Use of irbesartan to maintain sinus rhythm in patients with long-lasting persistent atrial fibrillation: a prospective and randomized study

Renin-angiotensin system component expression in the HL-1 atrial cell line and in a pig model of atrial fibrillation

OBJECTIVES

Local atrial tissue angiotensin II (AngII) level is elevated in atrial fibrillation (AF), but the mechanism is unknown. We hypothesized that atrial myocytes express all components of the renin-angiotensin system (RAS) and investigated whether rapid depolarization alone is sufficient to increase paracrine AngII production by up-regulating RAS component expression.

METHODS

In the HL-1 atrial cell line, rapid depolarization was induced by rapid field electrical stimulation (RES) at 1.0 V/cm and 600/min (10 Hz) in atrial HL-1 cells. In a pig model of AF, AF was induced by atrial pacing at 600/min in 10 adult pigs and 10 sham-operated pigs for comparison.

RESULTS

In atrial myocytes, RES induced a sustained elevation of intracellular calcium, and up-regulation of angiotensin-converting enzyme (ACE), chymase and angiotensinogen, resulting in increased AngII production. RES-induced AngII production was attenuated by enalapril [ACE inhibitor (ACEI)] and chymostatin (chymase inhibitor). Conditioned medium from RES-stimulated atrial myocytes increased [3H]leucine uptake and atrial natriuretic peptide expression in atrial myocytes, and [3H]proline uptake and collagen type 1 alpha 1 expression in atrial fibroblasts. Both were attenuated by co-incubation with the AngII type 1 receptor blocker (ARB) losartan. In the porcine model, significant structural changes and a similar pattern of changes of RAS components were noted in AF pigs.

CONCLUSIONS

Atrial cells expressed all components of RAS and rapid depolarization alone was sufficient to up-regulate RAS components, increase paracrine AngII production and induce atrial structural changes, which are attenuated by ACEI, ARB and chymase inhibitor.

The renin-angiotensin-aldosterone system (RAAS) and cardiac arrhythmias

The role of the renin-angiotensin-aldosterone system (RAAS) in many cardiovascular disorders, including hypertension, cardiac hypertrophy, and atherosclerosis, is well established, whereas its relationship with cardiac arrhythmias is a new area of investigation. Atrial fibrillation and malignant ventricular tachyarrhythmias, especially in the setting of cardiac hypertrophy or failure, seem to be examples of RAAS-related arrhythmias because treatment with RAAS modulators, including angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and mineralocorticoid receptor blockers, reduces the incidence of these arrhythmias. RAAS has a multitude of electrophysiological effects and can potentially cause arrhythmia through a variety of mechanisms. We review new experimental results that suggest that RAAS has proarrhythmic effects on membrane and sarcoplasmic reticulum ion channels and that increased oxidative stress is likely contributing to the increased arrhythmic incidence. A summary of ongoing clinical trials that will address the clinical usefulness of RAAS modulators for prevention or treatment of arrhythmias is presented.

Non-antiarrhythmic medications for atrial fibrillation: from bench to clinical practice

Many treatment modalities have been developed over the years for the management of atrial fibrillation (AF). While they are still considered the first line of treatment for suppression of AF, antiarrhythmics often lead to treatment failure, complications and undesired consequences. Pulmonary vein ablation is an invasive procedure which is not always curative. Recently, there have been a variety of studies reporting the potential antiarrhythmic effects of various nonantiarrhythmic agents. This paper aims to provide a comprehensive review of the findings reported thus far about the antiarrhythmic effects of agents which are not antiarrhythmic drugs themselves, but which have been found to offer promise in the prevention and treatment of AF.

Atrial fibrillation and morbidity and mortality in a cohort of long-term hemodialysis patients

BACKGROUND

Atrial fibrillation is associated with increased mortality and hospitalization in the general population. Data about mortality, morbidity, and hospitalization in hemodialysis patients with atrial fibrillation are limited.

SETTING & PARTICIPANTS

All patients (n = 476) in 5 dialysis centers in Lombardia, Italy, as of June 2003 were enrolled and followed up until June 2006 (median age, 69 years; median hemodialysis duration, 45.2 months; and median follow-up, 36 months). 127 patients had atrial fibrillation at enrollment.

PREDICTORS & OUTCOME

A Cox model was used to relate: (1) atrial fibrillation, age, hemodialysis therapy duration, and comorbid conditions to all-cause and cardiovascular mortality; (2) angiotensin-converting enzyme (ACE)-inhibitor treatment and comorbid conditions to new onset of atrial fibrillation; and (3) atrial fibrillation and comorbid conditions on hospitalization.

RESULTS

There were 167 deaths (39.5% from cardiovascular disease). In multivariable models, atrial fibrillation was independently associated with increased mortality (hazard ratio [HR], 1.65; 95% confidence interval [CI], 1.18 to 2.31). This was more notable for cardiovascular (HR, 2.15; 95% CI, 1.27 to 3.64) than noncardiovascular mortality (HR, 1.39; 95% CI, 0.89 to 2.15). New-onset atrial fibrillation occurred in 35 of 349 individuals (4.1 events/100 person-years); the risk of incident atrial fibrillation was lower in those using ACE-inhibitor therapy (HR, 0.29; 95% CI, 0.10 to 0.82) and higher in those with left ventricular hypertrophy (HR, 2.55; 95% CI, 1.04 to 6.26). There were 539 hospitalizations during 3 years, with 114 hospitalizations in 162 patients with atrial fibrillation and 155 hospitalizations in 314 patients without atrial fibrillation (HR, 1.54; 95% CI, 1.18 to 2.01). Rates of stroke did not significantly differ by atrial fibrillation status (P = 0.4).

