Improvement in left ventricular function by ablation of atrioventricular nodal conduction in selected patients with lone atrial fibrillation

Radiofrequency catheter ablation for atrial fibrillation

Until recently, catheter-based radiofrequency ablation for atrial fibrillation was limited to palliative approaches of either atrioventricular node ablation or modification. It is now recognized that at least a proportion of patients with paroxysmal atrial fibrillation may be suitable for curative ablation of an underlying single arrhythmogenic focus. With the intense interest in this area, a catheter-based cure involving endocardial linear lesion creation for patients with chronic or paroxysmal atrial fibrillation may not be far in the future.

Atrial fibrillation: antiarrhythmic therapy versus rate control with antithrombotic therapy

Atrial fibrillation is a major health problem in the United States, but the best strategies for treating it have not been rigorously determined in clinical studies. Specifically, there is a paucity of data comparing the approach of maintaining sinus rhythm using prophylactic antiarrhythmic drug therapy with the approach of controlling the ventricular response to atrial fibrillation while reducing embolic events with concomitant antithrombotic therapy. Until ongoing randomized trials are completed, which patients benefit most from a specific approach cannot be determined with certainty. In general, the most reasonable strategies include (1) the restoration of sinus rhythm (without prophylactic antiarrhythmic therapy) after the patient's first episode of atrial fibrillation; and (2) the maintenance of sinus rhythm (including the use of prophylactic antiarrhythmic therapy) in patients who remain symptomatic despite adequate rate control, and who are not at high risk for proarrhythmia and/or are unlikely to maintain sinus rhythm. The risks and benefits need to be carefully weighed in patients with truly asymptomatic atrial fibrillation. Many patients may require multiple attempts to maintain sinus rhythm. Current investigative treatment modalities (e.g., ablation techniques, atrial implantable cardioverter-defibrillators, new antiarrhythmic agents) are likely to alter the current approaches to atrial fibrillation.

Clinical improvement after atrioventricular nodal ablation for atrial fibrillation does not correlate with improved ejection fraction

A retrospective review of 15 patients with atrial fibrillation and class III to IV congestive heart failure who underwent atrioventricular nodal ablation demonstrated a marked improvement in their functional abilities. This improvement, however, could not be explained by the improvement in ejection fraction alone.

Nonpharmacologic treatment of atrial fibrillation: current and evolving strategies

Atrial fibrillation is the most common cardiac arrhythmia requiring treatment. Limitations of medical treatment have prompted development of nonpharmacologic therapies for this arrhythmia. These are aimed at ventricular rate control during atrial fibrillation, termination of the arrhythmia, and/or prevention of recurrences. Ventricular rate control can be achieved with transcatheter ablation or modification of the atrioventricular node. The MAZE operation is effective in preventing arrhythmia recurrence, but because it requires cardiac surgery, its appeal is limited. Development of the technique for direct transcatheter ablation of atrial fibrillation is eagerly anticipated and may represent the standard curative treatment of the future. In appropriately selected patients, implantable device therapy may play an important role in the treatment of paroxysmal atrial fibrillation.

Bradycardia-induced polymorphic ventricular tachycardia after radiofrequency catheter modification of atrioventricular junction

We report the case of a 59-year-old man with a dilated nonischemic cardiomyopathy who had chronic rapid atrial fibrillation despite several therapies. Radiofrequency modification of the atrioventricular (AV) junction slowed the mean ventricular rate from 120 beats per minute (bpm) to 60 bpm. Five hours after the procedure and during the following 1 week, despite ventricular pacing at 90 bpm, the patient developed nonsustained or sustained polymorphic ventricular tachycardias. Finally, pacing at 90 bpm was successfully used in this patient. In conclusion, patients who have undergone modification of AV conduction may be at high risk of life-threatening ventricular arrhythmias in the first week following the procedure.

Tachycardia-induced atrial myopathy: an important mechanism in the pathophysiology of atrial fibrillation?

