium channel blocker group, and 55.2% and 21.1% in the digoxin group, respectively. After adjustment for differences in baseline characteristics, there were no significant differences in time to hospitalization or death for any group. In the AFFIRM trial, the initial rate control drug used was not associated with statistically significant differences in time to hospitalization or death after controlling for differences in baseline characteristics. There is limited data at present to guide the selection of rate control agents in patients with atrial fibrillation.

Advances in the management of atrial fibrillation with a special focus on non-pharmacological approaches to prevent thromboembolism: a review of current recommendations

Atrial fibrillation (AFIB) is the most common heart rhythm abnormality and is associated with significant morbidity and mortality. While the treatment of AFIB involves strategies of rate with or without rhythm control, it is also essential to strategize appropriate therapies to prevent thromboembolic complications arising from AFIB. Previously, anticoagulation was the main treatment option which exposed patients to higher than usual risk of bleeding. However, with the advent of new technology, novel therapeutic options aimed at surgical or percutaneous exclusion or occlusion of the left atrial appendage in preventing thromboembolic complications from AFIB have evolved. This review evaluates recent advances and therapeutic options in treating AFIB with a special focus on both surgical and percutaneous interventions which can reduce and/or eliminate thromboembolic complications of AFIB.

Digoxin for atrial fibrillation and atrial flutter: A systematic review with meta-analysis and trial sequential analysis of randomised clinical trials

Background

During recent years, systematic reviews of observational studies have compared digoxin to no digoxin in patients with atrial fibrillation or atrial flutter, and the results of these reviews suggested that digoxin seems to increase the risk of all-cause mortality regardless of concomitant heart failure. Our objective was to assess the benefits and harms of digoxin for atrial fibrillation and atrial flutter based on randomized clinical trials.

Methods

We searched CENTRAL, MEDLINE, Embase, LILACS, SCI-Expanded, BIOSIS for eligible trials comparing digoxin versus placebo, no intervention, or other medical interventions in patients with atrial fibrillation or atrial flutter in October 2016. Our primary outcomes were all-cause mortality, serious adverse events, and quality of life. Our secondary outcomes were heart failure, stroke, heart rate control, and conversion to sinus rhythm. We performed both random-effects and fixed-effect meta-analyses and chose the more conservative result as our primary result. We used Trial Sequential Analysis (TSA) to control for random errors. We used GRADE to assess the quality of the body of evidence.

Results

28 trials (n = 2223 participants) were included. All were at high risk of bias and reported only short-term follow-up. When digoxin was compared with all control interventions in one analysis, we found no evidence of a difference on all-cause mortality (risk ratio (RR), 0.82; TSA-adjusted confidence interval (CI), 0.02 to 31.2; I² = 0%); serious adverse events (RR, 1.65; TSA-adjusted CI, 0.24 to 11.5; I² = 0%); quality of life; heart failure (RR, 1.05; TSA-adjusted CI, 0.00 to 1141.8; I² = 51%); and stroke (RR, 2.27; TSA-adjusted CI, 0.00 to 7887.3; I² = 17%). Our analyses on acute heart rate control (within 6 hours of treatment onset) showed firm evidence of digoxin being superior compared with placebo (mean difference (MD), -12.0 beats per minute (bpm); TSA-adjusted CI, -17.2 to -6.76; I² = 0%) and inferior compared with beta blockers (MD, 20.7 bpm; TSA-adjusted CI, 14.2 to 27.2; I² = 0%). Meta-analyses on acute heart rate control showed that digoxin was inferior compared with both calcium antagonists (MD, 21.0 bpm; TSA-adjusted CI, -30.3 to 72.3) and with amiodarone (MD, 14.7 bpm; TSA-adjusted CI, -0.58 to 30.0; I² = 42%), but in both comparisons TSAs showed that we lacked information. Meta-analysis on acute conversion to sinus rhythm showed that digoxin compared with amiodarone reduced the probability of converting atrial fibrillation to sinus rhythm, but TSA showed that we lacked information (RR, 0.54; TSA-adjusted CI, 0.13 to 2.21; I² = 0%).

Conclusions

The clinical effects of digoxin on all-cause mortality, serious adverse events, quality of life, heart failure, and stroke are unclear based on current evidence. Digoxin seems to be superior compared with placebo in reducing the heart rate, but inferior compared with beta blockers. The long-term effect of digoxin is unclear, as no trials reported long-term follow-up. More trials at low risk of bias and low risk of random errors assessing the clinical effects of digoxin are needed.

Systematic review registration

PROSPERO CRD42016052935

A review of rate control in atrial fibrillation, and the rationale and protocol for the RATE-AF trial

BACKGROUND AND OBJECTIVE

Atrial fibrillation (AF) is common and causes impaired quality of life, an increased risk of stroke and death as well as frequent hospital admissions. The majority of patients with AF require control of heart rate. In this article , we summarise the limited evidence from clinical trials that guides prescription, and present the rationale and protocol for a new randomised trial. As rate control has not yet been shown to reduce mortality, there is a clear need to compare the impact of therapy on quality of life, cardiac function and exercise capacity. Such a trial should concentrate on the long-term effects of treatment in the largest proportion of patients with AF, those with symptomatic permanent AF, with the aim of improving patient well-being.

DESIGN AND INTERVENTION

The RAte control Therapy Evaluation in permanent Atrial Fibrillation (RATE-AF) trial will enrol 160 participants with a prospective, randomised, open-label, blinded end point design comparing initial rate control with digoxin or bisoprolol. This will be the first head-to-head randomised trial of digoxin and beta-blockers in AF.

PARTICIPANTS

Recruited patients will be aged ≥60 years with permanent AF and symptoms of breathlessness (equivalent to New York Heart Association class II or above), with few exclusion criteria to maximise generalisability to routine clinical practice.