LIMITATIONS

Because of the observational nature of this study, results for treatment need confirmation in future trials.

CONCLUSIONS

Atrial fibrillation is associated with greater total and cardiovascular mortality. Patients with atrial fibrillation were hospitalized more frequently than patients without atrial fibrillation. ACE inhibitors may decrease the risk of new-onset atrial fibrillation.

Renin-angiotensin system gene polymorphisms and atrial fibrillation: a regression approach for the detection of gene-gene interactions in a large hospitalized population

OBJECTIVES

To test the association between renin-angiotensin system gene variants and atrial fibrillation (AF) using a regression approach.

METHODS

A total of 1,236 consecutive patients (227 with AF and 1,009 with normal sinus rhythm as controls) were recruited. Angiotensin-converting enzyme (ACE) gene I/D polymorphism; T174M, M235T, G-6A, A-20C, G-152A and G-217A polymorphisms of the angiotensinogen (AGT) gene, and A1166C polymorphism of the angiotensin II type I receptor (AT1R) gene were genotyped. We used a regression approach based on a generalized linear model to evaluate haplotype effects and to detect gene-gene interactions by incorporating interaction terms in the model.

RESULTS

In single-locus analyses, no locus was associated with AF. After adjustment for AF risk factors, we found significant differences in the global AGT gene haplotype profile (the global score statistic = 30.364, p = 0.001) and individual haplotype frequencies between AF patients and controls. Furthermore, significant 2-way gene-gene interactions between ACE I/D polymorphism and AGT gene haplotypes and between AT1R A1166C polymorphism and AGT gene haplotypes, and 3-way interaction between ACE I/D, AT1R A1166C and AGT gene haplotypes were detected.

CONCLUSIONS

These results are compatible with the concept of multilocus and multigene effects in determining the risk of complex diseases such as AF, which would be missed with conventional single-locus approaches.

Exercise-induced improvement in atrial depolarization abnormality in a patient after treatment with beta-adrenergic blockers

Abnormal atrial depolarization, characterized by P waves >or=110 ms on the electrocardiogram, can manifest as partial or advanced interatrial conduction delay or interatrial block (IAB). Progression from partial to advanced IAB has been shown to be altered by the use of angiotensin-converting enzyme inhibitors and beta-adrenergic blockers. We previously reported that advanced IAB, denoted by biphasic P waves in leads II, II and aVF, can revert intermittently to its partial counterpart. However, potential factors that could induce such resolution remain unknown. We present the first known case of resolution of advanced IAB to partial IAB occurring during graded exercise, following treatment with a beta-adrenergic blocker. Only continued study of these and other novel factors will help us understand the exact pathophysiology of both, partial and advanced IAB.

Structural and functional remodeling of the left atrium: clinical and therapeutic implications for atrial fibrillation

Left atrial (LA) structural and functional remodeling reflects a spectrum of pathophysiological changes that have occurred in response to specific stressors. These changes include alterations at the levels of ionic channels, cellular energy balance, neurohormonal expression, inflammatory response, and physiologic adaptations. There is convincing evidence demonstrating an important pathophysiological association between LA remodeling and atrial fibrillation (AF). Measures that will prevent, attenuate, or halt these processes of LA remodeling may have a major public health impact with respect to the epidemic of AF. In this review, we describe the mechanisms involved in LA remodeling and highlight the existing and potential therapeutic options for its reversal, and implications for AF development.

Future of antiarrhythmic drugs

PURPOSE OF REVIEW

This article briefly summarizes the principal mechanisms of action of contemporary antiarrhythmic agents, delineates their limitations in the treatment of cardiac arrhythmias, and discusses why there is a need for new cardiac antiarrhythmic drugs.

RECENT FINDINGS

In recent years, the limited efficacy and proarrhythmic potential of classic antiarrhythmic drugs have focused attention on nonpharmacologic approaches to treatment of cardiac arrhythmias. Despite the current success of ablative therapy and implantable defibrillators, the need is still pressing for new antiarrhythmic drugs. Evolving knowledge about the molecular mechanisms of cardiac arrhythmias provides innovative strategies for discovering new cardiac antiarrhythmic drugs. Some of these have already led to the development of new compounds on the verge of clinical use, and others hold great promise for future drug development.

SUMMARY

Cardiac arrhythmias are associated with significant morbidity and mortality in developed countries. Antiarrhythmic drug therapy was traditionally the mainstay of arrhythmia treatment; however, the inefficacy of drug treatment and the potential that antiarrhythmic drugs can provoke life-threatening arrhythmias have generated interest in new approaches to antiarrhythmic drug development. Improved understanding of the cellular and molecular basis of cardiac arrhythmias holds the promise of identifying novel approaches for the treatment of cardiac arrhythmias. These approaches may target traditional and newly discovered cardiac ion channels, as well as new molecular and signaling pathways that modulate arrhythmic substrates.

Drug therapy for atrial fibrillation

Atrial fibrillation (AF) is the most frequently diagnosed arrhythmia. Prevalence increases with age, and the overall incidence is expected to increase as the population continues to age. Choice of pharmacologic therapy for atrial fibrillation depends on whether or not the goal of treatment is maintaining sinus rhythm or tolerating atrial fibrillation with adequate control of ventricular rates. New antiarrhythmic drugs are being tested in clinical trials. Drugs that target remodeling and inflammation are being tested for their use as prevention of AF or as adjunctive therapy.