The atrial myocardium of patients with chronic atrial fibrillation (AF) is often abnormal in its histologic features and in its electrophysiologic properties. These abnormalities have been interpreted in some cases as the cause of AF and in others as a consequence of AF. We believe that both are the case. We will review the features of this atrial myopathy and discuss the likely mechanisms and consequences of the process.

Heart failure and atrial fibrillation: current concepts and controversies

Heart failure and atrial fibrillation are very common, particularly in the elderly. Owing to common risk factors both disorders are often present in the same patient. In addition, there is increasing evidence of a complex, reciprocal relation between heart failure and atrial fibrillation. Thus heart failure may cause atrial fibrillation, with electromechanical feedback and neurohumoral activation playing an important mediating role. In addition, atrial fibrillation may promote heart failure; in particular, when there is an uncontrolled ventricular rate, tachycardiomyopathy may develop and thereby heart failure. Eventually, a vicious circle between heart failure and atrial fibrillation may form, in which neurohumoral activation and subtle derangement of rate control are involved. Treatment should aim at unloading of the heart, adequate control of ventricular rate, and correction of neurohumoral activation. Angiotensin converting enzyme inhibitors may help to achieve these goals. Treatment should also include an attempt to restore sinus rhythm through electrical cardioversion, though appropriate timing of cardioversion is difficult. His bundle ablation may be used to achieve adequate rate control in drug refractory cases.

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.

Long-term follow-up after radiofrequency modification of the atrioventricular node in patients with atrial fibrillation

OBJECTIVES

The purpose of this study was to describe the long-term follow-up results in 62 patients with atrial fibrillation and an uncontrolled ventricular rate, who underwent radiofrequency modification of the atrioventricular (AV) node.

BACKGROUND

Previous studies in small numbers of patients have suggested that radiofrequency modification may be effective in controlling the ventricular rate in patients with atrial fibrillation, but long-term follow-up data have been lacking.

METHODS

The subjects of this study were 62 consecutive patients (mean age +/- SD 65 +/- 14 years; 43 with structural heart disease) who underwent an attempt at radiofrequency modification of the AV node because of symptomatic, drug-refractory atrial fibrillation with an uncontrolled ventricular rate. The atrial fibrillation was chronic in 46 patients and paroxysmal in 16. Radiofrequency energy was applied to the posteroseptal or mid-septal right atrium to lower the ventricular rate in atrial fibrillation to 120 to 130 beats/min during an infusion of 4 micrograms/min of isoproterenol.

RESULTS

Short-term control of the ventricular rate was successfully achieved without the induction of pathologic AV block in 50 (81%) of 62 patients. Inadvertent high degree AV block occurred in 10 (16%) of 62 patients, with the AV block occurring at the time of the procedure in 6 patients and 36 to 72 h after the procedure in 4. During 19 +/- 8 months of follow-up (range 4 to 33), 5 (10%) of 50 patients had a symptomatic recurrence of an uncontrolled rate during atrial fibrillation. Overall, adequate rate control at rest and during exertion, without pathologic AV block, was achieved long term in 45 (73%) of 62 patients. Among 37 patients with a successful outcome, left ventricular ejection fraction increased from (mean +/- SD) 0.44 +/- 0.14 to 0.51 +/- 0.10 one year later (p < 0.001). Complications other than AV block included polymorphic ventricular tachycardia 10 to 24 h after the procedure in two patients who had a predisposing factor for ventricular tachycardia and sudden death 1 to 5 months after the procedure in two patients with idiopathic dilated cardiomyopathy, one of whom had a pacemaker for AV block.

CONCLUSIONS

In approximately 70% of properly selected patients with atrial fibrillation and an uncontrolled ventricular rate, radiofrequency modification of the AV node results in excellent long-term control of the ventricular rate at rest and during exertion.

