Auricular fibrillation without other evidence of heart disease; a cause of reversible heart failure

The association of left atrial size and occurrence of atrial fibrillation: a prospective cohort study from the Canadian Registry of Atrial Fibrillation

BACKGROUND

The effect of left atrial (LA) dimension on the recurrence of atrial fibrillation (AF) has been examined in small studies. We evaluated the effect of LA dimension on the occurrence of AF using 2- and 4-year echocardiographic data in a large cohort of patients with new onset AF.

METHODS

The Canadian Registry of AF (CARAF) enrolled subjects with AF at the first electrocardiographically confirmed diagnosis. Patients were classified at 2 and 4 years as no recurrent AF (No RAF), paroxysmal AF (PAF), or chronic AF (CAF) based on clinical symptoms and electrocardiographic documentation. The association between baseline, 2-, and 4-year LA dimensions with occurrence of AF as determined by echocardiography was evaluated using a multivariate analysis.

RESULTS

The No RAF group (n = 176) had a significantly smaller LA dimension (36.9 +/- 6.8 mm) at baseline compared to the CAF group (n = 227) (42.8 +/- 7.5 mm, P <.0001). The No RAF and PAF (n = 153) groups did not have a significant change in LA dimension at 2 or 4 years. Only those with CAF had a significant increase in LA dimension at 2 and 4 years, +1.39 mm (95% CI 0.01-2.8) and +3.48 mm (95% CI 1.8-5.2), respectively.

CONCLUSIONS

A larger baseline LA dimension is associated with progression to CAF. Patients with no or paroxysmal recurrence had no change in LA dimension over a 4-year period. These findings have implications in tailoring modes of therapy in patients with AF.

Ventricular rate control during atrial fibrillation and AV node modifications: past, present, and future

Atrial fibrillation (AF) is the most common arrhythmia. Currently there are two broad strategic treatment options for AF: rhythm control and rate control. For rhythm control, the treatment is directed toward restoring and maintaining the sinus rhythm. For rate control, the intention is to slow ventricular rate while allowing AF to continue. In both cases anticoagulation therapy is recommended. The results of currently available clinical trials demonstrated clearly that rate control is not inferior to rhythm control. Thus, rate control is an acceptable primary therapy for many AF patients. The rate control can be achieved essentially by depressing or modifying the filtering properties of the atrioventricular (AV) node. This can be attained by medications that depress the impulse transmission within the AV node, by anatomic modification of the AV communications, as well as by autonomic manipulations that produce AV node negative dromotropic effect. We are reviewing current clinical and newer experimental modalities aimed at enhancing the lifesaving function of this remarkable nodal structure.

The role of atrial dilatation in the domestication of atrial fibrillation

Numerous clinical investigations as well as recent experimental studies have demonstrated that atrial fibrillation (AF) is a progressive arrhythmia. With time paroxysmal AF becomes persistent and the success rate of cardioversion of persistent AF declines. Electrical remodeling (shortening of atrial refractoriness) develops within the first days of AF and contributes to the increase in stability of the arrhythmia. However, 'domestication of AF' must also depend on other mechanisms since the persistence of AF continues to increase after electrical remodeling has been completed. During the first days of AF in the goat, electrical and contractile remodeling (loss of atrial contractility) followed exactly the same time course suggesting that they are due to the same underlying mechanism. Contractile remodeling not only enhances the risk of atrial thrombus formation, it also enhances atrial dilatation by increasing the compliance of the fibrillating atrium. In goats with chronic AV-block atrial dilatation increased the duration of artificially induced AF-episodes but did not change atrial refractoriness or the AF cycle length. When AF was maintained a couple of days in these animals, a shortening of the atrial refractory period did occur. However, the AF cycle length did not decrease. Long lasting episodes of AF with a long AF cycle length and a wide excitable gap suggest that in this model AF is mainly promoted by conduction disturbances. Chronic atrial stretch induces activation of numerous signaling pathways leading to cellular hypertrophy, fibroblast proliferation and tissue fibrosis. The resulting electroanatomical substrate in dilated atria is characterized by increased non-uniform anisotropy and macroscopic slowing of conduction, promoting reentrant circuits in the atria. Prevention of electroanatomical remodeling by blockade of pathways activated by chronic atrial stretch therefore provides a promising strategy for future treatment of AF.

Echocardiographic changes and predictors of arrhythmia recurrence after long-term use of the atrial defibrillator

BACKGROUND

The patient-activated atrial defibrillator allows patients to cardiovert themselves from atrial fibrillation soon after the onset of symptoms. The long-term effects of early cardioversion from persistent atrial fibrillation on left ventricular performance and left atrial size are unknown.

METHODS

Eighteen patients, mean age 63.4, 83% male, had the Jewel((R)) AF atrial defibrillator implanted for persistent atrial fibrillation only. Transthoracic echocardiography was performed 3-monthly following implant. Parasternal long axis measurements were taken using conventional M-mode techniques.