OUTCOME MEASURES

The primary outcome is patient-reported quality of life, with secondary outcomes including echocardiographic ventricular function, exercise capacity and biomarkers of cellular and clinical response. Follow-up will occur at 6 and 12 months, with feasibility components to inform the design of a future trial powered to detect a difference in hospital admission. The RATE-AF trial will underpin an integrated approach to management including biomarkers, functions and symptoms that will guide future research into optimal, personalised rate control in patients with AF.

ETHICS AND DISSEMINATION

East Midlands-Derby Research Ethics Committee (16/EM/0178); peer-reviewed publications.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT02391337; ISRCTN: 95259705. Pre-results.

New-onset atrial fibrillation in critically ill patients

New-onset atrial fibrillation is a common problem in critically ill patients, with reported incidence ranging from 5% to 46%. It is associated with significant morbidity and mortality. The present review summarizes studies investigating new-onset atrial fibrillation conducted in the critical care setting, focusing on the etiology, management of the hemodynamically unstable patient, rate versus rhythm control, ischemic stroke risk and anticoagulation. Recommendations for an approach to management in the intensive care unit are drawn from the results of these studies.

Evidence for active regulation of pro-osteogenic signaling in advanced aortic valve disease

OBJECTIVE

To test the hypothesis that valvular calcium deposition, pro-osteogenic signaling, and function can be altered in mice with advanced aortic valve disease.

METHODS AND RESULTS

"Reversa" mice were given a Western-type diet for 12 months and screened for the presence of aortic valve stenosis. Mice with advanced valve disease were assigned to 1 of 2 groups: (1) those with continued progression for 2 months and (2) those with regression for 2 months, in which lipid lowering was accomplished by a genetic switch. Control mice were normocholesterolemic for 14 months. Mice with advanced valve disease had massive valvular calcification that was associated with increases in bone morphogenetic protein signaling, Wnt/β-catenin signaling, and markers of osteoblastlike cell differentiation. Remarkably, reducing plasma lipids with a genetic switch dramatically reduced markers of pro-osteogenic signaling and significantly reduced valvular calcium deposition. Nevertheless, despite a marked reduction in valvular calcium deposition, valve function remained markedly impaired. Phosphorylated Smad2 levels and myofibroblast activation (indexes of profibrotic signaling) remained elevated.

CONCLUSIONS

Molecular processes that contribute to valvular calcification and osteogenesis remain remarkably labile during the end stages of aortic valve stenosis. Although reductions in valvular calcium deposition were not sufficient to improve valvular function in the animals studied, these findings demonstrate that aortic valve calcification is a remarkably dynamic process that can be modified therapeutically, even in the presence of advanced aortic valve disease.

Rate Control in Atrial Fibrillation

Rate control may now be adopted as a first-choice therapy in a variety of patients, especially older relatively asymptomatic patients with hypertension or other underlying heart diseases. The goal of rate control therapy is to minimize symptoms, improve quality of life, decrease the risk of development of heart failure, and prevent thromboembolic complications. A lenient rate control approach may be the initial therapeutic strategy. If symptoms persist, a stricter rate control approach may be adopted. Although long-term randomized studies are lacking, the evidence available suggests that a β-blocker with or without digoxin is the first-choice rate control therapy.

Combination therapy with digoxin and diltiazem controls ventricular rate in chronic atrial fibrillation in dogs better than digoxin or diltiazem monotherapy: a randomized crossover study in 18 dogs

BACKGROUND

Atrial fibrillation (AF) with excessively high ventricular rates (VR) occurs in dogs with advanced heart disease. Rate control improves clinical signs in these patients. Optimal drug therapy and target VR remain poorly defined.

HYPOTHESIS

Digoxin-diltiazem combination therapy reduces VR more than either drug alone in dogs with high VR AF.

ANIMALS

Eighteen client-owned dogs (>15 kg) with advanced heart disease, AF, and average VR on 24-hour Holter > 140 beats per minute (bpm).

METHODS

After baseline Holter recording, dogs were randomized to digoxin or diltiazem monotherapy, or combination therapy. Repeat Holter evaluation was obtained after 2 weeks; dogs were then crossed over to the other arm (monotherapy or combination therapy) for 2 weeks and a third Holter was acquired. Twenty-four hour average VR, absolute and relative VR changes from baseline, and percent time spent within prespecified VR ranges (>140, 100-140, and <100 bpm) were compared. Correlations between serum drug concentrations and VR were examined.

RESULTS

Digoxin (median, 164 bpm) and diltiazem (median, 158 bpm) decreased VR from baseline (median, 194 bpm) less than the digoxin-diltiazem combination (median, 126 bpm) (P < .008 for each comparison). With digoxin-diltiazem, VR remained <140 bpm for 85% of the recording period, but remained >140 bpm for 88% of the recording period with either monotherapy. Serum drug concentrations did not correlate with VR.

CONCLUSIONS AND CLINICAL IMPORTANCE

At the dosages used in this study, digoxin-diltiazem combination therapy provided a greater rate control than either drug alone in dogs with AF.

Long-term management of atrial fibrillation

In the past decade, catheter ablation techniques and implantable devices have revolutionized the treatment of ventricular arrhythmias, junctional arrhythmias, and atrial flutter. For most patients presenting with atrial fibrillation (AF), the treatment available today is similar to that used a century ago, although nonpharmacologic strategies of therapy have begun to emerge for selected cases. There have been important recent advances in our understanding of the pathophysiology of AF and its complications, and it may be possible to improve patient management by refinement of the way in which current drugs are used.