Angiotensin II receptor blockers and cardiovascular protection: focus on left ventricular hypertrophy regression and atrial fibrillation prevention

Left ventricular hypertrophy (LVH) and atrial fibrillation (AF) are strong predictors of cardiovascular (CV) morbidity and mortality, independently of blood pressure levels and other modifiable and nonmodifiable risk factors. The actions of circulating and tissue angiotensin II, mediated by AT1 receptors, play an important role in the development of a wide spectrum of cardiovascular alterations, including LVH, atrial enlargement and AF. Growing experimental and clinical evidence suggests that antihypertensive drugs may exert different effects on LVH regression and new onset AF in the setting of arterial hypertension. Since a number of large and adequately designed studies have found angiotensin II receptor blockers (ARBs) to be more effective in reducing LVH than beta-blockers and data are also available showing their effectiveness in preventing new or recurrent AF, it is reasonable to consider this class of drugs among first line therapies in patients with hypertension and LVH (a very high risk phenotype predisposing to AF) and as adjunctive therapy to antiarrhythmic agents in patients undergoing pharmacological or electrical cardioversion of AF.

Atrial fibrillation: insights from clinical trials and novel treatment options

Atrial fibrillation (AF) is the most common encountered sustained arrhythmia in clinical practice. The last decade the result of large 'rate' versus 'rhythm' control trials have been published that have changed the current day practise of AF treatment. It has become clear that rate control is at least equally effective as a rhythm control strategy in ameliorating morbidity as well as mortality. Moreover, in each individual patient the risk of thromboembolic events should be assessed and antithrombotic treatment be initiated. There have also been great advances in understanding the mechanisms of AF. Experimental studies showed that as a result of electrical and structural remodelling of the atria, 'AF begets AF'. Pharmacological prevention of atrial electrical remodelling has been troublesome, but it seems that blockers of the renin angiotensin system, and perhaps statins, may reduce atrial structural remodelling by preventing atrial fibrosis. Clinical studies demonstrated that the pulmonary veins exhibit foci that can act as initiator and perpetuator of the arrhythmia. Isolation of the pulmonary veins using radiofrequency catheter ablation usually abolishes AF. The most promising advances in the pharmacological treatment of AF include atrial specific antiarrhythmic drugs and direct thrombin inhibitors. In the present review we will describe the results of recent experimental studies, discuss the latest clinical trials, and we will focus on novel treatment modalities.

Effects of statin therapy on preventing atrial fibrillation in coronary disease and heart failure

BACKGROUND

Statins are associated with decreased incidence of life-threatening arrhythmias in patients with cardiomyopathy and reduce death and hospitalization in congestive heart failure (CHF). We hypothesized that statin use will reduce incident atrial fibrillation (AF) in patients with coronary heart disease (CHD), including those with CHF.

METHODS

A cohort of 17,741 patients with CHD examined between 1994 and 1997 at 5 Veterans Affairs medical facilities was assembled. Patients with known AF, warfarin treatment, liver disease, or no follow-up visits were excluded. The final cohort included 13,783 patients. The primary outcome was time to development of AF. Propensity scores were used to balance statin-treated and untreated patients with respect to baseline characteristics. Time from the initial visit to development of AF was analyzed with a Cox regression model, using statin treatment as a time-varying covariate.

RESULTS

Among the 13,783 patients, 5417 (39%) received statin treatment. Statin-treated patients were younger with fewer comorbid conditions. After propensity adjustment, the baseline characteristics of the statin-treated and untreated patients were similar. During an average follow-up of 4.8 years, 1979 (14%) patients developed AF. In the overall study population there was no difference in AF incidence with statin treatment (hazard ratio 1.0, 95% CI 0.88-1.14, P = .9). However, AF was less common among statin-treated patients with CHF (hazard ratio 0.57, 95% CI 0.33-1.00, P = .04).

CONCLUSIONS

We did not find any effect of statin treatment on AF incidence in patients with CHD; however, AF was reduced in a subset of patients with CHF.

Role of inflammation in initiation and perpetuation of atrial fibrillation: a systematic review of the published data

Atrial fibrillation (AF) is the most common arrhythmia in clinical practice. Recent studies have indicated that inflammation might play a significant role in the initiation, maintenance, and perpetuation of AF. Inflammatory markers such as interleukin-6 and C-reactive protein are elevated in AF and correlate to longer duration of AF, success of cardioversion, and thrombogenesis. Furthermore, the inflammatory process might be modulated by the use of statins, angiotensin-converting enzyme inhibitors, or glucocorticoids. The purpose of this study is to analyze the current published reports on the relationship between inflammation and AF and the potential therapeutic options available to modulate the inflammatory milieu in AF.

Non-Antiarrhythmic Drugs in Atrial Fibrillation: A Review of Non-Antiarrhythmic Agents in Prevention of Atrial Fibrillation

This article reviews current evidence of non-antiarrhythmic agents for the prevention and maintenance of sinus rhythm in patients with atrial fibrillation. These nontraditional agents include angiotensin converting enzyme inhibitors, angiotensin receptor blockers, antiinflammatory agents, calcium channel blockers, and beta-blockers. The mechanisms of action and clinical trials regarding the effectiveness of these agents in atrial fibrillation prevention are reviewed.

Depressive symptoms predict recurrence of atrial fibrillation after cardioversion

OBJECTIVE

The aim of this study was to evaluate whether depressive symptoms and the type-D personality are predictive of early recurrence of atrial fibrillation (or atrial flutter; AF) after successful electrical cardioversion (CV).

BACKGROUND

Depressive symptoms are associated with an adverse prognosis in patients with coronary artery disease, congestive heart failure, and ventricular arrhythmias. Anger and hostility have been shown to be predictive of development of AF. However, little is known about the effects of depression on AF.