RESULTS

Over follow-up of 28.0+/-9 months, 377 episodes of persistent atrial fibrillation were terminated by patient-activated cardioversion (median 15 per patient). Echocardiographic measurements at implant were; left atrium 44+/-6 mm, left ventricular end-diastolic diameter 49+/-7 mm, left ventricular end-systolic diameter 34+/-7 mm, fractional shortening 33+/-10% and ejection fraction 65+/-17%. After 1 year there had been a significant decrease in mean left atrial size to 41+/-6 mm (P=0.02) and an increase in mean ejection fraction to 73+/-8% (P=0.04). At long-term follow-up however, all parameters reverted to pre-implant levels. Baseline echocardiographic variables did not predict which patients would demonstrate serial increases in sinus rhythm duration between shocks during long-term follow-up. Patients on antiarrhythmic drug therapy however were more likely to demonstrate "sinus rhythm begetting sinus rhythm".

CONCLUSIONS

Use of the atrial defibrillator for spontaneous persistent atrial fibrillation is associated with a medium-term (1 year) reduction in left atrial size and an increase in ejection fraction. These changes were not maintained in the long-term. Synergistic therapy with antiarrhythmic drugs may prolong periods of sinus rhythm between arrhythmia recurrences.

[Permanent atrial fibrillation in heart disease in Spain. The CARDIOTENS study 1999]

INTRODUCTION AND OBJECTIVE

Atrial fibrillation is the most common arrhythmia seen in clinical practice. The objective of this study was to know the frequency of atrial fibrillation and the characteristics of patients with atrial fibrillation in the Cardiotens study.

MATERIAL AND METHOD

A cross-section study with systematic selection of the study sample. All 32,051 outpatients seen on the same day by 1,159 physicians specialized in primary-care (79%) and cardiology (21%) were prospectively added to a database including history of cardiac disease (heart failure, coronary disease or atrial fibrillation), blood pressure, and ongoing treatment.

RESULTS

Atrial fibrillation was present in 25% of patients with previous cardiovascular disease (6,194 patients), the prevalence being 4.8% (1,540/32,051) of the study population. Atrial fibrillation was more frequent in females 29%, (810/2,837) than in males, 22% (730/3,367), p < 0.005). Atrial fibrillation was present in 33% (469/1,420) of patients with heart failure and in 12% (387/3,226) of those with coronary heart disease. Arterial hypertension was diagnosed in 25% of the patients with atrial fibrillation. Only 33% of them were treated with oral anticoagulants (41% of the patients seen by cardiologists and 26% by primary-care physicians, p < 0.005). The antiarrhythmic drug most often used was digoxin (36%).

CONCLUSIONS

Atrial fibrillation had the same frequency and epidemiology in Spain as in other Western countries. Antithrombotic therapy is underused by primary-care physicians and cardiologists.

Tachycardia-induced cardiomyopathy

Systolic dysfunction associated with chronic tachyarrhythmias, known as tachycardia-induced cardiomyopathy, is a reversible form of heart failure characterized by left ventricular dilatation that is usually reversible once the tachyarrhythmia is controlled. Its development is related to both atrial and ventricular arrhythmias. The diagnosis is usually made following observation of a marked improvement in systolic function after normalization of heart rate. Clinicians should be aware that patients with unexplained systolic dysfunction may have tachycardia-induced cardiomyopathy, and that controlling the arrhythmia may result in improvement and even complete normalization of systolic function.

Anti-thrombotic strategies for patients with atrial fibrillation and heart failure

Atrial fibrillation occurs commonly in the setting of congestive heart failure and, in fact can cause left ventricular dysfunction due to a rapid ventricular response over time, termed tachycardia-mediated cardiomyopathy. The combination of atrial fibrillation and congestive heart failure leads to a high risk of stroke for the patient and appropriate antithrombotic therapy can minimize this incidence of stroke. Stroke risk can be markedly reduced by treatment with warfarin and complications of anticoagulation minimized by close attention to maintaining the INR between 2.0 and 3.0.

Prevention of and medical therapy for atrial arrhythmias in heart failure

A large proportion of heart failure patients suffer from atrial arrhythmias, prime amongst them being atrial fibrillation (AF). Ventricular dysfunction and the syndrome of heart failure can also be a concomitant pathology in up to 50% of patients with AF. However this association is more than just due to shared risk factors, research from animal and human studies suggest a causal relationship between AF and heart failure. There are numerous reports of tachycardia-induced heart failure where uncontrolled ventricular rate in AF results in heart failure, which is reversible with cardioversion to sinus rhythm or ventricular rate control. However the relationship extends beyond tachycardia-induced cardiomyopathy. Optimal treatment of AF may delay progressive ventricular dysfunction and the onset of heart failure whilst improved management of heart failure can prevent AF or improve ventricular rate control. Prevention and treatment of atrial arrhythmias, and in particular atrial fibrillation, is therefore an important aspect of the management of patients with heart failure. This review describes the incidence and possible predictors of AF and other atrial arrhythmias in patients with heart failure and discusses the feasibility of primary prevention. The evidence for the management of atrial fibrillation in heart failure is systematically reviewed and the strategies of rate versus rhythm control discussed in light of the prevailing evidence.