Heart rate control in patients with atrial fibrillation referred for exercise testing

Clinical practice guidelines for patients with atrial fibrillation (AF) recommended a heart rate (HR) of 60 to 80 beats/min at rest and 90 to 115 at moderate exercise. The degree to which HR control at rest and with exercise in patients with AF complies with these recommendations is unknown. HR at rest and at peak exercise was retrospectively examined in 1,097 consecutive patients with AF referred for exercise myocardial perfusion imaging. In a subgroup of 195 patients, HR was also measured at an intermediate "moderate" level. Median HR at rest was 80 beats/min, at the upper end of the recommended range of 60 to 80. Only patients administered a beta blocker (BB; 31%) had lower (p <0.001) median HRs at rest. Median HR at moderate exercise was 128 beats/min, higher than the range of 90 to 115 recommended by the guidelines. Only patients administered a BB had significantly reduced HRs (p <0.003) at moderate exercise. Median peak exercise HR was 147 beats/min. Forty-five percent of patients exceeded their age-predicted maximal HR. Patients administered BBs were significantly less likely (p <0.01) to exceed their age-predicted maximal HR. In conclusion, in patients with AF, HR control at rest and during exercise often did not comply with guideline recommendations. Regimens including a BB were more effective in achieving HR control.

Mineral surface in calcified plaque is like that of bone: further evidence for regulated mineralization

OBJECTIVE

Cell biological studies demonstrate remarkable similarities between mineralization processes in bone and vasculature, but knowledge of the components acting to initiate mineralization in atherosclerosis is limited. The molecular level microenvironment at the organic-inorganic interface holds a record of the mechanisms controlling mineral nucleation. This study was undertaken to compare the poorly understood interface in mineralized plaque with that of bone, which is considerably better characterized.

METHODS AND RESULTS

Solid state nuclear magnetic resonance (SSNMR) spectroscopy provides powerful tools for studying the organic-inorganic interface in calcium phosphate biominerals. The rotational echo double resonance (REDOR) technique, applied to calcified human plaque, shows that this interface predominantly comprises sugars, most likely glycosaminoglycans (GAGs). In this respect, and in the pattern of secondary effects seen to protein (mainly collagen), calcified plaque strongly resembles bone.

CONCLUSIONS

The similarity between biomineral formed under highly controlled (bone) and pathological (plaque) conditions suggests that the control mechanisms are more similar than previously thought, and may be adaptive. It is strong further evidence for regulation of plaque mineralization by osteo/chondrocytic vascular smooth muscle cells.

Rate control in permanent atrial fibrillation

Guidelines on the use of digoxin are inconsistent with evidence from randomised trials

Digoxin and mortality in atrial fibrillation: a prospective cohort study

OBJECTIVE

The Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study showed that rhythm-control treatment of patients with atrial fibrillation (AF) offered no survival advantage over a rate-control strategy. In a subgroup analysis of that study, it was found that digoxin increased the death rate [relative risk (RR) = 1.42), but it was suggested that this may have been attributable to prescription of digoxin for patients at greater risk of death, such as those with congestive heart failure (CHF). No study has investigated a priori the effect of digoxin on mortality in patients with AF. This study aimed to address this question.

METHODS

Using data from the Registry of Information and Knowledge about Swedish Heart Intensive care Admissions (RIKS-HIA), we studied the 1-year mortality among patients admitted to coronary care units with AF, CHF, or AF+CHF with or without digoxin (n = 60,764) during 1995-2003. Adjustment for differences in background characteristics and other medications and treatments was made by propensity scoring.

RESULTS

Twenty percent of patients with AF without CHF in this cohort were discharged with digoxin. This group had a higher mortality rate than the corresponding group not given digoxin [adjusted RR 1.42 (95% CI 1.29-1.56)], whereas no such difference was seen among patients with CHF with or without AF, although these patients had a nearly three-times higher mortality.

CONCLUSION

The results suggest that long-term therapy with digoxin is an independent risk factor for death in patients with AF without CHF.

Mineralocorticoid Receptor Activation Promotes Vascular Cell Calcification

OBJECTIVE

Clinical studies demonstrate that mineralocorticoid receptor (MR) antagonism improves outcomes in cardiovascular patients and that vascular calcification correlates with adverse cardiac events. We have recently demonstrated that human vascular smooth muscle cells (VSMCs) express functional MRs that, in response to aldosterone, modulate expression of osteogenic genes including alkaline phosphatase (ALP) and bone morphogenetic protein-2 (BMP2). This study examines the effects of MR activation by aldosterone on the process of in vitro vascular calcification.

METHODS AND RESULTS

Using immunoblotting and adenoviral promoter-reporter assays, we demonstrated that calcifying vascular cells (CVCs), an in vitro model of vascular calcification, express MRs that mediate both aldosterone- and cortisol-stimulated gene transcription. In this model, aldosterone stimulated ALP activity, an early marker of osteoblastic differentiation, as well as mineralization. Aldosterone antagonism with spironolactone abolished both effects implicating CVC MRs in the mechanism of aldosterone-stimulated vascular calcification. Inhibition of BMP2 signaling by overexpression of dominant negative BMP2 receptor did not attenuate aldosterone-induced osteoblastic differentiation.

CONCLUSIONS

Aldosterone activation of MR promotes osteoblastic differentiation and mineralization of VSMCs independent of BMP2 signaling. These data provide a mechanistic link between hormone-mediated VSMC MR activation and vascular calcification, two processes associated with increased risk of cardiovascular ischemic events in humans.

Dexamethasone downregulates calcification-inhibitor molecules and accelerates osteogenic differentiation of vascular pericytes: implications for vascular calcification

Vascular calcification is present in many pathological conditions and is recognized as a strong predictor of future cardiovascular events. Current evidence suggests that it is a regulated process involving inducing and inhibitory molecules. Glucocorticoids have great clinical importance as antiinflammatory drugs and can act as potent inducers of osteogenic differentiation in vitro. The effect of glucocorticoids on vascular cells in vivo remains obscure. Pericytes are pluripotent cells that can differentiate into osteoblasts, and recent evidence suggests that they could participate in vascular calcification. We hypothesized that the synthetic glucocorticoid dexamethasone would enhance the rate of pericyte differentiation and mineralization in vitro with a concomitant suppression of calcification-inhibitory molecules. Three weeks of dexamethasone treatment induced a 2-fold increase in (1) alkaline phosphatase activity, (2) calcium deposition, and (3) the number of nodules formed in vitro; and a reduction in the expression of matrix Gla protein (MGP), osteopontin (OPN), and vascular calcification-associated factor (VCAF) mRNAs. The glucocorticoid receptor antagonist Org 34116 abolished dexamethasone-accelerated pericyte differentiation, nodule formation, and mineralization. Data obtained using Org 34116, the transcription inhibitor actinomycin D, and the protein synthesis inhibitor cyclohexamide suggest that MGP, OPN, and VCAF mRNA abundance are controlled at different and multiple levels by dexamethasone. This is the first report showing that dexamethasone enhances the osteogenic differentiation of pericytes and downregulates genes associated with inhibition of mineralization. Our study highlights the need for further investigation into the long-term consequences of prolonged glucocorticoid therapy on vascular calcification.

