The effect of cardioversion on exercise capacity in patients with atrial fibrillation

Is breathing frequency a potential means for monitoring exercise intensity in people with atrial fibrillation and coronary heart disease when heart rate is mitigated?

PURPOSE

Moderate-intensity aerobic exercise is safe and beneficial in atrial fibrillation (AF) and coronary heart disease (CHD). Irregular or rapid heart rates (HR) in AF and other heart conditions create a challenge to using HR to monitor exercise intensity. The purpose of this study was to assess the potential of breathing frequency (BF) to monitor exercise intensity in people with AF and CHD without AF.

METHODS

This observational study included 30 AF participants (19 Male, 70.7 ± 8.7 yrs) and 67 non-AF CHD participants (38 Male, 56.9 ± 11.4 yrs). All performed an incremental maximal exercise test with pulmonary gas exchange.

RESULTS

Peak aerobic power in AF ( V ˙ O2peak; 17.8 ± 5.0 ml.kg-1.min-1) was lower than in CHD (26.7 ml.kg-1.min-1) (p < .001). BF responses in AF and CHD were similar (BF peak: AF 34.6 ± 5.4 and CHD 36.5 ± 5.0 breaths.min-1; p = .106); at the 1st ventilatory threshold (BF@VT-1: AF 23.2 ± 4.6; CHD 22.4 ± 4.6 breaths.min-1; p = .240). % V ˙ O2peak at VT-1 were similar in AF and CHD (AF: 59%; CHD: 57%; p = .656).

CONCLUSION

With the use of wearable technologies on the rise, that now include BF, this first study provides an encouraging potential for BF to be used in AF and CHD. As the supporting data are based on incremental ramp protocol results, further research is required to assess BF validity to manage exercise intensity during longer bouts of exercise.

Factors Contributing to Exercise Intolerance in Patients With Atrial Fibrillation

BACKGROUND

Reduced exercise capacity and exercise intolerance are commonly reported by individuals with atrial fibrillation (AF). Our objectives were to evaluate the contributing factors to reduced exercise capacity and describe the association between subjective measures of exercise intolerance versus objective measures of exercise capacity.

METHODS

Two hundred and three (203) patients with non-permanent AF and preserved ejection fraction undergoing cardiopulmonary exercise testing (CPET) were recruited. Clinical characteristics, AF-symptom evaluation, and transthoracic echocardiography measures were collected. Peak oxygen consumption (VO_2peak) was calculated during CPET as an objective measure of exercise capacity. We assessed the impact of 16 pre-defined clinical features, comorbidities and cardiac functional parameters on VO_2peak.

RESULTS

Across this cohort (Age 66±11 years, 40.4% female and 32% in AF), the mean VO_2peak was 20.3±6.3 mL/kg/min. 24.9% of patients had a VO_2peak considered low (<16 mL/kg/min). In multivariable analysis, echocardiography-derived estimates of elevated left ventricular (LV) filling pressure (E/E') and reduced chronotropic index were significantly associated with lower VO_2peak. The presence of AF at the time of testing was not significantly associated with VO_2peak but was associated with elevated minute ventilation to carbon dioxide production indicating impaired ventilatory efficiency. There was a poor association between VO_2peak and subjectively reported exercise intolerance and exertional dyspnoea.

CONCLUSION

Reduced exercise capacity in AF patients is associated with elevated LV filling pressure and reduced chronotropic response rather than rhythm status. Subjectively reported exercise intolerance is not a sensitive assessment of reduced exercise capacity. These findings have important implications for understanding reduced exercise capacity amongst AF patients and the approach to management in this cohort. (ACTRN12619001343190).

Early improvement of daily physical activity after catheter ablation for atrial fibrillation in an accelerometer assessment: A prospective pilot study

Background

Catheter ablation improves physical activity in patients with atrial fibrillation (AF). However, continuous daily evaluation and time course of improvement in physical activity after ablation have not been fully assessed. This prospective study was conducted to evaluate the daily physical activities and changes in the physical performance in patients undergoing catheter ablation for AF by continuous monitoring of a portable accelerometer.

Methods

Ten patients scheduled for catheter ablation for AF were fitted with a uniaxial accelerometer prior to and 6 months after the procedure. This study evaluated changes in daily steps, activity intensity, and activity duration. We also evaluated changes in activity intensity using a short version of the International Physical Activity Questionnaire (IPAQ).

Results

The maximum daily steps significantly increased from baseline to postablation (baseline, 9,232 [6,716–11,485]; after 1–3 months, 11,605 [8,285–14,802]; and after 4–6 months, 11,412 [8,939–13,808], p = .020). Similarly, Δ maximum‐mean daily steps increased significantly (baseline, 2,431 [1,199–6,181]; after 1–3 months, 4,674 [4,164–6,474]; and after 4–6 months, 4,871 [3,657–6,117], p = .014). These improvements were more pronounced in patients with paroxysmal and symptomatic AF. The total IPAQ score significantly improved from baseline to after 6 months ablation (from 1,170 [693–3,930] to 4,312 [1,865–6,569], p = .037). All patients were recurrence‐free from AF after ablation.