Difficult cases in heart failure: reversible cardiomyopathy due to atrial fibrillation in a 46-year-old patient

The authors describe the challenging case of a 46-year-old patient who presented with a 2-week history of exertional dyspnea, paroxysmal nocturnal dyspnea, and orthopnea. He was found to have left ventricular failure and atrial fibrillation with a rapid ventricular rate. Initial work-up revealed dilated cardiomyopathy with marked left ventricular dysfunction, without any obvious cause. He received standard medical therapy for left ventricular dysfunction and his symptoms improved. Electrical cardioversion to sinus rhythm and maintenance resulted in complete recovery of left ventricular function within 6 months. (c)2001 CHF, Inc.

In patients with chronic atrial fibrillation and left ventricular systolic dysfunction, restoration of sinus rhythm confers substantial benefit

STUDY OBJECTIVES

To evaluate the benefit of sinus rhythm (SR) restoration in patients with chronic controlled atrial fibrillation (AF) and left ventricular systolic dysfunction (LVSD).

DESIGN

Prospective case-control study on the short-term outcome (6 to 9 months) of clinical and echocardiographic variables following attempted cardioversion.

SETTING

Outpatient clinic of a university hospital.

PATIENTS

Fifteen men and 5 women, ranging in age from 40 to 76 years, who had chronic controlled (mean [+/- SD] ventricular rate, 82 +/- 10 beats/min) AF and left ventricular fractional shortening (LVFS) of < 28% at baseline. Control was provided by retrospective paired echocardiographic examinations of six AF patients, plus the study cases with potentially unsuccessful cardioversion or early recurrence of AF.

INTERVENTIONS

Attempt to restore SR with amiodarone or electrical countershock.

MEASUREMENTS AND RESULTS

Conversion was attained in 17 patients, but AF recurred early in 4 patients, 3 of whom had proven ischemic LVSD. In the 13 patients with sustained SR, LVFS increased from 20 +/- 4% to 31 +/- 6% (p < 0.0001). In contrast, no changes were detected in the control group (n = 13). This improvement was paralleled by decreases in left ventricular (LV) end-diastolic dimension (from 55 +/- 7 to 51 +/- 6 mm; p = 0.014), LV mass (from 181 +/- 28 to 159 +/- 37 g; p = 0.015), and left atrial diameter (from 45 +/- 9 mm to 42 +/- 7; p = 0.003). A marked decrease in heart rate (from 82 +/- 9 to 64 +/- 5 beats/min; p < 0.0001) and a reduction in New York Heart Association functional class (from 2.3 +/- 0.9 to 1.2 +/- 0.4; p = 0.0007) also were observed in patients with sustained SR but not among subjects in the control group.

CONCLUSIONS

Even when adequate control of the ventricular rate has been achieved, the LV function of patients with chronic AF greatly improves after restoration and maintenance of SR.

Tachycardia-related cardiomyopathy: a common cause of ventricular dysfunction in patients with atrial fibrillation referred for atrioventricular ablation

OBJECTIVE

To determine the frequency of tachycardia-related cardiomyopathy in patients with atrial fibrillation and systolic dysfunction referred for atrioventricular node ablation.

PATIENTS AND METHODS

This prospective multicenter cohort study was conducted at 16 tertiary care centers. The ejection fraction was measured before and 3 and 12 months after atrioventricular node ablation. Patients with reduced systolic function (ejection fraction < or = 45%) before atrioventricular ablation were included in this study. Patients whose ejection fraction increased by at least 15 percentage points and to higher than 45% were considered to have tachycardia-related cardiomyopathy.

RESULTS

Of 63 patients with systolic dysfunction, 48 had at least 1 adequate follow-up echocardiographic study. Sixteen (25%) of the 63 had marked improvement in the ejection fraction (mean +/- SD change, 27 +/- 8 percentage points) to a value higher than 45% after ablation.

CONCLUSIONS

Tachycardia-related cardiomyopathy is common in patients with atrial fibrillation and systolic dysfunction referred for atrioventricular node ablation. This diagnosis should be considered in all patients in whom systolic dysfunction occurs subsequent to or concomitant with onset of atrial fibrillation.

Clinical relevance of silent atrial fibrillation: prevalence, prognosis, quality of life, and management