Arterial calcifications seen on mammograms: cardiovascular risk factors, pregnancy, and lactation

PURPOSE

To retrospectively assess if mammographic calcium deposits are related to coronary heart disease (CHD) risk factors and reproductive factors in a subset of women participating in the European Prospective Investigation into Cancer and Nutrition study.

MATERIALS AND METHODS

The study was approved by the institutional review board of the University Medical Center Utrecht; informed consent was obtained. Mammograms were evaluated by two radiologists for the presence of breast arterial calcifications (BAC) in the Prospect cohort, a breast cancer screening population of women aged 49-70 years (mean, 57 years) within the European Prospective Investigation into Cancer and Nutrition study. Cardiovascular risk factors and reproductive factors were examined for independent effects on the prevalence of BAC. Logistic regression analysis was performed.

RESULTS

BAC was present in 194 of 1699 (11%) women and increased with age to 20% in the highest quartile of age (mean, 66 years). The odds ratio was 4.7 in the highest versus the lowest quartile of age (95% confidence interval [CI], 2.9, 7.6). After adjustment for age, no significant association was found between BAC and traditional cardiovascular risk factors. Current smoking was inversely related to BAC (odds ratio, 0.6; 95% CI: 0.4, 0.9). BAC was prevalent in 2.5% of nulliparous women, in 9% of women with one or two children, and in 17% of women with three or more children (odds ratio, 7.2; 95% CI: 2.9, 18.0). Breast feeding after pregnancy was significantly associated with BAC in women who ever were pregnant (odds ratio, 2.2; 95% CI: 1.4, 3.6).

CONCLUSION

Calcifications in arteries on mammograms are associated with increasing age, pregnancy, and lactation but not with various cardiovascular risk factors.

The safety of digoxin as a pharmacological treatment of atrial fibrillation

Digoxin has traditionally been the drug of choice for ventricular rate control in patients with chronic atrial fibrillation (AF), with or without heart failure (HF) with systolic dysfunction. In patients with permanent AF, digoxin monotherapy is ineffective to control ventricular rate during exercise, but the combination of digoxin with a beta-blocker or a non-dihydropyridine calcium channel antagonist can control heart rate both at rest and during exercise. Only a few randomised, controlled studies have evaluated the adverse effects of digoxin in patients with AF in a systematic way and side effects requiring drug withdrawal have rarely been reported. When reported, the most frequent adverse effects were cardiac arrhythmias (ventricular arrhythmias, AV block of varying degrees and sinus pauses). This evidence suggested that, in contrast to other antiarrhythmic drugs, digoxin is a safe drug in patients with AF. However, this safety profile can be erroneous due to the short follow-up of the studies and patient selection. Because patients with HF have been excluded in most studies, the safety profile of digoxin in this population has not been directly addressed. Early recognition that an arrhythmia is related to digoxin intoxication as well as recognition of concomitant medications or medical conditions that may directly alter the pharmacokinetic profile of digoxin, or indirectly alter its cardiac effects by pharmacodynamic interactions remain essential for safe and effective use of digoxin in patients with AF.

Rate control in atrial fibrillation: looking beyond the average heart rate

PURPOSE OF REVIEW

The aim of this article is to provide a perspective on rate control in atrial fibrillation which emphasizes patient wellbeing (exercise tolerance, symptoms, quality of life) over attempts to reduce resting or exercise heart rate to an arbitrary range.

RECENT FINDINGS

Recent trials of rhythm versus rate control strategies of treatment in patients with atrial fibrillation suggest that rate control is a viable first line strategy in many patients. The adverse consequences of atrial fibrillation with rapid ventricular response are partly due to factors other than rate itself, such as irregularity of ventricular response, and variable changes in autonomic nervous system output. Digoxin, calcium channel blockers, and beta-blockers cause a similar reduction in resting heart rate. Beta blockers are the most potent at reducing exercise heart rate, followed by calcium channel blockers and digoxin. Exercise tolerance is occasionally improved by digoxin, sometimes improved by calcium channel blockers and not improved by (and sometimes decreased by) beta-blockers. Information about quality of life with different rate control regimens is sparse.

SUMMARY

Rate control in atrial fibrillation provides important benefits to patients in terms of symptoms, quality of life and prevention of late consequences of uncontrolled rate (such as tachycardia induced cardiomyopathy). Restricting treatment objectives to achievement of a specific heart rate range on resting or exercise electrocardiogram may result in lack of patient benefit or worsened symptoms. Understanding the nuances of rate control when treating individual patients and interpreting existing evidence allows patients to experience the most benefit from this treatment strategy.

Atrial Fibrillation

Our understanding of the pathophysiology and clinical consequences of atrial fibrillation has led to an evidence-based revolution in the management of atrial fibrillation over the last decade. As we improve in our ability to detect recurrent atrial fibrillation and treat it definitively, the patients who benefit from long-term anticoagulation may change. We can expect, however,that stroke prevention through systemic anticoagulation will be a cornerstone of atrial fibrillation management for decades to come. Innovations in anticoagulation therapy will make the use of these medications safer. Finally, as we further understand the underlying mechanisms of the development of atrial fibrillation, the pursuit of preventative therapy will be an investigational focus of great import.

