Adequate Rate Control Research Articles

Catheter Ablation for Atrial Fibrillation in Congestive Heart Failure

Congestive heart failure and atrial fibrillation often coexist, and each adversely affects the other with respect to management and prognosis. We prospectively evaluated the effect of catheter ablation for atrial fibrillation on left ventricular function in patients with heart failure. We studied 58 consecutive patients with congestive heart failure and a left ventricular ejection fraction of less than 45 percent who were undergoing catheter ablation for atrial fibrillation. We selected as controls 58 patients without congestive heart failure who were undergoing ablation for atrial fibrillation, matched according to age, sex, and classification of atrial fibrillation. We evaluated the patients' left ventricular function and dimensions, symptom score, exercise capacity, and quality of life at baseline and at months 1, 3, 6, and 12. After a mean (+/-SD) of 12+/-7 months, 78 percent of the patients with congestive heart failure and 84 percent of the controls remained in sinus rhythm (P=0.34) (69 percent and 71 percent, respectively, were in sinus rhythm without the administration of antiarrhythmic drugs). The patients with congestive heart failure had significant improvement in left ventricular function (increases in the ejection fraction and fractional shortening of 21+/-13 percent and 11+/-7 percent, respectively; P<0.001 for both comparisons), left ventricular dimensions (decreases in the diastolic and systolic diameters of 6+/-6 mm and 8+/-7 mm, respectively; P=0.03 and P<0.001, respectively), exercise capacity, symptoms, and quality of life. The ejection fraction improved significantly not only in patients without concurrent structural heart disease (24+/-10 percent, P<0.001) and those with inadequate rate control before ablation (23+/-10 percent, P<0.001), but also in those with coexisting heart disease (16+/-14 percent, P<0.001) and adequate rate control before ablation (17+/-15 percent, P<0.001). Restoration and maintenance of sinus rhythm by catheter ablation without the use of drugs in patients with congestive heart failure and atrial fibrillation significantly improve cardiac function, symptoms, exercise capacity, and quality of life.

The Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study: Approaches to control rate in atrial fibrillation

ObjectivesWe sought to evaluate approaches used to control rate, the effectiveness of rate control, and switches from one drug class to another in the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study. BackgroundThe AFFIRM study showed that atrial fibrillation (AF) can be treated effectively with rate control and anticoagulation, but drug efficacy to control rate remains uncertain. MethodsPatients (n = 2,027) randomized to rate control in the AFFIRM study were given rate-controlling drugs by their treating physicians. Standardized rate-control efficacy criteria developed a priori included resting heart rate and 6-min walk tests and/or ambulatory electrocardiographic results. ResultsAverage follow-up was 3.5 ± 1.3 years. Initial treatment included a beta-adrenergic blocker (beta-blocker) alone in 24%, a calcium channel blocker alone in 17%, digoxin alone in 16%, a beta-blocker and digoxin in 14%, or a calcium channel blocker and digoxin in 14% of patients. Overall rate control was achieved in 70% of patients given beta-blockers as the first drug (with or without digoxin), 54% with calcium channel blockers (with or without digoxin), and 58% with digoxin alone. Adequate overall rate control was achieved in 58% of patients with the first drug or combination. Multivariate analysis revealed an association between first drug class and several clinical variables. There were more changes to beta-blockers than to the other two-drug classes (p < 0.0001). ConclusionsRate control in AF is possible in the majority of patients with AF. Beta-blockers were the most effective drugs. To achieve the goal of adequate rate control in all patients, frequent medication changes and drug combinations were needed.

Maintenance of sinus rhythm in patients with atrial fibrillation. an AFFIRM substudy of the first antiarrhythmic drug

We sought to evaluate approaches used to control rate, the effectiveness of rate control, and switches from one drug class to another in the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study.The AFFIRM study showed that atrial fibrillation (AF) can be treated effectively with rate control and anticoagulation, but drug efficacy to control rate remains uncertain.Patients (n = 2,027) randomized to rate control in the AFFIRM study were given rate-controlling drugs by their treating physicians. Standardized rate-control efficacy criteria developed a priori included resting heart rate and 6-min walk tests and/or ambulatory electrocardiographic results.Average follow-up was 3.5 ± 1.3 years. Initial treatment included a beta-adrenergic blocker (beta-blocker) alone in 24%, a calcium channel blocker alone in 17%, digoxin alone in 16%, a beta-blocker and digoxin in 14%, or a calcium channel blocker and digoxin in 14% of patients. Overall rate control was achieved in 70% of patients given beta-blockers as the first drug (with or without digoxin), 54% with calcium channel blockers (with or without digoxin), and 58% with digoxin alone. Adequate overall rate control was achieved in 58% of patients with the first drug or combination. Multivariate analysis revealed an association between first drug class and several clinical variables. There were more changes to beta-blockers than to the other two-drug classes (p < 0.0001).Rate control in AF is possible in the majority of patients with AF. Beta-blockers were the most effective drugs. To achieve the goal of adequate rate control in all patients, frequent medication changes and drug combinations were needed.