Impact on ventricular function and quality of life of transcatheter ablation of the atrioventricular junction in chronic atrial fibrillation with a normal ventricular response

We assessed left ventricular function and quality of life after atrioventricular junction ablation and pacemaker implant in 14 patients with chronic atrial fibrillation and normal ventricular response. A significant improvement in left ventricular ejection fraction, fractional shortening, and functional capacity were observed at follow-up, suggesting that in patients with chronic atrial fibrillation a regular heart beat may be preferable over rate control.

Efficacy of serial electrical cardioversion therapy in patients with chronic atrial fibrillation after valve replacement and implications for surgery to cure atrial fibrillation

Chronic atrial fibrillation (AF) occurs often in the setting of mitral and aortic valve disease. Eventually, these patients undergo valve replacement which improves cardiac function but does not prevent AF. This study investigates which patient may benefit from additional surgery for the cure of AF performed in combination with valve surgery. Seventy-four patients were retrospectively included from our prospective database of patients referred for serial cardioversion therapy between 1986 and 1993. All these patients had chronic AF after valve replacement. After the first electrical cardioversion, patients did not receive antiarrhythmic drugs. Relapses were managed by repeated cardioversions, and then antiarrhythmic drugs were instituted. After a median follow-up of 7 years (range 1.3 to 23), 39 patients had intractable AF. Multivariate analysis revealed that patients with a history of chronic AF before surgery (risk ratio 5.4, confidence intervals 2.5 to 11.3, p = 0.0001) had a poor arrhythmia outcome. In addition, Kaplan-Meier survival analysis demonstrated a lower success rate (p = 0.0017) in patients with mitral valve disease than in those with aortic valve disease. Congestive heart failure (41% vs 6%, p = 0.0007) and cardiovascular mortality (23% vs 9%, p = 0.09) were seen most often in patients with an unsuccessful cardioversion strategy. Thus, patients scheduled for mitral valve surgery with a history of chronic AF should be considered candidates for additional surgery for AF concomitantly performed during valve surgery.

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.

Reversal of heart failure with sotalol in a case of incessant supraventricular tachycardia

Supraventricular tachycardia inducing severe left ventricular enlargement and dysfunction was treated with sotalol in a 17-year-old man, in whom radiofrequency ablation had been unsuccessful. Restoration of sinus rhythm overwhelmed the negative inotropic effect of the drug and caused full reversion to normal of the left ventricular dimensions and function.

Quality of life and outcomes after radiofrequency His-bundle catheter ablation and permanent pacemaker implantation: impact of treatment in paroxysmal and established atrial fibrillation

One hundred seven patients underwent atrioventricular (AV)-junctional ablation and pacing for atrial fibrillation, and 90 were alive 2.3 +/- 1.2 years later. Quality of life index (1.9 +/- 1.2 to 3.6 +/- 1.1; 3.6 +/- 1.1; p<0.001) and ease of activities of daily living (2 +/- 0.4 to 2.4 +/- 0.3; p<0.001) were significantly improved. Doctor visits (10 +/- 13 to 5.06 +/-7; p<0.03), hospital admissions (2.8 +/- 6.8 vs 0.17 +/- 0.54; p<0.03, and antiarrhythmic drug trials (6.2 +/- 4 to 0.46 +/- 1.5; p<0.001) decreased significantly after treatment. Congestive heart failure episodes decreased from 18 before to 8 afterward. Twenty-eight of 36 patients with dual-chamber pacemakers remained in a dual-chamber mode at follow-up. Radiofrequency AV-junctional catheter ablation and pacing is a highly successful form of treatment for medically refractory atrial fibrillation.