Identification and characterization of vascular calcification-associated factor, a novel gene upregulated during vascular calcification in vitro and in vivo

OBJECTIVE

Vascular calcification, with its increasing clinical sequelae, presents an important and unresolved dilemma in cardiac and vascular practice. We aimed to identify molecules involved in this process to develop strategies for treatment or prevention.

METHODS AND RESULTS

Using subtractive hybridization, a novel cDNA, designated vascular calcification-associated factor (VCAF), has been isolated from a bovine retinal pericyte cDNA library generated during the differentiation and mineralization of these cells in vitro. RNA ligase-mediated rapid amplification of cDNA ends was used to compile the 740-bp bovine cDNA sequence. Database searching reveals that VCAF has novel nucleotide/amino acid sequences. RNA analysis confirms that VCAF is upregulated in mineralized pericytes and is present in human calcified arteries but not noncalcified arteries. Protein analysis using a VCAF antibody confirms the presence of an 18-kDa protein in calcified nodules but not in confluent pericytes. Adenoviral antisense VCAF gene delivery reduces VCAF protein levels and accelerates pericyte differentiation compared with controls.

CONCLUSIONS

We demonstrate the isolation of a novel gene, VCAF, which is upregulated during vascular calcification in vitro and in vivo. Antisense VCAF gene delivery accelerates pericyte differentiation, implicating a role for VCAF in this clinically significant pathological process.

Angiotensin II and aldosterone regulate gene transcription via functional mineralocortocoid receptors in human coronary artery smooth muscle cells

Inhibition or blockade of the angiotensin-aldosterone system consistently decreases ischemic cardiovascular events in clinical trials. The steroid hormone aldosterone acts by binding to the mineralocorticoid receptor (MR), a ligand activated transcription factor that is a member of the nuclear hormone receptor superfamily. MR binds and is activated by aldosterone and cortisol with equal affinity, but MR activation by cortisol is diminished in tissues that express the cortisol-inactivating enzyme 11-beta-hydroxysteroid-dehydrogenase-2 (11betaHSD2). Although previous studies support that the vasculature is a target tissue of aldosterone, MR-mediated gene expression in vascular cells has not been demonstrated or systematically explored. We investigated whether functional MR and 11betaHSD2 are expressed in human blood vessels. Human coronary and aortic vascular smooth muscle cells (VSMCs) express mRNA and protein for both MR and 11betaHSD2. The endogenous VSMC MR mediates aldosterone-dependent gene expression, which is blocked by the competitive MR antagonist spironolactone. Inhibition of 11betaHSD2 in coronary artery VSMCs enhances gene transactivation by cortisol, supporting that the VSMC 11betaHSD2 is functional. Angiotensin II also activates MR-mediated gene transcription in coronary artery VSMCs. Angiotensin II activation of MR-mediated gene expression is inhibited by both the AT1 receptor blocker losartan and by spironolactone, but not by aldosterone synthase inhibition. Microarray and quantitative RT-PCR experiments show that aldosterone activates expression of endogenous human coronary VSMC genes, including several involved in vascular fibrosis, inflammation, and calcification. These data support a new MR-dependent mechanism by which aldosterone and angiotensin II influence ischemic cardiovascular events, and suggest that ACE inhibitors and MR antagonists may decrease clinical ischemic events by inhibiting MR-dependent gene expression in vascular cells.

Impact of informed consent requirements on cardiac arrest research in the United States: exception from consent or from research?

INTRODUCTION

Research in patients with life-threatening illness such as cardiac arrest is challenging since they can not consent. The Food and Drug Administration addressed research under emergency conditions by publishing new criteria for exception from informed consent in 1996. We systematically reviewed randomized trials over a 10-year period to assess the impact of these regulations.

METHODS

Case-control study of published trials for cardiac arrest (cases) and atrial fibrillation (controls.) Studies were identified by using structured searches of MEDLINE and EMBASE from 1992 to 2002. Included were studies using random allocation in humans with cardiac arrest or atrial fibrillation prior to enrollment. Excluded were duplicate publications. Number of American trials, foreign trials and proportion of trials of American origin were compared by using regression analysis. Changes in cardiac arrest versus atrial fibrillation trials were calculated as risk differences.

RESULTS

Of 4982 identified cardiac arrest studies, 57 (1.1%) were randomized trials. The number of American cardiac arrest trials decreased by 15% (95% CI: 8, 22%) annually (P = 0.05). The proportion of cardiac arrest trials of American origin decreased by 16% (95% CI: 10, 22%) annually (P = 0.006). Of 5596 identified atrial fibrillation studies, 197 trials (3.5%) were randomized trials. The risk difference between cardiac arrest versus atrial fibrillation trials being of American origin decreased significantly (annual difference -5.8% (95% CI: -10, -0.1%), P = 0.03).

INTERPRETATION

Fewer American cardiac arrest trials were published during the last decade, when federal consent requirements changed. Regulatory requirements for clinical trials may inhibit improvements in care and threaten public health.

Use of beta-blockers in atrial fibrillation

Atrial fibrillation is the most common arrhythmia in the general population and is frequently associated with organic heart disease. beta-adrenoceptor antagonists (b-blockers) are very effective in preventing atrial fibrillation after coronary artery bypass surgery. It has been shown recently that the beta-blocker metoprolol controlled release/extended release (CR/XL) is also effective in maintaining sinus rhythm after conversion of atrial fibrillation. There is concern that class I antiarrhythmic drugs, such as quinidine, disopyramide, and flecainide in particular, may increase mortality. The risk of proarrhythmia associated with beta-blocker treatment is very low. Therefore b-blockers, such as metoprolol CR/XL, may be the first line of treatment to maintain sinus rhythm, especially after myocardial infarction and in patients with chronic heart failure and in those with arterial hypertension. In patients with persistent atrial fibrillation, AV-nodal conduction-slowing drugs, such as calcium channel antagonists and beta-blockers are used to control the ventricular rate during atrial fibrillation. Several studies clearly show that beta-blockers alone, or in combination with digoxin are very effective in controlling the ventricular rate at rest and during exercise. beta-blockers are effective in maintaining sinus rhythm and controlling the ventricular rate during atrial fibrillation. Given these effects and their favorable effects on mortality, beta-blockers should be considered as first-line agents in the management of patients with atrial fibrillation.

The Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study

OBJECTIVES

We sought to evaluate approaches used to control rate, the effectiveness of rate control, and switches from one drug class to another in the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study.

BACKGROUND

The AFFIRM study showed that atrial fibrillation (AF) can be treated effectively with rate control and anticoagulation, but drug efficacy to control rate remains uncertain.

METHODS

Patients (n = 2,027) randomized to rate control in the AFFIRM study were given rate-controlling drugs by their treating physicians. Standardized rate-control efficacy criteria developed a priori included resting heart rate and 6-min walk tests and/or ambulatory electrocardiographic results.

RESULTS

Average follow-up was 3.5 +/- 1.3 years. Initial treatment included a beta-adrenergic blocker (beta-blocker) alone in 24%, a calcium channel blocker alone in 17%, digoxin alone in 16%, a beta-blocker and digoxin in 14%, or a calcium channel blocker and digoxin in 14% of patients. Overall rate control was achieved in 70% of patients given beta-blockers as the first drug (with or without digoxin), 54% with calcium channel blockers (with or without digoxin), and 58% with digoxin alone. Adequate overall rate control was achieved in 58% of patients with the first drug or combination. Multivariate analysis revealed an association between first drug class and several clinical variables. There were more changes to beta-blockers than to the other two-drug classes (p < 0.0001).

CONCLUSIONS

Rate control in AF is possible in the majority of patients with AF. Beta-blockers were the most effective drugs. To achieve the goal of adequate rate control in all patients, frequent medication changes and drug combinations were needed.

Pharmacological rate control of atrial fibrillation

To control ventricular rate in patients with AF, physicians should seek to control heart rate at rest and with exertion. The goal has to be achieved while minimizing costs and adverse effects. For emergency use, i.v. diltiazem or esmolol are drugs useful because of their rapid onset of action. They have to be used with caution in patients with concomitant left ventricular failure symptoms, however. For most patients with AF, chronic control of the ventricular rate can be achieved with one drug. For the chronic control of ventricular rate in patients with AF and normal ventricular function, diltiazem, atenolol, are metoprolol are probably the drugs of choice. For patients with AF and structurally abnormal hearts, atenolol, metoprolol, or carvedilol are appropriate choices. Adequate ventricular rate control by pharmacological agents should be evaluated by either 24-hour Holter monitoring or a submaximal stress test to determine the resting and exercise ventricular rate. If the mean ventricular rate is not close to 80 beats per minute, or the heart rate on moderate exertion is not between 90 to 115 beats per minute, a second agent to control the rate should be added. Excessive reductions in ventricular rates that could limit exercise tolerance should be avoided.

Advanced coronary and carotid arteriopathy in young adults with childhood-onset chronic renal failure

BACKGROUND

Cardiovascular mortality is excessive in young adults with end-stage renal disease (ESRD). The factors contributing to ESRD-related vascular disease are incompletely understood. Young adults with childhood-onset chronic renal failure (CRF) are uniquely suited for risk factor assessment because of their long-term exposure at an age when vascular pathology in the general population is still minimal.

METHODS AND RESULTS

We used novel noninvasive technologies to screen for coronary and carotid artery disease in 39 patients with ESRD aged 19 to 39 years with childhood-onset CRF presently treated by dialysis or renal transplantation. Coronary artery calcification burden was assessed by CT scan with ECG gating and the intima-media thickness (IMT) of the carotid arteries by high-resolution ultrasound. Coronary artery calcifications were present in 92% of patients; calcium scores exceeded the 95th age- and sex-specific percentiles >10-fold on average. Carotid IMT was significantly increased compared with matched control subjects. Both coronary calcium scores and IMT were associated with cumulative dialysis and ESRD time and the cumulative serum calcium-phosphate product. Coronary calcium scores were strongly correlated with C-reactive protein and Chlamydia pneumoniae seropositivity, time-averaged mean serum parathyroid hormone, and plasma homocysteine. C-reactive protein and parathyroid hormone independently predicted coronary calcium accumulation. Smoking, obesity, and HbA1c were correlated with IMT in the control subjects but not in the patients.

CONCLUSIONS

Young adults with childhood-onset CRF have a high prevalence of arteriopathy associated with indicators of microinflammation, hyperparathyroidism, calcium-phosphate overload, and hyperhomocysteinemia but not traditional atherogenic risk factors. These risk factors persist even after successful renal transplantation.

Calcium deposition with or without bone formation in the lung

Pulmonary calcification and ossification occurs with a number of systemic and pulmonary conditions. Specific symptoms are often lacking, but calcification may be a marker of disease severity and its chronicity. Pathophysiologic states predisposing to pulmonary calcification and ossification include hypercalcemia, a local alkaline environment, and previous lung injury. Factors such as enhanced alkaline phosphatase activity, active angiogenesis, and mitogenic effects of growth factors may also contribute. The clinical classification of pulmonary calcification includes both metastatic calcification, in which calcium deposits in previously normal lung or dystrophic calcification, which occurs in previously injured lung. Pulmonary ossification can be idiopathic or can result from a variety of underlying pulmonary, cardiac, or extracardiopulmonary disorders. The diagnosis of pulmonary calcification and ossification requires various imaging techniques, including chest radiography, computed tomographic scanning, and bone scintigraphy. Interpretation of the presence of and the specific pattern of calcification or ossification may obviate the need for invasive biopsy. In this review, specific conditions causing pulmonary calcification or ossification that may impact diagnostic and treatment decisions are highlighted. These include metastatic calcification caused by chronic renal failure and orthotopic liver transplantation, dystrophic calcification caused by granulomatous disorders, DNA viruses, parasitic infections, pulmonary amyloidosis, vascular calcification, the idiopathic disorder pulmonary alveolar microlithiasis, and various forms of pulmonary ossification.