METHODS

Fifty-four patients with persistent AF completed the Hospital Anxiety and Depression Scale (HADS) and the Type D Scale (DS-14) prior to elective electrical CV. Patients with a successful CV were followed for 2 months.

RESULTS

During the follow-up period, 27 patients (50%) had recurrence of the arrhythmia. Depressive mood (HADS depression scale >7) was the only significant nonsomatic predictor of recurrence, which was observed in 85% of depressed versus 39% of nondepressed patients [odds ratio=8.6; 95% confidence interval (CI)=1.7-44.0, P=.004]. HADS anxiety scores and the presence of the type-D personality pattern were not associated with recurrence of AF. On multivariate Cox regression analysis, including variables with a prevalence >10% of the total study population and a univariate discriminative effect yielding a P value of <.2, a HADS depression score >7 was found to be the only independently predictive variable of arrhythmia recurrence (hazard ratio=2.7; 95% CI=1.05-7.2; P=.046).

CONCLUSIONS

Our results indicate that depressive mood is a major risk factor for recurrence of AF after electrical CV. Heightened adrenergic tone and a proinflammatory state are possible mechanisms responsible for the observed association. Identification of depression may be of value prior to the decision to perform electrical CV.

Angiotensin II Type 1 Receptor Inhibition is Associated with Reduced Tachyarrhythmia-Induced Ventricular Interstitial Fibrosis in a Goat Atrial Fibrillation Model

BACKGROUND

Using a goat animal model, we tested the hypothesis that angiotensin-II inhibition reduces fibrotic degeneration of both the atrial and ventricular myocardium as well as AF induction susceptibility.

METHODS

We studied three groups of five goats over a 6-month period. The study animals in the first two groups were implanted with a pacemaker capable of maintaining AF with burst pacing. Additionally, in one group, goats were administered candesartan (AF+candesartan group). The third group (SR group) of animals served as control. Animals were tested for AF induction on day 0, 1, 30, 90 and 180. A "Vulnerability Index" (VI) for AF induction was calculated, defined as the ratio of total time in AF per number of bursts needed to induce sustained AF, in each session. At the end of the study, all four heart chambers were examined and fibrosis quantified.

RESULTS

Both AF goat groups developed cardiomegaly due to tachy-cardiomyopathy. Although, the VI was significantly increased in AF group over time (28.8+/-43 to 284.7+/-291, p=0.045), this was not the case for AF+candesartan group (30.3+/-40 to 170.8+/-243, p=0.23). Histology revealed a significant increase of fibrous tissue in goats with induced AF, noticeable in all four heart chambers, compared to controls. However, the degree of fibrosis was significantly lower in AF animals on candesartan.

CONCLUSIONS

Our study demonstrated a beneficial effect of angiotensin II inhibition on tachyarrhythmia-induced ventricular fibrosis. It is also consistent with previous studies indicating a reduction in burst-induced AF susceptibility in goats and confirms the favorable effects in atrial structural remodeling.

Atrial fibrillation: challenges and opportunities

Atrial fibrillation (AF) is the most common sustained arrhythmia encountered in clinical practice. There are many pharmacological and nonpharmacological options available for AF patients. There is, however, a great deal of dissatisfaction with the available treatments of this arrhythmia. Furthermore, AF management remains associated with many challenges that make the treatment of AF a vexing problem. The present overview discusses these challenges and explores the opportunities associated with them.

New antiarrhythmic treatment of atrial fibrillation

Antiarrhythmic pharmaceutical development for the treatment of atrial fibrillation (AF) is moving in several directions. The efficacy of existing drugs, such as carvedilol, for rate control and, possibly, suppression of AF, is more appreciated. Efforts are being made to modify existing agents, such as amiodarone, in an attempt to ameliorate safety and adverse effect concerns. This has resulted in promising data from the deiodinated amiodarone analog, dronedarone, and further work with celivarone and ATI-2042. In an attempt to minimize ventricular proarrhythmia, atrial selective drugs, such as intravenous vernakalant, have demonstrated efficacy in terminating AF in addition to promising data in suppression recurrences when used orally. Several other atrial selective drugs are being developed by multiple manufacturers. Other novel therapeutic mechanisms, such as drugs that enhance GAP junction conduction, are being developed to achieve more effective drug therapy than is offered by existing compounds. Finally, nonantiarrhythmic drugs, such as angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, high-mobility group coenzyme A enzyme inhibitors and omega-3 fatty acids/fish oil, appear to have a role in suppressing AF in certain patient subtypes. Future studies will clarify the role of these drugs in treating AF.

Impact of ramipril on the incidence of atrial fibrillation: results of the Heart Outcomes Prevention Evaluation study

OBJECTIVES

We evaluated the effect of angiotensin-converting enzyme (ACE) inhibitor ramipril on the incidence of atrial fibrillation (AF) in patients enrolled in the Heart Outcomes Prevention Evaluation trial.

BACKGROUND

Atrial fibrillation is the most common arrhythmia affecting the general population and is associated with increased morbidity and mortality. Retrospective secondary analyses of some of the large trials of ACE inhibitors have suggested that ACE inhibitors may prevent AF.

METHODS

We evaluated the occurrence of AF by reviewing the electrocardiogram tracings at entry, at 2 years, and at the end of the study, as well as hospitalizations among 8335 high-risk participants from the Heart Outcomes Prevention Evaluation study, > or = 55 years, without known heart failure or left ventricular (LV) systolic dysfunction and followed for a median period of 4.5 years. We compared the impact of ramipril and matched placebo on occurrence of AF. The results were compared to similar trials.