Conclusions

The physical activity improved significantly even in the early phase following catheter ablation. The effect of suppressing AF on activity levels was apparent soon after the procedure.

A high BNP level predicts an improvement in exercise tolerance after a successful catheter ablation of persistent atrial fibrillation

INTRODUCTION

Restoration of sinus rhythm (SR) by catheter ablation (CA) of atrial fibrillation (AF) improves exercise tolerance. However, it is still unclear what characteristics of patients are contributing to an improvement in exercise tolerance after CA of AF without heart failure.

METHODS AND RESULTS

This study consisted of 51 consecutive patients with persistent or long-standing persistent AF without heart failure who were restored to SR for over 6 months by a successful CA. Exercise tolerance was evaluated by cardiopulmonary exercise testing before and 3 and 6 months after CA. The clinical characteristics contributing to an improvement in exercise tolerance was elucidated. The peak oxygen uptake (VO₂ )% significantly increased from 101.4 ± 20.3% to 110.9 ± 19.9% 3 months after the CA (P < .001). The improvement rate in the peak VO₂ % exhibited a positive correlation to the baseline brain natriuretic peptide (BNP; ρ = 0.39, P < .01), but not to the age, AF duration, left ventricular ejection fraction, or left atrial size. The linear regression analysis revealed that the baseline BNP was an independent predictor of an improvement in the peak VO₂ % (coefficients = 0.32; 95% confidence interval = 0.08, 0.54; P = .01). The peak VO₂ % improved significantly in the patients whose baseline BNP level was greater than 100 pg/mL, compared to the others (P < .01). These favorable findings were also observed 6 months after the CA.

CONCLUSION

Elimination of persistent AF by CA was associated with an improvement in exercise tolerance. This was particularly true in patients with high BNP values at baseline.

Left atrial deformation analysis by speckle tracking echocardiography to predict exercise capacity after myocardial infarction

INTRODUCTION

Left atrial (LA) size and function are associated with outcome after myocardial infarction (MI). In this study we aimed to assess the impact of LA function as a predictor of exercise capacity through speckle tracking echocardiography.

METHODS

A total of 94 patients (mean age 54.8±11.0 years; 82% male) were enrolled one month after MI. Echocardiography was used to assess LA volumes and various indices of LA conduit, contraction and reservoir function. LA deformation was assessed by two-dimensional speckle tracking to calculate strain and strain rate at different phases of the cardiac cycle. Exercise capacity was assessed by oxygen uptake (VO₂) on cardiopulmonary exercise testing.

RESULTS

Increased LA volumes, especially LA volume before atrial contraction, were correlated with reduced peak VO₂ and reduced VO₂ at anaerobic threshold. Decreased peak VO₂ was associated with reduced LA conduit function (ρ=0.24; p=0.02), but not with LA booster function (ρ=-0.07; p=0.53). Lower peak atrial longitudinal strain was associated with worse exercise capacity (ρ=0.24; p=0.02).

CONCLUSIONS

After MI, increased LA volumes were markers of decreased functional capacity that was associated with decreased LA conduit function, but not with LA contractile function. In these patients, LA longitudinal strain analysis may be useful to predict reduced exercise capacity.

Control of Heart Rate Versus Rhythm in Rheumatic Atrial Fibrillation: A Randomized Study

Background: Patients with rheumatic heart disease with atrial fibrillation incur significant morbidity and mortality. Which approach, ventricular rate control or maintenance of sinus rhythm, in this setting might be superior is not known. The role of amiodarone in this patient population for maintaining sinus rhythm has not been evaluated.

Methods and Results: We prospectively studied 144 patients with chronic rheumatic atrial fibrillation in a double-blind protocol in which rhythm control (group I), comprising 48 patients each with amiodarone (group Ia) and placebo (group Ib), were compared with each other and with patients in a ventricular rate control group (group II) in which the effects by diltiazem were determined (n = 48, open-label). Direct current cardioversion was attempted in group I. The mean age of the study population was 38.6 ± 10.3 years, left atrial size, 4.7 ±0.6 cm; atrial fibrillation duration, 6.1 ± 5.4 years; and 72.9% had valvular interventions performed. At 1 year, 45 patients with sinus rhythm in group I compared with 48 in group II demonstrated an increase in exercise time (2.6 ± 1.9 vs. 0.6 ± 2.5 min, P = .001), improvement in New York Heart Association class of 1 or more ( P = .002), and improvement in the quality-of-life score of one or greater ( P = 0.01) with no difference in hospitalizations, systemic bleeds, or thromboembolism. Five patients died in group II; none died in group I ( P =.02). In group I, 73 of 87 (83.9%) patients converted to sinus rhythm and 45 of 86 (52.3%) patients maintained the rhythm at 1 year. Conversion rates were 38 of 43 (88.4%) with amiodarone versus 34 of 44 (77.3%) with placebo ( P = .49); the corresponding rate for maintaining sinus rhythm was 29 of 42 (69.1%) versus 16 of 44 (36.4%) ( P = .008). A larger number of electrical cardioversions were required in the placebo group (2.1 vs. 1.4, P = .011).