Inappropriate use of digoxin in older hospitalized heart failure patients

BACKGROUND

Older adults are more likely to suffer from the adverse effects of digoxin. Studies have described the inappropriate use of digoxin in various populations. The objective of this study was to determine the correlates of inappropriate digoxin use in older heart failure patients.

METHODS

We studied older hospitalized heart failure patients with documented left ventricular (LV) function evaluation and electrocardiography. Digoxin use was considered inappropriate if patients had preserved LV systolic function (ejection fraction greater > or =40%) or if they had no atrial fibrillation (AF). We compared baseline patient characteristics by indication for digoxin and tested statistical significance using Pearson's chi-square analysis and Student's t tests. Using logistic regression, we determined the correlates of inappropriate use and initiation of digoxin.

RESULTS

Subjects (N = 603) had a mean age of 79 (+/-7) years; 59% were women, and 18% were African American. A total of 376 patients (62%) were discharged on digoxin, and 223 (37%) had no indication for its use. Half of the patients without an indication for digoxin received the drug. Of 132 patients without an indication and not already on digoxin, 38 (29%) were initiated on it. After adjustment for various patient and care characteristics, prior digoxin use (adjusted odds ratio [OR] 11.47, 95% confidence interval [CI] 5.72-23.02) and pulse > or =100/min (adjusted OR 2.33, 95% CI 1.10-4.94) were associated with inappropriate digoxin use. Pulse > or =100/min was also associated with inappropriate initiation of the drug (adjusted OR 2.95, 95% CI 1.28-6.78).

CONCLUSIONS

Inappropriate use of digoxin was common and was associated with prior use. Tachycardia was associated with inappropriate use and initiation. Electrocardiography and echocardiography should be performed in all older heart failure patients. Digoxin therapy should not be initiated or continued in patients without any evidence of LV systolic dysfunction or chronic AF.

Smooth muscle cell phenotypic transition associated with calcification: upregulation of Cbfa1 and downregulation of smooth muscle lineage markers

Bovine aortic smooth muscle cell (BASMC) cultures undergo mineralization on addition of the organic phosphate donor, beta-glycerophosphate (betaGP). Mineralization is characterized by apatite deposition on collagen fibrils and the presence of matrix vesicles, as has been described in calcified vascular lesions in vivo as well as in bone and teeth. In the present study, we used this model to investigate the molecular mechanisms driving vascular calcification. We found that BASMCs lost their lineage markers, SM22alpha and smooth muscle alpha-actin, within 10 days of being placed under calcifying conditions. Conversely, the cells gained an osteogenic phenotype as indicated by an increase in expression and DNA-binding activity of the transcription factor, core binding factor alpha1 (Cbfa1). Moreover, genes containing the Cbfa1 binding site, OSE2, including osteopontin, osteocalcin, and alkaline phosphatase were elevated. The relevance of these in vitro findings to vascular calcification in vivo was further studied in matrix GLA protein null (MGP(-/-)) mice whose arteries spontaneously calcify. We found that arterial calcification was associated with a similar loss in smooth muscle markers and a gain of osteopontin and Cbfa1 expression. These data demonstrate a novel association of vascular calcification with smooth muscle cell phenotypic transition, in which several osteogenic proteins including osteopontin, osteocalcin, and the bone determining factor Cbfa1 are gained. The findings suggest a positive role for SMCs in promoting vascular calcification.

Differential expression of bone matrix regulatory proteins in human atherosclerotic plaques

In the present study, we examined the expression of regulators of bone formation and osteoclastogenesis in human atherosclerosis because accumulating evidence suggests that atherosclerotic calcification shares features with bone calcification. The most striking finding of this study was the constitutive immunoreactivity of matrix Gla protein, osteocalcin, and bone sialoprotein in nondiseased aortas and the absence of bone morphogenetic protein (BMP)-2, BMP-4, osteopontin, and osteonectin in nondiseased aortas and early atherosclerotic lesions. When atherosclerotic plaques demonstrated calcification or bone formation, BMP-2, BMP-4, osteopontin, and osteonectin were upregulated. Interestingly, this upregulation was associated with a sustained immunoreactivity of matrix Gla protein, osteocalcin, and bone sialoprotein. The 2 modulators of osteoclastogenesis (osteoprotegerin [OPG] and its ligand, OPGL) were present in the nondiseased vessel wall and in early atherosclerotic lesions. In advanced calcified lesions, OPG was present in bone structures, whereas OPGL was only present in the extracellular matrix surrounding calcium deposits. The observed expression patterns suggest a tight regulation of the expression of bone matrix regulatory proteins during human atherogenesis. The expression pattern of both OPG and OPGL during atherogenesis might suggest a regulatory role of these proteins not only in osteoclastogenesis but also in atherosclerotic calcification.

Bone formation and inflammation in cardiac valves

BACKGROUND

For nearly a century, the mechanical failure of calcified heart valves was attributed to a passive degenerative process. Recently, several case reports described bone formation in surgically excised heart valves and suggested an unexpected process of tissue repair.

METHODS AND RESULTS

We studied the prevalence and pathology of heterotopic ossification in 347 surgically excised heart valves (256 aortic, 91 mitral) in 324 consecutive patients (182 men, 142 women; mean age 68 years) who underwent cardiac valve replacement surgery between 1994 and 1998. The valves were examined microscopically to determine the prevalence and features of bone formation and remodeling. Two hundred eighty-eight valves (83%) had dystrophic calcification. Mature lamellar bone with hematopoietic elements and active bone remodeling were present in 36 valves (13%) with dystrophic calcification. Endochondral bone formation, similar to that seen in normal fracture repair, was identified in 4 valves. Microfractures were present in 92% of all valves with ossification. Neoangiogenesis was found in all valves with ossification. Bone morphogenetic proteins 2 and 4 (BMP 2/4), potent osteogenic morphogens, were expressed by myofibroblasts and preosteoblasts in areas adjacent to B- and T-lymphocyte infiltration in valves where ossification was identified. Mast cells were present in calcified and ossified valves and were especially prominent in atheromatous regions.