A bit allocation scheme for a class of embedded wavelet video encoders

In this paper, we investigate bit allocation strategies for a class of embedded wavelet video encoders. They take advantage of the precise control that such coders have over the bit-rate of each frame. We first show that a piecewise-linear model suits the rate × distortion characteristics of these encoders better than an exponential model, specially in low bit-rate applications. Then, we use an effective iterative procedure for dealing with the problem of frame dependency which yields improved rate × distortion results. Two types of embedded wavelet coders, using scalar and vector quantization, are tested. The results are encouraging, showing that the adoption of an adequate rate-control strategy can improve both objective and subjective quality of video sequences encoded using such embedded wavelet video encoders.

Atrial flutter

Atrial flutter (AFl) is an arrhythmia resulting from reentry in a macroreentrant circuit, most commonly in the right atrium. Typical AFl uses the narrow isthmus of right atrial tissue between the tricuspid valve annulus and the inferior vena cava orifice as part of the macroreentrant circuit. The treatment of AFl is directed toward achieving the following four goals. 1) In the presence of AFl, adequate rate control is required, which can be achieved in most but not all patients by oral or intravenous digoxin, calcium channel blockers, or beta-blockers, alone or in combination. 2) Anticoagulation with warfarin should be considered in patients with recurrent AFl, especially those over 70 years of age, and those with a history of atrial fibrillation, stroke, or structural heart disease. 3) Conversion to sinus rhythm can be achieved in up to 70% of patients with intravenous ibutilide, but this should be reserved for patients with either normal hearts or only mild left ventricular dysfunction. Direct-current cardioversion is nearly 100% effective and is ideal for patients with left ventricular dysfunction. 4) Long-term maintenance of sinus rhythm may be achieved in up to 50% to 60% of patients by using antiarrhythmic drugs, including sotalol, amiodarone, dofetilide, propafenone, and flecainide, but with the potential for causing significant proarrhythmia and side effects. Radiofrequency catheter ablation may cure over 90% of patients with type 1 AFl (using the tricuspid valve to inferior vena cava isthmus), and from 70% to 90% of patients with atypical AFl. Newer mapping techniques, such as electroanatomic mapping, are likely to further reduce procedure time and improve success rates.

Prävention von Vorhofarrhythmien durch Stimulation

Atrial fibrillation is the most frequent arrhythmia. It can impair quality of life considerably. Due to thromboembolic complications it contributes to the patients' morbidity and mortality and to the costs for their medical treatment. In chronic atrial fibrillation there is a need for adequate anticoagulation and heart rate control. In paroxysmal and intermittent atrial fibrillation it should be sought to prevent its progression to chronic atrial fibrillation. Since atrial fibrillation initiates negative processes of remodeling within the atrial myocardium, it has the tendency to perpetuate itself. From a theoretical point of view, it can be expected that all means which prevent episodes of atrial fibrillation or which terminate it immediately after its onset, are able to prevent or at least to delay the progression to chronic atrial fibrillation. Pharmacologic treatment is usually used to prevent recurrences of atrial fibrillation. Based on the actual data it can also be expected that pacemakers with special preventive pacing algorithms are able to reduce the atrial arrhythmic burden. Besides consequent overdrive pacing, more sophisticated algorithms like "suppression of premature atrial contractions", "post exercise response", "automatic rest rate" or "post mode-switch pacing" have been developed. They can be applied either alone or in combination with special lead positions (interatrial septal pacing or pacing of the triangle of Koch) or special stimulation configurations like dual site right atrial pacing or biatrial pacing. These pacing strategies cover the most relevant onset mechanisms of atrial fibrillation. Furthermore, there are algorithms to treat atrial tachyarrhythmias actively by antitachycardia pacing (ATP). First clinical results have shown that about 2/3 of the diagnosed atrial tachyarrhythmias could be terminated by these means immediately after their onset. This article gives an overview over the principles of pacing in the management of atrial arrhythmias and ongoing clinical trials in this field. Before a definite judgement on the clinical relevance of these new preventive and therapeutic pacing strategies can be given, the results of these ongoing controlled clinical studies have to be analyzed.

Part 6: Advanced Cardiovascular Life Support

Part 6: Advanced Cardiovascular Life Support

INAPPROPRIATE SINUS TACHYCARDIA: Diagnosis and Treatment

Inappropriate sinus tachycardia is characterized by consistently elevated heart rates and exaggerated responses to minimal physiologic activity. The syndrome of inappropriate sinus tachycardia is defined by the clinical presentation of palpitations and presyncope that commonly appear to be out of proportion to the severity of the tachycardia. The development of a potentially curative procedure for patients suffering from inappropriate sinus tachycardia has renewed interest in the treatment of such patients. Continued research directed at the pathophysiology of inappropriate sinus tachycardia and what the optimal end point for achieving adequate rate control by radiofrequency catheter ablation without the need for the implantation of a permanent pacemaker is required. The optimal treatment may be the use of drugs that specifically inhibit sinus node pacemaker current.