Although first described about 100yr ago, atrial fibrillation (AF) is now recognized as the most common of all arrhythmias. It has a substantial morbidity and presents a considerable health care burden. Improved diagnosis and an ageing population with an increased likelihood of underlying cardiac disease results in AF in more than 1% of population. AF is associated with an approximately two-fold increase in mortality, largely due to stroke which occurs at an annual rate of 5-7%. Another risk to survival is heart failure, which is aggravated by poor control of the ventricular rate during AF. Usually AF is associated with a variety of symptoms: palpitations, dyspnea, chest discomfort, fatigue, dizziness, and syncope. Paroxysmal AF is likely to be symptomatic and frequently presents with specific symptoms, while permanent AF is usually associated with less specific symptoms. However, in at least one third of patients, no obvious symptoms or noticeable degradation of quality of life are observed. This asymptomatic, or silent, AF is diagnosed incidentally during routine physical examinations, pre-operative assessments or population surveys. Recently, a very large incidence of generally short paroxysms of AF has been seen in patients with implantable pacemakers or defibrillators and these arrhythmias are often silent. Pharmacological suppression of arrhythmia may be associated with a conversion from a symptomatic to an asymptomatic form of AF. Holter monitoring and transtelephonic monitoring studies have demonstrated that asymptomatic episodes of AF exceed symptomatic paroxysms by twelve-fold or more. Although symptoms may not stem directly from AF, the risk of complications is probably the same for symptomatic and asymptomatic patients. AF is found incidentally in about 25% of admissions for a stroke. Studies in patients with little or no awareness of their arrhythmia condition indicate that unrecognized and untreated AF may cause congestive heart failure. In patients with coronary bypass, AF may not only represent risk for immediate postoperative morbidity and increase hospital resource utilization, but being unrecognized, may produce a significant impact on long-term survival and quality of life. Although silent AF merits consideration for anticoagulation and rate control therapy according to standard criteria, whether antiarrhythmic therapy is relevant in this condition remains unclear.

Management of atrial fibrillation: therapeutic options and clinical decisions

Atrial fibrillation (AF) is the most common, sustained tachyarrhythmia seen in clinical practice. Although it is not immediately life threatening, AF can cause troublesome symptoms and poses a risk of stroke. The patient's clinical status is often complicated by the presence of other cardiovascular or concomitant diseases. As a result, management of the patient with AF involves many questions and choices, all of which must be individualized. There are 3 general strategies for the management of patients with AF, including (1) restoration and maintenance of sinus rhythm, (2) control of ventricular rate, and (3) prevention of stroke. More than 1 strategy may be appropriate in some patients. Furthermore, either pharmacologic or nonpharmacologic options can be chosen in certain situations. Although some data from randomized clinical trials are available to aid in clinical decision-making, only the benefits of anticoagulation are supported by substantial evidence. This article explores practical approaches to several management issues and scenarios for which there are limited relevant clinical data. These include: (1) patient selection for ventricular rate control and assessment of treatment, (2) choice of antiarrhythmic drug for maintenance of sinus rhythm, (3) inpatient versus outpatient initiation of therapy, (4) definition of antiarrhythmic drug success, (5) methods of transthoracic direct cardioversion, and (6) prediction and prevention of AF after cardiac surgery.

Effect of rhythm regularization on left ventricular contractility in patients with atrial fibrillation

In 10 patients with atrial fibrillation, echocardiographic measures of left ventricular function-interval relations were used to assess contractility and to test the hypothesis that rhythm regularization produces a higher contractile state than is seen when the rhythm is irregular. Regularization, following direct-current cardioversion, did not augment ventricular contractility above that seen during atrial fibrillation.

Classification of atrial fibrillation

Atrial fibrillation (AF) is the subject of several overlapping schemes of classification in which the subgroups are often poorly defined. New methods of classification have been applied to accommodate new information and new concepts. These are often appropriate only in limited circumstances and may lead to confusion if applied out of context. We will describe the principal schemes used to classify AF and discuss the limitations of each.

Resolution of cardiomyopathy after ablation of atrial flutter

OBJECTIVES

We sought to serially assess left ventricular (LV) function before and after catheter ablation of atrial flutter (AFI).

BACKGROUND

The relation of tachycardia-induced cardiomyopathy to AFI and its response to direct catheter ablation are unknown.

METHODS

LV function was assessed in a series of 59 consecutive patients with successful radiofrequency ablation (RFA) of AFI before and after the procedure. Eleven patients had dilated cardiomyopathy (LV ejection fraction [LVEF] <50%) and congestive heart failure (CHF) symptoms and are the subject of this report. LV function was assessed by LVEF on two-dimensional echocardiography and functional status by New York Heart Association (NYHA) CHF classification.

RESULTS

Patients were 59 +/- 8 years old, and were all male. Five patients had a preablation diagnosis of idiopathic cardiomyopathy. The preablation LVEF was 30.9 +/- 11.0% and improved to 41.3 +/- 16% (p = 0.005) when measured 7 months after successful ablation. NYHA CHF class improved from 2.6 +/- 0.5 to 1.6 +/- 0.9 (p = 0.002). Six (55%) of 11 patients had normalization of the LVEF, with complete resolution of CHF symptoms. A lower preablation LVEF and functional class predicted nonresolution of dilated cardiomyopathy (p = 0.002 and 0.001, respectively).

CONCLUSIONS

Restoration of normal sinus rhythm by RFA in patients with chronic AFI and cardiomyopathy substantially improved LV function. Resolution of dilated cardiomyopathy occurred in the majority of patients. Tachycardia-induced cardiomyopathy may be a more common mechanism of LV dysfunction in patients with AFI than expected, and aggressive treatment of this arrhythmia should be considered.