Conclusions: Maintenance of sinus rhythm is superior to ventricular rate control in patients with rheumatic atrial fibrillation with respect to effects on exercise capacity, quality of life, morbidity, and possibly mortality. Sinus rhythm could be restored in most patients, and amiodarone was superior to placebo in the restoration and maintenance of sinus rhythm.

Exercise heart rate acceleration patterns during atrial fibrillation and sinus rhythm

BACKGROUND

Patients with atrial fibrillation sustain a significant lower exercise tolerance compared to those in sinus rhythm, even while seemingly in adequate rate-control.

METHODS

Exercise testing was performed during atrial fibrillation and after electric cardioversion for 30 patients who were initially treated with AV modifying agents and were considered in adequate rate control. Heart rate parameters were obtained during all exercise stages, and a graphic display of heart rate acceleration was obtained. For those patients who remained in sinus rhythm, an additional exercise test was performed after 1 month.

RESULTS

During atrial fibrillation, heart rate at the completion of Bruce stage 1 and the peak exercise heart rate were significantly higher when compared to sinus rhythm (120 ± 10 bpm vs. 98 ± 11 bpm and 164 ± 16 bpm vs. 129 ± 11 bpm respectively, p < 0.001 for both). The time to peak exercise heart rate was significantly shorter during atrial fibrillation (3.5 ± 1 min vs. 6.5 ± 1.5 min, p < 0.001), and the total exercise duration was subsequently shorter as well (6 ± 2 min vs. 8.5 ± 2 min, p < 0.001). Treatment with beta-blockers prior to exercise did not affect the earlier peaking of the heart rate. After 1 month, similar time to peak heart rate and similar exercise performance were observed among patients, who remained in sinus rhythm, when compared to to the post-cardioversion exercise test.

CONCLUSIONS

In patients with atrial fibrillation, exercise heart rate acceleration displays a specific pattern of early peaking. Earlier heart rate peaking occurs regardless of ample rate control while at rest or mild physical activity and contributes to overall lower exercise performance.

Correlation between heart rate control during exercise and exercise capacity in patients with chronic atrial fibrillation

BACKGROUND

Rate control is an acceptable alternative to rhythm control in patients with chronic atrial fibrillation (AF).

HYPOTHESIS

The aim of this study of AF patients was to understand the correlation between their exercise capacity and both heart rate (HR) and HR variation index during exercise.

METHODS

The exercise capacity of 85 male patients with chronic AF was measured using a cardiopulmonary exercise test (CPX). Within this population, we compared the exercise tolerance of patients with a normal chronotropic response (maximal HR 85%-115% that of the maximal age-predicted HR during CPX) to those whose HR response exceeded this range. Two similar comparisons were made by dividing the subject population according to (1) whether or not their HR variation index (HRVI) during CPX exceeded 10 bpm/min, and (2) whether their HR during the 6-minute walk test exceeded 110 bpm.

RESULTS

Patients with an HRVI not over 10 bpm/min showed higher maximal oxygen uptake compared to patients with a higher HRVI (26.7 ± 6.1 vs 22.8 ± 4.8 mL O(2) /kg/min, P = 0.002) and a longer distance walked during CPX (705.6 ± 200.3 vs 520.9 ± 155.5 m, P<0.001). No other significant influence on exercise capacity was seen. Multivariate regression analysis revealed that both the body mass index and the HRVI during CPX were independent predictors of the maximal oxygen uptake.

CONCLUSIONS

Better HRVI control on CPX was correlated with better exercise capacity in patients with chronic AF.

Echocardiographic predictors of functional capacity in endomyocardial fibrosis patients

AIMS

Endomyocardial fibrosis (EMF) is a restrictive cardiomyopathy manifested mainly by diastolic heart failure. It is recognized that diastole is an important determinant of exercise capacity. The purpose of this study was to determine whether resting echocardiographic parameters might predict oxygen consumption (VO(2p)) by ergoespirometry and the prognostic role of functional capacity in EMF patients.

METHODS AND RESULTS

A total of 32 patients with biventricular EMF (29 women, 55.3 +/- 11.4 years) were studied by echocardiography and ergoespirometry. The relationship between the echocardiographic indexes and the percentage of predicted VO(2p) (%VO(2p)) was investigated by the 'stepwise' linear regression analysis. The median VO(2p) was 11 +/- 3 mL/kg/min and the %VO(2p) was 53 +/- 9%. There was a correlation of %VO(2p) with an average of A' at four sites of the mitral annulus (A' peak, r = 0.471, P = 0.023), E'/A' of the inferior mitral annulus (r = -0.433, P = 0.044), and myocardial performance index (r = -0.352, P = 0.048). On multiple regression analysis, only A' peak was an independent predictor of %VO(2p) (%VO(2p)= 26.34 + 332.44 x A' peak). EMF patients with %VO(2p)< 53% had an increased mortality rate with a relative risk of 8.47.

CONCLUSION

In EMF patients, diastolic function plays an important role in determining the limitations to exercise and %VO(2p) has a prognostic value.

Persistent atrial fibrillation worsens heart rate variability, activity and heart rate, as shown by a continuous monitoring by implantable biventricular pacemakers in heart failure patients

BACKGROUND

Atrial fibrillation (AF) induces loss of atrial contribution, heart rate irregularity, and fast ventricular rate.