RESULTS

Over the 4.5 years follow-up, the incidence of new AF was low (2.1%, 177/8335), and ramipril did not significantly reduce the rate of new AF compared with placebo (86/4291 [2.0%] vs 91/4044 [2.2%]) with an odds ratio of 0.92 (95% confidence interval, 0.68-1.24; P = .57). These results added to the previous ACE inhibitor trials (excluding trials in patients with LV dysfunction) showed no significant reduction in new AF among patients treated with these agents (1088/20,930 [5.0%] vs 1343/22,878 [5.9%]; relative risk, 0.92; 95% confidence interval, 0.80-1.05).

CONCLUSION

Although the incidence of AF was low, treatment with ramipril in this population without known LV systolic dysfunction did not significantly reduce this dysrhythmia.

Relation of Interleukin-6 and C-Reactive Protein Levels to Sinus Maintenance After Pharmacological Cardioversion in Persistent Atrial Fibrillation

OBJECT

The aim of this study was to investigate whether interleukin-6 (IL-6) and C-reactive protein (CRP) have significant relation to sinus maintenance after pharmacological conversion of long-lasting atrial fibrillation (AF) with respect to use of renin-angiotensin-aldosterone system (RAS) inhibitors.

METHODS

We studied 35 consecutive patients with AF lasting > or =1 month who had successful pharmacological cardioversion with bepridil alone or in combination with aprindine. The IL-6 and CRP levels in plasma were measured after pharmacological restoration of sinus rhythm.

RESULTS

During the 1-year follow-up period, sinus rhythm was maintained in 20 patients (Group I), and the other 15 patients had recurrence of AF (Group II). Both plasma levels of IL-6 and CRP were significantly lower in Group I than in Group II (IL-6: 1.19 +/- 0.51 versus 1.84 +/- 0.66 ng/L, P < 0.005; CRP: 0.59 +/- 0.40 versus 1.24 +/- 0.79 mg/L, P < 0.005). The use of RAS inhibitors and left atrial dimension and the left ventricular ejection fraction showed no differences between the 2 groups. There was significant positive correlation between levels of IL-6 and CRP.

CONCLUSION

In long-lasting persistent AF, lower levels of IL-6 and CRP appear to be associated with maintenance of sinus rhythm after pharmacological cardioversion irrespective of the use of RAS inhibitors. Further studies are needed to clarify the role of RAS inhibitors.

Novel pharmacological therapies for atrial fibrillation

PURPOSE OF REVIEW

Atrial fibrillation is a common yet difficult cardiac rhythm to treat. Limitations of the currently available medications, increasing complexity of atrial fibrillation patient populations and the prevalence of the condition have made new drug development crucial. Our understanding of the pathophysiology of atrial fibrillation has increased tremendously over the years. The importance of electrical remodeling and structural remodeling has been widely appreciated and has opened new avenues for pharmacological research.

RECENT FINDINGS

Novel ion channel blockers have targeted atrial-specific ion channels or a combination of ion channels in order to maximize efficacy and minimize proarrhythmic risk. Understanding of atrial fibrillation as a metabolically complex condition with activation of multiple signaling cascades has fuelled drug development in a new direction. Exciting new drugs inhibiting fibrosis, cellular hypertrophy and improving cell-cell communication may help treat chronic atrial fibrillation in the future.

SUMMARY

Continuing progress in our knowledge of the ionic and structural remodeling in atrial fibrillation will only accelerate the search for a safe antidote. In the future focal pharmacological modulation may help target specific targets in diverse populations. The potential of many of these pharmacotherapies, however, will need to be tested in large randomized trials before our faith in them is realized.

The effect of angiotensin receptor blockers for preventing atrial fibrillation

Atrial fibrillation is the most common sustained cardiac arrhythmia in clinical practice, and causes significant burden to patients and health care systems. Clinicians treat existing atrial fibrillation with anticoagulation and/or drugs that utilize either a rate or rhythm control strategy. It remains unclear how best to reduce cardiovascular morbidity and mortality in this population. Prevention of atrial fibrillation using angiotensin receptor blockers, which affect ion currents and refractoriness in atrial myocytes, regress or prevent atrial fibrosis, decrease left atrial size, regress left ventricular hypertrophy, modulate sympathetic nerve activity, reduce inflammation, and reduce blood pressure, may become an important and desirable alternative.

Effect of renin-angiotensin aldosteron system blockers on postoperative atrial fibrillation

BACKGROUND

No randomized studies have been conducted to evaluate the effects of renin-angiotensin aldosteron system blockers on postoperative atrial fibrillation (AF). The aim of this study was to evaluate the effect of angiotensin converting-enzyme inhibitors (ACEIs) and ACEI plus candesartan, an angiotensin receptor blocker on postoperative AF.

METHODS

A group of consecutive patients undergoing coronary artery bypass and/or valve surgery was studied (n=128). The patients were randomized to ACEI group (n=49) and ACEI plus candesartan group (n=49). Thirty patients not on ACEI or angiotensin receptor blocker constituted the control group.

RESULTS

The rate of postoperative AF was higher in the control group (33.3%) compared to the ACEI group (12.2%, p=0.02) or ACEI plus candesartan group (10.2%, p=0.01). With the Cox proportional model, univariable negative predictors of postoperative AF, were the use of ACEI (RR 0.34, 95% CI 0.12 to 0.93, p=0.03) and the use of ACEI plus candesartan (RR 0.28, 95% CI 0.09 to 0.83, p=0.02); the positive predictor of postoperative AF was age>or=65 (RR 3.10, 95% CI 1.30 to 7.37, p=0.01). With the multivariable Cox proportional model, the only predictor of postoperative AF was age>or=65 (RR 9.70, 95% CI 2.04 to 46.1, p=0.004).