Rhythm management in atrial fibrillation--with a primary emphasis on pharmacological therapy: Part 1

Atrial fibrillation (AF) is the most common, sustained, symptomatic tachyarrhythmia that clinicians are called upon to manage. Management strategies include ventricular rate control coupled with anticoagulation, versus restoration and maintenance of sinus rhythm. Rate control may be achieved pharmacologically, with agents that impair AV nodal conduction directly and/or by increasing parasympathetic/sympathetic balance, or by modifying or ablating the AV nodal region anatomically. Rhythm control may be achieved by electrical or pharmacological conversion followed by maintenance of sinus rhythm by pharmacological (or occasionally ablative) therapies. This article will present current approaches to rate and rhythm control issues in AF. Part 1, the current manuscript, details approaches to rate control and includes a drug selection algorithmic conclusion. It also introduces the subject of the pursuit of sinus rhythm. Parts 2 and 3, to be published in subsequent editions of PACE, will deal with therapeutic measures to restore and maintain sinus rhythm.

Interval-dependent changes in left ventricular contractile state in lone atrial fibrillation and in atrial fibrillation associated with coronary artery disease

In atrial fibrillation (AF), beat-to-beat changes in left ventricular (LV) systolic performance are caused by variations in filling (preload), aortic pressure (afterload), and ventricular inotropic or contractile state. These factors are known to be influenced by the preceding diastolic or RR interval (RR1), but the independent impact of variations in the pre-preceding RR interval (RR2) on contractile state is not well defined. This aspect was studied in 10 patients with lone AF and 8 with coronary artery disease by measuring LV peak ejection velocity (V[pe] Doppler echocardiography) in 80 to 100 consecutive cardiac cycles. V(pe) was plotted against RR1 for beats with a short RR2 and for beats with a long RR2. Such function-interval plots indicate a direct relation between V(pe) and RR1 (for RR1 = 500 to 1,000 ms). In lone AF, the slope (linear fit) of V(pe) versus RR1 was similar for short and long RR2 (slopes = 46 and 50 s[-1]). V(pe), calculated from best linear fit and a common RR1, was consistently higher when RR2 was short than when it was long. At an RR1 = 750 ms, V(pe) (% of max) was 87 +/- 6% when RR2 was short versus 76 +/- 6% when RR2 was long, p <0.05. Results were similar in patients with coronary artery disease and the observed interval-dependent potentiation of contractile state was preserved in patients with a low ejection fraction. By comparing V(pe) at a common RR1, the effects of time-dependent changes in LV preload and afterload are minimized if not abolished. Thus, differences in V(pe) reflect differences in contractile state caused by variations in RR2. Data confirm interval-dependent alterations in contractile state that are likely an expression of the force-frequency relation. Studies of LV function in AF should incorporate a consideration of cycle length-dependent changes in LV contractile state.

Tachycardia-induced cardiomyopathy: a review of animal models and clinical studies

The increasing prevalence of congestive heart failure has focused importance on the search for potentially reversible etiologies of cardiomyopathy. The concept that incessant or chronic tachycardias can lead to ventricular dysfunction that is reversible is supported by both animal models of chronic rapid pacing as well as human studies documenting improvement in ventricular function with tachycardia rate or rhythm control. Sustained rapid pacing in experimental animal models can produce severe biventricular systolic dysfunction. Hemodynamic changes occur as soon as 24 h after rapid pacing, with continued deterioration in ventricular function for up to 3 to 5 weeks, resulting in end-stage heart failure. The recovery from pacing-induced cardiomyopathy demonstrates that the myopathic process associated with rapid heart rates is largely reversible. Within 48 h after termination of pacing, hemodynamic variables approach control levels, and left ventricular ejection fraction shows significant recovery with subsequent normalization after 1 to 2 weeks. In humans, descriptions of reversal of cardiomyopathy with rate or rhythm control of incessant or chronic tachycardias have been reported with atrial tachycardias, accessory pathway reciprocating tachycardias, atrioventricular (AV) node reentry and atrial fibrillation (AF) with rapid ventricular responses. Control of AF rapid ventricular responses has been demonstrated to improve ventricular dysfunction with cardioversion to sinus rhythm, pharmacologic ventricular rate control and AV junction ablation and permanent ventricular pacing. The investigation of potential tachycardia-induced cardiomyopathy in patients with heart failure requires further prospective confirmation in larger numbers of patients, with study of mechanisms, patient groups affected and optimal therapies.