OBJECTIVES

The objectives of the study were to accurately measure AF incidence and to investigate the mutual temporal patterns of AF and heart failure (HF) in patients indicated to cardiac resynchronization therapy.

METHODS

Four hundred ten consecutive patients (70% male, age 69 +/- 11) with advanced HF (NYHA = 3.0 +/- 0.6), low ejection fraction (EF = 27 +/- 9%), and ventricular conduction delay (QRS = 165 +/- 29 ms) received a biventricular pacemaker. Enrolled patients were divided into two groups: G1 = 249 patients with no AF history, G2 = 161 patients with history of paroxysmal/persistent AF.

RESULTS

In a median follow-up of 13 months, AF episodes longer than 5 minutes occurred in 105 of 249 (42.2%) G1 patients and 76 of 161 (47.2%) G2 patients, while AF episodes longer than one day occurred in 14 of 249 (5.6%) G1 patients and in 36 of 161 (22.4%) G2 patients. Device diagnostics monitored daily values of patient activity, night heart rate (NHR), and heart rate variability (HRV). Comparing 30-day periods before AF onset and during persistent AF, significant (P < 0.0001) changes were observed in patient activity, which decreased from 221 +/- 13 to 162 +/- 12 minutes, and in NHR, which increased from 68 +/- 3 to 94 +/- 7 bpm. HRV significantly decreased (from 75 +/- 5 ms before AF onset to 60 +/- 6 ms after AF termination). NHR during AF was significantly (P < 0.01) and inversely correlated (R(2)= 0.73) with activity, with a significant lower activity associated with NHR >or= 88 bpm.

CONCLUSION

AF is frequent in HF patients. Persistent AF is associated with statistically significant decrease in patient activity and HRV and NHR increase.

Exercise capacity in atrial fibrillation: a substudy of the Sotalol-Amiodarone Atrial Fibrillation Efficacy Trial (SAFE-T)

BACKGROUND

Therapy for chronic atrial fibrillation (AF) focuses on rate versus rhythm control, but little is known about the effects of common therapeutic interventions on exercise tolerance in AF.

METHODS

Six hundred fifty-five patients with chronic AF underwent maximal exercise testing at baseline and 8 weeks, 6 months, and 1 year after randomization to sotalol, amiodarone, or placebo therapy and attempted direct current cardioversion. Analyses of baseline determinants of exercise capacity, predictors of change in exercise capacity at 6 months and 1 year, and the short- and long-term effects of cardioversion on exercise capacity were made.

RESULTS

Age, obesity, and presence of symptoms accompanying AF were inversely associated with baseline exercise capacity, but these factors accounted for only 10% of the variance in exercise capacity. Patients most likely to benefit from cardioversion were those most limited initially, younger, not obese or hypertensive, and with an uncontrolled ventricular rate at baseline. Conversion to sinus rhythm (SR) resulted in significant reductions in resting (approximately 25 beat/min) and peak exercise (approximately 40 beat/min) heart rates at 6 months and 1 year (P < .001). Successful cardioversion improved exercise capacity by 15% at 8 weeks, and these improvements were maintained throughout the year. This improvement was observed both among those who maintained SR and those with intermittent AF.

CONCLUSION

Cardioversion resulted in a sustained improvement in exercise capacity over the course of 1 year, and this improvement was similar between those in SR and those with SR and recurrent AF. Patients most likely to improve with treatment tended to be younger and nonobese and have the greatest limitations initially.

Atrial fibrillation is associated with increased neurohumoral activation and reduced exercise tolerance in patients with non-ischemic dilated cardiomyopathy

OBJECTIVES

To assess atrial fibrillation (AF) associated differences in proinflammatory cytokines, natriuretic peptide levels and exercise capacity in patients with heart failure (HF) secondary to non-ischemic dilated cardiomyopathy (NIDC).

METHODS

We studied 147 NIDC patients, mean age 58.3+/-12.5 years, left ventricular (LV) ejection fraction 27.8+/-10.9% and NYHA class II-III. Neurohumoral activation was assessed by measurement of interleukin IL-1, IL-6, tumor necrosis factor-a (TNF-a), its soluble receptors sTNFR I and II, N-terminal atrial (NT-ANP) and -brain (NT-BNP) natriuretic peptide levels, and functional class was assessed by cardiopulmonary exercise test.

RESULTS

Forty patients (27.5%) had chronic AF and they did not differ in age, LV ejection fraction or HF duration compared to patients in sinus rhythm (SR). AF was associated with increased levels of IL-6 (p=0.001), TNF-a (p=0.002), sTNFRI (p=0.023), NT-ANP (p<0.001) and NT-BNP (p=0.003), decreased exercise duration (p<0.001) and slightly reduced maximal oxygen consumption at peak exercise (p=0.07) compared to SR patients. No significant differences in cytokine and natriuretic peptide levels or exercise tolerance were noted when patients in AF were compared to the subgroup of SR with restrictive LV filling pattern. Multivariate analysis showed that NT-ANP (p=0.003) and IL-6 (p=0.006) plasma levels were independently associated with the presence of AF in our patient population.