CONCLUSIONS

Heterotopic ossification consisting of mature lamellar bone formation and active bone remodeling is a relatively common and unexpected finding in end-stage valvular heart disease and may be associated with repair of pathological microfractures in calcified cardiac valves.

Management of patients with syncope and cardiac arrhythmias in an emergency department observation unit

Syncope is an ideal condition for the emergency observation setting because of its difficulty in diagnosis, many causes, high liability, and variable diagnostic approaches. Hospital admissions can be averted with appropriate patient selection for a short-term observation period. Atrial fibrillation is a common presenting condition in the emergency department. With aggressive management, the appropriately selected patient can have restoration of sinus rhythm and be safely discharged home.

Dexamethasone enhances In vitro vascular calcification by promoting osteoblastic differentiation of vascular smooth muscle cells

Vascular calcification is often associated with atherosclerotic lesions. Moreover, the process of atherosclerotic calcification has several features similar to the mineralization of skeletal tissue. Therefore, we hypothesized that vascular smooth muscle cells might acquire osteoblastic characteristics during the development of atherosclerotic lesions. In the present study, we investigated the effect of dexamethasone (Dex), which is well known to be a potent stimulator of osteoblastic differentiation in vitro, on vascular calcification by using an in vitro calcification model. We demonstrated that Dex increased bovine vascular smooth muscle cell (BVSMC) calcification in a dose- and time-dependent manner. Dex also enhanced several phenotypic markers of osteoblasts, such as alkaline phosphatase activity, procollagen type I carboxy-terminal peptide production, and cAMP responses to parathyroid hormone in BVSMCs. We also examined the effects of Dex on human osteoblast-like (Saos-2) cells and compared its effects on BVSMCs and Saos-2 cells. The effects of Dex on alkaline phosphatase activity and the cAMP response to parathyroid hormone in BVSMCs were less prominent than those in Saos-2 cells. Interestingly, we detected that Osf2/Cbfa1, a key transcription factor in osteoblastic differentiation, was expressed in both BVSMCs and Saos-2 cells and that Dex increased the gene expression of both transcription factors. These findings suggest that Dex may enhance osteoblastic differentiation of BVSMCs in vitro.

Effect of betaxolol on the hemodynamic, gas exchange, and cardiac output response to exercise in chronic atrial fibrillation

BACKGROUND

beta-blockade controls the ventricular response to exercise in chronic atrial fibrillation (AF), but the effects of beta-blockers on exercise capacity in AF have been debated.

METHODS

Twelve men with AF (65+/-8 years) participated in a randomized, double-blind, placebo-controlled study of betaxolol (20 mg daily). Patients underwent maximal exercise testing with ventilatory gas exchange analysis, and a separate, submaximal test (50% of maximum) during which cardiac output was measured by a CO2 rebreathing technique.

RESULTS

After betaxolol therapy, heart rate was reduced both at rest (92+/-27 vs 62+/-12 beats/min; p < 0.001) and at peak exercise (173+/-22 vs 116+/-24 beats/min; p < 0.001). Maximal oxygen uptake (VO2) was reduced by 19% after betaxolol (21.8+/-5.3 with placebo vs 17.6+/-5.1 mL/kg/min with betaxolol; p < 0.05), with similar reductions observed for maximal exercise time, minute ventilation, and CO2 production. VO2 was reduced by a similar extent (19%) at the ventilatory threshold. Submaximal cardiac output was reduced by 15% during betaxolol therapy (12.9+/-2.3 vs 10.9+/-1.3 L/min; p < 0.05), and stroke volume was higher (88.0+/-21 vs 105.6+/-19 mL/beat; p < 0.05).

CONCLUSION

Betaxolol therapy in patients with AF effectively controlled the ventricular rate at rest and during exercise, but also caused considerable reductions in maximal VO2 and cardiac output during exercise. The observed increase in stroke volume could not adequately compensate for reduced heart rate to maintain VO2 during exercise.

Treatment strategies for atrial fibrillation

Atrial fibrillation is the most common arrhythmia observed in clinical practice, occurring in 0.4% of the general population and in up to 4% of people greater than 60 years old. It is often associated with other cardiovascular disorders, such as hypertension, coronary artery disease, or cardiomyopathy. Critical evaluation and management of patients with atrial fibrillation requires knowledge of etiology, prognosis, and treatment options of this arrhythmia. On initial presentation, emergency electrical cardioversion should be performed if the patient is hemodynamically unstable. If the patient is stable, initial rate control is recommended, using atrioventricular nodal blocking agents. Further treatment mainly depends upon the duration of the episode. Patients who are in atrial fibrillation <48 hours can be safely cardioverted. Patients who are in atrial fibrillation for >48 hours are commonly anticoagulated for 3 to 4 weeks before and after cardioversion because of the risk of thromboembolism formation in the left atrial appendage. An alternate strategy, which is especially attractive when immediate cardioversion is desired, is transesophageal echocardiography to exclude left atrial thrombus followed by prompt cardioversion. After cardioversion, sinus rhythm can be maintained with class I and III drugs, such as flecainide and propafenone or amiodarone and sotalol. New treatment options, such as atrial defibrillation, atrioventricular junctional ablation, or modification of atrial pacing to prevent atrial fibrillation, are currently under investigation. Although atrial fibrillation is so common in clinical practice, it still remains difficult to treat. Conversion and maintenance to sinus rhythm with antiarrhythmic drug therapy has not shown any improvement in mortality, and some patients may benefit more from ventricular rate control. This review article discusses different treatment strategies for patients with atrial fibrillation.