Refractory Heart Failure: A Therapeutic Approach

Optimal “triple therapy” for patients with chronic congestive heart failure (CHF) includes diuretics, digoxin, and either angiotensin-converting enzyme inhibitors or hydralazine plus nitrates. Refractory CHF is defined as symptoms of CHF at rest or repeated exacerbations of CHF despite “optimal” triple-drug therapy. Most patients with refractory CHF require hemodynamic monitoring and treatment in the intensive care unit. If easily reversible causes of refractory CHF cannot be identified, then more aggressive medical and surgical interventions are necessary. The primary goal of intervention is to improve hemodynamics to palliate CHF symptoms and signs (i.e., dyspnea, fatigue, edema). Secondary goals include improved vital organ and tissue perfusion, discharge from the intensive care unit, and, in appropriate patients, bridge to cardiac transplantation. Medical interventions include inotropic resuscitation (e.g., adrenergic agents, phosphodiesterase inhibitors, allied nonglycoside inodilators), load resuscitation (e.g., afterload and preload reduction with nitroprusside or nitroglycerin; preload reduction with diuretics and diuretic facilitators, such as dopaminergic agents or ultrafiltration), and electrical resuscitation (e.g., prevention of sudden death, correction of new or rapid atrial fibrillation, or dual chamber pacing in the setting of relative prolongation of the PR interval and diastolic mitral/tricuspid regurgitation). Surgical interventions are temporizing (e.g., intra-aortic balloon pump and other mechanical assist devices) or definitive (e.g., coronary artery revascularization, valvular surgery, and cardiac transplantation). Although these interventions may improve immediate survival in the short term, only coronary artery revascularization and cardiac transplantation have been shown to improve long-term survival.

Radiofrequency catheter ablation versus modification of the AV node for control of rapid ventricular response in atrial fibrillation

Atrial fibrillation is a common arrhythmia, which is frequently difficult to control. Symptoms and ventricular dysfunction may be caused by a rapid ventricular response to atrial fibrillation. Radiofrequency catheter ablation techniques for ventricular rate control have been developed, including AV node modification and AV node ablation with pacemaker implantation. For both AV node modification and ablation, radiofrequency energy is applied via a 4-mm tipped electrode catheter. For AV node ablation radiofrequency energy is applied near the compact AV node or His bundle via the right atrium, or occasionally at the His bundle via the left ventricle. For AV node modification radiofrequency energy is applied in the low middle or posterior septal right atrium near the tricuspid valve annulus. Both techniques can effectively control ventricular response to atrial fibrillation and the associated symptoms, although AV node modification is effective in only about 70% of patients compared to AV node ablation, which is effective in nearly 100%. In patients responding to AV node modification, maximal and mean ventricular response to atrial fibrillation is reduced by 25% to 35% chronically. Inadvertent AV block may occur during attempted AV node modification. It seems appropriate to attempt AV node modification prior to AV node ablation in patients with refractory atrial fibrillation and rapid ventricular response, in order to avoid the need for permanent pacemaker implantation. Although unproven, studies suggest that the mechanism by which AV node modification achieves ventricular rate control may be slow-pathway ablation in the low posterior septal right atrium.

Should every patient with atrial fibrillation have the rhythm converted to sinus rhythm?

Atrial fibrillation is the most common atrial tachyarrhythmia. Consideration for the potential conversion of atrial fibrillation and the subsequent maintenance of sinus rhythm may be related to underlying pathology. Typically, extra cardiac factors such as thyroid hyperactivity help to determine initial therapy. Intrinsic cardiac factors may also influence the clinician's decision regarding potential cardioversion and maintenance of sinus rhythm. Some acute events such as pericarditis and the effects of cardiac trauma may resolve and result in spontaneous restoration of sinus rhythm. Other cardiac events such as acute myocardial infarction with or without atrial ischemia, valvular disease, and others may result in the precipitation of atrial fibrillation. The major reasons to consider cardioversion, either medically or electrically, are ventricular rate control, hemodynamic improvement, sense of well being, and the avoidance of embolism. Certain clinical situations (e.g., Wolff-Parkinson-White syndrome) require urgent restoration of sinus rhythm in light of the potential for extremely rapid ventricular rates. It has been suggested that all antiarrhythmic drug administration should be initiated in the hospital setting, but the brief period of drug administration in an inpatient setting does not protect the patient from potential, late-onset proarrhythmic events. Both antiarrhythmic drug therapy and electric cardioversion are useful for restoration of sinus rhythm in both acute and chronic atrial fibrillation. The most important negative aspect of drug conversion of atrial fibrillation may be the potential development of a proarrhythmic drug effect. Although controversial, conversion (medical or electrical) is probably indicated in every patient with the first episode of persistent atrial fibrillation, even if the patient is asymptomatic.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of atrioventricular junction radiofrequency ablation in patients with chronic atrial fibrillation and flutter on quality of life and cardiac performance

The purpose of this study was to evaluate the effects of atrioventricular junction radiofrequency ablation on the quality of life, exercise performance, and echocardiographic parameters in 23 patients with chronic, severely symptomatic, drug-refractory atrial fibrillation or flutter. Initially, patients were randomized to receive ablation plus pacemaker therapy (n = 12) or pacemaker therapy alone (n = 11). After 15 days, palpitations decreased by 92% and 37% (p = 0.004), rest dyspnea by 79% and 40% (p = NS), effort dyspnea by 65% and 30% (p = 0.03), exercise intolerance by 54% and 17% (p = 0.005), and asthenia by 67% and 31% (p = 0.02) in the 2 groups, respectively. At the end of this short-term study, control patients also underwent ablation therapy, and a 3-month intrapatient follow-up study was performed in 22 patients. New York Heart Association functional class > or = 3 was present in 14 patients (64%) before, but in only 3 patients (14%) after ablation therapy (p = 0.002); specific activity scale functional class > or = 3 was present in 9 patients (41%) before, but in only 5 (23%) after ablation therapy (p = NS). Exercise duration during standardized stress testing increased by a mean of 63 +/- 93 seconds (15% increase) (p = 0.001). In the 9 patients with depressed left ventricular systolic function, echocardiographic fractional shortening increased by 34% (from 23 +/- 5% to 31 +/- 9%) (p = 0.003). In the remaining 13 patients with normal systolic function, fractional shortening decreased by 10% (from 40 +/- 5% to 36 +/- 6%) (p = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Chronotropic response to exercise in patients with atrial fibrillation: relation to functional state