CONCLUSION

AF is associated with increased inflammatory state, natriuretic peptide levels and reduced exercise capacity in patients with HF secondary to NIDC. These findings suggest that the presence of AF in HF represents a more advanced stage of the syndrome.

Quality of Life and Exercise Performance in Patients in Sinus Rhythm Versus Persistent Atrial Fibrillation

OBJECTIVES

The purpose of this study was to determine quality of life (QOL) and exercise performance (EP) in patients with persistent atrial fibrillation (AF) converted to sinus rhythm (SR) compared with those remaining in or reverting to AF.

BACKGROUND

Restoration of SR in patients with AF improving QOL and EP remains controversial.

METHODS

Patients with persistent AF were randomized double-blind to amiodarone, sotalol, or placebo. Those not achieving SR at day 28 were cardioverted and classified into SR or AF groups at 8 weeks (n = 624) and 1 year (n = 556). The QOL (SF-36), symptom checklist (SCL), specific activity scale (SAS), AF severity scale (AFSS), and EP were assessed.

RESULTS

Favorable changes were seen in SR patients at 8 weeks in physical functioning (p < 0.001), physical role limitations (p = 0.03), general health (p = 0.002), and vitality (p < 0.001), and at 1 year in general health (p = 0.007) and social functioning (p = 0.02). Changes in the scores for SCL severity (p = 0.01), functional capacity (p = 0.003), and AFSS symptom burden (p < 0.001) at 8 weeks and in SCL severity (p < 0.01) and AF symptom burden (p < 0.001) at 1 year showed significant improvements in SR versus AF. Symptomatic patients were more likely to have improvement. The EP in SR versus AF was greater from baseline to 8 weeks (p = 0.01) and to 1 year (p = 0.02). The EP correlated with physical functioning and functional capacity except in the AF group at 1 year.

CONCLUSIONS

In patients with persistent AF, restoration and maintenance of SR was associated with improvements in QOL measures and EP. There was a strong correlation between QOL measures and EP.

Comparison of rate control and rhythm control in patients with atrial fibrillation after percutaneous mitral balloon valvotomy: a randomised controlled study

OBJECTIVE

To compare rate control and rhythm control strategies in patients with atrial fibrillation (AF) after percutaneous mitral balloon valvotomy (PMV).

METHODS

183 patients with AF after successful PMV, with AF duration <or= 12 months and post-PMV left atrial (LA) size <or= 45 mm, were studied in a prospective, randomised trial. The primary end point was improvement in AF-related symptoms. Secondary study end points were 6 min walk tests, quality of life (QOL), normalisation of LA size, number of hospital admissions and duration of hospital stay.

RESULTS

Over one year, 2% patients in the rate control group had sinus rhythm, as compared with 96% of patients in the rhythm control group (p < 0.001). A greater proportion of patients reported improvement in symptoms in the rhythm control group than in the rate control group (p < 0.0001 at every visit time). Walking distance in a 6 min walk test, QOL and LA size normalisation were better in the rhythm control group than in the rate control group. The strategy of rhythm control was associated with similar numbers of hospital admissions but with longer duration of hospital admissions. Drug-related side effect did not differ between the rate control and rhythm control groups. During the follow-up period, no patients in either group had embolic or transitory ischaemic neurological events.

CONCLUSIONS

In patients with AF after PMV, AF duration <or= 12 months and post-PMV LA size <or= 45 mm, sinus rhythm was easy and safe to achieve and maintain. Moreover, patients benefited from restoration and maintenance of sinus rhythm in terms of improved AF-related symptoms, 6 min walk tests and QOL, and of LA size normalisation. Rhythm control should therefore be considered as the preferred initial therapy for this group of patients. The optimal strategy to treat AF after PMV should be individualised.

Amiodarone versus sotalol for atrial fibrillation

BACKGROUND

The optimal pharmacologic means to restore and maintain sinus rhythm in patients with atrial fibrillation remains controversial.

METHODS

In this double-blind, placebo-controlled trial, we randomly assigned 665 patients who were receiving anticoagulants and had persistent atrial fibrillation to receive amiodarone (267 patients), sotalol (261 patients), or placebo (137 patients) and monitored them for 1 to 4.5 years. The primary end point was the time to recurrence of atrial fibrillation beginning on day 28, determined by means of weekly transtelephonic monitoring.

RESULTS

Spontaneous conversion occurred in 27.1 percent of the amiodarone group, 24.2 percent of the sotalol group, and 0.8 percent of the placebo group, and direct-current cardioversion failed in 27.7 percent, 26.5 percent, and 32.1 percent, respectively. The median times to a recurrence of atrial fibrillation were 487 days in the amiodarone group, 74 days in the sotalol group, and 6 days in the placebo group according to intention to treat and 809, 209, and 13 days, respectively, according to treatment received. Amiodarone was superior to sotalol (P<0.001) and to placebo (P<0.001), and sotalol was superior to placebo (P<0.001). In patients with ischemic heart disease, the median time to a recurrence of atrial fibrillation was 569 days with amiodarone therapy and 428 days with sotalol therapy (P=0.53). Restoration and maintenance of sinus rhythm significantly improved the quality of life and exercise capacity. There were no significant differences in major adverse events among the three groups.