CONCLUSION

ACEI alone and ACEI plus candesartan decrease the incidence of postoperative AF compared to the control group. Candesartan has no additional effect on the rates of postoperative AF when added to ACEI.

Evolution of Left Atrial Systolic and Diastolic Functions in Different Stages of Hypertension: Distinct Effects of Blood Pressure Control

BACKGROUND

To evaluate the left atrial (LA) volume, and LA systolic (contractile) and diastolic (expansion) functions in different stages of hypertension with or without atrial fibrillation (AF), as well as the effects of good blood pressure control.

METHODS

A prospective observational study. Individuals including 22 normotensive controls, 23 patients with mild hypertension, 20 with severe hypertension, and 17 with hypertension and paroxysmal AF were recruited for paired echocardiography studies at baseline and 6 months after control of hypertension.

RESULTS

With increasing severity of hypertension, left ventricular (LV) diastolic function deteriorated with decreasing LV septal E'/A' and increasing E/E' ratios. LA expansion index was reduced in parallel. LA expansion index was correlated positively with LV E'/A' (r = 0.43, p = 0.022) and inversely with LV E/E' (r = 0.49, p = 0.009). Significant improvement of LV diastolic function and LA expansion index preceded the reduction of LA volume after blood pressure control. In patients with paroxysmal AF, LA volume reduction was more evident in patients receiving angiotensin-converting enzyme inhibitors or angiotensin II type 1 receptor blockers.

CONCLUSIONS

With progressive LV diastolic dysfunction in hypertension, there was a corresponding deterioration in LA diastolic function. Effective blood pressure control for 6 months improved LA diastolic function.

Candesartan in the prevention of relapsing atrial fibrillation

BACKGROUND

Several studies have indicated that treatment with angiotensin converting enzyme (ACE) inhibitors and angiotensin II type 1 receptor blockers (ARBs) may reduce the incidence of atrial fibrillation (AF) in hypertensive patients and patients with left ventricular dysfunction. However, there is limited data on the effect of ACE-inhibitors and ARBs in patients undergoing electrical cardioversion for persistent AF. We hypothesized that treatment with the ARB candesartan, without adjunct antiarrhythmic therapy, would reduce the recurrence rate of AF after successful cardioversion.

METHODS

In a double blind, placebo-controlled study, 171 patients with persistent AF were randomized to receive candesartan 8 mg once daily (n=86) or placebo (n=85) for 3-6 weeks before and candesartan 16 mg once daily or placebo for 6 months after electrical cardioversion. Primary endpoint was recurrence of AF.

RESULTS

A total of 68 patients in the candesartan group and 69 patients in the placebo group were successfully cardioverted. Forty-eight patients (71%) in the candesartan group and 45 (65%) in the placebo group had a recurrence of AF during 6 months follow-up. Median time to recurrence was 8 and 9 days in the candesartan and placebo groups, respectively. The differences between the groups were not statistically significant.

CONCLUSION

Treatment with the ARB candesartan for 3-6 weeks before and 6 months after electrical cardioversion had no effect on the recurrence rate of AF.

Use of predictive markers to improve cardiovascular protection

Together with other modifiable cardiovascular risk factors, hypertension heavily contributes to the global burden of cardiovascular morbidity and mortality, as well as to the increase in individual absolute cardiovascular risk. Comparison of the effectiveness of different therapies in reducing the incidence of major cardiovascular events has classically required the evaluation of major 'hard' end points. In view of the long natural history of hypertension, however, it appears very useful to monitor modifications in measurable 'intermediate' end points or 'disease markers'. This approach may provide more accurate individual risk stratification and a better evaluation of the efficacy of a given treatment in preventing or modifying the course of target organ damage. This may represent a valuable and affordable strategy in clinical practice allowing the evaluation of both patient prognosis and the effectiveness of antihypertensive treatment over time.

The effects of statins and renin-angiotensin system blockers on atrial fibrillation recurrence following antral pulmonary vein isolation

INTRODUCTION

Ablation has emerged as a major treatment option for atrial fibrillation (AF). However, this procedure is limited by a significant rate of AF recurrence. We aimed to examine the effects of statins, angiotensin-converting enzyme inhibitors (ACE-I), and angiotensin receptor blockers (ARB) on the recurrence rate of AF following ablation.

METHODS

We conducted a retrospective study of 177 consecutive patients (mean age = 56 +/- 11 yrs, 69% males) who underwent ablation for paroxysmal (n = 132) or persistent AF (n = 45). Patients were treated with ACE-I (n = 31) or ARB (n = 18) or statins (n = 50) prior to ablation and for the duration of follow-up.

RESULTS

After a mean follow-up of 13.8 +/- 8.6 months, 72% of patients were free of AF. For patients taking statins, 33 of 50 (60%) were free of AF. In patients treated with ACE-I, 17 of 31 (55%) were free from AF, while in the group of patients treated with ARB, 17 of 18 (94%) were free from AF. Using Cox regression analysis to correct for baseline variables, treatment with statins did not decrease the recurrence rate (HR = 1.10 [95% CI: 0.55-2.27] p = 0.79); nor did treatment with renin angiotensin system (RAS) blockers (HR 0.94 [95% CI: 0.46-1.93] p = 0.87). However, subgroup analysis showed that treatment with ARB was associated with a trend towards lower AF recurrence [HR 0.17, (95% CI: 0.02-1.34) p = 0.09].

CONCLUSIONS

Even though statins and RAS blockers possess anti-inflammatory properties, they did not decrease the recurrence of AF following ablation. However, the subset of patients taking ARB exhibited a trend towards lower AF recurrence. Larger, randomized studies are needed to address this observation.