OBJECTIVE

To determine the relation between functional capacity and heart rate response to exercise in patients with atrial fibrillation.

SUBJECTS

73 consecutive patients with chronic atrial fibrillation.

MAIN OUTCOME MEASURES

Relation between functional capacity, measured as peak oxygen consumption (peak VO2; ml/min/kg), and heart rate at all stages of exercise in univariate and multivariate analyses.

RESULTS

Peak VO2 showed no correlation with resting heart rate, but it showed a negative correlation with heart rate during the first stage of exercise (r = -0.94, p < 0.01). Indeed, heart rate during the early stages of exercise (stages 1-5) was higher in patients with a peak VO2 less than or equal to 20 ml/mm/kg than in those with a peak VO2 greater than 20 ml/min/kg (heart rate 140 v 125 beats/min, p < 0.05). At maximal exercise, however, peak VO2 was positively correlated with heart rate (r = 2.15, p < 0.0001).

CONCLUSION

In patients with atrial fibrillation and impaired functional capacity heart rate at low levels of exercise is augmented but maximal heart rate attenuated compared with patients with preserved functional capacity. Excessive heart rate responses to minor exercise may have deleterious effects on left ventricular function and thereby further limit functional capacity.

Catheter ablation induced reversal of chronic left ventricular dysfunction in permanent junctional tachycardia

Three patients with the permanent form of junctional tachycardia are reported. All had a normal cardiac function when the rhythm disorder was discovered. The basis for tachycardia in the three cases was atrioventricular junctional reentry whose retrograde limb was a concealed posteroseptal accessory pathway. Because of the development of heart failure over the years, one patient had His bundle ablation combined with pacemaker insertion, and the others underwent catheter ablation of the accessory pathway. Reversal of left ventricular involvement, as assessed by chest X ray and echocardiography was noted in every patient. Ejection fraction in one patient, measured by radionuclide angiography, returned to normal 3 months later. Thus catheter ablation of permanent junctional tachycardia can effectively suppress rhythmic cardiomyopathy.

Left ventricular dysfunction due to atrial fibrillation in patients initially believed to have idiopathic dilated cardiomyopathy

Ten patients aged 22 to 80 years (median 57) with severe left ventricular (LV) dysfunction and atrial fibrillation (AF) with rapid ventricular response were evaluated after therapy. Because most patients were unaware of their arrhythmia, duration was usually unknown. All patients had heart failure symptoms; 9 presented with New York Heart Association class III or IV disability, and 1 with class II disability. Initial LV ejection fraction ranged from 12 to 30% (median 25). No patient had symptomatic coronary artery disease (4 underwent angiography). Myocarditis and infiltrative processes were excluded by biopsy in 5 patients. All patients were considered initially to have idiopathic dilated cardiomyopathy with secondary AF. Ventricular rate was controlled in all patients, with sinus rhythm restored in 5. At follow-up (median 30 months, range 3 to 56), all patients were asymptomatic. LV ejection fraction after treatment ranged from 40 to 64% (median 52). It is concluded that in some patients initially considered to have idiopathic dilated cardiomyopathy, AF with rapid ventricular response may be the primary cause rather than the consequence of severe LV dysfunction. LV dysfunction may be completely reversible with ventricular rate control.

Improvement in left ventricular systolic function after successful radiofrequency His bundle ablation for drug refractory, chronic atrial fibrillation and recurrent atrial flutter

Incessant supraventricular tachyarrhythmia may lead to a reversible impairment of left ventricular (LV) function. This issue was investigated in 10 patients (aged 64 +/- 13 years) who underwent radiofrequency His bundle ablation for control of drug refractory, chronic atrial fibrillation (n = 9) and recurrent atrial flutter (n = 1). LV function was assessed by 2-dimensional guided M-mode echocardiography within 24 hours (baseline) and 49 +/- 18 days (follow-up) after successful ablation, both during VVI pacing at 70 beats/min. Fractional shortening increased from 28 +/- 9% at baseline to 35 +/- 8% at follow-up (p = 0.006). This increase in fractional shortening was due to a significant reduction of end-systolic diameter from 41 +/- 10 to 36 +/- 10 mm (p = 0.02), whereas there was no appreciable change in end-diastolic diameter (56 +/- 7 to 55 +/- 10 mm; p = 0.5). These changes were substantially greater in patients with baseline impairment of LV function (fractional shortening less than 27%). Fractional shortening increased by 12% (p = 0.14) in patients with normal LV function (n = 5) and by 44% (p = 0.02) in those with impaired LV function at baseline (n = 5). The greater increase in fractional shortening in patients with preexisting LV impairment was due to a more pronounced decline in end-systolic dimensions (-11.9%; p = 0.08) compared with that of patients with normal LV function at baseline (-9.21%; p = 0.2). End-diastolic diameter showed no significant change in either group (-3.53% [p = 0.8] and -0.58% [p = 0.4]).(ABSTRACT TRUNCATED AT 250 WORDS)