Assessment of left ventricular function after radiofrequency and direct current atrioventricular node ablation

BACKGROUND

There is limited information available regarding the effect of catheter ablation of the antioventricular (AV) junction on left ventricular (LV) function. Both deterioration and improvement in LV function have been reported following direct current (DC) ablation of the AV junction. The deterioration of LV function following DC ablation of the AV junction may be due to the accompanying barotrauma, DC arcing and direct coagulation, or even the effects of chronic ventricular pacing. If this deterioration of LV function was a result of the accompanying effects of DC shock, the use of radiofrequency ablation (RF) should not result in deterioration of LV function.

AIM

To study LV function before and after different methods of AV junction ablation and in patients with chronic ventricular pacing without AV junction ablation.

MATERIAL

This study assessed LV function in patients following RF ablation, low energy DC ablation of the AV junction and compared the results with our previously reported finding in patients who had AV junction ablation using high energy DC shock. A group of patients undergoing permanent single chamber ventricular pacemaker implantation without AV junction ablation were selected as controls.

METHODS

All patients were paced in the ventricle at 110 beats/minute during LV function assessment by radionuclide angiography. Global LV function and segmental wall motion abnormalities were assessed before, immediately following and three months after ablation.

RESULTS

In the high energy DC ablation group, a fall in global LV function (50 +/- 3.0% to 43 +/- 3.0%, p = 0.02) and impairment of segmental wall motion were detected. Low energy DC ablation resulted in segmental wall motion impairment similar to high energy DC but without affecting global ejection fraction (47.0% +/- 6.7 to 45.5% +/- 3.1, p > 0.05). Neither RF ablation (44.0% +/- 3.3 to 45.3% +/- 3.5, p > 0.05), nor chronic pacing (46.7% +/- 4.9 to 47.0% +/- 2.9 p > 0.05) had any effect on global or segmental LV function.

CONCLUSIONS

Low energy DC or RF ablation of the AV junction does not affect global LV ejection fraction. The deterioration of global LV function after high energy DC shock ablation appears to be related to the accompanying effects of DC energy and not to the effects of chronic ventricular pacing.

Effects of lisinopril in patients with heart failure and chronic atrial fibrillation

Although atrial fibrillation is common in patients with heart failure, patients with atrial fibrillation are often excluded from congestive heart failure trials or are not analyzed separately. Consequently, while the effect of angiotensin-converting enzyme inhibitors in patients with sinus rhythm is well established, the effect on patients with atrial fibrillation is unknown. The authors hypothesized that these agents might be particularly effective in this patient category, given their antiadrenergic properties and the importance of adequate rate control. Therefore, the effects of lisinopril 10 mg once daily were evaluated in 30 patients with congestive heart failure and chronic atrial fibrillation (mean age, 68 +/- 6 years) in a double-blind, randomized, placebo-controlled trial. All patients were in New York Heart Association class II or III and were stable on conventional therapy (digoxin, diuretics, nitrates). After 6 weeks, mean peak oxygen consumption increased from 14.7 +/- 3.4 to 15.9 +/- 2.9 mL/min/kg in the lisinopril group (P = .034). Plasma norepinephrine levels during exercise and at peak exercise tended to be lower when the patients were taking lisinopril (10.8 +/- 4.2 to 8.9 +/- 4.4 nmol/L and 16.3 +/- 9.2 to 14.3 +/- 7.7 nmol/L, P < .1). Heart rate during exercise and ambulatory monitoring was not significantly affected. Left ventricular fractional shortening tended to increase after lisinopril (23 +/- 7 to 27 +/- 9%, P = .073). Left atrial volume was unchanged, as were plasma atrial natriuretic peptide levels. After subsequent electrical cardioversion, treatment was continued for 6 more weeks, allowing assessment of the effect of lisinopril on maintenance of sinus rhythm; maintenance of sinus rhythm was 71% in the lisinopril group and 36% in the placebo group (P = NS). This study shows that treatment with an angiotensin- converting enzyme inhibitor improves peak oxygen consumption in patients with congestive heart failure and chronic atrial fibrillation. Attenuation of adrenergic drive during exercise may play a role in mediating this effect.