Angiotensin converting enzyme inhibitor and angiotensin receptor blockade use in relation to outcomes in anticoagulated patients with atrial fibrillation

BACKGROUND

The renin-angiotensin-aldosterone-system (RAAS) plays an important role in atrial fibrillation (AF). Evidence shows that blocking the RAAS with angiotensin converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) has a definite role in preventing new onset AF and in maintaining sinus rhythm in recurrent AF. Our aim was to determine if ACEI/ARB treatment was associated with clinical outcomes [stroke/systemic embolic events (SEE), mortality] in a controlled, anticoagulated AF population.

METHODS

An ancillary retrospective cross-sectional and longitudinal analysis of participants in the Stroke Prevention using an ORal Thrombin Inhibitor in AF (SPORTIF) III and V trials, in relation to use (or nonuse) of ACEI/ARBs.

RESULTS

Rates of stroke/SEEs, mortality or major bleeding were no different between users and nonusers in the whole cohort, or in relation to the presence/absence of hypertension, coronary artery disease and previous stroke/transient ischaemic attack, nor amongst those aged <75 years. Patients aged > or = 75 years taking ACEIs or ARBs had lower mortality (HR 0.71, 95% CI 0.52-0.95), but no significant influence on other end-points was noted. Diabetics and those with left ventricular dysfunction on ximelagatran had a higher odds ratio of abnormal liver enzyme levels. There was no apparent benefit of ACEIs or ARBs on other event rates.

CONCLUSIONS

This analysis from two large randomized trials of anticoagulation has not demonstrated a significant benefit of ACEI or ARB use amongst AF patients, except amongst elderly subjects.

Relation of C-reactive protein to long-term risk of recurrence of atrial fibrillation after electrical cardioversion

The aim of this study is to assess the role of C-reactive protein (CRP) in predicting long-term risk of atrial fibrillation (AF) recurrence after electrical cardioversion. CRP levels are associated with the presence of AF and failure of electrical or pharmacologic cardioversion, but no previous study has assessed their predictive role in long-term follow-up after successful electrical cardioversion. One hundred two consecutive patients (age 67 +/- 11 years; 58 men) with nonvalvular persistent AF who underwent successful biphasic electrical cardioversion were studied. High-sensitivity CRP was measured immediately before cardioversion. Follow-up was performed up to 1 year in all cases. Patients were divided into 4 groups according to CRP quartiles. Patients in the lowest CRP quartile (<1.9 mg/L) had significantly lower rates of AF recurrence (4% vs 33% at 3 months in the other 3 groups combined, p = 0.007, and 28% vs 60% at 1 year, p = 0.01). The 4 groups were similar in age, gender, ejection fraction, and left atrial size. Survival analysis confirmed that patients in the lowest CRP quartile had a lower recurrence rate (p = 0.02). Cox regression analyses using age, gender, hypertension, diabetes, ejection fraction, left atrial diameter, use of antiarrhythmic drugs, angiotensin-converting enzyme inhibitors or angiotensin II antagonists, and statins, and CRP quartiles as covariates showed that only CRP was independently associated with AF recurrence during follow-up (hazard ratio 4.98, 95% confidence interval 1.75 to 14.26, p = 0.003). In conclusion, low CRP is associated with long-term maintenance of sinus rhythm after cardioversion for nonvalvular AF.

Angiotensin II increases expression of alpha1C subunit of L-type calcium channel through a reactive oxygen species and cAMP response element-binding protein-dependent pathway in HL-1 myocytes

Angiotensin II (Ang II) is involved in the pathogenesis of atrial fibrillation (AF). L-type calcium channel (LCC) expression is altered in AF remodeling. We investigated whether Ang II modulates LCC current through transcriptional regulation, by using murine atrial HL-1 cells, which have a spontaneous calcium transient, and an in vivo rat model. Ang II increased LCC alpha1C subunit mRNA and protein levels and LCC current density, which resulted in an augmented calcium transient in atrial myocytes. An approximately 2-kb promoter region of LCC alpha1C subunit gene was cloned to the pGL3 luciferase vector. Ang II significantly increased promoter activity in a concentration- and time-dependent manner. Truncation and mutational analysis of the LCC alpha1C subunit gene promoter showed that cAMP response element (CRE) (-1853 to -1845) was an important cis element in Ang II-induced LCC alpha1C subunit gene expression. Transfection of dominant-negative CRE binding protein (CREB) (pCMV-CREBS133A) abolished the Ang II effect. Ang II (1 micromol/L, 2 hours) induced serine 133 phosphorylation of CREB and binding of CREB to CRE and increased LCC alpha1C subunit gene promoter activity through a protein kinase C/NADPH oxidase/reactive oxygen species pathway, which was blocked by the Ang II type 1 receptor blocker losartan and the antioxidant simvastatin. In the rat model, Ang II infusion increased LCC alpha1C subunit expression and serine 133 phosphorylation of CREB, which were attenuated by oral losartan and simvastatin. In summary, Ang II induced LCC alpha1C subunit expression via a protein kinase C-, reactive oxygen species-, and CREB-dependent pathway and was blocked by losartan and simvastatin.

Potential factors that affect electrocardiographic progression of interatrial block

INTRODUCTION

Interatrial block (IAB; P wave > or = 110 ms) is associated with atrial tachyarrhythmias and left atrial electromechanical dysfunction. This subtle abnormality is highly prevalent and may exist as partial (pIAB) or advanced IAB (aIAB). Indeed, theoretically pIAB could progress to aIAB with worsening interatrial conduction over time. However, this has been poorly investigated. We retrospectively appraised this phenomenon and also evaluated the influence of common clinical factors such as coronary artery disease (CAD), hypertension (HTN), and use of antihypertensive medications.