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.

Management of atrial fibrillation in the setting of heart failure.

Heart failure is often complicated by atrial fibrillation. Once atrial fibrillation has started it further enhances heart failure due to uncontrolled rate with shortened filling time and provocation of tachycardiomyopathy. Absent atrial kick and irregularity of the ventricular rhythm also contribute. Considering these mechanisms, restoration of sinus rhythm is most beneficial but is associated with frequent recurrences. Before cardioversion heart failure must be treated. ACE inhibition, initiated before cardioversion, may enhance maintenance of sinus rhythm by reducing neurohumoral activation. As a consequence, arrhythmogenic factors diminish and ventricular function may improve. beta-blockade and amiodarone may have similar effects. If cardioversion fails, adequate rate control is mandatory to prevent progressive ventricular dysfunction. Digitalis is the treatment of first choice, but when the heart rate remains uncontrolled low-dose beta-blockade should be given. If the ventricular rate remains uncontrolled despite drugs, atrioventricular node ablation with implantation of a pacemaker may be considered. Not only patients with idiopathic heart failure and atrial fibrillation, but also those with significant underlying heart disease may benefit from this intervention. In atrial fibrillation patients undergoing cardiac surgery for heart failure due to valvular disease, additional arrhythmia surgery may be contemplated.

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 midseptal right atrium to lower the ventricular rate in atrial fibrillation to 120 to 130 beats/min during an infusion of 4 μg/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 ∼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.(J Am Coll Cardiol 1997;27:113–21)>

The effect of atrial fibrillation and the ventricular rate control on exercise capacity

Atrial fibrillation (AF) is a common cardiac arrhythmia, affecting approximately 1.5 million patients in the United States. This study was designed to determine the effect of AF and the ventricular rate control during AF on cardiovascular performance as measured by exercise endurance on a standard Bruce protocol. Sixty-three patients with AF who underwent exercise stress testing during both sinus rhythm and AF were analyzed. Heart rate, blood pressure, heart rate acceleration, exercise duration, and left ventricular (LV) systolic function were measured. Atrial fibrillation resulted in a small but statistically significant decrease in exercise endurance (426 +/- 180 vs. 402 +/- 168 s, p < 0.05). The drop in exercise tolerance was consistent regardless of the underlying heart condition or adequate ventricular rate control during AF. Heart rate in AF was consistently faster than in sinus rhythm, at rest, and at peak exercise (63 vs. 79 beats/min and 125 vs. 149 beats/min, respectively, p < 0.001). Our analyses indicated that (1) the loss of atrioventricular synchrony had minimal effect on cardiovascular performance in patients with preserved LV function, (2) the decrease in cardiovascular performance was related to loss of atrioventricular synchrony but not to underlying heart disease or ventricular rate control, and (3) compensation for the loss of the atrial contribution was provided by consistently faster heart rate during AF.

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 doubleblind, randomized, placebo-controlled trial. All patients were in New York Heart Association class 11 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 niL/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.

Efficacy of oral diltiazem to control ventricular response in chronic atrial fibrillation at rest and during exercise

Although digoxin is often the first choice for control of ventricular response in chronic atrial fibrillation, it fails to slow exercise rates. Diltiazem, a calcium channel antagonist that slows atrioventricular conduction, was administered to 16 patients who failed to achieve adequate rate control on low level exercise testing despite digoxin therapy. Therapeutic response to diltiazem was assessed with submaximal and maximal exercise tests and 24 hour ambulatory electrocardiographic monitoring. During the diltiazem treatment phase, ventricular response at rest diminished (96 +/- 17 versus 69 +/- 10 beats/min, p less than 0.001) as did rate during submaximal exercise (155 +/- 28 versus 116 +/- 26, p less than 0.001), maximal exercise (163 +/- 14 versus 133 +/- 26, p less than 0.001) and average ventricular response during 24 hour monitoring (87 +/- 13 versus 69 +/- 10, p less than 0.001). Rate at rest decreased 26 +/- 15% and submaximal exercise rate diminished 24 +/- 12%. Thirteen (81%) of the 16 patients exhibited at least 15% slowing of rate at rest and during submaximal exercise. Eleven patients (69%) reported alleviation of symptoms. There was no change in serum digoxin levels during diltiazem treatment (1.3 +/- 0.5 versus 1.3 +/- 0.6 ng/ml, p = NS). On withdrawal of diltiazem, ventricular response returned to baseline values. Diltiazem is an effective agent for control of ventricular response, both at rest and during exercise, in digoxin-treated patients with chronic atrial fibrillation.