Exercise and morphologic comparison of chronic atrial fibrillation and normal sinus rhythm

A Computational Study on the Relation between Resting Heart Rate and Atrial Fibrillation Hemodynamics under Exercise

AIMS

Clinical data indicating a heart rate (HR) target during rate control therapy for permanent atrial fibrillation (AF) and assessing its eventual relationship with reduced exercise tolerance are lacking. The present study aims at investigating the impact of resting HR on the hemodynamic response to exercise in permanent AF patients by means of a computational cardiovascular model.

METHODS

The AF lumped-parameter model was run to simulate resting (1 Metabolic Equivalent of Task-MET) and various exercise conditions (4 METs: brisk walking; 6 METs: skiing; 8 METs: running), considering different resting HR (70 bpm for the slower resting HR-SHR-simulations, and 100 bpm for the higher resting HR-HHR-simulations). To compare relative variations of cardiovascular variables upon exertion, the variation comparative index (VCI)-the absolute variation between the exercise and the resting values in SHR simulations referred to the absolute variation in HHR simulations-was calculated at each exercise grade (VCI4, VCI6 and VCI8).

RESULTS

Pulmonary venous pressure underwent a greater increase in HHR compared to SHR simulations (VCI4 = 0.71, VCI6 = 0.73 and VCI8 = 0.77), while for systemic arterial pressure the opposite is true (VCI4 = 1.15, VCI6 = 1.36, VCI8 = 1.56).

CONCLUSIONS

The computational findings suggest that a slower, with respect to a higher resting HR, might be preferable in permanent AF patients, since during exercise pulmonary venous pressure undergoes a slighter increase and systemic blood pressure reveals a more appropriate increase.

Symptoms In Atrial Fibrillation: A Contemporary Review And Future Directions

Atrial fibrillation (AF) is the most prevalent arrhythmia leading to hospital admissions in the United States. The majority of patients with AF report symptoms associated with this condition that can lead to a decrease in health related quality of life (HRQOL) and functional status. Therefore, along with reducing the risk of stroke and mortality, improvements in such symptoms are important therapeutic goals in the management of patients with AF. Our current understanding of how AF and symptoms are linked is hampered by the dominant assessment paradigm, where symptoms thought to be associated with AF are measured at a single point in time (frequently at a clinic visit). Unfortunately, this "static" snapshot does not capture the variability of symptoms and heart rhythm within a person over time and does not shed light on how symptoms are related to heart rhythm. This focused review summarizes current methods for assessing symptoms including generic and AF-specific HRQOL and functional status tools. It also describes gaps in the current assessment paradigm and where future research using mobile applications and digital technology might be able to assist with patient care.

Reciprocal relations between physical disability, subjective health, and atrial fibrillation: the Framingham Heart Study

BACKGROUND

Atrial fibrillation (AF)-related symptoms and physical performance are relied upon to guide therapeutic management of patients with AF. We sought to understand whether AF predisposes to or is a result of physical disability and poor subjective health in the community.

METHODS

We studied relations between physical disability (Rosow-Breslau Functional Health Scale), subjective health (self-report) and incident AF, and the converse, in the Framingham Heart Study.

RESULTS

In 3,609 participants (age 73 ± 8 years, 59% women), a subset of 861 participants (24%) had prevalent physical disability at baseline. During 5.8 ± 1.8 years of follow-up, 555 participants (10-year age- and sex-adjusted incidence rate 13%) developed incident AF. Prevalent physical disability was related to incident AF (multivariable-adjusted hazard ratio 1.25, 95% CI 1.02-1.54, P = .03). In 3,525 participants, prevalent poor subjective health (n = 333) also was related to incident AF (n = 552, multivariable-adjusted hazard ratio 1.31, 95% CI 1.00-1.70, P = .048). Conversely, in 2,080 participants (age 69 ± 6 years, 55% women), interim AF (n = 106) was associated with newly reported physical disability (n = 573) at a follow-up examination (multivariable-adjusted odds ratio 1.58, 95% CI 1.08-2.31, P = .01). In 1,954 participants, interim AF (n = 96) likewise was related to newly reported poor subjective health (n = 224, multivariable-adjusted odds ratio 1.83, 95% CI 1.10-3.02, P = .02).

CONCLUSIONS

Physical disability and poor subjective health were related to incident AF in a community-based cohort. Conversely, interim AF was related to newly reported physical disability and poor subjective health. Because AF guidelines incorporate symptoms, it is essential to clarify the temporality and mechanisms linking physical disability, subjective health, and AF.

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.

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.

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.

What determines the heart rate response to exercise in patients with atrial fibrillation?

We evaluated the factors that determine the heart rate response to exercise in 60 patients with atrial fibrillation (25 men and 35 women, with a mean age of 61+/-10 years) who underwent symptom limited cardiopulmonary exercise testing with blood sampling of atrial natriuretic peptide (ANP), 2-dimensional echocardiography and cardiac catheterization. Atrial muscles resected during the Maze operation were examined histologically in 12 patients. The heart rate response to exercise depended on the severity of the atrial organic injury, which was expressed as left atrial diameter, ANP secretion during the maximal exercise testing and the histological findings of atrial tissue. Conversely, we believe that the severity of the atrial injury can be predicted from the heart rate response to exercise in patients with atrial fibrillation.

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.