Lone atrial fibrillation and stroke

We studied 21 consecutive patients from the Lausanne Stroke Registry, who had first-ever ischemic stroke and lone atrial fibrillation, with a standard protocol of investigations including brain CT, and non-invasive cardiac and arterial tests. Rarity of associated risk factors and extracranial; arterial disease, presence of distal intracerebral occlusions on early angiography, and topography of cerebral infarct suggested that cardioembolism was the cause of stroke, though echocardiographic evidence for an atrial thrombus was uncommon. There was no recurrence during a post-stroke 14-day phase, during which anticoagulant and antiaggregant therapies were systematically avoided. Though low, the main risk of stroke recurrence was 0.99 per 100 patient-years during a mean follow-up period of 4.8 years, including a mean duration of anticoagulant therapy of 2.3 years in 18 patients. On the other hand, no death, severe cardiac events, or disabling anticoagulation-related hemorrhages occurred.

The challenge of cardiomyopathy

The combined clinical and pathophysiologic characteristics and diagnostic features as well as current concepts of pathogenesis, therapy and prevention of the principal forms of cardiomyopathy are reviewed. These include hypertrophic cardiomyopathy, dilated cardiomyopathy, restrictive cardiomyopathy and specific cardiac muscle disease. Emphasis is placed on recent developments and unresolved questions requiring application of newer techniques of molecular biology and genetics and adult myocyte culturing.

Dilated cardiomyopathy and myocarditis: natural history, etiology, clinical manifestations, and management

This monograph begins and ends with a statement of uncertainty regarding many aspects of dilated cardiomyopathy. Natural history studies identify patients with widely differing outcomes. A host of prognostic factors have emerged, yet it would appear that the major determinants of survival are as yet unrecognized. The diagnosis remains primarily one of exclusion, and management is largely nonspecific and supportive. The frequency of sudden cardiac death is well documented, but the ability to accurately identify patients at risk and the efficacy of antiarrhythmic therapy is unestablished. The emerging success of cardiac transplantation is a source of encouragement. The causes of dilated cardiomyopathy remain a source of intense investigation. Accumulating evidence (much of it circumstantial) does, however, implicate a viral etiology and perhaps altered function of the immunoregulatory system. However, the disparity between the severity of functional disturbance with the relative lack of histologic markers of cellular necrosis implies a disturbance at a cellular level. The etiology or etiologies remain elusive. Future investigation directed at fundamental aspects of cardiac cellular biology may provide the answers.

The natural history of lone atrial fibrillation. A population-based study over three decades

From 1950 to 1980, 3623 patients from Olmsted County, Minnesota, were found to have atrial fibrillation. Ninety-seven of these patients (2.7 percent), who were 60 years old or younger at diagnosis, had lone atrial fibrillation (atrial fibrillation in the absence of overt cardiovascular disease or precipitating illness), and their data were reviewed to determine the incidence of thromboemboli. Twenty of these patients (21 percent) had an isolated episode of atrial fibrillation, 56 (58 percent) had recurrent atrial fibrillation, and 21 (22 percent) had chronic atrial fibrillation. The total follow-up period was 1440 person-years, with a mean of 14.8 years per patient. The mean age at diagnosis was 44 years. Nineteen cardiovascular events occurred in 17 patients; 4 patients had strokes thought to be due to emboli from atrial fibrillation, and 4 had myocardial infarctions without overt evidence of previous coronary artery disease. The probability of survival at 15 years was 94 percent among the patients with lone atrial fibrillation. At 15 years, 1.3 percent of the patients had had a stroke on a cumulative actuarial basis. On an actuarial basis, there was no difference in survival or in survival free of stroke among the patients with the three types of lone atrial fibrillation (i.e., isolated, recurrent, and chronic). We conclude that lone atrial fibrillation in patients under the age of 60 at diagnosis is associated with a very low risk of stroke. This suggests that routine anticoagulation may not be warranted.

Transient atrial fibrillation in a patient with acute ureterolithiasis

A 34-year-old woman with symptoms associated with a confirmed ureteral calculus was found to be in atrial fibrillation on arrival at the emergency department. When her symptoms had improved, it was noted that the atrial fibrillation had reverted spontaneously to a sinus rhythm. Subsequent evaluation did not reveal a common etiology of the atrial fibrillation. Transient atrial fibrillation has been associated with many diverse conditions. It has not been previously reported in association with acute ureterolithiasis.