Newer developments in the management of atrial fibrillation

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia encountered in clinical practice. Unlike reentrant supraventricular tachycardia and malignant ventricular tachyarrhythmias, for which highly effective and safe nonpharmacologic therapies are available, the treatment of AF remains controversial and often problematic. Whereas electrical cardioversion restores sinus rhythm in most patients with AF, the maintenance of sinus rhythm often requires membrane-active antiarrhythmic drugs that may increase mortality by inducing ventricular proarrhythmia. The control of ventricular response rate, often associated with oral anticoagulation to prevent thromboembolic complications, is an alternative strategy in AF management. The relative efficacy and risks of these strategies and their respective role in different patient subgroups remain to be established. This article focuses on newer developments in the management of AF, including prospects for improved methods to maintain sinus rhythm, newer approaches to rate control, controversies regarding the use of oral anticoagulation, and novel nonpharmacologic therapies. These newer developments may lead over the next 10 years to a revolution in the management of AF as profound as that produced over the last 10 years by nonpharmacologic therapy of other arrhythmias.

Prospective study of left ventricular function after radiofrequency ablation of atrioventricular junction in patients with atrial fibrillation

BACKGROUND

In patients with drug resistant incessant supraventricular tachycardia, radiofrequency induced ablation of the atrioventricular junction and pacemaker implantation have hitherto been considered a treatment of last resort.

OBJECTIVE

To assess the short and long term effects of ablation of the atrioventricular junction on systolic and diastolic left ventricular function in patients with atrial fibrillation with and without impaired left ventricular function.

PATIENTS

29 patients (19 men; mean age 65 (SD 7) years (range 50-76)) undergoing ablation of the atrioventricular junction for drug refractory atrial fibrillation were examined a mean of 2, 65, and 216 days after ablation of the bundle of His.

MAIN OUTCOME MEASURES

Left ventricular ejection fraction and early filling deceleration times (Edec) were assessed by Doppler echocardiography after 1 to 2 hours of ventricular pacing at a rate of 80 beats/minute.

RESULTS

In 14 patients with a left ventricular ejection fraction < 50% left ventricular ejection fraction increased significantly from 32% (11%) to 39% (11%) (65 days) and 45% (11%) (216 days) (P < 0.001); Edec increased from 142 (46) ms to 169 (57) ms (65 days) and 167 (56) ms (216 days) (P < 0.05). In 15 patients with an ejection fraction > or = 50% at the initial examination no significant change in systolic function was observed.

CONCLUSIONS

In patients with left ventricular dysfunction long term improvement of systolic and diastolic left ventricular function was seen after ablation of the atrioventricular junction for rate control of atrial fibrillation. This procedure had no adverse effects on normal left ventricular function.

A new pacemaker for paroxysmal atrial fibrillation treated with radiofrequency ablation of the AV junction

Atrial fibrillation is a relative contraindication to atrial synchronous pacing because of the risk of the tracking of rapid atrial rhythms by the pacemaker. In this study, we describe the clinical results of an AV synchronous rate responsive pacemaker with an original algorithm, which is able to sense pathological increments in atrial rate and automatically to switch into a non-AV synchronous mode of pacing. This pacemaker was implanted in 12 patients who had undergone radiofrequency ablation of the AV junction in order to cure severely symptomatic, drug refractory, paroxysmal atrial fibrillation. In an acute, intrapatient comparison between the standard AV synchronous mode and the automatic switching mode, ventricular tracking of atrial fibrillation occurred in 35% and 4% of total beats at rest and in 24% and 2% of total beats during exercise, respectively (P < 0.001). During 5 +/- 4 months of follow-up, no further tachyarrhythmia related symptoms occurred. In conclusion, the standard DDDR mode is unable to eliminate ventricular tracking of atrial fibrillation, thus undermining the efficacy of AV junction ablation therapy. The automatic switching mode eliminates this adverse effect of dual chamber pacing.