METHODS

Between January 2003 and June 2004, 27 patients who had aIAB on routine 12-lead ECGs were identified. Past serial ECGs of each patient were evaluated for evidence of change in IAB type. Medical records of respective patients were then reviewed for HTN, type of antihypertensive medication used, and other common comorbidities.

RESULTS

Median progression time from pIAB to aIAB was shorter (42 months; mean +/- SD = 39.2 +/- 30.5) compared to that of normal P wave (P-normal) to aIAB (66 months; mean +/- SD = 64.2 +/- 25.6). Use of angiotensin-converting enzyme inhibitors (ACEIs) appeared to significantly delay the progression time in patients who progressed from pIAB to aIAB (50.1 +/- 28.3 vs 10 +/- 10.4 months; P = 0.04). Beta-adrenergic blocker use alone did not significantly affect either progression time but when used in conjunction with ACEIs, appeared to slow such progression.

CONCLUSION

Progression time from pIAB to aIAB is shorter compared to that of P-normal to aIAB. Given the consequences of IAB, awareness of such progression could be important for clinicians in anticipating potential sequelae.

[Inflammatory state in patients with atrial fibrillation before and after electrical cardioversion]

OBJECTIVE

To assess the inflammatory state in patients with persistent atrial fibrillation and to determine the predictive value in the success of cardioversion and recurrence at 30 days.

DESIGN

Prospective observational case-control study.

PATIENTS

We included consecutively 49 patients with atrial fibrillation previously to scheduled electrical cardioversion in Coronary Care Unit. Clinical and echocardiographic variables were registered and High-sensivity C-reactive protein, interleukin-1beta, interleukin-6 and Tumour Necrosis Factor-alpha were measured. At 30-days follow-up, rhythm and biomarkers were reassessed. As control groups, we recruited 27 healthy volunteers and 16 patients matched for age, gender and cardiovascular risk factors.

RESULTS

Median age was 66 +/- 10 years and 38% were women. All the markers were higher in patients than in both control groups (p < 0.05). FNT-alpha and Interleukin-6 levels were higher in non-cardiovertors but only an enlarged atria was related to unsuccessful cardioversion (p = 0.036). High-sensivity C-reactive protein values in the higher cuartile tended to be related to recurrence of persistent atrial fibrillation (p = 0.06).

CONCLUSIONS

There is an increased inflammatory state in patients with atrial fibrillation. FNT-alpha and Interleukin-6 levels were increased in non-cardiovertors, but no biomarker was associated with success of cardioversion or rhythm state at 30-days. However, higher levels of hs-CRP showed a trend to be related to recurrence of atrial fibrillation.

Renin-angiotensin system and cardiovascular risk

The renin-angiotensin system is a major regulatory system of cardiovascular and renal function. Basic research has revealed exciting new aspects, which could lead to novel or modified therapeutic approaches. Renin-angiotensin system blockade exerts potent antiatherosclerotic effects, which are mediated by their antihypertensive, anti-inflammatory, antiproliferative, and oxidative stress lowering properties. Inhibitors of the system-ie, angiotensin converting enzyme inhibitors and angiotensin receptor blockers, are now first-line treatments for hypertensive target organ damage and progressive renal disease. Their effects are greater than expected by their ability to lower blood pressure alone. Angiotensin receptor blockers reduce the frequency of atrial fibrillation and stroke. Renin-angiotensin system blockade delays or avoids the onset of type 2 diabetes and prevents cardiovascular and renal events in diabetic patients. Thus, blockade of this system will remain a cornerstone of our strategies to reduce cardiovascular risk.

Do we need pharmacological therapy for atrial fibrillation in the ablation era?

Management of atrial fibrillation (AF) remains one of the most difficult problems of modern cardiology. Pharmacological antiarrhythmic therapy is used both for termination of episodes of AF and for prevention of AF recurrences. Recently, major trials have compared the strategy of maintenance of sinus rhythm, called rhythm control, with the strategy of heart rate control during AF and found that the rhythm control strategy was not superior to rate control in terms of mortality. Although subsequent analysis identified rhythm control as a factor of improved survival, these large trials have markedly influenced the management of AF. One of the hypotheses explaining the non-superiority of the rhythm control strategy was that the benefit of sinus rhythm was offset by the side effects of antiarrhythmic agents. As a consequence, attention was directed to non-pharmacological therapies, particularly to catheter ablation of the trigger or/and the atrial substrate using radiofrequency current or cryothermia. However, despite the reported good results of various types of interventions in the hands of highly qualified teams, catheter ablation cannot be applied to all patients with AF or to all types of AF. Furthermore, catheter ablation of AF requires sophisticated electrophysiologic laboratories equipped with expensive imaging techniques and a well-trained staff that cannot be available in sufficient number to cover the growing epidemic of AF with acceptable efficacy and safety even in rich countries. Therefore, there is still a need for pharmacological therapy aimed at the prevention of AF recurrences for the majority of AF patients. So far, attempts to provide the physician with efficient antiarrhythmic agents having a good safety profile have not been successful. However, recent research resulted in promising new approaches including prevention of AF using converting enzyme inhibitors or angiotensin 2 receptor blockers, new antiarrhythmic agents with multichannel effects such as dronedarone and tedisamil and atrial specific agents that theoretically should have no ventricular proarrhythmic effect as they target specific atrial channels such as I(KAch) and I(Kur) which are absent at the ventricular level. Other possible mechanisms of AF that represent potential targets, such as modification of stretch-activated ion channels, intervention of altered connexin expression and altered gap-junctional conductance, are currently investigated.