CONCLUSIONS

Amiodarone and sotalol are equally efficacious in converting atrial fibrillation to sinus rhythm. Amiodarone is superior for maintaining sinus rhythm, but both drugs have similar efficacy in patients with ischemic heart disease. Sustained sinus rhythm is associated with an improved quality of life and improved exercise performance.

Acute reductions in ventricular myocardial tissue velocities after direct current cardioversion of atrial fibrillation

BACKGROUND

Cardioversion by direct current (DC) and other methods can cause atrial "stunning." There are case reports of acute pulmonary edema after DC cardioversion, but whether acute ventricular dysfunction is a general consequence of DC cardioversion is unknown. We have investigated whether DC cardioversion acutely affects myocardial velocity assessed by Doppler tissue imaging.

METHODS

40 patients (30 with atrial fibrillation and 10 with atrial flutter) undergoing elective DC cardioversion underwent transthoracic echocardiography with Doppler tissue imaging before and immediately after cardioversion, and after follow-up. Peak systolic velocity was derived for 6 ventricular segments using Doppler tissue imaging.

RESULTS

Immediately after DC cardioversion of atrial fibrillation, peak systolic velocity decreased in basal lateral (4.3 +/- 2.0-3.3 +/- 1.7 cm/s, P <.001), mitral annulus-septal (3.8 +/- 1.0-3.5 +/- 0.9, P <.05), mitral annulus-lateral (4.9 +/- 1.6-4.1 +/- 1.7, P <.001), and tricuspid annular (7.8 +/- 2.0-7.0 +/- 1.2, P <.03) segments, even though left ventricular ejection fraction was unchanged. In contrast, for the atrial flutter group there were no significant changes in peak systolic velocity in any segment post-DC cardioversion. Follow up studies were performed after sustained in sinus rhythm in both atrial fibrillation and atrial flutter groups. For both groups, increased peak systolic velocity was found in all 6 segments on follow-up (all P <.05).

CONCLUSIONS

DC cardioversion causes subclinical, acute reversible reduction in left ventricular peak systolic velocity in patients with atrial fibrillation. The causes of this reduction in myocardial contractile velocity and the circumstances in which acute dysfunction become clinically significant warrant further investigation.

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.

Impaired exercise-induced vasodilatation in chronic atrial fibrillation--role of endothelium-derived nitric oxide

Exercise capacity is often reduced in patients with atrial fibrillation (AF), but very few studies have focused on changes in endothelial function as a potential mechanism for the exercise limitation. The present study used using venous occlusion plethysmography to investigate whether nitric oxide (NO)-mediated vasodilatation is attenuated during exercise in patients with AF by measuring forearm blood flow (FBF) in 10 patients at rest and immediately after 2 levels of rhythmic handgrip exercise, before and after inhibition of NO synthesis with N(G)-monomethyl-L-arginine (L-NMMA, 100 micromol). The measurements were repeated 1 day after restoration of sinus rhythm by cardioversion. FBF responses to graded doses of acetylcholine (ACh) were also observed before and after cardioversion. Heart rate decreased after cardioversion, but blood pressure did not change. FBF at rest was not affected by cardioversion, but at the highest level of exercise it increased from 28.4+/-2.3 ml x min(-1) x dl(-1) before to 39.4+/-3.2 ml x min(-1) x dl(-1) after cardioversion (p<0.05). L-NMMA significantly decreased FBF at rest (p<0.01) and depressed the increase in FBF response to exercise after (p<0.01), but not before cardioversion. The FBF response to ACh was also accelerated significantly after cardioversion. The present results provide new evidence that NO bioavailability is depressed at rest and during exercise in patients with AF.

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.

Exercise performance and training in cardiac patients with atrial fibrillation

PURPOSE

Exercise training in cardiac patients with chronic atrial fibrillation (AF) has received little attention in the literature. Therefore, this study compared exercise performance and the effect of an exercise training program over a period of 3 months in patients with and without AF.

METHODS

Data in patients with AF (n = 19) were compared with a control group of patients in sinus rhythm (n = 44), drawn from a database of 2,116 patients. Patients performed a maximal exercise test on the bicycle until exhaustion before and after an ambulatory exercise training program where exercise training was offered 3 times a week for 3 months.

RESULTS

Before training, peak oxygen uptake (VO2) was significantly lower in patients with AF compared with the control group (1271 +/- 368 versus 1496 +/- 414 mL/min, P < 0.05). Exercise training significantly increased peak VO2 in both groups (+31%, P < 0.001 in AF and +25%, P < 0.001 in the control group). The gain in peak VO2 did not significantly differ between both groups. A significant decrease in resting heart rate was achieved in both groups after exercise training. AF was also a significant and independent determinant of peak VO2 in the total database, but not of the change in peak VO2.

CONCLUSIONS

Exercise training significantly improves exercise performance in cardiac patients with AF. AF affects exercise performance but does not impair the beneficial effects of training. Patients with chronic AF should therefore not be dissuaded from participating in exercise training after a cardiac event.

Signal-averaged P wave duration predicts early recurrence of atrial fibrillation after cardioversion

Thirty-two patients had signal-averaged P wave duration measured after electrical cardioversion of AF, and were followed for 1 year or until there was a recurrence. The use of antiarrhythmic medications was left to the discretion of the attending physician. Among 20 patients not taking antiarrhythmic medication, the 11 patients who had a recurrence of AF within 3 months of cardioversion had a significantly longer signal-averaged P wave duration compared to the 9 patients who did not (148 +/- 17 vs 135 +/- 20 ms, P = 0.005). There was no difference in clinical parameters or left atrial diameter. A signal-averaged P wave duration cutoff anywhere between 130 and 135 ms correctly classified 85% of patients with a sensitivity of 81% and a specificity of 89%. In patients taking antiarrhythmic medications, signal-averaged P wave duration did not correlate with the risk of recurrence. In patients not taking antiarrhythmic medications, signal-averaged P wave duration can be used to predict the risk of an early recurrence of AF after cardioversion. The poor predictive value in patients taking antiarrhythmics may be due to changes in the atrial refractory period, which are not reflected in P wave duration.

Cardiac performance early after cardioversion from atrial fibrillation

BACKGROUND

The mechanism for early improvement in cardiac function after cardioversion from atrial fibrillation is unknown.

METHODS

We measured ventricular volumes and load-independent contractility during atrial fibrillation and within 24 hours after cardioversion to sinus rhythm in 15 adult patients (10 men, 5 women; mean age 63+/-4 years, range 31 to 81 years). Duration of atrial fibrillation ranged from <1 day to 6 months.

RESULTS

After cardioversion, left ventricular ejection fraction increased from 51%+/-4% to 61%+/-4% (P=.001, 95% confidence intervals for the difference, 7% to 15%), stroke volume increased from 57+/-4 mL to 76+/-6 mL (P < .001, 95% confidence intervals 8 to 32 mL), and mean cycle length increased from 0.77+/-.04 seconds in atrial fibrillation to 1.02+/-.04 seconds in sinus rhythm (P=.002, 95% confidence intervals, 0.1 to 0.4 seconds). Cardiac contractility, as expressed by the slope and the intercept of the relation between rate-corrected circumferential velocity of fiber shortening and end-systolic wall stress (Vcfc/ESWS) remained unaltered in 13 of 15 patients, suggesting that intrinsic inotropic state was unchanged immediately after return of normal sinus rhythm. Finally, a significant correlation was observed between improvement in stroke volume and peak A-wave velocity (r=0.79, P=.035).

CONCLUSION

Both left ventricular stroke volume and ejection fraction increase immediately after cardioversion, whereas intrinsic cardiac contractility is largely unchanged. These data suggest that the mechanism of this increase is enhanced left ventricular diastolic filling due mostly to increased cycle length and return of left atrial mechanical function.

Predictors of primary atrial fibrillation and concomitant clinical and hemodynamic changes in patients with chronic heart failure: a prospective study in 344 patients with baseline sinus rhythm

OBJECTIVES

This study investigated the incidence, predisposing factors and significance of the onset of atrial fibrillation (AF) in patients with chronic congestive heart failure (CHF).

BACKGROUND

The association between CHF and AF is well documented, but the factors that predispose to the onset of the arrhythmia and its impact remain controversial. Methods. We prospectively followed up 344 patients with CHF and sinus rhythm (SR). Over a period of 19 +/- 12 months (mean +/- SD), 28 patients developed atrial fibrillation (AF), which became chronic in 18.

RESULTS

At baseline, no differences were found in any clinical and hemodynamic variables between patients who developed chronic AF and those who did not. Reversible AF occurring during follow-up and lower mitral flow velocity at atrial contraction as detected at the last evaluation in SR were independent predictors of the subsequent development of chronic AF. When AF occurred, New York Heart Association functional class worsened (from 2.4 +/- 0.5 to 2.9 +/- 0.6, p = 0.0001), peak exercise oxygen consumption declined (from 16 +/- 5 to 11 +/- 5 ml/kg per min, p = 0.002), cardiac index decreased (from 2.2 +/- 0.4 to 1.8 +/- 0.4, p = 0.0008), and mitral and tricuspid regurgitation increased (from grade 1.8 +/- 1.1 to grade 2.4 +/- 1.4, p = 0.0001 and from grade 1.0 +/- 1.2 to grade 1.8 +/- 1.2, p = 0.001, respectively). Systemic thromboembolism occurred in 3 of the 18 patients with AF. Nine of 18 patients died after AF, and the occurrence of AF was a predictor of major cardiac events.

CONCLUSIONS

In patients with CHF, reversible AF and reduction of left atrial contribution to left ventricular filling predict the subsequent development of chronic AF. The onset of AF is associated with clinical and hemodynamic deterioration and may predispose to systemic thromboembolism and poorer prognosis.

Acute treatment of atrial fibrillation: why and when to maintain sinus rhythm

Although not usually immediately life threatening, atrial fibrillation (AFib) poses a significant long-term risk to health. The best-documented and probably largest long-term risk in this condition is from thromboembolic complications, but this has been shown to be largely overcome by moderate intensity anticoagulation. In addition, however, AFib has significant detrimental effects on exercise capacity and overall quality of life, can cause or exacerbate heart failure, and imposes significant health-care burdens. Cardioversion, usually by transthoracic direct current shock, restores sinus rhythm in > 80% of patients, but recurrence of AFib over the weeks and months that follow decreases the value of this strategy. Antiarrhythmic drugs lessen the recurrence rate and add to the overall efficacy of achieving the treatment goal of restoring and maintaining sinus rhythm, rather than accepting permanent AFib with ventricular rate control and long-term thromboembolic prophylaxis. Whereas clear evidence exists that abolishing AFib makes patients feel better in the short-to-medium term, data on the economic viability or long-term efficacy of such a strategy are sparse. Management trials in AFib currently ongoing will provide some answers, but the decision as to whether restoring sinus rhythm is feasible and realistic in individual patients will remain a decision to be made on a case-by-case basis.

Atrial fibrillation is associated with a lower exercise capacity in male chronic heart failure patients

OBJECTIVE

To study the influence of atrial fibrillation on peak oxygen uptake (peak VO2) in chronic heart failure. An unfavourable effect of atrial fibrillation has been shown in several patient populations, but the results have not been consistent in chronic heart failure.

METHODS

Data were analysed from male heart transplant candidates who were able to perform graded bicycle ergometry until exhaustion with respiratory gas analysis and measurement of heart rate. Patients in atrial fibrillation (n = 18) were compared with patients in sinus rhythm (n = 93).

RESULTS

Age, weight, height, and aetiology of chronic heart failure did not differ significantly between the two groups. Cardiac catheterisation at supine rest showed that heart rate was comparable, but that stroke volume and cardiac output were lower (p < 0.05) in atrial fibrillation. Systolic and diastolic left ventricular function, assessed by radionuclide angiography at rest, were not significantly different. Peak VO2 (mean (SD): 13.8 (3.6) v 17.1 (5.6) ml/kg/min; p < 0.01) and peak work load (78 (27) v 98 (36) W; p < 0.05) were lower in the patients with atrial fibrillation, though respiratory gas exchange ratio and Borg score were similar in the two groups. Patients with atrial fibrillation had a higher heart rate sitting at rest before exercise (93 (16) v 84 (16) beats/min) and at peak effort (156 (23) v 140 (25) beats/min) (p < 0.05).

CONCLUSIONS

Atrial fibrillation is associated with a 20% lower peak VO2 in patients with chronic heart failure, suggesting that preserved atrial contraction or a regular rhythm, or both, are critical to maintain cardiac output and exercise performance.

The medical management of atrial fibrillation

Atrial fibrillation is an extremely common arrhythmia that is associated with significant sequelae. Certain aspects of therapy, such as anticoagulation, are studied in well-constructed randomized trials. Other therapy, such as the maintenance of sinus rhythm with antiarrhythmic agents, is supported by limited evidence. This article reviews the epidemiology and medical treatment of this arrhythmia, addressing anticoagulation, ventricular rate control, and restoration and maintenance of sinus rhythm. Randomized trials in progress that attempt to answer important questions in the management of atrial fibrillation are also discussed.

Electrocardiographic nature of restored sinus rhythm after Cox maze procedure in patients with chronic atrial fibrillation who also had other cardiac surgery

OBJECTIVE

To characterise heart rate variability and high frequency components of restored sinus rhythm after the maze procedure. The maze procedure for chronic atrial fibrillation may prevent thrombotic events and improve the quality of life. However, the electrocardiographic nature of restored sinus rhythm after the maze procedure has not been fully elucidated.

PATIENTS AND METHODS

Between March 1993 and August 1995, 104 consecutive patients undergoing the maze procedure in combination with other cardiac surgery were studied. There were 100 long-term survivors (78 with mitral valve disease, 9 with aortic valve disease, 8 with congenital heart disease, and 5 others). Twenty age-matched patients with mitral valve disease who were in normal sinus rhythm preoperatively were enrolled as a control group. 30 days after surgery, the presence of arrhythmias and the circadian changes of heart rate variability were estimated by ambulatory electrocardiographic monitoring and the filtered P duration was evaluated by signal-averaged electrocardiogram.

RESULTS

Restoration of sinus rhythm was observed in 73 of 100 cases. Subjects were classified into three groups according to their postoperative ambulatory electro-cardiographic monitoring findings: patients in group 1 (n = 73) (1a: 58 regular sinus rhythm; 1b: 15 sinus rhythm with frequent premature atrial contractions (> 1000/day); patients in group 2 (n = 21) still had persistent atrial fibrillation; and patients in group 3 (n = 6) required permanent pacemaker implantation because of sick sinus syndrome. The success rate of restoration of sinus rhythm was 88.3% if left atrial diameter was small (< 65 mm). Circadian changes in the low frequency to high frequency power ratio in group 1a were significantly diminished compared with control group (P < 0.01). Furthermore, the filtered P duration in group 1a (150 (20) ms) and group 1b (158 (23) ms) were longer than in the control group (122 (11) ms) (P < 0.01).

CONCLUSIONS

The maze procedure may result in a decreased sinus response and non-uniform transmission of impulses in the atrium.